CA2496213A1 - Metalloprotease activation of myostatin, and methods of modulating myostatin activity - Google Patents

Abstract

It has been determined that metalloprotease cleavage of a myostatin pro peptide results in activation of a latent inactive myostatin to an active form. Accordingly, methods of identifying agents that modulate metalloprotease mediated activation of myostatin are provided, as are agents identified using such methods. Also provided are methods of modulating muscle growth in an organism by increasing or decreasing metalloprotease mediated cleavage of a myostatin pro peptide.

Description

METALLOPROTEASE ACTIVATION OF MYOSTATIN, AND METHODS OF MODULATING MYOSTATIN ACTIVITY
[0001] This invention was made in part with government support under Grant Nos. HD35887, AR47746, a,nd GM63471 awarded by the National Institutes of Health.
The United States government has certain rights in this invention.
BACKGROUND OF THE INVENTION
Field of the Invention

[0002] The invention relates generally to metalloprotease regulation of myostatin activity, and more specifically to methods of using agonists or antagonists of the BMP-1/TLD family of metalloproteases to modulate myostatin activity including, for example, to regulate muscle development in an organism, to methods of identifying agonists and antagonists of such metalloproteases, and to agonists and antagonists so identified.
Background Information

[0003] Myostatin is a transforming growth factor-13 (TGF-13) family member that is essential for proper regulation of skeletal muscle growth. Myostatin is a secreted protein that is expressed specifically by cells of the skeletal muscle lineage during embryonic development and in adult animals; low levels of myostatin mRNA also axe present in fat cells in adults animals. During early embryogenesis, myostatin mRNA is detectable in the myotome compartment of developing somites. At later embryonic stages and in postnatal life, myostatin is expressed widely in all slceletal muscles that have been examined.

[0004] The function of myostatin was elucidated by gene targeting studies in mice.
Mice lacking myostatin demonstrated a dramatic and widespread increase in skeletal muscle mass due to muscle fiber hyperplasia and hypertrophy, indicating that myostatin is a negative regulator of muscle growth. The myostatin gene is highly conserved across evolution, with the predicted mature myostatin protein sequence being identical among mice, rats, humans, chickens, turlceys, and pigs, and highly homologous even with respect to aquatic organisms. The function of myostatin also is conserved, with mutations in the myostatin gene correlating to the double muscling phenotype in cattle.

JHLTl 800-3 WO

[0005] The role of myostatin in regulating muscle growth and development indicates that methods and compositions that regulate myostatin activity can have a broad variety of applications, including, for example, for treating human diseases and for improving livestock production. With respect to human therapeutic applications, inhibitors of myostatin expression or function can provide a clinical benefit in the treatment of muscle wasting disorders such as muscular dystrophy, cachexia, and sarcopenia. In addition, myostatin deficient animals have a significant reduction in fat accumulation, and the loss of myostatin is protective against the development of obesity and type II
diabetes in genetic models in mice. As such, modulation of myostatin activity also can be useful in the treatment of metabolic disorders such as obesity and type II diabetes.
Further in this respect, inhibitors of myostatin expression or function not only can be useful for increasing the efficiency of livestock production, but also can result in the production of meat with a lower fat content.

[0006] Various strategies for manipulating the biological activities of myostatin have been described. Myostatin is synthesized as a precursor protein that undergoes proteolytic processing to generate an N-terminal fragment termed the "pro peptide" and a C-terminal fragment, a disulfide-linlced dimer of which is the biologically active species. Currently described strategies for inhibiting myostatin activity have utilized molecules that can bind the myostatin C-terminal dimer and inhibit its activity. For example, myostatin binds two activin type II receptors, Act RIIA and Act RIIB, ih vitro, and expression of a truncated dominant negative form of Act RIIB in transgenic mice resulted in the mice having increases in muscle mass comparable to that of transgenic myostatin knock out mice.

[0007] The myostatin pro peptide also has been used to inhibit myostatin activity.
Following proteolytic processing, the myostatin pro peptide remains non-covalently associated with the C-terminal dimer and maintains the dimer in a latent, inactive state.
The pro peptide has been shown to block the activity of the purified myostatin C-terminal dimer in various in vita o assays, and overexpression of the pro peptide in transgenic mice resulted in a phenotype characteristic of the myostatin null mutation.
Follistatin is another protein that acts as a myostatin inhibitor. Follistatin can bind and inhibit the activity of a variety of TGF-l3 family members, including myostatin, and transgenic mice overexpressing follistatin in muscle have dramatic increases in muscle growth, consistent with inhibition of myostatin activity.

[0008] The above described inhibitors of myostatin each specifically interact with mature myostatin to inhibit its activity. While inhibiting the activity of a protein such as myostatin using an agent that directly interacts with the protein provides great specificity, such a method can require that all or most of the proteins be bound by the agent for the inhibitory effect to be manifest. An alternative way to inhibit the activity of a protein, particularly a protein that, itself must be activated by a second protein such as an enzyme in order for the first protein to be functional, is to target the second protein. Such a method can be advantageous because activating proteins such as enzymes generally are present at much lower levels than their substrates. As such, there is a greater likelihood that all or most of an activating protein such as an enzyme can be inhibited.

[0009] With respect to myostatin, at least two proteases are known to be involved in processing promyostatin, the primary gene product, into a signal peptide, a pro peptide and a C-terminal fragment, the latter of which forms homodimers that have biological myostatin activity. Unfortunately, these proteases also can act on a variety of other proteins and, therefore, agents that target and inhibit these proteases, for example, signal peptidase, likely would have diverse and deleterious effects if administered to a living organism. Thus, a need exists to identify biological molecules that are more specifically involved in regulating myostatin activation and activity. The present invention satisfies this need and provides additional advantages.

SUMMARY OF THE INVENTION

[0010] The present invention is based on the identification of proteases that cleave myostatin pro peptide, including when the myostatin pro peptide is present in a complex with a rnyostatin C-terminal dimer. As such, the proteases can convert a latent inactive myostatin complex, which comprises a myostatin pro peptide associated with a C-terminal myostatin polypeptide, to active myostatin, which is a negative regulator of muscle growth and development. Such proteases, which are exemplified by the metalloprotease bone morphogenic protein-1/tolloid (BMP-1/TLD) family of proteins, provide targets for drugs that can increase or decrease the protease activity and, therefore, increase or decrease myostatin activity. Accordingly, the present invention provides agents that modulate metalloprotease mediated myostatin pro peptide cleavage and activation of myostatin, as well as methods of using such agents, for example, to modulate myostatin activity in an organism. Methods of identifying such agents also are provided.

[0011] The present invention relates to a method of modulating myostatin activation.
Such a method can be performed, for example, by contacting a latent myostatin complex, which includes a myostatin pro peptide and a myostatin C-terminal fragment, particularly a C-terminal fragment dimer, with a metalloprotease that can cleave the myostatin pro peptide, and with an agent that can increase or decrease proteolytic cleavage of the pro peptide by the metalloprotease, thereby modulating myostatin activation.
The metalloprotease can be any metalloprotease that can cleave the myostatin pro peptide, particularly when the pro peptide comprises a latent myostatin complex, including, for example, a BMP-1/TLD family member such as BMP-1, TLD, tolloid-life protein-1 (TLL-1), or tolloid-like protein-2 (TLL-2), particularly mammalian BMP-1/TLD
family members such as mammalian (m) TLD (mTLD), mTLL-l, and mTLL-2.

[0012] A method of the invention can be used to increase the level of myostatin activation (i.e., above a baseline level of myostatin activation in the absence of an agent), for example, by contacting a latent myostatin complex and metalloprotease with an agent that increases proteolytic cleavage of the pro peptide by the metallopxotease;
or can be used to decrease the level of myostatin activation (below a baseline level), for example, by contacting a latent myostatin complex and metalloprotease with an agent that decreases proteolytic cleavage of the pro peptide by the metalloprotease. The method can be performed if2 vitro, using, for example, cells or a tissue in culture, a cell extract, or substantially purified reagents, including substantially purified metalloprotease and/or latent myostatin complex; or can be performed in vivo, for example, in a cell or tissue, either of which can be in situ in an organism or isolated from an organism (e.g., a cell ex vivo, which can be in culture). Thus, the method can be performed by contacting a sample comprising a latent myostatin complex and metalloprotease (e.g., a tissue sample and/or a biological fluid) with an agent i~c vitro, or the contacting can be performed ivy vivo, for example, by administering the agent to a subject.

[0013] Free myostatin pro peptide, latent myostatin complex, and a metalloprotease that can cleave a myostatin pro peptide can be present intracellularly or extracellularly.
However, the pro peptide or latent myostatin complex generally is not present in the same cells or cell type as the metalloprotease and, therefore, cleavage of myostatin pro peptide by the metalloprotease generally occurs extracellularly upon contact of the metalloprotease with the pro peptide. As such, contacting of an agent with the pro peptide, complex, and/or metalloprotease will depend in part on how the agent acts to modulate the cleavage. For example, where the agent can bind to and alter the conformation of the metalloprotease so as to inhibit its cleavage activity with respect to a myostatin pro peptide, cells that produce the metalloprotease can be contacted with the agent such that the secreted metalloprotease lacks such activity, or the agent can be administered to a medium into which the metalloprotease is secreted (e.g., into the bloodstream of a living organism) such that, upon contact with the agent in the medium, the cleavage of the pro peptide by the metalloprotease is reduced or inhibited. In comparison, where the agent acts, for example, to destabilize an interaction of the metalloprotease and the pro peptide, or where the agent acts as a competitive or non-competitive inhibitor of the metalloprotease with respect to the pro peptide, the agent generally is contacted with the medium in which the metalloprotease and pro peptide are likely to interact (e.g., the blood).

[0014] In one embodiment, the agent decreases proteolytic activity of a metalloprotease that cleaves myostatin pro peptide from a latent myostatin complex, thereby reducing or inhibiting myostatin activation below a level of myostatin activation that occurs or would occur in the absence of the agent. Where such an agent is administered to a subject, the agent can result in increased muscle mass or decreased fat content or both in the subject.
The subject can be any subject in which myostatin is expressed, particularly a vertebrate organism, for example, animals that are raised as a food source, such as a mammalian species (e.g., an ovine, porcine species, or bovine species), avian species (e.g, chickens or a turkeys), or a piscine species (e.g., salmon, trout, or cod). The subject also can be a human subject, for example, a subject suffering from a muscular disorder (e.g., a dystonia or dystrophy), a subject suffering from wasting disorder (e.g., cachexia), or a subject suffering from clinical obesity or other metabolic disorder such as type II
diabetes. In another embodiment, the agent increases proteolytic activity of a metalloprotease that cleaves myostatin pro peptide from a latent myostatin complex, thereby increasing myostatin activation above a level, if any, of myostatin activation that occurs or would occur in the absence of the agent. Where such an agent is administered to a subject, the agent can result in decreased muscle mass or increased fat content or both in the subject.

[0015] The present invention also relates to a method of increasing muscle mass in a subject. Such a method can be performed, for example, by administering to the subject an agent that reduces or inhibits proteolytic cleavage of a myostatin pro peptide by a protease that cleaves myostatin pro peptide, thereby preventing activation of latent myostatin in the cell and increasing muscle mass in the subject. The metalloprotease can be any metalloprotease, pal-ticularly a BMP-1/TLD family member such as BMP-1, TLD, TLL-1, or TLL-2, including mTLD, mTLL-1 and mTLL-2. The subject in which muscle mass is to be increased generally is vertebrate, for example, a domesticated or farm animal, including a mammal such as an ovine species, a porcine species, or a bovine species; an avian species such as a chiclcen or a turkey; or a piscine species; or can be a human subj ect.

[0016] The present invention further relates to a method for ameliorating a metabolic disorder in a subject. Such a method can be performed, for example, by administering to the subject an agent that reduces or inhibits the proteolytic cleavage of a myostatin pro peptide by a protease that cleaves myostatin pro peptide, thereby preventing activation of latent myostatin in the cell and ameliorating the metabolic disorder. The metabolic disorder can be any such disorder associated with increased or undesirable myostatin activation or activity, including, for example, a muscle wasting disorder such as is associated with muscular dystrophy, cachexia (e.g., associated with a cancer or acquired immunodeficiency disease), or sarcopenia; or a metabolic disorder such as clinical obesity or type 2 diabetes. The subject in which the metabolic disorder is ameliorated can be any subject, and generally is a vertebrate subject, for example, a domesticated animal such as a cat or dog, or an animal raised as a source of food (e.g., cattle, sheep, pigs, or fish); or can be a human subject. Amelioration of the disorder can be identified using any assay generally used to monitor the particular metabolic disorder, for example, a glucose tolerance test for diabetes, or a serum leptin assay for body fat analysis.

[0017] The present invention also relates to a method of identifying an agent that modulates metalloprotease mediated myostatin pro peptide cleavage and activation of latent myostatin. Such a screening method can be performed, for example, by contacting a myostatin pro peptide, a metalloprotease that can cleave the myostatin pro peptide, and a test agent, under conditions sufficient for cleavage of the pro peptide by the metalloprotease; and detecting a change in the amount of cleavage of the pro peptide in the absence of the test agent as compared to the presence of the test agent, thereby identifying the test agent as an agent that modulates metalloprotease mediated activation of the latent myostatin. The myostatin pro peptide can be in an isolated form, or can be a component of a latent myostatin complex that further contains a myostatin C-terminal fragment or a myostatin C-terminal dimes.

[0018] Where a test agent is identified as having metalloprotease mediated myostatin modulating activity, a screening assay of the invention can further include a step of determining an amount by which the agent increases or decreases myostatin pro peptide cleavage or myostatin activation. For example, where an agent is identified that increases the proteolytic activity of the metalloprotease above a basal level in a cell, a method of the invention can further include determining an amount by which the agent increases myostatin activation above the basal level. As such, a method of the invention provides a means to obtain agents or panels of agents that variously modulate myostatin activation by a metalloprotease. Such a method further provides a means to determine amounts of a particular agent useful for providing a desired level of myostatin activity.

[0019] A difference in the amount of cleavage of the pro peptide due to contact with a test agent can be detected, for example, by detecting the pro peptide or a cleavage product of the pro peptide using a method such as electrophoresis, chromatography, or mass spectrometry, which can detect a myostatin pro peptide or cleavage product thereof based on its size, charge, or both; an immunological based assay such as an immunoblot analysis, an enzyme-linked immunosorption assay (ELISA), or the like, which utilizes an antibody specific for the intact pro peptide or the cleaved pro peptide, but not an antibody that binds both the intact and the cleaved pro peptide; or a fluorescence based assay, including, for example, a fluorescence resonance energy transfer (FRET) assay, wherein fluorescence of the intact pro peptide is quenched, and the quenching is relieved upon cleavage of the pro peptide. Depending on the relative amount of intact myostatin pro peptide, pro peptide cleavage product, or a combination thereof that is detected, a test agent can be identified as an agent that increases or decreases metalloprotease mediated myostatin pro peptide cleavage and activation of the latent myostatin.

[0020] A difference in the amount of cleavage of the pro peptide also can be detected by detecting a change in binding of myostatin to a myostatin receptor i~ vitro or expressed on a cell surface, or by detecting a change in a myostatin mediated signal transduction in a cell expressing a myostatin receptor. Where the assay is a cell based assay, the cell can be one that expresses an endogenous myostatin receptor, for example, L6 myocytes, or can be a cell expressing a transgene encoding the myostatin receptor, for example, a cell transfected with a polynucleotide encoding an activin receptor such as an activin type II
receptor. Myostatin mediated signal transduction can be detected at any level in the signal transduction pathway, including from binding of myostatin to a cell surface receptor to expression of a gene that is regulated due to myostatin binding to a myostatin receptor, wherein, in a screening assay of the invention, the signal transduction is dependent on metalloprotease mediated cleavage of a myostatin pro peptide and activation of a latent myostatin complex. As such, myostatin mediated signal transduction can be detected by detecting myostatin binding to a myostatin receptor using a receptor binding assay, or by detecting expression of a myostatin regulated gene, including, for example, a reporter gene, which can comprise, for example, a TGF-(3 regulatory element operatively linked to a polynucleotide encoding a detectable polypeptide. Accordingly, the present invention provides agents that modulate metalloprotease mediated myostatin pro peptide cleavage and myostatin activation, wherein the agents are identified using a screening assay of the invention. The present methods also are useful for confirming that an agent modulates metalloprotease mediated myostatin pro peptide cleavage and myostatin activation, including, if desired, the specific activity of the agent.

[0021] The present invention also relates to an agent that modulates metalloprotease mediated activation of latent myostatin. The agent can be an agonist or an antagonist of znetalloprotease mediated activation of latent myostatin, and can reduce or inhibit metalloprotease mediated activation of latent myostatin, or can increase metalloprotease mediated activation of latent myostatin. An agent that modulates metalloprotease mediated activation of latent myostatin can be any type of molecule, including, for example, a peptide agent, a polynucleotide agent, an antibody agent, or a small organic molecule agent.

[0022] An agent that modulates metalloprotease mediated activation of latent myostatin is exemplified herein by a peptide agent. A peptide agent can include, for example, a peptide portion of a myostatin polypeptide, or a derivative of such a peptide portion of myostatin. In one embodiment, a derivative of a peptide portion of myostatin is a peptide that corresponds to a myostatin pro peptide. In one aspect of this embodiment, the derivative is a pro peptide having a mutation of the metalloprotease cleavage site, for example, a substitution, deletion, or insertion of an amino acid at or in sufficient proximity to the cleavage site such that the metalloprotease has increased or decreased cleavage activity with respect to the peptide agent. In another aspect of this embodiment, the derivative of a peptide portion of myostatin is a peptide agent that reduces or inhibits metalloprotease mediated activation of latent myostatin. The agent that modulates metalloprotease mediated activation of latent myostatin can be operatively linked to a second molecule, which facilitates the action or activity of the agent, or increases or decreases the stability of the agent in a particular environment. For example, a peptide agent can be stabilized by operatively linking the peptide agent to a polypeptide such as an Fc domain of an antibody molecule, thereby increasing the half life of the peptide agent ih vivo.
BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 demonstrates that incubation of the myostatin complex (MSTN;
C-terminal myostatin dimer and pro peptide) with mTLL-1 resulted in a dramatic increase in expression of a luciferase reporter gene (stippled bar; see Example 2), the expression of which is regulated in transfected rhabdomyosarcoma cells upon contact of the cells with active myostatin. Only background expression was observed in cells contacted with myostatin complex, alone (solid bar), or with mTLL-1, alone (hatched bar).

[0024] Figure 2 shows a standard curve generated using the luciferase reporter assay, wherein the transfected cells (see Figure 1, above) were contacted with the specified amounts of active purified C-terminal myostatin dimer (diamonds). Control luciferase activity (no myostatin) is shown by the circles.

[0025] Figures 3A to 3E show deternzination of cleavage of the myostatin pro peptide by BMP-1/TLD family of proteinases.

[0026] Figures 3A and 3B show detection of a pro peptide degradation product in CHO
cell conditioned media. Conditioned media prepared from CHO cells expressing the pro peptide (Figure 3A) or wild type and mutant forms of pro peptide/Fc fusion proteins (Figure 3B) were analyzed by SDS-PAGE followed by western blot analysis using antibodies directed against either the myostatin pro peptide (Figure 3A) or IgG
(Figure 3B). Note that mutation of D76 to A resulted in loss of the degradation product.

[0027] Figure 3C shows purification of wild type and mutant pro peptide/C-terminal dimer complexes. Protein complexes were analyzed by SDS-PAGE in the presence or absence of 13-mercaptoethanol followed by western blot analysis, as indicated.
Note that like the wild type pro peptide, the D76A mutant pro peptide purified in a complex with the C-terminal dimer. The pro peptide degradation product did not co-puxify with and was thus not part of the complex. Bands denoted by the asterislc indicate misfolded myostatin species, which were evident under non-reducing conditions.

[0028] Figures 3D and 3E show cleavage of the pro peptide by BMP-1/TLD
proteinases. Wild type and mutant complexes were incubated with purified proteinases and analyzed by SDS-PAGE followed by western blotting using antibodies directed against the pro peptide. Incubations were carried out with 1 ~,g latent complex and 250 ng proteinase for 16 hours at 37°C, except that in Figure 3D, the samples were incubated with an additional 250 ng BMP-1 for 4 more hours. In Figuxe 3E, lanes labeled "no enzyme"
indicate samples incubated for 16 hours at 37°C in the absence of enzyme. Note that all enzymes were capable of generating the cleavage product and that the D76A
mutant protein was completely resistant to cleavage.

(0029] Figures 4A to 4D show activation of latent myostatin activity by BMP-proteinases. In Figures 4B to 4D, black bars represent wild type, and gray bars represent D76A mutant complexes. Note that although heat treatment activated both the wild type and mutant complexes (Figure 4B), each proteinase was capable of activating only the wild type complex (Figures 4C and 4D). ~ < 0.05, * p < 0.01.

(0030] Figure 4A shows activation of pGL3-(CAGA)12-luciferase reporter gene activity by purified myostatin C-terminal dimer.
(003I] Figure 4B shows activation of the myostatin pro peptide/C-terminal dimer latent complex by heat treatment. Control (no myostatin (MSTN)) is indicated.
[0032] Figure 4C and 4D show activation of the myostatin pro peptide/C-terminal dimer latent complex by BMP-1/TLD proteinases. The samples used for the reporter assays in Figures 4C and 4D are the same samples shown in Figures 3D and 3E, respectively.
[0033] Figure 5 shows inhibition of reporter gene activity by wild type and mutant pro peptide/Fc fusion proteins in vitro. A204 cells transfected with the reporter construct JHUl 800-3 WO

were incubated with 10 nghnl of purified myostatin C-terminal dimer and various concentrations of wild type (dark) or D76A mutant (light) pro peptide/Fc fusion protein.
Note that the wild type and mutant proteins were equally effective in blocking myostatin activity.
DETAILED DESCRIPTION OF THE INVENTION
[0034] The present invention is based on the identification of proteases that cleave myostatin pro peptide, including when the pro peptide is present in a complex with a myostatin C-terminal dimer, thereby converting Latent inactive myostatin complex to active myostatin. Proteases having such rnyostatin pro peptide cleaving activity axe exemplified by the metalloprotease bone morphogenic protein-1/tolloid (BMP-1/TLD) family of proteins. As such, the proteases provide targets and reagents for identifying drugs that can increase or decrease the protease activity, ox can increase or decrease myostatin pro peptide cleavage mediated by the proteases, and, therefore, increase or decrease myostatin activity.
[0035] Myostatin (growth differentiation factor-8; GDF-8) is expressed as a pre-proprotein, promyostatin, which includes a signal peptide (amino acid residues about 1 to 20), the myostatin pro peptide domain (amino acid residues about 20 to 262 or 263) and the myostatin C-terminal domain (amino acid residues about 267 or 268 to 375).
Promyostatin polypeptides and encoding polynucleotides are highly conserved evolutionarily (see McPherron and Lee, P~oc. Natl. Acad. ~'ci., USA 94:12457, 1997;
GenBank Acc. Nos. AF019619, AF019620, AF019621, AF019622, AF019623, AF019624, AF019625, AF019626, and AF019627; U.S. Pat. No. 5,994,618, each of which is incorporated herein by reference). Promyostatin polynucleotides and encoded polypeptides are exemplified herein by human promyostatin (SEQ ID NOS:1 and 2;
pro peptide is amino acid residues about 20 to 263), bovine promyostatin (SEQ
ID NOS:3 and 4; pro peptide is amino acid residues about 20 to 262), chicken promyostatin (SEQ ID
NOS:S and 6; pro peptide is amino acid residues about 20 to 262), and zebrafish promyostatin (SEQ ID NOS:7 and 8; pro peptide is amino acid residues about 20 to 262).

[0036] Myostatin is activated by two proteolytic cleavage events - a first removing the signal sequence (approximately the first 20 N-terminal amino acid residues of promyostatin; see, for example, SEQ TD N0:2), and a second at a tetrabasic processing site (at about amino acid residues 263 to 266 of promyostatin) - resulting in the generation of a 26 l~Da N-terminal pro peptide (approximately amino acid residues 20 to 262 or 263) and a 12.5 lcDa C-terminal peptide (approximately amino acid residue 266 or 267 to the C-terminus); a dimer of the C-terminal peptide is biologically active. Upon secretion from cells, the myostatin C-terminal dimer is maintained in a latent, inactive state due to its remaining bound to the myostatin pro peptide (Lee and McPherron, P~oc. Natl.
Acad. Sci., LISA 98:9306-9311, 2001, which is incorporated herein by reference). The latent myostatin complex that circulates in the blood of adult mice can be activated ire vitr~o by treatment with acid (Zimmers et al., Science 296:1486-1488, 2002, which is incorporated herein by reference).
[0037] Mice in which the myostatin gene has been knocl~ed out show increased muscle mass, and further exhibit a significant reduction in fat accumulation with increasing age as compared to wild type littermates (McPherron and Lee, J. Clih. Invest. 109:595-f01, 2002, which is incorporated herein by reference). Conversely, over-expression of myostatin ih vivo produces the signs and symptoms characteristic of the muscle wasting syndrome, cachexia (Zimmers et al., sup~~a, 2002). The muscle wasting observed in mice having increased levels of circulating myostatin can be partially reversed by introducing myostatin binding agents such as the myostatin pro peptide and follistatin to the mice (Zimmers et al., supra, 2002). These results confirmed that the observed muscle wasting was due to increased myostatin, and indicate that methods for decreasing the level of active myostatin or otherwise reducing or inhibiting myostatin activity can be useful for ameliorating muscle wasting. In view of the highly conserved nature of myostatin among species as diverse as fish and humans, these results indicate that myostatin also can be involved in the cachexia associated with various disorders in humans, mcludzng, for example, cancer, acquired imnnunodeficiency syndrome (AIDS), and sepsis, as well as in neuromuscular disorders such as muscular dystrophy (see Gonzalez-Kadavid et al., Proc.
Natl. Acad. Med., USA 95:14938-14943, 1998, which is incorporated herein by reference).

[0038] Proper slceletal muscle function also is involved in maintaining normal glucose metabolism, and skeletal muscle resistance to insulin stimulated glucose uptalce is the earliest manifestation of non-insulin dependent (type 2) diabetes (see McPherron and Lee, supj°a, 2002). In two mouse models of obesity and diabetes, loss of myostatin prevented an increase in adipose tissue mass with age and attenuated the obese and diabetic phenotype in the mouse models (McPherron and Lee, supra, 2002). As such, methods that modulate myostatin activity also can be useful for reducing body fat in an individual, and for treating disorders associated with abnormal muscle function or obesity, for example, type 2 diabetes.
[0039] As disclosed hexein, the myostatin pro peptide, either in a free form or when part of a complex with the myostatin C-terminal dimer, can be cleaved by members of the BMP-1/TLD family of metalloproteases, and such cleavage releases the myostatin C-terminal dimer from the inhibitory effects of the pro peptide, thus generating active myostatin. As such, the BMP-1/TLD proteases provide a target for drugs that can modulate myostatin activity and, therefore, increase or decrease muscle mass or reduce or prevent obesity in an organism. Accordingly, the invention provides methods of identifying agents that modulate metalloprotease mediated myostatin pro peptide cleavage, and that modulate metalloprotease mediated activation of latent myostatin.
[0040] A screening method of the invention can be performed, for example, by contacting a myostatin pro peptide, a metalloprotease that can cleave the myostatin pro peptide, and a test agent, under conditions sufficient for cleavage of the pro peptide by the metalloprotease; and detecting a change in the amount of cleavage of the pro peptide in the absence of the test agent as compared to the presence of the test agent, thereby identifying the test agent as an agent that modulates metalloprotease mediated myostatin pro peptide cleavage. The myostatin pro peptide can be in an isolated form, or can be a component of a latent myostatin complex that fuxther contains a myostatin C-terminal fragment or a myostatin C-terminal dimer.
(0041] A metalloprotease examined according to a screening assay of the invention can be any protease that cleaves a myostatin pro peptide, particularly a metalloprotease that cleaves the pro peptide when it is in a latent myostatin complex with a C-terminal myostatin fragment or dimer thereof, such that active myostatin is generated from the latent myostatin complex. Such metalloproteases are exemplified by the BMP-family of metalloproteases, which includes four mammalian proteins, BMP-1 (Wozney et al., Science 242:1528-1534, 1988), mammalian Tolloid (mTLD; Takahara et al., J. Biol.
Ch.em. 269:32572-32578, 1994), mammalian Tolloid-like-1 (mTLL-I; Takahara et al., Gehomics 34:157-165, 1996), and mammalian Tolloid-like-2 (mTLL-2; Scott et al., Level.
Biol. 213:283-300, 1999). The BMP-1/TLD family of metalloproteases, in turn, are members of a larger family of proteins, the astacin family, which includes proteases that are expressed in various vertebrate and invertebrate organisms, including, for example, Xehopus (Xolloid; UVS.2), fish (choriolysin H and L; zebrafish Tolloid), sea urchin (BP-10 and SpAN), and hydra (HMP-1; see, for example, Li et aL, P~oc. Natl.
Acad. Sci., USA 93 : S 127-513 0, 1996, which is incorporated herein by reference). As such, the screening assays of the invention can be practiced using any of various metalloproteases and, therefore, allow an identification of agents that can be useful, for example, for modulating myostatin activation in a variety of different organisms.
[0042] BMP-1 and mTLD are encoded by alternatively spliced mRNAs from a single gene (Takahara et al., supra, 1994), whereas mTLL-I and mTLL-2 are encoded by distinct genes. The BMP-1/TLD family of proteases is known to have a role in regulating the activity of at least three classes of substrates. First, BMP-l, mTLD, and mTLL-1 axe capable of processing procollagen precursors into the mature monomers required for assembly into the multimeric fibers that axe normally present in the extracellular matrix (Kessler et al., Science 271:360-362, 1996; Li et al., sup~~a, 1996). Second, BMP-1, InTLD, mTLL-1 and mTLL-2 each can process pro-Iysyl oxidase into the mature, biologically active enzyme (Uzel et al., J. Br.'ol. Chem. 276:22537-22543, 2001). Third, BMP-1 and mTLL-1 can cleave chordin (Scott et al., supra, 1999), which normally binds various members of the BMP subgroup of the TGF-l3 superfamily and maintains them in a latent state (Blader et al., Science 278:1937-1940, 1997; Maxques et al., Cell 91:417-26, 1997; Piccolo et al., Cell 91:407-416, 1997). Cleavage of chordin by these metalloproteases releases the BMP from the inhibitory effect of chordin. As such, BMP-1 and TLL-1 are believed have a role in modulating the effects of the BMPs during a variety of morphogenic processes. As disclosed herein, BMP-1/TLD family members, including BMP-1, rnTLD, mTLL-1 and mTLL-2 also can cleave the myostatin pro peptide, either in its flee form or when bound to the myostatin C-terminal dimer (latent myostatin complex), wherein cleavage of the pro peptide results in activation of the myostatin C-terminal diner (see Examples 1 and 2).
[0043] A test agent that can be examined according to a method of the invention can be any type of molecule, including, for example, a peptide, peptide derivative such as a peptide hydroxamate or a phosphinic peptide, peptoid, polynucleotide, or small organic molecule (see Example 3). Thus, the term "test agent" is used broadly herein to mean any compound that is being examined for agonist or antagonist activity with respect to metalloprotease mediated myostatin pro peptide cleavage or myostatin activation.
Although the method generally is used as a screening assay to identify previously unluzown molecules (test agents) that can act as agonist or antagonist agents, the method also can be used to confirm that an agent known to have a particular activity in fact has the activity, for example, in standardizing the activity of the agent; and can be used to screen derivatives or other modified forms or mimics of such known agents.
[0044] A screening method of the invention conveniently can be adapted to high throughput analysis and, therefore, can be used to screen combinatorial libraries of test agents, which can be a library of random test agents, biased test agents, or variegated test agents (see, for example, U.S. Pat. No. 5,571,698, which is incorporated herein by reference), in order to identify those agents that can modulate metalloprotease mediated cleavage of a myostatin pro peptide and, therefore, myostatin activity.
Methods fox preparing a combinatorial Library of molecules that can be tested for a desired activity are well known in the art and include, for example, methods of malting a phage display library of peptides, which can be constrained peptides (see, for example, U.S. Pat. No.
5,622,699; U.S.
Pat. No. 5,206,347; Scott and Smith, Seiehce 249:386-390, 1992; Markland et al., Gehe 109:13-19,1991; each of which is incorporated herein by reference); a peptide library (U.S. Pat. No. 5,264,563, which is incorporated herein by reference); a library of peptide derivative compounds such as a hydroxamate compound library, reverse hydroxamate compound library, a carboxylate compound Iibraxy, thiol compound library, a phosphinic peptide library, or phosphonate compound library (see, for example, Dive et al., Biochem.
Soc. T~ahs. 28:4SS-460, 2000; Ye and Marshall, Peptides: The Wave of the Future (Lebl and Houghten, ed.; American Peptide Society, 2001), each of wluch is incorporated herein by reference); a peptidomimetic library (Blondelle et al., T~ ef~ds Ahal.
Chem. 14:83-92, 1995, which is incorporated herein by reference); a nucleic acid library (O'Connell et al., Pr~oc. Natl. Acad. Sci., USA 93:5883-5887, 1996; Tuerk and Gold, Science 249:S0S-510, I 990; Gold et al., Ahn. Rev Biochem. 64:763-797, 1995; each of which is incorporated herein by reference); an oligosaccharide library (York et al., Cap°b.
Res. 285:99-128, 1996;
Liang et al., Science 274:1 S20-1522, 1996; Ding et al., Adv Expt. Med. Biol.
376:261-269, 1995; each of which is incorporated herein by reference); a lipoprotein library (de Kruif et al., FEBS Lett. 399:232-236, 1996, which is incorporated herein by reference); a glycoprotein or glycolipid library (Karaoglu et al., J. Cell Biol. I30:S67-577, I99S, which is incorporated herein by reference); or a chemical library containing, for example, drugs or other pharmaceutical agents (Gordon et al., J. Med. Chem. 37:1385-1401, 1994; Eclcer and Crooke, BioTechnology 13:351-360, 1995; each of which is incorporated herein by reference).
(0045] Polynucleotides can be particularly useful as agents that can modulate metalloprotease mediated myostatin pro peptide cleavage or myostatin activation because nucleic acid molecules having binding specificity for cellular targets, including cellular polypeptides, exist naturally, and because synthetic molecules having such specificity can be readily prepared and identified (see, for example, U.S. Pat. No. S,7S0,342, which is incorporated herein by reference). The term "polynucleotide" is used broadly herein to mean a sequence of two or more deoxyribonucleotides or ribonucleotides that axe linked together by a phosphodiester bond. As such, the term "polynucleotide" includes RNA and DNA, which can be a gene or a portion thereof, a cDNA, a synthetic polydeoxyxibonucleic acid sequence, or the like, and can be single stranded or double stranded, as well as a DNA/RNA hybrid. A polynucleotide can be a naturally occurring nucleic acid molecule, which can be isolated from a cell, or a synthetic molecule, which can be pxepaxed, for example, by methods of chemical synthesis or by enzymatic methods such as by the polymerase chain reaction (PCR).
[0046] A polynucleotide agent (or test agent) can contain nucleoside or nucleotide analogs, or a baclcbone bond other than a phosphodiester bond. In general, the nucleotides comprising a polynucleotide are naturally occurring deoxyribonucleotides, such as adenine, cytosine, guanine or thymine linked to 2'-deoxyribose, or ribonucleotides such as adenine, cytosine, guanine or uracil linked to ribose. However, a polynucleotide also can contain nucleotide analogs, including non-naturally occurring synthetic nucleotides or modified naturally occurring nucleotides. Such nucleotide analogs are well lcnown in the art and commercially available, as are polynucleotides containing such nucleotide analogs (Lin et al., Nucl. Acids Res. 22:5220-5234, 1994; Jellinek et al., Biochemistry 34:11363-11372, 1995; Pagratis et al., Nature Biotechhol. I 5:68-73, 1997, each of which is incorporated herein by reference).
[0047] The covalent bond linking the nucleotides of a polynucleotide generally is a phosphodiester bond. However, the covalent bond also can be any of numerous other bonds, including a thiodiester bond, a phosphorothioate bond, a peptide-like bond or any other bond known to those in the art as useful for linking nucleotides to produce synthetic polynucleotides (see, for example, Tam et al., Nucl. Acids Res. 22:977-986, 1994; Ecker and Croolce, BioTechnology 13:351360, 1995, each of which is incorporated herein by reference). The incorporation of non-naturally occurring nucleotide analogs or bonds linking the nucleotides or analogs can be particularly useful where the polynucleotide is to be exposed to an environment that can contain a nucleolytic activity, including, for example, a tissue culture medium or upon administration to a living subject, since the modified polynucleotides can be less susceptible to degradation.
[0048] A polynucleotide comprising naturally occurring nucleotides and phosphodiester bonds can be chemically synthesized or can be produced using recombinant DNA methods, using an appropriate polynucleotide as a template. In comparison, a polynucleotide comprising nucleotide analogs or covalent bonds other than phosphodiester bonds generally will be chemically synthesized, although an enzyme such JHUl X00-3W0 as T7 polymerase can incorporate certain types of nucleotide analogs into a polynucleotide and, therefore, can be used to produce such a polynucleotide recombinantly fiom an appropriate template (Jellinelc et al., supra, 1995).
[0049] Similarly, peptides, as exemplified herein (see Examples 3 and 4) can be useful as agents for modulating metalloprotease mediated myostatin activation, or as test agents to screen for such activity. Peptide agents (or test peptides) can contain one or more D-amino acids and/or L-amino acids; and/or one or more amino acid analogs, for example, an amino acid that has been derivatized or otherwise modified at its reactive side chain. In addition, one or more peptide bonds in the peptide can be modified, and a reactive group at the amino terminus or the carboxy terminus or both can be modified.
Peptides containing D-amino acids, or L-amino acid analogs, or the like, can have improved stability to a protease, an oxidizing agent or other reactive material the peptide may encounter in a biological environment, and, therefore, can be particularly useful in performing a method of modulating metalloprotease mediated myostatin activation as disclosed herein. As disclosed herein, the stability of a peptide agent (or test agent) also can be improved by generating (or linking) a fusion protein comprising the peptide and a second polypeptide (e.g., an Fc domain of an antibody) that increases the half life of the peptide agent i~ vivo (see Example 4; see, also, U.S. Patent Application Publication No. US 2003/0104406 Al, which is incorporated herein by reference). Peptides also can be modified to have decreased stability in a biological environment, if desired, such that the period of time the peptide is active in the envirozunent is reduced.
[0050] Test agents also can be antibodies that are raised against and specifically bind one or more epitopes of a metalloprotease that cleaves a myostatin pro peptide; or against an epitope of the pro peptide, which can be an isolated pro peptide or a pro peptide component of a latent myostatin complex; or a complex of the metallopxotease and pro peptide. As used herein, the term "antibody" is used in its broadest sense to include polyclonal and monoclonal antibodies, as well as antigen binding fragments of such antibodies. The term "binds specifically" or "specific binding activity" or the like, when used in reference to an antibody, means that an interaction of the antibody and a particular epitope has a dissociation constant of at least about 1 x 10-6 M, generally at least about 1 x 10-~ M, usually at least about 1 x 10-8 M, and particularly at least about 1 x 10-9 M or 1 x 10-I° M or less. As such, Fab, F(ab')2, Fd and Fv fragments of an antibody that retain specific binding activity are included within the definition of an antibody.
In addition to specifically binding a particular epitope, an antibody agent modulates the protease cleavage activity of a metalloprotease for a myostatin pro peptide, including increasing or decreasing such activity.
[0051] The term "antibody" as used herein includes naturally occurring antibodies as well as non-naturally occurring antibodies, including, for example, single chain antibodies, chimeric, bifunctional and hmnanized antibodies, as well as antigen-binding fragments thereof. Such non-naturally occurring antibodies can be constructed using solid phase peptide synthesis, can be produced recombinantly or can be obtained, for example, by screening combinatorial Libraries consisting of variable heavy chains and variable light chains (see Huse et al., Science 246:1275-1281, 1989, which is incorporated herein by reference). These and other methods of making, for example, chimeric, humaiuzed, CDR-grafted, single chain, and bifunctional antibodies are well known (Winter and Harris, Immu~col. Today 14:243-246, 1993; Ward et al., Natuf°e 341:544-546, 1989; Harlow and Lane, Antibodies: A laborato~~y manual (Cold Spring Harbor Laboratory Press, 1999);
Hilyard et al., Protein Enginee~i~cg: A practical approach (IRL Press 1992);
Borrabeck, Antibody Ehgirzeeri~ag, 2d ed. (Oxford University Press 1995); each of which is incorporated herein by reference).
[0052] A panel of test agent antibodies conveniently can be obtained by immunizing an animal using a peptide portion of a myostatin pro peptide or of a metalloprotease, particularly a BMP-lITLD family member. Where such a peptide portion of the pro peptide or metalloprotease is non-immunogenic, it can be made immunogenic by coupling the hapten to a carrier molecule such as bovine serum albumin (BSA) or keyhole limpet hemocyanin (KLH), or by expressing the peptide portion as a fusion protein.
Various other carrier molecules and methods for coupling a hapten to a carrier molecule are well Known in the ai-t (see, for example, by Harlow and Lane, supra, 1999). Methods for raising polyclonal antibodies, for example, in a rabbit, goat, mouse or other mammal, are well known in the art (see, for example, Green et al., "Production of Polyclonal JHUl 800-3 WO

Antisera," in Immufzochey~zical Protocols (Manson, ed., Hoxnana Press 1992), pages 1-5;
Coligan et al., "Production of Polyclonal Antisera in Rabbits, Rats, Mice and Hamsters,"
in Cup y~. P~~otocols Immu~col. (1992), section 2.4.1; each ox which is incorporated herein by reference). In addition, monoclonal antibodies can be obtained using methods that are well known and routine in the art (see, for example, Kohler and Milstein, Nature 256:495, 1975, which is incorporated herein by reference; see, also, Harlow and Lane, supra, 1999).
Fox example, spleen cells from a mouse immunized with a myostatin receptor, or an epitopic fragment thereof, can be fused to an appropriate myeloma cell Iine such as SP/02 myeloma cells to produce hybridoma cells. Cloned hybridoma cell lines can be screened using labeled antigen to identify clones that secrete monoclonal antibodies having the appropriate specificity, and hybridomas expressing antibodies having a desirable specificity and affinity can be isolated and utilized as a continuous source of the antibodies. A recombinant phage that expresses, for example, a single chain antibody that modulates metalloprotease mediated cleavage of myostatin pro peptide also provides an antibody that can used for preparing standardized kits.
(0053] Monoclonal antibodies can be isolated and purified from hybridoma cultures by a variety of well established techniques, including, for example, affinity chromatography with Protein-A SEPHAROSE gel, size exclusion chromatography, and ion exchange chromatography (Coligan et al., sup~~a, 1992, see sections 2.7.1-2.7.12 and sections 2.9.1-2.9.3; see, also, Barnes et al., "Purification of Imrnunoglobulin G
(IgG)," in Meth.
Molec. Biol. 10:79-104 (Humana Press 1992), which is incorporated herein by refexence).
Methods of ih vit~~o and in vivo multiplication of monoclonal antibodies are well known in the art. Multiplication ih vitf°o can be carried out in suitable culture media such as Dulbecco's Modified Eagle Medium or RPMI 1640 medium, optionally replenished by a mammalian serum such as fetal calf serum or trace elements and growth sustaining supplements such as normal mouse peritoneal exudate cells, spleen cells, bone marrow macrophages. Production in vitro provides relatively pure antibody preparations and allows scale-up to yield large amounts of the desired antibodies. Large scale hybridoma cultivation can be carried out by homogenous suspension culture in an airlift reactor, in a continuous stirrer reactor, or in immobilized or entrapped cell culture.
Multiplication If2 vlVO Call be carried out by injecting cell clones into mammals histocompatible with the parent cells, for example, syngeneic mice, to cause growth of antibody producing tumors.
Optionally, the animals are primed with a hydrocarbon, especially oils such as pristane (tetramethylpentadecane) prior to injection. After one to three weeks, the desired monoclonal antibody is recovered from the body fluid of the animal.
[0054] Thexapeutic applications for antibody agents identified according to a screening assay of the invention also are provided. Where the therapeutic procedure is for treating a human subject, the antibodies can be derived from a subhuman primate antibody (see, for example, Goldenberg et al., Intl. Publ. WO 91111465, 1991; and Losman et al., Ihtl. J.
Cancer 46:310, 1990, each of which is incorporated herein by reference). A
therapeutically useful antibody for human treatment also can be derived from a "humanized" monoclonal antibody. Humanized monoclonal antibodies are produced by transferring mouse complementarity determining regions from heavy and light variable chains of the mouse imlnunoglobulin into a human variable domain, and then substituting human residues in the framework regions of the marine counterparts. The use of antibody components derived from humanized monoclonal antibodies obviates potential problems associated with the immunogenicity of marine constant regions. General techniques for cloning marine immunoglobulin variable domains are known (see, for example, Orlandi et al., P~oc. Natl. Acad. Sci., USA 86:3833, 1989, which is hereby incorporated in its entirety by reference). Techniques for producing humanized monoclonal antibodies also are known (see, for example, Jones et al., Nature 321:522, 1986; Riechmarlrl et al., Natuf°e 332:323, 1988; Verhoeyen et al., SciefZCe 239:134, 1988; Carter et al., Proc.
Natl. Acad.
Sci., USA 89:4285, 1992; Sandhu, Crit. Rev. Biotechhol. 12:437, 1992; and Singer et al., J. Immufzol. 150:2844, 1993; each of which is incorporated herein by reference).
Alternatively, the antibodies can be derived from human antibody fragments isolated from a combinatorial ilrllnunoglobulin library (see, for example, Barbas et al., METHODS: A
Companion to Methods ifa Immunology 2:119, 1991; Winter et al., A~~. Rev.
Immunol.
12:433, 1994; each of which is incorporated herein by reference).
[0055] The antibodies also can be derived from human monoclonal antibodies, which, for example, can be obtained from transgenic mice that have been genetically modified to JHUl 800-3 WO

produce specific human antibodies in response to antigenic challenge. In this technique, elements of the human heavy and light chain loci are introduced into strains of mice derived from embryonic stem cell lines that contain targeted disruptions of the endogenous heavy and light chain loci. The transgenic mice can synthesize human antibodies specific for human antigens, and the mice can be used to produce human antibody-secreting hybridomas. Methods for obtaining human antibodies from transgenic mice are well known (see, fox example, by Green et al., Nature Genet. 7:13, 1994; Lonberg et al., Nature 368:856, 1994; and Taylor et al., Intl. ImnZUnol. 6:579, 1994; each of which is incorporated herein by xeference), and commercial sources of human antibodies are available (Abgenix, Inc.; Fremont CA).
[0056] Antigen binding fragments of an antibody can be prepared by proteolytic hydrolysis of the antibody or by expression in E. coli of DNA encoding the fragment.
Antibody fragments can be obtained by pepsin or papain digestion of whole antibodies by conventional methods. For example, mtibody fragments can be produced by enzymatic cleavage of antibodies with pepsin to provide a SS fragment, F(ab')2. This fragment can be further cleaved using a thiol reducing agent, and optionally a bloclcing group for the sulfliydryl groups resulting from cleavage of disulf de linkages, to produce 3.SS Fab' monovalent fragments. Alternatively, an enzymatic cleavage using pepsin produces two monovalent Fab' fragments and an Fc fragment directly (see, for example, Goldenberg, U.S. Pat. Nos. 4,036,945 and 4,331,647, each of which is incorporated by reference, and references contained therein; Nisonhoff et al., Arch. Biochena. Biophys.
89:230, 1960;
Porter, Biochem. J. 73:119, 1959; Edelman et al., Meth. Enzymol. 1:422 (Academic Press 1967), each of which is incorporated herein by reference; see, also, Coligan et al., supra, 1992, see sections 2.8.1-2.8.10 and 2.10.1-2.10.4).
[0057] Other methods of cleaving antibodies, such as separation of heavy chains to form monovalent light/heavy chain fragments, further cleavage of fragments, or other enzymatic, chemical, or genetic techniques can also be used, provided the fragments specifically bind to the antigen that is recognized by the intact antibody.
For example, Fv fragments comprise an association of Vg and VL chains; this association can be rllul8oo-3wo noncovalent (mbar et al., P~°oc. Natl. Acad. Sci., USA 69:2659, 1972).
Alternatively, the variable chains can be linked by an intermolecular disulfide bond or cross-linked by chemicals such as glutaraldehyde ( Sandhu, supy~a, 1992). Preferably, the Fv fragments comprise Vg and VL chains connected by a peptide linker. These single-chain antigen binding proteins (sFv) are prepared by constructing a structural gene comprising DNA
sequences encoding the Vg and VL domains connected by an oligonucleotide. The structural gene is inserted into an expression vector, which is subsequently introduced into a host cell such as E. coli. The recombinant host cells synthesize a single polypeptide chain with a linker peptide bridging the two V domains. Methods for producing sFvs are described, for example, by Whitlow et al., METHODS: A Companion to Methods in Ehzymology 2:97, 1991; Bird et al., Science 242:423-426, 1988; Ladner et al., U.S. Pat.
No. 4,946,778; Pack et al., BioTechhology 11:1271-1277, 1993; each of which is incorpoxated herein by reference; see, also Sandhu, supra, 1992. Another form of an antibody fragment is a peptide coding for a single complementaxity-determining region (CDR). CDR peptides ("minimal recognition units") can be obtained by constructing genes encoding the CDR of an antibody of interest. Such genes are prepared, for example, by using the polymerase chain reaction to synthesize the variable region from RNA of antibody-producing cells (see, for example, Larriclc et al., METHODS: A
Compa~ioh to Methods in Enzymology 2:106, 1991, which is incorporated herein by reference).
[0058] A difference in the amount of cleavage of the pro peptide due to contact with a test agent can be detected, for example, by detecting the pro peptide and/or a cleavage product of the pro peptide using a method such as electrophoresis, chromatography, or mass spectrometry (see, for example, Thies et al., Growth Factors 18:251-259, 2001, which is incorporated herein by reference), which can detect a myostatin pro peptide ox cleavage pxoduct thereof based on its size, charge, or both; an immunological based assay such as an immunoblot analysis, an enzyme-linked immunosorption assay (ELISA), or the like, which utilizes an antibody specific for the intact pro peptide or the cleaved pro peptide, but not both; or a fluorescence based assay, including, for example, a fluorescence resonance energy transfer (FRET) assay, wherein fluorescence of the intact pro peptide is quenched, and the quenching is relieved upon cleavage of the pro peptide.

Where an increased amount of a cleavage product of the pro peptide is detected in the presence of (or following contact with) the test agent as compared to an amount of cleavage product in the absence of the test agent, the test agent is identified as an agent that can increase metalloprotease mediated activation of the latent myostatin.
Similarly, where a decreased amount of the pro peptide is detected in the presence of (or following contact with) the test agent as compared to an amount of pro peptide in the absence of the test agent, the test agent is identified as an agent that can increase metalloprotease mediated activation of the latent myostatin. Conversely, where a decreased amount of a cleavage product of the pro peptide is detected in the presence of (or following contact with) the test agent as compared to an amount of cleavage product in the absence of the test agent, the test agent is identified as an agent that can decrease metalloprotease mediated activation of the latent myostatin. Where a greater amount of the pro peptide is detected in the presence of (or following contact with) the test agent as compared to an amount of pro peptide in the absence of the test agent, the test agent is identified as an agent that can decrease metalloprotease mediated activation of the latent myostatin. Such activity can be confirmed using a cell based or animal assay by detecting, for example, a change in myostatin mediated signal transduction activity due to the agent.
[0059] A difference in the amount of cleavage of the pro peptide also can be detected by detecting a change in binding of myostatin to a myostatin receptor, or by detecting a change in a myostatin mediated signal transduction in a cell expressing a myostatin receptor. Cells useful for performing a screening assay of the invention include, for example, cells from mammals, birds, fish, yeast, or D~osophila. Such functional assays can directly indicate that a test agent modulates metalloprotease mediated myostatin activation. A cell useful for such a method can be one that expresses an endogenous myostatin receptor, for example, L6 myocytes, or can be a cell genetically modified, transiently or stably, to express a transgene encoding the myostatin receptor, for example, an activin receptor such as an activin type II receptor (Thies et al., sups a, 2001).
Myostatin mediated signal transduction can be detected at any level in the signal transduction pathway, including from binding of myostatin to a cell surface receptor to expression of a gene that is regulated by myostatin, which, in a screening assay of the invention, is dependent on metalloprotease mediated cleavage of a myostatin pro peptide and myostatin activation.
[0060] Metalloprotease mediated myostatin activation and consequent myostatin mediated signal transduction can be detected by measuring myostatin binding to a myostatin receptor using a receptor binding assay, which can be an i~
vitf°o assay or cell based assay. Metalloprotease mediated myostatin activation and consequent myostatin mediated signal transduction also can be detected by measuring expression of a myostatin regulated gene, which can be a reporter gene comprising, for example, a TGF-(3 regulatory element operatively linked to a polynucleotide encoding a detectable label.
Expression of the reporter gene can be detected, for example, by detecting an RNA transcript of the reporter gene sequence, or by detecting a polypeptide encoded by the reporter gene or an activity of the encoded polypeptide. A polypeptide reporter can be, for example, [3-lactamase, chloramphenicol acetyltransferase, adenosine deaminase, aminoglycoside phosphotransferase, dihydrofolate reductase, hygromycin-B phosphotransferase, thymidine lcinase, (3-galactosidase, luciferase, or xanthine guanine phosphoribosyltransferase, and can be detected, for example, by detecting radioactivity, luminescence, chemiluminescence, fluorescence, enzymatic activity, or specific binding due to the reporter polypeptide, or survival in a selective medium of cells expressing the reporter polypeptide. Methods for introducing a transgene such as a polynucleotide encoding a myostatin receptor or a reporter gene under conditions such that a polypeptide encoded by the transgene can be expressed are disclosed herein or otherwise known in the art.
[0061] Generally, a reporter gene includes a coding sequence, which encodes the reporter polynucleotide or polypeptide, operatively linked to one or more transcription and, as appropriate, translation regulatory elements, and can be contained in a vector, particularly an expression vector. If desired, the coding sequence can further encode an operatively linked peptide tag such as a His-6 tag, which can be detected using a divalent cation such as nickel ion, cobalt ion, or the like; a FLAG epitope, which can be detected using an anti-FLAG antibody (see, for example, Hopp et al., BioTechnology 6:1204, 1988,;
U.S. Pat. No. 5,011,912, each of which is incorporated herein by reference); a c-myc epitope, which can be detected using an antibody specific for the epitope;
biotin, which can be detected using streptavidin or avidin; glutathione S-transferase, which can be detected using glutathione; or an Fc domain of an antibody, which can be detected using Protein A
or an anti-Fc antibody, either of which, can, but need not, be detectably labeled or attached to a solid support or, in turn, detected using a second antibody. As such, it will be recognized that various means for detecting a particular tagged molecule also can be used to isolate the tagged molecule.
[0062] As used herein, the term "operatively linked" means that two or more molecules are positioned with respect to each other such that they act as a single unit and effect a function attributable to one or both molecules or a combination thereof. For example, a polynucleotide sequence encoding a reporter polypeptide can be operatively linked to a regulatory element, in which case the regulatory element confers its regulatory effect on the polynucleotide similarly to the way in which the regulatory element would effect a polynucleotide sequence with which it normally is associated with in a cell. A
first polynucleotide coding sequence also can be operatively linlced to a second (or more) coding sequence such that a chimeric polypeptide can be expressed from the operatively linked coding sequences. The chimeric polypeptide can be a fusion polypeptide, in which the two (or more) encoded peptides are translated into a single polypeptide (see, e.g., Example 4), i.e., are covalently bound through a peptide bond; or can be translated as two discrete peptides that, upon translation, can associate with each other to form a stable complex.
[0063] A polynucleotide such as a reporter gene can be contained in a vector, which can facilitate manipulation of the polynucleotide, including introduction of the polynucleotide into a target cell. The vector can be a cloning vector, which is useful for maintaining the polynucleotide, or can be an expression vector, which contains, in addition to the polynucleotide, regulatory elements useful for expressing the polynucleotide and, where the polynucleotide encodes a polypeptide, for expressing the encoded peptide in a particular cell. An expression vector can contain the expression elements necessary to achieve, for example, sustained transcription of the encoding polynucleotide, or the regulatory elements can be operatively linked to the polynucleotide prior to its being cloned into the vector.
[0064] An expression vector (or the polynucleotide) generally contains or encodes a promoter sequence, which can provide constitutive or, if desired, inducible, tissue specific, or developmental stage specific expression of the encoding polynucleotide, a poly-A
recognition sequence, and a ribosome recognition site or internal ribosome entry site, or .
other regulatory elements such as an enhancer, which can be tissue specific.
The vector also can contain elements required for replication in a prokaryotic or eukaryotic host system or both, as desired. Such vectors, which include plasmid vectors and viral vectors such as bacteriophage, baculovirus, retrovirus, Ientivirus, adenovirus, vaccinia virus, semlilci forest virus and adeno-associated virus vectors, are well known and can be purchased from a commercial source (Promega, Madison WI; Stratagene, La Jolla CA;
GIBCO/BRL, Gaithersburg MD) or can be constructed by one skilled in the art (see, for example, Meth. Efzzymol. Vol. 185, Goeddel, ed. (Academic Press, Inc., 1990);
Jolly, Cage. Gene They: 1:51-64, 1994; Flotte, J. Bioenerg. Biomemb. 25:37-42, 1993;
I~irshenbaum et al., J. Clih. Invest. 92:381-387, 1993; each of which is incorporated herein by reference).
[0065] A polynucleotide encoding a reporter polypeptide can be operatively linced, for example, to a tissue specific regulatory element, for example, a muscle cell specific regulatory element, wherein expression of the reporter polypeptide is restricted to the muscle cells in an individual, or to muscle cells in a mixed population of cells in culture, for example, an organ culture. Muscle cell specific regulatory elements include, for example, the muscle creative kinase promoter (Sternberg et al., Mol. Cell.
Biol. 8:2896-2909, 1988, which is incorporated herein by reference) and the myosin light chain enhancer/promoter (Donoghue et al., P~oc. Natl. Acad. Sci., USA 88:5847-5851, 1991, which is incorporated herein by reference).
[0066] Viral expression vectors can be particularly useful for introducing a polynucleotide into a cell, including, if desired, into a cell in a subject.
Viral vectors provide the advantage that they can infect host cells with relatively high efficiency and can infect specific cell types. Viral vectors have been developed for use in particular host systems, particularly mammalian systems and include, fox example, retroviral vectors, other lentivirus vectors such as those based on the human immunodeficiency virus (HIV), adenovirus vectors, adeno-associated virus vectors, herpesvirus vectors, vaccinia virus vectors, and the like (see Miller and Rosman, BioTech~iques 7:980-990, 1992;
Anderson et al., Nature 392:25-30 Suppl., 1998; Verma and Somia, Nature 389:239-242, 1997;
Wilson, New Ehgl. J. Med. 334:1185-1187, 1996, each of which is incorporated herein by reference).
[0067] A polynucleotide such as a reporter gene or a polynucleotide agent, which can be contained in a vector, can be introduced into a cell by any of a variety of methods (Sambrook et al., Molecular Clohirrg: A labor°atory manual (Cold Spring harbor Laboratory Press 1989); Ausubel et al., Current P~°otocols irc Molecular Biology (John Wiley and Sons, Baltimore, MD 1987, and supplements through 1995), each of which is incorporated herein by reference). Such methods include, for example, transfection, lipofeetion, microinjection, biolistic methods, electroporation and, with viral vectors, infection; and can include the use of liposomes, microemulsions or the like, which can facilitate introduction of tile polynucleotide into the cell and can protect the polynucleotide from degradation prior to its introduction into the cell. The selection of a particular method will depend, for example, on the cell into which the polynucleotide is to be introduced, as well as whether the cell is isolated in culture, or is in a tissue or organ in culture or irc situ.
[0068] Where a test agent is identified as having myostatin modulating activity, the screening assay can further include a step of determining an amount by which the agent increases or decreases myostatin activation. For example, where an agent is identified that increases the proteolytic activity of the metalloprotease for the myostatin pro peptide above a baseline level of activity in a particular system, for example, in an ih vitro assay using purified reagents or irc vivo in a subject, the method can further include determining an amount by which the agent increases myostatin activation above the basal level. As such, different agents or panels of agents can be obtained that increase or decrease myostatin activation by a metalloprotease in a relatively defined amount. Such a method fixrther provides a means to determine amounts of a particular agent useful for providing a desired level of myostatin activity. As such, the present invention provides agents and panels of agents that modulate metalloprotease mediated myostatin activation, such agents being useful as medicaments to modulate myostatin activation in a subject, for example, in a subject having a metabolic disorder such as muscular dystrophy, muscle wasting, obesity, or type 2 diabetes.
[0069] Accordingly, the invention provides methods of modulating metalloprotease mediated myostatin activation. As used herein, the term "modulate," when used in reference to an effect on metalloprotease mediated cleavage of myostatin pro peptide or metalloprotease mediated myostatin activation, means that the amount of pro peptide cleavage or myostatin activation either is increased or is reduced or inhibited. The terms "increase" and "reduce or inhibit" are used in reference to the effect of an agent on a baseline level of metalloprotease mediated myostatin pro peptide cleavage or myostatin activation. The baseline level of activity can be a level of cleavage or activation that is identified as occurring in an in vitro assay using purified pro peptide and metalloprotease under defined conditions, or using a biological sample such as a cell or tissue extract obtained from a subject, which can, but need not, be a normal healthy individual; or a level of cleavage or activation that occurs in vivo in a subject. The terms "reduce or inhibit" are used together herein because it is recognized that, in some cases, the level of metalloprotease mediated myostatin pro peptide cleavage or myostatin activation can be reduced below a level that can be detected by a particular assay. As such, it may not be determinable using such an assay as to whether, for example, a low level of myostatin pro peptide cleavage remains, or whether such cleavage is completely inhibited.
[0070] A method of modulating metalloprotease mediated myostatin pro peptide cleavage or myostatin activation can be performed, for example, by contacting a latent myostatin complex, which includes a myostatin pro peptide and a myostatin C-terminal fragment, particularly a C-terminal fragment dimer, with a metalloprotease that can cleave the myostatin pro peptide, and with an agent that can increase or decrease proteolytic cleavage of the pro peptide mediated by the metalloprotease. The metalloprotease can be any metalloprotease that can cleave the myostatin pro peptide, particularly when the

31 pro peptide comprises a latent myostatin complex, including, fox example, a family member such as BMP-1, mTLD, mTLL-1, or mTLL-2. The agent can act in any way to modulate metalloprotease mediated cleavage of the myostatin pro peptide, including, for example, by increasing or decreasing the proteolytic activity of the metalloprotease, by competing with the pro peptide for the metalloprotease, by facilitating contact of the metalloprotease and a latent myostatin complex comprising the pro peptide, or by inducing a conformational change in the latent myostatin complex such that it is a less fit (or more fit) substrate for the metalloprotease.
[0071] A method of modulating metalloprotease mediated myostatin activation can be practiced with respect to any subject that expresses myostatin, including vertebrates and invertebrates. For example, the subject can be a human, mouse, cow, pig, sheep, goat, dog, cat, chicken, turkey, zebrafish, salmon, finfish, other aquatic organisms and other species. Examples of aquatic organisms include those belonging to the class Pisci~ca, such as trout, char, ayu, carp, crucian carp, goldfish, roach, whitebait, eel, conger eel, sardine, flying fish, sea bass, sea bream, parrot bass, snapper, mackerel, horse mackerel, tuna, bonto, yellowtail, rockfish, fluke, sole, flounder, blowfish, filefish; those belonging to the class Cephalopods, such as squid, cuttlefish, octopus; those belonging to the class Pelecypoda, such as clams (e.g., hardshell, Manila, Quahog, Surf, Soft-shell);
cockles, mussels, periwinkles; scallops (e.g., sea, bay, calloo); conch, snails, sea cucumbers; ark shell; oysters (e.g., C. vi~gihica, Gulf, New Zealand, Pacific); those belonging to the class Gastr~opoda such as turban shell, abalone (e.g. green, pink, red); and those belonging to the class C~ustacea such as lobster, including but not limited to Spiny, Rock, and American; prawn; shrimp, including but not limited to M. y osehbe~gii, P.
styll~olls, P. ihdicus, P. jepohious, P. mohodo~, P. va~cuemel, M. ensis, S n~elautho, N.
~o~°vegious, cold water shrimp; crab, including, but not limited to, Blue, rook, stone, king, queen, snow, bromn, dungeness, Jonah, Mangrove, soft-shelled; squilla, krill, langostinos;
crayfish/crawfish, including, but not limited, to Blue, Macron, Red Claw, Red Swamp, Soft-shelled, white; Ah~celida; Chordata, including, but not limited to, reptiles such as alligators and turtles; A~phibia, including frogs; and Echihodey~mata, including, but not limited to, sea urchins.

32 [0072] A method of modulating metalloprotease mediated myostatin activity can be performed i~ vitr~o or ex vivo using cells or a tissue in culture, a cell or tissue extract, a biological fluid such as a serum or plasma sample, or substantially purified reagents, including substantially purified metalloprotease and/or latent myostatin complex (see, for example, Thies et al., supf~a, 2001 ). Where the method is performed in vitt°o, the agent can be contacted with sample comprising the metalloprotease and latent myostatin complex by adding the agent to the sample, which generally is in a culture medium or other buffered solution. For example, where the method is performed using cells in culture, the agent can be added to the culture medium such that it contacts the metalloprotease and/or pro peptide, one or both of which can be present in cells in the culture or secreted into the medium. The agent can be selected such that it is soluble in the sample medium, or can be formulated to increase solubility, if desired.
[0073] A method of modulating myostatin activation also can be performed i~
vivo, including in a living subject, including with respect to cells or a tissue in situ in a subject.
In general, such a method is performed by administering the agent to the subject and, therefore, the agent generally is formulated in a composition suitable for administration to the subject. As such, compositions containing an agent that can modulate metalloprotease mediated myostatin activation are pxovided, such compositions including the agent in a pharmaceutically acceptable carrier. Such compositions are useful as medicaments for treating a subject suffering from a muscular and/or metabolic disorder as disclosed herein, and are useful for administration to animals such as farm animals used for labor or as food products.
[0074] A composition for administration to a living subject generally includes the agent in a pharmaceutically acceptable carrier. Pharmaceutically acceptable carriers are well l~nown in the art and include, for example, aqueous solutions such as watex or physiologically buffered saline or other solvents or vehicles such as glycols, glycerol, oils such as olive oil or injectable organic esters. Apharmaceutically acceptable carrier can contain physiologically acceptable compounds that act, for example, to stabilize or to increase the absorption of the agent. Such physiologically acceptable compounds include, for example, carbohydrates, such as glucose, sucrose or dextrans, antioxidants, such as

33 ascorbic acid ox glutathione, chelating agents, low molecular weight proteins or other stabilizers ox excipients. One skilled in the art would know that the choice of a pharmaceutically acceptable carrier, including a physiologically acceptable compound, depends, for example, on the physico-chemical characteristics of the agent to be administered, and on the route of administration of the composition, which can be, for example, orally or parenterally such as intravenously, and by injection, intubation, or other such method known in the art. The composition also can contain one or more additional reagent, including, for example, nutrients or vitamins or, where the composition is administered for a therapeutic purpose, a diagnostic reagent or therapeutic agent relevant to the disorder being treated.
(0075] The agent can be incorporated within an encapsulating material such as into an oil-in-water emulsion, a microemulsion, micelle, mixed micelle, liposome, microsphere ox other polymer matrix (see, for example, Gregoriadis, Liposome Technology Vol.
1 (CRC
Press, Boca Raton, FL 1984); Fraley, et al., Trends Biochem. Sci. 6:77 (1981), each of which is incorporated herein by reference). Liposomes, for example, which consist of phospholipids or other lipids, are nontoxic, physiologically acceptable and metabolizable carriers that axe relatively simple to make and administer. "Stealth"
liposomes (see, for example, U.S. Pat. Nos. 5,882,679; 5,395,619; and 5,225,212, each of which is incorporated herein by reference) are an example of such encapsulating materials particularly useful for preparing a composition useful for practicing a method of the invention, and other "maslced" liposomes similarly can be used, such liposomes extending the time that the therapeutic agent remains in the circulation. Cationic liposomes, for example, also can be modified with specific receptors or ligands (Morishita et al., J. Clin.
Ifwest. 91:2580-2585 (1993), which is incorporated hexein by refexence).
(0076] The route of administration of a pharmaceutical composition containing an agent that modulates metalloprotease mediated myostatin activation will depend, in part, on the chemical structure of the molecule. Polypeptides and polynucleotides, for example, are not particularly useful when administered orally because they can be degraded in the digestive tract. However, methods for chemically modifying polypeptides, for example, to render them less susceptible to degradation by endogenous proteases or more absorbable

34 tluough the alimentary tract are well known (see, for example, Blondelle et al., supra, 1995; Ecker and Croolc, supra, 1995). In addition, a peptide agent can be prepared using D-amino acids, or can contain one or more domains based on peptidomimetics, which are organic molecules that mimic the structures of peptide domains; or based on a peptoid such as a vinylogous peptoid.
(0077] A composition as disclosed herein can be administered to a subject by various routes including, for example, orally or parenterally, such as intravenously, intramuscularly, subcutaneously, intraorbitally, intracapsularly, intraperitoneally, intrarectally, intracisternally or by passive or facilitated absorption through the skin using, for example, a shin patch or transdermal iontophoresis, respectively.
Furthermore, the composition can be administered by injection, intubation, orally or topically, the latter of which can be passive, for example, by direct application of an ointment, or active, for example, using a nasal spray or inhalant, in which case one component of the composition is an appropriate propellant.
[0078] The phamnaceutical composition can be formulated as an oral formulation, such as a tablet, or a solution or suspension form; or can comprise an admixture with an organic or inorganic carrier or excipient suitable for enteral or parenteral applications, and can be compounded, for example, with the usual non-toxic, pharmaceutically acceptable carriers for tablets, pellets, capsules, suppositories, solutions, emulsions, suspensions, or other form suitable for use. The carriers, in addition to those disclosed above, can include glucose, lactose, mannose, gum acacia, gelatin, mannitol, starch paste, magnesium trisilicate, talc, corn starch, keratin, colloidal silica, potato starch, urea, medium chain length triglycerides, dextrans, and other carriers suitable for use in manufacturing preparations, in solid, semisolid, or liquid form. In addition auxiliary, stabilizing, thickening or coloring agents and perfumes can be used, for example a stabilizing dry agent such as triulose (sea, for example, U.S. Pat.
No. 5,314,695).
[0079] The total amount of an agent to be administered in practicing a method of the invention can be achninistered to a subject as a single dose, either as a bolus or by infusion over a relatively short period of time, or can be administered using a fractionated treatment protocol, in which multiple doses are administered over a prolonged period of time. It will be recogiuzed that the amount of the pharmaceutical composition, for example, to treat obesity in a subject depends on many factors including the age and general health of the subject as well as the route of administration and the number of treatments to be administered. In view of these factors, the skilled artisan would adjust the particular dose as necessary. In general, the formulation of the composition and the routes and frequency of administration are determined, initially, using Phase I and Phase II
clinical trials.
[0080] A method of the invention can be used to increase the level of myostatin activation (i.e., above a baseline level of myostatin activation in the absence of an agent), for example, by contacting a latent myostatin complex and/or metalloprotease with an agent that increases proteolytic activity of the metalloprotease; or can be used to decrease the level of myostatin activation (below a baseline level), for example, by contacting a latent myostatin complex and/or metalloprotease with an agent that decreases metalloprotease mediated proteolytic activity of myostatin pro peptide. The agent can be one that decreases proteolytic activity of a metallopxotease that cleaves myostatin pro peptide of a latent myostatin complex, thereby reducing or inhibiting myostatin activation below a level of myostatin activation that occurs or would occur in the absence of the agent. Where such an agent is administered to a subject, the agent can result in increased muscle mass or decreased fat content or both in the subject. For example, the subject can be a human subject suffering from a muscle wasting disorder, wherein increased muscle mass can ameliorate the signs and symptoms of the disorder.
Alternatively, the agent can be one that increases metalloprotease mediated proteolytic cleavage of myostatin pro 'peptide fiom a latent myostatin complex, thereby increasing myostatin activation above a level, if any, of myostatin activation that occurs or would occur in the absence of the agent. Where such an agent is administered to a subject, the agent can result in decreased muscle mass or increased fat content or both in the subject.
Such a subject can be, for example, an undesirable organism such as an invasive fish species or rodents, wherein decreased muscle mass and/or increased fat content places the invasive species at a competitive disadvantage in the environment.

[0081] Accordingly, in one embodiment, the invention provides a method of increasing muscle mass or reducing the fat content or both of a subject by modulating proteolytic cleavage of a myostatin pro peptide by a metalloprotease such as a BMP-1/TLD
family metalloprotease. Such a method can be performed, for example, by administering to the subject an agent that reduces or inhibits the proteolytic activity of a protease that cleaves myostatin pro peptide, thereby preventing activation of latent myostatin and increasing muscle mass in the subject. The subject in which muscle mass is to be increased can be any subject in which myostatin is expressed, particularly a vertebrate organism, including domesticated animals (e.g., a feline or canine species), farm animals or animals that are raised as a food source, including maxmnalian species (e.g., an ovine, porcine, or bovine species), avian species (e.g., chickens or turkeys), and piscine species (e.g., salmon, trout, or cod). For example, where such a method is performed on an organism that is useful as a food source, the protein content of the food can be increased, the cholesterol level can be decreased, and the quality of the foodstuff can be improved. Thus, a method of the invention can be performed on any eukaryotic organism that expresses myostatin and relies on metalloprotease mediated cleavage of myostatin pro peptide to activate myostatin, including a vertebrate organism, for example, mammalian, avian or piscine organism, or an invertebrate organism, for example, a mollusk, echinoderm, gastropod or cephalopod. In one embodiment, the subject is a human subject, for example, a subject suffering from a metabolic disorder such as a muscular disorder (e.g., a dystonia or dystrophy), a wasting disorder (e.g., cachexia), clinical obesity, or type 2 diabetes.
[0082] As such, the invention also provides a method for ameliorating a metabolic disorder in a subject by administering an agent that modulates metalloprotease mediated myostatin activation in the subject. As used herein, the term "ameliorate,"
when used in reference to a metabolic disorder, means that signs or symptoms associated with the disorder are lessened. Amelioration of the disorder can be identif ed using any assay generally used by the skilled clinician to monitor the particular metabolic disorder, for example, a glucose tolerance test for monitoring diabetes, or a serum leptin assay for body fat analysis (McPherron and Lee, supra, 2002). Amelioration of a metabolic disorder such as obesity or cachexia can be monitored simply by measuring the subject's body weight.

[0083] Heterozygous myostatin lmock-out mice have increased skeletal muscle mass, although to a lesser extent than that observed in homozygous mutant mice, indicating that myostatin acts in a dose-dependent manner in vivo. Furthermore, overexpression of myostatin in animals has the opposite effect with respect to muscle growth.
For example, nude mice carrying myostatin-expressing tumors developed a wasting syndrome characterized by a dramatic loss of muscle and fat weight, and resembling cachexia as occurs in patients with chronic diseases such as cancer or AIDS. In addition, the serum levels of myostatin immunoreactive material have been correlated with the status of patients with respect to muscle wasting (Gonzalez-Kadavid et al., supra, 1998). Thus, patients with AIDS, who also showed signs of cachexia as measured by loss of total body weight, had slightly increased serum levels of myostatin immunoreactive material compared to either normal males without AIDS or to AIDS patients that did not have weight loss. Myostatin not only affects muscle mass, but also affects the overall metabolism of an organism. For example, myostatin is expressed in adipose tissue, and myostatin deficient mice have a dramatic reduction in fat accumulation as the animals age.
The overall anabolic effect on muscle tissue that results in response to decreased myostatin activity can alter the overall metabolism of the organism and affect the storage of energy in the form of fat, as demonstrated by the introduction of a myostatin mutation into an obese mouse strain (agouti lethal yellow (Ay) mice), which suppressed fat accumulation by five-fold. Abnormal glucose metabolism also was partially suppressed in agouti mice contaiiung the myostatin mutation.
[0084] As such, the agents and methods of the present invention, which reduce or inhibit metalloprotease mediated myostatin activation, can be used to treat or prevent metabolic diseases such as obesity and type 2 diabetes. The methods of the invention are useful, for example, for ameliorating various metabolic disorders, including, for example, the cachexia associated with chronic diseases such as cancer (see Norton et al., Crit. Rev.
~r~col. Hematol. 7:289-327, 1987, wluch is incorporated herein by reference), as well as conditions such as type 2 diabetes, obesity, and other metabolic disorders. As used herein, the term "metabolic disorder" refers to a condition that is characterized, at least in part, by an abnormal amount, development or metabolic activity of muscle and/or adipose tissue.

Such metabolic disorders include, for example, obesity; muscle wasting disorders such as muscular dystrophy, neuromuscular diseases, cachexia, and anorexia; and disorders such as type 2 diabetes, wluch generally, but not necessarily, is associated with obesity. The term "abnormal," when used in reference to the amount, development or metabolic activity of muscle and/or adipose tissue, is used in a relative sense in comparison to an amount, development or metabolic activity that a skilled clinician or other relevant artisan would recognze as being normal or ideal. Such normal or ideal values are known to the clinician and are based on average values generally observed or desired in a healthy individual in a corresponding population. For example, the clinician would know that obesity is associated with a body weight that is about twenty percent above an "ideal"
weight range for a person of a paxticular height and body type, However, the clinician would recognize that a body builder is not necessarily obese simply by virtue of having a body weight that is twenty percent or more above the weight expected for a person of the same height and body type in an otherwise corresponding population. Similarly, the artisan would know that a patient presenting with what appears to abnormally decreased muscle activity could be identified as having abnormal muscle development, for example, by subjecting the patient to various strength tests and comparing the results with those expected for an average healthy individual in a corresponding population.
[0085] A method for ameliorating a metabolic disorder in a subject can be performed, for example, by administering to the subj ect an agent that reduces or inhibits the proteolytic activity of a protease that cleaves myostatin pro ,peptide, thereby preventing activation of latent myostatin in the cell and ameliorating the metabolic disorder. As indicated above, the metabolic disorder can be any disorder associated with increased or undesirably high myostatin activation or activity, including, for example, a muscle wasting disorder such as is associated with muscular dystrophy, cachexia (e.g., associated with a cancer or acquired immunodeficiency disease), or sarcopenia; or a metabolic disorder such as clinical obesity or type 2 diabetes. By way of example, sarcopenia is a metabolic disorder that is characterized by a loss of skeletal muscle mass, quality, and strength, and can lead to frailty in the elderly. Examples of skeletal muscle properties that contribute to its overall quality include contractility, fiber size and type, and glucose uptake and metabolism. Sarcopenia has important consequences because the loss of lean body mass reduces function, and because a loss of approximately 40% of lean body mass generally is fatal (see, for example, Roubenoff and Castaneda, J. Amen. Med. Assfz. 286, 2001). A
method of the invention provides a means to ameliorate sarcopenia by reducing or inhibiting metalloprotease mediated myostatin activation, thereby allowing increased muscle growth and development in the subject.
[0086] The following examples are intended to illustrate but not limit the invention.

CLEAVE MYOSTATIN PRO PEPTIDE
[0087] This example demonstrates that the members of the bone morphogenic protein-1/Tolloid (BMP-1/TLD) family of metalloproteases cleave the myostatin pro peptide.
[0088] Five hundred ng of purified myostatin pro peptide or of purified latent myostatin complex comprising the pro peptide and C-terminal dimer (Lee and McPherron, sups a, 2001) was incubated overnight at 37°C with 100 ng purified BMP-1, mTLD, mTLL-1, or mTLL-2 (Scott et al., Devel. Biol. 213:283-300, 1999, which is incorporated herein by reference). Reaction products were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) followed by western blot analysis using antiserum raised against the myostatin pro peptide (Lee and McPherron, supra, 2001).
[0089] A discrete proteolytic cleavage product of the pro peptide was detected in each reaction containing one of the four proteases, but not in control reactions that did not contain a protease. Moreover, each of the proteases cleaved the pro peptide whether it was in a purified form or in a complex with the myostatin C-terminal dimer. These results demonstrate that the BMP-I/TLD metalloproteases cleave the myostatin pro peptide.

METALLOPROTEASE CLEAVAGE OF MYOSTATIN PRO PEPTIDE
ACTIVATES LATENT MYOSTATIN
[0090] This example demonstrates that cleavage of the myostatin pro peptide by a BMP-1/TLD metalloprotease activates latent myostatin.
[009I] Purified myostatin pro peptide and C-terminal diner complex was incubated with mTLL-1, then examined using a reporter gene assay that specifically detects myostatin activity. A204 rhabdomyosarcoma cells were Hansfected with the pGL3-(CAGA)12 luciferase reporter gene construct, which comprises the luciferase coding sequence linked to the TGF-(3 responsive GAGA sequence from the promoter of the TGF-(3 inducible PAI-1 gene (Thies et al., supra, 2001). The transfected cells were contacted with either untreated pro peptide/C-terminal diner complex or complex that had been pre-incubated with mTLL-1. Incubation of the complex with mTLL-1 dramatically increased the amount of luciferase activity detected in the reporter cell assay, whereas no change was observed in cells treated with mTLL-1 alone or with the myostatin complex alone (Figure 1).
[0092] In order to determine the extent of myostatin activation by mTLL-l, a standard curve was generated using purified myostatin C-terminal diner in the reporter gene assay (Figure 2), then the amount of luciferase activity in cells treated with the mTLL-1 Heated complex was compared to the standard curve. A comparison of the amount of myostatin activity present in the mTLL-1-treated sample and the degree of proteolytic processing of the pro peptide by mTLL-1 in this sample revealed that at least about 50% of the proteolytically-cleaved myostatin complex was active in the reporter assay.
These results demonstrate that cleavage of the myostatin pro peptide in a complex of the pro peptide and myostatin C-terminal diner by the BMP-lITLD metalloprotease, mTLL-1, activates myostatin.

Peptide Substrates for Tolloid Family Members [0093] A series of three peptides each of 10, 20, 30, 40, or 50 amino acid residues was synthesized based on the sequence of the myostatin pro peptide, and encompassing the BMP-1/TLD metalloprotease cleavage site (amino acid residues "RD" as shown in bold, below, in wild type peptides; SEQ ID NOS:9, 12, 15, 18, and 21). Peptides in which the arginine residue at the P1 position just upstream of the cleavage site was changed to a glutamine residue (SEQ ID NOS:10, 13, 16, 19, and 22; see bold), and peptides in which the aspartic acid at the P 1' position just downstream of the cleavage site was changed to an alanine (SEQ ID NOS:11, 14, 17, 20, and 23; see bold), also were synthesized.
The sequences of the peptides are shown below:
[0094] 50-mer [0095] KDVIRQLLPKAPPLRELIDQYDVQRDDSSDGSLEDDDYHATTETIITMPT
(SEQ ID N0:9) [0096] KDVIRQLLPI~APPLRELIDQYDVQQDDSSDGSLEDDDYHATTETIITMPT
(SEQ ID NO:10) [0097] KDVIRQLLPI~APPLRELIDQYDVQRADSSDGSLEDDDYHATTETIITMPT
(SEQ ID NO:l 1) [0098] 40-mer:
[0099] QLLPKAPPLRELIDQYDVQRDDSSDGSLEDDDYHATTETI (SEQ ID
N0:12);
[0100] QLLPKAPPLRELIDQYDVQQDDSSDGSLEDDDYHATTETI (SEQ ID
N0:13); and [0101] QLLPI~APPLRELIDQYDVQRADSSDGSLEDDDYHATTETI (SEQ ID
N0:14).

[0102] 30-mer:
[0103] APPLRELIDQYDVQRDDSSDGSLEDDDYHA (SEQ ID NO:15);
[0104] APPLRELIDQYDVQQDDSSDGSLEDDDYHA (SEQ ID N0:16); and [OI05] APPLRELIDQYDVQRADSSDGSLEDDDYHA (SEQ ID N0:17).
[0106] 20-mer:
[0107] ELIDQYDVQRDDSSDGSLED (SEQ ID NO:18);
[0108] ELIDQYDVQQDDSSDGSLED (SEQ ID N0:19); and [0109] ELIDQYDVQRADSSDGSLED (SEQ ID N0:20).
[0110] 10-mer:
[0111] YDVQRDDSSD (SEQ ID N0:21);
[0112] YDVQQDDSSD (SEQ ID N0:22); and [OlI3] YDVQRADSSD (SEQ ID N0:23).
[0114] Peptides were supplied as lyophilized powders and stock solutions of 1.0 mM
were prepared in 60% acetonitrile - 0.1 %trifluoroacetic acid (TFA) and 40%
water.
Activity of the enzymes on the peptide substrates was assessed by combining 70 ql of water, 20 ~,1 of either mock conditioned medium or conditioned medium containing the protein of interest, and 10 ~,l of synthetic peptide. Samples were incubated overnight at either room temperature or 37°C, then reactions were quenched by reducing the pH
through the addition of 1.0 pl of 0.1 % TFA. Each aliquot was applied to a 2 cm C 18 guard column cartridge (Supelco) and peptides were eluted using an acetonitrile gradient (0 - 40% over 20 minutes) in 0.1 % TFA. Peaks corresponding to cleaved peptide fragments were identified and confirmed using mass spectrometry. The 40-mer, 30-mer, and 20-mer wild type and R->Q mutant peptides were cleaved by conditioned media containing TLL-2, whereas the peptides containing the D->A mutation at the P1' position were not cleaved; the 50-mer was insoluble under the conditions used, and the cleavage products of the 10-mer were difficult to detect due to their small size (i.e., 5-mers).

ACTIVATION OF LATENT MYOSTATIN BY

[0115] This example demonstrates that BMP-1/TLL family members can cleave and activate latent myostatin.
[0116] Myostatin purification and analysis. The generation of CHO cell lines overexpressing myostatin was described previouslys° 6 (numbered references listed at end of Example 4). Similar strategies were used to generate CHO lines expressing mutant forms of full-length human myostatin and pro peptide/Fc fusion proteins (see U.S. Publ.
No. US 2003/0104406 A1). Mutant human full-length myostatin sequences were based on SEQ ID NO:2, and the mutant pro peptide sequences were based on amino acid residues 24 to 266 of SEQ ID N0:2. Myostatin pro peptide/C-terminal dimer complexes were purified from the conditioned medium of CHO expressing cells as described5.
Pro peptide/Fc fusion proteins were purified using a Protein A-SEPHAROSE gel column.
Antibodies directed against bacterially-produced myostatin C-terminal domain and pro peptide were as describedl> s.
[0117] Proteinase and reporter gene assays. Purified BMP-l, mTLD, mTLL-1, and mTLL-2 proteinases were prepared as describedls. Myostatin activity was measured using the pGL3-(CAGA)12-luciferase reporter assay in A204 rhabdomyosarcoma cells as described6. A standard curve using purified myostatin C-terminal dimer was generated for each set of assays in order to quantify myostatin activity.
[0118] Injection of mice. Female BALB/c mice (Charles River) weighing 17g to 19g were injected intraperitoneally on days 1, 4, 8, 15, and 22 either with PBS
alone or with various proteins diluted in PBS; doses of proteins administered were as follows:
pro peptide/Fc fusion proteins - I mg/kg or 10 mg/kg; IgG2am (control antibody) -mg/kg; and JA16 (myostatin neutralizing antibody) - 60 mg/kg. Mice were sacrificed on day 29 for muscle analysis. Muscles from both sides of each animal were dissected and weighed; the average weight was used for each muscle.
[0119] The generation of Chinese hamster ovary (CHO) cells overexpressing myostatin has been describeds' 6. Lilce other TGF-13 family members, myostatin produced by CHO
cells is cleaved at a dibasic site to generate an N-terminal pro peptide and a disulfide-linlced dirner of C-terminal fragments. In the course of characterizing the secretion of myostatin by these cells, the presence was noted of a discrete cleavage product of the pro peptide (as detected by western blot analysis using antibodies specific for the pro peptide). This cleavage product was detected in the conditioned medium of CHO cells transfected with expression constructs containing either the full-length myostatin precursor protein (not shown) or the myostatin pro peptide alone in the absence of the C-terminal domain (Figure 3A). Because the myostatin pro peptide can maintain the C-terminal dimer in a latent state both in vitros' 6 and in vivo~' $, and because proteolytic cleavage of the TGF-l3 pro peptide is believed to be one mechanism for activating latent TGF-131o-i49 a role for cleavage of the myostatin pro peptide in regulating myostatin latency was investigated.
[0120] N-terminal sequencing revealed that the pro peptide degradation product detected in CHO cell conditioned medium resulted from proteolytic cleavage between arginine 75 and aspartate 76. In order to determine whether either of these amino acid residues is essential for proteolytic cleavage, CHO cell lines expressing mutant versions of the pro peptide, in which either the arginine or aspartate residue was changed to glutamine or alanine, respectively, were generated. To enhance stability of these proteins for in vivo studies (see below), the mutant pro peptides were fused with an Fc domain.
Although changing the arginine to glutamine had no effect on proteolytic cleavage, no degradation product could be detected in conditioned medium prepared from CHO cells expressing the aspartate to alanine mutant pro peptide/Fc fusion protein (Figure 3B; see, also, Example 3). The requirement for aspartate at the cleavage site suggested that members of the BMP-1/TLD family of metalloproteinases were responsible for generating this degradation product. A number of substrates have been identified for manunalian members of the BMP-1/TLD family, and in nearly every case, proteolytic cleavage has been shown to occur immediately N-terminal to an aspartate residuels,i6.
Furthermore, mutagenesis studies have documented the importance of the aspartate residue in rendering these sites susceptible to proteolytic cleavagel~. As there were no apparent reports of other proteinases with a similar specificity or requirement for an aspartate residue just C-terminal to the scissile bond in protein substrates, the ability of members of the BMP-1/TLD family to cleave the myostatin pro peptide in vitro was investigated [0121] Myostatin was purified from the conditioned medium of overproducing CHO
ce11s5. After successive fractionation on hydroxyapatite, lentil lectin SEPHAROSE gel, DEAE agarose, and heparin SEPHAROSE gel, a purified preparation of the myostatin latent complex was obtained that consisted of the N-terminal pro peptide bound non-covalently to the C-terminal dimer (Figure 3C). As shown in Figure 3D, incubation of the purified latent complex with purified BMP-1 resulted in complete cleavage of the pro peptide to generate a single product with an electrophoretic mobility identical to that detected in conditioned medium prepared from CHO cells engineered to overproduce myostatin. N-terminal sequencing of BMP-1-treated pro peptide confirmed that cleavage occurred immediately N-terminal to aspartate 76.
[0122] The ability of the other mammalian members of the BMP-1/TLD family, including mTLD, mTLL-l, and mTLL-2, to cleave the pro peptide also was tested.
For these experiments, enzyme concentrations were used that resulted in only partial cleavage, thus allowing a comparison of the relative activities of the four enzymes. As shown in Figure 3E, incubation of the latent complex with each of the four proteinases resulted in cleavage of the pro peptide. Three of the proteinases, BMP-l, mTLL-l, and mTLL-2, were approximately equally effective in cleaving the pro peptide, while mTLD
was consistently less active than the other three, even though the same mTLD
preparation was fully active against known substrates such as procollagen. All four of these proteinases also cleaved pro peptide that had been purif ed away from the C-terminal dimer.
[0123] In order to determine the effect of proteolytic cleavage of the pro peptide on myostatin latency, myostatin biological activity was measured in latent complexes treated with each of the four proteinases. For this purpose, a reporter gene assay was used in which A204 rhabdomyosarcoma cells were transfected with the pGL3-(CAGA)la-luciferase construct and incubated with myostatin6. As described previously, the addition of purified myostatin C-terminal dimer to these cells resulted in an increase in luciferase activity above basal levels (Figure 4A). In contrast, purified znyostatin latent complex was inactive in this assay, but could be activated by incubation at 80°C
for 5 minutes (Figure 4B). As shown in Figure 4C, the latent complex was also activated by pretreatment with BMP-1. Based on quantification of myostatin activity relative to a standard curve, cleavage of the pro peptide by BMP-1 was approximately as effective as heat treatment in activating the latent complex. The latent complex was also activated by pretreatment with the other proteinases, and the extent of activation correlated roughly with the extent of proteolytic cleavage by these enzymes (Figure 4D).
[0124] The requirement for aspartate at the cleavage site also was examined. A
CHO
cell line expressing high levels of a mutant form of myostatin, in which aspartate 76 was changed to alanine, was generated and the latent complex was purified from the conditioned medium of these cells. As shown in Figure 3C, the mutation had no effect on the ability of the pro peptide to bind to the C-terminal diner; the mutant pro peptide and C-terminal diner remained tightly associated throughout the purification.
Moreover, the mutant pro peptide maintained the complex in a latent form that could be activated by heating, as assessed by the luciferase reporter assay (Figure 4B). However, the mutant pro peptide in the latent complex was completely resistant to proteolysis by each of the four proteinases, BMP-1, mTLD, mTLL-1, and mTLL-2 (Figures 3D and E), and was resistant to activation by these proteinases (Figures 4C and 4D).
[0125] Finally, the role of proteolytic cleavage of the pro peptide in vivo was investigated by examining the effect of injecting wild type and mutant versions of the pro peptide into mice. As determined in previous experiments, the half life of wild type pro peptide after intraperitoneal injections into mice could be increased from approximately 2 hours to 5 to 7 days by fusing the pro peptide to an Fc domain. For this reason, CHO cell lines expressing wild type or mutant (aspartate 76 to alanine) pro peptide fused to an Fc domain were generated, and the fusion proteins were purified using a Protein A SEPHAROSE gel column. The aspartate to alanine mutation did not affect the activity of the pro peptide ivc vitro, as the purified wild type and mutant pro peptide/Fc fusion proteins were equally.effective in inhibiting the activity of the purified myostatin C-temninal dimer in the reporter gene assay (Figure 5).
(0126] In order to assess the activities of these proteins in viva, adult mice were given weekly injections of purified wild type or mutant pro peptide/Fc fusion proteins and sacrificed after four weeks fox muscle analysis. For comparison, a set of mice also was injected with the JA16 myostatin neutralizing monoclonal antibody, which causes an approximately 2,5-30% increase in muscle mass after 12 weeks of treatmentl8.
As shown in Table 1 (below), injection of wild type pro peptide/Fc fusion protein had no effect on muscle mass at doses of 1 and 10 mglkg/weelc. Similarly, little or no effect was seen following injection of the aspartate to alanine mutant pro peptide/Fc fusion protein at a dose of 1 mg/lcg/weelc. However, injection of the mutant pro peptide/Fc fusion protein at mg/kg/weelc led to a statistically significant (p < 0.0001) increase of 18-27%
in the weight of each skeletal muscle examined. This magnitude of increase in muscle weights observed at the higher dose of the mutant pro peptide/Fc fusion protein was approximately twice that seen following injection of the JA16 myostatin neutralizing monoclonal antibody, which resulted in muscle weight increases of 10-16%.
(0127] These results demonstrate that members of the BMP-1/TLD family of metalloproteinases cleave myostatin pro peptide bound to the C-terminal dimer and activate the latent complex. Furthermore, a mutant form of the pro peptide that was resistant to cleavage by BMP-1/TLD proteinases caused increases in muscle mass when inj ected into adult mice, presumably by forming latent complexes incapable of being activated by this group of proteinases. This general mechanism for regulating the activity of the C-terminal dimer has been described for certain other TGF-13 family members. In the case of TGF-13, proteolytic cleavage of its associated pro peptide by plasminl°' 11 or by matrix metalloproteinasesla-is is believed to be one mechanism for activating latency ih viva. In the case of the BMPs, members of the BMP-lITLD family appear to play an important role in regulating the activity of the C-terminal dimer by cleaving and inactivating the BMP antagonist chordinls,ia-za.

[0128] All four manunalian proteinases in the BMP-1/TLD family can cleave the myostatin pro peptide in vitf o, and one or more can be involved in regulating myostatin activity in vivo. In this regard, mTLL-2, unlike the other three proteinases, is expressed specifically in skeletal muscle during embryonic developmentls. The identification of the specific proteinase or proteinases involved in regulating myostatin latency will provide targets for identifying agents useful for modulating muscle mass, and will allow targeting of these enzymes for the development of novel muscle enhancing agents for both human therapeutic and agricultural applications.
Table 1 pectoralis triceps quadriceps gastrocnemius tibialis PBS (n=10) 82.82.8 85.51.6 142.02.6 95.51.5 32.60.8 IgG2am(lOmg~kg,n=10)87.81.6 148.42.3 98.72.1 33.80.9 87.71.9 wild type (1 mg/kg,85.3 1.8 145.7 96.0 1.4 33.2 n=10) 84.3 1.6 2.2 0.4 D76A(1 mg/kg,n=9) 90.02.0 150.72.9''97.72.2 34.10.6 89.43.5 wild type(lOmg/kg,n=10)88.52.7 147.14.0 98.22.2 33.30.8 87.53.4 D76A (10 mg/kg, 102.1 175.6 112.6 l.lb40.3 n=10)105.1 1.26 1.26 d 1.2~~ d 1.2"~
' ' d JA16 (60 mg/kg, 94.8 l.lf160.3 104.9 l.lr37.5 n=10) 96.0 1.2r l.lb Llr ap < 0.05 (vs. PBS) by < 0.0001 (vs. PBS) < 0.05 (vs. JA16) p < 0.01 (vs. JA16) ~a < 0.001 (vs. JA16) p < 0.001 (vs. PBS) Each of the following publications is incorporated herein by reference:
1. McPherron, A. C., Lawler, A. M. & Lee, S.-J. Regulation of skeletal muscle mass in mice by a new TGF-13 superfamily member. Natu>"e 387, 83-90 (1997).
2. Bogdanovich, S. et al. Functional improvement of dystrophic muscle by myostatin blockade. Natuf°e 420, 4I8-421 (2002).

3. Wagner, K. R., McPherron, A. G., Winik, N. & Lee, S.-J. Loss of myostatin attenuates severity of muscular dystrophy in mdx mice. Ahn Neuj~ol 52, 832-836 (2002).
4. McPherron, A. C. & Lee, S.-J. Suppression of body fat accumulation in myostatin-deficient mice. J Clip Invest 109, 595-601 (2002).
5. Lee, S.-J. & McPherron, A. Regulation of myostatin activity and muscle growth.
Proc Natl Acad Sci USA 98, 9306-9311 (2001).
6. Thies, R. et al. GDF-8 propeptide binds to GDF-8 and antagonizes biological activity by inhibiting GDF-8 receptor binding. Growth Factors 18, 251-259 (2001 ).
7. Zimtners, T. et al. Induction of cachexia in mice by systemically administered myostatin. Sciehce 296, 1486-1488 (2002).
8. Hill, J. J. et al. The myostatin propeptide and the follistatin-related gene are inhibitory binding proteins of myostatin in normal serum. JBiol Chem 277, 40741 (2002).
9. Hill, J. J., Qiu, Y., Hewiclc, R. M. & Wolfman, N. M. Regulation of myostatin isZ
vivo by GASP-1: a novel protein with protease inhibitor and follistatin domains.
Mol Endoef°in 17, 1144-1154 (2003).
10. Lyons, R. M., Keslfi-Oja, J. ~ Moses, H. L. Proteolytic activation of latent transforming growth factor-13 from fibroblast-conditioned medium. J. Cell Biol.
106, 1659-1665 (1988).

11. Sato, E. & Riflcin, D. Inhibition of endothelial cell movement by pexicytes and smooth muscle cells: activation of a latent transforming growth factor-131-like molecule by plasmin during co-culture. JCell Biol 109, 309-315 (1989).
12. Yu, ~. ~ Stamenkovic, I. Cell surface-localized matrix metalloproteinase-9 proteolytically activates TGF-13 and promotes tumor invasion and angiogenesis.
Genes Dev 14, 163-176 (2000).
13. D'Angelo, M., Billings, P., Pacifici, M., Leboy, P. & Thorsten, K.
Authentic matrix vesicles contain active metalloproteases (MMP). JBiol Chem 276, 11347-11353 (2001).
14. Maeda, S., Dean, D., Gay, L, Schwartz, 2. & Boyan, B. Activation of latent transforming growth factor 131 by stromelysin 1 in extracts of growth plate chondrocyte-derived matrix vesicles. JBone Min Res 16, 1281-1290 (2001).
15. Scott, I. et al. Mammalian BMP-llTolloid-related metalloproteinases, including novel family member mammalian Tolloid-like 2, have differential enzymatic activities and distributions of expression relevant to patterning and skeletogenesis.
Dev Biol 213, 283-300 (1999).
16. Scott, I. C. et al. Bone morphogenetic protein-1 processes probiglycan.
JBiol Chefn 275, 30504-30511 (2000).
17. Lee, S.-T., Kessler, E. & Greenspan, D. S. Analysis of site-directed mutations in human pro-a2(I) collagen which bloclc cleavage by the C-proteinase. JBiol Chem 265, 21992-21996 (1990).
18. Whittemore, L.-A. et al. Inhibition of myostatin in adult mice increases skeletal muscle mass and strength. BBRC 300, 965-971 (2003).

19. Blader, P., Rastegar, S., Fischer, N. & Strahle, U. Cleavage of the BMP-4 antagonist chordin by zebrafish tolloid. Science 278, 1937-1940 (1997).
20. Piccolo, S. et al. Cleavage of chordin by Xolloid metalloprotease suggests a role for proteolytic processing in the regulation of Spemann organizer activity.
Cell 91, 407-416 (1997).
21. Marques, G. et al. Production of a DPP activity gradient in the early Drosophila embryo tluough the opposing actions of the SOG and TLD proteins. Cell 91, 417-426 (1997).
22. Pappano, W., Steiglitz, B., Scott, I. C., I~eene, D. R. & Greenspan, D. S.
Use of BmpllTlll doubly homozygous null mice and proteomics to identify and validate in vivo substrates of BMP-1 tolloid-like metalloproteinases. Mol Cell Biol 23, 4428-4438 (2003).
(0129] Although the invention has been described with refexence to the above examples, it will be understood that modifications and variations are encompassed within the spirit and scope of the invention. Accordingly, the invention is limited only by the following claims.

SEQUENCE LISTING
<1l0> Johns Hopkins University LEE, Se-Jin McPHERRON, Alexandra GREENSPAN, Daniel S.
PAPPANO, William N.
WOLFMAN, Neil TOMKINSON, Kathy <120> METALLOPROTEASE ACTIVATION OF MYOSTATIN, AND METHODS OF MODULATING
MYOSTATIN ACTIVTTY
<130> JHU1800-3W0 <150> US 60/486,863 <l51> 2003-07-10 <150> US 60/439,164 <151> 2003-01-09 <150> US 60/411,133 <151> 2002-09-16 <160> 23 <170> PatentIn version 3.1 <210> 1 <211> 2743 <212> DNA
<2l3> Homo Sapiens <220>
<221> CDS
<222> (59)..(1183) <223>
<400> 1 aagaaaagta aaaggaagaa acaagaacaa gaaaaaagat tatattgatt ttaaaatc 58 atg caa aaa ctg caa ctc tgt gtt tat att tac ctg ttt atg ctg att 106 Met Gln Lys Leu Gln Leu Cys Val Tyr Ile Tyr Leu Phe Met Leu Ile gtt get ggt cca gtg gat cta aat gag aac agt gag caa aaa gaa aat 154 Val Ala Gly Pro Val Asp Leu Asn Glu Asn 5er Glu Gln Lys Glu Asn gtg gaa aaa gag ggg ctg tgt aat gca tgt act tgg aga caa aac act 202 Val Glu Lys Glu Gly Leu Cys Asn Ala Cys Thr Trp Arg Gln Asn Thr

35 40 45 aaa tct tca aga ata gaa gcc att aag ata caa atc ctc agt aaa ctt 250 Lys Ser Ser Arg Ile Glu Ala Ile Lys Ile Gln Ile Leu Ser Lys Leu cgt ctg gaa aca get cct aac atc agc aaa gat gtt ata aga caa ctt 298 Arg Leu Glu Thr Ala Pro Asn Ile Ser Lys Asp Val Ile Arg Gln Leu ttacccaaaget cctccactc cgggaactgatt gatcagtatgat gtc 346 LeuProLysAla ProProLeu ArgGluLeuIle AspGlnTyrAsp Val cagagggatgac agcagcgat ggctctttggaa gatgacgattat cac 394 GlnArgAspAsp SerSerAsp GlySerLeuGlu AspAspAspTyr His getacaacggaa acaatcatt accatgcctaca gagtctgatttt cta 442 AlaThrThrGlu ThrIleIle ThrMetProThr GluSerAspPhe Leu atgcaagtggat ggaaaaccc aaatgttgcttc tttaaatttagc tct 490 MetGlnValAsp GlyLysPro LysCysCysPhe PheLysPheSer Ser aaaatacaatac aataaagta gtaaaggcccaa ctatggatatat ttg 538 LysIleGlnTyr AsnLysVal ValLysAlaGln LeuTrpIleTyr Leu agacccgtcgag actcctaca acagtgtttgtg caaatcctgaga ctc 586 ArgProValGlu ThrProThr ThrValPheVal GlnIleLeuArg Leu atcaaacctatg aaagacggt acaaggtatact ggaatccgatct ctg 634 IleLysProMet LysAspGly ThrArgTyrThr GlyIleArgSer Leu 180 l85 190 aaacttgacatg aacccaggc actggtatttgg cagagcattgat gtg 682 LysLeuAspMet AsnProGly ThrGlyIleTrp GlnSerIleAsp Val aagacagtgttg caaaattgg ctcaaacaacct gaatccaactta ggc 730 LysThrValLeu GlnAsnTrp LeuLysGlnPro GluSerAsnLeu Gly attgaaataaaa getttagat gagaatggtcat gatcttgetgta acc 778 IleGluIleLys AlaLeuAsp GluAsnGlyHis AspLeuAlaVal Thr ttcccaggacca ggagaagat gggctgaatccg tttttagaggtc aag 826 PheProGlyPro GlyGluAsp GlyLeuAsnPro PheLeuGluVal Lys gtaacagacaca ccaaaaaga tccagaagggat tttggtcttgac tgt 874 ValThrAspThr ProLysArg SerArgArgAsp PheGlyLeuAsp Cys gatgagcactca acagaatca cgatgctgtcgt taccctctaact gtg 922 AspGluHisSer ThrGluSer ArgCysCysArg TyrProLeuThr Val gattttgaaget tttggatgg gattggattatc getcctaaaaga tat 970 AspPheGluAla PheGlyTrp AspTrpIleIle AlaProLysArg Tyr 290 295 . 300 aaggccaattac tgctctgga gagtgtgaattt gtatttttacaa aaa 1018 LysAlaAsnTyr CysSerGly GluCysGluPhe'ValPheLeuGln Lys tatcctcatact catctggta caccaagcaaac cccagaggttca gca 1066 Tyr Pro His Thr His Leu Val His Gln Ala Asn Pro Arg Gly Ser Ala ggc cct tgc tgt act ccc aca aag atg tct cca att aat atg cta tat 1114 Gly pro Cys Cys Thr Pro Thr Lys Met Ser Pro Ile Asn Met Leu Tyr ttt aat ggc aaa gaa caa ata ata tat ggg aaa att cca gcg atg gta 1162.
Phe Asn Gly Lys Glu Gln Ile Ile Tyr Gly Lys Ile Pro Ala Met Val gta gac cgc tgt ggg tgc tca tgagatttat attaagcgtt cataacttcc 1213 Val Asp Arg Cys Gly Cys Ser taaaacatgg aaggttttcc cctcaacaat tttgaagctg tgaaattaag taccacaggc 1273 tataggccta gagtatgcta cagtcactta agcataagct acagtatgta aactaaaagg 1333 gggaatatat gcaatggttg gcatttaacc atccaaacaa atcatacaag aaagttttat 1393 gatttccaga gtttttgagc tagaaggaga tcaaattaca tttatgttcc tatatattac 1453 aacatcggcg aggaaatgaa agcgattctc cttgagttct gatgaattaa aggagtatgc 1513 tttaaagtct atttctttaa agttttgttt aatatttaca gaaaaatcca catacagtat 1573 tggtaaaatg caggattgtt atataccatc attcgaatca tccttaaaca cttgaattta 1633 tattgtatgg tagtatactt ggtaagataa aattccacaa aaatagggat ggtgcagcat 1693 atgcaatttc cattcctatt ataattgaca cagtacatta acaatccatg ccaacggtgc 1753 taatacgata ggctgaatgt ctgaggctac caggtttatc acataaaaaa cattcagtaa 1813 aatagtaagt ttctcttttc ttcaggtgca ttttcctaca cctccaaatg aggaatggat 1873 tttctttaat gtaagaagaa tcatttttct agaggttggc tttcaattct gtagcatact 1933 tggagaaact gcattatctt aaaaggcagt caaatggtgt ttgtttttat caaaatgtca 1993 aaataacata cttggagaag tatgtaattt tgtctttgga aaattacaac actgcctttg 2053 caacactgca gtttttatgg taaaataata gaaatgatcg actetatcaa tattgtataa 2113 aaagactgaa acaatgcatt tatataatat gtatacaata ttgttttgta aataagtgtc 2173 tcctttttta tttactttgg tatattttta cactaaggac atttcaaatt aagtactaag 2233 gcacaaagac atgtcatgca tcacagaaaa gcaactactt atatttcaga gcaaattagc 2293 agattaaata gtggtcttaa aactccatat gttaatgatt agatggttat attacaatca 2353 ttttatattt ttttacatga ttaacattca cttatggatt catgatggct gtataaagtg 2413 aatttgaaat ttcaatggtt tactgtcatt gtgtttaaat ctcaacgttc cattatttta 2473 atacttgcaa aaacattact aagtatacca aaataattga ctctattatc tgaaatgaag 2533 aataaactga tgctatctca acaataactg ttacttttat tttataattt gataatgaat 2593 atatttctgc atttatttac ttctgttttg taaattggga ttttgttaat caaatttatt 2653 gtactatgac taaatgaaat tatttcttac atctaatttg tagaaacagt ataagttata 2713 ttaaagtgtt ttcacatttt tttgaaagac 2743 <210> 2 <211> 375 <212> PRT
<213> Homo Sapiens <400> 2 Met Gln Lys Leu Gln Leu Cys Val Tyr Ile Tyr Leu Phe Met Leu Ile Val Ala Gly Pro Val Asp Leu Asn Glu Asn Ser Glu Gln Lys Glu Asn Val Glu Lys Glu Gly Leu Cys Asn Ala Cys Thr Trp Arg Gln Asn Thr Lys Ser Ser Arg Ile Glu Ala Ile Lys Ile Gln Ile Leu Ser Lys Leu Arg Leu Glu Thr Ala Pro Asn Ile Ser Lys Asp Val Tle Arg Gln Leu Leu Pro Lys Ala Pro Pro Leu Arg Glu Leu I1e Asp Gln Tyr Asp Val Gln Arg Asp Asp Ser Ser Asp Gly Ser Leu Glu Asp Asp Asp Tyr His Ala Thr Thr Glu Thr Ile Ile Thr Met Pro Thr Glu Ser Asp Phe Leu Met Gln Val Asp Gly Lys Pro Lys Cys Cys Phe Phe Lys Phe Ser Ser Lys Ile Gln Tyr Asn Lys Val Val Lys Ala Gln Leu Trp Ile Tyr Leu Arg Pro Val Glu Thr Pro Thr Thr Val Phe Val Gln Ile Leu Arg Leu Ile Lys Pro Met Lys Asp Gly Thr Arg Tyr Thr Gly Ile Arg Ser Leu Lys Leu Asp Met Asn Pro Gly Thr Gly Ile Trp Gln Ser Ile Asp Val Lys Thr Val Leu Gln Asn Trp Leu Lys Gln Pro Glu Ser Asn Leu Gly Ile Glu Ile Lys Ala Leu Asp Glu Asn Gly His Asp Leu Ala Val Thr Phe Pro Gly Pro Gly Glu Asp Gly Leu Asn Pro Phe Leu Glu Val Lys Val Thr Asp Thr Pro Lys Arg Ser Arg Arg Asp Phe Gly Leu Asp Cys Asp Glu His Ser Thr Glu Ser Arg Cys Cys Arg Tyr Pro Leu Thr Val Asp Phe Glu Ala Phe Gly Trp Asp Trp Tle Ile Ala Pro Lys Arg Tyr Lys Ala Asn Tyr Cys Ser Gly Glu Cys Glu Phe Val Phe Leu Gln Lys Tyr Pro His Thr His Leu Val His Gln Ala Asn Pro Arg Gly Ser Ala Gly Pro Cys Cys Thr Pro Thr Lys Met Ser Pro Ile Asn Met Leu Tyr Phe Asn Gly Lys Glu Gln Ile Ile Tyr Gly Lys Ile Pro Ala Met Val Val Asp Arg Cys Gly Cys Ser <210> 3 <211> 1128 <212> DNA
<213> Bovine <220>
<221> CDS
<222> (1)..(1125) <223>
<400> 3 atg caa aaa ctg caa atc tct gtt tat att tac cta ttt atg ctg att 48 Met Gln Lys Leu Gln Ile Ser Val Tyr Ile Tyr Leu Phe Met Leu Ile 1 5 l0 15 gttgct.ggcccagtg gatctgaat gagaacagogag cagaaggaa aat 96 ValAlaGlyProVal AspLeuAsn GluAsnSerGlu GlnLysGlu Asn gtggaaaaagagggg ctgtgtaat gcatgtttgtgg agggaaaac act 144 ValGluLysGluGly LeuCysAsn AlaCysLeuTrp ArgGluAsn Thr acatcgtcaagacta gaagccata aaaatccaaatc ctcagtaaa ctt 192 ThrSerSerArgLeu GluAlaIle LysTleGlnIle LeuSerLys Leu cgcctggaaacaget cctaacatc agcaaagatget atcagacaa ctt 240 ArgLeuGluThrAla ProAsnIle SerLysAspAla IleArgGln Leu ttgccoaaggetcot ccactcetg gaaetgattgat cagttegat gtc 288 LeuProLysAlaPro ProLeuLeu GluLeuIleAsp GlnPheAsp Val cagagagatgccagc agtgacggc tccttggaagac gatgactac cac 336 GlnArgAspAlaSer SerAspGly SerLeuGluAsp AspAspTyr His gccaggaoggaaacg gtcattacc atgcccacggag tctgatctt cta 384 AlaArgThrGluThr ValIleThr MetProThrGlu SerAspLeu Leu acgcaagtggaagga aaacccaaa tgttgcttottt aaatttagc tct 432 ThrGlnValGluGly LysProLys CysCysPhePhe LysPheSer Ser aagatacaatacaat aaactagta aaggcccaactg tggatatat otg 480 LysI1eGlnTyrAsn LysLeuVal LysAlaGlnLeu TrpIleTyr Leu 145 l50 155 160 aggoctgtcaagact cctgogaca gtgtttgtgcaa atcctgaga ctc 528 ArgProValLysThr ProAlaThr ValPheValGln IleLeuArg Leu atcaaacccatgaaa gacggtaca aggtatactgga atccgatct ctg 576 IleLysProMetLys AspGlyThr ArgTyrThrGly IleArgSer Leu aaacttgacatgaac ccaggcact ggtatttggcag agcattgat gtg 624 LysLeuAspMetAsn ProGlyThr GlyIleTrpGln SerIleAsp Val aagacagtgttgcag aactggctc aaacaacotgaa tccaactta ggc 672 LysThrValLeuGln AsnTrpLeu LysGlnProGlu SerAsnLeu Gly 210 2l5 220 attgaaatcaaaget ttagatgag aatggccatgat cttgetgta aoe 720 21eGluIleLysAla LeuAspGlu AsnGlyHisAsp LeuAlaVal Thr ttcccagaaccagga gaagatgga ctgactccottt ttagaagtc aag 768 PheProGluProGly GluAspGly LeuThrProPhe LeuGluVal Lys gtaaca gacacaccaaaaaga tctaggaga gattttgggctt gattgt 816 ValThr AspThrProLysArg SerArgArg AspPheGlyLeu AspCys gatgaa cactccacagaatct cgatgctgt cgttaccctcta actgtg 864 AspGlu HisSerThrGluSer ArgCysCys ArgTyrProLeu ThrVal gatttt gaagettttggatgg gattggatt attgcacctaaa agatat 912 AspPhe GluAlaPheGlyTrp AspTrpIle IleAlaProLys ArgTyr aaggcc aattactgctctgga gaatgtgaa tttgtatttttg caaaag 960 LysAla AsnTyrCysSerGly GluCysGlu PheValPheLeu GlnLys 305 3l0 315 320 tatcct catacccatcttgtg caccaagca aaccccagaggt tcagcc 1008 TyrPro HisThrHisLeuVal HisGlnAla AsnProArgGly SerAla ggcccc tgctgtactcctaca aagatgtct ccaattaatatg ctatat 1056 GlyPro CysCysThrProThr LysMetSer ProIleAsnMet LeuTyr tttaat ggcgaaggacaaata atatacggg aagattccagcc atggta 1104 PheAsn GlyGluGlyGlnIle IleTyrGly LysIleProAla MetVal gtagat cgctgtgggtgttca tga 1128 ValAsp ArgCysGlyCysSer <210> 4 <211> 375 <212> PRT
<213> Bovine <400> 4 Met Gln Lys Leu Gln Ile Ser Val Tyr Ile Tyr Leu Phe Met Leu Ile Val Ala Gly Pro Val Asp Leu Asn Glu Asn Ser Glu Gln Lys Glu Asn Val Glu Lys Glu Gly Leu Cys Asn Ala Cys Leu Trp Arg Glu Asn Thr Thr Ser Ser Arg Leu Glu Ala Ile Lys Ile Gln Ile Leu Ser Lys Leu Arg Leu Glu Thr Ala Pro Asn Ile Ser Lys Asp Ala Ile Arg Gln Leu Leu Pro Lys Ala Pro Pro Leu Leu Glu Leu Ile Asp Gln Phe Asp Val Gln Arg Asp Ala Ser Ser Asp Gly Ser Leu Glu Asp Asp Asp Tyr His Ala Arg Thr Glu Thr Val Ile Thr Met Pro Thr Glu Ser Asp Leu Leu Thr Gln Val Glu Gly Lys Pro Lys Cys Cys Phe Phe Lys Phe Ser Ser 7.30 135 140 Lys Ile Gln Tyr Asn Lys Leu Val Lys Ala Gln Leu Trp Ile Tyr Leu Arg Pro Val Lys Thr Pro Ala Thr Val Phe Val Gln Ile Leu Arg Leu Ile Lys Pro Met Lys Asp Gly Thr Arg Tyr Thr Gly Ile Arg Ser Leu Lys Leu Asp Met Asn Pro Gly Thr Gly Ile Trp Gln Ser Ile Asp Val Lys Thr Val Leu Gln Asn Trp Leu Lys Gln Pro Glu Ser Asn Leu Gly Ile Glu Ile Lys Ala Leu Asp Glu Asn Gly His Asp Leu Ala Val Thr Phe Pro Glu Pro Gly Glu Asp Gly Leu Thr Pro Phe Leu Glu Val Lys 245 250 255 , Val Thr Asp Thr Pro Lys Arg Ser Arg Arg Asp Phe Gly Leu Asp Cys Asp Glu His Ser Thr Glu Ser Arg Cys Cys Arg Tyr Pro Leu Thr Val Asp Phe Glu Ala Phe Gly Trp Asp Trp I1e Ile Ala Pro Lys Arg Tyr Lys Ala Asn Tyr Cys Ser Gly Glu Cys Glu Phe Val Phe Leu Gln Lys Tyr Pro His Thr His Leu Val His Gln Ala Asn Pro Arg Gly Ser Ala Gly Pro Cys Cys Thr Pro Thr Lys Met Ser Pro Ile Asn Met Leu Tyr Phe Asn Gly Glu Gly Gln Ile Ile Tyr Gly Lys Ile Pro Ala Met Val Val Asp Arg Cys Gly Cys Ser <210> 5 <211> 1128 <212> DNA
<213> Callus gallus -<220>
<221> CDS
<222> (1) . . (1125) <223>
<400>

atgcaa aagctggcagtc tatgtttatatt tacctgtteatg cagatc 48 MetGln LysLeuAlaVal TyrValTyrIle TyrLeuPheMet GlnTle gcggtt gatocggtgget ctggatggoagt agtcagcccaca gagaac 96 AlaVal AspProValAla LeuAspGlySer SerGlnProThr GluAsn getgaa aaagacggactg tgcaatgettgt acgtggagacag aataca 144 AlaGlu LysAspGlyLeu CysAsnAlaCys ThrTrpArgGln AsnThr aaatcc tccagaatagaa gccataaaaatt caaatcctcagc aaactg 192 LysSer SerArgIleGlu AlaIleLysIle GlnIleLeuSer LysLeu cgcctg gaacaagcacct aacattagcagg gacgttattaag cagctt 240 ArgLeu GluGlnAlaPro AsnIleSerArg AspValIleLys GlnLeu ttaccc aaagetcctcca ctgcaggaactg attgatcagtat gatgtc 288 LeuPro LysAlaProPro LeuGlnGluLeu IleAspGlnTyr AspVal cagagg gacgacagtagc gatggctctttg gaagaegatgac tatcat 336 GlnArg AspAspSerSer AspGlySerLeu GluAspAspAsp TyrHis gccaca accgagacgatt atcacaatgcct acggagtctgat tttctt 384 AlaThr ThrGluThrIle IleThrMetPro ThrGluSerAsp PheLeu gtacaa atggagggaaaa ccaaaatgttgc ttctttaagttt agctct 432 ValGln MetGluGlyLys ProLysCysCys PhePheLysPhe SerSer aaaatacaatataacaaa gtagtaaag gcacaattatgg atatacttg 480 LysIleGlnTyrAsnLys ValValLys AIaGlnLeuTrp IleTyrLeu aggcaagtccaaaaacct acaacggtg tttgtgcagatc ctgagactc 528 ArgGlnValGlnLysPro ThrThrVal PheValGlnIle LeuArgLeu attaagcccatgaaagac ggtacaaga tatactggaatt ogatctttg 576 IleLysProMetLysAsp GlyThrArg TyrThrGlyIle ArgSerLeu aaacttgacatgaaccca ggcactggt atctggcagagt attgatgtg 624 LysLeuAspMetAsnPro GlyThrGly IleTrpGlnSer IleAspVal aagacagtgctgcaa aattggctc aaacagcctgaatcc aatttaggc 672 LysThrValLeuGln AsnTrpLeu LysGlnProGluSer AsnLeuGly atcgaaataaaaget tttgatgag actggacgagatctt getgtcaca 720 IleGluTleLysAla PheAspGlu ThrGlyArgAspLeu AlaValThr ttcccaggaccagga gaagatgga ttgaacccattttta gaggtcaga 768 PheProGlyProGly GluAspGly LeuAsnProPheLeu GluValArg gttacagacacaccg aaacggtcc cgcagagattttggc cttgactgt 816 ValThrAspThrPro LysArgSer ArgArgAspPheGly LeuAspCys gatgagcactcaacg gaatcccga tgttgtcgctacccg ctgacagtg 864 AspGluHisSerThr GluSerArg CysCysArgTyrPro LeuThrVal gatttc'gaagetttt ggatgggac tggattatagcacct aaaagatac 912 AspPheGluAlaPhe GlyTrpAsp TrpIleIleAlaPro LysArgTyr aaagccaattactgc tccggagaa tgcgaatttgtgttt ctacagaaa 960 LysAlaAsnTyrCys SerGlyGlu CysGluPheValPhe LeuGlnLys tacccgcacactcac ctggtacac caagcaaatcccaga ggctcagca 1008 TyrProHisThrHis LeuValHis GlnAlaAsnProArg GlySerAla ggcccttgctgcaca cccaccaag atgtcccctataaac atgctgtat 1056 GlyProCysCysThr ProThrLys MetSerProIleAsn MetLeuTyr ttcaatggaaaagaa caaataata tatggaaagatacca gccatggtt 1104 PheAsnGlyLysGlu GlnIleIle TyrGlyLysIlePro AlaMetVal gtagatcgttgcggg tgctcatga 1128 ValAspArgCysGly CysSer <2l0> 6 <211> 375 <212> PRT
<213> Gallus gallus <400> 6 M2t Gln Lys Leu Ala Val Tyr Val Tyr Ile Tyr Leu Phe Met GIn Tle Ala Val Asp Pro Val Ala Leu Asp Gly Ser Ser Gln Pro Thr Glu Asn Ala Glu Lys Asp Gly Leu Cys Asn Ala Cys Thr Trp Arg Gln Asn Thr Lys Ser Ser Arg Ile Glu Ala Ile Lys Ile Gln Ile Leu Ser Lys Leu Arg Leu Glu Gln Ala Pro Asn Ile Ser Arg Asp Val Ile Lys Gln Leu Leu Pro Lys Ala Pro Pro Leu Gln Glu Leu Ile Asp Gln Tyr Asp Val Gln Arg Asp Asp Ser Ser Asp Gly Ser Leu Glu Asp Asp Asp Tyr His loo 105 110 Ala Thr Thr Glu Thr Ile Ile Thr Met Pro Thr Glu Ser Asp Phe Leu Val Gln Met Glu Gly Lys Pro Lys Cys Cys Phe Phe Lys Phe Ser Ser Lys Ile Gln Tyr Asn Lys Val Val Lys Ala Gln Leu Trp Ile Tyr Leu Arg Gln Val Gln Lys Pro Thr Thr Val Phe Val Gln Tle Leu Arg Leu Ile Lys Pro Met Lys Asp Gly Thr Arg Tyr Thr Gly Ile Arg Ser Leu Lys Leu Asp Met Asn Pro Gly Thr Gly Ile Trp Gln Ser Ile Asp Val Lys Thr Val Leu Gln Asn Trp Leu Lys Gln Pro Glu Ser Asn Leu Gly Ile Glu Ile Lys Ala Phe Asp Glu Thr Gly Arg Asp Leu Ala Val Thr Phe Pro Gly Pro Gly Glu Asp Gly Leu Asn Pro Phe Leu Glu Val Arg Val Thr Asp Thr Pro Lys Arg Ser Arg Arg Asp Phe Gly Leu Asp Cys Asp Glu His Ser Thr Glu Ser Arg Cys Cys Arg Tyr Pro Leu Thr Val Asp Phe Glu Ala Phe Gly Trp Asp Trp Ile Ile Ala Pro Lys Arg Tyr Lys Ala Asn Tyr Cys Ser Gly Glu Cys Glu Phe Val Phe Leu Gln Lys Tyr Pro His Thr His Leu Val His Gln Ala Asn Pro Arg Gly Sex Ala Gly Pro Cys Cys Thr Pro Thr Lys Met Ser Pro Ile Asn Met Leu Tyr Phe Asn Gly Lys Glu Gln Ile Ile Tyr Gly Lys Ile Pro Ala Met Val Val Asp Arg Cys Gly Cys Ser <210> 7 <211> 1125 <212> DNA
<213> Danio rerio <220>
<221> CDS
<222> (1) . . (1122) <223>
<400> 7 atg cat ttt aca cag gtt tta att tct cta agt gta tta att gca tgt 48 Met His Phe Thr Gln Val Leu Ile Ser Leu Ser Val Leu Ile Ala Cys ggt cca gtg ggt tat gga gat ata acg gcg cac cag cag cct tcc aca 96 Gly Pro Val Gly Tyr Gly Asp Ile Thr Ala His Gln Gln Pro Ser Thr gccacggaggaa agcgagctgtgt tccacatgtgag ttcagacaacac 144 AlaThrGluGlu SerGluLeuCys SerThrCysGlu PheArgGlnHis agcaagctgatg agactgcatgcc atcaagtcccaa attcttagcaaa 192 SerLysLeuMet ArgLeuHisAla IleLysSerGln IleLeuSerLys ctccgactcaag caggetccaaac atcagccgggac gtggtcaagcag 240 LeuArgLeuLys GlnAlaProAsn IleSerArgAsp ValValLysGln ctgttacccaaa gcaccgcctttg caacaacttctg gatcagtacgat 288 LeuLeuProLys AlaProProLeu GlnGlnLeuLeu AspGlnTyrAsp gttttaggagat gacagtaaggat ggagetgtggaa gaggacgatgaa 336 ValLeuGlyAsp AspSerLysAsp GlyAlaValGlu GluAspAspGlu catgccaccaca gagaccatcatg accatggccaca gaacctgacccc 384 HisAlaThrThr GluThrIleMet ThrMetAlaThr GluProAspPro attgttcaagta gatcggaaaccg aagtgttgcttt ttctccttcagt 432 IleValGlnVal AspArgLysPro LysCysCysPhe PheSerPheSer ccgaagatccaa gcgaaccggatc gtaagagcgcag ctctgggttcat 480 ProLysTleGln AlaAsnArgIle ValArgAlaGln LeuTrpValHis ctgagaccggcg gaggaggcgacc accgtcttctta cagatatctcgg 528 LeuArgProAla GluGluAlaThr ThrValPheLeu GlnIleSerArg ctgatgoccgtt aaggacggagga agacaccgaata cgatccctgaaa 576 LeuMetProVal LysAspGlyGly ArgHisArgIle ArgSerLeuLys atcgacgtgaac gcaggagtcacg tcttggcagagt atagacgtaaag 624 IleAspValAsn AlaGlyValThr SerTrpGlnSer TleAspValLys caggtgctcacg gtgtggttaaaa caaccggagacc aaccgaggcatc 672 GlnValLeuThr ValTrpLeuLys GlnProGluThr AsnArgGlyIle gagattaacgca tatgacgcgaag ggaaacgacttg gccgtcacttca 720 GluIleAsnAla TyrAspAlaLys GlyAsnAspLeu AlaValThrSer accgagactggg gaggatggactg ctcccctttatg gaggtgaaaata 768 ThrGluThrGly GluAspGlyLeu LeuProPheMet GluValLysTle tcagagggccca aaacgaatccgg agggactccgga ctggactgcgat 816 SerGluGlyPro Lys IleArg ArgAspSerGIy LeuAspCysAsp Arg gagaattcctca gagtctcgctgctgc aggtaccct ctcactgtggac 864 GluAsnSerSer GluSerArgCysCys ArgTyrPro LeuThrValAsp ttcgaggacttt ggctgggactggatt attgetcca aaacgctataag 912 PheGluAspPhe GlyTrpAspTrpIle IleAlaPro LysArgTyrLys gcgaattactgt tcaggagaatgcgac tacatgtac ctgcagaagtat 960 AlaAsnTyrCys SerGlyGluCysAsp TyrMetTyr LeuGlnLysTyr ccccacacccat ctggtgaacaaggcc agtccgaga ggaacggetggg 1008 ProHisThrHis LeuValAsnLysAla SerProArg GlyThrAlaGly ccctgctgcact cccaccaagatgtct cccatcaac atgctttacttt 1056 ProCysCysThr ProThrLysMetSer ProIleAsn MetLeuTyrPhe aacggcaaagag cagatcatctacggc aagatccct tcgatggtagta 1104 AsnGlyLysGlu GlnIleIleTyrGly LysIlePro SerMetValVal gaccgctgtggc tgctcatga 1125 AspArgCysGly CysSer <210> 8 <211> 374 <212> PRT
<213> Danio rerio <400> 8 Met His Phe Thr Gln Val Leu Ile Ser Leu Ser Val Leu Ile Ala Cys Gly Pro Val Gly Tyr Gly Asp Tle Thr Ala His Gln Gln Pro Ser Thr Ala Thr Glu Glu Ser Glu Leu Cys Ser Thr Cys Glu Phe Arg Gln His Ser Lys Leu Met Arg Leu His Ala Ile Lys Ser Gln Ile Leu Ser Lys Leu Arg Leu Lys Gln Ala Pro Asn Ile Ser Arg Asp Val Val Lys Gln Leu Leu Pro Lys Ala Pro Pro Leu Gln Gln Leu Leu Asp Gln Tyr Asp Val Leu Gly Asp Asp Ser Lys Asp Gly Ala Val Glu Glu Asp Asp Glu His Ala Thr Thr Glu Thr Ile Met Thr Met Ala Thr Glu Pro Asp Pro 115 120 l25 Ile Val Gln Val Asp Arg Lys Pro Lys Cys Cys Phe Phe Ser Phe Ser Pro Lys Ile Gln Ala Asn Arg Ile Val Arg Ala Gln Leu Trp Val His l45 150 155 160 Leu Arg Pro Ala Glu Glu Ala Thr Thr Val Phe Leu Gln Ile Ser Arg Leu Met Pro Val Lys Asp Gly Gly Arg His Arg Ile Arg Ser Leu Lys Tle Asp Val Asn Ala Gly Val Thr Ser Trp Gln Ser Ile Asp Val Lys Gln Val Leu Thr Val Trp Leu Lys Gln Pro Glu Thr Asn Arg Gly Ile 2l0 215 220 Glu Ile Asn Ala Tyr Asp Ala Lys Gly Asn Asp Leu Ala Val Thr Ser Thr Glu Thr Gly Glu Asp Gly Leu Leu Pro Phe Met Glu Val Lys Ile Ser Glu Gly Pro Lys Arg Ile Arg Arg Asp Ser Gly Leu Asp Cys Asp Glu Asn Ser Ser Glu Ser Arg Cys Cys Arg Tyr Pro Leu Thr Val Asp Phe Glu Asp Phe Gly Trp Asp Trp Ile Ile Ala Pro Lys Arg Tyr Lys Ala Asn Tyr Cys Ser Gly Glu Cys Asp Tyr Met Tyr Leu Gln Lys Tyr Pro His Thr His Leu Val Asn Lys Ala Ser Pro Arg Gly Thr Ala Gly Pro Cys Cys Thr Pro Thr Lys Met Ser Pro Ile Asn Met Leu Tyr Phe Asn Gly Lys Glu Gln Ile Ile Tyr Gly Lys Ile Pro Ser Met Val Val Asp Arg Cys Gly Cys Ser <210> 9 <211> 50 <212> PRT
<213> Homo Sapiens <400> 9 Lys Asp Val Ile Arg Gln Leu Leu Pro Lys Ala Pro Pro Leu Arg Glu l 5 10 15 Leu Ile Asp Gln Tyr Asp Val Gln Arg Asp Asp Ser Ser Asp Gly Ser Leu Glu Asp Asp Asp Tyr His Ala Thr Thr Glu Thr Ile Ile Thr Met Pro Thr <210> 10 <2l1> 50 <212> PRT
<213> Artificial sequence <220>
<223> Mutant peptide portion of human myostatin <400> 10 Lys Asp Val Ile Arg Gln Leu Leu Pro Lys Ala Pro Pro Leu Arg Glu Leu Ile Asp Gln Tyr Asp Val Gln Gln Asp Asp Ser Ser Asp Gly Ser Leu Glu Asp Asp Asp Tyr His Ala Thr Thr Glu Thr Ile Ile Thr Met Pro Thr <210> 11 <211> 50 <212> PRT
<2l3> Artificial sequence <220>
<223> Mutant peptide portion of human myostatin <400> 11 Lys Asp Val Ile Arg Gln Leu Leu Pro Lys Ala Pro Pro Leu Arg Glu Leu Ile Asp Gln Tyr Asp Val Gln Arg Ala Asp Ser Ser Asp Gly Ser Leu Glu Asp Asp Asp Tyr His Ala Thr Thr Glu Thr Ile Ile Thr Met Pro Thr <210> 12 <211> 40 <212> PRT
<213> Homo Sapiens <400> 12 Gln Leu Leu Pro Lys Ala Pro Pro Leu Arg Glu Leu Ile Asp Gln Tyr Asp Val Gln Arg Asp Asp Ser Ser Asp Gly Ser Leu Glu Asp Asp Asp Tyr His Ala Thr Thr Glu Thr Ile <210> 13 <211> 40 <212> PRT
<213> Artificial sequence <220>
<223> Mutant peptide portion of human myostatin <400> 13 Gln Leu Leu Pro Lys Ala Pro Pro Leu Arg Glu Leu Ile Asp Gln Tyr Asp Val Gln Gln Asp Asp Ser Ser Asp Gly Ser Leu Glu Asp Asp Asp Tyr His Ala Thr Thr Glu Thr Ile <210> 14 <21l> 40 <2l2> PRT
<2l3> Artificial sequence <220>
<223> Mutant peptide portion of human myostatin <400> 14 Gln Leu Leu Pro Lys Ala Pro Pro Leu Arg Glu Leu Ile Asp Gln Tyr Asp Val Gln Arg Ala Asp Ser Ser Asp Gly Ser Leu Glu Asp Asp Asp Tyr His Ala Thr Thr Glu Thr Ile <210> 15 <211> 30 <212> PRT
<213> Homo sapiens <400> 15 Ala Pro Pro Leu Arg Glu Leu Ile Asp Gln Tyr Asp Val Gln Arg Asp Asp Ser Ser Asp Gly Ser Leu Glu Asp Asp Asp Tyr His Ala <210> 16 <211> 30 <212> PRT
<213> Artificial sequence <220>
<223> Mutant peptide portion of human myostatin <400> 16 Ala Pro Pro Leu Arg Glu Leu Ile Asp Gln Tyr Asp Val Gln Gln Asp Asp Ser Ser Asp Gly Ser Leu Glu Asp Asp Asp Tyr His Ala <210> 17 <211> 30 <212> PRT
<213> Artificial sequence <220>
<223> Mutant peptide portion of human myostatin <400> 17 Ala Pro Pro Leu Arg Glu Leu Ile Asp Gln Tyr Asp Val Gln Arg Ala Asp Ser Ser Asp Gly Ser Leu Glu Asp Asp Asp Tyr His Ala <210> 18 <211> 20 <212> PRT
<213> Homo Sapiens <400> 18 Glu Leu Ile Asp Gln Tyr Asp Val Gln Arg Asp Asp Ser Ser Asp Gly Ser Leu Glu Asp <210> 19 <211> 20 <212> PRT
<213> Artificial sequence <220>
<223> Mutant peptide portion of human myostatin <400> 19 Glu Leu Ile Asp Gln Tyr Asp Val Gln Gln Asp Asp Ser Ser Asp Gly Ser Leu Glu Asp <210> 20 <211> 20 <212> PRT
<213> Artificial sequence <220>
<223> Mutant peptide portion of human myostatin <400> 20 Glu Leu Ile Asp Gln Tyr Asp Val Gln Arg Ala Asp Ser Ser Asp Gly l 5 10 15 Ser Leu Glu Asp <210> 21 <211> 10 <212> PRT
<213> Homo sapiens <400> 21 Tyr Asp Val Gln Arg Asp Asp Ser Ser Asp 1 5 l0 <210> 22 <21l> 10 <212> PRT
<213> Artificial sequence <220>
<223> Mutant peptide portion of human myostatin <400> 22 Tyr Asp Val Gln Gln Asp Asp Ser Ser Asp <210> 23 <211> 10 <212> PRT
<213> Artificial sequence <220>
<223> Mutant peptide portion of human myostatin <400> 23 Tyr Asp Val Gln Arg Ala Asp Ser Ser Asp

Claims (66)

What is claimed is:

1. A method of modulating myostatin activation, comprising contacting a latent myostatin complex comprising a myostatin pro peptide and a myostatin C-terminal fragment, and a metalloprotease that can cleave the myostatin pro peptide, with an agent that increases or decreases proteolytic cleavage of the pro peptide by the metalloprotease, thereby modulating myostatin activation.

2. The method of claim 1, wherein the metalloprotease is a bone morphogenic protein-1/tolloid (BMP-1/TLD) family member.

3. The method of claim 2, wherein the BMP-1/TLD family member is BMP-1, TLD, tolloid-like protein-1 (TLL-1), or tolloid-like protein-2 (TLL-2).

4. The method of claim 2, wherein the BMP-1/TLD family member is BMP-1, mammalian TLD (mTLD), mammalian TLL-1 (mTLL-1), or mammalian TLL-2 (mTLL-2).

5. The method of claim 1, which comprises increasing myostatin activation, said method comprising contacting the latent myostatin complex and metalloprotease with an agent that increases proteolytic cleavage of the pro peptide by the metalloprotease, thereby increasing myostatin activation.

6. The method of claim 1, wherein said contacting is performed on a sample in vitro.

7. The method of claim 6, wherein the sample comprises a cell sample, a tissue sample, or a biological fluid sample.

The method of claim 1, wherein said contacting is performed in vivo, said method comprising administering the agent to a subject.

9. The method of claim 8, wherein the agent decreases proteolytic cleavage of the pro peptide by the metalloprotease, thereby reducing or inhibiting myostatin activation.

10. The method of claim 9, wherein, in the subject, muscle mass is increased, fat content is decreased, or a combination thereof.

11. The method of claim 10, wherein the subject is an animal raised as a food source.

12. The method of claim 11, wherein the animal is a mammalian species, an avian species, or a piscine species.

13. The method of claim 12, wherein mammalian species is an ovine species, a porcine species, or a bovine species.

14. The method of claim 12, wherein the avian species is a chicken or a turkey.

15. The method of claim 8, wherein the subject is a human subject.

16. A method of increasing muscle mass in a subject, comprising administering to the subject an agent that reduces or inhibits proteolytic cleavage of myostatin pro peptide by a protease, thereby preventing activation of latent myostatin and increasing muscle mass in the subject.

17. The method of claim 16, wherein metalloprotease is a bone morphogenic protein-1/tolloid (BMP-1/TLD) family member.

18. The method of claim 17, wherein the BMP-1/TLD family member is BMP-1, TLD, Tolloid-like (TLL) protein-1 (TLL-1), or TLL-2.

19. The method of claim 17, wherein the BMP-1/TLD family member is BMP-1, mammalian TLD (mTLD), mammalian TLL-1 (mTLL-1), or mammalian TLL-2 (mTLL-2).

20. The method of claim 16, wherein the subject is a vertebrate.

21. The method of claim 20, wherein the vertebrate is mammal.

22. The method of claim 21, wherein mammal is an ovine species, a porcine species, or a bovine species.

23. The method of claim 16, wherein the subject is a human subject.

24. The method of claim 20, wherein the vertebrate is an avian species.

25. The method of claim 24, wherein the avian species is a chicken or a turkey.

26. The method of claim 20, wherein the vertebrate is a piscine species.

27. A method for ameliorating a metabolic disorder in a subject, comprising administering to the subject an agent that reduces or inhibits the proteolytic cleavage of myostatin pro peptide by a protease, thereby preventing activation of latent myostatin and ameliorating the metabolic disorder.

28. The method of claim 27, wherein the metabolic disorder is a muscle wasting disorder.

29. The method of claim 28, wherein the muscle wasting disorder is associated with muscular dystrophy.

30. The method of claim 28, wherein the muscle wasting disorder is associated with cachexia.

31. The method of claim 30, wherein the cachexia is associated with cancer or acquired immunodeficiency disease.

32. The method of claim 28, wherein the muscle wasting disorder is sarcopenia.

33. The method of claim 27, wherein the metabolic disorder is obesity.

34. The method of claim 27, wherein the metabolic disorder is type II
diabetes.

35. The method of claim 27, wherein the subject is a vertebrate subject.

36. The method of claim 35, wherein the vertebrate subject is a domesticated animal.

37. The method of claim 27, wherein the subject is a human subject.

38. A method of identifying an agent that modulates metalloprotease mediated activation of latent myostatin, comprising:
a) contacting a myostatin pro peptide, a metalloprotease that can cleave the myostatin pro peptide, and a test agent, under conditions sufficient for cleavage of the pro peptide by the metalloprotease; and b) detecting a change in the amount of cleavage of the pro peptide in the absence of the test agent as compared to the presence of the test agent, thereby identifying the test agent as an agent that modulates metalloprotease mediated activation of the latent myostatin.

39. The method of claim 38, wherein the myostatin pro peptide comprises a latent myostatin complex comprising the myostatin pro peptide and a myostatin C-terminal fragment.

40. The method of claim 38, wherein the myostatin pro peptide comprises a latent myostatin complex comprising the myostatin pro peptide and a myostatin C-terminal dimer.

41. The method of claim 3 8, wherein detecting a difference in the amount of cleavage of the pro peptide comprises detecting the pro peptide or a cleavage product of the pro peptide.

42. The method of claim 41, wherein the amount of the pro peptide or cleavage product of the pro peptide is detected by electrophoresis, chromatography, or mass spectrometry.

43. The method of claim 41, comprising detecting an increased amount of a cleavage product of the pro peptide in the presence of the test agent as compared to an amount of cleavage product in the absence of the test agent, thereby identifying the test agent as an agent that increases mediated activation of the latent myostatin.

44. The method of claim 41, comprising detecting a decreased amount of the pro peptide in the presence of the test agent as compared to an amount of pro peptide in the absence of the test agent, thereby identifying the test agent as an agent that increases metalloprotease mediated activation of the latent myostatin.

45. The method of claim 41, comprising detecting an decreased amount of a cleavage product of the pro peptide in the presence of the test agent as compared to an amount of cleavage product in the absence of the test agent, thereby identifying the test agent as an agent that decreases metalloprotease mediated activation of the latent myostatin.

46. The method of claim 41, comprising detecting a greater amount of the pro peptide in the presence of the test agent as compared to an amount of pro peptide in the absence of the test agent, thereby identifying the test agent as an agent that decreases metalloprotease mediated activation of the latent myostatin.

47. The method of claim 38, further comprising determining an amount by which the agent modulates metalloprotease mediated activation of the latent myostatin.

48. The method of claim 38, wherein detecting a difference in the amount of cleavage of the pro peptide comprises detecting a change in myostatin mediated signal transduction in a cell expressing a myostatin receptor.

49. The method of claim 48, wherein the myostatin receptor is an activin receptor.

50. The method of claim 49, wherein the activin receptor is an activin type II
receptor.

51. The method of claim 48, wherein the myostatin receptor is expressed from a transgene.

52. The method of claim 48, wherein the cell contains a reporter gene responsive to myostatin mediated signal transduction, and wherein said detecting comprises detecting a change in reporter gene expression.

53. The method of claim 52, wherein the reporter gene comprises a transforming growth factor-beta (TGF- .beta.) regulatory element.

54. The method of claim 38, wherein the test agent is a peptide, a peptide hydroxamate, a phosphinic peptide, a peptoid, a polynucleotide, or a small organic molecule.

55. The method of claim 38, which is performed in a high throughput format.

56. The method of claim 55, which comprises contacting each of a plurality of samples comprising a myostatin pro peptide and a metalloprotease, with a test agent.

57. The method of claim 55, wherein the test agent comprises a plurality of test agents, and wherein at least one sample comprising a myostatin pro peptide and a metalloprotease of the plurality of samples is contacted with at least one test agent of the plurality of test agents.

58. The method of claim 57, wherein the plurality of test agents comprises a combinatorial library of test agents.

59. The method of claim 58, wherein the combinatorial library of test agents comprises a library of random test agents, biased test agents, or variegated test agents.

60. An agent identified by the method of claim 38.

61. An agent that modulates metallopxotease mediated activation of latent myostatin.

62. The agent of claim 61, which reduces or inhibits metalloprotease mediated activation of latent myostatin.

63. The agent of claim 61, which increases metalloprotease mediated activation of latent myostatin.

64. The agent of claim 61, which is a peptide agent, a polynucleotide agent, an antibody agent, or a small organic molecule agent.

65. The agent of claim 62, which is a peptide agent.

66. The agent of claim 65, wherein the peptide agent comprises a peptide portion of a myostatin polypeptide, or a derivative of said peptide portion.