Abstract
Myostatin, a muscle-specific transforming growth factor-β (TGF-β), negatively regulates skeletal muscle mass. The N-terminal prodomain of myostatin noncovalently binds to and suppresses the C-terminal mature domain (ligand) as an inactive circulating complex. However, which region of the myostatin prodomain is required to inhibit the biological activity of myostatin has remained unknown. We identified a 29-amino acid region that inhibited myostatin-induced transcriptional activity by 79% compared with the full-length prodomain. This inhibitory core resides near the N-terminus of the prodomain and includes an α-helix that is evolutionarily conserved among other TGF-β family members, but suppresses activation of myostatin and growth and differentiation factor 11 (GDF11) that share identical membrane receptors. Interestingly, the inhibitory core co-localized and co-immunoprecipitated with not only the ligand, but also its type I and type II membrane receptors. Deletion of the inhibitory core in the full-length prodomain removed all capacity for suppression of myostatin. A synthetic peptide corresponding to the inhibitory core (p29) ameliorates impaired myoblast differentiation induced by myostatin and GDF11, but not activin or TGF-β1. Moreover, intramuscular injection of p29 alleviated muscle atrophy and decreased the absolute force in caveolin 3-deficient limb-girdle muscular dystrophy 1C model mice. The injection suppressed activation of myostatin signaling and restored the decreased numbers of muscle precursor cells caused by caveolin 3 deficiency. Our findings indicate a novel concept for this newly identified inhibitory core of the prodomain of myostatin: that it not only suppresses the ligand, but also prevents two distinct membrane receptors from binding to the ligand. This study provides a strong rationale for the use of p29 in the amelioration of skeletal muscle atrophy in various clinical settings.
Highlights
Myostatin, a muscle-specific transforming growth factor-β (TGF-β) family member, plays crucial roles in negative regulation of skeletal muscle mass [1]
We revealed that the inhibitory core of the myostatin prodomain (42CTWRQNTKSSRIEAIKIQILSKLRLETAP70) resides near its N-terminus by expressing various prodomain regions as Fc fusion proteins in both HEK293 embryonic kidney cells, or A204 rhabdomyosarcoma cell
Our results are in contrast to those of a previous study in which a bacterially expressed GST-fused prodomain consisting of residues 42–98 had no inhibitory effect on in vitro myostatin-induced transcription [24]
Summary
A muscle-specific transforming growth factor-β (TGF-β) family member, plays crucial roles in negative regulation of skeletal muscle mass [1]. Similar to certain other TGF-β family members, myostatin is synthesized as a precursor, dimeric protein consisting of an Nterminal prodomain and C-terminal mature domain (ligand) [2,3]. Upon cleavage of the prodomain by bone morphogenetic protein (BMP)-1/tolloid family of metalloproteinases, the ligand recruits and phosphorylates two distinct membrane serine/threonine receptors, termed type I and II, which in turn activate the intracellular effector molecule Mad homolog (Smad) 2 and Smad, and subsequent Smad-responsive gene transcription [4,5]. The prodomain possesses the cleavage site for BMP-1/tolloid family of metalloproteinases [4], and the putative binding site for thrombospondin-1 (TSP-1), a major activator of the TGF-β1 ligand in recruitment of membrane receptors [6]. The regions critical for suppression of the myostatin signal have remained unknown
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
