title: Pregnancy-associated plasma protein-A regulates myoblast proliferation and differentiation through an insulin-like growth factor-dependent mechanism.
abstract: Pregnancy-associated plasma protein-A (PAPP-A), a member of the metalloproteinase superfamily, is an important regulator of mammalian growth and development. However, the role of PAPP-A and its mechanism of action in various cellular processes remain unknown. In this study, we have investigated the role of PAPP-A in skeletal myogenesis using C2C12 myoblasts. Recombinant PAPP-A was purified from the conditioned medium of HT1080 cells overexpressing PAPP-A. Treatment of C2C12 myoblasts with PAPP-A increased their proliferation in a dose- and time-dependent manner. Addition of exogenous PAPP-A also increased the myotube formation and the activity of creatine kinase in C2C12 cultures. Transient overexpression of the full-length PAPP-A-(1-1547), but not truncated protease-inactive N-terminal PAPP-A-(1-920) or C-terminal PAPP-A-(1100-1547), significantly enhanced the proliferation of C2C12 myoblasts. In vitro and in situ experiments demonstrated that PAPP-A cleaves insulin-like growth factor-binding protein (IGFBP)-2, but not IGFBP-3, in the conditioned medium of C2C12 myoblasts. Overexpression of PAPP-A led to degradation of the IGFBP-2 produced by C2C12 myoblasts and increased free IGF-I concentrations without affecting total IGF-I concentrations. Addition of protease-resistant IGFBP-4 completely abolished the PAPP-A-induced proliferation of C2C12 myoblasts. Our results demonstrate that 1) PAPP-A increases the proliferation and differentiation of myoblasts, 2) the stimulatory effect of PAPP-A on myogenesis is governed by its proteolytic activity, and 3) PAPP-A promotes skeletal myogenesis by increasing the amount of free IGFs via specific degradation of IGFBP-2 produced by myoblasts.
authors.affiliation: Musculoskeletal Disease Center, JL Pettis Memorial Veterans Affairs Medical Center, CA 92357, USA.
authors.forename: Ashok
authors.initials: A
authors.lastname: Kumar
authors.forename: Subburaman
authors.initials: S
authors.lastname: Mohan
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Newton
authors.forename: Mark
authors.initials: M
authors.lastname: Rehage
authors.forename: Kiet
authors.initials: K
authors.lastname: Tran
authors.forename: David J
authors.initials: DJ
authors.lastname: Baylink
authors.forename: Xuezhong
authors.initials: X
authors.lastname: Qin
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002460:Cell Line; D049109:Cell Proliferation; D005786:Gene Expression Regulation; D006801:Humans; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism*; D007335:Insulin-Like Growth Factor II / Q000235:genetics / Q000378:metabolism*; D032446:Myoblasts / Q000166:cytology* / Q000378:metabolism*; D011266:Pregnancy-Associated Plasma Protein-A / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins
chemical_list: D018971:Insulin-Like Growth Factor Binding Protein 2; D011994:Recombinant Proteins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D011266:Pregnancy-Associated Plasma Protein-A