A highly conserved insulin-like growth factor-binding protein (IGFBP-5) is expressed during myoblast differentiation

P. L. James, S. B. Jones, W. H. Busby, D. R. Clemmons, P. Rotwein

Research output: Contribution to journalArticle

133 Scopus citations

Abstract

Insulin-like growth factor-binding proteins (IGFBPs) are a family of secreted proteins that bind insulin-like growth factors I and II (IGFs I and II) and are capable of modulating IGF actions on target cells. We have shown previously that C2 myoblasts secrete a single ~29-kDa IGFBP during their terminal differentiation (Tollefsen, S. E., Lajara, R., McCusker, R. H., Clemmons, D. R., and Rotwein, P. (1989) J. Biol. Chem. 264, 13810-13817). In this study, we have purified the protein from C2 cell-conditioned media by conventional and IGF-affinity chromatography, cloned its cDNA by PCR-based and traditional library screening, and identified it as mouse IGFBP-5. The resultant 5561 nucleotide cDNA encodes a 252-amino acid mature protein (predicted M(r) ~28,400) that is 97% identical to rat and human IGFBP-5. In differentiating C2 myoblasts and in F3 azamyoblasts the >6-kilobase IGFBP-5 mRNA accumulates concomitantly with induction of myogenin mRNA, an early marker of muscle differentiation. Ligand blot analysis shows that IGFBP-5 protein is secreted within 12 h of the onset of differentiation in these cells and that it is the only IGFBP produced in several fusing skeletal muscle cell lines. In vivo, IGFBP-5 transcripts are expressed in a variety of mouse tissues including striated muscle, but, unlike other IGFBPs, it is barely detectable in liver. IGFBP-5 is more conserved than other IGFBPs in mammals; its conserved structure and sequence also extends to non-mammalian vertebrates. Hybridization of a mouse BP5 coding region probe to RNA from several chicken and Xenopus tissues demonstrated similarly sized transcripts in these species. A partial Xenopus cDNA is identical in 38/45 deduced amino acids to the mammalian proteins. Identification of an IGF-binding protein that is produced during myoblast differentiation provides a model system in which to study the potential modulatory role of IGFBPs in development.

Original languageEnglish (US)
Pages (from-to)22305-22312
Number of pages8
JournalJournal of Biological Chemistry
Volume268
Issue number30
StatePublished - Jan 1 1993

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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    James, P. L., Jones, S. B., Busby, W. H., Clemmons, D. R., & Rotwein, P. (1993). A highly conserved insulin-like growth factor-binding protein (IGFBP-5) is expressed during myoblast differentiation. Journal of Biological Chemistry, 268(30), 22305-22312.