Up-regulation of insulin-like growth factor binding protein-5 is independent of muscle cell differentiation, sensitive to rapamycin, but insensitive to wortmannin and LY294002

Endocrinology
S RousseC Dubois

Abstract

Skeletal myoblast differentiation is stimulated by insulin-like growth factors (IGFs). The autocrine action of IGFs is mediated through the type-1 IGF receptor (IGFR-1) and modulated by IGF binding proteins (IGFBPs) secreted by the cells. The mouse C2 myoblast cell line stably transfected with a vector producing IGF-II antisense RNA was used to show that specific IGFBP expression changes with the state of the cells: high levels of IGFBP-2 messenger RNA (mRNA) were found only in proliferating myoblasts, whereas IGFBP-3 mRNA was induced in quiescent cells. Secretion of IGFBP5 was strongly stimulated during differentiation. Insulin and IGF dose-response experiments showed that up-regulation of IGFBP-5 resulted from IGFR-1 activation. Drugs interfering with IGFR-1 signaling and inhibiting myoblast differentiation had different effects on IGFBP-5 up-regulation. Two phosphatidylinositol 3-kinase (PI 3-kinase) inhibitors, wortmaninn and LY294002 [2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one], failed to alter IGFBP-5 up-regulation, which persisted in the absence of differentiation. Rapamycin which indirectly prevents activation of the p70 ribosomal protein-S6 kinase (p70S6k), suppressed IGFBP-5 induction. Because the PI3-kinase inh...Continue Reading

Citations

Mar 23, 2018·Journal of Molecular Endocrinology·David R Clemmons
Jan 1, 2003·Developmental Dynamics : an Official Publication of the American Association of Anatomists·Xun ShenHarold S Bernstein
Dec 13, 2005·American Journal of Physiology. Regulatory, Integrative and Comparative Physiology·Charles H LangRobert A Frost
Jun 30, 2000·Biochemical and Biophysical Research Communications·S BayolC Brownson
Dec 8, 2004·Stem Cells·Annette P MeesonDaniel J Garry

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