Role of phospholipase C-γ1 in insulin-like growth factor I-induced muscle differentiation of H9c2 cardiac myoblasts

Abstract

Insulin-like growth factor-I (IGF-I) regulates muscle differentiation through phosphatidylinositol 3-kinase (PI 3-kinase). Also it was recently reported that PI 3-kinase is involved in the activation of phospholipase C-γ1 (PLC-γ1). We investigated whether PLC-γ1 therefore plays a role in IGF-I-induced muscle differentiation using H9c2 rat cardiac myoblasts as a model. IGF-I was able to activate PLC-γ1 via both PI 3-kinase-dependent and tyrosine phosphorylation-dependent mechanisms in this model. However, PI 3-kinase appeared to play a more important role than tyrosine phosphorylation in IGF-I activation of PLC-γ1. In addition, PLC-γ1 activation was independent of Akt/protein kinase B (Akt/PKB). Importantly, PLC-γ1 was involved in IGF-I-induced muscle differentiation in parallel with Akt/PKB. Taken together, these results suggest that IGF-I regulation of muscle differentiation is dependent on the activation of PLC-γ1 and Akt/PKB, both of which are downstream mediators of PI 3-kinase. © 2001 Academic Press.