Cross Talk of pp125 FAK and pp59 Lyn Non-Receptor Tyrosine Kinases to Insulin-Mimetic Signaling in Adipocytes

Abstract

ABSTRACT Signaling molecules downstream from the insulin receptor, such as the insulin receptor substrate protein 1 (IRS-1), are also activated by other receptor tyrosine kinases. Here we demonstrate that the non-receptor tyrosine kinases, focal adhesion kinase pp125 FAK and Src-class kinase pp59 Lyn , after insulin-independent activation by phosphoinositolglycans (PIG), can cross talk to metabolic insulin signaling in rat and 3T3-L1 adipocytes. Introduction by electroporation of neutralizing antibodies against pp59 Lyn and pp125 FAK into isolated rat adipocytes blocked IRS-1 tyrosine phosphorylation in response to PIG but not insulin. Introduction of peptides encompassing either the major autophosphorylation site of pp125 FAK , tyrosine 397, or its regulatory loop with the twin tyrosines 576 and 577 inhibited PIG-induced IRS-1 tyrosine phosphorylation and glucose transport. PIG-induced pp59 Lyn kinase activation and pp125 FAK tyrosine phosphorylation were impaired by the former and latter peptide, respectively. Up-regulation of pp125 FAK by integrin clustering diminished PIG-induced IRS-1 tyrosine phosphorylation and glucose transport in nonadherent but not adherent adipocytes. In conclusion, PIG induced IRS-1 tyrosine phosphorylation by causing (integrin antagonized) recruitment of IRS-1 and pp59 Lyn to the common signaling platform molecule pp125 FAK , where cross talk of PIG-like structures and extracellular matrix proteins to metabolic insulin signaling may converge, possibly for the integration of the demands of glucose metabolism and cell architecture.