Dynamin associates with Src-homology collagen (SHC) and becomes tyrosine phosphorylated in response to insulin

The activated insulin receptor phosphorylates docking proteins such as Src-Homology Collagen (Shc) and Insulin Receptor Substrate-1 (IRS-1), which then bind several proteins that contain a Src-Homology 2 (SH2) domain. Both Shc and IRS-1 associate with Growth Factor Receptor-Bound protein 2 (Grb2), an adaptor molecule. The hormone-receptor complex is then rapidly internalized through coated-pits. Dynamin, a 100 kDa protein with GTPase activity, is thought to play a crucial role in receptor-mediated endocytosis. In this study, we show that insulin induces tyrosine phosphorylation of dynamin in cells overexpressing human insulin receptors. Phosphorylation is observed rapidly, i.e, within 1 minute of insulin treatment. Moreover, exposure of cells to the hormone leads to co-immunoprecipitation of dynamin with Shc and with insulin receptor. Since dynamin constitutively associates with Grb2, it could be recruited to the insulin signaling complex through binding of Grb2 to tyrosine-phosphorylated Shc.