Protein–protein interaction in insulin signaling and the molecular mechanisms of insulin resistance

Schematic illustration of major signaling pathways of insulin action. The phosphorylated insulin receptor binds and phosphorylates IRS proteins and Shc, which bind differentially to various downstream signaling proteins. PI3-kinase is critical for metabolic actions of insulin, such as glucose transport, glycogen synthesis, and protein synthesis, whereas Grb-2/SOS complex, which activates the MAP kinase cascade, is critical in mitogenic response. PI3-kinase probably modulates the mitogenic response as well.