Ins

Insulin receptor substrate-1 (IRS-1) is a key mediator of insulin and insulin-like growth factor (IGF) signaling, serving as the primary substrate for their receptor tyrosine kinases. With a molecular weight of 160–190 kDa, IRS-1 undergoes tyrosine phosphorylation, enabling its interaction with signaling proteins such as the p85 subunit of phosphatidylinositol 3-kinase (PI3K), which facilitates glucose transporter translocation, and ASH/Grb2, which activates the Ras/MAPK cascade. Additionally, IRS-1 contains binding sites for other SH2-domain proteins, including Syp and Nck, contributing to diverse intracellular signaling events. To elucidate the physiological role of IRS-1 in vivo, mice with targeted disruption of the IRS-1 gene were generated. Homozygous knockout mice were viable but exhibited significant growth retardation during both embryonic and postnatal development. Furthermore, these mice demonstrated resistance to insulin, IGF-1, and IGF-2, indicating impaired glucose metabolism. These findings highlight the critical role of IRS-1 in insulin and IGF signaling while also suggesting the presence of IRS-1-independent pathways that compensate for metabolic regulation.