Myers M G, Backer J M, Sun X J, Shoelson S, Hu P, Schlessinger J, Yoakim M, Schaffhausen B, White M F
Joslin Diabetes Center, Department of Medicine, Harvard Medical School, Boston, MA 02215.
Proc Natl Acad Sci U S A. 1992 Nov 1;89(21):10350-4. doi: 10.1073/pnas.89.21.10350.
IRS-1 is an insulin receptor substrate that undergoes tyrosine phosphorylation and associates with the phosphatidylinositol (PtdIns) 3'-kinase immediately after insulin stimulation. Recombinant IRS-1 protein was tyrosine phosphorylated by the insulin receptor in vitro and associated with the PtdIns 3'-kinase from lysates of quiescent 3T3 fibroblasts. Bacterial fusion proteins containing the src homology 2 domains (SH2 domains) of the 85-kDa subunit (p85) of the PtdIns 3'-kinase bound quantitatively to tyrosine phosphorylated, but not unphosphorylated, IRS-1, and this association was blocked by phosphotyrosine-containing synthetic peptides. Moreover, the phosphorylated peptides and the SH2 domains each inhibited binding of PtdIns 3'-kinase to IRS-1. Phosphorylated IRS-1 activated PtdIns 3'-kinase in anti-p85 immunoprecipitates in vitro, and this activation was blocked by SH2 domain fusion proteins. These data suggest that the interaction between PtdIns 3'-kinase and IRS-1 is mediated by tyrosine phosphorylated motifs on IRS-1 and the SH2 domains of p85, and IRS-1 activates PtdIns 3'-kinase by binding to the SH2 domains of p85. Thus, IRS-1 likely serves to transmit the insulin signal by binding and regulating intracellular enzymes containing SH2 domains.
胰岛素受体底物-1（IRS-1）是一种胰岛素受体底物，在胰岛素刺激后立即发生酪氨酸磷酸化，并与磷脂酰肌醇（PtdIns）3'-激酶结合。重组IRS-1蛋白在体外被胰岛素受体酪氨酸磷酸化，并与静止的3T3成纤维细胞裂解物中的PtdIns 3'-激酶结合。含有PtdIns 3'-激酶85-kDa亚基（p85）的src同源2结构域（SH2结构域）的细菌融合蛋白与酪氨酸磷酸化的而非未磷酸化的IRS-1定量结合，并且这种结合被含磷酸酪氨酸的合成肽阻断。此外，磷酸化肽和SH2结构域均抑制PtdIns 3'-激酶与IRS-1的结合。磷酸化的IRS-1在体外抗p85免疫沉淀物中激活PtdIns 3'-激酶，并且这种激活被SH2结构域融合蛋白阻断。这些数据表明，PtdIns 3'-激酶与IRS-1之间的相互作用是由IRS-1上的酪氨酸磷酸化基序和p85的SH2结构域介导的，并且IRS-1通过与p85的SH2结构域结合来激活PtdIns 3'-激酶。因此，IRS-1可能通过结合和调节含有SH2结构域的细胞内酶来传递胰岛素信号。
