Myers M G, Mendez R, Shi P, Pierce J H, Rhoads R, White M F
Research Division, Joslin Diabetes Center and Harvard Medical School, Boston, Massachusetts 02215, USA.
J Biol Chem. 1998 Oct 9;273(41):26908-14. doi: 10.1074/jbc.273.41.26908.
Activation of tyrosine kinases by numerous growth factor and cytokine receptors leads to tyrosine phosphorylation of the insulin receptor substrate (IRS)-proteins. Tyrosine-phosphorylated motifs on the IRS proteins bind to the SH2 domains in proteins that mediate downstream signals, including phosphatidylinositol 3'-kinase, GRB-2, and SHP-2. We investigated the function of the two SHP-2 binding COOH-terminal tyrosines of IRS-1 by replacing them with phenylalanine (IRS-1(FCT)). IRS-1(FCT) failed to bind SHP-2 or mediate its tyrosine phosphorylation during insulin stimulation. Although several reports suggest a critical role for SHP-2 in insulin stimulated mitogen-activated protein kinase activation and cell proliferation, IRS-1(FCT) mediated these effects normally in 32D cells. Indeed, IRS-1(FCT) exhibited increased tyrosine phosphorylation, phosphatidylinositol 3'-kinase binding and activation of protein synthesis in response to insulin. These results suggest that SHP-2 attentuates the phosphorylation and downstream signal transmission of IRS-1 and that the interaction of IRS-1 and SHP-2 is an important regulatory event which attenuates insulin metabolic responses.
众多生长因子和细胞因子受体激活酪氨酸激酶，导致胰岛素受体底物（IRS）蛋白发生酪氨酸磷酸化。IRS蛋白上的酪氨酸磷酸化基序与介导下游信号的蛋白中的SH2结构域结合，这些蛋白包括磷脂酰肌醇3'-激酶、GRB-2和SHP-2。我们通过将IRS-1的两个与SHP-2结合的COOH末端酪氨酸替换为苯丙氨酸（IRS-1(FCT)），研究了它们的功能。在胰岛素刺激过程中，IRS-1(FCT)无法结合SHP-2或介导其酪氨酸磷酸化。尽管有几份报告表明SHP-2在胰岛素刺激的丝裂原活化蛋白激酶激活和细胞增殖中起关键作用，但IRS-1(FCT)在32D细胞中仍能正常介导这些效应。事实上，IRS-1(FCT)在对胰岛素的反应中表现出酪氨酸磷酸化增加、磷脂酰肌醇3'-激酶结合及蛋白质合成激活。这些结果表明，SHP-2减弱了IRS-1的磷酸化和下游信号传递，并且IRS-1与SHP-2的相互作用是一个重要的调节事件，它减弱了胰岛素的代谢反应。
