Noguchi T, Matozaki T, Horita K, Fujioka Y, Kasuga M
Second Department of Internal Medicine, Kobe University School of Medicine, Japan.
Mol Cell Biol. 1994 Oct;14(10):6674-82. doi: 10.1128/mcb.14.10.6674-6682.1994.
SH-PTP2 is a nontransmembrane human protein-tyrosine phosphatase that contains two Src homology 2 (SH2) domains and binds to insulin receptor substrate 1 (IRS-1) via these domains in response to insulin. The expression of a catalytically inactive mutant of SH-PTP2 (containing the mutation Cys-459-->Ser) in Chinese hamster ovary cells that overexpress human insulin receptors (CHO-IR cells) markedly attenuated insulin-stimulated Ras activation. Expression of mutant SH-PTP2 also inhibited MAP kinase activation in response to insulin but not in response to 12-O-tetradecanoyl phorbol-13-acetate. In contrast, the insulin-induced association of phosphoinositide 3-kinase activity with IRS-1 was not affected by the expression of inactive SH-PTP2. Furthermore, the expression of mutant SH-PTP2 had no effect on the binding of Grb2 to IRS-1, on the tyrosine phosphorylation of Shc, or on the formation of the complex between Shc and Grb2 in response to insulin. However, the amount of SH-PTP2 bound to IRS-1 in insulin-treated CHO-IR cells expressing mutant SH-PTP2 was greater than that observed in CHO-IR cells overexpressing wild-type SH-PTP2. Recombinant SH-PTP2 specifically dephosphorylated a synthetic phosphopeptide corresponding to the sequence surrounding Tyr-1172 of IRS-1, a putative binding site for SH-PTP2. Additionally, phenylarsine oxide, an inhibitor of protein-tyrosine phosphatases, inactivated SH-PTP2 in vitro and increased the insulin-induced association of SH-PTP2 with IRS-1. These results suggest that SH-PTP2 may regulate an upstream element necessary for Ras activation in response to insulin and that this upstream element may be required for the Grb2- or Shc-dependent pathway. Furthermore, these results are consistent with the notion that SH-PTP2 may bind to IRS-1 through its SH2 domains in response to insulin and dephosphorylate the phosphotyrosine residue to which it binds, thereby regulating its association with IRS-1.
SH-PTP2是一种非跨膜的人蛋白酪氨酸磷酸酶，它含有两个Src同源2（SH2）结构域，并在胰岛素作用下通过这些结构域与胰岛素受体底物1（IRS-1）结合。在中国仓鼠卵巢细胞（CHO-IR细胞）中过表达人胰岛素受体的情况下，表达SH-PTP2的催化无活性突变体（包含Cys-459→Ser突变）显著减弱了胰岛素刺激的Ras激活。突变体SH-PTP2的表达也抑制了胰岛素刺激的MAP激酶激活，但对12-O-十四烷酰佛波醇-13-乙酸酯刺激的MAP激酶激活无抑制作用。相反，胰岛素诱导的磷酸肌醇3激酶活性与IRS-1的结合不受无活性SH-PTP2表达的影响。此外，突变体SH-PTP2的表达对Grb2与IRS-1的结合、Shc的酪氨酸磷酸化或胰岛素刺激下Shc与Grb2复合物的形成均无影响。然而，在表达突变体SH-PTP2的胰岛素处理的CHO-IR细胞中，与IRS-1结合的SH-PTP2量比在过表达野生型SH-PTP2的CHO-IR细胞中观察到的量更大。重组SH-PTP2特异性地使对应于IRS-1的Tyr-1172周围序列的合成磷酸肽去磷酸化，Tyr-1172是SH-PTP2的一个假定结合位点。此外，蛋白酪氨酸磷酸酶抑制剂苯砷氧化物在体外使SH-PTP2失活，并增加了胰岛素诱导的SH-PTP2与IRS-1的结合。这些结果表明，SH-PTP2可能调节胰岛素刺激下Ras激活所必需的上游元件，并且这个上游元件可能是Grb2或Shc依赖性途径所必需的。此外，这些结果与以下观点一致：SH-PTP2可能在胰岛素作用下通过其SH2结构域与IRS-1结合，并使其结合的磷酸酪氨酸残基去磷酸化，从而调节其与IRS-1的结合。
