Chen D, Elmendorf J S, Olson A L, Li X, Earp H S, Pessin J E
Program in Molecular Biology, The University of Iowa, Iowa City, Iowa 52242, USA.
J Biol Chem. 1997 Oct 24;272(43):27401-10. doi: 10.1074/jbc.272.43.27401.
Similar to insulin, osmotic shock of 3T3L1 adipocytes stimulated an increase in glucose transport activity and translocation of GLUT4 protein from intracellularly localized vesicles to the plasma membrane. The docking/fusion of GLUT4 vesicles with the plasma membrane appeared to utilize a similar mechanism, since expression of a dominant interfering mutant of syntaxin-4 prevented both insulin- and osmotic shock-induced GLUT4 translocation. However, although the insulin stimulation of GLUT4 translocation and glucose transport activity was completely inhibited by wortmannin, activation by osmotic shock was wortmannin-insensitive. Furthermore, insulin stimulated the phosphorylation and activation of the Akt kinase, whereas osmotic shock was completely without effect. Surprisingly, treatment of cells with the tyrosine kinase inhibitor, genistein, or microinjection of phosphotyrosine antibody prevented both the insulin- and osmotic shock-stimulated translocation of GLUT4. In addition, osmotic shock induced the tyrosine phosphorylation of several discrete proteins including Cbl, p130(cas), and the recently identified soluble tyrosine kinase, calcium-dependent tyrosine kinase (CADTK). In contrast, insulin had no effect on CADTK but stimulated the tyrosine phosphorylation of Cbl and the tyrosine dephosphorylation of pp125(FAK) and p130(cas). These data demonstrate that the osmotic shock stimulation of GLUT4 translocation in adipocytes occurs through a novel tyrosine kinase pathway that is independent of both the phosphatidylinositol 3-kinase and the Akt kinase.
与胰岛素相似，3T3L1脂肪细胞的渗透休克刺激了葡萄糖转运活性的增加以及GLUT4蛋白从细胞内定位的囊泡向质膜的转位。GLUT4囊泡与质膜的对接/融合似乎利用了类似的机制，因为 syntaxin-4 的显性干扰突变体的表达阻止了胰岛素和渗透休克诱导的 GLUT4 转位。然而，虽然wortmannin完全抑制了胰岛素对GLUT4转位和葡萄糖转运活性的刺激，但渗透休克的激活对wortmannin不敏感。此外，胰岛素刺激了Akt激酶的磷酸化和激活，而渗透休克则完全没有作用。令人惊讶的是，用酪氨酸激酶抑制剂染料木黄酮处理细胞或显微注射磷酸酪氨酸抗体可阻止胰岛素和渗透休克刺激的GLUT4转位。此外，渗透休克诱导了几种离散蛋白的酪氨酸磷酸化，包括Cbl、p130(cas)和最近鉴定的可溶性酪氨酸激酶钙依赖性酪氨酸激酶(CADTK)。相比之下，胰岛素对CADTK没有影响，但刺激了Cbl的酪氨酸磷酸化以及pp125(FAK)和p130(cas)的酪氨酸去磷酸化。这些数据表明，脂肪细胞中GLUT4转位的渗透休克刺激是通过一条独立于磷脂酰肌醇3激酶和Akt激酶的新型酪氨酸激酶途径发生的。
