Akt activation is required at a late stage of insulin-induced GLUT4 translocation to the plasma membrane
Akt activation is required at a late stage of insulin-induced GLUT4 translocation to the plasma membrane
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DOI：
10.1210/me.2004-0413
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发表时间：
2005-04-01
影响因子：
--
通讯作者：
James, DE
中科院分区：
文献类型：
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作者：
van Dam, EM;Govers, R;James, DE
胰岛素刺激葡萄糖转运蛋白GLUT 4从细胞内囊泡转运至质膜（PM）。这涉及多个步骤以及多个细胞内区室。Ser/Thr激酶Akt参与了这一过程，但其确切作用尚不明确。为了开始剖析Akt在这些不同步骤中的作用，我们采用了低温阻断。在19 ℃下孵育3 T3-L1脂肪细胞后，GLUT 4在小的外周囊泡中积累，PM标记轻微增加，同时trans-Golgi网络标记减少。虽然胰岛素依赖的GLUT 4向PM的转运在19 ℃时受损，但我们仍然观察到囊泡向表面的运动。引人注目的是，胰岛素刺激的Akt活性，而不是磷脂酰肌醇3激酶活性，在19 ℃被阻断。与GLUT 4运输中的多步骤过程一致，胰岛素刺激的GLUT 4易位可以通过在19 ℃用胰岛素处理细胞来引发，而Akt活化的情况并非如此。这些数据暗示了GLUT 4易位中的两个胰岛素调节步骤：1）GLUT 4囊泡向细胞皮质的再分布-该过程是Akt-非依赖性的，并且在19 ℃时不被阻断;和2）GLUT 4囊泡与PM的对接和/或融合-该过程可能是葡萄糖转运的胰岛素调节中的主要Akt-依赖性步骤。
Insulin stimulates the translocation of glucose transporter GLUT4 from intracellular vesicles to the plasma membrane (PM). This involves multiple steps as well as multiple intracellular compartments. The Ser/Thr kinase Akt has been implicated in this process, but its precise role is ill defined. To begin to dissect the role of Akt in these different steps, we employed a low-temperature block. Upon incubation of 3T3-L1 adipocytes at 19 C, GLUT4 accumulated in small peripheral vesicles with a slight increase in PM labeling concomitant with reduced trans-Golgi network labeling. Although insulin-dependent translocation of GLUT4 to the PM was impaired at 19 C, we still observed movement of vesicles toward the surface. Strikingly, insulin-stimulated Akt activity, but not phosphatidylinositol 3 kinase activity, was blocked at 19 C. Consistent with a multistep process in GLUT4 trafficking, insulin-stimulated GLUT4 translocation could be primed by treating cells with insulin at 19 C, whereas this was not the case for Akt activation. These data implicate two insulin-regulated steps in GLUT4 translocation: 1) redistribution of GLUT4 vesicles toward the cell cortex-this process is Akt-independent and is not blocked at 19 C; and 2) docking and/or fusion of GLUT4 vesicles with the PM-this process may be the major Akt-dependent step in the insulin regulation of glucose transport.