Noda S, Kishi K, Yuasa T, Hayashi H, Ohnishi T, Miyata I, Nishitani H, Ebina Y
Department of Radiology, University of Tokushima School of Medicine, Japan.
J Med Invest. 2000 Feb;47(1-2):47-55.
We have developed a simple, direct and sensitive method to detect GLUT4 on the cell surface. Using this system, we found that PI3-kinase plays a key role in the signaling pathway of insulin-stimulated GLUT4 translocation. One of the down stream effectors of PI3-kinase is serine-threonine kinase Akt (protein kinase B, RAK-PK), but the involvement of Akt in insulin-stimulated GLUT4 translocation is controversial. To investigate whether Akt1 regulates insulin-stimulated GLUT4 translocation and glucose uptake in L6 myotubes, we established L6 myotubes stably expressing c-myc epitope-tagged GLUT4 (GLUT4myc) and mouse wild type (WT) Akt1. We found that overexpression of WT Akt1 promoted insulin-stimulated p70S6 kinase (p70S6K) activity and increased the basal activity of GSK3 beta, but did not promote insulin-stimulated GLUT4 translocation or glucose uptake. These data supported the result that Akt is not a main signaling molecule to transmit the signal of insulin-stimulated GLUT4 translocation or glucose uptake from insulin-activated PI3-kinase.
我们开发了一种简单、直接且灵敏的方法来检测细胞表面的葡萄糖转运蛋白4（GLUT4）。利用该系统，我们发现磷脂酰肌醇-3激酶（PI3-激酶）在胰岛素刺激的GLUT4转位信号通路中起关键作用。PI3-激酶的下游效应器之一是丝氨酸-苏氨酸激酶Akt（蛋白激酶B，RAK-PK），但Akt在胰岛素刺激的GLUT4转位中的作用存在争议。为了研究Akt1是否调节L6肌管中胰岛素刺激的GLUT4转位和葡萄糖摄取，我们构建了稳定表达c-myc表位标签的GLUT4（GLUT4myc）和小鼠野生型（WT）Akt1的L6肌管。我们发现WT Akt1的过表达促进了胰岛素刺激的p70核糖体蛋白S6激酶（p70S6K）活性，并增加了糖原合成酶激酶3β（GSK3β）的基础活性，但并未促进胰岛素刺激的GLUT4转位或葡萄糖摄取。这些数据支持了Akt不是从胰岛素激活的PI3-激酶传递胰岛素刺激的GLUT4转位或葡萄糖摄取信号的主要信号分子这一结果。
