Action of insulin receptor substrate-3 (IRS-3) and IRS-4 to stimulate translocation of GLUT4 in rat adipose cells.
Action of insulin receptor substrate-3 (IRS-3) and IRS-4 to stimulate translocation of GLUT4 in rat adipose cells.
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DOI：
10.1210/mend.13.3.0242
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发表时间：
1999-03
影响因子：
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通讯作者：
L. Zhou;H. Chen;P. Xu;L. Cong;S. Sciacchitano;Y. Li;D. Graham;A. R. Jacobs;S. Taylor;M. Quon
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文献类型：
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作者：
L. Zhou;H. Chen;P. Xu;L. Cong;S. Sciacchitano;Y. Li;D. Graham;A. R. Jacobs;S. Taylor;M. Quon
胰岛素受体通过磷酸化多种细胞内底物来启动胰岛素作用。以前，我们已经证明，胰岛素受体底物（IRS）-1和-2可以介导胰岛素的行动，以促进易位的GLUT 4葡萄糖转运蛋白的细胞表面在大鼠脂肪细胞。尽管IRS-1、-2和-4的总体结构相似，但IRS-3短约50%，并且在酪氨酸磷酸化位点方面有所不同。然而，如本研究所示，IRS-3和IRS-4也可以刺激GLUT 4的易位。用血凝素（HA）表位标记的GLUT 4（GLUT 4-HA）和人IRS-1、鼠IRS-3或人IRS-4的表达载体共转染大鼠脂肪细胞。IRS-1的过表达导致细胞表面GLUT 4-HA在不存在胰岛素的情况下孵育的细胞中增加2倍; IRS-3或IRS-4的过表达引起细胞表面GLUT 4-HA更大的增加。事实上，IRS-3在不存在胰岛素的情况下的作用比最大刺激浓度的胰岛素在不过表达IRS蛋白的细胞中的作用大约40%。由于磷脂酰肌醇（PI）3-激酶是胰岛素刺激的GLUT 4易位所必需的，我们还研究了一种突变IRS-3分子（IRS-3-F4），其中Phe取代了所有四个YXXM基序中的Tyr（预测结合并激活PI 3-激酶的磷酸化位点）。有趣的是，IRS-3-F4的过表达并不促进GLUT 4-HA的易位，但实际上抑制了胰岛素刺激GLUT 4-HA易位到细胞表面的能力。我们的数据表明，IRS-3和IRS-4是能够介导PI 3-激酶依赖的胰岛素在脂肪细胞中的代谢作用，IRS蛋白在介导GLUT 4易位中发挥生理作用。
The insulin receptor initiates insulin action by phosphorylating multiple intracellular substrates. Previously, we have demonstrated that insulin receptor substrates (IRS)-1 and -2 can mediate insulin's action to promote translocation of GLUT4 glucose transporters to the cell surface in rat adipose cells. Although IRS-1, -2, and -4 are similar in overall structure, IRS-3 is approximately 50% shorter and differs with respect to sites of tyrosine phosphorylation. Nevertheless, as demonstrated in this study, both IRS-3 and IRS-4 can also stimulate translocation of GLUT4. Rat adipose cells were cotransfected with expression vectors for hemagglutinin (HA) epitope-tagged GLUT4 (GLUT4-HA) and human IRS-1, murine IRS-3, or human IRS-4. Overexpression of IRS-1 led to a 2-fold increase in cell surface GLUT4-HA in cells incubated in the absence of insulin; overexpression of either IRS-3 or IRS-4 elicited a larger increase in cell surface GLUT4-HA. Indeed, the effect of IRS-3 in the absence of insulin was approximately 40% greater than the effect of a maximally stimulating concentration of insulin in cells not overexpressing IRS proteins. Because phosphatidylinositol (PI) 3-kinase is essential for insulin-stimulated translocation of GLUT4, we also studied a mutant IRS-3 molecule (IRS-3-F4) in which Phe was substituted for Tyr in all four YXXM motifs (the phosphorylation sites predicted to bind to and activate PI 3-kinase). Interestingly, overexpression of IRS-3-F4 did not promote translocation of GLUT4-HA, but actually inhibited the ability of insulin to stimulate translocation of GLUT4-HA to the cell surface. Our data suggest that IRS-3 and IRS-4 are capable of mediating PI 3-kinase-dependent metabolic actions of insulin in adipose cells, and that IRS proteins play a physiological role in mediating translocation of GLUT4.