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A study of the SUMO-conjugating enzyme Ubc9 as a novel regulatory factor of insulin sensitivity

SUMO结合酶 Ubc9 作为胰岛素敏感性新型调节因子的研究

基本信息

批准号：
18590974
负责人：
SHIBATA Hiroshi
金额：
$ 2.53万
依托单位：
Gunma University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18590974/
关键词：
insulin sensitivity adipocyte glucose transport sumoylation Ubc9 GLUT4 糖輸送

项目摘要

SUMO conjugating enzyme Ubc9 has been shown to upregulate GLUT4 in L6 myoblasts although the mechanism of action is undefined. Here we investigated the physiological significance of Ubc9 in GLUT4 turnover and subcellular targeting by adenovirus vector-mediated overexpression and by siRNA-mediated gene silencing of Ubc9 in 3T3-L1 adipocytes. Overexpression of Ubc9 resulted in inhibition of GLUT4 degradation and promotion of its targeting to the GLUT4 storage compartment (GSC), leading to an increase in GLUT4 level and insulinresponsive GLUT4 translocation and glucose transport. While long-term (6 hours and more) insulin stimulation caused GLUT4 downregulation by 40-50%, which was inhibited with lysosomal inhibitors and was associated with a selective reduction in GLUT4 in GSC, overexpression of Ubc9 antagonized these effects of insulin. By contrast, Ubc9 gene silencing with siRNA markedly accelerated the insulin-induced GLUT4 downregulation, whereas overexpression of the catalytically inactive mutant Ubc9-C93A increased GLUT4 and insulin-stimulated glucose transport to the level comparable to that with wild-type Ubc9. These results suggest that Ubc9 upregulates GLUT4 by inhibition of lysosomal sorting and promotes GLUT4 targeting to GSC by a mechanism unrelated to its catalytic activity. Thus, Ubc9 plays a indispensable role in expression and maintenance of the insulin-sensitive glucose transport system in adipocytes.

SUMO偶联酶Ubc9已被证明上调L6成肌细胞的GLUT4，尽管其作用机制尚不明确。本研究通过腺病毒载体介导的过表达和sirna介导的Ubc9基因沉默在3T3-L1脂肪细胞中研究了Ubc9在GLUT4转换和亚细胞靶向中的生理意义。Ubc9过表达可抑制GLUT4降解，促进其靶向GLUT4储存室（GSC），导致GLUT4水平升高，GLUT4易位和葡萄糖转运胰岛素反应性降低。虽然长期（6小时及以上）胰岛素刺激导致GLUT4下调40-50%，这被溶酶体抑制剂抑制，并与GSC中GLUT4的选择性降低有关，但Ubc9的过表达可拮抗胰岛素的这些作用。相比之下，用siRNA沉默Ubc9基因明显加速了胰岛素诱导的GLUT4下调，而催化失活突变体Ubc9- c93a的过表达使GLUT4和胰岛素刺激的葡萄糖转运增加到与野生型Ubc9相当的水平。这些结果表明，Ubc9通过抑制溶酶体分选上调GLUT4，并通过与其催化活性无关的机制促进GLUT4靶向GSC。因此，Ubc9在脂肪细胞中胰岛素敏感的葡萄糖转运系统的表达和维持中起着不可或缺的作用。