Peroxisome proliferator-activated receptor-γ represses GLUT4 promoter activity in primary adipocytes, and rosiglitazone alleviates this effect
Peroxisome proliferator-activated receptor-γ represses GLUT4 promoter activity in primary adipocytes, and rosiglitazone alleviates this effect
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DOI：
10.1074/jbc.m304654200
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发表时间：
2003-08-15
影响因子：
4.8
通讯作者：
Karnieli, E
中科院分区：
文献类型：
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作者：
Armoni, M;Kritz, N;Karnieli, E
过氧化物酶体增殖物激活受体-γ（PPARgamma）的合成噻唑烷二酮配体改善II型糖尿病中的胰岛素敏感性并诱导脂肪和肌肉中的GLUT 4 mRNA表达。然而，涉及的分子机制仍不清楚。我们研究了PPARgamma及其配体对原代大鼠脂肪细胞和共转染PPARgamma和GLUT 4启动子报告基因的CHO-K1细胞中GLUT 4基因表达的调节作用。PPARgamma 1和PPARgamma 2以剂量依赖性方式抑制GLUT 4启动子的活性。然而，天然配体15 δ-前列腺素J（2）增强了这种抑制作用，罗格列酮（Rg）完全缓解了这种抑制作用。配体结合缺陷突变体PPARgamma 1-L468 A/E471 A和PPARgamma 2-L496 A/E499 A保留了抑制作用，而Rg不影响PPARgamma 2-S112 A突变体抑制GLUT 4启动子活性的能力降低了50%。-66/+163 bp GLUT 4启动子区足以介导PPARgamma抑制作用。PPARgamma/维甲酸X受体-α异二聚体直接绑定到这个区域，而结合在Rg的存在下被废除。因此，我们表明，PPARgamma抑制转录活性的GLUT 4启动子通过直接和特异性结合的PPARgamma/类维生素A X受体-α的GLUT 4启动子。这种作用需要在PPARgamma上有一个完整的Ser（112）磷酸化位点，Rg通过其配体结合结构域发挥作用而完全缓解。这些数据表明了一种新的机制，Rg通过将PPARgamma从GLUT 4基因启动子上分离来发挥其抗糖尿病作用，从而导致GLUT 4表达增加和胰岛素敏感性增强。
The synthetic thiazolidinedione ligands of peroxisome proliferator-activated receptor-gamma (PPARgamma) improve insulin sensitivity in type II diabetes and induce GLUT4 mRNA expression in fat and muscle. However, the molecular mechanisms involved are still unclear. We studied the regulatory effects of PPARgamma and its ligands on GLUT4 gene expression in primary rat adipocytes and CHO-K1 cells cotransfected with PPARgamma and the GLUT4 promoter reporter. PPARgamma1 and PPARgamma2 repressed the activity of the GLUT4 promoter in a dose-dependent manner. Whereas this repression was augmented by the natural ligand 15Delta-prostaglandin J(2), it was completely alleviated by rosiglitazone (Rg). Ligand binding-defective mutants PPARgamma1-L468A/E471A and PPARgamma2-L496A/E499A retained the repression effect, which was unaffected by Rg, whereas the PPARgamma2-S112A mutant exhibited a 50% reduced capacity to repress GLUT4 promoter activity. The -66/+163 bp GLUT4 promoter region was sufficient to mediate PPARgamma inhibitory effects. The PPARgamma/retinoid X receptor-alpha heterodimer directly bound to this region, whereas binding was abolished in the presence of Rg. Thus, we show that PPARgamma represses transcriptional activity of the GLUT4 promoter via direct and specific binding of PPARgamma/retinoid X receptor-alpha to the GLUT4 promoter. This effect requires an intact Ser(112) phosphorylation site on PPARgamma and is completely alleviated by Rg, acting via its ligand-binding domain. These data suggest a novel mechanism by which Rg exerts its antidiabetic effects via detaching PPARgamma from the GLUT4 gene promoter, thus leading to increased GLUT4 expression and enhanced insulin sensitivity.