Antagonism of glucocorticoid receptor transactivity and cell growth inhibition by transforming growth factor-beta through AP-1-mediated transcriptional repression.
Antagonism of glucocorticoid receptor transactivity and cell growth inhibition by transforming growth factor-beta through AP-1-mediated transcriptional repression.
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DOI：
10.1016/s1357-2725(02)00057-2
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发表时间：
2002-12
期刊：
影响因子：
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通讯作者：
S. Periyasamy;E. R. Sánchez
中科院分区：
文献类型：
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作者：
S. Periyasamy;E. R. Sánchez
我们研究了糖皮质激素受体（GR）和转化生长因子-β（TGF-β）信号通路的相互作用，因为它们相互参与调节细胞的生长、发育和分化。这种串扰事件的大多数研究都集中在糖皮质激素（GC）对TGF-β反应的影响上。在这项工作中，我们表明TGF-β可以拮抗地塞米松（Dex）介导的小鼠纤维肉瘤L929细胞的生长抑制。TGF-β还以浓度依赖性方式抑制GR介导的报告基因（pMMTV-CAT）的表达，其IC 50为5 ng/ml。在10 ng/ml的TGF-β下观察到最大抑制（76%）。相反，Dex抑制TGF-β介导的启动子（p3 TP-Lux）在这些相同细胞中的活性。由于TGF-β对GR介导的基因表达的抑制发生在Dex介导的GR核转位之后，我们得出结论，TGF-β对GR信号传导的抑制发生在GR介导的转录活性水平。然而，使用pGRE 2 E1 B-CAT最小启动子构建体，TGF-β并不抑制GR介导的基因表达，这表明TGF-β并不抑制内在GR活性，而是需要不同于GR的DNA结合因子。由于MMTV启动子含有几个推定的AP-1结合位点，我们假设AP-1，一种由c-jun和c-fos蛋白组成的转录因子，可能参与TGF-β抑制GR功能。姜黄素是AP-1表达的有效抑制剂，在没有TGF-β的情况下，完全消除了TGF-β对GR介导的基因表达的抑制作用，而不影响GR活性，并且该药物阻断了TGF-β诱导的AP-1与来自MMTV序列的反应元件的结合。此外，姜黄素消除了TGF-β对Dex诱导的生长抑制的抑制。总的来说，我们的数据表明，TGF-β可以拮抗GR的生长抑制特性，通过阻断GR在复杂的启动子的反式作用，通过一种机制，涉及转录抑制DNA结合的AP-1。
We have examined the interaction of the glucocorticoid receptor (GR) and transforming growth factor-β (TGF-β) signal pathways because of their mutual involvement in the regulation of cell growth, development and differentiation. Most studies of this cross-talk event have focused on the effects of glucocorticoids (GCs) on TGF-β responses. In this work, we show that TGF-β can antagonize dexamethasone (Dex)-mediated growth suppression in mouse fibrosarcoma L929 cells. TGF-β also repressed GR-mediated reporter (pMMTV-CAT) gene expression in a concentration-dependent manner, with an IC50of 5ng/ml of TGF-β. Maximal inhibition (76%) was observed at 10ng/ml of TGF-β. Conversely, Dex inhibited TGF-β-mediated promoter (p3TP-Lux) activity in these same cells. As TGF-β inhibition of GR-mediated gene expression occurred after Dex-mediated nuclear translocation of GR, we conclude that TGF-β inhibition of GR signaling occurs at the level of GR-mediated transcription activity. However, TGF-β did not repress GR-mediated gene expression using the pGRE2E1B-CAT minimal promoter construct, suggesting that TGF-β did not inhibit intrinsic GR activity but, rather, required DNA-binding factor(s) distinct from GR. As the MMTV promoter contains several putative AP-1 binding sites, we hypothesized that AP-1, a transcription factor composed of c-jun and c-fos proteins, might be involved in the TGF-β inhibition of GR functions. Curcumin, a potent inhibitor of AP-1 expression, completely abolished the inhibitory effect of TGF-β on GR-mediated gene expression without affecting GR activity in the absence of TGF-β, and this drug blocked TGF-β-induced binding of AP-1 to a response element derived from the MMTV sequence. Furthermore, curcumin abolished TGF-β inhibition of Dex-induced growth suppression. Taken as a whole, our data suggest that TGF-β can antagonize the growth inhibitory properties of GR by blocking GR transactivity at complex promoters through a mechanism involving transcriptional repression by DNA-bound AP-1.