The activated glucocorticoid receptor inhibits the transcription factor T-bet by direct protein-protein interaction
The activated glucocorticoid receptor inhibits the transcription factor T-bet by direct protein-protein interaction
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DOI：
10.1096/fj.06-7452com
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发表时间：
2007-04-01
期刊：
影响因子：
4.8
通讯作者：
Arzt, Eduardo
中科院分区：
文献类型：
--
作者：
Liberman, Ana C.;Refojo, Damian;Arzt, Eduardo
糖皮质激素(GCs)通过调节多种转录因子(Tf)发挥免疫抑制作用，其中包括激活蛋白(AP)-1、核因子-kappaB和NFAT。GCS抑制Th1细胞因子，促进向Th2分化转变。Th1表型取决于Tf T-bet。在本研究中，我们研究了T-bet对GC的调节。我们发现GCs抑制T-bet转录活性。我们发现糖皮质激素受体(GR)与T-bet在物理上相互作用，无论是在转基因细胞系中，还是在含有内源性GR和T-bet的原代脾细胞培养中。这种相互作用也阻止了依赖GR的转录。我们在体外和体内的内源性结合部位都表明，抑制T-bet的机制进一步涉及减少T-bet与DNA的结合。利用GR的特定突变，我们证明了GR的第一个锌指区域是T-bet抑制所必需的。此外，GCS还在mRNA和蛋白表达水平上抑制T-bet，揭示了GR对T-bet的另一层作用。最后，我们研究了GR/T-bet相互作用对干扰素-γ的功能影响，结果表明GCs抑制了T-bet在其启动子上的转录活性。鉴于T-bet在T细胞分化和炎症中的重要作用，我们认为GR抑制与T-bet的相互作用可能是GCs免疫抑制特性的一个重要机制。
Glucocorticoids (GCs) immunosuppression acts via regulation of several transcription factors (TF), including activating protein (AP)-1, NF-kappa B, and NFAT. GCs inhibit Th1 cytokines and promote a shift toward Th2 differentiation. Th1 phenotype depends on TF T-bet. In this study, we examined GC regulation of T-bet. We found that GCs inhibit T-bet transcriptional activity. We show that glucocorticoid receptor (GR) physically interacts with T-bet both in transfected cell lines and in primary splenocyte cultures with endogenous GR and T-bet. This interaction also blocks GR-dependent transcription. We show both in vitro and in vivo at endogenous binding sites that the mechanism underlying T-bet inhibition further involves reduction of T-bet binding to DNA. Using specific mutations of GR, we demonstrate that the first zinc finger region of GR is required for T-bet inhibition. GCs additionally inhibit T-bet both at mRNA and protein expression levels, revealing another layer of GR action on T-bet. Finally, we examined the functional consequences of GR/T-bet interaction on IFN-gamma, showing that GCs inhibit transcriptional activity of T-bet on its promoter. In view of the crucial role of T-bet in T cell differentiation and inflammation, we propose that GR inhibitory interaction with T-bet may be an important mechanism underlying the immunosuppressive properties of GCs.