The dominant negative activity of the human glucocorticoid receptor β isoform -: Specificity and mechanisms of action
The dominant negative activity of the human glucocorticoid receptor β isoform -: Specificity and mechanisms of action
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DOI：
10.1074/jbc.274.39.27857
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发表时间：
1999-09-24
影响因子：
4.8
通讯作者：
Cidlowski, JA
中科院分区：
文献类型：
--
作者：
Oakley, RH;Jewell, CM;Cidlowski, JA
人糖皮质激素受体基因的选择性剪接产生一种非激素结合剪接变体（hGR β），其与野生型受体（hGR α）的区别仅在于羧基末端。以前我们已经证明hGR β抑制hGR α的转录活性，这与广泛性和组织特异性糖皮质激素抵抗患者中hGR β表达升高的报道一致。hGR β在调节靶细胞对糖皮质激素敏感性中的潜在作用促使我们进一步评估其在其他模型系统中的显性负活性，并研究其作用方式。我们在多种细胞类型中证明了hGR β抑制hGR α介导的小鼠乳腺肿瘤病毒启动子的激活。相反，孕激素和雄激素受体激活该启动子的能力仅受hGR β的微弱影响。hGR β还抑制hGR α介导的NF-κ B应答启动子的抑制，但不干扰hGR α的同源下调。我们表明，hGR β可以与热休克蛋白热休克蛋白90，虽然比hGR α具有较低的亲和力。此外，在没有糖皮质激素的情况下，hGR β结合含GR的DNA的能力比hGR α更大。糖皮质激素治疗增强hGR α，但不是hGR β，结合DNA。此外，我们证明了hGR α和hGR β可以在异源二聚体中相互物理关联。最后，我们表明，占主导地位的负活性的hGR β驻留在其独特的羧基末端15个氨基酸。总之，我们的研究结果表明，形成转录受损的hGR α-hGR β异二聚体是一个重要的组成部分的机制，负责显性负活性的hGR β。
Alternative splicing of the human glucocorticoid receptor gene generates a nonhormone binding splice variant (hGR beta) that differs from the wild-type receptor (hGR alpha) only at the carboxyl terminus. Previously we have shown that hGR beta inhibits the transcriptional activity of hGR alpha, which is consistent with reports of ele vated hGR beta expression in patients with generalized and tissue-specific glucocorticoid resistance. The potential role of hGR beta in the regulation of target cell sensitivity to glucocorticoids prompted us to further evaluate its dominant negative activity in other model systems and to investigate its mode of action. We demonstrate in multiple cell types that hGR beta inhibits hGR alpha-mediated activation of the mouse mammary tumor virus promoter. In contrast, the ability of the progesterone and androgen receptors to activate this promoter is only weakly affected by hGR beta. hGR beta also inhibits hGR alpha-mediated repression of an NF-kappa B-responsive promoter but does not interfere with homologous down-regulation of hGR alpha. We show that hGR beta can associate with the heat shock protein hsp90 although with lower affinity than hGR alpha. In addition, hGR beta binds GRE-containing DNA with a greater capacity than hGR alpha in the absence of glucocorticoids. Glucocorticoid treatment enhances hGR alpha, but not hGR beta, binding to DNA. Moreover, we demonstrate that hGR alpha and hGR beta can physically associate with each other in a heterodimer. Finally, we show that the dominant negative activity of hGR beta resides within its unique carboxyl-terminal 15 amino acids. Taken together, our results suggest that formation of transcriptionally impaired hGR alpha-hGR beta heterodimers is an important component of the mechanism responsible for the dominant negative activity of hGR beta.