A conformational switch in the ligand-binding domain regulates the dependence of the glucocorticoid receptor on Hsp90.
A conformational switch in the ligand-binding domain regulates the dependence of the glucocorticoid receptor on Hsp90.
复制标题
配体结合域中的构象转换调节糖皮质激素受体对 Hsp90 的依赖性。
DOI：
10.1016/j.jmb.2007.02.057
复制
发表时间：
2007
影响因子：
5.6
通讯作者：
Darimont,BD
中科院分区：
文献类型：
--
作者：
Ricketson,D;Hostick,U;Fang,L;Yamamoto,KR;Darimont,BD
类固醇激素受体(SRs)是一种转录因子，通过改变配体的基因表达来发挥调节开关的作用。SRS的高度保守的配体结合区是一种精确而通用的分子开关，可以采用不同的构象。配体、DNA反应元件和转录共调控因子对这些构象的不同稳定以基因和细胞特异的方式控制SRS的活性。就糖皮质激素受体(GR)而言，高亲和力的配体结合需要LBD与热休克蛋白90(Hsp90)的相互作用。在这里，我们证明了GR的配体结合能力对Hsp90的依赖可以通过替换连接埋藏的配体结合口袋和溶剂暴露的辅调节分子相互作用表面的变构网络中的单个氨基酸来改变。每一个已鉴定的突变都明显改变了不同GR构象之间的平衡，表明SRS对Hsp90的依赖可能与这些受体构象动力学的差异有关。我们的结果表明，Hsp90通过利用变构网络间接稳定GR配体结合口袋，同时允许受体保持结构上的未连接。因此，除了确保GR配体结合口袋与配体的可及性外，Hsp90似乎还使激素和辅助调节因子能够作为变构效应，这构成了GR对配体的基因特异性和细胞特异性反应的基础。
Steroid hormone receptors (SRs) are transcription factors that act as regulatory switches by altering gene expression in response to ligands. The highly conserved ligand-binding domain of SRs is a precise but versatile molecular switch that can adopt distinct conformations. Differential stabilization of these conformations by ligands, DNA response elements and transcriptional coregulators controls the activity of SRs in a gene-specific and cell-specific manner. In the case of the glucocorticoid receptor (GR), high-affinity ligand binding requires the interaction of the LBD with the heat shock protein 90 (Hsp90). Here, we show that the dependence of the ligand binding ability of GR on Hsp90 can be modified by the replacement of single amino acids within an allosteric network that connects the buried ligand-binding pocket and a solvent-exposed coregulator interaction surface. Each of the identified mutations altered the equilibrium between alternative GR conformations distinctively, indicating that the Hsp90 dependence of SRs may correlate with differences in the conformational dynamics of these receptors. Our results suggest that Hsp90 stabilizes the GR ligand-binding pocket indirectly by utilizing the allosteric network, while allowing the receptor to remain structurally uncommitted. Thus, in addition to ensuring the accessibility of the GR ligand-binding pocket to ligands, Hsp90 seems to enable hormones and coregulators to act as allosteric effectors, which forms the basis for gene-specific and cell-specific responses of GR to ligands.