Regulatory Mechanics of Constitutive Androstane Receptors: Basal and Ligand-Directed Actions.
Regulatory Mechanics of Constitutive Androstane Receptors: Basal and Ligand-Directed Actions.
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组成型雄甾烷受体的调节机制：基础和配体定向作用。
DOI：
10.1021/acs.jcim.9b00695
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发表时间：
2019
影响因子：
5.6
通讯作者：
Shen,Tongye
中科院分区：
文献类型：
--
作者：
Pham,Bill;Arons,AveryBancroft;Vincent,JeremyG;Fernandez,EliasJ;Shen,Tongye
构造性雄烷受体(CAR)是一种核激素受体，主要作用于感知和代谢外源物质。该受体的基础活性相对较高，在没有配体的情况下被认为是活性的。过度激活可促进药物毒性和肿瘤生长。因此，治疗方法寻求反向激动剂来抑制或调节CAR活性。为了促进我们对CAR调控机制的理解，我们用计算和实验的方法阐明了CAR激活和失活的三个方面：(1)配体依赖的作用，(2)配体-同源异构体的特异性，和(3)结构活性。对于配体依赖的作用，我们检查了配体结合的模拟，并确定了两组配体诱导的接触，通过共激活子结合促进CAR激活(H11-H12接触)或通过辅阻遏子结合失活(H4-H11接触)。为了同源同源，我们解决了一个令人费解的事实，即小鼠CAR(MCAR)和人类CAR(Hcar)对同一配体(Citco)的反应不同，尽管它们的序列有很高的同源性。我们发现，与mCAR相比，HCAR的螺旋H7与配体CITCO的结合更强，因此CITCO诱导的激活更强。对于基本活性，我们报告了计算机生成的未连接CAR结构和关键突变(mCAR的V209A和N333D)基于细胞的转录测试结果。我们的结果表明，CAR的基本构象与激动剂结合的形式有显著的共同特征，螺旋HX对构象活性有重要的贡献。总之，这些发现对于理解结构性活性受体以及针对它们的药物分子的设计都是有用的。
Constitutive androstane receptor (CAR) is a nuclear hormone receptor that primarily functions in sensing and metabolizing xenobiotics. The basal activity of this receptor is relatively high, and CAR is deemed active in the absence of ligand. The (over)activation can promote drug toxicity and tumor growth. Thus, therapeutic treatments seek inverse agonists to inhibit or modulate CAR activities. To advance our understanding of the regulatory mechanisms of CAR, we used computational and experimental approaches to elucidate three aspects of CAR activation and inactivation: (1) ligand-dependent actions, (2) ligand-orthologue specificity, and (3) constitutive activity. For ligand-dependent actions, we examined the ligand-bound simulations and identified two sets of ligand-induced contacts promoting CAR activation via coactivator binding (H11–H12 contact) or inactivation via corepressor binding (H4–H11 contact). For orthologue specificity, we addressed a puzzling fact that murine CAR (mCAR) and human CAR (hCAR) respond differently to the same ligand (CITCO), despite their high sequence homology. We found that the helix H7 of hCAR is responsible for a stronger binding of the ligandCITCOcompared to mCAR, hence a strongerCITCO-induced activation. For basal activity, we reported computer-generated unliganded CAR structures and critical mutagenesis (mCAR’s V209A and N333D) results of a cell-based transcription assay. Our results reveal that the basal conformation of CAR shares prominent features with the agonist-bound form, and helix HXhas an important contribution to the constitutive activity. These findings altogether can be useful for the understanding of constitutively active receptors and the design of drug molecules targeting them.