Minhang Hospital and Department of Medicinal Chemistry at School of Pharmacy, Fudan University, 201203, Shanghai, China.
Acta Pharmacol Sin. 2019 Nov;40(11):1480-1489. doi: 10.1038/s41401-019-0259-z. Epub 2019 Jul 17.
The retinoic acid receptor-related orphan receptor (ROR) γt receptor is a member of nuclear receptors, which is indispensable for the expression of pro-inflammatory cytokine IL-17. RORγt has been established as a drug target to design and discover novel treatments for multiple inflammatory and immunological diseases. It is important to elucidate the molecular mechanisms of how RORγt is activated by an agonist, and how the transcription function of RORγt is interrupted by an inverse agonist. In this study we performed molecular dynamics simulations on four different RORγt systems, i.e., the apo protein, protein bound with agonist, protein bound with inverse agonist in the orthosteric-binding pocket, and protein bound with inverse agonist in the allosteric-binding pocket. We found that the orthosteric-binding pocket in the apo-form RORγt was mostly open, confirming that apo-form RORγt was constitutively active and could be readily activated (ca. tens of nanoseconds scale). The tracked data from MD simulations supported that RORγt could be activated by an agonist binding at the orthosteric-binding pocket, because the bound agonist helped to enhance the triplet His479-Tyr502-Phe506 interactions and stabilized H12 structure. The stabilized H12 helped RORγt to form the protein-binding site, and therefore made the receptor ready to recruit a coactivator molecule. We also showed that transcription function of RORγt could be interrupted by the binding of inverse agonist at the orthosteric-binding pocket or at the allosteric-binding site. After the inverse agonist was bound, H12 either structurally collapsed, or reorientated to a different position, at which the presumed protein-binding site was not able to be formed.
维甲酸相关孤儿受体 (ROR) γt 受体是核受体家族的一员，对于促炎细胞因子 IL-17 的表达是不可或缺的。RORγt 已被确立为药物靶点，用于设计和发现治疗多种炎症和免疫性疾病的新疗法。阐明激动剂如何激活 RORγt、反向激动剂如何阻断 RORγt 的转录功能的分子机制非常重要。在这项研究中，我们对四个不同的 RORγt 系统进行了分子动力学模拟，即apo 蛋白、与激动剂结合的蛋白、与正位结合口袋中的反向激动剂结合的蛋白、与变构结合口袋中的反向激动剂结合的蛋白。我们发现 apo 形式的 RORγt 的正位结合口袋大部分是开放的，这证实了 apo 形式的 RORγt 是组成型激活的，并且可以很容易地被激活（大约在纳秒级）。MD 模拟的跟踪数据支持 RORγt 可以通过结合在正位结合口袋的激动剂来激活，因为结合的激动剂有助于增强三联体 His479-Tyr502-Phe506 相互作用并稳定 H12 结构。稳定的 H12 有助于 RORγt 形成蛋白质结合位点，从而使受体准备好招募共激活子分子。我们还表明，反向激动剂结合在正位结合口袋或变构结合位点可以阻断 RORγt 的转录功能。反向激动剂结合后，H12 要么结构塌陷，要么重新定向到一个不同的位置，在这个位置，假定的蛋白质结合位点不能形成。
