Division of Nephrology, Department of Medicine, The University of Alabama at Birmingham, Birmingham, Alabama.
Department of Biostatistics, The University of Alabama at Birmingham, Birmingham, Alabama.
Biophys J. 2022 Jul 5;121(13):2490-2502. doi: 10.1016/j.bpj.2022.06.006. Epub 2022 Jun 6.
Endothelin-1 and -3 (ET1 and ET3) are potent vasoconstricting isopeptides that are involved in the pathophysiology of various diseases, such as cardiovascular and renal diseases. The two ETs exert their effects by binding to two G-protein-coupled receptors (GPCRs), the endothelin ET receptor (ETR) and the endothelin ET receptor (ETR). ETR and ETR reveal different preferences in the recognition of the two ETs: The binding affinity of ETR with ET1 is much higher than that with ET3, while the binding affinities of ETR with the two ETs are similar. Recently, the structures of ETR with ET1 and ET3 were determined. These crystal structures provide detailed descriptions of how ETR interacts with ET1 and ET3. However, the knowledge of how ETR recognizes the two isopeptides is still lacking. Based on the structure of ETR in complex with ET1, the structures of ETR with ET1 and ET3 were modeled. Then, molecular dynamics simulations were performed to study how ETR discriminates the two ETs. Simulation results demonstrate that ET1 has greater binding free energy with ETR than ET3, which is in agreement with the binding affinity data of ETR. By interaction energy analysis, the key residues of ETR that discriminate between ET1 and ET3 are identified. Structural and dynamical analyses indicate that, compared with ET3, ET1 is more stable in binding with ETR. Furthermore, the orientation change of W319 in the conserved CWxP motif that plays an important role in the signaling function of GPCRs was observed. Through the orientation change of this residue, the difference in the orthosteric pocket volume resulting from the binding of ET1 and ET3 on the extracellular side of ETR leads to a conformational difference of TM6 on the intracellular side of ETR. This study elucidates the molecular mechanism of how ETR selects the isopeptides ET1 and ET3.
内皮素-1 和 -3（ET1 和 ET3）是两种强效的血管收缩异构肽，参与多种疾病的病理生理学过程，如心血管疾病和肾脏疾病。这两种 ET 通过与两种 G 蛋白偶联受体（GPCR），即内皮素 ET 受体（ETR）和内皮素 ET 受体（ETR）结合发挥作用。ETR 和 ETR 在识别这两种 ET 时表现出不同的偏好：ETR 与 ET1 的结合亲和力远高于 ET3，而 ETR 与这两种 ET 的结合亲和力相似。最近，ETR 与 ET1 和 ET3 的结构已被确定。这些晶体结构提供了 ETR 如何与 ET1 和 ET3 相互作用的详细描述。然而，关于 ETR 如何识别这两种异构肽的知识仍然缺乏。基于 ETR 与 ET1 复合物的结构，构建了 ETR 与 ET1 和 ET3 的结构模型。然后，进行了分子动力学模拟，以研究 ETR 如何区分这两种 ET。模拟结果表明，ET1 与 ETR 的结合自由能大于 ET3，这与 ETR 的结合亲和力数据一致。通过相互作用能分析，确定了 ETR 中区分 ET1 和 ET3 的关键残基。结构和动力学分析表明，与 ET3 相比，ET1 与 ETR 的结合更稳定。此外，观察到在保守的 CWxP 基序中起重要作用的 W319 残基的取向变化，该基序在 GPCR 的信号转导功能中发挥作用。通过该残基的取向变化，ET1 和 ET3 结合导致 ETR 细胞外侧变构口袋体积的差异，导致 ETR 细胞内侧 TM6 的构象差异。这项研究阐明了 ETR 选择异构肽 ET1 和 ET3 的分子机制。
