Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, 3052, Australia.
Australian Research Council Centre for Cryo-Electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, 3052, Australia.
Nat Commun. 2023 Sep 6;14(1):5440. doi: 10.1038/s41467-023-41199-5.
The M muscarinic acetylcholine receptor (M mAChR) has emerged as a drug target of high therapeutic interest due to its expression in regions of the brain involved in the regulation of psychosis, cognition, and addiction. The mAChR agonist, xanomeline, has provided significant improvement in the Positive and Negative Symptom Scale (PANSS) scores in a Phase II clinical trial for the treatment of patients suffering from schizophrenia. Here we report the active state cryo-EM structure of xanomeline bound to the human M mAChR in complex with the heterotrimeric G transducer protein. Unexpectedly, two molecules of xanomeline were found to concomitantly bind to the monomeric M mAChR, with one molecule bound in the orthosteric (acetylcholine-binding) site and a second molecule in an extracellular vestibular allosteric site. Molecular dynamic simulations supports the structural findings, and pharmacological validation confirmed that xanomeline acts as a dual orthosteric and allosteric ligand at the human M mAChR. These findings provide a basis for further understanding xanomeline's complex pharmacology and highlight the myriad of ways through which clinically relevant ligands can bind to and regulate GPCRs.
M 毒蕈碱型乙酰胆碱受体（M mAChR）作为一种具有高治疗价值的药物靶点，已经引起了广泛关注，因为它在大脑中与调节精神分裂症、认知和成瘾相关的区域表达。mAChR 激动剂 xanomeline 在治疗精神分裂症患者的 II 期临床试验中，显著改善了阳性和阴性症状量表（PANSS）评分。在此，我们报告了 xanomeline 与人 M mAChR 与异三聚体 G 转导蛋白复合物的结合的活性状态冷冻电镜结构。出乎意料的是，发现了两个 xanomeline 分子同时结合到单体 M mAChR 上，一个分子结合在正位（乙酰胆碱结合）位点，另一个分子结合在细胞外前庭变构位点。分子动力学模拟支持结构发现，药理学验证证实 xanomeline 作为一种双重正位和变构配体，作用于人 M mAChR。这些发现为进一步了解 xanomeline 的复杂药理学提供了基础，并强调了临床上相关配体可以通过多种方式结合并调节 GPCR。
