Mas-related G protein-coupled receptors (Mrgprs) are a newly discovered class of G protein-coupled receptors consisting of more than 50 members in recent years. MRGPRX1 can be activated by bovine adrenal medulla peptide 8–22 (BAM8–22), triggering Ca²⁺ influx and then causing pain and itch. It is very important for the discovery of analgesic and antipruritic drugs to elucidate the molecular mechanism of MRGPRX1 recognizing BAM8–22. Here, we identified the functional domains and residues of the receptor MRGPRX1 activating BAM8–22 through molecular model, mutation and living cell calcium imaging. The molecular docking predicted that BAM8–22 interacted with N-terminal, TM4, TM5, TM6 and ECL3 of MRGPRX1. Both ECL3 and TM6 domains were further revealed to play a critical role in the BAM8–22-induced MRGPRX1 activation, whereas TM3 region performed a secondary function. Moreover, the mutation F237A of MRGPRX1 completely lost the activation ability of BAM8–22. These results were consistent with the cryogenic electron microscopy (cryo-EM) structure of MRGPRX1-G_αq in complex with BAM8–22 reported most recently. Taken together, our work shows insights into the molecular mechanism of the interaction between the receptor MRGPRX1 and the peptide agonist BAM8–22, and will also provide some valuable clues for the design of analgesic and antipruritic drugs targeting MRGPRX1.

Mas相关G蛋白偶联受体(Mrgprs)是近年来新发现的一类G蛋白偶联受体，由50多个成员组成。MRGPRX1 可被牛肾上腺髓质肽 8-22 (BAM8-22) 激活，触发 Ca ²⁺流入然后引起疼痛和瘙痒。阐明MRGPRX1识别BAM8-22的分子机制对于镇痛止痒药物的发现非常重要。在这里，我们通过分子模型、突变和活细胞钙成像确定了激活 BAM8-22 的受体 MRGPRX1 的功能域和残基。分子对接预测 BAM8-22 与 MRGPRX1 的 N 端、TM4、TM5、TM6 和 ECL3 相互作用。进一步揭示 ECL3 和 TM6 结构域在 BAM8-22 诱导的 MRGPRX1 激活中起关键作用，而 TM3 区域执行次要功能。此外，MRGPRX1的突变F237A完全丧失了BAM8-22的激活能力。_{这些结果与 MRGPRX1-G αq}的低温电子显微镜 (cryo-EM) 结构一致与最近报道的 BAM8-22 复合。综上所述，我们的工作揭示了受体 MRGPRX1 与肽激动剂 BAM8-22 相互作用的分子机制，也将为靶向 MRGPRX1 的镇痛和止痒药物的设计提供一些有价值的线索。