Abstract

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 Ca 2+ 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.