Substance p serves as a balanced agonist for mrgprx2 and a single tyrosine residue is required for β‐arrestin recruitment and receptor internalization

Abstract

The neuropeptide substance P (SP) mediates neurogenic inflammation and pain and contributes to atopic dermatitis in mice through the activation of mast cells (MCs) via Mas‐related G protein‐coupled receptor (GPCR)‐B2 (MrgprB2, human ortholog MRGPRX2). In addition to G proteins, certain MRGPRX2 agonists activate an additional signaling pathway that involves the recruitment of β‐arrestins, which contributes to receptor internalization and desensitization (balanced agonists). We found that SP caused β‐arrestin recruitment, MRGPRX2 internalization, and desensitization. These responses were independent of G proteins, indicating that SP serves as a balanced agonist for MRGPRX2. A tyrosine residue in the highly conserved NPxxY motif contributes to the activation and internalization of many GPCRs. We have previously shown that Tyr279 of MRGPRX2 is essential for G protein‐mediated signaling and degranulation. To assess its role in β‐arrestin‐mediated MRGPRX2 regulation, we replaced Tyr279 in the NPxxY motif of MRGPRX2 with Ala (Y279A). Surprisingly, we found that, unlike the wild‐type receptor, Y279A mutant of MRGPRX2 was resistant to SP‐induced β‐arrestin recruitment and internalization. This study reveals the novel findings that activation of MRGPRX2 by SP is regulated by β‐arrestins and that a highly conserved tyrosine residue within MRGPRX2’s NPxxY motif contributes to both G protein‐ and β‐arrestinmediated responses.