MRGPRX2 facilitates IgE-mediated systemic anaphylaxis in a newly established knock-in mouse model

Maram Bawazir; Sangita Sutradhar; Saptarshi Roy; Hydar Ali

doi:10.1016/j.jaci.2024.11.021

MRGPRX2 facilitates IgE-mediated systemic anaphylaxis in a newly established knock-in mouse model

J Allergy Clin Immunol. 2024 Nov 22:S0091-6749(24)01238-7. doi: 10.1016/j.jaci.2024.11.021. Online ahead of print.

Authors

Maram Bawazir¹, Sangita Sutradhar², Saptarshi Roy², Hydar Ali³

Affiliations

¹ Department of Basic and Translational Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pa; Department of Oral Diagnostic Sciences, Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi Arabia. Electronic address: mmbawazir@kau.edu.sa.
² Department of Basic and Translational Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pa.
³ Department of Basic and Translational Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pa. Electronic address: alih@upenn.edu.

PMID: 39581296
DOI: 10.1016/j.jaci.2024.11.021

Abstract

Background: In addition to FcεRI, a subtype of human mast cells (MCs) expresses Mas-related G protein-coupled receptor X2 (MRGPRX2; mouse counterpart MrgprB2). Although MrgprB2 contributes to IgE-mediated passive systemic anaphylaxis (PSA) in vivo, an MRGPRX2 inhibitor, compound 9 (C9), does not block MrgprB2- or IgE-mediated MC degranulation in vitro.

Objective: Our aim was to generate mice expressing human MRGPRX2 to study receptor function in vitro and PSA in vivo.

Methods: The clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9-mediated gene editing approach was utilized to replace endogenous MrgprB2 with human MRGPRX2 in mice (MRGPRX2-KI mice). MRGPRX2 expression in the skin, gingiva, trachea, and colon were evaluated by using an anti-human MRGPRX2 antibody. Peritoneal MCs (PMCs) cultured from wild-type, MRGPRX2-KI, and MrgprB2^-/- mice were used to study agonists-induced degranulation. The effects of selective MRGPRX2 inhibitors (C9 and compound 9-6 [C9-6]) on substance P- or IgE-mediated MC degranulation in vitro and IgE-mediated PSA in vivo were tested.

Results: MRGPRX2-expressing MCs were present in tissues of MRGPRX2-KI mice. Most of the agonists tested induced greater degranulation at lower concentrations in PMCs from MRGPRX2-KI mice than in cells from wild-type mice. Furthermore, C9 and C9-6 inhibited degranulation in MRGPRX2-KI PMCs in response to substance P. In contrast, they had no effect on IgE-mediated degranulation in vitro but did inhibit PSA in MRGPRX2-KI mice in vivo.

Conclusions: MRGPRX2-KI mice provide a readily available source of primary MCs for signaling studies. Furthermore, transactivation of MRGPRX2 contributes to IgE-mediated PSA, suggesting that MRGPRX2-KI mice could be utilized as a preclinical model for testing novel therapeutics targeting MRGPRX2 and its cross talk with FcεRI.

Keywords: FcεRI; LL-37; MRGPRX2; MRGPRX2 knock-in; Mast cells; Substance P; anaphylaxis.