Functional Impact of MRGPRX2 Single-Nucleotide Polymorphisms on Drug-Induced Cellular Responses In Vitro

Background: Recent evidence indicates that the Mas-related G protein–coupled receptor X2 (MRGPRX2) can be activated by several drugs, including neuromuscular blocking agents, fluoroquinolones, and vancomycin. However, the contribution of this mechanism to drug hypersensitivity reactions (DHRs) observed in clinical practice remains incompletely understood. Single-nucleotide polymorphisms (SNPs) in the MRGPRX2 gene may alter receptor reactivity and thereby influence drug tolerance. In this study, we investigated whether selected SNPs—previously described in patients with DHRs (N62S, S313R), known but not previously tested with drugs (S325L, E164R), and predicted in silico (W248L)—affect in vitro responses to representative drug ligands. Methods: RBL-2H3 cells were transiently transfected with wild-type (WT) MRGPRX2 or its variants. Cell-surface expression of MRGPRX2 was assessed by flow cytometry. Intracellular calcium mobilization was measured after stimulation with ciprofloxacin, atracurium, and vancomycin; substance P served as a reference agonist and assay buffer as a negative control. Results: All variants exhibited comparable levels of cell-surface expression. No responses were observed in the presence of assay buffer. The S313R and S325L variants showed responses comparable to WT, with a tendency toward enhanced responses to substance P. In contrast, the E164R variant displayed a loss-of-function phenotype (p < 0.05 for all ligands vs. WT, S313R, and S325L variants), as did the in silico-predicted W248L variant (p < 0.05 for all ligands vs. WT, S313R, and S325L variants). The N62S variant demonstrated slightly reduced responses to the tested agonists compared with WT. Conclusions: Our findings indicate that under the investigated experimental conditions with ciprofloxacin, atracurium, and vancomycin: (1) N62S-transfected RBL-2H3 cells did not exhibit enhanced responses to the tested drug ligands; (2) the W248L variant exhibited the predicted loss-of-function phenotype, suggesting that in silico modeling may help assess the pathogenicity of specific MRGPRX2 variants; and (3) the remaining variants showed only partial concordance with previously published data, possibly reflecting differences in experimental design or assay conditions and highlighting the need for replication studies.