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Updated: Nov 22, 2025
Isolation of Peritoneum-derived Mast Cells and Their Functional Characterization with Ca2+-imaging and Degranulation Assays
Published on: July 4, 2018
Inflamed Ulcerative Colitis Regions Associated With MRGPRX2-Mediated Mast Cell Degranulation and Cell Activation
Ernie Chen1, Ling-Shiang Chuang1, Mamta Giri1
1The Charles Bronfman Institute for Personalized Medicine, Icahn School of Medicine at Mount Sinai, New York; Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York.
Background & Aims:
Recent literature has implicated a key role for mast cells in murine models of colonic inflammation, but their role in human ulcerative colitis (UC) is not well established. A major advance has been the identification of mrgprb2 (human orthologue, MRGPX2) as mediating IgE-independent mast cell activation. We sought to define mechanisms of mast cell activation and MRGPRX2 in human UC.
Methods:
Colon tissues were collected from patients with UC for bulk RNA sequencing and lamina propria cells were isolated for MRGPRX2 activation studies and single-cell RNA sequencing. Genetic association of all protein-altering G-protein coupled receptor single-nucleotide polymorphism was performed in an Ashkenazi Jewish UC case-control cohort. Variants of MRGPRX2 were transfected into Chinese hamster ovary (CHO) and human mast cell (HMC) 1.1 cells to detect genotype-dependent effects on β-arrestin recruitment, IP-1 accumulation, and phosphorylated extracellular signal-regulated kinase.
Results:
Mast cell-specific mediators and adrenomedullin (proteolytic precursor of PAMP-12, an MRGPRX2 agonist) are up-regulated in inflamed compared to uninflamed UC. MRGPRX2 stimulation induces carboxypeptidase secretion from inflamed UC. Of all protein-altering GPCR alleles, a unique variant of MRGPRX2, Asn62Ser, was most associated with and was bioinformatically predicted to alter arrestin recruitment. We validated that the UC protective serine allele enhances β-arrestin recruitment, decreases IP-1, and increases phosphorylated extracellular signal-regulated kinase with MRGPRX2 agonists. Single-cell RNA sequencing defines that adrenomedullin is expressed by activated fibroblasts and epithelial cells and that interferon gamma is a key upstream regulator of mast cell gene expression.
Conclusion:
Inflamed UC regions are distinguished by MRGPRX2-mediated activation of mast cells, with decreased activation observed with a UC-protective genetic variant. These results define cell modules of UC activation and a new therapeutic target.
Insights
Mast cells and MRGPRX2 are key in ulcerative colitis (UC) inflammation. A protective genetic variant of MRGPRX2 reduces mast cell activation, offering a potential therapeutic target for UC.
Area of Science:
- Gastroenterology
- Immunology
- Genetics
Background:
- Mast cells are implicated in murine colonic inflammation, but their role in human ulcerative colitis (UC) remains unclear.
- The identification of MRGPRX2 (human orthologue of mrgprb2) as a mediator of IgE-independent mast cell activation is a significant advance.
- Understanding mast cell activation mechanisms and MRGPRX2's role in human UC is crucial.
Purpose of the Study:
- To define the mechanisms of mast cell activation in human UC.
- To investigate the role of MRGPRX2 in UC pathogenesis.
- To identify potential therapeutic targets for UC.
Main Methods:
- Colon tissues from UC patients were analyzed using bulk and single-cell RNA sequencing.
- Lamina propria cells were isolated for MRGPRX2 activation studies.
- Genetic association studies of GPCR single-nucleotide polymorphisms were performed in an Ashkenazi Jewish UC cohort, with MRGPRX2 variants functionally validated in cell lines.
Main Results:
- Mast cell mediators and adrenomedullin are upregulated in inflamed UC tissues.
- MRGPRX2 stimulation in inflamed UC leads to carboxypeptidase secretion.
- A UC-protective MRGPRX2 variant (Asn62Ser) enhances beta-arrestin recruitment and alters downstream signaling, while adrenomedullin is expressed by activated fibroblasts and epithelial cells.
Conclusions:
- Inflamed UC tissues exhibit MRGPRX2-mediated mast cell activation.
- A UC-protective genetic variant of MRGPRX2 is associated with decreased mast cell activation.
- These findings highlight specific cellular pathways in UC and identify MRGPRX2 as a potential therapeutic target.
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