ROLES OF MAST CELL G PROTEIN-COUPLED RECEPTOR KINASE 2 (GRK2) IN ALLERGY AND INFLAMMATION

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Degree type
PhD
Graduate group
Pharmacology
Discipline
Immunology and Infectious Disease
Pharmacology, Toxicology and Environmental Health
Subject
Allergy
Anaphylaxis
GRK2
Mast Cells
MrgprB2
Paroxetine
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Copyright date
01/01/2022
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Author
Thapaliya, Monica
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Abstract

In addition to high-affinity IgE receptor (FcεRI), a subtype of mast cells (MCs) found primarily in human skin, expresses a G protein-coupled receptor (GPCR) known as MRGPRX2 (mouse counterpart MrgprB2). Following agonist stimulation, GPCRs couple to G proteins to cause cellular activation but most receptors are also phosphorylated by GPCR Kinases (GRKs) to promote their desensitization. MCs express GRK2 but its role on the regulation of MRGPRX2/B2 and FcRI function has not been studied in detail. For the present study, we generated mice with MC-specific deletion of GRK2 and utilized GRK2 inhibitors to determine if it differentially regulates MrgprB2 and FcεRI-mediated MC activation in vitro to modulate vascular permeability, rosacea, cutaneous anaphylaxis, and itch in vivo. Utilizing peritoneal MCs (PMCs) that express MrgprB2, we showed that the absence of GRK2 resulted in enhanced β-hexosaminidase release in response to compound 48/80 (C48/80) but significantly reduced tryptase release in response to the Cathelicidin LL37. Furthermore, absence of GRK2 resulted in increased cutaneous vascular permeability in response to C48/80 in vivo. By contrast, LL37-injection induced rosacea-like erythema, generation of matrix metalloproteinase 9 (MMP9), chemokine, CXCL2, and the recruitment of MCs and inflammatory cells in control mice but these responses were substantially reduced in GRK2-deleted mice. IgE-mediated anaphylaxis and itch were also significantly reduced in the absence of GRK2. Furthermore, in vitro studies with primary lung-derived MCs, which do not express MrgprB2, demonstrated that GRK2 deletion resulted in a significant reduction of IgE-mediated tyrosine phosphorylation of STAT5, calcium mobilization, and degranulation. GRK2 inhibitors (paroxetine and its analog CCG258747) inhibited FcεRI-induced calcium mobilization and degranulation, and their intravenous administration in mice resulted in substantial reduction of IgE-mediated anaphylaxis. However, both compounds induced calcium mobilization and degranulation via MRGPRX2 and MrgprB2 in vitro, and increased cutaneous vascular permeability in vivo. These findings suggest that while GRK2 regulation in MrgprB2 is most likely agonist dependent, it promotes IgE-mediated anaphylaxis and itch likely via tyrosine phosphorylation of STAT5.

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Ali, Hydar
Date of degree
2022
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