G Protein Coupled Receptor Kinase 2 (GRK2): A Novel Regulator of FcεRI-mediated Mast Cell Responses.

Monica Thapaliya

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Thapaliya, Monica, Ali, Hydar
University of Pennsylvania School of Dental Medicine, Department of Basic and Translational Sciences

Introduction

Aggregation of high affinity Immunoglobulin E (IgE) receptor (FcεRI) by allergen on mast cell results in the manifestation of allergic diseases such as allergic rhinitis, asthma, food allergy and eczema. Plethora of studies have reported G protein coupled receptor (GPCR) Kinase 2 (GRK2), a well-known regulator of GPCR, in the regulation of vascular function, immunity and inflammation. However, its role in allergic reaction is not understood. Utilizing shRNA-mediated knockdown and retroviral overexpression, it is reported that GRK2 regulates FcεRI in vitro, despite being a non-GPCR. However, the physiological relevance of this finding and the in vivo implication is not known. Thus, this study is aimed at elucidating the role of GRK2 in mast cell mediated allergic response in physiologically relevant murine system.

Methods

GRK2 global knockout is embryonic lethal. Thus, mast cell specific GRK2 knockout mice were generated via Cre-Lox breeding. Using primary lung mast cells from these mice, the role of GRK2 in both FcεRI-induced early mast cell response (degranulation via βeta-hexosaminidase release and Lysosomal-associated membrane protein 1 (LAMP-1) expression) and late mast cell response (cytokine/chemokine: IL13/CCL3 generation via ELISA) was tested. Furthermore, the role if GRK2 was tested in vivo using mast cell mediated passive cutaneous anaphylaxis model.

Results

We found that both early and late FcεRI-induced mast cell responses are significantly reduced in GRK2 knockout lung mast cells compared to control. As expected, we found that FcεRI- induced vascular permeability (a measure of degranulation readout in vivo) in passive cutaneous anaphylaxis model is also significantly reduced in GRK2 knockout mice compared to control. These findings show that GRK2 positively modulates FcεRI response both in vitro and in vivo.

Conclusion

GRK2 promotes FcεRI-mediated allergic response in mast cells.