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Regulation of C3a receptor signaling in human mast cells by G protein coupled receptor kinases.

Abstract

BACKGROUND

The complement component C3a activates human mast cells via its cell surface G protein coupled receptor (GPCR) C3aR. For most GPCRs, agonist-induced receptor phosphorylation leads to receptor desensitization, internalization as well as activation of downstream signaling pathways such as ERK1/2 phosphorylation. Previous studies in transfected COS cells overexpressing G protein coupled receptor kinases (GRKs) demonstrated that GRK2, GRK3, GRK5 and GRK6 participate in agonist-induced C3aR phosphorylation. However, the roles of these GRKs on the regulation of C3aR signaling and mediator release in human mast cells remain unknown.

METHODOLOGY/PRINCIPAL FINDINGS

We utilized lentivirus short hairpin (sh)RNA to stably knockdown the expression of GRK2, GRK3, GRK5 and GRK6 in human mast cell lines, HMC-1 and LAD2, that endogenously express C3aR. Silencing GRK2 or GRK3 expression caused a more sustained Ca(2+) mobilization, attenuated C3aR desensitization, and enhanced degranulation as well as ERK1/2 phosphorylation when compared to shRNA control cells. By contrast, GRK5 or GRK6 knockdown had no effect on C3aR desensitization, but caused a significant decrease in C3a-induced mast cell degranulation. Interestingly, GRK5 or GRK6 knockdown rendered mast cells more responsive to C3a for ERK1/2 phosphorylation.

CONCLUSION/SIGNIFICANCE

This study demonstrates that GRK2 and GRK3 are involved in C3aR desensitization. Furthermore, it reveals the novel finding that GRK5 and GRK6 promote C3a-induced mast cell degranulation but inhibit ERK1/2 phosphorylation via C3aR desensitization-independent mechanisms. These findings thus reveal a new level of complexity for C3aR regulation by GRKs in human mast cells.

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  • Authors+Show Affiliations

    ,

    Department of Pathology, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.

    , ,

    Source

    PloS one 6:7 2011 pg e22559

    MeSH

    Cell Degranulation
    Cell Line
    Complement C3a
    G-Protein-Coupled Receptor Kinases
    Gene Knockdown Techniques
    Humans
    Lentivirus
    Mast Cells
    Mitogen-Activated Protein Kinase 1
    Mitogen-Activated Protein Kinase 3
    Phosphorylation
    Protein Transport
    RNA, Small Interfering
    Receptors, Complement
    Signal Transduction

    Pub Type(s)

    Journal Article
    Research Support, N.I.H., Extramural

    Language

    eng

    PubMed ID

    21799898