By releasing multiple pro-inflammatory mediators upon activation, mast cells are critical effector cells in the pathogenesis of allergic inflammation. The traditional viewpoint of antigen-dependent mast cell activation is that of a Th 2 -driven process whereby antigen-specific IgE molecules are produced by B cells followed by binding of the IgE to high affinity IgE receptors (FcεRI) expressed on mast cells. Subsequent antigen-dependent aggregation of the FcεRI initiates an intracellular signalling cascade that culminates in mediator release. Mast cell responses, including cell growth, survival, chemotaxis, and cell adhesion, however, can also be regulated by other receptors expressed on mast cells. Furthermore, FcεRI-mediated mast cell mediator release can be significantly modified by ligation of specific classes of these receptors. One such class of receptors is the G protein-coupled receptors (GPCR). In this review, we describe how sub-populations of GPCRs can either enhance or inhibit FcεRI-mediated mast cell activation depending on the particular G protein utilized for relaying signalling. Furthermore, we discuss the potential mechanisms whereby the signalling responses utilized by the FcεRI for mast cell activation are influenced by those initiated by GPCRs to produce these diverse responses.
KeywordsMast cells; FcεRI; G protein-coupled receptors; IgE; antigen; signalling
Mast cell activationMast cells play a role in both the innate and adaptive immune responses which contribute to the body's defence mechanisms against invading pathogens and parasites [1][2][3]. However, when mast cells are inappropriately activated following antigen exposure, the resulting release of multiple pro-inflammatory mediators leads to the initiation of the clinical manifestations associated with allergic inflammation [4]. This response occurs as a consequence of the antigen binding to IgE molecules which occupy high affinity receptors for IgE (FcεRI) on the mast cell surface and resulting cross-linking of these receptors [5,6]. FcεRI aggregation induces a cascade of intracellular signalling events which lead to the rapid release of histamine and proteolytic enzymes, as a consequence of degranulation, and the release of leukotrienes (LTs) and prostaglandins (PGs), as a result of phospholipase A 2 (PLA 2 )-mediated phospholipid hydrolysis [4,7]. Following enhanced gene expression, a variety of cytokines and chemokines * To whom correspondence be addressed: agilfillan@niaid.nih.gov, Bldg 10, Room 11C206, LAD, NIAID, NIH, 10 Center Drive, Bethesda, USA, MD 20892-1881, Phone: 301 496 8757, Fax: 301 480 8384. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the...