FcεRIγ-ITAM Is Differentially Required for Mast Cell Function In Vivo

Abstract

The cross-linking of IgE-bound FcεRI by Ags triggers mast cell activation leading to allergic reactions. The in vivo contribution of FcεRIγ signaling to IgE/FcεRI-mediated mast cell responses has not yet been elucidated. In this study FcεRIγ−/− mast cells were reconstituted with either wild-type or mutant FcεRIγ in transgenic mice and transfected mast cells in vitro. We demonstrate that FcεRIγ-immunoreceptor tyrosine-based activation motif is essential for degranulation, cytokine production, and PG synthesis as well as for passive systemic anaphylaxis. Recent reports have suggested that cell surface FcεRI expression and mast cell survival are regulated by IgE in the absence of Ag, although the molecular mechanism is largely unknown. We also found that the promotion of mast cell survival by IgE without Ags is mediated by signals through the FcεRIγ-immunoreceptor tyrosine-based activation motif. In contrast, the IgE-mediated up-regulation of FcεRI is independent of FcεRIγ signaling. These results indicate that FcεRIγ-mediated signals differentially regulate the receptor expression, activation, and survival of mast cells and systemic anaphylaxis.

Signaling pathways activated by a protease allergen in basophils

“…The wild-type and mutant constructs of FcRγ were designed similarly to those published previously (24,49) and as we have described in a recent publication (27). The wild-type FcRγ sequence was isolated using basophil cDNA for the PCR.…”

Leukotriene B4 Augments and Restores FcγRs-dependent Phagocytosis in Macrophages

“…1. The YF mutant is deficient in transducing the signals induced by FcR␥ in mast cells and basophils, but surface expression of FcRs remains intact (25,26). Phagocytosis in cells expressing WT FcR␥ was readily apparent and was further enhanced by LTB 4 (Fig.…”

“…Retroviral Transfection-cDNAs encoding WT and mutant (YF) FcR␥ in pMX-IRES-rCD2 were transiently transfected into the packaging cell line, Phoenix (25,26). The cultured media were collected and used as viral suspensions.…”

Fc receptor γ-chain, a constitutive component of the IL-3 receptor, is required for IL-3-induced IL-4 production in basophils

“…4a). The ITAM of FcRγ is known to be dispensable for the transport of FcεRI to the cell surface in mast cells 32 . Consistently, when introduced retrovirally into FcRγ-deficient BM-derived basophils, both wild-type FcRγ and FcRγ-∆ITAM restored the expression of FcεRI on the cell surface to the similar levels, mirroring the comparable levels of wild-type and the mutant FcRγ (Fig.…”

“…6c online) and a control sequence (5'-TCTTAATCGCGTATAAGGC-3') were used as target sequences together with their respective antisense sequences to construct the retrovirus vectors expressing shRNA based on pSINsi-mU6 that contained a neomycin-resistant cassette (TAKARA Bio). The cDNAs encoding wild-type and ITAM mutant FcRγ (FcRγ-∆ITAM) were previously described 32 . SpeI-NotI-excised cDNA fragments expressing full-length or ∆ITAM FcRγ were inserted into pMX-IRES-rCD2 vector.…”