The high-affinity IgE receptor, FcεRI, which is composed of α-, β-, and γ-subunits, plays an important role in IgE-mediated allergic responses. TGF-β1 has been reported to suppress FcεRI and stem cell factor receptor c-Kit expression on mast cell surfaces and to suppress mast cell activation induced by cross-linking of FcεRI. However, the molecular mechanism by which these expressions and activation are suppressed by TGF-β1 remains unclear. In this study, we found that the expression of Ets homologous factor (Ehf) is significantly up-regulated by TGF-β1 in mouse bone marrow-derived mast cells (BMMCs). But the roles of Ehf in mast cells has not been reported. Here, we show that the transcription factor Ehf contributes to TGF-β1 induced suppression of FceRI and c-Kit expression, and FceRI-mediated activation, through down-regulation of GATA-1, GATA-2, and Stat5 expression in mast cells.
BMMCs were generated by culturing bone marrow cells isolated from BALB/c mice . Two-weeks cultured bone marrow cells were cultured in BMMC medium in the presence of SCF, and recombinant murine IL-9 with or without recombinant human TGF-β1. Two-weeks cultured bone marrow cells were cultured for a further 14 days in media containing IL-3/SCF/IL-9/TGF-β1 , or were transfected with a retroviral vector or lentiviral vector encoding the FLAG-tagged mouse Ehf or siEhf gene or mock vector.
TGF-β1 suppresses the expression of the transcription factors GATA-1, GATA-2, and PU.1, which are positive regulators of the transcription of genes encoding FcεRIα, FcεRIβ, and c-Kit, in mouse bone marrow-derived mast cells (BMMCs). In addition, the expression of Ets homologous factor (Ehf), a member of the Ets family of transcriptional factors, is up-regulated by TGF-β/Smad signaling in BMMCs. Forced expression of Ehf repressed the transcription of genes encoding FcεRIα, FcεRIβ, and c-Kit, resulting in a reduction in cell surface expressions of FcεRI and c-Kit. Furthermore, forced expression of Ehf suppressed FcεRI-mediated degranulation and IL-6 and IL-13 production. The mRNA levels of Gata1, Gata2, and Stat5b were lower in BMMCs stably expressing Ehf compared with control cells.
TGF-β1 suppresses FcεRI and c-Kit expression, and suppresses FcεRI-mediated activation, through up-regulation of Ehf in mast cells.