The Transcription Factor Ehf Is Involved in TGF-β–Induced Suppression of FcεRI and c-Kit Expression and FcεRI-Mediated Activation in Mast Cells

FceRI, 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 FceRI and stem cell factor receptor c-Kit expression on mast cell surfaces and to suppress mast cell activation induced by cross-linking of FceRI. 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), a member of the Ets family transcriptional factors, is upregulated by TGF-β/Smad signaling in mouse bone marrow–derived mast cells (BMMCs). Forced expression of Ehf in BMMCs repressed the transcription of genes encoding FceRIα, FceRIβ, and c-Kit, resulting in a reduction in cell surface FceRI and c-Kit expression. Additionally, forced expression of Ehf suppressed FceRI-mediated degranulation and cytokine production. Ehf inhibited the promoter activity of genes encoding FceRIα, FceRIβ, and c-Kit by binding to these gene promoters. Furthermore, the mRNA levels of Gata1 , Gata2 , and Stat5b were lower in BMMCs stably expressing Ehf compared with control cells. Because GATA-1 and GATA-2 are positive regulators of FceRI and c-Kit expression, decreased expression of GATAs may be also involved in the reduction of FceRI and c-Kit expression. Decreased expression of Stat5 may contribute to the suppression of cytokine production by BMMCs. In part, mast cell response to TGF-β1 was mimicked by forced expression of Ehf, suggesting that TGF-β1 suppresses FceRI and c-Kit expression and suppresses FceRI-mediated activation through upregulation of Ehf.