Roles of the transmembrane domain and the cytoplasmic domain of Fc?RI? in immunoglobulin E-mediated up-regulation of surface Fc?RI expression

Summary Background Human mast cells express both FcɛRIα and FcγRIα. IgE up-regulates FcɛRIα expression, but IgG1 does not up-regulate FcγRIα expression. The transmembrane domain (TM) of FcγRIα determines the stability of cell surface expression of this receptor. Objective The aim of this study was to clarify the roles of the TM and cytoplasmic domain (CY) of FcɛRIα in IgE-mediated FcɛRI up-regulation. Methods Chimeric receptors created by domain shuffling between FcɛRIα and FcγRIα were transduced into human mast cell line HMC-1. Cell surface expression of the chimeric receptors and the effect of IgE or IgG1 on chimeric receptor expression were examined by FACS. The association of the chimeric receptors with FcRγ was investigated by immunoprecipitation. Results The results showed that the TM and CY of FcɛRIα are not essential for IgE-mediated up-regulation of surface FcɛRI. Conclusion The extracellular domain of each Fc receptor determines the diversity of Ig-regulated Fc receptor expression.