Suzuki K, Hirose T, Matsuda H, Hasegawa S, Okumura K, Ra C
Department of Immunology, Juntendo University School of Medicine, Tokyo, Japan.
Mol Immunol. 1998 Apr;35(5):259-70. doi: 10.1016/s0161-5890(98)00047-9.
The Fc receptor (FcR) gamma subunit was originally discovered as a homodimeric subunit of the high-affinity IgE receptor (FcepsilonRI). But it was recently found to be a common signal-generating subunit of Fc receptors including IgG Fc receptors (FcgammaRs) and IgA Fc receptor (FcalphaR), and furthermore to generate a signal also with stimuli through non-immune receptors. In addition, it plays an essential role in cell-surface expression of the FcepsilonRI and the FcgammaRIIIA isoform and also regulates cell-surface expression and ligand-binding affinity of the FcgammaRI. In this report, we addressed the possibility that the FcRgamma could affect the correct folding of the IgE-binding region of the FcepsilonRIalpha subunit by using the chimeric receptor molecules constructed from human FcepsilonRIalpha and FcRgamma. Furthermore, we demonstrated that the seven amino acid residues in the C-terminal region on the extracellular domain of the FcepsilonRlalpha were essential for maintaining the IgE-binding activity of the FcepsilonRIalpha exodomain on the cell membrane and/or may affect the correct folding of the alpha subunit itself within the cell.
Fc受体（FcR）γ亚基最初被发现是高亲和力IgE受体（FcepsilonRI）的同二聚体亚基。但最近发现它是包括IgG Fc受体（FcgammaRs）和IgA Fc受体（FcalphaR）在内的Fc受体的共同信号产生亚基，此外，它还能通过非免疫受体的刺激产生信号。此外，它在FcepsilonRI和FcgammaRIIIA异构体的细胞表面表达中起重要作用，还调节FcgammaRI的细胞表面表达和配体结合亲和力。在本报告中，我们通过使用由人FcepsilonRIalpha和FcRgamma构建的嵌合受体分子，探讨了FcRgamma是否会影响FcepsilonRIalpha亚基IgE结合区域正确折叠的可能性。此外，我们证明，FcepsilonRlalpha细胞外结构域C末端区域的七个氨基酸残基对于维持细胞膜上FcepsilonRIalpha胞外域的IgE结合活性至关重要，和/或可能影响细胞内α亚基自身的正确折叠。
