Fcγ receptors: Gene structure and receptor function

Abstract
Molecular studies of murine FcγR have revealed much exciting new information about the structure and regulation of FcγRI and FcγRII genes and of the FcγRI protein. The FcγRI gene is composed of six exons, whereas the FcγRII gene is composed of ten. The extracellular domains are encoded by individual exons in both genes (three in FcγRI and two in FcγRII); however, the FcγRII gene shows greatest complexity in the region encoding the cytoplasmic tail and membrane spanning region, which is encoded by four exons compared to only one in the FcγRI gene. Expression of FcγRII is controlled by elements within the first 641 bases upstream of the transcription initiation site. The function of the domains of FcγRI has been defined with the surprising finding that in the absence of the third domain the first two extracellular domains function as a broadly specific low affinity FcγRII-like receptor.