Determinants of the phagocytic signal mediated by the type IIIA Fc gamma receptor, XXXX : sequence requirements and interaction with protein- @entity669 kinases.

@entity1522 @entity10255 @entity4071 @entity669 @entity6755
The Fc gamma receptor-associated gamma and zeta subunits contain a conserved cytoplasmic motif, termed the immunoglobulin gene @entity669 activation motif, which contains a pair of YXXL sequences. The @entity669 residues within these YXXL sequences have been shown to be required for transduction of a phagocytic signal. We have previously reported that the gamma subunit of the type IIIA Fc gamma receptor ( @entity4071 ) is approximately 6 times more efficient in mediating phagocytosis than the zeta subunit of @entity4071 . By exchanging regions of the cytoplasmic domains of the homologous gamma and zeta chains, we observed that the cytoplasmic area of the gamma chain bearing a pair of the conserved YXXL sequences is important in phagocytic signaling. Further specificity of phagocytic signaling is largely determined by the two internal XX @entity1522 in the YXXL sequences. In contrast, the flanking @entity1522 of the YXXL sequences including the seven intervening @entity1522 between the two YXXL sequences do not significantly affect the phagocytic signal. Furthermore, the protein- @entity669 kinase @entity10255 , but not the related kinase @entity6755 , stimulated @entity4071 -mediated phagocytosis. @entity6755 , however, increased phagocytosis when coexpressed with the Src family kinase Fyn. These data demonstrate the importance of the two specific @entity1522 within the gamma subunit YXXL cytoplasmic sequences in phagocytic signaling and explain the difference in phagocytic efficiency of the gamma and zeta chains. These results indicate the importance of @entity10255 in @entity4071 -mediated phagocytosis and demonstrate that @entity6755 and @entity10255 differ in their requirement for a Src-related kinase in signal transduction.
