ASSOCIATION OF IMMUNOGLOBULIN-G FC RECEPTOR-II WITH SRC-LIKE PROTEIN-TYROSINE KINASE FGR IN NEUTROPHILS

The interaction of Fc receptors with antibody-antigen complexes activates multiple biological functions in hematopoietic cells. Recently, protein-tyrosine phosphorylation has been suggested to be involved in Fc receptor-mediated cell signaling. Here we show that the Src-like protein-tyrosine kinase Fgr, which is specifically expressed in mature myelomonocytic cells, coimmunoprecipitates with IgG Fc receptor II (FcgammaRII), but not with FcgammaRIII from detergent lysates of human peripheral neutrophils. Crosslinking of FcgammaRII induced a rapid increase in the tyrosine kinase activity and comodulation of Fgr. These results suggest that Fgr is physically and functionally associated with FcgammaRII and involved in FcgammaRII-mediated signal transduction pathways.