Tyrosine phosphorylation and Fcγ receptor-mediated phagocytosis

AbstractPhagocytosis of IgG-opsonized particulate material in hematopoietic cells is mediated by Fcγ receptors (FcγRs). Interaction of the receptors with Fc domains of IgG triggers transduction of phagocytic signal in which a key role is played by phosphorylation of tyrosine residues of the receptors. These residues are arranged into a specific motif (immunoreceptor tyrosine-based activation motif; ITAM) which is located either in the cytoplasmic part of FcγRIIA or in γ chains associated with FcγRI and FcγRIIIA. The conserved tyrosine residues are phosphorylated by, and associate with, tyrosine kinases of Src and Syk families. Coordinated action of these components initiates numerous intracellular events leading finally to local rearrangement of the actin-based cytoskeleton and internalization of the particles