Clustering of the high affinity Fc receptor for immunoglobulin G (Fc gamma RI) results in phosphorylation of its associated gamma-chain.
We are investigating the role of gamma-chain in functions mediated by the high affinity Fc receptor for IgG (Fc gamma RI). In a previous study, we found that gamma-chain, which is a member of the family of zeta-chain proteins, associates with Fc gamma RI. Here we show that clustering of Fc gamma RI leads to a rapid and transient tyrosine phosphorylation of gamma-chain in U937 cells. The response was limited to Fc gamma RI activation, and no phosphorylation of gamma-chain was observed after cross-linking of monoclonal antibodies to other surface receptors on these cells. The gamma-chain phosphorylated after Fc gamma RI clustering was the gamma-chain associated with the receptor. We also identified Syk as one of the kinases associated with the receptor complex. Upon Fc gamma RI activation, Syk, but not ZAP-70, was phosphorylated, and reimmunoadsorption experiments of phosphoproteins from immune complex in vitro kinase assays indicated that Syk is part of the activated gamma-chain-Fc gamma RI complex. These results suggest that gamma-chain links Fc gamma RI to intracellular transduction pathways.
Duchemin
A M
AM
Department of Internal Medicine, Ohio State University College of Medicine, Columbus 43210.
Ernst
L K
LK
Anderson
C L
CL
D000255:Adenosine Triphosphate / Q000378:metabolism; D000911:Antibodies, Monoclonal; D015153:Blotting, Western; D002460:Cell Line; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism*; D046911:Macromolecular Substances; D010766:Phosphorylation; D019000:Phosphotyrosine; D017452:Receptors, IgG / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000032:analysis / Q000378:metabolism
D000911:Antibodies, Monoclonal; D007074:Immunoglobulin G; D046911:Macromolecular Substances; D017452:Receptors, IgG; D019000:Phosphotyrosine; D014443:Tyrosine; D000255:Adenosine Triphosphate