Tyrosine phosphorylation of a gamma-chain homodimer associated with Fc gamma RIII (CD16) in cultured human monocytes.
The efficient expression of transmembrane-anchored Fc gamma RIIIa requires the presence of other peptides, such as the gamma-chain of the IgE receptor I or the zeta-chain of the TCR. We found that Fc gamma RIIIa in cultured human monocytes is specifically associated with the gamma-chain homodimer, and that the gamma-chains in this complex are phosphorylated on tyrosine residues. Anti-Fc gamma RIII immunoprecipitates, which were prepared from 1% digitonin lysates of cultured human monocytes, incorporated phosphate into a homodimer consisting of two 14-kDa polypeptides when incubated with [gamma-32P]ATP. Identity of this co-associated structure of Fc gamma RIIIa as the gamma-chain dimer was confirmed by elution of the protein from the anti-Fc gamma RIII immunoabsorbent with 1% Nonidet P-40 detergent and reimmunoprecipitation with anti-gamma-chain antibody. Phosphoamino acid analysis showed that the gamma-chain exclusively contained phosphotyrosine. The gamma-chain was also phosphorylated when electropermeabilized cells were activated by cross-linking Fc gamma RIIIa. The gamma-chain may play an important role in signal transduction via Fc gamma RIIIa in human macrophages.
Masuda
M
M
Central Laboratory of The Netherlands Red Cross Blood Transfusion Service, Amsterdam.
Verhoeven
A J
AJ
Roos
D
D
D002478:Cells, Cultured; D006801:Humans; D009000:Monocytes / Q000378:metabolism*; D010766:Phosphorylation; D017452:Receptors, IgG / Q000737:chemistry / Q000378:metabolism*; D015398:Signal Transduction; D014443:Tyrosine / Q000378:metabolism*
D017452:Receptors, IgG; D014443:Tyrosine