Tyrosine phosphorylation and association of Fc gamma RII and p72(Syk) not limited to the Fc gamma RII signalling pathway

摘要

The tyrosine kinase p72(Syk) plays a critical role in platelet signal transduction. It associates with the platelet receptor for the Fc domain of IgGs, Fc gamma RII, following stimulation by Fc gamma RII cross-linking Here, we show that p72(Syk) and Fc gamma RII tyrosine phosphorylation and association occured following platelet stimulation by: (1) two monoclonal antibodies, which form a bridge between a target antigen and Fc gamma RII, and (2) the G-protein-coupled receptor agonist thrombin. The kinetics of the p72(Syk)/Fc gamma RII association depended on the signalling pathway (i.e., the antigen targeted or the thrombin receptor). We established a direct relationship between the level of Fc gamma RII phosphorylation and the detection of its association with p72(Syk). Inhibition of p72(Syk) by piceatannol resulted in partial or total inhibition of Fc gamma RII phosphorylation, after immunological activation or addition of thrombin, respectively, suggesting that p72(Syk) participates in Fc gamma RII phosphorylation. The results provide evidence that p72(Syk)/Fc gamma RII association is not restricted to immunological activation. (C) 2000 Elsevier Science Inc. All rights reserved. [References: 28]