Distinctive functions of Syk N-terminal and C-terminal SH2 domains in the signaling cascade elicited by oxidative stress in B cells

Syk plays a crucial role in the transduction of oxidative stress signaling: . In this paper, we investigated the roles of Src homology 2 (SH2) domains of Syk in oxidative stress signaling, using Syk-negative DT40 cells express ing the N- or C-terminal SH2 domain mutant [mSH2(N) or mSH2(C)] of Syk. Tyr osine phosphorylation of Syk in cells expressing mSH2(N) Syk after H2O2 tre atment was higher than that in cells expressing wild-type Syk or mSH2(C) Sy k. The tyrosine phosphorylation of wild-type Syk and mSH2(C) Syk, but not t hat of mSH2(N), was sensitive to PP2, a specific inhibitor of Src-family pr otein-tyrosine kinase. In oxidative stress, the C-terminal SH2 domain of Sy k was demonstrated to be required for induction of tyrosine phosphorylation of cellular proteins, phospholipase C (PLC)-gamma 2 phosphorylation, inosi tol 1,4,5-triphosphate (IP3) generation, Ca2+ release from intracellular st ores, and c-Jun N-terminal kinase activation. In contrast, in mSH2(N) Syk-e xpressing cells, tyrosine phosphorylation of intracellular proteins includi ng PLC-gamma 2 was markedly induced in oxidative stress. the enhanced phosp horylation of mSH2(N) Syk and PLC-gamma 2, however did not link to Ca2+ mob ilization from intracellular pools and IP3 generation. Thus, the N- and C-t erminal SH2 domains of Syk possess distinctive functions in oxidative stres s signaling.