Cooperation of tyrosine kinases p72(syk) and p53/56(lyn) regulates calcium mobilization in chicken B cell oxidant stress signaling

A chicken B cell line DT40 and its syk-negative or lyn-negative mutants were used to investigate the roles of protein-tyrosine kinases in oxidant stress signaling. The data presented here for wild-type cells demonstrate that hydrogen peroxide stimulates p53/56(lyn)-dependent tyrosine phosphorylation and activation of p72(syk), and induces a rapid and prolonged elevation of intracellular calcium, which consists of calcium release from intracellular stores and influx from the extracellular space. Hydrogen-peroxide-triggered calcium mobilization was impaired in both syk-negative and lyn-negative cells, which was mainly due to the loss of calcium release from intracellular stores. Further studies indicated that inositol trisphosphate production was also abolished in both syk-negative and lyn-negative cells, which is consistent with the loss of calcium release. Taken together, these observations suggest that the defect of p72(syk) or p53/56(lyn) was responsible for the abnormality of calcium mobilization in both lyn-negative and syk-negative cells, and that both p72(syk) and p53/56(lyn) might regulate calcium mobilization through the phosphatidylinositol pathway in B cell oxidant stress signaling.