Activation of src tyrosine kinases by peroxynitrite

In this study, we demonstrate that the phosphorylation activity of five tyr osine kinases of the arc family from both human erythrocytes (lyn, hck and c-fgr) and bovine synaptosomes (lyn and fyn) was stimulated by treatment wi th 30-250 mu M peroxynitrite, This effect was not observed with syk, a non- src family tyrosine kinase, Treatment of kinase immunoprecipitates with 0.0 1-10 mu M peroxynitrite showed that the interaction of these enzymes with t he oxidant also activated the src kinases, Higher concentrations of peroxyn itrite inhibited the activity of all kinases, indicating enzyme inactivatio n. The addition of bicarbonate (1.3 mM CO2) did not modify the upregulation of src kinases but significantly protected the kinases against peroxynitri te-mediated inhibition. Upregulation of src kinase activity by 1 mu M perox ynitrite was 3.5-5-fold in erythrocytes and 1.2-2-fold in synaptosomes, but this could be the result, at least in part, of the higher basal level of s rc kinase activity in synaptosomes, Our results indicate that peroxynitrite can upregulate the tyrosine phosphorylation signal through the activation of src kinases, (C) 1999 Federation of European Biochemical Societies.