Peroxynitrite-dependent activation of src tyrosine kinases lyn and hck in erythrocytes is under mechanistically different pathways of redox control

Peroxynitrite, the product of superoxide and nitric oxide radicals, is considered one of the major oxidants formed in vivo under intense oxidative stress. We have previously reported the upregulation by peroxynitrite of src kinase activity in red blood cells. In this study, we investigated the mechanisms of peroxynitrite action and we demonstrate that two src kinases (lyn and hck) are activated through different pathways involving cysteine-dependent or -independent oxidations. Activation of hck by peroxynitrite or by hydrogen peroxide could be explained by reversible SH redox changes, whereas lyn was unaffected by hydrogen peroxide and its direct activation by peroxynitrite occurred through a still unknown modification(s) not reverted by SH reduction or inhibited by SH alkylation. Moreover, lyn could be activated also downstream by peroxynitrite-activated hck. The cross talk between lyn and hck was selective, since activated hck did not activate the non-src kinase syk. This study illustrates the complexity of redox-dependent src regulation and suggests that one reason for src heterogeneity may be a peculiar difference in their sensitivity to physiological oxidants. Irrespectively of the activation pathway, the final effect of peroxynitrite is the amplification of tyrosine-dependent signaling, a finding of general interest in nitric oxide-related pathophysiology.