The effects of oxidative stress inducing agents on cell signalling

Reversibie phosphorylation of protein tyrosine residues by protein tyrosine kinases (PTK) mediated by polypeptide growth factor receptors (e.g. epidermal growth factor receptor, platelet derived growth factor receptor, insulin receptor) is a signalling process implicated in a variety of processes such as cellular proliferation, differentiation and transformation. On the other hand, many reports converged to the idea that cellular phosphotyrosine levels are regulated by a family of enzymes referred to as protein tyrosine phosphatases (PTP). An essential cysteine residue located in the conserved catalytic domain is responsible for PTP activity. Furthermore, inhibition of PTP activities by oxidative stress inducing agents has been recently documented. It is well known that free radicais and other oxidants at high concentrations are toxic to cells. However, at low concentrations these species may act as modulators/mediators of signal transduction processes in the presence and absence of polypeptide growth factors. Thus, in this article we reviewed our contribution in the general context of the redox modulation of PTK and PTP mediated signal transduction pathways.