Protein S-Nitrosylation and its Relevance to Redox Control of Cell Signaling

Abstract

Understanding the mechanism of how free radicals regulate signaling is critical to distinguish between normal physiology and cellular toxicity both caused by reactive species. Different types of oxidative modification such as S-nitrosylation,S-glutathionylation, di-sulphide bond formation, sulphenic acid formation, have been proposed to mediate redox control of cell signaling. However, physiological relevance of these modifications is somehow missing. Following up on our previous study that demonstrates that O2- activates survival kinase Akt through S-nitrosylation of the tumor suppressor PTEN, our current study deciphers the mechanistic aspect of how oxidative signal by O2- is transformed into nitrosative signal. We also provide evidence that physiologically relevant concentration of H2O2 predominately induces protein S-nitrosylation over non-SNO modifications. We demonstrate that protein S-nitrosylation induced by O2- and H2O2 is both mediated by common S-nitrosylating species, ONOO- although the pathways to formation of ONOO- are different in each case. Moreover, we show that oxidation of proteins that occurs following incubation with PDGF, EGF and 10% FBS is by protein S-nitrosylation. Again, we find that the relevant S-nitrosylating species that mediates growth factors-induced protein S-nitrosylation is ONOO-. Removal of ONOO prevents protein S-nitrosylation as well as activation of Akt induced by O2-, H2O2 and PDGF demonstrating protein S-nitrosylation is of relevance to redox control of cell signaling.