S-Nitrosylation

S-Nitrosylation specifically attaches to a thiol group to form an S-nitrosothiol (SNO). Where the thiol group belongs to a subset of specific cysteine residues in proteins, the resulting SNO is an S-nitrosoprotein. S-Nitrosylation is a form of post-translational protein modification with similarities to phosphorylation.S-Nitrosylation meets the criteria for validation as a signaling mechanism in that it is stimulus evoked, precisely targeted, reversible, spatiotemporally restricted and necessary for specific cell responses. The first protein whose activity was shown to be regulated by S-nitrosylation in this fashion was the NMDA-type glutamate receptor in the brain.S-Nitrosylation has since been shown to be ubiquitous in biology, having been demonstrated to occur in all phylogenetic Kingdoms and has been described as the prototypic redox-based signalling mechanism, hypothesized to have evolved on primordial Earth.

The reverse process of S-nitrosylation is termed denitrosylation, which in addition to occurring spontaneously in the presence of metal ions and under conditions of photolysis, has recently been demonstrated to be an enzymically controlled process. S-Nitrosoglutathione reductase (GSNOR), which accelerates the decomposition of S-nitrosoglutathione (GSNO) and other SNO-proteins, is an alcohol dehydrogenase class III isoenzyme which has been shown to be conserved from bacteria to humans. Similarly, the thioredoxin/thioredoxin reductase system catalyzes the denitrosylation of a number of S-nitrosoproteins Aberrant or dysregulated denitrosylation or S-nitrosylation has been associated with stroke (cerebral ischemia) and a number of chronic degenerative diseases, including Parkinson's and Alzheimer's disease and Amyotrophic Lateral Sclerosis (ALS). There is an emerging role of S-nitrosylation in cancer biology.S-Nitrosylation of EGFR and Src activates an oncogenic signaling network in human basal-like breast cancer

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