S-Nitrosylation is precisely targeted,[2] reversible,[3] spatiotemporally restricted[4][5] and necessary for a wide range of cellular responses,[6] including the prototypic example of red blood cell mediated autoregulation of blood flow that is essential for vertebrate life.[7] Although originally thought to involve multiple chemical routes in vivo, accumulating evidence suggests that S-nitrosylation depends on enzymatic activity, entailing three classes of enzymes (S-nitrosylases) that operate in concert to conjugate NO to proteins, drawing analogy to ubiquitinylation.[8] Beside enzymatic activity, hydrophobicity and low pka values also play a key role in regulating the process.[6]S-Nitrosylation was first described by Stamler et al. and proposed as a general mechanism for control of protein function, including examples of both active and allosteric regulation of proteins by endogenous and exogenous sources of NO.[9][10][11] The redox-based chemical mechanisms for S-nitrosylation in biological systems were also described concomitantly.[12] Important examples of proteins whose activities were subsequently shown to be regulated by S-nitrosylation include the NMDA-type glutamate receptor in the brain.[13][14] Aberrant S-nitrosylation following stimulation of the NMDA receptor would come to serve as a prototypic example of the involvement of S-nitrosylation in disease.[15]S-Nitrosylation similarly contributes to physiology and dysfunction of cardiac, airway and skeletal muscle and the immune system, reflecting wide-ranging functions in cells and tissues.[16][17][18] It is estimated that ~70% of the proteome is subject to S-nitrosylation and the majority of those sites are conserved.[19]S-Nitrosylation is also known to show up in mediating pathogenicity in Parkinson's disease systems.[20]S-Nitrosylation is thus established as ubiquitous in biology, having been demonstrated to occur in all phylogenetic kingdoms[21] and has been described as the prototypic redox-based signalling mechanism,[22]
Denitrosylation
The reverse of S-nitrosylation is denitrosylation, principally an enzymically controlled process. Multiple enzymes have been described to date, which fall into two main classes mediating denitrosylation of protein and low molecular weight SNOs, respectively. S-Nitrosoglutathione reductase (GSNOR) is exemplary of the low molecular weight class; it accelerates the decomposition of S-nitrosoglutathione (GSNO) and of SNO-proteins in equilibrium with GSNO. The enzyme is highly conserved from bacteria to humans.[23]Thioredoxin (Trx)-related proteins, including Trx1 and 2 in mammals, catalyze the direct denitrosylation of S-nitrosoproteins[24][25][26] (in addition to their role in transnitrosylation[27]). Aberrant S-nitrosylation (and denitrosylation) has been implicated in multiple diseases, including heart disease,[18] cancer and asthma[28][29][17] as well as neurological disorders, including stroke,[30] chronic degenerative diseases (e.g., Parkinson's and Alzheimer's disease)[31][32][33] and amyotrophic lateral sclerosis (ALS).[34]
Transnitrosylation
Another interesting aspect of S-nitrosylation includes the protein protein transnitrosylation, which is the transfer of an NO moiety from a SNO to the free thiols in another protein. Thioredoxin (Txn), a protein disulfide oxidoreductase for the cytosol and caspase 3 are a good example where transnitrosylation is significant in regulating cell death.[6] Another example include, the structural changes in mammalian Hb to SNO-Hb under oxygen depleted conditions helps it to bind to AE1 (Anion Exchange, a membrane protein) and in turn gets transnitrosylated the later.[35] Cdk5 (a neuronal-specific kinase) is known get nitrosylated at cysteine 83 and 157 in different neurodegenerative diseases like AD. This SNO-Cdk5 in turn is nitrosylated Drp1, the nitrosylated form of which can be considered as a therapeutic target.[36]
^Padgett CM, Whorton AR (September 1995). "S-nitrosoglutathione reversibly inhibits GAPDH by S-nitrosylation". The American Journal of Physiology. 269 (3 Pt 1): C739 –C749. doi:10.1152/ajpcell.1995.269.3.C739. PMID7573405.
^Stamler JS, Simon DI, Osborne JA, Mullins M, Jaraki O, Michel T, Singel D, Loscalzo J (1992). "Comparison of properties of nitric oxide". In Moncada S, Marletta MA, Hibbs JB (eds.). The biology of nitric oxide: proceedings of the 2nd International Meeting on the Biology of Nitric Oxide, London. London: Portland Press. pp. 20–23. OCLC29356699.
^Lei SZ, Pan ZH, Aggarwal SK, Chen HS, Hartman J, Sucher NJ, Lipton SA (June 1992). "Effect of nitric oxide production on the redox modulatory site of the NMDA receptor-channel complex". Neuron. 8 (6): 1087–1099. doi:10.1016/0896-6273(92)90130-6. PMID1376999. S2CID24701634.
^Lipton SA, Choi YB, Pan ZH, Lei SZ, Chen HS, Sucher NJ, et al. (August 1993). "A redox-based mechanism for the neuroprotective and neurodestructive effects of nitric oxide and related nitroso-compounds". Nature. 364 (6438): 626–632. Bibcode:1993Natur.364..626L. doi:10.1038/364626a0. PMID8394509. S2CID4355073.
^Sircar E, Rai SR, Wilson MA, Schlossmacher MG, Sengupta R (June 2021). "Neurodegeneration: Impact of S-nitrosylated Parkin, DJ-1 and PINK1 on the pathogenesis of Parkinson's disease". Archives of Biochemistry and Biophysics. 704: 108869. doi:10.1016/j.abb.2021.108869. PMID33819447. S2CID233036980.
^Stoyanovsky DA, Tyurina YY, Tyurin VA, Anand D, Mandavia DN, Gius D, et al. (November 2005). "Thioredoxin and lipoic acid catalyze the denitrosation of low molecular weight and protein S-nitrosothiols". Journal of the American Chemical Society. 127 (45): 15815–15823. doi:10.1021/ja0529135. PMID16277524.
^Sengupta R, Ryter SW, Zuckerbraun BS, Tzeng E, Billiar TR, Stoyanovsky DA (July 2007). "Thioredoxin catalyzes the denitrosation of low-molecular mass and protein S-nitrosothiols". Biochemistry. 46 (28): 8472–8483. doi:10.1021/bi700449x. PMID17580965.
^Wu C, Liu T, Wang Y, Yan L, Cui C, Beuve A, Li H (2018). "Biotin Switch Processing and Mass Spectrometry Analysis of S-Nitrosated Thioredoxin and Its Transnitrosation Targets". Nitric Oxide. Methods in Molecular Biology. Vol. 1747. pp. 253–266. doi:10.1007/978-1-4939-7695-9_20. ISBN978-1-4939-7694-2. PMC7136013. PMID29600465.
^Aranda E, López-Pedrera C, De La Haba-Rodriguez JR, Rodriguez-Ariza A (January 2012). "Nitric oxide and cancer: the emerging role of S-nitrosylation". Current Molecular Medicine. 12 (1): 50–67. doi:10.2174/156652412798376099. PMID22082481.