Redox Proteomics Applied to the Thiol Secretome

Abstract

Word count: 6800 excluding references Number of references: 113Number of greyscale and color illustrations: 7 greyscale and 5 color (online only)Ghezzi 2 AbstractStudies of redox proteomics to identify glutathionylated proteins have so far been focused on intracellular proteins. However, plasma proteins have been described as glutathionylated. The present review discusses the redox state of protein cysteines in relation to their cellular distribution. We focus in particular on the redox state of proteins secreted under inflammatory conditions and that may act as soluble mediators (cytokines). We describe the various approaches used to detect secreted glutathionylated proteins, the only thiol modification studied so far in secreted proteins, and the specific problems presented in the study of the secretome. This review will deal with a particular aspect of redox proteomics, the analysis of secreted proteins and their possible function. Ghezzi 3 Redox state of proteins in the context of their localization Redox proteomics of the thiol proteomeAccording to the Oxford English Dictionary, proteomics is "the study or analysis of the set of proteins expressed by an organism" and we commonly apply the term to high-throughput techniques of protein identification. As such, the history of redox proteomics started in 2002 when various groups published the first reports of the identification of oxidized proteins by modifying the existing proteomic techniques.Two of these papers were aimed at carbonylated proteins (19,20) and others at protein glutathionylation (33,37,61) or overall protein thiol oxidation (60) .This review will deal with the redox states of protein thiols. Biochemistry textbooks and protein databases classify cysteines in proteins as either free or engaged in a disulfide bond. However, "free" cysteines can be reversibly or irreversibly oxidized to various forms. In particular, in addition to forming structural disulfides, cysteines can form transient, reversible disulfides with another protein cysteine, with free cysteine (cysteinylation) or with the cysteine in the tripeptide glutathione (GSH;; glutamylcystenyl-glycine). Fig. 1 lists the most important oxidation state of sulfur in cysteine.These forms of oxidation, due to their reversibility, are of great interest in the context of redox regulation, as a means by which the redox state of the cell can regulate protein functions (43-45).Specific proteins undergoing glutathionylation were described even before the term "proteomics" became popular (in the late 1990s, according to Google books ngram viewer -https://books.google.com/ngrams). Two proteins have been identified as undergoing glutathionylation in two separate papers, an unidentified 30 kDa cytosolic Ghezzi 4protein in oxidant-treated rat liver (79), and actin in human neutrophils during oxidative burst (22). Although these were not the result of high-throughput studies, some of the technologies used were then adapted for two-dimensional gels for further studies and are at the basis of current red...

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Follicular Fluid redox involvement for ovarian follicle growth

“…The diversity of modifications exhibited by oxidized cysteine thiol group [66] is evidence of its versatility and ability to acquire unique functional properties [67]. Such modifications, apart from the simple disulfide bond formation, include the glutathionylation and nitrosylation and other forms of increasing thiol level of oxidation as are the sulfenic, the sulfinic and the sulfonic acid modifications [66, 67]. …”

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