Thioredoxin 1-Mediated Post-Translational Modifications: Reduction, Transnitrosylation, Denitrosylation, and Related Proteomics Methodologies

Despite the significance of redox post-translational modifications (PTMs) in regulating diverse signal transduction pathways, the enzymatic systems that catalyze reversible and specific oxidative or reductive modifications have yet to be firmly established. Thioredoxin 1 (Trx1) is a conserved antioxidant protein that is well known for its disulfide reductase activity. Interestingly, Trx1 is also able to transnitrosylate or denitrosylate (defined as processes to transfer or remove a nitric oxide entity to/from substrates) specific proteins. An intricate redox regulatory mechanism has recently been uncovered that accounts for the ability of Trx1 to catalyze these different redox PTMs. In this review, we will summarize the available evidence in support of Trx1 as a specific disulfide reductase, and denitrosylation and transnitrosylation agent, as well as the biological significance of the diverse array of Trx1-regulated pathways and processes under different physiological contexts. The dramatic progress in redox proteomics techniques has enabled the identification of an increasing number of proteins, including peroxiredoxin 1, whose disulfide bond formation and nitrosylation status are regulated by Trx1. This review will also summarize the advancements of redox proteomics techniques for the identification of the protein targets of Trx1-mediated PTMs. Collectively, these studies have shed light on the mechanisms that regulate Trx1-mediated reduction, transnitrosylation, and denitrosylation of specific target proteins, solidifying the role of Trx1 as a master regulator of redox signal transduction. Antioxid. Redox Signal. 15, 2565–2604. I. Introduction II. Trx Systems A. Trx1 and related proteins B. PTMs of Trx1 III. Trx Regulation of Target Proteins by Disulfide Bond Reduction A. Trx regulation of cellular redox balance B. Trx regulation of signal transduction and transcription C. Trx function at the system level D. Protein oxidation and Trx reduction specificity and mechanism IV. Proteomics Approaches for the Identification of Trx Reduction Targets A. Strategies B. Gel-based proteomics approaches C. MS-based proteomics approaches D. Targeted proteomics approaches E. Strengths, limitations and complementarity V. Nitrosylation A. S-nitrosylation and signal transduction B. Regulation of the specificity of nitrosylation C. Transnitrosylation and denitrosylation of proteins VI. Regulation of Nitrosylation by Trx A. Transnitrosylation by Trx1 B. Denitrosylation by Trx C. Functional significance of Trx-mediated regulation of nitrosylation VII. Proteomics Strategies for the Identification of Trx Transnitrosylation/Denitrosylation Targets A. Strategies B. Biotin switch technique C. Gel-based approaches D. MS-based approaches E. Advanced proteomics approaches F. Strengths, limitations and complementarity VIII. Conclusions