The Structure of the Thioredoxin–Triosephosphate Isomerase Complex Provides Insights into the Reversible Glutathione-Mediated Regulation of Triosephosphate Isomerase

A Global Profile of Reversible and Irreversible Cysteine Redox Post-Translational Modifications During Myocardial Ischemia/Reperfusion Injury and Antioxidant Intervention

Aims: Cysteine (Cys) is a major target for redox post-translational modifications (PTMs) that occur in response to changes in the cellular redox environment. We describe multiplexed, peptide-based enrichment and quantitative mass spectrometry (MS) applied to globally profile reversible redox Cys PTM in rat hearts during ischemia/reperfusion (I/R) in the presence or absence of an aminothiol antioxidant, N-2-mercaptopropionylglycine (MPG). Parallel fractionation also allowed identification of irreversibly oxidized Cys peptides (Cys-SO₂H/SO₃H). Results: We identified 4505 reversibly oxidized Cys peptides of which 1372 were significantly regulated by ischemia and/or I/R. An additional 219 peptides (247 sites) contained Cys-SO₂H/Cys-SO₃H modifications, and these were predominantly identified from hearts subjected to I/R (n = 168 peptides). Parallel reaction monitoring MS (PRM-MS) enabled relative quantitation of 34 irreversibly oxidized Cys peptides. MPG attenuated a large cluster of I/R-associated reversibly oxidized Cys peptides and irreversible Cys oxidation to less than nonischemic controls (n = 24 and 34 peptides, respectively). PRM-MS showed that Cys sites oxidized during ischemia and/or I/R and "protected" by MPG were largely mitochondrial, and were associated with antioxidant functions (peroxiredoxins 5 and 6) and metabolic processes, including glycolysis. Metabolomics revealed I/R induced changes in glycolytic intermediates that were reversed in the presence of MPG, which were consistent with irreversible PTM of triose phosphate isomerase and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), altered GAPDH enzyme activity, and reduced I/R glycolytic payoff as evidenced by adenosine triphosphate and NADH levels. Innovation: Novel enrichment and PRM-MS approaches developed here enabled large-scale relative quantitation of Cys redox sites modified by reversible and irreversible PTM during I/R and antioxidant remediation. Conclusions: Cys sites identified here are targets of reactive oxygen species that can contribute to protein dysfunction and the pathogenesis of I/R.

Redox Regulation of STAT1 and STAT3 Signaling

STAT1 and STAT3 are nuclear transcription factors that regulate genes involved in cell cycle, cell survival and immune response. The cross-talk between these signaling pathways determines how cells integrate the environmental signals received ultimately translating them in transcriptional regulation of specific sets of genes. Despite being activated downstream of common cytokine and growth factors, STAT1 and STAT3 play essentially antagonistic roles and the disruption of their balance directs cells from survival to apoptotic cell death or from inflammatory to anti-inflammatory responses. Different mechanisms are proposed to explain this yin-yang relationship. Considering the redox aspect of STATs proteins, this review attempts to summarize the current knowledge of redox regulation of STAT1 and STAT3 signaling focusing the attention on the post-translational modifications that affect their activity.

Thioredoxin and glutaredoxin regulate metabolism through different multiplex thiol switches

The aim of the present study was to define the role of Trx and Grx on metabolic thiol redox regulation and identify their protein and metabolite targets. The hepatocarcinoma-derived HepG2 cell line under both normal and oxidative/nitrosative conditions by overexpression of NO synthase (NOS3) was used as experimental model. Grx1 or Trx1 silencing caused conspicuous changes in the redox proteome reflected by significant changes in the reduced/oxidized ratios of specific Cys's including several glycolytic enzymes. Cys⁹¹ of peroxiredoxin-6 (PRDX6) and Cys¹⁵³ of phosphoglycerate mutase-1 (PGAM1), that are known to be involved in progression of tumor growth, are reported here for the first time as specific targets of Grx1. A group of proteins increased their Cys_RED/Cys_OX ratio upon Trx1 and/or Grx1 silencing, including caspase-3 Cys¹⁶³, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) Cys²⁴⁷ and triose-phosphate isomerase (TPI) Cys²⁵⁵ likely by enhancement of NOS3 auto-oxidation. The activities of several glycolytic enzymes were also significantly affected. Glycolysis metabolic flux increased upon Trx1 silencing, whereas silencing of Grx1 had the opposite effect. Diversion of metabolic fluxes toward synthesis of fatty acids and phospholipids was observed in siRNA-Grx1 treated cells, while siRNA-Trx1 treated cells showed elevated levels of various sphingomyelins and ceramides and signs of increased protein degradation. Glutathione synthesis was stimulated by both treatments. These data indicate that Trx and Grx have both, common and specific protein Cys redox targets and that down regulation of either redoxin has markedly different metabolic outcomes. They reflect the delicate sensitivity of redox equilibrium to changes in any of the elements involved and the difficulty of forecasting metabolic responses to redox environmental changes.

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Trx1 and Grx1 Cys redox targets are abundant among Glycolytic enzymes.

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PRDX6-Cys⁹¹ and PGAM-Cys¹⁵³ are specific targets of Grx1.

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Down regulation of thioredoxin and glutaredoxin have different metabolic outcomes.

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Glutathione synthesis and membrane lipid composition are sensitive to Trx1 and Grx1 down regulation.

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Redoxins down regulation also induce target Cys reductive changes under NOS3 overexpression.

Toxicity of copper oxide nanoparticles in the blue mussel, Mytilus edulis: a redox proteomic investigation

Relatively little is known about the fate and effects of nanomaterials even in relatively simple organisms such as Mytilus edulis. Here, copper oxide nanoparticles (CuO NP) are shown to induce dose-dependent toxic effects at the biochemical, physiological and tissue levels in the blue mussel. Stable CuO NP suspensions were sized by differential light scattering and nanoparticle tracking analysis to yield average particle diameters of approximately 100 nm. These were administered to M. edulis, at doses of 400, 700 and 1000 ppb. Ingested copper was predominantly located in the gill tissue with small amounts in digestive gland. Fifteen coomassie-stained spots were excised from two dimensional gel electrophoresis separations of gill tissue extacts and identified by peptide mass fingerprinting. These contained six unique proteins (alpha- and beta-tubulin, actin, tropomyosin, triosephosphate isomerase and Cu-Zn superoxide dismutase). Of these, two spots (actin and triosephosphate isomerase) showed decreased protein thiols while three (alpha-tubulin, tropomyosin and Cu-Zn superoxide dismutase) showed increased carbonylation which is indicative of protein oxidation of cytoskeleton and enzymes in response to CuO NP. The neutral red retention time (NRRT) assay revealed toxicity due to the CuO NPs which was comparable with toxic metal oxide nanoparticles such as chromium and cobalt. In contrast, non-toxic titanium and gold metal oxide nanoparticles gave no NRRT effects at similar NP concentrations. Histology revealed deposition of pigmented brown cells in response to CuO NP, located predominantly along the mantle and gill margin but also lining digestive tubules and some of the sinuses and distributed throughout the connective tissue and in the adductor muscle.