Project description:Oxidative stress is harmful for organism and occurs when the cells exposed to superoxid, hydrogen peroxide and alkylhydroperoxides. In microorganism, the glutathione- and thioredoxin-dependent reduction systems are universal and play an important role in response to defending oxidative stress. The _-glutamylcysteine synthetase (_-GCS) is an essential enzyme to biosynthesize the tripeptide glutathione (GSH) in organism. Similarly, thioredoxin reductase is an important enzyme in thioredoxin-dependent reduction system. In Clostridium acetobutylicum, the _-glutamylcysteine synthetase (encoded by CAC1539, gcs) and thioredoxin reductase (encoded by CAC1548, trxB) were inactivated using ClosTron technology. The gcs mutant grew insufficiently and consumed less glucose in the phosphate-limited continuous culture and exhibited more sensitive to oxidative stress. The trxB mutant just exhibited lower growth rate and less glucose uptake in the solventogenic phase, compared to wild type. The DNA microarrays were performed to investigate the transcripome difference between wild type and the mutants. In gcs mutant, the genes related to chemotaxis and flagella biosynthesis proteins were induced significantly and in the trxB mutant, the sporulation genes were induced largely. Based on the phenotypes and transcriptome comparison results, the relationship between GSH- and Trx-dependent induction systems was discussed in Clostridium acetobutylicum.
Project description:The Ras-related Rap1A GTPase is implicated in pancreas β-cell insulin secretion, and is stimulated by the cAMP sensor Epac2, a guanine exchange factor and activator of Rap1 GTPase. In this study we examined the differential proteomic profiles by nanoLC-ESI-MS/MS of pancreata from C57BL/6 Rap1A-deficient (Null) and control wild-type (WT) mice, to assess targets of Rap1A potentially involved in insulin regulation. We identified 77 overlapping identifier proteins in both groups, 8 distinct identifier proteins in Null versus 56 distinct identifier proteins in WT mice pancreas. Functional enrichment analysis showed 4 of the 8 Null unique proteins, ERO1-like protein β (Ero1lβ), triosephosphate isomerase (TP1), 14-3-3 protein γ and kallikrein-1, were exclusively involved in insulin biogenesis, with role in insulin metabolism. Specifically, the mRNA expression of Ero1lβ and TP1 was significantly (p<0.05) increased in Null versus WT pancreas. Rap1A-deficiency significantly affected glucose tolerance during the first 15-30 min of glucose challenge, but showed no impact on insulin sensitivity. Ex vivo glucose-stimulated insulin secretion (GSIS) studies on isolated Null islets showed significantly impaired GSIS. Furthermore, in GSIS-impaired islets, the cAMP-Epac2-Rap1A pathway was significantly compromised as compared to WT. Altogether, these studies underscore an essential role of Rap1A GTPase in pancreas physiological function
Project description:Reactive oxygen species (ROS) have been implicated as mediators of pancreatic β-cell damage. While β-cells are thought to be vulnerable to oxidative damage, we have shown, using inhibitors and acute depletions, that thioredoxin reductase, thioredoxin, and peroxiredoxins are the primary mediators of antioxidant defense in β-cells. However, the role of this antioxidant cycle in maintaining redox homeostasis and β-cell survival in vivo remains unclear. Here, we generated mice with a β-cell specific knockout of thioredoxin reductase 1 (Txnrd1.fl/fl; Ins1.Cre/+, βKO). Despite blunted glucose-stimulated insulin secretion, knockout mice maintain normal whole body glucose homeostasis. Unlike pancreatic islets with acute Txnrd1 inhibition, βKO islets do not demonstrate increased sensitivity to continuous ROS. RNA-sequencing analysis revealed that Txnrd1-deficient β-cells have increased expression of Nuclear factor erythroid 2-related factor 2 (Nrf2)-regulated genes, and altered expression of genes involved in heme and glutathione metabolism, suggesting an adaptive response. Txnrd1-deficient β-cells also have decreased expression of factors controlling β-cell function and identity which may explain the mild functional impairment. Together, these results suggest that Txnrd1-knockout β-cells compensate for loss of this essential antioxidant pathway by increasing expression of Nrf2-regulated antioxidant genes, allowing for protection from excess ROS at the expense of normal β-cell function and identity.
Project description:The Saccharomyces cerevisiae Yap1p transcription factor is required for the H2O2-dependent activation of many antioxidant genes including the TRX2 gene encoding thioredoxin 2. To identify factors that regulate Yap1p activity, we carried out a genetic screen for mutants that show elevated expression of a TRX2-HIS3 fusion in the absence of H2O2. Two independent mutants isolated in this screen carried mutations in the TRR1 gene encoding thioredoxin reductase. Northern blot and whole-genome expression analysis revealed that the basal expression of most Yap1p targets and many other H2O2-inducible genes is elevated in Deltatrr1 mutants in the absence of external stress. In Deltatrr1 mutants treated with H2O2, the Yap1p targets, as well as genes comprising a general environmental stress response and genes encoding protein-folding chaperones, are hyperinduced. However, despite the elevated expression of genes encoding antioxidant enzymes, Deltatrr1 mutants are extremely sensitive to H2O2. The results suggest that cells lacking thioredoxin reductase have diminished capacity to detoxify oxidants and/or to repair oxidative stress-induced damage and that the thioredoxin system is involved in the redox regulation of Yap1p transcriptional activity. Groups of assays that are related as part of a time series. Using regression correlation
Project description:The Saccharomyces cerevisiae Yap1p transcription factor is required for the H2O2-dependent activation of many antioxidant genes including the TRX2 gene encoding thioredoxin 2. To identify factors that regulate Yap1p activity, we carried out a genetic screen for mutants that show elevated expression of a TRX2-HIS3 fusion in the absence of H2O2. Two independent mutants isolated in this screen carried mutations in the TRR1 gene encoding thioredoxin reductase. Northern blot and whole-genome expression analysis revealed that the basal expression of most Yap1p targets and many other H2O2-inducible genes is elevated in Deltatrr1 mutants in the absence of external stress. In Deltatrr1 mutants treated with H2O2, the Yap1p targets, as well as genes comprising a general environmental stress response and genes encoding protein-folding chaperones, are hyperinduced. However, despite the elevated expression of genes encoding antioxidant enzymes, Deltatrr1 mutants are extremely sensitive to H2O2. The results suggest that cells lacking thioredoxin reductase have diminished capacity to detoxify oxidants and/or to repair oxidative stress-induced damage and that the thioredoxin system is involved in the redox regulation of Yap1p transcriptional activity. Groups of assays that are related as part of a time series. Keywords: time_series_design
Project description:Genetic disruption of thioredoxin reductase 1 protects against acetaminophen (APAP) toxicity. To determine the role of the thioredoxin system on xenobiotic metabolism we challeneged wildtype and txnrd1liver-null mice with acetaminophen.
Project description:Glutathione plays a tremendous role in regulating the homeostasis of redox state, and appears to be essential for proper development of the root nodules. Glutathione peroxidase catalyzes the reduction of peroxides by oxidation of GSH to oxidized GSH (GSSG), which can in turn be reduced by glutathione reductase (GR). However, it has not been determined whether the R. leguminosarum Gpx or GR is required during symbiotic interactions with pea. To characterise the role of glutathione-dependent enzymes in the symbiotic process, single and double mutants were made in gpxA and gorA genes. All the mutations did not affect the growth of R. leguminosarum, but they increased the sensitivity of R. leguminosarum strains to H2O2. The gorA mutant can induce the formation of normal nodules, while the gpxA single and double mutants exhibited an abnormal nodulation phenotype coupled to more than 50% reduction in nitrogen-fifixing capacity, this defect in nodulation was characterized by the formation of undeveloped and ineffective nodules. In addition, the gorA and gpxA double mutant was severely impaired in rhizosphere colonization. LC-MS/MS analysis quantitative proteomics techniques were employed to compare differential gpxA mutant root bacteroids in response to the wild type infection. Sixty differentially expressed proteins were identified including seven up-regulated and twenty down-regulated proteins. By sorting the down-regulated proteins according to metabolic function, eight proteins were transporter protein, seven proteins were dehydrogenases and deoxygenases. Moreover, three down-regulation proteins are directly involved in nodule process.
Project description:The thioredoxin-1 (Trx1) system is a key player of the cellular redox balance and a sensor of energy and glucose metabolism. Here we report critical c-Myc-dependent activation of the Trx1 system during glucose-driven T cell expansion during development and immune responses but endogenous Trx1-repression during quiescence. Thioredoxin-reductase-1 (Txnrd1)-deletion in CD4-CD8- thymocytes prevented their expansion, while deletion in CD4+CD8+ thymocytes did not affect further maturation and peripheral homeostasis of T-cells. Moreover, B cell development was Txnrd1-independent. Txnrd1 was critical for expansion of activated T cells. Unbiased metabolomics revealed that Txnrd1 is necessary for donating reducing equivalent to ribonucleotide reductase (RNR) at the last step of nucleotide biosynthesis. Impaired availability of 2’-deoxyribonucleotides induced the DNA damage response and cell cycle arrest of Txnrd1-deficient T cells. These results uncover a pivotal role of the Trx1 system in metabolic reprograming of thymic and peripheral T cells and provide a rationale for targeting of Txnrd1 in T-cell leukemia.