Thioredoxin reductase is a major regulator of metabolism in leukemia cells.
Ontology highlight
ABSTRACT:
SUBMITTER: Karunanithi S
PROVIDER: S-EPMC8380733 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:It is generally accepted that intracellular oxidative stress induced by proteasome inhibitors is a byproduct of endoplasmic reticulum (ER) stress. Here we report a mechanism underlying the ability of proteasome inhibitors bortezomib (BTZ) and carfilzomib (CFZ) to directly induce oxidative and ER stresses in multiple myeloma (MM) cells via transcriptional repression of a gene encoding mitochondrial thioredoxin reductase (TXNRD2). TXNRD2 is critical for maintenance of intracellular red-ox status and detoxification of reactive oxygen species. Depletion of TXNRD2 to the levels detected in BTZ- or CFZ-treated cells causes oxidative stress, ER stress and death similar to those induced by proteasome inhibitors. Reciprocally, restoration of near-wildtype TXNRD2 amounts in MM cells treated with proteasome inhibitors reduces oxidative stress, ER stress and cell death by ~46%, ~35% and ~50%, respectively, compared with cells with unrestored TXNRD2 levels. Moreover, cells from three MM cell lines selected for resistance to BTZ demonstrate elevated levels of TXNRD2, indirectly confirming its functional role in BTZ resistance. Accordingly, ectopic expression of TXNRD2 in MM cell xenografts in immunocompromised mice blunts therapeutic effects of BTZ. Our data identify TXNRD2 as a potentially clinically relevant target, inhibition of which is critical for proteasome inhibitor-dependent cytotoxicity, oxidative stress and ER stress.
| S-EPMC5436048 | biostudies-literature
Project description:The mammalian thioredoxin reductases (TrxRs) are a family of selenium-containing pyridine nucleotide-disulphide oxidoreductases with mechanistic and sequence identity, including a conserved -Cys-Val-Asn-Val-Gly-Cys- redox catalytic site, to glutathione reductases. TrxRs catalyse the NADPH-dependent reduction of the redox protein thioredoxin (Trx), as well as of other endogenous and exogenous compounds. The broad substrate specificity of mammalian TrxRs is due to a second redox-active site, a C-terminal -Cys-SeCys- (where SeCys is selenocysteine), that is not found in glutathione reductase or Escherichia coli TrxR. There are currently two confirmed forms of mammalian TrxRs, TrxR1 and TrxR2, and it is possible that other forms will be identified. The availability of Se is a key factor determining TrxR activity both in cell culture and in vivo, and the mechanism(s) for the incorporation of Se into TrxRs, as well as the regulation of TrxR activity, have only recently begun to be investigated. The importance of Trx to many aspects of cell function make it likely that TrxRs also play a role in protection against oxidant injury, cell growth and transformation, and the recycling of ascorbate from its oxidized form. Since TrxRs are able to reduce a number of substrates other than Trx, it is likely that additional biological effects will be discovered for TrxR. Furthermore, inhibiting TrxR with drugs may lead to new treatments for human diseases such as cancer, AIDS and autoimmune diseases.
| S-EPMC1220815 | biostudies-other
Project description:Selenium is an essential trace element in mammals, but is toxic at high levels. It is best known for its cancer prevention activity, but cancer cells are more sensitive to selenite toxicity than normal cells. Since selenite treatment leads to oxidative stress, and the Trx (thioredoxin) system is a major antioxidative system, we examined the interplay between TR1 (Trx reductase 1) and Trx1 deficiencies and selenite toxicity in DT cells, a malignant mouse cell line, and the corresponding parental NIH 3T3 cells. TR1-deficient cells were far more sensitive to selenite toxicity than Trx1-deficient or control cells. In contrast, this effect was not seen in cells treated with hydrogen peroxide, suggesting that the increased sensitivity of TR1 deficiency to selenite was not due to oxidative stress caused by this compound. Further analyses revealed that only TR1-deficient cells manifested strongly enhanced production and secretion of glutathione, which was associated with increased sensitivity of the cells to selenite. The results suggest a new role for TR1 in cancer that is independent of Trx reduction and compensated for by the glutathione system. The results also suggest that the enhanced selenite toxicity of cancer cells and simultaneous inhibition of TR1 can provide a new avenue for cancer therapy.
| S-EPMC3508724 | biostudies-literature
Project description:Over-expression of genetically encoded thioredoxin reductase 1 (TrxR1) TrxR1 can be toxic to cells due to the formation of a truncated version of the enzyme. We developed a new mammalian cell-based model to investigate TrxR1 activity. Fusion of the HIV-derived cell penetrating peptide (TAT) enabled efficient cellular uptake of purified TrxR1 containing 21 genetically encoded amino acids, including selenocysteine. The TAT peptide did not significantly alter the catalytic activity of TrxR1 in vitro. We monitored TrxR1-dependent redox activity in human cells using a TrxR1-specific red fluorescent live-cell reporter. Using programmed selenocysteine incorporation in Escherichia coli, our approach allowed efficient production of active recombinant human selenoprotein TrxR1 for delivery to the homologous context of the mammalian cell. The delivered TAT-TrxR1 showed robust activity in live cells and provided a novel platform to study TrxR1 biology in human cells.
| S-EPMC9595596 | biostudies-literature
Project description:Thioredoxin plays a crucial role in a wide number of physiological processes, which span from reduction of nucleotides to deoxyriboucleotides to the detoxification from xenobiotics, oxidants and radicals. The redox function of Thioredoxin is critically dependent on the enzyme Thioredoxin NADPH Reductase (TrxR). In view of its indirect involvement in the above mentioned physio/pathological processes, inhibition of TrxR is an important clinical goal. As a general rule, the affinities and mechanisms of binding of TrxR inhibitors to the target enzyme are known with scarce precision and conflicting results abound in the literature. A relevant analysis of published results as well as the experimental procedures is therefore needed, also in view of the critical interest of TrxR inhibitors. We review the inhibitors of TrxR and related flavoreductases and the classical treatment of reversible, competitive, non competitive and uncompetitive inhibition with respect to TrxR, and in some cases we are able to reconcile contradictory results generated by oversimplified data analysis.
| S-EPMC4275836 | biostudies-literature
Project description:Identification of targets of the protein disulfide reductase thioredoxin using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) and thiol specific differential labeling with isotope-coded affinity tags (ICAT). Reduction of specific target disulfides is quantified by measuring ratios of cysteine residues labeled with the heavy (13C) and light (12C) ICAT reagents in peptides derived from tryptic digests of Trx-treated and non-treated samples. Keywords: protein, LC-MS/MS, ICAT
2008-11-20 | GSE11650 | GEO
Project description:UnlabelledStaphylococcus aureus is capable of causing a remarkable spectrum of disease, ranging from mild skin eruptions to life-threatening infections. The survival and pathogenic potential of S. aureus depend partly on its ability to sense and respond to changes in its environment. Spx is a thiol/oxidative stress sensor that interacts with the C-terminal domain of the RNA polymerase RpoA subunit, leading to changes in gene expression that help sustain viability under various conditions. Using genetic and deep-sequencing methods, we show that spx is essential in S. aureus and that a previously reported Δspx strain harbored suppressor mutations that allowed it to grow without spx One of these mutations is a single missense mutation in rpoB (a P-to-L change at position 519 encoded by rpoB [rpoB-P519L]) that conferred high-level resistance to rifampin. This mutation alone was found to be sufficient to bypass the requirement for spx The generation of rifampin resistance libraries led to the discovery of an additional rpoB mutation, R484H, which supported strains with the spx disruption. Other rifampin resistance mutations either failed to support the Δspx mutant or were recovered at unexpectedly low frequencies in genetic transduction experiments. The amino acid residues encoded by rpoB-P519L and -R484H map in close spatial proximity and comprise a highly conserved region of RpoB. We also discovered that multicopy expression of either trxA (encoding thioredoxin) or trxB (encoding thioredoxin reductase) supports strains with the deletion of spx Our results reveal intriguing properties, especially of RNA polymerase, that compensate for the loss of an essential gene that is a key mediator of diverse processes in S. aureus, including redox and thiol homeostasis, antibiotic resistance, growth, and metabolism.ImportanceThe survival and pathogenicity of S. aureus depend on complex genetic programs. An objective for combating this insidious organism entails dissecting genetic regulatory circuits and discovering promising new targets for therapeutic intervention. In this study, we discovered that Spx, an RNA polymerase-interacting stress regulator implicated in many stress responses in S. aureus, including responses to oxidative and cell wall antibiotics, is essential. We describe two mechanisms that suppress the lethality of spx disruption. One mechanism highlights how only certain rifampin resistance-encoding alleles of RpoB confer new properties on RNA polymerase, with important mechanistic implications. We describe additional stress conditions where the loss of spx is deleterious, thereby highlighting Spx as a multifaceted regulator and attractive drug discovery target.
| S-EPMC5019056 | biostudies-literature
Project description:Curcumin, a plant polyphenol, is a widely studied chemopreventive agent with demonstrated antitumor activities in preclinical studies and low toxicity profiles in multiple clinical trials against human malignancies. We previously showed that curcumin radiosensitizes cervical tumor cells without increasing the cytotoxic effects of radiation on normal human fibroblasts. Here we report that an inhibitory activity of curcumin on the antioxidant enzyme thioredoxin reductase-1 (TxnRd1) is required for curcumin-mediated radiosensitization of squamous carcinoma cells. Stable knockdown of TxnRd1 in both HeLa and FaDu cells nearly abolished curcumin-mediated radiosensitization. TxnRd1 knockdown cells showed decreased radiation-induced reactive oxygen species and sustained extracellular signal-regulated kinase 1/2 activation, which we previously showed was required for curcumin-mediated radiosensitization. Conversely, overexpressing catalytically active TxnRd1 in HEK293 cells, with low basal levels of TxnRd1, increased their sensitivity to curcumin alone and to the combination of curcumin and ionizing radiation. These results show the critical role of TxnRd1 in curcumin-mediated radiosensitization and suggest that TxnRd1 levels in tumors could have clinical value as a predictor of response to curcumin and radiotherapy.
| S-EPMC2831122 | biostudies-literature
Project description:Thioredoxins h are ubiquitous proteins reduced by NADPH- thioredoxin reductase (NTR). They are able to reduce disulphides in target proteins. In monocots, thioredoxins h accumulate at high level in seeds and show a predominant localization in the nucleus of seed cells. These results suggest that the NTR-thioredoxin h system probably plays an important role in seed physiology. To date, the study of this system in monocots is limited by the lack of information about NTR. In the present study, we describe the cloning of a full-length cDNA encoding NTR from wheat ( Triticum aestivum ). The polypeptide deduced from this cDNA shows close similarity to NTRs from Arabidopsis, contains FAD- and NADPH-binding domains and a disulphide probably interacting with the disulphide at the active site of thioredoxin h. Wheat NTR was expressed in Escherichia coli as a His-tagged protein. The absorption spectrum of the purified recombinant protein is typical of flavoenzymes. Furthermore, it showed NADPH-dependent thioredoxin h reduction activity, thus confirming that the cDNA clone reported in the present study encodes wheat NTR. Using the His-tagged NTR and TRXhA (wheat thioredoxin h ), we successfully reconstituted the wheat NTR-thioredoxin h system in vitro, as shown by the insulin reduction assay. A polyclonal antibody was raised against wheat NTR after immunization of rabbits with the purified His-tagged protein. This antibody efficiently detected a single polypeptide of the corresponding molecular mass in seed extracts and it allowed the analysis of the pattern of accumulation of NTR in different wheat organs and developmental stages. NTR shows a wide distribution in wheat, but, surprisingly, its accumulation in seeds is low, in contrast with the level of thioredoxins h.
| S-EPMC1222897 | biostudies-other
Project description:Energetic nutrients are oxidized to sustain high intracellular NADPH/NADP+ ratios. NADPH-dependent reduction of thioredoxin-1 (Trx1) disulfide and glutathione disulfide by thioredoxin reductase-1 (TrxR1) and glutathione reductase (Gsr), respectively, fuels antioxidant systems and deoxyribonucleotide synthesis. Mouse livers lacking both TrxR1 and Gsr sustain these essential activities using an NADPH-independent methionine-consuming pathway; however, it remains unclear how this reducing power is distributed. Here, we show that liver-specific co-disruption of the genes encoding Trx1, TrxR1, and Gsr (triple-null) causes dramatic hepatocyte hyperproliferation. Thus, even in the absence of Trx1, methionine-fueled glutathione production supports hepatocyte S phase deoxyribonucleotide production. Also, Trx1 in the absence of TrxR1 provides a survival advantage to cells under hyperglycemic stress, suggesting that glutathione, likely via glutaredoxins, can reduce Trx1 disulfide in vivo. In triple-null livers like in many cancers, deoxyribonucleotide synthesis places a critical yet relatively low-volume demand on these reductase systems, thereby favoring high hepatocyte turnover over sustained hepatocyte integrity.
| S-EPMC5730093 | biostudies-literature