APR-246/PRIMA-1MET inhibits thioredoxin reductase 1 and converts the enzyme to a dedicated NADPH oxidase.
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ABSTRACT:
SUBMITTER: Peng X
PROVIDER: S-EPMC3920950 | biostudies-other | 2013
REPOSITORIES: biostudies-other
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Project description:Mammalian thioredoxin reductase (TrxR) is an NADPH-dependent homodimer with three redox-active centers per subunit: a FAD, an N-terminal domain dithiol (Cys(59)/Cys(64)), and a C-terminal cysteine/selenocysteine motif (Cys(497)/Sec(498)). TrxR has multiple roles in antioxidant defense. Opposing these functions, it may also assume a pro-oxidant role under some conditions. In the absence of its main electron-accepting substrates (e.g. thioredoxin), wild-type TrxR generates superoxide (O ), which was here detected and quantified by ESR spin trapping with 5-diethoxyphosphoryl-5-methyl-1-pyrroline-N-oxide (DEPMPO). The peroxidase activity of wild-type TrxR efficiently converted the O adduct (DEPMPO/HOO(*)) to the hydroxyl radical adduct (DEPMPO/HO(*)). This peroxidase activity was Sec-dependent, although multiple mutants lacking Sec could still generate O . Variants of TrxR with C59S and/or C64S mutations displayed markedly reduced inherent NADPH oxidase activity, suggesting that the Cys(59)/Cys(64) dithiol is required for O generation and that O is not derived directly from the FAD. Mutations in the Cys(59)/Cys(64) dithiol also blocked the peroxidase and disulfide reductase activities presumably because of an inability to reduce the Cys(497)/Sec(498) active site. Although the bulk of the DEPMPO/HO(*) signal generated by wild-type TrxR was due to its combined NADPH oxidase and Sec-dependent peroxidase activities, additional experiments showed that some free HO(*) could be generated by the enzyme in an H(2)O(2)-dependent and Sec-independent manner. The direct NADPH oxidase and peroxidase activities of TrxR characterized here give insights into the full catalytic potential of this enzyme and may have biological consequences beyond those solely related to its reduction of thioredoxin.
| S-EPMC2898413 | biostudies-literature
Project description:The tumor suppressor p53 is commonly inactivated in human tumors, allowing evasion of p53-dependent apoptosis and tumor progression. The small molecule APR-246 (PRIMA-1Met) can reactive mutant p53 in tumor cells and trigger cell death by apoptosis. The thioredoxin (Trx) and glutaredoxin (Grx) systems are important as antioxidants for maintaining cellular redox balance and providing electrons for thiol-dependent reactions like those catalyzed by ribonucleotide reductase and peroxiredoxins (Prxs). We show here that the Michael acceptor methylene quinuclidinone (MQ), the active form of APR-246, is a potent direct inhibitor of Trx1 and Grx1 by reacting with sulfhydryl groups in the enzymes. The inhibition of Trx1 and Grx1 by APR-246/MQ is reversible and the inhibitory efficiency is dependent on the presence of glutathione. APR-246/MQ also inhibits Trxs in mutant p53-expressing Saos-2 His-273 cells, showing modification of Trx1 and mitochondrial Trx2. Inhibition of the Trx and Grx systems leads to insufficient reducing power to deoxyribonucleotide production for DNA replication and repair and peroxiredoxin for removal of ROS. We also demonstrate that APR-246 and MQ inhibit ribonucleotide reductase (RNR) in vitro and in living cells. Our results suggest that APR-246 induces tumor cell death through both reactivations of mutant p53 and inhibition of cellular thiol-dependent redox systems, providing a novel strategy for cancer therapy.
| S-EPMC6107631 | biostudies-literature
Project description:Low-molecular-weight (low Mr ) thioredoxin reductases (TrxRs) are homodimeric NADPH-dependent dithiol flavoenzymes that reduce thioredoxins (Trxs) or Trx-like proteins involved in the activation networks of enzymes, such as the bacterial class Ib ribonucleotide reductase (RNR). During the last few decades, TrxR-like ferredoxin/flavodoxin NADP+ oxidoreductases (FNRs) have been discovered and characterized in several types of bacteria, including those not encoding the canonical plant-type FNR. In Bacillus cereus, a TrxR-like FNR has been shown to reduce the flavodoxin-like protein NrdI in the activation of class Ib RNR. However, some species only encode TrxR and lack the homologous TrxR-like FNR. Due to the structural similarity between TrxRs and TrxR-like FNRs, as well as variations in their occurrence in different microorganisms, we hypothesized that low Mr TrxR may be able to replace TrxR-like FNR in, for example, the reduction of NrdI. In this study, characterization of TrxR from B. cereus has revealed a weak FNR activity toward NrdI reduction. Additionally, the crystal structure shows that only one out of two binding sites of the B. cereus TrxR homodimer is occupied with NADPH, indicating a possible asymmetric co-substrate binding in TrxR.
| S-EPMC8564101 | biostudies-literature
Project description:Plant chloroplasts have versatile thioredoxin systems including two thioredoxin reductases and multiple types of thioredoxins. Plastid-localized NADPH-dependent thioredoxin reductase (NTRC) contains both reductase (NTRd) and thioredoxin (TRXd) domains in a single polypeptide and forms homodimers. To study the action of NTRC and NTRC domains in vivo, we have complemented the ntrc knockout line of Arabidopsis with the wild type and full-length NTRC genes, in which 2-Cys motifs either in NTRd, or in TRXd were inactivated. The ntrc line was also transformed either with the truncated NTRd or TRXd alone. Overexpression of wild-type NTRC promoted plant growth by increasing leaf size and biomass yield of the rosettes. Complementation of the ntrc line with the full-length NTRC gene containing an active reductase but an inactive TRXd, or vice versa, recovered wild-type chloroplast phenotype and, partly, rosette biomass production, indicating that the NTRC domains are capable of interacting with other chloroplast thioredoxin systems. Overexpression of truncated NTRd or TRXd in ntrc background did not restore wild-type phenotype. Modeling of the three-dimensional structure of the NTRC dimer indicates extensive interactions between the NTR domains and the TRX domains further stabilize the dimeric structure. The long linker region between the NTRd and TRXd, however, allows flexibility for the position of the TRXd in the dimer. Supplementation of the TRXd in the NTRC homodimer model by free chloroplast thioredoxins indicated that TRXf is the most likely partner to interact with NTRC. We propose that overexpression of NTRC promotes plant biomass yield both directly by stimulation of chloroplast biosynthetic and protective pathways controlled by NTRC and indirectly via free chloroplast thioredoxins. Our data indicate that overexpression of chloroplast thiol redox-regulator has a potential to increase biofuel yield in plant and algal species suitable for sustainable bioenergy production.
| S-EPMC3792407 | biostudies-literature
Project description:Thioredoxins (Trxs) are protein disulfide reductases that regulate the intracellular redox environment and are important for seed germination in plants. Trxs are in turn regulated by NADPH-dependent thioredoxin reductases (NTRs), which provide reducing equivalents to Trx using NADPH to recycle Trxs to the active form. Here, the first crystal structure of a cereal NTR, HvNTR2 from Hordeum vulgare (barley), is presented, which is also the first structure of a monocot plant NTR. The structure was determined at 2.6 A resolution and refined to an R(cryst) of 19.0% and an R(free) of 23.8%. The dimeric protein is structurally similar to the structures of AtNTR-B from Arabidopsis thaliana and other known low-molecular-weight NTRs. However, the relative position of the two NTR cofactor-binding domains, the FAD and the NADPH domains, is not the same. The NADPH domain is rotated by 25 degrees and bent by a 38% closure relative to the FAD domain in comparison with AtNTR-B. The structure may represent an intermediate between the two conformations described previously: the flavin-oxidizing (FO) and the flavin-reducing (FR) conformations. Here, analysis of interdomain contacts as well as phylogenetic studies lead to the proposal of a new reaction scheme in which NTR-Trx interactions mediate the FO to FR transformation.
| S-EPMC2733882 | biostudies-literature
Project description:Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by loss of tolerance to self nucleic acids. The source of autoantigen that drives disease onset and progression is unclear. A candidate source of autoantigen is the neutrophil extracellular trap (NET), which releases nucleic acids into the extracellular environment, generating a structure composed of DNA coated with antimicrobial proteins. On the basis of in vitro and patient correlative studies, several groups have suggested that NETs may provide lupus autoantigens. The observation that NET release (NETosis) relies on activity of the phagocyte NADPH (reduced form of nicotinamide adenine dinucleotide phosphate) oxidase (Nox2) in neutrophils of both humans and mice provided a genetic strategy to test this hypothesis in vivo. Therefore, we crossed an X-linked nox2 null allele onto the lupus-prone MRL.Fas(lpr) genetic background and assessed immune activation, autoantibody generation, and SLE pathology. Counter to the prevailing hypothesis, Nox2-deficient lupus-prone mice had markedly exacerbated lupus, including increased spleen weight, increased renal disease, and elevated and altered autoantibody profiles. Moreover, heterozygous female mice, which have Nox2 deficiency in 50% of neutrophils, also had exacerbated lupus and altered autoantibody patterns, suggesting that failure to undergo normal Nox2-dependent cell death may result in release of immunogenic self-constituents that stimulate lupus. Our results indicate that NETosis does not contribute to SLE in vivo; instead, Nox2 acts to inhibit disease pathogenesis, making this enzyme an important target for further study and a candidate for therapeutic intervention.
| S-EPMC3704198 | biostudies-literature
Project description:2-Cys peroxiredoxins (Prxs) play important roles in the protection of chloroplast proteins from oxidative damage. Arabidopsis NADPH-dependent thioredoxin reductase isotype C (AtNTRC) was identified as efficient electron donor for chloroplastic 2-Cys Prx-A. There are three isotypes (A, B, and C) of thioredoxin reductase (TrxR) in Arabidopsis. AtNTRA contains only TrxR domain, but AtNTRC consists of N-terminal TrxR and C-terminal thioredoxin (Trx) domains. AtNTRC has various oligomer structures, and Trx domain is important for chaperone activity. Our previous experimental study has reported that the hybrid protein (AtNTRA-(Trx-D)), which was a fusion of AtNTRA and Trx domain from AtNTRC, has formed variety of structures and shown strong chaperone activity. But, electron transfer mechanism was not detected at all. To find out the reason of this problem with structural basis, we performed two different molecular dynamics (MD) simulations on AtNTRC and AtNTRA-(Trx-D) proteins with same cofactors such as NADPH and flavin adenine dinucleotide (FAD) for 50 ns. Structural difference has found from superimposition of two structures that were taken relatively close to average structure. The main reason that AtNTRA-(Trx-D) cannot transfer the electron from TrxR domain to Trx domain is due to the difference of key catalytic residues in active site. The long distance between TrxR C153 and disulfide bond of Trx C387-C390 has been observed in AtNTRA-(Trx-D) because of following reasons: i) unstable and unfavorable interaction of the linker region, ii) shifted Trx domain, and iii) different or weak interface interaction of Trx domains. This study is one of the good examples for understanding the relationship between structure formation and reaction activity in hybrid protein. In addition, this study would be helpful for further study on the mechanism of electron transfer reaction in NADPH-dependent thioredoxin reductase proteins.
| S-EPMC3459921 | biostudies-literature
Project description:Tight control of cellular redox homeostasis is essential for protection against oxidative damage and for maintenance of normal metabolism as well as redox signaling events. Under oxidative stress conditions, the tripeptide glutathione can switch from its reduced form (GSH) to oxidized glutathione disulfide (GSSG), and thus, forms an important cellular redox buffer. GSSG is normally reduced to GSH by 2 glutathione reductase (GR) isoforms encoded in the Arabidopsis genome, cytosolic GR1 and GR2 dual-targeted to chloroplasts and mitochondria. Measurements of total GR activity in leaf extracts of wild-type and 2 gr1 deletion mutants revealed that approximately 65% of the total GR activity is attributed to GR1, whereas approximately 35% is contributed by GR2. Despite the lack of a large share in total GR activity, gr1 mutants do not show any informative phenotype, even under stress conditions, and thus, the physiological impact of GR1 remains obscure. To elucidate its role in plants, glutathione-specific redox-sensitive GFP was used to dynamically measure the glutathione redox potential (E(GSH)) in the cytosol. Using this tool, it is shown that E(GSH) in gr1 mutants is significantly shifted toward more oxidizing conditions. Surprisingly, dynamic reduction of GSSG formed during induced oxidative stress in gr1 mutants is still possible, although significantly delayed compared with wild-type plants. We infer that there is functional redundancy in this critical pathway. Integrated biochemical and genetic assays identify the NADPH-dependent thioredoxin system as a backup system for GR1. Deletion of both, NADPH-dependent thioredoxin reductase A and GR1, prevents survival due to a pollen lethal phenotype.
| S-EPMC2690020 | biostudies-literature
Project description:In natural growth habitats, plants face constant, unpredictable changes in light conditions. To avoid damage to the photosynthetic apparatus on thylakoid membranes in chloroplasts, and to avoid wasteful reactions, it is crucial to maintain a redox balance both within the components of photosynthetic electron transfer chain and between the light reactions and stromal carbon metabolism under fluctuating light conditions. This requires coordinated function of the photoprotective and regulatory mechanisms, such as non-photochemical quenching (NPQ) and reversible redistribution of excitation energy between photosystem II (PSII) and photosystem I (PSI). In this paper, we show that the NADPH-dependent chloroplast thioredoxin system (NTRC) is involved in the control of the activation of these mechanisms. In plants with altered NTRC content, the strict correlation between lumenal pH and NPQ is partially lost. We propose that NTRC contributes to downregulation of a slow-relaxing constituent of NPQ, whose induction is independent of lumenal acidification. Additionally, overexpression of NTRC enhances the ability to adjust the excitation balance between PSII and PSI, and improves the ability to oxidize the electron transfer chain during changes in light conditions. Thiol regulation allows coupling of the electron transfer chain to the stromal redox state during these changes.
| S-EPMC6850073 | biostudies-literature
Project description:Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer worldwide. Mutations of TP53 may reach 70% - 85% in HNSCC patients without human papillomavirus (HPV) infection. Recurrence rate remains particularly high for HNSCC patients with mutations in the TP53 gene although patients are responsive to surgery, irradiation, and chemotherapy early in the treatment. p53-Reactivation and Induction of Massive Apoptosis-1 (PRIMA-1) and its methylated analogue PRIMA-1Met (also known as APR-246) are quinuclidine compounds that rescue the DNA-binding activity of mutant p53 (mut-p53) and restore the potential of wild-type p53. In the current report, we demonstrated that inhibition of poly (ADP-ribose) polymerase-1 (PARP-1) with 6(5H)-phenanthridinone (PHEN) and N-(6-Oxo-5,6-dihydrophenanthridin-2-yl)-(N, N-dimethylamino) acetamide hydrochloride (PJ34) sensitizes UMSCC1, UMSCC14, and UMSCC17A, three HNSCC cell lines to the treatment of APR-246. PHEN enhances APR-246-induced apoptosis, but not programmed necrosis or autophagic cell death in HNSCC cells. The PARP-1 inhibition-induced sensitization of HNSCC cells to APR-246 is independent of TP53 mutation. Instead, PARP-1 inhibition promotes APR-246-facilitated inactivation of thioredoxin reductase 1 (TrxR1), leading to ROS accumulation and DNA damage. Overexpression of TrxR1 or application of antioxidant N-acetyl-L-cysteine (NAC) depletes the ROS increase, reduces DNA damage, and decreases cell death triggered by APR-246/PHEN in HNSCC cells. Thus, we have characterized a new function of PARP-1 inhibitor in HNSCC cells by inactivation of TrxR1 and elevation of ROS and provide a novel therapeutic strategy for HNSCC by the combination of PARP-1 inhibitors and APR-246.
| S-EPMC5788606 | biostudies-literature