| 1. |
- Prigge, Justin R., et al.
(författare)
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Hepatocyte Hyperproliferation upon Liver-Specific Co-disruption of Thioredoxin-1, Thioredoxin Reductase-1, and Glutathione Reductase
- 2017
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Ingår i: Cell Reports. - : Cell Press. - 2211-1247. ; 19:13, s. 2771-2781
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Tidskriftsartikel (refereegranskat)abstract
- 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 (triplenull) 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.
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| 2. |
- Stafford, William C., et al.
(författare)
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Irreversible inhibition of cytosolic thioredoxin reductase 1 as a mechanistic basis for anticancer therapy
- 2018
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Ingår i: Science Translational Medicine. - : AMER ASSOC ADVANCEMENT SCIENCE. - 1946-6234 .- 1946-6242. ; 10:428
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Tidskriftsartikel (refereegranskat)abstract
- Cancer cells adapt to their inherently increased oxidative stress through activation of the glutathione (GSH) and thioredoxin (TXN) systems. Inhibition of both of these systems effectively kills cancer cells, but such broad inhibition of antioxidant activity also kills normal cells, which is highly unwanted in a clinical setting. We therefore evaluated targeting of the TXN pathway alone and, more specifically, selective inhibition of the cytosolic selenocysteine-containing enzyme TXN reductase 1 (TXNRD1). TXNRD1 inhibitors were discovered in a large screening effort and displayed increased specificity compared to pan-TXNRD inhibitors, such as auranofin, that also inhibit the mitochondrial enzyme TXNRD2 and additional targets. For our lead compounds, TXNRD1 inhibition correlated with cancer cell cytotoxicity, and inhibitor-triggered conversion of TXNRD1 from an antioxidant to a pro-oxidant enzyme correlated with corresponding increases in cellular production of H2O2. In mice, the most specific TXNRD1 inhibitor, here described as TXNRD1 inhibitor 1 (TRi-1), impaired growth and viability of human tumor xenografts and syngeneic mouse tumors while having little mitochondrial toxicity and being better tolerated than auranofin. These results display the therapeutic anticancer potential of irreversibly targeting cytosolic TXNRD1 using small molecules and present potent and selective TXNRD1 inhibitors. Given the pronounced up-regulation of TXNRD1 in several metastatic malignancies, it seems worthwhile to further explore the potential benefit of specific irreversible TXNRD1 inhibitors for anticancer therapy.
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| 3. |
- Arnér, Elias S. J., et al.
(författare)
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Analysis of the inhibition of mammalian thioredoxin, thioredoxin reductase, and glutaredoxin by cis-diamminedichloroplatinum (II) and its major metabolite, the glutathione-platinum complex
- 2001
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Ingår i: Free Radical Biology & Medicine. - : Elsevier. - 0891-5849 .- 1873-4596. ; 31:10, s. 1170-1178
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Tidskriftsartikel (refereegranskat)abstract
- Several studies have demonstrated a correlation between cellular toxicity of cis-diamminedichloroplatinum (II) (cisplatin, CDDP) and inhibited intracellular activity of the thioredoxin system, i.e., thioredoxin (Trx), thioredoxin reductase (TrxR), and NADPH. Conversely, increased cellular activity of the Trx system confers resistance to CDDP. In this study, we have analyzed the interaction of CDDP with Trx and TrxR in order to clarify the mechanism. The inhibition with time-dependent kinetics by CDDP of NADPH-reduced (but not oxidized) TrxR was irreversible, strongly suggesting covalent modification of the reduced selenocysteine-containing active site. Assuming second order kinetics, the rate constant of TrxR inhibition by CDDP was 21 +/- 3 M(-1) x s(-1). Transplatin was found to be an even more efficient inhibitor, with a second order rate constant of 84 +/- 22 M(-1) x s(-1), whereas carboplatin (up to 1 mM) gave no inhibition of the enzyme under the same conditions. Escherichia coli Trx or human or bacterial glutaredoxin (Grx) activities were in comparison only slightly or not at all inhibited by either CDDP, transplatin, or carboplatin. However, glutaredoxins were found to be inhibited by the purified glutathione adduct of cisplatin, bis-(glutathionato)platinum(II) (GS-Platinum complex, GS-Pt), with an IC50 = 350 microM in the standard beta-hydroxyethyl disulfide-coupled assay for human Grx. Also the mammalian Trx system was inhibited by GS-Pt with similar efficiency (IC(50) = 325 microM), whereas neither the E. coli Trx system nor glutathione reductase were inhibited. Formation of GS-Pt is a major route for cellular elimination of CDDP. The fact that GS-Pt inhibits the mammalian Trx as well as Grx systems shows that CDDP may exert effects at several stages of its metabolism, including after conjugation with GSH, which are intimately linked with the cellular disulfide/dithiol redox regulatory systems.
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| 4. |
- Arnér, Elias S J
(författare)
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Redox pioneer : Professor Arne Holmgren
- 2011
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Ingår i: Antioxidants and Redox Signaling. - Stockholm : Karolinska Institutet, Dept of Medical Biochemistry and Biophysics. - 1557-7716 .- 1523-0864.
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Tidskriftsartikel (refereegranskat)abstract
- Dr. Arne Holmgren (Ph.D., 1968) is recognized here as a redox pioneer, because he has published at least one article on redox biology that has been cited over 1000 times and has published at least 10 articles, each cited over 100 times. He is widely known for his seminal discoveries and in-depth studies of thioredoxins, thioredoxin reductases, and glutaredoxins. Dr. Holmgren, active throughout his career at Karolinska Institutet, Sweden, has led the field of research about these classes of proteins for more than 45 years, continuously building upon his sequence determination of Escherichia coli thioredoxin in the late 1960s and discovery of the thioredoxin fold in the 1970s. He discovered and named glutaredoxin and he determined the structure and function of several members of these glutathione-dependent disulfide oxidoreductases. He still continues to broaden the frontiers of knowledge of thioredoxin and glutaredoxin systems. The thioredoxin fold is today recognized as one of the most common protein folds and the intriguing complexity of redox systems, redox signaling, and redox control of cellular function is constantly increasing. The legacy of Dr. Holmgren's research is therefore highly relevant and important also in the context of present science. In a tribute to his work, questions need to be addressed toward the physiological importance of redox signaling and the impact of glutaredoxin and thioredoxin systems on health and disease. Dr. Holmgren helped lay the foundation for the redox biology field and opened new vistas in the process. He is truly a redox pioneer.
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| 5. |
- Carlström, Karl E., et al.
(författare)
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Characterization of More Selective Central Nervous System Nrf2-Activating Novel Vinyl Sulfoximine Compounds Compared to Dimethyl Fumarate
- 2020
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Ingår i: NEUROTHERAPEUTICS. - : SPRINGER. - 1933-7213 .- 1878-7479. ; 17, s. 1142-1152
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Tidskriftsartikel (refereegranskat)abstract
- The Nrf2 transcription factor is a key regulator of redox reactions and considered the main target for the multiple sclerosis (MS) drug dimethyl fumarate (DMF). However, exploration of additional Nrf2-activating compounds is motivated, since DMF displays significant off-target effects and has a relatively poor penetrance to the central nervous system (CNS). We de novo synthesized eight vinyl sulfone and sulfoximine compounds (CH-1-CH-8) and evaluated their capacity to activate the transcription factors Nrf2, NF kappa B, and HIF1 in comparison with DMF using the pTRAF platform. The novel sulfoximine CH-3 was the most promising candidate and selected for further comparison in vivo and later an experimental model for traumatic brain injury (TBI). CH-3 and DMF displayed comparable capacity to activate Nrf2 and downstream transcripts in vitro, but with less off-target effects on HIF1 from CH-3. This was verified in cultured microglia and oligodendrocytes (OLs) and subsequently in vivo in rats. Following TBI, DMF lowered the number of leukocytes in blood and also decreased axonal degeneration. CH-3 preserved or increased the number of pre-myelinating OL. While both CH-3 and DMF activated Nrf2, CH-3 showed less off-target effects and displayed more selective OL associated effects. Further studies with Nrf2-acting compounds are promising candidates to explore potential myelin protective or regenerative effects in demyelinating disorders.
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| 6. |
- Cheng, Qing, et al.
(författare)
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Preclinical PET imaging of EGFR levels : pairing a targeting with a non-targeting Sel-tagged Affibody-based tracer to estimate the specific uptake
- 2016
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Ingår i: EJNMMI Research. - : Springer. - 2191-219X. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Background: Though overexpression of epidermal growth factor receptor (EGFR) in several forms of cancer is considered to be an important prognostic biomarker related to poor prognosis, clear correlations between biomarker assays and patient management have been difficult to establish. Here, we utilize a targeting directly followed by a non-targeting tracer-based positron emission tomography (PET) method to examine some of the aspects of determining specific EGFR binding in tumors. Methods: The EGFR-binding Affibody molecule Z(EGFR:2377) and its size-matched non-binding control Z(Taq:3638) were recombinantly fused with a C-terminal selenocysteine-containing Sel-tag (Z(EGFR:2377)-ST and Z(Taq:3638)-ST). The proteins were site-specifically labeled with DyLight488 for flow cytometry and ex vivo tissue analyses or with C-11 for in vivo PET studies. Kinetic scans with the C-11-labeled proteins were performed in healthy mice and in mice bearing xenografts from human FaDu (squamous cell carcinoma) and A431 (epidermoid carcinoma) cell lines. Changes in tracer uptake in A431 xenografts over time were also monitored, followed by ex vivo proximity ligation assays (PLA) of EGFR expressions. Results: Flow cytometry and ex vivo tissue analyses confirmed EGFR targeting by ZE(GFR:2377)-ST-DyLight488. [Methyl-C-11]-labeled Z(EGFR:2377)-ST-CH3 and Z(Taq:3638)-ST-CH3 showed similar distributions in vivo, except for notably higher concentrations of the former in particularly the liver and the blood. [Methyl-C-11]-Z(EGFR:2377)-ST-CH3 successfully visualized FaDu and A431 xenografts with moderate and high EGFR expression levels, respectively. However, in FaDu tumors, the non-specific uptake was large and sometimes equally large, illustrating the importance of proper controls. In the A431 group observed longitudinally, non-specific uptake remained at same level over the observation period. Specific uptake increased with tumor size, but changes varied widely over time in individual tumors. Total (membranous and cytoplasmic) EGFR in excised sections increased with tumor growth. There was no positive correlation between total EGFR and specific tracer uptake, which, since Z(EGFR:2377) binds extracellularly and is slowly internalized, indicates a discordance between available membranous and total EGFR expression levels. Conclusions: Same-day in vivo dual tracer imaging enabled by the Sel-tag technology and C-11-labeling provides a method to non-invasively monitor membrane-localized EGFR as well as factors affecting non-specific uptake of the PET ligand.
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| 7. |
- Collins, Ruairi, et al.
(författare)
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Biochemical discrimination between selenium and sulfur 1 : a single residue provides selenium specificity to human selenocysteine lyase
- 2012
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Ingår i: PLoS One. - Stockholm : Karolinska Institutet, Dept of Medical Biochemistry and Biophysics. - 1932-6203.
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Tidskriftsartikel (refereegranskat)abstract
- Selenium and sulfur are two closely related basic elements utilized in nature for a vast array of biochemical reactions. While toxic at higher concentrations, selenium is an essential trace element incorporated into selenoproteins as selenocysteine (Sec), the selenium analogue of cysteine (Cys). Sec lyases (SCLs) and Cys desulfurases (CDs) catalyze the removal of selenium or sulfur from Sec or Cys and generally act on both substrates. In contrast, human SCL (hSCL) is specific for Sec although the only difference between Sec and Cys is the identity of a single atom. The chemical basis of this selenium-over-sulfur discrimination is not understood. Here we describe the X-ray crystal structure of hSCL and identify Asp146 as the key residue that provides the Sec specificity. A D146K variant resulted in loss of Sec specificity and appearance of CD activity. A dynamic active site segment also provides the structural prerequisites for direct product delivery of selenide produced by Sec cleavage, thus avoiding release of reactive selenide species into the cell. We thus here define a molecular determinant for enzymatic specificity discrimination between a single selenium versus sulfur atom, elements with very similar chemical properties. Our findings thus provide molecular insights into a key level of control in human selenium and selenoprotein turnover and metabolism.
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| 8. |
- Dammeyer, Pascal, et al.
(författare)
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Cisplatin and oxaliplatin are toxic to cochlear outer hair cells and both target thioredoxin reductase in organ of Corti cultures
- 2014
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Ingår i: Acta Oto-Laryngologica. - : Informa UK Limited. - 0001-6489 .- 1651-2251. ; 134:5, s. 448-454
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Tidskriftsartikel (refereegranskat)abstract
- Conclusion: Inhibition of thioredoxin reductase (TrxR) may be a contributing factor in cisplatin- induced ototoxicity. Direct exposure of organ of Corti to cisplatin and oxaliplatin gives equal loss of hair cells. Objectives: Platinum- containing drugs are known to target the anti- oxidant selenoprotein TrxR in cancer cells. Two such anti- cancer, platinum- containing drugs, cisplatin and oxaliplatin, have different side effects. Only cisplatin induces hearing loss, i.e. has an ototoxic side effect that is not seen after treatment with oxaliplatin. The objective of this study was to evaluate if TrxR is a target in the cochlea. Loss of outer hair cells was also compared when cisplatin and oxaliplatin were administered directly to the organ of Corti. Methods: Organ of Corti cell culture was used for direct exposure to cisplatin and oxaliplatin. Hair cells were evaluated and the level of TrxR was assessed. Immunohistochemical staining for TrxR was performed. An animal model was used to evaluate the effect on TrxR after treatment with cisplatin and oxaliplatin in vivo. Results: Direct exposure of cochlear organotypic cultures to either cisplatin or oxaliplatin induced comparable levels of outer hair cell loss and inhibition of TrxR, demonstrating that both drugs are similarly ototoxic provided that the cochlea becomes directly exposed.
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| 9. |
- Johansson, Ann-Louise, et al.
(författare)
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Biochemical discrimination between selenium and sulfur 2 : mechanistic investigation of the selenium specificity of human selenocysteine lyase
- 2012
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Ingår i: PLoS One. - Stockholm : Karolinska Institutet, Dept of Medical Biochemistry and Biophysics. - 1932-6203.
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Tidskriftsartikel (refereegranskat)abstract
- Selenium is an essential trace element incorporated into selenoproteins as selenocysteine. Selenocysteine (Sec) lyases (SCLs) and cysteine (Cys) desulfurases (CDs) catalyze the removal of selenium or sulfur from Sec or Cys, respectively, and generally accept both substrates. Intriguingly, human SCL (hSCL) is specific for Sec even though the only difference between Sec and Cys is a single chalcogen atom. The crystal structure of hSCL was recently determined and gain-of-function protein variants that also could accept Cys as substrate were identified. To obtain mechanistic insight into the chemical basis for its substrate discrimination, we here report time-resolved spectroscopic studies comparing the reactions of the Sec-specific wild-type hSCL and the gain-of-function D146K/H389T variant, when given Cys as a substrate. The data are interpreted in light of other studies of SCL/CD enzymes and offer mechanistic insight into the function of the wild-type enzyme. Based on these results and previously available data we propose a reaction mechanism whereby the Sec over Cys specificity is achieved using a combination of chemical and physico-mechanical control mechanisms.
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| 10. |
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| 11. |
- Katsu-Jimenez, Yurika, et al.
(författare)
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Absence of TXNIP in Humans Leads to Lactic Acidosis and Low Serum Methionine Linked to Deficient Respiration on Pyruvate
- 2019
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Ingår i: Diabetes. - : AMER DIABETES ASSOC. - 0012-1797 .- 1939-327X. ; 68:4, s. 709-723
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Tidskriftsartikel (refereegranskat)abstract
- Thioredoxin-interacting protein (TXNIP) is an -arrestin that can bind to and inhibit the antioxidant protein thioredoxin (TXN). TXNIP expression is induced by glucose and promotes -cell apoptosis in the pancreas, and deletion of its gene in mouse models protects against diabetes. TXNIP is currently studied as a potential new target for antidiabetic drug therapy. In this study, we describe a family with a mutation in the TXNIP gene leading to nondetectable expression of TXNIP protein. Symptoms of affected family members include lactic acidosis and low serum methionine levels. Using patient-derived TXNIP-deficient fibroblasts and myoblasts, we show that oxidative phosphorylation is impaired in these cells when given glucose and pyruvate but normalized with malate. Isolated mitochondria from these cells appear to have normal respiratory function. The cells also display a transcriptional pattern suggestive of a high basal activation of the Nrf2 transcription factor. We conclude that a complete lack of TXNIP in human is nonlethal and leads to specific metabolic distortions that are, at least in part, linked to a deficient respiration on pyruvate. The results give important insights into the impact of TXNIP in humans and thus help to further advance the development of antidiabetic drugs targeting this protein.
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| 12. |
- Locy, Morgan L, et al.
(författare)
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Thioredoxin reductase inhibition elicits Nrf2-mediated responses in Clara cells : implications for oxidant-induced lung injury
- 2012
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Ingår i: Antioxidants and Redox Signaling. - Stockholm : Karolinska Institutet, Dept of Medical Biochemistry and Biophysics. - 1557-7716 .- 1523-0864.
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Tidskriftsartikel (refereegranskat)abstract
- Aims: Pulmonary oxygen toxicity contributes to lung injury in newborn and adult humans.We previously reported that thioredoxin reductase (TrxR1) inhibition with aurothioglucose (ATG) attenuates hyperoxic lung injury in adult mice. The present studies tested the hypothesis that TrxR1 inhibition protects against the effects of hyperoxia via nuclear factor E2-related factor 2 (Nrf2)-dependent mechanisms. Results: Both pharmacologic and siRNA-mediated TrxR1 inhibition induced robust Nrf2 responses in murine-transformed Clara cells (mtCC). While TrxR1 inhibition did not alter the susceptibility of cells to the effects of hyperoxia, glutathione (GSH) depletion after TrxR1 inhibition markedly enhanced the hyperoxic susceptibility of cultured mtCCs. Finally, in vivo data revealed dose-dependent increases in the expression of the Nrf2 target gene NADPH:quinone oxidoreductase 1 (NQO1) in the lungs of ATGtreated adult mice. Innovation: TrxR1 inhibition activates Nrf2-dependent antioxidant responses in mtCCs in vitro and in adult murine lungs in vivo, providing a plausible mechanism for the protective effects of TrxR1 inhibition in vivo. Conclusion: GSH-dependent enzyme systems in mtCCs may be of greater importance for protection against hyperoxic exposure than are TrxR-dependent systems. The induction of Nrf2 activation via TrxR1 inhibition represents a novel therapeutic strategy that attenuates oxidant-mediated lung injury. Similar expression levels of TrxR1 in newborn and adult mouse or human lungs broaden the potential clinical applicability of the present findings to both neonatal and adult oxidant lung injury.
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| 13. |
- Nalvarte, Ivan, et al.
(författare)
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Overexpression of enzymatically active human cytosolic and mitochondrial thioredoxin reductase in HEK-293 cells : Effect on cell growth and differentiation
- 2004
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Ingår i: Journal of Biological Chemistry. - : American Society for Biochemistry and Molecular Biology. - 0021-9258 .- 1083-351X. ; 279:52, s. 54510-54517
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Tidskriftsartikel (refereegranskat)abstract
- The mammalian thioredoxin reductases (TrxR) are selenoproteins containing a catalytically active selenocysteine residue (Sec) and are important enzymes in cellular redox control. The cotranslational incorporation of Sec, necessary for activity, is governed by a stem-loop structure in the 3'-untranslated region of the mRNA and demands adequate selenium availability. The complicated translation machinery required for Sec incorporation is a major obstacle in isolating mammalian cell lines stably overexpressing selenoproteins. In this work we report on the development and characterization of stably transfected human embryonic kidney 293 cells that overexpress enzymatically active selenocysteine-containing cytosolic TrxR1 or mitochondrial TrxR2. We demonstrate that the overexpression of selenium-containing TrxR1 results in lower expression and activity of the endogenous selenoprotein glutathione peroxidase and that the activity of overexpressed TrxRs, rather than the protein amount, can be increased by selenium supplementation in the cell growth media. We also found that the TrxR-overexpressing cells grew slower over a wide range of selenium concentrations, which was an effect apparently not related to increased apoptosis nor to fatally altered intracellular levels of reactive oxygen species. Most surprisingly, the TrxR1- or TrxR2-overexpressing cells also induced novel expression of the epithelial markers CK18, CK-Cam5.2, and BerEP4, suggestive of a stimulation of cellular differentiation.
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| 14. |
- Nordman, Tomas, et al.
(författare)
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Regeneration of the antioxidant ubiquinol by lipoamide dehydrogenase, thioredoxin reductase and glutathione reductase
- 2003
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Ingår i: Biofactors. - : IOS Press. - 0951-6433 .- 1872-8081. ; 18:1-4, s. 45-50
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Tidskriftsartikel (refereegranskat)abstract
- Ubiquinol is a powerful antioxidant, which is oxidized in action and needs to be replaced or regenerated to be capable of a sustained effort. This article summarises current knowledge of extramitochondrial reduction of ubiquinone by three flavoenzymes, i.e. lipoamide dehydrogenase, glutathione reductase and thioredoxin reductase, belonging to the same pyridine nucleotide-disulfide oxidoreductase family. These three enzymes are the most efficient extramitochondrial ubiquinone reductases so far described. The reduction of ubiquinone by lipoamide dehydrogenase and glutathione reductase is potently stimulated by zinc and the highest rate of reduction is achieved at acidic pH and the rates are equal with either NADPH or NADH as co-factors. The most efficient ubiquinone reductases are mammalian cytosolic thioredoxin reductases, which are selenoenzymes with a number of biological functions. Reduction of ubiquinone by thioredoxin reductase is in contrast to the other two enzymes investigated, inhibited by zinc and shows a sharp physiological pH optimum at pH 7.5. Furthermore, the reaction is selenium dependent as revealed from experiments using truncated and mutant forms of the enzyme and also in a cellular context by selenium treatment of transfected thioredoxin reductase overexpressing stable cell lines. The reduction of ubiquinone by the three enzymes offers a multifunctional system for extramitochondrial regeneration of an important antioxidant.
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| 15. |
- Saei, Amir Ata, et al.
(författare)
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Comprehensive chemical proteomics for target deconvolution of the redox active drug auranofin
- 2020
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Ingår i: Redox Biology. - : Elsevier BV. - 2213-2317. ; 32
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Tidskriftsartikel (refereegranskat)abstract
- Chemical proteomics encompasses novel drug target deconvolution methods in which compound modification is not required. Herein we use Thermal Proteome Profiling, Functional Identification of Target by Expression Proteomics and multiplexed redox proteomics for deconvolution of auranofin targets to aid elucidation of its mechanisms of action. Auranofin (Ridaura (R)) was approved for treatment of rheumatoid arthritis in 1985. Because several clinical trials are currently ongoing to repurpose auranofin for cancer therapy, comprehensive characterization of its targets and effects in cancer cells is important. Together, our chemical proteomics tools confirmed thioredoxin reductase 1 (TXNRD1, EC:1.8.1.9) as a main auranofin target, with perturbation of oxidoreductase pathways as the top mechanism of drug action. Additional indirect targets included NFKB2 and CHORDC1. Our comprehensive data can be used as a proteomic signature resource for further analyses of the effects of auranofin. Here we also assessed the orthogonality and complementarity of different chemical proteomics methods that can furnish invaluable mechanistic information and thus the approach can facilitate drug discovery efforts in general.
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| 16. |
- Saei, Amir Ata, et al.
(författare)
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System-wide identification and prioritization of enzyme substrates by thermal analysis
- 2021
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Despite the immense importance of enzyme-substrate reactions, there is a lack of general and unbiased tools for identifying and prioritizing substrate proteins that are modified by the enzyme on the structural level. Here we describe a high-throughput unbiased proteomics method called System-wide Identification and prioritization of Enzyme Substrates by Thermal Analysis (SIESTA). The approach assumes that the enzymatic post-translational modification of substrate proteins is likely to change their thermal stability. In our proof-of-concept studies, SIESTA successfully identifies several known and novel substrate candidates for selenoprotein thioredoxin reductase 1, protein kinase B (AKT1) and poly-(ADP-ribose) polymerase-10 systems. Wider application of SIESTA can enhance our understanding of the role of enzymes in homeostasis and disease, opening opportunities to investigate the effect of post-translational modifications on signal transduction and facilitate drug discovery.
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| 17. |
- Selvaraj, Karthik, et al.
(författare)
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Cytotoxic unsaturated electrophilic compounds commonly target the ubiquitin proteasome system
- 2019
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Ingår i: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- A large number of natural products have been advocated as anticancer agents. Many of these compounds contain functional groups characterized by chemical reactivity. It is not clear whether distinct mechanisms of action can be attributed to such compounds. We used a chemical library screening approach to demonstrate that a substantial fraction (similar to 20%) of cytotoxic synthetic compounds containing Michael acceptor groups inhibit proteasome substrate processing and induce a cellular response characteristic of proteasome inhibition. Biochemical and structural analyses showed binding to and inhibition of proteasome-associated cysteine deubiquitinases, in particular ubiquitin specific peptidase 14 (USP14). The results suggested that compounds bind to a crevice close to the USP14 active site with modest affinity, followed by covalent binding. A subset of compounds was identified where cell death induction was closely associated with proteasome inhibition and that showed significant antineoplastic activity in a zebrafish embryo model. These findings suggest that proteasome inhibition is a relatively common mode of action by cytotoxic compounds containing Michael acceptor groups and help to explain previous reports on the antineoplastic effects of natural products containing such functional groups.
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| 18. |
- Stenvall, Jörgen, et al.
(författare)
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Selenoprotein TRXR-1 and GSR-1 are essential for removal of old cuticle during molting in Caenorhabditis elegans
- 2011
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 108:3, s. 1064-1069
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Tidskriftsartikel (refereegranskat)abstract
- Selenoproteins, in particular thioredoxin reductase, have been implicated in countering oxidative damage occurring during aging but the molecular functions of these proteins have not been extensively investigated in different animal models. Here we demonstrate that TRXR-1 thioredoxin reductase, the sole selenoprotein in Caenorhabditis elegans, does not protect against acute oxidative stress but functions instead together with GSR-1 glutathione reductase to promote the removal of old cuticle during molting. We show that the oxidation state of disulfide groups in the cuticle is tightly regulated during the molting cycle, and that when trxr-1 and gsr-1 function is reduced, disulfide groups in the cuticle remain oxidized. A selenocysteine-to-cysteine TRXR-1 mutant fails to rescue molting defects. Furthermore, worms lacking SELB-1, the C. elegans homolog of Escherichia coli SelB or mammalian EFsec, a translation elongation factor known to be specific for selenocysteine in E. coli, fail to incorporate selenocysteine, and display the same phenotype as those lacking trxr-1. Thus, TRXR-1 function in the reduction of old cuticle is strictly selenocysteine dependent in the nematode. Exogenously supplied reduced glutathione reduces disulfide groups in the cuticle and induces apolysis, the separation of old and new cuticle, strongly suggesting that molting involves the regulated reduction of cuticle components driven by TRXR-1 and GSR-1. Using dauer larvae, we demonstrate that aged worms have a decreased capacity to molt, and decreased expression of GSR-1. Together, our results establish a function for the selenoprotein TRXR-1 and GSR-1 in the removal of old cuticle from the surface of epidermal cells.
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| 19. |
- Wang, Xin, et al.
(författare)
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The 19S Deubiquitinase Inhibitor b-AP15 Is Enriched in Cells and Elicits Rapid Commitment to Cell Death
- 2014
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Ingår i: Molecular Pharmacology. - 0026-895X .- 1521-0111. ; 85:6, s. 932-945
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Tidskriftsartikel (refereegranskat)abstract
- b-AP15 [(3E, 5E)-3,5-bis[(4-nitrophenyl) methylidene]-1-(prop-2enoyl) piperidin-4-one] is a small molecule inhibitor of the ubiquitin specific peptidase (USP) 14/ubiquitin carboxyl-terminal hydrolase (UCH) L5 deubiquitinases of the 19S proteasome that shows antitumor activity in a number of tumor models, including multiple myeloma. b-AP15 contains an alpha,beta-unsaturated carbonyl unit that is likely to react with intracellular nucleophiles such as cysteine thiolates by Michael addition. We found that binding of b-AP15 to USP14 is partially reversible, and that inhibition of proteasome function is reversible in cells. Despite reversible binding, tumor cells are rapidly committed to apoptosis/cell death after exposure to b-AP15. We show that b-AP15 is rapidly taken up from the medium and enriched in cells. Enrichment provides an explanation of the stronger potency of the compound in cellular assays compared with in vitro biochemical assays. Cellular uptake was impaired by 30-minute pretreatment of cells with low concentrations of N-ethylmaleimide (10 mu M), suggesting that enrichment was thiol dependent. We report that in addition to inhibition of deubiquitinases, b-AP15 inhibits the selenoprotein thioredoxin reductase (TrxR). Whereas proteasome inhibition was closely associated with cell death induction, inhibition of TrxR was not. TrxR inhibition is, however, likely to contribute to triggering of oxidative stress observed with b-AP15. Furthermore, we present structure-activity, in vivo pharmacokinetic, and hepatocyte metabolism data for b-AP15. We conclude that the strong enrichment of b-AP15 in cells and a rapid commitment to apoptosis/cell death are factors that likely contribute to the strong antitumor activity of this compound.
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| 20. |
- Wållberg, Helena, et al.
(författare)
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HER2-Positive Tumors Imaged Within 1 Hour Using a Site-Specifically C-11-Labeled Sel-Tagged Affibody Molecule
- 2012
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Ingår i: Journal of Nuclear Medicine. - Stockholm : Society of Nuclear Medicine. - 0161-5505 .- 1535-5667 .- 2159-662X. ; 53:9, s. 1446-1453
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Tidskriftsartikel (refereegranskat)abstract
- A rapid, reliable method for distinguishing tumors or metastases that overexpress human epidermal growth factor receptor 2 (HER2) from those that do not is highly desired for individualizing therapy and predicting prognoses. In vivo imaging methods are available but not yet in clinical practice; new methodologies improving speed, sensitivity, and specificity are required. Methods: A HER2-binding Affibody molecule, Z(HER2:342), was recombinantly fused with a C-terminal selenocysteine-containing tetrapeptide Sel-tag, allowing site-specific labeling with either C-11 or Ga-68, followed by biodistribution studies with small-animal PET. Dosimetry data for the 2 radiotracers were compared. Imaging of HER2-expressing human tumor xenografts was performed using the C-11-labeled Affibody molecule. Results: Both the C-11- and Ga-68-labeled tracers initially cleared rapidly from the blood, followed by a slower decrease to 4-5 percentage injected dose per gram of tissue at 1 h. Final retention in the kidneys was much lower (>5-fold) for the C-11-labeled protein, and its overall absorbed dose was considerably lower. C-11-Z(HER2:342) showed excellent tumor-targeting capability, with almost 10 percentage injected dose per gram of tissue in HER2-expressing tumors within 1 h. Specificity was demonstrated by preblocking binding sites with excess ligand, yielding significantly reduced radiotracer uptake (P = 0.002), comparable to uptake in tumors with low HER2 expression. Conclusion: To our knowledge, the Sel-tagging technique is the first that enables site-specific C-11-radiolabeling of proteins. Here we present the finding that, in a favorable combination between radionuclide half-life and in vivo pharmacokinetics of the Affibody molecules, C-11-labeled Set-tagged Z(HER2:342) can successfully be used for rapid and repeated PET studies of HER2 expression in tumors.
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| 21. |
- Xia, Ling, et al.
(författare)
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The mammalian cytosolic selenoenzyme thioredoxin reductase reduces ubiquinone. A novel mechanism for defense against oxidative stress
- 2003
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Ingår i: Journal of Biological Chemistry. - : American Society for Biochemistry and Molecular Biology. - 0021-9258 .- 1083-351X. ; 278:4, s. 2141-2146
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Tidskriftsartikel (refereegranskat)abstract
- The selenoprotein thioredoxin reductase (TrxR1) is an essential antioxidant enzyme known to reduce many compounds in addition to thioredoxin, its principle protein substrate. Here we found that TrxR1 reduced ubiquinone-10 and thereby regenerated the antioxidant ubiquinol-10 (Q10), which is important for protection against lipid and protein peroxidation. The reduction was time- and dose-dependent, with an apparent K(m) of 22 microm and a maximal rate of about 12 nmol of reduced Q10 per milligram of TrxR1 per minute. TrxR1 reduced ubiquinone maximally at a physiological pH of 7.5 at similar rates using either NADPH or NADH as cofactors. The reduction of Q10 by mammalian TrxR1 was selenium dependent as revealed by comparison with Escherichia coli TrxR or selenium-deprived mutant and truncated mammalian TrxR forms. In addition, the rate of reduction of ubiquinone was significantly higher in homogenates from human embryo kidney 293 cells stably overexpressing thioredoxin reductase and was induced along with increasing cytosolic TrxR activity after the addition of selenite to the culture medium. These data demonstrate that the selenoenzyme thioredoxin reductase is an important selenium-dependent ubiquinone reductase and can explain how selenium and ubiquinone, by a combined action, may protect the cell from oxidative damage.
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| 22. |
- Zhang, Xiaonan, et al.
(författare)
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Repurposing of auranofin: Thioredoxin reductase remains a primary target of the drug
- 2019
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Ingår i: Biochimie. - : ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER. - 0300-9084 .- 1638-6183. ; 162, s. 46-54
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Tidskriftsartikel (refereegranskat)abstract
- Auranofin is a gold (1)-containing compound used for the treatment of rheumatic arthritis. Auranofin has anticancer activity in animal models and is approved for clinical trials for lung and ovarian carcinomas. Both the cytosolic and mitochondrial forms of the selenoprotein thioredoxin reductase (TrxR) are well documented targets of auranofin. Auranofin was recently reported to also inhibit proteasome activity at the level of the proteasome-associated deubiquitinases (DUBs) UCHL5 and USP14. We here set out to re-examine the molecular mechanism underlying auranofin cytotoxicity towards cultured cancer cells. The effects of auranofin on the proteasome were examined in cells and in vitro, effects on DUB activity were assessed using different substrates. The cellular response to auranofin was compared to that of the 20S proteasome inhibitor bortezomib and the 19S DUB inhibitor b-AP15 using proteomics. Auranofin was found to inhibit mitochondrial activity and to an induce oxidative stress response at IC50 doses. At 2-3-fold higher doses, auranofin inhibits proteasome processing in cells. At such supra-pharmacological concentrations USP14 activity was inhibited. Analysis of protein expression profiles in drug-exposed tumor cells showed that auranofin induces a response distinct from that of the 20S proteasome inhibitor bortezomib and the DUB inhibitor b-AP15, both of which induced similar responses. Our results support the notion that the primary mechanism of action of auranofin is TrxR inhibition and suggest that proteasome DUB inhibition is an off-target effect. Whether proteasome inhibition will contribute to the antineoplastic effect of auranofin in treated patients is unclear but remains a possibility. (C) 2019 Elsevier B.V. and Societe Francaise de Biochimie et Biologie Moleculaire (SFBBM). All rights reserved.
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