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Thakkar Y, Moustakas H, Moelijker N, Hendriks G, Brandsma I, Pfuhler S, Api AM. Utility of ToxTracker in animal alternative testing strategy for fragrance materials. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2023; 64:234-243. [PMID: 36762970 DOI: 10.1002/em.22532] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 01/23/2023] [Accepted: 01/31/2023] [Indexed: 05/03/2023]
Abstract
To determine the utility of the ToxTracker assay in animal alternative testing strategies, the genotoxic potential of four fragrance materials (2-octen-4-one, lauric aldehyde, veratraldehyde, and p-methoxy cinnamaldehyde) were tested in the ToxTracker assay. These materials have been previously evaluated in an in vitro as well as in vivo micronucleus assay, conducted as per OECD guidelines. In addition to these studies, reconstructed human skin micronucleus studies were conducted on all four materials. All four materials were positive in an in vitro micronucleus assay but were negative in both in vivo and 3D skin micronucleus assays. The ToxTracker assay, in combination with in silico methods to predict metabolism was used to identify mechanisms for the misleading positive outcomes observed in the in vitro micronucleus assays. The results show that the ToxTracker assay, in conjunction with in silico predictions, can provide the information needed to aid in the identification of an appropriate animal alternative follow-up assay, for substances with positive results in the standard in vitro test battery. Thus, the ToxTracker assay is a valuable tool to identify the genotoxic potential of fragrance materials and can aid with replacing animal-based follow-up testing with appropriate animal alternative assay(s).
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Affiliation(s)
- Yax Thakkar
- Research Institute for Fragrance Materials, Inc, Woodcliff Lake, New Jersey, USA
| | - Holger Moustakas
- Research Institute for Fragrance Materials, Inc, Woodcliff Lake, New Jersey, USA
| | | | | | | | - Stefan Pfuhler
- The Procter & Gamble Company, Mason Business Centre, Mason, Ohio, USA
| | - Anne Marie Api
- Research Institute for Fragrance Materials, Inc, Woodcliff Lake, New Jersey, USA
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2
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Boisvert L, Derr R, Osterlund T, Hendriks G, Brandsma I. Quantitative interpretation of ToxTracker dose-response data for potency comparisons and mode-of-action determination. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2023; 64:132-143. [PMID: 36645179 DOI: 10.1002/em.22525] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Revised: 12/11/2022] [Accepted: 12/19/2022] [Indexed: 06/17/2023]
Abstract
ToxTracker is an in vitro mammalian stem cell-based reporter assay that detects activation of specific cellular signaling pathways (DNA damage, oxidative stress, and/or protein damage) upon chemical exposure using flow cytometry. Here we used quantitative methods to empirically analyze historical control data, and dose-response data across a wide range of reference chemicals. First, we analyzed historical control data to define a fold-change threshold for identification of a significant positive response. Next, we used the benchmark dose (BMD) combined-covariate approach for potency ranking of a set of more than 120 compounds; the BMD values were used for comparative identification of the most potent inducers of each reporter. Lastly, we used principal component analysis (PCA) to investigate functional and statistical relationships between the ToxTracker reporters. The PCA results, based on the BMD results for all substances, indicated that the DNA damage (Rtkn, Bscl2) and p53 (Btg2) reporters are functionally complementary and indicative of genotoxic stress. The oxidative stress (Srxn1 and Blvrb) and protein stress (Ddit3) reporters are independent indicators of cellular stress, and essential for toxicological profiling using the ToxTracker assay. Overall, dose-response modeling of multivariate ToxTracker data can be used for potency ranking and mode-of-action determination. In the future, IVIVE (in vitro to in vivo extrapolation) methods can be employed to determine in vivo AED (administered equivalent dose) values that can in turn be used for human health risk assessment.
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Affiliation(s)
- Lorrie Boisvert
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
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3
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A tiered approach to investigate the inhalation toxicity of cobalt substances. Tier 2 b: Reactive cobalt substances induce oxidative stress in ToxTracker and activate hypoxia target genes. Regul Toxicol Pharmacol 2022; 129:105120. [PMID: 35038485 DOI: 10.1016/j.yrtph.2022.105120] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Revised: 12/17/2021] [Accepted: 01/06/2022] [Indexed: 12/12/2022]
Abstract
Cobalt metal and cobalt sulfate are carcinogenic in rodents following inhalation exposure. The pre-carcinogenic effects associated with exposure to these cobalt substances include oxidative stress and genotoxicity. Some, but not all, cobalt substances induce in vitro clastogenicity or an increase in micronuclei. As a result, these substances are classified genotoxic carcinogens, having major impacts on their risk assessment, e.g. assumption of a non-thresholded dose response. Here, we investigated the potential of nine cobalt substances to cause genotoxicity and oxidative stress using the ToxTracker assay, with an extension to measure biomarkers of hypoxia. None of the nine tested substances activated the DNA damage markers in ToxTracker, and five substances activated the oxidative stress response reporters. The same five substances also activated the expression of several hypoxia target genes. Consistent with the lower tier of testing found in the preceding paper of this series, these compounds can be grouped based on their ability to release bioavailable cobalt ion and to trigger subsequent key events.
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4
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Czekala L, Chapman F, Simms L, Rudd K, Trelles Sticken E, Wieczorek R, Bode LM, Pani J, Moelijker N, Derr R, Brandsma I, Hendriks G, Stevenson M, Walele T. The in vitro ToxTracker and Aneugen Clastogen Evaluation extension assay as a tool in the assessment of relative genotoxic potential of e-liquids and their aerosols. Mutagenesis 2021; 36:129-142. [PMID: 33769537 PMCID: PMC8166346 DOI: 10.1093/mutage/geaa033] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2020] [Accepted: 11/24/2020] [Indexed: 12/14/2022] Open
Abstract
In vitro (geno)toxicity assessment of electronic vapour products (EVPs), relative to conventional cigarette, currently uses assays, including the micronucleus and Ames tests. Whilst informative on induction of a finite endpoint and relative risk posed by test articles, such assays could benefit from mechanistic supplementation. The ToxTracker and Aneugen Clastogen Evaluation analysis can indicate the activation of reporters associated with (geno)toxicity, including DNA damage, oxidative stress, the p53-related stress response and protein damage. Here, we tested for the different effects of a selection of neat e-liquids, EVP aerosols and Kentucky reference 1R6F cigarette smoke samples in the ToxTracker assay. The assay was initially validated to assess whether a mixture of e-liquid base components, propylene glycol (PG) and vegetable glycerine (VG) had interfering effects within the system. This was achieved by spiking three positive controls into the system with neat PG/VG or phosphate-buffered saline bubbled (bPBS) PG/VG aerosol (nicotine and flavour free). PG/VG did not greatly affect responses induced by the compounds. Next, when compared to cigarette smoke samples, neat e-liquids and bPBS aerosols (tobacco flavour; 1.6% freebase nicotine, 1.6% nicotine salt or 0% nicotine) exhibited reduced and less complex responses. Tested up to a 10% concentration, EVP aerosol bPBS did not induce any ToxTracker reporters. Neat e-liquids, tested up to 1%, induced oxidative stress reporters, thought to be due to their effects on osmolarity in vitro. E-liquid nicotine content did not affect responses induced. Additionally, spiking nicotine alone only induced an oxidative stress response at a supraphysiological level. In conclusion, the ToxTracker assay is a quick, informative screen for genotoxic potential and mechanisms of a variety of (compositionally complex) samples, derived from cigarettes and EVPs. This assay has the potential for future application in the assessment battery for next-generation (smoking alternative) products, including EVPs.
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Affiliation(s)
- Lukasz Czekala
- Group Science and Regulatory Affairs, Imperial Brands PLC, Bristol, UK
| | - Fiona Chapman
- Group Science and Regulatory Affairs, Imperial Brands PLC, Bristol, UK
| | - Liam Simms
- Group Science and Regulatory Affairs, Imperial Brands PLC, Bristol, UK
| | - Kathryn Rudd
- Group Science and Regulatory Affairs, Imperial Brands PLC, Bristol, UK
| | - Edgar Trelles Sticken
- Reemtsma Cigarettenfabriken GmbH, an Imperial Brands PLC Company, Albert-Einstein-Ring-7, D-22761 Hamburg, Germany
| | - Roman Wieczorek
- Reemtsma Cigarettenfabriken GmbH, an Imperial Brands PLC Company, Albert-Einstein-Ring-7, D-22761 Hamburg, Germany
| | - Lisa Maria Bode
- Reemtsma Cigarettenfabriken GmbH, an Imperial Brands PLC Company, Albert-Einstein-Ring-7, D-22761 Hamburg, Germany
| | - Jutta Pani
- Reemtsma Cigarettenfabriken GmbH, an Imperial Brands PLC Company, Albert-Einstein-Ring-7, D-22761 Hamburg, Germany
| | - Nynke Moelijker
- Toxys B.V., Robert Boyleweg 4, 2333 CG Leiden, The Netherlands
| | - Remco Derr
- Toxys B.V., Robert Boyleweg 4, 2333 CG Leiden, The Netherlands
| | - Inger Brandsma
- Toxys B.V., Robert Boyleweg 4, 2333 CG Leiden, The Netherlands
| | - Giel Hendriks
- Toxys B.V., Robert Boyleweg 4, 2333 CG Leiden, The Netherlands
| | - Matthew Stevenson
- Group Science and Regulatory Affairs, Imperial Brands PLC, Bristol, UK
| | - Tanvir Walele
- Group Science and Regulatory Affairs, Imperial Brands PLC, Bristol, UK
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5
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Baschiera E, Sorrentino U, Calderan C, Desbats MA, Salviati L. The multiple roles of coenzyme Q in cellular homeostasis and their relevance for the pathogenesis of coenzyme Q deficiency. Free Radic Biol Med 2021; 166:277-286. [PMID: 33667628 DOI: 10.1016/j.freeradbiomed.2021.02.039] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 02/13/2021] [Accepted: 02/26/2021] [Indexed: 12/11/2022]
Abstract
Coenzyme Q (CoQ) is a redox active lipid that plays a central role in cellular homeostasis. It was discovered more than 60 years ago because of its role as electron transporter in the mitochondrial respiratory chain. Since then it has become evident that CoQ has many other functions, not directly related to bioenergetics. It is a cofactor of several mitochondrial dehydrogenases involved in the metabolism of lipids, amino acids, and nucleotides, and in sulfide detoxification. It is a powerful antioxidant and it is involved in the control of programmed cell death by modulating both apoptosis and ferroptosis. CoQ deficiency is a clinically and genetically heterogeneous group of disorders characterized by the impairment of CoQ biosynthesis. CoQ deficient patients display defects in cellular bioenergetics, but also in the other pathways in which CoQ is involved. In this review we will focus on the functions of CoQ not directly related to the respiratory chain, and on how their impairment is relevant for the pathophysiology of CoQ deficiency. A better understanding of the complex set of events triggered by CoQ deficiency will allow to design novel approaches for the treatment of this condition.
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Affiliation(s)
- Elisa Baschiera
- Clinical Genetics Unit, Department of Women and Children's Health, University of Padova and IPR Città Della Speranza, Padova, Italy
| | - Ugo Sorrentino
- Clinical Genetics Unit, Department of Women and Children's Health, University of Padova and IPR Città Della Speranza, Padova, Italy
| | - Cristina Calderan
- Clinical Genetics Unit, Department of Women and Children's Health, University of Padova and IPR Città Della Speranza, Padova, Italy
| | - Maria Andrea Desbats
- Clinical Genetics Unit, Department of Women and Children's Health, University of Padova and IPR Città Della Speranza, Padova, Italy
| | - Leonardo Salviati
- Clinical Genetics Unit, Department of Women and Children's Health, University of Padova and IPR Città Della Speranza, Padova, Italy.
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6
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Nesbitt NM, Malone LE, Liu Z, Jares A, Gnatenko DV, Ma Y, Zhu W, Bahou WF. Divergent erythroid megakaryocyte fates in Blvrb-deficient mice establish non-overlapping cytoprotective functions during stress hematopoiesis. Free Radic Biol Med 2021; 164:164-174. [PMID: 33359909 PMCID: PMC8311568 DOI: 10.1016/j.freeradbiomed.2020.12.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 11/17/2020] [Accepted: 12/13/2020] [Indexed: 12/27/2022]
Abstract
Cytoprotective mechanisms of heme oxygenases function by derivatizing heme to generate carbon monoxide, ferrous iron, and isomeric biliverdins, followed by rapid NAD(P)H-dependent biliverdin reduction to the antioxidant bilirubin using two non-overlapping biliverdin reductases that display biliverdin isomer-restricted redox activity. Although cytoprotective functions of heme oxygenases are widely recognized, concomitant effects of downstream biliverdin reductases remain incomplete. A computational model predicated on murine hematopoietic single-cell transcriptomic data identified Blvrb as a biological driver linked to the tumor necrosis factor stress pathway as a predominant source of variation defining hematopoietic cell heterogeneity. In vivo studies using Blvrb-deficient mice established the dispensable role of Blvrb in steady-state hematopoiesis, although model validation using aged Blvrb-deficient mice established an important cytoprotective function in stress hematopoiesis with dichotomous megakaryocyte-biased hematopoietic recovery. Defective stress erythropoiesis was evident in Blvrb-/- spleens and in bone marrow erythroid development, occurring in conjunction with defective lipid peroxidation as a marker of oxidant mishandling. Cell autonomous effects on megakaryocyte lineage bias were documented using multipotential progenitor assays. These data provide the first physiological function of murine Blvrb in a non-redundant pathway of stress cytoprotection. Divergent effects on erythroid/megakaryocyte lineage speciation impute a novel redox-regulated mechanism for lineage partitioning.
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Affiliation(s)
- Natasha M Nesbitt
- Department of Medicine, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Lisa E Malone
- Department of Medicine, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Zhaoyan Liu
- Department of Applied Mathematics and Statistics, Stony Brook University, Stony Brook, NY, 11727, USA
| | - Alexander Jares
- Department of Pathology, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Dmitri V Gnatenko
- Department of Medicine, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Yupo Ma
- Department of Pathology, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Wei Zhu
- Department of Applied Mathematics and Statistics, Stony Brook University, Stony Brook, NY, 11727, USA
| | - Wadie F Bahou
- Department of Medicine, Stony Brook University, Stony Brook, NY, 11794, USA.
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7
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Duff MR, Redzic JS, Ryan LP, Paukovich N, Zhao R, Nix JC, Pitts TM, Agarwal P, Eisenmesser EZ. Structure, dynamics and function of the evolutionarily changing biliverdin reductase B family. J Biochem 2021; 168:191-202. [PMID: 32246827 DOI: 10.1093/jb/mvaa039] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Accepted: 03/19/2020] [Indexed: 11/14/2022] Open
Abstract
Biliverdin reductase B (BLVRB) family members are general flavin reductases critical in maintaining cellular redox with recent findings revealing that BLVRB alone can dictate cellular fate. However, as opposed to most enzymes, the BLVRB family remains enigmatic with an evolutionarily changing active site and unknown structural and functional consequences. Here, we applied a multi-faceted approach that combines X-ray crystallography, NMR and kinetics methods to elucidate the structural and functional basis of the evolutionarily changing BLVRB active site. Using a panel of three BLVRB isoforms (human, lemur and hyrax) and multiple human BLVRB mutants, our studies reveal a novel evolutionary mechanism where coenzyme 'clamps' formed by arginine side chains at two co-evolving positions within the active site serve to slow coenzyme release (Positions 14 and 78). We find that coenzyme release is further slowed by the weaker binding substrate, resulting in relatively slow turnover numbers. However, different BLVRB active sites imposed by either evolution or mutagenesis exhibit a surprising inverse relationship between coenzyme release and substrate turnover that is independent of the faster chemical step of hydride transfer also measured here. Collectively, our studies have elucidated the role of the evolutionarily changing BLVRB active site that serves to modulate coenzyme release and has revealed that coenzyme release is coupled to substrate turnover.
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Affiliation(s)
- Michael R Duff
- Biochemistry & Cellular and Molecular Biology Department, University of Tennessee, 1311 Cumberland Ave., Knoxville, TN 37996, USA
| | - Jasmina S Redzic
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Colorado Denver, 12801 E 17th Ave., Aurora, CO 80045, USA
| | - Lucas P Ryan
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Colorado Denver, 12801 E 17th Ave., Aurora, CO 80045, USA
| | - Natasia Paukovich
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Colorado Denver, 12801 E 17th Ave., Aurora, CO 80045, USA
| | - Rui Zhao
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Colorado Denver, 12801 E 17th Ave., Aurora, CO 80045, USA
| | - Jay C Nix
- Molecular Biology Consortium, Advanced Light Source, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, CA 94720, USA
| | - Todd M Pitts
- Division of Medical Oncology, School of Medicine, University of Colorado, 12801 E 17th Ave., Aurora, CO 80045, USA
| | - Pratul Agarwal
- Biochemistry & Cellular and Molecular Biology Department, University of Tennessee, 1311 Cumberland Ave., Knoxville, TN 37996, USA
| | - Elan Zohar Eisenmesser
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Colorado Denver, 12801 E 17th Ave., Aurora, CO 80045, USA
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8
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Redzic JS, Duff MR, Blue A, Pitts TM, Agarwal P, Eisenmesser EZ. Modulating Enzyme Function via Dynamic Allostery within Biliverdin Reductase B. Front Mol Biosci 2021; 8:691208. [PMID: 34095235 PMCID: PMC8173106 DOI: 10.3389/fmolb.2021.691208] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Accepted: 04/30/2021] [Indexed: 11/17/2022] Open
Abstract
The biliverdin reductase B (BLVRB) class of enzymes catalyze the NADPH-dependent reduction of multiple flavin substrates and are emerging as critical players in cellular redox regulation. However, the role of dynamics and allostery have not been addressed, prompting studies here that have revealed a position 15 Å away from the active site within human BLVRB (T164) that is inherently dynamic and can be mutated to control global micro-millisecond motions and function. By comparing the inherent dynamics through nuclear magnetic resonance (NMR) relaxation approaches of evolutionarily distinct BLVRB homologues and by applying our previously developed Relaxation And Single Site Multiple Mutations (RASSMM) approach that monitors both the functional and dynamic effects of multiple mutations to the single T164 site, we have discovered that the most dramatic mutagenic effects coincide with evolutionary changes and these modulate coenzyme binding. Thus, evolutionarily changing sites distal to the active site serve as dynamic "dials" to globally modulate motions and function. Despite the distal dynamic and functional coupling modulated by this site, micro-millisecond motions span an order of magnitude in their apparent kinetic rates of motions. Thus, global dynamics within BLVRB are a collection of partially coupled motions tied to catalytic function.
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Affiliation(s)
- Jasmina S Redzic
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Colorado Denver, Denver, CO, United States
| | - Michael R Duff
- Biochemistry and Cellular and Molecular Biology Department, University of Tennessee, Knoxville, TN, United States
| | - Ashley Blue
- National High Magnetic Field Laboratory, Tallahassee, FL, United States
| | - Todd M Pitts
- Division of Medical Oncology, School of Medicine, University of Colorado, Aurora, CO, United States
| | - Pratul Agarwal
- Department of Physiological Sciences and High Performance Computing Center, Oklahoma State University, Stillwater, OK, United States
| | - Elan Zohar Eisenmesser
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Colorado Denver, Denver, CO, United States
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9
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Tasnim H, Landry AP, Fontenot CR, Ding H. Exploring the FMN binding site in the mitochondrial outer membrane protein mitoNEET. Free Radic Biol Med 2020; 156:11-19. [PMID: 32445867 PMCID: PMC7434653 DOI: 10.1016/j.freeradbiomed.2020.05.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 05/06/2020] [Accepted: 05/06/2020] [Indexed: 12/17/2022]
Abstract
MitoNEET is a mitochondrial outer membrane protein that hosts a redox active [2Fe-2S] cluster in the C-terminal cytosolic domain. Increasing evidence has shown that mitoNEET has an essential role in regulating energy metabolism in human cells. Previously, we reported that the [2Fe-2S] clusters in mitoNEET can be reduced by the reduced flavin mononucleotide (FMNH2) and oxidized by oxygen or ubiquinone-2, suggesting that mitoNEET may act as a novel redox enzyme catalyzing electron transfer from FMNH2 to oxygen or ubiquinone. Here, we explore the FMN binding site in mitoNEET by using FMN analogs and find that lumiflavin, like FMN, at nanomolar concentrations can mediate the redox transition of the mitoNEET [2Fe-2S] clusters in the presence of flavin reductase and NADH (100 μM) under aerobic conditions. The electron paramagnetic resonance (EPR) measurements show that both FMN and lumiflavin can dramatically change the EPR spectrum of the reduced mitoNEET [2Fe-2S] clusters and form a covalently bound complex with mitoNEET under blue light exposure, suggesting that FMN/lumiflavin has specific interactions with the [2Fe-2S] clusters in mitoNEET. In contrast, lumichrome, another FMN analog, fails to mediate the redox transition of the mitoNEET [2Fe-2S] clusters and has no effect on the EPR spectrum of the reduced mitoNEET [2Fe-2S] clusters under blue light exposure. Instead, lumichrome can effectively inhibit the FMNH2-mediated reduction of the mitoNEET [2Fe-2S] clusters, indicating that lumichrome may act as a potential inhibitor to block the electron transfer activity of mitoNEET.
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Affiliation(s)
- Homyra Tasnim
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Aaron P Landry
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Chelsey R Fontenot
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Huangen Ding
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, 70803, USA.
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10
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Brandsma I, Moelijker N, Derr R, Hendriks G. Aneugen Versus Clastogen Evaluation and Oxidative Stress-Related Mode-of-Action Assessment of Genotoxic Compounds Using the ToxTracker Reporter Assay. Toxicol Sci 2020; 177:202-213. [DOI: 10.1093/toxsci/kfaa103] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Abstract
Understanding the mode-of-action (MOA) of genotoxic compounds and differentiating between direct DNA interaction and indirect genotoxicity is crucial for their reliable safety assessment. ToxTracker is a stem cell-based reporter assay that detects activation of various cellular responses that are associated with genotoxicity and cancer. ToxTracker consists of 6 different GFP reporter cell lines that can detect the induction of DNA damage, oxidative stress, and protein damage in a single test. The assay can thereby provide insight into the MOA of compounds. Genotoxicity is detected in ToxTracker by activation of 2 independent GFP reporters. Activation of the Bscl2-GFP reporter is associated with induction of DNA adducts and subsequent inhibition of DNA replication and the Rtkn-GFP reporter is activated following the formation of DNA double-strand breaks. Here, we show that the differential activation of these 2 genotoxicity reporters could be used to further differentiate between a DNA reactive and clastogenic or a non-DNA-reactive aneugenic MOA of genotoxic compounds. For further classification of aneugenic and clastogenic compounds, the ToxTracker assay was extended with cell cycle analysis and aneuploidy assessment. The extension was validated using a selection of 16 (genotoxic) compounds with a well-established MOA. Furthermore, indirect genotoxicity related to the production of reactive oxygen species was investigated using the DNA damage and oxidative stress ToxTracker reporters in combination with different reactive oxygen species scavengers. With these new extensions, ToxTracker was able to accurately classify compounds as genotoxic or nongenotoxic and could discriminate between DNA-reactive compounds, aneugens, and indirect genotoxicity caused by oxidative stress.
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Affiliation(s)
| | | | - Remco Derr
- Toxys B.V., 2333 CG Leiden, The Netherlands
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11
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Paukovich N, Xue M, Elder JR, Redzic JS, Blue A, Pike H, Miller BG, Pitts TM, Pollock DD, Hansen K, D'Alessandro A, Eisenmesser EZ. Biliverdin Reductase B Dynamics Are Coupled to Coenzyme Binding. J Mol Biol 2018; 430:3234-3250. [PMID: 29932944 DOI: 10.1016/j.jmb.2018.06.015] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Revised: 06/05/2018] [Accepted: 06/06/2018] [Indexed: 12/28/2022]
Abstract
Biliverdin reductase B (BLVRB) is a newly identified cellular redox regulator that catalyzes the NADPH-dependent reduction of multiple substrates. Through mass spectrometry analysis, we identified high levels of BLVRB in mature red blood cells, highlighting the importance of BLVRB in redox regulation. The BLVRB conformational changes that occur during conezyme/substrate binding and the role of dynamics in BLVRB function, however, remain unknown. Through a combination of NMR, kinetics, and isothermal titration calorimetry studies, we determined that BLVRB binds its coenzyme 500-fold more tightly than its substrate. While the active site of apo BLVRB is highly dynamic on multiple timescales, active site dynamics are largely quenched within holo BLVRB, in which dynamics are redistributed to other regions of the enzyme. We show that a single point mutation of Arg78➔Ala leads to both an increase in active site micro-millisecond motions and an increase in the microscopic rate constants of coenzyme binding. This demonstrates that altering BLVRB active site dynamics can directly cause a change in functional characteristics. Our studies thus address the solution behavior of apo and holo BLVRB and identify a role of enzyme dynamics in coenzyme binding.
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Affiliation(s)
- Natasia Paukovich
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Colorado Denver, School of Medicine, Aurora, CO 80045, USA
| | - Mengjun Xue
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Colorado Denver, School of Medicine, Aurora, CO 80045, USA
| | - James R Elder
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Colorado Denver, School of Medicine, Aurora, CO 80045, USA
| | - Jasmina S Redzic
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Colorado Denver, School of Medicine, Aurora, CO 80045, USA
| | - Ashley Blue
- National High Magnetic Field Laboratory, Tallahassee, FL 32310, USA
| | - Hamish Pike
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Colorado Denver, School of Medicine, Aurora, CO 80045, USA
| | - Brian G Miller
- Department of Chemistry & Biochemistry, Florida State University, Tallahassee, FL 32310, USA
| | - Todd M Pitts
- Division of Medical Oncology, School of Medicine, Aurora, CO 80045, USA
| | - David D Pollock
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Colorado Denver, School of Medicine, Aurora, CO 80045, USA
| | - Kirk Hansen
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Colorado Denver, School of Medicine, Aurora, CO 80045, USA
| | - Angelo D'Alessandro
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Colorado Denver, School of Medicine, Aurora, CO 80045, USA
| | - Elan Zohar Eisenmesser
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Colorado Denver, School of Medicine, Aurora, CO 80045, USA.
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12
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Nesbitt NM, Zheng X, Li Z, Manso JA, Yen WY, Malone LE, Ripoll-Rozada J, Pereira PJB, Mantle TJ, Wang J, Bahou WF. In silico and crystallographic studies identify key structural features of biliverdin IXβ reductase inhibitors having nanomolar potency. J Biol Chem 2018; 293:5431-5446. [PMID: 29487133 DOI: 10.1074/jbc.ra118.001803] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 02/23/2018] [Indexed: 12/20/2022] Open
Abstract
Heme cytotoxicity is minimized by a two-step catabolic reaction that generates biliverdin (BV) and bilirubin (BR) tetrapyrroles. The second step is regulated by two non-redundant biliverdin reductases (IXα (BLVRA) and IXβ (BLVRB)), which retain isomeric specificity and NAD(P)H-dependent redox coupling linked to BR's antioxidant function. Defective BLVRB enzymatic activity with antioxidant mishandling has been implicated in metabolic consequences of hematopoietic lineage fate and enhanced platelet counts in humans. We now outline an integrated platform of in silico and crystallographic studies for the identification of an initial class of compounds inhibiting BLVRB with potencies in the nanomolar range. We found that the most potent BLVRB inhibitors contain a tricyclic hydrocarbon core structure similar to the isoalloxazine ring of flavin mononucleotide and that both xanthene- and acridine-based compounds inhibit BLVRB's flavin and dichlorophenolindophenol (DCPIP) reductase functions. Crystallographic studies of ternary complexes with BLVRB-NADP+-xanthene-based compounds confirmed inhibitor binding adjacent to the cofactor nicotinamide and interactions with the Ser-111 side chain. This residue previously has been identified as critical for maintaining the enzymatic active site and cellular reductase functions in hematopoietic cells. Both acridine- and xanthene-based compounds caused selective and concentration-dependent loss of redox coupling in BLVRB-overexpressing promyelocytic HL-60 cells. These results provide promising chemical scaffolds for the development of enhanced BLVRB inhibitors and identify chemical probes to better dissect the role of biliverdins, alternative substrates, and BLVRB function in physiologically relevant cellular contexts.
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Affiliation(s)
| | - Xiliang Zheng
- the State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, ChangChun, Jilin 130022, China
| | | | - José A Manso
- the IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135 Porto, Portugal.,the i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal, and
| | | | | | - Jorge Ripoll-Rozada
- the IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135 Porto, Portugal.,the i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal, and
| | - Pedro José Barbosa Pereira
- the IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135 Porto, Portugal.,the i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal, and
| | - Timothy J Mantle
- the Department of Biochemistry, Trinity College, Dublin 2, Ireland
| | - Jin Wang
- Chemistry and Physics, State University of New York at Stony Brook, Stony Brook, New York 11794-8151,
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13
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Qiao ZY, Lai WJ, Lin YX, Li D, Nan XH, Wang Y, Wang H, Fang QJ. Polymer–KLAK Peptide Conjugates Induce Cancer Cell Death through Synergistic Effects of Mitochondria Damage and Autophagy Blockage. Bioconjug Chem 2017; 28:1709-1721. [DOI: 10.1021/acs.bioconjchem.7b00176] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
| | | | - Yao-Xin Lin
- University of Chinese Academy of Sciences, Beijing 100049, PR China
| | - Dan Li
- University of Chinese Academy of Sciences, Beijing 100049, PR China
| | - Xiao-Hui Nan
- University of Chinese Academy of Sciences, Beijing 100049, PR China
| | - Yi Wang
- University of Chinese Academy of Sciences, Beijing 100049, PR China
| | | | - Qiao-Jun Fang
- University of Chinese Academy of Sciences, Beijing 100049, PR China
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14
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Wang Y, Landry AP, Ding H. The mitochondrial outer membrane protein mitoNEET is a redox enzyme catalyzing electron transfer from FMNH 2 to oxygen or ubiquinone. J Biol Chem 2017; 292:10061-10067. [PMID: 28461337 DOI: 10.1074/jbc.m117.789800] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Revised: 04/29/2017] [Indexed: 01/20/2023] Open
Abstract
Increasing evidence suggests that mitoNEET, a target of the type II diabetes drug pioglitazone, is a key regulator of energy metabolism in mitochondria. MitoNEET is anchored to the mitochondrial outer membrane via its N-terminal α helix domain and hosts a redox-active [2Fe-2S] cluster in its C-terminal cytosolic region. The mechanism by which mitoNEET regulates energy metabolism in mitochondria, however, is not fully understood. Previous studies have shown that mitoNEET specifically interacts with the reduced flavin mononucleotide (FMNH2) and that FMNH2 can quickly reduce the mitoNEET [2Fe-2S] clusters. Here we report that the reduced mitoNEET [2Fe-2S] clusters can be readily oxidized by oxygen. In the presence of FMN, NADH, and flavin reductase, which reduces FMN to FMNH2 using NADH as the electron donor, mitoNEET mediates oxidation of NADH with a concomitant reduction of oxygen. Ubiquinone-2, an analog of ubiquinone-10, can also oxidize the reduced mitoNEET [2Fe-2S] clusters under anaerobic or aerobic conditions. Compared with oxygen, ubiquinone-2 is more efficient in oxidizing the mitoNEET [2Fe-2S] clusters, suggesting that ubiquinone could be an intrinsic electron acceptor of the reduced mitoNEET [2Fe-2S] clusters in mitochondria. Pioglitazone or its analog NL-1 appears to inhibit the electron transfer activity of mitoNEET by forming a unique complex with mitoNEET and FMNH2 The results suggest that mitoNEET is a redox enzyme that may promote oxidation of NADH to facilitate enhanced glycolysis in the cytosol and that pioglitazone may regulate energy metabolism in mitochondria by inhibiting the electron transfer activity of mitoNEET.
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Affiliation(s)
- Yiming Wang
- From the Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803
| | - Aaron P Landry
- From the Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803
| | - Huangen Ding
- From the Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803
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15
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Takao H, Hirabayashi K, Nishigaya Y, Kouriki H, Nakaniwa T, Hagiwara Y, Harada J, Sato H, Yamazaki T, Sakakibara Y, Suiko M, Asada Y, Takahashi Y, Yamamoto K, Fukuyama K, Sugishima M, Wada K. A substrate-bound structure of cyanobacterial biliverdin reductase identifies stacked substrates as critical for activity. Nat Commun 2017; 8:14397. [PMID: 28169272 PMCID: PMC5309722 DOI: 10.1038/ncomms14397] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Accepted: 12/23/2016] [Indexed: 01/20/2023] Open
Abstract
Biliverdin reductase catalyses the last step in haem degradation and produces the major lipophilic antioxidant bilirubin via reduction of biliverdin, using NAD(P)H as a cofactor. Despite the importance of biliverdin reductase in maintaining the redox balance, the molecular details of the reaction it catalyses remain unknown. Here we present the crystal structure of biliverdin reductase in complex with biliverdin and NADP+. Unexpectedly, two biliverdin molecules, which we designated the proximal and distal biliverdins, bind with stacked geometry in the active site. The nicotinamide ring of the NADP+ is located close to the reaction site on the proximal biliverdin, supporting that the hydride directly attacks this position of the proximal biliverdin. The results of mutagenesis studies suggest that a conserved Arg185 is essential for the catalysis. The distal biliverdin probably acts as a conduit to deliver the proton from Arg185 to the proximal biliverdin, thus yielding bilirubin.
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Affiliation(s)
- Haruna Takao
- Organization for Promotion of Tenure Track, University of Miyazaki, Miyazaki 889-1692, Japan
- Graduate School of Medicine and Veterinary Medicine, University of Miyazaki, Miyazaki 889-1692, Japan
| | - Kei Hirabayashi
- Organization for Promotion of Tenure Track, University of Miyazaki, Miyazaki 889-1692, Japan
| | - Yuki Nishigaya
- Advanced Analysis Center, National Agriculture and Food Research Organization, Ibaraki 305-8602, Japan
| | - Haruna Kouriki
- Organization for Promotion of Tenure Track, University of Miyazaki, Miyazaki 889-1692, Japan
| | - Tetsuko Nakaniwa
- Department of Biological Sciences, Graduate School of Science, Osaka University, Osaka 560-0043, Japan
| | - Yoshinori Hagiwara
- Department of Biochemistry and Applied Chemistry, National Institute of Technology, Kurume College, Fukuoka 830-8555, Japan
| | - Jiro Harada
- Department of Medical Biochemistry, Kurume University School of Medicine, Fukuoka 830-0011, Japan
| | - Hideaki Sato
- Department of Medical Biochemistry, Kurume University School of Medicine, Fukuoka 830-0011, Japan
| | - Toshimasa Yamazaki
- Advanced Analysis Center, National Agriculture and Food Research Organization, Ibaraki 305-8602, Japan
| | - Yoichi Sakakibara
- Department of Biochemistry and Applied Biosciences, Faculty of Agriculture, University of Miyazaki, Miyazaki 889-2192, Japan
| | - Masahito Suiko
- Department of Biochemistry and Applied Biosciences, Faculty of Agriculture, University of Miyazaki, Miyazaki 889-2192, Japan
| | - Yujiro Asada
- Department of Pathology, Faculty of Medicine, University of Miyazaki, Miyazaki 889-1692, Japan
| | - Yasuhiro Takahashi
- Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama 338-8570, Japan
| | - Ken Yamamoto
- Department of Medical Biochemistry, Kurume University School of Medicine, Fukuoka 830-0011, Japan
| | - Keiichi Fukuyama
- Department of Biological Sciences, Graduate School of Science, Osaka University, Osaka 560-0043, Japan
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Osaka 565-0871, Japan
| | - Masakazu Sugishima
- Department of Medical Biochemistry, Kurume University School of Medicine, Fukuoka 830-0011, Japan
| | - Kei Wada
- Organization for Promotion of Tenure Track, University of Miyazaki, Miyazaki 889-1692, Japan
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16
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Chu WT, Nesbitt NM, Gnatenko DV, Li Z, Zhang B, Seeliger MA, Browne S, Mantle TJ, Bahou WF, Wang J. Enzymatic Activity and Thermodynamic Stability of Biliverdin IXβ Reductase Are Maintained by an Active Site Serine. Chemistry 2017; 23:1891-1900. [PMID: 27897348 DOI: 10.1002/chem.201604517] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Indexed: 11/10/2022]
Abstract
Biliverdin reductase IXβ (BLVRB) is a crucial enzyme in heme metabolism. Recent studies in humans have identified a loss-of-function mutation (Ser111Leu) that unmasks a fundamentally important role in hematopoiesis. We have undertaken experimental and thermodynamic modeling studies to provide further insight into the role of the cofactor in substrate accessibility and protein folding properties regulating BLVRB catalytic mechanisms. Site-directed mutagenesis with molecular dynamic (MD) simulations establish the critical role of NAD(P)H-dependent conformational changes on substrate accessibility by forming the "hydrophobic pocket", along with identification of a single key residue (Arg35) modulating NADPH/NADH selectivity. Loop80 and Loop120 block the hydrophobic substrate binding pocket in apo BLVRB (open), whereas movement of these structures after cofactor binding results in the "closed" (catalytically active) conformation. Both enzymatic activity and thermodynamic stability are affected by mutation(s) involving Ser111, which is located in the core of the BLVRB active site. This work 1) elucidates the crucial role of Ser111 in enzymatic catalysis and thermodynamic stability by active site hydrogen bond network; 2) defines a dynamic model for apo BLVRB extending beyond the crystal structure of the binary BLVRB/NADP+ complex; 3) provides a structural basis for the "encounter" and "equilibrium" states of the binary complex, which are regulated by NAD(P)H.
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Affiliation(s)
- Wen-Ting Chu
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin, 130022, P. R. China
| | - Natasha M Nesbitt
- Department of Medicine, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Dmitri V Gnatenko
- Department of Medicine, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Zongdong Li
- Department of Medicine, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Beibei Zhang
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Markus A Seeliger
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Seamus Browne
- Department of Biochemistry, Trinity College, Dublin 2, Ireland
| | | | - Wadie F Bahou
- Department of Medicine, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Jin Wang
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin, 130022, P. R. China.,Department of Chemistry and Physics, Stony Brook University, Stony Brook, NY, 11794, USA
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17
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Landry AP, Wang Y, Cheng Z, Crochet RB, Lee YH, Ding H. Flavin nucleotides act as electron shuttles mediating reduction of the [2Fe-2S] clusters in mitochondrial outer membrane protein mitoNEET. Free Radic Biol Med 2017; 102:240-247. [PMID: 27923678 PMCID: PMC5209285 DOI: 10.1016/j.freeradbiomed.2016.12.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Revised: 10/18/2016] [Accepted: 12/01/2016] [Indexed: 10/20/2022]
Abstract
MitoNEET, a primary target of type II diabetes drug pioglitazone, has an essential role in regulating energy metabolism, iron homeostasis, and production of reactive oxygen species in mitochondria. Structurally, mitoNEET is anchored to the mitochondrial outer membrane via its N-terminal transmembrane α-helix. The C-terminal cytosolic domain of mitoNEET hosts a redox active [2Fe-2S] cluster via three cysteine and one histidine residues. Here we report that the reduced flavin nucleotides can rapidly reduce the mitoNEET [2Fe-2S] clusters under anaerobic or aerobic conditions. In the presence of NADH and flavin reductase, 1 molecule of flavin nucleotide is sufficient to reduce about 100 molecules of the mitoNEET [2Fe-2S] clusters in 4min under aerobic conditions. The electron paramagnetic resonance (EPR) measurements show that flavin mononucleotide (FMN), but not flavin adenine dinucleotide (FAD), has a specific interaction with mitoNEET. Molecular docking models further reveal that flavin mononucleotide binds mitoNEET at the region between the N-terminal transmembrane α-helix and the [2Fe-2S] cluster binding domain. The closest distance between the [2Fe-2S] cluster and the bound flavin mononucleotide in mitoNEET is about 10Å, which could facilitate rapid electron transfer from the reduced flavin nucleotide to the [2Fe-2S] cluster in mitoNEET. The results suggest that flavin nucleotides may act as electron shuttles to reduce the mitoNEET [2Fe-2S] clusters and regulate mitochondrial functions in human cells.
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Affiliation(s)
- Aaron P Landry
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Yiming Wang
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Zishuo Cheng
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Robert B Crochet
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Yong-Hwan Lee
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Huangen Ding
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
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18
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Mohamed AE, Condic-Jurkic K, Ahmed FH, Yuan P, O'Mara ML, Jackson CJ, Coote ML. Hydrophobic Shielding Drives Catalysis of Hydride Transfer in a Family of F 420H 2-Dependent Enzymes. Biochemistry 2016; 55:6908-6918. [PMID: 27951661 DOI: 10.1021/acs.biochem.6b00683] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A family of flavin/deazaflavin-dependent oxidoreductases (FDORs) from mycobacteria has been recently characterized and found to play a variety of catalytic roles, including the activation of prodrugs such as the candidate anti-tuberculosis drug pretomanid (PA-824). However, our understanding of the catalytic mechanism used by these enzymes is relatively limited. To address this, we have used a combination of quantum mechanics and molecular dynamics calculations to study the catalytic mechanism of the activation of pretomanid by the deazaflavin-dependent nitroreductase (Ddn) from Mycobacterium tuberculosis. The preferred pathway involves an initial hydride transfer step from the deprotonated cofactor (i.e., F420H-), with subsequent protonation, before a series of spontaneous intramolecular reactions to form the final reactive nitrogen species. The most likely proton source is a hydroxonium ion within the solvent accessible active site. Intriguingly, catalysis of the rate-determining hydride transfer step is aided by three tyrosine residues that form a hydrophobic barrier around the active site that, upon reaction, is then disrupted to allow increased water accessibility to facilitate the subsequent proton transfer step. The catalytic mechanism we propose is consistent with previous experimental observations of the Ddn enzyme and will inform the design of improved prodrugs in the future.
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Affiliation(s)
- A Elaaf Mohamed
- Research School of Chemistry, Australian National University , Canberra, ACT 2601, Australia
| | - Karmen Condic-Jurkic
- Research School of Chemistry, Australian National University , Canberra, ACT 2601, Australia
| | - F Hafna Ahmed
- Research School of Chemistry, Australian National University , Canberra, ACT 2601, Australia
| | - Peng Yuan
- Research School of Chemistry, Australian National University , Canberra, ACT 2601, Australia
| | - Megan L O'Mara
- Research School of Chemistry, Australian National University , Canberra, ACT 2601, Australia
| | - Colin J Jackson
- Research School of Chemistry, Australian National University , Canberra, ACT 2601, Australia
| | - Michelle L Coote
- ARC Centre of Excellence for Electromaterials Science, Research School of Chemistry, Australian National University , Canberra, ACT 2601, Australia
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19
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Ahmed FH, Mohamed AE, Carr PD, Lee BM, Condic-Jurkic K, O'Mara ML, Jackson CJ. Rv2074 is a novel F420 H2 -dependent biliverdin reductase in Mycobacterium tuberculosis. Protein Sci 2016; 25:1692-709. [PMID: 27364382 DOI: 10.1002/pro.2975] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Accepted: 06/29/2016] [Indexed: 12/12/2022]
Abstract
Bilirubin is a potent antioxidant that is produced from the reduction of the heme degradation product biliverdin. In mammalian cells and Cyanobacteria, NADH/NADPH-dependent biliverdin reductases (BVRs) of the Rossmann-fold have been shown to catalyze this reaction. Here, we describe the characterization of Rv2074 from Mycobacterium tuberculosis, which belongs to a structurally and mechanistically distinct family of F420 H2 -dependent BVRs (F-BVRs) that are exclusively found in Actinobacteria. We have solved the crystal structure of Rv2074 bound to its cofactor, F420 , and used this alongside molecular dynamics simulations, site-directed mutagenesis and NMR spectroscopy to elucidate its catalytic mechanism. The production of bilirubin by Rv2074 could exploit the anti-oxidative properties of bilirubin and contribute to the range of immuno-evasive mechanisms that have evolved in M. tuberculosis to allow persistent infection.
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Affiliation(s)
- F Hafna Ahmed
- Research School of Chemistry, The Australian National University, Canberra, ACT, 2601, Australia
| | - A Elaaf Mohamed
- Research School of Chemistry, The Australian National University, Canberra, ACT, 2601, Australia
| | - Paul D Carr
- Research School of Chemistry, The Australian National University, Canberra, ACT, 2601, Australia
| | - Brendon M Lee
- Research School of Chemistry, The Australian National University, Canberra, ACT, 2601, Australia
| | - Karmen Condic-Jurkic
- Research School of Chemistry, The Australian National University, Canberra, ACT, 2601, Australia
| | - Megan L O'Mara
- Research School of Chemistry, The Australian National University, Canberra, ACT, 2601, Australia
| | - Colin J Jackson
- Research School of Chemistry, The Australian National University, Canberra, ACT, 2601, Australia
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20
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Wu Y, Wu RWK, Cheu KW, Williams ID, Krishna S, Slavic K, Gravett AM, Liu WM, Wong HN, Haynes RK. Methylene Homologues of Artemisone: An Unexpected Structure-Activity Relationship and a Possible Implication for the Design of C10-Substituted Artemisinins. ChemMedChem 2016; 11:1469-79. [PMID: 27273875 DOI: 10.1002/cmdc.201600011] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Revised: 05/13/2016] [Indexed: 11/12/2022]
Abstract
We sought to establish if methylene homologues of artemisone are biologically more active and more stable than artemisone. The analogy is drawn with the conversion of natural O- and N-glycosides into more stable C-glycosides that may possess enhanced biological activities and stabilities. Dihydroartemisinin was converted into 10β-cyano-10-deoxyartemisinin that was hydrolyzed to the α-primary amide. Reduction of the β-cyanide and the α-amide provided the respective methylamine epimers that upon treatment with divinyl sulfone gave the β- and α-methylene homologues, respectively, of artemisone. Surprisingly, the compounds were less active in vitro than artemisone against P. falciparum and displayed no appreciable activity against A549, HCT116, and MCF7 tumor cell lines. This loss in activity may be rationalized in terms of one model for the mechanism of action of artemisinins, namely the cofactor model, wherein the presence of a leaving group at C10 assists in driving hydride transfer from reduced flavin cofactors to the peroxide during perturbation of intracellular redox homeostasis by artemisinins. It is noted that the carba analogue of artemether is less active in vitro than the O-glycoside parent toward P. falciparum, although extrapolation of such activity differences to other artemisinins at this stage is not possible. However, literature data coupled with the leaving group rationale suggest that artemisinins bearing an amino group attached directly to C10 are optimal compounds.
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Affiliation(s)
- Yuet Wu
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P.R. China
| | - Ronald Wai Kung Wu
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P.R. China
| | - Kwan Wing Cheu
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P.R. China
| | - Ian D Williams
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P.R. China
| | - Sanjeev Krishna
- Centre for Infection, Division of Cellular and Molecular Medicine, St. George's Hospital, University of London, SW17 0RE, UK
| | - Ksenija Slavic
- Centre for Infection, Division of Cellular and Molecular Medicine, St. George's Hospital, University of London, SW17 0RE, UK
| | - Andrew M Gravett
- Department of Oncology, Division of Cellular and Molecular Medicine, St. George's Hospital, University of London, Jenner Wing, London, SW17 0RE, UK
| | - Wai M Liu
- Department of Oncology, Division of Cellular and Molecular Medicine, St. George's Hospital, University of London, Jenner Wing, London, SW17 0RE, UK
| | - Ho Ning Wong
- Centre of Excellence for Pharmaceutical Sciences, Faculty of Health Sciences, North-West University, Potchefstroom, 2520, South Africa.,Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P.R. China
| | - Richard K Haynes
- Centre of Excellence for Pharmaceutical Sciences, Faculty of Health Sciences, North-West University, Potchefstroom, 2520, South Africa. , .,Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P.R. China. ,
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21
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Hendriks G, Derr RS, Misovic B, Morolli B, Calléja FMGR, Vrieling H. The Extended ToxTracker Assay Discriminates Between Induction of DNA Damage, Oxidative Stress, and Protein Misfolding. Toxicol Sci 2016; 150:190-203. [PMID: 26719371 PMCID: PMC5009621 DOI: 10.1093/toxsci/kfv323] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Chemical exposure of cells may damage biomolecules, cellular structures, and organelles thereby jeopardizing cellular homeostasis. A multitude of defense mechanisms have evolved that can recognize specific types of damaged molecules and will initiate distinct cellular programs aiming to remove the damage inflicted and prevent cellular havoc. As a consequence, quantitative assessment of the activity of the cellular stress responses may serve as a sensitive reporter for the induction of specific types of damage. We have previously developed the ToxTracker assay, a mammalian stem cell-based genotoxicity assay employing two green fluorescent protein reporters specific for DNA damage and oxidative stress. We have now expanded the ToxTracker assay with an additional four reporter cell lines to include monitoring of additional stress signaling pathways. This panel of six green fluorescent protein reporters is able to discriminate between different primary reactivity of chemicals being their ability to react with DNA and block DNA replication, induce oxidative stress, activate the unfolded protein response, or cause a general P53-dependent cellular stress response. Extensive validation using the compound library suggested by the European Centre for the Validation of Alternative Methods (ECVAM) and a large panel of reference chemicals shows that the ToxTracker assay has an outstanding sensitivity and specificity. In addition, we developed Toxplot, a dedicated software tool for automated data analysis and graphical representation of the test results. Rapid and reliable identification by the ToxTracker assay of specific biological reactivity can significantly improve in vitro human hazard assessment of chemicals.
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Affiliation(s)
- Giel Hendriks
- Department of Human Genetics, Leiden University Medical Center, 2300RC Leiden, The Netherlands
| | - Remco S Derr
- Department of Human Genetics, Leiden University Medical Center, 2300RC Leiden, The Netherlands
| | - Branislav Misovic
- Department of Human Genetics, Leiden University Medical Center, 2300RC Leiden, The Netherlands
| | - Bruno Morolli
- Department of Human Genetics, Leiden University Medical Center, 2300RC Leiden, The Netherlands
| | - Fabienne M G R Calléja
- Department of Human Genetics, Leiden University Medical Center, 2300RC Leiden, The Netherlands
| | - Harry Vrieling
- Department of Human Genetics, Leiden University Medical Center, 2300RC Leiden, The Netherlands
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22
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Haynes RK, Cheu KW, Chan HW, Wong HN, Li KY, Tang MMK, Chen MJ, Guo ZF, Guo ZH, Sinniah K, Witte AB, Coghi P, Monti D. Interactions between artemisinins and other antimalarial drugs in relation to the cofactor model--a unifying proposal for drug action. ChemMedChem 2012; 7:2204-26. [PMID: 23112085 DOI: 10.1002/cmdc.201200383] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Revised: 09/30/2012] [Indexed: 01/14/2023]
Abstract
Artemisinins are proposed to act in the malaria parasite cytosol by oxidizing dihydroflavin cofactors of redox-active flavoenzymes, and under aerobic conditions by inducing their autoxidation. Perturbation of redox homeostasis coupled with the generation of reactive oxygen species (ROS) ensues. Ascorbic acid-methylene blue (MB), N-benzyl-1,4-dihydronicotinamide (BNAH)-MB, BNAH-lumiflavine, BNAH-riboflavin (RF), and NADPH-FAD-E. coli flavin reductase (Fre) systems at pH 7.4 generate leucomethylene blue (LMB) and reduced flavins that are rapidly oxidized in situ by artemisinins. These oxidations are inhibited by the 4-aminoquinolines piperaquine (PPQ), chloroquine (CQ), and others. In contrast, the arylmethanols lumefantrine, mefloquine (MFQ), and quinine (QN) have little or no effect. Inhibition correlates with the antagonism exerted by 4-aminoquinolines on the antimalarial activities of MB, RF, and artemisinins. Lack of inhibition correlates with the additivity/synergism between the arylmethanols and artemisinins. We propose association via π complex formation between the 4-aminoquinolines and LMB or the dihydroflavins; this hinders hydride transfer from the reduced conjugates to the artemisinins. The arylmethanols have a decreased tendency to form π complexes, and so exert no effect. The parallel between chemical reactivity and antagonism or additivity/synergism draws attention to the mechanism of action of all drugs described herein. CQ and QN inhibit the formation of hemozoin in the parasite digestive vacuole (DV). The buildup of heme-Fe(III) results in an enhanced efflux from the DV into the cytosol. In addition, the lipophilic heme-Fe(III) complexes of CQ and QN that form in the DV are proposed to diffuse across the DV membrane. At the higher pH of the cytosol, the complexes decompose to liberate heme-Fe(III) . The quinoline or arylmethanol reenters the DV, and so transfers more heme-Fe(III) out of the DV. In this way, the 4-aminoquinolines and arylmethanols exert antimalarial activities by enhancing heme-Fe(III) and thence free Fe(III) concentrations in the cytosol. The iron species enter into redox cycles through reduction of Fe(III) to Fe(II) largely mediated by reduced flavin cofactors and likely also by NAD(P)H-Fre. Generation of ROS through oxidation of Fe(II) by oxygen will also result. The cytotoxicities of artemisinins are thereby reinforced by the iron. Other aspects of drug action are emphasized. In the cytosol or DV, association by π complex formation between pairs of lipophilic drugs must adversely influence the pharmacokinetics of each drug. This explains the antagonism between PPQ and MFQ, for example. The basis for the antimalarial activity of RF mirrors that of MB, wherein it participates in redox cycling that involves flavoenzymes or Fre, resulting in attrition of NAD(P)H. The generation of ROS by artemisinins and ensuing Fenton chemistry accommodate the ability of artemisinins to induce membrane damage and to affect the parasite SERCA PfATP6 Ca(2+) transporter. Thus, the effect exerted by artemisinins is more likely a downstream event involving ROS that will also be modulated by mutations in PfATP6. Such mutations attenuate, but cannot abrogate, antimalarial activities of artemisinins. Overall, parasite resistance to artemisinins arises through enhancement of antioxidant defense mechanisms.
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Affiliation(s)
- Richard K Haynes
- Department of Chemistry, Institute of Molecular Technology for Drug Discovery and Synthesis, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, PR China.
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Fu G, Liu H, Doerksen RJ. Molecular modeling to provide insight into the substrate binding and catalytic mechanism of human biliverdin-IXα reductase. J Phys Chem B 2012; 116:9580-94. [PMID: 22823425 DOI: 10.1021/jp301456j] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Human biliverdin-IXα reductase (hBVR-A) catalyzes the conversion of biliverdin-IXα to bilirubin-IXα in the last step of heme degradation and is a key enzyme in regulating a wide range of cellular responses. Though the X-ray structure of hBVR-A is available including cofactor, a crystal structure with a bound substrate would be even more useful as a starting point for protein-structure-based inhibitor design, but none have been reported. The present study employed induced fit docking (IFD) to study the substrate binding modes to hBVR-A of biliverdin-IXα and four analogues. The proposed substrate binding modes were examined further by performing molecular dynamics (MD) simulations followed by molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) calculations. The predicted binding free energies for the five biliverdin-IXα analogues match well with the relative potency of their reported experimental binding affinities, supporting that the proposed binding modes are reasonable. Furthermore, the ternary complex structure of hBVR-A binding with biliverdin-IXα and the electron donor cofactor NADPH obtained from MD simulations was exploited to investigate the catalytic mechanism, by calculating the reaction energy profile using the quantum mechanics/molecular mechanics (QM/MM) method. On the basis of our calculations, the energetically preferred pathway consists of an initial protonation of the pyrrolic nitrogen on the biliverdin substrate followed by hydride transfer to yield the reduction product. This conclusion is consistent with a previous mechanistic study on human biliverdin IXβ reductase (hBVR-B).
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Affiliation(s)
- Gang Fu
- Department of Medicinal Chemistry, School of Pharmacy, University of Mississippi, University, Mississippi 38677, United States
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Haynes RK, Cheu KW, Li KY, Tang MMK, Wong HN, Chen MJ, Guo ZF, Guo ZH, Coghi P, Monti D. A partial convergence in action of methylene blue and artemisinins: antagonism with chloroquine, a reversal with verapamil, and an insight into the antimalarial activity of chloroquine. ChemMedChem 2011; 6:1603-15. [PMID: 21994127 DOI: 10.1002/cmdc.201100184] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2011] [Revised: 06/13/2011] [Indexed: 12/19/2022]
Abstract
Artemisinins rapidly oxidize leucomethylene blue (LMB) to methylene blue (MB); they also oxidize dihydroflavins such as the reduced conjugates RFH₂ of riboflavin (RF), and FADH₂ of the cofactor flavin adenine dinucleotide (FAD), to the corresponding flavins. Like the artemisinins, MB oxidizes FADH₂, but unlike artemisinins, it also oxidizes NAD(P)H. Like MB, artemisinins are implicated in the perturbation of redox balance in the malaria parasite by interfering with parasite flavoenzyme disulfide reductases. The oxidation of LMB by artemisinin is inhibited by chloroquine (CQ), an inhibition that is abruptly reversed by verapamil (VP). CQ also inhibits artemisinin-mediated oxidation of RFH₂ generated from N-benzyl-1,4-dihydronicotinamide (BNAH)-RF, or FADH₂ generated from NADPH or NADPH-Fre, an effect that is also modulated by verapamil. The inhibition likely proceeds by the association of LMB or dihydroflavin with CQ, possibly involving donor-acceptor or π complexes that hinder oxidation by artemisinin. VP competitively associates with CQ, liberating LMB or dihydroflavin from their respective CQ complexes. The observations explain the antagonism between CQ-MB and CQ-artemisinins in vitro, and are reconcilable with CQ perturbing intraparasitic redox homeostasis. They further suggest that a VP-CQ complex is a means by which VP reverses CQ resistance, wherein such a complex is not accessible to the putative CQ-resistance transporter (PfCRT).
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Affiliation(s)
- Richard K Haynes
- Department of Chemistry, Institute of Molecular Technology for Drug Discovery and Synthesis, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P.R. China.
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Haynes RK, Cheu KW, Tang MMK, Chen MJ, Guo ZF, Guo ZH, Coghi P, Monti D. Reactions of Antimalarial Peroxides with Each of Leucomethylene Blue and Dihydroflavins: Flavin Reductase and the Cofactor Model Exemplified. ChemMedChem 2010; 6:279-91. [DOI: 10.1002/cmdc.201000508] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2010] [Indexed: 11/07/2022]
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Vogel M, Lawson M, Sippl W, Conrad U, Roos W. Structure and mechanism of sanguinarine reductase, an enzyme of alkaloid detoxification. J Biol Chem 2010; 285:18397-406. [PMID: 20378534 DOI: 10.1074/jbc.m109.088989] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Sanguinarine reductase is a plant enzyme that prevents the cytotoxic effects of benzophenanthridine alkaloids, which are the main phytoalexins of Papaveraceae. The enzyme catalyzes the reduction of sanguinarine, the most toxic benzophenanthridine, which re-enters the cytoplasm after its primary accumulation in the cell wall region has reached a threshold concentration. We present the sequence of the gene and protein of sanguinarine reductase isolated from cell cultures of Eschscholzia californica. High sequence similarities indicate that the enzyme evolved from a plant-specific branch of the ubiquitous Rossmann fold NAD(P)H/NAD(P)(+) binding reductases, with NADP-dependent epimerases or hydroxysteroid reductases as the most likely ancestors. Based on the x-ray structure of a close homolog, a three-dimensional model of the spatial conformation and catalytic site of sanguinarine reductase was established and used for in silico screening of known three-dimensional structures. Surprisingly, the enzyme shares high structural similarity with enzymes of human and bacterial origin, which have similar functions as the plant homologs but bear little amino acid sequence similarity. Using site-directed mutagenesis, a series of recombinant enzymes was generated and assayed to reveal the impact of individual amino acids and peptides in the catalytic process. It appears that relatively few innovations were required to generate this selective catalyst for alkaloid detoxication, notably an insertion of 13 amino acids and the generation of a novel catalytic triad of Cys-Asp-His were sufficient.
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Affiliation(s)
- Matthias Vogel
- Department of Pharmaceutical Biology, Laboratory of Molecular Cell Biology, the Martin-Luther-University of Halle-Wittenberg, 06120 Halle, Saale, Germany
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Hayes JM, Mantle TJ. The effect of pH on the initial rate kinetics of the dimeric biliverdin-IXalpha reductase from the cyanobacterium Synechocystis PCC6803. FEBS J 2009; 276:4414-25. [PMID: 19614741 DOI: 10.1111/j.1742-4658.2009.07149.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Biliverdin-IXalpha reductase from Synechocystis PCC6803 (sBVR-A) is a stable dimer and this behaviour is observed under a range of conditions. This is in contrast to all other forms of BVR-A, which have been reported to behave as monomers, and places sBVR-A in the dihydrodiol dehydrogenase/N-terminally truncated glucose-fructose oxidoreductase structural family of dimers. The cyanobacterial enzyme obeys an ordered steady-state kinetic mechanism at pH 5, with NADPH being the first to bind and NADP(+) the last to dissociate. An analysis of the effect of pH on k(cat) with NADPH as cofactor reveals a pK of 5.4 that must be protonated for effective catalysis. Analysis of the effect of pH on k(cat)/K(m)(NADPH) identifies pK values of 5.1 and 6.1 in the free enzyme. Similar pK values are identified for biliverdin binding to the enzyme-NADPH complex. The lower pK values in the free enzyme (pK 5.1) and enzyme-NADPH complex (pK 4.9) are not evident when NADH is the cofactor, suggesting that this ionizable group may interact with the 2'-phosphate of NADPH. His84 is implicated as a crucial residue for sBVR-A activity because the H84A mutant has less than 1% of the activity of the wild-type and exhibits small but significant changes in the protein CD spectrum. Binding of biliverdin to sBVR-A is conveniently monitored by following the induced CD spectrum for biliverdin. Binding of biliverdin to wild-type sBVR-A induces a P-type spectrum. The H84A mutant shows evidence for weak binding of biliverdin and appears to bind a variant of the P-configuration. Intriguingly, the Y102A mutant, which is catalytically active, binds biliverdin in the M-configuration.
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Affiliation(s)
- Jerrard M Hayes
- School of Biochemistry and Immunology, Trinity College, Dublin, Ireland.
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