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Li J, Yang S, Wu Y, Wang R, Liu Y, Liu J, Ye Z, Tang R, Whiteway M, Lv Q, Yan L. Alternative Oxidase: From Molecule and Function to Future Inhibitors. ACS OMEGA 2024; 9:12478-12499. [PMID: 38524433 PMCID: PMC10955580 DOI: 10.1021/acsomega.3c09339] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Revised: 01/31/2024] [Accepted: 02/07/2024] [Indexed: 03/26/2024]
Abstract
In the respiratory chain of the majority of aerobic organisms, the enzyme alternative oxidase (AOX) functions as the terminal oxidase and has important roles in maintaining metabolic and signaling homeostasis in mitochondria. AOX endows the respiratory system with flexibility in the coupling among the carbon metabolism pathway, electron transport chain (ETC) activity, and ATP turnover. AOX allows electrons to bypass the main cytochrome pathway to restrict the generation of reactive oxygen species (ROS). The inhibition of AOX leads to oxidative damage and contributes to the loss of adaptability and viability in some pathogenic organisms. Although AOXs have recently been identified in several organisms, crystal structures and major functions still need to be explored. Recent work on the trypanosome alternative oxidase has provided a crystal structure of an AOX protein, which contributes to the structure-activity relationship of the inhibitors of AOX. Here, we review the current knowledge on the development, structure, and properties of AOXs, as well as their roles and mechanisms in plants, animals, algae, protists, fungi, and bacteria, with a special emphasis on the development of AOX inhibitors, which will improve the understanding of respiratory regulation in many organisms and provide references for subsequent studies of AOX-targeted inhibitors.
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Affiliation(s)
- Jiye Li
- School
of Pharmacy, Naval Medical University, Shanghai 200433, China
- Institute
of Medicinal Biotechnology, Chinese Academy
of Medical Sciences and Peking Union Medical College, Beijing 100050, China
| | - Shiyun Yang
- School
of Pharmacy, Naval Medical University, Shanghai 200433, China
| | - Yujie Wu
- School
of Pharmacy, Naval Medical University, Shanghai 200433, China
| | - Ruina Wang
- School
of Pharmacy, Naval Medical University, Shanghai 200433, China
| | - Yu Liu
- School
of Pharmacy, Naval Medical University, Shanghai 200433, China
| | - Jiacun Liu
- School
of Pharmacy, Naval Medical University, Shanghai 200433, China
| | - Zi Ye
- School
of Pharmacy, Naval Medical University, Shanghai 200433, China
| | - Renjie Tang
- Beijing
South Medical District of Chinese PLA General Hospital, Beijing 100072, China
| | - Malcolm Whiteway
- Department
of Biology, Concordia University, Montreal, H4B 1R6 Quebec, Canada
| | - Quanzhen Lv
- School
of Pharmacy, Naval Medical University, Shanghai 200433, China
- Basic
Medicine Innovation Center for Fungal Infectious Diseases, (Naval Medical University), Ministry of Education, Shanghai 200433, China
- Key
Laboratory of Biosafety Defense (Naval Medical University), Ministry
of Education, Shanghai 200433, China
- Shanghai
Key Laboratory of Medical Biodefense, Shanghai 200433, China
| | - Lan Yan
- School
of Pharmacy, Naval Medical University, Shanghai 200433, China
- Basic
Medicine Innovation Center for Fungal Infectious Diseases, (Naval Medical University), Ministry of Education, Shanghai 200433, China
- Key
Laboratory of Biosafety Defense (Naval Medical University), Ministry
of Education, Shanghai 200433, China
- Shanghai
Key Laboratory of Medical Biodefense, Shanghai 200433, China
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Ibrahim MK, Haria A, Mehta NV, Degani MS. Antimicrobial potential of quaternary phosphonium salt compounds: a review. Future Med Chem 2023; 15:2113-2141. [PMID: 37929337 DOI: 10.4155/fmc-2023-0188] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Accepted: 09/11/2023] [Indexed: 11/07/2023] Open
Abstract
Given that mitochondrial dysregulation is a biomarker of many cancers, cationic quaternary phosphonium salt (QPS) conjugation is a widely utilized strategy for anticancer drug design. QPS-conjugated compounds exhibit greater cell permeation and accumulation in negatively charged mitochondria, and thus, show enhanced activity. Phylogenetic similarities between mitochondria and bacteria have provided a rationale for exploring the antibacterial properties of mitochondria-targeted compounds. Additionally, due to the importance of mitochondria in the survival of pathogenic microbes, including fungi and parasites, this strategy can be extended to these organisms as well. This review examines recent literature on the antimicrobial activities of various QPS-conjugated compounds and provides future directions for exploring the medicinal chemistry of these compounds.
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Affiliation(s)
- Mahin K Ibrahim
- Department of Pharmaceutical Sciences & Technology, Institute of Chemical Technology, Nathalal Parekh Marg, Mumbai, 400019, Maharashtra, India
| | - Akash Haria
- Department of Pharmaceutical Sciences & Technology, Institute of Chemical Technology, Nathalal Parekh Marg, Mumbai, 400019, Maharashtra, India
| | - Namrashee V Mehta
- Department of Pharmaceutical Sciences & Technology, Institute of Chemical Technology, Nathalal Parekh Marg, Mumbai, 400019, Maharashtra, India
| | - Mariam S Degani
- Department of Pharmaceutical Sciences & Technology, Institute of Chemical Technology, Nathalal Parekh Marg, Mumbai, 400019, Maharashtra, India
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Steverding D, do Nascimento LG, Perez-Castillo Y, de Sousa DP. Gallic Acid Alkyl Esters: Trypanocidal and Leishmanicidal Activity, and Target Identification via Modeling Studies. Molecules 2022; 27:molecules27185876. [PMID: 36144611 PMCID: PMC9501172 DOI: 10.3390/molecules27185876] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Revised: 09/07/2022] [Accepted: 09/08/2022] [Indexed: 11/16/2022] Open
Abstract
Eight gallic acid alkyl esters (1−8) were synthesized via Fischer esterification and evaluated for their trypanocidal and leishmanicidal activity using bloodstream forms of Trypanosoma brucei and promastigotes of Leishmania major. The general cytotoxicity of the esters was evaluated with human HL-60 cells. The compounds displayed moderate to good trypanocidal but zero to low leishmanicidal activity. Gallic acid esters with alkyl chains of three or four carbon atoms in linear arrangement (propyl (4), butyl (5), and isopentyl (6)) were found to be the most trypanocidal compounds with 50% growth inhibition values of ~3 μM. On the other hand, HL-60 cells were less susceptible to the compounds, thus, resulting in moderate selectivity indices (ratio of cytotoxic to trypanocidal activity) of >20 for the esters 4−6. Modeling studies combining molecular docking and molecular dynamics simulations suggest that the trypanocidal mechanism of action of gallic acid alkyl esters could be related to the inhibition of the T. brucei alternative oxidase. This suggestion is supported by the observation that trypanosomes became immobile within minutes when incubated with the esters in the presence of glycerol as the sole substrate. These results indicate that gallic acid alkyl esters are interesting compounds to be considered for further antitrypanosomal drug development.
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Affiliation(s)
- Dietmar Steverding
- Bob Champion Research and Education Building, Norwich Medical School, University of East Anglia, Norwich NR4 7UQ, UK
- Correspondence: (D.S.); (D.P.d.S.)
| | - Lázaro Gomes do Nascimento
- Laboratory of Pharmaceutical Chemistry, Department of Pharmaceutical Sciences, Federal University of Paraíba, João Pessoa 58051-900, PB, Brazil
| | - Yunierkis Perez-Castillo
- Bio-Cheminformatics Research Group, Universidad de Las Américas, Quito 170516, Ecuador
- Facultad de Ingeniería y Ciencias Aplicadas, Área de Ciencias Aplicadas, Universidad de Las Américas, Quito 170516, Ecuador
| | - Damião Pergentino de Sousa
- Laboratory of Pharmaceutical Chemistry, Department of Pharmaceutical Sciences, Federal University of Paraíba, João Pessoa 58051-900, PB, Brazil
- Correspondence: (D.S.); (D.P.d.S.)
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Identification and Functional Characterization of a Putative Alternative Oxidase (Aox) in Sporisorium reilianum f. sp. zeae. J Fungi (Basel) 2022; 8:jof8020148. [PMID: 35205901 PMCID: PMC8877474 DOI: 10.3390/jof8020148] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 01/26/2022] [Accepted: 01/28/2022] [Indexed: 12/04/2022] Open
Abstract
The mitochondrial electron transport chain consists of the classical protein complexes (I–IV) that facilitate the flow of electrons and coupled oxidative phosphorylation to produce metabolic energy. The canonical route of electron transport may diverge by the presence of alternative components to the electron transport chain. The following study comprises the bioinformatic identification and functional characterization of a putative alternative oxidase in the smut fungus Sporisorium reilianum f. sp. zeae. This alternative respiratory component has been previously identified in other eukaryotes and is essential for alternative respiration as a response to environmental and chemical stressors, as well as for developmental transitionaoxs during the life cycle of an organism. A growth inhibition assay, using specific mitochondrial inhibitors, functionally confirmed the presence of an antimycin-resistant/salicylhydroxamic acid (SHAM)-sensitive alternative oxidase in the respirasome of S. reilianum. Gene disruption experiments revealed that this enzyme is involved in the pathogenic stage of the fungus, with its absence effectively reducing overall disease incidence in infected maize plants. Furthermore, gene expression analysis revealed that alternative oxidase plays a prominent role in the teliospore developmental stage, in agreement with favoring alternative respiration during quiescent stages of an organism’s life cycle.
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Xing Y, Zhang S, Qu G, Dai J, Yao J, Feng B. Discovery and Validation of a Novel Target of Molluscicides against Oncomelania hupensis, the Intermediate Host of Schistosoma japonicum. Acta Trop 2021; 221:106003. [PMID: 34118205 DOI: 10.1016/j.actatropica.2021.106003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Revised: 05/31/2021] [Accepted: 06/01/2021] [Indexed: 11/25/2022]
Abstract
In this study, 196 strains of actinomycetes isolated from marshland soil samples were tested for molluscicidal activity against Oncomelania hupensis. Five strains demonstrated molluscicidal activity, of which the molluscicidal efficiency of Actinomycetes strain A183 was the maximum. After the fermentation supernatant of actinomycetes A183 was extracted with ethyl acetate (EWEA), the LC50 of the EWEA after leaching for 48 h and 72 h were 0.2688 and 0.2195 mg/L, respectively. The effect of EWEA on the key points of energy metabolism was determined. We noted that 1 mg/L of EWEA (A813) significantly reduced the activity of mitochondrial respiratory chain complex I (P < 0.05), while no significant changes were observed in the activities of complexes II, III, and IV. In addition, EWEA (A813) could decrease the membrane potential of O. hupensis purified mitochondria in vitro. The LC50 of the 3 uncoupler (FCCP, DNP, and Tyrphostin A9) after immersion for 24 h were 0.065, 0.135, and 0.110 mg/L, respectively; LC50 after 48 h treatment was 0.064, 0.124, and 0.082 mg/L, respectively; LC50 after 72 h treatment was 0.063, 0.129, and 0.061 mg/L, respectively, and all uncoupler showed strong molluscicidal activities, demonstrating that the mitochondrial membrane potential uncoupling is a potential target for molluscicides against O. hupensis. Moreover, the molluscicidal active substance of strain A183 needs to be further isolated, purified, and structurally characterized considering its promising potential applications.
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Song J, Zhou J, Zhang L, Li R. Mitochondria-Mediated Azole Drug Resistance and Fungal Pathogenicity: Opportunities for Therapeutic Development. Microorganisms 2020; 8:E1574. [PMID: 33066090 PMCID: PMC7600254 DOI: 10.3390/microorganisms8101574] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 10/09/2020] [Accepted: 10/09/2020] [Indexed: 12/16/2022] Open
Abstract
In recent years, the role of mitochondria in pathogenic fungi in terms of azole resistance and fungal pathogenicity has been a rapidly developing field. In this review, we describe the molecular mechanisms by which mitochondria are involved in regulating azole resistance and fungal pathogenicity. Mitochondrial function is involved in the regulation of drug efflux pumps at the transcriptional and posttranslational levels. On the one hand, defects in mitochondrial function can serve as the signal leading to activation of calcium signaling and the pleiotropic drug resistance pathway and, therefore, can globally upregulate the expression of drug efflux pump genes, leading to azole drug resistance. On the other hand, mitochondria also contribute to azole resistance through modulation of drug efflux pump localization and activity. Mitochondria further contribute to azole resistance through participating in iron homeostasis and lipid biosynthesis. Additionally, mitochondrial dynamics play an important role in azole resistance. Meanwhile, mitochondrial morphology is important for fungal virulence, playing roles in growth in stressful conditions in a host. Furthermore, there is a close link between mitochondrial respiration and fungal virulence, and mitochondrial respiration plays an important role in morphogenetic transition, hypoxia adaptation, and cell wall biosynthesis. Finally, we discuss the possibility for targeting mitochondrial factors for the development of antifungal therapies.
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Affiliation(s)
- Jinxing Song
- The Key Laboratory of Biotechnology for Medicinal Plants of Jiangsu Province and School of Life Science, Jiangsu Normal University, Xuzhou, Jiangsu 221116, China;
- Shandong Provincial Key Laboratory of Infection and Immunity, Jinan 250012, China;
| | - Jingwen Zhou
- The Key Laboratory of Biotechnology for Medicinal Plants of Jiangsu Province and School of Life Science, Jiangsu Normal University, Xuzhou, Jiangsu 221116, China;
| | - Lei Zhang
- Shandong Provincial Key Laboratory of Infection and Immunity, Jinan 250012, China;
| | - Rongpeng Li
- The Key Laboratory of Biotechnology for Medicinal Plants of Jiangsu Province and School of Life Science, Jiangsu Normal University, Xuzhou, Jiangsu 221116, China;
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Tian F, Lee SY, Woo SY, Chun HS. Alternative Oxidase: A Potential Target for Controlling Aflatoxin Contamination and Propagation of Aspergillus flavus. Front Microbiol 2020; 11:419. [PMID: 32256475 PMCID: PMC7092633 DOI: 10.3389/fmicb.2020.00419] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Accepted: 02/27/2020] [Indexed: 12/16/2022] Open
Abstract
Aflatoxins are among the most hazardous natural cereal contaminants. These mycotoxins are produced by Aspergillus spp. as polyketide secondary metabolites. Aflatoxigenic fungi including A. flavus express the alternative oxidase (AOX), which introduces a branch in the cytochrome-based electron transfer chain by coupling ubiquinol oxidation directly with the reduction of O2 to H2O. AOX is closely associated with fungal pathogenesis, morphogenesis, stress signaling, and drug resistance and, as recently reported, affects the production of mycotoxins such as sterigmatocystin, the penultimate intermediate in aflatoxin B1 biosynthesis. Thus, AOX might be considered a target for controlling the propagation of and aflatoxin contamination by A. flavus. Hence, this review summarizes the current understanding of fungal AOX and the alternative respiration pathway and the development and potential applications of AOX inhibitors. This review indicates that AOX inhibitors, either alone or in combination with current antifungal agents, are potentially applicable for developing novel, effective antifungal strategies. However, considering the conservation of AOX in fungal and plant cells, a deeper understanding of fungal alternative respiration and fungal AOX structure is needed, along with effective fungal-specific AOX inhibitors.
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Affiliation(s)
- Fei Tian
- Food Toxicology Laboratory, Advanced Food Safety Research Group, BK21 Plus, School of Food Science and Technology, Chung-Ang University, Anseong, South Korea
| | - Sang Yoo Lee
- Food Toxicology Laboratory, Advanced Food Safety Research Group, BK21 Plus, School of Food Science and Technology, Chung-Ang University, Anseong, South Korea
| | - So Young Woo
- Food Toxicology Laboratory, Advanced Food Safety Research Group, BK21 Plus, School of Food Science and Technology, Chung-Ang University, Anseong, South Korea
| | - Hyang Sook Chun
- Food Toxicology Laboratory, Advanced Food Safety Research Group, BK21 Plus, School of Food Science and Technology, Chung-Ang University, Anseong, South Korea
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The potential of respiration inhibition as a new approach to combat human fungal pathogens. Curr Genet 2019; 65:1347-1353. [PMID: 31172256 PMCID: PMC6820612 DOI: 10.1007/s00294-019-01001-w] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 05/24/2019] [Accepted: 05/27/2019] [Indexed: 02/06/2023]
Abstract
The respiratory chain has been proposed as an attractive target for the development of new therapies to tackle human fungal pathogens. This arises from the presence of fungal-specific electron transport chain components and links between respiration and the control of virulence traits in several pathogenic species. However, as the physiological roles of mitochondria remain largely undetermined with respect to pathogenesis, its value as a potential new drug target remains to be determined. The use of respiration inhibitors as fungicides is well developed but has been hampered by the emergence of rapid resistance to current inhibitors. In addition, recent data suggest that adaptation of the human fungal pathogen, Candida albicans, to respiration inhibitors can enhance virulence traits such as yeast-to-hypha transition and cell wall organisation. We conclude that although respiration holds promise as a target for the development of new therapies to treat human fungal infections, we require a more detailed understanding of the role that mitochondria play in stress adaption and virulence.
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Čermáková P, Kovalinka T, Ferenczyová K, Horváth A. Coenzyme Q 2 is a universal substrate for the measurement of respiratory chain enzyme activities in trypanosomatids. ACTA ACUST UNITED AC 2019; 26:17. [PMID: 30901308 PMCID: PMC6430614 DOI: 10.1051/parasite/2019017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 03/09/2019] [Indexed: 12/16/2022]
Abstract
The measurement of respiratory chain enzyme activities is an integral part of basic research as well as for specialized examinations in clinical biochemistry. Most of the enzymes use ubiquinone as one of their substrates. For current in vitro measurements, several hydrophilic analogues of native ubiquinone are used depending on the enzyme and the workplace. We tested five readily available commercial analogues and we showed that Coenzyme Q2 is the most suitable for the measurement of all tested enzyme activities. Use of a single substrate in all laboratories for several respiratory chain enzymes will improve our ability to compare data, in addition to simplifying the stock of chemicals required for this type of research.
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Affiliation(s)
- Petra Čermáková
- Department of Biochemistry, Faculty of Natural Sciences, Comenius University, Bratislava, Slovakia
| | - Tomáš Kovalinka
- Department of Biochemistry, Faculty of Natural Sciences, Comenius University, Bratislava, Slovakia
| | - Kristína Ferenczyová
- Department of Biochemistry, Faculty of Natural Sciences, Comenius University, Bratislava, Slovakia
| | - Anton Horváth
- Department of Biochemistry, Faculty of Natural Sciences, Comenius University, Bratislava, Slovakia
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10
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Ebiloma GU, Balogun EO, Cueto-Díaz EJ, de Koning HP, Dardonville C. Alternative oxidase inhibitors: Mitochondrion-targeting as a strategy for new drugs against pathogenic parasites and fungi. Med Res Rev 2019; 39:1553-1602. [PMID: 30693533 DOI: 10.1002/med.21560] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Revised: 11/07/2018] [Accepted: 12/08/2018] [Indexed: 12/11/2022]
Abstract
The alternative oxidase (AOX) is a ubiquitous terminal oxidase of plants and many fungi, catalyzing the four-electron reduction of oxygen to water alongside the cytochrome-based electron transfer chain. Unlike the classical electron transfer chain, however, the activity of AOX does not generate adenosine triphosphate but has functions such as thermogenesis and stress response. As it lacks a mammalian counterpart, it has been investigated intensely in pathogenic fungi. However, it is in African trypanosomes, which lack cytochrome-based respiration in their infective stages, that trypanosome alternative oxidase (TAO) plays the central and essential role in their energy metabolism. TAO was validated as a drug target decades ago and among the first inhibitors to be identified was salicylhydroxamic acid (SHAM), which produced the expected trypanocidal effects, especially when potentiated by coadministration with glycerol to inhibit anaerobic energy metabolism as well. However, the efficacy of this combination was too low to be of practical clinical use. The antibiotic ascofuranone (AF) proved a much stronger TAO inhibitor and was able to cure Trypanosoma vivax infections in mice without glycerol and at much lower doses, providing an important proof of concept milestone. Systematic efforts to improve the SHAM and AF scaffolds, aided with the elucidation of the TAO crystal structure, provided detailed structure-activity relationship information and reinvigorated the drug discovery effort. Recently, the coupling of mitochondrion-targeting lipophilic cations to TAO inhibitors has dramatically improved drug targeting and trypanocidal activity while retaining target protein potency. These developments appear to have finally signposted the way to preclinical development of TAO inhibitors.
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Affiliation(s)
- Godwin U Ebiloma
- Department of Applied Biology, Graduate School of Science and Technology, Kyoto Institute of Technology, Kyoto, Japan.,Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Emmanuel O Balogun
- Department of Biochemistry, Ahmadu Bello University, Zaria, Nigeria.,Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | | | - Harry P de Koning
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
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Meco-Navas A, Ebiloma GU, Martín-Domínguez A, Martínez-Benayas I, Cueto-Díaz EJ, Alhejely AS, Balogun EO, Saito M, Matsui M, Arai N, Shiba T, Harada S, de Koning HP, Dardonville C. SAR of 4-Alkoxybenzoic Acid Inhibitors of the Trypanosome Alternative Oxidase. ACS Med Chem Lett 2018; 9:923-928. [PMID: 30258542 DOI: 10.1021/acsmedchemlett.8b00282] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Accepted: 07/31/2018] [Indexed: 11/30/2022] Open
Abstract
The SAR of 4-hydroxybenzaldehyde inhibitors of the trypanosome alternative oxidase (TAO), a critical enzyme for the respiration of bloodstream forms of trypanosomes, was investigated. Replacing the aldehyde group with a methyl ester resulted in a 10-fold increase in TAO inhibition and activity against T. brucei. Remarkably, two analogues containing the 2-hydroxy-6-methyl scaffold (9e and 16e) displayed single digit nanomolar TAO inhibition, which constitute the most potent 4-alkoxybenzoic acid derivatives described to date. 9e was 50-times more potent against TAO and 10-times more active against T. brucei compared to its benzaldehyde analogue 1. The farnesyl derivative 16e was as potent a TAO inhibitor as ascofuranone with IC50 = 3.1 nM. Similar to ascofuranone derivatives, the 2-hydroxy and 6-methyl groups seemed essential for low nanomolar TAO inhibition of acid derivatives, suggesting analogous binding interactions with the TAO active site.
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Affiliation(s)
- Alejandro Meco-Navas
- Instituto de Química Médica, IQM-CSIC, Juan de la Cierva 3, E-28006 Madrid, Spain
| | - Godwin U. Ebiloma
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom
- Department of Applied Biology, Kyoto Institute of Technology, Kyoto 606-8585, Japan
| | - Ana Martín-Domínguez
- Instituto de Química Médica, IQM-CSIC, Juan de la Cierva 3, E-28006 Madrid, Spain
| | | | | | - Amani Saud Alhejely
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | | | - Machi Saito
- Department of Applied Biology, Kyoto Institute of Technology, Kyoto 606-8585, Japan
| | - Miho Matsui
- Department of Applied Biology, Kyoto Institute of Technology, Kyoto 606-8585, Japan
| | - Natsumi Arai
- Department of Applied Biology, Kyoto Institute of Technology, Kyoto 606-8585, Japan
| | - Tomoo Shiba
- Department of Applied Biology, Kyoto Institute of Technology, Kyoto 606-8585, Japan
| | - Shigeharu Harada
- Department of Applied Biology, Kyoto Institute of Technology, Kyoto 606-8585, Japan
| | - Harry P. de Koning
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom
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12
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Ebiloma GU, Ayuga TD, Balogun EO, Gil LA, Donachie A, Kaiser M, Herraiz T, Inaoka DK, Shiba T, Harada S, Kita K, de Koning HP, Dardonville C. Inhibition of trypanosome alternative oxidase without its N-terminal mitochondrial targeting signal (ΔMTS-TAO) by cationic and non-cationic 4-hydroxybenzoate and 4-alkoxybenzaldehyde derivatives active against T. brucei and T. congolense. Eur J Med Chem 2018; 150:385-402. [PMID: 29544150 DOI: 10.1016/j.ejmech.2018.02.075] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 02/22/2018] [Accepted: 02/23/2018] [Indexed: 11/28/2022]
Abstract
African trypanosomiasis is a neglected parasitic disease that is still of great public health relevance, and a severe impediment to agriculture in endemic areas. The pathogens possess certain unique metabolic features that can be exploited for the development of new drugs. Notably, they rely on an essential, mitochondrially-localized enzyme, Trypanosome Alternative Oxidase (TAO) for their energy metabolism, which is absent in the mammalian hosts and therefore an attractive target for the design of safe drugs. In this study, we cloned, expressed and purified the physiologically relevant form of TAO, which lacks the N-terminal 25 amino acid mitochondrial targeting sequence (ΔMTS-TAO). A new class of 32 cationic and non-cationic 4-hydroxybenzoate and 4-alkoxybenzaldehyde inhibitors was designed and synthesized, enabling the first structure-activity relationship studies on ΔMTS-TAO. Remarkably, we obtained compounds with enzyme inhibition values (IC50) as low as 2 nM, which were efficacious against wild type and multidrug-resistant strains of T. brucei and T. congolense. The inhibitors 13, 15, 16, 19, and 30, designed with a mitochondrion-targeting lipophilic cation tail, displayed trypanocidal potencies comparable to the reference drugs pentamidine and diminazene, and showed no cross-resistance with the critical diamidine and melaminophenyl arsenical classes of trypanocides. The cationic inhibitors 15, 16, 19, 20, and 30 were also much more selective (900 - 344,000) over human cells than the non-targeted neutral derivatives (selectivity >8-fold). A preliminary in vivo study showed that modest doses of 15 and 16 reduced parasitaemia of mice infected with T. b. rhodesiense (STIB900). These compounds represent a promising new class of potent and selective hits against African trypanosomes.
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Affiliation(s)
- Godwin U Ebiloma
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom; Department of Biochemistry, Kogi State University, Anyigba, Nigeria
| | - Teresa Díaz Ayuga
- Instituto de Química Médica, IQM-CSIC, Juan de la Cierva 3, E-28006 Madrid, Spain
| | - Emmanuel O Balogun
- Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, Japan; Department of Biochemistry, Ahmadu Bello University, Zaria 2222, Nigeria
| | - Lucía Abad Gil
- Instituto de Química Médica, IQM-CSIC, Juan de la Cierva 3, E-28006 Madrid, Spain
| | - Anne Donachie
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Marcel Kaiser
- Swiss Tropical and Public Health Institute, Socinstrasse, 57, CH-4002 Basel, Switzerland
| | - Tomás Herraiz
- Instituto de Ciencia y Tecnología de Alimentos y Nutrición, ICTAN-CSIC, Juan de la Cierva 3, E-28006 Madrid, Spain
| | - Daniel K Inaoka
- Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, Japan; School of Tropical Medicine and Global Health, Nagasaki University, Nagasaki, 852-8523, Japan
| | - Tomoo Shiba
- Department of Applied Biology, Kyoto Institute of Technology, Kyoto 606-8585, Japan
| | - Shigeharu Harada
- Department of Applied Biology, Kyoto Institute of Technology, Kyoto 606-8585, Japan
| | - Kiyoshi Kita
- Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, Japan; School of Tropical Medicine and Global Health, Nagasaki University, Nagasaki, 852-8523, Japan
| | - Harry P de Koning
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom.
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13
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Fueyo González FJ, Ebiloma GU, Izquierdo García C, Bruggeman V, Sánchez Villamañán JM, Donachie A, Balogun EO, Inaoka DK, Shiba T, Harada S, Kita K, de Koning HP, Dardonville C. Conjugates of 2,4-Dihydroxybenzoate and Salicylhydroxamate and Lipocations Display Potent Antiparasite Effects by Efficiently Targeting the Trypanosoma brucei and Trypanosoma congolense Mitochondrion. J Med Chem 2017; 60:1509-1522. [PMID: 28112515 DOI: 10.1021/acs.jmedchem.6b01740] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We investigated a chemical strategy to boost the trypanocidal activity of 2,4-dihydroxybenzoic acid (2,4-DHBA)- and salicylhydroxamic acid (SHAM)-based trypanocides with triphenylphosphonium and quinolinium lipophilic cations (LC). Three series of LC conjugates were synthesized that were active in the submicromolar (5a-d and 10d-f) to low nanomolar (6a-f) range against wild-type and multidrug resistant strains of African trypanosomes (Trypanosoma brucei brucei and T. congolense). This represented an improvement in trypanocidal potency of at least 200-fold, and up to >10 000-fold, compared with that of non-LC-coupled parent compounds 2,4-DHBA and SHAM. Selectivity over human cells was >500 and reached >23 000 for 6e. Mechanistic studies showed that 6e did not inhibit the cell cycle but affected parasite respiration in a dose-dependent manner. Inhibition of trypanosome alternative oxidase and the mitochondrial membrane potential was also studied for selected compounds. We conclude that effective mitochondrial targeting greatly potentiated the activity of these series of compounds.
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Affiliation(s)
| | - Godwin U Ebiloma
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow , Glasgow G12 8TA, United Kingdom.,Department of Biochemistry, Kogi State University , Anyigba 1008, Nigeria
| | | | - Victor Bruggeman
- Instituto de Química Médica, IQM-CSIC , Juan de la Cierva 3, E-28006 Madrid, Spain
| | | | - Anne Donachie
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow , Glasgow G12 8TA, United Kingdom
| | - Emmanuel Oluwadare Balogun
- Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo , Tokyo 113-0033, Japan.,Department of Biochemistry, Ahmadu Bello University , Zaria 2222, Nigeria
| | - Daniel Ken Inaoka
- Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo , Tokyo 113-0033, Japan.,School of Tropical Medicine and Global Health, Nagasaki University , Nagasaki, 852-8523, Japan
| | - Tomoo Shiba
- Department of Applied Biology, Kyoto Institute of Technology , Kyoto 606-8585, Japan
| | - Shigeharu Harada
- Department of Applied Biology, Kyoto Institute of Technology , Kyoto 606-8585, Japan
| | - Kiyoshi Kita
- Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo , Tokyo 113-0033, Japan.,School of Tropical Medicine and Global Health, Nagasaki University , Nagasaki, 852-8523, Japan
| | - Harry P de Koning
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow , Glasgow G12 8TA, United Kingdom
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14
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Abstract
SUMMARYNew drugs against Trypanosoma brucei, the causative agent of Human African Trypanosomiasis, are urgently needed to replace the highly toxic and largely ineffective therapies currently used. The trypanosome alternative oxidase (TAO) is an essential and unique mitochondrial protein in these parasites and is absent from mammalian mitochondria, making it an attractive drug target. The structure and function of the protein are now well characterized, with several inhibitors reported in the literature, which show potential as clinical drug candidates. In this review, we provide an update on the functional activity and structural aspects of TAO. We then discuss TAO inhibitors reported to date, problems encountered with in vivo testing of these compounds, and discuss the future of TAO as a therapeutic target.
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15
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Fragment screening reveals salicylic hydroxamic acid as an inhibitor of Trypanosoma brucei GPI GlcNAc-PI de-N-acetylase. Carbohydr Res 2013; 387:54-8. [PMID: 24589444 PMCID: PMC3991331 DOI: 10.1016/j.carres.2013.12.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Revised: 12/12/2013] [Accepted: 12/18/2013] [Indexed: 11/24/2022]
Abstract
First non-substrate analogue inhibitor of the trypanosome GPI pathway. Active against recombinant enzyme and cell-free system. Low molecular weight and good ligand efficiency.
The zinc-metalloenzyme GlcNAc-PI de-N-acetylase is essential for the biosynthesis of mature GPI anchors and has been genetically validated in the bloodstream form of Trypanosoma brucei, which causes African sleeping sickness. We screened a focused library of zinc-binding fragments and identified salicylic hydroxamic acid as a GlcNAc-PI de-N-acetylase inhibitor with high ligand efficiency. This is the first small molecule inhibitor reported for the trypanosome GPI pathway. Investigating the structure activity relationship revealed that hydroxamic acid and 2-OH are essential for potency, and that substitution is tolerated at the 4- and 5-positions.
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16
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Mallo N, Lamas J, Leiro JM. Evidence of an alternative oxidase pathway for mitochondrial respiration in the scuticociliate Philasterides dicentrarchi. Protist 2013; 164:824-36. [PMID: 24211656 DOI: 10.1016/j.protis.2013.09.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Revised: 09/25/2013] [Accepted: 09/28/2013] [Indexed: 11/17/2022]
Abstract
The presence of an alternative oxidase (AOX) in the mitochondria of the scuticociliate P. dicentrarchi was investigated. The mitochondrial oxygen consumption was measured in the presence of KCN, an inhibitor of cytochrome pathway (CP) respiration and salicylhydroxamic acid (SHAM), a specific inhibitor of alternative pathway (AP) respiration. AOX expression was monitored by western blotting with an AOX polyclonal antibody. The results showed that P. dicentrarchi possesses a branched mitochondrial electron transport chain with both cyanide-sensitive and -insensitive oxygen consumption. Mitochondrial respiration was partially inhibited by cyanide and completely inhibited by the combination of cyanide and SHAM, which is direct evidence for the existence of an AP in this ciliate. SHAM significantly inhibited in vitro growth of trophozoites both under normoxic and hypoxic conditions. AOX is a 42kD monomeric protein inducible by hypoxic conditions in experimental infections and by CP inhibitors such as cyanide and antimycin A, or by AP inhibitors such as SHAM. CP respiration was greatly stimulated during the exponential growth phase, while AP respiration increased during the stationary phase, in which AOX expression is induced. As the host does not possess AOX, and because during infection P. dicentrarchi respires via AP, it may be possible to develop inhibitors targeting the AP as a novel anti-scuticociliate therapy.
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Affiliation(s)
- Natalia Mallo
- Laboratorio de Parasitología, Departamento de Microbiología y Parasitología, Instituto de Investigación y Análisis Alimentarios, c/ Constantino Candeira s/n, 15782, Universidad de Santiago de Compostela; Santiago de Compostela (La Coruña, Spain)
| | - Jesús Lamas
- Departamento de Biología Celular y Ecología; Universidad de Santiago de Compostela; Santiago de Compostela, (La Coruña, Spain)
| | - José Manuel Leiro
- Laboratorio de Parasitología, Departamento de Microbiología y Parasitología, Instituto de Investigación y Análisis Alimentarios, c/ Constantino Candeira s/n, 15782, Universidad de Santiago de Compostela; Santiago de Compostela (La Coruña, Spain).
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17
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Taylor MC, McLatchie AP, Kelly JM. Evidence that transport of iron from the lysosome to the cytosol in African trypanosomes is mediated by a mucolipin orthologue. Mol Microbiol 2013; 89:420-32. [PMID: 23750752 PMCID: PMC3828870 DOI: 10.1111/mmi.12285] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/02/2013] [Indexed: 11/28/2022]
Abstract
Bloodstream-form Trypanosoma brucei acquire iron by receptor-mediated endocytosis of host transferrin. However, the mechanism(s) by which iron is then transferred from the lysosome to the cytosol are unresolved. Here, we provide evidence for the involvement of a protein (TbMLP) orthologous to the mammalian endolysosomal cation channel Mucolipin 1. In T. brucei, we show that this protein is localized to the single parasite lysosome. TbMLP null mutants could only be generated in the presence of an expressed ectopic copy, suggesting that the protein is essential. RNAi-mediated ablation resulted in a growth defect in vitro and led to a sevenfold increase in susceptibility to the iron-chelators deferoxamine and salicylhydroxamic acid. Conditional null mutants remained viable when the ectopic copy was repressed, but were hypersensitive to deferoxamine and displayed a growth defect similar to that observed following RNAi. The conditional nulls also retained virulence in vivo in the absence of the doxycycline inducer. These data provide strong evidence that TbMLP has a role in import of iron into the cytosol of African trypanosomes. They also indicate that even when expression is greatly reduced, there is sufficient protein, or an alternative mechanism, to provide the parasite with an adequate supply of cytosolic iron.
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Affiliation(s)
- Martin C Taylor
- Department of Pathogen Molecular Biology, London School of Hygiene and Tropical Medicine, Keppel St., London, WC1E 7HT, UK.
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18
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Fytas C, Zoidis G, Tzoutzas N, Taylor MC, Fytas G, Kelly JM. Novel lipophilic acetohydroxamic acid derivatives based on conformationally constrained spiro carbocyclic 2,6-diketopiperazine scaffolds with potent trypanocidal activity. J Med Chem 2011; 54:5250-4. [PMID: 21542562 PMCID: PMC3140774 DOI: 10.1021/jm200217m] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2011] [Indexed: 11/30/2022]
Abstract
We describe novel acetohydroxamic acid derivatives with potent activity against cultured bloodstream-form Trypanosoma brucei and selectivity indices of >1000. These analogues were derived from conformationally constrained, lipophilic, spiro carbocyclic 2,6-diketopiperazine (2,6-DKP) scaffolds by attaching acetohydroxamic acid moieties to the imidic nitrogen. Optimal activity was achieved by placing benzyl groups adjacent to the basic nitrogen of the 2,6-DKP core. S-Enantiomer 7d was the most active derivative against T. brucei (IC(50) = 6.8 nM) and T. cruzi (IC(50) = 0.21 μM).
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Affiliation(s)
- Christos Fytas
- Faculty of Pharmacy, Department of Pharmaceutical Chemistry, University of Athens, Panepistimioupoli-Zografou, GR-15771, Athens, Greece
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Nakamura K, Fujioka S, Fukumoto S, Inoue N, Sakamoto K, Hirata H, Kido Y, Yabu Y, Suzuki T, Watanabe YI, Saimoto H, Akiyama H, Kita K. Trypanosome alternative oxidase, a potential therapeutic target for sleeping sickness, is conserved among Trypanosoma brucei subspecies. Parasitol Int 2010; 59:560-4. [PMID: 20688188 DOI: 10.1016/j.parint.2010.07.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2010] [Revised: 07/17/2010] [Accepted: 07/23/2010] [Indexed: 11/16/2022]
Abstract
Trypanosoma brucei rhodesiense and T. b. gambiense are known causes of human African trypanosomiasis (HAT), or "sleeping sickness," which is deadly if untreated. We previously reported that a specific inhibitor of trypanosome alternative oxidase (TAO), ascofuranone, quickly kills African trypanosomes in vitro and cures mice infected with another subspecies, non-human infective T. b. brucei, in in vivo trials. As an essential factor for trypanosome survival, TAO is a promising drug target due to the absence of alternative oxidases in the mammalian host. This study found TAO expression in HAT-causing trypanosomes; its amino acid sequence was identical to that in non-human infective T. b. brucei. The biochemical understanding of the TAO including its 3 dimensional structure and inhibitory compounds against TAO could therefore be applied to all three T. brucei subspecies in search of a cure for HAT. Our in vitro study using T. b. rhodesiense confirmed the effectiveness of ascofuranone (IC(50) value: 1 nM) to eliminate trypanosomes in human infective strain cultures.
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Affiliation(s)
- Kosuke Nakamura
- Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, 7-3-1, Hongo, Tokyo 113-0033, Japan.
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20
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Jarmuszkiewicz W, Matkovic K, Koszela-Piotrowska I. Potassium channels in the mitochondria of unicellular eukaryotes and plants. FEBS Lett 2010; 584:2057-62. [PMID: 20083113 DOI: 10.1016/j.febslet.2010.01.023] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2009] [Revised: 01/05/2010] [Accepted: 01/12/2010] [Indexed: 10/20/2022]
Abstract
The functional characterisation of potassium channels found in the mitochondria of plants and unicellular eukaryotes is critically discussed herein, with a focus on the ATP-sensitive potassium channel and the large-conductance Ca(2+)-activated potassium channel (mitoBK(Ca) channel). The physiological functions of these channels are not completely understood. We discuss the functional connections and roles of potassium channels, uncoupling protein and alternative oxidase, three energy-dissipating systems that exist in the mitochondrial respiratory chain of plants and some unicellular eukaryotes, which include preventing the production of reactive oxygen species.
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Affiliation(s)
- Wieslawa Jarmuszkiewicz
- Laboratory of Bioenergetics, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznan, Poland.
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21
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Jarmuszkiewicz W, Woyda-Ploszczyca A, Antos-Krzeminska N, Sluse FE. Mitochondrial uncoupling proteins in unicellular eukaryotes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1797:792-9. [PMID: 20026010 DOI: 10.1016/j.bbabio.2009.12.005] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2009] [Revised: 11/27/2009] [Accepted: 12/03/2009] [Indexed: 11/29/2022]
Abstract
Uncoupling proteins (UCPs) are members of the mitochondrial anion carrier protein family that are present in the mitochondrial inner membrane and mediate free fatty acid (FFA)-activated, purine nucleotide (PN)-inhibited proton conductance. Since 1999, the presence of UCPs has been demonstrated in some non-photosynthesising unicellular eukaryotes, including amoeboid and parasite protists, as well as in non-fermentative yeast and filamentous fungi. In the mitochondria of these organisms, UCP activity is revealed upon FFA-induced, PN-inhibited stimulation of resting respiration and a decrease in membrane potential, which are accompanied by a decrease in membranous ubiquinone (Q) reduction level. UCPs in unicellular eukaryotes are able to divert energy from oxidative phosphorylation and thus compete for a proton electrochemical gradient with ATP synthase. Our recent work indicates that membranous Q is a metabolic sensor that might utilise its redox state to release the PN inhibition of UCP-mediated mitochondrial uncoupling under conditions of phosphorylation and resting respiration. The action of reduced Q (QH2) could allow higher or complete activation of UCP. As this regulatory feature was demonstrated for microorganism UCPs (A. castellanii UCP), plant and mammalian UCP1 analogues, and UCP1 in brown adipose tissue, the process could involve all UCPs. Here, we discuss the functional connection and physiological role of UCP and alternative oxidase, two main energy-dissipating systems in the plant-type mitochondrial respiratory chain of unicellular eukaryotes, including the control of cellular energy balance as well as preventive action against the production of reactive oxygen species.
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Affiliation(s)
- Wieslawa Jarmuszkiewicz
- Laboratory of Bioenergetics, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznan, Poland.
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Antibiotics LL-Z1272 identified as novel inhibitors discriminating bacterial and mitochondrial quinol oxidases. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:129-33. [DOI: 10.1016/j.bbabio.2008.11.016] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2008] [Revised: 11/21/2008] [Accepted: 11/26/2008] [Indexed: 11/19/2022]
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23
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McDonald AE. Alternative oxidase: an inter-kingdom perspective on the function and regulation of this broadly distributed 'cyanide-resistant' terminal oxidase. FUNCTIONAL PLANT BIOLOGY : FPB 2008; 35:535-552. [PMID: 32688810 DOI: 10.1071/fp08025] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2008] [Accepted: 07/11/2008] [Indexed: 06/11/2023]
Abstract
Alternative oxidase (AOX) is a terminal quinol oxidase located in the respiratory electron transport chain that catalyses the oxidation of quinol and the reduction of oxygen to water. However, unlike the cytochrome c oxidase respiratory pathway, the AOX pathway moves fewer protons across the inner mitochondrial membrane to generate a proton motive force that can be used to synthesise ATP. The energy passed to AOX is dissipated as heat. This appears to be very wasteful from an energetic perspective and it is likely that AOX fulfils some physiological function(s) that makes up for its apparent energetic shortcomings. An examination of the known taxonomic distribution of AOX and the specific organisms in which AOX has been studied has been used to explore themes pertaining to AOX function and regulation. A comparative approach was used to examine AOX function as it relates to the biochemical function of the enzyme as a quinol oxidase and associated topics, such as enzyme structure, catalysis and transcriptional expression and post-translational regulation. Hypotheses that have been put forward about the physiological function(s) of AOX were explored in light of some recent discoveries made with regard to species that contain AOX. Fruitful areas of research for the AOX community in the future have been highlighted.
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Affiliation(s)
- Allison E McDonald
- Department of Biology, The University of Western Ontario, Biological and Geological Sciences Building, London, Ontario N6A 5B7, Canada. Email
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