1
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Yoshino R, Yasuo N, Hagiwara Y, Ishida T, Inaoka DK, Amano Y, Tateishi Y, Ohno K, Namatame I, Niimi T, Orita M, Kita K, Akiyama Y, Sekijima M. Discovery of a Hidden Trypanosoma cruzi Spermidine Synthase Binding Site and Inhibitors through In Silico, In Vitro, and X-ray Crystallography. ACS OMEGA 2023; 8:25850-25860. [PMID: 37521650 PMCID: PMC10373461 DOI: 10.1021/acsomega.3c01314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 06/28/2023] [Indexed: 08/01/2023]
Abstract
In drug discovery research, the selection of promising binding sites and understanding the binding mode of compounds are crucial fundamental studies. The current understanding of the proteins-ligand binding model extends beyond the simple lock and key model to include the induced-fit model, which alters the conformation to match the shape of the ligand, and the pre-existing equilibrium model, selectively binding structures with high binding affinity from a diverse ensemble of proteins. Although methods for detecting target protein binding sites and virtual screening techniques using docking simulation are well-established, with numerous studies reported, they only consider a very limited number of structures in the diverse ensemble of proteins, as these methods are applied to a single structure. Molecular dynamics (MD) simulation is a method for predicting protein dynamics and can detect potential ensembles of protein binding sites and hidden sites unobservable in a single-point structure. In this study, to demonstrate the utility of virtual screening with protein dynamics, MD simulations were performed on Trypanosoma cruzi spermidine synthase to obtain an ensemble of dominant binding sites with a high probability of existence. The structure of the binding site obtained through MD simulation revealed pockets in addition to the active site that was present in the initial structure. Using the obtained binding site structures, virtual screening of 4.8 million compounds by docking simulation, in vitro assays, and X-ray analysis was conducted, successfully identifying two hit compounds.
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Affiliation(s)
- Ryunosuke Yoshino
- Transborder
Medical Research Center, University of Tsukuba, Tsukuba 305-8577, Japan
- Education
Academy of Computational Life Sciences (ACLS), Tokyo Institute of Technology, Yokohama 226-8501, Japan
| | - Nobuaki Yasuo
- Tokyo
Tech Academy for Convergence of Materials and Informatics (TAC-MI), Tokyo Institute of Technology, Meguro, Tokyo 152-8550, Japan
| | - Yohsuke Hagiwara
- Education
Academy of Computational Life Sciences (ACLS), Tokyo Institute of Technology, Yokohama 226-8501, Japan
- Medicinal
Chemistry Research Labs, Drug Discovery Research, Astellas Pharma Inc, Miyukigaoka, Tsukuba 305-8585, Japan
| | - Takashi Ishida
- School
of Computing, Tokyo Institute of Technology, Tokyo 152-8550, Japan
| | - Daniel Ken Inaoka
- School of
Tropical Medicine and Global Health, Nagasaki
University, Sakamoto, Nagasaki 852-8523, Japan
- Department
of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Yasushi Amano
- Medicinal
Chemistry Research Labs, Drug Discovery Research, Astellas Pharma Inc, Miyukigaoka, Tsukuba 305-8585, Japan
| | - Yukihiro Tateishi
- Medicinal
Chemistry Research Labs, Drug Discovery Research, Astellas Pharma Inc, Miyukigaoka, Tsukuba 305-8585, Japan
| | - Kazuki Ohno
- Education
Academy of Computational Life Sciences (ACLS), Tokyo Institute of Technology, Yokohama 226-8501, Japan
- Medicinal
Chemistry Research Labs, Drug Discovery Research, Astellas Pharma Inc, Miyukigaoka, Tsukuba 305-8585, Japan
| | - Ichiji Namatame
- Medicinal
Chemistry Research Labs, Drug Discovery Research, Astellas Pharma Inc, Miyukigaoka, Tsukuba 305-8585, Japan
| | - Tatsuya Niimi
- Medicinal
Chemistry Research Labs, Drug Discovery Research, Astellas Pharma Inc, Miyukigaoka, Tsukuba 305-8585, Japan
| | - Masaya Orita
- Medicinal
Chemistry Research Labs, Drug Discovery Research, Astellas Pharma Inc, Miyukigaoka, Tsukuba 305-8585, Japan
| | - Kiyoshi Kita
- School of
Tropical Medicine and Global Health, Nagasaki
University, Sakamoto, Nagasaki 852-8523, Japan
- Department
of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Yutaka Akiyama
- Education
Academy of Computational Life Sciences (ACLS), Tokyo Institute of Technology, Yokohama 226-8501, Japan
- School
of Computing, Tokyo Institute of Technology, Tokyo 152-8550, Japan
| | - Masakazu Sekijima
- Education
Academy of Computational Life Sciences (ACLS), Tokyo Institute of Technology, Yokohama 226-8501, Japan
- School
of Computing, Tokyo Institute of Technology, Tokyo 152-8550, Japan
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2
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The ChaC family of γ-glutamyl cyclotransferases is required for Leishmania to switch to a slow growth state and for long-term survival of the parasite. J Biol Chem 2022; 298:102510. [PMID: 36126772 PMCID: PMC9586994 DOI: 10.1016/j.jbc.2022.102510] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Revised: 09/12/2022] [Accepted: 09/14/2022] [Indexed: 11/24/2022] Open
Abstract
The ChaC family of γ-glutamyl cyclotransferases is conserved throughout all Kingdoms and catalyzes the degradation of GSH. So far, the ChaC family proteins in trypanosomal parasites are missing in the literature. Here, we report two members of the ChaC family of γ-glutamyl cyclotransferases (LmChaC2a and LmChaC2b) in the unicellular pathogen Leishmania. Activity measurements suggest that these proteins catalyze degradation of GSH but no other γ-glutamyl peptides. Recombinant LmChaC2a protein shows ∼17-fold lower catalytic efficiency (kcat ∼ 0.9 s−1) than LmChaC2b (kcat ∼ 15 s−1), although they showed comparable Km values (∼1.75 mM for LmChaC2a and ∼2.0 mM for LmChaC2b) toward GSH. qRT-PCR and Western blot analyses suggest that the LmChaC2a protein was found to be constitutively expressed, whereas LmChaC2b was regulated by sulfur stress. To investigate its precise physiological function in Leishmania, we generated overexpressed, knockout, and complement cell lines. Flow cytometric analyses show the presence of a higher intracellular GSH concentration and lower intracellular ROS level, indicative of a more reductive environment in null mutants. We found LmChaC2-expressing cells grow in GSH-containing sulfur-limited media, while the null mutants failed to grow, suggesting that LmChaC2 is crucial for cell growth with GSH as the only sulfur source. Null mutants, although reach the stationary phase rapidly, display impaired long-term survival, indicating that LmChaC2-mediated GSH degradation is necessary for prolonged survival. In vivo studies suggest that LmChaC2-dependent controlled GSH degradation promotes chronic infection by the parasite. Altogether, these data indicate that LmChaC2 plays an important role in GSH homeostasis in Leishmania.
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3
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Abstract
Trypanothione is the primary thiol redox carrier in Trypanosomatids whose biosynthesis and utilization pathways contain unique enzymes that include suitable drug targets against the human parasites in this family. Overexpression of the rate-limiting enzyme, γ-glutamylcysteine synthetase (GSH1), can increase the intracellular concentration of trypanothione. Melarsoprol directly inhibits trypanothione and has predicted the effects on downstream redox biology, including ROS management and dNTP synthesis that require further investigation. Thus, we hypothesized that melarsoprol treatment would inhibit DNA synthesis, which was tested using BrdU incorporation assays and cell cycle analyses. In addition, we analysed the effects of eflornithine, which interfaces with the trypanothione pathway, fexinidazole, because of the predicted effects on DNA synthesis, and pentamidine as an experimental control. We found that melarsoprol treatment resulted in a cell cycle stall and a complete inhibition of DNA synthesis within 24 h, which were alleviated by GSH1 overexpression. In contrast, the other drugs analysed had more subtle effects on DNA synthesis that were not significantly altered by GSH1 expression. Together these findings implicate DNA synthesis as a therapeutic target that warrants further investigation in the development of antitrypanosomal drugs.
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4
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Talevi A, Carrillo C, Comini M. The Thiol-polyamine Metabolism of Trypanosoma cruzi: Molecular Targets and Drug Repurposing Strategies. Curr Med Chem 2019; 26:6614-6635. [PMID: 30259812 DOI: 10.2174/0929867325666180926151059] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 07/23/2018] [Accepted: 09/10/2018] [Indexed: 12/18/2022]
Abstract
Chagas´ disease continues to be a challenging and neglected public health problem in many American countries. The etiologic agent, Trypanosoma cruzi, develops intracellularly in the mammalian host, which hinders treatment efficacy. Progress in the knowledge of parasite biology and host-pathogen interaction has not been paralleled by the development of novel, safe and effective therapeutic options. It is then urgent to seek for novel therapeutic candidates and to implement drug discovery strategies that may accelerate the discovery process. The most appealing targets for pharmacological intervention are those essential for the pathogen and, whenever possible, absent or significantly different from the host homolog. The thiol-polyamine metabolism of T. cruzi offers interesting candidates for a rational design of selective drugs. In this respect, here we critically review the state of the art of the thiolpolyamine metabolism of T. cruzi and the pharmacological potential of its components. On the other hand, drug repurposing emerged as a valid strategy to identify new biological activities for drugs in clinical use, while significantly shortening the long time and high cost associated with de novo drug discovery approaches. Thus, we also discuss the different drug repurposing strategies available with a special emphasis in their applications to the identification of drug candidates targeting essential components of the thiol-polyamine metabolism of T. cruzi.
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Affiliation(s)
- Alan Talevi
- Medicinal Chemistry, Department of Biological Sciences, Faculty of Exact Sciences, University of La Plata, La Plata, Argentina
| | - Carolina Carrillo
- Instituto de Ciencias y Tecnología Dr. César Milstein (ICT Milstein) - CONICET. Ciudad Autónoma de Buenos Aires, Argentina
| | - Marcelo Comini
- Institut Pasteur de Montevideo, Mataojo 2020, Montevideo 11400, Uruguay
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5
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Sayé M, Reigada C, Gauna L, Valera-Vera EA, Pereira CA, Miranda MR. Amino Acid and Polyamine Membrane Transporters in Trypanosoma cruzi: Biological Function and Evaluation as Drug Targets. Curr Med Chem 2019; 26:6636-6651. [PMID: 31218951 DOI: 10.2174/0929867326666190620094710] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Revised: 12/12/2018] [Accepted: 02/04/2019] [Indexed: 01/19/2023]
Abstract
Amino acids and polyamines are involved in relevant processes for the parasite Trypanosoma cruzi, like protein synthesis, stress resistance, life cycle progression, infection establishment and redox balance, among others. In addition to the biosynthetic routes of amino acids, T. cruzi possesses transport systems that allow the active uptake from the extracellular medium; and in the case of polyamines, the uptake is the unique way to obtain these compounds. The TcAAAP protein family is absent in mammals and its members are responsible for amino acid and derivative uptake, thus the TcAAAP permeases are not only interesting and promising therapeutic targets but could also be used to direct the entry of toxic compounds into the parasite. Although there is a treatment available for Chagas disease, its limited efficacy in the chronic stage of the disease, as well as the side effects reported, highlight the urgent need to develop new therapies. Discovery of new drugs is a slow and cost-consuming process, and even during clinical trials the drugs can fail. In this context, drug repositioning is an interesting and recommended strategy by the World Health Organization since costs and time are significantly reduced. In this article, amino acids and polyamines transport and their potential as therapeutic targets will be revised, including examples of synthetic drugs and drug repurposing.
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Affiliation(s)
- Melisa Sayé
- Universidad de Buenos Aires, Facultad de Medicina, Instituto de Investigaciones Medicas A. Lanari, Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad de Buenos Aires, Instituto de Investigaciones Médicas (IDIM), Laboratorio de Parasitología Molecular, Buenos Aires, Argentina
| | - Chantal Reigada
- Universidad de Buenos Aires, Facultad de Medicina, Instituto de Investigaciones Medicas A. Lanari, Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad de Buenos Aires, Instituto de Investigaciones Médicas (IDIM), Laboratorio de Parasitología Molecular, Buenos Aires, Argentina
| | - Lucrecia Gauna
- Universidad de Buenos Aires, Facultad de Medicina, Instituto de Investigaciones Medicas A. Lanari, Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad de Buenos Aires, Instituto de Investigaciones Médicas (IDIM), Laboratorio de Parasitología Molecular, Buenos Aires, Argentina
| | - Edward A Valera-Vera
- Universidad de Buenos Aires, Facultad de Medicina, Instituto de Investigaciones Medicas A. Lanari, Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad de Buenos Aires, Instituto de Investigaciones Médicas (IDIM), Laboratorio de Parasitología Molecular, Buenos Aires, Argentina
| | - Claudio A Pereira
- Universidad de Buenos Aires, Facultad de Medicina, Instituto de Investigaciones Medicas A. Lanari, Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad de Buenos Aires, Instituto de Investigaciones Médicas (IDIM), Laboratorio de Parasitología Molecular, Buenos Aires, Argentina
| | - Mariana R Miranda
- Universidad de Buenos Aires, Facultad de Medicina, Instituto de Investigaciones Medicas A. Lanari, Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad de Buenos Aires, Instituto de Investigaciones Médicas (IDIM), Laboratorio de Parasitología Molecular, Buenos Aires, Argentina
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6
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Abstract
Polyamines are polycationic organic amines that are required for all eukaryotic life, exemplified by the polyamine spermidine, which plays an essential role in translation. They also play more specialized roles that differ across species, and their chemical versatility has been fully exploited during the evolution of protozoan pathogens. These eukaryotic pathogens, which cause some of the most globally widespread infectious diseases, have acquired species-specific polyamine-derived metabolites with essential cellular functions and have evolved unique mechanisms that regulate their core polyamine biosynthetic pathways. Many of these parasitic species have lost enzymes and or transporters from the polyamine metabolic pathway that are found in the human host. These pathway differences have prompted drug discovery efforts to target the parasite polyamine pathways, and indeed, the only clinically approved drug targeting the polyamine biosynthetic pathway is used to manage human African trypanosomiasis. This Minireview will primarily focus on polyamine metabolism and function in Trypanosoma, Leishmania, and Plasmodium species, which are the causative agents of human African trypanosomiasis (HAT) and Chagas disease, Leishmaniasis, and malaria, respectively. Aspects of polyamine metabolism across a diverse group of protozoan pathogens will also be explored.
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Affiliation(s)
- Margaret A Phillips
- From the Departments of Biochemistry and Pharmacology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-9038
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7
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Vázquez C, Mejia-Tlachi M, González-Chávez Z, Silva A, Rodríguez-Zavala JS, Moreno-Sánchez R, Saavedra E. Buthionine sulfoximine is a multitarget inhibitor of trypanothione synthesis in Trypanosoma cruzi. FEBS Lett 2017; 591:3881-3894. [PMID: 29127710 DOI: 10.1002/1873-3468.12904] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Revised: 10/31/2017] [Accepted: 11/02/2017] [Indexed: 11/10/2022]
Abstract
Buthionine sulfoximine (BSO) induces decreased glutathione (GSH) and trypanothione [T(SH)2 ] pools in trypanosomatids, presumably because only gamma-glutamylcysteine synthetase (γECS) is blocked. However, some BSO effects cannot be explained by exclusive γECS inhibition; therefore, its effect on the T(SH)2 metabolism pathway in Trypanosoma cruzi was re-examined. Parasites exposed to BSO did not synthesize T(SH)2 even when supplemented with cysteine or GSH, suggesting trypanothione synthetase (TryS) inhibition by BSO. Indeed, recombinant γECS and TryS, but not GSH synthetase, were inhibited by BSO and kinetics and docking analyses on a TcTryS 3D model suggested BSO binding at the GSH site. Furthermore, parasites overexpressing γECS and TryS showed ~ 50% decreased activities after BSO treatment. These results indicated that BSO is also an inhibitor of TryS.
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Affiliation(s)
- Citlali Vázquez
- Departamento de Bioquímica, Instituto Nacional de Cardiología Ignacio Chávez, Mexico city, México
| | - Marlen Mejia-Tlachi
- Departamento de Bioquímica, Instituto Nacional de Cardiología Ignacio Chávez, Mexico city, México
| | - Zabdi González-Chávez
- Departamento de Bioquímica, Instituto Nacional de Cardiología Ignacio Chávez, Mexico city, México
| | - Aketzalli Silva
- Departamento de Bioquímica, Instituto Nacional de Cardiología Ignacio Chávez, Mexico city, México
| | | | - Rafael Moreno-Sánchez
- Departamento de Bioquímica, Instituto Nacional de Cardiología Ignacio Chávez, Mexico city, México
| | - Emma Saavedra
- Departamento de Bioquímica, Instituto Nacional de Cardiología Ignacio Chávez, Mexico city, México
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8
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Jin JX, Jin DC, Li FL, Cheng Y, Li WH, Ye ZC, Zhou YH. Expression Differences of Resistance-Related Genes Induced by Cycloxaprid Using qRT-PCR in the Female Adult of Sogatella furcifera (Hemiptera: Delphacidae). JOURNAL OF ECONOMIC ENTOMOLOGY 2017; 110:1785-1793. [PMID: 28854654 DOI: 10.1093/jee/tox155] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2016] [Accepted: 05/13/2017] [Indexed: 06/07/2023]
Abstract
As a newer cis-nitromethylene neonicotinoid pesticide at present, cycloxaprid has good industrialization prospects, including the management of imidacloprid-resistant populations, because this chemical have an excellent efficiency against rice planthoppers. Sogatella furcifera (Horváth) is the most economically important pest of rice worldwide and has developed resistance to many insecticides. This study focused on the expression change of these resistance genes, induced by cycloxaprid, involved in metabolic detoxification and receptor protein. Twenty-two differentially expressed genes (DEGs) that may be related with the insecticide resistance were found in the transcriptome of S. furcifera, including 2 cytochrome P450 genes, 2 glutathione S-transferase (GST) genes, 1 acid phosphatase (ACP) gene, 12 decarboxylase genes, 2 glycolipid genes, 1 cadherin gene, and 2 glycosyltransferase genes, which were up- or downregulated in response to an exposure of cycloxaprid. Furthermore, two P450 genes (CYP4 and CYP6 family, respectively), two decarboxylase genes, and one glycosyltransferase gene were validated by qRT-PCR. Expression differences of these genes verified successfully by qRT-PCR in response to different concentrations and times treated with cycloxaprid could explain the insecticide resistance mechanism under cycloxaprid stress in S. furcifera.
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Affiliation(s)
- Jian-Xue Jin
- The Provincial Key Laboratory for Agricultural Pest Management of Mountainous Regions, Institute of Entomology, Guizhou University, Guiyang, Guizhou 550025, P.R. China
- Institute of Plant Protection, Guizhou Academy of Agricultural Sciences, Guiyang, Guizhou 550006, P.R. China
| | - Dao-Chao Jin
- The Provincial Key Laboratory for Agricultural Pest Management of Mountainous Regions, Institute of Entomology, Guizhou University, Guiyang, Guizhou 550025, P.R. China
| | - Feng-Liang Li
- Institute of Plant Protection, Guizhou Academy of Agricultural Sciences, Guiyang, Guizhou 550006, P.R. China
| | - Ying Cheng
- Institute of Plant Protection, Guizhou Academy of Agricultural Sciences, Guiyang, Guizhou 550006, P.R. China
| | - Wen-Hong Li
- Institute of Plant Protection, Guizhou Academy of Agricultural Sciences, Guiyang, Guizhou 550006, P.R. China
| | - Zhao-Chun Ye
- Institute of Plant Protection, Guizhou Academy of Agricultural Sciences, Guiyang, Guizhou 550006, P.R. China
| | - Yu-Hang Zhou
- Institute of Plant Protection, Guizhou Academy of Agricultural Sciences, Guiyang, Guizhou 550006, P.R. China
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9
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Yoshino R, Yasuo N, Hagiwara Y, Ishida T, Inaoka DK, Amano Y, Tateishi Y, Ohno K, Namatame I, Niimi T, Orita M, Kita K, Akiyama Y, Sekijima M. In silico, in vitro, X-ray crystallography, and integrated strategies for discovering spermidine synthase inhibitors for Chagas disease. Sci Rep 2017; 7:6666. [PMID: 28751689 PMCID: PMC5532286 DOI: 10.1038/s41598-017-06411-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Accepted: 06/14/2017] [Indexed: 01/23/2023] Open
Abstract
Chagas disease results from infection by Trypanosoma cruzi and is a neglected tropical disease (NTD). Although some treatment drugs are available, their use is associated with severe problems, including adverse effects and limited effectiveness during the chronic disease phase. To develop a novel anti-Chagas drug, we virtually screened 4.8 million small molecules against spermidine synthase (SpdSyn) as the target protein using our super computer “TSUBAME2.5” and conducted in vitro enzyme assays to determine the half-maximal inhibitory concentration values. We identified four hit compounds that inhibit T. cruzi SpdSyn (TcSpdSyn) by in silico and in vitro screening. We also determined the TcSpdSyn–hit compound complex structure using X-ray crystallography, which shows that the hit compound binds to the putrescine-binding site and interacts with Asp171 through a salt bridge.
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Affiliation(s)
- Ryunosuke Yoshino
- Advanced Computational Drug Discovery Unit, Institute of Innovative Research, Tokyo Institute of Technology, 4259-J3-23, Nagatsuta-cho, Midori-ku, Yokohama, 226-8501, Japan.,Education Academy of Computational Life Sciences (ACLS), Tokyo Institute of Technology, Yokohama, 226-8501, Japan.,Global Scientific Information and Computing Center, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo, 152-8550, Japan.,Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, 113-8657, Japan.,Department of Computer Science, Graduate School of Information Science and Engineering, Tokyo Institute of Technology, Meguro-ku, Tokyo, 152-8550, Japan
| | - Nobuaki Yasuo
- Education Academy of Computational Life Sciences (ACLS), Tokyo Institute of Technology, Yokohama, 226-8501, Japan.,Department of Computer Science, Graduate School of Information Science and Engineering, Tokyo Institute of Technology, Meguro-ku, Tokyo, 152-8550, Japan
| | - Yohsuke Hagiwara
- Education Academy of Computational Life Sciences (ACLS), Tokyo Institute of Technology, Yokohama, 226-8501, Japan.,Medicinal Chemistry Research Labs, Drug Discovery Research, Astellas Pharma Inc, 21 Miyukigaoka, Tsukuba, Ibaraki, 305-8585, Japan
| | - Takashi Ishida
- Advanced Computational Drug Discovery Unit, Institute of Innovative Research, Tokyo Institute of Technology, 4259-J3-23, Nagatsuta-cho, Midori-ku, Yokohama, 226-8501, Japan.,Education Academy of Computational Life Sciences (ACLS), Tokyo Institute of Technology, Yokohama, 226-8501, Japan.,Department of Computer Science, Graduate School of Information Science and Engineering, Tokyo Institute of Technology, Meguro-ku, Tokyo, 152-8550, Japan
| | - Daniel Ken Inaoka
- Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan.,School of Tropical Medicine and Global Health, Nagasaki University, Sakamoto, Nagasaki, 852-8523, Japan
| | - Yasushi Amano
- Medicinal Chemistry Research Labs, Drug Discovery Research, Astellas Pharma Inc, 21 Miyukigaoka, Tsukuba, Ibaraki, 305-8585, Japan
| | - Yukihiro Tateishi
- Medicinal Chemistry Research Labs, Drug Discovery Research, Astellas Pharma Inc, 21 Miyukigaoka, Tsukuba, Ibaraki, 305-8585, Japan
| | - Kazuki Ohno
- Education Academy of Computational Life Sciences (ACLS), Tokyo Institute of Technology, Yokohama, 226-8501, Japan.,Medicinal Chemistry Research Labs, Drug Discovery Research, Astellas Pharma Inc, 21 Miyukigaoka, Tsukuba, Ibaraki, 305-8585, Japan.,Catalyst Inc., Risona Kudan Building 5F KS Floor, 1-5-6 Kudan Minami, Chiyoda-ku, Tokyo, 102-0074, Japan
| | - Ichiji Namatame
- Medicinal Chemistry Research Labs, Drug Discovery Research, Astellas Pharma Inc, 21 Miyukigaoka, Tsukuba, Ibaraki, 305-8585, Japan
| | - Tatsuya Niimi
- Medicinal Chemistry Research Labs, Drug Discovery Research, Astellas Pharma Inc, 21 Miyukigaoka, Tsukuba, Ibaraki, 305-8585, Japan
| | - Masaya Orita
- Medicinal Chemistry Research Labs, Drug Discovery Research, Astellas Pharma Inc, 21 Miyukigaoka, Tsukuba, Ibaraki, 305-8585, Japan
| | - Kiyoshi Kita
- Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan.,School of Tropical Medicine and Global Health, Nagasaki University, Sakamoto, Nagasaki, 852-8523, Japan
| | - Yutaka Akiyama
- Advanced Computational Drug Discovery Unit, Institute of Innovative Research, Tokyo Institute of Technology, 4259-J3-23, Nagatsuta-cho, Midori-ku, Yokohama, 226-8501, Japan.,Education Academy of Computational Life Sciences (ACLS), Tokyo Institute of Technology, Yokohama, 226-8501, Japan.,Department of Computer Science, Graduate School of Information Science and Engineering, Tokyo Institute of Technology, Meguro-ku, Tokyo, 152-8550, Japan
| | - Masakazu Sekijima
- Advanced Computational Drug Discovery Unit, Institute of Innovative Research, Tokyo Institute of Technology, 4259-J3-23, Nagatsuta-cho, Midori-ku, Yokohama, 226-8501, Japan. .,Education Academy of Computational Life Sciences (ACLS), Tokyo Institute of Technology, Yokohama, 226-8501, Japan. .,Global Scientific Information and Computing Center, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo, 152-8550, Japan. .,Department of Computer Science, Graduate School of Information Science and Engineering, Tokyo Institute of Technology, Meguro-ku, Tokyo, 152-8550, Japan.
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10
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Agnihotri P, Mishra AK, Mishra S, Sirohi VK, Sahasrabuddhe AA, Pratap JV. Identification of Novel Inhibitors of Leishmania donovani γ-Glutamylcysteine Synthetase Using Structure-Based Virtual Screening, Docking, Molecular Dynamics Simulation, and in Vitro Studies. J Chem Inf Model 2017; 57:815-825. [DOI: 10.1021/acs.jcim.6b00642] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Pragati Agnihotri
- Molecular
and Structural Biology Division, CSIR-Central Drug Research Institute, Lucknow-226031, India
| | - Arjun K. Mishra
- Molecular
and Structural Biology Division, CSIR-Central Drug Research Institute, Lucknow-226031, India
| | - Shikha Mishra
- Molecular
and Structural Biology Division, CSIR-Central Drug Research Institute, Lucknow-226031, India
| | - Vijay Kumar Sirohi
- Division
of Endocrinology, CSIR-Central Drug Research Institute, Lucknow-226031, India
| | - Amogh A. Sahasrabuddhe
- Molecular
and Structural Biology Division, CSIR-Central Drug Research Institute, Lucknow-226031, India
| | - J. Venkatesh Pratap
- Molecular
and Structural Biology Division, CSIR-Central Drug Research Institute, Lucknow-226031, India
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11
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Evaluation of Antigens for Development of a Serological Test for Human African Trypanosomiasis. PLoS One 2016; 11:e0168074. [PMID: 27936225 PMCID: PMC5148118 DOI: 10.1371/journal.pone.0168074] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Accepted: 11/27/2016] [Indexed: 11/19/2022] Open
Abstract
Background Control and elimination of human African trypanosomiasis (HAT) can be accelerated through the use of diagnostic tests that are more accurate and easier to deploy. The goal of this work was to evaluate the immuno-reactivity of antigens and identify candidates to be considered for development of a simple serological test for the detection of Trypanosoma brucei gambiense or T. b. rhodesiense infections, ideally both. Methodology/Principal Findings The reactivity of 35 antigens was independently evaluated by slot blot and ELISA against sera from both T. b. gambiense and T. b. rhodesiense infected patients and controls. The antigens that were most reactive by both tests to T. b. gambiense sera were the membrane proteins VSG LiTat 1.3, VSG LiTat 1.5 and ISG64. Reactivity to T. b. rhodesiense sera was highest with VSG LiTat 1.3, VSG LiTat 1.5 and SRA, although much lower than with T. b. gambiense samples. The reactivity of all possible combinations of antigens was also calculated. When the slot blot results of 2 antigens were paired, a VSG LiTat 1.3- ISG75 combination performed best on T. b. gambiense sera, while a VSG LiTat 1.3-VSG LiTat 1.5 combination was the most reactive using ELISA. A combination of SRA and either VSG LiTat 1.3 or VSG LiTat 1.5 had the highest reactivity on T. b. rhodesiense sera according to slot blot, while in ELISA, pairing SRA with either GM6 or VSG LiTat 1.3 yielded the best results. Conclusions This study identified antigens that were highly reactive to T. b. gambiense sera, which could be considered for developing a serological test for gambiense HAT, either individually or in combination. Antigens with potential for inclusion in a test for T. b. rhodesiense HAT were also identified, but because their reactivity was comparatively lower, a search for additional antigens would be required before developing a test for this form of the disease.
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Biochemical and biophysical characterization of Leishmania donovani gamma-glutamylcysteine synthetase. Biochem Biophys Rep 2016; 8:127-138. [PMID: 28955948 PMCID: PMC5613772 DOI: 10.1016/j.bbrep.2016.08.016] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Revised: 08/02/2016] [Accepted: 08/14/2016] [Indexed: 12/03/2022] Open
Abstract
γ-glutamylcysteine synthetase (Gcs) is a vital enzyme catalyzing the first and rate limiting step in the trypanothione biosynthesis pathway, the ATP-dependent ligation of L-Glutamate and L-Cysteine to form gamma-glutamylcysteine. The Trypanothione biosynthesis pathway is unique metabolic pathway essential for trypanosomatid survival rendering Gcs as a potential drug target. Here we report the cloning, expression, purification and characterization of L. donovani Gcs. Three other constructs of Gcs (GcsN, GcsC and GcsT) were designed on the basis of S. cerevisiae and E. coli Gcs crystal structures. The study shows Gcs possesses ATPase activity even in the absence of substrates L-glutamate and L-Cysteine. Divalent ions however plays an indispensable role in LdGcs ATPase activity. Isothermal titration calorimetry and fluorescence studies illustrates that L. donovani Gcs binds substrate in order ATP >L-glutamate>L-cysteine with Glu 92 and Arg 498 involved in ATP hydrolysis and Glu 92, Glu 55 and Arg 498 involved in glutamate binding. Homology modeling and molecular dynamic simulation studies provided the structural rationale of LdGcs catalytic activity and emphasized on the possibility of involvement of three Mg2+ ions along with Glutamates 52, 55, 92, 99, Met 322, Gln 328, Tyr 397, Lys 483, Arg 494 and Arg 498 in the catalytic function of L. donovani Gcs. L. donovani Gamma glutamylcysteine synthetase is a divalent dependent ATPase. Substrate binds in order ATP>> L-Glutamate> L-cysteine. Glu 92 and Arg 498 involved in ATP hydrolysis. Glu 92, Glu 55 and Arg 498 involved in glutamate binding.
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Leroux AE, Krauth-Siegel RL. Thiol redox biology of trypanosomatids and potential targets for chemotherapy. Mol Biochem Parasitol 2016; 206:67-74. [DOI: 10.1016/j.molbiopara.2015.11.003] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Revised: 11/09/2015] [Accepted: 11/18/2015] [Indexed: 02/08/2023]
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Role and Regulation of Glutathione Metabolism in Plasmodium falciparum. Molecules 2015; 20:10511-34. [PMID: 26060916 PMCID: PMC6272303 DOI: 10.3390/molecules200610511] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Revised: 05/11/2015] [Accepted: 06/01/2015] [Indexed: 11/30/2022] Open
Abstract
Malaria in humans is caused by one of five species of obligate intracellular protozoan parasites of the genus Plasmodium. P. falciparum causes the most severe disease and is responsible for 600,000 deaths annually, primarily in Sub-Saharan Africa. It has long been suggested that during their development, malaria parasites are exposed to environmental and metabolic stresses. One strategy to drug discovery was to increase these stresses by interfering with the parasites’ antioxidant and redox systems, which may be a valuable approach to disease intervention. Plasmodium possesses two redox systems—the thioredoxin and the glutathione system—with overlapping but also distinct functions. Glutathione is the most abundant low molecular weight redox active thiol in the parasites existing primarily in its reduced form representing an excellent thiol redox buffer. This allows for an efficient maintenance of the intracellular reducing environment of the parasite cytoplasm and its organelles. This review will highlight the mechanisms that are responsible for sustaining an adequate concentration of glutathione and maintaining its redox state in Plasmodium. It will provide a summary of the functions of the tripeptide and will discuss the potential of glutathione metabolism for drug discovery against human malaria parasites.
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Implications of Glutathione Levels in the Plasmodium berghei Response to Chloroquine and Artemisinin. PLoS One 2015; 10:e0128212. [PMID: 26010448 PMCID: PMC4444287 DOI: 10.1371/journal.pone.0128212] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Accepted: 04/23/2015] [Indexed: 11/19/2022] Open
Abstract
Malaria is one of the most devastating parasitic diseases worldwide. Plasmodium drug resistance remains a major challenge to malaria control and has led to the re-emergence of the disease. Chloroquine (CQ) and artemisinin (ART) are thought to exert their anti-malarial activity inducing cytotoxicity in the parasite by blocking heme degradation (for CQ) and increasing oxidative stress. Besides the contribution of the CQ resistance transporter (PfCRT) and the multidrug resistant gene (pfmdr), CQ resistance has also been associated with increased parasite glutathione (GSH) levels. ART resistance was recently shown to be associated with mutations in the K13-propeller protein. To analyze the role of GSH levels in CQ and ART resistance, we generated transgenic Plasmodium berghei parasites either deficient in or overexpressing the gamma-glutamylcysteine synthetase gene (pbggcs) encoding the rate-limiting enzyme in GSH biosynthesis. These lines produce either lower (pbggcs-ko) or higher (pbggcs-oe) levels of GSH than wild type parasites. In addition, GSH levels were determined in P. berghei parasites resistant to CQ and mefloquine (MQ). Increased GSH levels were detected in both, CQ and MQ resistant parasites, when compared to the parental sensitive clone. Sensitivity to CQ and ART remained unaltered in both pgggcs-ko and pbggcs-oe parasites when tested in a 4 days drug suppressive assay. However, recrudescence assays after the parasites have been exposed to a sub-lethal dose of ART showed that parasites with low levels of GSH are more sensitive to ART treatment. These results suggest that GSH levels influence Plasmodium berghei response to ART treatment.
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Ghosh AK, Sardar AH, Mandal A, Saini S, Abhishek K, Kumar A, Purkait B, Singh R, Das S, Mukhopadhyay R, Roy S, Das P. Metabolic reconfiguration of the central glucose metabolism: a crucial strategy of Leishmania donovani for its survival during oxidative stress. FASEB J 2015; 29:2081-98. [PMID: 25690656 DOI: 10.1096/fj.14-258624] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Accepted: 01/09/2015] [Indexed: 12/15/2022]
Abstract
Understanding the mechanism that allows the intracellular protozoan parasite Leishmania donovani (Ld) to respond to reactive oxygen species (ROS) is of increasing therapeutic importance because of the continuing resistance toward antileishmanial drugs and for determining the illusive survival strategy of these parasites. A shift in primary carbon metabolism is the fastest response to oxidative stress. A (14)CO2 evolution study, expression of glucose transporters together with consumption assays, indicated a shift in metabolic flux of the parasites from glycolysis toward pentose phosphate pathway (PPP) when exposed to different oxidants in vitro/ex vivo. Changes in gene expression, protein levels, and enzyme activities all pointed to a metabolic reconfiguration of the central glucose metabolism in response to oxidants. Generation of glucose-6-phosphate dehydrogenase (G6PDH) (∼5-fold) and transaldolase (TAL) (∼4.2-fold) overexpressing Ld cells reaffirmed that lethal doses of ROS were counterbalanced by effective manipulation of NADPH:NADP(+) ratio and stringent maintenance of reduced thiol content. The extent of protein carbonylation and accumulation of lipid peroxidized products were also found to be less in overexpressed cell lines. Interestingly, the LD50 of sodium antimony gluconate (SAG), amphotericin-B (AmB), and miltefosine were significantly high toward overexpressing parasites. Consequently, this study illustrates that Ld strategizes a metabolic reconfiguration for replenishment of NADPH pool to encounter oxidative challenges.
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Affiliation(s)
- Ayan K Ghosh
- *Division of Molecular Biology, Rajendra Memorial Research Institute of Medical Sciences (Indian Council of Medical Research), Agamkuan, Patna, Bihar, India; Department of Biotechnology, National Institute of Pharmaceutical Education and Research, Export Promotion Industrial Park, Hajipur, Vaishali, Bihar, India; Department of Microbiology, All India Institute of Medical Sciences, Phulwarisharif, Patna, Bihar, India; and Division of Infectious Diseases and Immunology, CSIR-Indian Institute of Chemical Biology, Jadavpur, Kolkata, India
| | - Abul H Sardar
- *Division of Molecular Biology, Rajendra Memorial Research Institute of Medical Sciences (Indian Council of Medical Research), Agamkuan, Patna, Bihar, India; Department of Biotechnology, National Institute of Pharmaceutical Education and Research, Export Promotion Industrial Park, Hajipur, Vaishali, Bihar, India; Department of Microbiology, All India Institute of Medical Sciences, Phulwarisharif, Patna, Bihar, India; and Division of Infectious Diseases and Immunology, CSIR-Indian Institute of Chemical Biology, Jadavpur, Kolkata, India
| | - Abhishek Mandal
- *Division of Molecular Biology, Rajendra Memorial Research Institute of Medical Sciences (Indian Council of Medical Research), Agamkuan, Patna, Bihar, India; Department of Biotechnology, National Institute of Pharmaceutical Education and Research, Export Promotion Industrial Park, Hajipur, Vaishali, Bihar, India; Department of Microbiology, All India Institute of Medical Sciences, Phulwarisharif, Patna, Bihar, India; and Division of Infectious Diseases and Immunology, CSIR-Indian Institute of Chemical Biology, Jadavpur, Kolkata, India
| | - Savita Saini
- *Division of Molecular Biology, Rajendra Memorial Research Institute of Medical Sciences (Indian Council of Medical Research), Agamkuan, Patna, Bihar, India; Department of Biotechnology, National Institute of Pharmaceutical Education and Research, Export Promotion Industrial Park, Hajipur, Vaishali, Bihar, India; Department of Microbiology, All India Institute of Medical Sciences, Phulwarisharif, Patna, Bihar, India; and Division of Infectious Diseases and Immunology, CSIR-Indian Institute of Chemical Biology, Jadavpur, Kolkata, India
| | - Kumar Abhishek
- *Division of Molecular Biology, Rajendra Memorial Research Institute of Medical Sciences (Indian Council of Medical Research), Agamkuan, Patna, Bihar, India; Department of Biotechnology, National Institute of Pharmaceutical Education and Research, Export Promotion Industrial Park, Hajipur, Vaishali, Bihar, India; Department of Microbiology, All India Institute of Medical Sciences, Phulwarisharif, Patna, Bihar, India; and Division of Infectious Diseases and Immunology, CSIR-Indian Institute of Chemical Biology, Jadavpur, Kolkata, India
| | - Ashish Kumar
- *Division of Molecular Biology, Rajendra Memorial Research Institute of Medical Sciences (Indian Council of Medical Research), Agamkuan, Patna, Bihar, India; Department of Biotechnology, National Institute of Pharmaceutical Education and Research, Export Promotion Industrial Park, Hajipur, Vaishali, Bihar, India; Department of Microbiology, All India Institute of Medical Sciences, Phulwarisharif, Patna, Bihar, India; and Division of Infectious Diseases and Immunology, CSIR-Indian Institute of Chemical Biology, Jadavpur, Kolkata, India
| | - Bidyut Purkait
- *Division of Molecular Biology, Rajendra Memorial Research Institute of Medical Sciences (Indian Council of Medical Research), Agamkuan, Patna, Bihar, India; Department of Biotechnology, National Institute of Pharmaceutical Education and Research, Export Promotion Industrial Park, Hajipur, Vaishali, Bihar, India; Department of Microbiology, All India Institute of Medical Sciences, Phulwarisharif, Patna, Bihar, India; and Division of Infectious Diseases and Immunology, CSIR-Indian Institute of Chemical Biology, Jadavpur, Kolkata, India
| | - Ruby Singh
- *Division of Molecular Biology, Rajendra Memorial Research Institute of Medical Sciences (Indian Council of Medical Research), Agamkuan, Patna, Bihar, India; Department of Biotechnology, National Institute of Pharmaceutical Education and Research, Export Promotion Industrial Park, Hajipur, Vaishali, Bihar, India; Department of Microbiology, All India Institute of Medical Sciences, Phulwarisharif, Patna, Bihar, India; and Division of Infectious Diseases and Immunology, CSIR-Indian Institute of Chemical Biology, Jadavpur, Kolkata, India
| | - Sushmita Das
- *Division of Molecular Biology, Rajendra Memorial Research Institute of Medical Sciences (Indian Council of Medical Research), Agamkuan, Patna, Bihar, India; Department of Biotechnology, National Institute of Pharmaceutical Education and Research, Export Promotion Industrial Park, Hajipur, Vaishali, Bihar, India; Department of Microbiology, All India Institute of Medical Sciences, Phulwarisharif, Patna, Bihar, India; and Division of Infectious Diseases and Immunology, CSIR-Indian Institute of Chemical Biology, Jadavpur, Kolkata, India
| | - Rupkatha Mukhopadhyay
- *Division of Molecular Biology, Rajendra Memorial Research Institute of Medical Sciences (Indian Council of Medical Research), Agamkuan, Patna, Bihar, India; Department of Biotechnology, National Institute of Pharmaceutical Education and Research, Export Promotion Industrial Park, Hajipur, Vaishali, Bihar, India; Department of Microbiology, All India Institute of Medical Sciences, Phulwarisharif, Patna, Bihar, India; and Division of Infectious Diseases and Immunology, CSIR-Indian Institute of Chemical Biology, Jadavpur, Kolkata, India
| | - Syamal Roy
- *Division of Molecular Biology, Rajendra Memorial Research Institute of Medical Sciences (Indian Council of Medical Research), Agamkuan, Patna, Bihar, India; Department of Biotechnology, National Institute of Pharmaceutical Education and Research, Export Promotion Industrial Park, Hajipur, Vaishali, Bihar, India; Department of Microbiology, All India Institute of Medical Sciences, Phulwarisharif, Patna, Bihar, India; and Division of Infectious Diseases and Immunology, CSIR-Indian Institute of Chemical Biology, Jadavpur, Kolkata, India
| | - Pradeep Das
- *Division of Molecular Biology, Rajendra Memorial Research Institute of Medical Sciences (Indian Council of Medical Research), Agamkuan, Patna, Bihar, India; Department of Biotechnology, National Institute of Pharmaceutical Education and Research, Export Promotion Industrial Park, Hajipur, Vaishali, Bihar, India; Department of Microbiology, All India Institute of Medical Sciences, Phulwarisharif, Patna, Bihar, India; and Division of Infectious Diseases and Immunology, CSIR-Indian Institute of Chemical Biology, Jadavpur, Kolkata, India
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Achcar F, Fadda A, Haanstra JR, Kerkhoven EJ, Kim DH, Leroux AE, Papamarkou T, Rojas F, Bakker BM, Barrett MP, Clayton C, Girolami M, Krauth-Siegel RL, Matthews KR, Breitling R. The silicon trypanosome: a test case of iterative model extension in systems biology. Adv Microb Physiol 2014; 64:115-43. [PMID: 24797926 DOI: 10.1016/b978-0-12-800143-1.00003-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The African trypanosome, Trypanosoma brucei, is a unicellular parasite causing African Trypanosomiasis (sleeping sickness in humans and nagana in animals). Due to some of its unique properties, it has emerged as a popular model organism in systems biology. A predictive quantitative model of glycolysis in the bloodstream form of the parasite has been constructed and updated several times. The Silicon Trypanosome is a project that brings together modellers and experimentalists to improve and extend this core model with new pathways and additional levels of regulation. These new extensions and analyses use computational methods that explicitly take different levels of uncertainty into account. During this project, numerous tools and techniques have been developed for this purpose, which can now be used for a wide range of different studies in systems biology.
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Affiliation(s)
- Fiona Achcar
- Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Abeer Fadda
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Jurgen R Haanstra
- Department of Pediatrics, Centre for Liver Digestive and Metabolic Diseases, and Systems Biology Centre for Energy Metabolism and Ageing, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands; Department of Molecular Cell Physiology, Faculty of Earth and Life Sciences, VU University Amsterdam, Amsterdam, The Netherlands
| | - Eduard J Kerkhoven
- Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, and Glasgow Polyomics, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom; Systems and Synthetic Biology Group, Department of Chemical and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden
| | - Dong-Hyun Kim
- Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, and Glasgow Polyomics, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | | | - Theodore Papamarkou
- The Department of Statistical Science and The Centre for Computational Statistics and Machine Learning University College London, London, United Kingdom
| | - Federico Rojas
- Centre for Immunity, Infection and Evolution, Institute for Immunology and Infection Research, School of Biological Sciences, Ashworth Laboratories, University of Edinburgh, Edinburgh, United Kingdom
| | - Barbara M Bakker
- Department of Pediatrics, Centre for Liver Digestive and Metabolic Diseases, and Systems Biology Centre for Energy Metabolism and Ageing, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Michael P Barrett
- Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, and Glasgow Polyomics, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Christine Clayton
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Mark Girolami
- The Department of Statistical Science and The Centre for Computational Statistics and Machine Learning University College London, London, United Kingdom
| | | | - Keith R Matthews
- Centre for Immunity, Infection and Evolution, Institute for Immunology and Infection Research, School of Biological Sciences, Ashworth Laboratories, University of Edinburgh, Edinburgh, United Kingdom
| | - Rainer Breitling
- Manchester Institute of Biotechnology, Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom.
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Genetic validation of Trypanosoma brucei glutathione synthetase as an essential enzyme. EUKARYOTIC CELL 2014; 13:614-24. [PMID: 24610661 DOI: 10.1128/ec.00015-14] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Human African trypanosomiasis (HAT) is a debilitating and fatal vector-borne disease. Polyamine biosynthesis is the target of one of the key drugs (eflornithine) used for the treatment of late-stage disease, suggesting that the pathway might be exploited for the identification of additional drug targets. The polyamine spermidine is required in trypanosomatid parasites for formation of a unique redox cofactor termed trypanothione, which is formed from the conjugation of glutathione to spermidine. Here we characterize recombinant Trypanosoma brucei glutathione synthetase (TbGS) and show that depletion of TbGS in blood-form parasites using a regulated knockout strategy leads to loss of trypanothione and to cell death as quantified by fluorescence-activated cell sorter (FACS) analysis. These data suggest that >97% depletion of TbGS is required before trypanothione is depleted and cell growth arrest is observed. Exogenous glutathione was able to partially compensate for the loss of TbGS, suggesting that parasites are able to transport intact glutathione. Finally, reduced expression of TbGS leads to increased levels of upstream glutathione biosynthetic enzymes and decreased expression of polyamine biosynthetic enzymes, providing evidence that the cells cross regulate the two branches of the trypanothione biosynthetic pathway to maintain spermidine and trypanothione homeostasis.
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Leroux AE, Haanstra JR, Bakker BM, Krauth-Siegel RL. Dissecting the catalytic mechanism of Trypanosoma brucei trypanothione synthetase by kinetic analysis and computational modeling. J Biol Chem 2013; 288:23751-64. [PMID: 23814051 PMCID: PMC3745322 DOI: 10.1074/jbc.m113.483289] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
In pathogenic trypanosomes, trypanothione synthetase (TryS) catalyzes the synthesis of both glutathionylspermidine (Gsp) and trypanothione (bis(glutathionyl)spermidine (T(SH)2)). Here we present a thorough kinetic analysis of Trypanosoma brucei TryS in a newly developed phosphate buffer system at pH 7.0 and 37 °C, mimicking the physiological environment of the enzyme in the cytosol of bloodstream parasites. Under these conditions, TryS displays Km values for GSH, ATP, spermidine, and Gsp of 34, 18, 687, and 32 μm, respectively, as well as Ki values for GSH and T(SH)2 of 1 mm and 360 μm, respectively. As Gsp hydrolysis has a Km value of 5.6 mm, the in vivo amidase activity is probably negligible. To obtain deeper insight in the molecular mechanism of TryS, we have formulated alternative kinetic models, with elementary reaction steps represented by linear kinetic equations. The model parameters were fitted to the extensive matrix of steady-state data obtained for different substrate/product combinations under the in vivo-like conditions. The best model describes the full kinetic profile and is able to predict time course data that were not used for fitting. This system's biology approach to enzyme kinetics led us to conclude that (i) TryS follows a ter-reactant mechanism, (ii) the intermediate Gsp dissociates from the enzyme between the two catalytic steps, and (iii) T(SH)2 inhibits the enzyme by remaining bound at its product site and, as does the inhibitory GSH, by binding to the activated enzyme complex. The newly detected concerted substrate and product inhibition suggests that TryS activity is tightly regulated.
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Affiliation(s)
- Alejandro E Leroux
- Biochemie-Zentrum der Universität Heidelberg, D-69120 Heidelberg, Germany
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Allmann S, Morand P, Ebikeme C, Gales L, Biran M, Hubert J, Brennand A, Mazet M, Franconi JM, Michels PAM, Portais JC, Boshart M, Bringaud F. Cytosolic NADPH homeostasis in glucose-starved procyclic Trypanosoma brucei relies on malic enzyme and the pentose phosphate pathway fed by gluconeogenic flux. J Biol Chem 2013; 288:18494-505. [PMID: 23665470 DOI: 10.1074/jbc.m113.462978] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
All living organisms depend on NADPH production to feed essential biosyntheses and for oxidative stress defense. Protozoan parasites such as the sleeping sickness pathogen Trypanosoma brucei adapt to different host environments, carbon sources, and oxidative stresses during their infectious life cycle. The procyclic stage develops in the midgut of the tsetse insect vector, where they rely on proline as carbon source, although they prefer glucose when grown in rich media. Here, we investigate the flexible and carbon source-dependent use of NADPH synthesis pathways in the cytosol of the procyclic stage. The T. brucei genome encodes two cytosolic NADPH-producing pathways, the pentose phosphate pathway (PPP) and the NADP-dependent malic enzyme (MEc). Reverse genetic blocking of those pathways and a specific inhibitor (dehydroepiandrosterone) of glucose-6-phosphate dehydrogenase together established redundancy with respect to H2O2 stress management and parasite growth. Blocking both pathways resulted in ∼10-fold increase of susceptibility to H2O2 stress and cell death. Unexpectedly, the same pathway redundancy was observed in glucose-rich and glucose-depleted conditions, suggesting that gluconeogenesis can feed the PPP to provide NADPH. This was confirmed by (i) a lethal phenotype of RNAi-mediated depletion of glucose-6-phosphate isomerase (PGI) in the glucose-depleted Δmec/Δmec null background, (ii) an ∼10-fold increase of susceptibility to H2O2 stress observed for the Δmec/Δmec/(RNAi)PGI double mutant when compared with the single mutants, and (iii) the (13)C enrichment of glycolytic and PPP intermediates from cells incubated with [U-(13)C]proline, in the absence of glucose. Gluconeogenesis-supported NADPH supply may also be important for nucleotide and glycoconjugate syntheses in the insect host.
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Affiliation(s)
- Stefan Allmann
- Faculty of Biology, Section of Genetics, Ludwig-Maximilians-Universität München, Biozentrum, Grosshadernerstrasse 2-4, D-82152 Martinsried, Germany
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Trypanothione: A unique bis-glutathionyl derivative in trypanosomatids. Biochim Biophys Acta Gen Subj 2013; 1830:3199-216. [DOI: 10.1016/j.bbagen.2013.01.013] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2012] [Revised: 01/11/2013] [Accepted: 01/16/2013] [Indexed: 11/21/2022]
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Lehane AM, McDevitt CA, Kirk K, Fidock DA. Degrees of chloroquine resistance in Plasmodium - is the redox system involved? INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE 2012; 2:47-57. [PMID: 22773965 DOI: 10.1016/j.ijpddr.2011.11.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Chloroquine (CQ) was once a very effective antimalarial drug that, at its peak, was consumed in the hundreds of millions of doses per year. The drug acts against the Plasmodium parasite during the asexual intraerythrocytic phase of its lifecycle. Unfortunately, clinical resistance to this drug is now widespread. Questions remain about precisely how CQ kills malaria parasites, and by what means some CQ-resistant (CQR) parasites can withstand much higher concentrations of the drug than others that also fall in the CQR category. In this review we investigate the evidence for and against the proposal that CQ kills parasites by generating oxidative stress. Further, we examine a long-held idea that the glutathione system of malaria parasites plays a role in CQ resistance. We conclude that there is strong evidence that glutathione levels modulate CQ response in the rodent malaria species P. berghei, but that a role for redox in contributing to the degree of CQ resistance in species infectious to humans has not been firmly established.
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Affiliation(s)
- Adele M Lehane
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY 10032, USA
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Abstract
SIGNIFICANCE Parasitic diseases affect hundreds of millions of people worldwide and represent major health problems. Treatment is becoming extremely difficult due to the emergence of drug resistance, the absence of effective vaccines, and the spread of insecticide-resistant vectors. Thus, identification of affordable and readily available drugs against resistant parasites is of global demand. RECENT ADVANCES Susceptibility of many parasites to oxidative stress is a well-known phenomenon. Therefore, generation of reactive oxygen species (ROS) or inhibition of endogenous antioxidant enzymes would be a novel therapeutic approach to develop antiparasitic drugs. This article highlights the unique metabolic pathways along with redox enzymes of unicellular (Plasmodium falciparum, Trypanosoma cruzi, Trypanosoma brucei, Leishmania donovani, Entamoeba histolytica, and Trichomonas vaginalis) and multicellular parasites (Schistosoma mansoni), which could be utilized to promote ROS-mediated toxicity. CRITICAL ISSUES Enzymes involved in various vital redox reactions could be potential targets for drug development. FUTURE DIRECTIONS The identification of redox-active antiparasitic drugs along with their mode of action will help researchers around the world in designing novel drugs in the future.
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Affiliation(s)
- Chinmay Pal
- Department of Infectious Diseases and Immunology, Indian Institute of Chemical Biology, Kolkata, India
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Abstract
SIGNIFICANCE Parasitic infections continue to be a major problem for global human health. Vaccines are practically not available and chemotherapy is highly unsatisfactory. One approach toward a novel antiparasitic drug development is to unravel pathways that may be suited as future targets. Parasitic organisms show a remarkable diversity with respect to the nature and functions of their main low-molecular-mass antioxidants and many of them developed pathways that do not have a counterpart in their mammalian hosts. RECENT ADVANCES Work of the last years disclosed the individual antioxidants employed by parasites and their distinct pathways. Entamoeba, Trichomonas, and Giardia directly use cysteine as main low-molecular-mass thiol but have divergent cysteine metabolisms. Malarial parasites rely exclusively on cysteine uptake and generate glutathione (GSH) as main free thiol as do metazoan parasites. Trypanosomes and Leishmania have a unique trypanothione-based thiol metabolism but employ individual mechanisms for their cysteine supply. In addition, some trypanosomatids synthesize ovothiol A and/or ascorbate. Various essential parasite enzymes such as trypanothione synthetase and trypanothione reductase in Trypanosomatids and the Schistosoma thioredoxin GSH reductase are currently intensively explored as drug target molecules. CRITICAL ISSUES Essentiality is a prerequisite but not a sufficient property of an enzyme to become a suited drug target. The availability of an appropriate in vivo screening system and many other factors are equally important. FUTURE DIRECTIONS The current organism-wide RNA-interference and proteome analyses are supposed to reveal many more interesting candidates for future drug development approaches directed against the parasite antioxidant defense systems.
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Flohé L. The trypanothione system and its implications in the therapy of trypanosomatid diseases. Int J Med Microbiol 2012; 302:216-20. [PMID: 22889611 DOI: 10.1016/j.ijmm.2012.07.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Biosynthesis and the use of trypanothione, a redox metabolite of parasitic trypanosomatids, are reviewed here with special emphasis on the development of trypanocidal drugs. This metabolic system is unique to and essential for the protozoal parasites. Selective inhibition of key elements of trypanothione metabolism, therefore, promises eradication of the parasites without affecting the host. Considering the metabolic importance and drugability of system components, inhibition of the enzymes for regeneration and de novo synthesis of trypanothione is rated as the most promising approach, while related peroxidases and redoxins are disregarded as targets because of limited chances to achieve selective inhibition. The organizational need to exploit the accumulating knowledge of trypanosomatid metabolism for medical practice is briefly addressed.
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Affiliation(s)
- Leopold Flohé
- Department of Chemistry, Otto-von-Guericke-Universität, Universitätsplatz 2, 39106 Magdeburg, Germany.
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26
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Lagos CF, Araya-Secchi R, Thomas P, Pérez-Acle T, Tapia RA, Salas CO. Molecular modeling of Trypanosoma cruzi glutamate cysteine ligase and investigation of its interactions with glutathione. J Mol Model 2012; 18:2055-64. [DOI: 10.1007/s00894-011-1224-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Accepted: 08/11/2011] [Indexed: 11/28/2022]
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Olin-Sandoval V, González-Chávez Z, Berzunza-Cruz M, Martínez I, Jasso-Chávez R, Becker I, Espinoza B, Moreno-Sánchez R, Saavedra E. Drug target validation of the trypanothione pathway enzymes through metabolic modelling. FEBS J 2012; 279:1811-33. [DOI: 10.1111/j.1742-4658.2012.08557.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Willert E, Phillips MA. Regulation and function of polyamines in African trypanosomes. Trends Parasitol 2011; 28:66-72. [PMID: 22192816 DOI: 10.1016/j.pt.2011.11.001] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2011] [Revised: 10/31/2011] [Accepted: 11/01/2011] [Indexed: 02/03/2023]
Abstract
The polyamine biosynthetic pathway is an important drug target for the treatment of human African trypanosomiasis (HAT), raising interest in understanding polyamine function and their mechanism of regulation. Polyamine levels are tightly controlled in mammalian cells, but similar regulatory mechanisms appear absent in trypanosomes. Instead trypanosomatid S-adenosylmethionine decarboxylase (AdoMetDC), which catalyzes a key step in the biosynthesis of the polyamine spermidine, is activated by dimerization with an inducible protein termed prozyme. Prozyme is an inactive paralog of the active AdoMetDC enzyme that evolved by gene duplication and is found only in the trypanosomatids. In Trypanosoma brucei, AdoMetDC activity appears to be controlled by regulation of prozyme protein levels, potentially at the translational level.
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Affiliation(s)
- Erin Willert
- Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, 6001 Forest Park Road, Dallas, TX 75390-9041, USA
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29
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Abstract
Glutathione (γ-glutamylcysteinyl-glycine, GSH) has vital functions as thiol redox buffer and cofactor of antioxidant and detoxification enzymes. Plasmodium falciparum possesses a functional GSH biosynthesis pathway and contains mM concentrations of the tripeptide. It was impossible to delete in P. falciparum the genes encoding γ-glutamylcysteine synthetase (γGCS) or glutathione synthetase (GS), the two enzymes synthesizing GSH, although both gene loci were not refractory to recombination. Our data show that the parasites cannot compensate for the loss of GSH biosynthesis via GSH uptake. This suggests an important if not essential function of GSH biosynthesis pathway for the parasites. Treatment with the irreversible inhibitor of γGCS L-buthionine sulfoximine (BSO) reduced intracellular GSH levels in P. falciparum and was lethal for their intra-erythrocytic development, corroborating the suggestion that GSH biosynthesis is important for parasite survival. Episomal expression of γgcs in P. falciparum increased tolerance to BSO attributable to increased levels of γGCS. Concomitantly expression of glutathione reductase was reduced leading to an increased GSH efflux. Together these data indicate that GSH levels are tightly regulated by a functional GSH biosynthesis and the reduction of GSSG.
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Affiliation(s)
- Eva-Maria Patzewitz
- Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity & Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, 120 University Place, Glasgow G12 8TA, UK.
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Kalidas S, Li Q, Phillips MA. A Gateway® compatible vector for gene silencing in bloodstream form Trypanosoma brucei. Mol Biochem Parasitol 2011; 178:51-5. [PMID: 21420443 DOI: 10.1016/j.molbiopara.2011.03.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2010] [Revised: 03/09/2011] [Accepted: 03/10/2011] [Indexed: 02/04/2023]
Abstract
RNA interference is the most rapid method for generation of conditional knockdown mutants in Trypanosoma brucei. The dual T7 promoter (pZJM) and the stem-loop vectors have been widely used to generate stable inducible RNAi cell lines with the latter providing tighter regulatory control. However, the steps for cloning stem-loop constructs are cumbersome requiring either multiple cloning steps or multi-fragment ligation reactions. We report the development of a vector (pTrypRNAiGate) derived from pLEW100 that utilizes the Gateway® recombination system to facilitate easy production of hairpin RNA constructs. This approach allows the final stem-loop RNAi construct to be generated from a single cloning step of the PCR-derived gene fragment followed by an in vitro recombination reaction. The new vector facilitates high-throughput applications for gene silencing and provides a tool for functional genomics in T. brucei.
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Affiliation(s)
- Savitha Kalidas
- Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390-9041, United States
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Jacobs RT, Nare B, Phillips MA. State of the art in African trypanosome drug discovery. Curr Top Med Chem 2011; 11:1255-74. [PMID: 21401507 PMCID: PMC3101707 DOI: 10.2174/156802611795429167] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2010] [Accepted: 11/25/2010] [Indexed: 11/22/2022]
Abstract
African sleeping sickness is endemic in sub-Saharan Africa where the WHO estimates that 60 million people are at risk for the disease. Human African trypanosomiasis (HAT) is 100% fatal if untreated and the current drug therapies have significant limitations due to toxicity and difficult treatment regimes. No new chemical agents have been approved since eflornithine in 1990. The pentamidine analog DB289, which was in late stage clinical trials for the treatment of early stage HAT recently failed due to toxicity issues. A new protocol for the treatment of late-stage T. brucei gambiense that uses combination nifurtomox/eflornithine (NECT) was recently shown to have better safety and efficacy than eflornithine alone, while being easier to administer. This breakthrough represents the only new therapy for HAT since the approval of eflornithine. A number of research programs are on going to exploit the unusual biochemical pathways in the parasite to identify new targets for target based drug discovery programs. HTS efforts are also underway to discover new chemical entities through whole organism screening approaches. A number of inhibitors with anti-trypanosomal activity have been identified by both approaches, but none of the programs are yet at the stage of identifying a preclinical candidate. This dire situation underscores the need for continued effort to identify new chemical agents for the treatment of HAT.
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Affiliation(s)
- Robert T. Jacobs
- SCYNEXIS, Inc., Research Triangle Park, North Carolina 27709-2878
| | - Bakela Nare
- SCYNEXIS, Inc., Research Triangle Park, North Carolina 27709-2878
| | - Margaret A. Phillips
- Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, 6001 Forest Park Rd, Dallas, Texas 75390-9041
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Yadav AK, Desai PR, Rai MN, Kaur R, Ganesan K, Bachhawat AK. Glutathione biosynthesis in the yeast pathogens Candida glabrata and Candida albicans: essential in C. glabrata, and essential for virulence in C. albicans. MICROBIOLOGY-SGM 2010; 157:484-495. [PMID: 20966090 DOI: 10.1099/mic.0.045054-0] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Redox pathways play a key role in pathogenesis. Glutathione, a central molecule in redox homeostasis in yeasts, is an essential metabolite, but its requirements can be met either from endogenous biosynthesis or from the extracellular milieu. In this report we have examined the importance of glutathione biosynthesis in two major human opportunistic fungal pathogens, Candida albicans and Candida glabrata. As the genome sequence of C. glabrata had suggested the absence of glutathione transporters, we initially investigated exogenous glutathione utilization in C. glabrata by disruption of the MET15 gene, involved in methionine biosynthesis. We observed an organic sulphur auxotrophy in a C. glabrata met15Δ strain; however, unlike its Saccharomyces cerevisiae counterpart, the C. glabrata met15Δ strain was unable to grow on exogenous glutathione. This inability to grow on exogenous glutathione was demonstrated to be due to the lack of a functional glutathione transporter, despite the presence of a functional glutathione degradation machinery (the Dug pathway). In the absence of the ability to obtain glutathione from the extracellular medium, we examined and could demonstrate that γ-glutamyl cysteine synthase, the first enzyme of glutathione biosynthesis, was essential in C. glabrata. Further, although γ-glutamyl cysteine synthase has been reported to be non-essential in C. albicans, we report here for what is believed to be the first time that the enzyme is required for survival in human macrophages in vitro, as well as for virulence in a murine model of disseminated candidiasis. The essentiality of γ-glutamyl cysteine synthase in C. glabrata, and its essentiality for virulence in C. albicans, make the enzyme a strong candidate for antifungal development.
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Affiliation(s)
- Amit Kumar Yadav
- Institute of Microbial Technology (CSIR), Sector 39-A, Chandigarh 160 036, India
| | | | - Maruti Nandan Rai
- Centre for DNA Fingerprinting and Diagnostics, Building 7, Gruhakalpa 5-4-399/B, Nampally, Hyderabad-500001, India
| | - Rupinder Kaur
- Centre for DNA Fingerprinting and Diagnostics, Building 7, Gruhakalpa 5-4-399/B, Nampally, Hyderabad-500001, India
| | - Kaliannan Ganesan
- Institute of Microbial Technology (CSIR), Sector 39-A, Chandigarh 160 036, India
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Manipulation of cellular GSH biosynthetic capacity via TAT-mediated protein transduction of wild-type or a dominant-negative mutant of glutamate cysteine ligase alters cell sensitivity to oxidant-induced cytotoxicity. Toxicol Appl Pharmacol 2009; 243:35-45. [PMID: 19914271 DOI: 10.1016/j.taap.2009.11.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2009] [Revised: 11/04/2009] [Accepted: 11/06/2009] [Indexed: 02/07/2023]
Abstract
The glutathione (GSH) antioxidant defense system plays a central role in protecting mammalian cells against oxidative injury. Glutamate cysteine ligase (GCL) is the rate-limiting enzyme in GSH biosynthesis and is a heterodimeric holoenzyme composed of catalytic (GCLC) and modifier (GCLM) subunits. As a means of assessing the cytoprotective effects of enhanced GSH biosynthetic capacity, we have developed a protein transduction approach whereby recombinant GCL protein can be rapidly and directly transferred into cells when coupled to the HIV TAT protein transduction domain. Bacterial expression vectors encoding TAT fusion proteins of both GCL subunits were generated and recombinant fusion proteins were synthesized and purified to near homogeneity. The TAT-GCL fusion proteins were capable of heterodimerization and formation of functional GCL holoenzyme in vitro. Exposure of Hepa-1c1c7 cells to the TAT-GCL fusion proteins resulted in the time- and dose-dependent transduction of both GCL subunits and increased cellular GCL activity and GSH levels. A heterodimerization-competent, enzymatically deficient GCLC-TAT mutant was also generated in an attempt to create a dominant-negative suppressor of GCL. Transduction of cells with a catalytically inactive GCLC(E103A)-TAT mutant decreased cellular GCL activity in a dose-dependent manner. TAT-mediated manipulation of cellular GCL activity was also functionally relevant as transduction with wild-type GCLC(WT)-TAT or mutant GCLC(E103A)-TAT conferred protection or enhanced sensitivity to H(2)O(2)-induced cell death, respectively. These findings demonstrate that TAT-mediated transduction of wild-type or dominant-inhibitory mutants of the GCL subunits is a viable means of manipulating cellular GCL activity to assess the effects of altered GSH biosynthetic capacity.
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Abstract
The protozoan parasitesTrypanosoma bruceiandTrypanosoma cruziare the causative agents of African trypanosomiasis and Chagas disease, respectively. These are debilitating infections that exert a considerable health burden on some of the poorest people on the planet. Treatment of trypanosome infections is dependent on a small number of drugs that have limited efficacy and can cause severe side effects. Here, we review the properties of these drugs and describe new findings on their modes of action and the mechanisms by which resistance can arise. We further outline how a greater understanding of parasite biology is being exploited in the search for novel chemotherapeutic agents. This effort is being facilitated by new research networks that involve academic and biotechnology/pharmaceutical organisations, supported by public–private partnerships, and are bringing a new dynamism and purpose to the search for trypanocidal agents.
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Mukherjee A, Roy G, Guimond C, Ouellette M. The γ-glutamylcysteine synthetase gene of Leishmania is essential and involved in response to oxidants. Mol Microbiol 2009; 74:914-27. [DOI: 10.1111/j.1365-2958.2009.06907.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Biterova EI, Barycki JJ. Mechanistic details of glutathione biosynthesis revealed by crystal structures of Saccharomyces cerevisiae glutamate cysteine ligase. J Biol Chem 2009; 284:32700-8. [PMID: 19726687 DOI: 10.1074/jbc.m109.025114] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Glutathione is a thiol-disulfide exchange peptide critical for buffering oxidative or chemical stress, and an essential cofactor in several biosynthesis and detoxification pathways. The rate-limiting step in its de novo biosynthesis is catalyzed by glutamate cysteine ligase, a broadly expressed enzyme for which limited structural information is available in higher eukaryotic species. Structural data are critical to the understanding of clinical glutathione deficiency, as well as rational design of enzyme modulators that could impact human disease progression. Here, we have determined the structures of Saccharomyces cerevisiae glutamate cysteine ligase (ScGCL) in the presence of glutamate and MgCl(2) (2.1 A; R = 18.2%, R(free) = 21.9%), and in complex with glutamate, MgCl(2), and ADP (2.7 A; R = 19.0%, R(free) = 24.2%). Inspection of these structures reveals an unusual binding pocket for the alpha-carboxylate of the glutamate substrate and an ATP-independent Mg(2+) coordination site, clarifying the Mg(2+) dependence of the enzymatic reaction. The ScGCL structures were further used to generate a credible homology model of the catalytic subunit of human glutamate cysteine ligase (hGCLC). Examination of the hGCLC model suggests that post-translational modifications of cysteine residues may be involved in the regulation of enzymatic activity, and elucidates the molecular basis of glutathione deficiency associated with patient hGCLC mutations.
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Affiliation(s)
- Ekaterina I Biterova
- Department of Biochemistry and the Redox Biology Center, University of Nebraska, Lincoln, Nebraska 68588-0664, USA
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RNA interference-mediated silencing of ornithine decarboxylase and spermidine synthase genes in Trypanosoma brucei provides insight into regulation of polyamine biosynthesis. EUKARYOTIC CELL 2009; 8:747-55. [PMID: 19304951 DOI: 10.1128/ec.00047-09] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Polyamine biosynthesis is a drug target for the treatment of African sleeping sickness; however, mechanisms regulating the pathway in Trypanosoma brucei are not well understood. Recently, we showed that RNA interference (RNAi)-mediated gene silencing or the inhibition of S-adenosylmethionine decarboxylase (AdoMetDC) led to the upregulation of the AdoMetDC activator, prozyme, and ornithine decarboxylase (ODC) proteins. To determine if this regulatory response is specific to AdoMetDC, we studied the effects of the RNAi-induced silencing of the spermidine synthase (SpdSyn) and ODC genes in bloodstream form T. brucei. The knockdown of either gene product led to the depletion of the polyamine and trypanothione pools and to cell death. Decarboxylated AdoMet levels were elevated, while AdoMet was not affected. There was no significant effect on the protein levels of other polyamine pathway enzymes. The treatment of parasites with the ODC inhibitor alpha-difluoromethylornithine gave similar results to those observed for ODC knockdown. Thus, the cellular response to the loss of AdoMetDC activity is distinctive, suggesting that AdoMetDC activity controls the expression levels of the other spermidine biosynthetic enzymes. RNAi-mediated cell death occurred more rapidly for ODC than for SpdSyn. Further, the ODC RNAi cells were rescued by putrescine, but not spermidine, suggesting that the depletion of both putrescine and spermidine is more detrimental than the depletion of spermidine alone. This finding may contribute to the effectiveness of ODC as a target for the treatment of African sleeping sickness, thus providing important insight into the mechanism of action of a key antitrypanosomal agent.
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Vega-Rodríguez J, Franke-Fayard B, Dinglasan RR, Janse CJ, Pastrana-Mena R, Waters AP, Coppens I, Rodríguez-Orengo JF, Jacobs-Lorena M, Serrano AE. The glutathione biosynthetic pathway of Plasmodium is essential for mosquito transmission. PLoS Pathog 2009; 5:e1000302. [PMID: 19229315 PMCID: PMC2636896 DOI: 10.1371/journal.ppat.1000302] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2008] [Accepted: 01/18/2009] [Indexed: 02/07/2023] Open
Abstract
Infection of red blood cells (RBC) subjects the malaria parasite to oxidative stress. Therefore, efficient antioxidant and redox systems are required to prevent damage by reactive oxygen species. Plasmodium spp. have thioredoxin and glutathione (GSH) systems that are thought to play a major role as antioxidants during blood stage infection. In this report, we analyzed a critical component of the GSH biosynthesis pathway using reverse genetics. Plasmodium berghei parasites lacking expression of gamma-glutamylcysteine synthetase (γ-GCS), the rate limiting enzyme in de novo synthesis of GSH, were generated through targeted gene disruption thus demonstrating, quite unexpectedly, that γ-GCS is not essential for blood stage development. Despite a significant reduction in GSH levels, blood stage forms of pbggcs− parasites showed only a defect in growth as compared to wild type. In contrast, a dramatic effect on development of the parasites in the mosquito was observed. Infection of mosquitoes with pbggcs− parasites resulted in reduced numbers of stunted oocysts that did not produce sporozoites. These results have important implications for the design of drugs aiming at interfering with the GSH redox-system in blood stages and demonstrate that de novo synthesis of GSH is pivotal for development of Plasmodium in the mosquito. The antioxidant systems of malaria parasites (Plasmodium spp.) are potential targets for the development of antimalarials. The glutathione (GSH) redox system constitutes one of the Plasmodium primary lines of defense against damage caused by reactive oxygen species and other forms of chemical stress. GSH is synthesized de novo by the sequential action of gamma-glutamylcysteine synthase (γ-GCS) and GSH synthase (GS). Biochemical studies have suggested that parasite survival depends on functional de novo GSH synthesis. Using reverse genetics we interrupted the GSH biosynthetic pathway in the rodent malaria Plasmodium berghei by disrupting the pbggcs gene. The mutation caused minor changes in parasite growth in the mammalian host but development in the mosquito was completely arrested at the oocyst stage. These results suggest that the GSH biosynthetic pathway, while essential for mosquito stage development, is not an appropriate target for antimalarials against blood stages of the parasite.
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Affiliation(s)
- Joel Vega-Rodríguez
- Department of Microbiology and Medical Zoology, University of Puerto Rico, School of Medicine, San Juan, Puerto Rico
| | | | - Rhoel R. Dinglasan
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, United States of America
| | - Chris J. Janse
- Department of Parasitology, Leiden University Medical Center, Leiden, The Netherlands
| | - Rebecca Pastrana-Mena
- Department of Microbiology and Medical Zoology, University of Puerto Rico, School of Medicine, San Juan, Puerto Rico
| | - Andrew P. Waters
- Department of Parasitology, Leiden University Medical Center, Leiden, The Netherlands
- Wellcome Trust Centre of Molecular Parasitology and Division of Infection and Immunity, University of Glasgow, Glasgow, United Kingdom
| | - Isabelle Coppens
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, United States of America
| | - José F. Rodríguez-Orengo
- Department of Biochemistry, University of Puerto Rico, School of Medicine, San Juan, Puerto Rico
| | - Marcelo Jacobs-Lorena
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, United States of America
| | - Adelfa E. Serrano
- Department of Microbiology and Medical Zoology, University of Puerto Rico, School of Medicine, San Juan, Puerto Rico
- * E-mail:
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Willert EK, Phillips MA. Regulated expression of an essential allosteric activator of polyamine biosynthesis in African trypanosomes. PLoS Pathog 2008; 4:e1000183. [PMID: 18949025 PMCID: PMC2562514 DOI: 10.1371/journal.ppat.1000183] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2008] [Accepted: 09/23/2008] [Indexed: 12/11/2022] Open
Abstract
Trypanosoma brucei is the causative agent of African sleeping sickness. The polyamine biosynthetic pathway has the distinction of being the target of the only clinically proven anti-trypanosomal drug with a known mechanism of action. Polyamines are essential for cell growth, and their metabolism is extensively regulated. However, trypanosomatids appear to lack the regulatory control mechanisms described in other eukaryotic cells. In T. brucei, S-adenosylmethionine decarboxylase (AdoMetDC) and ornithine decarboxylase (ODC) are required for the synthesis of polyamines and also for the unique redox-cofactor trypanothione. Further, trypanosomatid AdoMetDC is activated by heterodimer formation with a catalytically dead homolog termed prozyme, found only in these species. To study polyamine regulation in T. brucei, we generated inducible AdoMetDC RNAi and prozyme conditional knockouts in the mammalian blood form stage. Depletion of either protein led to a reduction in spermidine and trypanothione and to parasite death, demonstrating that prozyme activation of AdoMetDC is essential. Under typical growth conditions, prozyme concentration is limiting in comparison to AdoMetDC. However, both prozyme and ODC protein levels were significantly increased relative to stable transcript levels by knockdown of AdoMetDC or its chemical inhibition. Changes in protein stability do not appear to account for the increased steady-state protein levels, as both enzymes are stable in the presence of cycloheximide. These observations suggest that prozyme and ODC are translationally regulated in response to perturbations in the pathway. In conclusion, we describe the first evidence for regulation of polyamine biosynthesis in T. brucei and we demonstrate that the unique regulatory subunit of AdoMetDC is a key component of this regulation. The data support ODC and AdoMetDC as the key control points in the pathway and the likely rate-limiting steps in polyamine biosynthesis.
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Affiliation(s)
- Erin K. Willert
- Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
| | - Margaret A. Phillips
- Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
- * E-mail:
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Irigoín F, Cibils L, Comini MA, Wilkinson SR, Flohé L, Radi R. Insights into the redox biology of Trypanosoma cruzi: Trypanothione metabolism and oxidant detoxification. Free Radic Biol Med 2008; 45:733-42. [PMID: 18588970 DOI: 10.1016/j.freeradbiomed.2008.05.028] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2008] [Revised: 05/24/2008] [Accepted: 05/28/2008] [Indexed: 10/22/2022]
Abstract
Trypanosoma cruzi is the etiologic agent of Chagas' disease, an infection that affects several million people in Latin America. With no immediate prospect of a vaccine and problems associated with current chemotherapies, the development of new treatments is an urgent priority. Several aspects of the redox metabolism of this parasite differ enough from those in the mammalian host to be considered targets for drug development. Here, we review the information about a trypanosomatid-specific molecule centrally involved in redox metabolism, the dithiol trypanothione, and the main effectors of cellular antioxidant defense. We focus mainly on data from T. cruzi, making comparisons with other trypanosomatids whenever possible. In these parasites trypanothione participates in crucial thiol-disulfide exchange reactions and serves as electron donor in different metabolic pathways, from synthesis of DNA precursors to oxidant detoxification. Interestingly, the levels of several enzymes involved in trypanothione metabolism and oxidant detoxification increase during the transformation of T. cruzi to its mammalian-infective form and the overexpression of some of them has been associated with increased resistance to macrophage-dependent oxidative killing. Together, the evidence suggests a central role of the trypanothione-dependent antioxidant systems in the infection process.
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Affiliation(s)
- Florencia Irigoín
- Departmento de Histología y Embriología, Facultad de Medicina, Universidad de la República, Uruguay
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Abstract
This article provides an overview about the recent advances in the dissection of the peroxide metabolism of Trypanosomatidae. This family of protozoan organisms comprises the medically relevant parasites Trypanosoma brucei, Trypanosoma cruzi, and Leishmania spp. Over the past 10 years, three major families of peroxidases have been identified in these organisms: (a) 2-cysteine peroxiredoxins, (b) nonselenium glutathione peroxidases, and (c) ascorbate peroxidases. In trypanosomatids, these enzymes display the unique feature of using reducing equivalents derived from trypanothione, a dithiol found exclusively in these protozoa. The electron transfer between trypanothione and the peroxidases is mediated by a redox shuttle, which can either be tryparedoxin, ascorbate, or even glutathione. The preference for the intermediate molecule differs among each peroxidase and so does the specificity for the peroxide substrate. These observations, added to the fact that these peroxidases are distributed throughout different subcellular compartments, point to the existence of an elaborate peroxide metabolism in trypanosomatids. With the completion of the trypanosomatids genome, other molecules displaying peroxidase activity might be added to this list in the future.
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Affiliation(s)
- Helena Castro
- Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Porto, Portugal
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42
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Metabolic control analysis: a tool for designing strategies to manipulate metabolic pathways. J Biomed Biotechnol 2008; 2008:597913. [PMID: 18629230 PMCID: PMC2447884 DOI: 10.1155/2008/597913] [Citation(s) in RCA: 122] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2007] [Revised: 01/16/2008] [Accepted: 03/26/2008] [Indexed: 02/06/2023] Open
Abstract
The traditional experimental approaches used for changing the flux or the concentration of a particular metabolite of a metabolic pathway have been mostly based on the inhibition or over-expression of the presumed rate-limiting step. However, the attempts to manipulate a metabolic pathway by following such approach have proved to be unsuccessful. Metabolic Control Analysis (MCA) establishes how to determine, quantitatively, the degree of control that a given enzyme exerts on flux and on the concentration of metabolites, thus substituting the intuitive, qualitative concept of rate limiting step. Moreover, MCA helps to understand (i) the underlying mechanisms by which a given enzyme exerts high or low control and (ii) why the control of the pathway is shared by several pathway enzymes and transporters. By applying MCA it is possible to identify the steps that should be modified to achieve a successful alteration of flux or metabolite concentration in pathways of biotechnological (e.g., large scale metabolite production) or clinical relevance (e.g., drug therapy). The different MCA experimental approaches developed for the determination of the flux-control distribution in several pathways are described. Full understanding of the pathway properties when is working under a variety of conditions can help to attain a successful manipulation of flux and metabolite concentration.
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Krauth-Siegel RL, Comini MA. Redox control in trypanosomatids, parasitic protozoa with trypanothione-based thiol metabolism. Biochim Biophys Acta Gen Subj 2008; 1780:1236-48. [PMID: 18395526 DOI: 10.1016/j.bbagen.2008.03.006] [Citation(s) in RCA: 291] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2008] [Revised: 02/26/2008] [Accepted: 03/11/2008] [Indexed: 01/09/2023]
Abstract
Trypanosomes and leishmania, the causative agents of several tropical diseases, possess a unique redox metabolism which is based on trypanothione. The bis(glutathionyl)spermidine is the central thiol that delivers electrons for the synthesis of DNA precursors, the detoxification of hydroperoxides and other trypanothione-dependent pathways. Many of the reactions are mediated by tryparedoxin, a distant member of the thioredoxin protein family. Trypanothione is kept reduced by the parasite-specific flavoenzyme trypanothione reductase. Since glutathione reductases and thioredoxin reductases are missing, the reaction catalyzed by trypanothione reductase represents the only connection between the NADPH- and the thiol-based redox metabolisms. Thus, cellular thiol redox homeostasis is maintained by the biosynthesis and reduction of trypanothione. Nearly all proteins of the parasite-specific trypanothione metabolism have proved to be essential.
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Maya JD, Cassels BK, Iturriaga-Vásquez P, Ferreira J, Faúndez M, Galanti N, Ferreira A, Morello A. Mode of action of natural and synthetic drugs against Trypanosoma cruzi and their interaction with the mammalian host. Comp Biochem Physiol A Mol Integr Physiol 2007; 146:601-20. [PMID: 16626984 DOI: 10.1016/j.cbpa.2006.03.004] [Citation(s) in RCA: 219] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2005] [Revised: 03/09/2006] [Accepted: 03/09/2006] [Indexed: 01/07/2023]
Abstract
Current knowledge of the biochemistry of Trypanosoma cruzi has led to the development of new drugs and the understanding of their mode of action. Some trypanocidal drugs such as nifurtimox and benznidazole act through free radical generation during their metabolism. T. cruzi is very susceptible to the cell damage induced by these metabolites because enzymes scavenging free radicals are absent or have very low activities in the parasite. Another potential target is the biosynthetic pathway of glutathione and trypanothione, the low molecular weight thiol found exclusively in trypanosomatids. These thiols scavenge free radicals and participate in the conjugation and detoxication of numerous drugs. Inhibition of this key pathway could render the parasite much more susceptible to the toxic action of drugs such as nifurtimox and benznidazole without affecting the host significantly. Other drugs such as allopurinol and purine analogs inhibit purine transport in T. cruzi, which cannot synthesize purines de novo. Nitroimidazole derivatives such as itraconazole inhibit sterol metabolism. The parasite's respiratory chain is another potential therapeutic target because of its many differences with the host enzyme complexes. The pharmacological modulation of the host's immune response against T. cruzi infection as a possible chemotherapeutic target is discussed. A large set of chemicals of plant origin and a few animal metabolites active against T. cruzi are enumerated and their likely modes of action are briefly discussed.
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Affiliation(s)
- Juan Diego Maya
- Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, P.O. Box 70000, Santiago 7, Santiago, Chile
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Barrett MP, Gilbert IH. Targeting of toxic compounds to the trypanosome's interior. ADVANCES IN PARASITOLOGY 2006; 63:125-83. [PMID: 17134653 DOI: 10.1016/s0065-308x(06)63002-9] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Drugs can be targeted into African trypanosomes by exploiting carrier proteins at the surface of these parasites. This has been clearly demonstrated in the case of the melamine-based arsenical and the diamidine classes of drug that are already in use in the treatment of human African trypanosomiasis. These drugs can enter via an aminopurine transporter, termed P2, encoded by the TbAT1 gene. Other toxic compounds have also been designed to enter via this transporter. Some of these compounds enter almost exclusively through the P2 transporter, and hence loss of the P2 transporter leads to significant resistance to these particular compounds. It now appears, however, that some diamidines and melaminophenylarsenicals may also be taken up by other routes (of yet unknown function). These too may be exploited to target new drugs into trypanosomes. Additional purine nucleoside and nucleobase transporters have also been subverted to deliver toxic agents to trypanosomes. Glucose and amino acid transporters too have been investigated with a view to manipulating them to carry toxins into Trypanosoma brucei, and recent work has demonstrated that aquaglyceroporins may also have considerable potential for drug-targeting. Transporters, including those that carry lipids and vitamins such as folate and other pterins also deserve more attention in this regard. Some drugs, for example suramin, appear to enter via routes other than plasma-membrane-mediated transport. Receptor-mediated endocytosis has been proposed as a possible way in for suramin. Endocytosis also appears to be crucial in targeting natural trypanocides, such as trypanosome lytic factor (TLF) (apolipoprotein L1), into trypanosomes and this offers an alternative means of selectively targeting toxins to the trypanosome's interior. Other compounds may be induced to enter by increasing their capacity to diffuse over cell membranes; in this case depending exclusively on selective activity within the cell rather than selective uptake to impart selective toxicity. This review outlines studies that have aimed to exploit trypanosome nutrient uptake routes to selectively carry toxins into these parasites.
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Affiliation(s)
- Michael P Barrett
- Division of Infection & Immunity, Institute of Biomedical and Life Sciences, Glasgow Biomedical Research Centre, University of Glasgow, Glasgow G12 8QQ, UK
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Ariyanayagam M, Oza S, Guther M, Fairlamb A. Phenotypic analysis of trypanothione synthetase knockdown in the African trypanosome. Biochem J 2006; 391:425-32. [PMID: 16008527 PMCID: PMC1276942 DOI: 10.1042/bj20050911] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Trypanothione plays a pivotal role in defence against chemical and oxidant stress, thiol redox homoeostasis, ribonucleotide metabolism and drug resistance in parasitic kinetoplastids. In Trypanosoma brucei, trypanothione is synthesized from glutathione and spermidine by a single enzyme, TryS (trypanothione synthetase), with glutathionylspermidine as an intermediate. To examine the physiological roles of trypanothione, tetracycline-inducible RNA interference was used to reduce expression of TRYS. Following induction, TryS protein was reduced >10-fold and growth rate was reduced 2-fold, with concurrent 5-10-fold decreases in glutathionylspermidine and trypanothione and an up to 14-fold increase in free glutathione content. Polyamine levels were not significantly different from non-induced controls, and neither was the intracellular thiol redox potential, indicating that these factors are not responsible for the growth defect. Compensatory changes in other pathway enzymes were associated with prolonged suppression of TryS: an increase in trypanothione reductase and gamma-glutamylcysteine synthetase, and a transient decrease in ornithine decarboxylase. Depleted trypanothione levels were associated with increases in sensitivity to arsenical, antimonial and nitro drugs, implicating trypanothione metabolism in their mode of action. Escape mutants arose after 2 weeks of induction, with all parameters, including growth, returning to normal. Selective inhibitors of TryS are required to fully validate this novel drug target.
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Affiliation(s)
- Mark R. Ariyanayagam
- Division of Biological Chemistry and Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, U.K
| | - Sandra L. Oza
- Division of Biological Chemistry and Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, U.K
| | - Maria Lucia S. Guther
- Division of Biological Chemistry and Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, U.K
| | - Alan H. Fairlamb
- Division of Biological Chemistry and Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, U.K
- To whom correspondence should be addressed (email )
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47
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Abstract
Hydroperoxide metabolism in diverse pathogens is reviewed under consideration of involved enzymes as potential drug targets. The common denominator of the peroxidase systems of Trypanosoma, Leishmania, Plasmodium, and Mycobacterium species is the use of NAD(P)H to reduce hydroperoxides including peroxynitrite via a flavin-containing disulfide reductase, a thioredoxin (Trx)-related protein and a peroxidase that operates with thiol catalysis. In Plasmodium falciparum, thioredoxin- and glutathione dependent systems appear to be linked via glutaredoxin and plasmoredoxin to terminal thioredoxin peroxidases belonging to both, the peroxiredoxin (Prx) and glutathione peroxidase (GPx) family. In Mycobacterium tuberculosis, a catalase-type peroxidase is complemented by the typical 2-C-Prx AhpC that, in contrast to most bacteria, is reduced by TrxC, and an atypical 2-C-Prx reduced by TrxB or C. A most complex variation of the scheme is found in trypanosomatids, where the unique redox metabolite trypanothione reduces the thioredoxin-related tryparedoxin, which fuels Prx- and GPx-type peroxidases as well as ribonucleotide reductase. In Trypanosoma brucei and Leishmania donovani the system has been shown to be essential for viability and virulence by inversed genetics. It is concluded that optimum efficacy can be expected from inhibitors of the most upstream components of the redox cascades. For trypanosomatids attractive validated drug targets are trypanothione reductase and trypanothione synthetase; for mycobacteria thioredoxin reductase appears most appealing, while in Plasmodium simultaneous inhibition of both the thioredoxin and the glutathione pathway appears advisable to avoid mutual substitution in co-substrate supply to the peroxidases. Financial and organisational needs to translate the scientific progress into applicable drugs are discussed under consideration of the socio-economic impact of the addressed diseases.
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Affiliation(s)
- Timo Jaeger
- MOLISA GmbH, Molecular Links Sachsen-Anhalt, Universitätsplatz 2, D-39106 Magdeburg, Germany.
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Berriman M, Ghedin E, Hertz-Fowler C, Blandin G, Renauld H, Bartholomeu DC, Lennard NJ, Caler E, Hamlin NE, Haas B, Böhme U, Hannick L, Aslett MA, Shallom J, Marcello L, Hou L, Wickstead B, Alsmark UCM, Arrowsmith C, Atkin RJ, Barron AJ, Bringaud F, Brooks K, Carrington M, Cherevach I, Chillingworth TJ, Churcher C, Clark LN, Corton CH, Cronin A, Davies RM, Doggett J, Djikeng A, Feldblyum T, Field MC, Fraser A, Goodhead I, Hance Z, Harper D, Harris BR, Hauser H, Hostetler J, Ivens A, Jagels K, Johnson D, Johnson J, Jones K, Kerhornou AX, Koo H, Larke N, Landfear S, Larkin C, Leech V, Line A, Lord A, Macleod A, Mooney PJ, Moule S, Martin DMA, Morgan GW, Mungall K, Norbertczak H, Ormond D, Pai G, Peacock CS, Peterson J, Quail MA, Rabbinowitsch E, Rajandream MA, Reitter C, Salzberg SL, Sanders M, Schobel S, Sharp S, Simmonds M, Simpson AJ, Tallon L, Turner CMR, Tait A, Tivey AR, Van Aken S, Walker D, Wanless D, Wang S, White B, White O, Whitehead S, Woodward J, Wortman J, Adams MD, Embley TM, Gull K, Ullu E, Barry JD, Fairlamb AH, Opperdoes F, Barrell BG, Donelson JE, Hall N, Fraser CM, Melville SE, El-Sayed NM. The genome of the African trypanosome Trypanosoma brucei. Science 2005; 309:416-22. [PMID: 16020726 DOI: 10.1126/science.1112642] [Citation(s) in RCA: 1249] [Impact Index Per Article: 65.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
African trypanosomes cause human sleeping sickness and livestock trypanosomiasis in sub-Saharan Africa. We present the sequence and analysis of the 11 megabase-sized chromosomes of Trypanosoma brucei. The 26-megabase genome contains 9068 predicted genes, including approximately 900 pseudogenes and approximately 1700 T. brucei-specific genes. Large subtelomeric arrays contain an archive of 806 variant surface glycoprotein (VSG) genes used by the parasite to evade the mammalian immune system. Most VSG genes are pseudogenes, which may be used to generate expressed mosaic genes by ectopic recombination. Comparisons of the cytoskeleton and endocytic trafficking systems with those of humans and other eukaryotic organisms reveal major differences. A comparison of metabolic pathways encoded by the genomes of T. brucei, T. cruzi, and Leishmania major reveals the least overall metabolic capability in T. brucei and the greatest in L. major. Horizontal transfer of genes of bacterial origin has contributed to some of the metabolic differences in these parasites, and a number of novel potential drug targets have been identified.
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Affiliation(s)
- Matthew Berriman
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK.
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Hand CE, Honek JF. Biological chemistry of naturally occurring thiols of microbial and marine origin. JOURNAL OF NATURAL PRODUCTS 2005; 68:293-308. [PMID: 15730267 DOI: 10.1021/np049685x] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The presence of thiols in living systems is critical for the maintenance of cellular redox potentials and protein thiol-disulfide ratios, as well as for the protection of cells from reactive oxygen species. In addition to the well-studied tripeptide glutathione (gamma-Glu-Cys-Gly), a number of compounds have been identified that contribute to these essential cellular roles. This review provides a survey of the chemistry and biochemistry of several critically important and naturally occurring intracellular thiols such as coenzyme M, trypanothione, mycothiol, ergothioneine, and the ovothiols. Coenzyme M is a key thiol required for methane production in methogenic bacteria. Trypanothione and mycothiol are very important to the biochemistry of a number of human pathogens, and the enzymes utilizing these thiols have been recognized as important novel drug targets. Ergothioneine, although synthesized by fungi and the Actinomycetales bacteria, is present at significant physiological levels in humans and may contribute to single electron redox reactions in cells. The ovothiols appear to function as important modulators of reactive oxygen toxicity and appear to serve as small molecule mimics of glutathione peroxidase, a key enzyme in the detoxification of reactive oxygen species.
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Affiliation(s)
- Christine E Hand
- Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
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Krauth-Siegel RL, Bauer H, Schirmer RH. Dithiol Proteins as Guardians of the Intracellular Redox Milieu in Parasites: Old and New Drug Targets in Trypanosomes and Malaria-Causing Plasmodia. Angew Chem Int Ed Engl 2005; 44:690-715. [PMID: 15657967 DOI: 10.1002/anie.200300639] [Citation(s) in RCA: 245] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Parasitic diseases such as sleeping sickness, Chagas' heart disease, and malaria are major health problems in poverty-stricken areas. Antiparasitic drugs that are not only active but also affordable and readily available are urgently required. One approach to finding new drugs and rediscovering old ones is based on enzyme inhibitors that paralyze antioxidant systems in the pathogens. These antioxidant ensembles are essential to the parasites as they are attacked in the human host by strong oxidants such as peroxynitrite, hypochlorite, and H2O2. The pathogen-protecting system consists of some 20 thiol and dithiol proteins, which buffer the intraparasitic redox milieu at a potential of -250 mV. In trypanosomes and leishmania the network is centered around the unique dithiol trypanothione (N1,N8-bis(glutathionyl)spermidine). In contrast, malaria parasites have a more conservative dual antioxidative system based on glutathione and thioredoxin. Inhibitors of antioxidant enzymes such as trypanothione reductase are, indeed, parasiticidal but they can also delay or prevent resistance against a number of other antiparasitic drugs.
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Affiliation(s)
- R Luise Krauth-Siegel
- Universität Heidelberg, Biochemie-Zentrum, Im Neuenheimer Feld 504, D-69120 Heidelberg, Germany.
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