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Wendt C, Miranda K. Endocytosis in malaria parasites: An ultrastructural perspective of membrane interplay in a unique infection model. CURRENT TOPICS IN MEMBRANES 2024; 93:27-49. [PMID: 39181577 DOI: 10.1016/bs.ctm.2024.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/27/2024]
Abstract
Malaria remains a major global threat, representing a severe public health problem worldwide. Annually, it is responsible for a high rate of morbidity and mortality in many tropical developing countries where the disease is endemic. The causative agent of malaria, Plasmodium spp., exhibits a complex life cycle, alternating between an invertebrate vector, which transmits the disease, and the vertebrate host. The disease pathology observed in the vertebrate host is attributed to the asexual development of Plasmodium spp. inside the erythrocyte. Once inside the red blood cell, malaria parasites cause extensive changes in the host cell, increasing membrane rigidity and altering its normal discoid shape. Additionally, during their intraerythrocytic development, malaria parasites incorporate and degrade up to 70 % of host cell hemoglobin. This mechanism is essential for parasite development and represents an important drug target. Blocking the steps related to hemoglobin endocytosis or degradation impairs parasite development and can lead to its death. The ultrastructural analysis of hemoglobin endocytosis on Plasmodium spp. has been broadly explored along the years. However, it is only recently that the proteins involved in this process have started to emerge. Here, we will review the most important features related to hemoglobin endocytosis and catabolism on malaria parasites. A special focus will be given to the recent analysis obtained through 3D visualization approaches and to the molecules involved in these mechanisms.
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Affiliation(s)
- Camila Wendt
- Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho and Centro Nacional de Biologia Estrutural e Bioimagem, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil; Laboratório de Biomineralização, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
| | - Kildare Miranda
- Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho and Centro Nacional de Biologia Estrutural e Bioimagem, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
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2
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van Niekerk DD, du Toit F, Green K, Palm D, Snoep JL. A detailed kinetic model of glycolysis in Plasmodium falciparum-infected red blood cells for antimalarial drug target identification. J Biol Chem 2023; 299:105111. [PMID: 37517694 PMCID: PMC10474083 DOI: 10.1016/j.jbc.2023.105111] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Revised: 07/11/2023] [Accepted: 07/23/2023] [Indexed: 08/01/2023] Open
Abstract
Upon infection by the malaria parasite Plasmodium falciparum, the glycolytic rate of a red blood cell increases up to 100-fold, possibly contributing to lactic acidosis and hypoglycemia in patients with severe malaria. This dramatic increase in glucose uptake and metabolism was correctly predicted by a newly constructed detailed enzyme kinetic model of glucose metabolism in the trophozoite-infected red blood cell. Subsequently, we expanded the model to simulate an infected red blood cell culture, including the different asexual blood-stage forms of the malaria parasite. The model simulations were in good agreement with experimental data, for which the measured parasitic volume was an important parameter. Upon further analysis of the model, we identified glucose transport as a drug target that would specifically affect infected red blood cells, which was confirmed experimentally with inhibitor titrations. This model can be a first step in constructing a whole-body model for glucose metabolism in malaria patients to evaluate the contribution of the parasite's metabolism to the disease state.
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Affiliation(s)
- David D van Niekerk
- Department of Biochemistry, Stellenbosch University, Matieland, South Africa
| | - Francois du Toit
- Department of Biochemistry, Stellenbosch University, Matieland, South Africa
| | - Kathleen Green
- Department of Biochemistry, Stellenbosch University, Matieland, South Africa
| | - Danie Palm
- Department of Biochemistry, Stellenbosch University, Matieland, South Africa
| | - Jacky L Snoep
- Department of Biochemistry, Stellenbosch University, Matieland, South Africa; Molecular Cell Biology, Vrije Universiteit, Amsterdam, The Netherlands.
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3
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Nerlich C, Epalle NH, Seick P, Beitz E. Discovery and Development of Inhibitors of the Plasmodial FNT-Type Lactate Transporter as Novel Antimalarials. Pharmaceuticals (Basel) 2021; 14:1191. [PMID: 34832972 PMCID: PMC8624176 DOI: 10.3390/ph14111191] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Revised: 11/17/2021] [Accepted: 11/17/2021] [Indexed: 11/19/2022] Open
Abstract
Plasmodium spp. malaria parasites in the blood stage draw energy from anaerobic glycolysis when multiplying in erythrocytes. They tap the ample glucose supply of the infected host using the erythrocyte glucose transporter 1, GLUT1, and a hexose transporter, HT, of the parasite's plasma membrane. Per glucose molecule, two lactate anions and two protons are generated as waste that need to be released rapidly from the parasite to prevent blockage of the energy metabolism and acidification of the cytoplasm. Recently, the missing Plasmodium lactate/H+ cotransporter was identified as a member of the exclusively microbial formate-nitrite transporter family, FNT. Screening of an antimalarial compound selection with unknown targets led to the discovery of specific and potent FNT-inhibitors, i.e., pentafluoro-3-hydroxy-pent-2-en-1-ones. Here, we summarize the discovery and further development of this novel class of antimalarials, their modes of binding and action, circumvention of a putative resistance mutation of the FNT target protein, and suitability for in vivo studies using animal malaria models.
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Affiliation(s)
| | | | | | - Eric Beitz
- Department of Pharmaceutical and Medicinal Chemistry, Pharmaceutical Institute, Christian-Albrechts-University of Kiel, Gutenbergstr. 76, 24118 Kiel, Germany; (C.N.); (N.H.E.); (P.S.)
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4
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Walloch P, Hansen C, Priegann T, Schade D, Beitz E. Pentafluoro-3-hydroxy-pent-2-en-1-ones Potently Inhibit FNT-Type Lactate Transporters from all Five Human-Pathogenic Plasmodium Species. ChemMedChem 2021; 16:1283-1289. [PMID: 33336890 PMCID: PMC8247949 DOI: 10.1002/cmdc.202000952] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Indexed: 12/16/2022]
Abstract
The protozoan parasite Plasmodium falciparum causes the most severe and prevailing form of malaria in sub-Saharan Africa. Previously, we identified the plasmodial lactate transporter, PfFNT, a member of the microbial formate-nitrite transporter family, as a novel antimalarial drug target. With the pentafluoro-3-hydroxy-pent-2-en-1-ones, we discovered PfFNT inhibitors that potently kill P. falciparum parasites in vitro. Four additional human-pathogenic Plasmodium species require attention, that is, P. vivax, most prevalent outside of Africa, and the regional P. malariae, P. ovale and P. knowlesi. Herein, we show that the plasmodial FNT variants are highly similar in terms of protein sequence and functionality. The FNTs from all human-pathogenic plasmodia and the rodent malaria parasite were efficiently inhibited by pentafluoro-3-hydroxy-pent-2-en-1-ones. We further established a phenotypic yeast-based FNT inhibitor screen, and found very low compound cytotoxicity and monocarboxylate transporter 1 off-target activity on human cells, particularly of the most potent FNT inhibitor BH267.meta, allowing these compounds to proceed towards animal model malaria studies.
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Affiliation(s)
- Philipp Walloch
- Department of Pharmaceutical and Medicinal ChemistryChristian-Albrechts-University of KielGutenbergstr. 7624118KielGermany
| | - Christian Hansen
- Department of Pharmaceutical and Medicinal ChemistryChristian-Albrechts-University of KielGutenbergstr. 7624118KielGermany
| | - Till Priegann
- Department of Pharmaceutical and Medicinal ChemistryChristian-Albrechts-University of KielGutenbergstr. 7624118KielGermany
| | - Dennis Schade
- Department of Pharmaceutical and Medicinal ChemistryChristian-Albrechts-University of KielGutenbergstr. 7624118KielGermany
| | - Eric Beitz
- Department of Pharmaceutical and Medicinal ChemistryChristian-Albrechts-University of KielGutenbergstr. 7624118KielGermany
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5
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Walloch P, Henke B, Häuer S, Bergmann B, Spielmann T, Beitz E. Introduction of Scaffold Nitrogen Atoms Renders Inhibitors of the Malarial l-Lactate Transporter, PfFNT, Effective against the Gly107Ser Resistance Mutation. J Med Chem 2020; 63:9731-9741. [DOI: 10.1021/acs.jmedchem.0c00852] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Philipp Walloch
- Department of Pharmaceutical and Medicinal Chemistry, Christian-Albrechts-University of Kiel, 24118 Kiel, Germany
| | - Björn Henke
- Department of Pharmaceutical and Medicinal Chemistry, Christian-Albrechts-University of Kiel, 24118 Kiel, Germany
| | - Susan Häuer
- Department of Pharmaceutical and Medicinal Chemistry, Christian-Albrechts-University of Kiel, 24118 Kiel, Germany
| | - Bärbel Bergmann
- Bernhard-Nocht-Institute for Tropical Medicine, 20359 Hamburg, Germany
| | - Tobias Spielmann
- Bernhard-Nocht-Institute for Tropical Medicine, 20359 Hamburg, Germany
| | - Eric Beitz
- Department of Pharmaceutical and Medicinal Chemistry, Christian-Albrechts-University of Kiel, 24118 Kiel, Germany
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6
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Jay AG, Simard JR, Huang N, Hamilton JA. SSO and other putative inhibitors of FA transport across membranes by CD36 disrupt intracellular metabolism, but do not affect FA translocation. J Lipid Res 2020; 61:790-807. [PMID: 32102800 DOI: 10.1194/jlr.ra120000648] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Revised: 02/19/2020] [Indexed: 12/19/2022] Open
Abstract
Membrane-bound proteins have been proposed to mediate the transport of long-chain FA (LCFA) transport through the plasma membrane (PM). These proposals are based largely on reports that PM transport of LCFAs can be blocked by a number of enzymes and purported inhibitors of LCFA transport. Here, using the ratiometric pH indicator (2',7'-bis-(2-carboxyethyl)-5-(and-6-)-carboxyfluorescein and acrylodated intestinal FA-binding protein-based dual fluorescence assays, we investigated the effects of nine inhibitors of the putative FA transporter protein CD36 on the binding and transmembrane movement of LCFAs. We particularly focused on sulfosuccinimidyl oleate (SSO), reported to be a competitive inhibitor of CD36-mediated LCFA transport. Using these assays in adipocytes and inhibitor-treated protein-free lipid vesicles, we demonstrate that rapid LCFA transport across model and biological membranes remains unchanged in the presence of these purported inhibitors. We have previously shown in live cells that CD36 does not accelerate the transport of unesterified LCFAs across the PM. Our present experiments indicated disruption of LCFA metabolism inside the cell within minutes upon treatment with many of the "inhibitors" previously assumed to inhibit LCFA transport across the PM. Furthermore, using confocal microscopy and a specific anti-SSO antibody, we found that numerous intracellular and PM-bound proteins are SSO-modified in addition to CD36. Our results support the hypothesis that LCFAs diffuse rapidly across biological membranes and do not require an active protein transporter for their transmembrane movement.
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Affiliation(s)
- Anthony G Jay
- Department of Physiology and Biomedical Engineering,Mayo Clinic, Rochester, MN 55905; Departments of Biochemistry,Boston University School of Medicine, Boston, MA 02118. mailto:
| | - Jeffrey R Simard
- Physiology and Biophysics,Boston University School of Medicine, Boston, MA 02118; Pharmacology and Experimental Therapeutics,Boston University School of Medicine, Boston, MA 02118
| | - Nasi Huang
- Section of Infectious Diseases Department of Medicine,Boston University School of Medicine, Boston, MA 02118
| | - James A Hamilton
- Physiology and Biophysics,Boston University School of Medicine, Boston, MA 02118
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7
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Martin RE. The transportome of the malaria parasite. Biol Rev Camb Philos Soc 2019; 95:305-332. [PMID: 31701663 DOI: 10.1111/brv.12565] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Revised: 10/02/2019] [Accepted: 10/04/2019] [Indexed: 12/15/2022]
Abstract
Membrane transport proteins, also known as transporters, control the movement of ions, nutrients, metabolites, and waste products across the membranes of a cell and are central to its biology. Proteins of this type also serve as drug targets and are key players in the phenomenon of drug resistance. The malaria parasite has a relatively reduced transportome, with only approximately 2.5% of its genes encoding transporters. Even so, assigning functions and physiological roles to these proteins, and ascertaining their contributions to drug action and drug resistance, has been very challenging. This review presents a detailed critique and synthesis of the disruption phenotypes, protein subcellular localisations, protein functions (observed or predicted), and links to antimalarial drug resistance for each of the parasite's transporter genes. The breadth and depth of the gene disruption data are particularly impressive, with at least one phenotype determined in the parasite's asexual blood stage for each transporter gene, and multiple phenotypes available for 76% of the genes. Analysis of the curated data set revealed there to be relatively little redundancy in the Plasmodium transportome; almost two-thirds of the parasite's transporter genes are essential or required for normal growth in the asexual blood stage of the parasite, and this proportion increased to 78% when the disruption phenotypes available for the other parasite life stages were included in the analysis. These observations, together with the finding that 22% of the transportome is implicated in the parasite's resistance to existing antimalarials and/or drugs within the development pipeline, indicate that transporters are likely to serve, or are already serving, as drug targets. Integration of the different biological and bioinformatic data sets also enabled the selection of candidates for transport processes known to be essential for parasite survival, but for which the underlying proteins have thus far remained undiscovered. These include potential transporters of pantothenate, isoleucine, or isopentenyl diphosphate, as well as putative anion-selective channels that may serve as the pore component of the parasite's 'new permeation pathways'. Other novel insights into the parasite's biology included the identification of transporters for the potential development of antimalarial treatments, transmission-blocking drugs, prophylactics, and genetically attenuated vaccines. The syntheses presented herein set a foundation for elucidating the functions and physiological roles of key members of the Plasmodium transportome and, ultimately, to explore and realise their potential as therapeutic targets.
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Affiliation(s)
- Rowena E Martin
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory, Australia
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8
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Leopold SJ, Ghose A, Allman EL, Kingston HWF, Hossain A, Dutta AK, Plewes K, Chotivanich K, Day NPJ, Tarning J, Winterberg M, White NJ, Llinás M, Dondorp AM. Identifying the Components of Acidosis in Patients With Severe Plasmodium falciparum Malaria Using Metabolomics. J Infect Dis 2019; 219:1766-1776. [PMID: 30566600 PMCID: PMC6500555 DOI: 10.1093/infdis/jiy727] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Accepted: 12/15/2018] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Acidosis in severe Plasmodium falciparum malaria is associated with high mortality, yet the pathogenesis remains incompletely understood. The aim of this study was to determine the nature and source of metabolic acids contributing to acidosis in patients with severe falciparum malaria. METHODS A prospective observational study was conducted to characterize circulating acids in adults with P. falciparum malaria (n = 107) and healthy controls (n = 45) from Bangladesh using high-resolution liquid chromatography-mass spectrometry metabolomics. Additional in vitro P. falciparum culture studies were performed to determine if parasites release the acids detected in plasma from patients with severe malaria acidosis. RESULTS We identified previously unmeasured plasma acids strongly associated with acidosis in severe malaria. Metabolomic analysis of P. falciparum parasites in vitro showed no evidence that these acids are released by the parasite during its life cycle. Instead, 10 of the plasma acids could be mapped to a gut microbial origin. Patients with malaria had low L-citrulline levels, a plasma marker indicating reduced gut barrier integrity. Longitudinal data showed the clearance of these newly identified acids was delayed in fatal cases. CONCLUSIONS These data suggest that a compromise in intestinal barrier function may contribute significantly to the pathogenesis of life-threatening acidosis in severe falciparum malaria. CLINICAL TRIALS REGISTRATION NCT02451904.
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Affiliation(s)
- Stije J Leopold
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, United Kingdom
| | - Aniruddha Ghose
- Department of Internal Medicine, Chittagong Medical College Hospital, Bangladesh
| | - Erik L Allman
- Department of Biochemistry and Molecular Biology and Huck Center for Malaria Research
| | - Hugh W F Kingston
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, United Kingdom
| | - Amir Hossain
- Department of Internal Medicine, Chittagong Medical College Hospital, Bangladesh
| | - Asok Kumar Dutta
- Department of Internal Medicine, Chittagong Medical College Hospital, Bangladesh
| | - Katherine Plewes
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, United Kingdom
| | - Kesinee Chotivanich
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Nicholas P J Day
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, United Kingdom
| | - Joel Tarning
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, United Kingdom
| | - Markus Winterberg
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, United Kingdom
| | - Nicholas J White
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, United Kingdom
| | - Manuel Llinás
- Department of Biochemistry and Molecular Biology and Huck Center for Malaria Research
- Department of Chemistry, Pennsylvania State University, State College, PA
| | - Arjen M Dondorp
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, United Kingdom
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Cell Swelling Induced by the Antimalarial KAE609 (Cipargamin) and Other PfATP4-Associated Antimalarials. Antimicrob Agents Chemother 2018; 62:AAC.00087-18. [PMID: 29555632 DOI: 10.1128/aac.00087-18] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Accepted: 02/18/2018] [Indexed: 12/15/2022] Open
Abstract
For an increasing number of antimalarial agents identified in high-throughput phenotypic screens, there is evidence that they target PfATP4, a putative Na+ efflux transporter on the plasma membrane of the human malaria parasite Plasmodium falciparum For several such "PfATP4-associated" compounds, it has been noted that their addition to parasitized erythrocytes results in cell swelling. Here we show that six structurally diverse PfATP4-associated compounds, including the clinical candidate KAE609 (cipargamin), induce swelling of both isolated blood-stage parasites and intact parasitized erythrocytes. The swelling of isolated parasites is dependent on the presence of Na+ in the external environment and may be attributed to the osmotic consequences of Na+ uptake. The swelling of the parasitized erythrocyte results in an increase in its osmotic fragility. Countering cell swelling by increasing the osmolarity of the extracellular medium reduces the antiplasmodial efficacy of PfATP4-associated compounds, consistent with cell swelling playing a role in the antimalarial activity of this class of compounds.
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10
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Hapuarachchi SV, Cobbold SA, Shafik SH, Dennis ASM, McConville MJ, Martin RE, Kirk K, Lehane AM. The Malaria Parasite's Lactate Transporter PfFNT Is the Target of Antiplasmodial Compounds Identified in Whole Cell Phenotypic Screens. PLoS Pathog 2017; 13:e1006180. [PMID: 28178359 PMCID: PMC5298231 DOI: 10.1371/journal.ppat.1006180] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Accepted: 01/11/2017] [Indexed: 11/19/2022] Open
Abstract
In this study the ‘Malaria Box’ chemical library comprising 400 compounds with antiplasmodial activity was screened for compounds that perturb the internal pH of the malaria parasite, Plasmodium falciparum. Fifteen compounds induced an acidification of the parasite cytosol. Two of these did so by inhibiting the parasite’s formate nitrite transporter (PfFNT), which mediates the H+-coupled efflux from the parasite of lactate generated by glycolysis. Both compounds were shown to inhibit lactate transport across the parasite plasma membrane, and the transport of lactate by PfFNT expressed in Xenopus laevis oocytes. PfFNT inhibition caused accumulation of lactate in parasitised erythrocytes, and swelling of both the parasite and parasitised erythrocyte. Long-term exposure of parasites to one of the inhibitors gave rise to resistant parasites with a mutant form of PfFNT that showed reduced inhibitor sensitivity. This study provides the first evidence that PfFNT is a druggable antimalarial target. The emergence and spread of Plasmodium falciparum strains resistant to leading antimalarial drugs has intensified the need to discover and develop drugs that kill the parasite via new mechanisms. Here we screened compounds that are known to inhibit P. falciparum growth for their effects on the pH inside the parasite. We identified fifteen compounds that decrease the pH inside the parasite, and determined the mechanism by which two of these, MMV007839 and MMV000972, disrupt pH and kill the parasite. The two compounds were found to inhibit the P. falciparum formate nitrite transporter (PfFNT), a transport protein that is located on the parasite surface and that serves to remove the waste product lactic acid from the parasite. The compounds inhibited both the H+-coupled transport of lactate across the parasite plasma membrane and the transport of lactate by PfFNT expressed in Xenopus oocytes. In addition to disrupting pH, PfFNT inhibition led to a build-up of lactate in the parasite-infected red blood cell and the swelling of both the parasite and the infected red blood cell. Exposing parasites to MMV007839 over a prolonged time period gave rise to resistant parasites with a mutant form of PfFNT that was less sensitive to the compound. This study validates PfFNT as a novel antimalarial drug target.
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Affiliation(s)
| | - Simon A Cobbold
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Melbourne, VIC, Australia
| | - Sarah H Shafik
- Research School of Biology, Australian National University, Canberra, ACT, Australia
| | - Adelaide S M Dennis
- Research School of Biology, Australian National University, Canberra, ACT, Australia
| | - Malcolm J McConville
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Melbourne, VIC, Australia
| | - Rowena E Martin
- Research School of Biology, Australian National University, Canberra, ACT, Australia
| | - Kiaran Kirk
- Research School of Biology, Australian National University, Canberra, ACT, Australia
| | - Adele M Lehane
- Research School of Biology, Australian National University, Canberra, ACT, Australia
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11
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Golldack A, Henke B, Bergmann B, Wiechert M, Erler H, Blancke Soares A, Spielmann T, Beitz E. Substrate-analogous inhibitors exert antimalarial action by targeting the Plasmodium lactate transporter PfFNT at nanomolar scale. PLoS Pathog 2017; 13:e1006172. [PMID: 28178358 PMCID: PMC5298233 DOI: 10.1371/journal.ppat.1006172] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Accepted: 01/07/2017] [Indexed: 12/14/2022] Open
Abstract
Resistance against all available antimalarial drugs calls for novel compounds that hit unexploited targets in the parasite. Here, we show that the recently discovered Plasmodium falciparum lactate/proton symporter, PfFNT, is a valid druggable target, and describe a new class of fluoroalkyl vinylogous acids that potently block PfFNT and kill cultured parasites. The original compound, MMV007839, is derived from the malaria box collection of potent antimalarials with unknown targets and contains a unique internal prodrug principle that reversibly switches between a lipophilic transport form and a polar, substrate-analogous active form. Resistance selection of cultured P. falciparum parasites with sub-lethal concentrations of MMV007839 produced a single nucleotide exchange in the PfFNT gene; this, and functional characterization of the resulting PfFNT G107S validated PfFNT as a novel antimalarial target. From quantitative structure function relations we established the compound binding mode and the pharmacophore. The pharmacophore largely circumvents the resistance mutation and provides the basis for a medicinal chemistry program that targets lactate and proton transport as a new mode of antimalarial action.
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Affiliation(s)
- André Golldack
- Pharmaceutical Institute, Christian-Albrechts-University, Kiel, Germany
| | - Björn Henke
- Pharmaceutical Institute, Christian-Albrechts-University, Kiel, Germany
| | - Bärbel Bergmann
- Bernhard-Nocht-Institute for Tropical Medicine, Hamburg, Germany
| | - Marie Wiechert
- Pharmaceutical Institute, Christian-Albrechts-University, Kiel, Germany
| | - Holger Erler
- Pharmaceutical Institute, Christian-Albrechts-University, Kiel, Germany
| | | | - Tobias Spielmann
- Bernhard-Nocht-Institute for Tropical Medicine, Hamburg, Germany
| | - Eric Beitz
- Pharmaceutical Institute, Christian-Albrechts-University, Kiel, Germany
- * E-mail:
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12
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Waldecker M, Dasanna AK, Lansche C, Linke M, Srismith S, Cyrklaff M, Sanchez CP, Schwarz US, Lanzer M. Differential time-dependent volumetric and surface area changes and delayed induction of new permeation pathways in P. falciparum-infected hemoglobinopathic erythrocytes. Cell Microbiol 2016; 19. [PMID: 27450804 PMCID: PMC5298026 DOI: 10.1111/cmi.12650] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Revised: 07/01/2016] [Accepted: 07/15/2016] [Indexed: 12/31/2022]
Abstract
During intraerythrocytic development, Plasmodium falciparum increases the ion permeability of the erythrocyte plasma membrane to an extent that jeopardizes the osmotic stability of the host cell. A previously formulated numeric model has suggested that the parasite prevents premature rupture of the host cell by consuming hemoglobin (Hb) in excess of its own anabolic needs. Here, we have tested the colloid‐osmotic model on the grounds of time‐resolved experimental measurements on cell surface area and volume. We have further verified whether the colloid‐osmotic model can predict time‐dependent volumetric changes when parasites are grown in erythrocytes containing the hemoglobin variants S or C. A good agreement between model‐predicted and empirical data on both infected erythrocyte and intracellular parasite volume was found for parasitized HbAA and HbAC erythrocytes. However, a delayed induction of the new permeation pathways needed to be taken into consideration for the latter case. For parasitized HbAS erythrocyte, volumes diverged from model predictions, and infected erythrocytes showed excessive vesiculation during the replication cycle. We conclude that the colloid‐osmotic model provides a plausible and experimentally supported explanation of the volume expansion and osmotic stability of P. falciparum‐infected erythrocytes. The contribution of vesiculation to the malaria‐protective function of hemoglobin S is discussed.
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Affiliation(s)
- Mailin Waldecker
- Department of Infectious Diseases, Parasitology, Heidelberg University, Medical School, Im Neuenheimer Feld 324, Heidelberg, 69120, Baden-Württemberg, Germany
| | - Anil K Dasanna
- BioQuant, Heidelberg University, Im Neuenheimer Feld 267, Heidelberg, 69120, Baden-Württemberg, Germany.,Institute for Theoretical Physics, Heidelberg University, Philosophenweg 19, Heidelberg, 69120, Baden-Württemberg, Germany
| | - Christine Lansche
- Department of Infectious Diseases, Parasitology, Heidelberg University, Medical School, Im Neuenheimer Feld 324, Heidelberg, 69120, Baden-Württemberg, Germany
| | - Marco Linke
- BioQuant, Heidelberg University, Im Neuenheimer Feld 267, Heidelberg, 69120, Baden-Württemberg, Germany.,Institute for Theoretical Physics, Heidelberg University, Philosophenweg 19, Heidelberg, 69120, Baden-Württemberg, Germany
| | - Sirikamol Srismith
- Department of Infectious Diseases, Parasitology, Heidelberg University, Medical School, Im Neuenheimer Feld 324, Heidelberg, 69120, Baden-Württemberg, Germany
| | - Marek Cyrklaff
- Department of Infectious Diseases, Parasitology, Heidelberg University, Medical School, Im Neuenheimer Feld 324, Heidelberg, 69120, Baden-Württemberg, Germany
| | - Cecilia P Sanchez
- Department of Infectious Diseases, Parasitology, Heidelberg University, Medical School, Im Neuenheimer Feld 324, Heidelberg, 69120, Baden-Württemberg, Germany
| | - Ulrich S Schwarz
- BioQuant, Heidelberg University, Im Neuenheimer Feld 267, Heidelberg, 69120, Baden-Württemberg, Germany.,Institute for Theoretical Physics, Heidelberg University, Philosophenweg 19, Heidelberg, 69120, Baden-Württemberg, Germany
| | - Michael Lanzer
- Department of Infectious Diseases, Parasitology, Heidelberg University, Medical School, Im Neuenheimer Feld 324, Heidelberg, 69120, Baden-Württemberg, Germany
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13
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Holm-Bertelsen J, Bock S, Helmstetter F, Beitz E. High-level cell-free production of the malarial lactate transporter PfFNT as a basis for crystallization trials and directional transport studies. Protein Expr Purif 2016; 126:109-114. [PMID: 27345711 DOI: 10.1016/j.pep.2016.06.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Revised: 06/22/2016] [Accepted: 06/22/2016] [Indexed: 01/10/2023]
Abstract
The malaria parasite Plasmodium falciparum relies on the function of channel and transport proteins for the uptake of nutrients and the release of metabolic waste products. Inhibition of vital transport processes is an unexploited means for developing novel antimalarial drugs. The recently discovered plasmodial lactate transporter, PfFNT, represents a promising new drug target since the parasite's energy generation by anaerobic glycolysis depends on the rapid secretion of lactate. Yet, membrane proteins, in particular those of malaria parasites, are notoriously difficult to produce and purify in the native, functional form hampering crystallization and biophysical studies. Here, we show synthesis of milligram quantities of correctly folded PfFNT in a cell-free system. Solubilized PfFNT maintained its oligomeric, largely SDS-resistant quaternary structure and appears suitable for setting up crystallization trials. After reconstitution into proteoliposomes, PfFNT was functional as a transporter for formate, acetate, and lactate as determined by a light-scattering assay. Analysis of the accessibility of a protease cleavage site at the N-terminus revealed an even outside-in orientation of the total proteoliposomal PfFNT population that may be due to membrane curvature restrictions. Contrary to previous studies using heterologous expression in cell systems with oppositely oriented PfFNT, the proteoliposomes eventually allow for biophysical transport studies in the native, physiological direction.
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Affiliation(s)
- Julia Holm-Bertelsen
- Christian-Albrechts-University of Kiel, Department of Medicinal and Pharmaceutical Chemistry, Gutenbergstraße 76, 24118 Kiel, Germany
| | - Sinja Bock
- Christian-Albrechts-University of Kiel, Department of Medicinal and Pharmaceutical Chemistry, Gutenbergstraße 76, 24118 Kiel, Germany
| | - Folknand Helmstetter
- Christian-Albrechts-University of Kiel, Department of Medicinal and Pharmaceutical Chemistry, Gutenbergstraße 76, 24118 Kiel, Germany
| | - Eric Beitz
- Christian-Albrechts-University of Kiel, Department of Medicinal and Pharmaceutical Chemistry, Gutenbergstraße 76, 24118 Kiel, Germany.
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14
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Abstract
Some hours after invading the erythrocytes of its human host, the malaria parasite Plasmodium falciparum induces an increase in the permeability of the erythrocyte membrane to monovalent ions. The resulting net influx of Na(+) and net efflux of K(+), down their respective concentration gradients, converts the erythrocyte cytosol from an initially high-K(+), low-Na(+) solution to a high-Na(+), low-K(+) solution. The intraerythrocytic parasite itself exerts tight control over its internal Na(+), K(+), Cl(-), and Ca(2+) concentrations and its intracellular pH through the combined actions of a range of membrane transport proteins. The molecular mechanisms underpinning ion regulation in the parasite are receiving increasing attention, not least because PfATP4, a P-type ATPase postulated to be involved in Na(+) regulation, has emerged as a potential antimalarial drug target, susceptible to inhibition by a wide range of chemically unrelated compounds.
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Affiliation(s)
- Kiaran Kirk
- Research School of Biology, The Australian National University, Canberra, ACT 2601, Australia;
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15
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A lactate and formate transporter in the intraerythrocytic malaria parasite, Plasmodium falciparum. Nat Commun 2015; 6:6721. [PMID: 25823844 DOI: 10.1038/ncomms7721] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Accepted: 02/23/2015] [Indexed: 12/24/2022] Open
Abstract
The intraerythrocytic malaria parasite relies primarily on glycolysis to fuel its rapid growth and reproduction. The major byproduct of this metabolism, lactic acid, is extruded into the external medium. In this study, we show that the human malaria parasite Plasmodium falciparum expresses at its surface a member of the microbial formate-nitrite transporter family (PfFNT), which, when expressed in Xenopus laevis oocytes, transports both formate and lactate. The transport characteristics of PfFNT in oocytes (pH-dependence, inhibitor-sensitivity and kinetics) are similar to those of the transport of lactate and formate across the plasma membrane of mature asexual-stage P. falciparum trophozoites, consistent with PfFNT playing a major role in the efflux of lactate and hence in the energy metabolism of the intraerythrocytic parasite.
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16
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Penkler G, du Toit F, Adams W, Rautenbach M, Palm DC, van Niekerk DD, Snoep JL. Construction and validation of a detailed kinetic model of glycolysis in Plasmodium falciparum. FEBS J 2015; 282:1481-511. [PMID: 25693925 DOI: 10.1111/febs.13237] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Revised: 02/07/2015] [Accepted: 02/13/2015] [Indexed: 11/26/2022]
Abstract
UNLABELLED The enzymes in the Embden-Meyerhof-Parnas pathway of Plasmodium falciparum trophozoites were kinetically characterized and their integrated activities analyzed in a mathematical model. For validation of the model, we compared model predictions for steady-state fluxes and metabolite concentrations of the hexose phosphates with experimental values for intact parasites. The model, which is completely based on kinetic parameters that were measured for the individual enzymes, gives an accurate prediction of the steady-state fluxes and intermediate concentrations. This is the first detailed kinetic model for glucose metabolism in P. falciparum, one of the most prolific malaria-causing protozoa, and the high predictive power of the model makes it a strong tool for future drug target identification studies. The modelling workflow is transparent and reproducible, and completely documented in the SEEK platform, where all experimental data and model files are available for download. DATABASE The mathematical models described in the present study have been submitted to the JWS Online Cellular Systems Modelling Database (http://jjj.bio.vu.nl/database/penkler). The investigation and complete experimental data set is available on SEEK (10.15490/seek.1. INVESTIGATION 56).
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Affiliation(s)
- Gerald Penkler
- Department of Biochemistry, Stellenbosch University, Matieland, South Africa; Molecular Cell Physiology, Vrije Universiteit Amsterdam, The Netherlands
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17
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Identity of a Plasmodium lactate/H(+) symporter structurally unrelated to human transporters. Nat Commun 2015; 6:6284. [PMID: 25669138 DOI: 10.1038/ncomms7284] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Accepted: 01/12/2015] [Indexed: 11/09/2022] Open
Abstract
Maintenance of a high glycolytic flow rate is critical for the rapid growth and virulence of malarial parasites. The parasites release two moles of lactic acid per mole of glucose as the anaerobic end product. However, the molecular identity of the Plasmodium lactate transporter is unknown. Here we show that a member of the microbial formate-nitrite transporter family, PfFNT, acts as a lactate/proton symporter in Plasmodium falciparum. Besides L-lactate, PfFNT transports physiologically relevant D-lactate, as well as pyruvate, acetate and formate, and is inhibited by the antiplasmodial compounds phloretin, furosemide and cinnamate derivatives, but not by p-chloromercuribenzene sulfonate (pCMBS). Our data on PfFNT monocarboxylate transport are consistent with those obtained with living parasites. Moreover, PfFNT is the only transporter of the plasmodial glycolytic pathway for which structure information is available from crystals of homologous proteins, rendering it amenable to further evaluation as a novel antimalarial drug target.
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18
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Mariga ST, Kolko M, Gjedde A, Bergersen LH. Lactate transport and receptor actions in cerebral malaria. Front Neurosci 2014; 8:125. [PMID: 24904266 PMCID: PMC4032900 DOI: 10.3389/fnins.2014.00125] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Accepted: 04/22/2014] [Indexed: 01/09/2023] Open
Abstract
Cerebral malaria (CM), caused by Plasmodium falciparum infection, is a prevalent neurological disorder in the tropics. Most of the patients are children, typically with intractable seizures and high mortality. Current treatment is unsatisfactory. Understanding the pathogenesis of CM is required in order to identify therapeutic targets. Here, we argue that cerebral energy metabolic defects are probable etiological factors in CM pathogenesis, because malaria parasites consume large amounts of glucose metabolized mostly to lactate. Monocarboxylate transporters (MCTs) mediate facilitated transfer, which serves to equalize lactate concentrations across cell membranes in the direction of the concentration gradient. The equalizing action of MCTs is the basis for lactate’s role as a volume transmitter of metabolic signals in the brain. Lactate binds to the lactate receptor GPR81, recently discovered on brain cells and cerebral blood vessels, causing inhibition of adenylyl cyclase. High levels of lactate delivered by the parasite at the vascular endothelium may damage the blood–brain barrier, disrupt lactate homeostasis in the brain, and imply MCTs and the lactate receptor as novel therapeutic targets in CM.
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Affiliation(s)
- Shelton T Mariga
- Department of Neuroscience and Pharmacology, University of Copenhagen Copenhagen, Denmark
| | - Miriam Kolko
- Department of Neuroscience and Pharmacology, University of Copenhagen Copenhagen, Denmark ; Department of Ophthalmology, Roskilde Hospital Roskilde, Denmark
| | - Albert Gjedde
- Department of Neuroscience and Pharmacology, University of Copenhagen Copenhagen, Denmark
| | - Linda H Bergersen
- Department of Neuroscience and Pharmacology, University of Copenhagen Copenhagen, Denmark ; The Brain and Muscle Energy Group and SN-Lab, Department of Anatomy and Department of Oral Biology, Institute of Basic Medical Sciences and Centre for Molecular Biology and Neuroscience/SERTA Healthy Brain Aging Centre, University of Oslo Oslo, Norway
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19
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Abstract
As it grows and replicates within the erythrocytes of its host the malaria parasite takes up nutrients from the extracellular medium, exports metabolites and maintains a tight control over its internal ionic composition. These functions are achieved via membrane transport proteins, integral membrane proteins that mediate the passage of solutes across the various membranes that separate the biochemical machinery of the parasite from the extracellular environment. Proteins of this type play a key role in antimalarial drug resistance, as well as being candidate drug targets in their own right. This review provides an overview of recent work on the membrane transport biology of the malaria parasite-infected erythrocyte, encompassing both the parasite-induced changes in the membrane transport properties of the host erythrocyte and the cell physiology of the intracellular parasite itself.
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20
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Kim K, Yoon H, Diez-Silva M, Dao M, Dasari RR, Park Y. High-resolution three-dimensional imaging of red blood cells parasitized by Plasmodium falciparum and in situ hemozoin crystals using optical diffraction tomography. JOURNAL OF BIOMEDICAL OPTICS 2014; 19:011005. [PMID: 23797986 PMCID: PMC4019420 DOI: 10.1117/1.jbo.19.1.011005] [Citation(s) in RCA: 121] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2013] [Revised: 05/06/2013] [Accepted: 05/29/2013] [Indexed: 05/18/2023]
Abstract
We present high-resolution optical tomographic images of human red blood cells (RBC) parasitized by malaria-inducing Plasmodium falciparum (Pf)-RBCs. Three-dimensional (3-D) refractive index (RI) tomograms are reconstructed by recourse to a diffraction algorithm from multiple two-dimensional holograms with various angles of illumination. These 3-D RI tomograms of Pf-RBCs show cellular and subcellular structures of host RBCs and invaded parasites in fine detail. Full asexual intraerythrocytic stages of parasite maturation (ring to trophozoite to schizont stages) are then systematically investigated using optical diffraction tomography algorithms. These analyses provide quantitative information on the structural and chemical characteristics of individual host Pf-RBCs, parasitophorous vacuole, and cytoplasm. The in situ structural evolution and chemical characteristics of subcellular hemozoin crystals are also elucidated.
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Affiliation(s)
- Kyoohyun Kim
- Korea Advanced Institute of Science and Technology, Department of Physics, Daejeon 305-701, Republic of Korea
| | - HyeOk Yoon
- Korea Advanced Institute of Science and Technology, Department of Physics, Daejeon 305-701, Republic of Korea
| | - Monica Diez-Silva
- Massachusetts Institute of Technology, Department of Material Science and Engineering, Cambridge, Massachusetts 02142
| | - Ming Dao
- Massachusetts Institute of Technology, Department of Material Science and Engineering, Cambridge, Massachusetts 02142
| | - Ramachandra R. Dasari
- Massachusetts Institute of Technology, George R. Harrison Spectroscopy Laboratory, Cambridge, Massachusetts 02194
| | - YongKeun Park
- Korea Advanced Institute of Science and Technology, Department of Physics, Daejeon 305-701, Republic of Korea
- Address all correspondence to: YongKeun Park, Korea Advanced Institute of Science and Technology, Department of Physics, 291 Daehak-Ro Yusung-Gu, Daejeon 305-701, Republic of Korea. Tel: (82) 42-350-2514; Fax: (82) 42-350-7160; E-mail:
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21
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Cobbold SA, Vaughan AM, Lewis IA, Painter HJ, Camargo N, Perlman DH, Fishbaugher M, Healer J, Cowman AF, Kappe SHI, Llinás M. Kinetic flux profiling elucidates two independent acetyl-CoA biosynthetic pathways in Plasmodium falciparum. J Biol Chem 2013; 288:36338-50. [PMID: 24163372 DOI: 10.1074/jbc.m113.503557] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The malaria parasite Plasmodium falciparum depends on glucose to meet its energy requirements during blood-stage development. Although glycolysis is one of the best understood pathways in the parasite, it is unclear if glucose metabolism appreciably contributes to the acetyl-CoA pools required for tricarboxylic acid metabolism (TCA) cycle and fatty acid biosynthesis. P. falciparum possesses a pyruvate dehydrogenase (PDH) complex that is localized to the apicoplast, a specialized quadruple membrane organelle, suggesting that separate acetyl-CoA pools are likely. Herein, we analyze PDH-deficient parasites using rapid stable-isotope labeling and show that PDH does not appreciably contribute to acetyl-CoA synthesis, tricarboxylic acid metabolism, or fatty acid synthesis in blood stage parasites. Rather, we find that acetyl-CoA demands are supplied through a "PDH-like" enzyme and provide evidence that the branched-chain keto acid dehydrogenase (BCKDH) complex is performing this function. We also show that acetyl-CoA synthetase can be a significant contributor to acetyl-CoA biosynthesis. Interestingly, the PDH-like pathway contributes glucose-derived acetyl-CoA to the TCA cycle in a stage-independent process, whereas anapleurotic carbon enters the TCA cycle via a stage-dependent phosphoenolpyruvate carboxylase/phosphoenolpyruvate carboxykinase process that decreases as the parasite matures. Although PDH-deficient parasites have no blood-stage growth defect, they are unable to progress beyond the oocyst phase of the parasite mosquito stage.
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Affiliation(s)
- Simon A Cobbold
- From the Department of Biochemistry and Molecular Biology and Center for Infectious Disease Dynamics, Pennsylvania State University, State College, Pennsylvania 16802
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22
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Salcedo-Sora JE, Ward SA. The folate metabolic network of Falciparum malaria. Mol Biochem Parasitol 2013; 188:51-62. [PMID: 23454873 DOI: 10.1016/j.molbiopara.2013.02.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Revised: 02/04/2013] [Accepted: 02/11/2013] [Indexed: 01/07/2023]
Abstract
The targeting of key enzymes in the folate pathway continues to be an effective chemotherapeutic approach that has earned antifolate drugs a valuable position in the medical pharmacopoeia. The successful therapeutic use of antifolates as antimalarials has been a catalyst for ongoing research into the biochemistry of folate and pterin biosynthesis in malaria parasites. However, our understanding of the parasites folate metabolism remains partial and patchy, especially in relation to the shikimate pathway, the folate cycle, and folate salvage. A sizeable number of potential folate targets remain to be characterised. Recent reports on the parasite specific transport of folate precursors that would normally be present in the human host awaken previous hypotheses on the salvage of folate precursors or by-products. As the parasite progresses through its life-cycle it encounters very contrasting host cell environments that present radically different metabolic milieus and biochemical challenges. It would seem probable that as the parasite encounters differing environments it would need to modify its biochemistry. This would be reflected in the folate homeostasis in Plasmodium. Recent drug screening efforts and insights into folate membrane transport substantiate the argument that folate metabolism may still offer unexplored opportunities for therapeutic attack.
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Affiliation(s)
- J Enrique Salcedo-Sora
- Department of Parasitology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK.
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23
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Esposito A, Choimet JB, Skepper JN, Mauritz JMA, Lew VL, Kaminski CF, Tiffert T. Quantitative imaging of human red blood cells infected with Plasmodium falciparum. Biophys J 2010; 99:953-60. [PMID: 20682274 DOI: 10.1016/j.bpj.2010.04.065] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2009] [Revised: 04/14/2010] [Accepted: 04/20/2010] [Indexed: 11/24/2022] Open
Abstract
During its 48 h asexual reproduction cycle, the malaria parasite Plasmodium falciparum ingests and digests hemoglobin in excess of its metabolic requirements and causes major changes in the homeostasis of the host red blood cell (RBC). A numerical model suggested that this puzzling excess consumption of hemoglobin is necessary for the parasite to reduce the colloidosmotic pressure within the host RBC, thus preventing lysis before completion of its reproduction cycle. However, the validity of the colloidosmotic hypothesis appeared to be compromised by initial conflicts between model volume predictions and experimental observations. Here, we investigated volume and membrane area changes in infected RBCs (IRBCs) using fluorescence confocal microscopy on calcein-loaded RBCs. Substantial effort was devoted to developing and testing a new threshold-independent algorithm for the precise estimation of cell volumes and surface areas to overcome the shortfalls of traditional methods. We confirm that the volume of IRBCs remains almost constant during parasite maturation, suggesting that the reported increase in IRBCs' osmotic fragility results from a reduction in surface area and increased lytic propensity on volume expansion. These results support the general validity of the colloidosmotic hypothesis, settle the IRBC volume debate, and help to constrain the range of parameter values in the numerical model.
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Affiliation(s)
- Alessandro Esposito
- Department of Chemical Engineering, and Biotechnology, University of Cambridge, Cambridge, United Kingdom.
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24
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Mauritz JMA, Esposito A, Tiffert T, Skepper JN, Warley A, Yoon YZ, Cicuta P, Lew VL, Guck JR, Kaminski CF. Biophotonic techniques for the study of malaria-infected red blood cells. Med Biol Eng Comput 2010; 48:1055-63. [PMID: 20661776 DOI: 10.1007/s11517-010-0668-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2010] [Accepted: 07/11/2010] [Indexed: 12/23/2022]
Abstract
Investigation of the homeostasis of red blood cells upon infection by Plasmodium falciparum poses complex experimental challenges. Changes in red cell shape, volume, protein, and ion balance are difficult to quantify. In this article, we review a wide range of optical techniques for quantitative measurements of critical homeostatic parameters in malaria-infected red blood cells. Fluorescence lifetime imaging and tomographic phase microscopy, quantitative deconvolution microscopy, and X-ray microanalysis, are used to measure haemoglobin concentration, cell volume, and ion contents. Atomic force microscopy is briefly reviewed in the context of these optical methodologies. We also describe how optical tweezers and optical stretchers can be usefully applied to empower basic malaria research to yield diagnostic information on cell compliance changes upon malaria infection. The combined application of these techniques sheds new light on the detailed mechanisms of malaria infection providing potential for new diagnostic or therapeutic approaches.
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Affiliation(s)
- Jakob M A Mauritz
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge, UK
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25
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Exploiting the therapeutic potential of Plasmodium falciparum solute transporters. Trends Parasitol 2010; 26:284-96. [DOI: 10.1016/j.pt.2010.03.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2009] [Revised: 03/02/2010] [Accepted: 03/05/2010] [Indexed: 01/16/2023]
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26
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van Schalkwyk DA, Chan XW, Misiano P, Gagliardi S, Farina C, Saliba KJ. Inhibition of Plasmodium falciparum pH regulation by small molecule indole derivatives results in rapid parasite death. Biochem Pharmacol 2010; 79:1291-9. [DOI: 10.1016/j.bcp.2009.12.025] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2009] [Revised: 12/23/2009] [Accepted: 12/29/2009] [Indexed: 11/30/2022]
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27
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Henry RI, Cobbold SA, Allen RJW, Khan A, Hayward R, Lehane AM, Bray PG, Howitt SM, Biagini GA, Saliba KJ, Kirk K. An acid-loading chloride transport pathway in the intraerythrocytic malaria parasite, Plasmodium falciparum. J Biol Chem 2010; 285:18615-26. [PMID: 20332090 DOI: 10.1074/jbc.m110.120980] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The intraerythrocytic malaria parasite exerts tight control over its ionic composition. In this study, a combination of fluorescent ion indicators and (36)Cl(-) flux measurements was used to investigate the transport of Cl(-) and the Cl(-)-dependent transport of "H(+)-equivalents" in mature (trophozoite stage) parasites, isolated from their host erythrocytes. Removal of extracellular Cl(-), resulting in an outward [Cl(-)] gradient, gave rise to a cytosolic alkalinization (i.e. a net efflux of H(+)-equivalents). This was reversed on restoration of extracellular Cl(-). The flux of H(+)-equivalents was inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid and, when measured in ATP-depleted parasites, showed a pronounced dependence on the pH of the parasite cytosol; the flux was low at cytosolic pH values < 7.2 but increased steeply with cytosolic pH at values > 7.2. (36)Cl(-) influx measurements revealed the presence of a Cl(-) uptake mechanism with characteristics similar to those of the Cl(-)-dependent H(+)-equivalent flux. The intracellular concentration of Cl(-) in the parasite was estimated to be approximately 48 mm in situ. The data are consistent with the intraerythrocytic parasite having in its plasma membrane a 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid-sensitive transporter that, under physiological conditions, imports Cl(-) together with H(+)-equivalents, resulting in an intracellular Cl(-) concentration well above that which would occur if Cl(-) ions were distributed passively in accordance with the parasite's large, inwardly negative membrane potential.
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Affiliation(s)
- Roselani I Henry
- Research School of Biology, The Australian National University, Canberra, Australian Capital Territory 0200, Australia
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28
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Hill DA, Desai SA. Malaria parasite mutants with altered erythrocyte permeability: a new drug resistance mechanism and important molecular tool. Future Microbiol 2010; 5:81-97. [PMID: 20020831 DOI: 10.2217/fmb.09.109] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Erythrocytes infected with plasmodia, including those that cause human malaria, have increased permeability to a diverse collection of organic and inorganic solutes. While these increases have been known for decades, their mechanistic basis was unclear until electrophysiological studies revealed flux through one or more ion channels on the infected erythrocyte membrane. Current debates have centered on the number of distinct ion channels, which channels mediate the transport of each solute and whether the channels represent parasite-encoded proteins or human channels activated after infection. This article reviews the identification of the plasmodial surface anion channel and other proposed channels with an emphasis on two distinct channel mutants generated through in vitro selection. These mutants implicate parasite genetic elements in the parasite-induced permeability, reveal an important new antimalarial drug resistance mechanism and provide tools for molecular studies. We also critically examine the technical issues relevant to the detection of ion channels by electrophysiological methods; these technical considerations have general applicability for interpreting studies of various ion channels proposed for the infected erythrocyte membrane.
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Affiliation(s)
- David A Hill
- Department of Pathobiology, University of Pennsylvania, Philadelphia, PA, USA.
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29
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Skory CD, Hector RE, Gorsich SW, Rich JO. Analysis of a functional lactate permease in the fungus Rhizopus. Enzyme Microb Technol 2010. [DOI: 10.1016/j.enzmictec.2009.08.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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30
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Lim L, Linka M, Mullin KA, Weber AP, McFadden GI. The carbon and energy sources of the non-photosynthetic plastid in the malaria parasite. FEBS Lett 2009; 584:549-54. [DOI: 10.1016/j.febslet.2009.11.097] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2009] [Revised: 11/30/2009] [Accepted: 11/30/2009] [Indexed: 02/04/2023]
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31
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Rohrbach P. Imaging ion flux and ion homeostasis in blood stage malaria parasites. Biotechnol J 2009; 4:812-25. [DOI: 10.1002/biot.200900084] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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32
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Mauritz JMA, Esposito A, Ginsburg H, Kaminski CF, Tiffert T, Lew VL. The homeostasis of Plasmodium falciparum-infected red blood cells. PLoS Comput Biol 2009; 5:e1000339. [PMID: 19343220 PMCID: PMC2659444 DOI: 10.1371/journal.pcbi.1000339] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2008] [Accepted: 02/24/2009] [Indexed: 11/21/2022] Open
Abstract
The asexual reproduction cycle of Plasmodium falciparum, the parasite responsible for severe malaria, occurs within red blood cells. A merozoite invades a red cell in the circulation, develops and multiplies, and after about 48 hours ruptures the host cell, releasing 15–32 merozoites ready to invade new red blood cells. During this cycle, the parasite increases the host cell permeability so much that when similar permeabilization was simulated on uninfected red cells, lysis occurred before ∼48 h. So how could infected cells, with a growing parasite inside, prevent lysis before the parasite has completed its developmental cycle? A mathematical model of the homeostasis of infected red cells suggested that it is the wasteful consumption of host cell hemoglobin that prevents early lysis by the progressive reduction in the colloid-osmotic pressure within the host (the colloid-osmotic hypothesis). However, two critical model predictions, that infected cells would swell to near prelytic sphericity and that the hemoglobin concentration would become progressively reduced, remained controversial. In this paper, we are able for the first time to correlate model predictions with recent experimental data in the literature and explore the fine details of the homeostasis of infected red blood cells during five model-defined periods of parasite development. The conclusions suggest that infected red cells do reach proximity to lytic rupture regardless of their actual volume, thus requiring a progressive reduction in their hemoglobin concentration to prevent premature lysis. The parasite Plasmodium falciparum is responsible for severe malaria in humans. The 48 hour asexual reproduction cycle of the parasite within red blood cells is responsible for the symptoms in this disease. Within this period, the parasite causes massive changes in the host red cell, increasing some metabolic activities hundredfold, making it leaky to many nutrients and waste products, and consuming most of the cell's hemoglobin, far more than it needs for its own metabolism. The challenge that we faced was to explain how the infected cell maintained its integrity throughout such a violent cycle. Seeking clues, we developed a mathematical model of an infected cell in which we encoded our current knowledge and understanding of the complex processes that control cell homeostasis. We present here for the first time a detailed description of the model and a critical analysis of its predictions in relation to the available experimental evidence. The results support the view that host-cell integrity is maintained by the progressive reduction in the hemoglobin concentration within the host cell, resulting in a reduced rate and extent of swelling.
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Affiliation(s)
- Jakob M. A. Mauritz
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge, United Kingdom
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Alessandro Esposito
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge, United Kingdom
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
- * E-mail:
| | - Hagai Ginsburg
- Department of Biological Chemistry, Institute of Life Sciences, The Hebrew University, Jerusalem, Israel
| | - Clemens F. Kaminski
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge, United Kingdom
- School of Advanced Optical Technologies, Max-Planck-Research Group, Division III, University of Erlangen-Nuremberg, Erlangen, Germany
| | - Teresa Tiffert
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Virgilio L. Lew
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
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33
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Teng R, Junankar PR, Bubb WA, Rae C, Mercier P, Kirk K. Metabolite profiling of the intraerythrocytic malaria parasite Plasmodium falciparum by (1)H NMR spectroscopy. NMR IN BIOMEDICINE 2009; 22:292-302. [PMID: 19021153 DOI: 10.1002/nbm.1323] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
NMR spectroscopy was used to identify and quantify compounds in extracts prepared from mature trophozoite-stage Plasmodium falciparum parasites isolated by saponin-permeabilisation of the host erythrocyte. One-dimensional (1)H NMR spectroscopy and four two-dimensional NMR techniques were used to identify more than 50 metabolites. The intracellular concentrations of over 40 metabolites were estimated from the (1)H NMR spectra of extracts prepared by four extraction methods: perchloric acid, methanol/water, methanol/chloroform/water, and methanol alone. The metabolites quantified included: the majority of the biological alpha-amino acids; 4-aminobutyric acid; mono-, di- and tri-carboxylic acids; nucleotides; polyamines; myo-inositol; and phosphocholine and phosphoethanolamine. The parasites also contained a significant concentration (up to 12 mM) of the exogenous buffering agent, HEPES. Although the metabolite profiles obtained with each extraction method were broadly similar, perchloric acid was found to have significant advantages over the other extraction media.
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Affiliation(s)
- Rongwei Teng
- Biochemistry and Molecular Biology, The Australian National University, Canberra, ACT, Australia
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34
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Nkrumah LJ, Riegelhaupt PM, Moura P, Johnson DJ, Patel J, Hayton K, Ferdig MT, Wellems TE, Akabas MH, Fidock DA. Probing the multifactorial basis of Plasmodium falciparum quinine resistance: evidence for a strain-specific contribution of the sodium-proton exchanger PfNHE. Mol Biochem Parasitol 2009; 165:122-31. [PMID: 19428659 DOI: 10.1016/j.molbiopara.2009.01.011] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2008] [Revised: 01/15/2009] [Accepted: 01/20/2009] [Indexed: 01/10/2023]
Abstract
Quinine (QN) continues to be an important treatment option for severe malaria, however resistance to this drug has emerged in field isolates of the etiologic agent Plasmodium falciparum. Quantitative trait loci investigations of QN resistance have mapped three loci of this complex trait. Two coincide with pfcrt and pfmdr1, involved in resistance to chloroquine (CQ) and other quinoline-based antimalarials. A third locus on chromosome 13 contains the sodium-proton exchanger (pfnhe) gene. Previous studies have associated pfnhe polymorphisms with reduced QN sensitivity in culture-adapted field isolates. Here, we provide direct evidence supporting the hypothesis that pfnhe contributes to QN resistance. Using allelic exchange, we reduced pfnhe expression by introducing a truncated 3' untranslated region (UTR) from pfcrt into the endogenous pfnhe 3'UTR. Transfections were performed with 1BB5 and 3BA6 (both CQ- and QN-resistant) as well as GC03 (CQ- and QN-sensitive), all progenies of the HB3xDd2 genetic cross. RNA and protein analyses of the ensuing recombinant clones demonstrated a approximately 50% decrease in pfnhe expression levels. A statistically significant 30% decrease in QN IC(50) values was associated with these decreased expression levels in 1BB5 and 3BA6 but not in GC03. CQ, mefloquine and lumefantrine IC(50) values were unaltered. Cytosolic pH values were similar in all parental lines and recombinant clones. Our observations support a role for pfnhe in QN resistance in a strain-dependent manner, which might be contingent on pre-existing resistance to CQ and/or QN. These data bolster observations that QN resistance is a complex trait requiring the contribution of multiple transporter proteins.
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Affiliation(s)
- Louis J Nkrumah
- Department of Microbiology and Immunology, Albert Einstein College of Medicine of Yeshiva University, Bronx, NY 10461, USA
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35
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Ribaut C, Reybier K, Reynes O, Launay J, Valentin A, Fabre PL, Nepveu F. Electrochemical impedance spectroscopy to study physiological changes affecting the red blood cell after invasion by malaria parasites. Biosens Bioelectron 2008; 24:2721-5. [PMID: 19167879 DOI: 10.1016/j.bios.2008.12.018] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2008] [Revised: 11/28/2008] [Accepted: 12/03/2008] [Indexed: 11/27/2022]
Abstract
The malaria parasite, Plasmodium falciparum, invades human erythrocytes and induces dramatic changes in the host cell. The idea of this work was to use RBC modified electrode to perform electrochemical impedance spectroscopy (EIS) with the aim of monitoring physiological changes affecting the erythrocyte after invasion by the malaria parasite. Impedance cell-based devices are potentially useful to give insight into cellular behavior and to detect morphological changes. The modelling of impedance plots (Nyquist diagram) in equivalent circuit taking into account the presence of the cellular layer, allowed us pointing out specific events associated with the development of the parasite such as (i) strong changes in the host cell cytoplasm illustrated by changes in the film capacity, (ii) perturbation of the ionic composition of the host cell illustrated by changes in the film resistance, (iii) releasing of reducer (lactic acid or heme) and an enhanced oxygen consumption characterized by changes in the charge transfer resistance and in the Warburg coefficient characteristic of the redox species diffusion. These results show that the RBC-based device may help to analyze strategic events in the malaria parasite development constituting a new tool in antimalarial research.
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Affiliation(s)
- Clotilde Ribaut
- Université de Toulouse, UPS, INP, INSA, Laboratoire pharmacochimie des substances naturelles et pharmacophores redox, 118 route de Narbonne, F-31062 Toulouse cedex 9, France
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36
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Abstract
1. The monocarboxylate transporter (MCT, SLC16) family comprises 14 members, of which to date only MCT1-4 have been shown to carry monocarboxylates, transporting important metabolic compounds such as lactate, pyruvate and ketone bodies in a proton-coupled manner. The transport of such compounds is fundamental for metabolism, and the tissue locations, properties and regulation of these isoforms is discussed. 2. Of the other members of the MCT family, MCT8 (a thyroid hormone transporter) and TAT1 (an aromatic amino acid transporter) have been characterized more recently, and their physiological roles are reviewed herein. The endogenous substrates and functions of the remaining members of the MCT family await elucidation. 3. The MCT proteins have the typical twelve transmembrane-spanning domain (TMD) topology of membrane transporter proteins, and their structure-function relationship is discussed, especially in relation to the future impact of the single nucleotide polymorphism (SNP) databases and, given their ability to transport pharmacologically relevant compounds, the potential impact for pharmacogenomics.
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Affiliation(s)
- D Meredith
- School of Life Sciences, Oxford Brookes University, Headington, Oxford, UK.
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37
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Seeber F, Limenitakis J, Soldati-Favre D. Apicomplexan mitochondrial metabolism: a story of gains, losses and retentions. Trends Parasitol 2008; 24:468-78. [PMID: 18775675 DOI: 10.1016/j.pt.2008.07.004] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2008] [Revised: 07/11/2008] [Accepted: 07/17/2008] [Indexed: 11/15/2022]
Abstract
Apicomplexans form a large group of obligate intracellular parasites that occupy diverse environmental niches. To adapt to their hosts, these parasites have evolved sophisticated strategies to access host-cell nutrients and minimize exposure to the host's defence mechanisms. Concomitantly, they have drastically reshaped their own metabolic functions by retaining, losing or gaining genes for metabolic enzymes. Although several Apicomplexans remain experimentally intractable, bioinformatic analyses of their genomes have generated preliminary metabolic maps. Here, we compare the metabolic pathways of five Apicomplexans, focusing on their different mitochondrial functions, which highlight their adaptation to their individual intracellular habitats.
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Affiliation(s)
- Frank Seeber
- Molecular Parasitology, Institute for Biology, Humboldt University, Philippstr. 13, 10115 Berlin, Germany
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38
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Cassera MB, Merino EF, Peres VJ, Kimura EA, Wunderlich G, Katzin AM. Effect of fosmidomycin on metabolic and transcript profiles of the methylerythritol phosphate pathway in Plasmodium falciparum. Mem Inst Oswaldo Cruz 2007; 102:377-83. [PMID: 17568945 DOI: 10.1590/s0074-02762007000300019] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2007] [Accepted: 03/14/2007] [Indexed: 11/22/2022] Open
Abstract
In Plasmodium falciparum, the formation of isopentenyl diphosphate and dimethylallyl diphosphate, central intermediates in the biosynthesis of isoprenoids, occurs via the methylerythritol phosphate (MEP) pathway. Fosmidomycin is a specific inhibitor of the second enzyme of the MEP pathway, 1-deoxy-D-xylulose-5-phosphate reductoisomerase. We analyzed the effect of fosmidomycin on the levels of each intermediate and its metabolic requirement for the isoprenoid biosynthesis, such as dolichols and ubiquinones, throughout the intraerythrocytic cycle of P. falciparum. The steady-state RNA levels of the MEP pathway-associated genes were quantified by real-time polymerase chain reaction and correlated with the related metabolite levels. Our results indicate that MEP pathway metabolite peak precede maximum transcript abundance during the intraerythrocytic cycle. Fosmidomycin-treatment resulted in a decrease of the intermediate levels in the MEP pathway as well as in ubiquinone and dolichol biosynthesis. The MEP pathway associated transcripts were modestly altered by the drug, indicating that the parasite is not strongly responsive at the transcriptional level. This is the first study that compares the effect of fosmidomycin on the metabolic and transcript profiles in P. falciparum, which has only the MEP pathway for isoprenoid biosynthesis.
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Affiliation(s)
- María B Cassera
- Department of Biochemistry, Yeshiva University, The Bronx, NY, USA
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39
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Wang P, Wang Q, Sims PF, Hyde JE. Characterisation of exogenous folate transport in Plasmodium falciparum. Mol Biochem Parasitol 2007; 154:40-51. [PMID: 17509698 PMCID: PMC1906846 DOI: 10.1016/j.molbiopara.2007.04.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2007] [Revised: 04/03/2007] [Accepted: 04/03/2007] [Indexed: 12/02/2022]
Abstract
Folate salvage by Plasmodium falciparum is an important source of key cofactors, but little is known about the underlying mechanism. Using synchronised parasite cultures, we observed that uptake of this dianionic species against the negative-inward electrochemical gradient is highly dependent upon cell-cycle stage, temperature and pH, but not on mono- or divalent metal ions. Energy dependence was tested with different sugars; glucose was necessary for folate import, although fructose was also able to function in this role, unlike sugars that cannot be processed through the glycolytic pathway. Import into both infected erythrocytes and free parasites was strongly inhibited by the anion-channel blockers probenecid and furosemide, which are likely to be acting predominantly on specific folate transporters in both cases. Import was not affected by high concentrations of the antifolate drugs pyrimethamine and sulfadoxine, but was inhibited by the close folate analogue methotrexate. The pH optimum for folate uptake into infected erythrocytes was 6.5–7.0. Dinitrophenol and nigericin, which strongly facilitate the equilibration of H+ ions across biological membranes and thus abolish or substantially reduce the proton gradient, inhibited folate uptake profoundly. The ATPase inhibitor concanamycin A also greatly reduced folate uptake, further demonstrating a link to ATP-powered proton transport. These data strongly suggest that the principal folate uptake pathway in P. falciparum is specific, highly regulated, dependent upon the proton gradient across the parasite plasma membrane, and is likely to be mediated by one or more proton symporters.
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Affiliation(s)
| | | | | | - John E. Hyde
- Corresponding author. Tel.: +44 161 306 4185; fax: +44 161 306 5201.
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40
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Radzishevsky I, Krugliak M, Ginsburg H, Mor A. Antiplasmodial activity of lauryl-lysine oligomers. Antimicrob Agents Chemother 2007; 51:1753-9. [PMID: 17307975 PMCID: PMC1855553 DOI: 10.1128/aac.01288-06] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The ever evolving resistance of the most virulent malaria parasite, Plasmodium falciparum, to antimalarials necessitates the continuous development of new drugs. Our previous analysis of the antimalarial activities of the hemolytic antimicrobial peptides dermaseptins and their acylated derivatives implicated the importance of hydrophobicity and charge for drug action. Following these findings, an oligoacyllysine (OAK) tetramer designed to mimic the characteristics of dermaseptin was synthesized and assessed for its antimalarial activity in cultures of P. falciparum. The tetramer inhibited the growth of different plasmodial strains at low micromolar concentrations (mean 50% inhibitory concentration [IC(50)], 1.8 microM). A structure-activity relationship study involving eight derivatives unraveled smaller, more potent OAK analogs (IC(50)s, 0.08 to 0.14 microM). The most potent analogs were the most selective, with selectivity ratios of 3 orders of magnitude. Selectivity was strongly influenced by the self-assembly properties resulting from interactions between hydrophobic OAKs, as has been observed with conventional antimicrobial peptides. Further investigations performed with a representative OAK revealed that the ring and trophozoite stages of the parasite developmental cycle were equally sensitive to the compound. A shortcoming of the tested compound was the need for long incubation times in order for it to exert its full effect. Nevertheless, the encouraging results obtained in this study regarding the efficiency and selectivity of some compounds establish them as leads for further development.
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Affiliation(s)
- I Radzishevsky
- Department of Biotechnology & Food Engineering, Technion-Israel Institute of Technology, Haifa, Israel
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41
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Downie MJ, Saliba KJ, Howitt SM, Bröer S, Kirk K. Transport of nucleosides across the Plasmodium falciparum parasite plasma membrane has characteristics of PfENT1. Mol Microbiol 2006; 60:738-48. [PMID: 16629674 DOI: 10.1111/j.1365-2958.2006.05125.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Like all parasitic protozoa, the human malaria parasite Plasmodium falciparum lacks the enzymes required for de novo synthesis of purines and it is therefore reliant upon the salvage of these compounds from the external environment. P. falciparum equilibrative nucleoside transporter 1 (PfENT1) is a nucleoside transporter that has been localized to the plasma membrane of the intraerythrocytic form of the parasite. In this study we have characterized the transport of purine and pyrimidine nucleosides across the plasma membrane of 'isolated' trophozoite-stage P. falciparum parasites and compared the transport characteristics of the parasite with those of PfENT1 expressed in Xenopus oocytes. The transport of nucleosides into the parasite: (i) was, in the case of adenosine, inosine and thymidine, very fast, equilibrating within a few seconds; (ii) was of low affinity [K(m) (adenosine) = 1.45 +/- 0.25 mM; K(m) (thymidine) = 1.11 +/- 0.09 mM]; and (iii) showed 'cross-competition' for adenosine, inosine and thymidine, but not cytidine. The kinetic characteristics of nucleoside transport in intact parasites matched very closely those of PfENT1 expressed in Xenopus oocytes [K(m) (adenosine) = 1.86 +/- 0.28 mM; K(m) (thymidine) = 1.33 +/- 0.17 mM]. Furthermore, PfENT1 transported adenosine, inosine and thymidine, with a cross-competition profile the same as that seen for isolated parasites. The data are consistent with PfENT1 serving as a major route for the uptake of nucleosides across the parasite plasma membrane.
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Affiliation(s)
- Megan J Downie
- School of Biochemistry and Molecular Biology, The Australian National University, Canberra ACT 0200, Australia
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42
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Schistosoma mansoni: biochemical characterization of lactate transporters or similar proteins. Exp Parasitol 2006; 114:180-8. [PMID: 16682030 DOI: 10.1016/j.exppara.2006.03.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2005] [Revised: 03/08/2006] [Accepted: 03/09/2006] [Indexed: 11/30/2022]
Abstract
While in medium containing glucose, schistosomes exhibit homolactic fermentation. Accumulation of lactate acid in tissue fluid causes lowering of pH and a resultant inhibition of metabolic pathways. This requires lactate transporter protein in homolactic fermentors to facilitate the translocation of lactate(-) and [H(+)] across their plasma membrane. The ex-vivo experiment assessed lactic acid secretion by adult worms in absence and the presence of lactic acid transporter protein inhibitors. Phloretin and alpha-cyano-4-hydroxycinnamate caused a combined 25-35% inhibition of lactic acid secretion and probenecid increased this inhibition to 65% of control values. The removal of inhibitors resulted in 80% recovery of lactic acid secretion. In the in-vitro studies using vesicles isolated from adult worms and from schistosomula, the effects of phloretin and alpha-cyano-4-hydroxycinnamate were greater, each causing approximately 80% inhibition independently. The data obtained in this study demonstrate the presence of lactic acid transporters or similar proteins in Schistosoma mansoni.
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43
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Kirk K, Martin RE, Bröer S, Howitt SM, Saliba KJ. Plasmodium permeomics: membrane transport proteins in the malaria parasite. Curr Top Microbiol Immunol 2005; 295:325-56. [PMID: 16265897 DOI: 10.1007/3-540-29088-5_13] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Membrane transport proteins are integral membrane proteins that mediate the passage across the membrane bilayer of specific molecules and/or ions. Such proteins serve a diverse range of physiological roles, mediating the uptake of nutrients into cells, the removal of metabolic wastes and xenobiotics (including drugs), and the generation and maintenance of transmembrane electrochemical gradients. In this chapter we review the present state of knowledge of the membrane transport mechanisms underlying the cell physiology of the intraerythrocytic malaria parasite and its host cell, considering in particular physiological measurements on the parasite and parasitized erythrocyte, the annotation of transport proteins in the Plasmodium genome, and molecular methods used to analyze transport protein function.
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Affiliation(s)
- K Kirk
- School of Biochemistry and Molecular Biology, The Australian National University, 0200 Canberra, ACT, Australia.
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44
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Lisk G, Desai SA. The plasmodial surface anion channel is functionally conserved in divergent malaria parasites. EUKARYOTIC CELL 2005; 4:2153-9. [PMID: 16339732 PMCID: PMC1317498 DOI: 10.1128/ec.4.12.2153-2159.2005] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2005] [Accepted: 09/27/2005] [Indexed: 11/20/2022]
Abstract
The plasmodial surface anion channel (PSAC), a novel ion channel induced on human erythrocytes infected with Plasmodium falciparum, mediates increased permeability to nutrients and presumably supports intracellular parasite growth. Isotope flux studies indicate that other malaria parasites also increase the permeability of their host erythrocytes, but the precise mechanisms are unknown. Channels similar to PSAC or alternative mechanisms, such as the upregulation of endogenous host transporters, might fulfill parasite nutrient demands. Here we evaluated these possibilities with rhesus monkey erythrocytes infected with Plasmodium knowlesi, a parasite phylogenetically distant from P. falciparum. Tracer flux and osmotic fragility studies revealed dramatically increased permeabilities paralleling changes seen after P. falciparum infection. Patch-clamp of P. knowlesi-infected rhesus erythrocytes revealed an anion channel with striking similarities to PSAC: its conductance, voltage-dependent gating, pharmacology, selectivity, and copy number per infected cell were nearly identical. Our findings implicate a family of unusual anion channels highly conserved on erythrocytes infected with various malaria parasites. Together with PSAC's exposed location on the host cell surface and its central role in transport changes after infection, this conservation supports development of antimalarial drugs against the PSAC family.
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Affiliation(s)
- Godfrey Lisk
- The Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Disease, National Institutes of Health, Bethesda, Maryland 20892, USA
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45
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Vivas L, Easton A, Kendrick H, Cameron A, Lavandera JL, Barros D, de las Heras FG, Brady RL, Croft SL. Plasmodium falciparum: stage specific effects of a selective inhibitor of lactate dehydrogenase. Exp Parasitol 2005; 111:105-14. [PMID: 16098967 DOI: 10.1016/j.exppara.2005.06.007] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2005] [Revised: 06/09/2005] [Accepted: 06/29/2005] [Indexed: 11/26/2022]
Abstract
Plasmodium falciparum lactate dehydrogenase (PfLDH) is essential for ATP generation. Based on structural differences within the active site between P. falciparum and human LDH, we have identified a series of heterocyclic azole-based inhibitors that selectively bind within the PfLDH but not the human LDH (hLDH) active site and showed anti-malarial activity in vitro and in vivo. Here we expand on an azole, OXD1, from this series and found that the anti-P. falciparum activity was retained against a panel of strains independently of their anti-malarial drug sensitivity profile. Trophozoites had relatively higher PfLDH enzyme activity and PfLDH-RNA expression levels than rings and were the most susceptible stages to OXD1 exposure. This is probably linked to their increased energy requirements and consistent with glycolysis being an essential metabolic pathway for parasite survival within the erythrocyte. Further structural elaboration of these azoles could lead to the identification of compounds that target P. falciparum through such a novel mechanism and with more potent anti-malarial activity.
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Affiliation(s)
- Livia Vivas
- Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, WC1E 7HT, UK.
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46
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Biagini GA, Ward SA, Bray PG. Malaria parasite transporters as a drug-delivery strategy. Trends Parasitol 2005; 21:299-301. [PMID: 15923144 DOI: 10.1016/j.pt.2005.05.013] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2004] [Revised: 03/10/2005] [Accepted: 05/13/2005] [Indexed: 11/30/2022]
Abstract
The recent characterization of the choline carrier of the malaria parasite and its role in the selective delivery of novel antimalarial drugs has reignited interest in parasite transporters as a drug-delivery strategy. In this article, we discuss these findings in relation to the wider context of developing a sustainable antimalarial-drug-development portfolio.
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Affiliation(s)
- Giancarlo A Biagini
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, UK, L35 QA.
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47
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Desai SA, Alkhalil A, Kang M, Ashfaq U, Nguyen ML. Plasmodial surface anion channel-independent phloridzin resistance in Plasmodium falciparum. J Biol Chem 2005; 280:16861-7. [PMID: 15701633 DOI: 10.1074/jbc.m414629200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The plasmodial surface anion channel (PSAC) is an unusual ion channel induced on the human red blood cell membrane after infection with the malaria parasite, Plasmodium falciparum. Because PSAC is permeant to small metabolic precursors essential for parasite growth and is present on red blood cells infected with geographically divergent parasite isolates, it may be an ideal target for future antimalarial development. Here, we used chemically induced mutagenesis and known PSAC antagonists that inhibit in vitro parasite growth to examine whether resistance mutations in PSAC can be readily induced. Stable mutants resistant to phloridzin were generated and selected within 3 weeks after treatment with 1-methyl-3-nitro-1-nitrosoguanidine. These mutants were evaluated with osmotic lysis and electrophysiological transport assays, which indicate that PSAC inhibition by phloridzin is complex with at least two different modes of inhibition. Mutants resistant to the growth inhibitory effects of phloridzin expressed PSAC activity indistinguishable from that on sensitive parasites, indicating selection of resistance via mutations in one or more other parasite targets. Failure to induce mutations in PSAC activity is consistent with a highly constrained channel protein less susceptible to resistance mutations; whether this protein is parasite- or host-encoded remains to be determined.
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Affiliation(s)
- Sanjay A Desai
- Laboratory of Malaria and Vector Research, NIAID, National Institutes of Health, Bethesda, Maryland 20892, USA.
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Cassera MB, Gozzo FC, D'Alexandri FL, Merino EF, del Portillo HA, Peres VJ, Almeida IC, Eberlin MN, Wunderlich G, Wiesner J, Jomaa H, Kimura EA, Katzin AM. The Methylerythritol Phosphate Pathway Is Functionally Active in All Intraerythrocytic Stages of Plasmodium falciparum. J Biol Chem 2004; 279:51749-59. [PMID: 15452112 DOI: 10.1074/jbc.m408360200] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Two genes encoding the enzymes 1-deoxy-D-xylulose-5-phosphate synthase and 1-deoxy-D-xylulose-5-phosphate reductoisomerase have been recently identified, suggesting that isoprenoid biosynthesis in Plasmodium falciparum depends on the methylerythritol phosphate (MEP) pathway, and that fosmidomycin could inhibit the activity of 1-deoxy-D-xylulose-5-phosphate reductoisomerase. The metabolite 1-deoxy-D-xylulose-5-phosphate is not only an intermediate of the MEP pathway for the biosynthesis of isopentenyl diphosphate but is also involved in the biosynthesis of thiamin (vitamin B1) and pyridoxal (vitamin B6) in plants and many microorganisms. Herein we report the first isolation and characterization of most downstream intermediates of the MEP pathway in the three intraerythrocytic stages of P. falciparum. These include, 1-deoxy-D-xylulose-5-phosphate, 2-C-methyl-D-erythritol-4-phosphate, 4-(cytidine-5-diphospho)-2-C-methyl-D-erythritol, 4-(cytidine-5-diphospho)-2-C-methyl-D-erythritol-2-phosphate, and 2-C-methyl-D-erythritol-2,4-cyclodiphosphate. These intermediates were purified by HPLC and structurally characterized via biochemical and electrospray mass spectrometric analyses. We have also investigated the effect of fosmidomycin on the biosynthesis of each intermediate of this pathway and isoprenoid biosynthesis (dolichols and ubiquinones). For the first time, therefore, it is demonstrated that the MEP pathway is functionally active in all intraerythrocytic forms of P. falciparum, and de novo biosynthesis of pyridoxal in a protozoan is reported. Its absence in the human host makes both pathways very attractive as potential new targets for antimalarial drug development.
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Affiliation(s)
- María B Cassera
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, 05508-900 São Paulo, Brazil
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Biagini GA, Pasini EM, Hughes R, De Koning HP, Vial HJ, O'Neill PM, Ward SA, Bray PG. Characterization of the choline carrier of Plasmodium falciparum: a route for the selective delivery of novel antimalarial drugs. Blood 2004; 104:3372-7. [PMID: 15205262 DOI: 10.1182/blood-2004-03-1084] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Abstract
New drugs are urgently needed to combat the growing problem of drug resistance in Plasmodium falciparum malaria. The infected erythrocyte is a multicompartmental system, and its transporters are of interest as drug targets in their own right and as potential routes for the delivery of antimalarial drugs. Choline is an important nutrient that penetrates infected erythrocyte membranes through the endogenous carrier and through parasite-induced permeability pathways, but nothing is known about its transport into the intracellular parasite. Here we present the first characterization of choline transport across the parasite membrane. Transport exhibits Michaelis-Menten kinetics with an apparent Km of 25.0 ± 3.5 μM for choline. The carrier is inhibitor-sensitive, temperature-dependent, and Na+-independent, and it is driven by the proton-motive force. Highly active bis-amidine and bis-quaternary ammonium compounds are also known to penetrate the host erythrocyte membrane through parasite-induced permeability pathways. Here, we demonstrate that the parasite choline transporter mediates the delivery of these compounds to the intracellular parasite. Thus, the induced permeability pathways in the host erythrocyte membrane and the parasite choline transporter described here form a cooperative transport system that shows great promise for the selective targeting of new agents for the chemotherapy of malaria. (Blood. 2004;104: 3372-3377)
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Affiliation(s)
- Giancarlo A Biagini
- Molecular and Biochemical Parasitology Group, Liverpool School of Tropical Medicine, England
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Moriyama Y, Hayashi M, Yatsushiro S, Yamamoto A. Vacuolar proton pumps in malaria parasite cells. J Bioenerg Biomembr 2004; 35:367-75. [PMID: 14635782 DOI: 10.1023/a:1025785000544] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The malaria parasite is a unicellular protozoan parasite of the genus Plasmodium that causes one of the most serious infectious diseases for human beings. Like other protozoa, the malaria parasite possesses acidic organelles, which may play an essential role(s) in energy acquisition, resistance to antimalarial agents, and vesicular trafficking. Recent evidence has indicated that two types of vacuolar proton pumps, vacuolar H+-ATPase and vacuolar H+-pyrophosphatase, are responsible for their acidification. In this mini-review, we discuss the recent progress on vacuolar proton pumps in the malaria parasite.
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Affiliation(s)
- Yoshinori Moriyama
- Department of Biochemistry, Faculty of Pharmaceutical Sciences, Okayama University, Okayama 700-8530, Japan.
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