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Nascimento JF, Souza ROO, Alencar MB, Marsiccobetre S, Murillo AM, Damasceno FS, Girard RBMM, Marchese L, Luévano-Martinez LA, Achjian RW, Haanstra JR, Michels PAM, Silber AM. How much (ATP) does it cost to build a trypanosome? A theoretical study on the quantity of ATP needed to maintain and duplicate a bloodstream-form Trypanosoma brucei cell. PLoS Pathog 2023; 19:e1011522. [PMID: 37498954 PMCID: PMC10409291 DOI: 10.1371/journal.ppat.1011522] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 08/08/2023] [Accepted: 06/29/2023] [Indexed: 07/29/2023] Open
Abstract
ATP hydrolysis is required for the synthesis, transport and polymerization of monomers for macromolecules as well as for the assembly of the latter into cellular structures. Other cellular processes not directly related to synthesis of biomass, such as maintenance of membrane potential and cellular shape, also require ATP. The unicellular flagellated parasite Trypanosoma brucei has a complex digenetic life cycle. The primary energy source for this parasite in its bloodstream form (BSF) is glucose, which is abundant in the host's bloodstream. Here, we made a detailed estimation of the energy budget during the BSF cell cycle. As glycolysis is the source of most produced ATP, we calculated that a single parasite produces 6.0 x 1011 molecules of ATP/cell cycle. Total biomass production (which involves biomass maintenance and duplication) accounts for ~63% of the total energy budget, while the total biomass duplication accounts for the remaining ~37% of the ATP consumption, with in both cases translation being the most expensive process. These values allowed us to estimate a theoretical YATP of 10.1 (g biomass)/mole ATP and a theoretical [Formula: see text] of 28.6 (g biomass)/mole ATP. Flagellar motility, variant surface glycoprotein recycling, transport and maintenance of transmembrane potential account for less than 30% of the consumed ATP. Finally, there is still ~5.5% available in the budget that is being used for other cellular processes of as yet unknown cost. These data put a new perspective on the assumptions about the relative energetic weight of the processes a BSF trypanosome undergoes during its cell cycle.
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Affiliation(s)
- Janaina F. Nascimento
- Laboratory of Biochemistry of Tryps–LaBTryps, Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo–São Paulo, Brazil
| | - Rodolpho O. O. Souza
- Laboratory of Biochemistry of Tryps–LaBTryps, Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo–São Paulo, Brazil
| | - Mayke B. Alencar
- Laboratory of Biochemistry of Tryps–LaBTryps, Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo–São Paulo, Brazil
| | - Sabrina Marsiccobetre
- Laboratory of Biochemistry of Tryps–LaBTryps, Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo–São Paulo, Brazil
| | - Ana M. Murillo
- Laboratory of Biochemistry of Tryps–LaBTryps, Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo–São Paulo, Brazil
| | - Flávia S. Damasceno
- Laboratory of Biochemistry of Tryps–LaBTryps, Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo–São Paulo, Brazil
| | - Richard B. M. M. Girard
- Laboratory of Biochemistry of Tryps–LaBTryps, Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo–São Paulo, Brazil
| | - Letícia Marchese
- Laboratory of Biochemistry of Tryps–LaBTryps, Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo–São Paulo, Brazil
| | - Luis A. Luévano-Martinez
- Laboratory of Biochemistry of Tryps–LaBTryps, Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo–São Paulo, Brazil
| | - Renan W. Achjian
- Laboratory of Biochemistry of Tryps–LaBTryps, Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo–São Paulo, Brazil
| | - Jurgen R. Haanstra
- Systems Biology Lab, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Paul A. M. Michels
- School of Biological Sciences, The University of Edinburgh, Edinburgh, United Kingdom
| | - Ariel M. Silber
- Laboratory of Biochemistry of Tryps–LaBTryps, Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo–São Paulo, Brazil
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2
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Padrón-Nieves M, Ponte-Sucre A. Cellular Markers for the Identification of Chemoresistant Isolates in Leishmania. Methods Mol Biol 2020; 2116:755-769. [PMID: 32221953 DOI: 10.1007/978-1-0716-0294-2_44] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Markers to diagnose chemoresistance in infecting Leishmania parasites are urgently required. This is fundamental for patients who do not heal during or after treatment, as they are unresponsive, or patients who relapse at the end of the therapy, suffering from therapeutic failure. Glucose utilization is an indicator of cell viability that closely associates with metabolic activity. In Leishmania, glucose is a source of carbon atoms and is imported into the cell through specific transporters. In experimentally developed chemoresistant Leishmania parasites a significant decrease of the expression of glucose transporters as well as in the cellular accumulation glucose has been described. Alternatively, the electrical membrane potential is an essential parameter for the formation of the electromotive force needed for the acquisition of important nutrients and solutes (e.g., glucose) by cells, and changes in glucose concentration are suggested to constitute a physiological adaptation associated with a chemoresistant phenotype of Leishmania parasites. Here we describe easy methods to measure glucose uptake and the membrane potential in isolates from patient suffering leishmaniasis. Correlation between both parameters might be helpful to identify chemoresistant parasites. Results suggest that the measured kinetics of glucose utilization rate can be correlated with the plasma membrane potential and together used to differentiate between the performance of wild-type and reference parasites on the one hand and parasites isolated from patients with therapeutic failure on the other.
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Affiliation(s)
- Maritza Padrón-Nieves
- Laboratorio de Fisiología Molecular, Facultad de Medicina, Instituto de Medicina Experimental, Universidad Central de Venezuela, Caracas, Venezuela
| | - Alicia Ponte-Sucre
- Laboratorio de Fisiología Molecular, Facultad de Medicina, Instituto de Medicina Experimental, Universidad Central de Venezuela, Caracas, Venezuela.
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3
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Trypanosoma brucei: trypanocidal and cell swelling activities of lasalocid acid. Parasitol Res 2017; 116:3229-3233. [PMID: 28956164 PMCID: PMC5660140 DOI: 10.1007/s00436-017-5624-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Accepted: 09/18/2017] [Indexed: 10/24/2022]
Abstract
Chemotherapeutic treatment of human and animal trypanosomiasis is unsatisfactory because only a few drugs are available. As these drugs have poor efficacy and cause adverse reactions, more effective and tolerable medications are needed. As the polyether ionophore antibiotic lasalocid acid is used as medicated feed additive in cattle, the compound was tested for its trypanocidal and cytotoxic activity against bloodstream forms of Trypanosoma brucei and human myeloid HL-60 cells. The concentrations required of lasalocid acid to reduce the growth rate of trypanosomes by 50% and to kill the parasites were 1.75 and 10 μM, respectively. The ionophore displayed also cytotoxic activity against HL-60 cells but the human cells were about 10 to 14 times less sensitive indicating moderate selectivity. As the trypanocidal mechanism of action of polyether ionophore antibiotics is due to a sodium influx-induced cell swelling, the effect of lasalocid acid on cell volume change in bloodstream-form trypanosomes was investigated. Interestingly, lasalocid acid induced a much faster cell swelling in trypanosomes than the more trypanocidal related ionophore salinomycin. These results support further investigations of lasalocid acid and derivatives thereof as potential agents against African trypanosomiasis.
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4
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Russo-Abrahão T, Koeller CM, Steinmann ME, Silva-Rito S, Marins-Lucena T, Alves-Bezerra M, Lima-Giarola NL, de-Paula IF, Gonzalez-Salgado A, Sigel E, Bütikofer P, Gondim KC, Heise N, Meyer-Fernandes JR. H +-dependent inorganic phosphate uptake in Trypanosoma brucei is influenced by myo-inositol transporter. J Bioenerg Biomembr 2017; 49:183-194. [PMID: 28185085 DOI: 10.1007/s10863-017-9695-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Accepted: 01/22/2017] [Indexed: 10/20/2022]
Abstract
Trypanosoma brucei is an extracellular protozoan parasite that causes human African trypanosomiasis or "sleeping sickness". During the different phases of its life cycle, T. brucei depends on exogenous inorganic phosphate (Pi), but little is known about the transport of Pi in this organism. In the present study, we showed that the transport of 32Pi across the plasma membrane follows Michaelis-Menten kinetics and is modulated by pH variation, with higher activity at acidic pH. Bloodstream forms presented lower Pi transport in comparison to procyclic forms, that displayed an apparent K0.5 = 0.093 ± 0.008 mM. Additionally, FCCP (H+-ionophore), valinomycin (K+-ionophore) and SCH28080 (H+, K+-ATPase inhibitor) inhibited the Pi transport. Gene Tb11.02.3020, previously described to encode the parasite H+:myo-inositol transporter (TbHMIT), was hypothesized to be potentially involved in the H+:Pi cotransport because of its similarity with the Pho84 transporter described in S. cerevisiae and other trypanosomatids. Indeed, the RNAi mediated knockdown remarkably reduced TbHMIT gene expression, compromised cell growth and decreased Pi transport by half. In addition, Pi transport was inhibited when parasites were incubated in the presence of concentrations of myo-inositol that are above 300 μM. However, when expressed in Xenopus laevis oocytes, two-electrode voltage clamp experiments provided direct electrophysiological evidence that the protein encoded by TbHMIT is definitely a myo-inositol transporter that may be only marginally affected by the presence of Pi. These results confirmed the presence of a Pi carrier in T. brucei, similar to the H+-dependent inorganic phosphate system described in S. cerevisiae and other trypanosomatids. This transport system contributes to the acquisition of Pi and may be involved in the growth and survival of procyclic forms. In summary, this work presents the first description of a Pi transport system in T. brucei.
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Affiliation(s)
- Thais Russo-Abrahão
- Instituto de Microbiologia Professor Paulo de Góes, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.,Instituto de Bioquímica Médica Leopoldo de Meis, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941-590, Brazil.,Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagem, Rio de Janeiro, RJ, Brazil
| | - Carolina Macedo Koeller
- Instituto de Biofísica Carlos Chagas Filho, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941-590, Brazil
| | - Michael E Steinmann
- Institute of Biochemistry and Molecular Medicine, University of Bern, 3012, Bern, Switzerland
| | - Stephanie Silva-Rito
- Instituto de Bioquímica Médica Leopoldo de Meis, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941-590, Brazil.,Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagem, Rio de Janeiro, RJ, Brazil
| | - Thaissa Marins-Lucena
- Instituto de Bioquímica Médica Leopoldo de Meis, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941-590, Brazil.,Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagem, Rio de Janeiro, RJ, Brazil
| | - Michele Alves-Bezerra
- Instituto de Bioquímica Médica Leopoldo de Meis, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941-590, Brazil.,Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular, Rio de Janeiro, RJ, Brazil
| | - Naira Ligia Lima-Giarola
- Instituto de Bioquímica Médica Leopoldo de Meis, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941-590, Brazil.,Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagem, Rio de Janeiro, RJ, Brazil
| | - Iron Francisco de-Paula
- Instituto de Bioquímica Médica Leopoldo de Meis, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941-590, Brazil.,Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular, Rio de Janeiro, RJ, Brazil
| | - Amaia Gonzalez-Salgado
- Institute of Biochemistry and Molecular Medicine, University of Bern, 3012, Bern, Switzerland
| | - Erwin Sigel
- Institute of Biochemistry and Molecular Medicine, University of Bern, 3012, Bern, Switzerland
| | - Peter Bütikofer
- Institute of Biochemistry and Molecular Medicine, University of Bern, 3012, Bern, Switzerland
| | - Katia Calp Gondim
- Instituto de Bioquímica Médica Leopoldo de Meis, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941-590, Brazil.,Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular, Rio de Janeiro, RJ, Brazil
| | - Norton Heise
- Instituto de Biofísica Carlos Chagas Filho, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941-590, Brazil.
| | - José Roberto Meyer-Fernandes
- Instituto de Bioquímica Médica Leopoldo de Meis, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941-590, Brazil. .,Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagem, Rio de Janeiro, RJ, Brazil.
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5
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Steinmann ME, González-Salgado A, Bütikofer P, Mäser P, Sigel E. A heteromeric potassium channel involved in the modulation of the plasma membrane potential is essential for the survival of African trypanosomes. FASEB J 2015; 29:3228-37. [DOI: 10.1096/fj.15-271353] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Accepted: 03/31/2015] [Indexed: 11/11/2022]
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6
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Human trypanolytic factor APOL1 forms pH-gated cation-selective channels in planar lipid bilayers: relevance to trypanosome lysis. Proc Natl Acad Sci U S A 2015; 112:2894-9. [PMID: 25730870 DOI: 10.1073/pnas.1421953112] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Apolipoprotein L-1 (APOL1), the trypanolytic factor of human serum, can lyse several African trypanosome species including Trypanosoma brucei brucei, but not the human-infective pathogens T. brucei rhodesiense and T. brucei gambiense, which are resistant to lysis by human serum. Lysis follows the uptake of APOL1 into acidic endosomes and is apparently caused by colloid-osmotic swelling due to an increased ion permeability of the plasma membrane. Here we demonstrate that nanogram quantities of full-length recombinant APOL1 induce ideally cation-selective macroscopic conductances in planar lipid bilayers. The conductances were highly sensitive to pH: their induction required acidic pH (pH 5.3), but their magnitude could be increased 3,000-fold upon alkalinization of the milieu (pK(a) = 7.1). We show that this phenomenon can be attributed to the association of APOL1 with the bilayer at acidic pH, followed by the opening of APOL1-induced cation-selective channels upon pH neutralization. Furthermore, the conductance increase at neutral pH (but not membrane association at acidic pH) was prevented by the interaction of APOL1 with the serum resistance-associated protein, which is produced by T. brucei rhodesiense and prevents trypanosome lysis by APOL1. These data are consistent with a model of lysis that involves endocytic recycling of APOL1 and the formation of cation-selective channels, at neutral pH, in the parasite plasma membrane.
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7
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Achcar F, Fadda A, Haanstra JR, Kerkhoven EJ, Kim DH, Leroux AE, Papamarkou T, Rojas F, Bakker BM, Barrett MP, Clayton C, Girolami M, Krauth-Siegel RL, Matthews KR, Breitling R. The silicon trypanosome: a test case of iterative model extension in systems biology. Adv Microb Physiol 2014; 64:115-43. [PMID: 24797926 DOI: 10.1016/b978-0-12-800143-1.00003-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The African trypanosome, Trypanosoma brucei, is a unicellular parasite causing African Trypanosomiasis (sleeping sickness in humans and nagana in animals). Due to some of its unique properties, it has emerged as a popular model organism in systems biology. A predictive quantitative model of glycolysis in the bloodstream form of the parasite has been constructed and updated several times. The Silicon Trypanosome is a project that brings together modellers and experimentalists to improve and extend this core model with new pathways and additional levels of regulation. These new extensions and analyses use computational methods that explicitly take different levels of uncertainty into account. During this project, numerous tools and techniques have been developed for this purpose, which can now be used for a wide range of different studies in systems biology.
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Affiliation(s)
- Fiona Achcar
- Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Abeer Fadda
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Jurgen R Haanstra
- Department of Pediatrics, Centre for Liver Digestive and Metabolic Diseases, and Systems Biology Centre for Energy Metabolism and Ageing, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands; Department of Molecular Cell Physiology, Faculty of Earth and Life Sciences, VU University Amsterdam, Amsterdam, The Netherlands
| | - Eduard J Kerkhoven
- Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, and Glasgow Polyomics, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom; Systems and Synthetic Biology Group, Department of Chemical and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden
| | - Dong-Hyun Kim
- Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, and Glasgow Polyomics, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | | | - Theodore Papamarkou
- The Department of Statistical Science and The Centre for Computational Statistics and Machine Learning University College London, London, United Kingdom
| | - Federico Rojas
- Centre for Immunity, Infection and Evolution, Institute for Immunology and Infection Research, School of Biological Sciences, Ashworth Laboratories, University of Edinburgh, Edinburgh, United Kingdom
| | - Barbara M Bakker
- Department of Pediatrics, Centre for Liver Digestive and Metabolic Diseases, and Systems Biology Centre for Energy Metabolism and Ageing, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Michael P Barrett
- Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, and Glasgow Polyomics, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Christine Clayton
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Mark Girolami
- The Department of Statistical Science and The Centre for Computational Statistics and Machine Learning University College London, London, United Kingdom
| | | | - Keith R Matthews
- Centre for Immunity, Infection and Evolution, Institute for Immunology and Infection Research, School of Biological Sciences, Ashworth Laboratories, University of Edinburgh, Edinburgh, United Kingdom
| | - Rainer Breitling
- Manchester Institute of Biotechnology, Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom.
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Trypanosoma brucei eflornithine transporter AAT6 is a low-affinity low-selective transporter for neutral amino acids. Biochem J 2014; 463:9-18. [PMID: 24988048 DOI: 10.1042/bj20140719] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Amino acid transporters are crucial for parasite survival since the cellular metabolism of parasitic protozoa depends on the up-take of exogenous amino acids. Amino acid transporters are also of high pharmacological relevance because they may mediate uptake of toxic amino acid analogues. In the present study we show that the eflornithine transporter AAT6 from Trypanosoma brucei (TbAAT6) mediates growth on neutral amino acids when expressed in Saccharomyces cerevisiae mutants. The transport was electrogenic and further analysed in Xenopus laevis oocytes. Neutral amino acids, proline analogues, eflornithine and acivicin induced inward currents. For proline, glycine and tryptophan the apparent affinities and maximal transport rates increased with more negative membrane potentials. Proline-induced currents were dependent on pH, but not on sodium. Although proline represents the primary energy source of T. brucei in the tsetse fly, down-regulation of TbAAT6-expression by RNAi showed that in culture TbAAT6 is not essential for growth of procyclic form trypanosomes in the presence of glucose or proline as energy source. TbAAT6-RNAi lines of both bloodstream and procyclic form trypanosomes showed reduced susceptibility to eflornithine, whereas the sensitivity to acivicin remained unchanged, indicating that acivicin enters the cell by more than one transporter.
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9
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Leroux AE, Haanstra JR, Bakker BM, Krauth-Siegel RL. Dissecting the catalytic mechanism of Trypanosoma brucei trypanothione synthetase by kinetic analysis and computational modeling. J Biol Chem 2013; 288:23751-64. [PMID: 23814051 PMCID: PMC3745322 DOI: 10.1074/jbc.m113.483289] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
In pathogenic trypanosomes, trypanothione synthetase (TryS) catalyzes the synthesis of both glutathionylspermidine (Gsp) and trypanothione (bis(glutathionyl)spermidine (T(SH)2)). Here we present a thorough kinetic analysis of Trypanosoma brucei TryS in a newly developed phosphate buffer system at pH 7.0 and 37 °C, mimicking the physiological environment of the enzyme in the cytosol of bloodstream parasites. Under these conditions, TryS displays Km values for GSH, ATP, spermidine, and Gsp of 34, 18, 687, and 32 μm, respectively, as well as Ki values for GSH and T(SH)2 of 1 mm and 360 μm, respectively. As Gsp hydrolysis has a Km value of 5.6 mm, the in vivo amidase activity is probably negligible. To obtain deeper insight in the molecular mechanism of TryS, we have formulated alternative kinetic models, with elementary reaction steps represented by linear kinetic equations. The model parameters were fitted to the extensive matrix of steady-state data obtained for different substrate/product combinations under the in vivo-like conditions. The best model describes the full kinetic profile and is able to predict time course data that were not used for fitting. This system's biology approach to enzyme kinetics led us to conclude that (i) TryS follows a ter-reactant mechanism, (ii) the intermediate Gsp dissociates from the enzyme between the two catalytic steps, and (iii) T(SH)2 inhibits the enzyme by remaining bound at its product site and, as does the inhibitory GSH, by binding to the activated enzyme complex. The newly detected concerted substrate and product inhibition suggests that TryS activity is tightly regulated.
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Affiliation(s)
- Alejandro E Leroux
- Biochemie-Zentrum der Universität Heidelberg, D-69120 Heidelberg, Germany
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10
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Sanchez MA. Molecular identification and characterization of an essential pyruvate transporter from Trypanosoma brucei. J Biol Chem 2013; 288:14428-14437. [PMID: 23569205 DOI: 10.1074/jbc.m113.473157] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Pyruvate export is an essential physiological process for the bloodstream form of Trypanosoma brucei as the parasite would otherwise accumulate this end product of glucose metabolism to toxic levels. In the studies reported here, genetic complementation in Saccharomyces cerevisiae has been employed to identify a gene (TbPT0) that encodes this vital pyruvate transporter from T. brucei. Expression of TbPT0 in S. cerevisiae reveals that TbPT0 is a high affinity pyruvate transporter. TbPT0 belongs to a clustered multigene family consisting of five members, whose expression is up-regulated in the bloodstream form. Interestingly, TbPT family permeases are related to polytopic proteins from plants but not to characterized monocarboxylate transporters from mammals. Remarkably, inhibition of the TbPT gene family expression in bloodstream parasites by RNAi is lethal, confirming the physiological relevance of these transporters. The discovery of TbPT0 reveals for the first time the identity of the essential pyruvate transporter and provides a potential drug target against the mammalian life cycle stage of T. brucei.
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Affiliation(s)
- Marco A Sanchez
- Department of Molecular Microbiology and Immunology, Oregon Health & Science University, Portland, Oregon 97239.
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11
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Steverding D, Sexton DW. Trypanocidal activity of salinomycin is due to sodium influx followed by cell swelling. Parasit Vectors 2013; 6:78. [PMID: 23517602 PMCID: PMC3621689 DOI: 10.1186/1756-3305-6-78] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Accepted: 03/18/2013] [Indexed: 01/27/2023] Open
Abstract
Background The few currently available drugs for treatment of African trypanosomiasis are outdated and show problems with toxicity and resistance. Hence, there is an urgent need for the discovery and development of new anti-trypanosomal agents. Findings In this study, the ionophorous antibiotic salinomycin was investigated for its trypanocidal activity in vitro using culture-adapted bloodstream forms of Trypanosoma brucei. The concentrations of salinomycin to reduce the growth rate by 50% and to kill the parasites were 0.31 μM and 1 μM, respectively. The trypanocidal action of the ionophore was shown to be the result of an influx of Na+ resulting in an increased intracellular Na+ concentration followed by cell swelling. This mode of action differs from the mechanism for the anti-cancer activity of salinomycin reported to be by induction of apoptosis. Conclusion Here we have shown that salinomycin is an effective agent against bloodstream forms of T. brucei and might be a potential candidate for treatment of African trypanosomiasis.
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Affiliation(s)
- Dietmar Steverding
- BioMedical Research Centre, Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich, UK.
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12
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Jimenez V, Docampo R. Molecular and electrophysiological characterization of a novel cation channel of Trypanosoma cruzi. PLoS Pathog 2012; 8:e1002750. [PMID: 22685407 PMCID: PMC3369953 DOI: 10.1371/journal.ppat.1002750] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2012] [Accepted: 04/27/2012] [Indexed: 01/27/2023] Open
Abstract
We report the identification, functional expression, purification, reconstitution and electrophysiological characterization of a novel cation channel (TcCat) from Trypanosoma cruzi, the etiologic agent of Chagas disease. This channel is potassium permeable and shows inward rectification in the presence of magnesium. Western blot analyses with specific antibodies indicated that the protein is expressed in the three main life cycle stages of the parasite. Surprisingly, the parasites have the unprecedented ability to rapidly change the localization of the channel when they are exposed to different environmental stresses. TcCat rapidly translocates to the tip of the flagellum when trypomastigotes are submitted to acidic pH, to the plasma membrane when epimastigotes are submitted to hyperosmotic stress, and to the cell surface when amastigotes are released to the extracellular medium. Pharmacological block of TcCat activity also resulted in alterations in the trypomastigotes ability to respond to hyperosmotic stress. We also demonstrate the feasibility of purifying and reconstituting a functional ion channel from T. cruzi after recombinant expression in bacteria. The peculiar characteristics of TcCat could be important for the development of specific inhibitors with therapeutic potential against trypanosomes. The use of high-resolution electrophysiological techniques to study ion channels has provided a large amount of information on functional aspects of these important membrane proteins. However, the study of ion channels in unicellular eukaryotes has been limited to detection of ion conductances in large cells, gene identification studies, and pharmacological treatments to investigate the potential presence of different ion channels. In this paper we report the first identification, functional expression, purification, reconstitution, and electrophysiological characterization with single-molecule resolution of a novel cation channel (TcCat) from Trypanosoma cruzi. This is a novel channel that shares little sequence and functional similarities to other potassium channels and its peculiar characteristics could be important for the development of specific inhibitors with therapeutic potential against trypanosomiasis. Surprisingly, the parasites have the unprecedented ability to rapidly change the localization of the channel when they are exposed to different environmental stresses. We demonstrated the feasibility of purifying and reconstituting a functional ion channel from T. cruzi after recombinant expression in bacteria. In addition, we obtained yeast mutants that will provide a useful genetic system for studies of the assembly and composition of the channel.
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Affiliation(s)
- Veronica Jimenez
- Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, Athens, Georgia, United States of America
- * E-mail: (VJ); (RD)
| | - Roberto Docampo
- Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, Athens, Georgia, United States of America
- * E-mail: (VJ); (RD)
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13
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Electrophysiological-metabolic modeling of microbes: applications in fuel cells and environment analysis. Methods Mol Biol 2012. [PMID: 22639221 DOI: 10.1007/978-1-61779-827-6_14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
A formalism for simulating coupled metabolic and electrophysiological processes is presented. The resulting chemical kinetic and electrophysiological equations are solved numerically to create a cell simulator. Metabolic features of this simulator were adapted from Karyote, a multi-compartment biochemical cell modeling simulator. We present the mathematical formalism and its computational implementation as an integrated electrophysiological-metabolic model. Applications to Geobacter sulfurreducens in the environment and in a fuel cell are discussed.
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14
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Prole DL, Marrion NV. Identification of putative potassium channel homologues in pathogenic protozoa. PLoS One 2012; 7:e32264. [PMID: 22363819 PMCID: PMC3283738 DOI: 10.1371/journal.pone.0032264] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2011] [Accepted: 01/24/2012] [Indexed: 12/21/2022] Open
Abstract
K+ channels play a vital homeostatic role in cells and abnormal activity of these channels can dramatically alter cell function and survival, suggesting that they might be attractive drug targets in pathogenic organisms. Pathogenic protozoa lead to diseases such as malaria, leishmaniasis, trypanosomiasis and dysentery that are responsible for millions of deaths each year worldwide. The genomes of many protozoan parasites have recently been sequenced, allowing rational design of targeted therapies. We analyzed the genomes of pathogenic protozoa and show the existence within them of genes encoding putative homologues of K+ channels. These protozoan K+ channel homologues represent novel targets for anti-parasitic drugs. Differences in the sequences and diversity of human and parasite proteins may allow pathogen-specific targeting of these K+ channel homologues.
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Affiliation(s)
- David L Prole
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom.
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15
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Jimenez V, Henriquez M, Galanti N, Riquelme G. Electrophysiological characterization of potassium conductive pathways in Trypanosoma cruzi. J Cell Biochem 2011; 112:1093-102. [DOI: 10.1002/jcb.23023] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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16
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Abstract
The molecular mechanisms of K(+) homeostasis are only poorly understood for protozoan parasites. Trypanosoma brucei subsp. parasites, the causative agents of human sleeping sickness and nagana, are strictly extracellular and need to actively concentrate K(+) from their hosts' body fluids. The T. brucei genome contains two putative K(+) channel genes, yet the trypanosomes are insensitive to K(+) antagonists and K(+) channel-blocking agents, and they do not spontaneously depolarize in response to high extracellular K(+) concentrations. However, the trypanosomes are extremely sensitive to K(+) ionophores such as valinomycin. Surprisingly, T. brucei possesses a member of the Trk/HKT superfamily of monovalent cation permeases which so far had only been known from bacteria, archaea, fungi, and plants. The protein was named TbHKT1 and functions as a Na(+)-independent K(+) transporter when expressed in Escherichia coli, Saccharomyces cerevisiae, or Xenopus laevis oocytes. In trypanosomes, TbHKT1 is expressed in both the mammalian bloodstream stage and the Tsetse fly midgut stage; however, RNA interference (RNAi)-mediated silencing of TbHKT1 expression did not produce a growth phenotype in either stage. The presence of HKT genes in trypanosomatids adds a further piece to the enigmatic phylogeny of the Trk/HKT superfamily of K(+) transporters. Parsimonial analysis suggests that the transporters were present in the first eukaryotes but subsequently lost in several of the major eukaryotic lineages, in at least four independent events.
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17
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De Souza AM, Batista EJO, Pinheiro AADS, Carvalhaes M, Lopes AG, De Souza W, Caruso-Neves C. Entamoeba histolytica: ouabain-insensitive Na(+)-ATPase activity. Exp Parasitol 2007; 117:195-200. [PMID: 17574551 DOI: 10.1016/j.exppara.2007.04.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2007] [Revised: 04/19/2007] [Accepted: 04/24/2007] [Indexed: 11/18/2022]
Abstract
Our aim was to determine the presence of sodium pumps in Entamoeba histolytica. It is shown through the measurement of ouabain-sensitive ATPase activity and immunoblotting that E. histolytica does not express (Na(+)+K(+))ATPase. On the other hand, we observed a Na(+)-ATPase with the following characteristics: (1) stimulated by Na(+) or K(+), but these effects are not addictive; (2) the apparent affinity is similar for Na(+) and K(+) (K(0.5) = 13.3 +/- 3.7 and 15.4 +/- 3.1mM, respectively), as well as the V(max) (24.9 +/- 1.5 or 27.5 +/- 1.6 nmol Pi mg(-1)min(-1), respectively); (3) insensitive up to 2mM ouabain; and (4) inhibited by furosemide with an IC(50) of 0.12 +/- 0.004 mM. Furthermore, this enzyme forms a Na(+)- or K(+)-stimulated, furosemide- and hydroxylamine-sensitive ATP-driven acylphosphate phosphorylated intermediate.
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Affiliation(s)
- Aloa M De Souza
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21941-902 Rio de Janeiro, RJ, Brazil
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18
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Pays E, Vanhollebeke B, Vanhamme L, Paturiaux-Hanocq F, Nolan DP, Pérez-Morga D. The trypanolytic factor of human serum. Nat Rev Microbiol 2006; 4:477-86. [PMID: 16710327 DOI: 10.1038/nrmicro1428] [Citation(s) in RCA: 130] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
African trypanosomes (the prototype of which is Trypanosoma brucei brucei) are protozoan parasites that infect a wide range of mammals. Human blood, unlike the blood of other mammals, has efficient trypanolytic activity, and this needs to be counteracted by these parasites. Resistance to this activity has arisen in two subspecies of Trypanosoma brucei - Trypanosoma brucei rhodesiense and Trypanosoma brucei gambiense - allowing these parasites to infect humans, and this results in sleeping sickness in East Africa and West Africa, respectively. Study of the mechanism by which T. b. rhodesiense escapes lysis by human serum led to the identification of an ionic-pore-forming apolipoprotein - known as apolipoprotein L1 - that is associated with high-density-lipoprotein particles in human blood. In this Opinion article, we argue that apolipoprotein L1 is the factor that is responsible for the trypanolytic activity of human serum.
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Affiliation(s)
- Etienne Pays
- Laboratory of Molecular Parasitology, Institute of Molecular Biology and Medicine (IBMM), Université Libre de Bruxelles, 12 rue des Professeurs Jeener et Brachet, B-6041 Gosselies, Belgium.
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19
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Molina-Portela MDP, Lugli EB, Recio-Pinto E, Raper J. Trypanosome lytic factor, a subclass of high-density lipoprotein, forms cation-selective pores in membranes. Mol Biochem Parasitol 2005; 144:218-26. [PMID: 16202458 DOI: 10.1016/j.molbiopara.2005.08.018] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2005] [Accepted: 08/22/2005] [Indexed: 11/24/2022]
Abstract
Trypanosome lytic factor 1 (TLF1) is a subclass of human high-density lipoprotein that kills some African trypanosomes thereby protecting humans from infection. We have shown that TLF1 is a 500 kDa HDL complex composed of lipids and at least seven different proteins. Here we present evidence outlining a new paradigm for the mechanism of lysis; TLF1 forms cation-selective pores in membranes. We show that the replacement of external Na+ (23 Da) with the larger tetramethylammonium+, choline+ and tetraethylammonium+ ions (74 Da, 104 Da and 130 Da) ameliorates the osmotically driven swelling and lysis of trypanosomes by TLF1. Confirmation of cation pore-formation was obtained using small unilamellar vesicles incubated with TLF1; these showed the predicted change in membrane potential expected from an influx of sodium ions. Using planar lipid bilayer model membranes made from trypanosome lipids, which allow the detection of single channels, we found that TLF1 forms discrete ion-conducting channels (17 pS) that are selective for potassium ions over chloride ions. We propose that the initial influx of extracellular Na+ down its concentration gradient promotes the passive entry of Cl- through preexisting Cl- channels. The net influx of both Na+ and Cl- create an osmotic imbalance that leads to passive water diffusion. This loss of osmoregulation results in cytoplasmic vacuolization, cell swelling and ultimately trypanosome lysis.
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20
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Pérez-Morga D, Vanhollebeke B, Paturiaux-Hanocq F, Nolan DP, Lins L, Homblé F, Vanhamme L, Tebabi P, Pays A, Poelvoorde P, Jacquet A, Brasseur R, Pays E. Apolipoprotein L-I promotes trypanosome lysis by forming pores in lysosomal membranes. Science 2005; 309:469-72. [PMID: 16020735 DOI: 10.1126/science.1114566] [Citation(s) in RCA: 261] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Apolipoprotein L-I is the trypanolytic factor of human serum. Here we show that this protein contains a membrane pore-forming domain functionally similar to that of bacterial colicins, flanked by a membrane-addressing domain. In lipid bilayer membranes, apolipoprotein L-I formed anion channels. In Trypanosoma brucei, apolipoprotein L-I was targeted to the lysosomal membrane and triggered depolarization of this membrane, continuous influx of chloride, and subsequent osmotic swelling of the lysosome until the trypanosome lysed.
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MESH Headings
- 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid/pharmacology
- Amino Acid Sequence
- Animals
- Anions/metabolism
- Apolipoprotein L1
- Apolipoproteins/chemistry
- Apolipoproteins/genetics
- Apolipoproteins/metabolism
- Apolipoproteins/pharmacology
- Cells, Immobilized
- Chlorides/metabolism
- Colicins/chemistry
- Colicins/pharmacology
- Escherichia coli/drug effects
- Escherichia coli/growth & development
- Humans
- Intracellular Membranes/drug effects
- Intracellular Membranes/metabolism
- Intracellular Membranes/ultrastructure
- Ion Channels/metabolism
- Lipid Bilayers/chemistry
- Lipoproteins, HDL/chemistry
- Lipoproteins, HDL/genetics
- Lipoproteins, HDL/metabolism
- Lipoproteins, HDL/pharmacology
- Lysosomes/drug effects
- Lysosomes/metabolism
- Lysosomes/ultrastructure
- Models, Molecular
- Molecular Sequence Data
- Mutation
- Permeability
- Protein Conformation
- Protein Structure, Secondary
- Protein Structure, Tertiary
- Recombinant Proteins/metabolism
- Trypanosoma brucei brucei/drug effects
- Trypanosoma brucei brucei/metabolism
- Trypanosoma brucei brucei/ultrastructure
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Affiliation(s)
- David Pérez-Morga
- Laboratory of Molecular Parasitology, IBMM, Université Libre de Bruxelles, 12, rue des Profs Jeener et Brachet, B6041 Gosselies, Belgium
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21
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Allen RJW, Kirk K. The membrane potential of the intraerythrocytic malaria parasite Plasmodium falciparum. J Biol Chem 2003; 279:11264-72. [PMID: 14630911 DOI: 10.1074/jbc.m311110200] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The membrane potential (Deltapsi) of the mature asexual form of the human malaria parasite, Plasmodium falciparum, isolated from its host erythrocyte using a saponin permeabilization technique, was investigated using both the radiolabeled Deltapsi indicator tetraphenylphosphonium ([(3)H]TPP(+)) and the fluorescent Deltapsi indicator DiBAC(4)(3) (bis-oxonol). For isolated parasites suspended in a high Na(+), low K(+) solution, Deltapsi was estimated from the measured distribution of [(3)H]TPP(+) to be -95 +/- 2 mV. Deltapsi was reduced by the specific V-type H(+) pump inhibitor bafilomycin A(1), by the H(+) ionophore CCCP, and by glucose deprivation. Acidification of the parasite cytosol (induced by the addition of lactate) resulted in a transient hyperpolarization, whereas a cytosolic alkalinization (induced by the addition of NH(4)(+)) resulted in a transient depolarization. A decrease in the extracellular pH resulted in a membrane depolarization, whereas an increase in the extracellular pH resulted in a membrane hyperpolarization. The parasite plasma membrane depolarized in response to an increase in the extracellular K(+) concentration and hyperpolarized in response to a decrease in the extracellular K(+) concentration and to the addition of the K(+) channel blockers Ba(2+) or Cs(+) to the suspending medium. The data are consistent with Deltapsi of the intraerythrocytic P. falciparum trophozoite being due to the electrogenic extrusion of H(+) via the V-type H(+) pump at the parasite surface. The current associated with the efflux of H(+) is countered, in part, by the influx of K(+) via Ba(2+)- and Cs(+)-sensitive K(+) channels in the parasite plasma membrane.
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Affiliation(s)
- Richard J W Allen
- School of Biochemistry and Molecular Biology, Faculty of Science, Australian National University, Canberra, Australian Capital Territory 0200, Australia
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22
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Stiles JK, Kucerova Z, Sarfo B, Meade CA, Thompson W, Shah P, Xue L, Meade JC. Identification of surface-membrane P-type ATPases resembling fungal K(+)- and Na(+)-ATPases, in Trypanosoma brucei, Trypanosoma cruzi and Leishmania donovani. ANNALS OF TROPICAL MEDICINE AND PARASITOLOGY 2003; 97:351-66. [PMID: 12831521 DOI: 10.1179/000349803235002362] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
Genomic DNA fragments encoding nine, novel, P-type ATPases in trypanosomatid organisms were amplified in PCR, using degenerate oligonucleotide primers that recognize the ATP-binding and -phosphorylation sites present in all P-type ATPases. Subsequent phylogenetic analysis, based on the presence of conserved motifs in predicted peptide sequences for six Trypanosoma brucei, T. cruzi or Leishmania donovani PCR fragments, identified calcium-, proton- and phospholipid-translocating ATPases. DNA fragments that predict proteins homologous to the fungal, type-IID, P-type, ATPase pumps that transport Na(+) or K(+) ions were also present in T. brucei (TBCA1; 1022 nucleotides representing 340 amino acids), T. cruzi (TCNA1; 1022 nucleotides representing 340 amino acids) and L. donovani (LDCA1; 1031 nucleotides representing 343 amino acids). Southern blots showed that the Na(+)-ATPases were each present as a single-copy gene. The LDCA1 fragment was used to clone the complete LDCA1 gene from an L. donovani genomic-DNA library. The LDCA1 gene encodes a protein, of 1047 amino acids, with a predicted molecular mass of 115,501 Da. The results of analyses based on northern blots and the rapid amplification of cDNA ends (RACE) indicated that LDCA1 was expressed in promastigotes and amastigotes from axenic cultures and in animal-derived amastigotes. TBCA1 was expressed, as a 5.0-kb transcript, in procyclic culture stages and bloodstream trypomastigotes, with the 5.0-kb message up-regulated six-fold in the trypomastigote stage. Western blots probed with an antibody to the partial TBCA1 peptide identified a 150-kDa protein that was detected, by immunofluorescence, on the surface membrane of procyclic T. brucei.
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Affiliation(s)
- J K Stiles
- Department of Microbiology, Morehouse School of Medicine, 720 Westview Drive SW, Atlanta, GA 303010, USA.
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23
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Van der Heyden N, Docampo R. Significant differences between procyclic and bloodstream forms of Trypanosoma brucei in the maintenance of their plasma membrane potential. J Eukaryot Microbiol 2002; 49:407-13. [PMID: 12425529 DOI: 10.1111/j.1550-7408.2002.tb00220.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The plasma membrane potential (deltapsi) of procyclic and bloodstream trypomastigotes of Trypanosoma brucei was studied using the potentiometric fluorescent dye bisoxonol. Our results suggest that a proton pump plays a significant role in the regulation of deltapsi in procyclic and bloodstream forms, as evidenced by depolarization of the plasma membrane by H(+)-ATPase inhibitors (e.g. dicyclohexylcarbo-diimide, N-ethylmaleimide, diethylstilbestrol, and bafilomycin A1). In bloodstream stages the plasma membrane was significantly depolarized by ouabain only when the cells were incubated in sodium-rich buffers indicating that a sodium pump was being inhibited. In contrast, ouabain had no effect on the deltapsi of the procyclic stages in a sodium-rich buffer. However, it induced an additional significant depolarization in these stages when their plasma membrane was already partially depolarized by the H(+)-ATPase inhibitor dicyclohexylcarbo-diimide, indicating the presence of an ouabain-sensitive sodium pump whose activity is masked by the H(+)-ATPase. Unlike procyclic forms, the deltapsi of bloodstream-stage trypomastigotes was markedly sensitive to extracellular Na+ and K+ concentrations. Thus, there are significant differences between procyclic and bloodstream forms in the maintenance of the deltapsi and in their permeability to cations.
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Schnaufer A, Domingo GJ, Stuart K. Natural and induced dyskinetoplastic trypanosomatids: how to live without mitochondrial DNA. Int J Parasitol 2002; 32:1071-84. [PMID: 12117490 DOI: 10.1016/s0020-7519(02)00020-6] [Citation(s) in RCA: 135] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Salivarian trypanosomes are the causative agents of several diseases of major social and economic impact. The most infamous parasites of this group are the African subspecies of the Trypanosoma brucei group, which cause sleeping sickness in humans and nagana in cattle. In terms of geographical distribution, however, Trypanosoma equiperdum and Trypanosoma evansi have been far more successful, causing disease in livestock in Africa, Asia, and South America. In these latter forms the mitochondrial DNA network, the kinetoplast, is altered or even completely lost. These natural dyskinetoplastic forms can be mimicked in bloodstream form T. brucei by inducing the loss of kinetoplast DNA (kDNA) with intercalating dyes. Dyskinetoplastic T. brucei are incapable of completing their usual developmental cycle in the insect vector, due to their inability to perform oxidative phosphorylation. Nevertheless, they are usually as virulent for their mammalian hosts as parasites with intact kDNA, thus questioning the therapeutic value of attempts to target mitochondrial gene expression with specific drugs. Recent experiments, however, have challenged this view. This review summarises the data available on dyskinetoplasty in trypanosomes and revisits the roles the mitochondrion and its genome play during the life cycle of T. brucei.
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Affiliation(s)
- Achim Schnaufer
- Seattle Biomedical Research Institute, 4 Nickerson Street, Suite 200, Seattle, WA 98109, USA.
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25
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Nolan DP, Voorheis HP. Hydrogen ion gradients across the mitochondrial, endosomal and plasma membranes in bloodstream forms of trypanosoma brucei solving the three-compartment problem. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:4601-14. [PMID: 10903492 DOI: 10.1046/j.1432-1327.2000.01476.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Conditions for the use of both [14C]methylamine and 5, 5-dimethyl[14C]oxa-azolidine-2,4-dione (DMO) to measure the H+ concentration of intracellular compartments of monomorphic long thin bloodstream forms of Trypanosoma brucei were established. Neither probe was actively transported or bound to internal components of the cell and both probes equilibrated passively with a t1/2 close to 8 min. DMO was excluded from cells, while methylamine was accumulated but not metabolized. Solution of the three-compartment problem revealed that, when cells were respiring aerobically on glucose at an external pH of 7.5, the cytoplasmic pH was in the range 6.99-7.03, the pH of the mitochondrial matrix was 7.71-7.73, and the algebraic average pH of the various endosomal compartments was 5.19-5.50. Similar values were found when cells were respiring aerobically on glycerol. However, bloodstream forms of T. brucei could not maintain a constant internal H+ concentration outside the external pH range 7.0-7.5, and no evidence for the presence of an H+/Na+ exchanger was found. Full motility and levels of pyruvate production were maintained as the external pH was raised as high as 9.5, suggesting that these cells tolerate significant internal alkalinisation. However, both motility and pyruvate production were severely inhibited under acidic conditions, and the cells deteriorated rapidly below an external pH of 6.5. Physiologically, the plasma membrane of T. brucei had low permeability to H+ and the internal pH was unaffected by changes in Deltapsip, which is dominated by the potassium diffusion potential. However, in the presence of FCCP, the internal pH fell rapidly about 0.5 pH unit and came into equilibrium with Deltapsip. Oligomycin abolished the mitochondrial pH gradient (DeltapHm) selectively, whereas chloroquine abolished only the endosomal pH gradient (DeltapHe). The pH gradient across the plasma membrane (DeltapHp) alone could be abolished by careful osmotic swelling of cells. The plasma membrane had an inwardly directed proton-motive force (DeltaPp) of -52 mV and an inwardly directed sodium-motive force (DeltaNp) of -149 mV, whereas the mitochondrial inner membrane had only an inwardly directed DeltaPm of -195 mV. The pH gradient across the endosomal membranes was not accompanied by an electrical gradient. Consequently, endosomal membranes had an algebraically average outwardly directed DeltaPl within the range + 89 to +110 mV, depending on the measurement method.
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Affiliation(s)
- D P Nolan
- Department of Biochemistry, Trinity College, University of Dublin, Ireland
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