1
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Aldfer MM, Hulpia F, van Calenbergh S, De Koning HP. Mapping the transporter-substrate interactions of the Trypanosoma cruzi NB1 nucleobase transporter reveals the basis for its high affinity and selectivity for hypoxanthine and guanine and lack of nucleoside uptake. Mol Biochem Parasitol 2024; 258:111616. [PMID: 38401850 DOI: 10.1016/j.molbiopara.2024.111616] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Revised: 02/19/2024] [Accepted: 02/20/2024] [Indexed: 02/26/2024]
Abstract
Trypanosoma cruzi is a protozoan parasite and the etiological agent of Chagas disease, a debilitating and sometimes fatal disease that continues to spread to new areas. Yet, Chagas disease is still only treated with two related nitro compounds that are insufficiently effective and cause severe side effects. Nucleotide metabolism is one of the known vulnerabilities of T. cruzi, as they are auxotrophic for purines, and nucleoside analogues have been shown to have genuine promise against this parasite in vitro and in vivo. Since purine antimetabolites require efficient uptake through transporters, we here report a detailed characterisation of the T. cruzi NB1 nucleobase transporter with the aim of elucidating the interactions between TcrNB1 and its substrates and finding the positions that can be altered in the design of novel antimetabolites without losing transportability. Systematically determining the inhibition constants (Ki) of purine analogues for TcrNB1 yielded their Gibbs free energy of interaction, ΔG0. Pairwise comparisons of substrate (hypoxanthine, guanine, adenine) and analogues allowed us to determine that optimal binding affinity by TcrNB1 requires interactions with all four nitrogen residues of the purine ring, with N1 and N9, in protonation state, functioning as presumed hydrogen bond donors and unprotonated N3 and N7 as hydrogen bond acceptors. This is the same interaction pattern as we previously described for the main nucleobase transporters of Trypanosoma brucei spp. and Leishmania major and makes it the first of the ENT-family genes that is functionally as well as genetically conserved between the three main kinetoplast pathogens.
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Affiliation(s)
- Mustafa M Aldfer
- School of Infection and Immunity, Sir Graeme Davies Building, 120 University Place, University of Glasgow, GlasgowG12 8TA, UK
| | - Fabian Hulpia
- Laboratory for Medicinal Chemistry (Campus Heymans), Ghent University, Ottergemsesteenweg 460, 9000 Gent, Belgium
| | - Serge van Calenbergh
- Laboratory for Medicinal Chemistry (Campus Heymans), Ghent University, Ottergemsesteenweg 460, 9000 Gent, Belgium
| | - Harry P De Koning
- School of Infection and Immunity, Sir Graeme Davies Building, 120 University Place, University of Glasgow, GlasgowG12 8TA, UK.
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2
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Ungogo MA, Aldfer MM, Natto MJ, Zhuang H, Chisholm R, Walsh K, McGee M, Ilbeigi K, Asseri JI, Burchmore RJS, Caljon G, Van Calenbergh S, De Koning HP. Cloning and Characterization of Trypanosoma congolense and T. vivax Nucleoside Transporters Reveal the Potential of P1-Type Carriers for the Discovery of Broad-Spectrum Nucleoside-Based Therapeutics against Animal African Trypanosomiasis. Int J Mol Sci 2023; 24:ijms24043144. [PMID: 36834557 PMCID: PMC9960827 DOI: 10.3390/ijms24043144] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Revised: 02/01/2023] [Accepted: 02/02/2023] [Indexed: 02/09/2023] Open
Abstract
African Animal Trypanosomiasis (AAT), caused predominantly by Trypanosoma brucei brucei, T. vivax and T. congolense, is a fatal livestock disease throughout Sub-Saharan Africa. Treatment options are very limited and threatened by resistance. Tubercidin (7-deazaadenosine) analogs have shown activity against individual parasites but viable chemotherapy must be active against all three species. Divergence in sensitivity to nucleoside antimetabolites could be caused by differences in nucleoside transporters. Having previously characterized the T. brucei nucleoside carriers, we here report the functional expression and characterization of the main adenosine transporters of T. vivax (TvxNT3) and T. congolense (TcoAT1/NT10), in a Leishmania mexicana cell line ('SUPKO') lacking adenosine uptake. Both carriers were similar to the T. brucei P1-type transporters and bind adenosine mostly through interactions with N3, N7 and 3'-OH. Expression of TvxNT3 and TcoAT1 sensitized SUPKO cells to various 7-substituted tubercidins and other nucleoside analogs although tubercidin itself is a poor substrate for P1-type transporters. Individual nucleoside EC50s were similar for T. b. brucei, T. congolense, T. evansi and T. equiperdum but correlated less well with T. vivax. However, multiple nucleosides including 7-halogentubercidines displayed pEC50>7 for all species and, based on transporter and anti-parasite SAR analyses, we conclude that nucleoside chemotherapy for AAT is viable.
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Affiliation(s)
- Marzuq A. Ungogo
- School of Infection and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK
- Department of Veterinary Pharmacology and Toxicology, Ahmadu Bello University, Zaria 810107, Kaduna State, Nigeria
- Roslin Institute, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian EH25 9RG, UK
| | - Mustafa M. Aldfer
- School of Infection and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK
| | - Manal J. Natto
- School of Infection and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK
| | - Hainan Zhuang
- School of Infection and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK
| | - Robyn Chisholm
- School of Infection and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK
| | - Katy Walsh
- School of Infection and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK
| | - MarieClaire McGee
- School of Infection and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK
| | - Kayhan Ilbeigi
- Laboratory of Microbiology, Parasitology and Hygiene (LMPH), University of Antwerp, B-2610 Wilrijk, Belgium
| | - Jamal Ibrahim Asseri
- School of Infection and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK
| | - Richard J. S. Burchmore
- School of Infection and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK
| | - Guy Caljon
- Laboratory of Microbiology, Parasitology and Hygiene (LMPH), University of Antwerp, B-2610 Wilrijk, Belgium
| | - Serge Van Calenbergh
- Laboratory for Medicinal Chemistry (Campus Heymans), Ghent University, B-9000 Gent, Belgium
| | - Harry P. De Koning
- School of Infection and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK
- Correspondence:
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3
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Steketee PC, Dickie EA, Iremonger J, Crouch K, Paxton E, Jayaraman S, Alfituri OA, Awuah-Mensah G, Ritchie R, Schnaufer A, Rowan T, de Koning HP, Gadelha C, Wickstead B, Barrett MP, Morrison LJ. Divergent metabolism between Trypanosoma congolense and Trypanosoma brucei results in differential sensitivity to metabolic inhibition. PLoS Pathog 2021; 17:e1009734. [PMID: 34310651 PMCID: PMC8384185 DOI: 10.1371/journal.ppat.1009734] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 08/24/2021] [Accepted: 06/21/2021] [Indexed: 11/18/2022] Open
Abstract
Animal African Trypanosomiasis (AAT) is a debilitating livestock disease prevalent across sub-Saharan Africa, a main cause of which is the protozoan parasite Trypanosoma congolense. In comparison to the well-studied T. brucei, there is a major paucity of knowledge regarding the biology of T. congolense. Here, we use a combination of omics technologies and novel genetic tools to characterise core metabolism in T. congolense mammalian-infective bloodstream-form parasites, and test whether metabolic differences compared to T. brucei impact upon sensitivity to metabolic inhibition. Like the bloodstream stage of T. brucei, glycolysis plays a major part in T. congolense energy metabolism. However, the rate of glucose uptake is significantly lower in bloodstream stage T. congolense, with cells remaining viable when cultured in concentrations as low as 2 mM. Instead of pyruvate, the primary glycolytic endpoints are succinate, malate and acetate. Transcriptomics analysis showed higher levels of transcripts associated with the mitochondrial pyruvate dehydrogenase complex, acetate generation, and the glycosomal succinate shunt in T. congolense, compared to T. brucei. Stable-isotope labelling of glucose enabled the comparison of carbon usage between T. brucei and T. congolense, highlighting differences in nucleotide and saturated fatty acid metabolism. To validate the metabolic similarities and differences, both species were treated with metabolic inhibitors, confirming that electron transport chain activity is not essential in T. congolense. However, the parasite exhibits increased sensitivity to inhibition of mitochondrial pyruvate import, compared to T. brucei. Strikingly, T. congolense exhibited significant resistance to inhibitors of fatty acid synthesis, including a 780-fold higher EC50 for the lipase and fatty acid synthase inhibitor Orlistat, compared to T. brucei. These data highlight that bloodstream form T. congolense diverges from T. brucei in key areas of metabolism, with several features that are intermediate between bloodstream- and insect-stage T. brucei. These results have implications for drug development, mechanisms of drug resistance and host-pathogen interactions.
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Affiliation(s)
- Pieter C Steketee
- The Roslin Institute, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, United Kingdom
| | - Emily A Dickie
- Wellcome Centre for Integrative Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - James Iremonger
- The Roslin Institute, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, United Kingdom
| | - Kathryn Crouch
- Wellcome Centre for Integrative Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Edith Paxton
- The Roslin Institute, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, United Kingdom
| | - Siddharth Jayaraman
- The Roslin Institute, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, United Kingdom
| | - Omar A Alfituri
- The Roslin Institute, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, United Kingdom
| | | | - Ryan Ritchie
- Wellcome Centre for Integrative Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Achim Schnaufer
- Institute of Immunology and Infection Research, University of Edinburgh, Edinburgh, United Kingdom
| | - Tim Rowan
- Global Alliance for Livestock Veterinary Medicines, Edinburgh, United Kingdom
| | - Harry P de Koning
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Catarina Gadelha
- School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Bill Wickstead
- School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Michael P Barrett
- Wellcome Centre for Integrative Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom.,Glasgow Polyomics, University of Glasgow, Glasgow, United Kingdom
| | - Liam J Morrison
- The Roslin Institute, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, United Kingdom
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4
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Rico-Jiménez M, Ceballos-Pérez G, Gómez-Liñán C, Estévez AM. An RNA-binding protein complex regulates the purine-dependent expression of a nucleobase transporter in trypanosomes. Nucleic Acids Res 2021; 49:3814-3825. [PMID: 33744953 PMCID: PMC8053114 DOI: 10.1093/nar/gkab181] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2020] [Revised: 03/02/2021] [Accepted: 03/04/2021] [Indexed: 12/13/2022] Open
Abstract
Post-transcriptional regulation of gene expression is particularly important in trypanosomatid protozoa. RNA-binding proteins (RBPs) regulate mRNA stability and translation, yet information about how RBPs are able to link environmental cues to post-transcriptional control is scarce. In Trypanosoma brucei, we have previously characterized a short RNA stem-loop cis-element (PuRE, Purine Responsive Element) within the 3'-UTR of the NT8 nucleobase transporter mRNA that is necessary and sufficient to confer a strong repression of gene expression in response to purines. In this study, we have identified a protein complex composed of two RNA-binding proteins (PuREBP1 and PuREBP2) that binds to the PuRE in vitro and to NT8 mRNA in vivo. Depletion of PuREBP1 by RNA interference results in the upregulation of just NT8 and the mRNAs encoding the amino acid transporter AATP6 paralogues. Moreover, we found that the PuREBP1/2 complex is associated with only a handful of mRNAs, and that it is responsible for the observed purine-dependent regulation of NT8 expression.
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Affiliation(s)
- Miriam Rico-Jiménez
- Instituto de Parasitología y Biomedicina 'López-Neyra', IPBLN-CSIC, Parque Tecnológico de Ciencias de la Salud, Avda. del Conocimiento 17, 18016 Armilla, Granada, Spain
| | - Gloria Ceballos-Pérez
- Instituto de Parasitología y Biomedicina 'López-Neyra', IPBLN-CSIC, Parque Tecnológico de Ciencias de la Salud, Avda. del Conocimiento 17, 18016 Armilla, Granada, Spain
| | - Claudia Gómez-Liñán
- Instituto de Parasitología y Biomedicina 'López-Neyra', IPBLN-CSIC, Parque Tecnológico de Ciencias de la Salud, Avda. del Conocimiento 17, 18016 Armilla, Granada, Spain
| | - Antonio M Estévez
- Instituto de Parasitología y Biomedicina 'López-Neyra', IPBLN-CSIC, Parque Tecnológico de Ciencias de la Salud, Avda. del Conocimiento 17, 18016 Armilla, Granada, Spain
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5
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Campagnaro GD, de Koning HP. Purine and pyrimidine transporters of pathogenic protozoa - conduits for therapeutic agents. Med Res Rev 2020; 40:1679-1714. [PMID: 32144812 DOI: 10.1002/med.21667] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Revised: 02/12/2020] [Accepted: 02/18/2020] [Indexed: 02/06/2023]
Abstract
Purines and pyrimidines are essential nutrients for any cell. Most organisms are able to synthesize their own purines and pyrimidines, but this ability was lost in protozoans that adapted to parasitism, leading to a great diversification in transporter activities in these organisms, especially for the acquisition of amino acids and nucleosides from their hosts throughout their life cycles. Many of these transporters have been shown to have sufficiently different substrate affinities from mammalian transporters, making them good carriers for therapeutic agents. In this review, we summarize the knowledge obtained on purine and pyrimidine activities identified in protozoan parasites to date and discuss their importance for the survival of these parasites and as drug carriers, as well as the perspectives of developments in the field.
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Affiliation(s)
- Gustavo D Campagnaro
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, 120 University Place, Glasgow, UK
| | - Harry P de Koning
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, 120 University Place, Glasgow, UK
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6
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Campagnaro GD, de Freitas Nascimento J, Girard RB, Silber AM, de Koning HP. Cloning and characterisation of the Equilibrative Nucleoside Transporter family of Trypanosoma cruzi: ultra-high affinity and selectivity to survive in the intracellular niche. Biochim Biophys Acta Gen Subj 2018; 1862:2750-2763. [DOI: 10.1016/j.bbagen.2018.08.015] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Revised: 08/22/2018] [Accepted: 08/23/2018] [Indexed: 12/27/2022]
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7
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Campagnaro GD, Alzahrani KJ, Munday JC, De Koning HP. Trypanosoma brucei bloodstream forms express highly specific and separate transporters for adenine and hypoxanthine; evidence for a new protozoan purine transporter family? Mol Biochem Parasitol 2018; 220:46-56. [DOI: 10.1016/j.molbiopara.2018.01.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Revised: 01/10/2018] [Accepted: 01/19/2018] [Indexed: 10/18/2022]
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8
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Boswell-Casteel RC, Hays FA. Equilibrative nucleoside transporters-A review. NUCLEOSIDES NUCLEOTIDES & NUCLEIC ACIDS 2016; 36:7-30. [PMID: 27759477 DOI: 10.1080/15257770.2016.1210805] [Citation(s) in RCA: 125] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Equilibrative nucleoside transporters (ENTs) are polytopic integral membrane proteins that mediate the transport of nucleosides, nucleobases, and therapeutic analogs. The best-characterized ENTs are the human transporters hENT1 and hENT2. However, non-mammalian eukaryotic ENTs have also been studied (e.g., yeast, parasitic protozoa). ENTs are major pharmaceutical targets responsible for modulating the efficacy of more than 30 approved drugs. However, the molecular mechanisms and chemical determinants of ENT-mediated substrate recognition, binding, inhibition, and transport are poorly understood. This review highlights findings on the characterization of ENTs by surveying studies on genetics, permeant and inhibitor interactions, mutagenesis, and structural models of ENT function.
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Affiliation(s)
- Rebba C Boswell-Casteel
- a Department of Biochemistry and Molecular Biology , University of Oklahoma Health Sciences Center , Oklahoma City , OK , USA
| | - Franklin A Hays
- a Department of Biochemistry and Molecular Biology , University of Oklahoma Health Sciences Center , Oklahoma City , OK , USA.,b Stephenson Cancer Center , University of Oklahoma Health Sciences Center , Oklahoma City , OK , USA.,c Harold Hamm Diabetes Center , University of Oklahoma Health Sciences Center , Oklahoma City , OK , USA
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9
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Henriques C, Miller MP, Catanho M, de Carvalho TMU, Krieger MA, Probst CM, de Souza W, Degrave W, Amara SG. Identification and functional characterization of a novel arginine/ornithine transporter, a member of a cationic amino acid transporter subfamily in the Trypanosoma cruzi genome. Parasit Vectors 2015; 8:346. [PMID: 26109388 PMCID: PMC4486710 DOI: 10.1186/s13071-015-0950-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Accepted: 06/13/2015] [Indexed: 01/03/2023] Open
Abstract
Background Trypanosoma cruzi, the etiological agent of Chagas disease, is auxotrophic for arginine. It obtains this amino acid from the host through transporters expressed on the plasma membrane and on the membranes of intracellular compartments. A few cationic amino acid transporters have been characterized at the molecular level, such as the novel intracellular arginine/ornithine transporter, TcCAT1.1, a member of the TcCAT subfamily that is composed of four almost identical open reading frames in the T. cruzi genome. Methods The functional characterization of the TcCAT1.1 isoform was performed in two heterologous expression systems. TcCAT subfamily expression was evaluated by real-time PCR in polysomal RNA fractions, and the cellular localization of TcCAT1.1 fused to EGFP was performed by confocal and immunoelectron microscopy. Results In the S. cerevisiae expression system, TcCAT1.1 showed high affinity for arginine (Km = 0.085 ± 0.04 mM) and low affinity for ornithine (Km = 1.7 ± 0.2 mM). Xenopus laevis oocytes expressing TcCAT1.1 showed a 7-fold increase in arginine uptake when they were pre-loaded with arginine, indicating that transport is enhanced by substrates on the trans side of the membrane (trans-stimulation). Oocytes that were pre-loaded with [3H]-arginine displayed a 16-fold higher efflux of [3H]-arginine compared with that of the control. Analysis of polysomal RNA fractions demonstrated that the expression of members of the arginine transporter TcCAT subfamily is upregulated under nutritional stress and that this upregulation precedes metacyclogenesis. To investigate the cellular localization of the transporter, EGFP was fused to TcCAT1.1, and fluorescence microscopy and immunocytochemistry revealed the intracellular labeling of vesicles in the anterior region, in a network of tubules and vesicles. Conclusions TcCAT1.1 is a novel arginine/ornithine transporter, an exchanger expressed in intracellular compartments that is physiologically involved in arginine homeostasis throughout the T. cruzi life cycle. The properties and estimated kinetic parameters of TcCAT1.1 can be extended to other members of the TcCAT subfamily.
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Affiliation(s)
- Cristina Henriques
- Fundação Oswaldo Cruz, Fiocruz-Mato Grosso do Sul, Rua Gabriel Abrão 92-Jardim das Nações, Campo Grande, MS, 89081-746, Brazil. .,Instituto de Biofísica Carlos Chagas Filho-UFRJ, CCS-Bloco G-Laboratório de Ultraestrutura Celular Hertha Meyer, Rio de Janeiro, RJ, 21949-900, Brazil. .,Nucleo de Biologia Estrutural e Biomagens, Universidade Federal do Rio de Janeiro-CENABIO, Rio de Janeiro, RJ, Brazil.
| | - Megan P Miller
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15260, USA.
| | - Marcos Catanho
- Fiocruz, Instituto Oswaldo Cruz, Laboratório de Genômica Funcional e Bioinformática, Av. Brasil 4365, Manguinhos, 21040-900, Rio de Janeiro, RJ, Brazil.
| | - Técia Maria Ulisses de Carvalho
- Instituto de Biofísica Carlos Chagas Filho-UFRJ, CCS-Bloco G-Laboratório de Ultraestrutura Celular Hertha Meyer, Rio de Janeiro, RJ, 21949-900, Brazil.
| | | | | | - Wanderley de Souza
- Instituto de Biofísica Carlos Chagas Filho-UFRJ, CCS-Bloco G-Laboratório de Ultraestrutura Celular Hertha Meyer, Rio de Janeiro, RJ, 21949-900, Brazil. .,Nucleo de Biologia Estrutural e Biomagens, Universidade Federal do Rio de Janeiro-CENABIO, Rio de Janeiro, RJ, Brazil. .,Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Biomagens-INBEB, Rio de Janeiro, Brazil.
| | - Wim Degrave
- Fiocruz, Instituto Oswaldo Cruz, Laboratório de Genômica Funcional e Bioinformática, Av. Brasil 4365, Manguinhos, 21040-900, Rio de Janeiro, RJ, Brazil.
| | - Susan Gaye Amara
- National Institute of Mental Health, NIH Building 10 Center Driver, Room 4N222, MSC 1381, Bethesda, MD, 20892-1381, USA. .,Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15260, USA.
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10
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Geiger A, Ponton F, Simo G. Adult blood-feeding tsetse flies, trypanosomes, microbiota and the fluctuating environment in sub-Saharan Africa. ISME JOURNAL 2014; 9:1496-507. [PMID: 25500509 DOI: 10.1038/ismej.2014.236] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2014] [Revised: 11/03/2014] [Accepted: 11/06/2014] [Indexed: 01/01/2023]
Abstract
The tsetse fly vector transmits the protozoan Trypanosoma brucei, responsible for Human African Trypanosomiasis, one of the most neglected tropical diseases. Despite a recent decline in new cases, it is still crucial to develop alternative strategies to combat this disease. Here, we review the literature on the factors that influence trypanosome transmission from the fly vector to its vertebrate host (particularly humans). These factors include climate change effects to pathogen and vector development (in particular climate warming), as well as the distribution of host reservoirs. Finally, we present reports on the relationships between insect vector nutrition, immune function, microbiota and infection, to demonstrate how continuing research on the evolving ecology of these complex systems will help improve control strategies. In the future, such studies will be of increasing importance to understand how vector-borne diseases are spread in a changing world.
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Affiliation(s)
- Anne Geiger
- UMR 177, IRD-CIRAD, CIRAD TA A-17/G, Campus International de Baillarguet, Montpellier Cedex 5, France
| | - Fleur Ponton
- 1] School of Biological Sciences, The University of Sydney, Sydney, New South Wales, Australia [2] The Charles Perkins Centre, The University of Sydney, Sydney, New South Wales, Australia
| | - Gustave Simo
- Molecular Parasitology and Entomology Unit, Department of Biochemistry, Faculty of Science, University of Dschang, Dschang, Cameroon
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11
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Fernández-Moya SM, Carrington M, Estévez AM. A short RNA stem-loop is necessary and sufficient for repression of gene expression during early logarithmic phase in trypanosomes. Nucleic Acids Res 2014; 42:7201-9. [PMID: 24813448 PMCID: PMC4066783 DOI: 10.1093/nar/gku358] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
We have compared the transcriptomes of cultured procyclic Trypanosoma brucei cells in early and late logarithmic phases and found that ∼200 mRNAs were differentially regulated. In late log phase cells, the most upregulated mRNA encoded the nucleobase transporter NT8. The 3' untranslated region (UTR) of NT8 contains a short stem-loop cis-element that is necessary for the regulation of NT8 expression in response to external purine levels. When placed in the 3'-UTR of an unregulated transcript, the cis-element is sufficient to confer regulation in response to purines. To our knowledge, this is the first example of a discrete RNA element that can autonomously regulate gene expression in trypanosomes in response to an external factor and reveals an unprecedented purine-dependent signaling pathway that controls gene expression in eukaryotes.
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Affiliation(s)
- Sandra M Fernández-Moya
- Instituto de Parasitología y Biomedicina 'López-Neyra', IPBLN-CSIC, Parque Tecnológico de Ciencias de la Salud, Avda. del Conocimiento, s/n, 18016 Armilla, Granada, Spain
| | - Mark Carrington
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK
| | - Antonio M Estévez
- Instituto de Parasitología y Biomedicina 'López-Neyra', IPBLN-CSIC, Parque Tecnológico de Ciencias de la Salud, Avda. del Conocimiento, s/n, 18016 Armilla, Granada, Spain
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12
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Lüscher A, Lamprea-Burgunder E, Graf FE, de Koning HP, Mäser P. Trypanosoma brucei adenine-phosphoribosyltransferases mediate adenine salvage and aminopurinol susceptibility but not adenine toxicity. INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE 2013; 4:55-63. [PMID: 24596669 PMCID: PMC3940079 DOI: 10.1016/j.ijpddr.2013.12.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Revised: 11/30/2013] [Accepted: 12/03/2013] [Indexed: 11/30/2022]
Abstract
African trypanosomes possess two distinct adenine phosphoribosyltransferases. Trypanosoma brucei TbAPRT1 is cytosolic, TbAPRT2 localizes to the glycosome. Aprt1,2 null mutants are viable but do not incorporate adenine into nucleotides. Aprt1,2 null mutants are resistant to aminopurinol but still sensitive to adenine. Aminopurinol is a trypanocide with submicromolar activity against T. brucei.
African trypanosomes, like all obligate parasitic protozoa, cannot synthesize purines de novo and import purines from their hosts to build nucleic acids. The purine salvage pathways of Trypanosoma brucei being redundant, none of the involved enzymes is likely to be essential. Nevertheless they can be of pharmacological interest due to their role in activation of purine nucleobase or nucleoside analogues, which only become toxic when converted to nucleotides. Aminopurine antimetabolites, in particular, are potent trypanocides and even adenine itself is toxic to trypanosomes at elevated concentrations. Here we report on the T. brucei adenine phosphoribosyltransferases TbAPRT1 and TbAPRT2, encoded by the two genes Tb927.7.1780 and Tb927.7.1790, located in tandem on chromosome seven. The duplication is syntenic in all available Trypanosoma genomes but not in Leishmania. While TbAPRT1 is cytosolic, TbAPRT2 possesses a glycosomal targeting signal and co-localizes with the glycosomal marker aldolase. Interestingly, the distribution of glycosomal targeting signals among trypanosomatid adenine phosphoribosyltransferases is not consistent with their phylogeny, indicating that the acquisition of adenine salvage to the glycosome happened after the radiation of Trypanosoma. Double null mutant T. brucei Δtbaprt1,2 exhibited no growth phenotype but no longer incorporated exogenous adenine into the nucleotide pool. This, however, did not reduce their sensitivity to adenine. The Δtbaprt1,2 trypanosomes were resistant to the adenine isomer aminopurinol, indicating that it is activated by phosphoribosyl transfer. Aminopurinol was about 1000-fold more toxic to bloodstream-form T. brucei than the corresponding hypoxanthine isomer allopurinol. Aminopurinol uptake was not dependent on the aminopurine permease P2 that has been implicated in drug resistance.
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Affiliation(s)
- Alexandra Lüscher
- Institute of Cell Biology, University of Bern, 3012 Bern, Switzerland
| | | | - Fabrice E Graf
- Swiss Tropical and Public Health Institute, 4051 Basel, Switzerland ; University of Basel, 4000 Basel, Switzerland
| | - Harry P de Koning
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow G12 8RA, UK
| | - Pascal Mäser
- Swiss Tropical and Public Health Institute, 4051 Basel, Switzerland ; University of Basel, 4000 Basel, Switzerland
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Ritt JF, Raymond F, Leprohon P, Légaré D, Corbeil J, Ouellette M. Gene amplification and point mutations in pyrimidine metabolic genes in 5-fluorouracil resistant Leishmania infantum. PLoS Negl Trop Dis 2013; 7:e2564. [PMID: 24278495 PMCID: PMC3836990 DOI: 10.1371/journal.pntd.0002564] [Citation(s) in RCA: 21] [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: 07/08/2013] [Accepted: 10/15/2013] [Indexed: 12/02/2022] Open
Abstract
Background The human protozoan parasites Leishmania are prototrophic for pyrimidines with the ability of both de novo biosynthesis and uptake of pyrimidines. Methodology/Principal Findings Five independent L. infantum mutants were selected for resistance to the pyrimidine analogue 5-fluorouracil (5-FU) in the hope to better understand the metabolism of pyrimidine in Leishmania. Analysis of the 5-FU mutants by comparative genomic hybridization and whole genome sequencing revealed in selected mutants the amplification of DHFR-TS and a deletion of part of chromosome 10. Point mutations in uracil phosphorybosyl transferase (UPRT), thymidine kinase (TK) and uridine phosphorylase (UP) were also observed in three individual resistant mutants. Transfection experiments confirmed that these point mutations were responsible for 5-FU resistance. Transport studies revealed that one resistant mutant was defective for uracil and 5-FU import. Conclusion/Significance This study provided further insights in pyrimidine metabolism in Leishmania and confirmed that multiple mutations can co-exist and lead to resistance in Leishmania. The human protozoan parasites Leishmania present the ability of both de novo biosynthesis and uptake of pyrimidines. The pyrimidine pathway is not well understood in these parasites. In the hope to better understand the pyrimidine pathway in Leishmania, five independent L. infantum mutants were selected for resistance to the pyrimidine analogue 5-fluorouracil (5-FU). Analysis of the 5-FU mutants by comparative genomic hybridization and whole genome sequencing revealed the amplification of the main target enzyme DHFR-TS, and point mutations in three important metabolic enzymes. Transfection experiments confirmed that these point mutations were responsible for 5-FU resistance. Transport studies also revealed that one resistant mutant was defective for uracil and 5-FU import. Overall, this study provided further insights in pyrimidine metabolism in Leishmania and confirmed that multiple mutations can co-exist and lead to resistance in these protozoa.
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Affiliation(s)
- Jean-François Ritt
- Centre de recherche en Infectiologie du CHU de Québec and Département de Microbiologie, Infectiologie et Immunologie, Université Laval, Québec City, Québec, Canada
| | - Frédéric Raymond
- Centre de recherche en Infectiologie du CHU de Québec and Département de Microbiologie, Infectiologie et Immunologie, Université Laval, Québec City, Québec, Canada
| | - Philippe Leprohon
- Centre de recherche en Infectiologie du CHU de Québec and Département de Microbiologie, Infectiologie et Immunologie, Université Laval, Québec City, Québec, Canada
| | - Danielle Légaré
- Centre de recherche en Infectiologie du CHU de Québec and Département de Microbiologie, Infectiologie et Immunologie, Université Laval, Québec City, Québec, Canada
| | - Jacques Corbeil
- Centre de recherche en Infectiologie du CHU de Québec and Département de Microbiologie, Infectiologie et Immunologie, Université Laval, Québec City, Québec, Canada
| | - Marc Ouellette
- Centre de recherche en Infectiologie du CHU de Québec and Département de Microbiologie, Infectiologie et Immunologie, Université Laval, Québec City, Québec, Canada
- * E-mail:
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Jackson AP, Allison HC, Barry JD, Field MC, Hertz-Fowler C, Berriman M. A cell-surface phylome for African trypanosomes. PLoS Negl Trop Dis 2013; 7:e2121. [PMID: 23556014 PMCID: PMC3605285 DOI: 10.1371/journal.pntd.0002121] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Accepted: 02/04/2013] [Indexed: 11/29/2022] Open
Abstract
The cell surface of Trypanosoma brucei, like many protistan blood parasites, is crucial for mediating host-parasite interactions and is instrumental to the initiation, maintenance and severity of infection. Previous comparisons with the related trypanosomatid parasites T. cruzi and Leishmania major suggest that the cell-surface proteome of T. brucei is largely taxon-specific. Here we compare genes predicted to encode cell surface proteins of T. brucei with those from two related African trypanosomes, T. congolense and T. vivax. We created a cell surface phylome (CSP) by estimating phylogenies for 79 gene families with putative surface functions to understand the more recent evolution of African trypanosome surface architecture. Our findings demonstrate that the transferrin receptor genes essential for bloodstream survival in T. brucei are conserved in T. congolense but absent from T. vivax and include an expanded gene family of insect stage-specific surface glycoproteins that includes many currently uncharacterized genes. We also identify species-specific features and innovations and confirm that these include most expression site-associated genes (ESAGs) in T. brucei, which are absent from T. congolense and T. vivax. The CSP presents the first global picture of the origins and dynamics of cell surface architecture in African trypanosomes, representing the principal differences in genomic repertoire between African trypanosome species and provides a basis from which to explore the developmental and pathological differences in surface architectures. All data can be accessed at: http://www.genedb.org/Page/trypanosoma_surface_phylome. The African trypanosome (Trypanosoma brucei) is a single-celled, vector-borne parasite that causes Human African Trypanosomiasis (or ‘sleeping sickness’) throughout sub-Saharan Africa and, along with related species T. congolense and T. vivax, a similar disease in wild and domestic animals. Together, the African trypanosomes have significant effects on human and animal health and associated costs for socio-economic development in Africa. Genes expressed on the trypanosome cell surface are instrumental in causing disease and sustaining infection by resisting the host immune system. Here we compare repertoires of genes with predicted cell-surface expression in T. brucei, T. congolense and T. vivax and estimate the phylogeny of each predicted cell-surface gene family. This ‘cell-surface phylome’ (CSP) provides a detailed analysis of species-specific gene families and of gene gain and loss in shared families, aiding the identification of surface proteins that may mediate specific aspects of pathogenesis and disease progression. Overall, the CSP suggests that each trypanosome species has modified its surface proteome uniquely, indicating that T. brucei, T. congolense and T. vivax have subtly distinct mechanisms for interacting with both vertebrate and insect hosts.
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Affiliation(s)
- Andrew P Jackson
- Pathogen Genomics Group, Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, England, United Kingdom.
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15
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Munday JC, Rojas López KE, Eze AA, Delespaux V, Van Den Abbeele J, Rowan T, Barrett MP, Morrison LJ, de Koning HP. Functional expression of TcoAT1 reveals it to be a P1-type nucleoside transporter with no capacity for diminazene uptake. INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE 2013; 3:69-76. [PMID: 24533295 PMCID: PMC3862423 DOI: 10.1016/j.ijpddr.2013.01.004] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Revised: 01/19/2013] [Accepted: 01/23/2013] [Indexed: 11/26/2022]
Abstract
It has long been established that the Trypanosoma brucei TbAT1/P2 aminopurine transporter is involved in the uptake of diamidine and arsenical drugs including pentamidine, diminazene aceturate and melarsoprol. Accordingly, it was proposed that the closest Trypanosoma congolense paralogue, TcoAT1, might perform the same function in this parasite, and an apparent correlation between a Single Nucleotide Polymorphism (SNP) in that gene and diminazene tolerance was reported for the strains examined. Here, we report the functional cloning and expression of TcoAT1 and show that in fact it is the syntenic homologue of another T. brucei gene of the same Equilibrative Nucleoside Transporter (ENT) family: TbNT10. The T. congolense genome does not seem to contain a syntenic equivalent to TbAT1. Two TcoAT1 alleles, differentiated by three independent SNPs, were expressed in the T. brucei clone B48, a TbAT1-null strain that further lacks the High Affinity Pentamidine Transporter (HAPT1); TbAT1 was also expressed as a control. The TbAT1 and TcoAT1 transporters were functional and increased sensitivity to cytotoxic nucleoside analogues. However, only TbAT1 increased sensitivity to diamidines and to cymelarsan. Uptake of [3H]-diminazene was detectable only in the B48 cells expressing TbAT1 but not TcoAT1, whereas uptake of [3H]-inosine was increased by both TcoAT1 alleles but not by TbAT1. Uptake of [3H]-adenosine was increased by all three ENT genes. We conclude that TcoAT1 is a P1-type purine nucleoside transporter and the syntenic equivalent to the previously characterised TbNT10; it does not mediate diminazene uptake and is therefore unlikely to play a role in diminazene resistance in T. congolense.
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Affiliation(s)
- Jane C Munday
- Wellcome Trust Centre for Molecular Parasitology, University of Glasgow, Glasgow, United Kingdom ; Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Karla E Rojas López
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Anthonius A Eze
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Vincent Delespaux
- Institute of Tropical Medicine, Nationalestraat 155, B-2000 Antwerp, Belgium
| | - Jan Van Den Abbeele
- Institute of Tropical Medicine, Nationalestraat 155, B-2000 Antwerp, Belgium
| | - Tim Rowan
- GALVmed, Pentlands Science Park, Bush Loan, Edinburgh, United Kingdom
| | - Michael P Barrett
- Wellcome Trust Centre for Molecular Parasitology, University of Glasgow, Glasgow, United Kingdom ; Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Liam J Morrison
- Wellcome Trust Centre for Molecular Parasitology, University of Glasgow, Glasgow, United Kingdom ; Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom ; Roslin Institute, University of Edinburgh, Easter Bush, Midlothian, United Kingdom
| | - Harry P de Koning
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
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16
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Simo G, Herder S, Cuny G, Hoheisel J. Identification of subspecies specific genes differentially expressed in procyclic forms of Trypanosoma brucei subspecies. INFECTION GENETICS AND EVOLUTION 2010; 10:229-37. [DOI: 10.1016/j.meegid.2009.11.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2009] [Revised: 10/29/2009] [Accepted: 11/03/2009] [Indexed: 11/30/2022]
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17
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Two novel nucleobase/pentamidine transporters from Trypanosoma brucei. Mol Biochem Parasitol 2008; 163:67-76. [PMID: 18992774 DOI: 10.1016/j.molbiopara.2008.09.011] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2007] [Revised: 09/24/2008] [Accepted: 09/25/2008] [Indexed: 11/23/2022]
Abstract
African trypanosomes are unable to synthesize purines de novo and must salvage preformed purine nucleosides and nucleobases from their hosts. The Trypanosoma brucei genome project has identified 12 members of the equilibrative nucleoside transporter family, most of which have been characterized previously as nucleoside and/or nucleobase transporters. Here the 11th member of this family, TbNT11.1, has been functionally expressed in null mutants of Leishmania that are deficient in purine nucleoside or nucleobase uptake and identified as a high-affinity purine nucleobase transporter. Expression of TbNT11.1 in Xenopus oocytes revealed that it is also a transporter for the diamidine drug pentamidine that is the principal drug employed to treat early stage human African trypanosomiasis and may thus contribute to the uptake of this therapeutically important compound. In addition, characterization of the 12th member of the family, TbNT12.1, reveals that it is an adenine/pentamidine transporter.
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18
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Goldshmidt H, Sheiner L, Bütikofer P, Roditi I, Uliel S, Günzel M, Engstler M, Michaeli S. Role of protein translocation pathways across the endoplasmic reticulum in Trypanosoma brucei. J Biol Chem 2008; 283:32085-98. [PMID: 18768469 DOI: 10.1074/jbc.m801499200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The translocation of secretory and membrane proteins across the endoplasmic reticulum (ER) membrane is mediated by co-translational (via the signal recognition particle (SRP)) and post-translational mechanisms. In this study, we investigated the relative contributions of these two pathways in trypanosomes. A homologue of SEC71, which functions in the post-translocation chaperone pathway in yeast, was identified and silenced by RNA interference. This factor is essential for parasite viability. In SEC71-silenced cells, signal peptide (SP)-containing proteins traversed the ER, but several were mislocalized, whereas polytopic membrane protein biogenesis was unaffected. Surprisingly trypanosomes can interchangeably utilize two of the pathways to translocate SP-containing proteins except for glycosylphosphatidylinositol-anchored proteins, whose level was reduced in SEC71-silenced cells but not in cells depleted for SRP68, an SRP-binding protein. Entry of SP-containing proteins to the ER was significantly blocked only in cells co-silenced for the two translocation pathways (SEC71 and SRP68). SEC63, a factor essential for both translocation pathways in yeast, was identified and silenced by RNA interference. SEC63 silencing affected entry to the ER of both SP-containing proteins and polytopic membrane proteins, suggesting that, as in yeast, this factor is essential for both translocation pathways in vivo. This study suggests that, unlike bacteria or other eukaryotes, trypanosomes are generally promiscuous in their choice of mechanism for translocating SP-containing proteins to the ER, although the SRP-independent pathway is favored for glycosylphosphatidylinositol-anchored proteins, which are the most abundant surface proteins in these parasites.
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Affiliation(s)
- Hanoch Goldshmidt
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel
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Papageorgiou I, De Koning HP, Soteriadou K, Diallinas G. Kinetic and mutational analysis of the Trypanosoma brucei NBT1 nucleobase transporter expressed in Saccharomyces cerevisiae reveals structural similarities between ENT and MFS transporters. Int J Parasitol 2007; 38:641-53. [PMID: 18036529 DOI: 10.1016/j.ijpara.2007.10.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2007] [Revised: 10/04/2007] [Accepted: 10/08/2007] [Indexed: 02/04/2023]
Abstract
Parasitic protozoa are unable to synthesise purines de novo and thus depend on the uptake of nucleosides and nucleobases across their plasma membrane through specific transporters. A number of nucleoside and nucleobase transporters from Trypanosoma brucei brucei and Leishmania major have recently been characterised and shown to belong to the equilibrative nucleoside transporter (ENT) family. A number of studies have demonstrated the functional importance of particular transmembrane segments (TMS) in nucleoside-specific ENT proteins. TbNBT1, one of only three bona fide nucleobase-selective members of the ENT family, has previously been shown to be a high-affinity transporter for purine nucleobases and guanosine. In this study, we use the Saccharomyces cerevisiae expression system to build a biochemical model of how TbNBT1 recognises nucleobases. We next performed random in vitro and site-directed mutagenesis to identify residues critical for TbNBT1 function. The identification of residues likely to contribute to permeant binding, when combined with a structural model of TbNBT1 obtained by homology threading, yield a tentative three-dimensional model of the transporter binding site that is consistent with the binding model emerging from the biochemical data. The model strongly suggests the involvement of TMS5, TMS7 and TMS8 in TbNBT1 function. This situation is very similar to that concerning transporters of the major facilitator superfamily (MFS), one of which was used as a template for the threading. This point raises the possibility that ENT and MFS carriers, despite being considered evolutionarily distinct, might in fact share similar topologies and substrate translocations pathways.
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Affiliation(s)
- I Papageorgiou
- Department of Botany, University of Athens, Panepistimioupolis, Athens 15781, Greece
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20
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Lustig Y, Vagima Y, Goldshmidt H, Erlanger A, Ozeri V, Vince J, McConville MJ, Dwyer DM, Landfear SM, Michaeli S. Down-regulation of the trypanosomatid signal recognition particle affects the biogenesis of polytopic membrane proteins but not of signal peptide-containing proteins. EUKARYOTIC CELL 2007; 6:1865-75. [PMID: 17715370 PMCID: PMC2043396 DOI: 10.1128/ec.00134-07] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Protein translocation across the endoplasmic reticulum is mediated by the signal recognition particle (SRP). In this study, the SRP pathway in trypanosomatids was down-regulated by two approaches: RNA interference (RNAi) silencing of genes encoding SRP proteins in Trypanosoma brucei and overexpression of dominant-negative mutants of 7SL RNA in Leptomonas collosoma. The biogenesis of both signal peptide-containing proteins and polytopic membrane proteins was examined using endogenous and green fluorescent protein-fused proteins. RNAi silencing of SRP54 or SRP68 in T. brucei resulted in reduced levels of polytopic membrane proteins, but no effect on the level of signal peptide-containing proteins was observed. When SRP deficiency was achieved in L. collosoma by overexpression of dominant-negative mutated 7SL RNA, a major effect was observed on polytopic membrane proteins but not on signal peptide-containing proteins. This study included two trypanosomatid species, tested various protein substrates, and induced depletion of the SRP pathway by affecting either the levels of SRP binding proteins or that of SRP RNA. Our results demonstrate that, as in bacteria but in contrast to mammalian cells, the trypanosome SRP is mostly essential for the biogenesis of membrane proteins.
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Affiliation(s)
- Yaniv Lustig
- The Mina and Everard Goodman Faculty of Life Sciences, Bar Ilan University, Ramat Gan, Israel
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Barrett MP, Gilbert IH. Targeting of toxic compounds to the trypanosome's interior. ADVANCES IN PARASITOLOGY 2006; 63:125-83. [PMID: 17134653 DOI: 10.1016/s0065-308x(06)63002-9] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Drugs can be targeted into African trypanosomes by exploiting carrier proteins at the surface of these parasites. This has been clearly demonstrated in the case of the melamine-based arsenical and the diamidine classes of drug that are already in use in the treatment of human African trypanosomiasis. These drugs can enter via an aminopurine transporter, termed P2, encoded by the TbAT1 gene. Other toxic compounds have also been designed to enter via this transporter. Some of these compounds enter almost exclusively through the P2 transporter, and hence loss of the P2 transporter leads to significant resistance to these particular compounds. It now appears, however, that some diamidines and melaminophenylarsenicals may also be taken up by other routes (of yet unknown function). These too may be exploited to target new drugs into trypanosomes. Additional purine nucleoside and nucleobase transporters have also been subverted to deliver toxic agents to trypanosomes. Glucose and amino acid transporters too have been investigated with a view to manipulating them to carry toxins into Trypanosoma brucei, and recent work has demonstrated that aquaglyceroporins may also have considerable potential for drug-targeting. Transporters, including those that carry lipids and vitamins such as folate and other pterins also deserve more attention in this regard. Some drugs, for example suramin, appear to enter via routes other than plasma-membrane-mediated transport. Receptor-mediated endocytosis has been proposed as a possible way in for suramin. Endocytosis also appears to be crucial in targeting natural trypanocides, such as trypanosome lytic factor (TLF) (apolipoprotein L1), into trypanosomes and this offers an alternative means of selectively targeting toxins to the trypanosome's interior. Other compounds may be induced to enter by increasing their capacity to diffuse over cell membranes; in this case depending exclusively on selective activity within the cell rather than selective uptake to impart selective toxicity. This review outlines studies that have aimed to exploit trypanosome nutrient uptake routes to selectively carry toxins into these parasites.
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Affiliation(s)
- Michael P Barrett
- Division of Infection & Immunity, Institute of Biomedical and Life Sciences, Glasgow Biomedical Research Centre, University of Glasgow, Glasgow G12 8QQ, UK
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Valdés R, Liu W, Ullman B, Landfear SM. Comprehensive examination of charged intramembrane residues in a nucleoside transporter. J Biol Chem 2006; 281:22647-55. [PMID: 16769726 DOI: 10.1074/jbc.m602366200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Permeases of the equilibrative nucleoside transporter family mediate the uptake of nucleosides and/or nucleobases in a diverse array of eukaryotes and transport a host of drugs used for treatment of cancer, heart disease, AIDS, and parasitic infections. To identify residues that play central roles in transport function, we have systematically substituted by site-directed mutagenesis all the charged residues located within predicted transmembrane domains of the Leishmania donovani nucleoside transporter 1.1, LdNT1.1, which transports adenosine and the pyrimidine nucleosides. Substitution of three of these ten residues by uncharged amino acids resulted in loss of >95% transport activity, and we hence designated them "key" residues. These amino acids were Glu94, Lys153, and Arg404 located in transmembrane domains 2, 4, and 9, respectively. In addition, previous studies on the related LdNT2 inosine/guanosine transporter identified the highly conserved Asp389 and Arg393 (equivalent to Asp374 and Arg378 in LdNT1.1) in transmembrane domain 8 as key residues. Among these residues, the mutants in Arg393 (LdNT2) and Arg404 were strongly impaired in trafficking to the plasma membrane, but the other mutants were expressed with high to moderate efficiency at the cell surface, indicating that their mutation impaired transport activity per se. A conservative K153R substitution exhibited a change in substrate specificity, acquiring the ability to transport inosine, a nucleoside that is not a substrate for the wild-type LdNT1.1 permease. These results imply that the Glu94, Lys153, and Asp374 residues may play central roles in the mechanism of substrate translocation in LdNT1.1.
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Affiliation(s)
- Raquel Valdés
- Department of Molecular Microbiology and Immunology and Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon 97239, USA
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de Koning HP, Bridges DJ, Burchmore RJS. Purine and pyrimidine transport in pathogenic protozoa: From biology to therapy. FEMS Microbiol Rev 2005; 29:987-1020. [PMID: 16040150 DOI: 10.1016/j.femsre.2005.03.004] [Citation(s) in RCA: 146] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2004] [Revised: 03/22/2005] [Accepted: 03/24/2005] [Indexed: 01/10/2023] Open
Abstract
Purine salvage is an essential function for all obligate parasitic protozoa studied to date and most are also capable of efficient uptake of preformed pyrimidines. Much progress has been made in the identification and characterisation of protozoan purine and pyrimidine transporters. While the genes encoding protozoan or metazoan pyrimidine transporters have yet to be identified, numerous purine transporters have now been cloned. All protozoan purine transporter-encoding genes characterised to date have been of the Equilibrative Nucleoside Transporter family conserved in a great variety of eukaryote organisms. However, these protozoan transporters have been shown to be sufficiently different from mammalian transporters to mediate selective uptake of therapeutic agents. Recent studies are increasingly addressing the structure and substrate recognition mechanisms of these vital transport proteins.
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Affiliation(s)
- Harry P de Koning
- Institute of Biomedical and Life Sciences, Division of Infection and Immunity, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ, UK.
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Al-Salabi MI, de Koning HP. Purine nucleobase transport in amastigotes of Leishmania mexicana: involvement in allopurinol uptake. Antimicrob Agents Chemother 2005; 49:3682-9. [PMID: 16127040 PMCID: PMC1195421 DOI: 10.1128/aac.49.9.3682-3689.2005] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2005] [Revised: 05/05/2005] [Accepted: 05/22/2005] [Indexed: 11/20/2022] Open
Abstract
Nucleobase and nucleoside transporters play central roles in the biochemistry of parasitic protozoa, as they lack the ability to synthesize purines de novo and are absolutely reliant upon purine salvage from their hosts. Furthermore, such transporters are potentially critical to the pharmacology of these important human pathogens, because they mediate the uptake of purine analogues, as well as some nonpurine drugs, that can be selectively cytotoxic to the parasites. We here report the first identification and characterization of a purine nucleobase transporter in Leishmania amastigotes. Uptake of [3H]hypoxanthine by Leishmania mexicana amastigotes was mediated by a single high-affinity transporter, LmexNBT1, with a Km of 1.6 +/- 0.4 microM and high affinity for adenine, guanine, and xanthine but low affinity for nucleosides and pyrimidine nucleobases. Allopurinol, an antileishmanial hypoxanthine analogue, was apparently taken up by the same transporter. Using [3H]allopurinol, a Km value of 33.6 +/- 6.0 microM was obtained. All evidence was compatible with a model of a single purine nucleobase transporter being expressed in amastigotes. Using various purine nucleobase analogues, a model for the interactions between hypoxanthine and the transporter's permeant binding site was constructed. The binding interactions were compared with those of the LmajNBT1 transporter in Leishmania major promastigotes and found to be very similar.
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Affiliation(s)
- Mohammed I Al-Salabi
- Institute of Biomedical and Life Sciences, Division of Infection and Immunity, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ, United Kingdom
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Landfear SM, Ullman B, Carter NS, Sanchez MA. Nucleoside and nucleobase transporters in parasitic protozoa. EUKARYOTIC CELL 2004; 3:245-54. [PMID: 15075255 PMCID: PMC387651 DOI: 10.1128/ec.3.2.245-254.2004] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Scott M Landfear
- Department of Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, Oregon 97239-3098, USA.
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Sanchez MA, Drutman S, van Ampting M, Matthews K, Landfear SM. A novel purine nucleoside transporter whose expression is up-regulated in the short stumpy form of the Trypanosoma brucei life cycle. Mol Biochem Parasitol 2004; 136:265-72. [PMID: 15478805 DOI: 10.1016/j.molbiopara.2004.04.009] [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: 11/15/2022]
Abstract
Purine nucleoside and nucleobase transporters play a vital role in the metabolism and survival of Trypanosoma brucei because this parasitic protozoan is unable to synthesize purines de novo and thus must acquire preformed purines from its hosts. These parasites express a variety of nucleoside and nucleobase permeases with diverse substrate specificities and distinct patterns of expression during the trypanosome life cycle. We report here that expression of the newly characterized T. brucei nucleoside transporter 10 gene (TbNT10) is up-regulated in the short stumpy form of the life cycle, the bloodstream form of the parasite that is pre-adapted for infection of the tsetse fly vector. Functional expression of TbNT10 in Saccharomyces cerevisiae reveals that the TbNT10 gene encodes an adenosine/guanosine/inosine transporter with apparent Km values of approximately 1 microM and hence is a high affinity purine nucleoside transporter. The restricted expression of TbNT10 during the life cycle suggests that the functional properties of this permease may be specialized to support development and growth of the differentiated short stumpy form or to promote the transformation of short stumpy to procyclic forms within the insect vector.
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Affiliation(s)
- Marco A Sanchez
- Department of Molecular Microbiology & Immunology, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, L220, Portland, OR 97239, USA.
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Abstract
Drug resistance in African trypanosomes has been studied for almost a hundred years. Beginning with Paul Ehrlich's work that led to the chemoreceptor hypothesis, reduction of net drug uptake has emerged as the most frequent cause of resistance. This review, therefore, focuses on trypanosomal drug transporter genes. TbAT1 encodes purine permease P2, which mediates influx of melarsoprol and diamidines. Disruption of TbAT1 in Trypanosoma brucei reduced sensitivity to these trypanocides. TbMRPA encodes a putative trypanothione-conjugate efflux pump, and overexpression of TbMRPA in T. brucei causes melarsoprol resistance. It will be important to determine the role of TbAT1 and TbMRPA in sleeping sickness treatment failures.
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Affiliation(s)
- Pascal Mäser
- Institute of Cell Biology, University of Bern, Bern, Switzerland
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