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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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The Trypanosoma cruzi TcrNT2 Nucleoside Transporter Is a Conduit for the Uptake of 5-F-2'-Deoxyuridine and Tubercidin Analogues. Molecules 2022; 27:molecules27228045. [PMID: 36432150 PMCID: PMC9693223 DOI: 10.3390/molecules27228045] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2022] [Revised: 11/14/2022] [Accepted: 11/17/2022] [Indexed: 11/22/2022] Open
Abstract
Among the scarce validated drug targets against Chagas disease (CD), caused by Trypanosoma cruzi, the parasite's nucleoside salvage system has recently attracted considerable attention. Although the trypanocidal activity of tubercidin (7-deazapurine) has long been known, the identification of a class of 7-substituted tubercidin analogs with potent in vitro and in vivo activity and much-enhanced selectivity has made nucleoside analogs among the most promising lead compounds against CD. Here, we investigate the recently identified TcrNT2 nucleoside transporter and its potential role in antimetabolite chemotherapy. TcrNT2, expressed in a Leishmania mexicana cell line lacking the NT1 nucleoside transporter locus, displayed very high selectivity and affinity for thymidine with a Km of 0.26 ± 0.05 µM. The selectivity was explained by interactions of 2-oxo, 4-oxo, 5-Me, 3'-hydroxy and 5'-hydroxy with the transporter binding pocket, whereas a hydroxy group at the 2' position was deleterious to binding. This made 5-halogenated 2'-deoxyuridine analogues good substrates but 5-F-2'-deoxyuridine displayed disappointing activity against T. cruzi trypomastigotes. By comparing the EC50 values of tubercidin and its 7-substituted analogues against L. mexicana Cas9, Cas9ΔNT1 and Cas9ΔNT1+TcrNT2 it was shown that TcrNT2 can take up tubercidin and, at a minimum, a subset of the analogs.
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Nucleoside Transport and Nucleobase Uptake Null Mutants in Leishmania mexicana for the Routine Expression and Characterization of Purine and Pyrimidine Transporters. Int J Mol Sci 2022; 23:ijms23158139. [PMID: 35897714 PMCID: PMC9331716 DOI: 10.3390/ijms23158139] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 07/05/2022] [Accepted: 07/20/2022] [Indexed: 12/02/2022] Open
Abstract
The study of transporters is highly challenging, as they cannot be isolated or studied in suspension, requiring a cellular or vesicular system, and, when mediated by more than one carrier, difficult to interpret. Nucleoside analogues are important drug candidates, and all protozoan pathogens express multiple equilibrative nucleoside transporter (ENT) genes. We have therefore developed a system for the routine expression of nucleoside transporters, using CRISPR/cas9 to delete both copies of all three nucleoside transporters from Leishmania mexicana (ΔNT1.1/1.2/2 (SUPKO)). SUPKO grew at the same rate as the parental strain and displayed no apparent deficiencies, owing to the cells’ ability to synthesize pyrimidines, and the expression of the LmexNT3 purine nucleobase transporter. Nucleoside transport was barely measurable in SUPKO, but reintroduction of L. mexicana NT1.1, NT1.2, and NT2 restored uptake. Thus, SUPKO provides an ideal null background for the expression and characterization of single ENT transporter genes in isolation. Similarly, an LmexNT3-KO strain provides a null background for transport of purine nucleobases and was used for the functional characterization of T. cruzi NB2, which was determined to be adenine-specific. A 5-fluorouracil-resistant strain (Lmex5FURes) displayed null transport for uracil and 5FU, and was used to express the Aspergillus nidulans uracil transporter FurD.
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Campagnaro GD, Elati HAA, Balaska S, Martin Abril ME, Natto MJ, Hulpia F, Lee K, Sheiner L, Van Calenbergh S, de Koning HP. A Toxoplasma gondii Oxopurine Transporter Binds Nucleobases and Nucleosides Using Different Binding Modes. Int J Mol Sci 2022; 23:ijms23020710. [PMID: 35054895 PMCID: PMC8776092 DOI: 10.3390/ijms23020710] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 01/06/2022] [Accepted: 01/07/2022] [Indexed: 12/13/2022] Open
Abstract
Toxoplasma gondii is unable to synthesize purines de novo, instead salvages them from its environment, inside the host cell, for which they need high affinity carriers. Here, we report the expression of a T. gondii Equilibrative Nucleoside Transporter, Tg244440, in a Trypanosoma brucei strain from which nucleobase transporters have been deleted. Tg244440 transported hypoxanthine and guanine with similar affinity (Km ~1 µM), while inosine and guanosine displayed Ki values of 4.05 and 3.30 µM, respectively. Low affinity was observed for adenosine, adenine, and pyrimidines, classifying Tg244440 as a high affinity oxopurine transporter. Purine analogues were used to probe the substrate-transporter binding interactions, culminating in quantitative models showing different binding modes for oxopurine bases, oxopurine nucleosides, and adenosine. Hypoxanthine and guanine interacted through protonated N1 and N9, and through unprotonated N3 and N7 of the purine ring, whereas inosine and guanosine mostly employed the ribose hydroxy groups for binding, in addition to N1H of the nucleobase. Conversely, the ribose moiety of adenosine barely made any contribution to binding. Tg244440 is the first gene identified to encode a high affinity oxopurine transporter in T. gondii and, to the best of our knowledge, the first purine transporter to employ different binding modes for nucleosides and nucleobases.
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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, Glasgow G12 8TA, UK; (G.D.C.); (H.A.A.E.); (S.B.); (M.E.M.A.); (M.J.N.); (K.L.); (L.S.)
| | - Hamza A. A. Elati
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK; (G.D.C.); (H.A.A.E.); (S.B.); (M.E.M.A.); (M.J.N.); (K.L.); (L.S.)
| | - Sofia Balaska
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK; (G.D.C.); (H.A.A.E.); (S.B.); (M.E.M.A.); (M.J.N.); (K.L.); (L.S.)
| | - Maria Esther Martin Abril
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK; (G.D.C.); (H.A.A.E.); (S.B.); (M.E.M.A.); (M.J.N.); (K.L.); (L.S.)
| | - Manal J. Natto
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK; (G.D.C.); (H.A.A.E.); (S.B.); (M.E.M.A.); (M.J.N.); (K.L.); (L.S.)
| | - Fabian Hulpia
- Laboratory for Medicinal Chemistry, Campus Heymans, Ghent University, Ottergemsesteenweg 460, B-9000 Gent, Belgium; (F.H.); (S.V.C.)
| | - Kelly Lee
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK; (G.D.C.); (H.A.A.E.); (S.B.); (M.E.M.A.); (M.J.N.); (K.L.); (L.S.)
| | - Lilach Sheiner
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK; (G.D.C.); (H.A.A.E.); (S.B.); (M.E.M.A.); (M.J.N.); (K.L.); (L.S.)
- Wellcome Centre for Integrative Parasitology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK
| | - Serge Van Calenbergh
- Laboratory for Medicinal Chemistry, Campus Heymans, Ghent University, Ottergemsesteenweg 460, B-9000 Gent, Belgium; (F.H.); (S.V.C.)
| | - Harry P. de Koning
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK; (G.D.C.); (H.A.A.E.); (S.B.); (M.E.M.A.); (M.J.N.); (K.L.); (L.S.)
- Correspondence: ; Tel.: +44-141-3303753
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6
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Natto MJ, Miyamoto Y, Munday JC, AlSiari TA, Al-Salabi MI, Quashie NB, Eze AA, Eckmann L, De Koning HP. Comprehensive characterization of purine and pyrimidine transport activities in Trichomonas vaginalis and functional cloning of a trichomonad nucleoside transporter. Mol Microbiol 2021; 116:1489-1511. [PMID: 34738285 PMCID: PMC8688338 DOI: 10.1111/mmi.14840] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2021] [Revised: 10/30/2021] [Accepted: 10/30/2021] [Indexed: 11/30/2022]
Abstract
Trichomoniasis is a common and widespread sexually-transmitted infection, caused by the protozoan parasite Trichomonas vaginalis. T. vaginalis lacks the biosynthetic pathways for purines and pyrimidines, making nucleoside metabolism a drug target. Here we report the first comprehensive investigation into purine and pyrimidine uptake by T. vaginalis. Multiple carriers were identified and characterized with regard to substrate selectivity and affinity. For nucleobases, a high-affinity adenine transporter, a possible guanine transporter and a low affinity uracil transporter were found. Nucleoside transporters included two high affinity adenosine/guanosine/uridine/cytidine transporters distinguished by different affinities to inosine, a lower affinity adenosine transporter, and a thymidine transporter. Nine Equilibrative Nucleoside Transporter (ENT) genes were identified in the T. vaginalis genome. All were expressed equally in metronidazole-resistant and -sensitive strains. Only TvagENT2 was significantly upregulated in the presence of extracellular purines; expression was not affected by co-culture with human cervical epithelial cells. All TvagENTs were cloned and separately expressed in Trypanosoma brucei. We identified the main broad specificity nucleoside carrier, with high affinity for uridine and cytidine as well as purine nucleosides including inosine, as TvagENT3. The in-depth characterization of purine and pyrimidine transporters provides a critical foundation for the development of new anti-trichomonal nucleoside analogues.
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Affiliation(s)
- Manal J. Natto
- Institute of Infection, Immunity and Inflammation, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Yukiko Miyamoto
- Department of Medicine, University of California, San Diego, La Jolla, California 92093, United States
| | - Jane C. Munday
- Institute of Infection, Immunity and Inflammation, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Tahani A. AlSiari
- Institute of Infection, Immunity and Inflammation, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Mohammed I. Al-Salabi
- Institute of Infection, Immunity and Inflammation, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Neils B. Quashie
- Institute of Infection, Immunity and Inflammation, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
- Centre for Tropical Clinical Pharmacology and Therapeutics, University of Ghana Medical School, University of Ghana
| | - Anthonius A. Eze
- Institute of Infection, Immunity and Inflammation, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
- Current affiliation: Department of Medical Biochemistry, Faculty of Basic Medical Sciences, College of Medicine, University of Nigeria, Enugu Campus, Enugu, Nigeria
| | - Lars Eckmann
- Department of Medicine, University of California, San Diego, La Jolla, California 92093, United States
| | - Harry P. De Koning
- Institute of Infection, Immunity and Inflammation, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
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Alghamdi AH, Munday JC, Campagnaro GD, Gurvic D, Svensson F, Okpara CE, Kumar A, Quintana J, Martin Abril ME, Milić P, Watson L, Paape D, Settimo L, Dimitriou A, Wielinska J, Smart G, Anderson LF, Woodley CM, Kelly SPY, Ibrahim HM, Hulpia F, Al-Salabi MI, Eze AA, Sprenger T, Teka IA, Gudin S, Weyand S, Field M, Dardonville C, Tidwell RR, Carrington M, O'Neill P, Boykin DW, Zachariae U, De Koning HP. Positively selected modifications in the pore of TbAQP2 allow pentamidine to enter Trypanosoma brucei. eLife 2020; 9:56416. [PMID: 32762841 PMCID: PMC7473772 DOI: 10.7554/elife.56416] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Accepted: 08/06/2020] [Indexed: 11/25/2022] Open
Abstract
Mutations in the Trypanosoma brucei aquaporin AQP2 are associated with resistance to pentamidine and melarsoprol. We show that TbAQP2 but not TbAQP3 was positively selected for increased pore size from a common ancestor aquaporin. We demonstrate that TbAQP2’s unique architecture permits pentamidine permeation through its central pore and show how specific mutations in highly conserved motifs affect drug permeation. Introduction of key TbAQP2 amino acids into TbAQP3 renders the latter permeable to pentamidine. Molecular dynamics demonstrates that permeation by dicationic pentamidine is energetically favourable in TbAQP2, driven by the membrane potential, although aquaporins are normally strictly impermeable for ionic species. We also identify the structural determinants that make pentamidine a permeant although most other diamidine drugs are excluded. Our results have wide-ranging implications for optimising antitrypanosomal drugs and averting cross-resistance. Moreover, these new insights in aquaporin permeation may allow the pharmacological exploitation of other members of this ubiquitous gene family. African sleeping sickness is a potentially deadly illness caused by the parasite Trypanosoma brucei. The disease is treatable, but many of the current treatments are old and are becoming increasingly ineffective. For instance, resistance is growing against pentamidine, a drug used in the early stages in the disease, as well as against melarsoprol, which is deployed when the infection has progressed to the brain. Usually, cases resistant to pentamidine are also resistant to melarsoprol, but it is still unclear why, as the drugs are chemically unrelated. Studies have shown that changes in a water channel called aquaglyceroporin 2 (TbAQP2) contribute to drug resistance in African sleeping sickness; this suggests that it plays a role in allowing drugs to kill the parasite. This molecular ‘drain pipe’ extends through the surface of T. brucei, and should allow only water and a molecule called glycerol in and out of the cell. In particular, the channel should be too narrow to allow pentamidine or melarsoprol to pass through. One possibility is that, in T. brucei, the TbAQP2 channel is abnormally wide compared to other members of its family. Alternatively, pentamidine and melarsoprol may only bind to TbAQP2, and then ‘hitch a ride’ when the protein is taken into the parasite as part of the natural cycle of surface protein replacement. Alghamdi et al. aimed to tease out these hypotheses. Computer models of the structure of the protein were paired with engineered changes in the key areas of the channel to show that, in T. brucei, TbAQP2 provides a much broader gateway into the cell than observed for similar proteins. In addition, genetic analysis showed that this version of TbAQP2 has been actively selected for during the evolution process of T. brucei. This suggests that the parasite somehow benefits from this wider aquaglyceroporin variant. This is a new resistance mechanism, and it is possible that aquaglyceroporins are also larger than expected in other infectious microbes. The work by Alghamdi et al. therefore provides insight into how other germs may become resistant to drugs.
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Affiliation(s)
- Ali H Alghamdi
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Jane C Munday
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | | | - Dominik Gurvic
- Computational Biology Centre for Translational and Interdisciplinary Research, University of Dundee, Dundee, United Kingdom
| | - Fredrik Svensson
- IOTA Pharmaceuticals Ltd, St Johns Innovation Centre, Cambridge, United Kingdom
| | - Chinyere E Okpara
- Department of Chemistry, University of Liverpool, Liverpool, United Kingdom
| | - Arvind Kumar
- Chemistry Department, Georgia State University, Atlanta, United States
| | - Juan Quintana
- School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | | | - Patrik Milić
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Laura Watson
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Daniel Paape
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Luca Settimo
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Anna Dimitriou
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Joanna Wielinska
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Graeme Smart
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Laura F Anderson
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | | | - Siu Pui Ying Kelly
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Hasan Ms Ibrahim
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Fabian Hulpia
- Laboratory for Medicinal Chemistry, University of Ghent, Ghent, Belgium
| | - Mohammed I Al-Salabi
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Anthonius A Eze
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Teresa Sprenger
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Ibrahim A Teka
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Simon Gudin
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Simone Weyand
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Mark Field
- School of Life Sciences, University of Dundee, Dundee, United Kingdom.,Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Ceske Budejovice, Czech Republic
| | | | - Richard R Tidwell
- Department of Pathology and Lab Medicine, University of North Carolina at Chapel Hill, Chapel Hill, United States
| | - Mark Carrington
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Paul O'Neill
- Department of Chemistry, University of Liverpool, Liverpool, United Kingdom
| | - David W Boykin
- Chemistry Department, Georgia State University, Atlanta, United States
| | - Ulrich Zachariae
- Computational Biology Centre for Translational and Interdisciplinary Research, University of Dundee, Dundee, United Kingdom
| | - Harry P De Koning
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
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8
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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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9
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Hulpia F, Mabille D, Campagnaro GD, Schumann G, Maes L, Roditi I, Hofer A, de Koning HP, Caljon G, Van Calenbergh S. Combining tubercidin and cordycepin scaffolds results in highly active candidates to treat late-stage sleeping sickness. Nat Commun 2019; 10:5564. [PMID: 31804484 PMCID: PMC6895180 DOI: 10.1038/s41467-019-13522-6] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Accepted: 11/13/2019] [Indexed: 12/29/2022] Open
Abstract
African trypanosomiasis is a disease caused by Trypanosoma brucei parasites with limited treatment options. Trypanosoma is unable to synthesize purines de novo and relies solely on their uptake and interconversion from the host, constituting purine nucleoside analogues a potential source of antitrypanosomal agents. Here we combine structural elements from known trypanocidal nucleoside analogues to develop a series of 3’-deoxy-7-deazaadenosine nucleosides, and investigate their effects against African trypanosomes. 3’-Deoxytubercidin is a highly potent trypanocide in vitro and displays curative activity in animal models of acute and CNS-stage disease, even at low doses and oral administration. Whole-genome RNAi screening reveals that the P2 nucleoside transporter and adenosine kinase are involved in the uptake and activation, respectively, of this analogue. This is confirmed by P1 and P2 transporter assays and nucleotide pool analysis. 3’-Deoxytubercidin is a promising lead to treat late-stage sleeping sickness. Trypanosoma brucei relies on uptake and conversion of purines from the host, which constitutes a potential drug target. Here, Hulpia et al. combine structural elements from known trypanocidal nucleoside analogues and develop a potent trypanocide with curative activity in animal models of acute and late stage sleeping sickness.
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Affiliation(s)
- Fabian Hulpia
- Laboratory for Medicinal Chemistry (Campus Heymans), Ghent University, Ottergemsesteenweg 460, 9000, Gent, Belgium
| | - Dorien Mabille
- Laboratory of Microbiology, Parasitology and Hygiene (LMPH), University of Antwerp, Universiteitsplein 1, 2610, Wilrijk, Belgium
| | - Gustavo D Campagnaro
- College of Medical, Veterinary and Life Sciences, Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, G12 8TA, UK
| | - Gabriela Schumann
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012, Bern, Switzerland
| | - Louis Maes
- Laboratory of Microbiology, Parasitology and Hygiene (LMPH), University of Antwerp, Universiteitsplein 1, 2610, Wilrijk, Belgium
| | - Isabel Roditi
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012, Bern, Switzerland
| | - Anders Hofer
- Department of Medical Biochemistry and Biophysics, Umeå University, 901 87, Umeå, Sweden
| | - Harry P de Koning
- College of Medical, Veterinary and Life Sciences, Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, G12 8TA, UK
| | - Guy Caljon
- Laboratory of Microbiology, Parasitology and Hygiene (LMPH), University of Antwerp, Universiteitsplein 1, 2610, Wilrijk, Belgium
| | - Serge Van Calenbergh
- Laboratory for Medicinal Chemistry (Campus Heymans), Ghent University, Ottergemsesteenweg 460, 9000, Gent, Belgium.
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10
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Nucleoside analogue activators of cyclic AMP-independent protein kinase A of Trypanosoma. Nat Commun 2019; 10:1421. [PMID: 30926779 PMCID: PMC6440977 DOI: 10.1038/s41467-019-09338-z] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2018] [Accepted: 03/07/2019] [Indexed: 02/08/2023] Open
Abstract
Protein kinase A (PKA), the main effector of cAMP in eukaryotes, is a paradigm for the mechanisms of ligand-dependent and allosteric regulation in signalling. Here we report the orthologous but cAMP-independent PKA of the protozoan Trypanosoma and identify 7-deaza-nucleosides as potent activators (EC50 ≥ 6.5 nM) and high affinity ligands (KD ≥ 8 nM). A co-crystal structure of trypanosome PKA with 7-cyano-7-deazainosine and molecular docking show how substitution of key amino acids in both CNB domains of the regulatory subunit and its unique C-terminal αD helix account for this ligand swap between trypanosome PKA and canonical cAMP-dependent PKAs. We propose nucleoside-related endogenous activators of Trypanosoma brucei PKA (TbPKA). The existence of eukaryotic CNB domains not associated with binding of cyclic nucleotides suggests that orphan CNB domains in other eukaryotes may bind undiscovered signalling molecules. Phosphoproteome analysis validates 7-cyano-7-deazainosine as powerful cell-permeable inducer to explore cAMP-independent PKA signalling in medically important neglected pathogens.
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11
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Revisiting tubercidin against kinetoplastid parasites: Aromatic substitutions at position 7 improve activity and reduce toxicity. Eur J Med Chem 2019; 164:689-705. [DOI: 10.1016/j.ejmech.2018.12.050] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 11/09/2018] [Accepted: 12/20/2018] [Indexed: 02/05/2023]
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12
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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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13
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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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14
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Alzahrani KJH, Ali JAM, Eze AA, Looi WL, Tagoe DNA, Creek DJ, Barrett MP, de Koning HP. Functional and genetic evidence that nucleoside transport is highly conserved in Leishmania species: Implications for pyrimidine-based chemotherapy. Int J Parasitol Drugs Drug Resist 2017; 7:206-226. [PMID: 28453984 PMCID: PMC5407577 DOI: 10.1016/j.ijpddr.2017.04.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Revised: 04/14/2017] [Accepted: 04/18/2017] [Indexed: 11/28/2022]
Abstract
Leishmania pyrimidine salvage is replete with opportunities for therapeutic intervention with enzyme inhibitors or antimetabolites. Their uptake into cells depends upon specific transporters; therefore it is essential to establish whether various Leishmania species possess similar pyrimidine transporters capable of drug uptake. Here, we report a comprehensive characterization of pyrimidine transport in L. major and L. mexicana. In both species, two transporters for uridine/adenosine were detected, one of which also transported uracil and the antimetabolites 5-fluoruracil (5-FU) and 5F,2'deoxyuridine (5F,2'dUrd), and was designated uridine-uracil transporter 1 (UUT1); the other transporter mediated uptake of adenosine, uridine, 5F,2'dUrd and thymidine and was designated Nucleoside Transporter 1 (NT1). To verify the reported L. donovani model of two NT1-like genes encoding uridine/adenosine transporters, and an NT2 gene encoding an inosine transporter, we cloned the corresponding L. major and L. mexicana genes, expressing each in T. brucei. Consistent with the L. donovani reports, the NT1-like genes of either species mediated the adenosine-sensitive uptake of [3H]-uridine but not of [3H]-inosine. Conversely, the NT2-like genes mediated uptake of [3H]-inosine but not [3H]-uridine. Among pyrimidine antimetabolites tested, 5-FU and 5F,2'dUrd were the most effective antileishmanials; resistance to both analogs was induced in L. major and L. mexicana. In each case it was found that the resistant cells had lost the transport capacity for the inducing drug. Metabolomics analysis found that the mechanism of action of 5-FU and 5F-2'dUrd was similar in both Leishmania species, with major changes in deoxynucleotide metabolism. We conclude that the pyrimidine salvage system is highly conserved in Leishmania species - essential information for the development of pyrimidine-based chemotherapy.
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Affiliation(s)
- Khalid J H Alzahrani
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom; Department of Clinical Laboratory, College of Applied Medical Sciences, Taif University, Taif, Saudi Arabia
| | - Juma A M Ali
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom; Al Jabal Al Gharbi University, Gharyan, Libya
| | - Anthonius A Eze
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom; Department of Medical Biochemistry, College of Medicine, University of Nigeria, Enugu Campus, Enugu, Nigeria
| | - Wan Limm Looi
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Daniel N A Tagoe
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom; Wellcome Trust Centre for Molecular Parasitology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Darren J Creek
- Department of Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia
| | - Michael P Barrett
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom; Wellcome Trust Centre for Molecular Parasitology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, 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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15
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9-(2'-Deoxy-2'-Fluoro-β-d-Arabinofuranosyl) Adenine Is a Potent Antitrypanosomal Adenosine Analogue That Circumvents Transport-Related Drug Resistance. Antimicrob Agents Chemother 2017; 61:AAC.02719-16. [PMID: 28373184 PMCID: PMC5444181 DOI: 10.1128/aac.02719-16] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Accepted: 03/27/2017] [Indexed: 01/25/2023] Open
Abstract
Current chemotherapy against African sleeping sickness, a disease caused by the protozoan parasite Trypanosoma brucei, is limited by toxicity, inefficacy, and drug resistance. Nucleoside analogues have been successfully used to cure T. brucei-infected mice, but they have the limitation of mainly being taken up by the P2 nucleoside transporter, which, when mutated, is a common cause of multidrug resistance in T. brucei We report here that adenine arabinoside (Ara-A) and the newly tested drug 9-(2'-deoxy-2'-fluoro-β-d-arabinofuranosyl) adenine (FANA-A) are instead taken up by the P1 nucleoside transporter, which is not associated with drug resistance. Like Ara-A, FANA-A was found to be resistant to cleavage by methylthioadenosine phosphorylase, an enzyme that protects T. brucei against the antitrypanosomal effects of deoxyadenosine. Another important factor behind the selectivity of nucleoside analogues is how well they are phosphorylated within the cell. We found that the T. brucei adenosine kinase had a higher catalytic efficiency with FANA-A than the mammalian enzyme, and T. brucei cells treated with FANA-A accumulated high levels of FANA-A triphosphate, which even surpassed the level of ATP and led to cell cycle arrest, inhibition of DNA synthesis, and the accumulation of DNA breaks. FANA-A inhibited nucleic acid biosynthesis and parasite proliferation with 50% effective concentrations (EC50s) in the low nanomolar range, whereas mammalian cell proliferation was inhibited in the micromolar range. Both Ara-A and FANA-A, in combination with deoxycoformycin, cured T. brucei-infected mice, but FANA-A did so at a dose 100 times lower than that of Ara-A.
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16
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Mathieu C, Macêdo JP, Hürlimann D, Wirdnam C, Haindrich AC, Suter Grotemeyer M, González-Salgado A, Schmidt RS, Inbar E, Mäser P, Bütikofer P, Zilberstein D, Rentsch D. Arginine and Lysine Transporters Are Essential for Trypanosoma brucei. PLoS One 2017; 12:e0168775. [PMID: 28045943 PMCID: PMC5207785 DOI: 10.1371/journal.pone.0168775] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 12/06/2016] [Indexed: 12/14/2022] Open
Abstract
For Trypanosoma brucei arginine and lysine are essential amino acids and therefore have to be imported from the host. Heterologous expression in Saccharomyces cerevisiae mutants identified cationic amino acid transporters among members of the T. brucei AAAP (amino acid/auxin permease) family. TbAAT5-3 showed high affinity arginine uptake (Km 3.6 ± 0.4 μM) and high selectivity for L-arginine. L-arginine transport was reduced by a 10-times excess of L-arginine, homo-arginine, canavanine or arginine-β-naphthylamide, while lysine was inhibitory only at 100-times excess, and histidine or ornithine did not reduce arginine uptake rates significantly. TbAAT16-1 is a high affinity (Km 4.3 ± 0.5 μM) and highly selective L-lysine transporter and of the compounds tested, only L-lysine and thialysine were competing for L-lysine uptake. TbAAT5-3 and TbAAT16-1 are expressed in both procyclic and bloodstream form T. brucei and cMyc-tagged proteins indicate localization at the plasma membrane. RNAi-mediated down-regulation of TbAAT5 and TbAAT16 in bloodstream form trypanosomes resulted in growth arrest, demonstrating that TbAAT5-mediated arginine and TbAAT16-mediated lysine transport are essential for T. brucei. Growth of induced RNAi lines could partially be rescued by supplementing a surplus of arginine or lysine, respectively, while addition of both amino acids was less efficient. Single and double RNAi lines indicate that additional low affinity uptake systems for arginine and lysine are present in T. brucei.
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Affiliation(s)
| | - Juan P. Macêdo
- Institute of Plant Sciences, University of Bern, Bern, Switzerland
| | - Daniel Hürlimann
- Institute of Plant Sciences, University of Bern, Bern, Switzerland
| | - Corina Wirdnam
- Institute of Plant Sciences, University of Bern, Bern, Switzerland
| | | | | | | | - Remo S. Schmidt
- Swiss Tropical and Public Health Institute and University of Basel, Basel, Switzerland
| | - Ehud Inbar
- Faculty of Biology, Technion-Israel Institute of Technology, Haifa, Israel
| | - Pascal Mäser
- Swiss Tropical and Public Health Institute and University of Basel, Basel, Switzerland
| | - Peter Bütikofer
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
| | - Dan Zilberstein
- Faculty of Biology, Technion-Israel Institute of Technology, Haifa, Israel
| | - Doris Rentsch
- Institute of Plant Sciences, University of Bern, Bern, Switzerland
- * E-mail:
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17
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Vodnala M, Ranjbarian F, Pavlova A, de Koning HP, Hofer A. Trypanosoma brucei Methylthioadenosine Phosphorylase Protects the Parasite from the Antitrypanosomal Effect of Deoxyadenosine: IMPLICATIONS FOR THE PHARMACOLOGY OF ADENOSINE ANTIMETABOLITES. J Biol Chem 2016; 291:11717-26. [PMID: 27036940 DOI: 10.1074/jbc.m116.715615] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Indexed: 02/03/2023] Open
Abstract
Trypanosoma brucei causes African sleeping sickness for which no vaccine exists and available treatments are of limited use due to their high toxicity or lack of efficacy. T. brucei cultivated in the presence of deoxyadenosine accumulates high levels of dATP in an adenosine kinase-dependent process and dies within a few hours. Here we show that T. brucei treated with 1 mm deoxyadenosine accumulates higher dATP levels than mammalian cells but that this effect diminishes quickly as the concentration of the deoxynucleoside decreases. Radioactive tracer studies showed that the parasites are partially protected against lower concentrations of deoxyadenosine by the ability to cleave it and use the adenine for ATP synthesis. T. brucei methylthioadenosine phosphorylase (TbMTAP) was found to be responsible for the cleavage as indicated by the phosphate dependence of deoxyadenosine cleavage in T. brucei cell extracts and increased deoxyadenosine sensitivity in TbMTAP knockdown cells. Recombinant TbMTAP exhibited higher turnover number (kcat) and Km values for deoxyadenosine than for the regular substrate, methylthioadenosine. One of the reaction products, adenine, inhibited the enzyme, which might explain why TbMTAP-mediated protection is less efficient at higher deoxyadenosine concentrations. Consequently, T. brucei grown in the presence of adenine demonstrated increased sensitivity to deoxyadenosine. For deoxyadenosine/adenosine analogues to remain intact and be active against the parasite, they need to either be resistant to TbMTAP-mediated cleavage, which is the case with the three known antitrypanosomal agents adenine arabinoside, tubercidin, and cordycepin, or they need to be combined with TbMTAP inhibitors.
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Affiliation(s)
- Munender Vodnala
- From the Department of Medical Biochemistry and Biophysics, Umeå University, SE-901 87 Umeå, Sweden and
| | - Farahnaz Ranjbarian
- From the Department of Medical Biochemistry and Biophysics, Umeå University, SE-901 87 Umeå, Sweden and
| | - Anna Pavlova
- From the Department of Medical Biochemistry and Biophysics, Umeå University, SE-901 87 Umeå, Sweden and
| | - Harry P de Koning
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, Scotland, United Kingdom
| | - Anders Hofer
- From the Department of Medical Biochemistry and Biophysics, Umeå University, SE-901 87 Umeå, Sweden and
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18
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Munday JC, Tagoe DNA, Eze AA, Krezdorn JAM, Rojas López KE, Alkhaldi AAM, McDonald F, Still J, Alzahrani KJ, Settimo L, De Koning HP. Functional analysis of drug resistance-associated mutations in the Trypanosoma brucei adenosine transporter 1 (TbAT1) and the proposal of a structural model for the protein. Mol Microbiol 2015; 96:887-900. [PMID: 25708978 PMCID: PMC4755147 DOI: 10.1111/mmi.12979] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/21/2015] [Indexed: 02/01/2023]
Abstract
The Trypanosoma brucei aminopurine transporter P2/TbAT1 has long been implicated in the transport of, and resistance to, the diamidine and melaminophenyl arsenical classes of drugs that form the backbone of the pharmacopoeia against African trypanosomiasis. Genetic alterations including deletions and single nucleotide polymorphisms (SNPs) have been observed in numerous strains and clinical isolates. Here, we systematically investigate each reported mutation and assess their effects on transporter function after expression in a tbat1(-/-) T. brucei line. Out of a set of six reported SNPs from a reported 'resistance allele', none significantly impaired sensitivity to pentamidine, diminazene or melarsoprol, relative to the TbAT1-WT allele, although several combinations, and the deletion of the codon for residue F316, resulted in highly significant impairment. These combinations of SNPs, and ΔF316, also strongly impaired the uptake of [(3)H]-adenosine and [(3)H]-diminazene, identical to the tbat1(-/-) control. The TbAT1 protein model predicted that residues F19, D140 and F316 interact with the substrate of the transporter. Mutation of D140 to alanine resulted in an inactive transporter, whereas the mutation F19A produced a transporter with a slightly increased affinity for [(3)H]-diminazene but reduced the uptake rate. The results presented here validate earlier hypotheses of drug binding motifs for TbAT1.
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Affiliation(s)
- Jane C Munday
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, UK
- Wellcome Trust Centre for Molecular Parasitology, University of Glasgow, Glasgow, UK
| | - Daniel N A Tagoe
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, UK
- Department of Laboratory Technology, University of Cape Coast, Cape Coast, Ghana
| | - Anthonius A Eze
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, UK
- Department of Medical Biochemistry, College of Medicine, University of Nigeria, Enugu Campus, Enugu, Nigeria
| | - Jessica A M Krezdorn
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, UK
| | - Karla E Rojas López
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, UK
| | - Abdulsalam A M Alkhaldi
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, UK
- Department of Biology, College of Science, Aljouf University, Sakaka, Saudi Arabia
| | - Fiona McDonald
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, UK
| | - Jennifer Still
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, UK
| | - Khalid J Alzahrani
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, UK
- Faculty of Medical Sciences, Taif University, Taif, Saudi Arabia
| | - Luca Settimo
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, UK
- Department of Chemistry and Chemical Biology, 417 Egan Research Center, Northeastern University, 360 Huntington Avenue, Boston, MA, 02115, USA
| | - Harry P De Koning
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, UK
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19
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Alkhaldi AAM, Creek DJ, Ibrahim H, Kim DH, Quashie NB, Burgess KE, Changtam C, Barrett MP, Suksamrarn A, de Koning HP. Potent trypanocidal curcumin analogs bearing a monoenone linker motif act on trypanosoma brucei by forming an adduct with trypanothione. Mol Pharmacol 2014; 87:451-64. [PMID: 25527638 DOI: 10.1124/mol.114.096016] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
We have previously reported that curcumin analogs with a C7 linker bearing a C4-C5 olefinic linker with a single keto group at C3 (enone linker) display midnanomolar activity against the bloodstream form of Trypanosoma brucei. However, no clear indication of their mechanism of action or superior antiparasitic activity relative to analogs with the original di-ketone curcumin linker was apparent. To further investigate their utility as antiparasitic agents, we compare the cellular effects of curcumin and the enone linker lead compound 1,7-bis(4-hydroxy-3-methoxyphenyl)hept-4-en-3-one (AS-HK014) here. An AS-HK014-resitant line, trypanosomes adapted to AS-HK014 (TA014), was developed by in vitro exposure to the drug. Metabolomic analysis revealed that exposure to AS-HK014, but not curcumin, rapidly depleted glutathione and trypanothione in the wild-type line, although almost all other metabolites were unchanged relative to control. In TA014 cells, thiol levels were similar to untreated wild-type cells and not significantly depleted by AS-HK014. Adducts of AS-HK014 with both glutathione and trypanothione were identified in AS-HK014-exposed wild-type cells and reproduced by chemical reaction. However, adduct accumulation in sensitive cells was much lower than in resistant cells. TA014 cells did not exhibit any changes in sequence or protein levels of glutathione synthetase and γ-glutamylcysteine synthetase relative to wild-type cells. We conclude that monoenone curcuminoids have a different mode of action than curcumin, rapidly and specifically depleting thiol levels in trypanosomes by forming an adduct. This adduct may ultimately be responsible for the highly potent trypanocidal and antiparasitic activity of the monoenone curcuminoids.
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Affiliation(s)
- Abdulsalam A M Alkhaldi
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom (A.A.M.A, D.J.C., H.I., D.-H.K., N.B.Q., K.E.B., M.P.B., H.P.K.); Department of Biology, College of Science, Aljouf University, Skaka, Kingdom of Saudi Arabia (A.A.M.A); Department of Biochemistry and Molecular Biology, Bio21 Institute, University of Melbourne, Australia (D.J.C.); Faculty of Science, Department of Zoology, Sebha University, Libya (H.I.); Centre for Analytical Bioscience, School of Pharmacy, University of Nottingham, Nottingham, United Kingdom (D.-H.K.); Centre for Tropical Clinical Pharmacology and Therapeutics, University of Ghana Medical School, Accra, Ghana (N.B.Q.); Division of Physical Science, Faculty of Science and Technology, Huachiew Chalermprakiet University, Samutprakarn, Thailand (C.C.); Wellcome Trust Centre for Molecular Parasitology, University of Glasgow, Glasgow, United Kingdom (M.P.B.); and Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ramkhamhaeng University, Bangkok, Thailand (A.S.)
| | - Darren J Creek
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom (A.A.M.A, D.J.C., H.I., D.-H.K., N.B.Q., K.E.B., M.P.B., H.P.K.); Department of Biology, College of Science, Aljouf University, Skaka, Kingdom of Saudi Arabia (A.A.M.A); Department of Biochemistry and Molecular Biology, Bio21 Institute, University of Melbourne, Australia (D.J.C.); Faculty of Science, Department of Zoology, Sebha University, Libya (H.I.); Centre for Analytical Bioscience, School of Pharmacy, University of Nottingham, Nottingham, United Kingdom (D.-H.K.); Centre for Tropical Clinical Pharmacology and Therapeutics, University of Ghana Medical School, Accra, Ghana (N.B.Q.); Division of Physical Science, Faculty of Science and Technology, Huachiew Chalermprakiet University, Samutprakarn, Thailand (C.C.); Wellcome Trust Centre for Molecular Parasitology, University of Glasgow, Glasgow, United Kingdom (M.P.B.); and Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ramkhamhaeng University, Bangkok, Thailand (A.S.)
| | - Hasan Ibrahim
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom (A.A.M.A, D.J.C., H.I., D.-H.K., N.B.Q., K.E.B., M.P.B., H.P.K.); Department of Biology, College of Science, Aljouf University, Skaka, Kingdom of Saudi Arabia (A.A.M.A); Department of Biochemistry and Molecular Biology, Bio21 Institute, University of Melbourne, Australia (D.J.C.); Faculty of Science, Department of Zoology, Sebha University, Libya (H.I.); Centre for Analytical Bioscience, School of Pharmacy, University of Nottingham, Nottingham, United Kingdom (D.-H.K.); Centre for Tropical Clinical Pharmacology and Therapeutics, University of Ghana Medical School, Accra, Ghana (N.B.Q.); Division of Physical Science, Faculty of Science and Technology, Huachiew Chalermprakiet University, Samutprakarn, Thailand (C.C.); Wellcome Trust Centre for Molecular Parasitology, University of Glasgow, Glasgow, United Kingdom (M.P.B.); and Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ramkhamhaeng University, Bangkok, Thailand (A.S.)
| | - Dong-Hyun Kim
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom (A.A.M.A, D.J.C., H.I., D.-H.K., N.B.Q., K.E.B., M.P.B., H.P.K.); Department of Biology, College of Science, Aljouf University, Skaka, Kingdom of Saudi Arabia (A.A.M.A); Department of Biochemistry and Molecular Biology, Bio21 Institute, University of Melbourne, Australia (D.J.C.); Faculty of Science, Department of Zoology, Sebha University, Libya (H.I.); Centre for Analytical Bioscience, School of Pharmacy, University of Nottingham, Nottingham, United Kingdom (D.-H.K.); Centre for Tropical Clinical Pharmacology and Therapeutics, University of Ghana Medical School, Accra, Ghana (N.B.Q.); Division of Physical Science, Faculty of Science and Technology, Huachiew Chalermprakiet University, Samutprakarn, Thailand (C.C.); Wellcome Trust Centre for Molecular Parasitology, University of Glasgow, Glasgow, United Kingdom (M.P.B.); and Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ramkhamhaeng University, Bangkok, Thailand (A.S.)
| | - Neils B Quashie
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom (A.A.M.A, D.J.C., H.I., D.-H.K., N.B.Q., K.E.B., M.P.B., H.P.K.); Department of Biology, College of Science, Aljouf University, Skaka, Kingdom of Saudi Arabia (A.A.M.A); Department of Biochemistry and Molecular Biology, Bio21 Institute, University of Melbourne, Australia (D.J.C.); Faculty of Science, Department of Zoology, Sebha University, Libya (H.I.); Centre for Analytical Bioscience, School of Pharmacy, University of Nottingham, Nottingham, United Kingdom (D.-H.K.); Centre for Tropical Clinical Pharmacology and Therapeutics, University of Ghana Medical School, Accra, Ghana (N.B.Q.); Division of Physical Science, Faculty of Science and Technology, Huachiew Chalermprakiet University, Samutprakarn, Thailand (C.C.); Wellcome Trust Centre for Molecular Parasitology, University of Glasgow, Glasgow, United Kingdom (M.P.B.); and Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ramkhamhaeng University, Bangkok, Thailand (A.S.)
| | - Karl E Burgess
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom (A.A.M.A, D.J.C., H.I., D.-H.K., N.B.Q., K.E.B., M.P.B., H.P.K.); Department of Biology, College of Science, Aljouf University, Skaka, Kingdom of Saudi Arabia (A.A.M.A); Department of Biochemistry and Molecular Biology, Bio21 Institute, University of Melbourne, Australia (D.J.C.); Faculty of Science, Department of Zoology, Sebha University, Libya (H.I.); Centre for Analytical Bioscience, School of Pharmacy, University of Nottingham, Nottingham, United Kingdom (D.-H.K.); Centre for Tropical Clinical Pharmacology and Therapeutics, University of Ghana Medical School, Accra, Ghana (N.B.Q.); Division of Physical Science, Faculty of Science and Technology, Huachiew Chalermprakiet University, Samutprakarn, Thailand (C.C.); Wellcome Trust Centre for Molecular Parasitology, University of Glasgow, Glasgow, United Kingdom (M.P.B.); and Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ramkhamhaeng University, Bangkok, Thailand (A.S.)
| | - Chatchawan Changtam
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom (A.A.M.A, D.J.C., H.I., D.-H.K., N.B.Q., K.E.B., M.P.B., H.P.K.); Department of Biology, College of Science, Aljouf University, Skaka, Kingdom of Saudi Arabia (A.A.M.A); Department of Biochemistry and Molecular Biology, Bio21 Institute, University of Melbourne, Australia (D.J.C.); Faculty of Science, Department of Zoology, Sebha University, Libya (H.I.); Centre for Analytical Bioscience, School of Pharmacy, University of Nottingham, Nottingham, United Kingdom (D.-H.K.); Centre for Tropical Clinical Pharmacology and Therapeutics, University of Ghana Medical School, Accra, Ghana (N.B.Q.); Division of Physical Science, Faculty of Science and Technology, Huachiew Chalermprakiet University, Samutprakarn, Thailand (C.C.); Wellcome Trust Centre for Molecular Parasitology, University of Glasgow, Glasgow, United Kingdom (M.P.B.); and Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ramkhamhaeng University, Bangkok, Thailand (A.S.)
| | - Michael P Barrett
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom (A.A.M.A, D.J.C., H.I., D.-H.K., N.B.Q., K.E.B., M.P.B., H.P.K.); Department of Biology, College of Science, Aljouf University, Skaka, Kingdom of Saudi Arabia (A.A.M.A); Department of Biochemistry and Molecular Biology, Bio21 Institute, University of Melbourne, Australia (D.J.C.); Faculty of Science, Department of Zoology, Sebha University, Libya (H.I.); Centre for Analytical Bioscience, School of Pharmacy, University of Nottingham, Nottingham, United Kingdom (D.-H.K.); Centre for Tropical Clinical Pharmacology and Therapeutics, University of Ghana Medical School, Accra, Ghana (N.B.Q.); Division of Physical Science, Faculty of Science and Technology, Huachiew Chalermprakiet University, Samutprakarn, Thailand (C.C.); Wellcome Trust Centre for Molecular Parasitology, University of Glasgow, Glasgow, United Kingdom (M.P.B.); and Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ramkhamhaeng University, Bangkok, Thailand (A.S.)
| | - Apichart Suksamrarn
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom (A.A.M.A, D.J.C., H.I., D.-H.K., N.B.Q., K.E.B., M.P.B., H.P.K.); Department of Biology, College of Science, Aljouf University, Skaka, Kingdom of Saudi Arabia (A.A.M.A); Department of Biochemistry and Molecular Biology, Bio21 Institute, University of Melbourne, Australia (D.J.C.); Faculty of Science, Department of Zoology, Sebha University, Libya (H.I.); Centre for Analytical Bioscience, School of Pharmacy, University of Nottingham, Nottingham, United Kingdom (D.-H.K.); Centre for Tropical Clinical Pharmacology and Therapeutics, University of Ghana Medical School, Accra, Ghana (N.B.Q.); Division of Physical Science, Faculty of Science and Technology, Huachiew Chalermprakiet University, Samutprakarn, Thailand (C.C.); Wellcome Trust Centre for Molecular Parasitology, University of Glasgow, Glasgow, United Kingdom (M.P.B.); and Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ramkhamhaeng University, Bangkok, Thailand (A.S.)
| | - Harry P de Koning
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom (A.A.M.A, D.J.C., H.I., D.-H.K., N.B.Q., K.E.B., M.P.B., H.P.K.); Department of Biology, College of Science, Aljouf University, Skaka, Kingdom of Saudi Arabia (A.A.M.A); Department of Biochemistry and Molecular Biology, Bio21 Institute, University of Melbourne, Australia (D.J.C.); Faculty of Science, Department of Zoology, Sebha University, Libya (H.I.); Centre for Analytical Bioscience, School of Pharmacy, University of Nottingham, Nottingham, United Kingdom (D.-H.K.); Centre for Tropical Clinical Pharmacology and Therapeutics, University of Ghana Medical School, Accra, Ghana (N.B.Q.); Division of Physical Science, Faculty of Science and Technology, Huachiew Chalermprakiet University, Samutprakarn, Thailand (C.C.); Wellcome Trust Centre for Molecular Parasitology, University of Glasgow, Glasgow, United Kingdom (M.P.B.); and Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ramkhamhaeng University, Bangkok, Thailand (A.S.)
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20
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Valdés R, Elferich J, Shinde U, Landfear SM. Identification of the intracellular gate for a member of the equilibrative nucleoside transporter (ENT) family. J Biol Chem 2014; 289:8799-809. [PMID: 24497645 DOI: 10.1074/jbc.m113.546960] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Equilibrative nucleoside transporters of the SLC29 family play important roles in many physiological and pharmacological processes, including import of drugs for treatment of cancer, AIDS, cardiovascular, and parasitic diseases. However, no crystal structure is available for any member of this family. In previous studies we generated a computational model of the Leishmania donovani nucleoside transporter 1.1 (LdNT1.1) that captured this permease in the outward-closed conformation, and we identified the extracellular gate. In the present study we have modeled the inward-closed conformation of LdNT1.1 using the crystal structure of the Escherichia coli fucose transporter FucP and have identified four transmembrane helices whose ends close to form a predicted intracellular gate. We have tested this prediction by site-directed mutagenesis of relevant helix residues and by cross-linking of introduced cysteine pairs. The results are consistent with the predictions of the computational model and suggest that a similarly constituted gate operates in other members of the equilibrative nucleoside transporter family.
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Affiliation(s)
- Raquel Valdés
- From the Departments of Molecular Microbiology and Immunology and
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21
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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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22
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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: 49] [Impact Index Per Article: 4.5] [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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23
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Kuettel S, Greenwald J, Kostrewa D, Ahmed S, Scapozza L, Perozzo R. Crystal structures of T. b. rhodesiense adenosine kinase complexed with inhibitor and activator: implications for catalysis and hyperactivation. PLoS Negl Trop Dis 2011; 5:e1164. [PMID: 21629723 PMCID: PMC3101181 DOI: 10.1371/journal.pntd.0001164] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2010] [Accepted: 03/15/2011] [Indexed: 12/02/2022] Open
Abstract
Background The essential purine salvage pathway of Trypanosoma brucei bears interesting catalytic enzymes for chemotherapeutic intervention of Human African Trypanosomiasis. Unlike mammalian cells, trypanosomes lack de novo purine synthesis and completely rely on salvage from their hosts. One of the key enzymes is adenosine kinase which catalyzes the phosphorylation of ingested adenosine to form adenosine monophosphate (AMP) utilizing adenosine triphosphate (ATP) as the preferred phosphoryl donor. Methods and Findings Here, we present the first structures of Trypanosoma brucei rhodesiense adenosine kinase (TbrAK): the structure of TbrAK in complex with the bisubstrate inhibitor P1,P5-di(adenosine-5′)-pentaphosphate (AP5A) at 1.55 Å, and TbrAK complexed with the recently discovered activator 4-[5-(4-phenoxyphenyl)-2H-pyrazol-3-yl]morpholine (compound 1) at 2.8 Å resolution. Conclusions The structural details and their comparison give new insights into substrate and activator binding to TbrAK at the molecular level. Further structure-activity relationship analyses of a series of derivatives of compound 1 support the observed binding mode of the activator and provide a possible mechanism of action with respect to their activating effect towards TbrAK. Recently, we discovered that 4-[5-(4-phenoxyphenyl)-2H-pyrazol-3-yl]morpholine (compound 1) and its derivatives exhibit specific antitrypanosomal activity toward T. b. rhodesiense, the causative agent of the acute form of HAT. We found that compound 1 would target the parasite adenosine kinase (TbrAK), an important enzyme of the purine salvage pathway, by acting via hyperactivation of the enzyme. This represents a novel and hitherto unexplored strategy for the development of trypanocides. These findings prompted us to investigate the mechanism of action at the molecular level. The present study reports the first three-dimensional crystal structures of TbrAK in complex with the bisubstrate inhibitor AP5A, and in complex with the activator (compound 1). The subsequent structural analysis sheds light on substrate and activator binding, and gives insight into the possible mechanism leading to hyperactivation. Further structure-activity relationships in terms of TbrAK activation properties support the observed binding mode of compound 1 in the crystal structure and may open the field for subsequent optimization of this compound series.
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Affiliation(s)
- Sabine Kuettel
- Pharmaceutical Biochemistry Group, School of Pharmaceutical Sciences, University of Geneva, University of Lausanne, Lausanne, Switzerland
| | - Jason Greenwald
- Laboratory of Physical Chemistry, ETH Zurich, Zurich, Switzerland
| | - Dirk Kostrewa
- Gene Center Munich, Department of Biochemistry, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Shaheen Ahmed
- Pharmaceutical Biochemistry Group, School of Pharmaceutical Sciences, University of Geneva, University of Lausanne, Lausanne, Switzerland
| | - Leonardo Scapozza
- Pharmaceutical Biochemistry Group, School of Pharmaceutical Sciences, University of Geneva, University of Lausanne, Lausanne, Switzerland
- * E-mail: (LS); (RP)
| | - Remo Perozzo
- Pharmaceutical Biochemistry Group, School of Pharmaceutical Sciences, University of Geneva, University of Lausanne, Lausanne, Switzerland
- * E-mail: (LS); (RP)
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24
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Teka IA, Kazibwe AJN, El-Sabbagh N, Al-Salabi MI, Ward CP, Eze AA, Munday JC, Mäser P, Matovu E, Barrett MP, de Koning HP. The diamidine diminazene aceturate is a substrate for the high-affinity pentamidine transporter: implications for the development of high resistance levels in trypanosomes. Mol Pharmacol 2011; 80:110-6. [PMID: 21436312 DOI: 10.1124/mol.111.071555] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
African trypanosomiasis is a disease of humans and livestock in many areas south of the Sahara. Resistance to the few existing drugs is a major impediment to the control of these diseases, and we investigated how resistance to the main veterinary drug diminazene aceturate correlates with changes in drug transport in resistant strains. The strain tbat1(-/-), lacking the TbAT1/P2 aminopurine transporter implicated previously in diminazene transport, was adapted to higher levels of diminazene resistance. The resulting cell line was designated ABR and was highly cross-resistant to other diamidines and moderately resistant to cymelarsan. Procyclic trypanosomes were shown to be a convenient model to study diamidine uptake in Trypanosoma brucei brucei given the lack of TbAT1/P2 and a 10-fold higher activity of the high-affinity pentamidine transporter (HAPT1). Diminazene could be transported by HAPT1 in procyclic trypanosomes. This drug transport activity was lacking in the ABR line, as reported previously for the pentamidine-adapted line B48. The K(m) for diminazene transport in bloodstream tbat1(-/-) trypanosomes was consistent with uptake by HAPT1. Diminazene transport in ABR and B48 cells was reduced compared with tbat1(-/-), but their resistance phenotype was different: B48 displayed higher levels of resistance to pentamidine and the melaminophenyl arsenicals, whereas ABR displayed higher resistance to diminazene. These results establish a loss of HAPT1 function as a contributing factor to diminazene resistance but equally demonstrate for the first time that adaptations other than those determining the initial rates of drug uptake contribute to diamidine and arsenical resistance in African trypanosomes.
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Affiliation(s)
- Ibrahim A Teka
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
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25
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Trypanocidal furamidine analogues: influence of pyridine nitrogens on trypanocidal activity, transport kinetics, and resistance patterns. Antimicrob Agents Chemother 2011; 55:2352-61. [PMID: 21402852 DOI: 10.1128/aac.01551-10] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Current therapies for human African trypanosomiasis (HAT) are unsatisfactory and under threat from emerging drug resistance linked to the loss of transporters, e.g., the P2 aminopurine transporter (TbAT1). Here we compare the uptake and trypanocidal properties of furamidine (DB75), recently evaluated in clinical trials against stage 1 (haemolymphatic) HAT, and two aza analogues, DB820 and CPD0801 (DB829), which are candidate compounds for treatment of stage 2 (neurological) disease. Values of 50% inhibitory concentrations (IC50s) determined in vitro against both wild-type and transporter mutant parasites were submicromolar, with DB75 trypanotoxicity shown to be better than and DB820 trypanotoxicity similar to that of the widely used veterinary trypanocide diminazene, while CPD0801 was less active. Activity correlated with uptake and with the minimum drug exposure time necessary to kill trypanosomes: DB75 accumulated at double and 10-fold the rates of DB820 and CPD0801, respectively. All three compounds inhibited P2-mediated adenosine transport with similar Ki values, indicating affinity values for this permease in the low to submicromolar range. Uptake of DB75, DB820, and CPD0801 was significantly reduced in tbat1-/- parasites and was sensitive to inhibition by adenine, showing that all three compounds are substrates for the P2 transporter. Uptake in vitro was significantly less than that seen with parasites freshly isolated from infected rats, correlating with a downregulation of P2 activity in vitro. We conclude that DB75, DB820, and CPD0801 are actively accumulated by Trypanosoma brucei brucei, with P2 as the main transport route. The aza analogues of DB75 accumulate more slowly than furamidine itself and reveal less trypanocidal activity in standard in vitro drug sensitivity assays.
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26
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Klee N, Wong PE, Baragaña B, Mazouni FE, Phillips MA, Barrett MP, Gilbert IH. Selective delivery of 2-hydroxy APA to Trypanosoma brucei using the melamine motif. Bioorg Med Chem Lett 2010; 20:4364-6. [PMID: 20615694 PMCID: PMC2935964 DOI: 10.1016/j.bmcl.2010.06.070] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2010] [Revised: 06/10/2010] [Accepted: 06/11/2010] [Indexed: 11/25/2022]
Abstract
Trypanosoma brucei, the parasite that causes human African trypanosomiasis, is auxotrophic for purines and has specialist nucleoside transporters to import these metabolites. In particular, the P2 aminopurine transporter can also selectively accumulate melamine derivatives. In this Letter, we report the coupling of the melamine moiety to 2-hydroxy APA, a potent ornithine decarboxylase inhibitor, with the aim of selectively delivering this compound to the parasite. The best compound described here shows an increased in vitro trypanocidal activity compared with the parent.
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Affiliation(s)
- Nina Klee
- Division of Biological Chemistry and Drug Discovery, College of Life Science, University of Dundee, Sir James Black Centre, Dundee, UK
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27
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Evaluation of nucleoside hydrolase inhibitors for treatment of African trypanosomiasis. Antimicrob Agents Chemother 2010; 54:1900-8. [PMID: 20194690 DOI: 10.1128/aac.01787-09] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In this paper, we present the biochemical and biological evaluation of N-arylmethyl-substituted iminoribitol derivatives as potential chemotherapeutic agents against trypanosomiasis. Previously, a library of 52 compounds was designed and synthesized as potent and selective inhibitors of Trypanosoma vivax inosine-adenosine-guanosine nucleoside hydrolase (IAG-NH). However, when the compounds were tested against bloodstream-form Trypanosoma brucei brucei, only one inhibitor, N-(9-deaza-adenin-9-yl)methyl-1,4-dideoxy-1,4-imino-d-ribitol (UAMC-00363), displayed significant activity (mean 50% inhibitory concentration [IC(50)] +/- standard error, 0.49 +/- 0.31 microM). Validation in an in vivo model of African trypanosomiasis showed promising results for this compound. Several experiments were performed to investigate why only UAMC-00363 showed antiparasitic activity. First, the compound library was screened against T. b. brucei IAG-NH and inosine-guanosine nucleoside hydrolase (IG-NH) to confirm the previously demonstrated inhibitory effects of the compounds on T. vivax IAG-NH. Second, to verify the uptake of these compounds by T. b. brucei, their affinities for the nucleoside P1 and nucleoside/nucleobase P2 transporters of T. b. brucei were tested. Only UAMC-00363 displayed significant affinity for the P2 transporter. It was also shown that UAMC-00363 is concentrated in the cell via at least one additional transporter, since P2 knockout mutants of T. b. brucei displayed no resistance to the compound. Consequently, no cross-resistance to the diamidine or the melaminophenyl arsenical classes of trypanocides is expected. Third, three enzymes of the purine salvage pathway of procyclic T. b. brucei (IAG-NH, IG-NH, and methylthioadenosine phosphorylase [MTAP]) were investigated using RNA interference. The findings from all these studies showed that it is probably not sufficient to target only the nucleoside hydrolase activity to block the purine salvage pathway of T. b. brucei and that, therefore, it is possible that UAMC-00363 acts on an additional target.
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28
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Abstract
Parasitic protozoa cause devastating diseases across large regions of the globe, but a lack of economic incentives has resulted in the limited development of drugs against these "neglected diseases." Transporters expressed in the plasma membranes of these parasites offer potential for the development of new drugs. These permeases could be employed in two distinct strategies for drug development: (i) targeting selective delivery of drugs to the parasite and (ii) developing drugs that inhibit essential parasite permeases.
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Affiliation(s)
- S M Landfear
- Department of Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, Oregon, USA.
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29
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Hyde RJ, Cass CE, Young JD, Stephen A. Baldwin JD. The ENT family of eukaryote nucleoside and nucleobase transporters: recent advances in the investigation of structure/function relationships and the identification of novel isoforms. Mol Membr Biol 2009. [DOI: 10.1080/09687680118799] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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30
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Chollet C, Baliani A, Wong PE, Barrett MP, Gilbert IH. Targeted delivery of compounds to Trypanosoma brucei using the melamine motif. Bioorg Med Chem 2009; 17:2512-23. [PMID: 19250832 DOI: 10.1016/j.bmc.2009.01.058] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2008] [Revised: 01/21/2009] [Accepted: 01/25/2009] [Indexed: 11/29/2022]
Abstract
There is an urgent need for the development of new drugs for the treatment of human African trypanosomiasis. The causative organism, Trypanosoma brucei, has been shown to have some unusual plasma membrane transporters, in particular the P2 aminopurine transporter and related permeases, which have been used for the selective targeting of trypanocidal compounds to the organism. In this paper, we report the addition of melamine-based P2-targeting motifs to three different classes of compound in order to try and improve activity through increased selective uptake. The classes reported here are fluoroquinolones, difluoromethylornithine and artesunate derivatives.
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Affiliation(s)
- Constance Chollet
- Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Sir James Black Centre, Dundee DD1 5EH, UK
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31
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Baliani A, Peal V, Gros L, Brun R, Kaiser M, Barrett MP, Gilbert IH. Novel functionalized melamine-based nitroheterocycles: synthesis and activity against trypanosomatid parasites. Org Biomol Chem 2009; 7:1154-66. [PMID: 19262935 DOI: 10.1039/b813394h] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Human African trypanosomiasis (HAT), caused by the protozoan parasite Trypanosoma brucei spp., is a major health problem in sub-Saharan Africa. New drugs are urgently required for the disease. Selective uptake of toxic compounds into trypanosomes has been achieved by exploiting plasma membrane transporters. For example, the P2 aminopurine transporter, along with other transporters, selectively concentrates melamine and benzamidine moieties into trypanosomes. We have previously reported the use of the melamine motif to selectively target nitrofuran to the trypanosome. In this paper we report the further investigation of the structure activity relationships and the effect of the introduction of different functionalized substituents onto the melamine unit. Most of the compounds tested in vitro for their trypanocidal activity showed activities in the submicromolar range against T. b. rhodesiense.
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Affiliation(s)
- Alessandro Baliani
- School of Life Sciences, Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Sir James Black Centre, Dundee, DD1 5EH, UK
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32
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Leite MS, Thomaz R, Oliveira JHM, Oliveira PL, Meyer-Fernandes JR. Trypanosoma brucei brucei: effects of ferrous iron and heme on ecto-nucleoside triphosphate diphosphohydrolase activity. Exp Parasitol 2008; 121:137-43. [PMID: 19027737 DOI: 10.1016/j.exppara.2008.10.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2008] [Revised: 10/09/2008] [Accepted: 10/24/2008] [Indexed: 01/17/2023]
Abstract
Trypanosoma brucei brucei is the causative agent of animal African trypanosomiasis, also called nagana. Procyclic vector form resides in the midgut of the tsetse fly, which feeds exclusively on blood. Hemoglobin digestion occurs in the midgut resulting in an intense release of free heme. In the present study we show that the magnesium-dependent ecto-nucleoside triphosphate diphosphohydrolase (E-NTPDase) activity of procyclic T. brucei brucei is inhibited by ferrous iron and heme. The inhibition of E-NTPDase activity by ferrous iron, but not by heme, was prevented by pre-incubation of cells with catalase. However, antioxidants that permeate cells, such as PEG-catalase and N-acetyl-cysteine prevented the inhibition of E-NTPDase by heme. Ferrous iron was able to induce an increase in lipid peroxidation, while heme did not. Therefore, both ferrous iron and heme can inhibit E-NTPDase activity of T. brucei brucei by means of formation of reactive oxygen species, but apparently acting through distinct mechanisms.
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Affiliation(s)
- Milane S Leite
- Laboratório de Bioquímica Celular, Instituto de Bioquímica Médica, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, UFRJ, Cidade Universitária, Ilha do Fundão, Rio de Janeiro, Brazil
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33
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Gould MK, Vu XL, Seebeck T, de Koning HP. Propidium iodide-based methods for monitoring drug action in the kinetoplastidae: comparison with the Alamar Blue assay. Anal Biochem 2008; 382:87-93. [PMID: 18722997 DOI: 10.1016/j.ab.2008.07.036] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2008] [Revised: 07/23/2008] [Accepted: 07/25/2008] [Indexed: 11/19/2022]
Abstract
The urgent need for new drug development for African trypanosomiasis is widely recognized. This requires reliable and informative high-throughput assays. Currently, drug action is determined with a fluorimetric/colorimetric assay based on the metabolism of the dye Alamar Blue (resazurin) by live cells. However, this assay does not easily distinguish between cell death and growth arrest, or supply information about the rate at which test compounds affect these parameters. We report here an alternative fluorimetric assay, based on the interaction of propidium iodide with DNA, that allows either real-time monitoring of cell viability or the generation of EC(50) values at a predetermined time-point. The assay is highly sensitive and fluorescence readings easily correlate to numbers of parasites or DNA content. The EC(50) values were highly similar to those obtained with the standard Alamar Blue assay. The procedure lends itself readily to applications in drug development or resistance monitoring.
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Affiliation(s)
- Matthew K Gould
- Institute of Biomedical and Life Sciences, Division of Infection and Immunity, University of Glasgow, 120 University Place, Glasgow G128TA, UK
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34
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A comprehensive model of purine uptake by the malaria parasite Plasmodium falciparum: identification of four purine transport activities in intraerythrocytic parasites. Biochem J 2008; 411:287-95. [PMID: 18215139 DOI: 10.1042/bj20071460] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Plasmodium falciparum is incapable of de novo purine biosynthesis, and is absolutely dependent on transporters to salvage purines from the environment. Only one low-affinity adenosine transporter has been characterized to date. In the present study we report a comprehensive study of purine nucleobase and nucleoside transport by intraerythrocytic P. falciparum parasites. Isolated trophozoites expressed (i) a high-affinity hypoxanthine transporter with a secondary capacity for purine nucleosides, (ii) a separate high-affinity transporter for adenine, (iii) a low-affinity adenosine transporter, and (iv) a low-affinity/high-capacity adenine carrier. Hypoxanthine was taken up with 12-fold higher efficiency than adenosine. Using a parasite clone with a disrupted PfNT1 (P. falciparum nucleoside transporter 1) gene we found that the high-affinity hypoxanthine/nucleoside transport activity was completely abolished, whereas the low-affinity adenosine transport activity was unchanged. Adenine transport was increased, presumably to partly compensate for the loss of the high-affinity hypoxanthine transporter. We thus propose a model for purine salvage in P. falciparum, based on the highly efficient uptake of hypoxanthine by PfNT1 and a high capacity for purine nucleoside uptake by a lower affinity carrier.
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35
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Fang J, Rohloff P, Miranda K, Docampo R. Ablation of a small transmembrane protein of Trypanosoma brucei (TbVTC1) involved in the synthesis of polyphosphate alters acidocalcisome biogenesis and function, and leads to a cytokinesis defect. Biochem J 2008; 407:161-70. [PMID: 17635107 PMCID: PMC2049025 DOI: 10.1042/bj20070612] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Inorganic poly P (polyphosphate) is an abundant component of acidocalcisomes of Trypanosoma brucei. In the present study we report the presence of a protein homologous with the yeast Vtc1p (vacuolar transporter chaperone 1) in T. brucei that is essential for poly P synthesis, acidocalcisome biogenesis and cytokinesis. Localization studies in a cell line expressing a TbVTC1 fused to GFP (green fluorescent protein) revealed its co-localization with the V-H+-PPase (vacuolar H+-pyrophosphatase), a marker for acidocalcisomes. Western blot analysis of acidocalcisome fractions and immunogold electron microscopy using polyclonal antibodies against a fragment of TbVTC1 confirmed the acidocalcisome localization. Ablation of TbVTC1 expression by RNA interference caused an abnormal morphology of acidocalcisomes, indicating that their biogenesis was disturbed, with a decreased pyrophosphate-driven H+ uptake and Ca2+ content, a significant decrease in the amount of poly P and a deficient response to hyposmotic stress. Ablation of TbVTC1 expression for longer periods produced marked gross morphological alterations compatible with a defect in cytokinesis, followed by cell death. Overexpression of the TbVTC1 gene caused mild alterations in growth rate, but had no perceptible effect on acidocalcisome morphology. We propose that the PP(i)-driven H+ pumping deficiency induced by ablation of TbVTC1 leads to alterations in the protonmotive force of acidocalcisomes, which results in deficient fusion or budding of the organelles, decreased H+ and Ca2+ content, and decreased synthesis of poly P. A decrease in the poly P content would lead to osmotic sensitivity and defects in cytokinesis.
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Affiliation(s)
- Jianmin Fang
- Center for Tropical and Emerging Global Disease and Department of Cellular Biology, University of Georgia, Athens, GA 30602, U.S.A
| | - Peter Rohloff
- Center for Tropical and Emerging Global Disease and Department of Cellular Biology, University of Georgia, Athens, GA 30602, U.S.A
| | - Kildare Miranda
- Center for Tropical and Emerging Global Disease and Department of Cellular Biology, University of Georgia, Athens, GA 30602, U.S.A
| | - Roberto Docampo
- Center for Tropical and Emerging Global Disease and Department of Cellular Biology, University of Georgia, Athens, GA 30602, U.S.A
- To whom correspondence should be addressed (email )
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36
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Vodnala M, Fijolek A, Rofougaran R, Mosimann M, Mäser P, Hofer A. Adenosine kinase mediates high affinity adenosine salvage in Trypanosoma brucei. J Biol Chem 2007; 283:5380-8. [PMID: 18167353 DOI: 10.1074/jbc.m705603200] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
African sleeping sickness is caused by Trypanosoma brucei. This extracellular parasite lacks de novo purine biosynthesis, and it is therefore dependent on exogenous purines such as adenosine that is taken up from the blood and other body fluids by high affinity transporters. The general belief is that adenosine needs to be cleaved to adenine inside the parasites in order to be used for purine nucleotide synthesis. We have found that T. brucei also can salvage this nucleoside by adenosine kinase (AK), which has a higher affinity to adenosine than the cleavage-dependent pathway. The recombinant T. brucei AK (TbAK) preferably used ATP or GTP to phosphorylate both natural and synthetic nucleosides in the following order of catalytic efficiencies: adenosine > cordycepin > deoxyadenosine > adenine arabinoside (Ara-A) > inosine > fludarabine (F-Ara-A). TbAK differed from the AK of the related intracellular parasite Leishmania donovani by having a high affinity to adenosine (K m = 0.04-0.08 microm depending on [phosphate]) and by being negatively regulated by adenosine (K i = 8-14 microm). These properties make the enzyme functionally related to the mammalian AKs, although a phylogenetic analysis grouped it together with the L. donovani enzyme. The combination of a high affinity AK and efficient adenosine transporters yields a strong salvage system in T. brucei, a potential Achilles' heel making the parasites more sensitive than mammalian cells to adenosine analogs such as Ara-A. Studies of wild-type and AK knockdown trypanosomes showed that Ara-A inhibited parasite proliferation and survival in an AK-dependent manner by affecting nucleotide levels and by inhibiting nucleic acid biosynthesis.
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Affiliation(s)
- Munender Vodnala
- Department of Medical Biochemistry and Biophysics, Umeå University, SE-901 87 Umeå, Sweden
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37
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Turnock DC, Ferguson MAJ. Sugar nucleotide pools of Trypanosoma brucei, Trypanosoma cruzi, and Leishmania major. EUKARYOTIC CELL 2007; 6:1450-63. [PMID: 17557881 PMCID: PMC1951125 DOI: 10.1128/ec.00175-07] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The cell surface glycoconjugates of trypanosomatid parasites are intimately involved in parasite survival, infectivity, and virulence in their insect vectors and mammalian hosts. Although there is a considerable body of work describing their structure, biosynthesis, and function, little is known about the sugar nucleotide pools that fuel their biosynthesis. In order to identify and quantify parasite sugar nucleotides, we developed an analytical method based on liquid chromatography-electrospray ionization-tandem mass spectrometry using multiple reaction monitoring. This method was applied to the bloodstream and procyclic forms of Trypanosoma brucei, the epimastigote form of T. cruzi, and the promastigote form of Leishmania major. Five sugar nucleotides, GDP-alpha-d-mannose, UDP-alpha-d-N-acetylglucosamine, UDP-alpha-d-glucose, UDP-alpha-galactopyranose, and GDP-beta-l-fucose, were common to all three species; one, UDP-alpha-d-galactofuranose, was common to T. cruzi and L. major; three, UDP-beta-l-rhamnopyranose, UDP-alpha-d-xylose, and UDP-alpha-d-glucuronic acid, were found only in T. cruzi; and one, GDP-alpha-d-arabinopyranose, was found only in L. major. The estimated demands for each monosaccharide suggest that sugar nucleotide pools are turned over at very different rates, from seconds to hours. The sugar nucleotide survey, together with a review of the literature, was used to define the routes to these important metabolites and to annotate relevant genes in the trypanosomatid genomes.
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Affiliation(s)
- Daniel C Turnock
- Division of Biological Chemistry and Drug Discovery, Wellcome Trust Biocentre, College of Life Sciences, University of Dundee, Dow St., Dundee DD1 5EH, Scotland, United Kingdom
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38
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Spoerri I, Chadwick R, Renggli CK, Matthews K, Roditi I, Burkard G. Role of the stage-regulated nucleoside transporter TbNT10 in differentiation and adenosine uptake in Trypanosoma brucei. Mol Biochem Parasitol 2007; 154:110-4. [PMID: 17521750 PMCID: PMC2686105 DOI: 10.1016/j.molbiopara.2007.04.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2007] [Revised: 03/28/2007] [Accepted: 04/05/2007] [Indexed: 11/16/2022]
Affiliation(s)
- Iris Spoerri
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012 Bern, Switzerland
| | - Ruth Chadwick
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT, UK
| | | | - Keith Matthews
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT, UK
| | - Isabel Roditi
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012 Bern, Switzerland
- Corresponding author. Tel.: +41 31 631 46 47; fax: +41 31 631 46 84.
| | - Gabriela Burkard
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012 Bern, Switzerland
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39
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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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40
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Al-Salabi MI, Wallace LJM, Lüscher A, Mäser P, Candlish D, Rodenko B, Gould MK, Jabeen I, Ajith SN, de Koning HP. Molecular interactions underlying the unusually high adenosine affinity of a novel Trypanosoma brucei nucleoside transporter. Mol Pharmacol 2006; 71:921-9. [PMID: 17185380 DOI: 10.1124/mol.106.031559] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Trypanosoma brucei encodes a relatively high number of genes of the equilibrative nucleoside transporter (ENT) family. We report here the cloning and in-depth characterization of one T. brucei brucei ENT member, TbNT9/AT-D. This transporter was expressed in Saccharomyces cerevisiae and displayed a uniquely high affinity for adenosine (Km = 0.068 +/- 0.013 microM), as well as broader selectivity for other purine nucleosides in the low micromolar range, but was not inhibited by nucleobases or pyrimidines. This selectivity profile is consistent with the P1 transport activity observed previously in procyclic and long-slender bloodstream T. brucei, apart from the 40-fold higher affinity for adenosine than for inosine. We found that, like the previously investigated P1 activity of long/slender bloodstream trypanosomes, the 3'-hydroxy, 5'-hydroxy, N3, and N7 functional groups contribute to transporter binding. In addition, we show that the 6-position amine group of adenosine, but not the inosine 6-keto group, makes a major contribution to binding (DeltaG0 = 12 kJ/mol), explaining the different Km values of the purine nucleosides. We further found that P1 activity in procyclic and long-slender trypanosomes is pharmacologically distinct, and we identified the main gene encoding this activity in procyclic cells as NT10/AT-B. The presence of multiple P1-type nucleoside transport activities in T. brucei brucei facilitates the development of nucleoside-based treatments for African trypanosomiasis and would delay the onset of uptake-related drug resistance to such therapy. We show that both TbNT9/AT-D and NT10/AT-B transport a range of potentially therapeutic nucleoside analogs.
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Affiliation(s)
- Mohammed I Al-Salabi
- Institute of Biomedical and Life Sciences, Glasgow Biomedical Research Centre, University of Glasgow, Glasgow G12 8TA, United Kingdom
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41
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de Souza Leite M, Thomaz R, Fonseca FV, Panizzutti R, Vercesi AE, Meyer-Fernandes JR. Trypanosoma brucei brucei: biochemical characterization of ecto-nucleoside triphosphate diphosphohydrolase activities. Exp Parasitol 2006; 115:315-23. [PMID: 17141762 DOI: 10.1016/j.exppara.2006.09.002] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2006] [Revised: 08/28/2006] [Accepted: 09/01/2006] [Indexed: 01/17/2023]
Abstract
In this work we describe the ability of living cells of Trypanosoma brucei brucei to hydrolyze extracellular ATP. In these intact parasites there was a low level of ATP hydrolysis in the absence of any divalent metal (4.72+/-0.51 nmol Pi x 10(-7) cells x h(-1)). The ATP hydrolysis was stimulated by MgCl(2) and the Mg-dependent ecto-ATPase activity was 27.15+/-2.91 nmol Pi x 10(-7) cells x h(-1). This stimulatory activity was also observed when MgCl(2) was replaced by MnCl(2). CaCl(2) and ZnCl(2) were also able to stimulate the ATPase activity, although less than MgCl(2). The apparent K(m) for ATP was 0.61 mM. This ecto-ATPase activity was insensitive to inhibitors of other ATPase and phosphatase activities. To confirm that this Mg-dependent ATPase activity is an ecto-ATPase activity, we used an impermeable inhibitor, DIDS (4, 4'-diisothiocyanostylbene 2'-2'-disulfonic acid), as well as suramin, an antagonist of P(2) purinoreceptors and inhibitor of some ecto-ATPases. These two reagents inhibited the Mg(2+)-dependent ATPase activity in a dose-dependent manner. Living cells sequentially hydrolyzed the ATP molecule generating ADP, AMP and adenosine, and supplementation of the culture medium with ATP was able to sustain the proliferation of T. brucei brucei as well as adenosine supplementation. Furthermore, the E-NTPDase activity of T. brucei brucei is modulated by the availability of purines in the medium. These results indicate that this surface enzyme may play a role in the salvage of purines from the extracellular medium in T. brucei brucei.
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Affiliation(s)
- Milane de Souza Leite
- Instituto de Bioquímica Médica, CCS, Universidade Federal do Rio de Janeiro, Cidade Universitária, Rio de Janeiro, RJ, Brazil
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42
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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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43
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Gudin S, Quashie NB, Candlish D, Al-Salabi MI, Jarvis SM, Ranford-Cartwright LC, de Koning HP. Trypanosoma brucei: a survey of pyrimidine transport activities. Exp Parasitol 2006; 114:118-25. [PMID: 16620810 DOI: 10.1016/j.exppara.2006.02.018] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2005] [Revised: 02/23/2006] [Accepted: 02/24/2006] [Indexed: 11/24/2022]
Abstract
Purine uptake has been studied in many protozoan parasites in the last few years, and several of the purine transporters have been cloned. In contrast, very little is known about the salvage of preformed pyrimidines by protozoa, and no pyrimidine transporters have been cloned, yet chemotherapy based on pyrimidine nucleobases and nucleosides has been as effective as purine antimetabolites in the treatment of infectious and neoplastic disease. Here, we surveyed the presence of pyrimidine transporters in Trypanosoma brucei brucei. We could not detect any mediated uptake of thymine, thymidine or cytidine, but identified a very high-affinity transporter for cytosine, designated C1, with a K(m) value of 0.048+/-0.009 microM. We also confirmed the presence of the previously reported U1 uracil transporter and found it capable of mediating uridine uptake as well, with a K(m) of 33+/-5 microM. A higher-affinity U2 uridine transporter (K(m)=4.1+/-2.1 microM) was also identified, but efficiency of the C1 and U2-mediated transport was low. Pyrimidine antimetabolites were tested as potential trypanocidal agents and only 5-fluorouracil was found to be effective. This drug was efficiently taken up by bloodstream forms of T. b. brucei.
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Affiliation(s)
- Simon Gudin
- Division of Infection and Immunity, Institute of Biomedical and Life Sciences, University of Glasgow, Biomedical Research Center, Glasgow G12 8TA, UK
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44
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Chen KL, Xu MX, Li GY, Liang H, Xia ZL, Liu X, Zhang JS, Zhang AM, Wang DW. Identification of AtENT3 as the main transporter for uridine uptake in Arabidopsis roots. Cell Res 2006; 16:377-88. [PMID: 16617333 DOI: 10.1038/sj.cr.7310049] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Previous studies have shown that Arabidopsis equilibrative nucleoside transporters (AtENTs) possess transport activities when produced in yeast cells and are differentially expressed in Arabidopsis organs. Herein, we report further analysis on the nucleoside transport activities and transcriptional patterns of AtENT members. The recombinant proteins of AtENTs 3, 6, and 7, but not those of AtENTs 1, 2, 4, and 8, were found to transport thymidine with high affinity. Contrary to previous suggestion that AtENT1 may not transport uridine, this work showed that recombinant AtENT1 was a pH-dependent and high-affinity transporter of uridine. When grown on MS plates, the AtENT3 knockout plants were more tolerant to the cytotoxic uridine analog 5-fluorouridine than wild-type plants and the knockout plants of AtENT1 or AtENT6. Consistent with this observation, the AtENT3 knockout line exhibited a significantly decreased ability to take up [(3)H]uridine via the roots when compared with wild-type plants and the plants with mutated AtENT1 or AtENT6. This indicates that AtENT3, but not AtENTs 1 and 6, is the main transporter for uridine uptake in Arabidopsis roots. The transcription of AtENTs 1, 3, 4, 6, 7, and 8 was regulated in a complex manner during leaf development and senescence. In contrast, the six AtENT members were coordinately induced during seed germination. This work provides new information on the transport properties of recombinant AtENT proteins and new clues for future studies of the in vivo transport activities and physiological functions of the different ENT proteins in Arabidopsis plants.
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Affiliation(s)
- Kun Ling Chen
- School of Life Sciences, Northwest Agricultural and Forestry University, Yangling 712100, China
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45
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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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46
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Smith KM, Slugoski MD, Loewen SK, Ng AML, Yao SYM, Chen XZ, Karpinski E, Cass CE, Baldwin SA, Young JD. The Broadly Selective Human Na+/Nucleoside Cotransporter(hCNT3) Exhibits Novel Cation-coupled Nucleoside TransportCharacteristics. J Biol Chem 2005; 280:25436-49. [PMID: 15870078 DOI: 10.1074/jbc.m409454200] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The concentrative nucleoside transporter (CNT) protein family in humans is represented by three members, hCNT1, hCNT2, and hCNT3. hCNT3, a Na+/nucleoside symporter, transports a broad range of physiological purine and pyrimidine nucleosides as well as anticancer and antiviral nucleoside drugs, and belongs to a different CNT subfamily than hCNT1/2. H+-dependent Escherichia coli NupC and Candida albicans CaCNT are also CNT family members. The present study utilized heterologous expression in Xenopus oocytes to investigate the specificity, mechanism, energetics, and structural basis of hCNT3 cation coupling. hCNT3 exhibited uniquely broad cation interactions with Na+, H+, and Li+ not shared by Na+-coupled hCNT1/2 or H+-coupled NupC/CaCNT. Na+ and H+ activated hCNT3 through mechanisms to increase nucleoside apparent binding affinity. Direct and indirect methods demonstrated cation/nucleoside coupling stoichiometries of 2:1 in the presence of Na+ and both Na+ plus H+, but only 1:1 in the presence of H+ alone, suggesting that hCNT3 possesses two Na+-binding sites, only one of which is shared by H+. The H+-coupled hCNT3 did not transport guanosine or 3'-azido-3'-deoxythymidine and 2',3'-dideoxycytidine, demonstrating that Na+- and H+-bound versions of hCNT3 have significantly different conformations of the nucleoside binding pocket and/or translocation channel. Chimeric studies between hCNT1 and hCNT3 located hCNT3-specific cation interactions to the C-terminal half of hCNT3, setting the stage for site-directed mutagenesis experiments to identify the residues involved.
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Affiliation(s)
- Kyla M Smith
- Membrane Protein Research Group, Departments of Physiology and Oncology, University of Alberta Cross Cancer Institute, Edmonton, Alberta T6G 2H7, Canada
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47
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Natto MJ, Wallace LJM, Candlish D, Al-Salabi MI, Coutts SE, de Koning HP. Trypanosoma brucei: expression of multiple purine transporters prevents the development of allopurinol resistance. Exp Parasitol 2005; 109:80-6. [PMID: 15687014 DOI: 10.1016/j.exppara.2004.11.004] [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: 06/28/2004] [Revised: 11/03/2004] [Accepted: 11/18/2004] [Indexed: 11/26/2022]
Abstract
Allopurinol is a hypoxanthine analogue used to treat Leishmania infections that also displays activity against the related parasite Trypanosoma brucei. We have investigated the ease by which resistance to this drug is established in Trypanosoma brucei brucei and correlated this to the mechanisms by which it is accumulated by the parasite. Long-term exposure of procyclic T. b. brucei to 3mM allopurinol did not induce resistance. This appears to be related to the fact that allopurinol was taken up through two distinct nucleobase transporters, H1 and H4, both with high affinity for the drug. The apparent Km for [3H]allopurinol transport by H4 (2.1+/-0.4 microM) was determined by expressing the encoding gene in Saccharomyces cerevisiae. Long-term allopurinol exposure did not change Km (hypoxanthine), Ki (allopurinol), or Vmax values of either H1 or H4 transporters and the cells retained their ability to proliferate with hypoxanthine as sole purine source. This study shows that transport-related resistance to purine antimetabolites is not easily induced in Trypanosoma spp. as long as uptake is mediated by multiple transporters.
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Affiliation(s)
- Manal J Natto
- Division of Infection and Immunity, Institute of Biomedical and Life Sciences, University of Glasgow, Joseph Black Building, Glasgow G12 8QQ, UK
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48
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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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Biagini GA, Pasini EM, Hughes R, De Koning HP, Vial HJ, O'Neill PM, Ward SA, Bray PG. Characterization of the choline carrier of Plasmodium falciparum: a route for the selective delivery of novel antimalarial drugs. Blood 2004; 104:3372-7. [PMID: 15205262 DOI: 10.1182/blood-2004-03-1084] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Abstract
New drugs are urgently needed to combat the growing problem of drug resistance in Plasmodium falciparum malaria. The infected erythrocyte is a multicompartmental system, and its transporters are of interest as drug targets in their own right and as potential routes for the delivery of antimalarial drugs. Choline is an important nutrient that penetrates infected erythrocyte membranes through the endogenous carrier and through parasite-induced permeability pathways, but nothing is known about its transport into the intracellular parasite. Here we present the first characterization of choline transport across the parasite membrane. Transport exhibits Michaelis-Menten kinetics with an apparent Km of 25.0 ± 3.5 μM for choline. The carrier is inhibitor-sensitive, temperature-dependent, and Na+-independent, and it is driven by the proton-motive force. Highly active bis-amidine and bis-quaternary ammonium compounds are also known to penetrate the host erythrocyte membrane through parasite-induced permeability pathways. Here, we demonstrate that the parasite choline transporter mediates the delivery of these compounds to the intracellular parasite. Thus, the induced permeability pathways in the host erythrocyte membrane and the parasite choline transporter described here form a cooperative transport system that shows great promise for the selective targeting of new agents for the chemotherapy of malaria. (Blood. 2004;104: 3372-3377)
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Affiliation(s)
- Giancarlo A Biagini
- Molecular and Biochemical Parasitology Group, Liverpool School of Tropical Medicine, England
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50
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Matovu E, Stewart ML, Geiser F, Brun R, Mäser P, Wallace LJM, Burchmore RJ, Enyaru JCK, Barrett MP, Kaminsky R, Seebeck T, de Koning HP. Mechanisms of arsenical and diamidine uptake and resistance in Trypanosoma brucei. EUKARYOTIC CELL 2004; 2:1003-8. [PMID: 14555482 PMCID: PMC219364 DOI: 10.1128/ec.2.5.1003-1008.2003] [Citation(s) in RCA: 163] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Sleeping sickness, caused by Trypanosoma brucei spp., has become resurgent in sub-Saharan Africa. Moreover, there is an alarming increase in treatment failures with melarsoprol, the principal agent used against late-stage sleeping sickness. In T. brucei, the uptake of melarsoprol as well as diamidines is thought to be mediated by the P2 aminopurine transporter, and loss of P2 function has been implicated in resistance to these agents. The trypanosomal gene TbAT1 has been found to encode a P2-type transporter when expressed in yeast. Here we investigate the role of TbAT1 in drug uptake and drug resistance in T. brucei by genetic knockout of TbAT1. Tbat1-null trypanosomes were deficient in P2-type adenosine transport and lacked adenosine-sensitive transport of pentamidine and melaminophenyl arsenicals. However, the null mutants were only slightly resistant to melaminophenyl arsenicals and pentamidine, while resistance to other diamidines such as diminazene was more pronounced. Nevertheless, the reduction in drug sensitivity might be of clinical significance, since mice infected with tbat1-null trypanosomes could not be cured with 2 mg of melarsoprol/kg of body weight for four consecutive days, whereas mice infected with the parental line were all cured by using this protocol. Two additional pentamidine transporters, HAPT1 and LAPT1, were still present in the null mutant, and evidence is presented that HAPT1 may be responsible for the residual uptake of melaminophenyl arsenicals. High-level arsenical resistance therefore appears to involve the loss of more than one transporter.
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Affiliation(s)
- Enock Matovu
- Institute of Cell Biology, CH-3012 Bern, Switzerland
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