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Rajendran E, Hapuarachchi SV, Miller CM, Fairweather SJ, Cai Y, Smith NC, Cockburn IA, Bröer S, Kirk K, van Dooren GG. Cationic amino acid transporters play key roles in the survival and transmission of apicomplexan parasites. Nat Commun 2017; 8:14455. [PMID: 28205520 PMCID: PMC5316894 DOI: 10.1038/ncomms14455] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Accepted: 12/30/2016] [Indexed: 11/09/2022] Open
Abstract
Apicomplexans are obligate intracellular parasites that scavenge essential nutrients from their hosts via transporter proteins on their plasma membrane. The identities of the transporters that mediate amino acid uptake into apicomplexans are unknown. Here we demonstrate that members of an apicomplexan-specific protein family-the Novel Putative Transporters (NPTs)-play key roles in the uptake of cationic amino acids. We show that an NPT from Toxoplasma gondii (TgNPT1) is a selective arginine transporter that is essential for parasite survival and virulence. We also demonstrate that a homologue of TgNPT1 from the malaria parasite Plasmodium berghei (PbNPT1), shown previously to be essential for the sexual gametocyte stage of the parasite, is a cationic amino acid transporter. This reveals a role for cationic amino acid scavenging in gametocyte biology. Our study demonstrates a critical role for amino acid transporters in the survival, virulence and life cycle progression of these parasites.
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Affiliation(s)
- Esther Rajendran
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Sanduni V Hapuarachchi
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Catherine M Miller
- College of Public Health, Medical and Veterinary Sciences, James Cook University, Smithfield, Queensland 4878, Australia
| | - Stephen J Fairweather
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Yeping Cai
- John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Nicholas C Smith
- Queensland Tropical Health Alliance Research Laboratory, Australian Institute of Tropical Health and Medicine, James Cook University, Smithfield, Queensland 4878, Australia
| | - Ian A Cockburn
- John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Stefan Bröer
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Kiaran Kirk
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Giel G van Dooren
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia
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Targeting the Plasmodium vivax equilibrative nucleoside transporter 1 (PvENT1) for antimalarial drug development. INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE 2015; 6:1-11. [PMID: 26862473 PMCID: PMC4706624 DOI: 10.1016/j.ijpddr.2015.11.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Revised: 11/18/2015] [Accepted: 11/25/2015] [Indexed: 11/26/2022]
Abstract
Infection with Plasmodium falciparum and vivax cause most cases of malaria. Emerging resistance to current antimalarial medications makes new drug development imperative. Ideally a new antimalarial drug should treat both falciparum and vivax malaria. Because malaria parasites are purine auxotrophic, they rely on purines imported from the host erythrocyte via Equilibrative Nucleoside Transporters (ENTs). Thus, the purine import transporters represent a potential target for antimalarial drug development. For falciparum parasites the primary purine transporter is the P. falciparum Equilibrative Nucleoside Transporter Type 1 (PfENT1). Recently we identified potent PfENT1 inhibitors with nanomolar IC50 values using a robust, yeast-based high throughput screening assay. In the current work we characterized the Plasmodium vivax ENT1 (PvENT1) homologue and its sensitivity to the PfENT1 inhibitors. We expressed a yeast codon-optimized PvENT1 gene in Saccharomyces cerevisiae. PvENT1-expressing yeast imported both purines ([3H]adenosine) and pyrimidines ([3H]uridine), whereas wild type (fui1Δ) yeast did not. Based on radiolabel substrate uptake inhibition experiments, inosine had the lowest IC50 (3.8 μM), compared to guanosine (14.9 μM) and adenosine (142 μM). For pyrimidines, thymidine had an IC50 of 183 μM (vs. cytidine and uridine; mM range). IC50 values were higher for nucleobases compared to the corresponding nucleosides; hypoxanthine had a 25-fold higher IC50 than inosine. The archetypal human ENT1 inhibitor 4-nitrobenzylthioinosine (NBMPR) had no effect on PvENT1, whereas dipyridamole inhibited PvENT1, albeit with a 40 μM IC50, a 1000-fold less sensitive than human ENT1 (hENT1). The PfENT1 inhibitors blocked transport activity of PvENT1 and the five known naturally occurring non-synonymous single nucleotide polymorphisms (SNPs) with similar IC50 values. Thus, the PfENT1 inhibitors also target PvENT1. This implies that development of novel antimalarial drugs that target both falciparum and vivax ENT1 may be feasible. PvENT1 can be functionally expressed in Saccharomyces cerevisiae. PvENT1 transports purine and pyrimidine nucleosides and nucleobases but does not transport nucleotides. PvENT1 is inhibited by recently described PfENT1 inhibitors with similar potency. Identified PvENT1 non-synonymous SNPs do not change PfENT1 inhibitor potency. Plasmodium ENTs may be feasible target for development of novel antimalarial drugs.
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Key Words
- ACT, Artemisinin-based Combination Therapies
- CQ, chloroquine
- Drug development
- EC50, concentration causing 50% of maximal effect
- ENT, equilibrative nucleoside transporter
- EV, empty vector
- HTS, high throughput screen
- IC50, concentration causing 50% inhibition
- Malaria
- NBMPR, 4-nitrobenzylthioinosine
- Nucleoside/nucleobase transport
- Parasite
- PfENT1, P. falciparum ENT type 1
- Plasmodium vivax
- Purines
- PvENT1, P. vivax ENT type 1
- SDM, synthetic defined media
- SNP, single nucleotide polymorphism
- Single-nucleotide polymorphism (SNP)
- Transporter
- WHO, World Health Organization
- WT, wild type
- hENT1, human ENT type 1
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3
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Banerjee AK, Arora N, Murty USN. Aspartate carbamoyltransferase of Plasmodium falciparum as a potential drug target for designing anti-malarial chemotherapeutic agents. Med Chem Res 2012. [DOI: 10.1007/s00044-011-9757-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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4
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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: 40] [Impact Index Per Article: 2.5] [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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5
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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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Pabón A, Carmona J, Maestre A, Camargo M, Blair S. Inhibition of P. falciparum by steroids isolated from Solanum nudum. Phytother Res 2002; 16:59-62. [PMID: 11807967 DOI: 10.1002/ptr.1035] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Resistance to antimalarials has been widely reported and constitutes a major problem around the world. In Colombia, resistance of P. falciparum to chloroquine has been reported as 47%-97%, to amodiaquine 3%-7% and to sulfadoxine-pyrimethamine as 9%-13%. The search for new antimalarials is a priority and with this aim we studied the in vitro antimalarial activity of plants used by traditional healers. Incorporation of (3)H-hypoxanthine by the strain FCB-2 of P. falciparum was used to measure the degree of inhibition produced by the steroids SN-1 tumacone A (C(29)H(44)O(5)), SN-2 tumacone B (C(27)H(42)O(4)), SN-3 tumacoside A (C(35)H(54)O(10)), and SN-4 tumacoside B (C(33)H(52)O(9)). All compounds were obtained from the dried stems and leaves of Solanum nudum. The mean growth inhibition of P. falciparum was 71%, 56%, 21% and 12% with each of the compounds SN-1, SN-2, SN-3 and SN-4. These results constitute an important discovery since they may account for the antimalarial properties of extracts of Solanum nudum by a sensitive method. Future work should include study of the in vivo anti-malarial effect of these extracts.
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Affiliation(s)
- Adriana Pabón
- Malaria Group, Facultad de Medicina, Universidad de Antioquia, Medellín, Colombia
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7
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Abstract
The need for new antimalarials comes from the widespread resistance to those in current use. New antimalarial targets are required to allow the discovery of chemically diverse, effective drugs. The search for such new targets and new drug chemotypes will likely be helped by the advent of functional genomics and structure-based drug design. After validation of the putative targets as those capable of providing effective and safe drugs, targets can be used as the basis for screening compounds in order to identify new leads, which, in turn, will qualify for lead optimization work. The combined use of combinatorial chemistry--to generate large numbers of structurally diverse compounds--and of high throughput screening systems--to speed up the testing of compounds--hopefully will help to optimize the process. Potential chemotherapeutic targets in the malaria parasite can be broadly classified into three categories: those involved in processes occurring in the digestive vacuole, enzymes involved in macromolecular and metabolite synthesis, and those responsible for membrane processes and signalling. The processes occurring in the digestive vacuole include haemoglobin digestion, redox processes and free radical formation, and reactions accompanying haem release followed by its polymerization into haemozoin. Many enzymes in macromolecular and metabolite synthesis are promising potential targets, some of which have been established in other microorganisms, although not yet validated for Plasmodium, with very few exceptions (such as dihydrofolate reductase). Proteins responsible for membrane processes, including trafficking and drug transport and signalling, are potentially important also to identify compounds to be used in combination with antimalarial drugs to combat resistance.
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Affiliation(s)
- P L Olliaro
- UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases, Geneva, Switzerland
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8
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Smeijsters LJ, Zijlstra NM, de Vries E, Franssen FF, Janse CJ, Overdulve JP. The effect of (S)-9-(3-hydroxy-2-phosphonylmethoxypropyl) adenine on nuclear and organellar DNA synthesis in erythrocytic schizogony in malaria. Mol Biochem Parasitol 1994; 67:115-24. [PMID: 7838172 DOI: 10.1016/0166-6851(94)90101-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The very effective (ID50 = 47 nM) and selective antimalarial compound (S)-9-(3-hydroxy-2-phosphonylmethoxypropyl) adenine (HPMPA) abruptly arrests Plasmodium falciparum-cultured schizonts at concentrations between 1 and 10 x ID50 as soon as their DNA content reaches 8 times that of the haploid ringform stage. Even very high HPMPA concentrations do not inhibit the first 2-3 rounds of schizogonic DNA replication. Also, in the presence of HPMPA, replication of the 6-kb mitochondrial and 35-kb chloroplast-like DNA proceeds normally and in close concert with each other, both to a 16-fold amount within 5 h during the trophozoite stage. Hence the in in vitro assays HPMPApp-sensitive plasmodial DNA polymerase gamma-like enzyme (IC50 = 1 microM)--assumed to be involved in mitochondrial DNA replication--is not the target of HPMPA in vivo (living parasites), nor seems to be the DNA polymerization activities of the--in vitro also HPMPA-sensitive (IC50 = 38 microM)--DNA polymerase alpha or of any other nuclear DNA polymerase of Plasmodium. In vitro assays demonstrated that HPMPApp does not act as an alternative substrate for plasmodial polymerases, contradicting the suggestion that the observed delayed inhibition of plasmodial schizogony might be the result of DNA strand breakage caused by HPMPApp incorporation. Neither do results support the idea that the HPMPA-induced arrest of DNA replication might be due to chain termination as a result of such incorporation. We investigated whether arrest of DNA replication by HPMPA in schizonts could be explained by inhibition of the DNA synthesis rate limiting ribonucleotide reductase enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- L J Smeijsters
- Department of Parasitology, Faculty of Veterinary Medicine, University of Utrecht, Netherlands
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9
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Gero AM, Upston JM. Altered membrane permeability: a new approach to malaria chemotherapy. ACTA ACUST UNITED AC 1992; 8:283-6. [PMID: 15463641 DOI: 10.1016/0169-4758(92)90147-t] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
During its development: in the host erythrocyte, the malarial parasite causes profound alterations in the permeability of the host cell membrane. Nucleoside transport pathways, which are induced by the parasite in the host erythrocyte membrane, have properties significantly different from those of the host cell. Here, Annette Gero and Joanne Upston review the current knowledge o f the parasite-induced transporters and show that they can be used to selectively direct cytotoxic compounds into the parasite-infected cell, thereby indicating their chemotherapeutic potential.
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Affiliation(s)
- A M Gero
- School of Bio chemistry and Molecular Genetics, University of NSW, PO Box I, Kensington, NSW 2033, Australia
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10
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Choi I, Mikkelsen RB. Plasmodium falciparum: ATP/ADP transport across the parasitophorous vacuolar and plasma membranes. Exp Parasitol 1990; 71:452-62. [PMID: 2226706 DOI: 10.1016/0014-4894(90)90071-j] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Previous studies have shown that ATP is required for the growth of the intracellular parasite, Plasmodium, outside its host cell, the erythrocyte, and that bongkrekic acid, an inhibitor of mitochondrial ATP/ADP transporter, inhibits intraerythrocytic Plasmodium maturation. We have characterized ATP/ADP transport of Plasmodium falciparum, isolated by either immune lysis or N2-cavitation. [3H]ATP uptake was due to ATP/ADP exchange since ADP efflux was dependent on exogenous ATP in an approximate 1:1 stoichiometry and both ATP influx and ADP efflux were equally inhibited by atractyloside (Ki = 100 nM). ATP uptake was not inhibited by the nucleoside transport inhibitor, nitrobenzylthioinosine. Conversely, adenosine and hypoxanthine transport were insensitive to atractyloside. ATP influx was characterized by a Km = 0.14 mM and Vmax = 1.2 nmol ATP/min/10(6) cells. Substrate specificity studies for nucleotide-induced ADP efflux indicated a preference for an adenosine ring and triphosphate, but transport did not require a hydrolyzable phosphate bond. Protein synthesis was measured with free parasites starved of glucose. Addition of 1.0 mM ATP resulted in a 40% recovery of total protein synthetic capacity in a process inhibited by 500 nM atractyloside, suggesting that uptake of erythrocyte-derived ATP by P. falciparum may be essential for maintaining maximal rates of protein synthesis during specific stages of intra-erythrocytic parasite maturation.
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Affiliation(s)
- I Choi
- Department of Radiation Oncology, Medical College of Virginia, Richmond 23298
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11
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Ye ZG, Van Dyke K. Reversal of chloroquine resistance in falciparum malaria independent of calcium channels. Biochem Biophys Res Commun 1988; 155:476-81. [PMID: 2458107 DOI: 10.1016/s0006-291x(88)81111-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Racemic verapamil and close structural derivatives gallopamil and devapamil completely reverse chloroquine-resistance in falciparum malaria at 1-2 micromolar concentrations. If the R-(+) isomers of these calcium channel inhibitors are used, chloroquine-resistance is again completely reversed at similar doses. However, these R-(+) isomers do not bind to cardiovascular calcium channels which are stereospecific for the S-(-) isomer of the drugs. Further since calcium channel inhibition is not involved, toxicity associated with this activity can be avoided. Therefore it is possible that a series of R-(+) isomers could be found that alter the resistant state without possessing significant toxicity. It is postulated that these lipophilic drugs are interacting with the mechanism of resistance, possibly a multidrug resistance glycoprotein pump.
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Affiliation(s)
- Z G Ye
- Dept. of Pharmacology and Toxicology, West Virginia University Health Sciences Ctr., Morgantown 26506
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12
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Abstract
The asexual stages of Plasmodium living within the erythrocyte result in growth-related changes in the permeability properties of the red cell for substances such as glucose, amino acids, purine nucleosides, sodium, potassium, calcium, zinc, iron and several antimalarial drugs such as chloroquine, amodiaquine and mefloquine. In most cases such changes do not appear to be due to a modification in the affinity or specificity of red cell transporters; indeed, for most substances the membrane-associated transporters are either unaffected or are partially inactivated. In malaria-infected erythrocytes, where a striking increase in influx has been observed, it has been attributed to the insertion of parasite-encoded transporters into the red cell membrane or the formation of aqueous leaks and/or pores. Leak formation, in the vast majority of cases, does not appear to be dependent on the insertion of plasmodial proteins into the red cell membrane. However, since the data presently available are less than satisfactory for discriminating amongst the various possible transport mechanisms future studies will require painstaking efforts and carefully controlled conditions to discriminate amongst the various transport systems which are operational in the malaria-infected red cell and the parasite.
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Affiliation(s)
- I W Sherman
- Department of Biology, University of California, Riverside 92521
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13
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Hioki A, Yoshino M, Kano S, Ohtomo H. Pathophysiology of hypoxia in mice infected with Plasmodium berghei. Parasitol Res 1987; 73:298-302. [PMID: 3303017 DOI: 10.1007/bf00531081] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Pathophysiological significance of hypoxia in malarial infection was investigated in mice infected with Plasmodium berghei NK65. Intraperitoneal inoculation of mice with 1 X 10(7) parasitized red blood cells resulted in death of the hosts 6-7 days later. Anaemia of infected animals developed on day 4 after inoculation and oxygen affinity of whole blood, measured as P50 act pH, increased simultaneously. This change may be a physiological adaptive response to a reduction in oxygen delivery to the tissues to day 5. However, the blood oxygen supply on day 6 appeared to be deteriorating and this is thought to be an important factor contributing to the death of the host. The value of adenylate energy charge in red cells during malarial infection, however, was comparatively well-maintained. Allopurinol stimulated the multiplication of malaria parasites and seems to have induced collapse in host-parasite balance more rapidly. Decrease in blood pH and in blood oxygen transport may be important factors for the pathogenesis of the allopurinol-treated hosts.
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14
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Goff WL, Yunker CE. Babesia bovis: increased percentage parasitized erythrocytes in cultures and assessment of growth by incorporation of [3H]hypoxanthine. Exp Parasitol 1986; 62:202-10. [PMID: 3743714 DOI: 10.1016/0014-4894(86)90024-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Babesia bovis was established in continuous in vitro erythrocyte cultures using a modification of techniques developed previously. Using optimal conditions for maintaining continuous exponential growth, a threshold number of infected erythrocytes was obtained after which exponential growth ceased. However, at this level, individual parasite development continued resulting in a higher proportion of mature merozoite infected erythrocytes. Additionally, the percentage parasitized erythrocytes could be increased by reducing the concentration of total erythrocytes. Growth was assessed by determining the percentage parasitized erythrocytes and level of incorporation of [3H]hypoxanthine. Uninfected erythrocytes did not incorporate the radiolabeled purine while infected cultures incorporated it in direct proportion to the increase in percentage parasitized erythrocytes. Pulse labeling experiments indicated that the trophozoite form (the developmental stage prior to division that results in paired merozoites) incorporated the majority of this purine into nucleic acids.
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15
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Geary TG, Divo AA, Bonanni LC, Jensen JB. Nutritional requirements of Plasmodium falciparum in culture. III. Further observations on essential nutrients and antimetabolites. THE JOURNAL OF PROTOZOOLOGY 1985; 32:608-13. [PMID: 2866244 DOI: 10.1111/j.1550-7408.1985.tb03087.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
In a semi-defined minimal medium for cultivation of Plasmodium falciparum, ribose, mannose, fructose, galactose, and maltose could not replace glucose. Hypoxanthine was the preferred purine source for the parasite over adenine, guanine, inosine, adenosine and guanosine although all supported growth equally. Inhibitors of nucleoside uptake had low potency in killing the parasites but depressed incorporation of [3H]adenosine more than [3H]hypoxanthine. Glutamate could not be replaced by 5-oxoproline, indicating that the gamma-glutamyl transferase pathway for amino acid uptake is probably not found in this organism. Adenine, nicotinamide, and orotic acid could not supplement glutamine-deficient medium. The pyridoxine antagonists isoniazid and 4-deoxypyridoxine were reversed by amino acid supplementation, suggesting that transaminases may be targets of these drugs. Orotic acid, but not glutathione or its amino acid components, partially reversed the effects of 8-methylamino-8-desmethyl riboflavin. Thus, the flavin enzyme, dihydroorotic acid dehydrogenase, but not glutathione reductase, appears to be a target of this riboflavin antagonist. Five biotin antagonists had no significant activity. The choline antagonist 2-(tert-butylamino)ethanol and thiamin uptake inhibitors had nonspecific inhibitory effects, which were not reversed by the respective target vitamin. Buthionine sulfoximine and methionine sulfoximine, inhibitors of glutathione synthesis, had significant oxygen-dependent toxicity. Six sulfonamides showed marked variation in potency and efficacy. Sulfathiazole and sulfadoxine were reversed differentially by p-aminobenzoic acid, folic acid, and folinic acid. Folinic acid was more effective than folic acid at reversing the toxicity of the dihydrofolate reductase inhibitors aminopterin and pyrimethamine; p-amino-benzoic acid had no effect.
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16
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Schimandle CM, Tanigoshi L, Mole LA, Sherman IW. Purine nucleoside phosphorylase of the malarial parasite, Plasmodium lophurae. J Biol Chem 1985. [DOI: 10.1016/s0021-9258(18)89286-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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17
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Abstract
Plasmodium requires a living cell for growth and reproduction. Intraerythrocytically the parasite stores no reserve carbohydrate, relying entirely on host-supplied glucose and certain amino acids (glutamic acid) for its energy. Plasmodia are microaerophiles degrading glucose primarily to lactate rather than to CO2. The limited amounts of oxygen utilized may serve for biosynthetic purposes (e.g. pyrimidine biosynthesis) rather than being involved in an energy-yielding electron transport chain. Evidence for a parasite pentose pathway is weak since glucose-6-phosphate dehydrogenase has rarely been found; paradoxically, activity for 6-phosphogluconate dehydrogenase, the next enzyme in the pathway, is consistently identified. The parasites synthesize pyrimidines de novo, but being incapable of de novo purine biosynthesis they require preformed purines. Exogenously supplied purine, notably hypoxanthine derived from catabolism of erythrocytic ATP, is taken up and incorporated whereas pyrimidines are not. The capacity for de novo amino acid biosynthesis is limited and presumably haemoglobin supplies most of the amino acids required by the parasite. Degradation of haemoglobin, involving parasite proteases, notably a cathepsin D-like enzyme, leaves a characteristic golden-brown residue, haemozoin. Haemozoin consists of dimers of ferriprotoporphyrin IX, methaemoglobin and plasmodial proteins. For some species, isoleucine and methionine must be supplied exogenously for good plasmodial growth. Infected erythrocytes characteristically show altered permeability properties, changes which in large part contribute to parasite growth while at the same time impairing red cell function.
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Chulay JD, Haynes JD, Diggs CL. Plasmodium falciparum: assessment of in vitro growth by [3H]hypoxanthine incorporation. Exp Parasitol 1983; 55:138-46. [PMID: 6337059 DOI: 10.1016/0014-4894(83)90007-3] [Citation(s) in RCA: 131] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
To evaluate rapidly Plasmodium falciparum growth in Vitro, [3H]hypoxanthine was added to parasite microcultures and radioisotope incorporation was measured. When culture parameters were carefully controlled, [3H]hypoxanthine incorporation was proportional to the number of parasitized erythrocytes present. Factors affecting [3H]hypoxanthine incorporation included initial parasitemia, duration of culture, duration of radioisotope pulse, parasite stage, concentration of uninfected erythrocytes, the use of serum or plasma to supplement growth, and the concentration of a variety of purines in the culture medium. The method described can be used to measure inhibition of P. falciparum growth by immune serum and has previously been used to study antimalarial drug activity in vitro.
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Schwartzman JD, Pfefferkorn ER. Toxoplasma gondii: purine synthesis and salvage in mutant host cells and parasites. Exp Parasitol 1982; 53:77-86. [PMID: 7198995 DOI: 10.1016/0014-4894(82)90094-7] [Citation(s) in RCA: 101] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Abstract
Extracts of normal duckling erythrocytes catabolized AMP to IMP, inosine and hypoxanthine; adenosine and adenine were not formed from AMP. When erythrocyte-free Plasmodium lophurae, prepared by antibody lysis, were incubated in the presence of [14C]hypoxanthine approximately 60% of the label was recovered as purine nucleotides and there was not evidence of extracellular alteration of added hypoxanthine. However, when adenosine was added to suspensions of antibody- or saponin-prepared parasites extensive conversion to inosine and hypoxanthine occurred. This conversion was found to be the result of parasite lysis with release of cytosolic purine salvage pathway enzymes; plasmodial surface membrane ecto-enzymes were not responsible for adenosine catabolism. It appears that in vivo the intracellular plasmodium utilizes the normal erythrocytic process of purine turnover to avail itself of hypoxanthine, the red cell's end product, and at the same time the parasite avoids direct competition for adenosine essential to erythrocyte survival. Since the blood plasma of infected ducklings contained increased amounts of hypoxanthine it is possible that P. lophurae also utilizes this as a purine source.
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21
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Wong PC, Yeung SB. Pathways of purine ribonucleotide biosynthesis in the adult worm Metastrongylus apri (Nematoda: Metastrongyloidea) from pig lung. Mol Biochem Parasitol 1981; 2:285-93. [PMID: 7242568 DOI: 10.1016/0166-6851(81)90081-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The pathways of purine ribonucleotide synthesis and interconversion that are operative in the intact adult pig lung worm Metastrongylus apri were identified by radioisotope tracing. The rate of [14C]glycine incorporation into purines was low but sufficient to demonstrate synthesis de novo. Radioactively labelled adenine, hypoxanthine and guanine were readily taken up and converted to the corresponding mononucleotides. Most of the AMP and GMP formed were phosphorylated to the triphosphates. These two nucleotides were interconvertable by pathways in which IMP is an intermediate. Adenosine was converted to nucleotides by direct phosphorylation as well as via formation of hypoxanthine. The rate of synthesis of adenine nucleotides from hypoxanthine was 5-7 times that of guanine nucleotides; conversion of IMP to AMP and to xanthosine 5'-monophosphate were the rate-limiting steps.
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22
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Yamada KA, Sherman IW. Purine metabolizing enzymes of Plasmodium lophurae and its host cell, the duckling (Anas domesticus) erythrocyte. Mol Biochem Parasitol 1981; 2:349-58. [PMID: 6787422 DOI: 10.1016/0166-6851(81)90086-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Adenosine kinase, adenosine deaminase, hypoxanthine phosphoribosyltransferase, inosine-nucleoside phosphorylase, 5'-AMP deaminase and 5'-IMP nucleotidase were identified in cell-free extracts of duckling erythrocytes; no evidence for 5'-AMP nucleotidase and xanthine oxidase activity was found. The Km values for the duckling red cell enzymes were similar to those reported for human erythrocytes. Plasmodium lophurae extracts demonstrated similar enzyme activities except for 5'-AMP deaminase and 5'-IMP nucleotidase which were absent. It is proposed that during infection erythrocytic AMP is catabolized to IMP, inosine and hypoxanthine; the hypoxanthine is taken up by the plasmodium, utilized to form IMP, and this in turn is converted into adenine and guanine nucleotides.
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24
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Kidder GW, Dewey VC, Nolan LL. Transport and accumulation of purine bases by Crithidia fasciculata. J Cell Physiol 1978; 96:165-70. [PMID: 670302 DOI: 10.1002/jcp.1040960205] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The capacity for the rapid transport of purine bases by Crithidia fasciulata is found only in cells starved for purines. Cells grown in complete medium transport poorly. Rapid transport capability appears and then disappears during growth of purine-depleted cultures. This rapid transport appears to occur by a process of mediated diffusion. Two mechanisms are involved, one of low velocity and high affinity, the other of high velocity and low affinity. Accumulation of the bases within the cell occurs by their rapid conversion to ribonucleotides by phosphoribosyltransferases.
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25
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Toyé PJ, Sinden RE, Canning EU. The action of metabolic inhibitors on microgametogenesis in Plasmodium yoelii nigeriensis. ZEITSCHRIFT FUR PARASITENKUNDE (BERLIN, GERMANY) 1977; 53:133-41. [PMID: 919692 DOI: 10.1007/bf00380457] [Citation(s) in RCA: 36] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Mature gametocytes of Plasmodium yoelii nigeriensis were incubated in vitro with a variety of antibiotics whose activities were directed against DNA, RNA, protein and microtubule assembly. Following incubation for periods between 5 and 90 min, exflagellation was induced and the degree of inhibition produced by each drug was assayed microscopically. The results obtained show that de novo synthesis of axonemes and proteins is essential to the events of microgametogenesis. The inhibitory effect of actinomycin-D suggests that de novo RNA synthesis is also required. However, the inactivity of 8-azaguanine, a drug also effective against m-RNA metabolism, casts some doubt on the requirement for m-RNA synthesis. DNA synthesis is not required during the three successive mitotic division of the parasite genome during microgametogenesis. The mature microgametocyte therefore contains the 8c DNA required for microgamete production.
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Van Dyke K, Wilson M, Trush M, Taylor M, Stealey P. Plasmodium berghei: high pressure liquid chromatographic analysis of nucleotides from erythrocyte-free malarial parasites. Exp Parasitol 1977; 42:274-81. [PMID: 195832 DOI: 10.1016/0014-4894(77)90084-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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