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Lange JDT, Stoller JR, Edwards KA, Friesen JA. Identification, characterization, and cellular localization of Leishmania major CTP:phosphocholine cytidylyltransferase. Biochem Biophys Res Commun 2024; 738:150548. [PMID: 39154553 DOI: 10.1016/j.bbrc.2024.150548] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2024] [Revised: 08/01/2024] [Accepted: 08/13/2024] [Indexed: 08/20/2024]
Abstract
The eukaryotic parasite Leishmania is the causative agent of the disease leishmaniasis, the second largest parasitic killer in the world behind malaria. A large percentage of Leishmania membrane phospholipids is phosphatidylcholine (PC), formed via the Kennedy pathway, where the enzyme CTP: phosphocholine cytidylyltransferase (CCT) catalyzes the second, rate limiting step. Leishmania major CCT was expressed in non-pathogenic Leishmania tarentolae and exhibited activity that increased 10-fold in the presence of PC:oleate lipid vesicles. Confocal microscopy of L. tarentolae expressing L. major CCT fused to a red fluorescent protein revealed the enzyme is cytoplasmic but may associate with internal membranes. A truncated mutant of L. major CCT containing the catalytic domain was expressed in Escherichia coli and in vitro analysis of the enzyme showed catalysis was divalent cation-dependent and yielded a Vmax of 374 nmol/min/mg and Km values of 0.0648 mM and 3.74 mM, respectively, for the substrates CTP and phosphocholine.
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Affiliation(s)
- Justin D T Lange
- Department of Chemistry, Illinois State University, Normal, IL, 61790, USA
| | - Jeanette R Stoller
- Department of Chemistry, Illinois State University, Normal, IL, 61790, USA
| | - Kevin A Edwards
- School of Biological Sciences, Illinois State University, Normal, IL, 61790, USA
| | - Jon A Friesen
- Department of Chemistry, Illinois State University, Normal, IL, 61790, USA.
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2
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Izrael R, Marton L, Nagy GN, Pálinkás HL, Kucsma N, Vértessy BG. Identification of a nuclear localization signal in the Plasmodium falciparum CTP: phosphocholine cytidylyltransferase enzyme. Sci Rep 2020; 10:19739. [PMID: 33184408 PMCID: PMC7665022 DOI: 10.1038/s41598-020-76829-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Accepted: 11/02/2020] [Indexed: 12/30/2022] Open
Abstract
The phospholipid biosynthesis of the malaria parasite, Plasmodium falciparum is a key process for its survival and its inhibition is a validated antimalarial therapeutic approach. The second and rate-limiting step of the de novo phosphatidylcholine biosynthesis is catalysed by CTP: phosphocholine cytidylyltransferase (PfCCT), which has a key regulatory function within the pathway. Here, we investigate the functional impact of the key structural differences and their respective role in the structurally unique pseudo-heterodimer PfCCT protein in a heterologous cellular context using the thermosensitive CCT-mutant CHO-MT58 cell line. We found that a Plasmodium-specific lysine-rich insertion within the catalytic domain of PfCCT acts as a nuclear localization signal and its deletion decreases the nuclear propensity of the protein in the model cell line. We further showed that the putative membrane-binding domain also affected the nuclear localization of the protein. Moreover, activation of phosphatidylcholine biosynthesis by phospholipase C treatment induces the partial nuclear-to-cytoplasmic translocation of PfCCT. We additionally investigated the cellular function of several PfCCT truncated constructs in a CHO-MT58 based rescue assay. In absence of the endogenous CCT activity we observed that truncated constructs lacking the lysine-rich insertion, or the membrane-binding domain provided similar cell survival ratio as the full length PfCCT protein.
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Affiliation(s)
- Richard Izrael
- Institute of Enzymology, Research Centre for Natural Sciences, 1117, Budapest, Hungary.
- Doctoral School of Multidisciplinary Medical Sciences, University of Szeged, 6720, Szeged, Hungary.
- Department of Applied Biotechnology, Budapest University of Technology and Economics, 1111, Budapest, Hungary.
| | - Lívia Marton
- Institute of Enzymology, Research Centre for Natural Sciences, 1117, Budapest, Hungary
| | - Gergely N Nagy
- Institute of Enzymology, Research Centre for Natural Sciences, 1117, Budapest, Hungary
- Department of Applied Biotechnology, Budapest University of Technology and Economics, 1111, Budapest, Hungary
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK
| | - Hajnalka L Pálinkás
- Institute of Enzymology, Research Centre for Natural Sciences, 1117, Budapest, Hungary
- Doctoral School of Multidisciplinary Medical Sciences, University of Szeged, 6720, Szeged, Hungary
- Department of Applied Biotechnology, Budapest University of Technology and Economics, 1111, Budapest, Hungary
| | - Nóra Kucsma
- Institute of Enzymology, Research Centre for Natural Sciences, 1117, Budapest, Hungary
| | - Beáta G Vértessy
- Institute of Enzymology, Research Centre for Natural Sciences, 1117, Budapest, Hungary.
- Department of Applied Biotechnology, Budapest University of Technology and Economics, 1111, Budapest, Hungary.
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3
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Heterologous expression of CTP:phosphocholine cytidylyltransferase from Plasmodium falciparum rescues Chinese Hamster Ovary cells deficient in the Kennedy phosphatidylcholine biosynthesis pathway. Sci Rep 2018; 8:8932. [PMID: 29895950 PMCID: PMC5997628 DOI: 10.1038/s41598-018-27183-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Accepted: 04/23/2018] [Indexed: 01/10/2023] Open
Abstract
The plasmodial CTP:phosphocholine cytidylyltransferase (PfCCT) is a promising antimalarial target, which can be inhibited to exploit the need for increased lipid biosynthesis during the erythrocytic life stage of Plasmodium falciparum. Notable structural and regulatory differences of plasmodial and mammalian CCTs offer the possibility to develop species-specific inhibitors. The aim of this study was to use CHO-MT58 cells expressing a temperature-sensitive mutant CCT for the functional characterization of PfCCT. We show that heterologous expression of wild type PfCCT restores the viability of CHO-MT58 cells at non-permissive (40 °C) temperatures, whereas catalytically perturbed or structurally destabilized PfCCT variants fail to provide rescue. Detailed in vitro characterization indicates that the H630N mutation diminishes the catalytic rate constant of PfCCT. The flow cytometry-based rescue assay provides a quantitative readout of the PfCCT function opening the possibility for the functional analysis of PfCCT and the high throughput screening of antimalarial compounds targeting plasmodial CCT.
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4
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Membrane lipid compositional sensing by the inducible amphipathic helix of CCT. Biochim Biophys Acta Mol Cell Biol Lipids 2015; 1861:847-861. [PMID: 26747646 DOI: 10.1016/j.bbalip.2015.12.022] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Revised: 12/22/2015] [Accepted: 12/29/2015] [Indexed: 11/21/2022]
Abstract
The amphipathic helical (AH) membrane binding motif is recognized as a major device for lipid compositional sensing. We explore the function and mechanism of sensing by the lipid biosynthetic enzyme, CTP:phosphocholine cytidylyltransferase (CCT). As the regulatory enzyme in phosphatidylcholine (PC) synthesis, CCT contributes to membrane PC homeostasis. CCT directly binds and inserts into the surface of bilayers that are deficient in PC and therefore enriched in lipids that enhance surface charge and/or create lipid packing voids. These two membrane physical properties induce the folding of the CCT M domain into a ≥60 residue AH. Membrane binding activates catalysis by a mechanism that has been partially deciphered. We review the evidence for CCT compositional sensing, and the membrane and protein determinants for lipid selective membrane-interactions. We consider the factors that promote the binding of CCT isoforms to the membranes of the ER, nuclear envelope, or lipid droplets, but exclude CCT from other organelles and the plasma membrane. The CCT sensing mechanism is compared with several other proteins that use an AH motif for membrane compositional sensing. This article is part of a Special Issue entitled: The cellular lipid landscape edited by Tim P. Levine and Anant K. Menon.
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Cornell RB, Ridgway ND. CTP:phosphocholine cytidylyltransferase: Function, regulation, and structure of an amphitropic enzyme required for membrane biogenesis. Prog Lipid Res 2015; 59:147-71. [PMID: 26165797 DOI: 10.1016/j.plipres.2015.07.001] [Citation(s) in RCA: 91] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Revised: 07/07/2015] [Accepted: 07/07/2015] [Indexed: 12/12/2022]
Abstract
CTP:phosphocholine cytidylyltransferase (CCT) catalyzes a rate-limiting and regulated step in the CDP-choline pathway for the synthesis of phosphatidylcholine (PC) and PC-derived lipids. Control of CCT activity is multi-layered, and includes direct regulation by reversible membrane binding involving a built-in lipid compositional sensor. Thus CCT contributes to phospholipid compositional homeostasis. CCT also modifies the curvature of its target membrane. Knowledge of CCT structure and regulation of its catalytic function are relatively advanced compared to many lipid metabolic enzymes, and are reviewed in detail. Recently the genetic origins of two human developmental and lipogenesis disorders have been traced to mutations in the gene for CCTα.
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Affiliation(s)
- Rosemary B Cornell
- Department of Molecular Biology and Biochemistry and the Department of Chemistry, Simon Fraser University, Burnaby, B.C. V5A-1S6, Canada.
| | - Neale D Ridgway
- Departments of Pediatrics, and Biochemistry and Molecular Biology, Atlantic Research Centre, Dalhousie University, Halifax, Nova Scotia B3H-4H7, Canada
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Marton L, Nagy GN, Ozohanics O, Lábas A, Krámos B, Oláh J, Vékey K, Vértessy BG. Molecular Mechanism for the Thermo-Sensitive Phenotype of CHO-MT58 Cell Line Harbouring a Mutant CTP:Phosphocholine Cytidylyltransferase. PLoS One 2015; 10:e0129632. [PMID: 26083347 PMCID: PMC4470507 DOI: 10.1371/journal.pone.0129632] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Accepted: 05/10/2015] [Indexed: 01/27/2023] Open
Abstract
Control and elimination of malaria still represents a major public health challenge. Emerging parasite resistance to current therapies urges development of antimalarials with novel mechanism of action. Phospholipid biosynthesis of the Plasmodium parasite has been validated as promising candidate antimalarial target. The most prevalent de novo pathway for synthesis of phosphatidylcholine is the Kennedy pathway. Its regulatory and often also rate limiting step is catalyzed by CTP:phosphocholine cytidylyltransferase (CCT). The CHO-MT58 cell line expresses a mutant variant of CCT, and displays a thermo-sensitive phenotype. At non-permissive temperature (40°C), the endogenous CCT activity decreases dramatically, blocking membrane synthesis and ultimately leading to apoptosis. In the present study we investigated the impact of the analogous mutation in a catalytic domain construct of Plasmodium falciparum CCT in order to explore the underlying molecular mechanism that explains this phenotype. We used temperature dependent enzyme activity measurements and modeling to investigate the functionality of the mutant enzyme. Furthermore, MS measurements were performed to determine the oligomerization state of the protein, and MD simulations to assess the inter-subunit interactions in the dimer. Our results demonstrate that the R681H mutation does not directly influence enzyme catalytic activity. Instead, it provokes increased heat-sensitivity by destabilizing the CCT dimer. This can possibly explain the significance of the PfCCT pseudoheterodimer organization in ensuring proper enzymatic function. This also provide an explanation for the observed thermo-sensitive phenotype of CHO-MT58 cell line.
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Affiliation(s)
- Lívia Marton
- Institute of Enzymology, Research Centre for National Sciences, HAS, Budapest Hungary
- Doctoral School of Multidisciplinary Medical Science, University of Szeged, Szeged, Hungary
| | - Gergely N. Nagy
- Institute of Enzymology, Research Centre for National Sciences, HAS, Budapest Hungary
- Department of Applied Biotechnology and Food Science, Budapest University of Technology and Economics, Budapest, Hungary
| | - Olivér Ozohanics
- Institute of Organic Chemistry, Research Centre for National Sciences, HAS, Budapest, Hungary
| | - Anikó Lábas
- Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Budapest, Hungary
| | - Balázs Krámos
- Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Budapest, Hungary
| | - Julianna Oláh
- Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Budapest, Hungary
| | - Károly Vékey
- Institute of Organic Chemistry, Research Centre for National Sciences, HAS, Budapest, Hungary
| | - Beáta G. Vértessy
- Institute of Enzymology, Research Centre for National Sciences, HAS, Budapest Hungary
- Department of Applied Biotechnology and Food Science, Budapest University of Technology and Economics, Budapest, Hungary
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Contet A, Pihan E, Lavigne M, Wengelnik K, Maheshwari S, Vial H, Douguet D, Cerdan R. Plasmodium falciparum CTP:phosphocholine cytidylyltransferase possesses two functional catalytic domains and is inhibited by a CDP-choline analog selected from a virtual screening. FEBS Lett 2015; 589:992-1000. [PMID: 25771858 DOI: 10.1016/j.febslet.2015.03.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Accepted: 03/03/2015] [Indexed: 10/23/2022]
Abstract
Phosphatidylcholine is the major lipid component of the malaria parasite membranes and is required for parasite multiplication in human erythrocytes. Plasmodium falciparum CTP:phosphocholine cytidylyltransferase (PfCCT) is the rate-limiting enzyme of the phosphatidylcholine biosynthesis pathway and thus considered as a potential antimalarial target. In contrast to its mammalian orthologs, PfCCT contains a duplicated catalytic domain. Here, we show that both domains are catalytically active with similar kinetic parameters. A virtual screening strategy allowed the identification of a drug-size molecule competitively inhibiting the enzyme. This compound also prevented phosphatidylcholine biosynthesis in parasites and exerted an antimalarial effect. This study constitutes the first step towards a rationalized design of future new antimalarial agents targeting PfCCT.
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Affiliation(s)
- Alicia Contet
- Université Montpellier, CNRS, Dynamique des Interactions Membranaires Normales et Pathologiques, UMR 5235, Place Eugène Bataillon, 34095 Montpellier, France
| | - Emilie Pihan
- CNRS, Université Nice Sophia-Antipolis, Institut de Pharmacologie Moléculaire et Cellulaire, UMR 7275, 660, route des Lucioles, Sophia Antipolis, 06560 Valbonne, France
| | - Marina Lavigne
- Université Montpellier, CNRS, Dynamique des Interactions Membranaires Normales et Pathologiques, UMR 5235, Place Eugène Bataillon, 34095 Montpellier, France
| | - Kai Wengelnik
- Université Montpellier, CNRS, Dynamique des Interactions Membranaires Normales et Pathologiques, UMR 5235, Place Eugène Bataillon, 34095 Montpellier, France
| | - Sweta Maheshwari
- Université Montpellier, CNRS, Dynamique des Interactions Membranaires Normales et Pathologiques, UMR 5235, Place Eugène Bataillon, 34095 Montpellier, France
| | - Henri Vial
- Université Montpellier, CNRS, Dynamique des Interactions Membranaires Normales et Pathologiques, UMR 5235, Place Eugène Bataillon, 34095 Montpellier, France
| | - Dominique Douguet
- CNRS, Université Nice Sophia-Antipolis, Institut de Pharmacologie Moléculaire et Cellulaire, UMR 7275, 660, route des Lucioles, Sophia Antipolis, 06560 Valbonne, France.
| | - Rachel Cerdan
- Université Montpellier, CNRS, Dynamique des Interactions Membranaires Normales et Pathologiques, UMR 5235, Place Eugène Bataillon, 34095 Montpellier, France.
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Sen P, Vial HJ, Radulescu O. Kinetic modelling of phospholipid synthesis in Plasmodium knowlesi unravels crucial steps and relative importance of multiple pathways. BMC SYSTEMS BIOLOGY 2013; 7:123. [PMID: 24209716 PMCID: PMC3829661 DOI: 10.1186/1752-0509-7-123] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Accepted: 11/01/2013] [Indexed: 12/04/2022]
Abstract
BACKGROUND Plasmodium is the causal parasite of malaria, infectious disease responsible for the death of up to one million people each year. Glycerophospholipid and consequently membrane biosynthesis are essential for the survival of the parasite and are targeted by a new class of antimalarial drugs developed in our lab. In order to understand the highly redundant phospholipid synthethic pathways and eventual mechanism of resistance to various drugs, an organism specific kinetic model of these metabolic pathways need to be developed in Plasmodium species. RESULTS Fluxomic data were used to build a quantitative kinetic model of glycerophospholipid pathways in Plasmodium knowlesi. In vitro incorporation dynamics of phospholipids unravels multiple synthetic pathways. A detailed metabolic network with values of the kinetic parameters (maximum rates and Michaelis constants) has been built. In order to obtain a global search in the parameter space, we have designed a hybrid, discrete and continuous, optimization method. Discrete parameters were used to sample the cone of admissible fluxes, whereas the continuous Michaelis and maximum rates constants were obtained by local minimization of an objective function.The model was used to predict the distribution of fluxes within the network of various metabolic precursors.The quantitative analysis was used to understand eventual links between different pathways. The major source of phosphatidylcholine (PC) is the CDP-choline Kennedy pathway.In silico knock-out experiments showed comparable importance of phosphoethanolamine-N-methyltransferase (PMT) and phosphatidylethanolamine-N-methyltransferase (PEMT) for PC synthesis.The flux values indicate that, major part of serine derived phosphatidylethanolamine (PE) is formed via serine decarboxylation, whereas major part of phosphatidylserine (PS) is formed by base-exchange reactions.Sensitivity analysis of CDP-choline pathway shows that the carrier-mediated choline entry into the parasite and the phosphocholine cytidylyltransferase reaction have the largest sensitivity coefficients in this pathway, but does not distinguish a reaction as an unique rate-limiting step. CONCLUSION We provide a fully parametrized kinetic model for the multiple phospholipid synthetic pathways in P. knowlesi. This model has been used to clarify the relative importance of the various reactions in these metabolic pathways. Future work extensions of this modelling strategy will serve to elucidate the regulatory mechanisms governing the development of Plasmodium during its blood stages, as well as the mechanisms of action of drugs on membrane biosynthetic pathways and eventual mechanisms of resistance.
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Affiliation(s)
- Partho Sen
- Dynamique des Interactions Membranaires Normales et Pathologiques, UMR 5235 CNRS, UM1, UM2, CP 107, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France
| | - Henri J Vial
- Dynamique des Interactions Membranaires Normales et Pathologiques, UMR 5235 CNRS, UM1, UM2, CP 107, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France
| | - Ovidiu Radulescu
- Dynamique des Interactions Membranaires Normales et Pathologiques, UMR 5235 CNRS, UM1, UM2, CP 107, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France
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9
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Nagy GN, Marton L, Krámos B, Oláh J, Révész Á, Vékey K, Delsuc F, Hunyadi-Gulyás É, Medzihradszky KF, Lavigne M, Vial H, Cerdan R, Vértessy BG. Evolutionary and mechanistic insights into substrate and product accommodation of CTP:phosphocholine cytidylyltransferase from Plasmodium falciparum. FEBS J 2013; 280:3132-48. [PMID: 23578277 DOI: 10.1111/febs.12282] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2012] [Revised: 03/08/2013] [Accepted: 03/26/2013] [Indexed: 12/31/2022]
Abstract
The enzyme CTP:phosphocholine cytidylyltransferase (CCT) is essential in the lipid biosynthesis of Plasmodia (Haemosporida), presenting a promising antimalarial target. Here, we identified two independent gene duplication events of CCT within Apicomplexa and characterized a truncated construct of Plasmodium falciparum CCT that forms a dimer resembling the molecular architecture of CCT enzymes from other sources. Based on biophysical and enzyme kinetics methods, our data show that the CDP-choline product of the CCT enzymatic reaction binds to the enzyme considerably stronger than either substrate (CTP or choline phosphate). Interestingly, in the presence of Mg²⁺ , considered to be a cofactor of the enzyme, the binding of the CTP substrate is attenuated by a factor of 5. The weaker binding of CTP:Mg²⁺ , similarly to the related enzyme family of aminoacyl tRNA synthetases, suggests that, with lack of Mg²⁺ , positively charged side chain(s) of CCT may contribute to CTP accommodation. Thermodynamic investigations by isothermal titration calorimetry and fluorescent spectroscopy studies indicate that accommodation of the choline phosphate moiety in the CCT active site is different when it appears on its own as one of the substrates or when it is linked to the CDP-choline product. A tryptophan residue within the active site is identified as a useful internal fluorescence sensor of enzyme-ligand binding. Results indicate that the catalytic mechanism of Plasmodium falciparum CCT may involve conformational changes affecting the choline subsite of the enzyme.
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Affiliation(s)
- Gergely N Nagy
- Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest, Hungary.
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10
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Wein S, Maynadier M, Bordat Y, Perez J, Maheshwari S, Bette-Bobillo P, Tran Van Ba C, Penarete-Vargas D, Fraisse L, Cerdan R, Vial H. Transport and pharmacodynamics of albitiazolium, an antimalarial drug candidate. Br J Pharmacol 2012; 166:2263-76. [PMID: 22471905 PMCID: PMC3437492 DOI: 10.1111/j.1476-5381.2012.01966.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND AND PURPOSE Choline analogues, a new type of antimalarials, exert potent in vitro and in vivo antimalarial activity. This has given rise to albitiazolium, which is currently in phase II clinical trials to cure severe malaria. Here we dissected its mechanism of action step by step from choline entry into the infected erythrocyte to its effect on phosphatidylcholine (PC) biosynthesis. EXPERIMENTAL APPROACH We biochemically unravelled the transport and enzymatic steps that mediate de novo synthesis of PC and elucidated how albitiazolium enters the intracellular parasites and affects the PC biosynthesis. KEY RESULTS Choline entry into Plasmodium falciparum-infected erythrocytes is achieved both by the remnant erythrocyte choline carrier and by parasite-induced new permeability pathways (NPP), while parasite entry involves a poly-specific cation transporter. Albitiazolium specifically prevented choline incorporation into its end-product PC, and its antimalarial activity was strongly antagonized by choline. Albitiazolium entered the infected erythrocyte mainly via a furosemide-sensitive NPP and was transported into the parasite by a poly-specific cation carrier. Albitiazolium competitively inhibited choline entry via the parasite-derived cation transporter and also, at a much higher concentration, affected each of the three enzymes conducting de novo synthesis of PC. CONCLUSIONS AND IMPLICATIONS Inhibition of choline entry into the parasite appears to be the primary mechanism by which albitiazolium exerts its potent antimalarial effect. However, the pharmacological response to albitiazolium involves molecular interactions with different steps of the de novo PC biosynthesis pathway, which would help to delay the development of resistance to this drug.
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Affiliation(s)
- S Wein
- Dynamique des Interactions Membranaires Normales et Pathologiques, CNRS UMR 5235, Université Montpellier II, Montpellier, France
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11
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Ding Z, Taneva SG, Huang HKH, Campbell SA, Semenec L, Chen N, Cornell RB. A 22-mer segment in the structurally pliable regulatory domain of metazoan CTP: phosphocholine cytidylyltransferase facilitates both silencing and activating functions. J Biol Chem 2012; 287:38980-91. [PMID: 22988242 DOI: 10.1074/jbc.m112.402081] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
CTP:phosphocholine cytidylyltransferase (CCT), an amphitropic enzyme that regulates phosphatidylcholine synthesis, is composed of a catalytic head domain and a regulatory tail. The tail region has dual functions as a regulator of membrane binding/enzyme activation and as an inhibitor of catalysis in the unbound form of the enzyme, suggesting conformational plasticity. These functions are well conserved in CCTs across diverse phyla, although the sequences of the tail regions are not. CCT regulatory tails of diverse origins are composed of a long membrane lipid-inducible amphipathic helix (m-AH) followed by a highly disordered segment, reminiscent of the Parkinson disease-linked protein, α-synuclein, which we show shares a novel sequence motif with vertebrate CCTs. To unravel features required for silencing, we created chimeric enzymes by fusing the catalytic domain of rat CCTα to the regulatory tail of CCTs from Drosophila, Caenorhabditis elegans, or Saccharomyces cerevisiae or to α-synuclein. Only the tail domains of the two invertebrate CCTs were competent for both suppression of catalytic activity and for activation by lipid vesicles. Thus, both silencing and activating functions of the m-AH can tolerate significant changes in length and sequence. We identified a highly amphipathic 22-residue segment in the m-AH with features conserved among animal CCTs but not yeast CCT or α-synuclein. Deletion of this segment from rat CCT increased the lipid-independent V(max) by 10-fold, equivalent to the effect of deleting the entire tail, and severely weakened membrane binding affinity. However, membrane binding was required for additional increases in catalytic efficiency. Thus, full activation of CCT may require not only loss of a silencing conformation in the m-AH but a gain of an activating conformation, promoted by membrane binding.
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Affiliation(s)
- Ziwei Ding
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
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12
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González-Bulnes P, Bobenchik AM, Augagneur Y, Cerdan R, Vial HJ, Llebaria A, Ben Mamoun C. PG12, a phospholipid analog with potent antimalarial activity, inhibits Plasmodium falciparum CTP:phosphocholine cytidylyltransferase activity. J Biol Chem 2011; 286:28940-28947. [PMID: 21705805 DOI: 10.1074/jbc.m111.268946] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In the human malaria parasite Plasmodium falciparum, the synthesis of the major and essential membrane phospholipid, phosphatidylcholine, occurs via the CDP-choline and the serine decarboxylase phosphoethanolamine methylation (SDPM) pathways, which are fueled by host choline, serine, and fatty acids. Both pathways share the final two steps catalyzed by two essential enzymes, P. falciparum CTP:phosphocholine cytidylyltransferase (PfCCT) and choline-phosphate transferase (PfCEPT). We identified a novel class of phospholipid mimetics, which inhibit the growth of P. falciparum as well as Leishmania and Trypanosoma species. Metabolic analyses showed that one of these compounds, PG12, specifically blocks phosphatidylcholine biosynthesis from both the CDP-choline and SDPM pathways via inhibition of PfCCT. In vitro studies using recombinant PfCCT showed a dose-dependent inhibition of the enzyme by PG12. The potent antimalarial of this compound, its low cytotoxicity profile, and its established mode of action make it an excellent lead to advance for further drug development and efficacy in vivo.
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Affiliation(s)
- Patricia González-Bulnes
- Research Unit on BioActive Molecules (RUBAM), Departament de Química Biomèdica, Instituto de Química Avanzada de Cataluña IQAC, CSIC, Jordi Girona 18-26, 08034 Barcelona, Spain
| | - April M Bobenchik
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06520, and
| | - Yoann Augagneur
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06520, and
| | - Rachel Cerdan
- Dynamique des Interactions Membranaires Normales et Pathologiques, CNRS UMR 5235, Universite Montpellier II, 34095 Montpellier, France
| | - Henri J Vial
- Dynamique des Interactions Membranaires Normales et Pathologiques, CNRS UMR 5235, Universite Montpellier II, 34095 Montpellier, France
| | - Amadeu Llebaria
- Research Unit on BioActive Molecules (RUBAM), Departament de Química Biomèdica, Instituto de Química Avanzada de Cataluña IQAC, CSIC, Jordi Girona 18-26, 08034 Barcelona, Spain,.
| | - Choukri Ben Mamoun
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06520, and.
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Déchamps S, Shastri S, Wengelnik K, Vial HJ. Glycerophospholipid acquisition in Plasmodium - a puzzling assembly of biosynthetic pathways. Int J Parasitol 2010; 40:1347-65. [PMID: 20600072 DOI: 10.1016/j.ijpara.2010.05.008] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2010] [Revised: 05/24/2010] [Accepted: 05/25/2010] [Indexed: 01/06/2023]
Abstract
Throughout the Plasmodium life cycle, malaria parasites repeatedly undergo rapid cellular growth and prolific divisions, necessitating intense membrane neogenesis and, in particular, the acquisition of high amounts of phospholipids. At the intraerythrocytic stage, glycerophospholipids are the main parasite membrane constituents, which mostly originate from the Plasmodium-encoded enzymatic machinery. Several proteins and entire pathways have been characterized and their features reported, thereby generating a global view of glycerophospholipid synthesis across Plasmodium spp. The malaria parasite displays a panoply of pathways that are seldom found together in a single organism. The major glycerophospholipids are synthesized via ancestral prokaryotic CDP-diacylglycerol-dependent pathways and eukaryotic-type de novo pathways. The parasite exhibits additional reactions that bridge some of these routes and are otherwise restricted to some organisms, such as plants, while base-exchange mechanisms are largely unexplored in Plasmodium. Marked differences between Plasmodium spp. have also been reported in phosphatidylcholine and phosphatidylethanolamine synthesis. Little is currently known about glycerophospholipid acquisition at non-erythrocytic stages, but recent data reveal that intrahepatocytic parasites, oocysts and sporozoites import various host lipids, and that de novo fatty acid synthesis is only crucial at the late liver stage. More studies on the different Plasmodium developmental stages are needed, to further assemble the different pieces of this glycerophospholipid synthesis puzzle, which contains highly promising therapeutic targets.
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Affiliation(s)
- Sandrine Déchamps
- Dynamique des Interactions Membranaires Normales et Pathologiques, UMR 5235, Centre National de la Recherche Scientifique (CNRS) - Universite Montpellier 2, cc 107, Place Eugene Bataillon, 34095 Montpellier Cedex 05, France
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14
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Déchamps S, Wengelnik K, Berry-Sterkers L, Cerdan R, Vial HJ, Gannoun-Zaki L. The Kennedy phospholipid biosynthesis pathways are refractory to genetic disruption in Plasmodium berghei and therefore appear essential in blood stages. Mol Biochem Parasitol 2010; 173:69-80. [PMID: 20478340 DOI: 10.1016/j.molbiopara.2010.05.006] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2010] [Revised: 05/04/2010] [Accepted: 05/08/2010] [Indexed: 12/15/2022]
Abstract
Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) are the main membrane phospholipids (PLs) of Plasmodium parasites and can be generated by the de novo (Kennedy) CDP-choline and CDP-ethanolamine pathways and by the CDP-diacylglycerol dependent pathway. The Kennedy pathways initiate from exogenous choline and ethanolamine involving choline kinase (CK) and ethanolamine kinase (EK), followed by the choline-phosphate cytidylyltransferase (CCT) and ethanolamine-phosphate cytidylyltransferase (ECT) that catalyse the formation of CDP-choline and CDP-ethanolamine. Finally, in Plasmodium, PC and PE are apparently synthesized by a common choline/ethanolamine-phosphotransferase (CEPT). Here, we have studied the essential nature of the Kennedy pathways in Plasmodium berghei, a rodent malaria parasite. Sequence analysis of the P. berghei CEPT, CCT, ECT and CK enzymes revealed the presence of all catalytic domains and essential residues and motifs necessary for enzymatic activities. Constructs were designed for the generation of gene knockout and GFP-fusions of the cept, cct, ect and ck genes in P. berghei. We found that all four genes were consistently refractory to knockout attempts. At the same time, successful tagging of these proteins with GFP demonstrated that the loci were targetable and indicated that these genes are essential in P. berghei blood stage parasites. GFP-fusions of CCT, ECT and CK were found in the cytosol whereas the GFP-CEPT mainly localised in the endoplasmic reticulum. These results indicate that both CDP-choline and CDP-ethanolamine de novo pathways are essential for asexual P. berghei development and are non-redundant with other possible sources of PC and PE.
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Affiliation(s)
- Sandrine Déchamps
- Dynamique des Interactions Membranaires Normales et Pathologiques, UMR 5235, CNRS-Universite Montpellier 2, Place Eugene Bataillon, cc107, Montpellier 34095, Cedex 05, France
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15
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Braker JD, Hodel KJ, Mullins DR, Friesen JA. Identification of hydrophobic amino acids required for lipid activation of C. elegans CTP:phosphocholine cytidylyltransferase. Arch Biochem Biophys 2009; 492:10-6. [PMID: 19836342 DOI: 10.1016/j.abb.2009.10.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2009] [Revised: 10/09/2009] [Accepted: 10/10/2009] [Indexed: 11/18/2022]
Abstract
CTP:phosphocholine cytidylyltransferase (CCT), critical for phosphatidylcholine biosynthesis, is activated by translocation to the membrane surface. The lipid activation region of Caenorhabditis elegans CCT is between residues 246 and 266 of the 347 amino acid polypeptide, a region proposed to form an amphipathic alpha helix. When leucine 246, tryptophan 249, isoleucine 256, isoleucine 257, or phenylalanine 260, on the hydrophobic face of the helix, were changed individually to serine low activity was observed in the absence of lipid vesicles, similar to wild-type CCT, while lipid stimulated activity was reduced compared to wild-type CCT. Mutational analysis of phenylalanine 260 implicated this residue as a contributor to auto-inhibition of CCT while mutation of L246, W249, I256, and I257 simultaneously to serine resulted in significantly higher activity in the absence of lipid vesicles and an enzyme that was not lipid activated. These results support a concerted mechanism of lipid activation that requires multiple residues on the hydrophobic face of the putative amphipathic alpha helix.
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Affiliation(s)
- Jay D Braker
- Department of Chemistry, Illinois State University, Normal, IL 61790, USA
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16
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Tilley DM, Evans CR, Larson TM, Edwards KA, Friesen JA. Identification and Characterization of the Nuclear Isoform of Drosophila melanogaster CTP:Phosphocholine Cytidylyltransferase. Biochemistry 2008; 47:11838-46. [DOI: 10.1021/bi801161s] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Dana M. Tilley
- Department of Chemistry and Department of Biological Sciences, Illinois State University, Normal, Illinois 61790
| | - Chadrick R. Evans
- Department of Chemistry and Department of Biological Sciences, Illinois State University, Normal, Illinois 61790
| | - Troy M. Larson
- Department of Chemistry and Department of Biological Sciences, Illinois State University, Normal, Illinois 61790
| | - Kevin A. Edwards
- Department of Chemistry and Department of Biological Sciences, Illinois State University, Normal, Illinois 61790
| | - Jon A. Friesen
- Department of Chemistry and Department of Biological Sciences, Illinois State University, Normal, Illinois 61790
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17
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Sherman IW. References. ADVANCES IN PARASITOLOGY 2008. [DOI: 10.1016/s0065-308x(08)00430-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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18
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Choubey V, Guha M, Maity P, Kumar S, Raghunandan R, Maulik PR, Mitra K, Halder UC, Bandyopadhyay U. Molecular characterization and localization of Plasmodium falciparum choline kinase. Biochim Biophys Acta Gen Subj 2006; 1760:1027-38. [PMID: 16626864 DOI: 10.1016/j.bbagen.2006.03.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2005] [Revised: 02/24/2006] [Accepted: 03/01/2006] [Indexed: 10/24/2022]
Abstract
Generation of phosphocholine by choline kinase is important for phosphatidylcholine biosynthesis via Kennedy pathway and phosphatidylcholine biosynthesis is essential for intraerythrocytic growth of malaria parasite. A putative gene (Gene ID PF14_0020) in chromosome 14, having highest sequence homology with choline kinase, has been identified by BLAST searches from P. falciparum genome sequence database. This gene has been PCR amplified, cloned, over-expressed and characterized. Choline kinase activity of the recombinant protein (PfCK) was validated as it catalyzed the formation of phosphocholine from choline in presence of ATP. The K(m) values for choline and ATP are found to be 145+/-20 microM and 2.5+/-0.3 mM, respectively. PfCK can phosphorylate choline efficiently but not ethanolamine. Southern blotting indicates that PfCK is a single copy gene and it is a cytosolic protein as evidenced by Western immunoblotting and confocal microscopy. A model structure of PfCK was constructed based on the crystal structure of choline kinase of C. elegans to search the structural homology. Consistent with the homology modeling predictions, CD analysis indicates that the alpha and beta content of PfCK are 33% and 14%, respectively. Since choline kinase plays a vital role for growth and multiplication of P. falciparum during intraerythrocytic stages, we can suggest that this well characterized PfCK may be exploited in the screening of new choline kinase inhibitors to evaluate their antimalarial activity.
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Affiliation(s)
- Vinay Choubey
- Division of Drug Target Discovery and Development, Central Drug Research Institute, Chatter Manzil Palace, Mahatma Gandhi Marg, Lucknow-226001, Uttar Pradesh, India
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19
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Kent C. Regulatory enzymes of phosphatidylcholine biosynthesis: a personal perspective. Biochim Biophys Acta Mol Cell Biol Lipids 2005; 1733:53-66. [PMID: 15749057 DOI: 10.1016/j.bbalip.2004.12.008] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2004] [Revised: 12/14/2004] [Accepted: 12/17/2004] [Indexed: 12/22/2022]
Abstract
Phosphatidylcholine is a prominent constituent of eukaryotic and some prokaryotic membranes. This Perspective focuses on the two enzymes that regulate its biosynthesis, choline kinase and CTP:phosphocholine cytidylyltransferase. These enzymes are discussed with respect to their molecular properties, isoforms, enzymatic activities, and structures, and the possible molecular mechanisms by which they participate in regulation of phosphatidylcholine levels in the cell.
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20
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Jackowski S, Fagone P. CTP: Phosphocholine cytidylyltransferase: paving the way from gene to membrane. J Biol Chem 2004; 280:853-6. [PMID: 15536089 DOI: 10.1074/jbc.r400031200] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
- Suzanne Jackowski
- Protein Science Division, Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.
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21
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Helmink BA, Friesen JA. Characterization of a lipid activated CTP:phosphocholine cytidylyltransferase from Drosophila melanogaster. Biochim Biophys Acta Mol Cell Biol Lipids 2004; 1683:78-88. [PMID: 15238222 DOI: 10.1016/j.bbalip.2004.04.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2003] [Revised: 04/28/2004] [Accepted: 04/30/2004] [Indexed: 11/28/2022]
Abstract
CTP:phosphocholine cytidylyltransferase (CCT) is an enzyme critical for cellular phosphatidylcholine (PC) synthesis, converting phosphocholine and cytidine 5'-triphosphate (CTP) to CDP-choline. We have isolated a cDNA encoding an isoform of CCT from Drosophila melanogaster and expressed the recombinant native and 6 x -His-tagged forms using a baculovirus expression system in Spodoptera frugiperda (Sf9) insect cells. Immunoblot using anti-phospho amino acid antibodies reveals the enzyme is phosphorylated on serine and threonine residues, but not tyrosine. The purified native enzyme exhibits a V(max) value of 1352+/-159 nmol CDP-choline/min/mg, a K(m) value of 0.50+/-0.09 mM for phosphocholine, and a K' (Hill constant) value of 0.72+/-0.10 mM for CTP. The 6 x -His-tagged enzyme has similar properties with a V(max) value of 2254+/-253 nmol CDP-choline/min/mg, a K(m) value of 0.63+/-0.13 mM for phosphocholine and a K' for CTP equal to 0.81+/-0.20 mM. Each form of the enzyme was activated to a similar extent by synthetic PC vesicles containing 50 mol% oleate. The efficiency of lipid activation was greatest using PC vesicles containing diphosphatidylglycerol (DPG), significantly less efficient activation was seen when phosphatidylserine (PS) and phosphatidylinositol (PI) were incorporated into vesicles, and PC alone or PC vesicles containing phosphatidylethanolamine were the least efficient enzyme activators.
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Affiliation(s)
- Beth Ann Helmink
- Department of Chemistry, Illinois State University, Normal, IL 61790, USA
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22
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Larvor MP, Cerdan R, Gumila C, Maurin L, Seta P, Roustan C, Vial H. Characterization of the lipid-binding domain of the Plasmodium falciparum CTP:phosphocholine cytidylyltransferase through synthetic-peptide studies. Biochem J 2003; 375:653-61. [PMID: 12901716 PMCID: PMC1223718 DOI: 10.1042/bj20031011] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2003] [Accepted: 08/05/2003] [Indexed: 11/17/2022]
Abstract
Phospholipid biosynthesis plays a key role in malarial infection and is regulated by CCT (CTP:phosphocholine cytidylyltransferase). This enzyme belongs to the group of amphitropic proteins which are regulated by reversible membrane interaction. To assess the role of the putative membrane-binding domain of Plasmodium falciparum CCT (PfCCT), we synthesized three peptides, K21, V20 and K54 corresponding to residues 274-294, 308-327 and 274-327 of PfCCT respectively. Conformational behaviour of the peptides, their ability to bind to liposomes and to destabilize lipid bilayers, and their insertion properties were investigated by different biophysical techniques. The intercalation mechanisms of the peptides were refined further by using surface-pressure measurements on various monolayers at the air/water interface. In the present study, we show that the three studied peptides are able to bind to anionic and neutral phospholipids, and that they present an alpha-helical conformation upon lipid binding. Peptides V20 and the full-length K54 intercalate their hydrophobic parts into an anionic bilayer and, to a lesser extent, a neutral one for V20. Peptide K21 interacts only superficially with both types of phospholipid vesicles. Adsorption experiments performed at the air/water interface revealed that peptide K54 is strongly surface-active in the absence of lipid. Peptide V20 presents an atypical behaviour in the presence of phosphatidylserine. Whatever the initial surface pressure of a phosphatidylserine film, peptide V20 and phosphatidylserine entities seem linked together in a special organization involving electrostatic and hydrophobic interactions. We showed that PfCCT presents different lipid-dependence properties from other studied CCTs. Although the lipid-binding domain seems to be located in the C-terminal region of the enzyme, as with the mammalian counterpart, the membrane anchorage, which plays a key role in the enzyme regulation, is driven by two alpha-helices, which behave differently from one another.
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Affiliation(s)
- Marie-Pierre Larvor
- CNRS (UMR 5539) Laboratoire de Dynamique Moléculaire des Interactions Membranaires, Université Montpellier II, cc 107, Place Eugène Bataillon, 34095 Montpellier, cedex 5, France
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23
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Ancelin ML, Calas M, Vidal-Sailhan V, Herbuté S, Ringwald P, Vial HJ. Potent inhibitors of Plasmodium phospholipid metabolism with a broad spectrum of in vitro antimalarial activities. Antimicrob Agents Chemother 2003; 47:2590-7. [PMID: 12878524 PMCID: PMC166094 DOI: 10.1128/aac.47.8.2590-2597.2003] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
We characterized the potent in vitro antimalarial activity and biologic assessment of 13 phospholipid polar head analogs on a comparative basis. There was a positive relationship between the abilities of the drugs to inhibit parasite growth in culture and their abilities to specifically inhibit phosphatidylcholine biosynthesis of Plasmodium falciparum-infected erythrocytes. Maximal activity of G25 was observed for the trophozoite stage of the 48-h erythrocytic cycle (50% inhibitory concentration, 0.75 nM), whereas the schizont and ring stages were 12- and 213-fold less susceptible. The compounds exerted a rapid nonreversible cytotoxic effect, with complete clearance of parasitemia after 5 h of contact with the mature stages. The compounds were highly specific against P. falciparum, with much lower toxicity against three other mammalian cell lines, and the in vitro therapeutic indices ranged from 300 to 2,500,000. Finally, the monoquaternary ammonium E10 and two bis-ammonium salts, G5 and G25, were similarly active against multiresistant strains and fresh isolates of P. falciparum. This impressive selective in vitro toxicity against P. falciparum strongly highlights the clinical potential of these quaternary ammonium salts for malarial chemotherapy.
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Affiliation(s)
- Marie L Ancelin
- UMR 5539, CNRS, Université Montpellier II, 34095 Montpellier Cedex 5, France
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24
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Abstract
Parasitic protozoa are surrounded by membrane structures that have a different lipid and protein composition relative to membranes of the host. The parasite membranes are essential structurally and also for parasite specific processes, like host cell invasion, nutrient acquisition or protection against the host immune system. Furthermore, intracellular parasites can modulate membranes of their host, and trafficking of membrane components occurs between host membranes and those of the intracellular parasite. Phospholipids are major membrane components and, although many parasites scavenge these phospholipids from their host, most parasites also synthesise phospholipids de novo, or modify a large part of the scavenged phospholipids. It was recently shown that some parasites like Plasmodium have unique phospholipid metabolic pathways. This review will focus on new developments in research on phospholipid metabolism of parasitic protozoa in relation to parasite-specific membrane structures and function, as well as on several targets for interference with the parasite phospholipid metabolism with a view to developing new anti-parasitic drugs.
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Affiliation(s)
- Henri J Vial
- Dynamique Moléculaire des Interactions Membranaires, CNRS UMR 5539, cc107, Université Montpellier II, Place Eugène Bataillon, 34095 Montpellier, France.
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25
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Zufferey R, Mamoun CB. Choline transport in Leishmania major promastigotes and its inhibition by choline and phosphocholine analogs. Mol Biochem Parasitol 2002; 125:127-34. [PMID: 12467980 DOI: 10.1016/s0166-6851(02)00220-7] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Phosphatidylcholine is the most abundant phospholipid in the membranes of the human parasite Leishmania. The metabolic pathways leading to its biosynthesis are likely to play a critical role in parasite development and survival and may offer a good target for antileishmanial chemotherapy. Phosphatidylcholine synthesis via the CDP-choline pathway requires transport of the choline precursor from the host. Here, we report the first characterization of choline transport in this parasite, which is carrier-mediated and exhibits Michaelis-Menten kinetics with an apparent K(m) value of 2.5 microM for choline. This process is Na(+)-independent and requires an intact proton gradient to be fully functional. Choline transport into Leishmania is highly specific for choline and is inhibited by the choline carrier inhibitor hemicholinium-3, the channel blocker quinacrine, the antimalarial aminoquinolines quinine and quinidine, the antileishmanial phosphocholine analogs, miltefosine and edelfosine, and by choline analogs, most of which have antimalarial activities. Most importantly, choline analogs kill the promastigote form of the parasite in vitro in the low micromolar range. These results set the stage for the use of choline analogs in antileishmanial chemotherapy and shed new lights on the mechanism of action of the leishmanicidal phosphocholine analogs.
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Affiliation(s)
- Rachel Zufferey
- Department of Pathology, University of Connecticut Health Center, 263 Farmington Ave., Farmington, CT 06030, USA
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26
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Lund ED, Chu FLE. Phospholipid biosynthesis in the oyster protozoan parasite, Perkinsus marinus. Mol Biochem Parasitol 2002; 121:245-53. [PMID: 12034458 DOI: 10.1016/s0166-6851(02)00046-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Perkinsus marinus is a protozoan parasite that causes high mortality in its commercially and ecologically important host, the Eastern oyster Crassostrea virginica. In order to understand the host-parasite relationship in lipid metabolism, the ability of P. marinus to synthesize phospholipids from polar headgroup precursors was investigated. Pulse/chase experiments were conducted using radiolabled serine, choline, ethanolamine and inositol. Timecourse incubations revealed that in vitro cultured P. marinus meronts can utilize the cytidine diphosphate-diacylglycerol (CDP-DAG) pathway to synthesize phosphatidylinositol (PI) from inositol and phosphatidylserine (PS) from serine. Serine label was also incorporated into phosphatidylethanolamine (PE), phosphatidylcholine (PC) and lysophosphatidylcholine (LPC). Incubations of P. marinus cells with increasing concentrations of radiolabeled serine resulted in more radioactivity recovered in neutral lipids than in polar lipids at the highest substrate concentration tested (344 microM). This suggests that excess serine label was being utilized for fatty acid synthesis and stored as triacylglycerols. Additional incubations were conducted with radiolabeled choline and ethanolamine at concentrations equimolar to the highest serine concentration tested. Ethanolamine label was also incorporated into PE, PS, PC and LPC. Choline label was incorporated into PC. These results suggest the presence of three pathways for de novo synthesis of phospholipids in P. marinus: CDP-choline, CDP-ethanolamine and CDP-DAG. At equivalent substrate concentrations (344 microM) the highest incorporation of labeled substrate into total phospholipids was with serine followed by ethanolamine and choline, respectively. P. marinus phospholipid biosynthetic capabilities appear to be similar to those of Plasmodium and Trypanosoma species.
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Affiliation(s)
- Eric D Lund
- Virginia Institute of Marine Science, College of William and Mary, Gloucester Point, VA 23062, USA
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27
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Friesen JA, Liu MF, Kent C. Cloning and characterization of a lipid-activated CTP:phosphocholine cytidylyltransferase from Caenorhabditis elegans: identification of a 21-residue segment critical for lipid activation. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1533:86-98. [PMID: 11566446 DOI: 10.1016/s1388-1981(01)00145-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The genome of the nematode Caenorhabditis elegans contains several genes that appear to encode proteins similar to CTP:phosphocholine cytidylyltransferase (CCT). We have isolated a 1044-nucleotide cDNA clone from a C. elegans cDNA library that encodes the 347-amino acid version of CCT that is most similar to previously-identified CCTs. Native and His-tagged forms were expressed and purified using a baculovirus expression system. The enzyme was maximally activated by 5 microM phosphatidylcholine:oleate (50:50) vesicles with a k(cat) value in the presence of lipid 37-fold greater than the k(cat) value in the absence of lipid. To localize the region of C. elegans CCT critical for lipid activation, a series of C-terminal truncation mutants was analyzed. CCT truncated after amino acids 225 or 245 was quite active in the absence of lipids and not further activated in the presence of lipids, supporting the concept that the lipid-activation segment is inhibitory to catalysis in the absence of lipids. CCT truncated after amino acids 266, 281, or 319 was activated by lipid similar to wild-type enzyme. Kinetic analysis in the absence of lipid revealed the lipid-independent CCT truncated after amino acid 245 to have a k(cat) value 15-fold greater than either full-length CCT or CCT truncated after amino acid 266. We conclude that elements critical for activation of C. elegans CCT by lipids are contained within amino acids 246-266, that this region is inhibitory in the absence of lipids, and that the inhibition is relieved by the association of the enzyme with lipid.
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Affiliation(s)
- J A Friesen
- Department of Biological Chemistry, 4417 Medical Science I, University of Michigan Medical Center, Ann Arbor, MI 48109-0606, USA
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28
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Clement JM, Kent C. CTP:phosphocholine cytidylyltransferase: insights into regulatory mechanisms and novel functions. Biochem Biophys Res Commun 1999; 257:643-50. [PMID: 10208837 DOI: 10.1006/bbrc.1999.0512] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
A key regulatory enzyme in phosphatidylcholine biosynthesis, CTP:cholinephosphate cytidylyltransferase (CCT), catalyzes the formation of CDP-choline. This review discusses the essential features of CCT and addresses intriguing new insights into the catalytic and regulatory properties of this complex enzyme. Characterization of a lipid-binding segment in rat CCT is described and the role of lipids in CCT activation is discussed. An analysis of the phosphorylation domain is presented and possible physiological rationales for reversible phosphorylation of CCT are discussed. The nuclear localization of CCT is examined in the context of multiple CCT isoforms, as is recent evidence establishing a potential link between CCT activity and vesicular transport.
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Affiliation(s)
- J M Clement
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan, 48109, USA
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