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Gratraud P, Huws E, Falkard B, Adjalley S, Fidock DA, Berry L, Jacobs WR, Baird MS, Vial H, Kremer L. Oleic acid biosynthesis in Plasmodium falciparum: characterization of the stearoyl-CoA desaturase and investigation as a potential therapeutic target. PLoS One 2009; 4:e6889. [PMID: 19707292 PMCID: PMC2731242 DOI: 10.1371/journal.pone.0006889] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2009] [Accepted: 08/05/2009] [Indexed: 01/16/2023] Open
Abstract
Background Plasmodium falciparum parasitization of erythrocytes causes a substantial increase in the levels of intracellular fatty acids, notably oleic acid. How parasites acquire this monounsaturated fatty acid has remained enigmatic. Here, we report on the biochemical and enzymatic characterization of stearoyl-CoA desaturase (SCD) in P. falciparum. Methodology/Principal Findings Metabolic labeling experiments allowed us to demonstrate the production of oleic acid from stearic acid both in lysates of parasites incubated with [14C]-stearoyl-CoA and in parasite-infected erythrocytes labeled with [14C]-stearic acid. Optimal SCD activity was detected in schizonts, the stage of maximal membrane synthesis. This activity correlated with a late trophozoite stage-specific induction of PFE0555w transcripts. PFE0555w harbors a typical SCD signature. Similar to mammalian SCDs, this protein was found to be associated with the endoplasmic reticulum, as determined with PFE0555w-GFP tagged transgenic P. falciparum. Importantly, these parasites exhibited increased rates of stearic to oleic acid conversion, providing additional evidence that PFE0555w encodes the plasmodial SCD (PfSCD). These findings prompted us to assess the activity of sterculic acid analogues, known to be specific Δ9-desaturase inhibitors. Methyl sterculate inhibited the synthesis of oleic acid both with parasite lysates and infected erythrocytes, most likely by targeting PfSCD. This compound exhibited significant, rapid and irreversible antimalarial activity against asexual blood stages. This parasiticidal effect was antagonized by oleic acid. Conclusion/Significance Our study provides evidence that parasite-mediated fatty acid modification is important for blood-stage survival and provides a new strategy to develop a novel antimalarial therapeutic based on the inhibition of PfSCD.
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Affiliation(s)
- Paul Gratraud
- Laboratoire de Dynamique des Interactions Membranaires Normales et Pathologiques, Universités de Montpellier II et I, CNRS, UMR 5235, case 107, Montpellier, France
| | - Enlli Huws
- School of Chemistry, Bangor University, Bangor, Wales
| | - Brie Falkard
- Department of Microbiology, College of Physicians and Surgeons, Columbia University, New York, New York, United States of America
| | - Sophie Adjalley
- Department of Microbiology, College of Physicians and Surgeons, Columbia University, New York, New York, United States of America
| | - David A. Fidock
- Department of Microbiology, College of Physicians and Surgeons, Columbia University, New York, New York, United States of America
- Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, New York, United States of America
| | - Laurence Berry
- Laboratoire de Dynamique des Interactions Membranaires Normales et Pathologiques, Universités de Montpellier II et I, CNRS, UMR 5235, case 107, Montpellier, France
| | - William R. Jacobs
- Howard Hughes Medical Institute, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Mark S. Baird
- School of Chemistry, Bangor University, Bangor, Wales
| | - Henri Vial
- Laboratoire de Dynamique des Interactions Membranaires Normales et Pathologiques, Universités de Montpellier II et I, CNRS, UMR 5235, case 107, Montpellier, France
- INSERM, DIMNP, Montpellier, France
| | - Laurent Kremer
- Laboratoire de Dynamique des Interactions Membranaires Normales et Pathologiques, Universités de Montpellier II et I, CNRS, UMR 5235, case 107, Montpellier, France
- INSERM, DIMNP, Montpellier, France
- * E-mail:
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Treeck M, Struck NS, Haase S, Langer C, Herrmann S, Healer J, Cowman AF, Gilberger TW. A Conserved Region in the EBL Proteins Is Implicated in Microneme Targeting of the Malaria Parasite Plasmodium falciparum. J Biol Chem 2006. [DOI: 10.1016/s0021-9258(19)84113-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Treeck M, Struck NS, Haase S, Langer C, Herrmann S, Healer J, Cowman AF, Gilberger TW. A conserved region in the EBL proteins is implicated in microneme targeting of the malaria parasite Plasmodium falciparum. J Biol Chem 2006; 281:31995-2003. [PMID: 16935855 DOI: 10.1074/jbc.m606717200] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The proliferation of the malaria parasite Plasmodium falciparum within the human host is dependent upon invasion of erythrocytes. This process is accomplished by the merozoite, a highly specialized form of the parasite. Secretory organelles including micronemes and rhoptries play a pivotal role in the invasion process by storing and releasing parasite proteins. The mechanism of protein sorting to these compartments is unclear. Using a transgenic approach we show that trafficking of the most abundant micronemal proteins (members of the EBL-family: EBA-175, EBA-140/BAEBL, and EBA-181/JSEBL) is independent of their cytoplasmic and transmembrane domains, respectively. To identify the minimal sequence requirements for microneme trafficking, we generated parasites expressing EBA-GFP chimeric proteins and analyzed their distribution within the infected erythrocyte. This revealed that: (i) a conserved cysteine-rich region in the ectodomain is necessary for protein trafficking to the micronemes and (ii) correct sorting is dependent on accurate timing of expression.
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Affiliation(s)
- Moritz Treeck
- Bernhard Nocht Institute for Tropical Medicine, Malaria II, 20359 Hamburg, Germany
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Albano FR, Berman A, La Greca N, Hibbs AR, Wickham M, Foley M, Tilley L. A homologue of Sar1p localises to a novel trafficking pathway in malaria-infected erythrocytes. Eur J Cell Biol 1999; 78:453-62. [PMID: 10472798 DOI: 10.1016/s0171-9335(99)80072-7] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
We have identified a homologue of the GTP-binding protein, Sar1p, in Plasmodium falciparum. Sar1p is a small GTPase that is thought to play a crucial role in trafficking of proteins between the endoplasmic reticulum and the Golgi. The P.falciparum SAR1 gene is located on chromosome 4 and comprises two exons separated by a 508 bp intron. The deduced amino acid sequence of PfSar1p (GenBank accession number AF104306) shows 71% similarity (58% identity) to Sar1p from Saccharomyces cerevisiae. Expression of PfSar1p in erythrocytic stages of P. falciparum was confirmed by sequencing of a tryptic peptide derived from a polypeptide excised from an SDS-polyacrylamide gel. A recombinant protein corresponding to approximately 70% of the PfSar1p sequence was used to raise antibodies. The affinity-purified antiserum recognised a protein with an apparent molecular weight of 23 K in Western blots of malaria-infected erythrocytes but not in uninfected erythrocytes. PfSar1p was shown to be largely insoluble in non-ionic detergent and a low ionic strength buffer. Confocal immunofluorescence microscopy of malaria-infected erythrocytes was used to show that PfSar1p is located near the periphery of the parasite in discrete compartments, which appear to be distinct from the parasite endoplasmic reticulum. In addition, PfSar1p appears to be exported to structures outside the parasite in the erythrocyte cytoplasm. The export of PfSar1p to the erythrocyte cytosol is inhibited by treatment with brefeldin A. This provides the first evidence that the malaria parasite is capable of elaborating components of the classical vesicle-mediated trafficking machinery outside the boundaries of its own plasma membrane.
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Affiliation(s)
- F R Albano
- Department of Biochemistry, La Trobe University, Melbourne, Australia
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5
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Moura IC, Pudles J. A Plasmodium chabaudi chabaudi high molecular mass glycoprotein translocated to the host cell membrane by a non-classical secretory pathway. Eur J Cell Biol 1999; 78:186-93. [PMID: 10219568 DOI: 10.1016/s0171-9335(99)80097-1] [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: 11/26/2022] Open
Abstract
We have purified and characterized a novel high molecular mass glycoprotein of P. chabaudi chabaudi (Pc550gp) that is transported to the erythrocyte membrane during the intraerythrocytic cycle. Immuno fluorescence assays with polyclonal monospecific antibodies against Pc550gp show that the protein to be localized in the periphery of young trophozoite stages i.e., on the plasma membrane or parasitophorous vacuole membrane. However, in late trophozoites and schizonts the antigen is distributed in both parasite and host cell membranes. These results were confirmed by immunoblotting of isolated parasites and infected host cell membranes at different stages of parasite development. Moreover, alkali extraction of purified infected erythrocyte membranes at mature stages of parasite development does not solubilize Pc550gp, suggesting that it is an integral membrane protein. In addition proteinase K digestion of intact infected host cells induced the disappearance of Pc550gp. Further indicating its transmembrane nature and that it presents extracellular domains susceptible to proteolysis. Brefeldin A or low temperature (15 degrees C) treatment did not affect the translocation of Pc550gp from the parasite compartments to the erythrocyte membrane, indicating that the secretion of Pc550gp does not follow the classical transport pathway described in most eukaryotic cells.
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Affiliation(s)
- I C Moura
- Departamento de Parasitologia, Universidade de São Paulo, Brazil.
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6
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Francis SE, Banerjee R, Goldberg DE. Biosynthesis and maturation of the malaria aspartic hemoglobinases plasmepsins I and II. J Biol Chem 1997; 272:14961-8. [PMID: 9169469 DOI: 10.1074/jbc.272.23.14961] [Citation(s) in RCA: 103] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
During the intraerythrocytic stage of infection, the malaria parasite Plasmodium falciparum digests most of the host cell hemoglobin. Hemoglobin degradation occurs in the acidic digestive vacuole and is essential for the survival of the parasite. Two aspartic proteases, plasmepsins I and II, have been isolated from the vacuole and shown to make the initial cleavages in the hemoglobin molecule. We have studied the biosynthesis of these two enzymes. Plasmepsin I is synthesized and processed to the mature form soon after the parasite invades the red blood cell, while plasmepsin II synthesis is delayed until later in development. Otherwise, biosynthesis of the plasmepsins is identical. The proplasmepsins are type II integral membrane proteins that are transported through the secretory pathway before cleavage to the soluble form. They are not glycosylated in vivo, despite the presence of several potential glycosylation sites. Proplasmepsin maturation appears to require acidic conditions and is reversibly inhibited by the tripeptide aldehydes N-acetyl-L-leucyl-L-leucyl-norleucinal and N-acetyl-L-leucyl-L-leucyl-methional. These compounds are known to inhibit cysteine proteases and the chymotryptic activity of proteasomes but not aspartic proteases. However, proplasmepsin processing is not blocked by other cysteine protease inhibitors, nor by the proteasome inhibitor lactacystin. Processing is also not blocked by aspartic protease inhibitors. This inhibitor profile suggests that unlike most other aspartic proteases, proplasmepsin maturation may not be autocatalytic in vivo, but instead could require the action of an unusual processing enzyme. Compounds that block processing are expected to be potent antimalarials.
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Affiliation(s)
- S E Francis
- Howard Hughes Medical Institute, Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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Abstract
The malaria parasite, Plasmodium falciparum, requires large amounts of nutrients to sustain its rapid growth within the human red blood cell. A recently identified ion channel on the surface of the intraerythrocytic parasite may provide direct access to these nutrients in the red blood cell cytosol. Evidence supporting this role was obtained by incorporating this channel into planar lipid bilayers. In bilayers, this channel has conductance and gating properties identical to the in situ channel, passes soluble macromolecules of up to 1400 Da, and functions as a high capacity, low affinity molecular sieve. These properties, remarkably similar to those of a pore on Toxoplasma gondii (another protozoan parasite causing human disease), suggest a novel class of channels used by these intracellular parasites to acquire nutrients from host cytosol.
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Affiliation(s)
- S A Desai
- Division of Infectious Diseases and International Health, Duke University, Durham, NC 27710, USA
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Affiliation(s)
- S M Beverley
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA
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Stafford WH, Stockley RW, Ludbrook SB, Holder AA. Isolation, expression and characterization of the gene for an ADP-ribosylation factor from the human malaria parasite, Plasmodium falciparum. EUROPEAN JOURNAL OF BIOCHEMISTRY 1996; 242:104-13. [PMID: 8954160 DOI: 10.1111/j.1432-1033.1996.0104r.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
We have isolated an ADP-ribosylation factor (ARF) gene from the human malarial parasite, Plasmodium falciparum. The gene (P. falciparum arf1) has four introns and the exons encode a protein of 181 amino acids with high similarity to the mammalian class I ARF proteins 1-3 (> or = 74% amino acid identity). Southern hybridization suggests there is at least one additional arf in the P. falciparum genome. Northern analysis identified a single P. falciparum arf1 mRNA of 1.8 kb in the asexual blood stage form of the parasite. The P. falciparum arf1 mRNA levels are developmentally regulated, reaching a maximum during nuclear division towards the end of the intraerythrocytic cycle. P. falciparum arf1 cDNA was isolated by reverse-transcriptase polymerase chain reaction and used to express a recombinant protein in Escherichia coli. Recombinant P. falciparum ARF1 protein was purified with stoichiometric amounts of bound GDP, although intrinsic guanose triphosphatase activity of the protein could not be detected. The protein stimulated cholera-toxin-catalyzed ADP-ribosyltransferase activity in a reaction that was dependent upon the addition of both dimyristoylglycerophosphocholine and cholate. The protein bound GTP with first-order kinetics with an apparent rate constant, k', of 0.0145 (+/- 0.0019) min-1. These results suggest that P. falciparum ARF1 is a member of the class 1 ARF family and provide additional evidence for the existence of a classical secretory pathway in P. falciparum.
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Affiliation(s)
- W H Stafford
- Division of Parasitology, National Institute for Medical Research, Mill Hill, London, UK
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Haldar K, Elmendorf HG, Das A, Li WL, Ferguson DJ, Elford BC. In vitro secretory assays with erythrocyte-free malaria parasites. Methods Cell Biol 1995; 45:221-46. [PMID: 7707988 DOI: 10.1016/s0091-679x(08)61854-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- K Haldar
- Department of Microbiolgy and Immunology, Stanford University School of Medicine, California 94305
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Das A, Elmendorf HG, Li WI, Haldar K. Biosynthesis, export and processing of a 45 kDa protein detected in membrane clefts of erythrocytes infected with Plasmodium falciparum. Biochem J 1994; 302 ( Pt 2):487-96. [PMID: 8093001 PMCID: PMC1137254 DOI: 10.1042/bj3020487] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
During its asexual life cycle, the human malaria parasite Plasmodium falciparum exports numerous proteins beyond its surface to its host erythrocyte. We have studied the biosynthesis, processing and export of a 45 kDa parasite protein resident in membrane clefts in the erythrocyte cytoplasm. Our results indicate that this cleft protein is made as a single tightly membrane-bound 45 kDa polypeptide in ring- and trophozoite-infected erythrocytes (0-36 h in the life cycle). Using ring/trophozoite parasites released from erythrocytes, the 45 kDa protein is shown to be efficiently transported to the cell surface. This export is specifically blocked by the drug brefeldin A, and at 15 and 20 degrees C. These results indicate that transport blocks seen in the Golgi of mammalian cells are conserved in P. falciparum. Further, the newly synthesized 45 kDa protein passes through parasite Golgi compartments before its export to clefts in the erythrocyte. In mid-to-late-ring-infected erythrocytes, a fraction of the newly synthesized 45 kDa protein is processed to a second membrane-bound phosphorylated 47 kDa protein. The t1/2 of this processing step is about 4 h, suggesting that it occurs subsequent to protein export from the parasite. Evidence is presented that, in later trophozoite stages (24-36 h), the exported 45 and 47 kDa proteins are partially converted into soluble molecules in the intraerythrocytic space. Taken together, the results indicate that the lower eukaryote P. falciparum modulates a classical secretory pathway to support membrane export beyond its plasma membrane to clefts in the erythrocyte. Subsequent to export, phosphorylation and/or conversion into a soluble form may regulate the interactions of the 45 kDa protein with the clefts during parasite development.
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Affiliation(s)
- A Das
- Department of Microbiology and Immunology, Stanford University School of Medicine, CA 94305-5402
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