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Romano JD, Bano N, Coppens I. New host nuclear functions are not required for the modifications of the parasitophorous vacuole of Toxoplasma. Cell Microbiol 2007; 10:465-76. [PMID: 17970763 DOI: 10.1111/j.1462-5822.2007.01061.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The obligate intracellular parasite Toxoplasma develops within a parasitophorous vacuole (PV) uniquely adapted for its survival in mammalian cells. Post-invasion events extensively modify the PV, resulting in interactions with host cell structures. Recent studies emphasized that Toxoplasma is able to co-opt host gene expression, suggesting that host transcriptional activities are required for parasite infection. By using an experimental enucleation model, we investigated the potential need for Toxoplasma to modify its PV by modulating gene expression in the cell wherein it resides. Unexpectedly, cytoplasts can be actively invaded by Toxoplasma and sustain its replication inside a vacuole until egress and transmission to neighbouring cells. Although randomly distributed in the cytoplast, the PV associates with host centrosomes and the Golgi, is surrounded by host microtubules, and recruits host endoplasmic reticulum and mitochondria. Parasites are proficient in diverting exogenous nutrients from the endocytic network of cytoplasts. In enucleated cells invaded by an avirulent strain of T. gondii, the PV can normally transform into cysts. These observations suggest that new host nuclear functions are not proximately required for the post-invasion events underlying the remodelling of the host cell in which the parasites are confined, and therefore for the generation of infectious parasites in vitro.
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Affiliation(s)
- Julia D Romano
- Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, 615 N. Wolfe Street, Baltimore, MD 21205, USA
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2
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Clastre M, Goubard A, Prel A, Mincheva Z, Viaud-Massuart MC, Bout D, Rideau M, Velge-Roussel F, Laurent F. The methylerythritol phosphate pathway for isoprenoid biosynthesis in coccidia: presence and sensitivity to fosmidomycin. Exp Parasitol 2007; 116:375-84. [PMID: 17399705 DOI: 10.1016/j.exppara.2007.02.002] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2006] [Revised: 02/04/2007] [Accepted: 02/09/2007] [Indexed: 11/16/2022]
Abstract
The apicoplast is a recently discovered, plastid-like organelle present in most apicomplexa. The methylerythritol phosphate (MEP) pathway involved in isoprenoid biosynthesis is one of the metabolic pathways associated with the apicoplast, and is a new promising therapeutic target in Plasmodium falciparum. Here, we check the presence of isoprenoid genes in four coccidian parasites according to genome database searches. Cryptosporidium parvum and C. hominis, which have no plastid genome, lack the MEP pathway. In contrast, gene expression studies suggest that this metabolic pathway is present in several development stages of Eimeria tenella and in tachyzoites of Toxoplasma gondii. We studied the potential of fosmidomycin, an antimalarial drug blocking the MEP pathway, to inhibit E. tenella and T. gondii growth in vitro. The drug was poorly effective even at high concentrations. Thus, both fosmidomycin sensitivity and isoprenoid metabolism differs substantially between apicomplexan species.
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Affiliation(s)
- Marc Clastre
- EA2106 Biomolécules et Biotechnologies Végétales, UFR Sciences Pharmaceutiques, Université de Tours, 37200 Tours, France
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3
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Wanyiri JW, O'Connor R, Allison G, Kim K, Kane A, Qiu J, Plaut AG, Ward HD. Proteolytic processing of the Cryptosporidium glycoprotein gp40/15 by human furin and by a parasite-derived furin-like protease activity. Infect Immun 2006; 75:184-92. [PMID: 17043102 PMCID: PMC1828422 DOI: 10.1128/iai.00944-06] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The apicomplexan parasite Cryptosporidium causes diarrheal disease worldwide. Proteolytic processing of proteins plays a significant role in host cell invasion by apicomplexan parasites. In previous studies, we described gp40/15, a Cryptosporidium sp. glycoprotein that is proteolytically cleaved to yield two surface glycopeptides (gp40 and gp15), which are implicated in mediating infection of host cells. In the present study, we showed that biosynthetically labeled gp40/15 is processed in Cryptosporidium parvum-infected HCT-8 cells. We identified a putative furin cleavage site RSRR downward arrow in the deduced amino acid sequence of gp40/15 from C. parvum and from all Cryptosporidium hominis subtypes except subtype 1e. Both human furin and a protease activity present in a C. parvum lysate cleaved recombinant C. parvum gp40/15 protein into 2 peptides, identified as gp40 and gp15 by size and by immunoreactivity with specific antibodies. C. hominis gp40/15 subtype 1e, in which the RSRR sequence is replaced by ISKR, has an alternative furin cleavage site (KSISKR downward arrow) and was also cleaved by both furin and the C. parvum lysate. Site-directed mutagenesis of the C. parvum RSRR sequence to ASRR resulted in inhibition of cleavage by furin and the C. parvum lysate. Cleavage of recombinant gp40/15 and a synthetic furin substrate by the C. parvum lysate was inhibited by serine protease inhibitors, by the specific furin inhibitor decanoyl-Arg-Val-Lys-Arg-chloromethylketone (Dec-RVKR-cmk), and by calcium chelators, suggesting that the parasite expresses a Ca2+ dependent, furin-like protease activity. The furin inhibitor Dec-RVKR-cmk decreased C. parvum infection of HCT-8 cells, suggesting that a furin-like protease activity may be involved in mediating host-parasite interactions.
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Affiliation(s)
- Jane W Wanyiri
- Division of Geographic Medicine and Infectious Diseases, Tufts-New England Medical Center, 750 Washington Street, Boston, MA 02111, USA
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Crawford MJ, Thomsen-Zieger N, Ray M, Schachtner J, Roos DS, Seeber F. Toxoplasma gondii scavenges host-derived lipoic acid despite its de novo synthesis in the apicoplast. EMBO J 2006; 25:3214-22. [PMID: 16778769 PMCID: PMC1500979 DOI: 10.1038/sj.emboj.7601189] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2006] [Accepted: 05/17/2006] [Indexed: 11/09/2022] Open
Abstract
In contrast to other eukaryotes, which manufacture lipoic acid, an essential cofactor for several vital dehydrogenase complexes, within the mitochondrion, we show that the plastid (apicoplast) of the obligate intracellular protozoan parasite Toxoplasma gondii is the only site of de novo lipoate synthesis. However, antibodies specific for protein-attached lipoate reveal the presence of lipoylated proteins in both, the apicoplast and the mitochondrion of T. gondii. Cultivation of T. gondii-infected cells in lipoate-deficient medium results in substantially reduced lipoylation of mitochondrial (but not apicoplast) proteins. Addition of exogenous lipoate to the medium can rescue this effect, showing that the parasite scavenges this cofactor from the host. Exposure of T. gondii to lipoate analogues in lipoate-deficient medium leads to growth inhibition, suggesting that T. gondii might be auxotrophic for this cofactor. Phylogenetic analyses reveal the secondary loss of the mitochondrial lipoate synthase gene after the acquisition of the plastid. Our studies thus reveal an unexpected metabolic deficiency in T. gondii and raise the question whether the close interaction of host mitochondria with the parasitophorous vacuole is connected to lipoate supply by the host.
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Affiliation(s)
- Michael J Crawford
- Department of Biology, University of Pennsylvania, Philadelphia, PA, USA
| | | | - Manisha Ray
- Department of Biology, University of Pennsylvania, Philadelphia, PA, USA
| | | | - David S Roos
- Department of Biology, University of Pennsylvania, Philadelphia, PA, USA
| | - Frank Seeber
- FB Biologie, Parasitologie, Philipps Universität, Marburg, Germany
- FB Biologie, Parasitologie, Universität Marburg, Karl-von-Frisch-Str., 35043 Marburg, Germany. Tel.: +49 6421 2823498; Fax: +49 6421 2821531; E-mail:
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Réfega S, Girard-Misguich F, Bourdieu C, Péry P, Labbé M. Gene discovery in Eimeria tenella by immunoscreening cDNA expression libraries of sporozoites and schizonts with chicken intestinal antibodies. Vet Parasitol 2003; 113:19-33. [PMID: 12651215 DOI: 10.1016/s0304-4017(03)00033-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Specific antibodies were produced ex vivo from intestinal culture of Eimeria tenella infected chickens. The specificity of these intestinal antibodies was tested against different parasite stages. These antibodies were used to immunoscreen first generation schizont and sporozoite cDNA libraries permitting the identification of new E. tenella antigens. We obtained a total of 119 cDNA clones which were subjected to sequence analysis. The sequences coding for the proteins inducing local immune responses were compared with nucleotide or protein databases and with expressed sequence tags (ESTs) databases. We identified new Eimeria genes coding for heat shock proteins, a ribosomal protein, a pyruvate kinase and a pyridoxine kinase. Specific features of other sequences are discussed.
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Affiliation(s)
- Susana Réfega
- Laboratoire de Virologie et Immunologie Moléculaires INRA F 78352, Jouy-en-Josas, France
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Saliba KJ, Kirk K. Nutrient acquisition by intracellular apicomplexan parasites: staying in for dinner. Int J Parasitol 2001; 31:1321-30. [PMID: 11566300 DOI: 10.1016/s0020-7519(01)00258-2] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The intracellular forms of the apicomplexan parasites Plasmodium, Toxoplasma and Eimeria reside within a parasitophorous vacuole. The nutrients required by these intracellular parasites to support their high rate of growth and replication originate from the host cell which, in turn, takes up such compounds from the extracellular milieu. Solutes moving from the external medium to the interior of the parasite, are confronted by a series of three membranes --the host cell membrane, the parasitophorous vacuole membrane and the parasite plasma membrane. Each constitutes a potential permeability barrier which must be either crossed or bypassed. It is the mechanisms by which this occurs that are the subject of this review.
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Affiliation(s)
- K J Saliba
- School of Biochemistry and Molecular Biology, Faculty of Science, Australian National University, Canberra, A.C.T. 0200, Australia
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Baumeister S, Paprotka K, Bhakdi S, Lingelbach K. Selective permeabilization of infected host cells with pore-forming proteins provides a novel tool to study protein synthesis and viability of the intracellular apicomplexan parasites Plasmodium falciparum and Toxoplasma gondii. Mol Biochem Parasitol 2001; 112:133-7. [PMID: 11166394 DOI: 10.1016/s0166-6851(00)00343-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- S Baumeister
- FB Biologie/Zoologie, Philipps Universität Marburg, 35032 Marburg, Germany
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Swan DG, Phillips K, Tait A, Shiels BR. Evidence for localisation of a Theileria parasite AT hook DNA-binding protein to the nucleus of immortalised bovine host cells. Mol Biochem Parasitol 1999; 101:117-29. [PMID: 10413048 DOI: 10.1016/s0166-6851(99)00064-x] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Immortalisation of bovine leukocytes by the macroschizont stage of the tick transmitted protozoan parasite, Theileria annulata, results in the clonal expansion of infected cells and dissemination throughout the bovine host. The parasite-encoded factors which induce this unique transformation event have not been defined to date. In this study, a gene family (TashAT) has been characterised that encodes polypeptides with homology to known DNA-binding proteins. Expression of TashAT genes occurs at the intracellular macroschizont stage of the parasite life cycle and during differentiation to the merozoite, negative regulation of TashAT genes is detected early relative to other macroschizont genes. Interestingly, the early reduction in TashAT expression coincides with the initial decrease in host cell proliferation. One member of the family, TashAT2, was characterised in detail and the predicted polypeptide sequence was found to harbor three AT hook DNA-binding domains. Antisera generated against two distinct regions of TashAT2 both located the antigen to the host cell nucleus and, combined with protein translation inhibition and immunoprecipitation studies, provide evidence that this polypeptide could be transported from the parasite to this location. Further evidence for this postulation was provided by transfection studies which demonstrated that TashAT2 does encode the structural information required for localisation to the nucleus of a mammalian cell. Thus, TashAT2 is a potential candidate for a parasite-encoded factor that modulates host cell gene expression and may be involved in the control of host cell proliferation.
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Affiliation(s)
- D G Swan
- Department of Veterinary Parasitology, University of Glasgow, UK.
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Abstract
The past 10 years of research aimed at developing subunit vaccines against a number of apicomplexans, including Eimeria, Plasmodium and Toxoplasma, have, if anything, revealed the complex nature of parasite-host interactions. The Knowledge gained from this research has shown why developing a subunit vaccine based on a single recombinant antigen from one developmental stage of the parasite was an overly optimistic approach. Many apicomplexan parasites have acquired unique strategies to evade host immunity. The variable expression of genes encoding erythrocyte membrane protein 1 of Plasmodium falciparum [1] (Berendt et al. Parasitology 1994;108:S19-S28) exemplifies one such strategy. The particular mechanism for evading immune destruction depends on a number of interrelated factors, not least of which is the parasite life-cycle and the availability of susceptible hosts. The goal of any vaccine, be it an attenuated organism or a recombinant antigen, is to break the cycle of infection. The development of a recombinant vaccine against apicomplexan parasites will depend on identifying those antigens and intracellular processes that are vital to the parasite survival and those which exist merely as a way of evading immunity. The information that follows is a review of both molecular biology/biochemistry of eimerian parasites and factors that influence host immune responses to coccidia.
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Affiliation(s)
- M C Jenkins
- Immunology and Disease Resistance Laboratory, USDA, BARC-EAST, Beltsville, MD 20705, USA
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Bohne W, Roos DS. Stage-specific expression of a selectable marker in Toxoplasma gondii permits selective inhibition of either tachyzoites or bradyzoites. Mol Biochem Parasitol 1997; 88:115-26. [PMID: 9274873 DOI: 10.1016/s0166-6851(97)00087-x] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The establishment of culture conditions suitable for inducing differentiation of Toxoplasma gondii tachyzoites into parasites resembling the latent bradyzoite form has opened this important developmental transition to experimental analysis. In order to develop a genetic marker suitable for positive and negative selection during parasite differentiation. the T. gondii HXGPRT gene was placed under control of 5' flanking sequences derived from two bradyzoite-specific genes: BAG1 and LDH2. Random transgene integration at undefined genomic loci resulted in modest regulation (approximately 5-6-fold induction) above relatively high background levels (approximately 4% of wild-type controls). Integration of transgenes at a defined genomic position was achieved by targeting the uracil phosphoribosyl transferase (UPRT) locus using flanking homologous sequences and fluorouracil selection. This strategy was found to provide the added advantage of enhancing bradyzoite induction frequencies under conditions of pyrimidine starvation (low CO2). Constructs integrated in the direction of normal UPRT transcription exhibited moderate levels of inducibility, but transgenes integrated in the opposite direction were dramatically induced under differentiation conditions: 50-100-fold above the very low levels observed in tachyzoites (< 1% control). Positive selection (using mycophenolic acid) was shown to inhibit tachyzoites but not bradyzoites, while negative selection (using 8-azahypoxanthine) inhibited bradyzoites only. Stage-specific regulation of the HXGPRT selectable marker should permit genetic selections for the identification of mutants in the bradyzoite differentiation process.
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Affiliation(s)
- W Bohne
- Department of Biology, University of Pennsylvania, Philadelphia 19104-6018, USA
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Coombs GH, Denton H, Brown SM, Thong KW. Biochemistry of the coccidia. ADVANCES IN PARASITOLOGY 1997; 39:141-226. [PMID: 9241816 DOI: 10.1016/s0065-308x(08)60046-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- G H Coombs
- Institute of Biomedical and Life Sciences, University of Glasgow, UK
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