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Abstract
Ingestion of the obligate intracellular protozoan parasite Toxoplasma gondii causes an acute infection that leads to chronic infection of the host. To facilitate the acute phase of the infection, T. gondii manipulates the host response by secreting rhoptry organelle proteins (ROPs) into host cells during its invasion. A few key ROP proteins with signatures of kinases or pseudokinases (ROPKs) act as virulence factors that enhance parasite survival against host gamma interferon-stimulated innate immunity. However, the roles of these and other ROPK proteins in establishing chronic infection have not been tested. Here, we deleted 26 ROPK gene loci encoding 31 unique ROPK proteins of type II T. gondii and show that numerous ROPK proteins influence the development of chronic infection. Cyst burdens were increased in the Δrop16 knockout strain or moderately reduced in 11 ROPK knockout strains. In contrast, deletion of ROP5, ROP17, ROP18, ROP35, or ROP38/29/19 (ROP38, ROP29, and ROP19) severely reduced cyst burdens. Δrop5 and Δrop18 knockout strains were less resistant to host immunity-related GTPases (IRGs) and exhibited >100-fold-reduced virulence. ROP18 kinase activity and association with the parasitophorous vacuole membrane were necessary for resistance to host IRGs. The Δrop17 strain exhibited a >12-fold defect in virulence; however, virulence was not affected in the Δrop35 or Δrop38/29/19 strain. Resistance to host IRGs was not affected in the Δrop17, Δrop35, or Δrop38/29/19 strain. Collectively, these findings provide the first definitive evidence that the type II T. gondii ROPK proteome functions as virulence factors and facilitates additional mechanisms of host manipulation that are essential for chronic infection and transmission of T. gondii. Reactivation of chronic Toxoplasma gondii infection in individuals with weakened immune systems causes severe toxoplasmosis. Existing treatments for toxoplasmosis are complicated by adverse reactions to chemotherapy. Understanding key parasite molecules required for chronic infection provides new insights into potential mechanisms that can interrupt parasite survival or persistence in the host. This study reveals that key secreted rhoptry molecules are used by the parasite to establish chronic infection of the host. Certain rhoptry proteins were found to be critical virulence factors that resist innate immunity, while other rhoptry proteins were found to influence chronic infection without affecting virulence. This study reveals that rhoptry proteins utilize multiple mechanisms of host manipulation to establish chronic infection of the host. Targeted disruption of parasite rhoptry proteins involved in these biological processes opens new avenues to interfere with chronic infection with the goal to either eliminate chronic infection or to prevent recrudescent infections.
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102
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An improved method for introducing site-directed point mutation into the Toxoplasma gondii genome using CRISPR/Cas9. Parasitol Int 2016; 65:558-562. [PMID: 27167504 DOI: 10.1016/j.parint.2016.05.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2016] [Revised: 04/19/2016] [Accepted: 05/03/2016] [Indexed: 12/31/2022]
Abstract
Toxoplasma gondii is an obligate intracellular parasite in the phylum Apicomplexa. Due to the ease of genetic manipulations in T. gondii it serves as a model organism for intracellular parasites. We utilized CRISPR/Cas9, which can be designed to target a specific genomic locus, to introduce site-directed point mutations directly into the T. gondii genomes. This paper contains step-by-step protocols for: (1) designing the guide RNA sequence; (2) constructing the CRISPR/Cas9 construct for a target gene and preparing a donor sequence; and (3) transfecting the CRISPR/Cas9 modules into the parasite and selecting the parasite with the desired point mutation. In brief: T. gondii strains PRU∆ku80∆hxgprt or RH∆ku80∆hxgprt were nucleofected with pDHFR-SAG1::Cas9-U6::sgGeneA and a mutation donor sequence at a molar ratio of ~1:3. After 10days of 1μM pyrimethamine selection the parasite population was enriched for parasites with the desired point mutation. This technique was also applied to evaluate the importance of genes of interest by introducing either knock out or silence mutations at the same time and then tracking the population kinetics of the resultant T. gondii strains. In addition to previously established high efficient knock out and knock in strategies in Toxoplasma, the site directed point mutation technique presented in this manuscript provides another powerful tool set for T. gondii research.
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Blume M, Nitzsche R, Sternberg U, Gerlic M, Masters SL, Gupta N, McConville MJ. A Toxoplasma gondii Gluconeogenic Enzyme Contributes to Robust Central Carbon Metabolism and Is Essential for Replication and Virulence. Cell Host Microbe 2016; 18:210-20. [PMID: 26269956 DOI: 10.1016/j.chom.2015.07.008] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2014] [Revised: 05/25/2015] [Accepted: 07/14/2015] [Indexed: 10/23/2022]
Abstract
The expression of gluconeogenic enzymes is typically repressed when glucose is available. The protozoan parasite Toxoplasma gondii utilizes host glucose to sustain high rates of intracellular replication. However, despite their preferential utilization of glucose, intracellular parasites constitutively express two isoforms of the gluconeogenic enzyme fructose 1,6-bisphosphatase (TgFBP1 and TgFBP2). The rationale for constitutive expression of FBPases in T. gondii remains unclear. We find that conditional knockdown of TgFBP2 results in complete loss of intracellular growth in vitro under glucose-replete conditions and loss of acute virulence in mice. TgFBP2 deficiency was rescued by expression of catalytically active FBPase and was associated with altered glycolytic and mitochondrial TCA cycle fluxes, as well as dysregulation of glycolipid, amylopectin, and fatty acid biosynthesis. Futile cycling between gluconeogenic and glycolytic enzymes may constitute a regulatory mechanism that allows T. gondii to rapidly adapt to changes in nutrient availability in different host cells.
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Affiliation(s)
- Martin Blume
- Department of Biochemistry and Molecular Biology, Bio21 Institute of Molecular Science and Biotechnology, The University of Melbourne, Parkville, VIC 3010, Australia
| | - Richard Nitzsche
- Department of Molecular Parasitology, Humboldt University, Berlin 10115, Germany
| | - Ulrich Sternberg
- Department of Molecular Parasitology, Humboldt University, Berlin 10115, Germany
| | - Motti Gerlic
- Inflammation Division, The Walter and Eliza Hall Institute of Medical Research, and Department of Medical Biology, The University of Melbourne, Parkville, VIC 3010, Australia; Department of Clinical Microbiology and Immunology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Seth L Masters
- Inflammation Division, The Walter and Eliza Hall Institute of Medical Research, and Department of Medical Biology, The University of Melbourne, Parkville, VIC 3010, Australia
| | - Nishith Gupta
- Department of Molecular Parasitology, Humboldt University, Berlin 10115, Germany
| | - Malcolm J McConville
- Department of Biochemistry and Molecular Biology, Bio21 Institute of Molecular Science and Biotechnology, The University of Melbourne, Parkville, VIC 3010, Australia.
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Analysis of Noncanonical Calcium-Dependent Protein Kinases in Toxoplasma gondii by Targeted Gene Deletion Using CRISPR/Cas9. Infect Immun 2016; 84:1262-1273. [PMID: 26755159 DOI: 10.1128/iai.01173-15] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Accepted: 01/04/2016] [Indexed: 12/31/2022] Open
Abstract
Calcium-dependent protein kinases (CDPKs) are expanded in apicomplexan parasites, especially in Toxoplasma gondii where 14 separate genes encoding these enzymes are found. Although previous studies have shown that several CDPKs play a role in controlling invasion, egress, and cell division in T. gondii, the roles of most of these genes are unexplored. Here we developed a more efficient method for gene disruption using CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 (CRISPR-associated protein 9) that was modified to completely delete large, multiexonic genes from the genome and to allow serial replacement by recycling of the selectable marker using Cre-loxP. Using this system, we generated a total of 24 mutants in type 1 and 2 genetic backgrounds to ascertain the functions of noncanonical CDPKs. Remarkably, although we were able to confirm the essentiality of CDPK1 and CDPK7, the majority of CDPKs had no discernible phenotype for growth in vitro or infection in the mouse model. The exception to this was CDPK6, loss of which leads to reduced plaquing, fitness defect in a competition assay, and reduced tissue cyst formation in chronically infected mice. Our findings highlight the utility of CRISPR/Cas9 for rapid serial gene deletion and also suggest that additional models are needed to reveal the functions of many genes in T. gondii.
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105
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Abstract
Calcium ion signaling regulates central aspects of the biology controlling stage and life cycle transitions of apicomplexan parasites. In the current issue of Infection and Immunity, Long and coworkers (S. Long, Q. Wang, and L. D. Sibley, Infect Immun 84:1262-1273, 2016, http://dx.doi.org/10.1128/IAI.01173-15) describe a powerful genetic system enabling reliable serial genetic dissection of a large gene family encoding novel calcium-dependent protein kinases (CDPKs) that provides new insights into the roles of CDPKs during Toxoplasma gondii infection.
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106
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Recombination and Diversification of the Variant Antigen Encoding Genes in the Malaria Parasite Plasmodium falciparum. Microbiol Spectr 2016; 2. [PMID: 26104446 DOI: 10.1128/microbiolspec.mdna3-0022-2014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The most severe form of human malaria is caused by the protozoan parasite Plasmodium falciparum. These parasites invade and replicate within the circulating red blood cells of infected individuals leading to numerous disease manifestations, including severe anemia, altered circulation, and tissue inflammation. Malaria parasites are also known for their ability to maintain a chronic infection through antigenic variation, the ability to systematically alter the antigens displayed on the surface of infected cells and thereby avoid clearance by the host's antibody response. The genome of P. falciparum includes several large, multicopy gene families that encode highly variable forms of the surface proteins that are the targets of host immunity. Alterations in expression of genes within these families are responsible for antigenic variation. This process requires the continuous generation of new antigenic variants within these gene families, and studies have shown that new variants arise through extensive recombination and gene conversion events between family members. Malaria parasites possess an unusual complement of DNA repair pathways, thus the study of recombination between variant antigen encoding genes provides a unique view into the evolution of mobile DNA in an organism distantly related to the more closely studied model eukaryotes.
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107
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Skariah S, Walwyn O, Engelberg K, Gubbels MJ, Gaylets C, Kim N, Lynch B, Sultan A, Mordue DG. The FIKK kinase of Toxoplasma gondii is not essential for the parasite's lytic cycle. Int J Parasitol 2016; 46:323-32. [PMID: 26859096 DOI: 10.1016/j.ijpara.2016.01.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Revised: 01/05/2016] [Accepted: 01/07/2016] [Indexed: 10/22/2022]
Abstract
FIKK kinases are a novel family of kinases unique to the Apicomplexa. While most apicomplexans encode a single FIKK kinase, Plasmodium falciparum expresses 21 and piroplasms do not encode a FIKK kinase. FIKK kinases share a conserved C-terminal catalytic domain, but the N-terminal region is highly variable and contains no known functional domains. To date, FIKK kinases have been primarily studied in P. falciparum and Plasmodium berghei. Those that have been studied are exported from the parasite and associate with diverse locations in the infected erythrocyte cytosol or membrane. Deletion of individual P. falciparum FIKK kinases indicates that they may play a role in modification of the infected erythrocyte. The current study characterises the single FIKK gene in Toxoplasma gondii to evaluate the importance of the FIKK kinase in an apicomplexan that has a single FIKK kinase. The TgFIKK gene encoded a protein of approximately 280kDa. Endogenous tagging of the FIKK protein with Yellow Fluorescent Protein showed that the FIKK protein exclusively localised to the posterior end of tachyzoites. A Yellow Fluorescent Protein-tagged FIKK and a Ty-tagged FIKK both co-localised with T. gondii membrane occupation and recognition nexus protein to the basal complex and were localised apical to inner membrane complex protein-5 and Centrin2. Deletion of TgFIKK, surprisingly, had no detectable effect on the parasite's lytic cycle in vitro in human fibroblast cells or in acute virulence in vivo. Thus, our results clearly show that while the FIKK kinase is expressed in tachyzoites, it is not essential for the lytic cycle of T. gondii.
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Affiliation(s)
- S Skariah
- Weill Cornell Medical College in Qatar, Doha, Qatar
| | - O Walwyn
- Department of Microbiology and Immunology, New York Medical College, Valhalla, NY 10595, USA
| | - K Engelberg
- Department of Biology, Boston College, Chestnut Hill, MA 02467, USA
| | - M-J Gubbels
- Department of Biology, Boston College, Chestnut Hill, MA 02467, USA
| | - C Gaylets
- Department of Microbiology and Immunology, New York Medical College, Valhalla, NY 10595, USA
| | - N Kim
- Department of Microbiology and Immunology, New York Medical College, Valhalla, NY 10595, USA
| | - B Lynch
- Department of Microbiology and Immunology, New York Medical College, Valhalla, NY 10595, USA
| | - A Sultan
- Weill Cornell Medical College in Qatar, Doha, Qatar
| | - D G Mordue
- Department of Microbiology and Immunology, New York Medical College, Valhalla, NY 10595, USA.
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108
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Paredes-Santos TC, Tomita T, Yan Fen M, de Souza W, Attias M, Vommaro RC, Weiss LM. Development of dual fluorescent stage specific reporter strain of Toxoplasma gondii to follow tachyzoite and bradyzoite development in vitro and in vivo. Microbes Infect 2016; 18:39-47. [PMID: 26432517 PMCID: PMC4715970 DOI: 10.1016/j.micinf.2015.09.016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Revised: 09/11/2015] [Accepted: 09/14/2015] [Indexed: 11/23/2022]
Abstract
Toxoplasma gondii is a protozoan that infects 30% of humans as intermediate hosts. T Sexual reproduction can occur only within the intestinal tract of felines, however, infection in other mammals and birds is associated with asexual replication and interconversion between the tachyzoite and bradyzoite stages. Bradyzoites are slow growing forms found in tissue cysts in latent infection. Recently, our group described the biological behavior of the EGS strain that forms thick walled cysts spontaneously in tissue culture, constituting a useful tool for examining the developmental biology of T. gondii. To further improve the usefulness of this model, we constructed genetically modified EGS parasites that express fluorescent tags under the control of stage specific promoters. The promoter regions for SAG-1 (tachyzoite specific), BAG-1 and LDH-2 (bradyzoite specific) were amplified by PCR and plasmids were constructed with mCherry (redT) and sfGFP (greenB) sequences, respectively. Strains of parasites were selected using FACS to arrive at single fluorescent and dual fluorescent strains of EGS expressing tags in a stage specific manner. In cell cultures, vacuoles labeled by immunofluorescence assay using anti-CST-1 a marker for T. gondii cyst wall contained parasites that were positive for BAG1-GFP and negative for SAG1-mCherry. Tachyzoites and bradyzoites harvested from the mice expressed stage specific mCherry and GFP proteins, respectively. These new dual fluorescent transgenic EGS strains are a promising tool to elucidate the mechanisms of T. gondii differentiation both in vitro and in vivo.
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Affiliation(s)
- T C Paredes-Santos
- Universidade Federal do Rio de Janeiro, Instituto de Biofísica Carlos Chagas Filho, Rio de Janeiro, Brazil; Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagens, Rio de Janeiro, Brazil
| | - T Tomita
- Departments of Pathology and Medicine, Albert Einstein College of Medicine - AECOM, USA
| | - M Yan Fen
- Departments of Pathology and Medicine, Albert Einstein College of Medicine - AECOM, USA
| | - W de Souza
- Universidade Federal do Rio de Janeiro, Instituto de Biofísica Carlos Chagas Filho, Rio de Janeiro, Brazil; Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagens, Rio de Janeiro, Brazil
| | - M Attias
- Universidade Federal do Rio de Janeiro, Instituto de Biofísica Carlos Chagas Filho, Rio de Janeiro, Brazil; Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagens, Rio de Janeiro, Brazil
| | - R C Vommaro
- Universidade Federal do Rio de Janeiro, Instituto de Biofísica Carlos Chagas Filho, Rio de Janeiro, Brazil; Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagens, Rio de Janeiro, Brazil.
| | - L M Weiss
- Departments of Pathology and Medicine, Albert Einstein College of Medicine - AECOM, USA.
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109
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Regulation of Starch Stores by a Ca2+-Dependent Protein Kinase Is Essential for Viable Cyst Development in Toxoplasma gondii. Cell Host Microbe 2015; 18:670-81. [DOI: 10.1016/j.chom.2015.11.004] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Revised: 08/10/2015] [Accepted: 11/13/2015] [Indexed: 01/05/2023]
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110
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Lopez J, Bittame A, Massera C, Vasseur V, Effantin G, Valat A, Buaillon C, Allart S, Fox BA, Rommereim LM, Bzik DJ, Schoehn G, Weissenhorn W, Dubremetz JF, Gagnon J, Mercier C, Cesbron-Delauw MF, Blanchard N. Intravacuolar Membranes Regulate CD8 T Cell Recognition of Membrane-Bound Toxoplasma gondii Protective Antigen. Cell Rep 2015; 13:2273-86. [PMID: 26628378 DOI: 10.1016/j.celrep.2015.11.001] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Revised: 08/11/2015] [Accepted: 10/30/2015] [Indexed: 11/20/2022] Open
Abstract
Apicomplexa parasites such as Toxoplasma gondii target effectors to and across the boundary of their parasitophorous vacuole (PV), resulting in host cell subversion and potential presentation by MHC class I molecules for CD8 T cell recognition. The host-parasite interface comprises the PV limiting membrane and a highly curved, membranous intravacuolar network (IVN) of uncertain function. Here, using a cell-free minimal system, we dissect how membrane tubules are shaped by the parasite effectors GRA2 and GRA6. We show that membrane association regulates access of the GRA6 protective antigen to the MHC I pathway in infected cells. Although insertion of GRA6 in the PV membrane is key for immunogenicity, association of GRA6 with the IVN limits presentation and curtails GRA6-specific CD8 responses in mice. Thus, membrane deformations of the PV regulate access of antigens to the MHC class I pathway, and the IVN may play a role in immune modulation.
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Affiliation(s)
- Jodie Lopez
- INSERM, U1043, Toulouse 31300, France; CNRS, UMR 5282, Toulouse 31300, France; Centre de Physiopathologie de Toulouse Purpan (CPTP), Université de Toulouse, UPS, Toulouse 31300, France
| | - Amina Bittame
- CNRS, UMR 5163, Grenoble 38000, France; Laboratoire Adaptation et Pathogénie des Microorganismes (LAPM), Université Grenoble Alpes, Grenoble 38000, France
| | - Céline Massera
- CNRS, UMR 5163, Grenoble 38000, France; Laboratoire Adaptation et Pathogénie des Microorganismes (LAPM), Université Grenoble Alpes, Grenoble 38000, France
| | - Virginie Vasseur
- INSERM, U1043, Toulouse 31300, France; CNRS, UMR 5282, Toulouse 31300, France; Centre de Physiopathologie de Toulouse Purpan (CPTP), Université de Toulouse, UPS, Toulouse 31300, France
| | - Grégory Effantin
- Institut de Biologie Structurale (IBS), Université Grenoble Alpes, Grenoble 38044, France; CNRS, IBS, Grenoble 38044, France; CEA, IBS, Grenoble 38044, France; CNRS, Unit for Virus Host-Cell Interactions (UVHCI), Grenoble 38042, France
| | - Anne Valat
- CNRS, UMR 5163, Grenoble 38000, France; Laboratoire Adaptation et Pathogénie des Microorganismes (LAPM), Université Grenoble Alpes, Grenoble 38000, France
| | - Célia Buaillon
- INSERM, U1043, Toulouse 31300, France; CNRS, UMR 5282, Toulouse 31300, France; Centre de Physiopathologie de Toulouse Purpan (CPTP), Université de Toulouse, UPS, Toulouse 31300, France
| | - Sophie Allart
- INSERM, U1043, Toulouse 31300, France; CNRS, UMR 5282, Toulouse 31300, France; Centre de Physiopathologie de Toulouse Purpan (CPTP), Université de Toulouse, UPS, Toulouse 31300, France
| | - Barbara A Fox
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Lebanon, NH 03756, USA
| | - Leah M Rommereim
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Lebanon, NH 03756, USA
| | - David J Bzik
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Lebanon, NH 03756, USA
| | - Guy Schoehn
- Institut de Biologie Structurale (IBS), Université Grenoble Alpes, Grenoble 38044, France; CNRS, IBS, Grenoble 38044, France; CEA, IBS, Grenoble 38044, France; CNRS, Unit for Virus Host-Cell Interactions (UVHCI), Grenoble 38042, France
| | - Winfried Weissenhorn
- Institut de Biologie Structurale (IBS), Université Grenoble Alpes, Grenoble 38044, France; CNRS, IBS, Grenoble 38044, France; CEA, IBS, Grenoble 38044, France; CNRS, Unit for Virus Host-Cell Interactions (UVHCI), Grenoble 38042, France
| | | | - Jean Gagnon
- CNRS, UMR 5163, Grenoble 38000, France; Laboratoire Adaptation et Pathogénie des Microorganismes (LAPM), Université Grenoble Alpes, Grenoble 38000, France
| | - Corinne Mercier
- CNRS, UMR 5163, Grenoble 38000, France; Laboratoire Adaptation et Pathogénie des Microorganismes (LAPM), Université Grenoble Alpes, Grenoble 38000, France
| | - Marie-France Cesbron-Delauw
- CNRS, UMR 5163, Grenoble 38000, France; Laboratoire Adaptation et Pathogénie des Microorganismes (LAPM), Université Grenoble Alpes, Grenoble 38000, France
| | - Nicolas Blanchard
- INSERM, U1043, Toulouse 31300, France; CNRS, UMR 5282, Toulouse 31300, France; Centre de Physiopathologie de Toulouse Purpan (CPTP), Université de Toulouse, UPS, Toulouse 31300, France.
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111
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Hammoudi PM, Jacot D, Mueller C, Di Cristina M, Dogga SK, Marq JB, Romano J, Tosetti N, Dubrot J, Emre Y, Lunghi M, Coppens I, Yamamoto M, Sojka D, Pino P, Soldati-Favre D. Fundamental Roles of the Golgi-Associated Toxoplasma Aspartyl Protease, ASP5, at the Host-Parasite Interface. PLoS Pathog 2015; 11:e1005211. [PMID: 26473595 PMCID: PMC4608785 DOI: 10.1371/journal.ppat.1005211] [Citation(s) in RCA: 86] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2015] [Accepted: 09/16/2015] [Indexed: 11/18/2022] Open
Abstract
Toxoplasma gondii possesses sets of dense granule proteins (GRAs) that either assemble at, or cross the parasitophorous vacuole membrane (PVM) and exhibit motifs resembling the HT/PEXEL previously identified in a repertoire of exported Plasmodium proteins. Within Plasmodium spp., cleavage of the HT/PEXEL motif by the endoplasmic reticulum-resident protease Plasmepsin V precedes trafficking to and export across the PVM of proteins involved in pathogenicity and host cell remodelling. Here, we have functionally characterized the T. gondii aspartyl protease 5 (ASP5), a Golgi-resident protease that is phylogenetically related to Plasmepsin V. We show that deletion of ASP5 causes a significant loss in parasite fitness in vitro and an altered virulence in vivo. Furthermore, we reveal that ASP5 is necessary for the cleavage of GRA16, GRA19 and GRA20 at the PEXEL-like motif. In the absence of ASP5, the intravacuolar nanotubular network disappears and several GRAs fail to localize to the PVM, while GRA16 and GRA24, both known to be targeted to the host cell nucleus, are retained within the vacuolar space. Additionally, hypermigration of dendritic cells and bradyzoite cyst wall formation are impaired, critically impacting on parasite dissemination and persistence. Overall, the absence of ASP5 dramatically compromises the parasite’s ability to modulate host signalling pathways and immune responses. The opportunistic pathogen Toxoplasma gondii infects a large range of nucleated cells where it replicates intracellularly within a parasitophorous vacuole (PV) surrounded by a membrane (PVM). Parasites constitutively secrete dense-granule proteins (GRAs) both into and beyond the PV which participate in remodelling of the PVM, recruitment of host organelles, neutralization of the host cellular defences, and subversion of host cell functioning. In addition, the GRAs critically contribute to cyst wall formation, a process that critically ensures parasite persistence and transmission. To act as effector molecules, some of the GRAs must be translocated across the PVM. Within the related apicomplexan parasite P. falciparum, a repertoire of proteins exported beyond the PVM contain a motif cleaved by a specific protease, Plasmepsin V. Examination of the repertoire of GRAs in T. gondii revealed that some proteins exhibit such export-like motifs suggestive of protease involvement. In this study, we have functionally characterized the related aspartyl protease 5 (TgASP5) in both virulent and persistent T. gondii strains, and have investigated the phenotypic consequences of its deletion in the context of overall parasite biology, its intracellular niche, the infected host cells and the murine model. Our findings revealed fundamental roles of TgASP5 at the host-parasite interface.
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Affiliation(s)
- Pierre-Mehdi Hammoudi
- Department of Microbiology and Molecular Medicine, Centre Médical Universitaire, University of Geneva, Geneva, Switzerland
| | - Damien Jacot
- Department of Microbiology and Molecular Medicine, Centre Médical Universitaire, University of Geneva, Geneva, Switzerland
| | - Christina Mueller
- Department of Microbiology and Molecular Medicine, Centre Médical Universitaire, University of Geneva, Geneva, Switzerland
- Department of Immunoparasitology, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan
| | - Manlio Di Cristina
- Department of Chemistry, Biology and Biotechnology, University of Perugia, Perugia, Italy
| | - Sunil Kumar Dogga
- Department of Microbiology and Molecular Medicine, Centre Médical Universitaire, University of Geneva, Geneva, Switzerland
| | - Jean-Baptiste Marq
- Department of Microbiology and Molecular Medicine, Centre Médical Universitaire, University of Geneva, Geneva, Switzerland
| | - Julia Romano
- Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, United States of America
| | - Nicolò Tosetti
- Department of Microbiology and Molecular Medicine, Centre Médical Universitaire, University of Geneva, Geneva, Switzerland
| | - Juan Dubrot
- Department of Pathology and Immunology, Centre Médical Universitaire, University of Geneva, Geneva, Switzerland
| | - Yalin Emre
- Department of Pathology and Immunology, Centre Médical Universitaire, University of Geneva, Geneva, Switzerland
| | - Matteo Lunghi
- Department of Chemistry, Biology and Biotechnology, University of Perugia, Perugia, Italy
| | - Isabelle Coppens
- Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, United States of America
| | - Masahiro Yamamoto
- Department of Immunoparasitology, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan
| | - Daniel Sojka
- Department of Microbiology and Molecular Medicine, Centre Médical Universitaire, University of Geneva, Geneva, Switzerland
- Institute of Parasitology, Biology Centre of the Academy of Sciences of the Czech Republic, České Budějovice, Czech Republic
| | - Paco Pino
- Department of Microbiology and Molecular Medicine, Centre Médical Universitaire, University of Geneva, Geneva, Switzerland
| | - Dominique Soldati-Favre
- Department of Microbiology and Molecular Medicine, Centre Médical Universitaire, University of Geneva, Geneva, Switzerland
- * E-mail:
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112
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Martin HL, Alsaady I, Howell G, Prandovszky E, Peers C, Robinson P, McConkey GA. Effect of parasitic infection on dopamine biosynthesis in dopaminergic cells. Neuroscience 2015; 306:50-62. [PMID: 26297895 PMCID: PMC4577654 DOI: 10.1016/j.neuroscience.2015.08.005] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2015] [Revised: 08/02/2015] [Accepted: 08/03/2015] [Indexed: 12/31/2022]
Abstract
Infection by the neurotropic agent Toxoplasma gondii alters rodent behavior and can result in neuropsychiatric symptoms in humans. Little is understood regarding the effects of infection on host neural processes but alterations to dopaminergic neurotransmission are implicated. We have previously reported elevated levels of dopamine (DA) in infected dopaminergic cells however the involvement of the host enzymes and fate of the produced DA were not defined. In order to clarify the effects of infection on host DA biosynthetic enzymes and DA packaging we examined enzyme levels and activity and DA accumulation and release in T. gondii-infected neurosecretory cells. Although the levels of the host tyrosine hydroxylase (TH) and DOPA decarboxylase and AADC (DDC) did not change significantly in infected cultures, DDC was found within the parasitophorous vacuole (PV), the vacuolar compartment where the parasites reside, as well as in the host cytosol in infected dopaminergic cells. Strikingly, DDC was found within the intracellular parasite cysts in infected brain tissue. This finding could provide some explanation for observations of DA within tissue cysts in infected brain as a parasite-encoded enzyme with TH activity was also localized within tissue cysts. In contrast, cellular DA packaging appeared unchanged in single-cell microamperometry experiments and only a fraction of the increased DA was accessible to high potassium-induced release. This study provides some understanding of how this parasite produces elevated DA within dopaminergic cells without the toxic ramifications of free cytosolic DA. The mechanism for synthesis and packaging of DA by T. gondii-infected dopaminergic cells may have important implications for the effects of chronic T. gondii infection on humans and animals.
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Affiliation(s)
- H L Martin
- Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - I Alsaady
- Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - G Howell
- Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - E Prandovszky
- Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - C Peers
- Division of Cardiovascular and Diabetes Research, LIGHT, Faculty of Medicine and Health, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - P Robinson
- The Leeds Institute of Biomedical and Clinical Sciences, University of Leeds, Leeds LS9 7FT, United Kingdom
| | - G A McConkey
- Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom.
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113
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Lunghi M, Galizi R, Magini A, Carruthers VB, Di Cristina M. Expression of the glycolytic enzymes enolase and lactate dehydrogenase during the early phase ofToxoplasmadifferentiation is regulated by an intron retention mechanism. Mol Microbiol 2015; 96:1159-75. [DOI: 10.1111/mmi.12999] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/11/2015] [Indexed: 01/12/2023]
Affiliation(s)
- Matteo Lunghi
- Department of Chemistry, Biology and Biotechnology; University of Perugia; Perugia Italy
| | - Roberto Galizi
- Department of Experimental Medicine; University of Perugia; Perugia Italy
| | - Alessandro Magini
- Department of Chemistry, Biology and Biotechnology; University of Perugia; Perugia Italy
| | - Vern B. Carruthers
- Department of Microbiology and Immunology; University of Michigan Medical School; Ann Arbor MI USA
| | - Manlio Di Cristina
- Department of Chemistry, Biology and Biotechnology; University of Perugia; Perugia Italy
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114
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AMA1-deficient Toxoplasma gondii parasites transiently colonize mice and trigger an innate immune response that leads to long-lasting protective immunity. Infect Immun 2015; 83:2475-86. [PMID: 25847964 DOI: 10.1128/iai.02606-14] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Accepted: 03/25/2015] [Indexed: 11/20/2022] Open
Abstract
The apical membrane antigen 1 (AMA1) protein was believed to be essential for the perpetuation of two Apicomplexa parasite genera, Plasmodium and Toxoplasma, until we genetically engineered viable parasites lacking AMA1. The reduction in invasiveness of the Toxoplasma gondii RH-AMA1 knockout (RH-AMA1(KO)) tachyzoite population, in vitro, raised key questions about the outcome associated with these tachyzoites once inoculated in the peritoneal cavity of mice. In this study, we used AMNIS technology to simultaneously quantify and image the parasitic process driven by AMA1(KO) tachyzoites. We report their ability to colonize and multiply in mesothelial cells and in both resident and recruited leukocytes. While the RH-AMA1(KO) population amplification is rapidly lethal in immunocompromised mice, it is controlled in immunocompetent hosts, where immune cells in combination sense parasites and secrete proinflammatory cytokines. This innate response further leads to a long-lasting status immunoprotective against a secondary challenge by high inocula of the homologous type I or a distinct type II T. gondii genotypes. While AMA1 is definitively not an essential protein for tachyzoite entry and multiplication in host cells, it clearly assists the expansion of parasite population in vivo.
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115
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Nonreplicating, cyst-defective type II Toxoplasma gondii vaccine strains stimulate protective immunity against acute and chronic infection. Infect Immun 2015; 83:2148-55. [PMID: 25776745 DOI: 10.1128/iai.02756-14] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Accepted: 03/06/2015] [Indexed: 01/08/2023] Open
Abstract
Live attenuated vaccine strains, such as type I nonreplicating uracil auxotroph mutants, are highly effective in eliciting lifelong immunity to virulent acute infection by Toxoplasma gondii. However, it is currently unknown whether vaccine-elicited immunity can provide protection against acute infection and also prevent chronic infection. To address this problem, we developed nonreverting, nonreplicating, live attenuated uracil auxotroph vaccine strains in the type II Δku80 genetic background by targeting the deletion of the orotidine 5'-monophosphate decarboxylase (OMPDC) and uridine phosphorylase (UP) genes. Deletion of OMPDC induced a severe uracil auxotrophy with loss of replication, loss of virulence in mice, and loss of the ability to develop cysts and chronic infection. Vaccination of mice using type II Δku80 Δompdc mutants stimulated a fully protective CD8(+) T cell-dependent immunity that prevented acute infection by type I and type II strains of T. gondii, and this vaccination also severely reduced or prevented cyst formation after type II challenge infection. Nonreverting, nonreplicating, and non-cyst-forming Δompdc mutants provide new tools to examine protective immune responses elicited by vaccination with a live attenuated type II vaccine.
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116
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Mercier C, Cesbron-Delauw MF. Toxoplasma secretory granules: one population or more? Trends Parasitol 2015; 31:60-71. [PMID: 25599584 DOI: 10.1016/j.pt.2014.12.002] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Revised: 12/10/2014] [Accepted: 12/10/2014] [Indexed: 01/20/2023]
Abstract
In Toxoplasma gondii, dense granules are known as the storage secretory organelles of the so-called GRA proteins (for dense granule proteins), which are destined to the parasitophorous vacuole (PV) and the PV-derived cyst wall. Recently, newly annotated GRA proteins targeted to the host cell nucleus have enlarged this view. Here we provide an update on the latest developments on the Toxoplasma secreted proteins, which to date have been mainly studied at both the tachyzoite and bradyzoite stages, and we point out that recent discoveries could open the issue of a possible, yet uncharacterized, distinct secretory pathway in Toxoplasma.
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Affiliation(s)
- Corinne Mercier
- Laboratoire Adaptation et Pathogénie des Microorganismes (LAPM), CNRS UMR 5163 - Université Joseph Fourier, Grenoble, France.
| | - Marie-France Cesbron-Delauw
- Laboratoire Adaptation et Pathogénie des Microorganismes (LAPM), CNRS UMR 5163 - Université Joseph Fourier, Grenoble, France.
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117
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Reassessment of the role of aromatic amino acid hydroxylases and the effect of infection by Toxoplasma gondii on host dopamine. Infect Immun 2014; 83:1039-47. [PMID: 25547791 DOI: 10.1128/iai.02465-14] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Toxoplasma gondii infection has been described previously to cause infected mice to lose their fear of cat urine. This behavioral manipulation has been proposed to involve alterations of host dopamine pathways due to parasite-encoded aromatic amino acid hydroxylases. Here, we report successful knockout and complementation of the aromatic amino acid hydroxylase AAH2 gene, with no observable phenotype in parasite growth or differentiation in vitro and in vivo. Additionally, expression levels of the two aromatic amino acid hydroxylases were negligible both in tachyzoites and in bradyzoites. Finally, we were unable to confirm previously described effects of parasite infection on host dopamine either in vitro or in vivo, even when AAH2 was overexpressed using the BAG1 promoter. Together, these data indicate that AAH enzymes in the parasite do not cause global or regional alterations of dopamine in the host brain, although they may affect this pathway locally. Additionally, our findings suggest alternative roles for the AHH enzymes in T. gondii, since AAH1 is essential for growth in nondopaminergic cells.
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118
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Mouveaux T, Oria G, Werkmeister E, Slomianny C, Fox BA, Bzik DJ, Tomavo S. Nuclear glycolytic enzyme enolase of Toxoplasma gondii functions as a transcriptional regulator. PLoS One 2014; 9:e105820. [PMID: 25153525 PMCID: PMC4143315 DOI: 10.1371/journal.pone.0105820] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2014] [Accepted: 07/28/2014] [Indexed: 01/07/2023] Open
Abstract
Apicomplexan parasites including Toxoplasma gondii have complex life cycles within different hosts and their infectivity relies on their capacity to regulate gene expression. However, little is known about the nuclear factors that regulate gene expression in these pathogens. Here, we report that T. gondii enolase TgENO2 is targeted to the nucleus of actively replicating parasites, where it specifically binds to nuclear chromatin in vivo. Using a ChIP-Seq technique, we provide evidence for TgENO2 enrichment at the 5′ untranslated gene regions containing the putative promoters of 241 nuclear genes. Ectopic expression of HA-tagged TgENO1 or TgENO2 led to changes in transcript levels of numerous gene targets. Targeted disruption of TgENO1 gene results in a decrease in brain cyst burden of chronically infected mice and in changes in transcript levels of several nuclear genes. Complementation of this knockout mutant with ectopic TgENO1-HA fully restored normal transcript levels. Our findings reveal that enolase functions extend beyond glycolytic activity and include a direct role in coordinating gene regulation in T. gondii.
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Affiliation(s)
- Thomas Mouveaux
- Center for Infection and Immunity of Lille, CNRS UMR 8204, INSERM U 1019, Institut Pasteur de Lille, Université Lille Nord de France, Lille, France
| | - Gabrielle Oria
- Center for Infection and Immunity of Lille, CNRS UMR 8204, INSERM U 1019, Institut Pasteur de Lille, Université Lille Nord de France, Lille, France
| | - Elisabeth Werkmeister
- Center for Infection and Immunity of Lille, CNRS UMR 8204, INSERM U 1019, Institut Pasteur de Lille, Université Lille Nord de France, Lille, France
| | - Christian Slomianny
- Laboratory of Cell Physiology, INSERM U 1003, Université Lille Nord de France, Villeneuve d'Ascq, France
| | - Barbara A. Fox
- Department of Microbiology and Immunology, The Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, United States of America
| | - David J. Bzik
- Department of Microbiology and Immunology, The Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, United States of America
| | - Stanislas Tomavo
- Center for Infection and Immunity of Lille, CNRS UMR 8204, INSERM U 1019, Institut Pasteur de Lille, Université Lille Nord de France, Lille, France
- * E-mail:
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119
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Abstract
The protozoan parasite Toxoplasma gondii resides within a nonfusogenic vacuole during intracellular replication. Although the limiting membrane of this vacuole provides a protective barrier to acidification and degradation by lysosomal hydrolases, it also physically segregates the parasite from the host cytosol. Accordingly, it has been suggested that T. gondii acquires material from the host via membrane channels or transporters. The ability of the parasite to internalize macromolecules via endocytosis during intracellular replication has not been tested. Here, we show that Toxoplasma ingests host cytosolic proteins and digests them using cathepsin L and other proteases within its endolysosomal system. Ingestion was reduced in mutant parasites lacking an intravacuolar network of tubular membranes, implicating this apparatus as a possible conduit for trafficking to the parasite. Genetic ablation of proteins involved in the pathway is associated with diminished parasite replication and virulence attenuation. We show that both virulent type I and avirulent type II strain parasites ingest and digest host-derived protein, indicating that the pathway is not restricted to highly virulent strains. The findings provide the first definitive evidence that T. gondii internalizes proteins from the host during intracellular residence and suggest that protein digestion within the endolysosomal system of the parasite contributes to toxoplasmosis. Toxoplasma gondii causes significant disease in individuals with weak immune systems. Treatment options for this infection have drawbacks, creating a need to understand how this parasite survives within the cells it infects as a prelude to interrupting its survival strategies. This study reveals that T. gondii internalizes proteins from the cytoplasm of the cells it infects and degrades such proteins within a digestive compartment within the parasite. Disruption of proteins involved in the pathway reduced parasite replication and lessened disease severity. The identification of a novel parasite ingestion pathway opens opportunities to interfere with this process and improve the outcome of infection.
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120
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Butler CL, Lucas O, Wuchty S, Xue B, Uversky VN, White M. Identifying novel cell cycle proteins in Apicomplexa parasites through co-expression decision analysis. PLoS One 2014; 9:e97625. [PMID: 24841368 PMCID: PMC4026381 DOI: 10.1371/journal.pone.0097625] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Accepted: 04/22/2014] [Indexed: 11/26/2022] Open
Abstract
Hypothetical proteins comprise roughly half of the predicted gene complement of Toxoplasma gondii and Plasmodium falciparum and represent the largest class of uniquely functioning proteins in these parasites. Following the idea that functional relationships can be informed by the timing of gene expression, we devised a strategy to identify the core set of apicomplexan cell division cycling genes with important roles in parasite division, which includes many uncharacterized proteins. We assembled an expanded list of orthologs from the T. gondii and P. falciparum genome sequences (2781 putative orthologs), compared their mRNA profiles during synchronous replication, and sorted the resulting set of dual cell cycle regulated orthologs (744 total) into protein pairs conserved across many eukaryotic families versus those unique to the Apicomplexa. The analysis identified more than 100 ortholog gene pairs with unknown function in T. gondii and P. falciparum that displayed co-conserved mRNA abundance, dynamics of cyclical expression and similar peak timing that spanned the complete division cycle in each parasite. The unknown cyclical mRNAs encoded a diverse set of proteins with a wide range of mass and showed a remarkable conservation in the internal organization of ordered versus disordered structural domains. A representative sample of cyclical unknown genes (16 total) was epitope tagged in T. gondii tachyzoites yielding the discovery of new protein constituents of the parasite inner membrane complex, key mitotic structures and invasion organelles. These results demonstrate the utility of using gene expression timing and dynamic profile to identify proteins with unique roles in Apicomplexa biology.
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Affiliation(s)
- Carrie L. Butler
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America
| | - Olivier Lucas
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America
| | - Stefan Wuchty
- National Center for Biotechnology Information, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Bin Xue
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America
| | - Vladimir N. Uversky
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America
| | - Michael White
- Department of Global Health, College of Public Health, University of South Florida, Tampa, Florida, United States of America
- Florida Center for Drug Discovery and Innovation, University of South Florida, Tampa, Florida, United States of America
- * E-mail:
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121
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Abstract
UNLABELLED Toxoplasma gondii has become a model for studying the phylum Apicomplexa, in part due to the availability of excellent genetic tools. Although reverse genetic tools are available in a few widely utilized laboratory strains, they rely on special genetic backgrounds that are not easily implemented in natural isolates. Recent progress in modifying CRISPR (clustered regularly interspaced short palindromic repeats), a system of DNA recognition used as a defense mechanism in bacteria and archaea, has led to extremely efficient gene disruption in a variety of organisms. Here we utilized a CRISPR/CAS9-based system with single guide RNAs to disrupt genes in T. gondii. CRISPR/CAS9 provided an extremely efficient system for targeted gene disruption and for site-specific insertion of selectable markers through homologous recombination. CRISPR/CAS9 also facilitated site-specific insertion in the absence of homology, thus increasing the utility of this approach over existing technology. We then tested whether CRISPR/CAS9 would enable efficient transformation of a natural isolate. Using CRISPR/CAS9, we were able to rapidly generate both rop18 knockouts and complemented lines in the type I GT1 strain, which has been used for forward genetic crosses but which remains refractory to reverse genetic approaches. Assessment of their phenotypes in vivo revealed that ROP18 contributed a greater proportion to acute pathogenesis in GT1 than in the laboratory type I RH strain. Thus, CRISPR/CAS9 extends reverse genetic techniques to diverse isolates of T. gondii, allowing exploration of a much wider spectrum of biological diversity. IMPORTANCE Genetic approaches have proven very powerful for studying the biology of organisms, including microbes. However, ease of genetic manipulation varies widely among isolates, with common lab isolates often being the most amenable to such approaches. Unfortunately, such common lab isolates have also been passaged frequently in vitro and have thus lost many of the attributes of wild isolates, often affecting important traits, like virulence. On the other hand, wild isolates are often not amenable to standard genetic approaches, thus limiting inquiry about the genetic basis of biological diversity. Here we imported a new genetic system based on CRISPR/CAS9, which allows high efficiency of targeted gene disruption in natural isolates of T. gondii. This advance promises to bring the power of genetics to bear on the broad diversity of T. gondii strains that have been described recently.
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122
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Host cell subversion by Toxoplasma GRA16, an exported dense granule protein that targets the host cell nucleus and alters gene expression. Cell Host Microbe 2014; 13:489-500. [PMID: 23601110 DOI: 10.1016/j.chom.2013.03.002] [Citation(s) in RCA: 168] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Revised: 01/17/2013] [Accepted: 02/14/2013] [Indexed: 01/17/2023]
Abstract
After invading host cells, Toxoplasma gondii multiplies within a parasitophorous vacuole (PV) that is maintained by parasite proteins secreted from organelles called dense granules. Most dense granule proteins remain within the PV, and few are known to access the host cell cytosol. We identify GRA16 as a dense granule protein that is exported through the PV membrane and reaches the host cell nucleus, where it positively modulates genes involved in cell-cycle progression and the p53 tumor suppressor pathway. GRA16 binds two host enzymes, the deubiquitinase HAUSP and PP2A phosphatase, which exert several functions, including regulation of p53 and the cell cycle. GRA16 alters p53 levels in a HAUSP-dependent manner and induces nuclear translocation of the PP2A holoenzyme. Additionally, certain GRA16-deficient strains exhibit attenuated virulence, indicating the importance of these host alterations in pathogenesis. Therefore, GRA16 represents a potentially emerging subfamily of exported dense granule proteins that modulate host function.
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123
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Differential locus expansion distinguishes Toxoplasmatinae species and closely related strains of Toxoplasma gondii. mBio 2014; 5:e01003-13. [PMID: 24496792 PMCID: PMC3950507 DOI: 10.1128/mbio.01003-13] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Toxoplasma gondii is a human obligate intracellular parasite that has infected over 20% of the world population and has a vast intermediate host range compared to those of its nearest relatives Neospora caninum and Hammondia hammondi. While these 3 species have highly syntenic genomes (80 to 99%), in this study we examined and compared species-specific structural variations, specifically at loci that have undergone local (i.e., tandem) duplication and expansion. To do so, we used genomic sequence coverage analysis to identify and curate T. gondii and N. caninum loci that have undergone duplication and expansion (expanded loci [ELs]). The 53 T. gondii ELs are significantly enriched for genes with predicted signal sequences and single-exon genes and genes that are developmentally regulated at the transcriptional level. We validated 24 T. gondii ELs using comparative genomic hybridization; these data suggested significant copy number variation at these loci. High-molecular-weight Southern blotting for 3 T. gondii ELs revealed that copy number varies across T. gondii lineages and also between members of the same clonal lineage. Using similar methods, we identified 64 N. caninum ELs which were significantly enriched genes belonging to the SAG-related surface (SRS) antigen family. Moreover, there is significantly less overlap (30%) between the expanded gene sets in T. gondii and N. caninum than would be predicted by overall genomic synteny (81%). Consistent with this finding, only 59% of queried T. gondii ELs are similarly duplicated/expanded in H. hammondi despite over 99% genomic synteny between these species. Gene duplication, expansion, and diversification are a basis for phenotypic differences both within and between species. This study represents the first characterization of both the extent and degree of overlap in gene duplication and locus expansion across multiple apicomplexan parasite species. The most important finding of this study is that the locus duplications/expansions are quantitatively and qualitatively distinct, despite the high degree of genetic relatedness between the species. Given that these differential expansions are prominent species-specific genetic differences, they may also contribute to some of the more striking phenotypic differences between these species. More broadly, this work is important in providing further support for the idea that postspeciation selection events may have a dramatic impact on locus structure and copy number that overshadows selection on single-copy genes.
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124
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Bougdour A, Tardieux I, Hakimi MA. Toxoplasmaexports dense granule proteins beyond the vacuole to the host cell nucleus and rewires the host genome expression. Cell Microbiol 2014; 16:334-43. [DOI: 10.1111/cmi.12255] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Revised: 12/17/2013] [Accepted: 12/18/2013] [Indexed: 12/21/2022]
Affiliation(s)
- Alexandre Bougdour
- CNRS; UMR5163; LAPM; Grenoble 38041 France
- Université Joseph Fourier; Grenoble 38000 France
| | - Isabelle Tardieux
- Institut Cochin; INSERM U1016; CNRS UMR 8104; Université Paris Descartes; Paris 75014 France
| | - Mohamed-Ali Hakimi
- CNRS; UMR5163; LAPM; Grenoble 38041 France
- Université Joseph Fourier; Grenoble 38000 France
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125
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Tomita T, Bzik DJ, Ma YF, Fox BA, Markillie LM, Taylor RC, Kim K, Weiss LM. The Toxoplasma gondii cyst wall protein CST1 is critical for cyst wall integrity and promotes bradyzoite persistence. PLoS Pathog 2013; 9:e1003823. [PMID: 24385904 PMCID: PMC3873430 DOI: 10.1371/journal.ppat.1003823] [Citation(s) in RCA: 113] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2013] [Accepted: 10/25/2013] [Indexed: 11/18/2022] Open
Abstract
Toxoplasma gondii infects up to one third of the world's population. A key to the success of T. gondii as a parasite is its ability to persist for the life of its host as bradyzoites within tissue cysts. The glycosylated cyst wall is the key structural feature that facilitates persistence and oral transmission of this parasite. Because most of the antibodies and reagents that recognize the cyst wall recognize carbohydrates, identification of the components of the cyst wall has been technically challenging. We have identified CST1 (TGME49_064660) as a 250 kDa SRS (SAG1 related sequence) domain protein with a large mucin-like domain. CST1 is responsible for the Dolichos biflorus Agglutinin (DBA) lectin binding characteristic of T. gondii cysts. Deletion of CST1 results in reduced cyst number and a fragile brain cyst phenotype characterized by a thinning and disruption of the underlying region of the cyst wall. These defects are reversed by complementation of CST1. Additional complementation experiments demonstrate that the CST1-mucin domain is necessary for the formation of a normal cyst wall structure, the ability of the cyst to resist mechanical stress, and binding of DBA to the cyst wall. RNA-seq transcriptome analysis demonstrated dysregulation of bradyzoite genes within the various cst1 mutants. These results indicate that CST1 functions as a key structural component that confers essential sturdiness to the T. gondii tissue cyst critical for persistence of bradyzoite forms. Toxoplasma gondii causes severe encephalitis in immune compromised hosts after reactivation of brain cysts that persist for the life span of the host. The biological mechanisms of bradyzoite persistence within cysts are not fully understood. The glycosylated cyst wall is thought to play a crucial role in survival of bradyzoites during chronic infection as well as successful oral transmission of infection. Here we have identified the gene encoding cyst wall glycoprotein CST1. When we delete the CST1 gene, parasites form dramatically fragile brain cysts. Parasites lacking CST1 develop fewer brain cysts, show dysregulation of bradyzoite-specific gene expression and are less able to grow under stressed conditions. The rescue of these phenotypes requires the heavily glycosylated mucin domain of CST1. These studies demonstrate that the glycosylation of CST1 plays a significant role in the structural integrity and persistence of brain cysts. Agents that perturb CST1 glycosylation have the potential to disrupt formation of latent brain cysts, preventing chronic Toxoplasma infection.
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Affiliation(s)
- Tadakimi Tomita
- Department of Pathology, Albert Einstein College of Medicine, Bronx, New York, New York, United States of America
| | - David J. Bzik
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, United States of America
| | - Yan Fen Ma
- Department of Pathology, Albert Einstein College of Medicine, Bronx, New York, New York, United States of America
| | - Barbara A. Fox
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, United States of America
| | - Lye Meng Markillie
- Fundamental and Computational Sciences, Pacific Northwest National Laboratory, Richland, Washington, United States of America
| | - Ronald C. Taylor
- Fundamental and Computational Sciences, Pacific Northwest National Laboratory, Richland, Washington, United States of America
| | - Kami Kim
- Department of Pathology, Albert Einstein College of Medicine, Bronx, New York, New York, United States of America
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, New York, United States of America
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, New York, United States of America
| | - Louis M. Weiss
- Department of Pathology, Albert Einstein College of Medicine, Bronx, New York, New York, United States of America
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, New York, United States of America
- * E-mail:
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126
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Strategies to discover the structural components of cyst and oocyst walls. EUKARYOTIC CELL 2013; 12:1578-87. [PMID: 24096907 DOI: 10.1128/ec.00213-13] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Cysts of Giardia lamblia and Entamoeba histolytica and oocysts of Toxoplasma gondii and Cryptosporidium parvum are the infectious and sometimes diagnostic forms of these parasites. To discover the structural components of cyst and oocyst walls, we have developed strategies based upon a few simple assumptions. Briefly, the most abundant wall proteins are identified by monoclonal antibodies or mass spectrometry. Structural components include a sugar polysaccharide (chitin for Entamoeba, β-1,3-linked glucose for Toxoplasma, and β-1,3-linked GalNAc for Giardia) and/or acid-fast lipids (Toxoplasma and Cryptosporidium). Because Entamoeba cysts and Toxoplasma oocysts are difficult to obtain, studies of walls of nonhuman pathogens (E. invadens and Eimeria, respectively) accelerate discovery. Biochemical methods to dissect fungal walls work well for cyst and oocyst walls, although the results are often unexpected. For example, echinocandins, which inhibit glucan synthases and kill fungi, arrest the development of oocyst walls and block their release into the intestinal lumen. Candida walls are coated with mannans, while Entamoeba cysts are coated in a dextran-like glucose polymer. Models for cyst and oocyst walls derive from their structural components and organization within the wall. Cyst walls are composed of chitin fibrils and lectins that bind chitin (Entamoeba) or fibrils of the β-1,3-GalNAc polymer and lectins that bind the polymer (Giardia). Oocyst walls of Toxoplasma have two distinct layers that resemble those of fungi (β-1,3-glucan in the inner layer) or mycobacteria (acid-fast lipids in the outer layer). Oocyst walls of Cryptosporidium have a rigid bilayer of acid-fast lipids and inner layer of oocyst wall proteins.
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127
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Kirkman LA, Lawrence EA, Deitsch KW. Malaria parasites utilize both homologous recombination and alternative end joining pathways to maintain genome integrity. Nucleic Acids Res 2013; 42:370-9. [PMID: 24089143 PMCID: PMC3874194 DOI: 10.1093/nar/gkt881] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Malaria parasites replicate asexually within their mammalian hosts as haploid cells and are subject to DNA damage from the immune response and chemotherapeutic agents that can significantly disrupt genomic integrity. Examination of the annotated genome of the parasite Plasmodium falciparum identified genes encoding core proteins required for the homologous recombination (HR) pathway for repairing DNA double-strand breaks (DSBs), but surprisingly none of the components of the canonical non-homologous end joining (C-NHEJ) pathway were identified. To better understand how malaria parasites repair DSBs and maintain genome integrity, we modified the yeast I-SceI endonuclease system to generate inducible, site-specific DSBs within the parasite’s genome. Analysis of repaired genomic DNA showed that parasites possess both a typical HR pathway resulting in gene conversion events as well as an end joining (EJ) pathway for repair of DSBs when no homologous sequence is available. The products of EJ were limited in number and identical products were observed in multiple independent experiments. The repair junctions frequently contained short insertions also found in the surrounding sequences, suggesting the possibility of a templated repair process. We propose that an alternative end-joining pathway rather than C-NHEJ, serves as a primary method for repairing DSBs in malaria parasites.
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Affiliation(s)
- Laura A Kirkman
- Department of Internal Medicine, Division of Infectious Diseases and Department of Microbiology and Immunology, Weill Cornell Medical College, New York, NY 10065, USA
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128
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Camejo A, Gold DA, Lu D, McFetridge K, Julien L, Yang N, Jensen KDC, Saeij JPJ. Identification of three novel Toxoplasma gondii rhoptry proteins. Int J Parasitol 2013; 44:147-60. [PMID: 24070999 DOI: 10.1016/j.ijpara.2013.08.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2013] [Revised: 08/06/2013] [Accepted: 08/06/2013] [Indexed: 11/29/2022]
Abstract
The rhoptries are key secretory organelles from apicomplexan parasites that contain proteins involved in invasion and modulation of the host cell. Some rhoptry proteins are restricted to the posterior bulb (ROPs) and others to the anterior neck (RONs). As many rhoptry proteins have been shown to be key players in Toxoplasma invasion and virulence, it is important to identify, understand and characterise the biological function of the components of the rhoptries. In this report, we identified putative novel rhoptry genes by identifying Toxoplasma genes with similar cyclical expression profiles as known rhoptry protein encoding genes. Using this approach we identified two new rhoptry bulb (ROP47 and ROP48) and one new rhoptry neck protein (RON12). ROP47 is secreted and traffics to the host cell nucleus, RON12 was not detected at the moving junction during invasion. Deletion of ROP47 or ROP48 in a type II strain did not show major influence in in vitro growth or virulence in mice.
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Affiliation(s)
- Ana Camejo
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Daniel A Gold
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Diana Lu
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Kiva McFetridge
- Department of Biochemistry, Texas State University, San Marcos, TX 78666, USA
| | - Lindsay Julien
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Ninghan Yang
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Kirk D C Jensen
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Jeroen P J Saeij
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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129
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Braun L, Brenier-Pinchart MP, Yogavel M, Curt-Varesano A, Curt-Bertini RL, Hussain T, Kieffer-Jaquinod S, Coute Y, Pelloux H, Tardieux I, Sharma A, Belrhali H, Bougdour A, Hakimi MA. A Toxoplasma dense granule protein, GRA24, modulates the early immune response to infection by promoting a direct and sustained host p38 MAPK activation. ACTA ACUST UNITED AC 2013; 210:2071-86. [PMID: 24043761 PMCID: PMC3782045 DOI: 10.1084/jem.20130103] [Citation(s) in RCA: 187] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Toxoplasma gondii secretes a novel dense granule protein, GRA24, that traffics from the vacuole to the host cell nucleus where it prolongs p38a activation and correlates with proinflammatory cytokine production. Toxoplasma gondii, the causative agent of toxoplasmosis, is an obligate intracellular protozoan parasite that resides inside a parasitophorous vacuole. During infection, Toxoplasma actively remodels the transcriptome of its hosting cells with profound and coupled impact on the host immune response. We report that Toxoplasma secretes GRA24, a novel dense granule protein which traffics from the vacuole to the host cell nucleus. Once released into the host cell, GRA24 has the unique ability to trigger prolonged autophosphorylation and nuclear translocation of the host cell p38α MAP kinase. This noncanonical kinetics of p38α activation correlates with the up-regulation of the transcription factors Egr-1 and c-Fos and the correlated synthesis of key proinflammatory cytokines, including interleukin-12 and the chemokine MCP-1, both known to control early parasite replication in vivo. Remarkably, the GRA24–p38α complex is defined by peculiar structural features and uncovers a new regulatory signaling path distinct from the MAPK signaling cascade and otherwise commonly activated by stress-related stimuli or various intracellular microbes.
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Affiliation(s)
- Laurence Braun
- Centre National de la Recherche Scientifique (CNRS), UMR5163, Laboratoire Adaptation et Pathogénie des Microorganismes, F-38041 Grenoble, France
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Fox BA, Sanders KL, Chen S, Bzik DJ. Targeting tumors with nonreplicating Toxoplasma gondii uracil auxotroph vaccines. Trends Parasitol 2013; 29:431-7. [PMID: 23928100 DOI: 10.1016/j.pt.2013.07.001] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Revised: 06/28/2013] [Accepted: 07/04/2013] [Indexed: 12/15/2022]
Abstract
Toxoplasma gondii is an intracellular parasite that has evolved to actively control its invaded host cells. Toxoplasma triggers then actively regulates host innate interleukin-12 (IL-12) and interferon-γ (IFN-γ) responses that elicit T cell control of infection. A live, nonreplicating avirulent uracil auxotroph vaccine strain (cps) of Toxoplasma triggers novel innate immune responses that stimulate amplified CD8(+) T cell responses and life-long immunity in vaccinated mice. Here, we review recent reports showing that intratumoral treatment with cps activated immune-mediated regression of established solid tumors in mice. We speculate that a better understanding of host-parasite interaction at the molecular level and applying improved genetic models based on Δku80 Toxoplasma strains will stimulate development of highly effective immunotherapeutic cancer vaccine strategies using engineered uracil auxotrophs.
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Affiliation(s)
- Barbara A Fox
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, 1 Medical Center Drive, Lebanon, NH 03756, USA
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131
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Rommereim LM, Hortua Triana MA, Falla A, Sanders KL, Guevara RB, Bzik DJ, Fox BA. Genetic manipulation in Δku80 strains for functional genomic analysis of Toxoplasma gondii. J Vis Exp 2013:e50598. [PMID: 23892917 PMCID: PMC3735270 DOI: 10.3791/50598] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Targeted genetic manipulation using homologous recombination is the method of choice for functional genomic analysis to obtain a detailed view of gene function and phenotype(s). The development of mutant strains with targeted gene deletions, targeted mutations, complemented gene function, and/or tagged genes provides powerful strategies to address gene function, particularly if these genetic manipulations can be efficiently targeted to the gene locus of interest using integration mediated by double cross over homologous recombination. Due to very high rates of nonhomologous recombination, functional genomic analysis of Toxoplasma gondii has been previously limited by the absence of efficient methods for targeting gene deletions and gene replacements to specific genetic loci. Recently, we abolished the major pathway of nonhomologous recombination in type I and type II strains of T. gondii by deleting the gene encoding the KU80 protein1,2. The Δku80 strains behave normally during tachyzoite (acute) and bradyzoite (chronic) stages in vitro and in vivo and exhibit essentially a 100% frequency of homologous recombination. The Δku80 strains make functional genomic studies feasible on the single gene as well as on the genome scale1-4. Here, we report methods for using type I and type II Δku80Δhxgprt strains to advance gene targeting approaches in T. gondii. We outline efficient methods for generating gene deletions, gene replacements, and tagged genes by targeted insertion or deletion of the hypoxanthine-xanthine-guanine phosphoribosyltransferase (HXGPRT) selectable marker. The described gene targeting protocol can be used in a variety of ways in Δku80 strains to advance functional analysis of the parasite genome and to develop single strains that carry multiple targeted genetic manipulations. The application of this genetic method and subsequent phenotypic assays will reveal fundamental and unique aspects of the biology of T. gondii and related significant human pathogens that cause malaria (Plasmodium sp.) and cryptosporidiosis (Cryptosporidium).
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Affiliation(s)
- Leah M Rommereim
- Department of Microbiology and Immunology, The Geisel School of Medicine at Dartmouth, USA
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132
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Identification of dihydroorotate dehydrogenase as a relevant drug target for 1-hydroxyquinolones in Toxoplasma gondii. Mol Biochem Parasitol 2013; 190:6-15. [DOI: 10.1016/j.molbiopara.2013.05.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Revised: 05/28/2013] [Accepted: 05/28/2013] [Indexed: 11/20/2022]
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133
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Donor CD8+ T cells prevent Toxoplasma gondii de-encystation but fail to rescue the exhausted endogenous CD8+ T cell population. Infect Immun 2013; 81:3414-25. [PMID: 23817617 DOI: 10.1128/iai.00784-12] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Functional exhaustion of CD8(+) T cells due to increased expression of inhibitory molecule PD-1 (Programmed Death-1) causes reactivation of latent disease during later phases of chronic toxoplasmosis. Onset of disease recrudescence results in decreased parasite cyst burden concomitant with parasites undergoing stage conversion from a primarily encysted, quiescent bradyzoite to a fast-replicating, highly motile tachyzoite. Thus, reduced cyst burden is one of the early hallmarks of disease recrudescence. This was further validated by depleting gamma interferon (IFN-γ), a cytokine known to control latent toxoplasmosis, in chronically infected prerecrudescent mice. Since CD8(+) T cells (an important source of IFN-γ) lose their functionality during the later phases of chronic toxoplasmosis, we next examined if adoptive transfer of functional CD8(+) T cells from acutely infected donors to the chronically infected prerecrudescent hosts could impede parasite de-encystation and rescue exhausted CD8(+) T cells. While the transfer of immune CD8(+) T cells temporarily restricted the breakdown of cysts, the exhausted endogenous CD8(+) T cell population was not rescued. Over time, the donor population got deleted, resulting in parasite de-encystation and host mortality. Considering that donor CD8(+) T cells fail to become long-lived, one of the cardinal features of memory CD8(+) T cells, it bears the implication that memory CD8 differentiation is impaired during chronic toxoplasmosis. Moreover, our data strongly suggest that while adoptive immunotherapy can prevent parasite de-encystation transiently, reduced antigen burden in the chronic phase by itself is insufficient for rescue of exhausted CD8(+) T cells. The conclusions of this study have profound ramifications in designing immunotherapeutics against chronic toxoplasmosis.
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134
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ApiAP2 transcription factor restricts development of the Toxoplasma tissue cyst. Proc Natl Acad Sci U S A 2013; 110:6871-6. [PMID: 23572590 DOI: 10.1073/pnas.1300059110] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Cellular differentiation leading to formation of the bradyzoite tissue cyst stage is the underlying cause of chronic toxoplasmosis. Consequently, mechanisms responsible for controlling development in the Toxoplasma intermediate life cycle have long been sought. Here, we identified 15 Toxoplasma mRNAs induced in early bradyzoite development that encode proteins with apicomplexan AP2 (ApiAP2) DNA binding domains. Of these 15 mRNAs, the AP2IX-9 mRNA demonstrated the largest expression increase during alkaline-induced differentiation. At the protein level, we found that AP2IX-9 was restricted to the early bradyzoite nucleus and is repressed in tachyzoites and in mature bradyzoites from 30-d infected animals. Conditional overexpression of AP2IX-9 significantly reduced tissue cyst formation and conferred alkaline pH-resistant growth, whereas disruption of the AP2IX-9 gene increased tissue cyst formation, indicating AP2IX-9 operates as a repressor of bradyzoite development. Consistent with a role as a repressor, AP2IX-9 specifically inhibited the expression of bradyzoite mRNAs, including the canonical bradyzoite marker, bradyzoite antigen 1 (BAG1). Using protein binding microarrays, we established the AP2 domain of AP2IX-9 binds a CAGTGT DNA sequence motif and is capable of binding cis-regulatory elements controlling the BAG1 and bradyzoite-specific nucleoside triphosphatase (B-NTPase) promoters. The effect of AP2IX-9 on BAG1 expression was direct because this factor inhibits expression of a firefly luciferase reporter under the control of the BAG1 promoter in vivo, and epitope-tagged AP2IX-9 can be immunoprecipitated with the BAG1 promoter in parasite chromatin. Altogether, these results indicate AP2IX-9 restricts Toxoplasma commitment to develop the mature bradyzoite tissue cyst.
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135
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Hartmann A, Arroyo-Olarte RD, Imkeller K, Hegemann P, Lucius R, Gupta N. Optogenetic modulation of an adenylate cyclase in Toxoplasma gondii demonstrates a requirement of the parasite cAMP for host-cell invasion and stage differentiation. J Biol Chem 2013; 288:13705-17. [PMID: 23525100 DOI: 10.1074/jbc.m113.465583] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
BACKGROUND cAMP research in intracellular parasites remains underappreciated, and it requires a specific method for cyclic nucleotide regulation. RESULTS Optogenetic induction of cAMP in T. gondii affects host-cell invasion, stage-specific expression, and parasite differentiation. The underlying method allows a versatile control of parasite cAMP. CONCLUSIONS Optogenetic parasite strains offer valuable tools for dissecting cAMP-mediated processes. SIGNIFICANCE The method is applicable to other gene-tractable intertwined systems. Successful infection and transmission of the obligate intracellular parasite Toxoplasma gondii depends on its ability to switch between fast-replicating tachyzoite (acute) and quiescent bradyzoite (chronic) stages. Induction of cAMP in the parasitized host cells has been proposed to influence parasite differentiation. It is not known whether the parasite or host cAMP is required to drive this phenomenon. Other putative roles of cAMP for the parasite biology also remain to be identified. Unequivocal research on cAMP-mediated signaling in such intertwined systems also requires a method for an efficient and spatial control of the cAMP pool in the pathogen or in the enclosing host cell. We have resolved these critical concerns by expressing a photoactivated adenylate cyclase that allows light-sensitive control of the parasite or host-cell cAMP. Using this method, we reveal multiple roles of the parasite-derived cAMP in host-cell invasion, stage-specific expression, and asexual differentiation. An optogenetic method provides many desired advantages such as: (i) rapid, transient, and efficient cAMP induction in extracellular/intracellular and acute/chronic stages; (ii) circumvention of the difficulties often faced in cultures, i.e. poor diffusion, premature degradation, steady activation, and/or pleiotropic effects of cAMP agonists and antagonists; (iii) genetically encoded enzyme expression, thus inheritable to the cell progeny; and (iv) conditional and spatiotemporal control of cAMP levels. Importantly, a successful optogenetic application in Toxoplasma also illustrates its wider utility to study cAMP-mediated signaling in other genetically amenable two-organism systems such as in symbiotic and pathogen-host models.
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Affiliation(s)
- Anne Hartmann
- Departments of Molecular Parasitology, Humboldt University, 10115 Berlin, Germany
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136
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Gissot M, Walker R, Delhaye S, Alayi TD, Huot L, Hot D, Callebaut I, Schaeffer-Reiss C, Dorsselaer AV, Tomavo S. Toxoplasma gondii Alba proteins are involved in translational control of gene expression. J Mol Biol 2013; 425:1287-301. [PMID: 23454356 DOI: 10.1016/j.jmb.2013.01.039] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2012] [Revised: 12/29/2012] [Accepted: 01/26/2013] [Indexed: 10/27/2022]
Abstract
Molecular mechanisms controlling gene expression in apicomplexan parasites remain poorly understood. Here, we report the characterization of two Toxoplasma gondii homologs of the ancient archeal Alba proteins named TgAlba1 and TgAlba2. The targeted disruption of TgAlba1 and TgAlba2 genes in both virulent type I and avirulent type II strains of T. gondii reveals that TgAlba proteins may have an important role in regulating stress response. We found that although the steady-state level of the Tgalba2 transcript is increased in the ΔTgalba1 null mutant parasites, the cognate TgAlba2 protein is undetectable, suggesting that TgAlba1 is required for translation of TgAlba2. Using a tandem affinity purification tag strategy combined with proteomic analyses, we provide evidence that many factors known to be involved in the translation machinery are co-purified with TgAlba1 and TgAlba2. We further performed RNA pull-down and microarray analyses to show that TgAlba1 and TgAlba2 bind to more than 30 RNAs including their own transcripts. Moreover, we demonstrate that the tight translational regulation of the TgAlba2 endogenous transcript relies on the presence of both its 3' untranslated region and that of the TgAlba1 protein. Thus, our findings on TgAlba1 and TgAlba2 are consistent with a role in gene-specific translation.
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Affiliation(s)
- Mathieu Gissot
- Center for Infection and Immunity of Lille, CNRS UMR 8204, INSERM 1019, Université Lille Nord de France, Institut Pasteur de Lille, Lille, France
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137
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Bradyzoite pseudokinase 1 is crucial for efficient oral infectivity of the Toxoplasma gondii tissue cyst. EUKARYOTIC CELL 2013; 12:399-410. [PMID: 23291621 DOI: 10.1128/ec.00343-12] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The tissue cyst formed by the bradyzoite stage of Toxoplasma gondii is essential for persistent infection of the host and oral transmission. Bradyzoite pseudokinase 1 (BPK1) is a component of the cyst wall, but nothing has previously been known about its function. Here, we show that immunoprecipitation of BPK1 from in vitro bradyzoite cultures, 4 days postinfection, identifies at least four associating proteins: MAG1, MCP4, GRA8, and GRA9. To determine the role of BPK1, a strain of Toxoplasma was generated with the bpk1 locus deleted. This BPK1 knockout strain (Δbpk1) was investigated in vitro and in vivo. No defect was found in terms of in vitro cyst formation and no difference in pathogenesis or cyst burden 4 weeks postinfection (wpi) was detected after intraperitoneal (i.p.) infection with Δbpk1 tachyzoites, although the Δbpk1 cysts were significantly smaller than parental or BPK1-complemented strains at 8 wpi. Pepsin-acid treatment of 4 wpi in vivo cysts revealed that Δbpk1 parasites are significantly more sensitive to this treatment than the parental and complemented strains. Consistent with this, 4 wpi Δbpk1 cysts showed reduced ability to cause oral infection compared to the parental and complemented strains. Together, these data reveal that BPK1 plays a crucial role in the in vivo development and infectivity of Toxoplasma cysts.
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138
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Webster JP, Kaushik M, Bristow GC, McConkey GA. Toxoplasma gondii infection, from predation to schizophrenia: can animal behaviour help us understand human behaviour? J Exp Biol 2013; 216:99-112. [PMID: 23225872 PMCID: PMC3515034 DOI: 10.1242/jeb.074716] [Citation(s) in RCA: 104] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2012] [Accepted: 09/08/2012] [Indexed: 12/15/2022]
Abstract
We examine the role of the protozoan Toxoplasma gondii as a manipulatory parasite and question what role study of infections in its natural intermediate rodent hosts and other secondary hosts, including humans, may elucidate in terms of the epidemiology, evolution and clinical applications of infection. In particular, we focus on the potential association between T. gondii and schizophrenia. We introduce the novel term 'T. gondii-rat manipulation-schizophrenia model' and propose how future behavioural research on this model should be performed from a biological, clinical and ethically appropriate perspective.
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Affiliation(s)
- Joanne P. Webster
- Department of Infectious Disease Epidemiology, School of Public Health, Imperial College Faculty of Medicine, London, W2 1PG, UK
| | - Maya Kaushik
- Department of Infectious Disease Epidemiology, School of Public Health, Imperial College Faculty of Medicine, London, W2 1PG, UK
| | - Greg C. Bristow
- School of Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Glenn A. McConkey
- School of Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
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139
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Walker R, Gissot M, Croken MM, Huot L, Hot D, Kim K, Tomavo S. The Toxoplasma nuclear factor TgAP2XI-4 controls bradyzoite gene expression and cyst formation. Mol Microbiol 2012; 87:641-55. [PMID: 23240624 DOI: 10.1111/mmi.12121] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/03/2012] [Indexed: 01/14/2023]
Abstract
Toxoplasma gondii undergoes many phenotypic changes during its life cycle. The recent identification of AP2 transcription factors in T. gondii has provided a platform for studying the mechanisms controlling gene expression. In the present study, we report that a recombinant protein encompassing the TgAP2XI-4 AP2 domain was able to specifically bind to a DNA motif using gel retardation assays. TgAP2XI-4 protein is localized in the parasite nucleus throughout the tachyzoite life cycle in vitro, with peak expression occurring after cytokinesis. We found that the TgAP2XI-4 transcript level was higher in bradyzoite cysts isolated from brains of chronically infected mice than in the rapidly replicating tachyzoites. A knockout of the TgAP2XI-4 gene in both T. gondii virulent type I and avirulent type II strains reveals its role in modulating expression and promoter activity of genes involved in stage conversion of the rapidly replicating tachyzoites to the dormant cyst forming bradyzoites. Furthermore, mice infected with the type II KO mutants show a drastically reduced brain cyst burden. Thus, our results validate TgAP2XI-4 as a novel nuclear factor that regulates bradyzoite gene expression during parasite differentiation and cyst formation.
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Affiliation(s)
- Robert Walker
- Center for Infection and Immunity of Lille, UMR CNRS 8204, INSERM U 1019, Institut Pasteur de Lille, Université Lille Nord de France, Lille, France
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140
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A review of the infection, genetics, and evolution of Neospora caninum: from the past to the present. INFECTION GENETICS AND EVOLUTION 2012; 13:133-50. [PMID: 22985682 DOI: 10.1016/j.meegid.2012.08.012] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Revised: 08/05/2012] [Accepted: 08/07/2012] [Indexed: 12/30/2022]
Abstract
This paper is a review of current knowledge on Neospora caninum in the context of other apicomplexan parasites and with an emphasis on: life cycle, disease, epidemiology, immunity, control and treatment, evolution, genomes, and biological databases and web resources. N. caninum is an obligate, intracellular, coccidian, protozoan parasite of the phylum Apicomplexa. Infection can cause the clinical disease neosporosis, which most notably is associated with abortion in cattle. These abortions are a major root cause of economic loss to both the dairy and beef industries worldwide. N. caninum has been detected in every country in which a study has been specifically conducted to detect this parasite in cattle. The major mode of transmission in cattle is transplacental (or vertical) transmission and several elements of the N. caninum life cycle are yet to be studied in detail. The outcome of an infection is inextricably linked to the precise timing of the infection coupled with the status of the immune system of the dam and foetus. There is no community consensus as to whether it is the dam's pro-inflammatory cytotoxic response to tachyzoites that kills the foetus or the tachyzoites themselves. From economic analysis the most cost-effective approach to control neosporosis is a vaccine. The perfect vaccine would protect against both infection and the clinical disease, and this implies a vaccine is needed that can induce a non-foetopathic cell mediated immunity response. Researchers are beginning to capitalise on the vast potential of -omics data (e.g. genomes, transcriptomes, and proteomes) to further our understanding of pathogens but especially to identify vaccine and drug targets. The recent publication of a genome for N. caninum offers vast opportunities in these areas.
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141
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Hortua Triana MA, Huynh MH, Garavito MF, Fox BA, Bzik DJ, Carruthers VB, Löffler M, Zimmermann BH. Biochemical and molecular characterization of the pyrimidine biosynthetic enzyme dihydroorotate dehydrogenase from Toxoplasma gondii. Mol Biochem Parasitol 2012; 184:71-81. [PMID: 22580100 DOI: 10.1016/j.molbiopara.2012.04.009] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Revised: 04/20/2012] [Accepted: 04/23/2012] [Indexed: 01/27/2023]
Abstract
The pyrimidine biosynthesis pathway in the protozoan pathogen Toxoplasma gondii is essential for parasite growth during infection. To investigate the properties of dihydroorotate dehydrogenase (TgDHOD), the fourth enzyme in the T. gondii pyrimidine pathway, we expressed and purified recombinant TgDHOD. TgDHOD exhibited a specific activity of 84U/mg, a k(cat) of 89s(-1), a K(m)=60μM for l-dihydroorotate, and a K(m)=29μM for decylubiquinone (Q(D)). Quinones lacking or having short isoprenoid side chains yielded lower k(cat)s than Q(D). As expected, fumarate was a poor electron acceptor for this family 2 DHOD. The IC(50)s determined for A77-1726, the active derivative of the human DHOD inhibitor leflunomide, and related compounds MD249 and MD209 were, 91μM, 96μM, and 60μM, respectively. The enzyme was not significantly affected by brequinar or TTFA, known inhibitors of human DHOD, or by atovaquone. DSM190, a known inhibitor of Plasmodium falciparum DHOD, was a poor inhibitor of TgDHOD. TgDHOD exhibits a lengthy 157-residue N-terminal extension, consistent with a potential organellar targeting signal. We constructed C-terminally c-myc tagged TgDHODs to examine subcellular localization of TgDHOD in transgenic parasites expressing the tagged protein. Using both exogenous and endogenous expression strategies, anti-myc fluorescence signal colocalized with antibodies against the mitochondrial marker ATPase. These findings demonstrate that TgDHOD is associated with the parasite's mitochondrion, revealing this organelle as the site of orotate production in T. gondii. The TgDHOD gene appears to be essential because while gene tagging was successful at the TgDHOD gene locus, attempts to delete the TgDHOD gene were not successful in the KU80 background. Collectively, our study suggests that TgDHOD is an excellent target for the development of anti-Toxoplasma drugs.
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Sullivan WJ, Jeffers V. Mechanisms of Toxoplasma gondii persistence and latency. FEMS Microbiol Rev 2012; 36:717-33. [PMID: 22091606 PMCID: PMC3319474 DOI: 10.1111/j.1574-6976.2011.00305.x] [Citation(s) in RCA: 169] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2011] [Revised: 08/22/2011] [Accepted: 08/25/2011] [Indexed: 11/28/2022] Open
Abstract
Toxoplasma gondii is an obligate intracellular protozoan parasite that causes opportunistic disease, particularly in immunocompromised individuals. Central to its transmission and pathogenesis is the ability of the proliferative stage (tachyzoite) to convert into latent tissue cysts (bradyzoites). Encystment allows Toxoplasma to persist in the host and affords the parasite a unique opportunity to spread to new hosts without proceeding through its sexual stage, which is restricted to felids. Bradyzoite tissue cysts can cause reactivated toxoplasmosis if host immunity becomes impaired. A greater understanding of the molecular mechanisms orchestrating bradyzoite development is needed to better manage the disease. Here, we will review key studies that have contributed to our knowledge about this persistent form of the parasite and how to study it, with a focus on how cellular stress can signal for the reprogramming of gene expression needed during bradyzoite development.
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Affiliation(s)
- William J Sullivan
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
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The state of research for AIDS-associated opportunistic infections and the importance of sustaining smaller research communities. EUKARYOTIC CELL 2011; 11:90-7. [PMID: 22158712 DOI: 10.1128/ec.05143-11] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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