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Cordonnier C, Mandalasi M, Gigley J, Wohlfert EA, West CM, Blader IJ. The Toxoplasma oxygen-sensing protein, TgPhyA, is required for resistance to interferon gamma-mediated nutritional immunity in mice. PLoS Biol 2024; 22:e3002690. [PMID: 38857298 PMCID: PMC11192375 DOI: 10.1371/journal.pbio.3002690] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Revised: 06/21/2024] [Accepted: 05/23/2024] [Indexed: 06/12/2024] Open
Abstract
As Toxoplasma gondii disseminates through its host, the parasite must sense and adapt to its environment and scavenge nutrients. Oxygen (O2) is one such environmental factor and cytoplasmic prolyl 4-hydroxylases (PHDs) are evolutionarily conserved O2 cellular sensing proteins that regulate responses to changes in O2 availability. Toxoplasma expresses 2 PHDs. One of them, TgPHYa hydroxylates SKP1, a subunit of the SCF-E3 ubiquitin ligase complex. In vitro, TgPHYa is important for growth at low O2 levels. However, studies have yet to examine the role that TgPHYa or any other pathogen-encoded PHD plays in virulence and disease. Using a type II ME49 Toxoplasma TgPHYa knockout, we report that TgPHYa is important for Toxoplasma virulence and brain cyst formation in mice. We further find that while TgPHYa mutant parasites can establish an infection in the gut, they are unable to efficiently disseminate to peripheral tissues because the mutant parasites are unable to survive within recruited immune cells. Since this phenotype was abrogated in IFNγ knockout mice, we studied how TgPHYa mediates survival in IFNγ-treated cells. We find that TgPHYa is not required for release of parasite-encoded effectors into host cells that neutralize anti-parasitic processes induced by IFNγ. In contrast, we find that TgPHYa is required for the parasite to scavenge tryptophan, which is an amino acid whose levels are decreased after IFNγ up-regulates the tryptophan-catabolizing enzyme, indoleamine dioxygenase (IDO). We further find, relative to wild-type mice, that IDO knockout mice display increased morbidity when infected with TgPHYa knockout parasites. Together, these data identify the first parasite mechanism for evading IFNγ-induced nutritional immunity and highlight a novel role that oxygen-sensing proteins play in pathogen growth and virulence.
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Affiliation(s)
- Charlotte Cordonnier
- Department of Microbiology and Immunology, University at Buffalo School of Medicine, Buffalo, New York, United States of America
| | - Msano Mandalasi
- Department of Biochemistry & Molecular Biology, Center for Tropical & Emerging Global Diseases, University of Georgia, Athens, Georgia, United States of America
| | - Jason Gigley
- Department of Molecular Biology, University of Wyoming, Laramie, Wyoming, United States of America
| | - Elizabeth A. Wohlfert
- Department of Microbiology and Immunology, University at Buffalo School of Medicine, Buffalo, New York, United States of America
| | - Christopher M. West
- Department of Biochemistry & Molecular Biology, Center for Tropical & Emerging Global Diseases, University of Georgia, Athens, Georgia, United States of America
| | - Ira J. Blader
- Department of Microbiology and Immunology, University at Buffalo School of Medicine, Buffalo, New York, United States of America
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Nayeri T, Sarvi S, Daryani A. Effective factors in the pathogenesis of Toxoplasmagondii. Heliyon 2024; 10:e31558. [PMID: 38818168 PMCID: PMC11137575 DOI: 10.1016/j.heliyon.2024.e31558] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Revised: 05/11/2024] [Accepted: 05/17/2024] [Indexed: 06/01/2024] Open
Abstract
Toxoplasma gondii (T. gondii) is a cosmopolitan protozoan parasite in humans and animals. It infects about 30 % of the human population worldwide and causes potentially fatal diseases in immunocompromised hosts and neonates. For this study, five English-language databases (ScienceDirect, ProQuest, Web of Science, PubMed, and Scopus) and the internet search engine Google Scholar were searched. This review was accomplished to draw a global perspective of what is known about the pathogenesis of T. gondii and various factors affecting it. Virulence and immune responses can influence the mechanisms of parasite pathogenesis and these factors are in turn influenced by other factors. In addition to the host's genetic background, the type of Toxoplasma strain, the routes of transmission of infection, the number of passages, and different phases of parasite life affect virulence. The identification of virulence factors of the parasite could provide promising insights into the pathogenesis of this parasite. The results of this study can be an incentive to conduct more intensive research to design and develop new anti-Toxoplasma agents (drugs and vaccines) to treat or prevent this infection. In addition, further studies are needed to better understand the key agents in the pathogenesis of T. gondii.
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Affiliation(s)
- Tooran Nayeri
- Infectious and Tropical Diseases Research Center, Dezful University of Medical Sciences, Dezful, Iran
- Student Research Committee, Mazandaran University of Medical Sciences, Sari, Iran
| | - Shahabeddin Sarvi
- Department of Parasitology, School of Medicine, Mazandaran University of Medical Sciences, Sari, Iran
| | - Ahmad Daryani
- Department of Parasitology, School of Medicine, Mazandaran University of Medical Sciences, Sari, Iran
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Ribeiro E. Silva A, Diallo MA, Sausset A, Robert T, Bach S, Bussière FI, Laurent F, Lacroix-Lamandé S, Silvestre A. Overexpression of Eimeria tenella Rhoptry Kinase 2 Induces Early Production of Schizonts. Microbiol Spectr 2023; 11:e0013723. [PMID: 37260371 PMCID: PMC10434272 DOI: 10.1128/spectrum.00137-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Accepted: 05/04/2023] [Indexed: 06/02/2023] Open
Abstract
Eimeria tenella is an obligate intracellular parasite responsible for avian coccidiosis. Like other apicomplexan parasites, such as Toxoplasma gondii, cell invasion and intracellular development rely on apical organelle content discharge, named micronemes and rhoptries. Some rhoptry (ROP) kinases (ROPK) are key virulence factors in T. gondii. To date, among the 28 ropk genes carried by E. tenella, only two to four were confirmed by proteomic analysis or immunostaining to be expressed at the sporozoite stage. We have previously shown that EtROP1 is implicated in the inhibition of host cell apoptosis by interacting with the cellular p53. This work functionally described the second ROP kinase expressed at the sporozoite stage in E. tenella. EtROP2 is an active kinase that phosphorylates cell substrates of approximately 50 kDa. Its overexpression leads to the shortening of the prepatent period and to the early development of first-generation schizonts. Conduction of RNA sequencing analysis and reverse transcriptase quantitative PCR (RT-qPCR) on the host cell allowed us to identify the mitogen-activated protein kinase (MAPK) pathway and the transcription factor cFos to be upregulated by EtROP2. We also showed by immunofluorescence assay that the active kinase EtROP2 is implicated in the p38 MAPK pathway activation. We established here that EtROP2 activates the p38 MAPK pathway through a direct or indirect phosphorylation, leading to the overexpression of the master transcription factor cFos known to be implicated in E. tenella development. IMPORTANCE Rhoptries are specialized secretory organelles found in zoite stages of apicomplexan parasites. In addition to well-conserved rhoptry neck proteins, their protein consists mostly of kinase proteins, highly divergent from eukaryotic kinases. Some of those kinases are described as major virulence factors in Toxoplasma gondii, secreted into the host cell to hijack signaling pathways. Most of those kinases remain to be characterized in Eimeria tenella. Deciphering their cellular function is a prerequisite to supporting their relevance as a druggable target in development of new means of Eimeria tenella control. Secreted divergent kinases that interact with host cell partners to modulate pathways are good candidates, as they coevolve with their host targets to ensure their function within the host and are less prone to mutations that would lead to drug resistance. The absence of any orthologous kinase in host cells makes these parasite kinases a promising drug target candidate.
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Affiliation(s)
| | | | - Alix Sausset
- ISP, INRAE, Université de Tours, Nouzilly, France
| | - Thomas Robert
- Sorbonne Université, CNRS, UMR 8227, Integrative Biology of Marine Models Laboratory (LBI2M), Station Biologique de Roscoff, Roscoff, France
- Sorbonne Université, CNRS, FR 2424, Plateforme de Criblage KISSf (Kinase Inhibitor Specialized Screening Facility), Station Biologique de Roscoff, Roscoff, France
| | - Stéphane Bach
- Sorbonne Université, CNRS, UMR 8227, Integrative Biology of Marine Models Laboratory (LBI2M), Station Biologique de Roscoff, Roscoff, France
- Sorbonne Université, CNRS, FR 2424, Plateforme de Criblage KISSf (Kinase Inhibitor Specialized Screening Facility), Station Biologique de Roscoff, Roscoff, France
- Centre of Excellence for Pharmaceutical Sciences, North-West University, Potchefstroom, South Africa
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Gallego-López GM, Guzman EC, Knoll LJ, Skala M. Metabolic changes to host cells with Toxoplasma gondii infection. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.10.552811. [PMID: 37609172 PMCID: PMC10441426 DOI: 10.1101/2023.08.10.552811] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/24/2023]
Abstract
Toxoplasma gondii, the causative agent of toxoplasmosis, is an obligate intracellular parasite that infects warm-blooded vertebrates across the world. In humans, seropositivity rates of T. gondii range from 10% to 90%. Despite its prevalence, few studies address how T. gondii infection changes the metabolism of host cells. Here, we investigate how T. gondii manipulates the host cell metabolic environment by monitoring metabolic response over time using non-invasive autofluorescence lifetime imaging of single cells, seahorse metabolic flux analysis, reactive oxygen species (ROS) production, and metabolomics. Autofluorescence lifetime imaging indicates that infected host cells become more oxidized and have an increased proportion of bound NAD(P)H with infection. These findings are consistent with changes in mitochondrial and glycolytic function, decrease of intracellular glucose, fluctuations in lactate and ROS production in infected cells over time. We also examined changes associated with the pre-invasion "kiss and spit" process using autofluorescence lifetime imaging, which similarly showed a more oxidized host cell with an increased proportion of bound NAD(P)H over 48 hours. Glucose metabolic flux analysis indicated that these changes are driven by NADH and NADP+ in T. gondii infection. In sum, metabolic changes in host cells with T. gondii infection were similar during full infection, and kiss and spit. Autofluorescence lifetime imaging can non-invasively monitor metabolic changes in host cells over a microbial infection time-course.
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Affiliation(s)
- Gina M. Gallego-López
- Morgridge Institute for Research, Madison, WI, 53706
- Department of Medical Microbiology & Immunology, University of Wisconsin-Madison, Madison, WI, 53706
| | | | - Laura J. Knoll
- Department of Medical Microbiology & Immunology, University of Wisconsin-Madison, Madison, WI, 53706
| | - Melissa Skala
- Morgridge Institute for Research, Madison, WI, 53706
- Department of Biomedical Engineering, University of Wisconsin- Madison, WI 53706, USA
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The Toxoplasma Polymorphic Effector GRA15 Mediates Seizure Induction by Modulating Interleukin-1 Signaling in the Brain. mBio 2021; 12:e0133121. [PMID: 34154412 PMCID: PMC8262954 DOI: 10.1128/mbio.01331-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Toxoplasmic encephalitis can develop in individuals infected with the protozoan parasite Toxoplasma gondii and is typified by parasite replication and inflammation within the brain. Patients often present with seizures, but the parasite genes and host pathways involved in seizure development and/or propagation are unknown. We previously reported that seizure induction in Toxoplasma-infected mice is parasite strain dependent. Using quantitative trait locus mapping, we identify four loci in the Toxoplasma genome that potentially correlate with seizure development. In one locus, we identify the polymorphic virulence factor, GRA15, as a Toxoplasma gene associated with onset of seizures. GRA15 was previously shown to regulate host NF-κB-dependent gene expression during acute infections, and we demonstrate a similar role for GRA15 in brains of toxoplasmic encephalitic mice. GRA15 is important for increased expression of interleukin 1 beta (IL-1β) and other IL-1 pathway host genes, which is significant since IL-1 signaling is involved in onset of seizures. Inhibiting IL-1 receptor signaling reduced seizure severity in Toxoplasma-infected mice. These data reveal one mechanism by which seizures are induced during toxoplasmic encephalitis.
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López-Osorio S, Chaparro-Gutiérrez JJ, Gómez-Osorio LM. Overview of Poultry Eimeria Life Cycle and Host-Parasite Interactions. Front Vet Sci 2020; 7:384. [PMID: 32714951 PMCID: PMC7351014 DOI: 10.3389/fvets.2020.00384] [Citation(s) in RCA: 71] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Accepted: 05/29/2020] [Indexed: 11/13/2022] Open
Abstract
Apicomplexan parasites of the genus Eimeria are organisms which invade the intestinal tract, causing coccidiosis, an enteric disease of major economic importance worldwide. The disease causes high morbidity ranging from an acute, bloody enteritis with high mortality, to subclinical disease. However, the presence of intestinal lesions depends on the Eimeria species. The most important poultry Eimeria species are: E. tenella, E. necatrix, E. acervulina, E. maxima, E. brunetti, E. mitis, and E. praecox. Key points to better understanding the behavior of this species are the host-parasite interactions and its life cycle. The present paper reviews the literature available regarding the life cycle and the initial host-parasite interaction. More studies are needed to better understand these interactions in poultry Eimerias, taking into account that almost all the information available was generated from other apicomplexan parasites that generate human disease.
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Affiliation(s)
- Sara López-Osorio
- CIBAV Research Group, Facultad de Ciencias Agrarias, Universidad de Antioquia, Medellín, Colombia
| | | | - Luis M. Gómez-Osorio
- CIBAV Research Group, Facultad de Ciencias Agrarias, Universidad de Antioquia, Medellín, Colombia
- Alura Animal Health and Nutrition, Medellin, Colombia
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Ten Hoeve AL, Hakimi MA, Barragan A. Sustained Egr-1 Response via p38 MAP Kinase Signaling Modulates Early Immune Responses of Dendritic Cells Parasitized by Toxoplasma gondii. Front Cell Infect Microbiol 2019; 9:349. [PMID: 31681626 PMCID: PMC6797980 DOI: 10.3389/fcimb.2019.00349] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Accepted: 09/30/2019] [Indexed: 12/28/2022] Open
Abstract
As a response to a diverse array of external stimuli, early growth response protein 1 (Egr-1) plays important roles in the transcriptional regulation of inflammation and the cellular immune response. However, a number of intracellular pathogens colonize immune cells and the implication of Egr-1 in the host-pathogen interplay has remained elusive. Here, we have characterized the Egr-1 responses of primary murine and human dendritic cells (DCs) upon challenge with the obligate intracellular parasite Toxoplasma gondii. We report that live intracellular parasites induce a sustained high expression of Egr-1 in DCs, different from the immediate-early Egr-1 response to parasite lysates, inactivated parasites or LPS. Moreover, a distinct nuclear localization of elevated amounts of Egr-1 protein was detected in infected DCs, but not in by-stander DCs. The ERK1/2 MAPK signaling pathway mediated the canonical immediate-early Egr-1 response to soluble antigens in a MyD88/TLR-dependent fashion. In contrast, a non-canonical extended Egr-1 response that relied primarily on p38 MAPK signaling was induced by intracellular parasites and was exhibited similarly by MyD88-deficient and wildtype DCs. The extended phase Egr-1 response was dramatically reduced upon challenge of DCs with T. gondii parasites deficient in GRA24, a secreted p38-interacting protein. Further, Egr-1-silenced primary DCs maintained their migratory responses upon T. gondii challenge. Importantly, Egr-1 silencing led to elevated expression of co-stimulatory molecules (CD40, CD80) in Toxoplasma-infected DCs and in LPS-challenged immature DCs, indicating that Egr-1 responses suppressed maturation of DCs. Moreover, the IL-12 and IL-2 responses of Toxoplasma-challenged DCs were modulated in a GRA24-dependent fashion. Jointly, the data show that the Egr-1 responses of DCs to microbial external stimuli and intracellular stimuli can be selectively mediated by ERK1/2 or p38 MAPK signaling, and that Egr-1 can act as an intrinsic negative modulator of maturation in primary DCs.
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Affiliation(s)
- Arne L Ten Hoeve
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Mohamed-Ali Hakimi
- Institute for Advanced Biosciences, INSERM U1209, CNRS UMR5309, Université Grenoble Alpes, Grenoble, France
| | - Antonio Barragan
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
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Lis A, Wiley M, Vaughan J, Gray PC, Blader IJ. The Activin Receptor, Activin-Like Kinase 4, Mediates Toxoplasma Gondii Activation of Hypoxia Inducible Factor-1. Front Cell Infect Microbiol 2019; 9:36. [PMID: 30891432 PMCID: PMC6411701 DOI: 10.3389/fcimb.2019.00036] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Accepted: 02/04/2019] [Indexed: 12/11/2022] Open
Abstract
To grow and cause disease, intracellular pathogens modulate host cell processes. Identifying these processes as well as the mechanisms used by the pathogens to manipulate them is important for the development of more effective therapeutics. As an example, the intracellular parasite Toxoplasma gondii induces a wide variety of changes to its host cell, including altered membrane trafficking, cytoskeletal reorganization, and differential gene expression. Although several parasite molecules and their host targets have been identified that mediate- these changes, few are known to be required for parasite replication. One exception is the host cell transcription factor, hypoxia-inducible factor-1 (HIF-1), which is required for parasite replication in an oxygen-dependent manner. Toxoplasma activates HIF-1 by stabilizing the HIF-1α subunit, and this is dependent on the signaling from the Activin-Like Kinase (ALK) receptor superfamily. Here, we demonstrate that specific overexpression of the ALK family member, ALK4, increased HIF-1 activity in Toxoplasma-infected cells, and this increase required ALK4 kinase activity. Moreover, Toxoplasma stimulated ALK4 to dimerize with its co-receptor, ActRII, and also increased ALK4 kinase activity, thereby demonstrating that Toxoplasma activates the ALK4 receptor. ALK4 activation of HIF-1 was independent of canonical SMAD signaling but rather was dependent on the non-canonical Rho GTPase and JNK MAP kinase signaling pathways. Finally, Toxoplasma increased rates of ALK4 ubiquitination and turnover. These data provide the first evidence indicating that ALK4 signaling is a target for a microbial pathogen to manipulate its host cell.
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Affiliation(s)
- Agnieszka Lis
- Department of Microbiology and Immunology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, United States
| | - Mandi Wiley
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | | | | | - Ira J Blader
- Department of Microbiology and Immunology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, United States
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Faridnia R, Daryani A, Sarvi S, Sharif M, Kalani H. Vaccination against Toxoplasma gondii using rhoptry antigens: a systematic review. Comp Immunol Microbiol Infect Dis 2018; 59:32-40. [PMID: 30290885 DOI: 10.1016/j.cimid.2018.09.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Revised: 08/24/2018] [Accepted: 09/11/2018] [Indexed: 12/14/2022]
Abstract
Toxoplasma gondii is an obligate intracellular parasitic protozoan that infects a wide variety of vertebrates as intermediate hosts. The aim of the current systematic review study is to clarify the latest status of studies in the literature regarding rhoptry-associated recombinant proteins or rhoptry-associated recombinant DNAs as potential vaccines against toxoplasmosis. The search was performed systematically in 8 databases, four in English and four in Persian, up to February 2017. Overall, ROP2 was the most commonly used ROPs in DNA vaccines (27.27%) and protein vaccines (6.81%). Furthermore, regarding the type of adjuvants, route and dose of vaccination, animal models, challenge methods, and measurement of immune responses has been discussed in the text. It is hoped that this article help researchers to conduct more effective studies in the field of immunization against T. gondii.
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Affiliation(s)
- Roghiyeh Faridnia
- Student Research Committee, Mazandaran University of Medical Sciences, Sari, Iran
| | - Ahmad Daryani
- Toxoplasmosis Research Center, Mazandaran University of Medical Sciences, Sari, Iran.
| | - Shahabeddin Sarvi
- Toxoplasmosis Research Center, Mazandaran University of Medical Sciences, Sari, Iran
| | - Mehdi Sharif
- Toxoplasmosis Research Center, Mazandaran University of Medical Sciences, Sari, Iran
| | - Hamed Kalani
- Infectious Diseases Research Center, Golestan University of Medical Sciences, Gorgan, Iran
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10
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Abstract
Early electron microscopy studies revealed the elaborate cellular features that define the unique adaptations of apicomplexan parasites. Among these were bulbous rhoptry (ROP) organelles and small, dense granules (GRAs), both of which are secreted during invasion of host cells. These early morphological studies were followed by the exploration of the cellular contents of these secretory organelles, revealing them to be comprised of highly divergent protein families with few conserved domains or predicted functions. In parallel, studies on host-pathogen interactions identified many host signaling pathways that were mysteriously altered by infection. It was only with the advent of forward and reverse genetic strategies that the connections between individual parasite effectors and the specific host pathways that they targeted finally became clear. The current repertoire of parasite effectors includes ROP kinases and pseudokinases that are secreted during invasion and that block host immune pathways. Similarly, many secretory GRA proteins alter host gene expression by activating host transcription factors, through modification of chromatin, or by inducing small noncoding RNAs. These effectors highlight novel mechanisms by which T. gondii has learned to harness host signaling to favor intracellular survival and will guide future studies designed to uncover the additional complexity of this intricate host-pathogen interaction.
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11
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Pastor-Fernández I, Regidor-Cerrillo J, Álvarez-García G, Marugán-Hernández V, García-Lunar P, Hemphill A, Ortega-Mora LM. The tandemly repeated NTPase (NTPDase) from Neospora caninum is a canonical dense granule protein whose RNA expression, protein secretion and phosphorylation coincides with the tachyzoite egress. Parasit Vectors 2016; 9:352. [PMID: 27329357 PMCID: PMC4915099 DOI: 10.1186/s13071-016-1620-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Accepted: 06/01/2016] [Indexed: 12/26/2022] Open
Abstract
Background NTPases (also NTPDases) are enzymes with apyrase activity. They are widely distributed among eukaryotes, and also among members of the family Sarcocystidae. In Toxoplasma gondii, the TgNTPase accumulates in the dense granules, and has been commonly associated with the strain virulence. In the closely related Neospora caninum, the NcNTPase lacks nucleoside diphosphate hydrolase activity and appears to be more abundant in virulent isolates, indicating that it may contribute to the pathogenicity of neosporosis. However, so far no additional information on NcNTPase has been provided. Methods Herein, the NcNTPase coding sequences were analysed by different in silico and de novo sequencing approaches. A comparative analysis of NcNTPase and NcGRA7 in terms of protein dynamics, secretion, phosphorylation, and mRNA expression profiles during the tachyzoite lytic cycle was also carried out. Moreover, NcNTPase immunolocalization was analysed by confocal microscopy techniques over a set number of time-points. Results We describe the presence of three different loci containing three copies of the NcNTPase within the Nc-Liv genome, and report the existence of up to four different NcNTPase alleles in Nc-Liv. We also provide evidence for the occurrence of diverse protein species of the NcNTPase by two-dimensional gel electrophoresis. Both NcNTPase and NcGRA7 were similarly up-regulated and secreted during the egress and/or early invasion phases, and were phosphorylated. However, its secretion was not affected by the addition of calcium modulators such as A23187 and ethanol. NcNTPase and NcGRA7 localized in dense granules and parasitophorous vacuole membrane throughout the lytic cycle, although differed in their inmunolocalization during early invasion and egress. Conclusions The present study reveals the complexity of the NcNTPase loci in N. caninum. We hypothesize that the expression of different isoforms of the NcNTPase protein could contribute to parasite virulence. Our findings showed regulation of expression, secretion and phosphorylation of NcNTPase suggesting a potential role for progression through the tachyzoites lytic cycle. Electronic supplementary material The online version of this article (doi:10.1186/s13071-016-1620-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Iván Pastor-Fernández
- SALUVET, Animal Health Department, Faculty of Veterinary Sciences, Complutense University of Madrid, Ciudad Universitaria s/n, 28040, Madrid, Spain
| | - Javier Regidor-Cerrillo
- SALUVET, Animal Health Department, Faculty of Veterinary Sciences, Complutense University of Madrid, Ciudad Universitaria s/n, 28040, Madrid, Spain
| | - Gema Álvarez-García
- SALUVET, Animal Health Department, Faculty of Veterinary Sciences, Complutense University of Madrid, Ciudad Universitaria s/n, 28040, Madrid, Spain
| | - Virginia Marugán-Hernández
- SALUVET, Animal Health Department, Faculty of Veterinary Sciences, Complutense University of Madrid, Ciudad Universitaria s/n, 28040, Madrid, Spain
| | - Paula García-Lunar
- SALUVET, Animal Health Department, Faculty of Veterinary Sciences, Complutense University of Madrid, Ciudad Universitaria s/n, 28040, Madrid, Spain
| | - Andrew Hemphill
- Institute of Parasitology, Vetsuisse Faculty, University of Berne, Länggass-Strasse 122, CH-3012, Berne, Switzerland
| | - Luis M Ortega-Mora
- SALUVET, Animal Health Department, Faculty of Veterinary Sciences, Complutense University of Madrid, Ciudad Universitaria s/n, 28040, Madrid, Spain.
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Abstract
UNLABELLED During infections with the protozoan parasite Toxoplasma gondii, gamma-aminobutyric acid (GABA) is utilized as a carbon source for parasite metabolism and also to facilitate parasite dissemination by stimulating dendritic-cell motility. The best-recognized function for GABA, however, is its role in the nervous system as an inhibitory neurotransmitter that regulates the flow and timing of excitatory neurotransmission. When this pathway is altered, seizures develop. Human toxoplasmosis patients suffer from seizures, suggesting that Toxoplasma interferes with GABA signaling in the brain. Here, we show that while excitatory glutamatergic presynaptic proteins appeared normal, infection with type II ME49 Toxoplasma tissue cysts led to global changes in the distribution of glutamic acid decarboxylase 67 (GAD67), a key enzyme that catalyzes GABA synthesis in the brain. Alterations in GAD67 staining were not due to decreased expression but rather to a change from GAD67 clustering at presynaptic termini to a more diffuse localization throughout the neuropil. Consistent with a loss of GAD67 from the synaptic terminals, Toxoplasma-infected mice develop spontaneous seizures and are more susceptible to drugs that induce seizures by antagonizing GABA receptors. Interestingly, GABAergic protein mislocalization and the response to seizure-inducing drugs were observed in mice infected with type II ME49 but not type III CEP strain parasites, indicating a role for a polymorphic parasite factor(s) in regulating GABAergic synapses. Taken together, these data support a model in which seizures and other neurological complications seen in Toxoplasma-infected individuals are due, at least in part, to changes in GABAergic signaling. IMPORTANCE Infections of the central nervous system can cause seizures. While inflammation in the brain has been proposed to initiate the onset of the seizures, relatively little is known about how inflammation impacts the structure and function of the neurons. Here we used a parasite called Toxoplasma gondii that infects the brain and showed that seizures arise due to a defect in signaling of GABA, which is the neurotransmitter primarily responsible for preventing the onset of seizures.
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Abstract
Toxoplasmosis is the clinical and pathological consequence of acute infection with the obligate intracellular apicomplexan parasite Toxoplasma gondii. Symptoms result from tissue destruction that accompanies lytic parasite growth. This review updates current understanding of the host cell invasion, parasite replication, and eventual egress that constitute the lytic cycle, as well as the ways T. gondii manipulates host cells to ensure its survival. Since the publication of a previous iteration of this review 15 years ago, important advances have been made in our molecular understanding of parasite growth and mechanisms of host cell egress, and knowledge of the parasite's manipulation of the host has rapidly progressed. Here we cover molecular advances and current conceptual frameworks that include each of these topics, with an eye to what may be known 15 years from now.
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Affiliation(s)
- Ira J Blader
- Department of Microbiology and Immunology, University at Buffalo, Buffalo, New York 14127;
| | - Bradley I Coleman
- Department of Biology, Boston College, Chestnut Hill, Massachusetts 02467; , ,
| | - Chun-Ti Chen
- Department of Biology, Boston College, Chestnut Hill, Massachusetts 02467; , ,
| | - Marc-Jan Gubbels
- Department of Biology, Boston College, Chestnut Hill, Massachusetts 02467; , ,
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Hakimi MA, Bougdour A. Toxoplasma 's ways of manipulating the host transcriptome via secreted effectors. Curr Opin Microbiol 2015; 26:24-31. [DOI: 10.1016/j.mib.2015.04.003] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Revised: 04/06/2015] [Accepted: 04/08/2015] [Indexed: 12/12/2022]
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siRNA Screening Identifies the Host Hexokinase 2 (HK2) Gene as an Important Hypoxia-Inducible Transcription Factor 1 (HIF-1) Target Gene in Toxoplasma gondii-Infected Cells. mBio 2015; 6:e00462. [PMID: 26106078 PMCID: PMC4479703 DOI: 10.1128/mbio.00462-15] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Although it is established that oxygen availability regulates cellular metabolism and growth, little is known regarding how intracellular pathogens use host factors to grow at physiological oxygen levels. Therefore, large-scale human small interfering RNA screening was performed to identify host genes important for growth of the intracellular protozoan parasite Toxoplasma gondii at tissue oxygen tensions. Among the genes identified by this screen, we focused on the hexokinase 2 (HK2) gene because its expression is regulated by hypoxia-inducible transcription factor 1 (HIF-1), which is important for Toxoplasma growth. Toxoplasma increases host HK2 transcript and protein levels in a HIF-1-dependent manner. In addition, parasite growth at 3% oxygen is restored in HIF-1-deficient cells transfected with HK2 expression plasmids. Both HIF-1 activation and HK2 expression were accompanied by increases in host glycolytic flux, suggesting that enhanced HK2 expression in parasite-infected cells is functionally significant. Parasite dependence on host HK2 and HIF-1 expression is not restricted to transformed cell lines, as both are required for parasite growth in nontransformed C2C12 myoblasts and HK2 is upregulated in vivo following infection. While HK2 is normally associated with the cytoplasmic face of the outer mitochondrial membrane at physiological O2 levels, HK2 relocalizes to the host cytoplasm following infection, a process that is required for parasite growth at 3% oxygen. Taken together, our findings show that HIF-1-dependent expression and relocalization of HK2 represent a novel mechanism by which Toxoplasma establishes its replicative niche at tissue oxygen tensions. Little is known regarding how the host cell contributes to the survival of the intracellular parasite Toxoplasma gondii at oxygen levels that mimic those found in tissues. Our previous work showed that Toxoplasma activates the expression of an oxygen-regulated transcription factor that is required for growth. Here, we report that Toxoplasma regulates the abundance and activity of a key host metabolic enzyme, hexokinase 2, by activating HIF-1 and by promoting dissociation of hexokinase 2 from the mitochondrial membrane. Collectively, our data reveal HIF-1/hexokinase 2 as a novel target for an intracellular pathogen that acts by reprograming the host cell’s metabolism to create an environment conducive for parasite replication at physiological oxygen levels.
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Brown KM, Suvorova E, Farrell A, McLain A, Dittmar A, Wiley GB, Marth G, Gaffney PM, Gubbels MJ, White M, Blader IJ. Forward genetic screening identifies a small molecule that blocks Toxoplasma gondii growth by inhibiting both host- and parasite-encoded kinases. PLoS Pathog 2014; 10:e1004180. [PMID: 24945800 PMCID: PMC4055737 DOI: 10.1371/journal.ppat.1004180] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Accepted: 04/28/2014] [Indexed: 02/02/2023] Open
Abstract
The simultaneous targeting of host and pathogen processes represents an untapped approach for the treatment of intracellular infections. Hypoxia-inducible factor-1 (HIF-1) is a host cell transcription factor that is activated by and required for the growth of the intracellular protozoan parasite Toxoplasma gondii at physiological oxygen levels. Parasite activation of HIF-1 is blocked by inhibiting the family of closely related Activin-Like Kinase (ALK) host cell receptors ALK4, ALK5, and ALK7, which was determined in part by use of an ALK4,5,7 inhibitor named SB505124. Besides inhibiting HIF-1 activation, SB505124 also potently blocks parasite replication under normoxic conditions. To determine whether SB505124 inhibition of parasite growth was exclusively due to inhibition of ALK4,5,7 or because the drug inhibited a second kinase, SB505124-resistant parasites were isolated by chemical mutagenesis. Whole-genome sequencing of these mutants revealed mutations in the Toxoplasma MAP kinase, TgMAPK1. Allelic replacement of mutant TgMAPK1 alleles into wild-type parasites was sufficient to confer SB505124 resistance. SB505124 independently impacts TgMAPK1 and ALK4,5,7 signaling since drug resistant parasites could not activate HIF-1 in the presence of SB505124 or grow in HIF-1 deficient cells. In addition, TgMAPK1 kinase activity is inhibited by SB505124. Finally, mice treated with SB505124 had significantly lower tissue burdens following Toxoplasma infection. These data therefore identify SB505124 as a novel small molecule inhibitor that acts by inhibiting two distinct targets, host HIF-1 and TgMAPK1. Understanding how a compound blocks growth of an intracellular pathogen is important not only for developing these compounds into drugs that can be prescribed to patients, but also because these data will likely provide novel insight into the biology of these pathogens. Forward genetic screens are one established approach towards defining these mechanisms. But performing these screens with intracellular parasites has been limited not only because of technical limitations but also because the compounds may have off-target effects in either the host or parasite. Here, we report the first compound that kills a pathogen by simultaneously inhibiting distinct host- and parasite-encoded targets. Because developing drug resistance simultaneously to two targets is less likely, this work may highlight a new approach to antimicrobial drug discovery.
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Affiliation(s)
- Kevin M Brown
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - Elena Suvorova
- Departments of Molecular Medicine & Global Health, University of South Florida, Tampa, Florida, United States of America
| | - Andrew Farrell
- Department of Biology, Boston College, Chestnut Hill, Massachusetts, United States of America
| | - Aaron McLain
- Department of Microbiology and Immunology, University at Buffalo, Buffalo, New York, United States of America
| | - Ashley Dittmar
- Department of Microbiology and Immunology, University at Buffalo, Buffalo, New York, United States of America
| | - Graham B Wiley
- Arthritis and Clinical Immunology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, United States of America
| | - Gabor Marth
- Department of Biology, Boston College, Chestnut Hill, Massachusetts, United States of America
| | - Patrick M Gaffney
- Arthritis and Clinical Immunology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, United States of America
| | - Marc Jan Gubbels
- Department of Biology, Boston College, Chestnut Hill, Massachusetts, United States of America
| | - Michael White
- Departments of Molecular Medicine & Global Health, University of South Florida, Tampa, Florida, United States of America
| | - Ira J Blader
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America; Department of Microbiology and Immunology, University at Buffalo, Buffalo, New York, United States of America
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Beiting DP, Peixoto L, Akopyants NS, Beverley SM, Wherry EJ, Christian DA, Hunter CA, Brodsky IE, Roos DS. Differential induction of TLR3-dependent innate immune signaling by closely related parasite species. PLoS One 2014; 9:e88398. [PMID: 24505488 PMCID: PMC3914978 DOI: 10.1371/journal.pone.0088398] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2013] [Accepted: 12/31/2013] [Indexed: 12/20/2022] Open
Abstract
The closely related protozoan parasites Toxoplasma gondii and Neospora caninum display similar life cycles, subcellular ultrastructure, invasion mechanisms, metabolic pathways, and genome organization, but differ in their host range and disease pathogenesis. Type II (γ) interferon has long been known to be the major mediator of innate and adaptive immunity to Toxoplasma infection, but genome-wide expression profiling of infected host cells indicates that Neospora is a potent activator of the type I (α/β) interferon pathways typically associated with antiviral responses. Infection of macrophages from mice with targeted deletions in various innate sensing genes demonstrates that host responses to Neospora are dependent on the toll-like receptor Tlr3 and the adapter protein Trif. Consistent with this observation, RNA from Neospora elicits TLR3-dependent type I interferon responses when targeted to the host endo-lysosomal system. Although live Toxoplasma fail to induce type I interferon, heat-killed parasites do trigger this response, albeit much weaker than Neospora, and co-infection studies reveal that T. gondii actively suppresses the production of type I interferon. These findings reveal that eukaryotic pathogens can be potent inducers of type I interferon and that related parasite species interact with this pathway in distinct ways.
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Affiliation(s)
- Daniel P. Beiting
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- * E-mail:
| | - Lucia Peixoto
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Natalia S. Akopyants
- Department of Molecular Microbiology, Washington University, St. Louis, Missouri, United States of America
| | - Stephen M. Beverley
- Department of Molecular Microbiology, Washington University, St. Louis, Missouri, United States of America
| | - E. John Wherry
- Department of Microbiology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - David A. Christian
- Department of Pathobiology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Christopher A. Hunter
- Department of Pathobiology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Igor E. Brodsky
- Department of Pathobiology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - David S. Roos
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
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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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Yang N, Farrell A, Niedelman W, Melo M, Lu D, Julien L, Marth GT, Gubbels MJ, Saeij JPJ. Genetic basis for phenotypic differences between different Toxoplasma gondii type I strains. BMC Genomics 2013; 14:467. [PMID: 23837824 PMCID: PMC3710486 DOI: 10.1186/1471-2164-14-467] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Accepted: 07/03/2013] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Toxoplasma gondii has a largely clonal population in North America and Europe, with types I, II and III clonal lineages accounting for the majority of strains isolated from patients. RH, a particular type I strain, is most frequently used to characterize Toxoplasma biology. However, compared to other type I strains, RH has unique characteristics such as faster growth, increased extracellular survival rate and inability to form orally infectious cysts. Thus, to identify candidate genes that could account for these parasite phenotypic differences, we determined genetic differences and differential parasite gene expression between RH and another type I strain, GT1. Moreover, as differences in host cell modulation could affect Toxoplasma replication in the host, we determined differentially modulated host processes among the type I strains through host transcriptional profiling. RESULTS Through whole genome sequencing, we identified 1,394 single nucleotide polymorphisms (SNPs) and insertions/deletions (indels) between RH and GT1. These SNPs/indels together with parasite gene expression differences between RH and GT1 were used to identify candidate genes that could account for type I phenotypic differences. A polymorphism in dense granule protein, GRA2, determined RH and GT1 differences in the evasion of the interferon gamma response. In addition, host transcriptional profiling identified that genes regulated by NF-ĸB, such as interleukin (IL)-12p40, were differentially modulated by the different type I strains. We subsequently showed that this difference in NF-ĸB activation was due to polymorphisms in GRA15. Furthermore, we observed that RH, but not other type I strains, recruited phosphorylated IĸBα (a component of the NF-ĸB complex) to the parasitophorous vacuole membrane and this recruitment of p- IĸBα was partially dependent on GRA2. CONCLUSIONS We identified candidate parasite genes that could be responsible for phenotypic variation among the type I strains through comparative genomics and transcriptomics. We also identified differentially modulated host pathways among the type I strains, and these can serve as a guideline for future studies in examining the phenotypic differences among type I strains.
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Affiliation(s)
- Ninghan Yang
- Biology Department, Massachusetts Institute of Technology, 77 Massachusetts Ave, building 68-270, Cambridge, MA 02139, USA
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Ismail HAHA, Quan JH, Wei Z, Choi IW, Cha GH, Shin DW, Lee YH, Song CJ. Gene expression profiles in genetically different mice infected with Toxoplasma gondii: ALDH1A2, BEX2, EGR2, CCL3 and PLAU. THE KOREAN JOURNAL OF PARASITOLOGY 2012; 50:7-13. [PMID: 22451728 PMCID: PMC3309055 DOI: 10.3347/kjp.2012.50.1.7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/18/2011] [Revised: 01/14/2012] [Accepted: 01/15/2012] [Indexed: 11/23/2022]
Abstract
Toxoplasma gondii can modulate host cell gene expression; however, determining gene expression levels in intermediate hosts after T. gondii infection is not known much. We selected 5 genes (ALDH1A2, BEX2, CCL3, EGR2 and PLAU) and compared the mRNA expression levels in the spleen, liver, lung and small intestine of genetically different mice infected with T. gondii. ALDH1A2 mRNA expressions of both mouse strains were markedly increased at day 1-4 postinfection (PI) and then decreased, and its expressions in the spleen and lung were significantly higher in C57BL/6 mice than those of BALB/c mice. BEX2 and CCR3 mRNA expressions of both mouse strains were significantly increased from day 7 PI and peaked at day 15-30 PI (P<0.05), especially high in the spleen liver or small intestine of C57BL/6 mice. EGR2 and PLAU mRNA expressions of both mouse strains were significantly increased after infection, especially high in the spleen and liver. However, their expression patterns were varied depending on the tissue and mouse strain. Taken together, T. gondii-susceptible C57BL/6 mice expressed higher levels of these 5 genes than did T. gondii-resistant BALB/c mice, particularly in the spleen and liver. And ALDH1A2 and PLAU expressions were increased acutely, whereas BEX2, CCL3 and EGR2 expressions were increased lately. Thus, these demonstrate that host genetic factors exert a strong impact on the expression of these 5 genes and their expression patterns were varied depending on the gene or tissue.
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Affiliation(s)
- Hassan Ahmed Hassan Ahmed Ismail
- Department of Infection Biology, Research Institute for Medical Science, Chungnam National University School of Medicine, Daejeon 301-131, Korea
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21
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Regidor-Cerrillo J, Álvarez-García G, Pastor-Fernández I, Marugán-Hernández V, Gómez-Bautista M, Ortega-Mora LM. Proteome expression changes among virulent and attenuated Neospora caninum isolates. J Proteomics 2012; 75:2306-18. [PMID: 22343075 DOI: 10.1016/j.jprot.2012.01.039] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Revised: 01/25/2012] [Accepted: 01/30/2012] [Indexed: 11/30/2022]
Abstract
Neospora caninum is a cyst-forming parasite that has been recognised worldwide as a cause of cattle abortion and neuromuscular disease in dogs. Variations in genetic profiles, behaviour in vitro, and pathogenicity have been established among N. caninum isolates. However, it is unclear which parasite factors are implicated in this intra-specific diversity. Comparative analysis of protein expression patterns may define the determinants of biological diversity in N. caninum. Using DIGE and MALDI-TOF MS techniques, we quantified and identified differentially expressed proteins in the tachyzoite stage across three N. caninum isolates: the virulent Nc-Liv and Nc-Spain 7 isolates, and the attenuated Nc-Spain 1H isolate. Comparison between Nc-Spain 7 and Nc-Spain 1H extracts revealed 39 protein spots that were more abundant in Nc-Spain 7 and 21 in Nc-Spain 1H. Twenty-four spots were also increased in Nc-Spain 7 and 12 in Nc-Liv. Three protein spots were more abundant in the Nc-Liv extracts than in the Nc-Spain 1H extracts. MS analysis identified 11 proteins differentially expressed that are potentially involved in gliding motility and the lytic cycle of the parasite, and oxidative stress. These differences could help to explain variations in behaviour between isolates and provide a better knowledge of mechanisms associated with virulence.
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Affiliation(s)
- Javier Regidor-Cerrillo
- SALUVET, Animal Health Department, Faculty of Veterinary Sciences, Complutense University of Madrid, Ciudad Universitaria s/n, 28040 Madrid, Spain.
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22
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Stutz A, Kessler H, Kaschel ME, Meissner M, Dalpke AH. Cell invasion and strain dependent induction of suppressor of cytokine signaling-1 by Toxoplasma gondii. Immunobiology 2011; 217:28-36. [PMID: 22015046 DOI: 10.1016/j.imbio.2011.08.008] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2010] [Revised: 08/17/2011] [Accepted: 08/21/2011] [Indexed: 01/12/2023]
Abstract
Toxoplasma gondii is an intracellular parasite that has to cope with the microbicidal actions of IFNγ. Previously we reported that parasite-mediated induction of suppressor of cytokine signaling protein 1 (SOCS1) contributes to inhibition of IFNγ signaling. However, the signaling requirements remained elusive. We now show that induction of SOCS1 and inhibition of nitric oxide production by IFNγ was independent of stimulation of Toll-like receptors. Instead, infection by T. gondii resulted in induction of egr transcription factors which have been reported to regulate SOCS expression. Indeed, induction of egr2 as well as SOCS1 was dependent on p38 MAP kinase and blockade of egr inhibited SOCS1 expression. Moreover, we found that Mic8, a previously identified invasion factor of T. gondii, was necessary for SOCS1 regulation and escape of IFNγ mediated nitric oxide secretion within macrophages. Surprisingly, when further analyzing Mic8 deficient parasites we noted that inhibition of IFNγ mediated up-regulation of MHC-class II and ICAM1 molecules was independent of cell invasion. Furthermore, these inhibitory effects were equally observed in type I and II strains of T. gondii and were dependent on excreted and secreted antigens. In contrast, only the virulent RH type I strain additionally induced SOCS1 and efficiently inhibited nitric oxide secretion by IFNγ. The results show that T. gondii makes use of two different mechanisms to escape from IFNγ activity with one mode being strain dependent and relying on active cell invasion and SOCS1 induction.
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Affiliation(s)
- Andrea Stutz
- Dept. of Infectious Diseases - Medical Microbiology and Hygiene, University Heidelberg, 69120 Heidelberg, Germany
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23
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Rocchi MS, Bartley PM, Inglis NF, Collantes-Fernandez E, Entrican G, Katzer F, Innes EA. Selection of Neospora caninum antigens stimulating bovine CD4+ve T cell responses through immuno-potency screening and proteomic approaches. Vet Res 2011; 42:91. [PMID: 21813001 PMCID: PMC3167765 DOI: 10.1186/1297-9716-42-91] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Accepted: 08/03/2011] [Indexed: 11/23/2022] Open
Abstract
Neospora caninum is recognised worldwide as a major cause of bovine infectious abortion. There is a real need to develop effective strategies to control infection during pregnancy which may lead to either abortion or congenital transmission. Due to the intracellular nature of the parasite, cell-mediated immune (CMI) responses involving CD4+ve, CD8+ve, γ/δ TCR+ve T cells and NK cells, as well as production of IFN-γ, are thought to be important for protective immunity. In this study we applied a combination of proteomic and immunological approaches to identify antigens of N. caninum that are recognized by CD4+ve T cell lines derived from infected cattle. Initially, N. caninum tachyzoite Water Soluble Antigens (NcWSA) were fractionated by size-exclusion HPLC and then screened for immune-potency using CD4+ve T cell lines. LC-ESI-MS/MS (liquid chromatography electrospray ionisation tandem mass spectrometry) was employed to catalogue and identify the proteins comprising three immunologically selected fractions and led to the identification of six N. caninum target proteins as well as sixteen functional orthologues of Toxoplasma gondii. This approach allows the screening of biologically reactive antigenic fractions by the immune cells responsible for protection (such as bovine CD4+ve cells) and the subsequent identification of the stimulating components using tandem mass spectrometry.
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Affiliation(s)
- Mara S Rocchi
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Midlothian, EH26 0PZ, UK.
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Abstract
Intracellular parasitism has arisen only a few times during the long ancestry of protozoan parasites including in diverse groups such as microsporidians, kinetoplastids, and apicomplexans. Strategies used to gain entry differ widely from injection (e.g. microsporidians), active penetration of the host cell (e.g. Toxoplasma), recruitment of lysosomes to a plasma membrane wound (e.g. Trypanosoma cruzi), to host cell-mediated phagocytosis (e.g. Leishmania). The resulting range of intracellular niches is equally diverse ranging from cytosolic (e.g. T. cruzi) to residing within a non-fusigenic vacuole (e.g. Toxoplasma, Encephalitozoon) or a modified phagolysosome (e.g. Leishmania). These lifestyle choices influence access to nutrients, interaction with host cell signaling pathways, and detection by pathogen recognition systems. As such, intracellular life requires a repertoire of adaptations to assure entry-exit from the cell, as well as to thwart innate immune mechanisms and prevent clearance. Elucidating these pathways at the cellular and molecular level may identify key steps that can be targeted to reduce parasite survival or augment immunologic responses and thereby prevent disease.
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Affiliation(s)
- L David Sibley
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63100, USA.
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25
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Marugán-Hernández V, Álvarez-García G, Tomley F, Hemphill A, Regidor-Cerrillo J, Ortega-Mora L. Identification of novel rhoptry proteins in Neospora caninum by LC/MS-MS analysis of subcellular fractions. J Proteomics 2011; 74:629-42. [DOI: 10.1016/j.jprot.2011.02.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2010] [Revised: 02/01/2011] [Accepted: 02/02/2011] [Indexed: 11/30/2022]
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26
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Heath RJW, Leong JM, Visegrády B, Machesky LM, Xavier RJ. Bacterial and host determinants of MAL activation upon EPEC infection: the roles of Tir, ABRA, and FLRT3. PLoS Pathog 2011; 7:e1001332. [PMID: 21490959 PMCID: PMC3072376 DOI: 10.1371/journal.ppat.1001332] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2010] [Accepted: 03/10/2011] [Indexed: 11/23/2022] Open
Abstract
Infection of host cells by pathogenic microbes triggers signal transduction pathways leading to a multitude of host cell responses including actin cytoskeletal re-arrangements and transcriptional programs. The diarrheagenic pathogens Enteropathogenic E. coli (EPEC) and the related Enterohemorrhagic E. coli (EHEC) subvert the host-cell actin cytoskeleton to form attaching and effacing lesions on the surface of intestinal epithelial cells by injecting effector proteins via a type III secretion system. Here we use a MAL translocation assay to establish the effect of bacterial pathogens on host cell signaling to transcription factor activation. MAL is a cofactor of Serum response factor (SRF), a transcription factor with important roles in the regulation of the actin cytoskeleton. We show that EPEC induces nuclear accumulation of MAL-GFP. The translocated intimin receptor is essential for this process and phosphorylation of Tyrosine residues 454 and 474 is important. Using an expression screen we identify FLRT3, C22orf28 and TESK1 as novel activators of SRF. Importantly we demonstrate that ABRA (actin-binding Rho-activating protein, also known as STARS) is necessary for EPEC-induced nuclear accumulation of MAL and the novel SRF activator FLRT3, is a component of this pathway. We further demonstrate that ABRA is important for structural maintenance of EPEC pedestals. Our results uncover novel components in pathogen-activated cytoskeleton signalling to MAL activation. Many significant immune diseases are caused by bacterial pathogens that deliver effector proteins into their host. The pathogen uses these proteins to subvert the hosts' normal cytosolic defense in a way that services the pathogen. It is therefore important to understand the normal processes of a cell and how they are affected by bacterial infection. We have established the effect of bacteria on host cell signalling to the transcription factor serum response factor. Serum response factor is a widely expressed transcription factor that controls the expression of many important genes. We show that Enteropathogenic E. coli infection can activate serum response factor and that the effector protein Tir is essential for this activation. Furthermore, we identify new genes that are important in this infection-induced activation and show that they are important in maintaining structures necessary for Enteropathogenic E. coli infection.
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Affiliation(s)
- Robert J. W. Heath
- Center for Computational and Integrative Biology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
- Gastrointestinal Unit, Center for Inflammatory Bowel Disease, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - John M. Leong
- Department of Molecular Genetics and Microbiology, UMass Medical School, Worcester, Massachusetts, United States of America
| | - Balázs Visegrády
- Beatson Institute for Cancer Research, Garscube Estate, Bearsden, Glasgow, United Kingdom
| | - Laura M. Machesky
- Beatson Institute for Cancer Research, Garscube Estate, Bearsden, Glasgow, United Kingdom
| | - Ramnik J. Xavier
- Center for Computational and Integrative Biology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
- Gastrointestinal Unit, Center for Inflammatory Bowel Disease, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
- The Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
- * E-mail:
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27
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Wiley M, Teygong C, Phelps E, Radke J, Blader IJ. Serum response factor regulates immediate early host gene expression in Toxoplasma gondii-infected host cells. PLoS One 2011; 6:e18335. [PMID: 21479245 PMCID: PMC3066233 DOI: 10.1371/journal.pone.0018335] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Accepted: 02/25/2011] [Indexed: 11/02/2022] Open
Abstract
Toxoplasma gondii is a wide spread pathogen that can cause severe and even fatal disease in fetuses and immune-compromised hosts. As an obligate intracellular parasite, Toxoplasma must alter the environment of its host cell in order to establish its replicative niche. This is accomplished, in part, by secretion of factors into the host cell that act to modulate processes such as transcription. Previous studies demonstrated that genes encoding transcription factors such as c-jun, junB, EGR1, and EGR2 were amongst the host genes that were the most rapidly upregulated following infection. In cells stimulated with growth factors, these genes are regulated by a transcription factor named Serum Response Factor. Serum Response Factor is a ubiquitously expressed DNA binding protein that regulates growth and actin cytoskeleton genes via MAP kinase or actin cytoskeletal signaling, respectively. Here, we report that Toxoplasma infection leads to the rapid activation of Serum Response Factor. Serum Response Factor activation is a Toxoplasma-specific event since the transcription factor is not activated by the closely related protozoan parasite, Neospora caninum. We further demonstrate that Serum Response Factor activation requires a parasite-derived secreted factor that signals via host MAP kinases but independently of the host actin cytoskeleton. Together, these data define Serum Response Factor as a host cell transcription factor that regulates immediate early gene expression in Toxoplasma-infected cells.
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Affiliation(s)
- Mandi Wiley
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - Crystal Teygong
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - Eric Phelps
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - Jay Radke
- Department of Veterinary Molecular Biology & the Center for Immunotherapies to Zoonotic Diseases, Montana State University, Bozeman, Montana, United States of America
| | - Ira J. Blader
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
- * E-mail:
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Peixoto L, Chen F, Harb OS, Davis PH, Beiting DP, Brownback CS, Ouloguem D, Roos DS. Integrative genomic approaches highlight a family of parasite-specific kinases that regulate host responses. Cell Host Microbe 2010; 8:208-18. [PMID: 20709297 DOI: 10.1016/j.chom.2010.07.004] [Citation(s) in RCA: 171] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2009] [Revised: 04/21/2010] [Accepted: 07/14/2010] [Indexed: 12/24/2022]
Abstract
Apicomplexan parasites release factors via specialized secretory organelles (rhoptries, micronemes) that are thought to control host cell responses. In order to explore parasite-mediated modulation of host cell signaling pathways, we exploited a phylogenomic approach to characterize the Toxoplasma gondii kinome, defining a 44 member family of coccidian-specific secreted kinases, some of which have been previously implicated in virulence. Comparative genomic analysis suggests that "ROPK" genes are under positive selection, and expression profiling demonstrates that most are differentially expressed between strains and/or during differentiation. Integrating diverse genomic-scale analyses points to ROP38 as likely to be particularly important in parasite biology. Upregulating expression of this previously uncharacterized gene in transgenic parasites dramatically suppresses transcriptional responses in the infected cell. Specifically, parasite ROP38 downregulates host genes associated with MAPK signaling and the control of apoptosis and proliferation. These results highlight the value of integrative genomic approaches in prioritizing candidates for functional validation.
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Affiliation(s)
- Lucia Peixoto
- Department of Biology and Penn Genome Frontiers Institute, University of Pennsylvania, Philadelphia, PA 19104, USA
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Wiley M, Sweeney KR, Chan DA, Brown KM, McMurtrey C, Howard EW, Giaccia AJ, Blader IJ. Toxoplasma gondii activates hypoxia-inducible factor (HIF) by stabilizing the HIF-1alpha subunit via type I activin-like receptor kinase receptor signaling. J Biol Chem 2010; 285:26852-26860. [PMID: 20581113 PMCID: PMC2930684 DOI: 10.1074/jbc.m110.147041] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2010] [Revised: 06/25/2010] [Indexed: 12/14/2022] Open
Abstract
Toxoplasma gondii is an intracellular protozoan parasite that can cause devastating disease in fetuses and immune-compromised individuals. We previously reported that the alpha subunit of the host cell transcription factor, hypoxia-inducible factor-1 (HIF-1), is up-regulated by infection and necessary for Toxoplasma growth. Under basal conditions, HIF-1alpha is constitutively expressed but rapidly targeted for proteasomal degradation after two proline residues are hydroxylated by a family of prolyl hydroxylases (PHDs). The PHDs are alpha-ketoglutarate-dependent dioxygenases that have low K(m) values for oxygen, making them important cellular oxygen sensors. Thus, when oxygen levels decrease, HIF-1alpha is not hydroxylated, and HIF-1 is activated. How Toxoplasma activates HIF-1 under normoxic conditions remains unknown. Here, we report that Toxoplasma infection increases HIF-1alpha stability by preventing HIF-1alpha prolyl hydroxylation. Infection significantly decreases PHD2 abundance, which is the key prolyl hydroxylase for regulating HIF-1alpha. The effects of Toxoplasma on HIF-1alpha abundance and prolyl hydroxylase activity require activin-like receptor kinase signaling. Finally, parasite growth is severely diminished when signaling from this family of receptors is inhibited. Together, these data indicate that PHD2 is a key host cell factor for T. gondii growth and represent a novel mechanism by which a microbial pathogen subverts host cell signaling and transcription to establish its replicative niche.
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Affiliation(s)
- Mandi Wiley
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
| | - Kristin R Sweeney
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
| | - Denise A Chan
- Department of Radiation Oncology, University of California, San Francisco, California 94143; Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California 94305
| | - Kevin M Brown
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
| | - Curtis McMurtrey
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
| | - Eric W Howard
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
| | - Amato J Giaccia
- Department of Radiation Oncology, University of California, San Francisco, California 94143
| | - Ira J Blader
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
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Zeiner GM, Norman KL, Thomson JM, Hammond SM, Boothroyd JC. Toxoplasma gondii infection specifically increases the levels of key host microRNAs. PLoS One 2010; 5:e8742. [PMID: 20090903 PMCID: PMC2806928 DOI: 10.1371/journal.pone.0008742] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2009] [Accepted: 12/22/2009] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND The apicomplexan parasite Toxoplasma gondii can infect and replicate in virtually any nucleated cell in many species of warm-blooded animals; thus, it has evolved the ability to exploit well-conserved biological processes common to its diverse hosts. Here we have investigated whether Toxoplasma modulates the levels of host microRNAs (miRNAs) during infection. METHODOLOGY/PRINCIPAL FINDINGS Using microarray profiling and a combination of conventional molecular approaches we report that Toxoplasma specifically modulates the expression of important host microRNAs during infection. We show that both the primary transcripts for miR-17 approximately 92 and miR-106b approximately 25 and the pivotal miRNAs that are derived from miR-17 approximately 92 display increased abundance in Toxoplasma-infected primary human cells; a Toxoplasma-dependent up-regulation of the miR-17 approximately 92 promoter is at least partly responsible for this increase. The abundance of mature miR-17 family members, which are derived from these two miRNA clusters, remains unchanged in host cells infected with the closely related apicomplexan Neospora caninum; thus, the Toxoplasma-induced increase in their abundance is a highly directed process rather than a general host response to infection. CONCLUSIONS/SIGNIFICANCE Altered levels of miR-17 approximately 92 and miR-106b approximately 25 are known to play crucial roles in mammalian cell regulation and have been implicated in numerous hyperproliferative diseases although the mechanisms driving their altered expression are unknown. Hence, in addition to the implications of these findings on the host-pathogen interaction, Toxoplasma may represent a powerful probe for understanding the normal mechanisms that regulate the levels of key host miRNAs.
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Affiliation(s)
- Gusti M. Zeiner
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Kara L. Norman
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, United States of America
| | - J. Michael Thomson
- Department of Cell and Developmental Biology, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Scott M. Hammond
- Department of Cell and Developmental Biology, University of North Carolina, Chapel Hill, North Carolina, United States of America
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - John C. Boothroyd
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, United States of America
- * E-mail:
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The role of DNA microarrays in Toxoplasma gondii research, the causative agent of ocular toxoplasmosis. J Ocul Biol Dis Infor 2009; 2:214-222. [PMID: 20157353 PMCID: PMC2816810 DOI: 10.1007/s12177-009-9040-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2009] [Accepted: 11/06/2009] [Indexed: 12/11/2022] Open
Abstract
Ocular toxoplasmosis, which is caused by the protozoan parasite Toxoplasma gondii, is the leading cause of retinochoroiditis. Toxoplasma is an obligate intracellular pathogen that replicates within a parasitophorous vacuole. Infections are initiated by digestion of parasites deposited in cat feces or in undercooked meat. Parasites then disseminate to target tissues that include the retina where they then develop into long-lived asymptomatic tissue cysts. Occasionally, cysts reactivate and growth of newly emerged parasites must be controlled by the host’s immune system or disease will occur. The mechanisms by which Toxoplasma grows within its host cell, encysts, and interacts with the host’s immune system are important questions. Here, we will discuss how the use of DNA microarrays in transcriptional profiling, genotyping, and epigenetic experiments has impacted our understanding of these processes. Finally, we will discuss how these advances relate to ocular toxoplasmosis and how future research on ocular toxoplasmosis can benefit from DNA microarrays.
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Blader IJ, Saeij JP. Communication between Toxoplasma gondii and its host: impact on parasite growth, development, immune evasion, and virulence. APMIS 2009; 117:458-76. [PMID: 19400868 DOI: 10.1111/j.1600-0463.2009.02453.x] [Citation(s) in RCA: 128] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Toxoplasma gondii is an obligate intracellular protozoan parasite that can infect most warm-blooded animals and cause severe and life-threatening disease in developing fetuses and in immune-compromised patients. Although Toxoplasma was discovered over 100 years ago, we are only now beginning to appreciate the importance of the role that parasite modulation of its host has on parasite growth, bradyzoite development, immune evasion, and virulence. The goal of this review is to highlight these findings, to develop an integrated model for communication between Toxoplasma and its host, and to discuss new questions that arise out of these studies.
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Affiliation(s)
- Ira J Blader
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
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West CM, Nguyen P, van der Wel H, Metcalf T, Sweeney KR, Blader IJ, Erdos GW. Dependence of stress resistance on a spore coat heteropolysaccharide in Dictyostelium. EUKARYOTIC CELL 2009; 8:27-36. [PMID: 18996984 PMCID: PMC2620749 DOI: 10.1128/ec.00398-07] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2007] [Accepted: 09/01/2008] [Indexed: 11/20/2022]
Abstract
In Dictyostelium, sporulation occurs synchronously as prespore cells approach the apex of the aerial stalk during culmination. Each prespore cell becomes surrounded by its own coat comprised of a core of crystalline cellulose and a branched heteropolysaccharide sandwiched between heterogeneous cysteine-rich glycoproteins. The function of the heteropolysaccharide, which consists of galactose and N-acetylgalactosamine, is unknown. Two glycosyltransferase-like genes encoding multifunctional proteins, each with predicted features of a heteropolysaccharide synthase, were identified in the Dictyostelium discoideum genome. pgtB and pgtC transcripts were modestly upregulated during early development, and pgtB was further intensely upregulated at the time of heteropolysaccharide accumulation. Disruption of either gene reduced synthase-like activity and blocked heteropolysaccharide formation, based on loss of cytological labeling with a lectin and absence of component sugars after acid hydrolysis. Cell mixing experiments showed that heteropolysaccharide expression is spore cell autonomous, suggesting a physical association with other coat molecules during assembly. Mutant coats expressed reduced levels of crystalline cellulose based on chemical analysis after acid degradation, and cellulose was heterogeneously affected based on flow cytometry and electron microscopy. Mutant coats also contained elevated levels of selected coat proteins but not others and were sensitive to shear. Mutant spores were unusually susceptible to hypertonic collapse and damage by detergent or hypertonic stress. Thus, the heteropolysaccharide is essential for spore integrity, which can be explained by a role in the formation of crystalline cellulose and regulation of the protein content of the coat.
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Affiliation(s)
- Christopher M West
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
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