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Jimenéz-Ruiz E, Li W, Meissner M. Where is the EXIT? Phenotypic screens for new egress factors in apicomplexan parasites. Mol Microbiol 2024; 121:359-367. [PMID: 37740453 DOI: 10.1111/mmi.15166] [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: 06/23/2023] [Revised: 08/31/2023] [Accepted: 09/05/2023] [Indexed: 09/24/2023]
Abstract
Apicomplexans, such as Plasmodium and Toxoplasma are obligate intracellular parasites that invade, replicate and finally EXIT their host cell. During replication within a parasitophorous vacuole (PV), the parasites establish an extensive F-actin-containing network that connects individual parasites and is required for material exchange, recycling and the final steps of daughter cell assembly. After multiple rounds of replication, the parasites exit the host cell involving multiple signalling cascades, disassembly of the network, secretion of microneme proteins and activation of the acto-myosin motor. Blocking the host cell EXIT process leads to the formation of large PVs, making the screening for genes involved in exiting the cell relatively straightforward. Given that apicomplexans are highly diverse from other eukaryotes, approximately 30% of all genes are annotated as hypothetical, some apicomplexan-specific factors are likely to be critical during EXIT. This motivated several labs to design and perform forward genetic and phenotypic screens using various approaches, such as random insertion mutagenesis, temperature-sensitive mutants and, more recently, CRISPR/Cas9-mediated targeted editing and conditional mutagenesis. Here we will provide an overview of the technological developments over recent years and the most successful stories that led to the identification of new critical factors in Toxoplasma gondii.
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Affiliation(s)
- Elena Jimenéz-Ruiz
- Experimental Parasitology, Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität, LMU, Munich, Germany
| | - Wei Li
- Experimental Parasitology, Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität, LMU, Munich, Germany
| | - Markus Meissner
- Experimental Parasitology, Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität, LMU, Munich, Germany
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2
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González-Blanco G, García-Rivera G, Talmás-Rohana P, Orozco E, Galindo-Rosales JM, Vélez C, Salucedo-Cárdenas O, Azuara-Liceaga E, Rodríguez-Rodríguez MA, Nozaki T, Valdés J. An Unusual U2AF2 Inhibits Splicing and Attenuates the Virulence of the Human Protozoan Parasite Entamoeba histolytica. Front Cell Infect Microbiol 2022; 12:888428. [PMID: 35782149 PMCID: PMC9247205 DOI: 10.3389/fcimb.2022.888428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Accepted: 05/05/2022] [Indexed: 11/30/2022] Open
Abstract
E. histolytica is the etiological agent of intestinal amebiasis and liver abscesses, which still poses public health threat globally. Metronidazole is the drug of choice against amebiasis. However, metronidazole-resistant amoebic clinical isolates and strains have been reported recently, challenging the efforts for amebiasis eradication. In search of alternative treatments, E. histolytica transcriptomes have shown the association of genes involved in RNA metabolism with the virulence of the parasite. Among the upregulated genes in amoebic liver abscesses are the splicing factors EhU2AF2 and a paralog of EhSF3B1. For this reason and because EhU2AF2 contains unusual KH-QUA2 (84KQ) motifs in its lengthened C-terminus domain, here we investigated how the role of EhU2AF2 in pre-mRNA processing impacts the virulence of the parasite. We found that 84KQ is involved in splicing inhibition/intron retention of several virulence and non-virulence-related genes. The 84KQ domain interacts with the same domain of the constitutive splicing factor SF1 (SF1KQ), both in solution and when SF1KQ is bound to branchpoint signal RNA probes. The 84KQ–SF1KQ interaction prevents splicing complex E to A transition, thus inhibiting splicing. Surprisingly, the deletion of the 84KQ domain in EhU2AF2 amoeba transformants increased splicing and enhanced the in vitro and in vivo virulence phenotypes. We conclude that the interaction of the 84KQ and SF1KQ domains, probably involving additional factors, tunes down Entamoeba virulence by favoring intron retention.
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Affiliation(s)
- Gretter González-Blanco
- Departamento de Bioquímica, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV), CDMX, Mexico
| | - Guillermina García-Rivera
- Departamento de Infectómica y Patogénesis Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV), CDMX, Mexico
| | - Patricia Talmás-Rohana
- Departamento de Infectómica y Patogénesis Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV), CDMX, Mexico
| | - Ester Orozco
- Departamento de Infectómica y Patogénesis Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV), CDMX, Mexico
| | - José Manuel Galindo-Rosales
- Departamento de Bioquímica, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV), CDMX, Mexico
| | - Cristina Vélez
- Departamento de Biología Celular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV), CDMX, Mexico
| | - Odila Salucedo-Cárdenas
- Departamento de Histología, Facultad de Medicina, Universidad Autónoma de Nuevo León, Monterrey, Mexico
| | - Elisa Azuara-Liceaga
- Posgrado en Ciencias Genómicas, Universidad Autónoma de la Ciudad de México, CDMX, Mexico
| | - Mario Alberto Rodríguez-Rodríguez
- Departamento de Biología Celular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV), CDMX, Mexico
| | - Tomoyoshi Nozaki
- Laboratory of Biomedical Chemistry, Department of International Health, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Jesús Valdés
- Departamento de Bioquímica, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV), CDMX, Mexico
- *Correspondence: Jesús Valdés,
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3
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Xiao J, Savonenko A, Yolken RH. Strain-specific pre-existing immunity: A key to understanding the role of chronic Toxoplasma infection in cognition and Alzheimer's diseases? Neurosci Biobehav Rev 2022; 137:104660. [PMID: 35405182 DOI: 10.1016/j.neubiorev.2022.104660] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 03/31/2022] [Accepted: 04/06/2022] [Indexed: 12/22/2022]
Abstract
Toxoplasma exposure can elicit cellular and humoral immune responses. In the case of chronic Toxoplasma infection, these immune responses are long-lasting. Some studies suggest that pre-existing immunity from Toxoplasma infection can shape immune responses and resistance to other pathogens and brain insults later in life. Much evidence has been generated suggesting Toxoplasma infection may contribute to cognitive impairment in the elderly. However, there have also been studies that disagree with the conclusion. Toxoplasma has many strain types, with virulence being the most notable difference. There is also considerable variation in the outcomes following Toxoplasma exposure ranging from resolved to persistent infection. Therefore, the brain microenvironment, particularly cellular constituents, differs based on the infecting strain (virulent versus hypovirulent) and infection stage (resolved versus persistent). Such difference might play a critical role in determining the outcome of the host on subsequent challengings to the brain. The ability of Toxoplasma strains to set up distinct stages for neurodegenerative pathology through varying degrees of virulence provides unique experimental tools for characterizing these pathways.
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Affiliation(s)
- Jianchun Xiao
- Stanley Division of Developmental Neurovirology, Department of Pediatrics, Johns Hopkins School of Medicine, Baltimore, MD 21287, USA.
| | - Alena Savonenko
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Robert H Yolken
- Stanley Division of Developmental Neurovirology, Department of Pediatrics, Johns Hopkins School of Medicine, Baltimore, MD 21287, USA
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Li DF, Cui ZH, Wang LY, Zhang KH, Cao LT, Zheng SJ, Zhang LX. Tandem mass tag (TMT)-based proteomic analysis of Cryptosporidium andersoni oocysts before and after excystation. Parasit Vectors 2021; 14:608. [PMID: 34922597 PMCID: PMC8683822 DOI: 10.1186/s13071-021-05113-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Accepted: 11/29/2021] [Indexed: 11/28/2022] Open
Abstract
Background Cryptosporidium andersoni initiates infection by releasing sporozoites from oocysts through excystation. However, the proteins involved in excystation are unknown. Determining the proteins that participate in the excystation of C. andersoni oocysts will increase our understanding of the excystation process. Methods Cryptosporidium andersoni oocysts were collected and purified from the feces of naturally infected adult cows. Tandem mass tags (TMT), coupled with liquid chromatography–tandem mass spectrometry (LC–MS/MS) proteomic analysis, were used to investigate the proteomic expression profiles of C. andersoni oocysts before and after excystation. Results Proteomic analysis identified a total of 1586 proteins, of which 17 were differentially expressed proteins (DEPs) upon excystation. These included 10 upregulated and seven downregulated proteins. The 17 proteins had multiple biological functions associated with control of gene expression at the level of transcription and biosynthetic and metabolic processes. Quantitative real-time RT-PCR of eight selected genes validated the proteomic data. Conclusions This study provides information on the protein composition of C. andersoni oocysts as well as possible excystation factors. The data may be useful in identifying genes for diagnosis, vaccine development, and immunotherapy for Cryptosporidium. Graphical Abstract ![]()
Supplementary Information The online version contains supplementary material available at 10.1186/s13071-021-05113-6.
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Affiliation(s)
- Dong-Fang Li
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450000, Henan Province, People's Republic of China.,International Joint Research Laboratory for Zoonotic Diseases of Henan, Zhengzhou, 450000, Henan Province, People's Republic of China
| | - Zhao-Hui Cui
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450000, Henan Province, People's Republic of China.,International Joint Research Laboratory for Zoonotic Diseases of Henan, Zhengzhou, 450000, Henan Province, People's Republic of China
| | - Lu-Yang Wang
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450000, Henan Province, People's Republic of China.,International Joint Research Laboratory for Zoonotic Diseases of Henan, Zhengzhou, 450000, Henan Province, People's Republic of China
| | - Kai-Hui Zhang
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450000, Henan Province, People's Republic of China.,International Joint Research Laboratory for Zoonotic Diseases of Henan, Zhengzhou, 450000, Henan Province, People's Republic of China
| | - Le-Tian Cao
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450000, Henan Province, People's Republic of China.,International Joint Research Laboratory for Zoonotic Diseases of Henan, Zhengzhou, 450000, Henan Province, People's Republic of China
| | - Shuang-Jian Zheng
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450000, Henan Province, People's Republic of China.,International Joint Research Laboratory for Zoonotic Diseases of Henan, Zhengzhou, 450000, Henan Province, People's Republic of China
| | - Long-Xian Zhang
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, 450000, Henan Province, People's Republic of China. .,International Joint Research Laboratory for Zoonotic Diseases of Henan, Zhengzhou, 450000, Henan Province, People's Republic of China.
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5
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Hu Y, Yu L, Fan H, Huang G, Wu Q, Nie Y, Liu S, Yan L, Wei F. Genomic Signatures of Coevolution between Nonmodel Mammals and Parasitic Roundworms. Mol Biol Evol 2021; 38:531-544. [PMID: 32960966 PMCID: PMC7826172 DOI: 10.1093/molbev/msaa243] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Antagonistic coevolution between host and parasite drives species evolution. However, most of the studies only focus on parasitism adaptation and do not explore the coevolution mechanisms from the perspective of both host and parasite. Here, through the de novo sequencing and assembly of the genomes of giant panda roundworm, red panda roundworm, and lion roundworm parasitic on tiger, we investigated the genomic mechanisms of coevolution between nonmodel mammals and their parasitic roundworms and those of roundworm parasitism in general. The genome-wide phylogeny revealed that these parasitic roundworms have not phylogenetically coevolved with their hosts. The CTSZ and prolyl 4-hydroxylase subunit beta (P4HB) immunoregulatory proteins played a central role in protein interaction between mammals and parasitic roundworms. The gene tree comparison identified that seven pairs of interactive proteins had consistent phylogenetic topology, suggesting their coevolution during host–parasite interaction. These coevolutionary proteins were particularly relevant to immune response. In addition, we found that the roundworms of both pandas exhibited higher proportions of metallopeptidase genes, and some positively selected genes were highly related to their larvae’s fast development. Our findings provide novel insights into the genetic mechanisms of coevolution between nonmodel mammals and parasites and offer the valuable genomic resources for scientific ascariasis prevention in both pandas.
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Affiliation(s)
- Yibo Hu
- CAS Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China.,Center for Excellence in Animal Evolution and Genetics, Chinese Academy of Sciences, Kunming, China
| | - Lijun Yu
- CAS Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Huizhong Fan
- CAS Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Guangping Huang
- CAS Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Qi Wu
- CAS Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Yonggang Nie
- CAS Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.,Center for Excellence in Animal Evolution and Genetics, Chinese Academy of Sciences, Kunming, China
| | - Shuai Liu
- CAS Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Li Yan
- CAS Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Fuwen Wei
- CAS Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China.,Center for Excellence in Animal Evolution and Genetics, Chinese Academy of Sciences, Kunming, China
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6
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Wilson SK, Heckendorn J, Martorelli Di Genova B, Koch LL, Rooney PJ, Morrissette N, Lebrun M, Knoll LJ. A Toxoplasma gondii patatin-like phospholipase contributes to host cell invasion. PLoS Pathog 2020; 16:e1008650. [PMID: 32628723 PMCID: PMC7365478 DOI: 10.1371/journal.ppat.1008650] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 07/16/2020] [Accepted: 05/22/2020] [Indexed: 11/23/2022] Open
Abstract
Toxoplasma gondii is an obligate intracellular parasite that can invade any nucleated cell of any warm-blooded animal. In a previous screen to identify virulence determinants, disruption of gene TgME49_305140 generated a T. gondii mutant that could not establish a chronic infection in mice. The protein product of TgME49_305140, here named TgPL3, is a 277 kDa protein with a patatin-like phospholipase (PLP) domain and a microtubule binding domain. Antibodies generated against TgPL3 show that it is localized to the apical cap. Using a rapid selection FACS-based CRISPR/Cas-9 method, a TgPL3 deletion strain (ΔTgPL3) was generated. ΔTgPL3 parasites have defects in host cell invasion, which may be caused by reduced rhoptry secretion. We generated complementation clones with either wild type TgPL3 or an active site mutation in the PLP domain by converting the catalytic serine to an alanine, ΔTgPL3::TgPL3S1409A (S1409A). Complementation of ΔTgPL3 with wild type TgPL3 restored all phenotypes, while S1409A did not, suggesting that phospholipase activity is necessary for these phenotypes. ΔTgPL3 and S1409A parasites are also virtually avirulent in vivo but induce a robust antibody response. Vaccination with ΔTgPL3 and S1409A parasites protected mice against subsequent challenge with a lethal dose of Type I T. gondii parasites, making ΔTgPL3 a compelling vaccine candidate. These results demonstrate that TgPL3 has a role in rhoptry secretion, host cell invasion and survival of T. gondii during acute mouse infection.
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Affiliation(s)
- Sarah K. Wilson
- Department of Medical Microbiology and Immunology, University of Wisconsin—Madison, Linden Drive, Madison, Wisconsin, United States of America
| | | | - Bruno Martorelli Di Genova
- Department of Medical Microbiology and Immunology, University of Wisconsin—Madison, Linden Drive, Madison, Wisconsin, United States of America
| | - Lindsey L. Koch
- Department of Medical Microbiology and Immunology, University of Wisconsin—Madison, Linden Drive, Madison, Wisconsin, United States of America
| | - Peggy J. Rooney
- Stratatech Corporation, Charmany Drive, Madison, Wisconsin, United States of America
| | - Naomi Morrissette
- Department of Molecular Biology and Biochemistry, University of California Irvine, Irvine, California, United States of America
| | | | - Laura J. Knoll
- Department of Medical Microbiology and Immunology, University of Wisconsin—Madison, Linden Drive, Madison, Wisconsin, United States of America
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7
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Batugedara G, Lu XM, Saraf A, Sardiu ME, Cort A, Abel S, Prudhomme J, Washburn MP, Florens L, Bunnik EM, Le Roch KG. The chromatin bound proteome of the human malaria parasite. Microb Genom 2020; 6:e000327. [PMID: 32017676 PMCID: PMC7067212 DOI: 10.1099/mgen.0.000327] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Accepted: 12/20/2019] [Indexed: 12/15/2022] Open
Abstract
Proteins interacting with DNA are fundamental for mediating processes such as gene expression, DNA replication and maintenance of genome integrity. Accumulating evidence suggests that the chromatin of apicomplexan parasites, such as Plasmodium falciparum, is highly organized, and this structure provides an epigenetic mechanism for transcriptional regulation. To investigate how parasite chromatin structure is being regulated, we undertook comparative genomics analysis using 12 distinct eukaryotic genomes. We identified conserved and parasite-specific chromatin-associated domains (CADs) and proteins (CAPs). We then used the chromatin enrichment for proteomics (ChEP) approach to experimentally capture CAPs in P. falciparum. A topological scoring analysis of the proteomics dataset revealed stage-specific enrichments of CADs and CAPs. Finally, we characterized, two candidate CAPs: a conserved homologue of the structural maintenance of chromosome 3 protein and a homologue of the crowded-like nuclei protein, a plant-like protein functionally analogous to animal nuclear lamina proteins. Collectively, our results provide a comprehensive overview of CAPs in apicomplexans, and contribute to our understanding of the complex molecular components regulating chromatin structure and genome architecture in these deadly parasites.
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Affiliation(s)
- Gayani Batugedara
- Department of Molecular, Cell and Systems Biology, University of California Riverside, Riverside, CA 92521, USA
| | - Xueqing M. Lu
- Department of Molecular, Cell and Systems Biology, University of California Riverside, Riverside, CA 92521, USA
| | - Anita Saraf
- Stowers Institute for Medical Research, 1000 E. 50th Street, Kansas City, MO 64110, USA
| | - Mihaela E. Sardiu
- Stowers Institute for Medical Research, 1000 E. 50th Street, Kansas City, MO 64110, USA
| | - Anthony Cort
- Department of Molecular, Cell and Systems Biology, University of California Riverside, Riverside, CA 92521, USA
| | - Steven Abel
- Department of Molecular, Cell and Systems Biology, University of California Riverside, Riverside, CA 92521, USA
| | - Jacques Prudhomme
- Department of Molecular, Cell and Systems Biology, University of California Riverside, Riverside, CA 92521, USA
| | - Michael P. Washburn
- Stowers Institute for Medical Research, 1000 E. 50th Street, Kansas City, MO 64110, USA
- Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - Laurence Florens
- Stowers Institute for Medical Research, 1000 E. 50th Street, Kansas City, MO 64110, USA
| | - Evelien M. Bunnik
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - Karine G. Le Roch
- Department of Molecular, Cell and Systems Biology, University of California Riverside, Riverside, CA 92521, USA
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8
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Jeffers V, Tampaki Z, Kim K, Sullivan WJ. A latent ability to persist: differentiation in Toxoplasma gondii. Cell Mol Life Sci 2018; 75:2355-2373. [PMID: 29602951 PMCID: PMC5988958 DOI: 10.1007/s00018-018-2808-x] [Citation(s) in RCA: 89] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2017] [Revised: 03/01/2018] [Accepted: 03/26/2018] [Indexed: 01/08/2023]
Abstract
A critical factor in the transmission and pathogenesis of Toxoplasma gondii is the ability to convert from an acute disease-causing, proliferative stage (tachyzoite), to a chronic, dormant stage (bradyzoite). The conversion of the tachyzoite-containing parasitophorous vacuole membrane into the less permeable bradyzoite cyst wall allows the parasite to persist for years within the host to maximize transmissibility to both primary (felids) and secondary (virtually all other warm-blooded vertebrates) hosts. This review presents our current understanding of the latent stage, including the factors that are important in bradyzoite induction and maintenance. Also discussed are the recent studies that have begun to unravel the mechanisms behind stage switching.
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Affiliation(s)
- Victoria Jeffers
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, 46202, USA.
| | - Zoi Tampaki
- Departments of Medicine, Microbiology and Immunology, and Pathology, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
| | - Kami Kim
- Departments of Medicine, Microbiology and Immunology, and Pathology, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
- Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL, 33612, USA
| | - William J Sullivan
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, 46202, USA
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN, 46202, USA
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9
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Abstract
Entamoeba histolytica is the protozoan parasite that causes human amoebiasis. It is one of the leading parasitic disease burdens in tropical regions and developing countries, with spread to developed countries through migrants from and travellers to endemic regions.Understanding E. histolytica's invasion mechanisms requires an understanding of how it interacts with external cell components and how it engulfs and kills cells (phagocytosis). Recent research suggests that optimal phagocytosis requires signalling events from the cell surface to the nucleus via the cytoplasm, and the induction of several factors that are transported to the plasma membrane. Current research in other protozoans suggests the presence of proteins with nuclear localization signals, nuclear export signals and Ran proteins; however, there is limited literature on their functionality and their functional similarity to higher eukaryotes.Based on learnings from the development of antivirals, nuclear transport elements in E. histolytica may present viable, specific, therapeutic targets.In this review, we aim to summarize our limited knowledge of the eukaryotic nuclear transport mechanisms that are conserved and may function in E. histolytica.
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10
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Ávila AR, Cabezas-Cruz A, Gissot M. mRNA export in the apicomplexan parasite Toxoplasma gondii: emerging divergent components of a crucial pathway. Parasit Vectors 2018; 11:62. [PMID: 29370868 PMCID: PMC5785795 DOI: 10.1186/s13071-018-2648-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Accepted: 01/15/2018] [Indexed: 01/08/2023] Open
Abstract
Control of gene expression is crucial for parasite survival and is the result of a series of processes that are regulated to permit fine-tuning of gene expression in response to biological changes during the life-cycle of apicomplexan parasites. Control of mRNA nuclear export is a key process in eukaryotic cells but is poorly understood in apicomplexan parasites. Here, we review recent knowledge regarding this process with an emphasis on T. gondii. We describe the presence of divergent orthologs and discuss structural and functional differences in export factors between apicomplexans and other eukaryotic lineages. Undoubtedly, the use of the CRISPR/Cas9 system in high throughput screenings associated with the discovery of mRNA nuclear export complexes by proteomic analysis will contribute to identify these divergent factors. Ligand-based or structure-based strategies may be applied to investigate the potential use of these proteins as targets for new antiprotozoal agents.
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Affiliation(s)
- Andréa Rodrigues Ávila
- Instituto Carlos Chagas, FIOCRUZ, Rua Algacyr Munhoz Mader, 3775. CIC, Curitiba, PR, 81350-010, Brazil. .,UMR BIPAR, Animal Health Laboratory, ANSES, INRA, ENVA, Maisons Alfort, Cedex, France.
| | - Alexjandro Cabezas-Cruz
- UMR BIPAR, Animal Health Laboratory, ANSES, INRA, ENVA, Maisons Alfort, Cedex, France.,Institute of Parasitology, Biology Center, Czech Academy of Sciences, České Budějovice, Czech Republic.,Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic
| | - Mathieu Gissot
- University of Lille, CNRS, Inserm, CHU Lille, Institut Pasteur de Lille, U1019 - UMR 8204 - CIIL - Centre d'Infection et d'Immunité de Lille, F-59000, Lille, France.
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11
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Wilson SK, Knoll LJ. Patatin-like phospholipases in microbial infections with emerging roles in fatty acid metabolism and immune regulation by Apicomplexa. Mol Microbiol 2017; 107:34-46. [PMID: 29090840 DOI: 10.1111/mmi.13871] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2017] [Revised: 10/23/2017] [Accepted: 10/26/2017] [Indexed: 12/22/2022]
Abstract
Emerging lipidomic technologies have enabled researchers to dissect the complex roles of phospholipases in lipid metabolism, cellular signaling and immune regulation. Host phospholipase products are involved in stimulating and resolving the inflammatory response to pathogens. While many pathogen-derived phospholipases also manipulate the immune response, they have recently been shown to be involved in lipid remodeling and scavenging during replication. Animal and plant hosts as well as many pathogens contain a family of patatin-like phospholipases, which have been shown to have phospholipase A2 activity. Proteins containing patatin-like phospholipase domains have been identified in protozoan parasites within the Apicomplexa phylum. These parasites are the causative agents of some of the most widespread human diseases. Malaria, caused by Plasmodium spp., kills nearly half a million people worldwide each year. Toxoplasma and Cryptosporidium infect millions of people each year with lethal consequences in immunocompromised populations. Parasite-derived patatin-like phospholipases are likely effective drug targets and progress in the tools available to the Apicomplexan field will allow for a closer look at the interplay of lipid metabolism and immune regulation during host infection.
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Affiliation(s)
- Sarah K Wilson
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Laura J Knoll
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, 53706, USA
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12
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Milligan-Myhre K, Wilson SK, Knoll LJ. Developmental change in translation initiation alters the localization of a common microbial protein necessary for Toxoplasma chronic infection. Mol Microbiol 2016; 102:1086-1098. [PMID: 27671212 PMCID: PMC5161674 DOI: 10.1111/mmi.13538] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/22/2016] [Indexed: 11/28/2022]
Abstract
The Toxoplasma gondii cyst stage is resistant to drug therapy. To identify potential targets for new therapeutics, we screened insertional mutants of T. gondii for a reduced ability to form cysts in the brains of mice. In one of these mutants, named 38C3, the mutagenesis plasmid inserted into the mRNA of a protein that is highly conserved in microbes but is not present in humans. The mutation in 38C3 causes reduced brain cyst production during chronic infection, but does not affect acute virulence, so the disrupted gene and protein are called T. gondii Brain Colonization Protein 1 (TgBCP1). TgBCP1 has three potential in frame start codons that produce 51, 33 or 25 kDa proteins. In rapidly replicating tachyzoites, translation initiates at the third methionine, producing the 25 kDa form that is conserved in many bacteria and protozoans. Brain cysts exclusively express the 51 kDa form of TgBCP1, which is secreted from the parasites and localizes to the cyst wall. Only expression of the long form of TgBCP1 restored cyst formation in the 38C3 mutant. TgBCP1 is essential for cyst formation and is the first example of a developmental regulation in translation initiation site preference for a T. gondii protein.
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Affiliation(s)
| | - Sarah K. Wilson
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI 53706
| | - Laura J. Knoll
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI 53706
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13
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Vinayak S, Brooks CF, Naumov A, Suvorova ES, White MW, Striepen B. Genetic manipulation of the Toxoplasma gondii genome by fosmid recombineering. mBio 2014; 5:e02021. [PMID: 25467441 PMCID: PMC4324243 DOI: 10.1128/mbio.02021-14] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Accepted: 11/06/2014] [Indexed: 12/26/2022] Open
Abstract
UNLABELLED Apicomplexa are obligate intracellular parasites that cause important diseases in humans and animals. Manipulating the pathogen genome is the most direct way to understand the functions of specific genes in parasite development and pathogenesis. In Toxoplasma gondii, nonhomologous recombination is typically highly favored over homologous recombination, a process required for precise gene targeting. Several approaches, including the use of targeting vectors that feature large flanks to drive site-specific recombination, have been developed to overcome this problem. We have generated a new large-insert repository of T. gondii genomic DNA that is arrayed and sequenced and covers 95% of all of the parasite's genes. Clones from this fosmid library are maintained at single copy, which provides a high level of stability and enhances our ability to modify the organism dramatically. We establish a robust recombineering pipeline and show that our fosmid clones can be easily converted into gene knockout constructs in a 4-day protocol that does not require plate-based cloning but can be performed in multiwell plates. We validated this approach to understand gene function in T. gondii and produced a conditional null mutant for a nucleolar protein belonging to the NOL1/NOP2/SUN family, and we show that this gene is essential for parasite growth. We also demonstrate a powerful complementation strategy in the context of chemical mutagenesis and whole-genome sequencing. This repository is an important new resource that will accelerate both forward and reverse genetic analysis of this important pathogen. IMPORTANCE Toxoplasma gondii is an important genetic model to understand intracellular parasitism. We show here that large-insert genomic clones are effective tools that enhance homologous recombination and allow us to engineer conditional mutants to understand gene function. We have generated, arrayed, and sequenced a fosmid library of T. gondii genomic DNA in a copy control vector that provides excellent coverage of the genome. The fosmids are maintained in a single-copy state that dramatically improves their stability and allows modification by means of a simple and highly scalable protocol. We show here that modified and unmodified fosmid clones are powerful tools for forward and reverse genetics.
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Affiliation(s)
- Sumiti Vinayak
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia, USA
| | - Carrie F Brooks
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia, USA
| | - Anatoli Naumov
- Departments of Molecular Medicine & Global Health, University of South Florida, Tampa, Florida, USA
| | - Elena S Suvorova
- Departments of Molecular Medicine & Global Health, University of South Florida, Tampa, Florida, USA
| | - Michael W White
- Departments of Molecular Medicine & Global Health, University of South Florida, Tampa, Florida, USA
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Rose SL, Fulton JM, Brown CM, Natale F, Van Mooy BAS, Bidle KD. Isolation and characterization of lipid rafts inEmiliania huxleyi: a role for membrane microdomains in host-virus interactions. Environ Microbiol 2014; 16:1150-66. [DOI: 10.1111/1462-2920.12357] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Accepted: 12/05/2013] [Indexed: 01/21/2023]
Affiliation(s)
- Suzanne L. Rose
- Institute of Marine and Coastal Sciences; Rutgers University; New Brunswick NJ USA
| | - James M. Fulton
- Department of Marine Chemistry and Geochemistry; Woods Hole Oceanographic Institution; Woods Hole MA USA
| | - Christopher M. Brown
- Institute of Marine and Coastal Sciences; Rutgers University; New Brunswick NJ USA
| | - Frank Natale
- Institute of Marine and Coastal Sciences; Rutgers University; New Brunswick NJ USA
| | - Benjamin A. S. Van Mooy
- Department of Marine Chemistry and Geochemistry; Woods Hole Oceanographic Institution; Woods Hole MA USA
| | - Kay D. Bidle
- Institute of Marine and Coastal Sciences; Rutgers University; New Brunswick NJ USA
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15
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Smolarz B, Wilczyński J, Nowakowska D. DNA repair mechanisms and Toxoplasma gondii infection. Arch Microbiol 2014; 196:1-8. [PMID: 24337694 PMCID: PMC3890036 DOI: 10.1007/s00203-013-0944-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Revised: 10/15/2013] [Accepted: 11/23/2013] [Indexed: 01/22/2023]
Abstract
Lately, we can observe significant progress in understanding mechanism of DNA repair owing to fast methods of DNA sequence analysis from different organisms the revealing of structure and function of DNA repair proteins in prokaryota and eukaryota. The protozoan parasites survival depends on DNA repair systems. Better understanding of DNA repair systems can help in new antipathogen drug development. This review is aimed at updating our current knowledge of the various repair pathways by providing an overview of DNA repair genes regarding Toxoplasma gondii infections and the corresponding proteins, participating either directly in DNA repair, or in checkpoint control and signaling of DNA damage.
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Affiliation(s)
- Beata Smolarz
- Department of Fetal-Maternal Medicine and Gynecology, Polish Mother’s Memorial Hospital Research Institute, 281/289 Rzgowska Street, 93-338 Lodz, Poland
| | - Jan Wilczyński
- Department of Fetal-Maternal Medicine and Gynecology, Polish Mother’s Memorial Hospital Research Institute, 281/289 Rzgowska Street, 93-338 Lodz, Poland
| | - Dorota Nowakowska
- Department of Fetal-Maternal Medicine and Gynecology, Polish Mother’s Memorial Hospital Research Institute, 281/289 Rzgowska Street, 93-338 Lodz, Poland
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16
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Disruption of the expression of a non-coding RNA significantly impairs cellular differentiation in Toxoplasma gondii. Int J Mol Sci 2012; 14:611-24. [PMID: 23275028 PMCID: PMC3565285 DOI: 10.3390/ijms14010611] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Revised: 12/14/2012] [Accepted: 12/18/2012] [Indexed: 11/17/2022] Open
Abstract
The protozoan parasite Toxoplasma gondii is an important human and veterinary pathogen. Asexual replication of T. gondii in humans and intermediate hosts is characterized by two forms: rapidly growing “tachyzoites” and latent “bradyzoite” tissue cysts. Tachyzoites are responsible for acute illness and congenital neurological birth defects, while the more slowly dividing bradyzoite form can remain latent within the tissues for many years, representing a threat to immunocompromised patients. We have developed a genetic screen to identify regulatory genes that control parasite differentiation and have isolated mutants that fail to convert to bradyzoites. One of these mutants has an insertion disrupting a locus that encodes a developmentally regulated non-coding RNA transcript, named Tg-ncRNA-1. Microarray hybridizations suggest that Tg-ncRNA-1 is involved in the early steps of bradyzoite differentiation. Since Tg-ncRNA-1 does not contain an open reading frame, we used the algorithm Coding Potential Calculator (CPC) that evaluates the protein-coding potential of a transcript, to classify Tg-ncRNA-1. The CPC results strongly indicate that Tg-ncRNA-1 is a non-coding RNA (ncRNA). Interestingly, a previously generated mutant also contains an insertion in Tg-ncRNA-1. We show that both mutants have a decreased ability to form bradyzoites, and complementation of both mutants with wild-type Tg-ncRNA-1 restores the ability of the parasites to differentiate. It has been shown that an important part of bradyzoite differentiation is transcriptionally controlled, but this is the first time that a non-coding RNA is implicated in this process.
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Skariah S, Bednarczyk RB, McIntyre MK, Taylor GA, Mordue DG. Discovery of a novel Toxoplasma gondii conoid-associated protein important for parasite resistance to reactive nitrogen intermediates. THE JOURNAL OF IMMUNOLOGY 2012; 188:3404-15. [PMID: 22387554 DOI: 10.4049/jimmunol.1101425] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Toxoplasma gondii modifies its host cell to suppress its ability to become activated in response to IFN-γ and TNF-α and to develop intracellular antimicrobial effectors, including NO. Mechanisms used by T. gondii to modulate activation of its infected host cell likely underlie its ability to hijack monocytes and dendritic cells during infection to disseminate to the brain and CNS where it converts to bradyzoites contained in tissue cysts to establish persistent infection. To identify T. gondii genes important for resistance to the effects of host cell activation, we developed an in vitro murine macrophage infection and activation model to identify parasite insertional mutants that have a fitness defect in infected macrophages following activation but normal invasion and replication in naive macrophages. We identified 14 independent T. gondii insertional mutants out of >8000 screened that share a defect in their ability to survive macrophage activation due to macrophage production of reactive nitrogen intermediates (RNIs). These mutants have been designated counter-immune mutants. We successfully used one of these mutants to identify a T. gondii cytoplasmic and conoid-associated protein important for parasite resistance to macrophage RNIs. Deletion of the entire gene or just the region encoding the protein in wild-type parasites recapitulated the RNI-resistance defect in the counter-immune mutant, confirming the role of the protein in resistance to macrophage RNIs.
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Affiliation(s)
- Sini Skariah
- Department of Microbiology and Immunology, New York Medical College, Valhalla, NY 10595, USA
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18
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Cummins J, Gahan CG. Signature tagged mutagenesis in the functional genetic analysis of gastrointestinal pathogens. Gut Microbes 2012; 3:93-103. [PMID: 22555467 PMCID: PMC3370953 DOI: 10.4161/gmic.19578] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Signature tagged mutagenesis is a genetic approach that was developed to identify novel bacterial virulence factors. It is a negative selection method in which unique identification tags allow analysis of pools of mutants in mixed populations. The approach is particularly well suited to functional genetic analysis of the gastrointestinal phase of infection in foodborne pathogens and has the capacity to guide the development of novel vaccines and therapeutics. In this review we outline the technical principles underpinning signature-tagged mutagenesis as well as novel sequencing-based approaches for transposon mutant identification such as TraDIS (transposon directed insertion-site sequencing). We also provide an analysis of screens that have been performed in gastrointestinal pathogens which are a global health concern (Escherichia coli, Listeria monocytogenes, Helicobacter pylori, Vibrio cholerae and Salmonella enterica). The identification of key virulence loci through the use of signature tagged mutagenesis in mice and relevant larger animal models is discussed.
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Affiliation(s)
- Joanne Cummins
- Alimentary Pharmabiotic Centre; University College Cork; Cork, Ireland,Department of Microbiology; University College Cork; Cork, Ireland
| | - Cormac G.M. Gahan
- Alimentary Pharmabiotic Centre; University College Cork; Cork, Ireland,Department of Microbiology; University College Cork; Cork, Ireland,School of Pharmacy; University College Cork; Cork, Ireland,Correspondence to: Cormac G.M. Gahan,
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19
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Anderson-White B, Beck JR, Chen CT, Meissner M, Bradley PJ, Gubbels MJ. Cytoskeleton assembly in Toxoplasma gondii cell division. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2012; 298:1-31. [PMID: 22878103 PMCID: PMC4066374 DOI: 10.1016/b978-0-12-394309-5.00001-8] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Cell division across members of the protozoan parasite phylum Apicomplexa displays a surprising diversity between different species as well as between different life stages of the same parasite. In most cases, infection of a host cell by a single parasite results in the formation of a polyploid cell from which individual daughters bud in a process dependent on a final round of mitosis. Unlike other apicomplexans, Toxoplasma gondii divides by a binary process consisting of internal budding that results in only two daughter cells per round of division. Since T. gondii is experimentally accessible and displays the simplest division mode, it has manifested itself as a model for apicomplexan daughter formation. Here, we review newly emerging insights in the prominent role that assembly of the cortical cytoskeletal scaffold plays in the process of daughter parasite formation.
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Affiliation(s)
| | - Josh R. Beck
- University of California Los Angeles, Department of Microbiology, Immunology and Molecular Genetics, Los Angeles, CA 90095, USA
| | - Chun-Ti Chen
- Boston College, Department of Biology, Chestnut Hill, MA 02467, USA
| | - Markus Meissner
- Division of Infection and Immunity, Institute of Biomedical Life Sciences, Wellcome Centre for Molecular Parasitology, Glasgow Biomedical Research Centre, University of Glasgow, 120 University Place, Glasgow G12 8TA, UK
| | - Peter J. Bradley
- University of California Los Angeles, Department of Microbiology, Immunology and Molecular Genetics, Los Angeles, CA 90095, USA
| | - Marc-Jan Gubbels
- Boston College, Department of Biology, Chestnut Hill, MA 02467, USA
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20
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Payne TM, Payne AJ, Knoll LJ. A Toxoplasma gondii mutant highlights the importance of translational regulation in the apicoplast during animal infection. Mol Microbiol 2011; 82:1204-16. [PMID: 22059956 DOI: 10.1111/j.1365-2958.2011.07879.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Toxoplasma gondii is an obligate intracellular parasite of all warm-blooded animals. We previously described a forward genetic screen to identify T. gondii mutants defective in the establishment of a chronic infection. One of the mutants isolated was disrupted in the 3' untranslated region (3'UTR) of an orthologue of bacterial translation elongation factor G (EFG). The mutant does not have a growth defect in tissue culture. Genetic complementation of this mutant with the genomic locus of TgEFG restores virulence in an acute infection mouse model. Epitope tagged TgEFG localized to the apicoplast, via a non-canonical targeting signal, where it functions as an elongation factor for translation in the apicoplast. Comparisons of TgEFG expression constructs with wild-type or mutant 3'UTRs showed that a wild-type 3'UTR is necessary for translation of TgEFG. In tissue culture, the TgEFG transcript is equally abundant in wild-type and mutant parasites; however, during an animal infection, the TgEFG transcript is increased more than threefold in the mutant. These results highlight that in tissue culture, translation in the apicoplast can be diminished, but during an animal infection, translation in the apicoplast must be fully functional.
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Affiliation(s)
- T Matthew Payne
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI 53706, USA
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21
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O'Brien KB, Schultz-Cherry S, Knoll LJ. Parasite-mediated upregulation of NK cell-derived gamma interferon protects against severe highly pathogenic H5N1 influenza virus infection. J Virol 2011; 85:8680-8. [PMID: 21734055 PMCID: PMC3165849 DOI: 10.1128/jvi.05142-11] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Accepted: 06/23/2011] [Indexed: 02/01/2023] Open
Abstract
Outbreaks of influenza A viruses are associated with significant human morbidity worldwide. Given the increasing resistance to the available influenza drugs, new therapies for the treatment of influenza virus infection are needed. An alternative approach is to identify products that enhance a protective immune response. In these studies, we demonstrate that infecting mice with the Th1-inducing parasite Toxoplasma gondii prior to highly pathogenic avian H5N1 influenza virus infection led to decreased lung viral titers and enhanced survival. A noninfectious fraction of T. gondii soluble antigens (STAg) elicited an immune response similar to that elicited by live parasites, and administration of STAg 2 days after H5N1 influenza virus infection enhanced survival, lowered viral titers, and reduced clinical disease. STAg administration protected H5N1 virus-infected mice lacking lymphocytes, suggesting that while the adaptive immune response was not required for enhanced survival, it was necessary for STAg-mediated viral clearance. Mechanistically, we found that administration of STAg led to increased production of gamma interferon (IFN-γ) from natural killer (NK) cells, which were both necessary and sufficient for survival. Further, administration of exogenous IFN-γ alone enhanced survival from H5N1 influenza virus infection, although not to the same level as STAg treatment. These studies demonstrate that a noninfectious T. gondii extract enhances the protective immune response against severe H5N1 influenza virus infections even when a single dose is administered 2 days postinfection.
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Affiliation(s)
- Kevin B. O'Brien
- Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, Tennessee 38105
- Department of Medical Microbiology and Immunology, University of Wisconsin, Madison, Wisconsin 53706
| | - Stacey Schultz-Cherry
- Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, Tennessee 38105
| | - Laura J. Knoll
- Department of Medical Microbiology and Immunology, University of Wisconsin, Madison, Wisconsin 53706
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22
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Milligan-Myhre KC, Rooney PJ, Knoll LJ. Examination of a virulence mutant uncovers the ribosome biogenesis regulatory protein of Toxoplasma gondii. J Parasitol 2011; 97:1173-7. [PMID: 21736491 DOI: 10.1645/ge-2741.1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Several insertional mutants identified in a screen for Toxoplasma gondii that were defective in establishing a chronic infection had a common site of plasmid insertion. This insertion site was determined to be 43 bp upstream of the transcription initiation site of a gene whose predicted product has homology to ribosome biogenesis regulatory protein Rrs1p, an essential protein required for ribosome biogenesis in Saccharomyces cerevisiae. Northern blot analysis of this locus, termed TgRRS1 , showed that in the C3 mutant, the full-length transcript is down-regulated and at least 1 new smaller transcript is present. Restoration of the intact predicted promoter and locus to TgRRS1 insertional mutant strain C3 did not restore brain cyst formation to the levels of the parent strain. Epitope-tagged TgRRS1 was found to localize to the parasite nucleolus, in an area corresponding to the granular component region. TgRRS1 can serve as a marker for the sub-nucleolar granular component region of T. gondii.
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23
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Payne TM, Lund PJ, Knoll LJ. A transmembrane domain containing pellicle protein of Toxoplasma gondii enhances virulence and invasion after extracellular stress. Mol Biochem Parasitol 2011; 179:107-10. [PMID: 21669237 DOI: 10.1016/j.molbiopara.2011.05.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2010] [Revised: 05/07/2011] [Accepted: 05/27/2011] [Indexed: 11/19/2022]
Abstract
To identify Toxoplasma gondii genes important in the establishment of a persistent infection, we previously used signature-tagged mutagenesis to identify mutants with reduced cyst numbers in the brains of mice. One of the mutants, 95C5, has an insertion within a predicted six transmembrane domain protein, which localizes to the parasite pellicle, thus we named it transmembrane pellicle protein 1 (TgTPP1). Although the 95C5 mutant was found be reduced in its ability to form brain cysts, it is defective during acute infection. Addition of TgTPP1 expressed from its endogenous promoter restored the acute lethality of the 95C5 mutant to parental levels. The 95C5 mutant does not have a growth defect in standard tissue culture conditions; however, we found a significant defect in host cell penetration after extracellular stress. Overall, TgTPP1 may function during acute infection by enhancing the parasites ability to invade after extracellular stress.
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Affiliation(s)
- T Matthew Payne
- Department of Medical Microbiology and Immunology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53706, United States
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24
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Abstract
As biomedical research becomes increasingly data-intensive, it is increasingly essential to integrate genomic-scale datasets, so as to generate a more holistic picture of complex biological processes. The systems biology paradigm may differ in strategy from traditional reductionist scientific methods, but the goal remains the same: to generate tenable hypotheses driving the experimental elucidation of biological mechanisms. Intracellular pathogens provide an excellent opportunity for systems analysis, as many of these organisms are amenable to genetic manipulation, allowing their biology to be played off against that of the host. Moreover, many of the most fundamental biological properties of these microbes (host cell invasion, immune evasion, intracellular replication, long-term persistence) are directly linked to pathogenesis and readily quantifiable using genomic-scale technologies. In this review, we summarize and discuss some of the available and foreseeable functional genomics datasets pertaining to host-pathogen interactions and suggest that the host-pathogen interface represents a promising, tractable challenge for systems biological analysis. Success will require developing and leveraging new technologies, expanding data acquisition, and increasing public access to comprehensive datasets, to assemble quantitative and testable models of the host-pathogen relationship.
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Affiliation(s)
- Daniel P Beiting
- Department of Biology, Penn Genome Frontiers Institute, University of Pennsylvania, Philadelphia, PA 19104, USA
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25
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Involvement of a Toxoplasma gondii chromatin remodeling complex ortholog in developmental regulation. PLoS One 2011; 6:e19570. [PMID: 21655329 PMCID: PMC3104990 DOI: 10.1371/journal.pone.0019570] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2010] [Accepted: 04/12/2011] [Indexed: 01/18/2023] Open
Abstract
The asexual cycle of the parasite Toxoplasma gondii has two developmental stages: a rapidly replicating form called a tachyzoite and a slow growing cyst form called a bradyzoite. While the importance of ATP-independent histone modifications for gene regulation in T. gondii have been demonstrated, ATP-dependent chromatin remodeling pathways have not been examined. In this study we characterized C9, an insertional mutant showing reduced expression of bradyzoite differentiation marker BAG1, in cultured human fibroblasts. This mutant contains an insertion in the gene encoding TgRSC8, which is homologous to the Saccharomyces cerevisiae proteins Rsc8p (remodel the structure of chromatin complex subunit 8) and Swi3p (switch/sucrose non-fermentable [SWI/SNF]) of ATP-dependent chromatin-remodeling complexes. In the C9 mutant, TgRSC8 is the downstream open reading frame on a dicistronic transcript. Though protein was expressed from the downstream gene of the dicistron, TgRSC8 levels were decreased in C9 from those of wild-type parasites, as determined by western immunoblot and flow cytometry. As TgRSC8 localized to the parasite nucleus, we postulated a role in gene regulation. Transcript levels of several markers were assessed by quantitative PCR to test this hypothesis. The C9 mutant displayed reduced steady state transcript levels of bradyzoite-induced genes BAG1, LDH2, SUSA1, and ENO1, all of which were significantly increased with addition of TgRSC8 to the mutant. Transcript levels of some bradyzoite markers were unaltered in C9, or unable to be increased by complementation with TgRSC8, indicating multiple pathways control bradyzoite-upregulated genes. Together, these data suggest a role for TgRSC8 in control of bradyzoite-upregulated gene expression. Thus chromatin remodeling, by both ATP-independent and dependent mechanisms, is an important mode of gene regulation during stage differentiation in parasites.
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26
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Lescault PJ, Thompson AB, Patil V, Lirussi D, Burton A, Margarit J, Bond J, Matrajt M. Genomic data reveal Toxoplasma gondii differentiation mutants are also impaired with respect to switching into a novel extracellular tachyzoite state. PLoS One 2010; 5:e14463. [PMID: 21209930 PMCID: PMC3012682 DOI: 10.1371/journal.pone.0014463] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2010] [Accepted: 11/22/2010] [Indexed: 11/19/2022] Open
Abstract
Toxoplasma gondii pathogenesis includes the invasion of host cells by extracellular parasites, replication of intracellular tachyzoites, and differentiation to a latent bradyzoite stage. We present the analysis of seven novel T. gondii insertional mutants that do not undergo normal differentiation to bradyzoites. Microarray quantification of the variation in genome-wide RNA levels for each parasite line and times after induction allowed us to describe states in the normal differentiation process, to analyze mutant lines in the context of these states, and to identify genes that may have roles in initiating the transition from tachyzoite to bradyzoite. Gene expression patterns in wild-type parasites undergoing differentiation suggest a novel extracellular state within the tachyzoite stage. All mutant lines exhibit aberrant regulation of bradyzoite gene expression and notably some of the mutant lines appear to exhibit high proportions of the intracellular tachyzoite state regardless of whether they are intracellular or extracellular. In addition to the genes identified by the insertional mutagenesis screen, mixture model analysis allowed us to identify a small number of genes, in mutants, for which expression patterns could not be accounted for using the three parasite states – genes that may play a mechanistic role in switching from the tachyzoite to bradyzoite stage.
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Affiliation(s)
- Pamela J. Lescault
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America
| | - Ann B. Thompson
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America
| | - Veerupaxagouda Patil
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America
| | - Dario Lirussi
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America
| | - Amanda Burton
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America
| | - Juan Margarit
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America
| | - Jeffrey Bond
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America
| | - Mariana Matrajt
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America
- * E-mail:
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27
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Rooney PJ, Ayong L, Tobin CM, Moreno SNJ, Knoll LJ. TgVTC2 is involved in polyphosphate accumulation in Toxoplasma gondii. Mol Biochem Parasitol 2010; 176:121-6. [PMID: 21195114 DOI: 10.1016/j.molbiopara.2010.12.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2010] [Revised: 12/20/2010] [Accepted: 12/22/2010] [Indexed: 10/18/2022]
Abstract
Polyphosphate is found in every cell, having roles in diverse processes, including differentiation and response to stress. In this study, we characterize a Toxoplasma gondii mutant containing an insertion within the carboxy-terminal end of a homolog of Saccharomyces cerevisiae Vtc2p, a component of the polyphosphate synthetic machinery. Locus TgVTC2 encodes a 140kDa protein containing conserved SPX, VTC and transmembrane domains. TgVTC2 localizes in punctate spots within the cytoplasm that do not co-localize with known markers. The TgVTC2 mutant showed dramatically reduced polyphosphate accumulation, a defect restored by introduction of TgVTC2 to the mutant. Insertion within TgVTC2 resulted in increased transcript levels for two loci, including a putative FIKK kinase. These transcript levels were restored to wild-type levels upon complementation with the TgVTC2 locus. The TgVTC2 locus was refractory to knockout, and may be essential. Analysis of this TgVTC2 mutant will facilitate dissection of the T. gondii polyphosphate synthesis pathway.
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Affiliation(s)
- Peggy J Rooney
- Department of Medical Microbiology and Immunology, University of Wisconsin School of Medicine and Public Health, Microbial Sciences Building Room 3345, 1550 Linden Drive, Madison, WI 53706, USA
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Jammallo L, Eidell K, Davis PH, Dufort FJ, Cronin C, Thirugnanam S, Chiles TC, Roos DS, Gubbels MJ. An insertional trap for conditional gene expression in Toxoplasma gondii: identification of TAF250 as an essential gene. Mol Biochem Parasitol 2010; 175:133-43. [PMID: 21035508 DOI: 10.1016/j.molbiopara.2010.10.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2010] [Revised: 10/18/2010] [Accepted: 10/19/2010] [Indexed: 11/18/2022]
Abstract
Toxoplasmosis is characterized by fast lytic replication cycles leading to severe tissue lesions. Successful host cell invasion is essential for pathogenesis. The division cycle of Toxoplasma gondii is characterized by an unusual cell cycle progression and a distinct internal budding mechanism. To identify essential genes involved in the lytic cycle we devised an insertional gene trapping strategy using the Tet-transactivator system. In essence, a random, active promoter is displaced with a tetracycline regulatable promoter, which if in an essential gene, will result in a conditionally lethal phenotype upon tetracycline addition. We isolated eight mutants with growth defects, two of which displayed modest invasion defects, one of which had an additional cell cycle defect. The trapped loci were identified using expression microarrays, exploiting the tetracycline dependent expression of the trapped genes. In mutant 3.3H6 we identified TCP-1, a component of the chaperonin protein folding machinery under the control of the Tet promoter. However, this gene was not critical for growth of mutant 3.3H6. Subsequently, we identified a suppressor gene encoding a protein with a hypothetical function by guided cosmid complementation. In mutant 4.3B13, we identified TAF250, an RNA polymerase II complex component, as the trapped, essential gene. Furthermore, by mapping the plasmid insertion boundaries we identified multiple genomic rearrangements, which hint at a potential replication dependent DNA repair mechanism. Furthermore, these rearrangements provide an explanation for inconsistent locus rescue results observed by molecular biological approaches. Taken together, we have added an approach to identify and study essential genes in Toxoplasma.
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Affiliation(s)
- Lauren Jammallo
- Department of Biology, Boston College, Chestnut Hill, MA, USA
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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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Isolation of Toxoplasma gondii development mutants identifies a potential proteophosphogylcan that enhances cyst wall formation. Mol Biochem Parasitol 2009; 169:120-3. [PMID: 19879901 DOI: 10.1016/j.molbiopara.2009.10.006] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2009] [Revised: 10/13/2009] [Accepted: 10/20/2009] [Indexed: 11/20/2022]
Abstract
Within warm-blooded animals, Toxoplasma gondii switches from an actively replicating form called a tachyzoite into a slow growing encysted form called a bradyzoite. To uncover the genes involved in bradyzoite development, we screened over 8000 T. gondii insertional mutants by immunofluorescence microscopy. We identified nine bradyzoite development mutants that were defective in both cyst wall formation and expression of a bradyzoite specific heat shock protein. One of these mutants, named 42F5, contained an insertion into the predicted gene TGME49_097520. The disrupted protein is serine/proline-rich with homology to proteophosphoglycans from Leishmania. T. gondii proteophosphoglycan (GU182879) expressed from the native promoter was undetectable in tachyzoites, but bradyzoites show punctate spots within the parasite and staining around the parasitophorous vacuole. Complementation of the 42F5 mutant with GU182879 expressed from either the alpha-tubulin or native promoter restores cyst wall formation. Overall, GU182879 is upregulated in bradyzoites and enhances cyst wall component expression and assembly.
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A transmembrane domain-containing surface protein from Toxoplasma gondii augments replication in activated immune cells and establishment of a chronic infection. Infect Immun 2009; 77:3731-9. [PMID: 19581395 DOI: 10.1128/iai.00450-09] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Toxoplasma gondii mutants identified as defective in the establishment of chronic infection were screened to isolate those specifically impaired in their ability to replicate within activated macrophages. One of the identified mutants contains an insertion in the hypothetical gene TGME49_111670. Genetic complementation restores the ability of the mutant to replicate in immune cells and produce cysts in the brains of mice. While the mutant is more sensitive to nitric oxide than is its parental strain, it is not defective in its ability to suppress nitric oxide. The disrupted protein has no significant homology to proteins with known functions, but is predicted to have one transmembrane domain. Immunofluorescence shows the protein on the parasite surface, even in activated macrophages, colocalizing with a tachyzoite surface antigen, SAG1, and oriented with its C-terminal end external. Western analysis reveals that the protein is downregulated in bradyzoites. Despite the tachyzoite specificity of this protein, mice infected with the mutant succumb to acute infection similarly to those infected with the parent strain. Serum samples from mice with chronic T. gondii infection react to a polypeptide from TGME49_11670, indicating that the protein is seen by the immune system during infection. This study is the first to characterize a T. gondii surface protein that contains a transmembrane domain and show that the protein contributes to parasite replication in activated immune cells and the establishment of chronic infection.
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Frankel MB, Knoll LJ. The ins and outs of nuclear trafficking: unusual aspects in apicomplexan parasites. DNA Cell Biol 2009; 28:277-84. [PMID: 19348590 DOI: 10.1089/dna.2009.0853] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Apicomplexa is a phylum within the kingdom Protista that contains some of the most significant threats to public health. One of the members of this phylum, Toxoplasma gondii, is amenable to molecular genetic analyses allowing for the identification of factors critical for colonization and disease. A pathway found to be important for T. gondii pathogenesis is the Ran network of nuclear trafficking. Bioinformatics analysis of apicomplexan genomes shows that while Ran is well conserved, the key regulators of Ran--Regulator of Chromosome Condensation 1 and Ran GTPase activating protein--are either highly divergent or absent. Likewise, several import and export receptor molecules that are crucial for nuclear transport are either not present or have experienced genetic drift such that they are no longer recognizable by bioinformatics tools. In this minireview we describe the basics of nuclear trafficking and compare components within apicomplexans to defined systems in humans and yeast. A detailed analysis of the nuclear trafficking network in these eukaryotes is required to understand how this potentially unique cellular biological pathway contributes to host-parasite interactions.
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Affiliation(s)
- Matthew B Frankel
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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Narayanan NN, Grosic S, Tasma IM, Grant D, Shoemaker R, Bhattacharyya MK. Identification of candidate signaling genes including regulators of chromosome condensation 1 protein family differentially expressed in the soybean-Phytophthora sojae interaction. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 2009; 118:399-412. [PMID: 18825360 DOI: 10.1007/s00122-008-0895-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2007] [Accepted: 09/06/2008] [Indexed: 05/07/2023]
Abstract
Stem and root rot caused by the oomycete pathogen, Phytophthora sojae, is a serious soybean disease. Use of Phytophthora resistance genes (Rps) in soybean cultivars has been very effective in controlling this pathogen. Resistance encoded by Rps genes is manifested through activation of defense responses. In order to identify candidate signaling genes involved in the expression of Phytophthora resistance in soybean, a cDNA library was prepared from infected etiolated hypocotyl tissues of a Phytophthora resistant soybean cultivar harvested 2 and 4 h following P. sojae inoculation. In silico subtraction of 101,833 expressed sequence tags (ESTs) originating from unstressed cDNA libraries from 4,737 ESTs of this library resulted in identification of 204 genes that were absent in the unstressed libraries. Of the 204 identified genes, seven were P. sojae genes. Putative function of 91 of the 204 genes could not be assigned based on sequence comparison. Macroarray analyses of all 204 genes led to identification of 60 genes including 15 signaling-related soybean genes and three P. sojae genes, transcripts of which were induced twofold in P. sojae-infected tissues as compared to that in water controls. Eight soybean genes were down-regulated twofold following P. sojae infection as compared to water controls. Differential expression of a few selected genes was confirmed by conducting Northern and RT-PCR analyses. We have shown that two putative regulators of chromosome condensation 1 (RCC1) family proteins were down-regulated in the incompatible interaction. This observation suggested that the nucleocytoplasmic transport function for trafficking protein and non-coding RNA is suppressed during expression of race-specific Phytophthora resistance. Characterization of a cDNA library generated from tissues harvested almost immediately following P. sojae-infection of a resistant cultivar allowed us to identify many candidate signaling genes that are presumably involved in regulating the expression of defense-related pathways for expression of Phytophthora resistance in soybean.
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Frickel EM, Sahoo N, Hopp J, Gubbels MJ, Craver MPJ, Knoll LJ, Ploegh HL, Grotenbreg GM. Parasite stage-specific recognition of endogenous Toxoplasma gondii-derived CD8+ T cell epitopes. J Infect Dis 2008; 198:1625-33. [PMID: 18922097 PMCID: PMC4771975 DOI: 10.1086/593019] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
BACKGROUND BALB/c mice control infection with the obligate intracellular parasite Toxoplasma gondii and develop a latent chronic infection in the brain, as do immunocompetent humans. Interferon-gamma-producing CD8+ T cells provide essential protection against T. gondii infection, but the epitopes recognized have so far remained elusive. METHODS We employed caged major histocompatibility complex molecules to generate approximately 250 H-2L(d) tetramers and to distinguish T. gondii-specific CD8+ T cells in BALB/c mice. RESULTS We identified 2 T. gondii-specific H-2L(d)-restricted T cell epitopes, one from dense granule protein GRA4 and the other from rhoptry protein ROP7. H-2L(d)/GRA4 reactive T cells from multiple organ sources predominated 2 weeks after infection, while the reactivity of the H-2L(d)/ROP7 T cells peaked 6-8 weeks after infection. BALB/c animals infected with T. gondii mutants defective in establishing a chronic infection showed altered levels of antigen-specific T cells, depending on the T. gondii mutant used. CONCLUSIONS Our results shed light on the identity and the parasite stage-specificity of 2 CD8+ T cell epitopes recognized in the acute and chronic phase of infection with T. gondii.
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Affiliation(s)
- Eva-Maria Frickel
- Whitehead Institute for Biomedical Research, 9 Cambridge Center, Cambridge, MA 02142, USA
| | - Nivedita Sahoo
- Department of Biology, Boston College, Chestnut Hill, MA 02467, USA
| | - Johnathan Hopp
- Department of Biology, Boston College, Chestnut Hill, MA 02467, USA
| | - Marc-Jan Gubbels
- Department of Biology, Boston College, Chestnut Hill, MA 02467, USA
| | - Mary Patricia J. Craver
- Department of Medical Microbiology and Immunology, University of Wisconsin Medical School, Madison, Wisconsin 53706, USA
| | - Laura J. Knoll
- Department of Medical Microbiology and Immunology, University of Wisconsin Medical School, Madison, Wisconsin 53706, USA
| | - Hidde L. Ploegh
- Whitehead Institute for Biomedical Research, 9 Cambridge Center, Cambridge, MA 02142, USA
| | - Gijsbert M. Grotenbreg
- Whitehead Institute for Biomedical Research, 9 Cambridge Center, Cambridge, MA 02142, USA
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Frankel MB, Knoll LJ. Functional analysis of key nuclear trafficking components reveals an atypical Ran network required for parasite pathogenesis. Mol Microbiol 2008; 70:410-20. [PMID: 18761691 DOI: 10.1111/j.1365-2958.2008.06419.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Protozoan parasites represent major public health challenges. Many aspects of their cell biology are distinct from their animal hosts, providing potential therapeutic targets. Toxoplasma gondii is a protozoan parasite that contains a divergent regulator of chromosome condensation 1 (TgRCC1) that is required for virulence and efficient nuclear trafficking. RCC1 proteins function as a guanine exchange factor for Ras-related nuclear protein (Ran), an abundant GTPase responsible for the majority of nucleocytoplasmic transport. Here we show that while there are dramatic differences from well-conserved RCC1 proteins, TgRCC1 associates with chromatin, interacts with Ran and complements a mammalian temperature-sensitive RCC1 mutant cell line. During the investigation of TgRCC1, we observed several unprecedented phenotypes for TgRan, despite a high level of sequence conservation. The cellular distribution of TgRan is found throughout the parasite cell, whereas Ran in late branching eukaryotes is predominantly nuclear. Additionally, T. gondii tolerates at least low-level expression of dominant lethal Ran mutants. Wild type parasites expressing dominant negative TgRan grew similarly to wild type in standard tissue culture conditions, but were attenuated in serum-starved host cells and mice. These growth characteristics paralleled the TgRCC1 mutant and highlight the importance of the nuclear transport pathway for virulence of eukaryotic pathogens.
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Affiliation(s)
- Matthew B Frankel
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, 1300 University Avenue, Madison, WI 53706, USA
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The cell cycle and Toxoplasma gondii cell division: tightly knit or loosely stitched? Int J Parasitol 2008; 38:1343-58. [PMID: 18703066 DOI: 10.1016/j.ijpara.2008.06.004] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2008] [Revised: 06/10/2008] [Accepted: 06/13/2008] [Indexed: 01/20/2023]
Abstract
The flexibility displayed by apicomplexan parasites to vary their mode of replication has intrigued biologists since their discovery by electron microscopy in the 1960s and 1970s. Starting in the 1990s we began to understand the cell biology of the cytoskeleton elements driving cytokinesis. By contrast, the molecular mechanisms that regulate the various division modes and how they translate into the budding process that uniquely characterizes this parasite family are much less understood. Although growth mechanisms are a neglected area of study, it is an important pathogenic parameter as fast division rounds are associated with fulminant infection whereas slower growth attenuates virulence, as is exploited in some vaccine strains. In this review we summarize a recent body of cell biological experiments that are rapidly leading to an understanding of the events that yield successful mitosis and cytokinesis in Toxoplasma. We place these observations within a cell cycle context with comments on how these events may be regulated by known eukaryotic checkpoints active in fission and budding yeasts as well as mammalian cells. The presence of cell cycle control mechanisms in the Apicomplexa is supported by our findings that identify several cell cycle checkpoints in Toxoplasma. The progress of the cell cycle is ultimately controlled by cyclin-Cdk pair activities, which are present throughout the Apicomplexa. Although many of the known controllers of cyclin-Cdk activity are present, several key controls cannot readily be identified, suggesting that apicomplexan parasites deviate at these points from the higher eukaryotic models. Altogether, new insights in Toxoplasma replication are reciprocally applied to hypothesize how other division modes in the Toxoplasma life cycle and in other Apicomplexa species could be controlled in terms of cell cycle checkpoint regulation.
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Gubbels MJ, Lehmann M, Muthalagi M, Jerome ME, Brooks CF, Szatanek T, Flynn J, Parrot B, Radke J, Striepen B, White MW. Forward genetic analysis of the apicomplexan cell division cycle in Toxoplasma gondii. PLoS Pathog 2008; 4:e36. [PMID: 18282098 PMCID: PMC2242837 DOI: 10.1371/journal.ppat.0040036] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2007] [Accepted: 01/07/2008] [Indexed: 11/18/2022] Open
Abstract
Apicomplexa are obligate intracellular pathogens that have fine-tuned their proliferative strategies to match a large variety of host cells. A critical aspect of this adaptation is a flexible cell cycle that remains poorly understood at the mechanistic level. Here we describe a forward genetic dissection of the apicomplexan cell cycle using the Toxoplasma model. By high-throughput screening, we have isolated 165 temperature sensitive parasite growth mutants. Phenotypic analysis of these mutants suggests regulated progression through the parasite cell cycle with defined phases and checkpoints. These analyses also highlight the critical importance of the peculiar intranuclear spindle as the physical hub of cell cycle regulation. To link these phenotypes to parasite genes, we have developed a robust complementation system based on a genomic cosmid library. Using this approach, we have so far complemented 22 temperature sensitive mutants and identified 18 candidate loci, eight of which were independently confirmed using a set of sequenced and arrayed cosmids. For three of these loci we have identified the mutant allele. The genes identified include regulators of spindle formation, nuclear trafficking, and protein degradation. The genetic approach described here should be widely applicable to numerous essential aspects of parasite biology.
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Affiliation(s)
- Marc-Jan Gubbels
- Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, Athens, Georgia, United States of America
- Department of Biology, Boston College, Chestnut Hill, Massachusetts, United States of America
| | - Margaret Lehmann
- Department of Veterinary Molecular Biology, Montana State University, Bozeman, Montana, United States of America
| | - Mani Muthalagi
- Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, Athens, Georgia, United States of America
| | - Maria E Jerome
- Department of Veterinary Molecular Biology, Montana State University, Bozeman, Montana, United States of America
| | - Carrie F Brooks
- Department of Veterinary Molecular Biology, Montana State University, Bozeman, Montana, United States of America
| | - Tomasz Szatanek
- Department of Biology, Boston College, Chestnut Hill, Massachusetts, United States of America
| | - Jayme Flynn
- Department of Biology, Boston College, Chestnut Hill, Massachusetts, United States of America
| | - Ben Parrot
- Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, Athens, Georgia, United States of America
| | - Josh Radke
- Department of Veterinary Molecular Biology, Montana State University, Bozeman, Montana, United States of America
| | - Boris Striepen
- Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, Athens, Georgia, United States of America
- * To whom correspondence should be addressed. E-mail: (BS); (MWW)
| | - Michael W White
- Department of Veterinary Molecular Biology, Montana State University, Bozeman, Montana, United States of America
- * To whom correspondence should be addressed. E-mail: (BS); (MWW)
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Lavine MD, Knoll LJ, Rooney PJ, Arrizabalaga G. A Toxoplasma gondii mutant defective in responding to calcium fluxes shows reduced in vivo pathogenicity. Mol Biochem Parasitol 2007; 155:113-22. [PMID: 17643508 PMCID: PMC2034501 DOI: 10.1016/j.molbiopara.2007.06.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2007] [Revised: 06/14/2007] [Accepted: 06/14/2007] [Indexed: 11/20/2022]
Abstract
Toxoplasma gondii is an important opportunistic pathogen in immunocompromised individuals. Successful propagation in an infected host by this obligate intracellular parasite depends on its ability to enter and exit host cells. Egress from the cell can be artificially induced by causing fluxes of calcium within the parasite with the use of calcium ionophores. While this ionophore-induced egress (IIE) has been characterized in detail, it is not known whether it mimics a normal physiological process of the parasite. This is underscored by the fact that mutants in IIE do not exhibit strong defects in any of the normal growth characteristics of the parasite in tissue culture. We have isolated and characterized a T. gondii mutant that along with a delay in IIE exhibits a severe defect in establishing a successful infection in vivo. In tissue culture this mutant displays normal ability to invade, divide within cells and convert into the latent encysted bradyzoite form. Nevertheless, mice infected with this mutant are less likely to die and carry less brain cysts than those infected with wild type parasites. Thus, our results suggest that normal response to calcium fluxes plays an important role during in vivo development of T. gondii.
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Affiliation(s)
| | | | - Peggy J. Rooney
- University of Wisconsin-Madison, Dept Medical Microbiology and Immunology, 1300 University Avenue MSC 495, Madison, WI 53706
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