The Orphan Nuclear Receptor TLX Is an Enhancer of STAT1-Mediated Transcription and Immunity to Toxoplasma gondii

PLoS Biol. 2015 Jul 21;13(7):e1002200. doi: 10.1371/journal.pbio.1002200. eCollection 2015.

 

Beiting DP¹, Hidano S¹, Baggs JE², Geskes JM², Fang Q¹, Wherry EJ³, Hunter CA¹, Roos DS⁴, Cherry S³.

 

The protozoan parasite, Toxoplasma, like many intracellular pathogens, suppresses interferon gamma (IFN-γ)-induced signal transducer and activator of transcription 1 (STAT1) activity. We exploited this well-defined host-pathogen interaction as the basis for a high-throughput screen, identifying nine transcription factors that enhance STAT1 function in the nucleus, including the orphan nuclear hormone receptor TLX. Expression profiling revealed that upon IFN-γ treatment TLX enhances the output of a subset of IFN-γ target genes, which we found is dependent on TLX binding at those loci. Moreover, infection of TLX deficient mice with the intracellular parasite Toxoplasma results in impaired production of the STAT1-dependent cytokine interleukin-12 by dendritic cells and increased parasite burden in the brain during chronic infection. These results demonstrate a previously unrecognized role for this orphan nuclear hormone receptor in regulating STAT1 signaling and host defense and reveal that STAT1 activity can be modulated in a context-specific manner by such "modifiers."

PMID:

26196739

[PubMed - as supplied by publisher]

Cancer in the parasitic protozoans Trypanosoma brucei and Toxoplasma gondii

Proc Natl Acad Sci U S A. 2015 Jul 20. pii: 201502599. [Epub ahead of print]

 

Lun ZR¹, Lai DH², Wen YZ², Zheng LL², Shen JL³, Yang TB², Zhou WL², Qu LH², Hide G⁴, Ayala FJ⁵.

 

Cancer is a general name for more than 100 malignant diseases. It is postulated that all cancers start from a single abnormal cell that grows out of control. Untreated cancers can cause serious consequences and deaths. Great progress has been made in cancer research that has significantly improved our knowledge and understanding of the nature and mechanisms of the disease, but the origins of cancer are far from being well understood due to the limitations of suitable model systems and to the complexities of the disease. In view of the fact that cancers are found in various species of vertebrates and other metazoa, here, we suggest that cancer also occurs in parasitic protozoans such as Trypanosoma brucei, a blood parasite, and Toxoplasma gondii, an obligate intracellular pathogen. Without treatment, these protozoan cancers may cause severe disease and death in mammals, including humans. The simpler genomes of these single-cell organisms, in combination with their complex life cycles and fascinating life cycle differentiation processes, may help us to better understand the origins of cancers and, in particular, leukemias.

KEYWORDS:

evolution; malignancy; mammals; single-cell organisms; transmissible

PMID:

26195778

[PubMed - as supplied by publisher]

Alternative splicing mechanisms orchestrating post-transcriptional gene expression: intron retention and the intron-rich genome of apicomplexan parasites

Curr Genet. 2015 Jul 21. [Epub ahead of print]

 

Lunghi M¹, Spano F, Magini A, Emiliani C, Carruthers VB, Di Cristina M.

 

Apicomplexan parasites including Toxoplasma gondii and Plasmodium species have complex life cycles that include multiple hosts and differentiation through several morphologically distinct stages requiring marked changes in gene expression. This review highlights emerging evidence implicating regulation of mRNA splicing as a mechanism to prime these parasites for rapid gene expression upon differentiation. We summarize the most important insights in alternative splicing including its role in regulating gene expression by decreasing mRNA abundance via 'Regulated Unproductive Splicing and Translation'. As a related but less well-understood mechanism, we discuss also our recent work suggesting a role for intron retention for precluding translation of stage specific isoforms of T. gondii glycolytic enzymes. We additionally provide new evidence that intron retention might be a widespread mechanism during parasite differentiation. Supporting this notion, recent genome-wide analysis of Toxoplasma and Plasmodium suggests intron retention is more pervasive than heretofore thought. These findings parallel recent emergence of intron retention being more prevalent in mammals than previously believed, thereby adding to the established roles in plants, fungi and unicellular eukaryotes. Deeper mechanistic studies of intron retention will provide important insight into its role in regulating gene expression in apicomplexan parasites and more general in eukaryotic organisms.

PMID:

26194054

[PubMed - as supplied by publisher]

Parasite manipulation of the invariant chain (Ii/CD74) and the peptide editor H2-DM affects MHC-II antigen presentation during Toxoplasma gondii infection

Infect Immun. 2015 Jul 20. pii: IAI.00415-15. [Epub ahead of print]

 

Leroux LP¹, Nishi M¹, El-Hage S¹, Fox BA², Bzik DJ², Dzierszinski FS³.

 

Toxoplasma gondii is an obligate intracellular protozoan parasite. This apicomplexan is the causative agent of toxoplasmosis, a leading cause of central nervous system disease in AIDS. It has long been known that T. gondii interferes with major histocompatibility complex (MHC)-II antigen presentation to attenuate CD4⁺ T cell responses and establish persisting infections. Transcriptional down-regulation of MHC-II genes by T. gondii was previously established, but the precise mechanisms inhibiting MHC-II function are currently unknown. Here, we show that, in addition to transcriptional regulation of MHC-II, the parasite modulates the expression of key components of the MHC-II antigen presentation pathway, namely the MHC-II associated invariant chain (Ii or CD74) and the peptide editor H2-DM in professional antigen presenting cells (pAPCs). Genetic deletion of CD74 restored the ability of infected dendritic cells to present a parasite antigen in the context of MHC-II in vitro. CD74 mRNA and protein levels were surprisingly elevated in infected cells, whereas MHC-II and H2-DM expression was inhibited. CD74 accumulated mainly in the endoplasmic reticulum (ER), and this phenotype required live parasites, but not active replication. Finally, we compared the impact of genetic deletion of CD74 and H2-DM genes on parasite dissemination towards lymphoid organs in mice, as well as activation of CD4⁺ T cells, and interferon gamma (IFNγ) levels during acute infection. Cyst burdens and survival during the chronic phase of infection were also evaluated in wild-type and knockout mice. These results highlight that the infection is influenced by multiple levels of parasite manipulation of the MHC-II antigen presentation pathway.
Copyright © 2015, American Society for Microbiology. All Rights Reserved.

PMID:

26195549

[PubMed - as supplied by publisher]

Research advances in microneme protein 3 of Toxoplasma gondii

Parasit Vectors. 2015 Jul 22;8(1):384.

 

Wang Y¹, Yin H².

 

Toxoplasma gondii (T. gondii) is an obligate intracellular protozoan parasite. It has extensive host populations and is prevalent globally; T. gondii infection can cause a zoonotic parasitic disease. Microneme protein 3 (MIC3) is a secreted protein that is expressed in all stages of the T. gondii life cycle. It has strong immunoreactivity and plays an important role in the recognition, adhesion and invasion of host cells by T. gondii. This article reviews the molecular structure of MIC3, its role in the invasion of host cells by parasites, its relationship with parasite virulence, and its induction of immune protection to lay a solid foundation for an in-depth study of potential diagnostic agents and vaccines for preventing toxoplasmosis.

PMID:

26194005

[PubMed - as supplied by publisher]

Pyrimidinergic Receptor Activation Controls Toxoplasma gondii Infection in Macrophages

PLoS One. 2015 Jul 20;10(7):e0133502. doi: 10.1371/journal.pone.0133502.

 

Moreira-Souza AC¹, Marinho Y², Correa G¹, Santoro GF³, Coutinho CM⁴, Vommaro RC⁵, Coutinho-Silva R².

 

Infection by the protozoan parasite Toxoplasma gondii is highly prevalent worldwide and may have serious clinical manifestations in immunocompromised patients. T. gondii is an obligate intracellular parasite that infects almost any cell type in mammalian hosts, including immune cells. The immune cells express purinergic P2 receptors in their membrane - subdivided into P2Y and P2X subfamilies - whose activation is important for infection control. Here, we examined the effect of treatment with UTP and UDP in mouse peritoneal macrophages infected with T. gondii tachyzoites. Treatment with these nucleotides reduced parasitic load by 90%, but did not increase the levels of the inflammatory mediators NO and ROS, nor did it modulate host cell death by apoptosis or necrosis. On the other hand, UTP and UDP treatments induced early egress of tachyzoites from infected macrophages, in a Ca2+-dependent manner, as shown by scanning electron microscopy analysis, and videomicroscopy. In subsequent infections, prematurely egressed parasites had reduced infectivity, and could neither replicate nor inhibit the fusion of lysosomes to the parasitophorous vacuole. The use of selective agonists and antagonists of the receptor subtypes P2Y2 and P2Y4 and P2Y6 showed that premature parasite egress may be mediated by the activation of these receptor subtypes. Our results suggest that the activity of P2Y host cell receptors controls T. gondii infection in macrophages, highlighting the importance of pyrimidinergic signaling for innate immune system response against infection. Finally the P2Y receptors should be considered as new target for the development of drugs against T. gondii infection.

PMID:

26192447

[PubMed - as supplied by publisher]

Elucidating pathways of Toxoplasma gondii invasion in the gastrointestinal tract: Involvement of the tight junction protein occludin

Microbes Infect. 2015 Jul 13. pii: S1286-4579(15)00142-2. doi: 10.1016/j.micinf.2015.07.001. [Epub ahead of print]

 

Weight CM¹, Jones EJ¹, Horn N², Wellner N³, Carding SR⁴.

 

Toxoplasma gondii is an obligate intracellular parasite infecting one third of the world's population. The small intestine is the parasite's primary route of infection, although the pathway of epithelium transmigration remains unclear. Using an in vitro invasion assay and live imaging we showed that T. gondii (RH) tachyzoites infect and transmigrate between adjacent intestinal epithelial cells in polarized monolayers without altering barrier integrity, despite eliciting the production of specific inflammatory mediators and chemokines. During invasion, T. gondii co-localized with occludin. Reducing the levels of endogenous cellular occludin with specific small interfering RNAs significantly reduced the ability of T. gondii to penetrate between and infect epithelial cells. Furthermore, an in vitroinvasion and binding assays using recombinant occludin fragments established the capacity of the parasite to bind occludin and in particular to the extracellular loops of the protein. These findings provide evidence for occludin playing a role in the invasion of T. gondii in small intestinal epithelial cells.
Copyright © 2015. Published by Elsevier Masson SAS.

KEYWORDS:

Toxoplasma gondii; intestinal epithelial cells; invasion; occludin

PMID:

26183539

[PubMed - as supplied by publisher]

Disassembly activities of actin depolymerization factor (ADF) is associated with distinct cellular processes in apicomplexan parasites

Mol Biol Cell. 2015 Jul 8. pii: mbc.E14-10-1427. [Epub ahead of print]

 

Haase S¹, Zimmermann D², Olshina MA¹, Wilkinson M³, Fisher F³, Tan YH⁴, Stewart RJ¹, Tonkin CJ¹, Wong W¹, Kovar DR², Baum J⁵.

 

Proteins of the actin depolymerizing factor (ADF)/cofilin family have been shown to be crucial for the motility and survival of apicomplexan parasites. However, the mechanisms by which ADF proteins fulfill their function remains poorly understood. In this study we sought to investigate the comparative activities of ADF proteins from Toxoplasma gondii and Plasmodium falciparum, the human malaria parasite, using a conditional T. gondii ADF-knockout line complemented with ADF variants from either species. We show that P. falciparum ADF1 can fully restore native TgADF activity, demonstrating functional conservation between parasites. Strikingly, mutation of a key basic residue (Lys⁷²), previously implicated in disassembly in PfADF1, had no detectable phenotypic effect on parasite growth, motility or development. In contrast, organelle segregation was severely impaired when complementing with a TgADF mutant lacking the corresponding residue (Lys⁶⁸). Biochemical analyses of each ADF protein confirmed the reduced ability of lysine mutants to mediate actin depolymerization via filament disassembly though not severing, in contrast to previous reports. These data suggest that actin filament disassembly is essential for apicomplexan parasite development but not for motility as well as pointing to genus-specific coevolution between ADF proteins and their native actin.
© 2015 by The American Society for Cell Biology.

PMID:

26157165

[PubMed - as supplied by publisher]

Identification of Toxoplasma gondii protein fractions induce immune response against melanoma in mice

APMIS. 2015 Jul 8. doi: 10.1111/apm.12420. [Epub ahead of print]

 

Boghozian R¹, Saei A¹, Mirzaei R¹, Jamali A², Vaziri B³, Razavi A⁴, Hadjati J¹.

 

Dendritic cells (DCs) play a crucial role in the initiation of adaptive immune responses against tumor cells. We recently found that protein components of Toxoplasma gondii (T. gondii) could mature DCs efficiently. Therefore, in this study, we aimed to find the most effective protein components of T. gondii which are able to mature DCs and consequently instruct immune responses in tumor-bearing mice. Soluble tachyzoite antigens (STAgs) were fractionated by ammonium sulfate precipitation and subsequently by anion-exchange HPLC. Immature DCs (iDCs) were treated by these protein fractions and were monitored for IL-12p70 and IL-10 production. Moreover, the capacity of mature DCs (mDCs) to induce lymphocyte proliferation was investigated. Ultimately, we analyzed the ability of mDCs in instructing immune responses in tumor-bearing mice. We found that ammonium sulfate fraction one (A1) matured-DCs produced higher IL-12 level and IL-12/IL-10 ratio; therefore, this fraction was selected for further fractionation by anion-exchange HPLC. The results showed that anion-exchange HPLC fraction 14 (C14) matured-DCs secrete higher levels of IL-12p70 and IL-12p70/IL-10 ratio. Survival of the mice matured by A1 fraction increased significantly compared to other groups. Moreover, SDS-PAGE electrophoresis showed that different obtained fractions have distinct proteins based on their size. These results demonstrate that two protein fractions of T. gondii are able to mature DCs more efficient.
© 2015 APMIS. Published by John Wiley & Sons Ltd.

KEYWORDS:

Toxoplasma gondii ; Dendritic cells; immune response; tumor

PMID:

26152792

[PubMed - as supplied by publisher]

Integration of RNA-seq and proteomics data with genomics for improved genome annotation in Apicomplexan Parasites

Proteomics. 2015 Jul 7. doi: 10.1002/pmic.201500253. [Epub ahead of print]

 

de Monerri NC¹, Weiss LM^2,1.

 

While high quality genomic sequence data is available for many pathogenic organisms, the corresponding gene annotations are often plagued with inaccuracies that can hinder research that utilizes such genomic data. Experimental validation of gene models is clearly crucial in improving such gene annotations; the field of proteogenomics is an emerging area of research wherein proteomic data is applied to testing and improving genetic models. Krishna et al [Proteomics 2015, 00, 1-11] investigated whether incorporation of RNA-seq data into proteogenomics analyses can contribute significantly to validation studies of genome annotation, in two important parasitic organisms Toxoplasma gondii and Neospora caninum. They applied a systematic approach to combine new and previously published proteomics data from T. gondii and N. caninum with transcriptomics data, leading to substantially improved gene models for these organisms. This study illustrates the importance of incorporating experimental data from both proteomics and RNA-seq studies into routine genome annotation protocols. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.

KEYWORDS:

Apicomplexa; Neospora; Proteogenomics; Proteomics; Protozoa; Toxoplasma

PMID:

26152714

[PubMed - as supplied by publisher]

toxoMine: an integrated omics data warehouse for Toxoplasma gondii systems biology research

Database (Oxford). 2015 Jun 30;2015. pii: bav066. doi: 10.1093/database/bav066. Print 2015.

Rhee DB1, Croken MM2, Shieh KR3, Sullivan J4, Micklem G4, Kim K5, Golden A6.

Author information

Abstract

Toxoplasma gondii (T. gondii) is an obligate intracellular parasite that must monitor for changes in the host environment and respond accordingly; however, it is still not fully known which genetic or epigenetic factors are involved in regulating virulence traits of T. gondii. There are on-going efforts to elucidate the mechanisms regulating the stage transition process via the application of high-throughput epigenomics, genomics and proteomics techniques. Given the range of experimental conditions and the typical yield from such high-throughput techniques, a new challenge arises: how to effectively collect, organize and disseminate the generated data for subsequent data analysis. Here, we describe toxoMine, which provides a powerful interface to support sophisticated integrative exploration of high-throughput experimental data and metadata, providing researchers with a more tractable means toward understanding how genetic and/or epigenetic factors play a coordinated role in determining pathogenicity of T. gondii. As a data warehouse, toxoMine allows integration of high-throughput data sets with public T. gondii data. toxoMine is also able to execute complex queries involving multiple data sets with straightforward user interaction. Furthermore, toxoMine allows users to define their own parameters during the search process that gives users near-limitless search and query capabilities. The interoperability feature also allows users to query and examine data available in other InterMine systems, which would effectively augment the search scope beyond what is available to toxoMine. toxoMine complements the major community database ToxoDB by providing a data warehouse that enables more extensive integrative studies for T. gondii. Given all these factors, we believe it will become an indispensable resource to the greater infectious disease research community.Database URL: http://toxomine.org. 

© The Author(s) 2015. Published by Oxford University Press.

PMID:

 

26130662

 

[PubMed - in process] 

Role of CD4+Foxp3+ regulatory T cells in protection induced by a live, attenuated, replicating Type-I vaccine strain of Toxoplasma

Infect Immun. 2015 Jun 29. pii: IAI.00217-15. [Epub ahead of print]

 

Akbar H¹, Dimier-Poisson I¹, Moiré N².

 

Vaccination with the live attenuated Toxoplasma gondii Mic1.3KO strain induced long-lasting immunity against challenge with Toxoplasma gondii Type I and Type II strains. The involvement of T regulatory (Treg) cells in the protection mechanism was investigated. Intraperitoneal injection of Mic1.3KO induced a weak and transient influx of CD4⁺Foxp3⁺ T regulatory cells followed by recruitment/expansion of CD4⁺Foxp3^-CD25⁺ effector cells and control of the parasite at the site of infection. The local and systemic cytokine responses associated with this recruitment of Treg were of TH1/Treg-like type. In contrast, injection of RH, the wild-type strain from which the vaccinal strain is derived, induced a low CD4⁺Foxp3⁺ cell influx and uncontrolled multiplication of the parasites at this local site, followed by death of the mice. The associated local and systemic cytokine responses were of TH1/TH17-like type.In addition, in vivo Treg induction in the RH-infected mice with IL2/anti-IL2 complexes induced control of the parasite and a TH1/Treg cytokine response similar to the response after Mic1.3KO vaccination. These results suggest that Treg cells may contribute to the protective response after vaccination with Mic1.3KO.
Copyright © 2015, American Society for Microbiology. All Rights Reserved.

PMID:

26123802

[PubMed - as supplied by publisher]