scholarly journals Infection by Toxoplasma gondii Specifically Induces Host c-Myc and the Genes This Pivotal Transcription Factor Regulates

2014 ◽  
Vol 13 (4) ◽  
pp. 483-493 ◽  
Author(s):  
Magdalena Franco ◽  
Anjali J. Shastri ◽  
John C. Boothroyd
Keyword(s):  
Transcription Factor ◽  
Toxoplasma Gondii ◽  
Host Cell ◽  
Host Response ◽  
Neospora Caninum ◽  
Apicomplexan Parasite ◽  
Intracellular Growth ◽  
Terminal Protein ◽  
Content Type ◽  
Cell Functions

ABSTRACT Toxoplasma gondii infection has previously been described to cause dramatic changes in the host transcriptome by manipulating key regulators, including STATs, NF-κB, and microRNAs. Here, we report that Toxoplasma tachyzoites also mediate rapid and sustained induction of another pivotal regulator of host cell transcription, c-Myc. This induction is seen in cells infected with all three canonical types of Toxoplasma but not the closely related apicomplexan parasite Neospora caninum . Coinfection of cells with both Toxoplasma and Neospora still results in an increase in the level of host c-Myc, showing that c-Myc is actively upregulated by Toxoplasma infection (rather than repressed by Neospora ). We further demonstrate that this upregulation may be mediated through c-Jun N-terminal protein kinase (JNK) and is unlikely to be a nonspecific host response, as heat-killed Toxoplasma parasites do not induce this increase and neither do nonviable parasites inside the host cell. Finally, we show that the induced c-Myc is active and that transcripts dependent on its function are upregulated, as predicted. Hence, c-Myc represents an additional way in which Toxoplasma tachyzoites have evolved to specifically alter host cell functions during intracellular growth.

scholarly journals Toxoplasma gondii Rhoptry Discharge Correlates with Activation of the Early Growth Response 2 Host Cell Transcription Factor

2008 ◽  
Vol 76 (10) ◽  
pp. 4703-4712 ◽  
Author(s):  
Eric D. Phelps ◽  
Kristin R. Sweeney ◽  
Ira J. Blader
Keyword(s):  
Transcription Factor ◽  
Toxoplasma Gondii ◽  
Host Cell ◽  
Growth Response ◽  
Neospora Caninum ◽  
Early Growth ◽  
Apicomplexan Parasite ◽  
Host Cells ◽  
Early Growth Response ◽  
Cell Extracts

ABSTRACT Toxoplasma gondii is a ubiquitous apicomplexan parasite that can cause severe disease in fetuses and immune-compromised patients. Rhoptries, micronemes, and dense granules, which are secretory organelles unique to Toxoplasma and other apicomplexan parasites, play critical roles in parasite growth and virulence. To understand how these organelles modulate infected host cells, we sought to identify host cell transcription factors triggered by their release. Early growth response 2 (EGR2) is a host cell transcription factor that is rapidly upregulated and activated in Toxoplasma-infected cells but not in cells infected with the closely related apicomplexan parasite Neospora caninum. EGR2 upregulation occurred only when live parasites were in direct contact with the host cell and not from exposure to cell extracts that contain dense granule or micronemal proteins. When microneme-mediated attachment was blocked by pretreating parasites with a calcium chelator, EGR2 expression was significantly reduced. In contrast, when host cells were infected with parasites in the presence of cytochalasin D, which allows rhoptry secretion but prevents parasite invasion, EGR2 was activated. Finally, we demonstrate that Toxoplasma activation of host p38 mitogen-activated protein kinase is necessary but not sufficient for EGR2 activation. Collectively, these data indicate that EGR2 is specifically upregulated by a parasite-derived secreted factor that is most likely a resident rhoptry protein.

scholarly journals Toxoplasma Controls Host Cyclin E Expression through the Use of a Novel MYR1-Dependent Effector Protein, HCE1

mBio ◽  
2019 ◽  
Vol 10 (2) ◽  
Author(s):  
Michael W. Panas ◽  
Adit Naor ◽  
Alicja M. Cygan ◽  
John C. Boothroyd
Keyword(s):  
Transcription Factor ◽  
Toxoplasma Gondii ◽  
Cyclin E ◽  
Human Cells ◽  
Host Cells ◽  
Effector Protein ◽  
Dependent Manner ◽  
Content Type ◽  
Cell Functions ◽  
E2f Transcription Factor

ABSTRACT Toxoplasma gondii is an obligate intracellular parasite that establishes a favorable environment in the host cells in which it replicates. We have previously reported that it uses MYR-dependent translocation of dense granule proteins to elicit a key set of host responses related to the cell cycle, specifically, E2F transcription factor targets, including cyclin E. We report here the identification of a novel Toxoplasma effector protein that is exported from the parasitophorous vacuole in a MYR1-dependent manner and localizes to the host’s nucleus. Parasites lacking this inducer of host cyclin E (HCE1) are unable to modulate E2F transcription factor target genes and exhibit a substantial growth defect. Immunoprecipitation of HCE1 from infected host cells showed that HCE1 efficiently binds elements of the cyclin E regulatory complex, namely, DP1 and its partners E2F3 and E2F4. Expression of HCE1 in Neospora caninum, or in uninfected human foreskin fibroblasts (HFFs), showed localization of the expressed protein to the host nuclei and strong cyclin E upregulation. Thus, HCE1 is a novel effector protein that is necessary and sufficient to impact the E2F axis of transcription, resulting in co-opting of host functions to the advantage of Toxoplasma. IMPORTANCE Like most Apicomplexan parasites, Toxoplasma gondii has the remarkable ability to invade and establish a replicative niche within another eukaryotic cell, in this case, any of a large number of cell types in almost any warm-blooded animals. Part of the process of establishing this niche is the export of effector proteins to co-opt host cell functions in favor of the parasite. Here we identify a novel effector protein, HCE1, that the parasites export into the nucleus of human cells, where it modulates the expression of multiple genes, including the gene encoding cyclin E, one of the most crucial proteins involved in controlling when and whether a human cell divides. We show that HCE1 works through binding to specific transcription factors, namely, E2F3, E2F4, and DP1, that normally carefully regulate these all-important pathways. This represents a new way in which these consummately efficient infectious agents co-opt the human cells that they so efficiently grow within.

scholarly journals MYR1-Dependent Effectors Are the Major Drivers of a Host Cell’s Early Response to Toxoplasma , Including Counteracting MYR1-Independent Effects

mBio ◽  
2018 ◽  
Vol 9 (2) ◽  
Author(s):  
Adit Naor ◽  
Michael W. Panas ◽  
Nicole Marino ◽  
Michael J. Coffey ◽  
Christopher J. Tonkin ◽  
...  
Keyword(s):  
Toxoplasma Gondii ◽  
Host Cell ◽  
Expression Profiles ◽  
Parasitophorous Vacuole ◽  
Effector Proteins ◽  
Gene Set Enrichment Analysis ◽  
Host Cells ◽  
Content Type ◽  
Cell Functions ◽  
The Impact

ABSTRACT The obligate intracellular parasite Toxoplasma gondii controls its host cell from within the parasitophorous vacuole (PV) by using a number of diverse effector proteins, a subset of which require the aspartyl protease 5 enzyme (ASP5) and/or the recently discovered MYR1 protein to cross the PV membrane. To examine the impact these effectors have in the context of the entirety of the host response to Toxoplasma , we used RNA-Seq to analyze the transcriptome expression profiles of human foreskin fibroblasts infected with wild-type RH (RH-WT), RHΔ myr1 , and RHΔ asp5 tachyzoites. Interestingly, the majority of the differentially regulated genes responding to Toxoplasma infection are MYR1 dependent. A subset of MYR1 responses were ASP5 independent, and MYR1 function did not require ASP5 cleavage, suggesting the export of some effectors requires only MYR1. Gene set enrichment analysis of MYR1-dependent host responses suggests an upregulation of E2F transcription factors and the cell cycle and a downregulation related to interferon signaling, among numerous others. Most surprisingly, “hidden” responses arising in RHΔ myr1 - but not RH-WT-infected host cells indicate counterbalancing actions of MYR1-dependent and -independent activities. The host genes and gene sets revealed here to be MYR1 dependent provide new insight into the parasite’s ability to co-opt host cell functions. IMPORTANCE Toxoplasma gondii is unique in its ability to successfully invade and replicate in a broad range of host species and cells within those hosts. The complex interplay of effector proteins exported by Toxoplasma is key to its success in co-opting the host cell to create a favorable replicative niche. Here we show that a majority of the transcriptomic effects in tachyzoite-infected cells depend on the activity of a novel translocation system involving MYR1 and that the effectors delivered by this system are part of an intricate interplay of activators and suppressors. Removal of all MYR1-dependent effectors reveals previously unknown activities that are masked or hidden by the action of these proteins.

scholarly journals Toxoplasma gondii Development of Its Replicative Niche: in Its Host Cell and Beyond

2014 ◽  
Vol 13 (8) ◽  
pp. 965-976 ◽  
Author(s):  
Ira J. Blader ◽  
Anita A. Koshy
Keyword(s):  
Toxoplasma Gondii ◽  
Host Cell ◽  
Host Cells ◽  
Content Type ◽  
Obligate Intracellular ◽  
Cellular Processes ◽  
High Prevalence ◽  
Life Threatening ◽  
Cell Processes ◽  
Cellular Pathways

ABSTRACTIntracellular pathogens can replicate efficiently only after they manipulate and modify their host cells to create an environment conducive to replication. While diverse cellular pathways are targeted by different pathogens, metabolism, membrane and cytoskeletal architecture formation, and cell death are the three primary cellular processes that are modified by infections.Toxoplasma gondiiis an obligate intracellular protozoan that infects ∼30% of the world's population and causes severe and life-threatening disease in developing fetuses, in immune-comprised patients, and in certain otherwise healthy individuals who are primarily found in South America. The high prevalence ofToxoplasmain humans is in large part a result of its ability to modulate these three host cell processes. Here, we highlight recent work defining the mechanisms by whichToxoplasmainteracts with these processes. In addition, we hypothesize why some processes are modified not only in the infected host cell but also in neighboring uninfected cells.

scholarly journals Immediate Interferon Gamma Induction Determines Murine Host Compatibility Differences between Toxoplasma gondii and Neospora caninum

2020 ◽  
Vol 88 (4) ◽  
Author(s):  
Rachel S. Coombs ◽  
Matthew L. Blank ◽  
Elizabeth D. English ◽  
Yaw Adomako-Ankomah ◽  
Ifeanyi-Chukwu Samuel Urama ◽  
...  
Keyword(s):  
Toxoplasma Gondii ◽  
Immune Responses ◽  
Interferon Gamma ◽  
Neospora Caninum ◽  
Ectopic Expression ◽  
Parasite Burden ◽  
Interleukin 12 ◽  
Content Type ◽  
Ifn Γ ◽  
And Control

ABSTRACT Rodents are critical for the transmission of Toxoplasma gondii to the definitive feline host via predation, and this relationship has been extensively studied as a model for immune responses to parasites. Neospora caninum is a closely related coccidian parasite of ruminants and canines but is not naturally transmitted by rodents. We compared mouse innate immune responses to N. caninum and T. gondii and found marked differences in cytokine levels and parasite growth kinetics during the first 24 h postinfection (hpi). N. caninum-infected mice produced significantly higher levels of interleukin-12 (IL-12) and interferon gamma (IFN-γ) by as early as 4 hpi, but the level of IFN-γ was significantly lower or undetectable in T. gondii-infected mice during the first 24 hpi. “Immediate” IFN-γ and IL-12p40 production was not detected in MyD88−/− mice. However, unlike IL-12p40−/− and IFN-γ−/− mice, MyD88−/− mice survived N. caninum infections at the dose used in this study. Serial measures of parasite burden showed that MyD88−/− mice were more susceptible to N. caninum infections than wild-type (WT) mice, and control of parasite burdens correlated with a pulse of serum IFN-γ at 3 to 4 days postinfection in the absence of detectable IL-12. Immediate IFN-γ was partially dependent on the T. gondii mouse profilin receptor Toll-like receptor 11 (TLR11), but the ectopic expression of N. caninum profilin in T. gondii had no impact on early IFN-γ production or parasite proliferation. Our data indicate that T. gondii is capable of evading host detection during the first hours after infection, while N. caninum is not, and this is likely due to the early MyD88-dependent recognition of ligands other than profilin.

scholarly journals Differential Gamma Interferon- and Tumor Necrosis Factor Alpha-Driven Cytokine Response Distinguishes Acute Infection of a Metatherian Host with Toxoplasma gondii and Neospora caninum

2017 ◽  
Vol 85 (6) ◽  
Author(s):  
Shannon L. Donahoe ◽  
David N. Phalen ◽  
Bronwyn M. McAllan ◽  
Denis O'Meally ◽  
Milton M. McAllister ◽  
...  
Keyword(s):  
Immune Response ◽  
Toxoplasma Gondii ◽  
Tumor Necrosis Factor ◽  
Tumor Necrosis Factor Alpha ◽  
Tumor Necrosis ◽  
Neospora Caninum ◽  
Necrosis Factor Alpha ◽  
Content Type ◽  
Factor Alpha ◽  
Necrosis Factor

ABSTRACT Toxoplasma gondii and Neospora caninum (both Apicomplexa) are closely related cyst-forming coccidian parasites that differ significantly in their host ranges and ability to cause disease. Unlike eutherian mammals, Australian marsupials (metatherian mammals) have long been thought to be highly susceptible to toxoplasmosis and neosporosis because of their historical isolation from the parasites. In this study, the carnivorous fat-tailed dunnart (Sminthopsis crassicaudata) was used as a disease model to investigate the immune response and susceptibility to infection of an Australian marsupial to T. gondii and N. caninum. The disease outcome was more severe in N. caninum-infected dunnarts than in T. gondii-infected dunnarts, as shown by the severity of clinical and histopathological features of disease and higher tissue parasite burdens in the tissues evaluated. Transcriptome sequencing (RNA-seq) of spleens from infected dunnarts and mitogen-stimulated dunnart splenocytes was used to define the cytokine repertoires. Changes in mRNA expression during the time course of infection were measured using quantitative reverse transcription-PCR (qRT-PCR) for key Th1 (gamma interferon [IFN-γ] and tumor necrosis factor alpha [TNF-α]), Th2 (interleukin 4 [IL-4] and IL-6), and Th17 (IL-17A) cytokines. The results show qualitative differences in cytokine responses by the fat-tailed dunnart to infection with N. caninum and T. gondii. Dunnarts infected with T. gondii were capable of mounting a more effective Th1 immune response than those infected with N. caninum, indicating the role of the immune response in the outcome scenarios of parasite infection in this marsupial mammal.

scholarly journals In VitroEffects of Novel Ruthenium Complexes in Neospora caninum and Toxoplasma gondii Tachyzoites

2013 ◽  
Vol 57 (11) ◽  
pp. 5747-5754 ◽  
Author(s):  
Fabienne Barna ◽  
Karim Debache ◽  
Carsten A. Vock ◽  
Tatiana Küster ◽  
Andrew Hemphill
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Toxoplasma Gondii ◽  
Neospora Caninum ◽  
Ruthenium Complexes ◽  
Term Treatment ◽  
Content Type ◽  
Transmission Electron ◽  
Long Term Treatment

ABSTRACTUpon the screening of 16 antiproliferative compounds againstToxoplasma gondiiandNeospora caninum, two hydrolytically stable ruthenium complexes (compounds 16 and 18) exhibited 50% inhibitory concentrations of 18.7 and 41.1 nM (T. gondii) and 6.7 and 11.3 nM (N. caninum). To achieve parasiticidal activity with compound 16, long-term treatment (22 to 27 days at 80 to 160 nM) was required. Transmission electron microscopy demonstrated the rapid impact on and ultrastructural alterations in both parasites. These preliminary findings suggest that the potential of ruthenium-based compounds should thus be further exploited.

scholarly journals Two Phosphoglucomutase Paralogs Facilitate Ionophore-Triggered Secretion of the Toxoplasma Micronemes

mSphere ◽  
2017 ◽  
Vol 2 (6) ◽  
Author(s):  
Sudeshna Saha ◽  
Bradley I. Coleman ◽  
Rashmi Dubey ◽  
Ira J. Blader ◽  
Marc-Jan Gubbels
Keyword(s):  
Toxoplasma Gondii ◽  
Phosphatidic Acid ◽  
Host Cell ◽  
Lytic Cycle ◽  
Ionophore A23187 ◽  
Host Cell Invasion ◽  
Content Type ◽  
Apicomplexan Parasites ◽  
Genetic Deletion

ABSTRACT Ca2+-dependent exocytosis is essential for the life cycle of apicomplexan parasites. Toxoplasma gondii harbors a phosphoglucomutase (PGM) ortholog, PRP1, previously associated with Ca2+-dependent microneme secretion. Here it is shown that genetic deletion of either PRP1, its PGM2 ortholog, or both genes is dispensable for the parasite’s lytic cycle, including host cell egress and invasion. Depletion of the proteins abrogated high Ca2+-mediated microneme secretion induced by the ionophore A23187; however, the constitutive and phosphatidic acid-mediated release remained unaffected. Secretion mediated by the former pathway is not essential for tachyzoite survival or acute in vivo infection in the mice. Paralogs of the widely prevalent phosphoglucomutase (PGM) protein called parafusin function in calcium (Ca2+)-mediated exocytosis across eukaryotes. In Toxoplasma gondii, the parafusin-related protein 1 (PRP1) has been associated with Ca2+-dependent microneme organelle secretion required for essential processes like host cell invasion and egress. Using reverse genetics, we observed PRP1 to be dispensable for completion of the lytic cycle, including host cell invasion and egress by the parasite. However, the absence of the gene affected increased microneme release triggered by A23187, a Ca2+ ionophore used to raise the cytoplasmic Ca2+ concentration mimicking the physiological role of Ca2+ during invasion and egress. The basal levels of constitutive microneme release in extracellular parasites and phosphatidic acid-triggered microneme secretion were unaffected in the mutant. The phenotype of the deletion mutant of the second PGM-encoding gene in Toxoplasma, PGM2, was similar to the phenotype of the PRP1 deletion mutant. Furthermore, the ability of the tachyzoites to induce acute infection in the mice remained normal in the absence of both PGM paralogs. Our data thus reveal that the microneme secretion upon high Ca2+ flux is facilitated by the Toxoplasma PGM paralogs, PRP1 and PGM2. However, this protein-mediated release is neither essential for lytic cycle completion nor for acute virulence of the parasite. IMPORTANCE Ca2+-dependent exocytosis is essential for the life cycle of apicomplexan parasites. Toxoplasma gondii harbors a phosphoglucomutase (PGM) ortholog, PRP1, previously associated with Ca2+-dependent microneme secretion. Here it is shown that genetic deletion of either PRP1, its PGM2 ortholog, or both genes is dispensable for the parasite’s lytic cycle, including host cell egress and invasion. Depletion of the proteins abrogated high Ca2+-mediated microneme secretion induced by the ionophore A23187; however, the constitutive and phosphatidic acid-mediated release remained unaffected. Secretion mediated by the former pathway is not essential for tachyzoite survival or acute in vivo infection in the mice.

scholarly journals The Protozoan Parasite Toxoplasma gondii Selectively Reprograms the Host Cell Translatome

2018 ◽  
Vol 86 (9) ◽  
Author(s):  
Louis-Philippe Leroux ◽  
Julie Lorent ◽  
Tyson E. Graber ◽  
Visnu Chaparro ◽  
Laia Masvidal ◽  
...  
Keyword(s):  
Toxoplasma Gondii ◽  
Host Cell ◽  
Cell Activation ◽  
Immune Cell ◽  
Mrna Translation ◽  
Protozoan Parasite ◽  
Translational Efficiency ◽  
Type I ◽  
Content Type ◽  
Infection Inhibition

ABSTRACT The intracellular parasite Toxoplasma gondii promotes infection by targeting multiple host cell processes; however, whether it modulates mRNA translation is currently unknown. Here, we show that infection of primary murine macrophages with type I or II T. gondii strains causes a profound perturbation of the host cell translatome. Notably, translation of transcripts encoding proteins involved in metabolic activity and components of the translation machinery was activated upon infection. In contrast, the translational efficiency of mRNAs related to immune cell activation and cytoskeleton/cytoplasm organization was largely suppressed. Mechanistically, T. gondii bolstered mechanistic target of rapamycin (mTOR) signaling to selectively activate the translation of mTOR-sensitive mRNAs, including those with a 5′-terminal oligopyrimidine (5′ TOP) motif and those encoding mitochondrion-related proteins. Consistent with parasite modulation of host mTOR-sensitive translation to promote infection, inhibition of mTOR activity suppressed T. gondii replication. Thus, selective reprogramming of host mRNA translation represents an important subversion strategy during T. gondii infection.

scholarly journals Virus Evolution toward Limited Dependence on Nonessential Functions of the Host: the Case of Bacteriophage SPP1

2014 ◽  
Vol 89 (5) ◽  
pp. 2875-2883 ◽  
Author(s):  
Virginija Cvirkaite-Krupovic ◽  
Rut Carballido-López ◽  
Paulo Tavares
Keyword(s):  
Bacillus Subtilis ◽  
Host Cell ◽  
Exponential Growth ◽  
Receptor Protein ◽  
Exponential Growth Phase ◽  
Exact Nature ◽  
Lytic Bacteriophage ◽  
Content Type ◽  
Cell Functions ◽  
Bacteriophage Infection

ABSTRACTAll viruses are obligate intracellular parasites and depend on certain host cell functions for multiplication. However, the extent of such dependence and the exact nature of the functions provided by the host cell remain poorly understood. Here, we investigated if nonessentialBacillus subtilisgenes are necessary for multiplication of bacteriophage SPP1. Screening of a collection of 2,514 single-gene knockouts of nonessentialB. subtilisgenes yielded only a few genes necessary for efficient SPP1 propagation. Among these were genes belonging to theyukoperon, which codes for the Esat-6-like secretion system, including the SPP1 receptor protein YueB. In addition, we found that SPP1 multiplication was negatively affected by the absence of two other genes,putBandefp. The geneefpencodes elongation factor P, which enhances ribosome activity by alleviating translational stalling during the synthesis of polyproline-containing proteins. PutB is an enzyme involved in the proline degradation pathway that is required for infection in the post-exponential growth phase ofB. subtilis, when the bacterium undergoes a complex genetic reprogramming. TheputBknockout shortens significantly the window of opportunity for SPP1 infection during the host cell life cycle. This window is a critical parameter for competitive phage multiplication in the soil environment, whereB. subtilisrarely meets conditions for exponential growth. Our results in combination with those reported for other virus-host systems suggest that bacterial viruses have evolved toward limited dependence on nonessential host functions.IMPORTANCEA successful viral infection largely depends on the ability of the virus to hijack cellular machineries and to redirect the flow of building blocks and energy resources toward viral progeny production. However, the specific virus-host interactions underlying this fundamental transformation are poorly understood. Here, we report on the first systematic analysis of virus-host cross talk during bacteriophage infection in Gram-positive bacteria. We show that lytic bacteriophage SPP1 is remarkably independent of nonessential genes of its host,Bacillus subtilis, with only a few cellular genes being necessary for efficient phage propagation. We hypothesize that such limited dependence of the virus on its host results from a constant “evolutionary arms race” and might be much more widespread than currently thought.

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