Role of the 52 KDa thioredoxin protein disulfide isomerase of Toxoplasma gondii during infection to human cells

Exp Parasitol. 2016 Feb 17. pii: S0014-4894(16)30020-0. doi: 10.1016/j.exppara.2016.02.005. [Epub ahead of print]

Moncada D¹, Arenas A¹, Acosta A¹, Molina D¹, Hernández A¹, Cardona N¹, Yepes MG¹, Gomez-Marín JE².

Toxoplasma protein disulfide isomerase (PDI) is a 52 KDa thioredoxin of interest because have a great immunogenicity for humans. We cloned and produced a recombinant protein (recTgPDI) used to test its effect during infection to different human cell lines (epithelial and retinal). We also determine if there were differences in gen expression during in vitro infection. Expression of the gen was lower after entry into the host cells. PDI's inhibitors bacitracin and nitroblue tetrazolium reduced the percent of infected cells and small amounts of recTgPDI proteins interfered with the invasion step. All these results support a role of Toxoplasma PDI during the first steps of infection (adhesion and invasion). Toxoplasma PDI is a protein linked to early steps of invasion, it would be of importance to identify the host proteins substrates during invasion steps.
Copyright © 2016. Published by Elsevier Inc.

KEYWORDS:

Toxoplasma; protein disulfide isomerase; thioredoxins

PMID:

26896642

[PubMed - as supplied by publisher]

Neurons are the Primary Target Cell for the Brain-Tropic Intracellular Parasite Toxoplasma gondii

PLoS Pathog. 2016 Feb 19;12(2):e1005447. doi: 10.1371/journal.ppat.1005447. eCollection 2016.

Cabral CM1, Tuladhar S2, Dietrich HK1, Nguyen E1, MacDonald WR3, Trivedi T1, Devineni A1, Koshy AA1,2,4.

Author information

Abstract

Toxoplasma gondii, a common brain-tropic parasite, is capable of infecting most nucleated cells, including astrocytes and neurons, in vitro. Yet, in vivo, Toxoplasma is primarily found in neurons. In vitro data showing that interferon-γ-stimulated astrocytes, but not neurons, clear intracellular parasites suggest that neurons alone are persistently infected in vivo because they lack the ability to clear intracellular parasites. Here we test this theory by using a novel Toxoplasma-mouse model capable of marking and tracking host cells that directly interact with parasites, even if the interaction is transient. Remarkably, we find that Toxoplasma shows a strong predilection for interacting with neurons throughout CNS infection. This predilection remains in the setting of IFN-γ depletion; infection with parasites resistant to the major mechanism by which murine astrocytes clear parasites; or when directly injecting parasites into the brain. These findings, in combination with prior work, strongly suggest that neurons are not incidentally infected, but rather they are Toxoplasma's primary in vivo target.

PMID:

 

26895155

 

[PubMed - as supplied by publisher]

Human GBP1 does not localise to pathogen vacuoles but restricts Toxoplasma gondii

Cell Microbiol. 2016 Feb 13. doi: 10.1111/cmi.12579. [Epub ahead of print]

Johnston AC1, Piro A2, Clough B1, Siew M1, Virreira Winter S3, Coers J2, Frickel EM1.

Author information

Abstract

Guanylate binding proteins (GBPs) are a family of large interferon-inducible GTPases that are transcriptionally upregulated upon infection with intracellular pathogens. Murine GBPs (mGBPs) including mGBP1 and 2 localise to and disrupt pathogen-containing vacuoles (PVs) resulting in the cell-autonomous clearing or innate immune detection of PV-resident pathogens. Human GBPs (hGBPs) are known to exert antiviral host defence and activate the NLRP3 inflammasome, but it is unclear whether hGBPs can directly recognise and control intravacuolar pathogens. Here, we report that endogenous or ectopically expressed hGBP1 fails to associate with PVs formed in human cells by the bacterial pathogens Chlamydia trachomatis or Salmonella typhimurium or the protozoan pathogen Toxoplasma gondii. While we find that hGBP1 expression has no discernable effect on intracellular replication of C. trachomatis and S. typhimurium, we observed enhanced early Toxoplasma replication in CRISPR hGBP1-deleted human epithelial cells. We thus identified a novel role for hGBP1 in cell-autonomous immunity that is independent of PV translocation, as observed for mGBPs. This study highlights fundamental differences between human and murine GBPs and underlines the need to study the functions of GBPs at cellular locations away from PVs. This article is protected by copyright. All rights reserved.

This article is protected by copyright. All rights reserved.

PMID:

 

26874079

 

[PubMed - as supplied by publisher]

A new type of quinoxalinone derivatives affects viability, invasion, and intracellular growth of Toxoplasma gondii tachyzoites in vitro

Parasitol Res. 2016 Feb 18. [Epub ahead of print]

Rivera Fernández N1,2, Mondragón Castelán M2, González Pozos S3, Ramírez Flores CJ2, Mondragón González R4, Gómez de León CT2, Castro Elizalde KN2, Marrero Ponce Y5, Arán VJ6, Martins Alho MA6,7, Mondragón Flores R8.

Author information

Abstract

Quinoxalinone derivatives, identified as VAM2 compounds (7-nitroquinoxalin-2-ones), were evaluated against Toxoplasma gondii tachyzoites of the RH strain. The VAM2 compounds were previously synthesized based on the design obtained from an in silico prediction with the software TOMOCOMD-CARDD. From the ten VAM2 drugs tested, several showed a deleterious effect on tachyzoites. However, VAM2-2 showed the highest toxoplasmicidal activity generating a remarkable decrease in tachyzoite viability (in about 91 %) and a minimal alteration in the host cell. An evident inhibition of host cell invasion by tachyzoites previously treated with VAM2-2 was observed in a dose-dependent manner. In addition, remarkable alterations were observed in the pellicle parasite, such as swelling, roughness, and blebbing. Toxoplasma motility was inhibited, and subpellicular cytoskeleton integrity was altered, inducing a release of its components to the soluble fraction. VAM2-2 showed a clear and specific deleterious effect on tachyzoites viability, structural integrity, and invasive capabilities with limited effects in host cells morphology and viability. VAM2-2 minimum inhibitory concentration (MIC50) was determined as 3.3 μM ± 1.8. Effects of quinoxalinone derivatives on T. gondii provide the basis for a future therapeutical alternative in the treatment of toxoplasmosis.

KEYWORDS: 

Apicomplexan; In silico drug design; Pellicle; Quinoxalinone derivatives; TOMOCOMD-CARDD; Toxoplasma gondii

PMID:

 

26888289

 

[PubMed - as supplied by publisher]

Is Toxoplasma Gondii Infection Related to Brain and Behavior Impairments in Humans?

PLoS One. 2016 Feb 17;11(2):e0148435. doi: 10.1371/journal.pone.0148435.

Sugden K^1,2, Moffitt TE^1,2,3,4, Pinto L², Poulton R⁵, Williams BS^1,2, Caspi A^1,2,3,4.

BACKGROUND:

Toxoplasma gondii (T. gondii) is a protozoan parasite present in around a third of the human population. Infected individuals are commonly asymptomatic, though recent reports have suggested that infection might influence aspects of the host's behavior. In particular, Toxoplasma infection has been linked to schizophrenia, suicide attempt, differences in aspects of personality and poorer neurocognitive performance. However, these studies are often conducted in clinical samples or convenience samples.

METHODS/RESULTS:

In a population-representative birth-cohort of individuals tested for presence of antibodies to T. gondii (N = 837) we investigated the association between infection and four facets of human behavior: neuropsychiatric disorder (schizophrenia and major depression), poor impulse control (suicidal behavior and criminality), personality, and neurocognitive performance. Suicide attempt was marginally more frequent among individuals with T. gondii seropositivity (p = .06). Seropositive individuals also performed worse on one out of 14 measures of neuropsychological function.

CONCLUSION:

On the whole, there was little evidence that T. gondii was related to increased risk of psychiatric disorder, poor impulse control, personality aberrations or neurocognitive impairment.

PMID:

26886853

[PubMed - as supplied by publisher]

Basal body structure and composition in the apicomplexans Toxoplasma and Plasmodium

Cilia. 2016 Feb 4;5:3. doi: 10.1186/s13630-016-0025-5. eCollection 2015.

Francia ME1, Dubremetz JF2, Morrissette NS3.

Author information

Abstract

The phylum Apicomplexa encompasses numerous important human and animal disease-causing parasites, including the Plasmodium species, and Toxoplasma gondii, causative agents of malaria and toxoplasmosis, respectively. Apicomplexans proliferate by asexual replication and can also undergo sexual recombination. Most life cycle stages of the parasite lack flagella; these structures only appear on male gametes. Although male gametes (microgametes) assemble a typical 9+2 axoneme, the structure of the templating basal body is poorly defined. Moreover, the relationship between asexual stage centrioles and microgamete basal bodies remains unclear. While asexual stages of Plasmodium lack defined centriole structures, the asexual stages of Toxoplasma and closely related coccidian apicomplexans contain centrioles that consist of nine singlet microtubules and a central tubule. There are relatively few ultra-structural images of Toxoplasma microgametes, which only develop in cat intestinal epithelium. Only a subset of these include sections through the basal body: to date, none have unambiguously captured organization of the basal body structure. Moreover, it is unclear whether this basal body is derived from pre-existing asexual stage centrioles or is synthesized de novo. Basal bodies in Plasmodium microgametes are thought to be synthesized de novo, and their assembly remains ill-defined. Apicomplexan genomes harbor genes encoding δ- and ε-tubulin homologs, potentially enabling these parasites to assemble a typical triplet basal body structure. Moreover, the UNIMOD components (SAS6, SAS4/CPAP, and BLD10/CEP135) are conserved in these organisms. However, other widely conserved basal body and flagellar biogenesis elements are missing from apicomplexan genomes. These differences may indicate variations in flagellar biogenesis pathways and in basal body arrangement within the phylum. As apicomplexan basal bodies are distinct from their metazoan counterparts, it may be possible to selectively target parasite structures in order to inhibit microgamete motility which drives generation of genetic diversity in Toxoplasma and transmission for Plasmodium. 

KEYWORDS: 

Centriole; Coccidia; Flagellum; Malaria; Microgamete; Microtubule organizing center

PMID:

 

26855772

 

[PubMed] 

Tracing amino acid exchange during host-pathogen interaction by combined stable-isotope time-resolved Raman spectral imaging

Sci Rep. 2016 Feb 9;6:20811. doi: 10.1038/srep20811.

Naemat A1, Elsheikha HM2, Boitor RA1, Notingher I1.

Author information

Abstract

This study investigates the temporal and spatial interchange of the aromatic amino acid phenylalanine (Phe) between human retinal pigment epithelial cell line (ARPE-19) and tachyzoites of the apicomplexan protozoan parasite Toxoplasma gondii (T. gondii). Stable isotope labelling by amino acids in cell culture (SILAC) is combined with Raman micro-spectroscopy to selectively monitor the incorporation of deuterium-labelled Phe into proteins in individual live tachyzoites. Our results show a very rapid uptake of l-Phe(D8) by the intracellular growing parasite. T. gondii tachyzoites are capable of extracting l-Phe(D8) from host cells as soon as it invades the cell. l-Phe(D8) from the host cell completely replaces the l-Phe within T. gondii tachyzoites 7-9 hours after infection. A quantitative model based on Raman spectra allowed an estimation of the exchange rate of Phe as 0.5-1.6 × 10(4) molecules/s. On the other hand, extracellular tachyzoites were not able to consume l-Phe(D8) after 24 hours of infection. These findings further our understanding of the amino acid trafficking between host cells and this strictly intracellular parasite. In particular, this study highlights new aspects of the metabolism of amino acid Phe operative during the interaction between T. gondii and its host cell. 

PMID:

 

26857158

 

[PubMed - in process]

In vitro Activity of Sorghum bicolor Extracts, 3-deoxyanthocyanidins, Against Toxoplasma gondii

Exp Parasitol. 2016 Feb 5. pii: S0014-4894(16)30016-9. doi: 10.1016/j.exppara.2016.02.001. [Epub ahead of print]

Abugri DA1, Witola WH2, Jaynes JM3, Toufic N4.

Author information

Abstract

We investigated dried red leaf extracts of S. bicolor for activity against Toxoplasma gondii tachyzoites. S. bicolor red leaf extracts were obtained by bioassay-guided fractionation using ethanol and ethyl acetate as solvents. Analysis of the crude and fractionated extracts from S. bicolor using electrospray ionization mass spectrometry (ESI-MS) showed that they contained significant amounts of apigeninidin, luteolinidin, 7-methoxyapigeninidin, 5-methoxyapigeninidin, 5-methoxyluteolinidin, 5-7-dimethoxyapigeninidin or 5-7-dimethoxyluteolinidin, based on mass per charge (m/z). When tested in vitro, the IC50s for inhibitory activity against T. gondii tachyzoites' growth of the ethanol and ethyl acetate extracts were 2.3- and 4-fold, respectively, lower than their cytotoxic IC50s in mammalian cells. Ethyl acetate extracts fractionated in chloroform-methanol and chloroform had IC50s against T. gondii that were 56.1- and 3-fold lower than their respective cytotoxic IC50s in mammalian cells. These antiparasitic activities were found to be consistent with those of the respective pure 3-deoxyanthocyanidin compounds identified to be contained in the fractions in significant amounts. Further, we observed that, the position and number of methoxy groups possessed by the 3-deoyanthocyanidins influenced their antiparasitic activity. Together, our findings indicate that S. bicolor red-leaf 3-deoxyanthocyanidins-rich extracts have potent in vitro inhibitory activity against the proliferative stage of T. gondii parasites.

Copyright © 2016. Published by Elsevier Inc.

KEYWORDS: 

3-deoxyanthocyanidins extracts; Sorghum bicolor; Toxoplasma gondii; antiparasitic compounds

PMID:

 

26855040

 

[PubMed - as supplied by publisher]

A Systematic Meta-Analysis of Toxoplasma gondii Prevalence in Food Animals in the United States

Foodborne Pathog Dis. 2016 Feb 8. [Epub ahead of print]

Guo M1, Mishra A1, Buchanan RL1,2, Dubey JP3, Hill DE3, Gamble HR4, Jones JL5, Pradhan AK1,2.

Author information

Abstract

Toxoplasma gondii is a widely distributed protozoan parasite. The Centers for Disease Control and Prevention reported that T. gondii is one of three pathogens (along with Salmonella and Listeria), that together account for >70% of all deaths due to foodborne illness in the United States. Food animals are reservoirs for T. gondii and act as one of the sources for parasite transmission to humans. Based on limited population-based data, the Food and Agriculture Organization/World Health Organization estimated that approximately 22% of human T. gondii infections are meatborne. The objective of the current study was to conduct a systematic meta-analysis to provide a precise estimation of T. gondii infection prevalence in food animals produced in the United States. Four databases were searched to collect eligible studies. Prevalence was estimated in six animal categories (confinement-raised market pigs, confinement-raised sows, non-confinement-raised pigs, lamb, goats, and non-confinement-raised chickens) by a quality-effects model. A wide variation in prevalence was observed in each animal category. Animals raised outdoors or that have outdoor access had a higher prevalence as compared with animals raised indoors. T. gondii prevalence in non-confinement-raised pigs ranked the highest (31.0%) followed by goats (30.7%), non-confinement-raised chickens (24.1%), lambs (22.0%), confinement-raised sows (16.7%), and confinement-raised market pigs (5.6%). These results indicate that T. gondii-infected animals are a food safety concern. The computed prevalence can be used as an important input in quantitative microbial risk assessment models to further predict public health burden.

PMID:

 

26854596

 

[PubMed - as supplied by publisher]

Morbid attraction to leopard urine in Toxoplasma-infected chimpanzees

Curr Biol. 2016 Feb 8;26(3):R98-R99. doi: 10.1016/j.cub.2015.12.020.

Poirotte C1, Kappeler PM2, Ngoubangoye B3, Bourgeois S4, Moussodji M5, Charpentier MJ6.

Author information

Abstract

Parasites are sometimes capable of inducing phenotypic changes in their hosts to improve transmission [1]. Toxoplasma gondii, a protozoan that infects a broad range of warm-blooded species, is one example that supports the so-called 'parasite manipulation hypothesis': it induces modifications in rodents' olfactory preferences, converting an innate aversion for cat odor into attraction and probably favoring trophic transmission to feline species, its only definitive hosts [2]. In humans, T. gondii induces behavioral modifications such as personality changes, prolonged reaction times and decreased long-term concentration [3]. However, modern humans are not suitable intermediate hosts because they are no longer preyed upon by felines. Consequently, behavioral modifications in infected people are generally assumed to be side effects of toxoplasmosis or residual manipulation traits that evolved in appropriate intermediate hosts. An alternative hypothesis, however, states that these changes result from parasite manipulative abilities that evolved when human ancestors were still under significant feline predation [3,4]. As such, T. gondii also alters olfactory preferences in humans; infected men rate cat urine, but not tiger urine, as pleasant while non-infected men do not [5]. To unravel the origin of Toxoplasma-induced modifications in humans, we performed olfactory tests on a living primate still predated by a feline species. We found in our closest relative, the chimpanzee (Pan troglodytes troglodytes), that Toxoplasma-infected (TI) animals lost their innate aversion towards the urine of leopards (Panthera pardus), their only natural predator. By contrast, we observed no clear difference in the response of TI and Toxoplasma-non-infected (TN) animals towards urine collected from other definitive feline hosts that chimpanzees do not encounter in nature. Although the adaptive value of parasitically induced behavior should be assessed carefully, we suggest that the behavioral modification we report could increase the probability of chimpanzee predation by leopards for the parasite's own benefit. This possible parasite adaptation would hence suggest that Toxoplasma-induced modifications in modern humans are an ancestral legacy of our evolutionary past.

Copyright © 2016 Elsevier Ltd. All rights reserved.

PMID:

 

26859275

 

[PubMed - as supplied by publisher]

The FIKK kinase of Toxoplasma gondii is not essential for the parasite's lytic cycle

Int J Parasitol. 2016 Feb 6. pii: S0020-7519(16)00022-9. doi: 10.1016/j.ijpara.2016.01.001. [Epub ahead of print]

Skariah S1, Walwyn O2, Engelberg K3, Gubbels MJ3, Gaylets C2, Kim N2, Lynch B2, Sultan A1, Mordue DG4.

Author information

Abstract

FIKK kinases are a novel family of kinases unique to the Apicomplexa. While most apicomplexans encode a single FIKK kinase, Plasmodium falciparum expresses 21 and piroplasms do not encode a FIKK kinase. FIKK kinases share a conserved C-terminal catalytic domain, but the N-terminal region is highly variable and contains no known functional domains. To date, FIKK kinases have been primarily studied in P. falciparum and Plasmodium berghei. Those that have been studied are exported from the parasite and associate with diverse locations in the infected erythrocyte cytosol or membrane. Deletion of individual P. falciparum FIKK kinases indicates that they may play a role in modification of the infected erythrocyte. The current study characterizes the single FIKK gene in Toxoplasma gondii to evaluate the importance of the FIKK kinase in an apicomplexan that has a single FIKK kinase. The TgFIKK gene encoded a protein of approximately 280 kDa. Endogenous tagging of the FIKK protein with Yellow Fluorescent Protein (YFP) showed that the FIKK protein exclusively localized to the posterior end of tachyzoites. A YFP-tagged FIKK and a Ty-tagged FIKK both co-localized with T. gondii membrane occupation and recognition nexus protein (TgMORN1) to the basal complex and were localized apical to inner membrane complex protein-5 (IMC5) and Centrin2. Deletion of TgFIKK, surprisingly, had no detectable effect on the parasite's lytic cycle in vitro in human fibroblast cells or in acute virulence in vivo. Thus, our results clearly show that while the FIKK kinase is expressed in tachyzoites, it is not essential for the lytic cycle of T. gondii.

Copyright © 2016. Published by Elsevier Ltd.

KEYWORDS: 

Basal complex; FIKK kinase; Intracellular pathogen; Parasite; Serine threonine kinases; Toxoplasma

PMID:

 

26859096

 

[PubMed - as supplied by publisher]

Toll-Like Receptor 11 (TLR11) Interacts with Flagellin and Profilin through Disparate Mechanisms

PLoS One. 2016 Feb 9;11(2):e0148987. doi: 10.1371/journal.pone.0148987.

Hatai H1,2, Lepelley A1, Zeng W3, Hayden MS1,3, Ghosh S1.

Author information

Abstract

Toll-like receptors (TLRs) are innate immune receptors that sense a variety of pathogen-associated molecular patterns (PAMPs) by interacting with them and subsequently initiating signal transduction cascades that elicit immune responses. TLR11 has been shown to interact with two known protein PAMPs: Salmonella and E. coli flagellin FliC and Toxoplasma gondii profilin-like protein. Given the highly divergent biology of these pathogens recognized by TLR11, it is unclear whether common mechanisms are used to recognize these distinct protein PAMPs. Here we show that TLR11 interacts with these two PAMPs using different receptor domains. Furthermore, TLR11 binding to flagellin and profilin exhibits differential dependency on pH and receptor ectodomain cleavage.

PMID:

 

26859749

 

[PubMed - as supplied by publisher]

Toxoplasma gondii Arginine Methyltransferase 1 (PRMT1) Is Necessary for Centrosome Dynamics during Tachyzoite Cell Division

MBio. 2016 Feb 2;7(1). pii: e02094-15. doi: 10.1128/mBio.02094-15.

El Bissati K¹, Suvorova ES², Xiao H³, Lucas O², Upadhya R¹, Ma Y¹, Hogue Angeletti R³, White MW², Weiss LM⁴, Kim K⁵.

The arginine methyltransferase family (PRMT) has been implicated in a variety of cellular processes, including signal transduction, epigenetic regulation, and DNA repair pathways. PRMT1 is thought to be responsible for the majority of PRMT activity in Toxoplasma gondii, but its exact function is unknown. To further define the biological function of the PRMT family, we generated T. gondii mutants lacking PRMT1 (Δprmt1) by deletion of the PRMT1 gene. Δprmt1 parasites exhibit morphological defects during cell division and grow slowly, and this phenotype reverses in the Δprmt::PRMT1mRFP complemented strain. Tagged PRMT1 localizes primarily in the cytoplasm with enrichment at the pericentriolar material, and the strain lacking PRMT1 is unable to segregate progeny accurately. Unlike wild-type and complemented parasites, Δprmt1 parasites have abnormal daughter buds, perturbed centrosome stoichiometry, and loss of synchronous replication. Whole-genome expression profiling demonstrated differences in expression of cell-cycle-regulated genes in the Δprmt1 strain relative to the complemented Δprmt1::PRMT1mRFP and parental wild-type strains, but these changes do not correlate with a specific block in cell cycle. Although PRMT1's primary biological function was previously proposed to be methylation of histones, our studies suggest that PRMT1 plays an important role within the centrosome to ensure the proper replication of the parasite.

IMPORTANCE:

Apicomplexan parasites include several important pathogens, including Toxoplasma gondii, a major cause of opportunistic infections and congenital birth defects. These parasites divide using a unique form of cell division called endodyogeny that is different from those of most eukaryotes. PRMT1 is a conserved arginine methyltransferase that was thought to regulate gene expression of T. gondii by modifying histone methylation. Using genetic techniques, we show that disruption of PRMT1 affects the parasite's ability to perform accurate cell division. Our studies reveal an unexpected role for arginine methylation in centrosome biology and regulation of parasite replication.
Copyright © 2016 El Bissati et al.

PMID:

26838719

[PubMed - in process]

A Novel Secreted Protein, MYR1, Is Central to Toxoplasma's Manipulation of Host Cells

MBio. 2016 Feb 2;7(1). pii: e02231-15. doi: 10.1128/mBio.02231-15.

Franco M¹, Panas MW², Marino ND², Lee MC³, Buchholz KR², Kelly FD², Bednarski JJ⁴, Sleckman BP⁵, Pourmand N³, Boothroyd JC⁶.

The intracellular protozoan Toxoplasma gondii dramatically reprograms the transcriptome of host cells it infects, including substantially up-regulating the host oncogene c-myc. By applying a flow cytometry-based selection to infected mouse cells expressing green fluorescent protein fused to c-Myc (c-Myc-GFP), we isolated mutant tachyzoites defective in this host c-Myc up-regulation. Whole-genome sequencing of three such mutants led to the identification of MYR1 (Myc regulation 1; TGGT1_254470) as essential for c-Myc induction. MYR1 is a secreted protein that requires TgASP5 to be cleaved into two stable portions, both of which are ultimately found within the parasitophorous vacuole and at the parasitophorous vacuole membrane. Deletion of MYR1 revealed that in addition to its requirement for c-Myc up-regulation, the MYR1 protein is needed for the ability of Toxoplasma tachyzoites to modulate several other important host pathways, including those mediated by the dense granule effectors GRA16 and GRA24. This result, combined with its location at the parasitophorous vacuole membrane, suggested that MYR1 might be a component of the machinery that translocates Toxoplasma effectors from the parasitophorous vacuole into the host cytosol. Support for this possibility was obtained by showing that transit of GRA24 to the host nucleus is indeed MYR1-dependent. As predicted by this pleiotropic phenotype, parasites deficient in MYR1 were found to be severely attenuated in a mouse model of infection. We conclude, therefore, that MYR1 is a novel protein that plays a critical role in how Toxoplasma delivers effector proteins to the infected host cell and that this is crucial to virulence.

IMPORTANCE:

Toxoplasma gondii is an important human pathogen and a model for the study of intracellular parasitism. Infection of the host cell with Toxoplasma tachyzoites involves the introduction of protein effectors, including many that are initially secreted into the parasitophorous vacuole but must ultimately translocate to the host cell cytosol to function. The work reported here identified a novel protein that is required for this translocation. These results give new insight into a very unusual cell biology process as well as providing a potential handle on a pathway that is necessary for virulence and, therefore, a new potential target for chemotherapy.
Copyright © 2016 Franco et al.

PMID:

26838724

[PubMed - in process]

A MORN1-associated HAD phosphatase in the basal complex is essential for Toxoplasma gondii daughter budding

Cell Microbiol. 2016 Feb 3. doi: 10.1111/cmi.12574. [Epub ahead of print]

Engelberg K¹, Ivey FD¹, Lin A¹, Kono M², Lorestani A¹, Faugno-Fusci D¹, Gilberger TW^2,3,4, White M⁵, Gubbels MJ¹.

Apicomplexan parasites replicate by several budding mechanisms with two well-characterized examples being Toxoplasma endodyogeny and Plasmodium schizogony. Completion of budding requires the tapering of the nascent daughter buds toward the basal end, driven by contraction of the basal complex. This contraction is not executed by any of the known cell division associated contractile mechanisms and in order to reveal new components of the unusual basal complex we performed a yeast two-hybrid screen with its major scaffolding protein, TgMORN1. Here we report on a conserved protein with a haloacid dehalogenase (HAD) phosphatase domain, hereafter named HAD2a, identified by yeast two-hybrid. HAD2a has demonstrated enzyme-activity in vitro, localizes to the nascent daughter buds and co-localizes with MORN1 to the basal complex during its contraction. Conditional knockout of HAD2a in Toxoplasma interferes with basal complex assembly, which leads to incomplete cytokinesis and conjoined daughters that ultimately results in disrupted proliferation. In Plasmodium, we further confirmed localization of the HAD2a ortholog to the basal complex toward the end of schizogony. In conclusion, our work highlights an essential role for this HAD phosphatase across apicomplexan budding and suggests a regulatory mechanism of differential phosphorylation on the structure and/or contractile function of the basal complex.
This article is protected by copyright. All rights reserved.

PMID:

26840427

[PubMed - as supplied by publisher]

Extended epigenotype in a Rattus novergicus - Toxoplasma gondii association

Commun Integr Biol. 2015 Mar 4;8(1):e992743.

Vyas A¹.

Several studies demonstrate that rats (Rattus novergicus) infected with protozoan parasite Toxoplasma gondii exhibit lesser fear to cat odors. This is thought to increase transmission of the parasite to its definitive hosts, i.e. cats. This is an example of extended phenotype where a gene of an organism allegedly creates a phenotype in another organism. We examined a possible proximate mechanism for this phenotype, describing an epigenetic change in arginine vasopressin gene in medial amygdala of male rats. Exogenously mimicking medial amygdala DNA hypomethylation resulted in reduction of fear to cat odors in uninfected animals, thus suggesting sufficiency. Systemic blockade of infection-induced DNA hypomethylation countermanded infection-induced behavioral change, thus suggesting necessity. This leads us to propose an epigenetic basis for this extended phenotype.

KEYWORDS:

DNA methylation; MSRE; behavioral manipulation; fear; nonapeptide; parasite; testosterone

PMID:

26844540

[PubMed - as supplied by publisher]

Gliding Associated Proteins Play Essential Roles during the Formation of the Inner Membrane Complex of Toxoplasma gondii

PLoS Pathog. 2016 Feb 4;12(2):e1005403. doi: 10.1371/journal.ppat.1005403. eCollection 2016.

Harding CR¹, Egarter S¹, Gow M¹, Jiménez-Ruiz E¹, Ferguson DJ², Meissner M¹.

The inner membrane complex (IMC) of apicomplexan parasites is a specialised structure localised beneath the parasite's plasma membrane, and is important for parasite stability and intracellular replication. Furthermore, it serves as an anchor for the myosin A motor complex, termed the glideosome. While the role of this protein complex in parasite motility and host cell invasion has been well described, additional roles during the asexual life cycle are unknown. Here, we demonstrate that core elements of the glideosome, the gliding associated proteins GAP40 and GAP50 as well as members of the GAPM family, have critical roles in the biogenesis of the IMC during intracellular replication. Deletion or disruption of these genes resulted in the rapid collapse of developing parasites after initiation of the cell cycle and led to redistribution of other glideosome components.

PMID:

26845335

[PubMed - as supplied by publisher]

Vacuolar protein sorting mechanisms in apicomplexan parasites

Mol Biochem Parasitol. 2016 Feb 1. pii: S0166-6851(16)30007-X. doi: 10.1016/j.molbiopara.2016.01.007. [Epub ahead of print]

Jimenez-Ruiz E¹, Morlon-Guyot J², Daher W³, Meissner M⁴.

The phylum Apicomplexa comprises more than 5000 species including pathogens of clinical and economical importance. These obligate intracellular parasites possess a highly complex endomembrane system to build among others three morphologically distinct secretory organelles: rhoptries, micronemes and dense granules. Proteins released by these organelles are essential for invasion and hijacking of the host cell. Due to the complexity of the internal organization of these parasites, a wide panoply of trafficking factors was expected to be required for the correct sorting of proteins towards the various organelles. However, T. gondii and other apicomplexan parasites contain only a core set of these factors and several of the vacuolar protein sorting (VPS) homologs found in most eukaryotes have been lost in this phylum. In this review, we will summarise our current knowledge about the role of trafficking complexes in Toxoplasma gondii, highlighting recent studies focused on complexes formed by VPS proteins. We also present a novel, hypothetical model, suggesting the recycling of parasite membrane and micronemal proteins.
Copyright © 2016. Published by Elsevier B.V.

KEYWORDS:

Multi-subunit tethering complex; Toxoplasma gondii; microneme recycling; vesicular protein sorting

PMID:

26844642

[PubMed - as supplied by publisher]

The conserved apicomplexan Aurora kinase TgArk3 is involved in endodyogeny, duplication rate and parasite virulence

Cell Microbiol. 2016 Feb 2. doi: 10.1111/cmi.12571. [Epub ahead of print]

Berry L¹, Chen CT², Reininger L³, Carvalho TG⁴, El Hajj H⁵, Morlon-Guyot J¹, Bordat Y¹, Lebrun M¹, Gubbels MJ², Doerig C⁴, Daher W¹.

Aurora kinases are eukaryotic serine/threonine protein kinases that regulate key events associated with chromatin condensation, centrosome and spindle function, and cytokinesis. Elucidating the roles of Aurora kinases in apicomplexan parasites is crucial to understand the cell cycle control during Plasmodium schizogony or Toxoplasma endodyogeny. Here, we report on the localization of two previously uncharacterized Toxoplasma Aurora-related kinases (Ark2 and Ark3) in tachyzoites and of the uncharacterized Ark3 orthologue in Plasmodium falciparum erythrocytic stages. In T. gondii, we show that TgArk2 and TgArk3 concentrate at specific sub-cellular structures linked to parasite division: the mitotic spindle and intranuclear mitotic structures (TgArk2), and the outer core of the centrosome and the budding daughter cells cytoskeleton (TgArk3). By tagging the endogenous PfArk3 gene with the green fluorescent protein (GFP) in live parasites, we show that PfArk3 protein expression peaks late in schizogony and localizes at the periphery of budding schizonts. Disruption of the TgArk2 gene reveals no essential function for tachyzoite propagation in vitro, which is surprising giving that the P. falciparum and P. berghei orthologues are essential for erythrocyte schizogony. In contrast, knock-down of TgArk3 protein results in pronounced defects in parasite division and a major growth deficiency. TgArk3-depleted parasites display several defects, such as reduced parasite growth rate, delayed egress and parasite duplication, defect in rosette formation, reduced parasite size and invasion efficiency and lack of virulence in mice. Our study provides new insights into cell cycle control in Toxoplasma and malaria parasites, and highlights Aurora kinase 3 as potential drug target.

KEYWORDS:

apicomplexa; aurora kinases; centrosome; endodyogeny; plasmodium falciparum; replication; schizogony; spindle pole bodies; tet-inducible system; toxoplasma gondii

PMID:

26833682

[PubMed - as supplied by publisher]