scholarly journals Exit from Host Cells by the Pathogenic Parasite Toxoplasma gondii Does Not Require Motility

2007 ◽  
Vol 7 (1) ◽  
pp. 131-140 ◽  
Author(s):  
Mark D. Lavine ◽  
Gustavo Arrizabalaga
Keyword(s):  
Toxoplasma Gondii ◽  
Host Cell ◽  
Host Cells ◽  
Membrane Tension ◽  
Experimental Induction ◽  
Intracellular Parasites ◽  
Artificial Induction ◽  
Host Membrane ◽  
Parasite Motility ◽  
Parasite Egress

ABSTRACTThe process by which the intracellular parasiteToxoplasma gondiiexits its host cell is central to its propagation and pathogenesis. Experimental induction of motility in intracellular parasites results in parasite egress, leading to the hypothesis that egress depends on the parasite's actin-dependent motility. Using a novel assay to monitor egress without experimental induction, we have established that inhibiting parasite motility does not block this process, although treatment with actin-disrupting drugs does delay egress. However, using an irreversible actin inhibitor, we show that this delay is due to the disruption of host cell actin alone, apparently resulting from the consequent loss of membrane tension. Accordingly, by manipulating osmotic pressure, we show that parasite egress is delayed by releasing membrane tension and promoted by increasing it. Therefore, without artificial induction, egress does not depend on parasite motility and can proceed by mechanical rupture of the host membrane.

scholarly journals C-Mannosylation of Toxoplasma gondii proteins promotes attachment to host cells and parasite virulence

2019 ◽  
Vol 295 (4) ◽  
pp. 1066-1076 ◽  
Author(s):  
Andreia Albuquerque-Wendt ◽  
Damien Jacot ◽  
Nicolas Dos Santos Pacheco ◽  
Carla Seegers ◽  
Patricia Zarnovican ◽  
...  
Keyword(s):  
Toxoplasma Gondii ◽  
Protective Immunity ◽  
Host Cells ◽  
Apicomplexan Parasites ◽  
Tryptophan Residues ◽  
Parasite Survival ◽  
Parasite Motility ◽  
Parasite Egress ◽  
Thrombospondin Type 1 Repeats

C-Mannosylation is a common modification of thrombospondin type 1 repeats present in metazoans and recently identified also in apicomplexan parasites. This glycosylation is mediated by enzymes of the DPY19 family that transfer α-mannoses to tryptophan residues in the sequence WX2WX2C, which is part of the structurally essential tryptophan ladder. Here, deletion of the dpy19 gene in the parasite Toxoplasma gondii abolished C-mannosyltransferase activity and reduced levels of the micronemal protein MIC2. The loss of C-mannosyltransferase activity was associated with weakened parasite adhesion to host cells and with reduced parasite motility, host cell invasion, and parasite egress. Interestingly, the C-mannosyltransferase–deficient Δdpy19 parasites were strongly attenuated in virulence and induced protective immunity in mice. This parasite attenuation could not simply be explained by the decreased MIC2 level and strongly suggests that absence of C-mannosyltransferase activity leads to an insufficient level of additional proteins. In summary, our results indicate that T. gondii C-mannosyltransferase DPY19 is not essential for parasite survival, but is important for adhesion, motility, and virulence.

scholarly journals Rab11A regulates the constitutive secretory pathway during Toxoplasma gondii invasion of host cells and parasite replication

2019 ◽  
Author(s):  
Venugopal Kannan ◽  
Chehade Sylia ◽  
Werkmeister Elisabeth ◽  
Barois Nicolas ◽  
Periz Javier ◽  
...  
Keyword(s):  
Toxoplasma Gondii ◽  
Host Cell ◽  
Molecular Mechanisms ◽  
Transmembrane Protein ◽  
Small Gtpase ◽  
Host Cells ◽  
Dense Granules ◽  
Parasite Replication ◽  
Parasite Motility

SummaryToxoplasma gondii possesses an armada of secreted virulent factors that enable parasite invasion and survival into host cells. These factors are contained in specific secretory organelles, the rhoptries, micronemes and dense granules that release their content upon host cell recognition. Dense granules are secreted in a constitutive manner during parasite replication and play a crucial role in modulating host metabolic and immune responses. While the molecular mechanisms triggering rhoptry and microneme release upon host cell adhesion have been well studied, constitutive secretion remains a poorly explored aspect of T. gondii vesicular trafficking. Here, we investigated the role of the small GTPase Rab11A, a known regulator of exocytosis in eukaryotic cells. Our data revealed an essential role of Rab11A in promoting the cytoskeleton driven transport of DG and the release of their content into the vacuolar space. Rab11A also regulates transmembrane protein trafficking and localization during parasite replication, indicating a broader role of Rab11A in cargo exocytosis at the plasma membrane. Moreover, we found that Rab11A also regulates extracellular parasite motility and adhesion to host cells. In line with these findings, MIC2 secretion was altered in Rab11A-defective parasites, which also exhibited severe morphological defects. Strikingly, by live imaging we observed a polarized accumulation of Rab11A-positive vesicles and dense granules at the apical pole of extracellular motile parasites suggesting that a Rab11A-dependent apically polarized transport of cargo regulates parasite motility.

Host cells: mobilizable lipid resources for the intracellular parasite Toxoplasma gondii

2002 ◽  
Vol 115 (15) ◽  
pp. 3049-3059 ◽  
Author(s):  
Audra J. Charron ◽  
L. David Sibley
Keyword(s):  
Fatty Acids ◽  
Toxoplasma Gondii ◽  
Host Cell ◽  
Parasitophorous Vacuole ◽  
Host Cells ◽  
Intracellular Parasite ◽  
Head Groups ◽  
Intracellular Parasites ◽  
Successful Replication ◽  
Conjugated Compounds

Successful replication of the intracellular parasite Toxoplasma gondii within its parasitophorous vacuole necessitates a substantial increase in membrane mass. The possible diversion and metabolism of host cell lipids and lipid precursors by Toxoplasma was therefore investigated using radioisotopic and fluorophore-conjugated compounds. Confocal microscopic analyses demonstrated that Toxoplasma is selective with regards to both the acquisition and compartmentalization of host cell lipids. Lipids were compartmentalized into parasite endomembranes and, in some cases, were apparently integrated into the surrounding vacuolar membrane. Additionally,some labels became concentrated in discrete lipid bodies that were biochemically and morphologically distinct from the parasite apical secretory organelles. Thin layer chromatography established that parasites readily scavenged long-chain fatty acids as well as cholesterol, and in certain cases modified the host-derived lipids. When provided with radiolabeled phospholipid precursors, including polar head groups, phosphatidic acid and small fatty acids, intracellular parasites preferentially accrued phosphatidylcholine(PtdCho) over other phospholipids. Moreover, Toxoplasma was found to be competent to synthesize PtdCho from radiolabeled precursors obtained from its environment. Together, these studies underscore the ability of Toxoplasma gondii to divert and use lipid resources from its host, a process that may contribute to the biogenesis of parasite membranes.

scholarly journals 1,3,4-Thiadiazoles Effectively Inhibit Proliferation of Toxoplasma gondii

Cells ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 1053
Author(s):  
Lidia Węglińska ◽  
Adrian Bekier ◽  
Katarzyna Dzitko ◽  
Barbara Pacholczyk-Sienicka ◽  
Łukasz Albrecht ◽  
...  
Keyword(s):  
Toxoplasma Gondii ◽  
Host Cell ◽  
Cell Invasion ◽  
Direct Action ◽  
Human Fibroblasts ◽  
Imidazole Ring ◽  
Host Cells ◽  
In Vitro Assays ◽  
Host Cell Invasion

Congenital and acquired toxoplasmosis caused by the food- and water-born parasite Toxoplasma gondii (T. gondii) is one of the most prevalent zoonotic infection of global importance. T. gondii is an obligate intracellular parasite with limited capacity for extracellular survival, thus a successful, efficient and robust host cell invasion process is crucial for its survival, proliferation and transmission. In this study, we screened a series of novel 1,3,4-thiadiazole-2-halophenylamines functionalized at the C5 position with the imidazole ring (1b–12b) for their effects on T. gondii host cell invasion and proliferation. To achieve this goal, these compounds were initially subjected to in vitro assays to assess their cytotoxicity on human fibroblasts and then antiparasitic efficacy. Results showed that all of them compare favorably to control drugs sulfadiazine and trimethoprim in terms of T. gondii growth inhibition (IC50) and selectivity toward the parasite, expressed as selectivity index (SI). Subsequently, the most potent of them with meta-fluoro 2b, meta-chloro 5b, meta-bromo 8b, meta-iodo 11b and para-iodo 12b substitution were tested for their efficacy in inhibition of tachyzoites invasion and subsequent proliferation by direct action on established intracellular infection. All the compounds significantly inhibited the parasite invasion and intracellular proliferation via direct action on both tachyzoites and parasitophorous vacuoles formation. The most effective was para-iodo derivative 12b that caused reduction in the percentage of infected host cells by 44% and number of tachyzoites per vacuole by 93% compared to non-treated host cells. Collectively, these studies indicate that 1,3,4-thiadiazoles 1b–12b, especially 12b with IC50 of 4.70 µg/mL and SI of 20.89, could be considered as early hit compounds for future design and synthesis of anti-Toxoplasma agents that effectively and selectively block the invasion and subsequent proliferation of T. gondii into host cells.

scholarly journals Reduction in the mitochondrial membrane potential of Toxoplasma gondii after invasion of host cells

1984 ◽  
Vol 70 (1) ◽  
pp. 73-81
Author(s):  
K. Tanabe ◽  
K. Murakami
Keyword(s):  
Membrane Potential ◽  
Toxoplasma Gondii ◽  
Mitochondrial Membrane Potential ◽  
Mitochondrial Membrane ◽  
Protozoan Parasite ◽  
Fluorescent Dye ◽  
Host Cells ◽  
Intracellular Parasites ◽  
Neutral Compounds ◽  
Infected Cells

The membrane potential of Toxoplasma gondii, an obligatory intracellular protozoan parasite, was monitored with the cationic permeant fluorescent dye rhodamine 123 (R123). Fluorescence microscopy revealed R123 to be partitioned predominantly in a restricted part of the parasite, which consisted of twisted or branched tubules, or of granular bodies. These structures were frequently connected to each other. The dye retention by these structures was markedly reduced by treating R123-labelled parasites with the proton ionophore, carbonylcyanide m-chlorophenylhydrazone, the potassium ionophore, valinomycin and the inhibitor of electron transport, antimycin A. Thus, these structures are regarded as the parasite mitochondria. Another cationic fluorescent dye, rhodamine 6G, stained the parasite mitochondria, whereas a negatively charged fluorescent dye, fluorescein, and the neutral compounds, rhodamine 110 and rhodamine B, did not. This fact indicates that R123 monitored the parasite mitochondrial membrane potential. T. gondii-infected 3T3 cells were also stained with R123. In contrast to the mitochondria of extracellular parasites, those of intracellular parasites failed to take up the dye. The absence of fluorescence in intracellular parasites persisted until the infected host cells ruptured and liberated daughter parasites 1 day after infection. Parasites, liberated from the host cells, either spontaneously or artificially by passing the infected cells through a 27G needle, regained the ability to take up the dye. After direct microinjection of R123 into the vacuole in which the parasite grows and multiples, the dye appeared in the host-cell mitochondria but not in the parasite's mitochondria. Thus, we conclude that the mitochondrial membrane potential of T. gondii was reduced after invasion of host cells by the parasite.

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 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.

Invasion of Toxoplasma gondii occurs by active penetration of the host cell

1995 ◽  
Vol 108 (6) ◽  
pp. 2457-2464 ◽  
Author(s):  
J.H. Morisaki ◽  
J.E. Heuser ◽  
L.D. Sibley
Keyword(s):  
Toxoplasma Gondii ◽  
Host Cell ◽  
Tyrosine Phosphorylation ◽  
Host Cells ◽  
The Novel ◽  
Host Proteins ◽  
Host Cell Membrane ◽  
Membrane Ruffling ◽  
Obligate Intracellular ◽  
Obligate Intracellular Parasite

Toxoplasma gondii is an obligate intracellular parasite that infects a wide variety of vertebrate cells including macrophages. We have used a combination of video microscopy and fluorescence localization to examine the entry of Toxoplasma into macrophages and nonphagocytic host cells. Toxoplasma actively invaded host cells without inducing host cell membrane ruffling, actin microfilament reorganization, or tyrosine phosphorylation of host proteins. Invasion occurred rapidly and within 25–40 seconds the parasite penetrated into a tight-fitting vacuole formed by invagination of the plasma membrane. In contrast, during phagocytosis of Toxoplasma, extensive membrane ruffling captured the parasite in a loose-fitting phagosome that formed over a period of 2–4 minutes. Phagocytosis involved both reorganization of the host cytoskeleton and tyrosine phosphorylation of host proteins. In some cases, parasites that were first internalized by phagocytosis, were able to escape from the phagosome by a process analogous to invasion. These studies reveal that active penetration of the host cell by Toxoplasma is fundamentally different from phagocytosis or induced endocytic uptake. The novel ability to penetrate the host cell likely contributes to the capability of Toxoplasma-containing vacuoles to avoid endocytic processing.

Association of host cell endoplasmic reticulum and mitochondria with the Toxoplasma gondii parasitophorous vacuole membrane: a high affinity interaction

1997 ◽  
Vol 110 (17) ◽  
pp. 2117-2128 ◽  
Author(s):  
A.P. Sinai ◽  
P. Webster ◽  
K.A. Joiner
Keyword(s):  
Endoplasmic Reticulum ◽  
Toxoplasma Gondii ◽  
Host Cell ◽  
Parasitophorous Vacuole ◽  
Protozoan Parasite ◽  
Host Cells ◽  
Parasitophorous Vacuole Membrane ◽  
Vacuole Membrane ◽  
Protein Protein Interaction ◽  
High Affinity

The parasitophorous vacuole membrane (PVM) of the obligate intracellular protozoan parasite Toxoplasma gondii forms tight associations with host mitochondria and the endoplasmic reticulum (ER). We have used a combination of morphometric and biochemical approaches to characterize this unique phenomenon, which we term PVM-organelle association. The PVM is separated from associated mitochondria and ER by a mean distance of 12 and 18 nm, respectively. The establishment of PVM-organelle association is dependent on active parasite entry, but does not require parasite viability for its maintenance. Association is not a consequence of spatial constraints imposed on the growing vacuole. Morphometric analysis indicates that the extent of mitochondrial association with the PVM stays constant as the vacuole enlarges, whereas the extent of ER association decreases. Disruption of host cell microtubules partially blocks the establishment but not the maintenance of PVM-mitochondrial association, and has no significant effect on PVM-ER association. PVM-organelle association is maintained following disruption of infected host cells, as assessed by electron microscopy and by sub-cellular fractionation showing co-migration of fixed PVM and organelle markers. Taken together, the data suggest that a high affinity, potentially protein-protein interaction between parasite and organelle components is responsible for PVM-organelle association.

Besnoitia besnoiti and Toxoplasma gondii: two apicomplexan strategies to manipulate the host cell centrosome and Golgi apparatus

Parasitology ◽  
2014 ◽  
Vol 141 (11) ◽  
pp. 1436-1454 ◽  
Author(s):  
RITA CARDOSO ◽  
SOFIA NOLASCO ◽  
JOÃO GONÇALVES ◽  
HELDER C. CORTES ◽  
ALEXANDRE LEITÃO ◽  
...  
Keyword(s):  
Toxoplasma Gondii ◽  
Golgi Apparatus ◽  
Host Cell ◽  
Parasitophorous Vacuole ◽  
Host Cells ◽  
Besnoitia Besnoiti ◽  
Microtubule Cytoskeleton ◽  
Cytoskeleton Organization ◽  
Evolutionary Paths ◽  
The Impact

SUMMARYBesnoitia besnoiti and Toxoplasma gondii are two closely related parasites that interact with the host cell microtubule cytoskeleton during host cell invasion. Here we studied the relationship between the ability of these parasites to invade and to recruit the host cell centrosome and the Golgi apparatus. We observed that T. gondii recruits the host cell centrosome towards the parasitophorous vacuole (PV), whereas B. besnoiti does not. Notably, both parasites recruit the host Golgi apparatus to the PV but its organization is affected in different ways. We also investigated the impact of depleting and over-expressing the host centrosomal protein TBCCD1, involved in centrosome positioning and Golgi apparatus integrity, on the ability of these parasites to invade and replicate. Toxoplasma gondii replication rate decreases in cells over-expressing TBCCD1 but not in TBCCD1-depleted cells; while for B. besnoiti no differences were found. However, B. besnoiti promotes a reorganization of the Golgi ribbon previously fragmented by TBCCD1 depletion. These results suggest that successful establishment of PVs in the host cell requires modulation of the Golgi apparatus which probably involves modifications in microtubule cytoskeleton organization and dynamics. These differences in how T. gondii and B. besnoiti interact with their host cells may indicate different evolutionary paths.

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