Trafficking of malarial proteins to the host cell cytoplasm and erythrocyte surface membrane involves multiple pathways.

During the asexual stage of malaria infection, the intracellular parasite exports membranes into the erythrocyte cytoplasm and lipids and proteins to the host cell membrane, essentially "transforming" the erythrocyte. To investigate lipid and protein trafficking pathways within Plasmodium falciparum-infected erythrocytes, synchronous cultures are temporally analyzed by confocal fluorescence imaging microscopy for the production, location and morphology of exported membranes (vesicles) and parasite proteins. Highly mobile vesicles are observed as early as 4 h postinvasion in the erythrocyte cytoplasm of infected erythrocytes incubated in vitro with C6-NBD-labeled phospholipids. These vesicles are most prevalent in the trophozoite stage. An immunofluorescence technique is developed to simultaneously determine the morphology and distribution of the fluorescent membranes and a number of parasite proteins within a single parasitized erythrocyte. Parasite proteins are visualized with FITC- or Texas red-labeled monoclonal antibodies. Double-label immunofluorescence reveals that of the five parasite antigens examined, only one was predominantly associated with membranes in the erythrocyte cytoplasm. Two other parasite antigens localized only in part to these vesicles, with the majority of the exported antigens present in lipid-free aggregates in the host cell cytoplasm. Another parasite antigen transported into the erythrocyte cytoplasm is localized exclusively in lipid-free aggregates. A parasite plasma membrane (PPM) and/or parasitophorous vacuolar membrane (PVM) antigen which is not exported always colocalizes with fluorescent lipids in the PPM/PVM. Visualization of two parasite proteins simultaneously using FITC- and Texas red-labeled 2 degrees antibodies reveals that some parasite proteins are constitutively transported in the same vesicles, whereas other are segregated before export. Of the four exported antigens, only one appears to cross the barriers of the PPM and PVM through membrane-mediated events, whereas the others are exported across the PPM/PVM to the host cell cytoplasm and surface membrane through lipid (vesicle)-independent pathways.

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Eimeria canadensis (Protozoa, Sporozoea): ultrastructure of the host–parasite interface during development of first-generation schizonts in vitro

Canadian Journal of Zoology ◽

10.1139/z80-278 ◽

1980 ◽

Vol 58 (11) ◽

pp. 2018-2025 ◽

Cited By ~ 1

Author(s):

Bodo E. G. Mueller

Keyword(s):

Host Cell ◽

Parasitophorous Vacuole ◽

Eimeria Species ◽

Outer Zone ◽

Ultrastructural Observation ◽

Cell Cytoplasm ◽

Cell Organelles ◽

Host Cell Cytoplasm ◽

Host Parasite

Eimeria canadensis sporozoites were inoculated into monolayer cultures of Madin–Darby bovine kidney and primary bovine embryonic kidney cells. Sporozoites retained their shape for at least 9 days. At that time, the nucleus was enlarged and contained a prominent nucleolus, and amylopectin granules were no longer apparent. The width of the parasitophorous vacuole (pv) between host cell cytoplasm and parasite pellicle widened during transformation of sporozoites into multinucleate schizonts. Areas of altered host cell cytoplasm immediately adjacent to the pv membrane increased in size and became confluent, resulting in the formation of two distinct layers of cytoplasm. The outer zone contained the host cell nucleus, mitochondria, Golgi stacks, and ER, whereas the inner layer appeared granular and was void of all cell organelles except structures resembling ribosomes. Microfilaments were abundant at the border between inner and outer zone. In the most advanced stages observed, host cell organelles persisted only in the perinuclear region. The remaining, attenuated cytoplasm resembled the former inner zone.The novel ultrastructural observation of a bilayered cytoplasm of cells harbouring E. canadensis schizonts is compared with light microscope reports of similar effects caused by other Eimeria species of ruminants and with electron microscope findings of altered intestinal and abomasal cells of sheep harbouring "globidial" schizonts.

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Toxoplasma gondii reorganizes the host cell architecture during spontaneous cyst formation in vitro

Parasitology ◽

10.1017/s0031182017002050 ◽

2017 ◽

Vol 145 (8) ◽

pp. 1027-1038 ◽

Cited By ~ 5

Author(s):

T. C. Paredes-Santos ◽

E. S. Martins-Duarte ◽

W. de Souza ◽

M. Attias ◽

R. C. Vommaro

Keyword(s):

Toxoplasma Gondii ◽

Host Cell ◽

Cyst Wall ◽

Cyst Formation ◽

Acute Stage ◽

Host Cells ◽

Cell Cytoplasm ◽

Chronic Stage ◽

Host Cell Cytoplasm

AbstractToxoplasma gondii is an intracellular protozoan parasite that causes toxoplasmosis, a prevalent infection related to abortion, ocular diseases and encephalitis in immuno-compromised individuals. In the untreatable (and life-long) chronic stage of toxoplasmosis, parasitophorous vacuoles (PVs, containing T. gondii tachyzoites) transform into tissue cysts, containing slow-dividing bradyzoite forms. While acute-stage infection with tachyzoites involves global rearrangement of the host cell cytoplasm, focused on favouring tachyzoite replication, the cytoplasmic architecture of cells infected with cysts had not been described. Here, we characterized (by fluorescence and electron microscopy) the redistribution of host cell structures around T. gondii cysts, using a T. gondii strain (EGS) with high rates of spontaneous cystogenesis in vitro. Microtubules and intermediate filaments (but not actin microfilaments) formed a ‘cage’ around the cyst, and treatment with taxol (to inhibit microtubule dynamics) favoured cystogenesis. Mitochondria, which appeared adhered to the PV membrane, were less closely associated with the cyst wall. Endoplasmic reticulum (ER) profiles were intimately associated with folds in the cyst wall membrane. However, the Golgi complex was not preferentially localized relative to the cyst, and treatment with tunicamycin or brefeldin A (to disrupt Golgi or ER function, respectively) had no significant effect on cystogenesis. Lysosomes accumulated around cysts, while early and late endosomes were more evenly distributed in the cytoplasm. The endocytosis tracer HRP (but not BSA or transferrin) reached bradyzoites after uptake by infected host cells. These results suggest that T. gondii cysts reorganize the host cell cytoplasm, which may fulfil specific requirements of the chronic stage of infection.

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The Hydrophilic Translocator for Vibrio parahaemolyticus, T3SS2, Is Also Translocated

Infection and Immunity ◽

10.1128/iai.00402-12 ◽

2012 ◽

Vol 80 (8) ◽

pp. 2940-2947 ◽

Cited By ~ 12

Author(s):

Xiaohui Zhou ◽

Jennifer M. Ritchie ◽

Hirotaka Hiyoshi ◽

Tetsuya Iida ◽

Brigid M. Davis ◽

...

Keyword(s):

Host Cell ◽

Vibrio Parahaemolyticus ◽

Diarrheal Disease ◽

Host Cells ◽

Cell Cytoplasm ◽

Host Cell Membrane ◽

Membrane Pore ◽

Content Type ◽

Bacterial Proteins ◽

Host Cell Cytoplasm

ABSTRACTThe pathogenesis of the diarrheal disease caused byVibrio parahaemolyticus, a leading cause of seafood-associated enteritis worldwide, is dependent upon a type III secretion system, T3SS2. This apparatus enables the pathogen to inject bacterial proteins (effectors) into the cytosol of host cells and thereby modulate host processes. T3SS effector proteins transit into the host cell via a membrane pore (translocon) typically formed by 3 bacterial proteins. We have identified the third translocon protein for T3SS2: VopW, which was previously classified as an effector protein for a homologous T3SS inV. cholerae. VopW is a hydrophilic translocon protein; like other such proteins, it is not inserted into the host cell membrane but is required for insertion of the two hydrophobic translocators, VopB2 and VopD2, that constitute the membrane channel. VopW is not required for secretion of T3SS2 effectors into the bacterial culture medium; however, it is essential for transfer of these proteins into the host cell cytoplasm. Consequently, deletion ofvopWabrogates the virulence ofV. parahaemolyticusin several animal models of diarrheal disease. Unlike previously described hydrophilic translocators, VopW is itself translocated into the host cell cytoplasm, raising the possibility that it functions as both a translocator and an effector.

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Paromomycin and Geneticin Inhibit IntracellularCryptosporidium parvum without Trafficking through the Host Cell Cytoplasm: Implications for Drug Delivery

Infection and Immunity ◽

10.1128/iai.66.8.3874-3883.1998 ◽

1998 ◽

Vol 66 (8) ◽

pp. 3874-3883 ◽

Cited By ~ 44

Author(s):

Jeffrey K. Griffiths ◽

Ramaswamy Balakrishnan ◽

Giovanni Widmer ◽

Saul Tzipori

Keyword(s):

Host Cell ◽

Parasitophorous Vacuole ◽

Parasite Development ◽

Cell Cytoplasm ◽

Bacterial Killing ◽

Host Cell Cytoplasm ◽

Intracellular Parasites ◽

Mdbk Cells ◽

Major Route

ABSTRACT Cryptosporidium parvum, which causes intractable diarrhea and lethal wasting in people with AIDS, occupies an unusual intracellular but extracytoplasmic niche. No reliable therapy for cryptosporidiosis exists, though the aminoglycoside paromomycin is somewhat effective. We report that paromomycin and the related compound geneticin manifest their major in vitro anti-C. parvumactivity against intracellular parasites via a mechanism that does not require drug trafficking through the host cell cytoplasm. We used both normal and transformed aminoglycoside-resistant Caco-2 or MDBK cells in these studies. Timed-exposure experiments demonstrated that these drugs inhibit intracellular but not extracellular parasites. Apical but not basolateral exposure of infected cells to these drugs led to very significant parasite inhibition, indicating an apical topological restriction of action. We estimated intracytoplasmic concentrations of paromomycin, using an intracellular bacterial killing assay, and found that C. parvum infection did not lead to increased paromomycin concentrations compared to those in uninfected cells. Global [3H]paromomycin uptake by Caco-2 cells was ∼200-fold higher than the estimated intracytoplasmic paromomycin concentration, suggestive of host cell vesicular uptake and concentration (as has been reported with other cell lines). However, preinfection exposure of Caco-2 cells to paromomycin did not result in subsequent inhibition of parasite development, indicating that if exogenous paromomycin enters the infected host cell vesicular compartment, it does not effectively communicate with the parasite. Thus, the apical membranes overlying the parasite and parasitophorous vacuole may be the unsuspected major route of entry for paromomycin and may be of importance in the design and discovery of novel drug therapies for the otherwise untreatable C. parvum.

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Faculty Opinions recommendation of The Mycobacterium tuberculosis phagosome in human macrophages is isolated from the host cell cytoplasm.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1009414.126157 ◽

2002 ◽

Author(s):

Sergio Grinstein

Keyword(s):

Mycobacterium Tuberculosis ◽

Host Cell ◽

Cell Cytoplasm ◽

Human Macrophages ◽

Host Cell Cytoplasm

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Intracellular host cell membrane remodelling induced by SARS‐CoV‐2 infection in vitro

Biology of the Cell ◽

10.1111/boc.202000146 ◽

2021 ◽

Author(s):

Lucio Ayres Caldas ◽

Fabiana Avila Carneiro ◽

Fabio Luis Monteiro ◽

Ingrid Augusto ◽

Luiza Mendonça Higa ◽

...

Keyword(s):

Cell Membrane ◽

Host Cell ◽

Host Cell Membrane

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The RhopH complex is transferred to the host cell cytoplasm following red blood cell invasion by Plasmodium falciparum

Molecular and Biochemical Parasitology ◽

10.1016/j.molbiopara.2008.04.002 ◽

2008 ◽

Vol 160 (2) ◽

pp. 81-89 ◽

Cited By ~ 48

Author(s):

Laetitia Vincensini ◽

Gamou Fall ◽

Laurence Berry ◽

Thierry Blisnick ◽

Catherine Braun Breton

Keyword(s):

Plasmodium Falciparum ◽

Blood Cell ◽

Host Cell ◽

Cell Invasion ◽

Red Blood Cell ◽

Cell Cytoplasm ◽

Host Cell Cytoplasm

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Brefeldin A inhibits transport of the glycophorin-binding protein from Plasmodium falciparum into the host erythrocyte

Biochemical Journal ◽

10.1042/bj3000821 ◽

1994 ◽

Vol 300 (3) ◽

pp. 821-826 ◽

Cited By ~ 55

Author(s):

J Benting ◽

D Mattei ◽

K Lingelbach

Keyword(s):

Plasmodium Falciparum ◽

Golgi Apparatus ◽

Host Cell ◽

Protein Secretion ◽

Secretory Pathway ◽

Binding Protein ◽

Brefeldin A ◽

Cell Cytoplasm ◽

Parasite Cell ◽

Host Cell Cytoplasm

Plasmodium falciparum, a protozoan parasite of the human erythrocyte, causes the most severe form of malaria. During its intraerythrocytic development, the parasite synthesizes proteins which are exported into the host cell. The compartments involved in the secretory pathway of P. falciparum are still poorly characterized. A Golgi apparatus has not been identified, owing to the lack of specific protein markers and Golgi-specific post-translational modifications in the parasite. The fungal metabolite brefeldin A (BFA) is known to inhibit protein secretion in higher eukaryotes by disrupting the integrity of the Golgi apparatus. We have used the parasite-encoded glycophorin-binding protein (GBP), a soluble protein found in the host cell cytoplasm, as a marker to investigate the effects of BFA on protein secretion in the intracellular parasite. In the presence of BFA, GBP was not transported into the erythrocyte, but remained inside the parasite cell. The effect caused by BFA was reversible, and the protein could be chased into the host cell cytoplasm within 30 min. Transport of GBP from the BFA-sensitive site into the host cell did not require protein synthesis. Similar observations were made when infected erythrocytes were incubated at 15 degrees C. Incubation at 20 degrees C resulted in a reduction rather than a complete block of protein export. The relevance of our findings to the identification of compartments involved in protein secretion from the parasite cell is discussed.

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