scholarly journals Receptor for Retrograde Transport in the Apicomplexan Parasite Toxoplasma gondii

2005 ◽  
Vol 4 (2) ◽  
pp. 432-442 ◽  
Author(s):  
Stacy L. Pfluger ◽  
Holly V. Goodson ◽  
Jennifer M. Moran ◽  
Christine J. Ruggiero ◽  
Xin Ye ◽  
...  
Keyword(s):  
Toxoplasma Gondii ◽  
Membrane Trafficking ◽  
Cell Biology ◽  
Retrograde Transport ◽  
Stable Expression ◽  
Host Cells ◽  
Functional Assay ◽  
Obligate Intracellular ◽  
Intracellular Parasites ◽  
A Subunit

ABSTRACT Toxoplasma gondii and its apicomplexan relatives (such as Plasmodium falciparum, which causes malaria) are obligate intracellular parasites that rely on sequential protein release from specialized secretory organelles for invasion and multiplication within host cells. Because of the importance of these unusual membrane trafficking pathways for drug development and comparative cell biology, characterizing them is essential. In particular, it is unclear what role retrieval mechanisms play in parasite membrane trafficking or where they operate. Previously, we showed that T. gondii’s beta-COP (TgΒCOP; a subunit of coatomer protein complex I, COPI) and retrieval reporters localize exclusively to the zone between the parasite endoplasmic reticulum (ER) and Golgi apparatus. This suggested the existence of an HDEL receptor in T. gondii. We have now identified, cloned, and sequenced this receptor, TgERD2. TgERD2 localizes in a Golgi or ER pattern suggestive of the HDEL retrieval reporter (K. M. Hager, B. Striepen, L. G. Tilney, and D. S. Roos, J. Cell Sci. 112 :2631-2638, 1999). A functional assay reveals that TgERD2 is able to complement the Saccharomyces cerevisiae ERD2 null mutant. Retrieval studies reveal that stable expression of a fluorescent exogenous retrieval ligand results in a dispersal of βCOP signal throughout the cytoplasm and, surprisingly, results in βCOP staining of the vacuolar space of the parasite. In contrast, stable expression of TgERD2GFP does not appear to disturb βCOP staining. In addition to TgERD2, Toxoplasma contains two more divergent ERD2 relatives. Phylogenetic analysis reveals that these proteins belong to a previously unrecognized ERD2 subfamily common to plants and alveolate organisms and as such could represent mediators of parasite-specific retrieval functions. No evidence of class 2 ERD2 proteins was found in metazoan organisms or fungi.

scholarly journals Stage-Specific and Selective Delivery of Caged Azidosugars into the Intracellular Parasite Toxoplasma gondii by Using an Esterase-Ester Pair Technique

mSphere ◽  
2019 ◽  
Vol 4 (3) ◽  
Author(s):  
Tadakimi Tomita ◽  
Hua Wang ◽  
Peng Wu ◽  
Louis M. Weiss
Keyword(s):  
Toxoplasma Gondii ◽  
Small Molecules ◽  
Click Chemistry ◽  
Cell Biology ◽  
Host Cells ◽  
Intracellular Parasite ◽  
Content Type ◽  
Intracellular Parasites ◽  
Specific Manner ◽  
Selective Delivery

ABSTRACT Toxoplasma gondii is an obligate intracellular parasite that chronically infects up to a third of the human population. The parasites persist in the form of cysts in the central nervous system and serve as a reservoir for the reactivation of toxoplasmic encephalitis. The cyst wall is known to have abundant O-linked N-acetylgalactosamine glycans, but the existing metabolic labeling methods do not allow selective labeling of intracellular parasite glycoproteins without labeling of host glycans. In this study, we have integrated Cu(I)-catalyzed bioorthogonal click chemistry with a specific esterase-ester pair system in order to selectively deliver azidosugars to the intracellular parasites. We demonstrated that α-cyclopropyl modified GalNAz was cleaved by porcine liver esterase produced in the parasites but not in the host cells. Our proof-of-concept study demonstrates the feasibility and potential of this esterase-ester click chemistry approach for the selective delivery of small molecules in a stage-specific manner. IMPORTANCE Selective delivery of small molecules into intracellular parasites is particularly problematic due to the presence of multiple membranes and surrounding host cells. We have devised a method that can deliver caged molecules into an intracellular parasite, Toxoplasma gondii, that express an uncaging enzyme in a stage-specific manner without affecting host cell biology. This system provides a valuable tool for studying many intracellular parasites.

The importance of reverse genetics in determining gene function in apicomplexan parasites

Parasitology ◽  
1999 ◽  
Vol 118 (7) ◽  
pp. 53-61 ◽  
Author(s):  
M. SOETE ◽  
C. HETTMAN ◽  
D. SOLDATI
Keyword(s):  
Toxoplasma Gondii ◽  
Gene Function ◽  
Protein Trafficking ◽  
Cell Biology ◽  
Reverse Genetics ◽  
Regulation Of Gene Expression ◽  
Sequencing Project ◽  
Functional Roles ◽  
Obligate Intracellular ◽  
Intracellular Parasites

The phylum Apixomplexa includes obligate intracellular parasites that are of enormous medical and veterinary significance, as they are responsible for a wide variety of diseases including malaria, toxoplasmosis, coccidiosis, cryptosporidiosis, theileriosis and babesiosis. The EST sequencing projects in Toxoplasma gondii and the Plasmodium falciparum genome sequencing project have greatly accelerated gene discovery, revealing for example novel coding sequences restricted to the Apicomplexa. However, easy acquisition of sequence is almost useless if the function of any given gene cannot be tested. The establishment of transfection systems in Toxoplasma gondii, Neospora and in several Plasmodium species has provided us with the reverse genetics methods appropriate to the functional analysis of genes. Over the past few years, the discovery of novel genes coupled to the ability to introduce or modify genes has already contributed to a better understanding of cell biology and pathogenesis of these obligate intracellular parasites. Some insights into the complex processes of parasite invasion, differentiation, regulation of gene expression and protein trafficking are emerging although identification of the exact functional roles for many molecules is still awaiting more investigation. This review summarizes progress in this area. It also emphasises the tight link and synergy between Toxoplasma and malaria research. The use of reverse genetics does not guarantee the answer to gene function, so we can learn from both failed and successful experiments about how better and more efficiently to use ‘genomics’ to accelerate discoveries relevant to the understanding of parasitism by Apicomplexa.

scholarly journals Untargeted Metabolomics Uncovers the Essential Lysine Transporter in Toxoplasma gondii

Metabolites ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 476
Author(s):  
Joachim Kloehn ◽  
Matteo Lunghi ◽  
Emmanuel Varesio ◽  
David Dubois ◽  
Dominique Soldati-Favre
Keyword(s):  
Amino Acids ◽  
Toxoplasma Gondii ◽  
Rna Degradation ◽  
Major Facilitator Superfamily ◽  
Untargeted Metabolomics ◽  
Apicomplexan Parasites ◽  
Obligate Intracellular ◽  
Intracellular Parasites ◽  
Major Facilitator ◽  
Plasma Membrane Transporter

Apicomplexan parasites are responsible for devastating diseases, including malaria, toxoplasmosis, and cryptosporidiosis. Current treatments are limited by emerging resistance to, as well as the high cost and toxicity of existing drugs. As obligate intracellular parasites, apicomplexans rely on the uptake of many essential metabolites from their host. Toxoplasma gondii, the causative agent of toxoplasmosis, is auxotrophic for several metabolites, including sugars (e.g., myo-inositol), amino acids (e.g., tyrosine), lipidic compounds and lipid precursors (cholesterol, choline), vitamins, cofactors (thiamine) and others. To date, only few apicomplexan metabolite transporters have been characterized and assigned a substrate. Here, we set out to investigate whether untargeted metabolomics can be used to identify the substrate of an uncharacterized transporter. Based on existing genome- and proteome-wide datasets, we have identified an essential plasma membrane transporter of the major facilitator superfamily in T. gondii—previously termed TgApiAT6-1. Using an inducible system based on RNA degradation, TgApiAT6-1 was depleted, and the mutant parasite’s metabolome was compared to that of non-depleted parasites. The most significantly reduced metabolite in parasites depleted in TgApiAT6-1 was identified as the amino acid lysine, for which T. gondii is predicted to be auxotrophic. Using stable isotope-labeled amino acids, we confirmed that TgApiAT6-1 is required for efficient lysine uptake. Our findings highlight untargeted metabolomics as a powerful tool to identify the substrate of orphan transporters.

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 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.

scholarly journals Revisiting the role of Toxoplasma gondii ERK7 in the maintenance and stability of the apical complex

2021 ◽  
Author(s):  
Dominique Soldati-Favre ◽  
Nicolas Dos Santos Pacheco ◽  
Nicolò Tosetti ◽  
Aarti Krishnan ◽  
Romuald Haase
Keyword(s):  
Toxoplasma Gondii ◽  
Comparative Proteomics ◽  
Host Cells ◽  
Wild Type ◽  
Proteomics Analysis ◽  
Polar Ring ◽  
Intracellular Parasites ◽  
Apical Complex ◽  
Microneme Proteins

Toxoplasma gondii ERK7 is known to contribute to the integrity of the apical complex and to be involved only in the final step of the conoid biogenesis. In the absence of ERK7, mature parasites lose their conoid complex and are unable to glide, invade or egress from host cells. In contrast to a previous report, we show here that depletion of ERK7 phenocopies the depletion of the apical cap proteins AC9 or AC10. The absence of ERK7 leads to the loss of the apical polar ring, the disorganization of the basket of subpellicular microtubules and an impairment in micronemes secretion. Ultra-expansion microscopy (U-ExM) coupled to NHS-Ester staining on intracellular parasites offers an unprecedented level of resolution and highlights the disorganization of the rhoptries as well as the dilated plasma membrane at the apical pole in the absence of ERK7. Comparative proteomics analysis of wild-type and ERK7 or AC9 depleted parasites led to the disappearance of known, predicted, as well as putative novel components of the apical complex. In contrast, the absence of ERK7 led to an accumulation of microneme proteins, resulting from the defect in exocytosis of the organelles.

scholarly journals The proteasomal deubiquitinating enzyme PSMD14 regulates macroautophagy by controlling Golgi-to-ER retrograde transport

2020 ◽  
Author(s):  
HA Bustamante ◽  
K Cereceda ◽  
AE González ◽  
GE Valenzuela ◽  
Y Cheuquemilla ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Membrane Trafficking ◽  
Retrograde Transport ◽  
Deubiquitinating Enzyme ◽  
20S Proteasome ◽  
Biological Processes ◽  
Pharmacological Inhibition ◽  
Protein Membrane ◽  
A Subunit

ABSTRACTUbiquitination regulates several biological processes. Here, we search for ubiquitin-related genes implicated in protein membrane trafficking performing a High-Content siRNA Screening including 1,187 genes of the human “ubiquitinome” using Amyloid Precursor Protein (APP) as a reporter. We identified the deubiquitinating enzyme PSMD14, a subunit of the 19S regulatory particle of the proteasome, specific for K63-Ub chains in cells, as a novel key regulator of Golgi-to-endoplasmic reticulum (ER) retrograde transport. Silencing or pharmacological inhibition of PSMD14 caused a robust and rapid inhibition of Golgi-to-ER retrograde transport which leads to a potent blockage of macroautophagy by a mechanism associated with the retention of Atg9A and Rab1A at the Golgi apparatus. Because pharmacological inhibition of the proteolytic core of the 20S proteasome did not recapitulate these effects, we concluded that PSMD14, and their K-63-Ub chains, act as a crucial regulator factor for macroautophagy by controlling Golgi-to-ER retrograde transport.

scholarly journals Vitamin and cofactor acquisition in apicomplexans: Synthesis versus salvage

2019 ◽  
Vol 295 (3) ◽  
pp. 701-714 ◽  
Author(s):  
Aarti Krishnan ◽  
Joachim Kloehn ◽  
Matteo Lunghi ◽  
Dominique Soldati-Favre
Keyword(s):  
Toxoplasma Gondii ◽  
Nutrient Availability ◽  
Metabolic Reconstruction ◽  
Mammalian Host ◽  
Free Living ◽  
Apicomplexan Parasites ◽  
Obligate Intracellular ◽  
Functional Studies ◽  
Intracellular Parasites ◽  
Large Repertoire

The Apicomplexa phylum comprises diverse parasitic organisms that have evolved from a free-living ancestor. These obligate intracellular parasites exhibit versatile metabolic capabilities reflecting their capacity to survive and grow in different hosts and varying niches. Determined by nutrient availability, they either use their biosynthesis machineries or largely depend on their host for metabolite acquisition. Because vitamins cannot be synthesized by the mammalian host, the enzymes required for their synthesis in apicomplexan parasites represent a large repertoire of potential therapeutic targets. Here, we review recent advances in metabolic reconstruction and functional studies coupled to metabolomics that unravel the interplay between biosynthesis and salvage of vitamins and cofactors in apicomplexans. A particular emphasis is placed on Toxoplasma gondii, during both its acute and latent stages of infection.

scholarly journals Why should cell biologists study microbial pathogens?

2015 ◽  
Vol 26 (24) ◽  
pp. 4295-4301 ◽  
Author(s):  
Matthew D. Welch
Keyword(s):  
Infectious Diseases ◽  
Virulence Factors ◽  
Membrane Trafficking ◽  
Cell Biology ◽  
Basic Research ◽  
Host Cells ◽  
Microbial Pathogens ◽  
Cell Cycle Regulators ◽  
Cell Death Pathways ◽  
Cellular Pathways

One quarter of all deaths worldwide each year result from infectious diseases caused by microbial pathogens. Pathogens infect and cause disease by producing virulence factors that target host cell molecules. Studying how virulence factors target host cells has revealed fundamental principles of cell biology. These include important advances in our understanding of the cytoskeleton, organelles and membrane-trafficking intermediates, signal transduction pathways, cell cycle regulators, the organelle/protein recycling machinery, and cell-death pathways. Such studies have also revealed cellular pathways crucial for the immune response. Discoveries from basic research on the cell biology of pathogenesis are actively being translated into the development of host-targeted therapies to treat infectious diseases. Thus there are many reasons for cell biologists to incorporate the study of microbial pathogens into their research programs.

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