Toxoplasma gondii Archives - Center for Tropical and Emerging Global Diseases

Lipophilic bisphosphonates reduced cyst burden and ameliorated hyperactivity of mice chronically infected with Toxoplasma gondii

Donna Huber on October 10, 2024

Fig 1 Lipophilic bisphosphonates inhibited the viability of in vitro differentiated bradyzoites.

The current treatments for toxoplasmosis are only active against fast-growing tachyzoites, present in acute infections, with little effect on slow-growing bradyzoites within tissue cysts, present in latent chronic infections. The mitochondrion of Toxoplasma gondii is essential for its survival, and one of the major anti-parasitic drugs, atovaquone, inhibits the mitochondrial electron transport chain at the coenzyme Q:cytochrome c oxidoreductase site. Coenzyme Q (also known as ubiquinone [UQ]) consists of a quinone head and a lipophilic, isoprenoid tail that anchors UQ to membranes. The synthesis of the isoprenoid unit is essential for cell growth and is inhibited by lipophilic bisphosphonates, which inhibit the parasite growth. In this work, we investigated the effect of lipophilic bisphosphonates on the chronic stages of T. gondii. We discovered that three lipophilic bisphosphonates (BPH-1218, BPH-1236, and BPH-1238), effective for the acute infection, were also effective in controlling the development of chronic stages. We showed effectiveness by testing them against in vitro cysts and in vivo derived tissue cysts and, most importantly, these compounds reduced the cyst burden in the brains of chronically infected mice. We monitored the activity of infected mice non-invasively and continuously with a novel device termed the CageDot. A decrease in activity accompanied the acute phase, but mice recovered to normal activity and showed signs of hyperactivity when the chronic infection was established. Moreover, treatment with atovaquone or BPH-1218 ameliorated the hyperactivity observed during the chronic infection.IMPORTANCETreatment for toxoplasmosis is challenged by a lack of effective drugs to eradicate the chronic stages. Most of the drugs currently used are poorly distributed to the central nervous system, and they trigger allergic reactions in a large number of patients. There is a compelling need for safe and effective treatments for toxoplasmosis. Bisphosphonates (BPs) are analogs of inorganic pyrophosphate and are used for the treatment of bone disorders. BPs target the isoprenoid pathway and are effective against several experimental parasitic infections. Some lipophilic BPs can specifically inhibit the mitochondrial activity of Toxoplasma gondii by interfering with the mechanism by which ubiquinone is inserted into the inner mitochondrial membrane. In this work, we present the effect of three lipophilic BPs against T. gondii chronic stages. We also present a new strategy for the monitoring of animal activity during disease and treatment that is non-invasive and continuous.

Melissa A Sleda, Zaid F Pitafi, WenZhan Song, Eric Oldfield, Silvia N J Moreno. mBio. 2024 Oct 10:e0175624. doi: 10.1128/mbio.01756-24

The GPI sidechain of Toxoplasma gondii inhibits parasite pathogenesis

Donna Huber on September 20, 2024

Fig 5 Immunofluorescence analysis of PIGJ-3×HA shows its localization both inside and outside the rER.

Glycosylphosphatidylinositols (GPIs) are highly conserved anchors for eukaryotic cell surface proteins. The apicomplexan parasite, Toxoplasma gondii, is a widespread intracellular parasite of warm-blooded animals whose plasma membrane is covered with GPI-anchored proteins, and free GPIs called GIPLs. While the glycan portion is conserved, species differ in sidechains added to the triple mannose core. The functional significance of the Glcα1,4GalNAcβ1- sidechain reported in Toxoplasma gondii has remained largely unknown without understanding its biosynthesis. Here we identify and disrupt two glycosyltransferase genes and confirm their respective roles by serology and mass spectrometry. Parasites lacking the sidechain on account of deletion of the first glycosyltransferase, PIGJ, exhibit increased virulence during primary and secondary infections, suggesting it is an important pathogenesis factor. Cytokine responses, antibody recognition of GPI-anchored SAGs, and complement binding to PIGJ mutants are intact. By contrast, the scavenger receptor CD36 shows enhanced binding to PIGJ mutants, potentially explaining a subtle tropism for macrophages detected early in infection. Galectin-3, which binds GIPLs, exhibits an enhancement of binding to PIGJ mutants, and the protection of galectin-3 knockout mice from lethality suggests that Δpigj parasite virulence in this context is sidechain dependent. Parasite numbers are not affected by Δpigj early in the infection in wild-type mice, suggesting a breakdown of tolerance. However, increased tissue cysts in the brains of mice infected with Δpigj parasites indicate an advantage over wild-type strains. Thus, the GPI sidechain of T. gondii plays a crucial and diverse role in regulating disease outcomes in the infected host.IMPORTANCEThe functional significance of sidechain modifications to the glycosylphosphatidylinositol (GPI) anchor in parasites has yet to be determined because the glycosyltransferases responsible for these modifications have not been identified. Here we present identification and characterization of both Toxoplasmsa gondii GPI sidechain-modifying glycosyltransferases. Removal of the glycosyltransferase that adds the first GalNAc to the sidechain results in parasites without a sidechain on the GPI, and increased host susceptibility to infection. Loss of the second glycosyltransferase results in a sidechain with GalNAc alone, and no glucose added, and has negligible effect on disease outcomes. This indicates GPI sidechains are fundamental to host-parasite interactions.

Julia A Alvarez, Elisabet Gas-Pascual, Sahil Malhi, Juan C Sánchez-Arcila, Ferdinand Ngale Njume, Hanke van der Wel, Yanlin Zhao, Laura García-López, Gabriella Ceron, Jasmine Posada, Scott P Souza, George S Yap, Christopher M West, Kirk D C Jensen. mBio. 2024 Sep 20:e0052724. doi: 10.1128/mbio.00527-24

Oxygen-dependent regulation of F-box proteins in Toxoplasma gondii is mediated by Skp1 glycosylation

Donna Huber on September 20, 2024

Figure 8. Immunolocalization of FBXO13-HA3 and FBXO14-HA3.

A dynamic proteome is required for cellular adaption to changing environments including levels of O2, and the SKP1/CULLIN-1/F-box protein/RBX1 (SCF) family of E3 ubiquitin ligases contributes importantly to proteasome-mediated degradation. We examine, in the apicomplexan parasite Toxoplasma gondii, the influence on the interactome of SKP1 by its novel glycan attached to a hydroxyproline generated by PHYa, the likely ortholog of the HIFα PHD2 oxygen-sensor of human host cells. Strikingly, the representation of several putative F-box proteins (FBPs) is substantially reduced in PHYaΔ parasites grown in fibroblasts. One, FBXO13, is a predicted lysyl hydroxylase related to the human JmjD6 oncogene except for its F-box domain. The abundance of FBXO13, epitope-tagged at its genetic locus, was reduced in PHYaΔ parasites thus explaining its diminished presence in the SKP1 interactome. A similar effect was observed for FBXO14, a cytoplasmic protein of unknown function that may have co-evolved with PHYa in apicomplexans. Similar findings in glycosylation-mutant cells, rescue by proteasomal inhibitors, and unchanged transcript levels, suggested the involvement of the SCF in their degradation. The effect was selective, because FBXO1 was not affected by loss of PHYa. These findings are physiologically significant because the effects were phenocopied in parasites reared at 0.5% O2. Modest impact on steady-state SKP1 modification levels suggests that effects are mediated during a lag phase in hydroxylation of nascent SKP1. The dependence of FBP abundance on O2-dependent SKP1 modification likely contributes to the reduced virulence of PHYaΔ parasites owing to impaired ability to sense O2 as an environmental signal.

Msano N Mandalasi, Elisabet Gas-Pascual, Carlos Gustavo Baptista, Bowen Deng, Hanke van der Wel, John A W Kruijtzer, Geert-Jan Boons, Ira J Blader, Christopher M West. J Biol Chem. 2024 Sep 20:107801. doi: 10.1016/j.jbc.2024.107801.

A combination of four Toxoplasma gondii nuclear-targeted effectors protects against interferon gamma-driven human host cell death

Donna Huber on September 18, 2024

Fig 1 IFNγ stimulation following infection is countered by MYR1, preventing early tachyzoite egress and host cell death.

In both mice and humans, Type II interferon gamma (IFNγ) is crucial for the regulation of Toxoplasma gondii (T. gondii) infection, during acute or chronic phases. To thwart this defense, T. gondii secretes protein effectors hindering the host’s immune response. For example, T. gondii relies on the MYR translocon complex to deploy soluble dense granule effectors (GRAs) into the host cell cytosol or nucleus. Recent genome-wide loss-of-function screens in IFNγ-primed primary human fibroblasts identified MYR translocon components as crucial for parasite resistance against IFNγ-driven vacuole clearance. However, these screens did not pinpoint specific MYR-dependent GRA proteins responsible for IFNγ signaling blockade, suggesting potential functional redundancy. Our study reveals that T. gondii depends on the MYR translocon complex to prevent parasite premature egress and host cell death in human cells stimulated with IFNγ post-infection, a unique phenotype observed in various human cell lines but not in murine cells. Intriguingly, inhibiting parasite egress did not prevent host cell death, indicating this mechanism is distinct from those described previously. Genome-wide loss-of-function screens uncovered TgIST, GRA16, GRA24, and GRA28 as effectors necessary for a complete block of IFNγ response. GRA24 and GRA28 directly influenced IFNγ-driven transcription, GRA24’s action depended on its interaction with p38 MAPK, while GRA28 disrupted histone acetyltransferase activity of CBP/p300. Given the intricate nature of the immune response to T. gondii, it appears that the parasite has evolved equally elaborate mechanisms to subvert IFNγ signaling, extending beyond direct interference with the JAK/STAT1 pathway, to encompass other signaling pathways as well.

Henry B, Phillips AJ, Sibley LD, Rosenberg A. 2024. mBio 0:e02124-24. https://doi.org/10.1128/mbio.02124-24

The Toxoplasma gondii F-Box Protein L2 Functions as a Repressor of Stage Specific Gene Expression

Donna Huber on May 30, 2024

Fig 5. TgFBXL2 localizes to a perinucleolar compartment.

Toxoplasma gondii is a foodborne pathogen that can cause severe and life-threatening infections in fetuses and immunocompromised patients. Felids are its only definitive hosts, and a wide range of animals, including humans, serve as intermediate hosts. When the transmissible bradyzoite stage is orally ingested by felids, they transform into merozoites that expand asexually, ultimately generating millions of gametes for the parasite sexual cycle. However, bradyzoites in intermediate hosts differentiate exclusively to disease-causing tachyzoites, which rapidly disseminate throughout the host. Though tachyzoites are well-studied, the molecular mechanisms governing transitioning between developmental stages are poorly understood. Each parasite stage can be distinguished by a characteristic transcriptional signature, with one signature being repressed during the other stages. Switching between stages require substantial changes in the proteome, which is achieved in part by ubiquitination. F-box proteins mediate protein poly-ubiquitination by recruiting substrates to SKP1, Cullin-1, F-Box protein E3 ubiquitin ligase (SCF-E3) complexes. We have identified an F-box protein named Toxoplasma gondii F-Box Protein L2 (TgFBXL2), which localizes to distinct perinucleolar sites. TgFBXL2 is stably engaged in an SCF-E3 complex that is surprisingly also associated with a COP9 signalosome complex that negatively regulates SCF-E3 function. At the cellular level, TgFBXL2-depleted parasites are severely defective in centrosome replication and daughter cell development. Most remarkable, RNAseq data show that TgFBXL2 conditional depletion induces the expression of stage-specific genes including a a large cohort of genes necessary for sexual commitment. Together, these data suggest that TgFBXL2 is a latent guardian of stage specific gene expression in Toxoplasma and poised to remove conflicting proteins in response to an unknown trigger of development.

Carlos G Baptista, Sarah Hosking, Elisabet Gas-Pascual, Loic Ciampossine, Steven Abel, Mohamed-Ali Hakimi, Victoria Jeffers, Karine Le Roch, Christopher M West, Ira J Blader. PLoS Pathog. 2024 May 30;20(5):e1012269. doi: 10.1371/journal.ppat.1012269.

Two CTEGD trainees receive AHA fellowships

Donna Huber on March 12, 2024

by Donna Huber

Photos of Graduate student Baihetiya “Barna” Baierna and postdoctoral fellow Mayara Bertolini — Graduate student Baihetiya “Barna” Baierna and postdoctoral fellow Mayara Bertolini received fellowships from the American Heart Association, supporting their research and education. Both are studying parasites in the University of Georgia’s Center for Tropical and Emerging Global Diseases. (Photos courtesy of CTEGD)

Baihetiya “Barna” Baierna, a cellular biology graduate student in Silvia Moreno’s laboratory, received an American Heart Association Pre-doctoral Fellowship. It will fund her training for the next two years as she studies the mitochondrion of Toxoplasma gondii.

Baierna grew up wanting to follow in her mother’s footsteps as a scientist.

“My mom worked for the regional CDC in China and I was interested in science since a young age,” Baierna said.

After completing her undergraduate degree in biochemistry, she was sure she wanted to continue her training in graduate school. After being accepted into the Department of Cellular Biology program, she joined the Moreno Laboratory.

Toxoplasma gondii infects approximately one third of the world human population. The infection can cause serious complications in people with a suppressed immune system. Baierna’s research aims at validating novel T. gondii mitochondrial proteins as novel chemotherapeutic targets for improved chemotherapy of toxoplasmosis. This is important because the present drugs are not effective against the chronic stages of the infection. She has developed novel strategies for the discovery of new mitochondrial proteins and already found a novel enzymatic activity highly divergent from the mammalian counterpart. The outcome of this project will expand the knowledge of the T. gondii mitochondrion, as well as helping with the identification of viable drug targets.

“An AHA Fellowship is a very competitive award, but Barna deserves it and we are very proud of her,” said Moreno.

“Preparing the grant proposal was a great learning experience and it will help me with my career development,” said Baierna, “I’m very happy that it was funded.”

Mayara Bertolini, a post-doctoral fellow in Roberto Docampo’s laboratory, received an American Heart Association Post-doctoral Fellowship. It will support her training for one year.

After receiving her bachelor’s degree, Bertolini obtained her master’s degree in a lab that Docampo had set up in Brazil working on T. cruzi. From there she decided to pursue her Ph.D. at the University of Georgia. She completed her Ph.D. in 2023.

Trypanosoma cruzi is the parasite that causes Chagas disease. At least 6 million people, mostly in South America, are infected with the parasite. T. cruzi is transmitted to humans through the feces of an insect commonly referred to as the kissing bug. While Chagas disease was first discovered in 1909, there is still a lot that is unknown about the biology of T. cruzi. This lack of knowledge has hindered drug development. Bertolini’s project is focused on the role of polyphosphate during the Trypanosoma cruzi life cycle.

“This is the second fellowship from the AHA that Mayara has received. She got a two-year pre-doctoral fellowship before and has done outstanding work,” said Docampo.

“AHA Fellowships are very competitive and I’m thrilled my proposal was selected,” said Bertolini. “In addition to supporting my training, there is support for career development and networking opportunities.”

The story originally appeared at https://research.uga.edu/news/two-ctegd-trainees-receive-aha-fellowships/

Regulation of Calcium entry by cyclic GMP signaling in Toxoplasma gondii

Donna Huber on February 19, 2024

Figure 1. Calcium entry through the plasma membrane of extracellular T. gondii tachyzoites.

Ca²⁺ signaling impacts almost every aspect of cellular life. Ca²⁺ signals are generated through the opening of ion channels that permit the flow of Ca²⁺ down an electrochemical gradient. Cytosolic Ca²⁺ fluctuations can be generated through Ca²⁺ entry from the extracellular milieu or release from intracellular stores. In Toxoplasma gondii, Ca²⁺ ions play critical roles in several essential functions for the parasite like invasion of host cells, motility and egress. Plasma membrane Ca2+ entry in T. gondii was previously shown to be activated by cytosolic calcium and inhibited by the voltage-operated Ca²⁺ channel blocker nifedipine. However, Ca²⁺ entry in T. gondii did not show the classical characteristics of store regulation. In this work, we characterized the mechanism by which cytosolic Ca²⁺ regulates plasma membrane Ca²⁺ entry in extracellular T. gondii tachyzoites loaded with the Ca²⁺ indicator Fura 2. We compared the inhibition by nifedipine with the effect of the broad spectrum TRP channel inhibitor, anthranilic acid or ACA and we find that both inhibitors act on different Ca²⁺ entry activities. We demonstrate, using pharmacological and genetic tools, that an intracellular signaling pathway engaging cyclicGMP (cGMP), protein kinase G (PKG), Ca²⁺ and the phosphatidyl inositol phospholipase C (PI-PLC) affects Ca²⁺ entry and we present a model for crosstalk between cGMP and cytosolic Ca²⁺ for the activation of T. gondii‘s lytic cycle traits.

Miryam A Hortua Triana, Karla M Márquez-Nogueras, Mojtaba Sedigh Fazli, Shannon Quinn, Silvia N J Moreno. J Biol Chem. 2024 Feb 19:105771. doi: 10.1016/j.jbc.2024.105771

Diego Huet zeroes in on parasite that affects thousands each year

Donna Huber on January 8, 2024

by Donna Huber

From an early age, Diego Huet has been interested in the unusual and fascinating found in the natural world.

His early encounters with animals, plants and insects nurtured his curiosity about nature. Their striking colors and sometimes strange shapes drew his interest, and even today he continues to capture them through macro photography. It was this fascination that led him to the parasite he studies today.

“I was always drawn to ‘unconventional’ or ‘weird’ science,” said Huet, an assistant professor in the College of Pharmacy’s Department of Pharmaceutical and Biomedical Sciences and member of the Center for Tropical and Emerging Global Diseases. “But I also wanted to be hands on, which is what led me to molecular and cellular biology.”

As a doctoral student, Huet began studying Trypanosoma brucei, a parasite commonly transmitted by the tsetse fly. Wanting to study a different parasite as a postdoctoral researcher, he was torn between studying Plasmodium, which is the causative agent of malaria, and Toxoplasma gondii, a related parasite that is carried by cats. Both parasites, which belong to a group of organisms called apicomplexans, cause diseases in humans and animals, and there remain large knowledge gaps in our basic understanding of them. Ultimately, he chose the latter.

“Plasmodium is difficult to manipulate,” Huet said. “Toxoplasma is related to Plasmodium, but is easier to work with because it isn’t as complex, and what we learn about Toxo could also increase our knowledge of Plasmodium.”

Just as yeast and fruit flies are used as model organisms to study human biology, Toxoplasma can be used as a model for shared features of apicomplexan biology.

Besides aiding in the understanding of other parasites of human and veterinary concern, including parasites that cause malaria in tropical and subtropical regions of the world, Toxoplasma gondii also causes human and animal disease. More than 40 million people in the U.S. are estimated to carry T. gondii. Although most never show symptoms, it poses a major health threat to immunocompromised individuals and pregnant women as it can lead to miscarriage and birth defects. Toxoplasmosis, the disease caused by Toxoplasma, is considered a leading cause of death among foodborne illnesses though it can also be transmitted through contact with cat feces.

The Centers for Disease Control and Prevention has it listed as a neglected parasitic infection in the United States and a target for public health action.

Huet joined the faculty at the University of Georgia in 2019 and has developed a robust research program to expand knowledge of the basic biology of Toxoplasma.

In a recently published study in “mBio”, cellular biology doctoral candidate and Huet Lab member Madelaine Usey looked at proteins critical for mitochondrial function in T. gondii. The mitochondrion is considered the “powerhouse of the cell,” but it is an enzyme called ATP synthase that generates the cellular energy.

“Our findings are really exciting for drug discovery,” Usey said. “Many of the proteins that make up the ATP synthase are different in Toxoplasma compared to other organisms. In this study, we were able to figure out what two of those novel subunits are doing—they act as scaffolding for this enormous ATP synthase complex.”

These proteins are unique to Toxoplasma and could be used in drug discovery as targets since they are important for mitochondrial functioning.

Another project in Huet’s laboratory, which recently received funding through a grant from the National Institute of General Medical Sciences, investigates how organelles within the parasite communicate.

“Traditionally, we thought organelles send and receive calcium and other metabolites in much the same way we receive a package through the mail,” Huet said. “Cells form vesicles to transport materials to specific locations within the cell. The vesicles are labeled with proteins that act like a postal address, telling the vesicle where to go.”

However, cells can also exchange material through another process.

“When the organelles’ membranes get close together, they form what is called a membrane contact site,” Huet said. “In this case it is more like one organelle hand delivers the package to another.”

A membrane contact site is a specialized protein structure that organelles use for intracellular communication. However, it is not a well understood structure in apicomplexans. In addition, these parasites have additional organelles not found in traditional models like humans and yeast, so Huet is trying to understand how the organellar communication is happening in apicomplexans using Toxoplasma as a model.

Identifying such proteins and their functions could lead to better drug targets and better drug treatments, which all the neglected parasitic diseases need.

“Toxo’s genome isn’t well annotated,” Huet said. “Finding membrane contact site proteins is an arduous task—it’s a goal of my lab to identify some of them and their involvement in Toxoplasma membrane contact sites.”

This article was first published at https://research.uga.edu/news/diego-huet-zeroes-in-on-parasite-that-affects-thousands-each-year/

ATP synthase-associated coiled-coil-helix-coiled-coil-helix (CHCH) domain-containing proteins are critical for mitochondrial function in Toxoplasma gondii

Donna Huber on October 5, 2023

CHCH domain proteins associated with the T. gondii ATP synthase are essential for the lytic cycle. (A) Schematic representation of the CHCH domain size and location in ATPTG8 and ATPTG9. C represents cysteine residues and X represents any other amino acid residue.

Coiled-coil-helix-coiled-coil-helix (CHCH) domains consist of two pairs of cysteine residues that are oxidized to form disulfide bonds upon mitochondrial import. Proteins containing these domains play important roles in mitochondrial ultrastructure and in the biogenesis, function, and stability of electron transport chain complexes. Interestingly, recent investigations of the Toxoplasma gondii ATP synthase identified subunits containing CHCH domains. As CHCH domain proteins have never been found in any other ATP synthase, their role in T. gondii was unclear. Using conditional gene knockdown systems, we investigated two T. gondii ATP synthase subunits containing CHCH domains: ATPTG8 and ATPTG9. We show that these two subunits are essential for the lytic cycle as well as stability and function of the ATP synthase. Further, we illustrated that their knockdown disrupts multiple aspects of mitochondrial morphology, including ultrastructure and cristae density. Mutation of key cysteine residues in the CHCH domains also caused mis-localization of the proteins. Our work suggests that these proteins likely provide structural support to the exceptionally large T. gondii ATP synthase complex and that perturbations to the structural integrity of this complex result in deleterious downstream effects on the parasite mitochondrion. These investigations add to a growing body of work focused on the divergent aspects of the apicomplexan ATP synthase, which could ultimately uncover novel drug targets. IMPORTANCE Members of the coiled-coil-helix-coiled-coil-helix (CHCH) domain protein family are transported into the mitochondrial intermembrane space, where they play important roles in the biogenesis and function of the organelle. Unexpectedly, the ATP synthase of the apicomplexan Toxoplasma gondii harbors CHCH domain-containing subunits of unknown function. As no other ATP synthase studied to date contains this class of proteins, characterizing their function will be of broad interest to the fields of molecular parasitology and mitochondrial evolution. Here, we demonstrate that that two T. gondii ATP synthase subunits containing CHCH domains are required for parasite survival and for stability and function of the ATP synthase. We also show that knockdown disrupts multiple aspects of the mitochondrial morphology of T. gondii and that mutation of key residues in the CHCH domains caused mis-localization of the proteins. This work provides insight into the unique features of the apicomplexan ATP synthase, which could help to develop therapeutic interventions against this parasite and other apicomplexans, such as the malaria-causing parasite Plasmodium falciparum.

Madelaine M Usey, Diego Huet. mBio. 2023 Oct 5:e0176923. doi: 10.1128/mbio.01769-23.

Interorganellar Communication Through Membrane Contact Sites in Toxoplasma gondii

Donna Huber on August 6, 2023

Figure 1. Reported and potential MCSs between organelles of Toxoplasma gondii. Schematic representation showing proteins recently reported to be involved in MCSs, along with putative MCS candidates (indicated with “?”). For clarity purposes, only the central part of the parasite is shown. Abbreviations: AP, apicoplast; ER, endoplasmic reticulum; PLVAC, plant-like vacuolar compartment; IMC, inner membrane complex; TgTPC, T. gondii two pore channel; VDAC, voltage-dependent anion channel; LMF1, lasso maintenance factor 1.; MCS, membrane contact site.

Apicomplexan parasites are a group of protists that cause disease in humans and include pathogens like Plasmodium spp., the causative agent of malaria, and Toxoplasma gondii, the etiological agent of toxoplasmosis and one of the most ubiquitous human parasites in the world. Membrane contact sites (MCSs) are widespread structures within eukaryotic cells but their characterization in apicomplexan parasites is only in its very beginnings. Basic biological features of the T. gondii parasitic cycle support numerous organellar interactions, including the transfer of Ca²⁺ and metabolites between different compartments. In T. gondii, Ca²⁺ signals precede a series of interrelated molecular processes occurring in a coordinated manner that culminate in the stimulation of key steps of the parasite life cycle. Calcium transfer from the endoplasmic reticulum to other organelles via MCSs would explain the precision, speed, and efficiency that is needed during the lytic cycle of T. gondii. In this short review, we discuss the implications of these structures in cellular signaling, with an emphasis on their potential role in Ca²⁺ signaling.

Diego Huet, Silvia N J Moreno. Contact (Thousand Oaks). 2023 Aug 6;6:25152564231189064. doi: 10.1177/25152564231189064. eCollection 2023 Jan-Dec.

Tag: Toxoplasma gondii