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

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 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.

Calcium transfer from the ER to other organelles for optimal signaling in .

Unlabelled: Ca signaling in cells begins with the opening of Ca channels in either the plasma membrane (PM) or the endoplasmic reticulum (ER) and results in a dramatic increase in the physiologically low (<100 nM) cytosolic Ca level. The temporal and spatial Ca levels are well regulated to enable precise and specific activation of critical biological processes. Ca signaling regulates pathogenic features of apicomplexan parasites like which infects approximately one-third of the world's population.

Regulation of calcium entry by cyclic GMP signaling in Toxoplasma gondii.

Ca signaling impacts almost every aspect of cellular life. Ca signals are generated through the opening of ion channels that permit the flow of Ca down an electrochemical gradient. Cytosolic Ca fluctuations can be generated through Ca entry from the extracellular milieu or release from intracellular stores.

Interorganellar Communication Through Membrane Contact Sites in .

Apicomplexan parasites are a group of protists that cause disease in humans and include pathogens like ., the causative agent of malaria, and , 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.

A cathepsin C-like protease mediates the post-translation modification of secretory proteins for optimal invasion and egress.

Microbial pathogens use proteases for their infections, such as digestion of proteins for nutrients and activation of their virulence factors. As an obligate intracellular parasite, must invade host cells to establish its intracellular propagation. To facilitate invasion, the parasites secrete invasion effectors from microneme and rhoptry, two unique organelles in apicomplexans.

Analysis of the Interactome of the Tgj1 HSP40 Chaperone.

is an obligate intracellular apicomplexan that causes toxoplasmosis in humans and animals. Central to its dissemination and pathogenicity is the ability to rapidly divide in the tachyzoite stage and infect any type of nucleated cell. Adaptation to different cell contexts requires high plasticity in which heat shock proteins (Hsps) could play a fundamental role.

A cathepsin C-like protease post-translationally modifies secretory proteins for optimal invasion and egress.

Unlabelled: Microbial pathogens use proteases for their infections, such as digestion of proteins for nutrients and activation of their virulence factors. As an obligate intracellular parasite, must invade host cells to establish its intracellular propagation. To facilitate invasion, the parasites secrete invasion effectors from microneme and rhoptry, two unique organelles in apicomplexans.

The Toxoplasma plant-like vacuolar compartment (PLVAC).

Toxoplasma gondii belongs to the phylum Apicomplexa and is an important cause of congenital disease and infection in immunocompromised patients. T. gondii shares several characteristics with plants including a nonphotosynthetic plastid termed apicoplast and a multivesicular organelle that was named the plant-like vacuole (PLV) or vacuolar compartment (VAC).

The Heptaprenyl Diphosphate Synthase (Coq1) Is the Target of a Lipophilic Bisphosphonate That Protects Mice against Toxoplasma gondii Infection.

Prenyldiphosphate synthases catalyze the reaction of allylic diphosphates with one or more isopentenyl diphosphate molecules to form compounds such as farnesyl diphosphate, used in, e.g., sterol biosynthesis and protein prenylation, as well as longer "polyprenyl" diphosphates, used in ubiquinone and menaquinone biosynthesis.

Temporal and thermal profiling of the proteome implicates parasite Protein Phosphatase 1 in the regulation of Ca-responsive pathways.

Apicomplexan parasites cause persistent mortality and morbidity worldwide through diseases including malaria, toxoplasmosis, and cryptosporidiosis. Ca signaling pathways have been repurposed in these eukaryotic pathogens to regulate parasite-specific cellular processes governing the replicative and lytic phases of the infectious cycle, as well as the transition between them. Despite the presence of conserved Ca-responsive proteins, little is known about how specific signaling elements interact to impact pathogenesis.

In Vivo Efficacy of SQ109 against , spp. and and In Vitro Activity of SQ109 Metabolites.

SQ109 is an anti-tubercular drug candidate that has completed Phase IIb/III clinical trials for tuberculosis and has also been shown to exhibit potent in vitro efficacy against protozoan parasites including and spp. However, its in vivo efficacy against protozoa has not been reported. Here, we evaluated the activity of SQ109 in mouse models of spp.

A plastid two-pore channel essential for inter-organelle communication and growth of Toxoplasma gondii.

Two-pore channels (TPCs) are a ubiquitous family of cation channels that localize to acidic organelles in animals and plants to regulate numerous Ca-dependent events. Little is known about TPCs in unicellular organisms despite their ancient origins. Here, we characterize a TPC from Toxoplasma gondii, the causative agent of toxoplasmosis.

Ca entry at the plasma membrane and uptake by acidic stores is regulated by the activity of the V-H -ATPase in Toxoplasma gondii.

Ca is a universal intracellular signal that regulates many cellular functions. In Toxoplasma gondii, the controlled influx of extracellular and intracellular Ca into the cytosol initiates a signaling cascade that promotes pathogenic processes like tissue destruction and dissemination. In this work, we studied the role of proton transport in cytosolic Ca homeostasis and the initiation of Ca signaling.

The role of potassium and host calcium signaling in Toxoplasma gondii egress.

Toxoplasma gondii is an obligate intracellular parasite and replicates inside a parasitophorous vacuole (PV) within the host cell. The membrane of the PV (PVM) contains pores that permits for equilibration of ions and small molecules between the host cytosol and the PV lumen. Ca signaling is universal and both T.

Isolation and Characterization of Acidocalcisomes from Trypanosomatids.

Acidocalcisomes are membrane-bounded, electron-dense, acidic organelles, rich in calcium and polyphosphate. These organelles were first described in trypanosomatids and later found from bacteria to human cells. Some of the functions of the acidocalcisome are the storage of cations and phosphorus, participation in pyrophosphate (PP) and polyphosphate (polyP) metabolism, calcium signaling, maintenance of intracellular pH homeostasis, autophagy, and osmoregulation.

An Endoplasmic Reticulum CREC Family Protein Regulates the Egress Proteolytic Cascade in Malaria Parasites.

The endoplasmic reticulum (ER) is thought to play an essential role during egress of malaria parasites because the ER is assumed to be required for biogenesis and secretion of egress-related organelles. However, no proteins localized to the parasite ER have been shown to play a role in egress of malaria parasites. In this study, we generated conditional mutants of the ndoplasmic eticulum-resident alcium-binding protein (PfERC), a member of the CREC family.

Synthesis and biological evaluation of 1-alkylaminomethyl-1,1-bisphosphonic acids against Trypanosoma cruzi and Toxoplasma gondii.

As an extension of our project aimed at the search for new chemotherapeutic agents against Chagas disease and toxoplasmosis, several 1,1-bisphosphonates were designed, synthesized and biologically evaluated against Trypanosoma cruzi and Toxoplasma gondii, the etiologic agents of these diseases, respectively. In particular, and based on the antiparasitic activity exhibited by 2-alkylaminoethyl-1,1-bisphosphonates targeting farnesyl diphosphate synthase, a series of linear 2-alkylaminomethyl-1,1-bisphosphonic acids (compounds 21-33), that is, the position of the amino group was one carbon closer to the gem-phosphonate moiety, were evaluated as growth inhibitors against the clinically more relevant dividing form (amastigotes) of T. cruzi.

An ortholog of Plasmodium falciparum chloroquine resistance transporter (PfCRT) plays a key role in maintaining the integrity of the endolysosomal system in Toxoplasma gondii to facilitate host invasion.

Toxoplasma gondii is an apicomplexan parasite with the ability to use foodborne, zoonotic, and congenital routes of transmission that causes severe disease in immunocompromised patients. The parasites harbor a lysosome-like organelle, termed the "Vacuolar Compartment/Plant-Like Vacuole" (VAC/PLV), which plays an important role in maintaining the lytic cycle and virulence of T. gondii.

The Vacuolar Zinc Transporter TgZnT Protects Toxoplasma gondii from Zinc Toxicity.

Zinc (Zn) is the most abundant biological metal ion aside from iron and is an essential element in numerous biological systems, acting as a cofactor for a large number of enzymes and regulatory proteins. Zn must be tightly regulated, as both the deficiency and overabundance of intracellular free Zn are harmful to cells. Zn transporters (ZnTs) play important functions in cells by reducing intracellular Zn levels by transporting the ion out of the cytoplasm.

The Toxoplasma Vacuolar H-ATPase Regulates Intracellular pH and Impacts the Maturation of Essential Secretory Proteins.

Vacuolar-proton ATPases (V-ATPases) are conserved complexes that couple the hydrolysis of ATP to the pumping of protons across membranes. V-ATPases are known to play diverse roles in cellular physiology. We studied the Toxoplasma gondii V-ATPase complex and discovered a dual role of the pump in protecting parasites against ionic stress and in the maturation of secretory proteins in endosomal-like compartments.

Calcium signaling and the lytic cycle of the Apicomplexan parasite Toxoplasma gondii.

Toxoplasma gondii has a complex life cycle involving different hosts and is dependent on fast responses, as the parasite reacts to changing environmental conditions. T. gondii causes disease by lysing the host cells that it infects and it does this by reiterating its lytic cycle, which consists of host cell invasion, replication inside the host cell, and egress causing host cell lysis.

Characterization of Two EF-hand Domain-containing Proteins from Toxoplasma gondii.

The universal role of calcium (Ca ) as a second messenger in cells depends on a large number of Ca -binding proteins (CBP), which are able to bind Ca through specific domains. Many CBPs share a type of Ca -binding domain known as the EF-hand. The EF-hand motif has been well studied and consists of a helix-loop-helix structural domain with specific amino acids in the loop region that interact with Ca .

Tagging of Weakly Expressed Toxoplasma gondii Calcium-Related Genes with High-Affinity Tags.

Calcium ions regulate a diversity of cellular functions in all eukaryotes. The cytosolic Ca concentration is tightly regulated at the physiological cytosolic concentration of 50-100 nm. The Toxoplasma gondii genome predicts the presence of several genes encoding potential Ca channels, pumps, and transporters.

Detection of Weakly Expressed Trypanosoma cruzi Membrane Proteins Using High-Performance Probes.

Membrane proteins in trypanosomatids are, in general, weakly expressed and confirmation of their subcellular localization frequently requires their overexpression with epitope tags. However, overexpression can lead to mislocalization of the probes. Viswanathan et al.