Stage-specific function of sphingolipid synthases in African trypanosomes.

Unlabelled: The protozoan parasite is the only known eukaryote capable of synthesizing the three main phosphosphingolipids: sphingomyelin (SM), inositol phosphorylceramide (IPC), and ethanolamine phosphorylceramide (EPC). It has four paralogous genes encoding sphingolipid synthases (). TbSLS1 is a dedicated IPC synthase, TbSLS2 is a dedicated EPC synthase, and TbSLS3 and TbSLS4 are bifunctional SM/EPC synthases.

Venom alkaloids against Chagas disease parasite: search for effective therapies.

Chagas disease is an important disease affecting millions of patients in the New World and is caused by a protozoan transmitted by haematophagous kissing bugs. It can be treated with drugs during the early acute phase; however, effective therapy against the chronic form of Chagas disease has yet to be discovered and developed. We herein tested the activity of solenopsin alkaloids extracted from two species of fire ants against the protozoan parasite Trypanosoma cruzi, the aetiologic agent of Chagas disease.

Endocytosis and Exocytosis in Are Modulated by Bromoenol Lactone.

In the protozoan pathogen , endocytosis, and exocytosis occur mainly in the small area of the flagellar pocket membrane, which makes this parasite an interesting model of strikingly polarized internalization and secretion. Moreover, little is known about vesicle recognition and fusion mechanisms, which are essential for both endo/exocytosis in this parasite. In other cell types, vesicle fusion events require the activity of phospholipase A (PLA), including Ca-independent iPLA and soluble, Ca-dependent sPLA.

Tamoxifen inhibits the biosynthesis of inositolphosphorylceramide in Leishmania.

Previous work from our group showed that tamoxifen, an oral drug that has been in use for the treatment of breast cancer for over 40 years, is active both in vitro and in vivo against several species of Leishmania, the etiological agent of leishmaniasis. Using a combination of metabolic labeling with [H]-sphingosine and myo-[H]-inositol, alkaline hydrolysis, HPTLC fractionations and mass spectrometry analyses, we observed a perturbation in the metabolism of inositolphosphorylceramides (IPCs) and phosphatidylinositols (PIs) after treatment of L. amazonensis promastigotes with tamoxifen, with a significant reduction in the biosynthesis of the major IPCs (composed of d16:1/18:0-IPC, t16:0/C18:0-IPC, d18:1/18:0-IPC and t16:0/20:0-IPC) and PIs (sn-1-O-(C)alkyl -2-O-(C)acylglycerol-3-HPO-inositol and sn-1-O-(C)acyl-2-O-(C)acylglycerol-3-HPO-inositol) species.

Antibody Repertoires Identify β-Tubulin as a Host Protective Parasite Antigen in Mice Infected With .

Few studies investigate the major protein antigens targeted by the antibody diversity of infected mice with . To detect global IgG antibody specificities, sera from infected mice were immunoblotted against whole extracts. By proteomic analysis, we were able to identify the most immunogenic proteins.

Plasmodium falciparum invasion and intraerythrocytic development are impaired by 2', 3'-dialdehyde adenosine.

Purine nucleotide synthesis in protozoa takes place exclusively via the purine salvage pathway and S-adenosyl-l-homocysteine hydrolase (SAHH) is an important enzyme in the Plasmodium salvage pathway which is not present in erythrocytes. Here, we describe the antimalarial effect of 2'3'-dialdehyde adenosine or oxidized adenosine (oADO), inhibitor of SAHH, on in vitro infection of human erythrocytes by P. falciparum.

POM-1 inhibits P2 receptors and exhibits anti-inflammatory effects in macrophages.

Extracellular nucleotides can modulate the immunological response by activating purinergic receptors (P2Rs) on the cell surface of macrophages, dendritic, and other immune cells. In particular, the activation of P2X7R can induce release of cytokines and cell death as well as the uptake of large molecules through the cell membrane by a mechanism still poorly understood. Polyoxotungstate-1 (POM-1) has been proposed as a potent inhibitor of ecto-nucleotidases, enzymes that hydrolyze extracellular nucleotides, regulating the activity of P2Rs.

H-dependent inorganic phosphate uptake in Trypanosoma brucei is influenced by myo-inositol transporter.

Trypanosoma brucei is an extracellular protozoan parasite that causes human African trypanosomiasis or "sleeping sickness". During the different phases of its life cycle, T. brucei depends on exogenous inorganic phosphate (P), but little is known about the transport of P in this organism.

Capsular polysaccharides from Cryptococcus neoformans modulate production of neutrophil extracellular traps (NETs) by human neutrophils.

In the present study, we characterized the in vitro modulation of NETs (neutrophil extracellular traps) induced in human neutrophils by the opportunistic fungus Cryptococcus neoformans, evaluating the participation of capsular polysaccharides glucuronoxylomanan (GXM) and glucuronoxylomannogalactan (GXMGal) in this phenomenon. The mutant acapsular strain CAP67 and the capsular polysaccharide GXMGal induced NET production. In contrast, the wild-type strain and the major polysaccharide GXM did not induce NET release.

2´,3´-Dialdehyde of ATP, ADP, and adenosine inhibit HIV-1 reverse transcriptase and HIV-1 replication.

The 2´3´-dialdehyde of ATP or oxidized ATP (oATP) is a compound known for specifically making covalent bonds with the nucleotide-binding site of several ATP-binding enzymes and receptors. We investigated the effects of oATP and other oxidized purines on HIV-1 infection and we found that this compound inhibits HIV-1 and SIV infection by blocking early steps of virus replication. oATP, oxidized ADP (oADP), and oxidized Adenosine (oADO) impact the natural activity of endogenous reverse transcriptase enzyme (RT) in cell free virus particles and are able to inhibit viral replication in different cell types when added to the cell cultures either before or after infection.

Golgi UDP-GlcNAc:polypeptide O-α-N-Acetyl-d-glucosaminyltransferase 2 (TcOGNT2) regulates trypomastigote production and function in Trypanosoma cruzi.

All life cycle stages of the protozoan parasite Trypanosoma cruzi are enveloped by mucin-like glycoproteins which, despite major changes in their polypeptide cores, are extensively and similarly O-glycosylated. O-Glycan biosynthesis is initiated by the addition of αGlcNAc to Thr in a reaction catalyzed by Golgi UDP-GlcNAc:polypeptide O-α-N-acetyl-d-glucosaminyltransferases (ppαGlcNAcTs), which are encoded by TcOGNT1 and TcOGNT2. We now directly show that TcOGNT2 is associated with the Golgi apparatus of the epimastigote stage and is markedly downregulated in both differentiated metacyclic trypomastigotes (MCTs) and cell culture-derived trypomastigotes (TCTs).

Infection with Leishmania major induces a cellular stress response in macrophages.

We investigated early cellular responses induced by infection with Leishmania major in macrophages from resistant C57/BL6 mice. Infection increased production of reactive oxygen species by resident, but not inflammatory peritoneal macrophages. In addition, infection increased activation of stress-activated protein kinases/c-Jun N-terminal kinases (SAPK/JNK) in resident, but not in inflammatory peritoneal macrophages.

Molecular and functional characterization of the ceramide synthase from Trypanosoma cruzi.

In this study, we characterized ceramide synthase (CerS) of the protozoan parasite Trypanosoma cruzi at the molecular and functional levels. TcCerS activity was detected initially in a cell-free system using the microsomal fraction of epimastigote forms of T. cruzi, [(3)H]dihydrosphingosine or [(3)H]sphingosine, and fatty acids or acyl-CoA derivatives as acceptor or donor substrates, respectively.

Acidocalcisomes as calcium- and polyphosphate-storage compartments during embryogenesis of the insect Rhodnius prolixus Stahl.

Background: The yolk of insect eggs is a cellular domain specialized in the storage of reserve components for embryo development. The reserve macromolecules are stored in different organelles and their interactions with the embryo cells are mostly unknown. Acidocalcisomes are lysosome-related organelles characterized by their acidic nature, high electron density and large content of polyphosphate bound to several cations.

The Sphingolipid Biosynthetic Pathway Is a Potential Target for Chemotherapy against Chagas Disease.

The protozoan parasite Trypanosoma cruzi is the causative agent of human Chagas disease, for which there currently is no cure. The life cycle of T. cruzi is complex, including an extracellular phase in the triatomine insect vector and an obligatory intracellular stage inside the vertebrate host.

Molecular analysis of a UDP-GlcNAc:polypeptide alpha-N-acetylglucosaminyltransferase implicated in the initiation of mucin-type O-glycosylation in Trypanosoma cruzi.

Trypanosoma cruzi, the causative agent of Chagas disease, is surrounded by a mucin coat that plays important functions in parasite survival/invasion and is extensively O-glycosylated by Golgi and cell surface glycosyltransferases. The addition of the first sugar, alpha-N-acetylglucosamine (GlcNAc) linked to Threonine (Thr), is catalyzed by a polypeptide alpha-GlcNAc-transferase (pp-alphaGlcNAcT) which is unstable to purification. Here, a comparison of the genomes of T.

Na(+)-ATPase and protein kinase C are targets to 1-O-hexadecylphosphocoline (miltefosine) in Trypanosoma cruzi.

Miltefosine has been shown to be a very active compound against Trypanosoma cruzi. Here, we evaluated the effects of miltefosine on the activity of the Na(+)-ATPase and protein kinase C (PKC) present in the plasma membrane of T. cruzi.

The toxic effects of piperine against Trypanosoma cruzi: ultrastructural alterations and reversible blockage of cytokinesis in epimastigote forms.

In a previous work, we have investigated the effects of piperine and several of its chemical derivatives on the proliferation of the protozoan parasite Trypanosoma cruzi. It was observed that natural piperine is more active against intracellular amastigotes than axenically grown epimastigotes with IC50 values of 4.91 and 7.

Protozoan parasite-specific carbohydrate structures.

The carbohydrate moieties displayed by pathogenic protozoan parasites exhibit many unusual structural features and their expression is often developmentally regulated. These unique structures suggest a specific relationship between such carbohydrates and parasite pathogenicity. Studies of infected humans indicate that immune responses to protozoan parasites are elicited by glycan determinants on cell-surface or secreted molecules.

Cloning and characterization of the phosphoglucomutase of Trypanosoma cruzi and functional complementation of a Saccharomyces cerevisiae PGM null mutant.

Trypanosoma cruzi is the etiological agent of Chagas' disease, a chronic illness characterized by progressive cardiomyopathy and/or denervation of the digestive tract. The parasite surface is covered with glycoconjugates, such as mucin-type glycoproteins and glycoinositolphospholipids (GIPLs), whose glycans are rich in galactopyranose (Galp) and/or galactofuranose (Galf) residues. These molecules have been implicated in attachment of the parasite to and invasion of mammalian cells and in modulation of the host immune responses during infection.

B cell response during infection with the MAT a and MAT alpha mating types of Cryptococcus neoformans.

In the present study, we compared the B cell response of BALB/c and C57Bl/6 mice during Cryptococcus neoformans infection. This response was investigated using virulent serotype D forms of mating types alpha and a (MAT alpha and MAT a). C57Bl/6 mice showed massive (mainly cerebral) infection by both types, while BALB/c were resistant to infection.

Characterization of the inositol phosphorylceramide synthase activity from Trypanosoma cruzi.

IPC (inositol phosphorylceramide) synthase is an enzyme essential for fungal viability, and it is the target of potent antifungal compounds such as rustmicin and aureobasidin A. Similar to fungi and some other lower eukaryotes, the protozoan parasite Trypanosoma cruzi is capable of synthesizing free or protein-linked glycoinositolphospholipids containing IPC. As a first step towards understanding the importance and mechanism of IPC synthesis in T.

Nitrogen-fixing bacterium Burkholderia brasiliensis produces a novel yersiniose A-containing O-polysaccharide.

Burkholderia brasiliensis, a Gram-negative diazotrophic endophytic bacterium, was first isolated from roots, stems, and leaves of rice plant in Brazil. The polysaccharide moiety was released by ammonolysis from the B. brasiliensis lipopolysaccharide (LPS), allowing the unambiguous characterization of a 3,6-dideoxy-4-C-(1-hydroxyethyl)-D-xylo-hexose (yersiniose A), an uncommon feature for Burkholderia LPS.

Toxic effects of natural piperine and its derivatives on epimastigotes and amastigotes of Trypanosoma cruzi.

We describe herein an evaluation of trypanocidal effects of the natural alkaloid piperine and twelve synthetic derivatives against epimastigote and amastigote forms of the protozoan parasite Trypanosoma cruzi, the causative agent of the incurable human disease, Chagas' disease. The results obtained point to piperine as a suitable template for the development of new drugs with trypanocidal activity.

Glycoinositolphospholipid from Trypanosoma cruzi: structure, biosynthesis and immunobiology.

The pathogenic protozoan parasite Trypanosoma cruzi expresses on its surface an unusual family of glycoinositolphospholipids (GIPLs) closely related to glycosylphosphatidylinositol (GPI) anchors. Different parasite isolates express distinct GIPLs which fall into two series, depending on the substitution of the third mannosyl residue in the conserved glycan sequence Man4-(AEP)-GlcN-InsPO4 by ethanolamine phosphate or beta-galactofuranose. Although the exact role of these molecules in the cell biology and pathogenicity of T.