Special organelles of some pathogenic protozoa

Souza, Wanderley de

doi:10.1007/s00436-002-0696-2

Cited by 40 publications

(29 citation statements)

References 78 publications

(92 reference statements)

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“…In T. cruzi epimastigotes, ingested transferrin is transported to and stored at the reservosomes (Soares & De Souza 1991, De Souza 2002. These organelles are prelysosomal compartments (Soares et al 1992), and our data suggest that uncoated vesicles budding off from the long cytopharynx are directed to them.…”

Section: Discussionsupporting

confidence: 50%

Transferrin uptake may occur through detergent-resistant membrane domains at the cytopharynx of Trypanosoma cruzi epimastigote forms

Corrêa

Atella

Vargas

et al. 2007

Mem. Inst. Oswaldo Cruz

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Uptake of transferrin by epimastigote forms of the protozoan Trypanosoma cruzi occurs mainly through a cytostome/ cytopharynx, via uncoated endocytic vesicles that bud off from the bottom of the cytopharynx. We have here examined whether detergent-resistant membrane (DRM) domains might be involved in this process. Purified whole cell membrane fractions were assayed for cholesterol levels and used in dot blot analyses. Detergent-resistant membrane markers (cholera B toxin and anti-flotillin-1 antibody) presented positive reaction by dot blots in cholesterolrich/ protein-poor membrane sub-fractions. The positive dot blot fraction was submitted to lipid composition analysis, showing composition similar to that of raft fractions described for other eukaryotic cells.Immunofluorescence assays allowed the localization of punctual positive signal for flotillin-1, matching the precise cytostome/ cytopharynx location. These data were confirmed by immunofluorescence assays with the co-localization of flotillin-1 and the transferrin uptake site. Our data suggest that DRM domains occur and are integrated at the cytostome/ cytopharynx of T. cruzi epimastigotes, being the main route for transferrin uptake.Key words: cytopharynx -detergent-resistant membrane -endocytosis -Trypanosoma cruzi -ultrastructure The lipid raft model proposes that cholesterol and sphingolipids of the plasma membrane outer leaflet are not randomly distributed, but rather clustered into micro-domains that float in the lipid bilayer, characterizing detergent-resistant membrane (DRM) domains in eukaryotic cells (Rietveld & Simons 1998, Handcock 2006. Transmembrane proteins (receptors, adhesion molecules, and enzymes) in the lipid bilayer would either reside in, and thus become sorted into transport vesicles, or be excluded from the rafts, depending on partitioning imparted by their physical properties (Harder et al. 1998, Simons & Vaz 2004.Lipid rafts play a role in a wide range of important biological processes, including signal transduction pathways, apoptosis, cell adhesion and migration, organization of the cytoskeleton and protein sorting during both exocytosis and endocytosis (Simons & Toomre 2000, Harris & Siu 2002.Flotillins are cholesterol-binding proteins that associate with a subset of rafts named caveolae, and are frequently used as raft markers. The flotillin protein family consists of the small (45 kDa) proteins flotillin-1 and flotillin-2/ ESA (a close homologue of the epidermal surface antigen). These proteins induce caveolae formation, bind cholesterol, and interact with signaling molecules (Anderson 1998, Kiss et al. 2004. Lipid rafts can exist independently of caveolae, but they must exist prior to formation of caveolae for proper insertion of flotillin into membranes (Graf et al. 1999, Ikonen 2001.Trypanosomatid protozoa have a particular cell body array that allows uptake of nutrients only at a specific membrane site: the flagellar pocket (Morgan et al. 2001). Trypanosoma cruzi, the causative agent of Chagas disease in Latin America, a...

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Section: Discussionsupporting

confidence: 50%

Transferrin uptake may occur through detergent-resistant membrane domains at the cytopharynx of Trypanosoma cruzi epimastigote forms

Corrêa

Atella

Vargas

et al. 2007

Mem. Inst. Oswaldo Cruz

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“…These acidic organelles are electron dense, posses a surrounding membrane, have variable size, ranging from 200 ± S.E. 90 nm of diameter, and contain very high amounts of Mg, Ca, Na, Zn and short and long chain polyphosphates and low amounts of Cl, K and sulfur [for reviews see [18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

A proton pumping pyrophosphatase in acidocalcisomes of Herpetomonas sp.

Medeiros

Moreira

Miranda

et al. 2005

Molecular and Biochemical Parasitology

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Acidocalcisomes are acidic calcium storage organelles found in several microorganisms. They are characterized by their acidic nature, high electron density, high content of polyphosphates and several cations. Electron microscopy contrast tuned images of Herpetomonas sp. showed the presence of several electron dense organelles ranging from 100 to 300 nm in size. In addition, X-ray element mapping associated with energy-filtering transmission electron microscopy showed that most of the cations, namely Na, Mg, P, K, Fe and Zn, are located in their matrix. Using acridine orange as an indicator dye, a pyrophosphate-driven H + uptake was measured in cells permeabilized by digitonin. This uptake has an optimal pH of 6.5-6.7 and was inhibited by sodium fluoride (NaF) and imidodiphosphate (IDP), two H + -pyrophosphatase inhibitors. H + uptake was not promoted by ATP. Addition of 50 M Ca 2+ induced the release of H + , suggesting the presence of a Ca 2+ /H + countertransport system in the membranes of the acidic compartments. Na + was unable to release protons from the organelles. The pyrophosphate-dependent H + uptake was dependent of ion K + and inhibited by Na + Herpetomonas sp. immunolabeled with monoclonal antibodies raised against a Trypanosoma cruzi V-H + -pyrophosphatase shows intense fluorescence in cytoplasmatic organelles of size and distribution similar to the electron-dense vacuoles.Together, these results suggest that the electron dense organelles found in Herpetomonas sp. are homologous to the acidocalcisomes described in other trypanosomatids. They possess a vacuolar H + -pyrophosphatase and a Ca 2+ /H + antiport. However, in contrast to the other trypanosomatids so far studied, we were not able to measure any ATP promoted H + transport in the acidocalcisomes of this parasite.

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“…2b). Trypanosomatids have specific organelles and several distinct mechanisms controlling nuclear organization and control of gene expression (de Souza 2002;Clayton 2002). The trypanosomatid hypothetical proteins in the local database were submitted to PROSITE (Falquet et al 2002) and e-MOTIF (Nevill-Manning et al 1998).…”

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confidence: 99%

PROTOGIM: a novel tool to search motifs and domains in hypothetical proteins of protozoan genomes

et al. 2005

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Whole sequencing of protozoan trypanosomatid genomes revealed the presence of several predicted unknown genes coding for hypothetical proteins. Pairwise, alignment-based, computational methods available online are unable to identify the function of these sequences. To detect clues to identify the function of hypothetical proteins, a user-friendly, bioinformatic tool named PROTOzoan Gene Identification Motifs (PROTOGIM, available on http://www.biowebdb.org/protogim ) was developed, which allows the user to search functional patterns of hypothetical proteins through the screening of regular expression in the sequences. The analysis of 1,194 trypanosomatid hypothetical proteins through PROTOGIM resulted in an identification of motifs and domains in 98% of the cases, demonstrating the reliability and accuracy of the employed method. The added value of this tool is the possibility to modify or insert new regular expressions to perform an analysis against either one or several sequences at the same time. An in silico strategy along with biochemical and molecular characterizations creates new possibilities to find the functions of hypothetical proteins at the postgenome era.

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Special organelles of some pathogenic protozoa

Cited by 40 publications

References 78 publications

Transferrin uptake may occur through detergent-resistant membrane domains at the cytopharynx of Trypanosoma cruzi epimastigote forms

Transferrin uptake may occur through detergent-resistant membrane domains at the cytopharynx of Trypanosoma cruzi epimastigote forms

A proton pumping pyrophosphatase in acidocalcisomes of Herpetomonas sp.

PROTOGIM: a novel tool to search motifs and domains in hypothetical proteins of protozoan genomes

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