The Fine Structure of Trypanosoma congolense in Its Bloodstream Phase

Vickerman, K.

doi:10.1111/j.1550-7408.1969.tb02233.x

Cited by 118 publications

(54 citation statements)

References 34 publications

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“…3). TEM data for other kinetoplastids also support this hypothesis: double-membrane structures enclosing glycosomes can be observed in early micrographs of Trypanosoma congolense, 42 and glycosomal proteins were detected by immuno-EM within the lysosome of T. brucei during differentiation. 30 However, the observation that glycosome numbers do decrease in L. major Datg5 parasites during differentiation from promastigote to amastigote, and that some RFP-SQL localizes to lysosomal compartments in stationary phase Datg5 cells, indicates that glycosomes are also degraded by other mechanisms.…”

Section: Discussionsupporting

confidence: 63%

Glycosome turnover inLeishmania majoris mediated by autophagy

et al. 2014

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Abbreviations: ATG, autophagy-related; GFP, green fluorescent protein; mC, mCherry fluorescent protein; MVT, multivesicular tubule; RFP, red fluorescent protein; TEM, transmission electron microscopy.Autophagy is a central process behind the cellular remodeling that occurs during differentiation of Leishmania, yet the cargo of the protozoan parasite's autophagosome is unknown. We have identified glycosomes, peroxisome-like organelles that uniquely compartmentalize glycolytic and other metabolic enzymes in Leishmania and other kinetoplastid parasitic protozoa, as autophagosome cargo. It has been proposed that the number of glycosomes and their content change during the Leishmania life cycle as a key adaptation to the different environments encountered. Quantification of RFP-SQL-labeled glycosomes showed that promastigotes of L. major possess »20 glycosomes per cell, whereas amastigotes contain »10. Glycosome numbers were significantly greater in promastigotes and amastigotes of autophagy-defective L. major Datg5 mutants, implicating autophagy in glycosome homeostasis and providing a partial explanation for the previously observed growth and virulence defects of these mutants. Use of GFP-ATG8 to label autophagosomes showed glycosomes to be cargo in »15% of them; glycosome-containing autophagosomes were trafficked to the lysosome for degradation. The number of autophagosomes increased 10-fold during differentiation, yet the percentage of glycosome-containing autophagosomes remained constant. This indicates that increased turnover of glycosomes was due to an overall increase in autophagy, rather than an upregulation of autophagosomes containing this cargo. Mitophagy of the single mitochondrion was not observed in L. major during normal growth or differentiation; however, mitochondrial remnants resulting from stress-induced fragmentation colocalized with autophagosomes and lysosomes, indicating that autophagy is used to recycle these damaged organelles. These data show that autophagy in Leishmania has a central role not only in maintaining cellular homeostasis and recycling damaged organelles but crucially in the adaptation to environmental change through the turnover of glycosomes.

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Section: Discussionsupporting

confidence: 63%

Glycosome turnover inLeishmania majoris mediated by autophagy

et al. 2014

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“…DISCUSSION We identified a cysteine-rich transmembrane protein (CRAM) located at the flagellar pocket of the protozoan T. brucei. The flagellar pocket is the only area of the cell surface of the trypanosome proposed to function in (receptor-mediated) endocytosis (13,14,19,32,57,58,62). Since CRAM also localized to the lumen of vesicles located underneath the flageilar pocket, the protein is presumably internalized.…”

Section: Methodsmentioning

confidence: 99%

“…However, the flagellar pocket, a deep invagination of the plasma membrane where the flagellum extends from the cell, is not lined with this subpellicular microtubule network. The flagellar pocket is believed to be the site of uptake of nutrients and macromolecules, possibly via receptor-mediated endocytosis (13, 14,32,40,57,58,59,62). Here we characterize a conserved transmembrane protein localized in the flagellar pocket of T.…”

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confidence: 99%

Characterization of a cDNA encoding a cysteine-rich cell surface protein located in the flagellar pocket of the protozoan Trypanosoma brucei.

Lee¹,

Bihain²,

Russell³

et al. 1990

Mol. Cell. Biol.

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We have characterized a cDNA encoding a cysteine-rich, acidic integral membrane protein (CRAM) of the parasitic protozoa Trypanosoma brucei and Trypanosoma equiperdum. Unlike other membrane proteins of T. brucei, which are distributed throughout the cell surface, CRAM is concentrated in the flagellar pocket, an invagination of the cell surface of the trypanosome where endocytosis has been documented. Accordingly, CRAM also locates to vesicles located underneath the pocket, providing evidence of its internalization. CRAM has a predicted molecular mass of 130 kilodaltons and has a signal peptide, a transmembrane domain, and a 41-amino-acid cytoplasmic extension. A characteristic feature of CRAM is a large extracellular domain with a roughly 66-fold acidic, cysteine-rich 12-amino-acid repeat. CRAM is conserved among different protozoan species, including Trypanosoma cruzi, and CRAM has structural similarities with eucaryotic cell surface receptors. The most striking homology of CRAM is to the human low-density-lipoprotein receptor. We propose that CRAM functions as a cell surface receptor of different trypanosome species.The protozoan parasite Trypanosoma brucei, causative agent of sleeping sickness, survives in blood by undergoing antigenic variation of its variant cell surface glycoprotein (VSG) coat. The parasite is transmitted by the tsetse fly through ingestion in a bloodmeal and transfer with the tsetse fly saliva. In the tsetse fly, the bloodstream form trypanosomes differentiate into insect (procyclic) form trypanosomes, resulting in the loss of the protective VSG coat and the expression of a different and small family of cell surface proteins, the procyclic acidic repetitive proteins (or procyclins; 6, 7, 39, 44, 45, 55, 59). Both VSG and the procyclic acidic repetitive proteins are extracellular proteins anchored to the lipid bilayer by a covalently attached lipid moiety (12,15,43). Proteins with transmembrane domains have not been characterized in trypanosomes thus far.Previous studies led to the proposal that a low-densitylipoprotein (LDL) receptor, a transferrin receptor, a nucleoside transport receptor, and a growth factor receptor exist in T. brucei (13,14,26; G. Hide, A. Gray, C. M. Harrison, and A. Tait, Mol. Biochem. Parasitol., in press). A dense network of microtubules below the plasma membrane presumably prevents the uptake of cell surface receptors and their ligands through endocytosis. However, the flagellar pocket, a deep invagination of the plasma membrane where the flagellum extends from the cell, is not lined with this subpellicular microtubule network. The flagellar pocket is believed to be the site of uptake of nutrients and macromolecules, possibly via receptor-mediated endocytosis (13,14,32,40,57,58,59,62). Here we characterize a conserved transmembrane protein localized in the flagellar pocket of T.

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“…In addition, the flagellum of T. congolense, unlike other trypanosomatids, does not extensively protrude from the anterior end of the cell body (Vickerman, 1969;Vickerman & Tetley, 1990). However, this organelle appears to play a key role in the cell adhesion events which occur at different lifecycle stages within the insect vector and in animal hosts.…”

Section: Introductionmentioning

confidence: 99%

The interaction ofTrypanosoma congolensewith endothelial cells

1994

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SUMMARYFactors which affect adhesion of cultured Trypanosoma congolense bloodstream forms to mammalian feeder cells have been examined. Using an in vitro binding assay, the initial events following interaction of trypanosomes with bovine aorta endothelial (BAE) cells were monitored by both light-and electron microscopy. Metabolic inhibitors and other biochemicals were incubated with either cells or parasites, to test whether any inhibited the process. Our findings suggest that adhesion of the parasites is an active process requiring metabolic energy from the trypanosomes, but not from endothelial cells. We also provide data suggesting that T. congolense bloodstream forms possess a lectin-like domain, localized at distinct sites on their flagellar surface, which interacts with specific carbohydrate receptors, most likely sialic acid residues, on the endothelial cell plasma membrane. We also suggest that the cytoskeletal protein actin is probably involved in this interaction.

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The Fine Structure of Trypanosoma congolense in Its Bloodstream Phase

Cited by 118 publications

References 34 publications

Glycosome turnover inLeishmania majoris mediated by autophagy

Glycosome turnover inLeishmania majoris mediated by autophagy

Characterization of a cDNA encoding a cysteine-rich cell surface protein located in the flagellar pocket of the protozoan Trypanosoma brucei.

The interaction ofTrypanosoma congolensewith endothelial cells

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