Identification and characterization of an acidic major surface glycoprotein from procyclic stage Trypanosoma congolense

Beecroft, Robert P.; Roditi, Isabel; Pearson, Terry W.

doi:10.1016/0166-6851(93)90074-8

Cited by 79 publications

(41 citation statements)

References 35 publications

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“…A similar band was also detected in the African trypanosomes (Fig. 2, lanes 1 to 5), including bloodstream forms (lane 2). No other immunoreactive bands were seen.…”

supporting

confidence: 65%

The kinetoplastid membrane protein 11 of Leishmania donovani and African trypanosomes is a potent stimulator of T-lymphocyte proliferation

1995

Parasitology Today

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“…A similar band was also detected in the African trypanosomes (Fig. 2, lanes 1 to 5), including bloodstream forms (lane 2). No other immunoreactive bands were seen.…”

supporting

confidence: 65%

The kinetoplastid membrane protein 11 of Leishmania donovani and African trypanosomes is a potent stimulator of T-lymphocyte proliferation

1995

Parasitology Today

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“…In the present work, we describe the identification of novel abundant GPIanchored proteins in T. congolense procyclic forms that share a number of characteristics with T. brucei EP and GPEET and, thus, were named T. congolense procyclins. It is unclear why these proteins have not been detected in the past (5,6,40). Possible explanations include their extensive posttranslational modification, variation in the repeats between isolates/subspecies of T. congolense, altered expression levels in different strains or culture media, and the use of different protocols for protein extraction and analysis.…”

Section: Discussionmentioning

confidence: 99%

“…Over a decade ago, two groups simultaneously identified the first major surface antigen in T. congolense procyclic culture forms and named it GARP for glutamate-and alanine-rich protein (5,6). Only recently, this protein has been shown to be highly conserved among the T. congolense subgroups Savannah, Forest, and Kilifi and to be present in other trypanosomes of the subgenus Nannomonas (3).…”

mentioning

confidence: 99%

“…Only recently, this protein has been shown to be highly conserved among the T. congolense subgroups Savannah, Forest, and Kilifi and to be present in other trypanosomes of the subgenus Nannomonas (3). GARP, in contrast to the T. brucei procyclins, contains no amino acid repeats in the primary sequence, and yet the proteins from the two strains have been proposed to be functional equivalents because they share the properties of surface orientation, acidity, immunodominance, and stage specificity (5,6,21,36). In addition, they are attached to the cell membrane via similar GPI anchors (40,41).…”

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confidence: 99%

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Trypanosoma congolense Procyclins: Unmasking Cryptic Major Surface Glycoproteins in Procyclic Forms

et al. 2006

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In the tsetse fly, the protozoan parasite Trypanosoma congolense is covered by a dense layer of glycosylphosphatidylinositol (GPI)-anchored molecules. These include a protease-resistant surface molecule (PRS), which is expressed by procyclic forms early in infection, and a glutamic acid-and alanine-rich protein (GARP), which appears at later stages. Since neither of these surface antigens is expressed at intermediate stages, we investigated whether a GPI-anchored protein of 50 to 58 kDa, previously detected in procyclic culture forms, might constitute the coat of these parasites. We therefore partially purified the protein from T. congolense Kilifi procyclic forms, obtained an N-terminal amino acid sequence, and identified its gene. Detailed analyses showed that the mature protein consists almost exclusively of 13 heptapeptide repeats (EPGENGT). The protein is densely N glycosylated, with up to 13 high-mannose oligosaccharides ranging from Man 5 GlcNAc 2 to Man 9 GlcNAc 2 linked to the peptide repeats. The lipid moiety of the glycosylphosphatidylinositol is composed of sn-1-stearoyl-2-lyso-glycerol-3-HPO 4 -1-(2-O-acyl)-D-myo-inositol. Heavily glycosylated proteins with similar repeats were subsequently identified in T. congolense Savannah procyclic forms. Collectively, this group of proteins was named T. congolense procyclins to reflect their relationship to the EP and GPEET procyclins of T. brucei. Using an antiserum raised against the EPGENGT repeat, we show that T. congolense procyclins are expressed continuously in the fly midgut and thus form the surface coat of cells that are negative for both PRS and GARP.

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“…Within a group, the sequences are extremely similar (ϳ86% identity), but the longest conserved sequence that occurs in both the ␣ and ␤ 3Ј UTRs is a 16-mer which is predicted to form part of a stem-loop structure (20). The same sequence, with the same theoretical secondary structure, has also been found in the analogous gene from another species of trypanosome, Trypanosoma congolense, which codes for a major surface glycoprotein known as GARP (glutamic acid-and alanine-rich protein) (1,2). Although the procyclin and GARP proteins exhibit no sequence similarity, it is possible to express the latter in T. brucei, where it is correctly routed to the plasma membrane (21).…”

mentioning

confidence: 94%

Elements in the 3′ Untranslated Region of Procyclin mRNA Regulate Expression in Insect Forms of Trypanosoma brucei by Modulating RNA Stability and Translation

Furger

Schürch

Kurath

et al. 1997

Molecular and Cellular Biology

143

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Procyclins are the major surface glycoproteins of insect forms of Trypanosoma brucei. We have previously shown that a conserved 16-mer in the 3 untranslated region (UTR) of procyclin transcripts functions as a positive element in procyclic-form trypanosomes. A systematic analysis of the entire 297-base 3 UTR has now revealed additional elements which are involved in posttranscriptional regulation: a positive element which requires the first 40 bases of the 3 UTR and at least one negative element between nucleotides 101 and 173 (the LII domain). Deletion of either positive element resulted in a >8-fold reduction in the amount of protein but only an ϳ2-fold decrease in the steady-state level of mRNA, suggesting that regulation also occurred at the level of translation. In contrast, deletion of LII caused a threefold increase in the steady-state levels of both the mRNA and protein. LII-16-mer double deletions also gave high levels of expression, suggesting that the 16-mer functions as an antirepressor of the negative element rather than as an independent activator. All three elements have an effect on RNA turnover. When either positive element was deleted, the half-life (t 1/2 ) of the mRNA was reduced from ϳ50 min (the t 1/2 of the wild-type 3 UTR) to <15 min, whereas removal of the LII element resulted in an increased t 1/2 of ϳ100 min. We present a model of posttranscriptional regulation in which the negative domain is counteracted by two positive elements which shield it from nucleases and/or translational repressors.The differentiation of bloodstream forms of Trypanosoma brucei into procyclic forms which replicate in the tsetse fly midgut is marked by the synthesis of a new surface coat composed of procyclins (otherwise known as procyclic acidic repetitive proteins [PARPs]) and the shedding of the variant surface glycoprotein (VSG) coat, which covers the parasites in the mammalian host (31,42,54). It has been estimated that each cell is covered by approximately six million procyclin molecules (9) which are attached to the surface membrane by glycosylphosphatidylinositol (GPI) anchors (15, 16). The parasites divide by binary fission, with a population doubling time of ϳ9 to 10 h in culture, so there is a constant requirement for high levels of procyclin synthesis in order to maintain the density of the coat.Like the majority of genes in trypanosomatids, the procyclin genes form part of polycistronic transcription units (reviewed in reference 50). The trypanosome strain T. brucei 427 contains four procyclin expression sites which are located on separate chromosomes (43). Each expression site consists of tandemly linked procyclin genes (␣ and ␤), followed by a locus-specific procyclin-associated gene (PAG) (6, 28, 51). Two expression sites also contain an additional gene, GRESAG 2 (gene related to ESAG 2), which is very similar to a gene in the VSG expression site (4).When bloodstream form trypanosomes are triggered to differentiate into procyclic forms, there is a 5-to 10-fold increase in transcription initiatio...

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Identification and characterization of an acidic major surface glycoprotein from procyclic stage Trypanosoma congolense

Cited by 79 publications

References 35 publications

The kinetoplastid membrane protein 11 of Leishmania donovani and African trypanosomes is a potent stimulator of T-lymphocyte proliferation

The kinetoplastid membrane protein 11 of Leishmania donovani and African trypanosomes is a potent stimulator of T-lymphocyte proliferation

Trypanosoma congolense Procyclins: Unmasking Cryptic Major Surface Glycoproteins in Procyclic Forms

Elements in the 3′ Untranslated Region of Procyclin mRNA Regulate Expression in Insect Forms of Trypanosoma brucei by Modulating RNA Stability and Translation

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