scholarly journals The crystal structure and localization of Trypanosoma brucei invariant surface glycoproteins suggest a more permissive VSG coat in the tsetse-transmitted metacyclic stage

2018 ◽  
Author(s):  
Aitor Casas-Sánchez ◽  
Samïrah Perally ◽  
Raghavendran Ramaswamy ◽  
Lee R. Haines ◽  
Clair Rose ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Trypanosoma Brucei ◽  
Fluorescent Microscopy ◽  
Surface Antigens ◽  
Surface Proteins ◽  
Surface Glycoprotein ◽  
Invariant Surface ◽  
Helical Bundle ◽  
N Terminus ◽  
Key Features

AbstractTrypanosoma brucei spp. develop into mammalian-infectious metacyclic trypomastigotes inside the tsetse salivary glands. Besides acquiring a variant surface glycoprotein (VSG) coat, nothing is known about expression of invariant surface antigens by the metacyclic stage. Proteomic analysis of saliva from T. brucei-infected flies revealed a novel family of hypothetical GPI-anchored surface proteins herein named Metacyclic Invariant Surface Proteins (MISP). MISP are encoded by five homolog genes and share ~80% protein identity. The crystal structure of MISP N-terminus at 1.82 Å resolution revealed a triple helical bundle that shares key features with other trypanosome surface proteins. However, molecular modelling combined with live fluorescent microscopy suggest that MISP N-termini are extended above the metacyclic VSG coat, exposing immunogenic epitopes. Collectively, we suggest that the metacyclic cell surface architecture appears more permissive than bloodstream forms in terms of expression of invariant GPI-anchored glycoproteins, which could be exploited for the development of novel vaccines against African trypanosomiases.

Bloodstream form trypanosome plasma membrane proteins: antigenic variation and invariant antigens

Parasitology ◽  
2010 ◽  
Vol 137 (14) ◽  
pp. 2029-2039 ◽  
Author(s):  
ANGELA SCHWEDE ◽  
MARK CARRINGTON
Keyword(s):  
Plasma Membrane ◽  
Trypanosoma Brucei ◽  
Antigenic Variation ◽  
Adaptive Immune System ◽  
Surface Proteins ◽  
Surface Glycoprotein ◽  
Invariant Surface ◽  
Adaptive Immune ◽  
External Face

SUMMARYTrypanosoma bruceiis exposed to the adaptive immune system and complement in the blood of its mammalian hosts. The aim of this review is to analyse the role and regulation of the proteins present on the external face of the plasma membrane in the long-term persistence of an infection and transmission. In particular, the following are addressed: (1) antigenic variation of the variant surface glycoprotein (VSG), (2) the formation of an effective VSG barrier shielding invariant surface proteins, and (3) the rapid uptake of VSG antibody complexes combined with degradation of the immunoglobulin and recycling of the VSG.

Invariant surface proteins in bloodstream forms of Trypanosoma brucei

1994 ◽  
Vol 10 (2) ◽  
pp. 53-58 ◽  
Author(s):  
P. Overath ◽  
M. Chaudhri ◽  
D. Steverding ◽  
K. Ziegelbauer
Keyword(s):  
Trypanosoma Brucei ◽  
Surface Proteins ◽  
Invariant Surface

scholarly journals Characterization, Localization, Essentiality, and High-Resolution Crystal Structure of Glucosamine 6-Phosphate N -Acetyltransferase from Trypanosoma brucei

2011 ◽  
Vol 10 (7) ◽  
pp. 985-997 ◽  
Author(s):  
Karina Mariño ◽  
M. Lucia Sampaio Güther ◽  
Amy K. Wernimont ◽  
Wei Qiu ◽  
Raymond Hui ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Resolution ◽  
Trypanosoma Brucei ◽  
Protein Glycosylation ◽  
Surface Glycoprotein ◽  
Surface Coat ◽  
Content Type ◽  
Phosphate Analysis ◽  
Novel Drug

ABSTRACT A gene predicted to encode Trypanosoma brucei glucosamine 6-phosphate N -acetyltransferase ( TbGNA1 ; EC 2.3.1.4) was cloned and expressed in Escherichia coli . The recombinant protein was enzymatically active, and its high-resolution crystal structure was obtained at 1.86 Å. Endogenous TbGNA1 protein was localized to the peroxisome-like microbody, the glycosome. A bloodstream-form T. brucei GNA1 conditional null mutant was constructed and shown to be unable to sustain growth in vitro under nonpermissive conditions, demonstrating that there are no metabolic or nutritional routes to UDP-GlcNAc other than via GlcNAc-6-phosphate. Analysis of the protein glycosylation phenotype of the TbGNA1 mutant under nonpermissive conditions revealed that poly- N -acetyllactosamine structures were greatly reduced in the parasite and that the glycosylation profile of the principal parasite surface coat component, the variant surface glycoprotein (VSG), was modified. The significance of results and the potential of TbGNA1 as a novel drug target for African sleeping sickness are discussed.

scholarly journals Developmental Variation in Rab11-Dependent Trafficking in Trypanosoma brucei

2005 ◽  
Vol 4 (5) ◽  
pp. 971-980 ◽  
Author(s):  
Belinda S. Hall ◽  
Emma Smith ◽  
Wolfram Langer ◽  
Louisa A. Jacobs ◽  
David Goulding ◽  
...  
Keyword(s):  
Trypanosoma Brucei ◽  
Fluid Phase ◽  
Small Gtpase ◽  
Surface Proteins ◽  
Surface Glycoprotein ◽  
Primary Role ◽  
Flagellar Pocket ◽  
Developmentally Regulated ◽  
Developmental Variation ◽  
Fluid Phase Endocytosis

ABSTRACT In Trypanosoma brucei, endocytosis is developmentally regulated and is substantially more active in the mammalian infective stage, where it likely plays a role in immune evasion. The small GTPase TbRAB11 is highly expressed in the mammalian stage and mediates recycling of glycosylphosphatidylinositol-anchored proteins, including the variant surface glycoprotein (VSG) and the transferrin receptor, plus trafficking of internalized anti-VSG antibody and transferrin. No function has been assigned to TbRAB11 in the procyclic (insect) stage trypanosome. The importance of TbRAB11 to both bloodstream and procyclic form viability was assessed by RNA interference (RNAi). Suppression of TbRAB11 in the bloodstream form was rapidly lethal and led to cells with round morphology and an enlarged flagellar pocket. TbRAB11 RNAi was also lethal in procyclic forms, which also became rounded, but progression to cell death was significantly slower and the flagellar pocket remained normal. In bloodstream forms, silencing of TbRAB11 had no effect on exocytosis of newly synthesized VSG, fluid-phase endocytosis, or transferrin uptake, but export of internalized transferrin was inhibited. Lectin endocytosis assays revealed a block to postendosomal transport mediated by suppressing TbRAB11. By contrast, in procyclic forms, depletion of TbRAB11 blocks both fluid-phase endocytosis and internalization of surface proteins. In normal bloodstream forms, most VSG is recycled, but in procyclics, internalized surface proteins accumulated in the lysosome. These data demonstrate that TbRAB11 controls recycling and is essential in both life stages of T. brucei but that its primary role is subject to developmental variation.

scholarly journals Ubiquitylation and Developmental Regulation of Invariant Surface Protein Expression in Trypanosomes

2011 ◽  
Vol 10 (7) ◽  
pp. 916-931 ◽  
Author(s):  
Ka Fai Leung ◽  
Fay S. Riley ◽  
Mark Carrington ◽  
Mark C. Field
Keyword(s):  
Cell Surface ◽  
Protein Turnover ◽  
Full Length ◽  
Surface Proteins ◽  
Surface Glycoprotein ◽  
General Mechanism ◽  
Membrane Domain ◽  
Reporter Protein ◽  
Invariant Surface ◽  
Content Type

ABSTRACTThe cell surface ofTrypanosoma bruceiis dominated by the glycosylphosphatidylinositol-anchored variant surface glycoprotein (VSG), which is essential for immune evasion. VSG biosynthesis, trafficking, and turnover are well documented, buttrans-membrane domain (TMD) proteins, including the invariant surface glycoproteins (ISGs), are less well characterized. Internalization and degradation of ISG65 depend on ubiquitylation of conserved cytoplasmic lysines. Using epitope-tagged ISG75 and reporter chimeric proteins bearing the cytoplasmic andtrans-membrane regions of ISG75, together with multiple mutants with lysine-to-arginine mutations, we demonstrate that the cytoplasmic tail of ISG75 is both sufficient and necessary for endosomal targeting and degradation. The ISG75 chimeric reporter protein localized to endocytic organelles, while lysine-null versions were significantly stabilized at the cell surface. Importantly, ISG75 cytoplasmic lysines are modified by extensive oligoubiquitin chains and ubiquitylation is abolished in the lysine-null version. Furthermore, we find evidence for differential modes of turnover of ISG65 and ISG75. Full-length lysine-null ISG65 localization and protein turnover are significantly perturbed, but ISG75 localization and protein turnover are not, while ubiquitin conjugates can be detected for full-length lysine-null ISG75 but not ISG65. We find that the ISG75 ectodomain has a predicted coiled-coil, suggesting that ISG75 could be part of a complex, while ISG65 behaves independently. We also demonstrate a developmental stage-specific mechanism for exclusion of surface ISG expression in insect-stage cells by a ubiquitin-independent mechanism. We suggest that ubiquitylation may be a general mechanism for regulatingtrans-membrane domain surface proteins in trypanosomes.

Target of rapamycin (TOR) kinase in Trypanosoma brucei: an extended family

2013 ◽  
Vol 41 (4) ◽  
pp. 934-938 ◽  
Author(s):  
Manuel Saldivia ◽  
Antonio Barquilla ◽  
Jean-Mathieu Bart ◽  
Rosario Diaz-González ◽  
Michael N. Hall ◽  
...  
Keyword(s):  
Trypanosoma Brucei ◽  
Extended Family ◽  
Protozoan Parasite ◽  
Surface Proteins ◽  
Surface Glycoprotein ◽  
Target Of Rapamycin ◽  
Complex Life Cycle ◽  
Loss Of Function ◽  
Down Regulation ◽  
Tor Kinase

The complex life cycle of Trypanosoma brucei provides an excellent model system to understand signalling pathways that regulate development. We described previously the classical functions of TOR (target of rapamycin) 1 and TOR2 in T. brucei. In a more recent study, we described a novel TOR kinase, named TOR4, which regulates differentiation from the proliferative infective form to the quiescent form. In contrast with TOR1 loss-of-function, down-regulation of TOR4 triggers an irreversible differentiation process through the development of the insect pre-adapted quiescent form. TOR4 governs a signalling pathway distinct from those controlled by the conventional TOR complexes TORC1 and TORC2. Depletion of TOR4 induces all well-known characteristics of the quiescent developmental stage in trypanosomes, including expression of the PAD (proteins associated with differentiation) surface proteins and transcriptional down-regulation of the VSG (variant surface glycoprotein) gene. TOR4 kinase forms a structurally and functionally distinct complex named TORC4. TOR4 associates with LST8 (lethal with sec-13 protein 8) and other factors including an armadillo-domain-containing protein and the major vault protein, which probably serves as a scaffold for this kinase. Research in T. brucei, a protozoan parasite that diverged from the eukaryotic tree early in evolution, may help to uncover new functions of TOR kinases.

scholarly journals Structure of uridine diphosphateN-acetylglucosamine pyrophosphorylase fromEntamoeba histolytica

2015 ◽  
Vol 71 (5) ◽  
pp. 560-565
Author(s):  
Thomas E. Edwards ◽  
Anna S. Gardberg ◽  
Isabelle Q. H. Phan ◽  
Yang Zhang ◽  
Bart L. Staker ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Trypanosoma Brucei ◽  
Protein Glycosylation ◽  
The Other ◽  
Uridine Diphosphate ◽  
Allosteric Inhibitors ◽  
Amoebic Dysentery ◽  
Cell Wall Biogenesis ◽  
Human Enzyme ◽  
N Terminus

Uridine diphosphateN-acetylglucosamine pyrophosphorylase (UAP) catalyzes the final step in the synthesis of UDP-GlcNAc, which is involved in cell-wall biogenesis in plants and fungi and in protein glycosylation. Small-molecule inhibitors have been developed against UAP fromTrypanosoma bruceithat target an allosteric pocket to provide selectivity over the human enzyme. A 1.8 Å resolution crystal structure was determined of UAP fromEntamoeba histolytica, an anaerobic parasitic protozoan that causes amoebic dysentery. AlthoughE. histolyticaUAP exhibits the same three-domain global architecture as other UAPs, it appears to lack three α-helices at the N-terminus and contains two amino acids in the allosteric pocket that make it appear more like the enzyme from the human host than that from the other parasiteT. brucei. Thus, allosteric inhibitors ofT. bruceiUAP are unlikely to targetEntamoebaUAPs.

scholarly journals Active RNA Polymerase I of Trypanosoma brucei Harbors a Novel Subunit Essential for Transcription

2007 ◽  
Vol 27 (17) ◽  
pp. 6254-6263 ◽  
Author(s):  
Tu N. Nguyen ◽  
Bernd Schimanski ◽  
Arthur Günzl
Keyword(s):  
Rna Polymerase ◽  
Trypanosoma Brucei ◽  
Surface Antigens ◽  
Amino Acid Sequences ◽  
Rna Polymerase I ◽  
Surface Glycoprotein ◽  
Sequence Motif ◽  
Cell Surface Antigens ◽  
Conserved Sequence ◽  
Polymerase I

ABSTRACT A unique characteristic of the protistan parasite Trypanosoma brucei is a multifunctional RNA polymerase I which, in addition to synthesizing rRNA as in other eukaryotes, transcribes gene units encoding the major cell surface antigens variant surface glycoprotein and procyclin. Thus far, purification of this enzyme has revealed nine orthologues of known subunits but no active enzyme. Here, we have epitope tagged the specific subunit RPB6z and tandem affinity purified RNA polymerase I from crude extract. The purified enzyme was active in both a nonspecific and a promoter-dependent transcription assay and exhibited enriched protein bands with apparent sizes of 31, 29, and 27 kDa. p31 and its trypanosomatid orthologues were identified, but their amino acid sequences have no similarity to proteins of other eukaryotes, nor do they contain a conserved sequence motif. Nevertheless, p31 cosedimented with purified RNA polymerase I, and RNA interferance-mediated silencing of p31 was lethal, affecting the abundance of rRNA. Moreover, extract of p31-silenced cells exhibited a specific defect in transcription of class I templates, which was remedied by the addition of purified RNA polymerase I, and an anti-p31 serum completely blocked RNA polymerase I-mediated transcription. We therefore dubbed this novel functional component of T. brucei RNA polymerase I TbRPA31.

scholarly journals The endosomal TbTpr86/TbUsp7/SkpZ (TUS) complex controls surface protein abundance in trypanosomes

2020 ◽  
Author(s):  
Kayo Yamada ◽  
Farzana K. Yaqub ◽  
Martin Zoltner ◽  
Mark C. Field
Keyword(s):  
Cell Cycle Progression ◽  
Surface Protein ◽  
Surface Proteins ◽  
Surface Glycoprotein ◽  
Tetratricopeptide Repeat ◽  
Protein Abundance ◽  
Membrane Domain ◽  
Cycle Progression ◽  
Invariant Surface ◽  
Tetratricopeptide Repeat Protein

AbstractIn trypanosomes the orthologs of human USP7 and VDU1 control abundance of a cohort of surface proteins, including invariant surface glycoproteins (ISGs) by functioning as deubiquitinases (DUBs) Silencing TbUsp7 partially inhibits endocytosis and invariant surface glycoprotein turnover. As a component of cullin E3 ubiquitin ligases, S-phase kinase-associated protein 1 (Skp1) has crucial roles in cell cycle progression, transcriptional regulation, signal transduction and other processes in animals and fungi. Unexpectedly, trypanosomes possess multiple Skp1 paralogs, including a divergent paralog designated SkpZ. SkpZ is implicated in suramin-sensitivity and endocytosis and decreases in abundance following TbUsp7 knockdown and physically interacts with TbUsp7 and TbTpr86. The latter is a tetratricopeptide-repeat protein also implicated in suramin sensitivity and located close to the flagellar pocket/endosomes, consistent with a role in endocytosis. Further, silencing SkpZ reduced abundance of TbUsp7 and TbTpr86 and many trans-membrane domain surface proteins. Our data indicate that TbTpr86, TbUsp7 and SkpZ form the ‘TUS’ complex that regulates abundance of a significant cohort of trypanosome surface proteins.

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