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.

scholarly journals Black-necked spitting cobra (Naja nigricollis) phospholipases A2 cause Trypanosoma brucei death by blocking endocytosis through the flagellar pocket

2021 ◽  
Author(s):  
Andrea Martos-Esteban ◽  
Olivia J. S. Macleod ◽  
Isabella Maudlin ◽  
Konstantinos Kalogeropoulos ◽  
Jonas A. Jurgensen ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Trypanosoma Brucei ◽  
Antigenic Variation ◽  
Adaptive Immune Response ◽  
Surface Glycoprotein ◽  
Covalent Attachment ◽  
Mammalian Host ◽  
Flagellar Pocket ◽  
African Trypanosomes ◽  
External Face

African trypanosomes, such as Trypanosoma brucei, are flagellated protozoa which proliferate in mammals and cause a variety of diseases in people and animals. In a mammalian host, the external face of the African trypanosome plasma membrane is covered by a densely packed coat formed of variant surface glycoprotein (VSG), which counteracts the host adaptive immune response by antigenic variation. The VSG is attached to the external face of the plasma membrane by covalent attachment of the C-terminus to a glycosylphosphatidylinositol. As the trypanosome grows, newly synthesised VSG is added to the plasma membrane by vesicle fusion to the flagellar pocket, the sole location of exo- and endocytosis. Snake venoms contain dozens of components including proteases and phospholipases. Here, we investigated the effect of Naja nigricollis on T. brucei with the aim of describing the response of the trypanosome to hydrolytic attack on the VSG. We found no evidence for VGS hydrolysis however N. nigricollis venom caused: (i) an enlargement of the flagellar pocket, (ii) the Rab11 positive endosomal compartments to adopt an abnormal dispersed localisation, and (iii) a cell cycle arrest prior to cytokinesis. A single protein family, the phospholipases A2s present in N. nigricollis venom, was necessary and sufficient for the effects. This study provides new molecular insight into T. brucei biology and possibly describes mechanisms that could be exploited for T. brucei targeting.

scholarly journals Regulation of Antigenic Variation by Trypanosoma brucei Telomere Proteins Depends on Their Unique DNA Binding Activities

Pathogens ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 967
Author(s):  
Bibo Li ◽  
Yanxiang Zhao
Keyword(s):  
Nucleic Acid ◽  
Trypanosoma Brucei ◽  
Antigenic Variation ◽  
Dna Recombination ◽  
Surface Glycoprotein ◽  
Monoallelic Expression ◽  
Nucleic Acid Binding ◽  
Major Surface ◽  
Telomere Structure

Trypanosoma brucei causes human African trypanosomiasis and regularly switches its major surface antigen, Variant Surface Glycoprotein (VSG), to evade the host immune response. Such antigenic variation is a key pathogenesis mechanism that enables T. brucei to establish long-term infections. VSG is expressed exclusively from subtelomere loci in a strictly monoallelic manner, and DNA recombination is an important VSG switching pathway. The integrity of telomere and subtelomere structure, maintained by multiple telomere proteins, is essential for T. brucei viability and for regulating the monoallelic VSG expression and VSG switching. Here we will focus on T. brucei TRF and RAP1, two telomere proteins with unique nucleic acid binding activities, and summarize their functions in telomere integrity and stability, VSG switching, and monoallelic VSG expression. Targeting the unique features of TbTRF and TbRAP1′s nucleic acid binding activities to perturb the integrity of telomere structure and disrupt VSG monoallelic expression may serve as potential therapeutic strategy against T. brucei.

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.

scholarly journals Inositol phosphate pathway controls transcription of telomeric expression sites in trypanosomes

2015 ◽  
Vol 112 (21) ◽  
pp. E2803-E2812 ◽  
Author(s):  
Igor Cestari ◽  
Ken Stuart
Keyword(s):  
Plasma Membrane ◽  
Trypanosoma Brucei ◽  
Antigenic Variation ◽  
Inositol Phosphate ◽  
Rna Polymerase I ◽  
Surface Glycoprotein ◽  
Variant Surface Glycoprotein ◽  
Activator Protein 1 ◽  
African Trypanosomes ◽  
Polymerase I

African trypanosomes evade clearance by host antibodies by periodically changing their variant surface glycoprotein (VSG) coat. They transcribe only one VSG gene at a time from 1 of about 20 telomeric expression sites (ESs). They undergo antigenic variation by switching transcription between telomeric ESs or by recombination of the VSG gene expressed. We show that the inositol phosphate (IP) pathway controls transcription of telomeric ESs and VSG antigenic switching in Trypanosoma brucei. Conditional knockdown of phosphatidylinositol 5-kinase (TbPIP5K) or phosphatidylinositol 5-phosphatase (TbPIP5Pase) or overexpression of phospholipase C (TbPLC) derepresses numerous silent ESs in T. brucei bloodstream forms. The derepression is specific to telomeric ESs, and it coincides with an increase in the number of colocalizing telomeric and RNA polymerase I foci in the nucleus. Monoallelic VSG transcription resumes after reexpression of TbPIP5K; however, most of the resultant cells switched the VSG gene expressed. TbPIP5K, TbPLC, their substrates, and products localize to the plasma membrane, whereas TbPIP5Pase localizes to the nucleus proximal to telomeres. TbPIP5Pase associates with repressor/activator protein 1 (TbRAP1), and their telomeric silencing function is altered by TbPIP5K knockdown. These results show that specific steps in the IP pathway control ES transcription and antigenic switching in T. brucei by epigenetic regulation of telomere silencing.

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 Escaping the immune system by DNA repair and recombination in African trypanosomes

Open Biology ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 190182 ◽  
Author(s):  
Núria Sima ◽  
Emilia Jane McLaughlin ◽  
Sebastian Hutchinson ◽  
Lucy Glover
Keyword(s):  
Immune Response ◽  
Dna Repair ◽  
Trypanosoma Brucei ◽  
Antigenic Variation ◽  
Surface Glycoprotein ◽  
Variant Surface Glycoprotein ◽  
Surface Coat ◽  
African Trypanosomes ◽  
Active Expression ◽  
Expression Site

African trypanosomes escape the mammalian immune response by antigenic variation—the periodic exchange of one surface coat protein, in Trypanosoma brucei the variant surface glycoprotein (VSG), for an immunologically distinct one. VSG transcription is monoallelic, with only one VSG being expressed at a time from a specialized locus, known as an expression site. VSG switching is a predominantly recombination-driven process that allows VSG sequences to be recombined into the active expression site either replacing the currently active VSG or generating a ‘new’ VSG by segmental gene conversion. In this review, we describe what is known about the factors that influence this process, focusing specifically on DNA repair and recombination.

scholarly journals Chromosome structure: DNA nucleotide sequence elements of a subset of the minichromosomes of the protozoan Trypanosoma brucei.

1991 ◽  
Vol 11 (8) ◽  
pp. 3823-3834 ◽  
Author(s):  
M Weiden ◽  
Y N Osheim ◽  
A L Beyer ◽  
L H Van der Ploeg
Keyword(s):  
Trypanosoma Brucei ◽  
Antigenic Variation ◽  
Microscopic Analysis ◽  
The Body ◽  
Surface Glycoprotein ◽  
Main Body ◽  
Electron Microscopic ◽  
Protein Coding ◽  
Cell Surface Glycoprotein ◽  
Telomere Repeat

The genome of the protozoan Trypanosoma brucei contains a set of about 100 minichromosomes of about 50 to 150 kb in size. The small size of these chromosomes, their involvement in antigenic variation, and their mitotic stability make them ideal candidates for a structural analysis of protozoan chromosomes and their telomeres. We show that a subset of the minichromosomes is composed predominantly of simple-sequence DNA, with over 90% of the length of the minichromosome consisting of a tandem array of 177-bp repeats, indicating that these molecules have limited protein-coding capacity. Proceeding from the tip of the telomere to a chromosome internal position, a subset of the minichromosomes contained the GGGTTA telomere repeat, a 29-bp telomere-derived repeat, a region containing 74-bp G + C-rich direct repeats separated by approximately 155 bp of A + T-rich DNA that has a bent character, and 50 to 150 kb of the 177-bp repeat. Several of the minichromosome-derived telomeres did not encode protein-coding genes, indicating that the repertoire of telomeric variant cell surface glycoprotein genes is restricted to some telomeres only. The telomere organization in trypanosomes shares striking similarities to the organization of telomeres and subtelomeres in humans, yeasts, and plasmodia. An electron microscopic analysis of the minichromosomes showed that they are linear molecules without abnormal structures in the main body of the chromosome. The structure of replicating molecules indicated that minichromosomes probably have a single bidirectional origin of replication located in the body of the chromosome. We propose a model for the structure of the trypanosome minichromosomes.

scholarly journals The Genetic, Environmental, and Immunopathological Complexity of Autoantibody-Negative Rheumatoid Arthritis

2021 ◽  
Vol 22 (22) ◽  
pp. 12386
Author(s):  
Ludovico De Stefano ◽  
Bernardo D’Onofrio ◽  
Antonio Manzo ◽  
Carlomaurizio Montecucco ◽  
Serena Bugatti
Keyword(s):  
Rheumatoid Arthritis ◽  
Clinical Presentation ◽  
Adaptive Immune System ◽  
Response To Treatment ◽  
Targeted Intervention ◽  
Long Term Outcomes ◽  
Inflammatory Cascade ◽  
Adaptive Immune ◽  
Disease Subtypes

Differences in clinical presentation, response to treatment, and long-term outcomes between autoantibody-positive and -negative rheumatoid arthritis (RA) highlight the need for a better comprehension of the immunopathogenic events underlying the two disease subtypes. Whilst the drivers and perpetuators of autoimmunity in autoantibody-positive RA have started to be disclosed, autoantibody-negative RA remains puzzling, also due its wide phenotypic heterogeneity and its possible misdiagnosis. Genetic susceptibility appears to mostly rely on class I HLA genes and a number of yet unidentified non-HLA loci. On the background of such variable genetic predisposition, multiple exogeneous, endogenous, and stochastic factors, some of which are not shared with autoantibody-positive RA, contribute to the onset of the inflammatory cascade. In a proportion of the patients, the immunopathology of synovitis, at least in the initial stages, appears largely myeloid driven, with abundant production of proinflammatory cytokines and only minor involvement of cells of the adaptive immune system. Better understanding of the complexity of autoantibody-negative RA is still needed in order to open new avenues for targeted intervention and improve clinical outcomes.

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.

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