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Eirich P, Nesterov P, Shityakov S, Skorb EV, Sander B, Broscheit J, Dandekar T, Jones NG, Engstler M. The release of host-derived antibodies bound to the variant surface glycoprotein (VSG) of Trypanosoma brucei cannot be explained by pH-dependent conformational changes of the VSG dimer. OPEN RESEARCH EUROPE 2024; 4:87. [PMID: 38903703 PMCID: PMC11187536 DOI: 10.12688/openreseurope.16783.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Accepted: 01/26/2024] [Indexed: 06/22/2024]
Abstract
Background Trypanosoma brucei is a protozoan parasite that evades the mammalian host's adaptive immune response by antigenic variation of the highly immunogenic variant surface glycoprotein (VSG). VSGs form a dense surface coat that is constantly recycled through the endosomal system. Bound antibodies are separated in the endosome from the VSG and destroyed in the lysosome. For VSGs it has been hypothesized that pH-dependent structural changes of the VSG could occur in the more acidic environment of the endosome and hence, facilitate the separation of the antibody from the VSG. Methods We used size exclusion chromatography, where molecules are separated according to their hydrodynamic radius to see if the VSG is present as a homodimer at both pH values. To gain information about the structural integrity of the protein we used circular dichroism spectroscopy by exposing the VSG in solution to a mixture of right- and left-circularly polarized light and analysing the absorbed UV spectra. Evaluation of protein stability and molecular dynamics simulations at different pH values was performed using different computational methods. Results We show, for an A2-type VSG, that the dimer size is only slightly larger at pH 5.2 than at pH 7.4. Moreover, the dimer was marginally more stable at lower pH due to the higher affinity (ΔG = 353.37 kcal/mol) between the monomers. Due to the larger size, the predicted epitopes were more exposed to the solvent at low pH. Moderate conformational changes (ΔRMSD = 0.35 nm) in VSG were detected between the dimers at pH 5.2 and pH 7.4 in molecular dynamics simulations, and no significant differences in the protein secondary structure were observed by circular dichroism spectroscopy. Conclusions Thus, the dissociation of anti-VSG-antibodies in endosomes cannot be explained by changes in pH.
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Affiliation(s)
- Patrick Eirich
- Department of Cell & Developmental Biology, Biocentre, University of Würzburg, Würzburg, Bavaria, 97074, Germany
- Department of Anaesthesiology, Intensive Care, Emergency and Pain Medicine, Würzburg University Hospital, University of Würzburg, Würzburg, Bavaria, 97080, Germany
| | - Pavel Nesterov
- Infochemistry Scientific Center, Laboratory of Chemoinformatics, ITMO University, Saint Petersburg, Saint Petersburg, 191002, Russian Federation
| | - Sergey Shityakov
- Department of Anaesthesiology, Intensive Care, Emergency and Pain Medicine, Würzburg University Hospital, University of Würzburg, Würzburg, Bavaria, 97080, Germany
- Infochemistry Scientific Center, Laboratory of Chemoinformatics, ITMO University, Saint Petersburg, Saint Petersburg, 191002, Russian Federation
- Department of Bioinformatics, Biocentre, University of Würzburg, Würzburg, Bavaria, 97074, Germany
| | - Ekaterina V. Skorb
- Infochemistry Scientific Center, Laboratory of Chemoinformatics, ITMO University, Saint Petersburg, Saint Petersburg, 191002, Russian Federation
| | - Bodo Sander
- Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg, Würzburg, Bavaria, 97080, Germany
| | - Jens Broscheit
- Department of Anaesthesiology, Intensive Care, Emergency and Pain Medicine, Würzburg University Hospital, University of Würzburg, Würzburg, Bavaria, 97080, Germany
| | - Thomas Dandekar
- Department of Bioinformatics, Biocentre, University of Würzburg, Würzburg, Bavaria, 97074, Germany
| | - Nicola G. Jones
- Department of Cell & Developmental Biology, Biocentre, University of Würzburg, Würzburg, Bavaria, 97074, Germany
| | - Markus Engstler
- Department of Cell & Developmental Biology, Biocentre, University of Würzburg, Würzburg, Bavaria, 97074, Germany
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Iribarren PA, Di Marzio LA, Berazategui MA, Saura A, Coria L, Cassataro J, Rojas F, Navarro M, Alvarez VE. Depolymerization of SUMO chains induces slender to stumpy differentiation in T. brucei bloodstream parasites. PLoS Pathog 2024; 20:e1012166. [PMID: 38635823 PMCID: PMC11060531 DOI: 10.1371/journal.ppat.1012166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Revised: 04/30/2024] [Accepted: 04/01/2024] [Indexed: 04/20/2024] Open
Abstract
Trypanosoma brucei are protozoan parasites that cause sleeping sickness in humans and nagana in cattle. Inside the mammalian host, a quorum sensing-like mechanism coordinates its differentiation from a slender replicative form into a quiescent stumpy form, limiting growth and activating metabolic pathways that are beneficial to the parasite in the insect host. The post-translational modification of proteins with the Small Ubiquitin-like MOdifier (SUMO) enables dynamic regulation of cellular metabolism. SUMO can be conjugated to its targets as a monomer but can also form oligomeric chains. Here, we have investigated the role of SUMO chains in T. brucei by abolishing the ability of SUMO to polymerize. We have found that parasites able to conjugate only SUMO monomers are primed for differentiation. This was demonstrated for monomorphic lines that are normally unable to produce stumpy forms in response to quorum sensing signaling in mice, and also for pleomorphic cell lines in which stumpy cells were observed at unusually low parasitemia levels. SUMO chain mutants showed a stumpy compatible transcriptional profile and better competence to differentiate into procyclics. Our study indicates that SUMO depolymerization may represent a coordinated signal triggered during stumpy activation program.
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Affiliation(s)
- Paula Ana Iribarren
- Instituto de Investigaciones Biotecnológicas “Dr. Rodolfo Ugalde”–IIBIO (UNSAM-CONICET), San Martin, Buenos Aires, Argentina
| | - Lucía Ayelén Di Marzio
- Instituto de Investigaciones Biotecnológicas “Dr. Rodolfo Ugalde”–IIBIO (UNSAM-CONICET), San Martin, Buenos Aires, Argentina
| | - María Agustina Berazategui
- Instituto de Investigaciones Biotecnológicas “Dr. Rodolfo Ugalde”–IIBIO (UNSAM-CONICET), San Martin, Buenos Aires, Argentina
| | - Andreu Saura
- Instituto de Parasitología y Biomedicina “López-Neyra”, CSIC (IPBLN-CSIC), Granada, Spain
| | - Lorena Coria
- Instituto de Investigaciones Biotecnológicas “Dr. Rodolfo Ugalde”–IIBIO (UNSAM-CONICET), San Martin, Buenos Aires, Argentina
| | - Juliana Cassataro
- Instituto de Investigaciones Biotecnológicas “Dr. Rodolfo Ugalde”–IIBIO (UNSAM-CONICET), San Martin, Buenos Aires, Argentina
| | - Federico Rojas
- Biomedical and Life Sciences, Faculty of Health and Medicine, Lancaster University, Lancaster, United Kingdom
| | - Miguel Navarro
- Instituto de Parasitología y Biomedicina “López-Neyra”, CSIC (IPBLN-CSIC), Granada, Spain
| | - Vanina Eder Alvarez
- Instituto de Investigaciones Biotecnológicas “Dr. Rodolfo Ugalde”–IIBIO (UNSAM-CONICET), San Martin, Buenos Aires, Argentina
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3
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Đaković S, Zeelen JP, Gkeka A, Chandra M, van Straaten M, Foti K, Zhong J, Vlachou EP, Aresta-Branco F, Verdi JP, Papavasiliou FN, Stebbins CE. A structural classification of the variant surface glycoproteins of the African trypanosome. PLoS Negl Trop Dis 2023; 17:e0011621. [PMID: 37656766 PMCID: PMC10501684 DOI: 10.1371/journal.pntd.0011621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Revised: 09/14/2023] [Accepted: 08/23/2023] [Indexed: 09/03/2023] Open
Abstract
Long-term immune evasion by the African trypanosome is achieved through repetitive cycles of surface protein replacement with antigenically distinct versions of the dense Variant Surface Glycoprotein (VSG) coat. Thousands of VSG genes and pseudo-genes exist in the parasite genome that, together with genetic recombination mechanisms, allow for essentially unlimited immune escape from the adaptive immune system of the host. The diversity space of the "VSGnome" at the protein level was thought to be limited to a few related folds whose structures were determined more than 30 years ago. However, recent progress has shown that the VSGs possess significantly more architectural variation than had been appreciated. Here we combine experimental X-ray crystallography (presenting structures of N-terminal domains of coat proteins VSG11, VSG21, VSG545, VSG558, and VSG615) with deep-learning prediction using Alphafold to produce models of hundreds of VSG proteins. We classify the VSGnome into groups based on protein architecture and oligomerization state, contextualize recent bioinformatics clustering schemes, and extensively map VSG-diversity space. We demonstrate that in addition to the structural variability and post-translational modifications observed thus far, VSGs are also characterized by variations in oligomerization state and possess inherent flexibility and alternative conformations, lending additional variability to what is exposed to the immune system. Finally, these additional experimental structures and the hundreds of Alphafold predictions confirm that the molecular surfaces of the VSGs remain distinct from variant to variant, supporting the hypothesis that protein surface diversity is central to the process of antigenic variation used by this organism during infection.
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Affiliation(s)
- Sara Đaković
- Division of Structural Biology of Infection and Immunity, German Cancer Research Center, Heidelberg, Germany
| | - Johan P. Zeelen
- Division of Structural Biology of Infection and Immunity, German Cancer Research Center, Heidelberg, Germany
| | - Anastasia Gkeka
- Division of Immune Diversity, German Cancer Research Center, Heidelberg, Germany
| | - Monica Chandra
- Division of Structural Biology of Infection and Immunity, German Cancer Research Center, Heidelberg, Germany
- Division of Immune Diversity, German Cancer Research Center, Heidelberg, Germany
| | - Monique van Straaten
- Division of Structural Biology of Infection and Immunity, German Cancer Research Center, Heidelberg, Germany
| | - Konstantina Foti
- Division of Structural Biology of Infection and Immunity, German Cancer Research Center, Heidelberg, Germany
| | - Janet Zhong
- Division of Structural Biology of Infection and Immunity, German Cancer Research Center, Heidelberg, Germany
| | - Evi P. Vlachou
- Division of Immune Diversity, German Cancer Research Center, Heidelberg, Germany
| | - Francisco Aresta-Branco
- Division of Structural Biology of Infection and Immunity, German Cancer Research Center, Heidelberg, Germany
- Division of Immune Diversity, German Cancer Research Center, Heidelberg, Germany
| | - Joseph P. Verdi
- Division of Immune Diversity, German Cancer Research Center, Heidelberg, Germany
| | - F. Nina Papavasiliou
- Division of Immune Diversity, German Cancer Research Center, Heidelberg, Germany
| | - C. Erec Stebbins
- Division of Structural Biology of Infection and Immunity, German Cancer Research Center, Heidelberg, Germany
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4
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Sülzen H, Began J, Dhillon A, Kereïche S, Pompach P, Votrubova J, Zahedifard F, Šubrtova A, Šafner M, Hubalek M, Thompson M, Zoltner M, Zoll S. Cryo-EM structures of Trypanosoma brucei gambiense ISG65 with human complement C3 and C3b and their roles in alternative pathway restriction. Nat Commun 2023; 14:2403. [PMID: 37105991 PMCID: PMC10140031 DOI: 10.1038/s41467-023-37988-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Accepted: 04/06/2023] [Indexed: 04/29/2023] Open
Abstract
African Trypanosomes have developed elaborate mechanisms to escape the adaptive immune response, but little is known about complement evasion particularly at the early stage of infection. Here we show that ISG65 of the human-infective parasite Trypanosoma brucei gambiense is a receptor for human complement factor C3 and its activation fragments and that it takes over a role in selective inhibition of the alternative pathway C5 convertase and thus abrogation of the terminal pathway. No deposition of C4b, as part of the classical and lectin pathway convertases, was detected on trypanosomes. We present the cryo-electron microscopy (EM) structures of native C3 and C3b in complex with ISG65 which reveal a set of modes of complement interaction. Based on these findings, we propose a model for receptor-ligand interactions as they occur at the plasma membrane of blood-stage trypanosomes and may facilitate innate immune escape of the parasite.
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Affiliation(s)
- Hagen Sülzen
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo namesti 542/2, 16000, Prague, Czech Republic
- Faculty of Science, Charles University, Albertov 6, 12800, Prague 2, Czech Republic
| | - Jakub Began
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo namesti 542/2, 16000, Prague, Czech Republic
- Department of Immunobiology, University of Lausanne, Chemin des Boveresses 155, 1066, Epalinges, Switzerland
| | - Arun Dhillon
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo namesti 542/2, 16000, Prague, Czech Republic
| | - Sami Kereïche
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo namesti 542/2, 16000, Prague, Czech Republic
- First Faculty of Medicine, Charles University, Albertov 4, 12800, Prague, Czech Republic
| | - Petr Pompach
- Institute of Biotechnology of the Czech Academy of Sciences, 25250, Vestec, Czech Republic
| | - Jitka Votrubova
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo namesti 542/2, 16000, Prague, Czech Republic
| | - Farnaz Zahedifard
- Department of Parasitology, Faculty of Science, Charles University Prague, Biocev, 25250, Vestec, Czech Republic
| | - Adriana Šubrtova
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo namesti 542/2, 16000, Prague, Czech Republic
| | - Marie Šafner
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo namesti 542/2, 16000, Prague, Czech Republic
| | - Martin Hubalek
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo namesti 542/2, 16000, Prague, Czech Republic
| | - Maaike Thompson
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo namesti 542/2, 16000, Prague, Czech Republic
- University of Antwerp, Antwerp, Belgium
- Agidens, Industrial Machinery Manufacturing, Zwijndrecht, Antwerp, Belgium
| | - Martin Zoltner
- Department of Parasitology, Faculty of Science, Charles University Prague, Biocev, 25250, Vestec, Czech Republic
| | - Sebastian Zoll
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo namesti 542/2, 16000, Prague, Czech Republic.
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5
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Gkeka A, Aresta-Branco F, Triller G, Vlachou EP, van Straaten M, Lilic M, Olinares PDB, Perez K, Chait BT, Blatnik R, Ruppert T, Verdi JP, Stebbins CE, Papavasiliou FN. Immunodominant surface epitopes power immune evasion in the African trypanosome. Cell Rep 2023; 42:112262. [PMID: 36943866 DOI: 10.1016/j.celrep.2023.112262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Revised: 12/02/2022] [Accepted: 02/28/2023] [Indexed: 03/23/2023] Open
Abstract
The African trypanosome survives the immune response of its mammalian host by antigenic variation of its major surface antigen (the variant surface glycoprotein or VSG). Here we describe the antibody repertoires elicited by different VSGs. We show that the repertoires are highly restricted and are directed predominantly to distinct epitopes on the surface of the VSGs. They are also highly discriminatory; minor alterations within these exposed epitopes confer antigenically distinct properties to these VSGs and elicit different repertoires. We propose that the patterned and repetitive nature of the VSG coat focuses host immunity to a restricted set of immunodominant epitopes per VSG, eliciting a highly stereotyped response, minimizing cross-reactivity between different VSGs and facilitating prolonged immune evasion through epitope variation.
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Affiliation(s)
- Anastasia Gkeka
- Division of Immune Diversity, German Cancer Research Center, 69120 Heidelberg, Germany; Faculty of Biosciences, University of Heidelberg, 69120 Heidelberg, Germany; Panosome GmbH, 69123 Heidelberg, Germany
| | - Francisco Aresta-Branco
- Division of Immune Diversity, German Cancer Research Center, 69120 Heidelberg, Germany; Division of Structural Biology of Infection and Immunity, German Cancer Research Center, 69120 Heidelberg, Germany
| | - Gianna Triller
- Division of Immune Diversity, German Cancer Research Center, 69120 Heidelberg, Germany
| | - Evi P Vlachou
- Division of Immune Diversity, German Cancer Research Center, 69120 Heidelberg, Germany
| | - Monique van Straaten
- Division of Structural Biology of Infection and Immunity, German Cancer Research Center, 69120 Heidelberg, Germany
| | - Mirjana Lilic
- Laboratory of Structural Microbiology, the Rockefeller University, New York, NY 10065, USA
| | - Paul Dominic B Olinares
- Laboratory of Mass Spectrometry and Gaseous Ion Chemistry, the Rockefeller University, New York, NY 10065, USA
| | - Kathryn Perez
- Protein Expression and Purification Core Facility, EMBL Heidelberg, 69117 Heidelberg, Germany
| | - Brian T Chait
- Laboratory of Mass Spectrometry and Gaseous Ion Chemistry, the Rockefeller University, New York, NY 10065, USA
| | - Renata Blatnik
- Center for Molecular Biology of Heidelberg University, DKFZ-ZMBH Alliance, 69120 Heidelberg, Germany
| | - Thomas Ruppert
- Center for Molecular Biology of Heidelberg University, DKFZ-ZMBH Alliance, 69120 Heidelberg, Germany
| | - Joseph P Verdi
- Division of Immune Diversity, German Cancer Research Center, 69120 Heidelberg, Germany; Panosome GmbH, 69123 Heidelberg, Germany
| | - C Erec Stebbins
- Division of Structural Biology of Infection and Immunity, German Cancer Research Center, 69120 Heidelberg, Germany.
| | - F Nina Papavasiliou
- Division of Immune Diversity, German Cancer Research Center, 69120 Heidelberg, Germany.
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6
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Chandra M, Đaković S, Foti K, Zeelen JP, van Straaten M, Aresta-Branco F, Tihon E, Lübbehusen N, Ruppert T, Glover L, Papavasiliou FN, Stebbins CE. Structural similarities between the metacyclic and bloodstream form variant surface glycoproteins of the African trypanosome. PLoS Negl Trop Dis 2023; 17:e0011093. [PMID: 36780870 PMCID: PMC9956791 DOI: 10.1371/journal.pntd.0011093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 02/24/2023] [Accepted: 01/12/2023] [Indexed: 02/15/2023] Open
Abstract
During infection of mammalian hosts, African trypanosomes thwart immunity using antigenic variation of the dense Variant Surface Glycoprotein (VSG) coat, accessing a large repertoire of several thousand genes and pseudogenes, and switching to antigenically distinct copies. The parasite is transferred to mammalian hosts by the tsetse fly. In the salivary glands of the fly, the pathogen adopts the metacyclic form and expresses a limited repertoire of VSG genes specific to that developmental stage. It has remained unknown whether the metacyclic VSGs possess distinct properties associated with this particular and discrete phase of the parasite life cycle. We present here three novel metacyclic form VSG N-terminal domain crystal structures (mVSG397, mVSG531, and mVSG1954) and show that they mirror closely in architecture, oligomerization, and surface diversity the known classes of bloodstream form VSGs. These data suggest that the mVSGs are unlikely to be a specialized subclass of VSG proteins, and thus could be poor candidates as the major components of prophylactic vaccines against trypanosomiasis.
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Affiliation(s)
- Monica Chandra
- Division of Structural Biology of Infection and Immunity, German Cancer Research Center, Heidelberg, Germany
- Division of Immune Diversity, German Cancer Research Center, Heidelberg, Germany
| | - Sara Đaković
- Division of Structural Biology of Infection and Immunity, German Cancer Research Center, Heidelberg, Germany
| | - Konstantina Foti
- Division of Structural Biology of Infection and Immunity, German Cancer Research Center, Heidelberg, Germany
| | - Johan P. Zeelen
- Division of Structural Biology of Infection and Immunity, German Cancer Research Center, Heidelberg, Germany
| | - Monique van Straaten
- Division of Structural Biology of Infection and Immunity, German Cancer Research Center, Heidelberg, Germany
| | - Francisco Aresta-Branco
- Division of Structural Biology of Infection and Immunity, German Cancer Research Center, Heidelberg, Germany
- Division of Immune Diversity, German Cancer Research Center, Heidelberg, Germany
| | - Eliane Tihon
- Institut Pasteur, Université Paris Cité, Trypanosome Molecular Biology, Department of Parasites and Insect Vectors, Paris, France
| | - Nicole Lübbehusen
- Centre for Molecular Biology at the University of Heidelberg (ZMBH), DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Thomas Ruppert
- Centre for Molecular Biology at the University of Heidelberg (ZMBH), DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Lucy Glover
- Institut Pasteur, Université Paris Cité, Trypanosome Molecular Biology, Department of Parasites and Insect Vectors, Paris, France
| | - F. Nina Papavasiliou
- Division of Immune Diversity, German Cancer Research Center, Heidelberg, Germany
| | - C. Erec Stebbins
- Division of Structural Biology of Infection and Immunity, German Cancer Research Center, Heidelberg, Germany
- * E-mail:
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7
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Hempelmann A, Hartleb L, van Straaten M, Hashemi H, Zeelen JP, Bongers K, Papavasiliou FN, Engstler M, Stebbins CE, Jones NG. Nanobody-mediated macromolecular crowding induces membrane fission and remodeling in the African trypanosome. Cell Rep 2021; 37:109923. [PMID: 34731611 DOI: 10.1016/j.celrep.2021.109923] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 08/06/2021] [Accepted: 10/11/2021] [Indexed: 10/19/2022] Open
Abstract
The dense variant surface glycoprotein (VSG) coat of African trypanosomes represents the primary host-pathogen interface. Antigenic variation prevents clearing of the pathogen by employing a large repertoire of antigenically distinct VSG genes, thus neutralizing the host's antibody response. To explore the epitope space of VSGs, we generate anti-VSG nanobodies and combine high-resolution structural analysis of VSG-nanobody complexes with binding assays on living cells, revealing that these camelid antibodies bind deeply inside the coat. One nanobody causes rapid loss of cellular motility, possibly due to blockage of VSG mobility on the coat, whose rapid endocytosis and exocytosis are mechanistically linked to Trypanosoma brucei propulsion and whose density is required for survival. Electron microscopy studies demonstrate that this loss of motility is accompanied by rapid formation and shedding of nanovesicles and nanotubes, suggesting that increased protein crowding on the dense membrane can be a driving force for membrane fission in living cells.
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Affiliation(s)
- Alexander Hempelmann
- Division of Structural Biology of Infection and Immunity, German Cancer Research Center, Heidelberg 69120, Germany
| | - Laura Hartleb
- Department of Cell and Developmental Biology, Theodor-Boveri-Institute, Biocenter, Julius-Maximilians-Universität of Würzburg, Würzburg 97074, Germany
| | - Monique van Straaten
- Division of Structural Biology of Infection and Immunity, German Cancer Research Center, Heidelberg 69120, Germany
| | - Hamidreza Hashemi
- Division of Immune Diversity, German Cancer Research Center, Heidelberg 69120, Germany
| | - Johan P Zeelen
- Division of Structural Biology of Infection and Immunity, German Cancer Research Center, Heidelberg 69120, Germany
| | - Kevin Bongers
- Department of Cell and Developmental Biology, Theodor-Boveri-Institute, Biocenter, Julius-Maximilians-Universität of Würzburg, Würzburg 97074, Germany
| | - F Nina Papavasiliou
- Division of Immune Diversity, German Cancer Research Center, Heidelberg 69120, Germany
| | - Markus Engstler
- Department of Cell and Developmental Biology, Theodor-Boveri-Institute, Biocenter, Julius-Maximilians-Universität of Würzburg, Würzburg 97074, Germany
| | - C Erec Stebbins
- Division of Structural Biology of Infection and Immunity, German Cancer Research Center, Heidelberg 69120, Germany.
| | - Nicola G Jones
- Department of Cell and Developmental Biology, Theodor-Boveri-Institute, Biocenter, Julius-Maximilians-Universität of Würzburg, Würzburg 97074, Germany.
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8
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Garrison P, Umaer K, Bangs JD. The role of glycosylphosphatidylinositol phospholipase C in membrane trafficking in Trypanosoma brucei. Mol Biochem Parasitol 2021; 245:111409. [PMID: 34363902 DOI: 10.1016/j.molbiopara.2021.111409] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 07/29/2021] [Accepted: 08/03/2021] [Indexed: 11/25/2022]
Abstract
Glycosylphosphatidylinositol-phospholipase C (GPI-PLC) is an enzyme that has been implicated in GPI-dependent protein trafficking and phosphoinositide metabolism in the bloodstream stage of African trypanosomes. However, despite the fact that it is associated with the cytoplasmic face of internal organellar compartments, its role in general membrane trafficking has not been investigated. Using a GPI-PLC null cell line, we determine the effect of GPI-PLC deficiency on these processes. Biosynthetic trafficking of lysosomal cargo, soluble cathepsin L and membrane bound p67, are unaffected. Likewise, secretory transport, recycling and ultimate lysosomal turnover of the GPI-anchored and transmembrane glycoproteins, transferrin receptor and invariant surface glycoprotein 65, respectively, were unaffected. A significant decrease in the endocytic uptake of transferrin was observed, confirming a prior report, but ultimate delivery to the lysosome was unimpacted. These results contribute to our understanding of the roles of this enigmatic enzyme in trypanosome cell biology.
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Affiliation(s)
- Paige Garrison
- Department of Microbiology and Immunology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo (SUNY), Buffalo, NY, 14214, USA
| | - Khan Umaer
- Department of Microbiology and Immunology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo (SUNY), Buffalo, NY, 14214, USA
| | - James D Bangs
- Department of Microbiology and Immunology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo (SUNY), Buffalo, NY, 14214, USA.
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9
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Abstract
African trypanosomes utilize glycosylphosphatidylinositol (GPI)-anchored variant surface glycoprotein (VSG) to evade the host immune system. VSG turnover is thought to be mediated via cleavage of the GPI anchor by endogenous GPI-specific phospholipase C (GPI-PLC). However, GPI-PLC is topologically sequestered from VSG substrates in intact cells. Recently, A. J. Szempruch, S. E. Sykes, R. Kieft, L. Dennison, et al. (Cell 164:246–257, 2016, https://doi.org/10.1016/j.cell.2015.11.051) demonstrated the release of nanotubes that septate to form free VSG+ extracellular vesicles (EVs). Here, we evaluated the relative contributions of GPI hydrolysis and EV formation to VSG turnover in wild-type (WT) and GPI-PLC null cells. The turnover rate of VSG was consistent with prior measurements (half-life [t1/2] of ∼26 h) but dropped significantly in the absence of GPI-PLC (t1/2 of ∼36 h). Ectopic complementation restored normal turnover rates, confirming the role of GPI-PLC in turnover. However, physical characterization of shed VSG in WT cells indicated that at least 50% is released directly from cell membranes with intact GPI anchors. Shedding of EVs plays an insignificant role in total VSG turnover in both WT and null cells. In additional studies, GPI-PLC was found to have no role in biosynthetic and endocytic trafficking to the lysosome but did influence the rate of receptor-mediated endocytosis. These results indicate that VSG turnover is a bimodal process involving both direct shedding and GPI hydrolysis.
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10
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Umaer K, Aresta-Branco F, Chandra M, van Straaten M, Zeelen J, Lapouge K, Waxman B, Stebbins CE, Bangs JD. Dynamic, variable oligomerization and the trafficking of variant surface glycoproteins of Trypanosoma brucei. Traffic 2021; 22:274-283. [PMID: 34101314 DOI: 10.1111/tra.12806] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Revised: 05/14/2021] [Accepted: 06/04/2021] [Indexed: 12/20/2022]
Abstract
African trypanosomes cause disease in humans and livestock, avoiding host immunity by changing the expression of variant surface glycoproteins (VSGs); the major glycosylphosphatidylinositol (GPI) anchored antigens coating the surface of the bloodstream stage. Proper trafficking of VSGs is therefore critical to pathogen survival. The valence model argues that GPI anchors regulate progression and fate in the secretory pathway and that, specifically, a valence of two (VSGs are dimers) is critical for stable cell surface association. However, recent reports that the MITat1.3 (M1.3) VSG N-terminal domain (NTD) behaves as a monomer in solution and in a crystal structure challenge this model. We now show that the behavior of intact M1.3 VSG in standard in vivo trafficking assays is consistent with an oligomer. Nevertheless, Blue Native Gel electrophoresis and size exclusion chromatography-multiangle light scattering chromatography of purified full length M1.3 VSG indicates a monomer in vitro. However, studies with additional VSGs show that multiple oligomeric states are possible, and that for some VSGs oligomerization is concentration dependent. These data argue that individual VSG monomers possess different propensities to self-oligomerize, but that when constrained at high density to the cell surface, oligomeric species predominate. These results resolve the apparent conflict between the valence hypothesis and the M1.3 NTD VSG crystal structure.
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Affiliation(s)
- Khan Umaer
- Department of Microbiology and Immunology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo (SUNY), Buffalo, New York, USA.,Eurofins, Spring House, Pennsylvania, USA
| | - Francisco Aresta-Branco
- Division of Structural Biology of Infection and Immunity, German Cancer Research Center, Heidelberg, Germany.,Division of Immune Diversity, German Cancer Research Center, Heidelberg, Germany
| | - Monica Chandra
- Division of Structural Biology of Infection and Immunity, German Cancer Research Center, Heidelberg, Germany.,Faculty of Biosciences, University of Heidelberg, Heidelberg, Germany
| | - Monique van Straaten
- Division of Structural Biology of Infection and Immunity, German Cancer Research Center, Heidelberg, Germany
| | - Johan Zeelen
- Division of Structural Biology of Infection and Immunity, German Cancer Research Center, Heidelberg, Germany
| | - Karine Lapouge
- Protein Expression and Purification Core Facility, EMBL Heidelberg, Heidelberg, Germany
| | - Brandon Waxman
- Department of Microbiology and Immunology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo (SUNY), Buffalo, New York, USA
| | - C Erec Stebbins
- Division of Structural Biology of Infection and Immunity, German Cancer Research Center, Heidelberg, Germany
| | - James D Bangs
- Department of Microbiology and Immunology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo (SUNY), Buffalo, New York, USA
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11
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Structure of trypanosome coat protein VSGsur and function in suramin resistance. Nat Microbiol 2021; 6:392-400. [PMID: 33462435 PMCID: PMC7116837 DOI: 10.1038/s41564-020-00844-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Accepted: 11/30/2020] [Indexed: 01/28/2023]
Abstract
Suramin has been a primary early-stage treatment for African trypanosomiasis for nearly 100 yr. Recent studies revealed that trypanosome strains that express the variant surface glycoprotein (VSG) VSGsur possess heightened resistance to suramin. Here, we show that VSGsur binds tightly to suramin but other VSGs do not. By solving high-resolution crystal structures of VSGsur and VSG13, we also demonstrate that these VSGs define a structurally divergent subgroup of the coat proteins. The co-crystal structure of VSGsur with suramin reveals that the chemically symmetric drug binds within a large cavity in the VSG homodimer asymmetrically, primarily through contacts of its central benzene rings. Structure-based, loss-of-contact mutations in VSGsur significantly decrease the affinity to suramin and lead to a loss of the resistance phenotype. Altogether, these data show that the resistance phenotype is dependent on the binding of suramin to VSGsur, establishing that the VSG proteins can possess functionality beyond their role in antigenic variation.
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12
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Pinger J, Nešić D, Ali L, Aresta-Branco F, Lilic M, Chowdhury S, Kim HS, Verdi J, Raper J, Ferguson MAJ, Papavasiliou FN, Stebbins CE. African trypanosomes evade immune clearance by O-glycosylation of the VSG surface coat. Nat Microbiol 2018; 3:932-938. [PMID: 29988048 PMCID: PMC6108419 DOI: 10.1038/s41564-018-0187-6] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 06/04/2018] [Indexed: 11/09/2022]
Abstract
The African trypanosome Trypanosoma brucei spp. is a paradigm for antigenic variation, the orchestrated alteration of cell surface molecules to evade host immunity. The parasite elicits robust antibody-mediated immune responses to its variant surface glycoprotein (VSG) coat, but evades immune clearance by repeatedly accessing a large genetic VSG repertoire and 'switching' to antigenically distinct VSGs. This persistent immune evasion has been ascribed exclusively to amino-acid variance on the VSG surface presented by a conserved underlying protein architecture. We establish here that this model does not account for the scope of VSG structural and biochemical diversity. The 1.4-Å-resolution crystal structure of the variant VSG3 manifests divergence in the tertiary fold and oligomeric state. The structure also reveals an O-linked carbohydrate on the top surface of VSG3. Mass spectrometric analysis indicates that this O-glycosylation site is heterogeneously occupied in VSG3 by zero to three hexose residues and is also present in other VSGs. We demonstrate that this O-glycosylation increases parasite virulence by impairing the generation of protective immunity. These data alter the paradigm of antigenic variation by the African trypanosome, expanding VSG variability beyond amino-acid sequence to include surface post-translational modifications with immunomodulatory impact.
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Affiliation(s)
- Jason Pinger
- The Rockefeller University, Laboratory of Lymphocyte Biology, New York, NY, USA
| | - Dragana Nešić
- The Rockefeller University, Laboratory of Structural Microbiology, New York, NY, USA.,The Rockefeller University, Allen and Frances Adler Laboratory of Blood and Vascular Biology, New York, NY, USA
| | - Liaqat Ali
- Wellcome Centre for Anti-Infectives Research, School of Life Sciences, University of Dundee, Dundee, UK
| | - Francisco Aresta-Branco
- Division of Immune Diversity, German Cancer Research Center, Heidelberg, Germany.,Division of Structural Biology of Infection and Immunity, German Cancer Research Center, Heidelberg, Germany
| | - Mirjana Lilic
- The Rockefeller University, Laboratory of Structural Microbiology, New York, NY, USA.,The Rockefeller University, Laboratory of Molecular Biophysics, New York, NY, USA
| | - Shanin Chowdhury
- The Rockefeller University, Laboratory of Lymphocyte Biology, New York, NY, USA
| | - Hee-Sook Kim
- The Rockefeller University, Laboratory of Lymphocyte Biology, New York, NY, USA
| | - Joseph Verdi
- Department of Biological Sciences, Hunter College, City University of New York, New York, NY, USA
| | - Jayne Raper
- Department of Biological Sciences, Hunter College, City University of New York, New York, NY, USA
| | - Michael A J Ferguson
- Wellcome Centre for Anti-Infectives Research, School of Life Sciences, University of Dundee, Dundee, UK.
| | - F Nina Papavasiliou
- Division of Immune Diversity, German Cancer Research Center, Heidelberg, Germany.
| | - C Erec Stebbins
- Division of Structural Biology of Infection and Immunity, German Cancer Research Center, Heidelberg, Germany.
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13
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Martínez-García M, Bart JM, Campos-Salinas J, Valdivia E, Martínez-Bueno M, González-Rey E, Navarro M, Maqueda M, Cebrián R, Pérez-Victoria JM. Autophagic-related cell death of Trypanosoma brucei induced by bacteriocin AS-48. INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE 2018; 8:203-212. [PMID: 29649664 PMCID: PMC6039360 DOI: 10.1016/j.ijpddr.2018.03.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Revised: 03/02/2018] [Accepted: 03/08/2018] [Indexed: 11/24/2022]
Abstract
The parasitic protozoan Trypanosoma brucei is the causative agent of human African trypanosomiasis (sleeping sickness) and nagana. Current drug therapies have limited efficacy, high toxicity and/or are continually hampered by the appearance of resistance. Antimicrobial peptides have recently attracted attention as potential parasiticidal compounds. Here, we explore circular bacteriocin AS-48's ability to kill clinically relevant bloodstream forms of T. brucei gambiense, T. brucei rhodesiense and T. brucei brucei. AS-48 exhibited excellent anti-trypanosomal activity in vitro (EC50 = 1–3 nM) against the three T. brucei subspecies, but it was innocuous to human cells at 104-fold higher concentrations. In contrast to its antibacterial action, AS-48 does not kill the parasite through plasma membrane permeabilization but by targeting intracellular compartments. This was evidenced by the fact that vital dye internalization-prohibiting concentrations of AS-48 could kill the parasite at 37 °C but not at 4 °C. Furthermore, AS-48 interacted with the surface of the parasite, at least in part via VSG, its uptake was temperature-dependent and clathrin-depleted cells were less permissive to the action of AS-48. The bacteriocin also caused the appearance of myelin-like structures and double-membrane autophagic vacuoles. These changes in the parasite's ultrastructure were confirmed by fluorescence microscopy as AS-48 induced the production of EGFP-ATG8.2-labeled autophagosomes. Collectively, these results indicate AS-48 kills the parasite through a mechanism involving clathrin-mediated endocytosis of VSG-bound AS-48 and the induction of autophagic-like cell death. As AS-48 has greater in vitro activity than the drugs currently used to treat T. brucei infection and does not present any signs of toxicity in mammalian cells, it could be an attractive lead compound for the treatment of sleeping sickness and nagana. AS-48 kills Trypanosoma brucei efficiently and is innocuous in mammalian cells. It has greater in vitro activity than drugs currently in use. AS-48 must be internalized by the parasite in order to exert its trypanocidal effect. AS-48 uptake involves VSG binding and clathrin-mediated endocytosis. AS-48 induces an autophagic-related cell death.
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Affiliation(s)
- Marta Martínez-García
- Instituto de Parasitología y Biomedicina "López-Neyra", CSIC (IPBLN-CSIC), PTS Granada, Granada, Spain
| | - Jean-Mathieu Bart
- Centro Nacional de Medicina Tropical, Instituto de Salud Carlos III, Madrid, Spain; UMR INTERTRYP, Institut de Recherche pour le Développement, Montpellier, France
| | - Jenny Campos-Salinas
- Instituto de Parasitología y Biomedicina "López-Neyra", CSIC (IPBLN-CSIC), PTS Granada, Granada, Spain
| | - Eva Valdivia
- Departamento de Microbiología, Facultad de Ciencias, Universidad de Granada, Spain
| | | | - Elena González-Rey
- Instituto de Parasitología y Biomedicina "López-Neyra", CSIC (IPBLN-CSIC), PTS Granada, Granada, Spain
| | - Miguel Navarro
- Instituto de Parasitología y Biomedicina "López-Neyra", CSIC (IPBLN-CSIC), PTS Granada, Granada, Spain
| | - Mercedes Maqueda
- Departamento de Microbiología, Facultad de Ciencias, Universidad de Granada, Spain
| | - Rubén Cebrián
- Departamento de Microbiología, Facultad de Ciencias, Universidad de Granada, Spain.
| | - José M Pérez-Victoria
- Instituto de Parasitología y Biomedicina "López-Neyra", CSIC (IPBLN-CSIC), PTS Granada, Granada, Spain.
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14
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Structural basis for the shielding function of the dynamic trypanosome variant surface glycoprotein coat. Nat Microbiol 2017; 2:1523-1532. [PMID: 28894098 DOI: 10.1038/s41564-017-0013-6] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Accepted: 07/26/2017] [Indexed: 01/30/2023]
Abstract
The most prominent defence of the unicellular parasite Trypanosoma brucei against the host immune system is a dense coat that comprises a variant surface glycoprotein (VSG). Despite the importance of the VSG family, no complete structure of a VSG has been reported. Making use of high-resolution structures of individual VSG domains, we employed small-angle X-ray scattering to elucidate the first two complete VSG structures. The resulting models imply that the linker regions confer great flexibility between domains, which suggests that VSGs can adopt two main conformations to respond to obstacles and changes of protein density, while maintaining a protective barrier at all times. Single-molecule diffusion measurements of VSG in supported lipid bilayers substantiate this possibility, as two freely diffusing populations could be detected. This translates into a highly flexible overall topology of the surface VSG coat, which displays both lateral movement in the plane of the membrane and variation in the overall thickness of the coat.
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15
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Castillo-Acosta VM, Ruiz-Pérez LM, Etxebarria J, Reichardt NC, Navarro M, Igarashi Y, Liekens S, Balzarini J, González-Pacanowska D. Carbohydrate-Binding Non-Peptidic Pradimicins for the Treatment of Acute Sleeping Sickness in Murine Models. PLoS Pathog 2016; 12:e1005851. [PMID: 27662652 PMCID: PMC5035034 DOI: 10.1371/journal.ppat.1005851] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Accepted: 08/08/2016] [Indexed: 12/21/2022] Open
Abstract
Current treatments available for African sleeping sickness or human African trypanosomiasis (HAT) are limited, with poor efficacy and unacceptable safety profiles. Here, we report a new approach to address treatment of this disease based on the use of compounds that bind to parasite surface glycans leading to rapid killing of trypanosomes. Pradimicin and its derivatives are non-peptidic carbohydrate-binding agents that adhere to the carbohydrate moiety of the parasite surface glycoproteins inducing parasite lysis in vitro. Notably, pradimicin S has good pharmaceutical properties and enables cure of an acute form of the disease in mice. By inducing resistance in vitro we have established that the composition of the sugars attached to the variant surface glycoproteins are critical to the mode of action of pradimicins and play an important role in infectivity. The compounds identified represent a novel approach to develop drugs to treat HAT.
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Affiliation(s)
- Víctor M. Castillo-Acosta
- Instituto de Parasitología y Biomedicina “López-Neyra”, Consejo Superior de Investigaciones Científicas, Parque Tecnológico de Ciencias de la Salud, Armilla (Granada), Spain
| | - Luis M. Ruiz-Pérez
- Instituto de Parasitología y Biomedicina “López-Neyra”, Consejo Superior de Investigaciones Científicas, Parque Tecnológico de Ciencias de la Salud, Armilla (Granada), Spain
| | - Juan Etxebarria
- Glycotechnology Laboratory, CIC biomaGUNE, Parque Científico y Tecnológico de Gipuzkoa, San Sebastián, Spain
| | - Niels C. Reichardt
- Glycotechnology Laboratory, CIC biomaGUNE, Parque Científico y Tecnológico de Gipuzkoa, San Sebastián, Spain
- CIBER of Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), San Sebastián, Spain
| | - Miguel Navarro
- Instituto de Parasitología y Biomedicina “López-Neyra”, Consejo Superior de Investigaciones Científicas, Parque Tecnológico de Ciencias de la Salud, Armilla (Granada), Spain
| | - Yasuhiro Igarashi
- Biotechnology Research Center, Toyama Prefectural University, Imizu, Toyama, Japan
| | - Sandra Liekens
- KU Leuven, Rega Institute for Medical Research, Leuven, Belgium
| | - Jan Balzarini
- KU Leuven, Rega Institute for Medical Research, Leuven, Belgium
| | - Dolores González-Pacanowska
- Instituto de Parasitología y Biomedicina “López-Neyra”, Consejo Superior de Investigaciones Científicas, Parque Tecnológico de Ciencias de la Salud, Armilla (Granada), Spain
- * E-mail:
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16
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Aksoy E, Vigneron A, Bing X, Zhao X, O'Neill M, Wu YN, Bangs JD, Weiss BL, Aksoy S. Mammalian African trypanosome VSG coat enhances tsetse's vector competence. Proc Natl Acad Sci U S A 2016; 113:6961-6. [PMID: 27185908 PMCID: PMC4922192 DOI: 10.1073/pnas.1600304113] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Tsetse flies are biological vectors of African trypanosomes, the protozoan parasites responsible for causing human and animal trypanosomiases across sub-Saharan Africa. Currently, no vaccines are available for disease prevention due to antigenic variation of the Variant Surface Glycoproteins (VSG) that coat parasites while they reside within mammalian hosts. As a result, interference with parasite development in the tsetse vector is being explored to reduce disease transmission. A major bottleneck to infection occurs as parasites attempt to colonize tsetse's midgut. One critical factor influencing this bottleneck is the fly's peritrophic matrix (PM), a semipermeable, chitinous barrier that lines the midgut. The mechanisms that enable trypanosomes to cross this barrier are currently unknown. Here, we determined that as parasites enter the tsetse's gut, VSG molecules released from trypanosomes are internalized by cells of the cardia-the tissue responsible for producing the PM. VSG internalization results in decreased expression of a tsetse microRNA (mir-275) and interferes with the Wnt-signaling pathway and the Iroquois/IRX transcription factor family. This interference reduces the function of the PM barrier and promotes parasite colonization of the gut early in the infection process. Manipulation of the insect midgut homeostasis by the mammalian parasite coat proteins is a novel function and indicates that VSG serves a dual role in trypanosome biology-that of facilitating transmission through its mammalian host and insect vector. We detail critical steps in the course of trypanosome infection establishment that can serve as novel targets to reduce the tsetse's vector competence and disease transmission.
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Affiliation(s)
- Emre Aksoy
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, Yale University, New Haven, CT 06520
| | - Aurélien Vigneron
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, Yale University, New Haven, CT 06520
| | - XiaoLi Bing
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, Yale University, New Haven, CT 06520
| | - Xin Zhao
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, Yale University, New Haven, CT 06520
| | - Michelle O'Neill
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, Yale University, New Haven, CT 06520
| | - Yi-Neng Wu
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, Yale University, New Haven, CT 06520
| | - James D Bangs
- Department of Microbiology and Immunology, University at Buffalo (SUNY), Buffalo, NY 14214
| | - Brian L Weiss
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, Yale University, New Haven, CT 06520;
| | - Serap Aksoy
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, Yale University, New Haven, CT 06520;
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17
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Damerow M, Graalfs F, Güther MLS, Mehlert A, Izquierdo L, Ferguson MAJ. A Gene of the β3-Glycosyltransferase Family Encodes N-Acetylglucosaminyltransferase II Function in Trypanosoma brucei. J Biol Chem 2016; 291:13834-45. [PMID: 27189951 PMCID: PMC4919465 DOI: 10.1074/jbc.m116.733246] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Indexed: 11/06/2022] Open
Abstract
The bloodstream form of the human pathogen Trypanosoma brucei expresses oligomannose, paucimannose, and complex N-linked glycans, including some exceptionally large poly-N-acetyllactosamine-containing structures. Despite the presence of complex N-glycans in this organism, no homologues of the canonical N-acetylglucosaminyltransferase I or II genes can be found in the T. brucei genome. These genes encode the activities that initiate the elaboration of the Manα1-3 and Manα1-6 arms, respectively, of the conserved trimannosyl-N-acetylchitobiosyl core of N-linked glycans. Previously, we identified a highly divergent T. brucei N-acetylglucosaminyltransferase I (TbGnTI) among a set of putative T. brucei glycosyltransferase genes belonging to the β3-glycosyltransferase superfamily (Damerow, M., Rodrigues, J. A., Wu, D., Güther, M. L., Mehlert, A., and Ferguson, M. A. (2014) J. Biol. Chem. 289, 9328-9339). Here, we demonstrate that TbGT15, another member of the same β3-glycosyltransferase family, encodes an equally divergent N-acetylglucosaminyltransferase II (TbGnTII) activity. In contrast to multicellular organisms, where GnTII activity is essential, TbGnTII null mutants of T. brucei grow in culture and are still infectious to animals. Characterization of the large poly-N-acetyllactosamine containing N-glycans of the TbGnTII null mutants by methylation linkage analysis suggests that, in wild-type parasites, the Manα1-6 arm of the conserved trimannosyl core may carry predominantly linear poly-N-acetyllactosamine chains, whereas the Manα1-3 arm may carry predominantly branched poly-N-acetyllactosamine chains. These results provide further detail on the structure and biosynthesis of complex N-glycans in an important human pathogen and provide a second example of the adaptation by trypanosomes of β3-glycosyltransferase family members to catalyze β1-2 glycosidic linkages.
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Affiliation(s)
- Manuela Damerow
- From the Division of Biological Chemistry and Drug Discovery, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, United Kingdom
| | - Frauke Graalfs
- From the Division of Biological Chemistry and Drug Discovery, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, United Kingdom
| | - M Lucia S Güther
- From the Division of Biological Chemistry and Drug Discovery, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, United Kingdom
| | - Angela Mehlert
- From the Division of Biological Chemistry and Drug Discovery, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, United Kingdom
| | - Luis Izquierdo
- From the Division of Biological Chemistry and Drug Discovery, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, United Kingdom
| | - Michael A J Ferguson
- From the Division of Biological Chemistry and Drug Discovery, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, United Kingdom
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18
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Shimogawa MM, Saada EA, Vashisht AA, Barshop WD, Wohlschlegel JA, Hill KL. Cell Surface Proteomics Provides Insight into Stage-Specific Remodeling of the Host-Parasite Interface in Trypanosoma brucei. Mol Cell Proteomics 2015; 14:1977-88. [PMID: 25963835 DOI: 10.1074/mcp.m114.045146] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Indexed: 02/05/2023] Open
Abstract
African trypanosomes are devastating human and animal pathogens transmitted by tsetse flies between mammalian hosts. The trypanosome surface forms a critical host interface that is essential for sensing and adapting to diverse host environments. However, trypanosome surface protein composition and diversity remain largely unknown. Here, we use surface labeling, affinity purification, and proteomic analyses to describe cell surface proteomes from insect-stage and mammalian bloodstream-stage Trypanosoma brucei. The cell surface proteomes contain most previously characterized surface proteins. We additionally identify a substantial number of novel proteins, whose functions are unknown, indicating the parasite surface proteome is larger and more diverse than generally appreciated. We also show stage-specific expression for individual paralogs within several protein families, suggesting that fine-tuned remodeling of the parasite surface allows adaptation to diverse host environments, while still fulfilling universally essential cellular needs. Our surface proteome analyses complement existing transcriptomic, proteomic, and in silico analyses by highlighting proteins that are surface-exposed and thereby provide a major step forward in defining the host-parasite interface.
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Affiliation(s)
- Michelle M Shimogawa
- From the ‡Department of Microbiology, Immunology, and Molecular Genetics, University of California Los Angeles, Los Angeles, California, 90095
| | - Edwin A Saada
- From the ‡Department of Microbiology, Immunology, and Molecular Genetics, University of California Los Angeles, Los Angeles, California, 90095
| | - Ajay A Vashisht
- §Department of Biological Chemistry, University of California Los Angeles, Los Angeles, California 90095
| | - William D Barshop
- §Department of Biological Chemistry, University of California Los Angeles, Los Angeles, California 90095
| | - James A Wohlschlegel
- §Department of Biological Chemistry, University of California Los Angeles, Los Angeles, California 90095; ¶Molecular Biology Institute, University of California Los Angeles, Los Angeles, California 90095
| | - Kent L Hill
- From the ‡Department of Microbiology, Immunology, and Molecular Genetics, University of California Los Angeles, Los Angeles, California, 90095; ¶Molecular Biology Institute, University of California Los Angeles, Los Angeles, California 90095
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19
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Castillo-Acosta VM, Ruiz-Pérez LM, Van Damme EJM, Balzarini J, González-Pacanowska D. Exposure of Trypanosoma brucei to an N-acetylglucosamine-binding lectin induces VSG switching and glycosylation defects resulting in reduced infectivity. PLoS Negl Trop Dis 2015; 9:e0003612. [PMID: 25746926 PMCID: PMC4351956 DOI: 10.1371/journal.pntd.0003612] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Accepted: 02/10/2015] [Indexed: 12/22/2022] Open
Abstract
Trypanosoma brucei variant surface glycoproteins (VSG) are glycosylated by both paucimannose and oligomannose structures which are involved in the formation of a protective barrier against the immune system. Here, we report that the stinging nettle lectin (UDA), with predominant N-acetylglucosamine-binding specificity, interacts with glycosylated VSGs and kills parasites by provoking defects in endocytosis together with impaired cytokinesis. Prolonged exposure to UDA induced parasite resistance based on a diminished capacity to bind the lectin due to an enrichment of biantennary paucimannose and a reduction of triantennary oligomannose structures. Two molecular mechanisms involved in resistance were identified: VSG switching and modifications in N-glycan composition. Glycosylation defects were correlated with the down-regulation of the TbSTT3A and/or TbSTT3B genes (coding for oligosaccharyltransferases A and B, respectively) responsible for glycan specificity. Furthermore, UDA-resistant trypanosomes exhibited severely impaired infectivity indicating that the resistant phenotype entails a substantial fitness cost. The results obtained further support the modification of surface glycan composition resulting from down-regulation of the genes coding for oligosaccharyltransferases as a general resistance mechanism in response to prolonged exposure to carbohydrate-binding agents.
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Affiliation(s)
- Víctor M. Castillo-Acosta
- Instituto de Parasitología y Biomedicina “López-Neyra”, Consejo Superior de Investigaciones Científicas, Parque Tecnológico de Ciencias de la Salud, Granada, Spain
| | - Luis M. Ruiz-Pérez
- Instituto de Parasitología y Biomedicina “López-Neyra”, Consejo Superior de Investigaciones Científicas, Parque Tecnológico de Ciencias de la Salud, Granada, Spain
| | - Els J. M. Van Damme
- Laboratory of Biochemistry and Glycobiology, Department of Molecular Biotechnology, Ghent University, Ghent, Belgium
| | - Jan Balzarini
- Rega Institute for Medical Research, KU Leuven, Leuven, Belgium
| | - Dolores González-Pacanowska
- Instituto de Parasitología y Biomedicina “López-Neyra”, Consejo Superior de Investigaciones Científicas, Parque Tecnológico de Ciencias de la Salud, Granada, Spain
- * E-mail:
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20
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Sullivan L, Fleming J, Sastry L, Mehlert A, Wall SJ, Ferguson MAJ. Identification of sVSG117 as an immunodiagnostic antigen and evaluation of a dual-antigen lateral flow test for the diagnosis of human African trypanosomiasis. PLoS Negl Trop Dis 2014; 8:e2976. [PMID: 25033401 PMCID: PMC4102454 DOI: 10.1371/journal.pntd.0002976] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2014] [Accepted: 05/12/2014] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND The diagnosis of human African trypanosomiasis (HAT) caused by Trypanosoma brucei gambiense relies mainly on the Card Agglutination Test for Trypanosomiasis (CATT). There is no immunodiagnostic for HAT caused by T. b. rhodesiense. Our principle aim was to develop a prototype lateral flow test that might be an improvement on CATT. METHODOLOGY/PRINCIPLE FINDINGS Pools of infection and control sera were screened against four different soluble form variant surface glycoproteins (sVSGs) by ELISA and one, sVSG117, showed particularly strong immunoreactivity to pooled infection sera. Using individual sera, sVSG117 was shown to be able to discriminate between T. b. gambiense infection and control sera by both ELISA and lateral flow test. The sVSG117 antigen was subsequently used with a previously described recombinant diagnostic antigen, rISG65, to create a dual-antigen lateral flow test prototype. The latter was used blind in a virtual field trial of 431 randomized infection and control sera from the WHO HAT Specimen Biobank. CONCLUSION/SIGNIFICANCE In the virtual field trial, using two positive antigen bands as the criterion for infection, the sVSG117 and rISG65 dual-antigen lateral flow test prototype showed a sensitivity of 97.3% (95% CI: 93.3 to 99.2) and a specificity of 83.3% (95% CI: 76.4 to 88.9) for the detection of T. b. gambiense infections. The device was not as good for detecting T. b. rhodesiense infections using two positive antigen bands as the criterion for infection, with a sensitivity of 58.9% (95% CI: 44.9 to 71.9) and specificity of 97.3% (95% CI: 90.7 to 99.7). However, using one or both positive antigen band(s) as the criterion for T. b. rhodesiense infection improved the sensitivity to 83.9% (95% CI: 71.7 to 92.4) with a specificity of 85.3% (95% CI: 75.3 to 92.4). These results encourage further development of the dual-antigen device for clinical use.
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Affiliation(s)
- Lauren Sullivan
- Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Jennifer Fleming
- Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Lalitha Sastry
- Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Angela Mehlert
- Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Dundee, United Kingdom
| | | | - Michael A. J. Ferguson
- Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Dundee, United Kingdom
- * E-mail:
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21
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Damerow M, Rodrigues JA, Wu D, Güther MLS, Mehlert A, Ferguson MAJ. Identification and functional characterization of a highly divergent N-acetylglucosaminyltransferase I (TbGnTI) in Trypanosoma brucei. J Biol Chem 2014; 289:9328-39. [PMID: 24550396 PMCID: PMC3979372 DOI: 10.1074/jbc.m114.555029] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Trypanosoma brucei expresses a diverse repertoire of N-glycans, ranging from oligomannose and paucimannose structures to exceptionally large complex N-glycans. Despite the presence of the latter, no obvious homologues of known β1–4-galactosyltransferase or β1–2- or β1–6-N-acetylglucosaminyltransferase genes have been found in the parasite genome. However, we previously reported a family of putative UDP-sugar-dependent glycosyltransferases with similarity to the mammalian β1–3-glycosyltransferase family. Here we characterize one of these genes, TbGT11, and show that it encodes a Golgi apparatus resident UDP-GlcNAc:α3-d-mannoside β1–2-N-acetylglucosaminyltransferase I activity (TbGnTI). The bloodstream-form TbGT11 null mutant exhibited significantly modified protein N-glycans but normal growth in vitro and infectivity to rodents. In contrast to multicellular organisms, where the GnTI reaction is essential for biosynthesis of both complex and hybrid N-glycans, T. brucei TbGT11 null mutants expressed atypical “pseudohybrid” glycans, indicating that TbGnTII activity is not dependent on prior TbGnTI action. Using a functional in vitro assay, we showed that TbGnTI transfers UDP-GlcNAc to biantennary Man3GlcNAc2, but not to triantennary Man5GlcNAc2, which is the preferred substrate for metazoan GnTIs. Sequence alignment reveals that the T. brucei enzyme is far removed from the metazoan GnTI family and suggests that the parasite has adapted the β3-glycosyltransferase family to catalyze β1–2 linkages.
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Affiliation(s)
- Manuela Damerow
- From the Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Dundee DD1 5EH, United Kingdom and
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22
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Cordon-Obras C, Cano J, González-Pacanowska D, Benito A, Navarro M, Bart JM. Trypanosoma brucei gambiense adaptation to different mammalian sera is associated with VSG expression site plasticity. PLoS One 2013; 8:e85072. [PMID: 24376866 PMCID: PMC3871602 DOI: 10.1371/journal.pone.0085072] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Accepted: 11/21/2013] [Indexed: 11/18/2022] Open
Abstract
Trypanosoma brucei gambiense infection is widely considered an anthroponosis, although it has also been found in wild and domestic animals. Thus, fauna could act as reservoir, constraining the elimination of the parasite in hypo-endemic foci. To better understand the possible maintenance of T. b. gambiense in local fauna and investigate the molecular mechanisms underlying adaptation, we generated adapted cells lines (ACLs) by in vitro culture of the parasites in different mammalian sera. Using specific antibodies against the Variant Surface Glycoproteins (VSGs) we found that serum ACLs exhibited different VSG variants when maintained in pig, goat or human sera. Although newly detected VSGs were independent of the sera used, the consistent appearance of different VSGs suggested remodelling of the co-transcribed genes at the telomeric Expression Site (VSG-ES). Thus, Expression Site Associated Genes (ESAGs) sequences were analysed to investigate possible polymorphism selection. ESAGs 6 and 7 genotypes, encoding the transferrin receptor (TfR), expressed in different ACLs were characterised. In addition, we quantified the ESAG6/7 mRNA levels and analysed transferrin (Tf) uptake. Interestingly, the best growth occurred in pig and human serum ACLs, which consistently exhibited a predominant ESAG7 genotype and higher Tf uptake than those obtained in calf and goat sera. We also detected an apparent selection of specific ESAG3 genotypes in the pig and human serum ACLs, suggesting that other ESAGs could be involved in the host adaptation processes. Altogether, these results suggest a model whereby VSG-ES remodelling allows the parasite to express a specific set of ESAGs to provide selective advantages in different hosts. Finally, pig serum ACLs display phenotypic adaptation parameters closely related to human serum ACLs but distinct to parasites grown in calf and goat sera. These results suggest a better suitability of swine to maintain T. b. gambiense infection supporting previous epidemiological results.
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Affiliation(s)
- Carlos Cordon-Obras
- Instituto de Parasitología y Biomedicina "López-Neyra", CSIC, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Jorge Cano
- Centro Nacional de Medicina Tropical, Instituto de Salud Carlos III, Madrid, Spain
| | - Dolores González-Pacanowska
- Instituto de Parasitología y Biomedicina "López-Neyra", CSIC, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Agustin Benito
- Centro Nacional de Medicina Tropical, Instituto de Salud Carlos III, Madrid, Spain
| | - Miguel Navarro
- Instituto de Parasitología y Biomedicina "López-Neyra", CSIC, Consejo Superior de Investigaciones Científicas, Granada, Spain
- * E-mail:
| | - Jean-Mathieu Bart
- Instituto de Parasitología y Biomedicina "López-Neyra", CSIC, Consejo Superior de Investigaciones Científicas, Granada, Spain
- Centro Nacional de Medicina Tropical, Instituto de Salud Carlos III, Madrid, Spain
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23
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Castillo-Acosta VM, Vidal AE, Ruiz-Pérez LM, Van Damme EJM, Igarashi Y, Balzarini J, González-Pacanowska D. Carbohydrate-binding agents act as potent trypanocidals that elicit modifications in VSG glycosylation and reduced virulence in Trypanosoma brucei. Mol Microbiol 2013; 90:665-79. [PMID: 23926900 DOI: 10.1111/mmi.12359] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/04/2013] [Indexed: 01/19/2023]
Abstract
The surface of Trypanosoma brucei is covered by a dense coat of glycosylphosphatidylinositol-anchored glycoproteins. The major component is the variant surface glycoprotein (VSG) which is glycosylated by both paucimannose and oligomannose N-glycans. Surface glycans are poorly accessible and killing mediated by peptide lectin-VSG complexes is hindered by active endocytosis. However, contrary to previous observations, here we show that high-affinity carbohydrate binding agents bind to surface glycoproteins and abrogate growth of T. brucei bloodstream forms. Specifically, binding of the mannose-specific Hippeastrum hybrid agglutinin (HHA) resulted in profound perturbations in endocytosis and parasite lysis. Prolonged exposure to HHA led to the loss of triantennary oligomannose structures in surface glycoproteins as a result of genetic rearrangements that abolished expression of the oligosaccharyltransferase TbSTT3B gene and yielded novel chimeric enzymes. Mutant parasites exhibited markedly reduced infectivity thus demonstrating the importance of specific glycosylation patterns in parasite virulence.
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Affiliation(s)
- Víctor M Castillo-Acosta
- Instituto de Parasitología y Biomedicina 'López-Neyra'. Consejo Superior de Investigaciones Científicas, Parque Tecnológico de Ciencias de la Salud, Avenida del Conocimiento, s/n 18016, Armilla, Granada, Spain
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24
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Liu L, Xu YX, Caradonna KL, Kruzel EK, Burleigh BA, Bangs JD, Hirschberg CB. Inhibition of nucleotide sugar transport in Trypanosoma brucei alters surface glycosylation. J Biol Chem 2013; 288:10599-615. [PMID: 23443657 DOI: 10.1074/jbc.m113.453597] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nucleotide sugar transporters (NSTs) are indispensible for the biosynthesis of glycoproteins by providing the nucleotide sugars needed for glycosylation in the lumen of the Golgi apparatus. Mutations in NST genes cause human and cattle diseases and impaired cell walls of yeast and fungi. Information regarding their function in the protozoan parasite, Trypanosoma brucei, a causative agent of African trypanosomiasis, is unknown. Here, we characterized the substrate specificities of four NSTs, TbNST1-4, which are expressed in both the insect procyclic form (PCF) and mammalian bloodstream form (BSF) stages. TbNST1/2 transports UDP-Gal/UDP-GlcNAc, TbNST3 transports GDP-Man, and TbNST4 transports UDP-GlcNAc, UDP-GalNAc, and GDP-Man. TbNST4 is the first NST shown to transport both pyrimidine and purine nucleotide sugars and is demonstrated here to be localized at the Golgi apparatus. RNAi-mediated silencing of TbNST4 in the procyclic form caused underglycosylated surface glycoprotein EP-procyclin. Similarly, defective glycosylation of the variant surface glycoprotein (VSG221) as well as the lysosomal membrane protein p67 was observed in Δtbnst4 BSF T. brucei. Relative infectivity analysis showed that defects in glycosylation of the surface coat resulting from tbnst4 deletion were insufficient to impact the ability of this parasite to infect mice. Notably, the fact that inactivation of a single NST gene results in measurable defects in surface glycoproteins in different life cycle stages of the parasite highlights the essential role of NST(s) in glycosylation of T. brucei. Thus, results presented in this study provide a framework for conducting functional analyses of other NSTs identified in T. brucei.
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Affiliation(s)
- Li Liu
- Department of Molecular and Cell Biology, Boston University Goldman School of Dental Medicine, Boston, Massachusetts 02118, USA
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25
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Urbaniak MD, Mathieson T, Bantscheff M, Eberhard D, Grimaldi R, Miranda-Saavedra D, Wyatt P, Ferguson MAJ, Frearson J, Drewes G. Chemical proteomic analysis reveals the drugability of the kinome of Trypanosoma brucei. ACS Chem Biol 2012; 7:1858-65. [PMID: 22908928 PMCID: PMC3621575 DOI: 10.1021/cb300326z] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The protozoan parasite Trypanosoma brucei is the causative agent of African sleeping sickness, and there is an urgent unmet need for improved treatments. Parasite protein kinases are attractive drug targets, provided that the host and parasite kinomes are sufficiently divergent to allow specific inhibition to be achieved. Current drug discovery efforts are hampered by the fact that comprehensive assay panels for parasite targets have not yet been developed. Here, we employ a kinase-focused chemoproteomics strategy that enables the simultaneous profiling of kinase inhibitor potencies against more than 50 endogenously expressed T. brucei kinases in parasite cell extracts. The data reveal that T. brucei kinases are sensitive to typical kinase inhibitors with nanomolar potency and demonstrate the potential for the development of species-specific inhibitors.
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Affiliation(s)
- Michael D. Urbaniak
- Division of
Biological Chemistry
and Drug Discovery, College of Life Sciences, University
of Dundee, Dow Street, Dundee DD1 5EH, U.K
- E-mail: ;
| | - Toby Mathieson
- Cellzome AG, Meyerhofstrasse 1, D-69117 Heidelberg, Germany
| | | | - Dirk Eberhard
- Cellzome AG, Meyerhofstrasse 1, D-69117 Heidelberg, Germany
| | - Raffaella Grimaldi
- Division of
Biological Chemistry
and Drug Discovery, College of Life Sciences, University
of Dundee, Dow Street, Dundee DD1 5EH, U.K
| | - Diego Miranda-Saavedra
- World Premier International Immunology
Frontier Research Centre, Osaka University, 3-1 Yamadaoka, Suita 565-0871, Osaka, Japan
| | - Paul Wyatt
- Division of
Biological Chemistry
and Drug Discovery, College of Life Sciences, University
of Dundee, Dow Street, Dundee DD1 5EH, U.K
| | - Michael A. J. Ferguson
- Division of
Biological Chemistry
and Drug Discovery, College of Life Sciences, University
of Dundee, Dow Street, Dundee DD1 5EH, U.K
| | - Julie Frearson
- BioFocus, Chesterford
Park, Saffron Walden, Essex CB10 1XL, U.K
| | - Gerard Drewes
- Cellzome AG, Meyerhofstrasse 1, D-69117 Heidelberg, Germany
- E-mail: ;
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26
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Zelada-Guillén GA, Tweed-Kent A, Niemann M, Göringer HU, Riu J, Rius FX. Ultrasensitive and real-time detection of proteins in blood using a potentiometric carbon-nanotube aptasensor. Biosens Bioelectron 2012; 41:366-71. [PMID: 23017685 DOI: 10.1016/j.bios.2012.08.055] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2012] [Revised: 07/26/2012] [Accepted: 08/28/2012] [Indexed: 10/27/2022]
Abstract
Potentiometric sensing represents the preferred technique in many routine measurements of pH and ions. Unfortunately, the simplicity of the technique has not been exploited so far in high throughput biomolecular sensing. In this work, we demonstrate the capabilities of the hybrid functional material carbon nanotubes/aptamer for the creation of a new generation of nuclease-resistant aptasensors using the potentiometric transduction capabilities of single-walled carbon nanotubes in combination with the recognition capabilities of a protein-specific RNA aptamer. The aptasensor was used to detect and identify disease-related proteins at attomolar concentration values in a rapid and non-expensive way. The variable surface glycoprotein from African Trypanosomes was chosen as an ideal model system for a pathogenic exoantigen protein in a clinical sample. Variations in the electromotive force are achieved in real-time upon the direct addition of diluted real blood samples containing the target protein thus eliminating the need of preliminary matrix removal. This work would open the door to real-time diagnostic assays for a wide range of diseases, but also to the rapid molecular detection of several proteins in truly customizable protein biosensing platforms.
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Affiliation(s)
- Gustavo A Zelada-Guillén
- Department of Analytical and Organic Chemistry, Universitat Rovira i Virgili, C/Marcel·lí Domingo s/n, 43007 Tarragona, Catalonia, Spain.
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27
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Izquierdo L, Mehlert A, Ferguson MAJ. The lipid-linked oligosaccharide donor specificities of Trypanosoma brucei oligosaccharyltransferases. Glycobiology 2012; 22:696-703. [PMID: 22241825 PMCID: PMC3311286 DOI: 10.1093/glycob/cws003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We recently presented a model for site-specific protein N-glycosylation in Trypanosoma brucei whereby the TbSTT3A oligosaccharyltransferase (OST) first selectively transfers biantennary Man(5)GlcNAc(2) from the lipid-linked oligosaccharide (LLO) donor Man(5)GlcNAc(2)-PP-Dol to N-glycosylation sequons in acidic to neutral peptide sequences and TbSTT3B selectively transfers triantennary Man(9)GlcNAc(2) to any remaining sequons. In this paper, we investigate the specificities of the two OSTs for their preferred LLO donors by glycotyping the variant surface glycoprotein (VSG) synthesized by bloodstream-form T. brucei TbALG12 null mutants. The TbALG12 gene encodes the α1-6-mannosyltransferase that converts Man(7)GlcNAc(2)-PP-Dol to Man(8)GlcNAc(2)-PP-Dol. The VSG synthesized by the TbALG12 null mutant in the presence and the absence of α-mannosidase inhibitors was characterized by electrospray mass spectrometry both intact and as pronase glycopetides. The results show that TbSTT3A is able to transfer Man(7)GlcNAc(2) as well as Man(5)GlcNAc(2) to its preferred acidic glycosylation site at Asn263 and that, in the absence of Man(9)GlcNAc(2)-PP-Dol, TbSTT3B transfers both Man(7)GlcNAc(2) and Man(5)GlcNAc(2) to the remaining site at Asn428, albeit with low efficiency. These data suggest that the preferences of TbSTT3A and TbSTT3B for their LLO donors are based on the c-branch of the Man(9)GlcNAc(2) oligosaccharide, such that the presence of the c-branch prevents recognition and/or transfer by TbSTT3A, whereas the presence of the c-branch enhances recognition and/or transfer by TbSTT3B.
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Affiliation(s)
- Luis Izquierdo
- Division of Biological Chemistry and Drug Discovery, The College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
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28
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Nett IRE, Mehlert A, Lamont D, Ferguson MAJ. Application of electrospray mass spectrometry to the structural determination of glycosylphosphatidylinositol membrane anchors. Glycobiology 2010; 20:576-85. [PMID: 20100693 PMCID: PMC2850939 DOI: 10.1093/glycob/cwq007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The addition of glycosylphosphatidylinositol (GPI) anchors to proteins is an important posttranslational modification in eukaryotic cells. The complete structural elucidation of GPI anchors is a complex process that requires relatively large amounts of starting material. In this paper, we assess the degree of structural information that can be obtained by applying electrospray mass spectrometry and tandem mass spectrometry to permethylated GPI glycans prepared from a well-characterized GPI-anchored glycoprotein, the variant surface glycoprotein from Trypanosoma brucei. All GPI glycans contain a non-N-acetylated glucosamine residue, and permethylation leads to the formation of a fixed positive charge on the glycans, in the form of a quaternary amine. The permethylated glycans were detected as [M +- Na](2+-) ions, and tandem mass spectrometry of these ions produced substantial, albeit incomplete, structural information on the branching patterns and linkage types for various GPI glycoforms of the variant surface glycoprotein.
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Affiliation(s)
- Isabelle R E Nett
- Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK
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29
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Landeira D, Bart JM, Van Tyne D, Navarro M. Cohesin regulates VSG monoallelic expression in trypanosomes. J Cell Biol 2009; 186:243-54. [PMID: 19635842 PMCID: PMC2717648 DOI: 10.1083/jcb.200902119] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2009] [Accepted: 06/25/2009] [Indexed: 11/22/2022] Open
Abstract
Antigenic variation allows Trypanosoma brucei to evade the host immune response by switching the expression of 1 out of approximately 15 telomeric variant surface glycoprotein (VSG) expression sites (ESs). VSG ES transcription is mediated by RNA polymerase I in a discrete nuclear site named the ES body (ESB). However, nothing is known about how the monoallelic VSG ES transcriptional state is maintained over generations. In this study, we show that during S and G2 phases and early mitosis, the active VSG ES locus remains associated with the single ESB and exhibits a delay in the separation of sister chromatids relative to control loci. This delay is dependent on the cohesin complex, as partial knockdown of cohesin subunits resulted in premature separation of sister chromatids of the active VSG ES. Cohesin depletion also prompted transcriptional switching from the active to previously inactive VSG ESs. Thus, in addition to maintaining sister chromatid cohesion during mitosis, the cohesin complex plays an essential role in the correct epigenetic inheritance of the active transcriptional VSG ES state.
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Affiliation(s)
- David Landeira
- Instituto de Parasitología y Biomedicina López-Neyra, Consejo Superior de Investigaciones Cientificas, 18100 Granada, Spain
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30
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Izquierdo L, Schulz BL, Rodrigues JA, Güther MLS, Procter JB, Barton GJ, Aebi M, Ferguson MAJ. Distinct donor and acceptor specificities of Trypanosoma brucei oligosaccharyltransferases. EMBO J 2009; 28:2650-61. [PMID: 19629045 PMCID: PMC2722254 DOI: 10.1038/emboj.2009.203] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2009] [Accepted: 06/18/2009] [Indexed: 11/09/2022] Open
Abstract
Asparagine-linked glycosylation is catalysed by oligosaccharyltransferase (OTase). In Trypanosoma brucei OTase activity is catalysed by single-subunit enzymes encoded by three paralogous genes of which TbSTT3B and TbSTT3C can complement a yeast Δstt3 mutant. The two enzymes have overlapping but distinct peptide acceptor specificities, with TbSTT3C displaying an enhanced ability to glycosylate sites flanked by acidic residues. TbSTT3A and TbSTT3B, but not TbSTT3C, are transcribed in the bloodstream and procyclic life cycle stages of T. brucei. Selective knockdown and analysis of parasite protein N-glycosylation showed that TbSTT3A selectively transfers biantennary Man5GlcNAc2 to specific glycosylation sites whereas TbSTT3B selectively transfers triantennary Man9GlcNAc2 to others. Analysis of T. brucei glycosylation site occupancy showed that TbSTT3A and TbSTT3B glycosylate sites in acidic to neutral and neutral to basic regions of polypeptide, respectively. This embodiment of distinct specificities in single-subunit OTases may have implications for recombinant glycoprotein engineering. TbSTT3A and TbSTT3B could be knocked down individually, but not collectively, in tissue culture. However, both were independently essential for parasite growth in mice, suggesting that inhibiting protein N-glycosylation could have therapeutic potential against trypanosomiasis.
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Affiliation(s)
- Luis Izquierdo
- Division of Biological Chemistry and Drug Discovery, The College of Life Sciences, University of Dundee, Dundee, UK
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31
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Hanrahan O, Webb H, O'Byrne R, Brabazon E, Treumann A, Sunter JD, Carrington M, Voorheis HP. The glycosylphosphatidylinositol-PLC in Trypanosoma brucei forms a linear array on the exterior of the flagellar membrane before and after activation. PLoS Pathog 2009; 5:e1000468. [PMID: 19503825 PMCID: PMC2685982 DOI: 10.1371/journal.ppat.1000468] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2008] [Accepted: 05/11/2009] [Indexed: 11/30/2022] Open
Abstract
Bloodstream forms of Trypanosoma brucei contain a glycosylphosphatidylinositol-specific phospholipase C (GPI-PLC) that cleaves the GPI-anchor of the variable surface glycoprotein (VSG). Its location in trypanosomes has been controversial. Here, using confocal microscopy and surface labelling techniques, we show that the GPI-PLC is located exclusively in a linear array on the outside of the flagellar membrane, close to the flagellar attachment zone, but does not co-localize with the flagellar attachment zone protein, FAZ1. Consequently, the GPI-PLC and the VSG occupy the same plasma membrane leaflet, which resolves the topological problem associated with the cleavage reaction if the VSG and the GPI-PLC were on opposite sides of the membrane. The exterior location requires the enzyme to be tightly regulated to prevent VSG release under basal conditions. During stimulated VSG release in intact cells, the GPI-PLC did not change location, suggesting that the release mechanism involves lateral diffusion of the VSG in the plane of the membrane to the fixed position of the GPI-PLC. African trypanosomes cause sleeping sickness, for which current therapy is inadequate. The parasite protects its surface from the host immune system by regularly switching its surface coat. The glycosylphosphatidylinositol-PLC only occurs in the bloodstream form, where it removes the surface coat after it enters the tsetse fly vector. Activation of the enzyme in the bloodstream would be fatal for the parasite and it is, therefore, a potential drug target. However, therapeutic strategies have been hampered by confusion over the location of the GPI-PLC despite great effort by many labs. We have used a wide variety of techniques, including one completely novel method, that exploits the dependence of detection for partially buried surface proteins on the temperature of fixation, to identify the location of the GPI-PLC in relation to other markers unequivocally. All approaches consistently show that the GPI-PLC is located exclusively in the outer leaflet of the plasma membrane covering the flagellum, where it is confined to a narrow linear array adjacent to the flagellar attachment zone. Our data have resolved the question of how enzyme and substrate meet and also suggest that chemotherapeutic agents would be able to target the GPI-PLC in its exterior location.
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Affiliation(s)
- Orla Hanrahan
- School of Biochemistry and Immunology, Trinity College Dublin, Dublin, Ireland
| | - Helena Webb
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Robert O'Byrne
- School of Biochemistry and Immunology, Trinity College Dublin, Dublin, Ireland
| | - Elaine Brabazon
- School of Biochemistry and Immunology, Trinity College Dublin, Dublin, Ireland
| | | | - Jack D. Sunter
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Mark Carrington
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - H. Paul Voorheis
- School of Biochemistry and Immunology, Trinity College Dublin, Dublin, Ireland
- * E-mail:
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Nett IRE, Martin DMA, Miranda-Saavedra D, Lamont D, Barber JD, Mehlert A, Ferguson MAJ. The phosphoproteome of bloodstream form Trypanosoma brucei, causative agent of African sleeping sickness. Mol Cell Proteomics 2009; 8:1527-38. [PMID: 19346560 PMCID: PMC2716717 DOI: 10.1074/mcp.m800556-mcp200] [Citation(s) in RCA: 130] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The protozoan parasite Trypanosoma brucei is the causative agent
of human African sleeping sickness and related animal diseases, and it has over
170 predicted protein kinases. Protein phosphorylation is a key regulatory
mechanism for cellular function that, thus far, has been studied in
T.brucei principally through putative kinase mRNA knockdown
and observation of the resulting phenotype. However, despite the relatively
large kinome of this organism and the demonstrated essentiality of several
T. brucei kinases, very few specific phosphorylation sites
have been determined in this organism. Using a gel-free, phosphopeptide
enrichment-based proteomics approach we performed the first large scale
phosphorylation site analyses for T.brucei. Serine, threonine,
and tyrosine phosphorylation sites were determined for a cytosolic protein
fraction of the bloodstream form of the parasite, resulting in the
identification of 491 phosphoproteins based on the identification of 852 unique
phosphopeptides and 1204 phosphorylation sites. The phosphoproteins detected in
this study are predicted from their genome annotations to participate in a wide
variety of biological processes, including signal transduction, processing of
DNA and RNA, protein synthesis, and degradation and to a minor extent in
metabolic pathways. The analysis of phosphopeptides and phosphorylation sites
was facilitated by in-house developed software, and this automated approach was
validated by manual annotation of spectra of the kinase subset of proteins.
Analysis of the cytosolic bloodstream form T. brucei kinome
revealed the presence of 44 phosphorylated protein kinases in our data set that
could be classified into the major eukaryotic protein kinase groups by applying
a multilevel hidden Markov model library of the kinase catalytic domain.
Identification of the kinase phosphorylation sites showed conserved
phosphorylation sequence motifs in several kinase activation segments,
supporting the view that phosphorylation-based signaling is a general and
fundamental regulatory process that extends to this highly divergent lower
eukaryote.
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Affiliation(s)
- Isabelle R E Nett
- Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Dundee, Scotland, United Kingdom
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Figueiredo LM, Janzen CJ, Cross GA. A histone methyltransferase modulates antigenic variation in African trypanosomes. PLoS Biol 2008; 6:e161. [PMID: 18597556 PMCID: PMC2443197 DOI: 10.1371/journal.pbio.0060161] [Citation(s) in RCA: 122] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2008] [Accepted: 05/23/2008] [Indexed: 11/18/2022] Open
Abstract
To evade the host immune system, several pathogens periodically change their cell-surface epitopes. In the African trypanosomes, antigenic variation is achieved by tightly regulating the expression of a multigene family encoding a large repertoire of variant surface glycoproteins (VSGs). Immune evasion relies on two important features: exposing a single type of VSG at the cell surface and periodically and very rapidly switching the expressed VSG. Transcriptional switching between resident telomeric VSG genes does not involve DNA rearrangements, and regulation is probably epigenetic. The histone methyltransferase DOT1B is a nonessential protein that trimethylates lysine 76 of histone H3 in Trypanosoma brucei. Here we report that transcriptionally silent telomeric VSGs become partially derepressed when DOT1B is deleted, whereas nontelomeric loci are unaffected. DOT1B also is involved in the kinetics of VSG switching: in ΔDOT1B cells, the transcriptional switch is so slow that cells expressing two VSGs persist for several weeks, indicating that monoallelic transcription is compromised. We conclude that DOT1B is required to maintain strict VSG silencing and to ensure rapid transcriptional VSG switching, demonstrating that epigenetics plays an important role in regulating antigenic variation in T. brucei. The surface of Trypanosoma brucei, a unicellular parasite that lives in the bloodstream of its mammalian host, is coated with glycoprotein (VSG) molecules. To evade elimination by the immune system, this parasite replaces its coat with one tailored from another glycoprotein variant. Even though there are hundreds of VSG genes in the genome, this process, called antigenic variation, works because all are silenced except for the one that encodes the current coat. In this work, we show that the chromatin-modifying enzyme DOT1B helps to epigenetically regulate the number of VSGs each parasite can have at a time at the surface and how fast each parasite can switch from one coat to another. In parasites lacking DOT1B, silent VSG genes become partially active and the switch from one VSG to another slows down, allowing two different VSGs to appear on the surface of an individual parasite at the same time. Our studies reveal the importance of epigenetics in regulating VSG genes and provide new insights toward the understanding of this unique survival device. Antigenic variation in Trypanosoma brucei relies on monoallelic expression of a multigene family. New evidence shows that a chromatin-modifying enzyme prevents simultaneous expression of different proteins at the parasite's surface.
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Affiliation(s)
- Luisa M Figueiredo
- Laboratory of Molecular Parasitology, the Rockefeller University, New York, New York, United States of America
| | | | - George A.M Cross
- Laboratory of Molecular Parasitology, the Rockefeller University, New York, New York, United States of America
- * To whom correspondence should be addressed. E-mail:
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Manthri S, Güther MLS, Izquierdo L, Acosta-Serrano A, Ferguson MAJ. Deletion of the TbALG3 gene demonstrates site-specific N-glycosylation and N-glycan processing in Trypanosoma brucei. Glycobiology 2008; 18:367-83. [PMID: 18263655 DOI: 10.1093/glycob/cwn014] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
We recently suggested a novel site-specific N-glycosylation mechanism in Trypanosoma brucei whereby some protein N-glycosylation sites selectively receive Man9GlcNAc2 from Man9GlcNAc2-PP-Dol while others receive Man5GlcNA(2 from Man5GlcNAc2-PP-Dol. In this paper, we test this model by creating procyclic and bloodstream form null mutants of TbALG3, the gene that encodes the alpha-mannosyltransferase that converts Man5GlcNAc2-PP-Dol to Man6GlcNAc2-PP-Dol. The procyclic and bloodstream form TbALG3 null mutants grow with normal kinetics, remain infectious to mice and tsetse flies, respectively, and have normal morphology. However, both forms display aberrant N-glycosylation of their major surface glycoproteins, procylcin, and variant surface glycoprotein, respectively. Specifically, procyclin and variant surface glycoprotein N-glycosylation sites that are modified with Man9GlcNAc2 and processed no further than Man5GlcNAc2 in the wild type are glycosylated less efficiently but processed to complex structures in the mutant. These data confirm our model and refine it by demonstrating that the biantennary glycan transferred from Man5GlcNAc2-PP-Dol is the only route to complex N-glycans in T. brucei and that Man9GlcNAc2-PP-Dol is strictly a precursor for oligomannose structures. The origins of site-specific Man5GlcNAc2 or Man9GlcNAc2 transfer are discussed and an updated model of N-glycosylation in T. brucei is presented.
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Affiliation(s)
- Sujatha Manthri
- The Division of Biological Chemistry and Drug Discovery, The Wellcome Trust Biocentre, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK
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Saerens D, Stijlemans B, Baral TN, Nguyen Thi GT, Wernery U, Magez S, De Baetselier P, Muyldermans S, Conrath K. Parallel selection of multiple anti-infectome Nanobodies without access to purified antigens. J Immunol Methods 2008; 329:138-50. [DOI: 10.1016/j.jim.2007.10.005] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2007] [Revised: 09/21/2007] [Accepted: 10/03/2007] [Indexed: 12/20/2022]
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36
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Stijlemans B, Baral TN, Guilliams M, Brys L, Korf J, Drennan M, Van Den Abbeele J, De Baetselier P, Magez S. A glycosylphosphatidylinositol-based treatment alleviates trypanosomiasis-associated immunopathology. THE JOURNAL OF IMMUNOLOGY 2007; 179:4003-14. [PMID: 17785839 DOI: 10.4049/jimmunol.179.6.4003] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The GPI-anchored trypanosome variant surface glycoprotein (VSG) triggers macrophages to produce TNF, involved in trypanosomiasis-associated inflammation and the clinical manifestation of sleeping sickness. Aiming at inhibiting immunopathology during experimental Trypanosoma brucei infections, a VSG-derived GPI-based treatment approach was developed. To achieve this, mice were exposed to the GPI before an infectious trypanosome challenge. This GPI-based strategy resulted in a significant prolonged survival and a substantial protection against infection-associated weight loss, liver damage, acidosis, and anemia; the latter was shown to be Ab-independent and correlated with reduced macrophage-mediated RBC clearance. In addition, GPI-based treatment resulted in reduced circulating serum levels of the inflammatory cytokines TNF and IL-6, abrogation of infection-induced LPS hypersensitivity, and an increase in circulating IL-10. At the level of trypanosomiasis-associated macrophage activation, the GPI-based treatment resulted in an impaired secretion of TNF by VSG and LPS pulsed macrophages, a reduced expression of the inflammatory cytokine genes TNF, IL-6, and IL-12, and an increased expression of the anti-inflammatory cytokine gene IL-10. In addition, this change in cytokine pattern upon GPI-based treatment was associated with the expression of alternatively activated macrophage markers. Finally, the GPI-based treatment also reduced the infection-associated pathology in Trypanosoma congolense and Trypanosoma evansi model systems as well as in tsetse fly challenge experiments, indicating potential field applicability for this intervention strategy.
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MESH Headings
- Anemia/therapy
- Animals
- Antigens, CD1/physiology
- Antigens, CD1d
- B-Lymphocyte Subsets/drug effects
- B-Lymphocyte Subsets/pathology
- Disease Models, Animal
- Glycosylphosphatidylinositols/therapeutic use
- Inflammation Mediators/therapeutic use
- Lymphopenia/immunology
- Lymphopenia/parasitology
- Lymphopenia/therapy
- Macrophage Activation/drug effects
- Macrophage Activation/immunology
- Male
- Mice
- Mice, Inbred BALB C
- Mice, Inbred C3H
- Mice, Inbred C57BL
- Mice, Knockout
- Signal Transduction/drug effects
- Signal Transduction/immunology
- Trypanosoma brucei brucei/chemistry
- Trypanosoma brucei brucei/immunology
- Trypanosoma brucei brucei/pathogenicity
- Trypanosomiasis, African/immunology
- Trypanosomiasis, African/pathology
- Trypanosomiasis, African/therapy
- Variant Surface Glycoproteins, Trypanosoma/therapeutic use
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Affiliation(s)
- Benoît Stijlemans
- Laboratory of Cellular and Molecular Immunology, Vrije Universiteit Brussels, Pleinlaan 2, Brussels, Belgium.
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37
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Sutterwala SS, Creswell CH, Sanyal S, Menon AK, Bangs JD. De novo sphingolipid synthesis is essential for viability, but not for transport of glycosylphosphatidylinositol-anchored proteins, in African trypanosomes. EUKARYOTIC CELL 2007; 6:454-64. [PMID: 17220466 PMCID: PMC1828920 DOI: 10.1128/ec.00283-06] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
De novo sphingolipid synthesis is required for the exit of glycosylphosphatidylinositol (GPI)-anchored membrane proteins from the endoplasmic reticulum in yeast. Using a pharmacological approach, we test the generality of this phenomenon by analyzing the transport of GPI-anchored cargo in widely divergent eukaryotic systems represented by African trypanosomes and HeLa cells. Myriocin, which blocks the first step of sphingolipid synthesis (serine + palmitate --> 3-ketodihydrosphingosine), inhibited the growth of cultured bloodstream parasites, and growth was rescued with exogenous 3-ketodihydrosphingosine. Myriocin also blocked metabolic incorporation of [3H]serine into base-resistant sphingolipids. Biochemical analyses indicate that the radiolabeled lipids are not sphingomyelin or inositol phosphorylceramide, suggesting that bloodstream trypanosomes synthesize novel sphingolipids. Inhibition of de novo sphingolipid synthesis with myriocin had no adverse effect on either general secretory trafficking or GPI-dependent trafficking in trypanosomes, and similar results were obtained with HeLa cells. A mild effect on endocytosis was seen for bloodstream trypanosomes after prolonged incubation with myriocin. These results indicate that de novo synthesis of sphingolipids is not a general requirement for secretory trafficking in eukaryotic cells. However, in contrast to the closely related kinetoplastid Leishmania major, de novo sphingolipid synthesis is essential for the viability of bloodstream-stage African trypanosomes.
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Affiliation(s)
- Shaheen S Sutterwala
- Department of Medical Microbiology and Immunology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53706, USA
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38
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Uemura A, Watarai S, Kushi Y, Kasama T, Ohnishi Y, Kodama H. Analysis of neutral glycosphingolipids from Trypanosoma brucei. Vet Parasitol 2006; 140:264-72. [PMID: 16806714 DOI: 10.1016/j.vetpar.2006.04.028] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/10/2006] [Indexed: 11/16/2022]
Abstract
Neutral glycosphingolipids (GSLs) were isolated from Trypanosoma brucei and analyzed by thin-layer chromatography (TLC), TLC/secondary ion mass spectrometry (TLC/SIMS), and liposome immune lysis assay (LILA). Three species of neutral GSLs, designated as N-1, -2, and -3 were separated on TLC. N-1 GSL migrated very close to glucosylceramide (GlcCer) and N-2 GSL showed the same mobility as lactosylceramide (LacCer). On the other hand, the mobility of N-3 GSL on the TLC plate was slower than globotetraosylceramide (Gb4). In order to characterize the molecular species of neutral GSLs from T. brucei, N-1, -2 and -3 GSLs were analyzed by TLC/SIMS. The TLC/SIMS analysis of N-1 of the parasites revealed a series of (M-H)- ions from m/z 698 to 825 representing the molecular mass range of ceramide monohexoside (CMH) (GlcCer or galactosylceramide). On the other hand, the TLC/SIMS spectra of N-2 GSL revealed a series of (M-H)- ions from m/z 944-987 indicating the molecular mass range of LacCer. In the TLC/SIMS analysis of N-3 GSL, however, the characteristic molecular ions that can elucidate the structure of N-3 GSL were not obtained. In order to confirm the results obtained from TLC/SIMS, N-1, -2, and -3, GSLs were tested by LILA with specific antibodies against GlcCer, LacCer, and Gb4, respectively. N-1 GSL had reactivity to anti-GlcCer antibody and N-2 GSL reacted with the antibody against LacCer. However, N-3 GSL was not recognized by anti-Gb4 antibody. Using anti-GlcCer and anti-LacCer antibodies, furthermore, we studied the expression of GlcCer and LacCer in T. brucei parasites. Both GlcCer and LacCer were detected on the cell surface of T. brucei.
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Affiliation(s)
- Akiko Uemura
- Laboratory of Veterinary Immunology, Division of Veterinary Science, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan
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Jones DC, Mehlert A, Güther MLS, Ferguson MAJ. Deletion of the Glucosidase II Gene in Trypanosoma brucei Reveals Novel N-Glycosylation Mechanisms in the Biosynthesis of Variant Surface Glycoprotein. J Biol Chem 2005; 280:35929-42. [PMID: 16120601 DOI: 10.1074/jbc.m509130200] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The trypanosomatids are generally aberrant in their protein N-glycosylation pathways. However, protein N-glycosylation in the African trypanosome Trypanosoma brucei, etiological agent of human African sleeping sickness, is not well understood. Here, we describe the creation of a bloodstream-form T. brucei mutant that is deficient in the endoplasmic reticulum enzyme glucosidase II. Characterization of the variant surface glycoprotein, the main glycoprotein synthesized by the parasite with two N-glycosylation sites, revealed unexpected changes in the N-glycosylation of this molecule. Structural characterization by mass spectrometry, nuclear magnetic resonance spectroscopy, and chemical and enzymatic treatments revealed that one of the two glycosylation sites was occupied by conventional oligomannose structures, whereas the other accumulated unusual structures in the form of Glcalpha1-3Manalpha1-2Manalpha1-2Manalpha1-3(Manalpha1-6)Manbeta1-4GlcNAcbeta1-4GlcNAc, Glcalpha1-3Manalpha1-2Manalpha1-2Manalpha1-3(GlcNAcbeta1-2Manalpha1-6)Manbeta1-4GlcNAcbeta1-4GlcNAc, and Glcalpha1-3Manalpha1-2Manalpha1-2Manalpha1-3(Galbeta1-4GlcNAcbeta1-2Manalpha1-6)Manbeta1-4GlcNAcbeta1-4GlcNAc. The possibility that these structures might arise from Glc1Man9GlcNAc2 by unusually rapid alpha-mannosidase processing was ruled out using a mixture of alpha-mannosidase inhibitors. The results suggest that bloodstream-form T. brucei can transfer both Man9GlcNAc2 and Man5GlcNAc2 to the variant surface glycoprotein in a site-specific manner and that, unlike organisms that transfer exclusively Glc3Man9GlcNAc2, the T. brucei UDP-Glc: glycoprotein glucosyltransferase and glucosidase II enzymes can use Man5GlcNAc2 and Glc1Man5GlcNAc2, respectively, as their substrates. The ability to transfer Man5GlcNAc2 structures to N-glycosylation sites destined to become Man(4-3)GlcNAc2 or complex structures may have evolved as a mechanism to conserve dolichol-phosphate-mannose donors for glycosylphosphatidylinositol anchor biosynthesis and points to fundamental differences in the specificities of host and parasite glycosyltransferases that initiate the synthesis of complex N-glycans.
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Affiliation(s)
- Deuan C Jones
- Division of Biological Chemistry and Molecular Microbiology, School of Life Sciences, The Wellcome Trust Biocentre, University of Dundee, Dundee DD1 5EH, United Kingdom
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40
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Uemura A, Watarai S, Ohnishi Y, Kodama H. Protective effect of antiganglioside antibodies against experimental Trypanosoma brucei infection in mice. J Parasitol 2005; 91:73-8. [PMID: 15856875 DOI: 10.1645/ge-3375] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Liposome-associated ganglioside antigens (ganglioside GM1 or bovine brain gangliosides) were prepared to facilitate the potential protective efficacy for Trypanosoma brucei. Mice were immunized with liposome-associated ganglioside GM1 or bovine brain gangliosides intraperitoneally (i.p.). After immunization, significantly higher antigen-specific IgG and IgM antibodies were detected in sera than in the nonimmunized control group. When sera from immunized mice were analyzed for isotype distribution, antigen-specific IgG1, IgG2a, and IgG3 antibody responses were also noted. After immunization, mice were challenged i.p. with 1 x 10(2) cells of T. brucei. Sixty percentage of liposome-associated ganglioside GM1-immunized mice survived the infection, and all the mice immunized with bovine brain gangliosides-containing liposomes survived. However, all control mice died within 7 days after infection. These data demonstrate that liposomes containing ganglioside antigens have the potential usefulness for the induction of a protective immune response against T. brucei infection and suggest the possibility of developing vaccines that may ultimately be used for the prevention of trypanosomiasis.
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Affiliation(s)
- Akiko Uemura
- Laboratory of Veterinary Immunology, Division of Veterinary Science, Graduate School of Agriculture and Biological Sciences, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan
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41
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Jones D, Mehlert A, Ferguson MAJ. The N-glycan glucosidase system in Trypanosoma brucei. Biochem Soc Trans 2005; 32:766-8. [PMID: 15494010 DOI: 10.1042/bst0320766] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Reactions involving removal and addition of glucose to N-glycans in the ER (endoplasmic reticulum) are performed in higher eukaryotes by glucosidases I and II and the UDP-glucose:glycoprotein glucosyltransferase respectively. Monoglucosylated N-glycan structures have been implicated in glycoprotein folding or ER quality control. Components of the system appear across a range of organisms; however, the precise combination differs between organisms. We have identified putative components of the system in the protozoal organism Trypanosoma brucei by local alignment searching. The function of one of these components, a glucosidase II alpha-subunit homologue, has been confirmed by phenotyping a null mutant, and an ectopic expression cell line. A combination of MS, methylation linkage analysis, exoglycosidase digestion and partial acetolysis have been used to characterize three novel N-glycan structures on the variant surface glycoprotein of the null mutant. On the basis of our results, we propose that two N-glycan precursors are available for transfer to variant surface glycoprotein (variant 221) in the ER of T. brucei; only one of these precursors is glucosylated after transfer.
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Affiliation(s)
- D Jones
- School of Life Sciences, University of Dundee, Dundee DD1 5EH, UK.
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42
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Roper JR, Güther MLS, Macrae JI, Prescott AR, Hallyburton I, Acosta-Serrano A, Ferguson MAJ. The suppression of galactose metabolism in procylic form Trypanosoma brucei causes cessation of cell growth and alters procyclin glycoprotein structure and copy number. J Biol Chem 2005; 280:19728-36. [PMID: 15767252 DOI: 10.1074/jbc.m502370200] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Galactose metabolism is essential in bloodstream form Trypanosoma brucei and is initiated by the enzyme UDP-Glc 4'-epimerase. Here, we show that the parasite epimerase is a homodimer that can interconvert UDP-Glc and UDP-Gal but not UDP-GlcNAc and UDP-GalNAc. The epimerase was localized to the glycosomes by immunofluorescence microscopy and subcellular fractionation, suggesting a novel compartmentalization of galactose metabolism in this organism. The epimerase is encoded by the TbGALE gene and procyclic form T. brucei single-allele knockouts, and conditional (tetracycline-inducible) null mutants were constructed. Under non-permissive conditions, conditional null mutant cultures ceased growth after 8 days and resumed growth after 15 days. The resumption of growth coincided with constitutive re-expression epimerase mRNA. These data show that galactose metabolism is essential for cell growth in procyclic form T. brucei. The epimerase is required for glycoprotein galactosylation. The major procyclic form glycoproteins, the procyclins., were analyzed in TbGALE single-allele knockouts and in the conditional null mutant after removal of tetracycline. The procyclins contain glycosylphosphatidylinositol membrane anchors with large poly-N-acetyl-lactosamine side chains. The single allele knockouts exhibited 30% reduction in procyclin galactose content. This example of haploid insufficiency suggests that epimerase levels are close to limiting in this life cycle stage. Similar analyses of the conditional null mutant 9 days after the removal of tetracycline showed that the procyclins were virtually galactose-free and greatly reduced in size. The parasites compensated, ultimately unsuccessfully, by expressing 10-fold more procyclin. The implications of these data with respect to the relative roles of procyclin polypeptide and carbohydrate are discussed.
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Affiliation(s)
- Janine R Roper
- Division of Biological Chemistry and Molecular Microbiology, The School of Life Sciences, University of Dundee, Scotland, UK
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43
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Hülsmeier AJ, Köhler P. Giardia duodenalis: direct experimental evidence for the absence of a glycosylphosphatidylinositol anchor in a variant surface protein. Exp Parasitol 2005; 109:49-52. [PMID: 15639139 DOI: 10.1016/j.exppara.2004.10.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2004] [Revised: 09/11/2004] [Accepted: 10/20/2004] [Indexed: 11/24/2022]
Abstract
The trophozoites of Giardia duodenalis express variant surface proteins (VSPs) that cover the entire surface of the cell and can be altered by antigenic variation. In the present study, a VSP (VSPH7) expressed by the Giardia GS isolate was purified using Triton-X-114 extraction/phase partitioning and a combination of column chromatography methods. The purified VSP was typed by mass spectrometric fingerprint mapping and peptide sequencing and found to share 58-99.8% peptide identity with the VSPH7 protein sequence previously deduced from the cloned cDNA. Carbohydrate compositional analyses consistently showed the presence of galactose in the VSP preparations but a direct association of carbohydrate with the VSPH7 could not be established. Analysis of the C-terminal part of the purified VSPH7 by off-blot myo-inositol analysis provided for the first time direct experimental evidence that this protein is not modified via a GPI lipid.
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Affiliation(s)
- Andreas J Hülsmeier
- Institute of Parasitology, University of Zurich, Winterthurerstrasse 266a, 8057 Zurich, Switzerland
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44
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Atrih A, Richardson JM, Prescott AR, Ferguson MAJ. Trypanosoma brucei glycoproteins contain novel giant poly-N-acetyllactosamine carbohydrate chains. J Biol Chem 2004; 280:865-71. [PMID: 15509560 DOI: 10.1074/jbc.m411061200] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The flagellar pocket of the bloodstream form of the African sleeping sickness parasite Trypanosoma brucei contains material that binds the beta-d-galactose-specific lectin ricin (Brickman, M. J., and Balber, A. E. (1990) J. Protozool. 37, 219-224). Glycoproteins were solubilized from bloodstream form T. brucei cells in 8 M urea and 3% SDS and purified by ricin affinity chromatography. Essentially all binding of ricin to these glycoproteins was abrogated by treatment with peptide N-glycosidase, showing that the ricin ligands are attached to glycoproteins via N-glycosidic linkages to asparagine residues. Glycans released by peptide N-glycosidase were resolved by Bio-Gel P-4 gel filtration into two fractions: a low molecular mass mannose-rich fraction and a high molecular mass galactose and N-acetylglucosamine-rich fraction. The latter fraction was further separated by high pH anion exchange chromatography and analyzed by gas chromatography mass spectrometry, one- and two-dimensional NMR, electrospray mass spectrometry, and methylation linkage analysis. The high molecular mass ricin-binding N-glycans are based on a conventional Manalpha1-3(Manalpha1-6)Manbeta1-4-GlcNAcbeta1-4GlcNAc core structure and contain poly-N-acetyllactosamine chains. A significant proportion of these structures are extremely large and of unusual structure. They contain an average of 54 N-acetyllactosamine (Galbeta1-4GlcNAc) repeats per glycan, linked mostly by -4GlcNAcbeta1-6Galbeta1-interrepeat linkages, with an average of one -4GlcNAcbeta1-3(-4GlcNAcbeta1-6)Galbeta1- branch point in every six repeats. These structures, which also bind tomato lectin, are twice the size reported for the largest mammalian poly-N-acetyllactosamine N-linked glycans and also differ in their preponderance of -4GlcNAcbeta1-6Galbeta1- over -4GlcNacbeta1-3Galbeta1- interrepeat linkages. Molecular modeling suggests that -4GlcNAcbeta1-6Galbeta1- interrepeat linkages produce relatively compact structures that may give these giant N-linked glycans unique physicochemical properties. Fluorescence microscopy using fluorescein isothiocyanatericin indicates that ricin ligands are located mainly in the flagellar pocket and in the endosomal/lysosomal system of the trypanosome.
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Affiliation(s)
- Abdelmadjid Atrih
- Division of Biological Chemistry and Molecular Microbiology, the School of Life Sciences, University of Dundee, Dundee DD1 5EH, United Kingdom
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Uzcanga GL, Perrone T, Noda JA, Pérez-Pazos J, Medina R, Hoebeke J, Bubis J. Variant Surface Glycoprotein fromTrypanosomaevansiIs Partially Responsible for the Cross-Reaction betweenTrypanosomaevansiandTrypanosoma vivax†. Biochemistry 2004; 43:595-606. [PMID: 14730963 DOI: 10.1021/bi0301946] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Salivarian trypanosomes use antigenic variation of their variant-specific surface glycoprotein (VSG) coat as a defense against the host immune system. Although about 1000 VSG and pseudo-VSG genes are scattered throughout the trypanosome genome, each trypanosome expresses only one VSG, while the rest of the genes are transcriptionally silent. A 64-kDa glycosylated cross-reacting antigen between Trypanosoma evansi and Trypanosoma vivax (p64), which was purified from the TEVA1 T. evansi Venezuelan isolate, was proven here to represent the soluble form of a VSG. Initially, a biochemical characterization of p64 was carried out. Gel filtration chromatography, sedimentation, and chemical cross-linking provided evidences of the dimeric nature of p64. The hydrodynamic parameters indicated that p64 is asymmetrical with a frictional ratio f/fo = 1.57. Isoelectric focusing and two-dimensional polyacrylamide gel electrophoresis revealed that p64 contained two isoforms with isoelectric points of 6.8-6.9 and 7.1-7.2. When p64 and three p64 Staphylococcus aureus V8 proteolytic fragments were sequenced, the same N-termini sequence was obtained: Ala-Pro-Ile-Thr-Asp-Ala-Asp-Leu-Gly-Pro-Ala-Gln-Ile-Ala-Asp, which displayed a significant homology with a putative Trypanosoma brucei VSG gene located on chromosome 4. Additionally, immunofluorescence microscopy on T. evansi and T. vivax established that p64 and its T. vivax homologue were confined to the surface of both parasites. An immunological characterization of this antigen was also carried out using several Venezuelan T. evansi isolates expressing different VSGs, which were obtained from naturally infected animals. Although sera from animals infected with the various T. evansi isolates recognized p64, only one isolate, besides TEVA1, contained polypeptides that were recognized by anti-p64 antibodies. All these results together with prior evidences [Uzcanga, G. et al. (2002) Parasitology 124, 287-299] confirmed that p64 is the soluble form of a T. evansi VSG, containing common epitopes recognized by sera from animals infected with T. evansi or T. vivax. Despite the huge repertoire of VSG genes existing on bloodstream trypanosomes, our data also demonstrated the potential use of a VSG variant from the TEVA1 T. evansi isolate as a diagnostic reagent.
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Affiliation(s)
- Graciela L Uzcanga
- Departamento de Biología Celular, Universidad Simón Bolívar, Caracas, Venezuela
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Gruszynski AE, DeMaster A, Hooper NM, Bangs JD. Surface coat remodeling during differentiation of Trypanosoma brucei. J Biol Chem 2003; 278:24665-72. [PMID: 12716904 DOI: 10.1074/jbc.m301497200] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
African trypanosomes (Trypanosoma brucei) are digenetic parasites whose lifecycle alternates between the mammalian bloodstream and the midgut of the tsetse fly vector. In mammals, proliferating long slender parasites transform into non-diving short stumpy forms, which differentiate into procyclic forms when ingested by the tsetse fly. A hallmark of differentiation is the replacement of the bloodstream stage surface coat composed of variant surface glycoprotein (VSG) with a new coat composed of procylin. An undefined endoprotease and endogenous glycosylphosphatidylinositol-specific phospholipase C (GPI-PLC) have been implicated in releasing the old VSG coat. However, GPI hydrolysis has been considered unimportant because (i) GPI-PLC null mutants are fully viable and (ii) cytosolic GPI-PLC is localized away from cell surface VSG. Utilizing an in vitro differentiation assay with pleomorphic strains we have investigated these modes of VSG release. Shedding is initially by GPI hydrolysis, which ultimately accounts for a substantial portion of total release. Surface biotinylation assays indicate that GPI-PLC does gain access to extracellular VSG, suggesting that this mode is primed in the starting short stumpy population. Proteolytic release is up-regulated during differentiation and is stereoselectively inhibited by peptidomimetic collagenase inhibitors, implicating a zinc metalloprotease. This protease may be related to TbMSP-B, a trypanosomal homologue of Leishmania major surface protease (MSP) described in the accompanying paper (LaCount, D. J., Gruszynski, A. E., Grandgenett, P. M., Bangs, J. D., and Donelson, J. E. (2003) J. Biol. Chem. 278, 24658-24664). Overall, our results demonstrate that surface coat remodeling during differentiation has multiple mechanisms and that GPI-PLC plays a more significant role in VSG release than previously thought.
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Affiliation(s)
- Amy E Gruszynski
- Department of Biomolecular Chemistry, University of Wisconsin Medical School, Madison 53706, USA
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Wang J, Böhme U, Cross GAM. Structural features affecting variant surface glycoprotein expression in Trypanosoma brucei. Mol Biochem Parasitol 2003; 128:135-45. [PMID: 12742580 DOI: 10.1016/s0166-6851(03)00055-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The glycosylphosphatidylinositol (GPI)-anchored variant surface glycoprotein (VSG) of Trypanosoma brucei is the most abundant GPI-anchored protein expressed on any cell, and is an essential virulence factor. To determine what structural features affect efficient expression of VSG, we made a series of mutations in two VSGs. Inserting 18 amino acids, between the amino- and carboxy-terminal domains, reduced the expression of VSG 221 to about 3% of the wild-type level. When this insertion was combined with deletion of the single carboxy-terminal subdomain, expression was reduced a further three-fold. In VSG 117, which contains two carboxy-terminal subdomains, point mutation of the intervening N-glycosylation site reduced expression about 15-fold. Deleting the most carboxy-terminal subdomain and intervening region, including the N-glycosylation site, reduced expression to 15-20% of wild type VSG, and deletion of both subdomains reduced expression to <1%. Despite their low abundance, all VSG mutants were GPI anchored on the cell surface. Our results suggest that, for a protein to be efficiently displayed on the surface of bloodstream-form T. brucei, it is essential that it contains the conserved structural motifs of a T. brucei VSG. Serum resistance-associated protein (SRA), which confers human infectivity on T. brucei, strongly resembles a VSG deletion mutant. Expression of three epitope-tagged versions of SRA in T. brucei conferred total resistance to human serum. SRA possesses a canonical GPI signal sequence, but we were unable to obtain unequivocal evidence for the presence of a GPI anchor. SRA was not released during osmotic lysis, indicating that it is not GPI anchored on the cell surface.
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Affiliation(s)
- Jun Wang
- Laboratory of Molecular Parasitology, The Rockefeller University, Box 185, 1230 York Avenue, New York, NY 10021-6399, USA
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48
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Lorger M, Engstler M, Homann M, Göringer HU. Targeting the variable surface of African trypanosomes with variant surface glycoprotein-specific, serum-stable RNA aptamers. EUKARYOTIC CELL 2003; 2:84-94. [PMID: 12582125 PMCID: PMC141160 DOI: 10.1128/ec.2.1.84-94.2003] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
African trypanosomes cause sleeping sickness in humans and Nagana in cattle. The parasites multiply in the blood and escape the immune response of the infected host by antigenic variation. Antigenic variation is characterized by a periodic change of the parasite protein surface, which consists of a variant glycoprotein known as variant surface glycoprotein (VSG). Using a SELEX (systematic evolution of ligands by exponential enrichment) approach, we report the selection of small, serum-stable RNAs, so-called aptamers, that bind to VSGs with subnanomolar affinity. The RNAs are able to recognize different VSG variants and bind to the surface of live trypanosomes. Aptamers tethered to an antigenic side group are capable of directing antibodies to the surface of the parasite in vitro. In this manner, the RNAs might provide a new strategy for a therapeutic intervention to fight sleeping sickness.
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Affiliation(s)
- Mihaela Lorger
- Department of Microbiology and Genetics, Darmstadt University of Technology, 64287 Darmstadt, Germany
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Böhme U, Cross GAM. Mutational analysis of the variant surface glycoprotein GPI-anchor signal sequence inTrypanosoma brucei. J Cell Sci 2002; 115:805-16. [PMID: 11865036 DOI: 10.1242/jcs.115.4.805] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
The variant surface glycoproteins (VSG) of Trypanosoma brucei are anchored to the cell surface via a glycosylphosphatidylinositol (GPI) anchor. All GPI-anchored proteins are synthesized with a C-terminal signal sequence,which is replaced by a GPI-anchor in a rapid post-translational transamidation reaction. VSG GPI signal sequences are extraordinarily conserved. They contain either 23 or 17 amino acids, a difference that distinguishes the two major VSG classes, and consist of a spacer sequence followed by a more hydrophobic region. The ω amino acid, to which GPI is transferred, is either Ser,Asp or Asn, the ω+2 amino acid is always Ser, and the ω+7 amino acid is almost always Lys. In order to determine whether this high conservation is necessary for GPI anchoring, we introduced several mutations into the signal peptide. Surprisingly, changing the most conserved amino acids, at positions ω+1, ω+2 and ω+7, had no detectable effect on the efficiency of GPI-anchoring or on protein abundance. Several more extensive changes also had no discernable impact on GPI-anchoring. Deleting the entire 23 amino-acid signal sequence or the 15 amino-acid hydrophobic region generated proteins that were not anchored. Instead of being secreted, these truncated proteins accumulated in the endoplasmic reticulum prior to lysosomal degradation. Replacing the GPI signal sequence with a proven cell-surface membrane-spanning domain reduced expression by about 99%and resulted not in cell surface expression but in accumulation close to the flagellar pocket and in non-lysosomal compartments. These results indicate that the high conservation of the VSG GPI signal sequence is not necessary for efficient expression and GPI attachment. Instead, the GPI anchor is essential for surface expression of VSG. However, because the VSG is a major virulence factor, it is possible that small changes in the efficiency of GPI anchoring,undetectable in our experiments, might have influenced the evolution of VSG GPI signal sequences.
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Affiliation(s)
- Ulrike Böhme
- Laboratory of Molecular Parasitology, The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA
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Denny PW, Field MC, Smith DF. GPI-anchored proteins and glycoconjugates segregate into lipid rafts in Kinetoplastida. FEBS Lett 2001; 491:148-53. [PMID: 11226438 DOI: 10.1016/s0014-5793(01)02172-x] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The plasma membranes of the divergent eukaryotic parasites, Leishmania and Trypanosoma, are highly specialised, with a thick coat of glycoconjugates and glycoproteins playing a central role in virulence. Unusually, the majority of these surface macro-molecules are attached to the plasma membrane via a glycosylphosphatidylinositol (GPI) anchor. In mammalian cells and yeast, many GPI-anchored molecules associate with sphingolipid and cholesterol-rich detergent-resistant membranes, known as lipid rafts. Here we show that GPI-anchored parasite macro-molecules (but not the dual acylated Leishmania surface protein (hydrophilic acylated surface protein) or a subset of the GPI-anchored glycoinositol phospholipid glycolipids) are enriched in a sphingolipid/sterol-rich fraction resistant to cold detergent extraction. This observation is consistent with the presence of functional lipid rafts in these ancient, highly polarised organisms.
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Affiliation(s)
- P W Denny
- Wellcome Trust Laboratories for Molecular Parasitology, Department of Biochemistry, Imperial College of Science, Technology and Medicine, SW7 1AZ, London, UK.
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