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Faria JRC, Tinti M, Marques CA, Zoltner M, Yoshikawa H, Field MC, Horn D. An allele-selective inter-chromosomal protein bridge supports monogenic antigen expression in the African trypanosome. Nat Commun 2023; 14:8200. [PMID: 38081826 PMCID: PMC10713589 DOI: 10.1038/s41467-023-44043-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Accepted: 11/28/2023] [Indexed: 12/18/2023] Open
Abstract
UPF1-like helicases play roles in telomeric heterochromatin formation and X-chromosome inactivation, and also in monogenic variant surface glycoprotein (VSG) expression via VSG exclusion-factor-2 (VEX2), a UPF1-related protein in the African trypanosome. We show that VEX2 associates with chromatin specifically at the single active VSG expression site on chromosome 6, forming an allele-selective connection, via VEX1, to the trans-splicing locus on chromosome 9, physically bridging two chromosomes and the VSG transcription and splicing compartments. We further show that the VEX-complex is multimeric and self-regulates turnover to tightly control its abundance. Using single cell transcriptomics following VEX2-depletion, we observed simultaneous derepression of many other telomeric VSGs and multi-allelic VSG expression in individual cells. Thus, an allele-selective, inter-chromosomal, and self-limiting VEX1-2 bridge supports monogenic VSG expression and multi-allelic VSG exclusion.
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Affiliation(s)
- Joana R C Faria
- Wellcome Centre for Anti-Infectives Research, Biological Chemistry and Drug Discovery, School of Life Sciences, University of Dundee, Dundee, UK.
- Biology Department, University of York, York, UK.
- York Biomedical Research Institute, University of York, York, UK.
| | - Michele Tinti
- Wellcome Centre for Anti-Infectives Research, Biological Chemistry and Drug Discovery, School of Life Sciences, University of Dundee, Dundee, UK
| | - Catarina A Marques
- Wellcome Centre for Anti-Infectives Research, Biological Chemistry and Drug Discovery, School of Life Sciences, University of Dundee, Dundee, UK
- Wellcome Centre for Integrative Parasitology, University of Glasgow, Glasgow, UK
| | - Martin Zoltner
- Wellcome Centre for Anti-Infectives Research, Biological Chemistry and Drug Discovery, School of Life Sciences, University of Dundee, Dundee, UK
- Faculty of Science, Charles University in Prague, Biocev, Vestec, Czech Republic
| | - Harunori Yoshikawa
- Gene Regulation and Expression, School of Life Sciences, University of Dundee, Dundee, UK
- Division of Cell Signaling, Fujii Memorial Institute of Medical Sciences, Institute of Advanced Medical Sciences, Tokushima University, Tokushima, Japan
| | - Mark C Field
- Wellcome Centre for Anti-Infectives Research, Biological Chemistry and Drug Discovery, School of Life Sciences, University of Dundee, Dundee, UK
- Biology Centre, Czech Academy of Sciences, Institute of Parasitology, České Budějovice, Czech Republic
| | - David Horn
- Wellcome Centre for Anti-Infectives Research, Biological Chemistry and Drug Discovery, School of Life Sciences, University of Dundee, Dundee, UK.
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2
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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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3
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Escrivani DO, Scheidt V, Tinti M, Faria J, Horn D. Competition among variants is predictable and contributes to the antigenic variation dynamics of African trypanosomes. PLoS Pathog 2023; 19:e1011530. [PMID: 37459347 PMCID: PMC10374056 DOI: 10.1371/journal.ppat.1011530] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Revised: 07/27/2023] [Accepted: 07/03/2023] [Indexed: 07/28/2023] Open
Abstract
Several persistent pathogens employ antigenic variation to continually evade mammalian host adaptive immune responses. African trypanosomes use variant surface glycoproteins (VSGs) for this purpose, transcribing one telomeric VSG expression-site at a time, and exploiting a reservoir of (sub)telomeric VSG templates to switch the active VSG. It has been known for over fifty years that new VSGs emerge in a predictable order in Trypanosoma brucei, and differential activation frequencies are now known to contribute to the hierarchy. Switching of approximately 0.01% of dividing cells to many new VSGs, in the absence of post-switching competition, suggests that VSGs are deployed in a highly profligate manner, however. Here, we report that switched trypanosomes do indeed compete, in a highly predictable manner that is dependent upon the activated VSG. We induced VSG gene recombination and switching in in vitro culture using CRISPR-Cas9 nuclease to target the active VSG. VSG dynamics, that were independent of host immune selection, were subsequently assessed using RNA-seq. Although trypanosomes activated VSGs from repressed expression-sites at relatively higher frequencies, the population of cells that activated minichromosomal VSGs subsequently displayed a competitive advantage and came to dominate. Furthermore, the advantage appeared to be more pronounced for longer VSGs. Differential growth of switched clones was also associated with wider differences, affecting transcripts involved in nucleolar function, translation, and energy metabolism. We conclude that antigenic variants compete, and that the population of cells that activates minichromosome derived VSGs displays a competitive advantage. Thus, competition among variants impacts antigenic variation dynamics in African trypanosomes and likely prolongs immune evasion with a limited set of antigens.
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Affiliation(s)
- Douglas O Escrivani
- Wellcome Centre for Anti-Infectives Research, School of Life Sciences, University of Dundee, Dow Street, Dundee, United Kingdom
| | - Viktor Scheidt
- Wellcome Centre for Anti-Infectives Research, School of Life Sciences, University of Dundee, Dow Street, Dundee, United Kingdom
| | - Michele Tinti
- Wellcome Centre for Anti-Infectives Research, School of Life Sciences, University of Dundee, Dow Street, Dundee, United Kingdom
| | - Joana Faria
- Wellcome Centre for Anti-Infectives Research, School of Life Sciences, University of Dundee, Dow Street, Dundee, United Kingdom
| | - David Horn
- Wellcome Centre for Anti-Infectives Research, School of Life Sciences, University of Dundee, Dow Street, Dundee, United Kingdom
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4
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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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5
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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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6
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Abstract
African trypanosomes are bloodstream protozoan parasites that infect mammals including humans, where they cause sleeping sickness. Long-lasting infection is required to favor parasite transmission between hosts. Therefore, trypanosomes have developed strategies to continuously escape innate and adaptive responses of the immune system, while also preventing premature death of the host. The pathology linked to infection mainly results from inflammation and includes anemia and brain dysfunction in addition to loss of specificity and memory of the antibody response. The serum of humans contains an efficient trypanolytic factor, the membrane pore-forming protein apolipoprotein L1 (APOL1). In the two human-infective trypanosomes, specific parasite resistance factors inhibit APOL1 activity. In turn, many African individuals express APOL1 variants that counteract these resistance factors, enabling them to avoid sleeping sickness. However, these variants are associated with chronic kidney disease, particularly in the context of virus-induced inflammation such as coronavirus disease 2019. Vaccination perspectives are discussed.
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Affiliation(s)
- Etienne Pays
- Laboratory of Molecular Parasitology, Université Libre de Bruxelles, Gosselies, Belgium;
| | - Magdalena Radwanska
- Laboratory for Biomedical Research, Ghent University Global Campus, Incheon, South Korea.,Department of Biomedical Molecular Biology, Ghent University, Ghent, Belgium;
| | - Stefan Magez
- Laboratory for Biomedical Research, Ghent University Global Campus, Incheon, South Korea.,Laboratory of Cellular and Molecular Immunology, Vrije Universiteit Brussel, Brussels, Belgium; .,Department of Biochemistry and Microbiology, Ghent University, Ghent, Belgium
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7
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Williams DL, Sikora VM, Hammer MA, Amin S, Brinjikji T, Brumley EK, Burrows CJ, Carrillo PM, Cromer K, Edwards SJ, Emri O, Fergle D, Jenkins MJ, Kaushik K, Maydan DD, Woodard W, Clowney EJ. May the Odds Be Ever in Your Favor: Non-deterministic Mechanisms Diversifying Cell Surface Molecule Expression. Front Cell Dev Biol 2022; 9:720798. [PMID: 35087825 PMCID: PMC8787164 DOI: 10.3389/fcell.2021.720798] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2021] [Accepted: 11/24/2021] [Indexed: 12/30/2022] Open
Abstract
How does the information in the genome program the functions of the wide variety of cells in the body? While the development of biological organisms appears to follow an explicit set of genomic instructions to generate the same outcome each time, many biological mechanisms harness molecular noise to produce variable outcomes. Non-deterministic variation is frequently observed in the diversification of cell surface molecules that give cells their functional properties, and is observed across eukaryotic clades, from single-celled protozoans to mammals. This is particularly evident in immune systems, where random recombination produces millions of antibodies from only a few genes; in nervous systems, where stochastic mechanisms vary the sensory receptors and synaptic matching molecules produced by different neurons; and in microbial antigenic variation. These systems employ overlapping molecular strategies including allelic exclusion, gene silencing by constitutive heterochromatin, targeted double-strand breaks, and competition for limiting enhancers. Here, we describe and compare five stochastic molecular mechanisms that produce variety in pathogen coat proteins and in the cell surface receptors of animal immune and neuronal cells, with an emphasis on the utility of non-deterministic variation.
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Affiliation(s)
- Donnell L. Williams
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
- Department of Molecular, Cellular and Developmental Biology, The University of Michigan, Ann Arbor, MI, United States
| | - Veronica Maria Sikora
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Max A. Hammer
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Sayali Amin
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Taema Brinjikji
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Emily K. Brumley
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Connor J. Burrows
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Paola Michelle Carrillo
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Kirin Cromer
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Summer J. Edwards
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Olivia Emri
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Daniel Fergle
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - M. Jamal Jenkins
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
- Department of Molecular, Cellular and Developmental Biology, The University of Michigan, Ann Arbor, MI, United States
| | - Krishangi Kaushik
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Daniella D. Maydan
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Wrenn Woodard
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - E. Josephine Clowney
- Department of Molecular, Cellular and Developmental Biology, The University of Michigan, Ann Arbor, MI, United States
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8
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Knüsel S, Jenni A, Benninger M, Bütikofer P, Roditi I. Persistence of Trypanosoma brucei as early procyclic forms and social motility are dependent on glycosylphosphatidylinositol transamidase. Mol Microbiol 2021; 117:802-817. [PMID: 34954848 PMCID: PMC9303471 DOI: 10.1111/mmi.14873] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Revised: 12/10/2021] [Accepted: 12/21/2021] [Indexed: 12/04/2022]
Abstract
Glycosylphosphatidylinositol (GPI)‐linked molecules are surface‐exposed membrane components that influence the infectivity, virulence and transmission of many eukaryotic pathogens. Procyclic (insect midgut) forms of Trypanosoma brucei do not require GPI‐anchored proteins for growth in suspension culture. Deletion of TbGPI8, and inactivation of the GPI:protein transamidase complex, is tolerated by cultured procyclic forms. Using a conditional knockout, we show TbGPI8 is required for social motility (SoMo). This collective migration by cultured early procyclic forms has been linked to colonization of the tsetse fly digestive tract. The SoMo‐negative phenotype was observed after a lag phase with respect to loss of TbGPI8 and correlated with an unexpectedly slow loss of procyclins, the major GPI‐anchored proteins. Procyclins are not essential for SoMo, however, suggesting a requirement for at least one other GPI‐anchored protein. Loss of TbGPI8 initiates the transition from early to late procyclic forms; this effect was observed in a subpopulation in suspension culture, and was more pronounced when cells were cultured on SoMo plates. Our results indicate two, potentially interlinked, scenarios that may explain the previously reported failure of TbGPI8 deletion mutants to establish a midgut infection in the tsetse fly: interference with stage‐specific gene expression and absence of SoMo.
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Affiliation(s)
- Sebastian Knüsel
- Institute of Cell Biology, University of Bern, 3012, Bern, Switzerland
| | - Aurelio Jenni
- Institute of Biochemistry and Molecular Medicine, University of Bern, 3012, Bern, Switzerland.,Graduate School for Chemical and Biomedical Sciences, University of Bern, 3012, Bern, Switzerland
| | - Mattias Benninger
- Institute of Cell Biology, University of Bern, 3012, Bern, Switzerland
| | - Peter Bütikofer
- Institute of Biochemistry and Molecular Medicine, University of Bern, 3012, Bern, Switzerland
| | - Isabel Roditi
- Institute of Cell Biology, University of Bern, 3012, Bern, Switzerland
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9
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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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10
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Spatial integration of transcription and splicing in a dedicated compartment sustains monogenic antigen expression in African trypanosomes. Nat Microbiol 2021; 6:289-300. [PMID: 33432154 PMCID: PMC7610597 DOI: 10.1038/s41564-020-00833-4] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Accepted: 11/16/2020] [Indexed: 12/13/2022]
Abstract
Highly selective gene expression is a key requirement for antigenic variation in several pathogens, allowing evasion of host immune responses and maintenance of persistent infections 1. African trypanosomes, parasites that cause lethal diseases in humans and livestock, employ an antigenic variation mechanism that involves monogenic antigen expression from a pool of >2600 antigen-coding genes 2. In other eukaryotes, the expression of individual genes can be enhanced by mechanisms involving the juxtaposition of otherwise distal chromosomal loci in the three-dimensional nuclear space 3–5. However, trypanosomes lack classical enhancer sequences or regulated transcription initiation 6,7. In this context, it has remained unclear how genome architecture contributes to monogenic transcription elongation and transcript processing. Here, we show that the single expressed antigen coding gene displays a specific inter-chromosomal interaction with a major mRNA splicing locus. Chromosome conformation capture (Hi-C) revealed a dynamic reconfiguration of this inter-chromosomal interaction upon activation of another antigen. Super-resolution microscopy showed the interaction to be heritable and splicing dependent. We find a specific association of the two genomic loci with the antigen exclusion complex, whereby VEX1 occupied the splicing locus and VEX2 the antigen coding locus. Following VEX2 depletion, loss of monogenic antigen expression was accompanied by increased interactions between previously silent antigen genes and the splicing locus. Our results reveal a mechanism to ensure monogenic expression, where antigen transcription and mRNA splicing occur in a specific nuclear compartment. These findings suggest a new means of post-transcriptional gene regulation.
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11
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Torrecilhas AC, Soares RP, Schenkman S, Fernández-Prada C, Olivier M. Extracellular Vesicles in Trypanosomatids: Host Cell Communication. Front Cell Infect Microbiol 2020; 10:602502. [PMID: 33381465 PMCID: PMC7767885 DOI: 10.3389/fcimb.2020.602502] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Accepted: 11/04/2020] [Indexed: 12/13/2022] Open
Abstract
Trypanosoma cruzi, Trypanosoma brucei and Leishmania (Trypanosomatidae: Kinetoplastida) are parasitic protozoan causing Chagas disease, African Trypanosomiasis and Leishmaniases worldwide. They are vector borne diseases transmitted by triatomine bugs, Tsetse fly, and sand flies, respectively. Those diseases cause enormous economic losses and morbidity affecting not only rural and poverty areas but are also spreading to urban areas. During the parasite-host interaction, those organisms release extracellular vesicles (EVs) that are crucial for the immunomodulatory events triggered by the parasites. EVs are involved in cell-cell communication and can act as important pro-inflammatory mediators. Therefore, interface between EVs and host immune responses are crucial for the immunopathological events that those diseases exhibit. Additionally, EVs from these organisms have a role in the invertebrate hosts digestive tracts prior to parasite transmission. This review summarizes the available data on how EVs from those medically important trypanosomatids affect their interaction with vertebrate and invertebrate hosts.
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Affiliation(s)
- Ana Claudia Torrecilhas
- Departamento de Ciências Farmacêuticas, Federal University of Sao Paulo (UNIFESP), Diadema, Brazil
| | | | - Sergio Schenkman
- Departamento de Microbiologia, Imunologia e Parasitologia, UNIFESP, São Paulo, Brazil
| | | | - Martin Olivier
- The Research Institute of the McGill University Health Centre, McGill University, Montréal, QC, Canada
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Damasceno JD, Marques CA, Black J, Briggs E, McCulloch R. Read, Write, Adapt: Challenges and Opportunities during Kinetoplastid Genome Replication. Trends Genet 2020; 37:21-34. [PMID: 32993968 PMCID: PMC9213392 DOI: 10.1016/j.tig.2020.09.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Revised: 08/31/2020] [Accepted: 09/01/2020] [Indexed: 12/31/2022]
Abstract
The genomes of all organisms are read throughout their growth and development, generating new copies during cell division and encoding the cellular activities dictated by the genome’s content. However, genomes are not invariant information stores but are purposefully altered in minor and major ways, adapting cellular behaviour and driving evolution. Kinetoplastids are eukaryotic microbes that display a wide range of such read–write genome activities, in many cases affecting critical aspects of their biology, such as host adaptation. Here we discuss the range of read–write genome changes found in two well-studied kinetoplastid parasites, Trypanosoma brucei and Leishmania, focusing on recent work that suggests such adaptive genome variation is linked to novel strategies the parasites use to replicate their unconventional genomes. Polycistronic transcription dominates and shapes kinetoplastid genomes, inevitably leading to clashes with DNA replication. By harnessing the resultant DNA damage for adaptation, kinetoplastids have huge potential for dynamic read–write genome variation. Major origins of DNA replication are confined to the boundaries of polycistronic transcription units in the Trypanosoma brucei and Leishmania genomes, putatively limiting DNA damage. Subtelomeres may lack this arrangement, generating read–write hotspots. In T. brucei, early replication of the highly transcribed subtelomeric variant surface glycoprotein (VSG) expression site may ensure replication-transcription clashes within this site to trigger DNA recombination, an event critical for antigenic variation. Leishmania genomes show extensive aneuploidy and copy number variation. Notably, DNA replication requires recombination factors and relies on post-S phase replication of subtelomeres. Evolution of compartmentalised DNA replication programmes underpin important aspects of genome biology in kinetoplastids, illustrating the consolidation of genome maintenance strategies to promote genome plasticity.
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Affiliation(s)
- Jeziel D Damasceno
- The Wellcome Centre for Integrative Parasitology, University of Glasgow, Institute of Infection, Immunity and Inflammation, Sir Graeme Davies Building, 120 University Place, Glasgow, G12 8TA, UK.
| | - Catarina A Marques
- The Wellcome Centre for Integrative Parasitology, University of Glasgow, Institute of Infection, Immunity and Inflammation, Sir Graeme Davies Building, 120 University Place, Glasgow, G12 8TA, UK
| | - Jennifer Black
- The Wellcome Centre for Integrative Parasitology, University of Glasgow, Institute of Infection, Immunity and Inflammation, Sir Graeme Davies Building, 120 University Place, Glasgow, G12 8TA, UK
| | - Emma Briggs
- The Wellcome Centre for Integrative Parasitology, University of Glasgow, Institute of Infection, Immunity and Inflammation, Sir Graeme Davies Building, 120 University Place, Glasgow, G12 8TA, UK; Institute for Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FL, UK
| | - Richard McCulloch
- The Wellcome Centre for Integrative Parasitology, University of Glasgow, Institute of Infection, Immunity and Inflammation, Sir Graeme Davies Building, 120 University Place, Glasgow, G12 8TA, UK.
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13
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Swiatczak B. Genomic Stress Responses Drive Lymphocyte Evolvability: An Ancient and Ubiquitous Mechanism. Bioessays 2020; 42:e2000032. [PMID: 32767393 DOI: 10.1002/bies.202000032] [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: 02/22/2020] [Revised: 07/03/2020] [Indexed: 12/15/2022]
Abstract
Somatic diversification of antigen receptor genes depends on the activity of enzymes whose homologs participate in a mutagenic DNA repair in unicellular species. Indeed, by engaging error-prone polymerases, gap filling molecules and altered mismatch repair pathways, lymphocytes utilize conserved components of genomic stress response systems, which can already be found in bacteria and archaea. These ancient systems of mutagenesis and repair act to increase phenotypic diversity of microbial cell populations and operate to enhance their ability to produce fit variants during stress. Coopted by lymphocytes, the ancient mutagenic processing systems retained their diversification functions instilling the adaptive immune cells with enhanced evolvability and defensive capacity to resist infection and damage. As reviewed here, the ubiquity and conserved character of specialized variation-generating mechanisms from bacteria to lymphocytes highlight the importance of these mechanisms for evolution of life in general.
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Affiliation(s)
- Bartlomiej Swiatczak
- Department of History of Science and Scientific Archeology, University of Science and Technology of China, 96 Jinzhai Rd., Hefei, 230026, China
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14
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Magez S, Pinto Torres JE, Obishakin E, Radwanska M. Infections With Extracellular Trypanosomes Require Control by Efficient Innate Immune Mechanisms and Can Result in the Destruction of the Mammalian Humoral Immune System. Front Immunol 2020; 11:382. [PMID: 32218784 PMCID: PMC7078162 DOI: 10.3389/fimmu.2020.00382] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 02/18/2020] [Indexed: 12/17/2022] Open
Abstract
Salivarian trypanosomes are extracellular parasites that affect humans, livestock, and game animals around the world. Through co-evolution with the mammalian immune system, trypanosomes have developed defense mechanisms that allow them to thrive in blood, lymphoid vessels, and tissue environments such as the brain, the fat tissue, and testes. Trypanosomes have developed ways to circumvent antibody-mediated killing and block the activation of the lytic arm of the complement pathway. Hence, this makes the innate immune control of the infection a crucial part of the host-parasite interaction, determining infection susceptibility, and parasitemia control. Indeed, trypanosomes use a combination of several independent mechanisms to avoid clearance by the humoral immune system. First, perpetuated antigenic variation of the surface coat allows to escape antibody-mediated elimination. Secondly, when antibodies bind to the coat, they are efficiently transported toward the endocytosis pathway, where they are removed from the coat proteins. Finally, trypanosomes engage in the active destruction of the mammalian humoral immune response. This provides them with a rescue solution in case antigenic variation does not confer total immunological invisibility. Both antigenic variation and B cell destruction pose significant hurdles for the development of anti-trypanosome vaccine strategies. However, developing total immune escape capacity and unlimited growth capabilities within a mammalian host is not beneficial for any parasite, as it will result in the accelerated death of the host itself. Hence, trypanosomes have acquired a system of quorum sensing that results in density-dependent population growth arrest in order to prevent overpopulating the host. The same system could possibly sense the infection-associated host tissue damage resulting from inflammatory innate immune responses, in which case the quorum sensing serves to prevent excessive immunopathology and as such also promotes host survival. In order to put these concepts together, this review summarizes current knowledge on the interaction between trypanosomes and the mammalian innate immune system, the mechanisms involved in population growth regulation, antigenic variation and the immuno-destructive effect of trypanosomes on the humoral immune system. Vaccine trials and a discussion on the role of innate immune modulation in these trials are discussed at the end.
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Affiliation(s)
- Stefan Magez
- Laboratory for Biomedical Research, Ghent University Global Campus, Incheon, South Korea.,Department of Biochemistry and Microbiology, Ghent University, Ghent, Belgium.,Laboratory of Cellular and Molecular Immunology, Vrije Universiteit Brussel, Brussels, Belgium
| | | | - Emmanuel Obishakin
- Laboratory for Biomedical Research, Ghent University Global Campus, Incheon, South Korea.,Biotechnology Division, National Veterinary Research Institute, Vom, Nigeria
| | - Magdalena Radwanska
- Laboratory for Biomedical Research, Ghent University Global Campus, Incheon, South Korea.,Department of Biomedical Molecular Biology, Ghent University, Ghent, Belgium
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15
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Aitken EH, Mahanty S, Rogerson SJ. Antibody effector functions in malaria and other parasitic diseases: a few needles and many haystacks. Immunol Cell Biol 2020; 98:264-275. [DOI: 10.1111/imcb.12320] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 01/02/2020] [Accepted: 01/28/2020] [Indexed: 12/13/2022]
Affiliation(s)
- Elizabeth H Aitken
- Department of Medicine The Doherty Institute The University of Melbourne 792 Elizabeth Street Melbourne VIC 3000 Australia
| | - Siddhartha Mahanty
- Department of Medicine The Doherty Institute The University of Melbourne 792 Elizabeth Street Melbourne VIC 3000 Australia
| | - Stephen J Rogerson
- Department of Medicine The Doherty Institute The University of Melbourne 792 Elizabeth Street Melbourne VIC 3000 Australia
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