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Shimogawa MM, Wijono AS, Wang H, Zhang J, Sha J, Szombathy N, Vadakkan S, Pelayo P, Jonnalagadda K, Wohlschlegel J, Zhou ZH, Hill KL. FAP106 is an interaction hub for assembling microtubule inner proteins at the cilium inner junction. Nat Commun 2023; 14:5225. [PMID: 37633952 PMCID: PMC10460401 DOI: 10.1038/s41467-023-40230-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Accepted: 07/14/2023] [Indexed: 08/28/2023] Open
Abstract
Motility of pathogenic protozoa depends on flagella (synonymous with cilia) with axonemes containing nine doublet microtubules (DMTs) and two singlet microtubules. Microtubule inner proteins (MIPs) within DMTs influence axoneme stability and motility and provide lineage-specific adaptations, but individual MIP functions and assembly mechanisms are mostly unknown. Here, we show in the sleeping sickness parasite Trypanosoma brucei, that FAP106, a conserved MIP at the DMT inner junction, is required for trypanosome motility and functions as a critical interaction hub, directing assembly of several conserved and lineage-specific MIPs. We use comparative cryogenic electron tomography (cryoET) and quantitative proteomics to identify MIP candidates. Using RNAi knockdown together with fitting of AlphaFold models into cryoET maps, we demonstrate that one of these candidates, MC8, is a trypanosome-specific MIP required for parasite motility. Our work advances understanding of MIP assembly mechanisms and identifies lineage-specific motility proteins that are attractive targets to consider for therapeutic intervention.
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Affiliation(s)
- Michelle M Shimogawa
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Angeline S Wijono
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Hui Wang
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, Los Angeles, CA, 90095, USA
- Department of Bioengineering, University of California Los Angeles, Los Angeles, CA, 90095, USA
- California NanoSystems Institute, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Jiayan Zhang
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, Los Angeles, CA, 90095, USA
- California NanoSystems Institute, University of California Los Angeles, Los Angeles, CA, 90095, USA
- Molecular Biology Institute, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Jihui Sha
- Department of Biological Chemistry, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Natasha Szombathy
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Sabeeca Vadakkan
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Paula Pelayo
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Keya Jonnalagadda
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - James Wohlschlegel
- Department of Biological Chemistry, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Z Hong Zhou
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, Los Angeles, CA, 90095, USA.
- California NanoSystems Institute, University of California Los Angeles, Los Angeles, CA, 90095, USA.
- Molecular Biology Institute, University of California Los Angeles, Los Angeles, CA, 90095, USA.
| | - Kent L Hill
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, Los Angeles, CA, 90095, USA.
- California NanoSystems Institute, University of California Los Angeles, Los Angeles, CA, 90095, USA.
- Molecular Biology Institute, University of California Los Angeles, Los Angeles, CA, 90095, USA.
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2
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Sáez Conde J, Dean S. Structure, function and druggability of the African trypanosome flagellum. J Cell Physiol 2022; 237:2654-2667. [PMID: 35616248 PMCID: PMC9323424 DOI: 10.1002/jcp.30778] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Revised: 04/20/2022] [Accepted: 04/25/2022] [Indexed: 11/29/2022]
Abstract
African trypanosomes are early branching protists that cause human and animal diseases, termed trypanosomiases. They have been under intensive study for more than 100 years and have contributed significantly to our understanding of eukaryotic biology. The combination of conserved and parasite‐specific features mean that their flagellum has gained particular attention. Here, we discuss the different structural features of the flagellum and their role in transmission and virulence. We highlight the possibilities of targeting flagellar function to cure trypanosome infections and help in the fight to eliminate trypanosomiases.
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Affiliation(s)
- Julia Sáez Conde
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, UK
| | - Samuel Dean
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, UK
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Dean S. Basic Biology of Trypanosoma brucei with Reference to the Development of Chemotherapies. Curr Pharm Des 2021; 27:1650-1670. [PMID: 33463458 DOI: 10.2174/1381612827666210119105008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 12/01/2020] [Accepted: 12/08/2020] [Indexed: 11/22/2022]
Abstract
Trypanosoma brucei are protozoan parasites that cause the lethal human disease African sleeping sickness and the economically devastating disease of cattle, Nagana. African sleeping sickness, also known as Human African Trypanosomiasis (HAT), threatens 65 million people and animal trypanosomiasis makes large areas of farmland unusable. There is no vaccine and licensed therapies against the most severe, late-stage disease are toxic, impractical and ineffective. Trypanosomes are transmitted by tsetse flies, and HAT is therefore predominantly confined to the tsetse fly belt in sub-Saharan Africa. They are exclusively extracellular and they differentiate between at least seven developmental forms that are highly adapted to host and vector niches. In the mammalian (human) host they inhabit the blood, cerebrospinal fluid (late-stage disease), skin, and adipose fat. In the tsetse fly vector they travel from the tsetse midgut to the salivary glands via the ectoperitrophic space and proventriculus. Trypanosomes are evolutionarily divergent compared with most branches of eukaryotic life. Perhaps most famous for their extraordinary mechanisms of monoallelic gene expression and antigenic variation, they have also been investigated because much of their biology is either highly unconventional or extreme. Moreover, in addition to their importance as pathogens, many researchers have been attracted to the field because trypanosomes have some of the most advanced molecular genetic tools and database resources of any model system. The following will cover just some aspects of trypanosome biology and how its divergent biochemistry has been leveraged to develop drugs to treat African sleeping sickness. This is by no means intended to be a comprehensive survey of trypanosome features. Rather, I hope to present trypanosomes as one of the most fascinating and tractable systems to do discovery biology.
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Affiliation(s)
- Samuel Dean
- Warwick Medical School, University of Warwick, Coventry, CV4 7AL, United Kingdom
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4
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Imhof S, Zhang J, Wang H, Bui KH, Nguyen H, Atanasov I, Hui WH, Yang SK, Zhou ZH, Hill KL. Cryo electron tomography with volta phase plate reveals novel structural foundations of the 96-nm axonemal repeat in the pathogen Trypanosoma brucei. eLife 2019; 8:e52058. [PMID: 31710293 PMCID: PMC6974359 DOI: 10.7554/elife.52058] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Accepted: 11/11/2019] [Indexed: 12/12/2022] Open
Abstract
The 96-nm axonemal repeat includes dynein motors and accessory structures as the foundation for motility of eukaryotic flagella and cilia. However, high-resolution 3D axoneme structures are unavailable for organisms among the Excavates, which include pathogens of medical and economic importance. Here we report cryo electron tomography structures of the 96-nm repeat from Trypanosoma brucei, a protozoan parasite in the Excavate lineage that causes African trypanosomiasis. We examined bloodstream and procyclic life cycle stages, and a knockdown lacking DRC11/CMF22 of the nexin dynein regulatory complex (NDRC). Sub-tomogram averaging yields a resolution of 21.8 Å for the 96-nm repeat. We discovered several lineage-specific structures, including novel inter-doublet linkages and microtubule inner proteins (MIPs). We establish that DRC11/CMF22 is required for the NDRC proximal lobe that binds the adjacent doublet microtubule. We propose that lineage-specific elaboration of axoneme structure in T. brucei reflects adaptations to support unique motility needs in diverse host environments.
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Affiliation(s)
- Simon Imhof
- Department of Microbiology, Immunology and Molecular GeneticsUniversity of California, Los AngelesLos AngelesUnited States
| | - Jiayan Zhang
- Department of Microbiology, Immunology and Molecular GeneticsUniversity of California, Los AngelesLos AngelesUnited States
- Molecular Biology InstituteUniversity of California, Los AngelesLos AngelesUnited States
- California NanoSystems InstituteUniversity of California, Los AngelesLos AngelesUnited States
| | - Hui Wang
- Department of Microbiology, Immunology and Molecular GeneticsUniversity of California, Los AngelesLos AngelesUnited States
- California NanoSystems InstituteUniversity of California, Los AngelesLos AngelesUnited States
- Department of BioengineeringUniversity of California, Los AngelesLos AngelesUnited States
| | - Khanh Huy Bui
- Department of Anatomy and Cell BiologyMcGill UniversityMontrealUnited States
| | - Hoangkim Nguyen
- Department of Microbiology, Immunology and Molecular GeneticsUniversity of California, Los AngelesLos AngelesUnited States
| | - Ivo Atanasov
- California NanoSystems InstituteUniversity of California, Los AngelesLos AngelesUnited States
| | - Wong H Hui
- California NanoSystems InstituteUniversity of California, Los AngelesLos AngelesUnited States
| | - Shun Kai Yang
- Department of Anatomy and Cell BiologyMcGill UniversityMontrealUnited States
| | - Z Hong Zhou
- Department of Microbiology, Immunology and Molecular GeneticsUniversity of California, Los AngelesLos AngelesUnited States
- Molecular Biology InstituteUniversity of California, Los AngelesLos AngelesUnited States
- California NanoSystems InstituteUniversity of California, Los AngelesLos AngelesUnited States
- Department of BioengineeringUniversity of California, Los AngelesLos AngelesUnited States
| | - Kent L Hill
- Department of Microbiology, Immunology and Molecular GeneticsUniversity of California, Los AngelesLos AngelesUnited States
- Molecular Biology InstituteUniversity of California, Los AngelesLos AngelesUnited States
- California NanoSystems InstituteUniversity of California, Los AngelesLos AngelesUnited States
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Ichikawa M, Bui KH. Microtubule Inner Proteins: A Meshwork of Luminal Proteins Stabilizing the Doublet Microtubule. Bioessays 2018; 40. [PMID: 29430673 DOI: 10.1002/bies.201700209] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2017] [Revised: 01/05/2018] [Indexed: 11/11/2022]
Abstract
Motile eukaryotic cilia and flagella are hair-like organelles responsible for cell motility and mucociliary clearance. Using cryo-electron tomography, it has been shown that the doublet microtubule, the cytoskeleton core of the cilia and flagella, has microtubule inner protein structures binding periodically inside its lumen. More recently, single-particle cryo-electron microscopy analyses of isolated doublet microtubules have shown that microtubule inner proteins form a meshwork inside the doublet microtubule. High-resolution structures revealed new types of interactions between the microtubule inner proteins and the tubulin lattice. In addition, they offered insights into the potential roles of microtubule inner proteins in the stabilization and assembly of the doublet microtubule. Herein, we review our new insights into microtubule inner proteins from the doublet microtubule together with the current body of literature on microtubule inner proteins.
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Affiliation(s)
- Muneyoshi Ichikawa
- Department of Anatomy and Cell Biology, McGill University, Montréal, Québec, Canada H3A 0C7
| | - Khanh Huy Bui
- Department of Anatomy and Cell Biology, McGill University, Montréal, Québec, Canada H3A 0C7.,Groupe de Recherche Axé sur la Structure des Protéines (GRASP), Montréal, Québec, Canada H3A 0C7
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6
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Zabeo D, Heumann JM, Schwartz CL, Suzuki-Shinjo A, Morgan G, Widlund PO, Höög JL. A lumenal interrupted helix in human sperm tail microtubules. Sci Rep 2018; 8:2727. [PMID: 29426884 PMCID: PMC5807425 DOI: 10.1038/s41598-018-21165-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 01/26/2018] [Indexed: 01/16/2023] Open
Abstract
Eukaryotic flagella are complex cellular extensions involved in many human diseases gathered under the term ciliopathies. Currently, detailed insights on flagellar structure come mostly from studies on protists. Here, cryo-electron tomography (cryo-ET) was performed on intact human spermatozoon tails and showed a variable number of microtubules in the singlet region (inside the end-piece). Inside the microtubule plus end, a novel left-handed interrupted helix which extends several micrometers was discovered. This structure was named Tail Axoneme Intra-Lumenal Spiral (TAILS) and binds directly to 11 protofilaments on the internal microtubule wall, in a coaxial fashion with the surrounding microtubule lattice. It leaves a gap over the microtubule seam, which was directly visualized in both singlet and doublet microtubules. We speculate that TAILS may stabilize microtubules, enable rapid swimming or play a role in controlling the swimming direction of spermatozoa.
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Affiliation(s)
- Davide Zabeo
- Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, 41390, Sweden
| | - John M Heumann
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO, 80309, USA
| | - Cindi L Schwartz
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO, 80309, USA
| | - Azusa Suzuki-Shinjo
- Krefting Research Centre, University of Gothenburg, Gothenburg, 41390, Sweden
| | - Garry Morgan
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO, 80309, USA
| | - Per O Widlund
- Sahlgrenska Academy, University of Gothenburg, Gothenburg, 41390, Sweden
| | - Johanna L Höög
- Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, 41390, Sweden.
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7
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Vaughan S, Gull K. Basal body structure and cell cycle-dependent biogenesis in Trypanosoma brucei. Cilia 2016; 5:5. [PMID: 26862392 PMCID: PMC4746817 DOI: 10.1186/s13630-016-0023-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Accepted: 01/19/2016] [Indexed: 11/10/2022] Open
Abstract
Basal bodies are microtubule-based organelles that assemble cilia and flagella, which are critical for motility and sensory functions in all major eukaryotic lineages. The core structure of the basal body is highly conserved, but there is variability in biogenesis and additional functions that are organism and cell type specific. Work carried out in the protozoan parasite Trypanosoma brucei has arguably produced one of the most detailed dissections of basal body structure and biogenesis within the context of the flagellar pocket and associated organelles. In this review, we provide a detailed overview of the basic basal body structure in T. brucei along with the accessory structures and show how basal body movements during the basal body duplication cycle orchestrate cell and organelle morphogenesis. With this in-depth three-dimensional knowledge, identification of many basal body genes coupled with excellent genetic tools makes it an attractive model organism to study basal body biogenesis and maintenance.
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Affiliation(s)
- Sue Vaughan
- Department of Biological and Medical Sciences, Faculty of Health and Life Science, Oxford Brookes University, Oxford, OX3 0BP UK
| | - Keith Gull
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford, OX1 3RE UK
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8
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Basal body multipotency and axonemal remodelling are two pathways to a 9+0 flagellum. Nat Commun 2015; 6:8964. [PMID: 26667778 PMCID: PMC4682162 DOI: 10.1038/ncomms9964] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 10/21/2015] [Indexed: 02/07/2023] Open
Abstract
Eukaryotic cilia/flagella exhibit two characteristic ultrastructures reflecting two main functions; a 9+2 axoneme for motility and a 9+0 axoneme for sensation and signalling. Whether, and if so how, they interconvert is unclear. Here we analyse flagellum length, structure and molecular composition changes in the unicellular eukaryotic parasite Leishmania during the transformation of a life cycle stage with a 9+2 axoneme (the promastigote) to one with a 9+0 axoneme (the amastigote). We show 9+0 axonemes can be generated by two pathways: by de novo formation and by restructuring of existing 9+2 axonemes associated with decreased intraflagellar transport. Furthermore, pro-basal bodies formed under conditions conducive for 9+2 axoneme formation can form a 9+0 axoneme de novo. We conclude that pro-centrioles/pro-basal bodies are multipotent and not committed to form either a 9+2 or 9+0 axoneme. In an alternative pathway structures can also be removed from existing 9+2 axonemes to convert them to 9+0. Whether basal bodies are pre-committed to form 9+2 motile or 9+0 sensory axonemes and whether interconversion occurs between the two types of axonemes is not clear. Here, the authors used the unicellular eukaryote Leishmania as a model system to demonstrate that 9+0 axonemes can be formed de novo or by restructuring of 9+2 axonemes.
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Gluenz E, Wheeler RJ, Hughes L, Vaughan S. Scanning and three-dimensional electron microscopy methods for the study of Trypanosoma brucei and Leishmania mexicana flagella. Methods Cell Biol 2015; 127:509-42. [PMID: 25837406 PMCID: PMC4419368 DOI: 10.1016/bs.mcb.2014.12.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Three-dimensional electron microscopy tools have revolutionized our understanding of cell structure and molecular complexes in biology. Here, we describe methods for studying flagellar ultrastructure and biogenesis in two unicellular parasites-Trypanosoma brucei and Leishmania mexicana. We describe methods for the preparation of these parasites for scanning electron microscopy cellular electron tomography, and serial block face scanning electron microscopy (SBFSEM). These parasites have a highly ordered cell shape and form, with a defined positioning of internal cytoskeletal structures and organelles. We show how knowledge of these can be used to dissect cell cycles in both parasites and identify the old flagellum from the new in T. brucei. Finally, we demonstrate the use of SBFSEM three-dimensional models for analysis of individual whole cells, demonstrating the excellent potential this technique has for future studies of mutant cell lines.
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Affiliation(s)
- Eva Gluenz
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | | | - Louise Hughes
- Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, UK
| | - Sue Vaughan
- Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, UK
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Ralston KS, Kabututu ZP, Melehani JH, Oberholzer M, Hill KL. The Trypanosoma brucei flagellum: moving parasites in new directions. Annu Rev Microbiol 2009; 63:335-62. [PMID: 19575562 PMCID: PMC3821760 DOI: 10.1146/annurev.micro.091208.073353] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
African trypanosomes are devastating human and animal pathogens. Trypanosoma brucei rhodesiense and T. b. gambiense subspecies cause the fatal human disease known as African sleeping sickness. It is estimated that several hundred thousand new infections occur annually and the disease is fatal if untreated. T. brucei is transmitted by the tsetse fly and alternates between bloodstream-form and insect-form life cycle stages that are adapted to survive in the mammalian host and the insect vector, respectively. The importance of the flagellum for parasite motility and attachment to the tsetse fly salivary gland epithelium has been appreciated for many years. Recent studies have revealed both conserved and novel features of T. brucei flagellum structure and composition, as well as surprising new functions that are outlined here. These discoveries are important from the standpoint of understanding trypanosome biology and identifying novel drug targets, as well as for advancing our understanding of fundamental aspects of eukaryotic flagellum structure and function.
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Affiliation(s)
- Katherine S. Ralston
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, California 90095
| | - Zakayi P. Kabututu
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, California 90095
| | - Jason H. Melehani
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, California 90095
| | - Michael Oberholzer
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, California 90095
| | - Kent L. Hill
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, California 90095
- Molecular Biology Institute, University of California, Los Angeles, California 90095
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Axoneme beta-tubulin sequence determines attachment of outer dynein arms. Curr Biol 2008; 18:911-4. [PMID: 18571413 DOI: 10.1016/j.cub.2008.05.031] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2008] [Revised: 05/13/2008] [Accepted: 05/14/2008] [Indexed: 11/25/2022]
Abstract
Axonemes of motile eukaryotic cilia and flagella have a conserved structure of nine doublet microtubules surrounding a central pair of microtubules. Outer and inner dynein arms on the doublets mediate axoneme motility [1]. Outer dynein arms (ODAs) attach to the doublets at specific interfaces [2-5]. However, the molecular contacts of ODA-associated proteins with tubulins of the doublet microtubules are not known. We report here that attachment of ODAs requires glycine 56 in the beta-tubulin internal variable region (IVR). We show that in Drosophila spermatogenesis, a single amino acid change at this position results in sperm axonemes markedly deficient in ODAs. Moreover, we found that axonemal beta-tubulins throughout the phylogeny have invariant glycine 56 and a strongly conserved IVR, whereas nonaxonemal beta-tubulins vary widely in IVR sequences. Our data reveal a deeply conserved physical requirement for assembly of the macromolecular architecture of the motile axoneme. Amino acid 56 projects into the microtubule lumen [6]. Imaging studies of axonemes indicate that several proteins may interact with the doublet-microtubule lumen [3, 4, 7, 8]. This region of beta-tubulin may determine the conformation necessary for correct attachment of ODAs, or there may be sequence-specific interaction between beta-tubulin and a protein involved in ODA attachment or stabilization.
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12
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Biogenesis of the trypanosome endo-exocytotic organelle is cytoskeleton mediated. PLoS Biol 2008; 6:e105. [PMID: 18462016 PMCID: PMC2365980 DOI: 10.1371/journal.pbio.0060105] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2007] [Accepted: 03/17/2008] [Indexed: 12/31/2022] Open
Abstract
Trypanosoma brucei is a protozoan parasite that is used as a model organism to study such biological phenomena as gene expression, protein trafficking, and cytoskeletal biogenesis. In T. brucei, endocytosis and exocytosis occur exclusively through a sequestered organelle called the flagellar pocket (FP), an invagination of the pellicular membrane. The pocket is the sole site for specific receptors thus maintaining them inaccessible to components of the innate immune system of the mammalian host. The FP is also responsible for the sorting of protective parasite glycoproteins targeted to, or recycling from, the pellicular membrane, and for the removal of host antibodies from the cell surface. Here, we describe the first characterisation of a flagellar pocket cytoskeletal protein, BILBO1. BILBO1 functions to form a cytoskeleton framework upon which the FP is made and which is also required and essential for FP biogenesis and cell survival. Remarkably, RNA interference (RNAi)-mediated ablation of BILBO1 in insect procyclic-form parasites prevents FP biogenesis and induces vesicle accumulation, Golgi swelling, the aberrant repositioning of the new flagellum, and cell death. Cultured bloodstream-form parasites are also nonviable when subjected to BILBO1 RNAi. These results provide the first molecular evidence for cytoskeletally mediated FP biogenesis. Trypanosomes are ubiquitous unicellular parasites that infect humans, animals, insects, and plants. African, Asian, and some South American trypanosomes have evolved the amazing ability to change their surface coat proteins, an essential strategy for their survival. The surface coat proteins are recycled and targeted to the surface of the parasite via an endocytic and exocytotic organelle called the flagellar pocket, which is sequestered in the trypanosome cell's cytoplasm. The flagellar pocket is also used to remove host-derived antibodies that are bound to the surface of the parasite, making this organelle critical for the parasite's evasion of the host immune system. We describe a novel protein, “BILBO1,” which was identified from the insect-form parasite of the African trypanosome Trypanosoma brucei. We show that BILBO1 is part of a ring or horseshoe-like cytoskeletal structure that is located in a region of the flagellar pocket called the collar. When BILBO1 transcripts were knocked down with inducible RNA interference, trypanosome cells became arrested in a post-mitotic cell-cycle stage. Induced cells lost the normal flagellum-to-cell-body attachment, were unable to regulate endocytosis and exocytosis, and most importantly, were unable to construct a new flagellar pocket. These results provide molecular evidence for the idea that flagellar pocket biogenesis is cytoskeletally mediated. RNAi of the parasite protein BILBO1 prevents the biogenesis of the endocytic and exocytotic organelle in Trypanosoma brucei, kills the parasite, and reveals novel insights into how this pathogen organizes and uses one of its distinctive organelles.
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Cyrklaff M, Kudryashev M, Leis A, Leonard K, Baumeister W, Menard R, Meissner M, Frischknecht F. Cryoelectron tomography reveals periodic material at the inner side of subpellicular microtubules in apicomplexan parasites. ACTA ACUST UNITED AC 2007; 204:1281-7. [PMID: 17562819 PMCID: PMC2118598 DOI: 10.1084/jem.20062405] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Microtubules are dynamic cytoskeletal structures important for cell division, polarity, and motility and are therefore major targets for anticancer and antiparasite drugs. In the invasive forms of apicomplexan parasites, which are highly polarized and often motile cells, exceptionally stable subpellicular microtubules determine the shape of the parasite, and serve as tracks for vesicle transport. We used cryoelectron tomography to image cytoplasmic structures in three dimensions within intact, rapidly frozen Plasmodium sporozoites. This approach revealed microtubule walls that are extended at the luminal side by an additional 3 nm compared to microtubules of mammalian cells. Fourier analysis revealed an 8-nm longitudinal periodicity of the luminal constituent, suggesting the presence of a molecule interacting with tubulin dimers. In silico generation and analysis of microtubule models confirmed this unexpected topology. Microtubules from extracted sporozoites and Toxoplasma gondii tachyzoites showed a similar density distribution, suggesting that the putative protein is conserved among Apicomplexa and serves to stabilize microtubules.
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Affiliation(s)
- Marek Cyrklaff
- Department of Molecular Structural Biology, Max Planck Institute for Biochemistry, 82152 Martinsried, Germany.
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14
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Linck RW, Stephens RE. Functional protofilament numbering of ciliary, flagellar, and centriolar microtubules. ACTA ACUST UNITED AC 2007; 64:489-95. [PMID: 17366641 DOI: 10.1002/cm.20202] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
This article discusses the current state of knowledge about the evolutionarily conserved structure of ciliary, flagellar and centriolar microtubules, and formally proposes a functional numbering convention for their protofilaments.
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Affiliation(s)
- Richard W Linck
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minnesota 55455, USA
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