1
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Gray S, Fort C, Wheeler RJ. Intraflagellar transport speed is sensitive to genetic and mechanical perturbations to flagellar beating. J Cell Biol 2024; 223:e202401154. [PMID: 38829962 PMCID: PMC11148470 DOI: 10.1083/jcb.202401154] [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: 01/31/2024] [Revised: 05/01/2024] [Accepted: 05/13/2024] [Indexed: 06/05/2024] Open
Abstract
Two sets of motor proteins underpin motile cilia/flagella function. The axoneme-associated inner and outer dynein arms drive sliding of adjacent axoneme microtubule doublets to periodically bend the flagellum for beating, while intraflagellar transport (IFT) kinesins and dyneins carry IFT trains bidirectionally along the axoneme. Despite assembling motile cilia and flagella, IFT train speeds have only previously been quantified in immobilized flagella-mechanical immobilization or genetic paralysis. This has limited investigation of the interaction between IFT and flagellar beating. Here, in uniflagellate Leishmania parasites, we use high-frequency, dual-color fluorescence microscopy to visualize IFT train movement in beating flagella. We discovered that adhesion of flagella to a microscope slide is detrimental, reducing IFT train speed and increasing train stalling. In flagella free to move, IFT train speed is not strongly dependent on flagella beat type; however, permanent disruption of flagella beating by deletion of genes necessary for formation or regulation of beating showed an inverse correlation of beat frequency and IFT train speed.
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Affiliation(s)
- Sophie Gray
- Nuffield Department of Medicine, Peter Medawar Building for Pathogen Research, University of Oxford, Oxford, UK
| | - Cecile Fort
- Nuffield Department of Medicine, Peter Medawar Building for Pathogen Research, University of Oxford, Oxford, UK
| | - Richard John Wheeler
- Nuffield Department of Medicine, Peter Medawar Building for Pathogen Research, University of Oxford, Oxford, UK
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2
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Grossman-Haham I, Coudray N, Yu Z, Wang F, Zhang N, Bhabha G, Vale RD. Structure of the radial spoke head and insights into its role in mechanoregulation of ciliary beating. Nat Struct Mol Biol 2021; 28:20-28. [PMID: 33318704 PMCID: PMC7855469 DOI: 10.1038/s41594-020-00519-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Accepted: 09/16/2020] [Indexed: 11/14/2022]
Abstract
Motile cilia power cell locomotion and drive extracellular fluid flow by propagating bending waves from their base to tip. The coordinated bending of cilia requires mechanoregulation by the radial spoke (RS) protein complexes and the microtubule central pair (CP). Despite their importance for ciliary motility across eukaryotes, the molecular function of the RSs is unknown. Here, we reconstituted the Chlamydomonas reinhardtii RS head that abuts the CP and determined its structure using single-particle cryo-EM to 3.1-Å resolution, revealing a flat, negatively charged surface supported by a rigid core of tightly intertwined proteins. Mutations in this core, corresponding to those involved in human ciliopathies, compromised the stability of the recombinant complex, providing a molecular basis for disease. Partially reversing the negative charge on the RS surface impaired motility in C. reinhardtii. We propose that the RS-head architecture is well-suited for mechanoregulation of ciliary beating through physical collisions with the CP.
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Affiliation(s)
- Iris Grossman-Haham
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA, USA
| | - Nicolas Coudray
- Department of Cell Biology, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY, USA
- Applied Bioinformatics Laboratories, New York University School of Medicine, New York, NY, USA
| | - Zanlin Yu
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA
| | - Feng Wang
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA
| | - Nan Zhang
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA, USA
| | - Gira Bhabha
- Department of Cell Biology, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY, USA
| | - Ronald D Vale
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA.
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3
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Poghosyan E, Iacovache I, Faltova L, Leitner A, Yang P, Diener DR, Aebersold R, Zuber B, Ishikawa T. The structure and symmetry of the radial spoke protein complex in Chlamydomonas flagella. J Cell Sci 2020; 133:jcs245233. [PMID: 32694165 DOI: 10.1242/jcs.245233] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 06/25/2020] [Indexed: 12/27/2022] Open
Abstract
The radial spoke is a key element in a transducer apparatus controlling the motility of eukaryotic cilia. The transduction biomechanics is a long-standing question in cilia biology. The radial spoke has three regions - a spoke head, a bifurcated neck and a stalk. Although the neck and the stalk are asymmetric, twofold symmetry of the head has remained controversial. In this work we used single particle cryo-electron microscopy (cryo-EM) analysis to generate a 3D structure of the whole radial spoke at unprecedented resolution. We show the head region at 15 Å (1.5 nm) resolution and confirm twofold symmetry. Using distance constraints generated by cross-linking mass spectrometry, we locate two components, RSP2 and RSP4, at the head and neck regions. Our biophysical analysis of isolated RSP4, RSP9, and RSP10 affirmed their oligomeric state. Our results enable us to redefine the boundaries of the regions and propose a model of organization of the radial spoke component proteins.
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Affiliation(s)
- Emiliya Poghosyan
- Paul Scherrer Institute, Department of Biology and Chemistry, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
- ETH Zurich, Department of Biology, Wolfgang-Pauli-Strasse 27, 8093 Zürich, Switzerland
| | - Ioan Iacovache
- University of Bern, Institute of Anatomy, Baltzerstrasse 2, 3012 Bern, Switzerland
| | - Lenka Faltova
- Paul Scherrer Institute, Department of Biology and Chemistry, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Alexander Leitner
- ETH Zurich, Department of Biology, Institute of Molecular Systems Biology, Otto-Stern-Weg 3, 8093 Zürich, Switzerland
| | - Pinfen Yang
- Department of Biological Sciences, Marquette University, Milwaukee, WI 53233, USA
| | - Dennis R Diener
- Paul Scherrer Institute, Department of Biology and Chemistry, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Ruedi Aebersold
- ETH Zurich, Department of Biology, Institute of Molecular Systems Biology, Otto-Stern-Weg 3, 8093 Zürich, Switzerland
- University of Zurich, Faculty of Science, Rämistrasse 71, 8006 Zürich, Switzerland
| | - Benoit Zuber
- University of Bern, Institute of Anatomy, Baltzerstrasse 2, 3012 Bern, Switzerland
| | - Takashi Ishikawa
- Paul Scherrer Institute, Department of Biology and Chemistry, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
- ETH Zurich, Department of Biology, Wolfgang-Pauli-Strasse 27, 8093 Zürich, Switzerland
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4
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Structure and beating behavior of the sperm motility apparatus in aquatic animals. Theriogenology 2019; 135:152-163. [DOI: 10.1016/j.theriogenology.2019.06.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 05/28/2019] [Accepted: 06/04/2019] [Indexed: 01/03/2023]
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5
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Zhu X, Poghosyan E, Rezabkova L, Mehall B, Sakakibara H, Hirono M, Kamiya R, Ishikawa T, Yang P. The roles of a flagellar HSP40 ensuring rhythmic beating. Mol Biol Cell 2018; 30:228-241. [PMID: 30427757 PMCID: PMC6589562 DOI: 10.1091/mbc.e18-01-0047] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
HSP40s are regarded as cochaperones, perpetually shuttling client polypeptides to HSP70s for refolding. However, many HSP40s that are central for disparate processes diverge from this paradigm. To elucidate the noncanonical mechanisms, we investigated HSP40 in the radial spoke (RS) complex in flagella. Disruption of the gene by the MRC1 transposon in Chlamydomonas resulted in jerky flagella. Traditional electron microscopy, cryo-electron tomography, and sub-tomogram analysis revealed RSs of various altered morphologies that, unexpectedly, differed between the two RS species. This indicates that HSP40 locks the RS into a functionally rigid conformation, facilitating its interactions with the adjacent central pair apparatus for transducing locally varied mechanical feedback, which permits rhythmic beating. Missing HSP40, like missing RSs, could be restored in a tip-to-base direction when HSP40 mutants fused with a HSP40 donor cell. However, without concomitant de novo RS assembly, the repair was exceedingly slow, suggesting HSP40/RS-coupled intraflagellar trafficking and assembly. Biochemical analysis and modeling uncovered spoke HSP40’s cochaperone traits. On the basis of our data, we propose that HSP40 accompanies its client RS precursor when traveling to the flagellar tip. Upon arrival, both refold in concert to assemble into the mature configuration. HSP40’s roles in chaperoning and structural maintenance shed new light on its versatility and flagellar biology.
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Affiliation(s)
- Xiaoyan Zhu
- Department of Biological Sciences, Marquette University, Milwaukee, WI 53233
| | - Emiliya Poghosyan
- Laboratory of Biomolecular Research, Division of Biology and Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
| | - Lenka Rezabkova
- Laboratory of Biomolecular Research, Division of Biology and Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
| | - Bridget Mehall
- Department of Biological Sciences, Marquette University, Milwaukee, WI 53233
| | - Hitoshi Sakakibara
- National Institute of Information and Communications Technology (NICT), Advanced ICT Research Institute, Hyogo 651-2492, Japan
| | - Masafumi Hirono
- Department of Frontier Bioscience, Hosei University, Tokyo 184-8584, Japan
| | - Ritsu Kamiya
- Department of Life Science, Faculty of Science, Gakushuin University, Tokyo 171-8588, Japan
| | - Takashi Ishikawa
- Laboratory of Biomolecular Research, Division of Biology and Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
| | - Pinfen Yang
- Department of Biological Sciences, Marquette University, Milwaukee, WI 53233
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6
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Zhu X, Poghosyan E, Gopal R, Liu Y, Ciruelas KS, Maizy Y, Diener DR, King SM, Ishikawa T, Yang P. General and specific promotion of flagellar assembly by a flagellar nucleoside diphosphate kinase. Mol Biol Cell 2017; 28:3029-3042. [PMID: 28877983 PMCID: PMC5662260 DOI: 10.1091/mbc.e17-03-0156] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Revised: 08/25/2017] [Accepted: 08/30/2017] [Indexed: 12/20/2022] Open
Abstract
NDK5 promotes assembly of motile cilia and flagella with its structure and protein phosphorylation–related reactions instead of the canonical NDK activity. The novel mechanisms and dominant-negative effect of mutated functional NDK5 reveal the remarkable versatility of a molecular platform that is used in diverse cellular processes. Nucleoside diphosphate kinases (NDKs) play a central role in diverse cellular processes using the canonical NDK activity or alternative mechanisms that remain poorly defined. Our study of dimeric NDK5 in a flagellar motility control complex, the radial spoke (RS), has revealed new modalities. The flagella in Chlamydomonas ndk5 mutant were paralyzed, albeit only deficient in three RS subunits. RS morphology appeared severely changed in averaged cryo-electron tomograms, suggesting that NDK5 is crucial for the intact spokehead formation as well as RS structural stability. Intriguingly, ndk5’s flagella were also short, resembling those of an allelic spoke-less mutant. All ndk5’s phenotypes were rescued by expressions of NDK5 or a mutated NDK5 lacking the canonical kinase activity. Importantly, the mutated NDK5 that appeared fully functional in ndk5 cells elicited a dominant-negative effect in wild-type cells, causing paralyzed short flagella with hypophosphorylated, less abundant, but intact RSs, and accumulated hypophosphorylated NDK5 in the cell body. We propose that NDK5 dimer is an RS structural subunit with an additional mechanism that uses cross-talk between the two NDK monomers to accelerate phosphorylation-related assembly of RSs and entire flagella.
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Affiliation(s)
- Xiaoyan Zhu
- Department of Biological Sciences, Marquette University, Milwaukee, WI 53233
| | - Emiliya Poghosyan
- Biomolecular Research Laboratory, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
| | - Radhika Gopal
- Department of Biological Sciences, Marquette University, Milwaukee, WI 53233
| | - Yi Liu
- Department of Biological Sciences, Marquette University, Milwaukee, WI 53233
| | - Kristine S Ciruelas
- Department of Biological Sciences, Marquette University, Milwaukee, WI 53233
| | - Yousif Maizy
- Department of Biological Sciences, Marquette University, Milwaukee, WI 53233
| | - Dennis R Diener
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520
| | - Stephen M King
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT 06030-3305
| | - Takashi Ishikawa
- Biomolecular Research Laboratory, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
| | - Pinfen Yang
- Department of Biological Sciences, Marquette University, Milwaukee, WI 53233
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7
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Zhu X, Liu Y, Yang P. Radial Spokes-A Snapshot of the Motility Regulation, Assembly, and Evolution of Cilia and Flagella. Cold Spring Harb Perspect Biol 2017; 9:cshperspect.a028126. [PMID: 27940518 DOI: 10.1101/cshperspect.a028126] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Propulsive forces generated by cilia and flagella are used in events that are critical for the thriving of diverse eukaryotic organisms in their environments. Despite distinctive strokes and regulations, the majority of them adopt the 9+2 axoneme that is believed to exist in the last eukaryotic common ancestor. Only a few outliers have opted for a simpler format that forsakes the signature radial spokes and the central pair apparatus, although both are unnecessary for force generation or rhythmicity. Extensive evidence has shown that they operate as an integral system for motility control. Recent studies have made remarkable progress on the radial spoke. This review will trace how the new structural, compositional, and evolutional insights pose significant implications on flagella biology and, conversely, ciliopathy.
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Affiliation(s)
- Xiaoyan Zhu
- The Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin 53201
| | - Yi Liu
- The Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin 53201
| | - Pinfen Yang
- The Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin 53201
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8
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Onoufriadis A, Shoemark A, Schmidts M, Patel M, Jimenez G, Liu H, Thomas B, Dixon M, Hirst RA, Rutman A, Burgoyne T, Williams C, Scully J, Bolard F, Lafitte JJ, Beales PL, Hogg C, Yang P, Chung EMK, Emes RD, O'Callaghan C, Bouvagnet P, Mitchison HM. Targeted NGS gene panel identifies mutations in RSPH1 causing primary ciliary dyskinesia and a common mechanism for ciliary central pair agenesis due to radial spoke defects. Hum Mol Genet 2014; 23:3362-74. [PMID: 24518672 PMCID: PMC4049301 DOI: 10.1093/hmg/ddu046] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Primary ciliary dyskinesia (PCD) is an inherited chronic respiratory obstructive disease with randomized body laterality and infertility, resulting from cilia and sperm dysmotility. PCD is characterized by clinical variability and extensive genetic heterogeneity, associated with different cilia ultrastructural defects and mutations identified in >20 genes. Next generation sequencing (NGS) technologies therefore present a promising approach for genetic diagnosis which is not yet in routine use. We developed a targeted panel-based NGS pipeline to identify mutations by sequencing of selected candidate genes in 70 genetically undefined PCD patients. This detected loss-of-function RSPH1 mutations in four individuals with isolated central pair (CP) agenesis and normal body laterality, from two unrelated families. Ultrastructural analysis in RSPH1-mutated cilia revealed transposition of peripheral outer microtubules into the ‘empty’ CP space, accompanied by a distinctive intermittent loss of the central pair microtubules. We find that mutations in RSPH1, RSPH4A and RSPH9, which all encode homologs of components of the ‘head’ structure of ciliary radial spoke complexes identified in Chlamydomonas, cause clinical phenotypes that appear to be indistinguishable except at the gene level. By high-resolution immunofluorescence we identified a loss of RSPH4A and RSPH9 along with RSPH1 from RSPH1-mutated cilia, suggesting RSPH1 mutations may result in loss of the entire spoke head structure. CP loss is seen in up to 28% of PCD cases, in whom laterality determination specified by CP-less embryonic node cilia remains undisturbed. We propose this defect could arise from instability or agenesis of the ciliary central microtubules due to loss of their normal radial spoke head tethering.
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Affiliation(s)
- Alexandros Onoufriadis
- Molecular Medicine Unit and Birth Defects Research Centre, Institute of Child Health, University College London, London WC1N 1EH, UK Present address: Department of Medical and Molecular Genetics, Division of Genetics and Molecular Medicine, King's College London School of Medicine, Guy's Hospital, London SE1 9RT, UK
| | - Amelia Shoemark
- Department of Paediatric Respiratory Medicine, Royal Brompton and Harefield NHS Trust, Sydney Street, London SW3 6NP, UK
| | - Miriam Schmidts
- Molecular Medicine Unit and Birth Defects Research Centre, Institute of Child Health, University College London, London WC1N 1EH, UK
| | - Mitali Patel
- Molecular Medicine Unit and Birth Defects Research Centre, Institute of Child Health, University College London, London WC1N 1EH, UK
| | - Gina Jimenez
- Laboratoire Cardiogénétique, Equipe d'Accueil 4173, Université Lyon 1, Hôpital Nord-Ouest, Villefranche sur Saône, Lyon, France Laboratoire Cardiogénétique, Hospices Civils de Lyon, Groupe Hospitalier Est, 69677 Bron, France
| | - Hui Liu
- Laboratoire Cardiogénétique, Equipe d'Accueil 4173, Université Lyon 1, Hôpital Nord-Ouest, Villefranche sur Saône, Lyon, France Laboratoire Cardiogénétique, Hospices Civils de Lyon, Groupe Hospitalier Est, 69677 Bron, France
| | - Biju Thomas
- Department of Infection, Immunity and Inflammation, Division of Child Health, CSB, University of Leicester, Leicester LE2 7LX, UK
| | - Mellisa Dixon
- Department of Paediatric Respiratory Medicine, Royal Brompton and Harefield NHS Trust, Sydney Street, London SW3 6NP, UK
| | - Robert A Hirst
- Department of Infection, Immunity and Inflammation, Division of Child Health, CSB, University of Leicester, Leicester LE2 7LX, UK
| | - Andrew Rutman
- Department of Infection, Immunity and Inflammation, Division of Child Health, CSB, University of Leicester, Leicester LE2 7LX, UK
| | - Thomas Burgoyne
- Institute of Ophthalmology, University College London, London EC1V 9EL, UK
| | - Christopher Williams
- Department of Infection, Immunity and Inflammation, Division of Child Health, CSB, University of Leicester, Leicester LE2 7LX, UK
| | - Juliet Scully
- Molecular Medicine Unit and Birth Defects Research Centre, Institute of Child Health, University College London, London WC1N 1EH, UK
| | - Florence Bolard
- Service de Pneumologie, Centre Hospitalier Régional de Roubaix, Hôpital Victor Provo, Roubaix, France
| | - Jean-Jacques Lafitte
- Département de Pneumologie, Centre Hospitalier Régional Universitaire de Lille, Hôpital Albert Calmette, Université Lille 2, Lille, France
| | - Philip L Beales
- Molecular Medicine Unit and Birth Defects Research Centre, Institute of Child Health, University College London, London WC1N 1EH, UK
| | - Claire Hogg
- Department of Paediatric Respiratory Medicine, Royal Brompton and Harefield NHS Trust, Sydney Street, London SW3 6NP, UK
| | - Pinfen Yang
- Department of Biology, Marquette University, Milwaukee, WI 53233, USA
| | - Eddie M K Chung
- General and Adolescent Paediatric Unit, Institute of Child Health, University College London, London, UK
| | - Richard D Emes
- School of Veterinary Medicine and Science, University of Nottingham, Leicestershire LE12 5RD, UK Advanced Data Analysis Centre, University of Nottingham, Sutton Bonington Campus, Leicestershire LE12 5RD, UK
| | - Christopher O'Callaghan
- Department of Infection, Immunity and Inflammation, Division of Child Health, CSB, University of Leicester, Leicester LE2 7LX, UK Department of Respiratory Medicine, Portex Unit, Institute of Child Health, University College London and Great Ormond Street Hospital, 30 Guilford Street, London WC1N 1EH, UK
| | | | - Patrice Bouvagnet
- Laboratoire Cardiogénétique, Equipe d'Accueil 4173, Université Lyon 1, Hôpital Nord-Ouest, Villefranche sur Saône, Lyon, France Laboratoire Cardiogénétique, Hospices Civils de Lyon, Groupe Hospitalier Est, 69677 Bron, France Service de Cardiologie Pédiatrique, Hospices Civils de Lyon, Groupe Hospitalier Est, 69677 Bron, France
| | - Hannah M Mitchison
- Molecular Medicine Unit and Birth Defects Research Centre, Institute of Child Health, University College London, London WC1N 1EH, UK
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Sivadas P, Dienes JM, St Maurice M, Meek WD, Yang P. A flagellar A-kinase anchoring protein with two amphipathic helices forms a structural scaffold in the radial spoke complex. ACTA ACUST UNITED AC 2013; 199:639-51. [PMID: 23148234 PMCID: PMC3494852 DOI: 10.1083/jcb.201111042] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Amphipathic helices in the A-kinase anchoring protein RSP3 bind to spoke proteins involved in the assembly and modulation of the flagellar radial spoke complex, expanding the repertoire of these versatile helical protein motifs. A-kinase anchoring proteins (AKAPs) contain an amphipathic helix (AH) that binds the dimerization and docking (D/D) domain, RIIa, in cAMP-dependent protein kinase A (PKA). Many AKAPs were discovered solely based on the AH–RIIa interaction in vitro. An RIIa or a similar Dpy-30 domain is also present in numerous diverged molecules that are implicated in critical processes as diverse as flagellar beating, membrane trafficking, histone methylation, and stem cell differentiation, yet these molecules remain poorly characterized. Here we demonstrate that an AKAP, RSP3, forms a dimeric structural scaffold in the flagellar radial spoke complex, anchoring through two distinct AHs, the RIIa and Dpy-30 domains, in four non-PKA spoke proteins involved in the assembly and modulation of the complex. Interestingly, one AH can bind both RIIa and Dpy-30 domains in vitro. Thus, AHs and D/D domains constitute a versatile yet potentially promiscuous system for localizing various effector mechanisms. These results greatly expand the current concept about anchoring mechanisms and AKAPs.
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Affiliation(s)
- Priyanka Sivadas
- Department of Biological Sciences, Marquette University, Milwaukee, WI 53201, USA
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10
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Judelson HS, Shrivastava J, Manson J. Decay of genes encoding the oomycete flagellar proteome in the downy mildew Hyaloperonospora arabidopsidis. PLoS One 2012; 7:e47624. [PMID: 23077652 PMCID: PMC3471859 DOI: 10.1371/journal.pone.0047624] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Accepted: 09/19/2012] [Indexed: 11/19/2022] Open
Abstract
Zoospores are central to the life cycles of most of the eukaryotic microbes known as oomycetes, but some genera have lost the ability to form these flagellated cells. In the plant pathogen Phytophthora infestans, genes encoding 257 proteins associated with flagella were identified by comparative genomics. These included the main structural components of the axoneme and basal body, proteins involved in intraflagellar transport, regulatory proteins, enzymes for maintaining ATP levels, and others. Transcripts for over three-quarters of the genes were up-regulated during sporulation, and persisted to varying degrees in the pre-zoospore stage (sporangia) and motile zoospores. Nearly all of these genes had orthologs in other eukaryotes that form flagella or cilia, but not species that lack the organelle. Orthologs of 211 of the genes were also absent from a sister taxon to P. infestans that lost the ability to form flagella, the downy mildew Hyaloperonospora arabidopsidis. Many of the genes retained in H. arabidopsidis were also present in other non-flagellates, suggesting that they play roles both in flagella and other cellular processes. Remnants of the missing genes were often detected in the H. arabidopsidis genome. Degradation of the genes was associated with local compaction of the chromosome and a heightened propensity towards genome rearrangements, as such regions were less likely to share synteny with P. infestans.
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Affiliation(s)
- Howard S Judelson
- Department of Plant Pathology and Microbiology, University of California Riverside, Riverside, California, United States of America.
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11
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Anomalies in the motion dynamics of long-flagella mutants of Chlamydomonas reinhardtii. J Biol Phys 2012; 39:1-14. [PMID: 23860831 DOI: 10.1007/s10867-012-9282-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Accepted: 08/06/2012] [Indexed: 10/27/2022] Open
Abstract
Chlamydomonas reinhardtii has long been used as a model organism in studies of cell motility and flagellar dynamics. The motility of the well-conserved '9+2' axoneme in its flagella remains a subject of immense curiosity. Using high-speed videography and morphological analyses, we have characterized long-flagella mutants (lf1, lf2-1, lf2-5, lf3-2, and lf4) of C. reinhardtii for biophysical parameters such as swimming velocities, waveforms, beat frequencies, and swimming trajectories. These mutants are aberrant in proteins involved in the regulation of flagellar length and bring about a phenotypic increase in this length. Our results reveal that the flagellar beat frequency and swimming velocity are negatively correlated with the length of the flagella. When compared to the wild-type, any increase in the flagellar length reduces both the swimming velocities (by 26-57%) and beat frequencies (by 8-16%). We demonstrate that with no apparent aberrations/ultrastructural deformities in the mutant axonemes, it is this increased length that has a critical role to play in the motion dynamics of C. reinhardtii cells, and, provided there are no significant changes in their flagellar proteome, any increase in this length compromises the swimming velocity either by reduction of the beat frequency or by an alteration in the waveform of the flagella.
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12
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The DPY-30 domain and its flanking sequence mediate the assembly and modulation of flagellar radial spoke complexes. Mol Cell Biol 2012; 32:4012-24. [PMID: 22851692 DOI: 10.1128/mcb.06602-11] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
RIIa is known as the dimerization and docking (D/D) domain of the cyclic AMP (cAMP)-dependent protein kinase. However, numerous molecules, including radial spoke protein 2 (RSP2) in Chlamydomonas flagella, also contain an RIIa or a similar DPY-30 domain. To elucidate new roles of D/D domain-containing proteins, we investigated a panel of RSP2 mutants. An RSP2 mutant had paralyzed flagella defective in RSP2 and multiple subunits near the spokehead. New transgenic strains lacking only the DPY-30 domain in RSP2 were also paralyzed. In contrast, motility was restored in strains that lacked only RSP2's calmodulin-binding C-terminal region. These cells swam normally in dim light but could not maintain typical swimming trajectories under bright illumination. In both deletion transgenic strains, the subunits near the spokehead were restored, but their firm attachment to the spokestalk required the DPY-30 domain. We postulate that the DPY-30-helix dimer is a conserved two-prong linker, required for normal motility, organizing duplicated subunits in the radial spoke stalk and formation of a symmetrical spokehead. Further, the dispensable calmodulin-binding region appears to fine-tune the spokehead for regulation of "steering" motility in the green algae. Thus, in general, D/D domains may function to localize molecular modules for both the assembly and modulation of macromolecular complexes.
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Gupta A, Diener DR, Sivadas P, Rosenbaum JL, Yang P. The versatile molecular complex component LC8 promotes several distinct steps of flagellar assembly. ACTA ACUST UNITED AC 2012; 198:115-26. [PMID: 22753897 PMCID: PMC3392930 DOI: 10.1083/jcb.201111041] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
LC8 is present in various molecular complexes. However, its role in these complexes remains unclear. We discovered that although LC8 is a subunit of the radial spoke (RS) complex in Chlamydomonas flagella, it was undetectable in the RS precursor that is converted into the mature RS at the tip of elongating axonemes. Interestingly, LC8 dimers bound in tandem to the N-terminal region of a spoke phosphoprotein, RS protein 3 (RSP3), that docks RSs to axonemes. LC8 enhanced the binding of RSP3 N-terminal fragments to purified axonemes. Likewise, the N-terminal fragments extracted from axonemes contained LC8 and putative spoke-docking proteins. Lastly, perturbations of RSP3's LC8-binding sites resulted in asynchronous flagella with hypophosphorylated RSP3 and defective associations between LC8, RSs, and axonemes. We propose that at the tip of flagella, an array of LC8 dimers binds to RSP3 in RS precursors, triggering phosphorylation, stalk base formation, and axoneme targeting. These multiple effects shed new light on fundamental questions about LC8-containing complexes and axoneme assembly.
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Affiliation(s)
- Anjali Gupta
- Department of Biological Sciences, Marquette University, Milwaukee, WI 53201, USA
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