1
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Liu H, Welburn JPI. A circle of life: platelet and megakaryocyte cytoskeleton dynamics in health and disease. Open Biol 2024; 14:240041. [PMID: 38835242 DOI: 10.1098/rsob.240041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2024] [Accepted: 04/24/2024] [Indexed: 06/06/2024] Open
Abstract
Platelets are blood cells derived from megakaryocytes that play a central role in regulating haemostasis and vascular integrity. The microtubule cytoskeleton of megakaryocytes undergoes a critical dynamic reorganization during cycles of endomitosis and platelet biogenesis. Quiescent platelets have a discoid shape maintained by a marginal band composed of microtubule bundles, which undergoes remarkable remodelling during platelet activation, driving shape change and platelet function. Disrupting or enhancing this process can cause platelet dysfunction such as bleeding disorders or thrombosis. However, little is known about the molecular mechanisms underlying the reorganization of the cytoskeleton in the platelet lineage. Recent studies indicate that the emergence of a unique platelet tubulin code and specific pathogenic tubulin mutations cause platelet defects and bleeding disorders. Frequently, these mutations exhibit dominant negative effects, offering valuable insights into both platelet disease mechanisms and the functioning of tubulins. This review will highlight our current understanding of the role of the microtubule cytoskeleton in the life and death of platelets, along with its relevance to platelet disorders.
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Affiliation(s)
- Haonan Liu
- Wellcome Trust Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3BF, UK
| | - Julie P I Welburn
- Wellcome Trust Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3BF, UK
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2
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Vermeulen BJ, Böhler A, Gao Q, Neuner A, Župa E, Chu Z, Würtz M, Jäkle U, Gruss OJ, Pfeffer S, Schiebel E. γ-TuRC asymmetry induces local protofilament mismatch at the RanGTP-stimulated microtubule minus end. EMBO J 2024; 43:2062-2085. [PMID: 38600243 PMCID: PMC11099078 DOI: 10.1038/s44318-024-00087-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Revised: 03/15/2024] [Accepted: 03/18/2024] [Indexed: 04/12/2024] Open
Abstract
The γ-tubulin ring complex (γ-TuRC) is a structural template for de novo microtubule assembly from α/β-tubulin units. The isolated vertebrate γ-TuRC assumes an asymmetric, open structure deviating from microtubule geometry, suggesting that γ-TuRC closure may underlie regulation of microtubule nucleation. Here, we isolate native γ-TuRC-capped microtubules from Xenopus laevis egg extract nucleated through the RanGTP-induced pathway for spindle assembly and determine their cryo-EM structure. Intriguingly, the microtubule minus end-bound γ-TuRC is only partially closed and consequently, the emanating microtubule is locally misaligned with the γ-TuRC and asymmetric. In the partially closed conformation of the γ-TuRC, the actin-containing lumenal bridge is locally destabilised, suggesting lumenal bridge modulation in microtubule nucleation. The microtubule-binding protein CAMSAP2 specifically binds the minus end of γ-TuRC-capped microtubules, indicating that the asymmetric minus end structure may underlie recruitment of microtubule-modulating factors for γ-TuRC release. Collectively, we reveal a surprisingly asymmetric microtubule minus end protofilament organisation diverging from the regular microtubule structure, with direct implications for the kinetics and regulation of nucleation and subsequent modulation of microtubules during spindle assembly.
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Affiliation(s)
- Bram Ja Vermeulen
- Zentrum für Molekulare Biologie, Universität Heidelberg, DKFZ-ZMBH Allianz, Heidelberg, Germany
| | - Anna Böhler
- Zentrum für Molekulare Biologie, Universität Heidelberg, DKFZ-ZMBH Allianz, Heidelberg, Germany
| | - Qi Gao
- Zentrum für Molekulare Biologie, Universität Heidelberg, DKFZ-ZMBH Allianz, Heidelberg, Germany
| | - Annett Neuner
- Zentrum für Molekulare Biologie, Universität Heidelberg, DKFZ-ZMBH Allianz, Heidelberg, Germany
| | - Erik Župa
- Zentrum für Molekulare Biologie, Universität Heidelberg, DKFZ-ZMBH Allianz, Heidelberg, Germany
| | - Zhenzhen Chu
- Institut für Genetik, Universität Bonn, Bonn, Germany
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education, Beijing), Lymphoma Department, Peking University Cancer Hospital & Institute, Beijing, China
| | - Martin Würtz
- Zentrum für Molekulare Biologie, Universität Heidelberg, DKFZ-ZMBH Allianz, Heidelberg, Germany
| | - Ursula Jäkle
- Zentrum für Molekulare Biologie, Universität Heidelberg, DKFZ-ZMBH Allianz, Heidelberg, Germany
| | | | - Stefan Pfeffer
- Zentrum für Molekulare Biologie, Universität Heidelberg, DKFZ-ZMBH Allianz, Heidelberg, Germany.
| | - Elmar Schiebel
- Zentrum für Molekulare Biologie, Universität Heidelberg, DKFZ-ZMBH Allianz, Heidelberg, Germany.
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3
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Aher A, Urnavicius L, Xue A, Neselu K, Kapoor TM. Structure of the γ-tubulin ring complex-capped microtubule. Nat Struct Mol Biol 2024:10.1038/s41594-024-01264-z. [PMID: 38609661 DOI: 10.1038/s41594-024-01264-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Accepted: 03/04/2024] [Indexed: 04/14/2024]
Abstract
Microtubules are composed of α-tubulin and β-tubulin dimers positioned head-to-tail to form protofilaments that associate laterally in varying numbers. It is not known how cellular microtubules assemble with the canonical 13-protofilament architecture, resulting in micrometer-scale α/β-tubulin tracks for intracellular transport that align with, rather than spiral along, the long axis of the filament. We report that the human ~2.3 MDa γ-tubulin ring complex (γ-TuRC), an essential regulator of microtubule formation that contains 14 γ-tubulins, selectively nucleates 13-protofilament microtubules. Cryogenic electron microscopy reconstructions of γ-TuRC-capped microtubule minus ends reveal the extensive intra-domain and inter-domain motions of γ-TuRC subunits that accommodate luminal bridge components and establish lateral and longitudinal interactions between γ-tubulins and α-tubulins. Our structures suggest that γ-TuRC, an inefficient nucleation template owing to its splayed conformation, can transform into a compacted cap at the microtubule minus end and set the lattice architecture of cellular microtubules.
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Affiliation(s)
- Amol Aher
- Laboratory of Chemistry and Cell Biology, The Rockefeller University, New York, NY, USA
| | - Linas Urnavicius
- Laboratory of Chemistry and Cell Biology, The Rockefeller University, New York, NY, USA
| | - Allen Xue
- Laboratory of Chemistry and Cell Biology, The Rockefeller University, New York, NY, USA
| | - Kasahun Neselu
- Simons Electron Microscopy Center, New York Structural Biology Center, New York, NY, USA
| | - Tarun M Kapoor
- Laboratory of Chemistry and Cell Biology, The Rockefeller University, New York, NY, USA.
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4
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Beaumale E, Van Hove L, Pintard L, Joly N. Microtubule-binding domains in Katanin p80 subunit are essential for severing activity in C. elegans. J Cell Biol 2024; 223:e202308023. [PMID: 38329452 PMCID: PMC10853069 DOI: 10.1083/jcb.202308023] [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: 08/03/2023] [Revised: 11/22/2023] [Accepted: 01/09/2024] [Indexed: 02/09/2024] Open
Abstract
Microtubule-severing enzymes (MSEs), such as Katanin, Spastin, and Fidgetin play essential roles in cell division and neurogenesis. They damage the microtubule (MT) lattice, which can either destroy or amplify the MT cytoskeleton, depending on the cellular context. However, little is known about how they interact with their substrates. We have identified the microtubule-binding domains (MTBD) required for Katanin function in C. elegans. Katanin is a heterohexamer of dimers containing a catalytic subunit p60 and a regulatory subunit p80, both of which are essential for female meiotic spindle assembly. Here, we report that p80-like(MEI-2) dictates Katanin binding to MTs via two MTBDs composed of basic patches. Substituting these patches reduces Katanin binding to MTs, compromising its function in female meiotic-spindle assembly. Structural alignments of p80-like(MEI-2) with p80s from different species revealed that the MTBDs are evolutionarily conserved, even if the specific amino acids involved vary. Our findings highlight the critical importance of the regulatory subunit (p80) in providing MT binding to the Katanin complex.
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Affiliation(s)
- Eva Beaumale
- Université Paris Cité, CNRS, Institut Jacques Monod, Paris, France
| | - Lucie Van Hove
- Université Paris Cité, CNRS, Institut Jacques Monod, Paris, France
| | - Lionel Pintard
- Université Paris Cité, CNRS, Institut Jacques Monod, Paris, France
| | - Nicolas Joly
- Université Paris Cité, CNRS, Institut Jacques Monod, Paris, France
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5
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Pemberton JG, Tenkova T, Felgner P, Zimmerberg J, Balla T, Heuser J. Defining the EM-signature of successful cell-transfection. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.07.583927. [PMID: 38496608 PMCID: PMC10942431 DOI: 10.1101/2024.03.07.583927] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/19/2024]
Abstract
In this report, we describe the architecture of Lipofectamine 2000 and 3000 transfection- reagents, as they appear inside of transfected cells, using classical transmission electron microscopy (EM). We also demonstrate that they provoke consistent structural changes after they have entered cells, changes that not only provide new insights into the mechanism of action of these particular transfection-reagents, but also provide a convenient and robust method for identifying by EM which cells in any culture have been successfully transfected. This also provides clues to the mechanism(s) of their toxic effects, when they are applied in excess. We demonstrate that after being bulk-endocytosed by cells, the cationic spheroids of Lipofectamine remain intact throughout the entire time of culturing, but escape from their endosomes and penetrate directly into the cytoplasm of the cell. In so doing, they provoke a stereotypical recruitment and rearrangement of endoplasmic reticulum (ER), and they ultimately end up escaping into the cytoplasm and forming unique 'inclusion-bodies.' Once free in the cytoplasm, they also invariably develop dense and uniform coatings of cytoplasmic ribosomes on their surfaces, and finally, they become surrounded by 'annulate' lamellae' of the ER. In the end, these annulate-lamellar enclosures become the ultrastructural 'signatures' of these inclusion-bodies, and serve to positively and definitively identify all cells that have been effectively transfected. Importantly, these new EM-observations define several new and unique properties of these classical Lipofectamines, and allow them to be discriminated from other lipoidal or particulate transfection-reagents, which we find do not physically break out of endosomes or end up in inclusion bodies, and in fact, provoke absolutely none of these 'signature' cytoplasmic reactions.
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6
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Brito C, Serna M, Guerra P, Llorca O, Surrey T. Transition of human γ-tubulin ring complex into a closed conformation during microtubule nucleation. Science 2024; 383:870-876. [PMID: 38305685 DOI: 10.1126/science.adk6160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Accepted: 01/22/2024] [Indexed: 02/03/2024]
Abstract
Microtubules are essential for intracellular organization and chromosome segregation. They are nucleated by the γ-tubulin ring complex (γTuRC). However, isolated vertebrate γTuRC adopts an open conformation that deviates from the microtubule structure, raising the question of the nucleation mechanism. In this study, we determined cryo-electron microscopy structures of human γTuRC bound to a nascent microtubule. Structural changes of the complex into a closed conformation ensure that γTuRC templates the 13-protofilament microtubules that exist in human cells. Closure is mediated by a latch that interacts with incorporating tubulin, making it part of the closing mechanism. Further rearrangements involve all γTuRC subunits and the removal of the actin-containing luminal bridge. Our proposed mechanism of microtubule nucleation by human γTuRC relies on large-scale structural changes that are likely the target of regulation in cells.
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Affiliation(s)
- Cláudia Brito
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Marina Serna
- Structural Biology Programme, Spanish National Cancer Research Centre (CNIO), Madrid, Spain
| | - Pablo Guerra
- Cryo-Electron Microscopy Platform-IBMB CSIC, Joint Electron Microscopy Center at ALBA (JEMCA), Barcelona, Spain
| | - Oscar Llorca
- Structural Biology Programme, Spanish National Cancer Research Centre (CNIO), Madrid, Spain
| | - Thomas Surrey
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain
- Universitat Pompeu Fabra (UPF), Barcelona, Spain
- Catalan Institution for Research and Advanced Studies (ICREA), Barcelona, Spain
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Falconieri A, Coppini A, Raffa V. Microtubules as a signal hub for axon growth in response to mechanical force. Biol Chem 2024; 405:67-77. [PMID: 37674311 DOI: 10.1515/hsz-2023-0173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Accepted: 08/12/2023] [Indexed: 09/08/2023]
Abstract
Microtubules are highly polar structures and are characterized by high anisotropy and stiffness. In neurons, they play a key role in the directional transport of vesicles and organelles. In the neuronal projections called axons, they form parallel bundles, mostly oriented with the plus-end towards the axonal termination. Their physico-chemical properties have recently attracted attention as a potential candidate in sensing, processing and transducing physical signals generated by mechanical forces. Here, we discuss the main evidence supporting the role of microtubules as a signal hub for axon growth in response to a traction force. Applying a tension to the axon appears to stabilize the microtubules, which, in turn, coordinate a modulation of axonal transport, local translation and their cross-talk. We speculate on the possible mechanisms modulating microtubule dynamics under tension, based on evidence collected in neuronal and non-neuronal cell types. However, the fundamental question of the causal relationship between these mechanisms is still elusive because the mechano-sensitive element in this chain has not yet been identified.
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Affiliation(s)
| | - Allegra Coppini
- Department of Biology, Università di Pisa, Pisa, 56127, Italy
| | - Vittoria Raffa
- Department of Biology, Università di Pisa, Pisa, 56127, Italy
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8
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Aher A, Urnavicius L, Xue A, Neselu K, Kapoor TM. Structure of the γ-tubulin ring complex-capped microtubule. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.20.567916. [PMID: 38045257 PMCID: PMC10690160 DOI: 10.1101/2023.11.20.567916] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2023]
Abstract
Microtubules are composed of α/β-tubulin dimers positioned head-to-tail to form protofilaments that associate laterally in varying numbers. It is not known how cellular microtubules assemble with the canonical 13-protofilament architecture, resulting in micrometer-scale α/β-tubulin tracks for intracellular transport that align with, rather than spiral along, the filament's long-axis. We report that the human ∼2.3MDa γ-tubulin ring complex (γ-TuRC), an essential regulator of microtubule formation that contains 14 γ-tubulins, selectively nucleates 13-protofilament microtubules. Cryo-EM reconstructions of γ-TuRC-capped microtubule minus-ends reveal the extensive intra- and inter-domain motions of γ-TuRC subunits that accommodate its actin-containing luminal bridge and establish lateral and longitudinal interactions between γ- and α-tubulins. Our structures reveal how free γ-TuRC, an inefficient nucleation template due to its splayed conformation, transforms into a stable cap that blocks addition or loss of α/β-tubulins from minus-ends and sets the lattice architecture of cellular microtubules. One Sentence Summary Structural insights into how the γ-tubulin ring complex nucleates and caps a 13-protofilament microtubule.
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9
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Zhou J, Wang A, Song Y, Liu N, Wang J, Li Y, Liang X, Li G, Chu H, Wang HW. Structural insights into the mechanism of GTP initiation of microtubule assembly. Nat Commun 2023; 14:5980. [PMID: 37749104 PMCID: PMC10519996 DOI: 10.1038/s41467-023-41615-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2022] [Accepted: 09/08/2023] [Indexed: 09/27/2023] Open
Abstract
In eukaryotes, the dynamic assembly of microtubules (MT) plays an important role in numerous cellular processes. The underlying mechanism of GTP triggering MT assembly is still unknown. Here, we present cryo-EM structures of tubulin heterodimer at their GTP- and GDP-bound states, intermediate assembly states of GTP-tubulin, and final assembly stages of MT. Both GTP- and GDP-tubulin heterodimers adopt similar curved conformations with subtle flexibility differences. In head-to-tail oligomers of tubulin heterodimers, the inter-dimer interface of GDP-tubulin exhibits greater flexibility, particularly in tangential bending. Cryo-EM of the intermediate assembly states reveals two types of tubulin lateral contacts, "Tube-bond" and "MT-bond". Further, molecular dynamics (MD) simulations show that GTP triggers lateral contact formation in MT assembly in multiple sequential steps, gradually straightening the curved tubulin heterodimers. Therefore, we propose a flexible model of GTP-initiated MT assembly, including the formation of longitudinal and lateral contacts, to explain the nucleation and assembly of MT.
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Affiliation(s)
- Ju Zhou
- State Key Laboratory of Membrane Biology, Tsinghua University, Beijing, 100084, China
- Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084, China
- Beijing Frontier Research Center for Biological Structures, Tsinghua University, Beijing, 100084, China
- University of California Berkeley, Berkeley, CA, USA
| | - Anhui Wang
- Laboratory of Molecular Modeling and Design, State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Science, 457 Zhongshan Road, Dalian, 116023, China
| | - Yinlong Song
- Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084, China
- Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, Utrecht, Netherlands
| | - Nan Liu
- State Key Laboratory of Membrane Biology, Tsinghua University, Beijing, 100084, China
- Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084, China
- Beijing Frontier Research Center for Biological Structures, Tsinghua University, Beijing, 100084, China
| | - Jia Wang
- State Key Laboratory of Membrane Biology, Tsinghua University, Beijing, 100084, China
- Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084, China
- Beijing Frontier Research Center for Biological Structures, Tsinghua University, Beijing, 100084, China
| | - Yan Li
- Laboratory of Molecular Modeling and Design, State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Science, 457 Zhongshan Road, Dalian, 116023, China
| | - Xin Liang
- Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Guohui Li
- Laboratory of Molecular Modeling and Design, State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Science, 457 Zhongshan Road, Dalian, 116023, China
| | - Huiying Chu
- Laboratory of Molecular Modeling and Design, State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Science, 457 Zhongshan Road, Dalian, 116023, China.
| | - Hong-Wei Wang
- State Key Laboratory of Membrane Biology, Tsinghua University, Beijing, 100084, China.
- Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084, China.
- Beijing Frontier Research Center for Biological Structures, Tsinghua University, Beijing, 100084, China.
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10
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Chandra S, Chatterjee R, Olmsted ZT, Mukherjee A, Paluh JL. Axonal transport during injury on a theoretical axon. Front Cell Neurosci 2023; 17:1215945. [PMID: 37636588 PMCID: PMC10450981 DOI: 10.3389/fncel.2023.1215945] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Accepted: 07/12/2023] [Indexed: 08/29/2023] Open
Abstract
Neurodevelopment, plasticity, and cognition are integral with functional directional transport in neuronal axons that occurs along a unique network of discontinuous polar microtubule (MT) bundles. Axonopathies are caused by brain trauma and genetic diseases that perturb or disrupt the axon MT infrastructure and, with it, the dynamic interplay of motor proteins and cargo essential for axonal maintenance and neuronal signaling. The inability to visualize and quantify normal and altered nanoscale spatio-temporal dynamic transport events prevents a full mechanistic understanding of injury, disease progression, and recovery. To address this gap, we generated DyNAMO, a Dynamic Nanoscale Axonal MT Organization model, which is a biologically realistic theoretical axon framework. We use DyNAMO to experimentally simulate multi-kinesin traffic response to focused or distributed tractable injury parameters, which are MT network perturbations affecting MT lengths and multi-MT staggering. We track kinesins with different motility and processivity, as well as their influx rates, in-transit dissociation and reassociation from inter-MT reservoirs, progression, and quantify and spatially represent motor output ratios. DyNAMO demonstrates, in detail, the complex interplay of mixed motor types, crowding, kinesin off/on dissociation and reassociation, and injury consequences of forced intermingling. Stalled forward progression with different injury states is seen as persistent dynamicity of kinesins transiting between MTs and inter-MT reservoirs. DyNAMO analysis provides novel insights and quantification of axonal injury scenarios, including local injury-affected ATP levels, as well as relates these to influences on signaling outputs, including patterns of gating, waves, and pattern switching. The DyNAMO model significantly expands the network of heuristic and mathematical analysis of neuronal functions relevant to axonopathies, diagnostics, and treatment strategies.
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Affiliation(s)
- Soumyadeep Chandra
- Electrical and Computer Science Engineering, Purdue University, West Lafayette, IN, United States
| | - Rounak Chatterjee
- Department of Electronics, Electrical and Systems Engineering, University of Birmingham, Birmingham, United Kingdom
| | - Zachary T. Olmsted
- Nanobioscience, College of Nanoscale Science and Engineering, State University of New York Polytechnic Institute, Albany, NY, United States
- Department of Neurosurgery, Ronald Reagan UCLA Medical Center, University of California, Los Angeles, Los Angeles, CA, United States
| | - Amitava Mukherjee
- Nanobioscience, College of Nanoscale Science and Engineering, State University of New York Polytechnic Institute, Albany, NY, United States
- School of Computing, Amrita Vishwa Vidyapeetham (University), Kollam, Kerala, India
| | - Janet L. Paluh
- Nanobioscience, College of Nanoscale Science and Engineering, State University of New York Polytechnic Institute, Albany, NY, United States
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11
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Puri D, Barry BJ, Engle EC. TUBB3 and KIF21A in neurodevelopment and disease. Front Neurosci 2023; 17:1226181. [PMID: 37600020 PMCID: PMC10436312 DOI: 10.3389/fnins.2023.1226181] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Accepted: 07/17/2023] [Indexed: 08/22/2023] Open
Abstract
Neuronal migration and axon growth and guidance require precise control of microtubule dynamics and microtubule-based cargo transport. TUBB3 encodes the neuronal-specific β-tubulin isotype III, TUBB3, a component of neuronal microtubules expressed throughout the life of central and peripheral neurons. Human pathogenic TUBB3 missense variants result in altered TUBB3 function and cause errors either in the growth and guidance of cranial and, to a lesser extent, central axons, or in cortical neuronal migration and organization, and rarely in both. Moreover, human pathogenic missense variants in KIF21A, which encodes an anterograde kinesin motor protein that interacts directly with microtubules, alter KIF21A function and cause errors in cranial axon growth and guidance that can phenocopy TUBB3 variants. Here, we review reported TUBB3 and KIF21A variants, resulting phenotypes, and corresponding functional studies of both wildtype and mutant proteins. We summarize the evidence that, in vitro and in mouse models, loss-of-function and missense variants can alter microtubule dynamics and microtubule-kinesin interactions. Lastly, we highlight additional studies that might contribute to our understanding of the relationship between specific tubulin isotypes and specific kinesin motor proteins in health and disease.
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Affiliation(s)
- Dharmendra Puri
- Department of Neurology, Boston Children’s Hospital, Harvard Medical School, Boston, MA, United States
- F. M. Kirby Neurobiology Center, Boston Children’s Hospital, Boston, MA, United States
- Howard Hughes Medical Institute, Chevy Chase, MD, United States
| | - Brenda J. Barry
- Department of Neurology, Boston Children’s Hospital, Harvard Medical School, Boston, MA, United States
- F. M. Kirby Neurobiology Center, Boston Children’s Hospital, Boston, MA, United States
- Howard Hughes Medical Institute, Chevy Chase, MD, United States
| | - Elizabeth C. Engle
- Department of Neurology, Boston Children’s Hospital, Harvard Medical School, Boston, MA, United States
- F. M. Kirby Neurobiology Center, Boston Children’s Hospital, Boston, MA, United States
- Howard Hughes Medical Institute, Chevy Chase, MD, United States
- Department of Ophthalmology, Boston Children’s Hospital, Harvard Medical School, Boston, MA, United States
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12
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Li Z, Du W, Yang J, Lai DH, Lun ZR, Guo Q. Cryo-Electron Tomography of Toxoplasma gondii Indicates That the Conoid Fiber May Be Derived from Microtubules. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2206595. [PMID: 36840635 DOI: 10.1002/advs.202206595] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Revised: 02/04/2023] [Indexed: 05/18/2023]
Abstract
Toxoplasma gondii (T. gondii) is the causative agent of toxoplasmosis and can infect numerous warm-blooded animals. An improved understanding of the fine structure of this parasite can help elucidate its replication mechanism. Previous studies have resolved the ultrastructure of the cytoskeleton using purified samples, which eliminates their cellular context. Here the application of cryo-electron tomography to visualize T. gondii tachyzoites in their native state is reported. The fine structure and cellular distribution of the cytoskeleton are resolved and analyzed at nanometer resolution. Additionally, the tachyzoite structural characteristics are annotated during its endodyogeny for the first time. By comparing the structural features in mature tachyzoites and their daughter buds, it is proposed that the conoid fiber of the Apicomplexa originates from microtubules. This work represents the detailed molecular anatomy of T. gondii, particularly during the budding replication stage of tachyzoite, and provides a reference for further studies of this fascinating organism.
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Affiliation(s)
- Zhixun Li
- State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, School of Life Sciences, Peking University, Beijing, 100871, P. R. China
| | - Wenjing Du
- State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, School of Life Sciences, Peking University, Beijing, 100871, P. R. China
| | - Jiong Yang
- MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou, 510275, P. R. China
| | - De-Hua Lai
- MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou, 510275, P. R. China
| | - Zhao-Rong Lun
- MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou, 510275, P. R. China
| | - Qiang Guo
- State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, School of Life Sciences, Peking University, Beijing, 100871, P. R. China
- Changping Laboratory, Yard 28, Science Park Road, Beijing, 102206, P. R. China
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13
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Küppers M, Albrecht D, Kashkanova AD, Lühr J, Sandoghdar V. Confocal interferometric scattering microscopy reveals 3D nanoscopic structure and dynamics in live cells. Nat Commun 2023; 14:1962. [PMID: 37029107 PMCID: PMC10081331 DOI: 10.1038/s41467-023-37497-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Accepted: 03/16/2023] [Indexed: 04/09/2023] Open
Abstract
Bright-field light microscopy and related phase-sensitive techniques play an important role in life sciences because they provide facile and label-free insights into biological specimens. However, lack of three-dimensional imaging and low sensitivity to nanoscopic features hamper their application in many high-end quantitative studies. Here, we demonstrate that interferometric scattering (iSCAT) microscopy operated in the confocal mode provides unique label-free solutions for live-cell studies. We reveal the nanometric topography of the nuclear envelope, quantify the dynamics of the endoplasmic reticulum, detect single microtubules, and map nanoscopic diffusion of clathrin-coated pits undergoing endocytosis. Furthermore, we introduce the combination of confocal and wide-field iSCAT modalities for simultaneous imaging of cellular structures and high-speed tracking of nanoscopic entities such as single SARS-CoV-2 virions. We benchmark our findings against simultaneously acquired fluorescence images. Confocal iSCAT can be readily implemented as an additional contrast mechanism in existing laser scanning microscopes. The method is ideally suited for live studies on primary cells that face labeling challenges and for very long measurements beyond photobleaching times.
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Affiliation(s)
- Michelle Küppers
- Max Planck Institute for the Science of Light, 91058, Erlangen, Germany
- Max-Planck-Zentrum für Physik und Medizin, 91058, Erlangen, Germany
- Department of Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91058, Erlangen, Germany
| | - David Albrecht
- Max Planck Institute for the Science of Light, 91058, Erlangen, Germany
- Max-Planck-Zentrum für Physik und Medizin, 91058, Erlangen, Germany
| | - Anna D Kashkanova
- Max Planck Institute for the Science of Light, 91058, Erlangen, Germany
- Max-Planck-Zentrum für Physik und Medizin, 91058, Erlangen, Germany
| | - Jennifer Lühr
- Max Planck Institute for the Science of Light, 91058, Erlangen, Germany
- Max-Planck-Zentrum für Physik und Medizin, 91058, Erlangen, Germany
| | - Vahid Sandoghdar
- Max Planck Institute for the Science of Light, 91058, Erlangen, Germany.
- Max-Planck-Zentrum für Physik und Medizin, 91058, Erlangen, Germany.
- Department of Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91058, Erlangen, Germany.
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14
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Río-Bergé C, Cong Y, Reggiori F. Getting on the right track: Interactions between viruses and the cytoskeletal motor proteins. Traffic 2023; 24:114-130. [PMID: 35146839 DOI: 10.1111/tra.12835] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Revised: 02/06/2022] [Accepted: 02/07/2022] [Indexed: 11/29/2022]
Abstract
The cytoskeleton is an essential component of the cell and it is involved in multiple physiological functions, including intracellular organization and transport. It is composed of three main families of proteinaceous filaments; microtubules, actin filaments and intermediate filaments and their accessory proteins. Motor proteins, which comprise the dynein, kinesin and myosin superfamilies, are a remarkable group of accessory proteins that mainly mediate the intracellular transport of cargoes along with the cytoskeleton. Like other cellular structures and pathways, viruses can exploit the cytoskeleton to promote different steps of their life cycle through associations with motor proteins. The complexity of the cytoskeleton and the differences among viruses, however, has led to a wide diversity of interactions, which in most cases remain poorly understood. Unveiling the details of these interactions is necessary not only for a better comprehension of specific infections, but may also reveal new potential drug targets to fight dreadful diseases such as rabies disease and acquired immunodeficiency syndrome (AIDS). In this review, we describe a few examples of the mechanisms that some human viruses, that is, rabies virus, adenovirus, herpes simplex virus, human immunodeficiency virus, influenza A virus and papillomavirus, have developed to hijack dyneins, kinesins and myosins.
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Affiliation(s)
- Clàudia Río-Bergé
- Department of Biomedical Sciences of Cells & Systems, Molecular Cell Biology Section, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Yingying Cong
- Department of Biomedical Sciences of Cells & Systems, Molecular Cell Biology Section, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Fulvio Reggiori
- Department of Biomedical Sciences of Cells & Systems, Molecular Cell Biology Section, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
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15
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Iwanski MK, Kapitein LC. Cellular cartography: Towards an atlas of the neuronal microtubule cytoskeleton. Front Cell Dev Biol 2023; 11:1052245. [PMID: 37035244 PMCID: PMC10073685 DOI: 10.3389/fcell.2023.1052245] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Accepted: 02/28/2023] [Indexed: 04/11/2023] Open
Abstract
Microtubules, one of the major components of the cytoskeleton, play a crucial role during many aspects of neuronal development and function, such as neuronal polarization and axon outgrowth. Consequently, the microtubule cytoskeleton has been implicated in many neurodevelopmental and neurodegenerative disorders. The polar nature of microtubules is quintessential for their function, allowing them to serve as tracks for long-distance, directed intracellular transport by kinesin and dynein motors. Most of these motors move exclusively towards either the plus- or minus-end of a microtubule and some have been shown to have a preference for either dynamic or stable microtubules, those bearing a particular post-translational modification or those decorated by a specific microtubule-associated protein. Thus, it becomes important to consider the interplay of these features and their combinatorial effects on transport, as well as how different types of microtubules are organized in the cell. Here, we discuss microtubule subsets in terms of tubulin isotypes, tubulin post-translational modifications, microtubule-associated proteins, microtubule stability or dynamicity, and microtubule orientation. We highlight techniques used to study these features of the microtubule cytoskeleton and, using the information from these studies, try to define the composition, role, and organization of some of these subsets in neurons.
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16
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Integrated multimodality microscope for accurate and efficient target-guided cryo-lamellae preparation. Nat Methods 2023; 20:268-275. [PMID: 36646896 PMCID: PMC9911353 DOI: 10.1038/s41592-022-01749-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Accepted: 12/06/2022] [Indexed: 01/18/2023]
Abstract
Cryo-electron tomography (cryo-ET) is a revolutionary technique for resolving the structure of subcellular organelles and macromolecular complexes in their cellular context. However, the application of the cryo-ET is hampered by the sample preparation step. Performing cryo-focused ion beam milling at an arbitrary position on the sample is inefficient, and the target of interest is not guaranteed to be preserved when thinning the cell from several micrometers to less than 300 nm thick. Here, we report a cryogenic correlated light, ion and electron microscopy (cryo-CLIEM) technique that is capable of preparing cryo-lamellae under the guidance of three-dimensional confocal imaging. Moreover, we demonstrate a workflow to preselect and preserve nanoscale target regions inside the finished cryo-lamellae. By successfully preparing cryo-lamellae that contain a single centriole or contact sites between subcellular organelles, we show that this approach is generally applicable, and shall help in innovating more applications of cryo-ET.
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17
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Farmer VJ, Zanic M. Beyond the GTP-cap: Elucidating the molecular mechanisms of microtubule catastrophe. Bioessays 2023; 45:e2200081. [PMID: 36398561 PMCID: PMC10648283 DOI: 10.1002/bies.202200081] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Revised: 11/03/2022] [Accepted: 11/04/2022] [Indexed: 11/19/2022]
Abstract
Almost 40 years since the discovery of microtubule dynamic instability, the molecular mechanisms underlying microtubule dynamics remain an area of intense research interest. The "standard model" of microtubule dynamics implicates a "cap" of GTP-bound tubulin dimers at the growing microtubule end as the main determinant of microtubule stability. Loss of the GTP-cap leads to microtubule "catastrophe," a switch-like transition from microtubule growth to shrinkage. However, recent studies, using biochemical in vitro reconstitution, cryo-EM, and computational modeling approaches, challenge the simple GTP-cap model. Instead, a new perspective on the mechanisms of microtubule dynamics is emerging. In this view, highly dynamic transitions between different structural conformations of the growing microtubule end - which may or may not be directly linked to the nucleotide content at the microtubule end - ultimately drive microtubule catastrophe.
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Affiliation(s)
- Veronica J. Farmer
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, Tennessee, USA
| | - Marija Zanic
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, Tennessee, USA
- Department of Biomolecular and Chemical Engineering, Department of Biochemistry, Vanderbilt University, Nashville, Tennessee, USA
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18
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Kulkarni R, Thakur A, Kumar H. Microtubule Dynamics Following Central and Peripheral Nervous System Axotomy. ACS Chem Neurosci 2022; 13:1358-1369. [PMID: 35451811 DOI: 10.1021/acschemneuro.2c00189] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Disturbance in the neuronal network leads to instability in the microtubule (MT) railroad of axons, causing hindrance in the intra-axonal transport and making it difficult to re-establish the broken network. Peripheral nervous system (PNS) neurons can stabilize their MTs, leading to the formation of regeneration-promoting structures called "growth cones". However, central nervous system (CNS) neurons lack this intrinsic reparative capability and, instead, form growth-incompetent structures called "retraction bulbs", which have a disarrayed MT network. It is evident from various studies that although axonal regeneration depends on both cell-extrinsic and cell-intrinsic factors, any therapy that aims at axonal regeneration ultimately converges onto MTs. Understanding the neuronal MT dynamics will help develop effective therapeutic strategies in diseases where the MT network gets disrupted, such as spinal cord injury, traumatic brain injury, multiple sclerosis, and amyotrophic lateral sclerosis. It is also essential to know the factors that aid or inhibit MT stabilization. In this review, we have discussed the MT dynamics postaxotomy in the CNS and PNS, and factors that can directly influence MT stability in various diseases.
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Affiliation(s)
- Riya Kulkarni
- National Institute of Pharmaceutical Education and Research, Ahmedabad, Opposite Air Force Station, Palaj, Gandhinagar, Gujarat 382355, India
| | - Akshata Thakur
- National Institute of Pharmaceutical Education and Research, Ahmedabad, Opposite Air Force Station, Palaj, Gandhinagar, Gujarat 382355, India
| | - Hemant Kumar
- National Institute of Pharmaceutical Education and Research, Ahmedabad, Opposite Air Force Station, Palaj, Gandhinagar, Gujarat 382355, India
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19
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Liu C, Chen Y, Xie Y, Xiang M. Tubulin Post-translational Modifications: Potential Therapeutic Approaches to Heart Failure. Front Cell Dev Biol 2022; 10:872058. [PMID: 35493101 PMCID: PMC9039000 DOI: 10.3389/fcell.2022.872058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 03/09/2022] [Indexed: 11/13/2022] Open
Abstract
In recent decades, advancing insights into the mechanisms of cardiac dysfunction have focused on the involvement of microtubule network. A variety of tubulin post-translational modifications have been discovered to fine-tune the microtubules’ properties and functions. Given the limits of therapies based on conserved structures of the skeleton, targeting tubulin modifications appears to be a potentially promising therapeutic strategy. Here we review the current understanding of tubulin post-translational modifications in regulating microtubule functions in the cardiac system. We also discussed how altered modifications may lead to a range of cardiac dysfunctions, many of which are linked to heart failure.
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Affiliation(s)
- Chang Liu
- Department of Cardiology, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Yuwen Chen
- Department of Cardiology, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Yao Xie
- Department of Cardiology, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Meixiang Xiang
- Department of Cardiology, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
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20
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Kliuchnikov E, Klyshko E, Kelly MS, Zhmurov A, Dima RI, Marx KA, Barsegov V. Microtubule assembly and disassembly dynamics model: Exploring dynamic instability and identifying features of Microtubules' Growth, Catastrophe, Shortening, and Rescue. Comput Struct Biotechnol J 2022; 20:953-974. [PMID: 35242287 PMCID: PMC8861655 DOI: 10.1016/j.csbj.2022.01.028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 01/26/2022] [Accepted: 01/27/2022] [Indexed: 12/21/2022] Open
Abstract
Microtubules (MTs), a cellular structure element, exhibit dynamic instability and can switch stochastically from growth to shortening; but the factors that trigger these processes at the molecular level are not understood. We developed a 3D Microtubule Assembly and Disassembly DYnamics (MADDY) model, based upon a bead-per-monomer representation of the αβ-tubulin dimers forming an MT lattice, stabilized by the lateral and longitudinal interactions between tubulin subunits. The model was parameterized against the experimental rates of MT growth and shortening, and pushing forces on the Dam1 protein complex due to protofilaments splaying out. Using the MADDY model, we carried out GPU-accelerated Langevin simulations to access dynamic instability behavior. By applying Machine Learning techniques, we identified the MT characteristics that distinguish simultaneously all four kinetic states: growth, catastrophe, shortening, and rescue. At the cellular 25 μM tubulin concentration, the most important quantities are the MT length L , average longitudinal curvatureκ long , MT tip width w , total energy of longitudinal interactions in MT latticeU long , and the energies of longitudinal and lateral interactions required to complete MT to full cylinderU long add andU lat add . At high 250 μM tubulin concentration, the most important characteristics are L ,κ long , number of hydrolyzed αβ-tubulin dimersn hyd and number of lateral interactions per helical pitchn lat in MT lattice, energy of lateral interactions in MT latticeU lat , and energy of longitudinal interactions in MT tipu long . These results allow greater insights into what brings about kinetic state stability and the transitions between states involved in MT dynamic instability behavior.
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Affiliation(s)
| | - Eugene Klyshko
- Department of Chemistry, University of Massachusetts, Lowell, MA 01854, USA
| | - Maria S. Kelly
- Department of Chemistry, University of Cincinnati, Cincinnati, OH 45221, USA
| | - Artem Zhmurov
- KTH Royal Institute of Technology, Stockholm, Sweden
| | - Ruxandra I. Dima
- Department of Chemistry, University of Cincinnati, Cincinnati, OH 45221, USA
| | - Kenneth A. Marx
- Department of Chemistry, University of Massachusetts, Lowell, MA 01854, USA
| | - Valeri Barsegov
- Department of Chemistry, University of Massachusetts, Lowell, MA 01854, USA
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21
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Garnett JA, Atherton J. Structure Determination of Microtubules and Pili: Past, Present, and Future Directions. Front Mol Biosci 2022; 8:830304. [PMID: 35096976 PMCID: PMC8795688 DOI: 10.3389/fmolb.2021.830304] [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: 12/07/2021] [Accepted: 12/28/2021] [Indexed: 11/30/2022] Open
Abstract
Historically proteins that form highly polymeric and filamentous assemblies have been notoriously difficult to study using high resolution structural techniques. This has been due to several factors that include structural heterogeneity, their large molecular mass, and available yields. However, over the past decade we are now seeing a major shift towards atomic resolution insight and the study of more complex heterogenous samples and in situ/ex vivo examination of multi-subunit complexes. Although supported by developments in solid state nuclear magnetic resonance spectroscopy (ssNMR) and computational approaches, this has primarily been due to advances in cryogenic electron microscopy (cryo-EM). The study of eukaryotic microtubules and bacterial pili are good examples, and in this review, we will give an overview of the technical innovations that have enabled this transition and highlight the advancements that have been made for these two systems. Looking to the future we will also describe systems that remain difficult to study and where further technical breakthroughs are required.
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Affiliation(s)
- James A. Garnett
- Centre for Host-Microbiome Interactions, Faculty of Dental, Oral and Craniofacial Sciences, King’s College London, London, United Kingdom
| | - Joseph Atherton
- Randall Centre for Cell and Molecular Biophysics, King’s College London, London, United Kingdom
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22
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Structural transitions in the GTP cap visualized by cryo-electron microscopy of catalytically inactive microtubules. Proc Natl Acad Sci U S A 2022; 119:2114994119. [PMID: 34996871 PMCID: PMC8764682 DOI: 10.1073/pnas.2114994119] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/23/2021] [Indexed: 01/27/2023] Open
Abstract
Microtubules (MTs) are polymers of αβ-tubulin heterodimers that stochastically switch between growth and shrinkage phases. This dynamic instability is critically important for MT function. It is believed that GTP hydrolysis within the MT lattice is accompanied by destabilizing conformational changes and that MT stability depends on a transiently existing GTP cap at the growing MT end. Here, we use cryo-electron microscopy and total internal reflection fluorescence microscopy of GTP hydrolysis-deficient MTs assembled from mutant recombinant human tubulin to investigate the structure of a GTP-bound MT lattice. We find that the GTP-MT lattice of two mutants in which the catalytically active glutamate in α-tubulin was substituted by inactive amino acids (E254A and E254N) is remarkably plastic. Undecorated E254A and E254N MTs with 13 protofilaments both have an expanded lattice but display opposite protofilament twists, making these lattices distinct from the compacted lattice of wild-type GDP-MTs. End-binding proteins of the EB family have the ability to compact both mutant GTP lattices and to stabilize a negative twist, suggesting that they promote this transition also in the GTP cap of wild-type MTs, thereby contributing to the maturation of the MT structure. We also find that the MT seam appears to be stabilized in mutant GTP-MTs and destabilized in GDP-MTs, supporting the proposal that the seam plays an important role in MT stability. Together, these structures of catalytically inactive MTs add mechanistic insight into the GTP state of MTs, the stability of the GTP- and GDP-bound lattice, and our overall understanding of MT dynamic instability.
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23
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Abstract
Microtubules are dynamic cytoskeletal filaments composed of αβ-tubulin heterodimers. Historically, the dynamics of single tubulin interactions at the growing microtubule tip have been inferred from steady-state growth kinetics. However, recent advances in the production of recombinant tubulin and in high-resolution optical and cryo-electron microscopies have opened new windows into understanding the impacts of specific intermolecular interactions during growth. The microtubule lattice is held together by lateral and longitudinal tubulin-tubulin interactions, and these interactions are in turn regulated by the GTP hydrolysis state of the tubulin heterodimer. Furthermore, tubulin can exist in either an extended or a compacted state in the lattice. Growing evidence has led to the suggestion that binding of microtubule-associated proteins (MAPs) or motors can induce changes in tubulin conformation and that this information can be communicated through the microtubule lattice. Progress in understanding how dynamic tubulin-tubulin interactions control dynamic instability has benefitted from visualizing structures of growing microtubule plus ends and through stochastic biochemical models constrained by experimental data. Here, we review recent insights into the molecular basis of microtubule growth and discuss how MAPs and regulatory proteins alter tubulin-tubulin interactions to exert their effects on microtubule growth and stability.
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Affiliation(s)
- Joseph M Cleary
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA 16802, USA
| | - William O Hancock
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA 16802, USA.
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24
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Jurgens JA, Barry BJ, Lemire G, Chan WM, Whitman MC, Shaaban S, Robson CD, MacKinnon S, England EM, McMillan HJ, Kelly C, Pratt BM, O’Donnell-Luria A, MacArthur DG, Boycott KM, Hunter DG, Engle EC. Novel variants in TUBA1A cause congenital fibrosis of the extraocular muscles with or without malformations of cortical brain development. Eur J Hum Genet 2021; 29:816-826. [PMID: 33649541 PMCID: PMC8110841 DOI: 10.1038/s41431-020-00804-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Revised: 12/12/2020] [Accepted: 12/17/2020] [Indexed: 01/31/2023] Open
Abstract
Variants in multiple tubulin genes have been implicated in neurodevelopmental disorders, including malformations of cortical development (MCD) and congenital fibrosis of the extraocular muscles (CFEOM). Distinct missense variants in the beta-tubulin encoding genes TUBB3 and TUBB2B cause MCD, CFEOM, or both, suggesting substitution-specific mechanisms. Variants in the alpha tubulin-encoding gene TUBA1A have been associated with MCD, but not with CFEOM. Using exome sequencing (ES) and genome sequencing (GS), we identified 3 unrelated probands with CFEOM who harbored novel heterozygous TUBA1A missense variants c.1216C>G, p.(His406Asp); c.467G>A, p.(Arg156His); and c.1193T>G, p.(Met398Arg). MRI revealed small oculomotor-innervated muscles and asymmetrical caudate heads and lateral ventricles with or without corpus callosal thinning. Two of the three probands had MCD. Mutated amino acid residues localize either to the longitudinal interface at which α and β tubulins heterodimerize (Met398, His406) or to the lateral interface at which tubulin protofilaments interact (Arg156), and His406 interacts with the motor domain of kinesin-1. This series of individuals supports TUBA1A variants as a cause of CFEOM and expands our knowledge of tubulinopathies.
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Affiliation(s)
- Julie A. Jurgens
- F.M. Kirby Neurobiology Center, Boston Children’s Hospital, Boston, MA USA ,Department of Neurology, Boston Children’s Hospital, Boston, MA USA ,Department of Neurology, Harvard Medical School, Boston, MA USA ,Broad Institute of MIT and Harvard, Cambridge, MA USA
| | - Brenda J. Barry
- Department of Neurology, Boston Children’s Hospital, Boston, MA USA ,Howard Hughes Medical Institute, Chevy Chase, MD USA
| | - Gabrielle Lemire
- Children’s Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, ON Canada
| | - Wai-Man Chan
- F.M. Kirby Neurobiology Center, Boston Children’s Hospital, Boston, MA USA ,Department of Neurology, Boston Children’s Hospital, Boston, MA USA ,Department of Neurology, Harvard Medical School, Boston, MA USA ,Broad Institute of MIT and Harvard, Cambridge, MA USA ,Howard Hughes Medical Institute, Chevy Chase, MD USA
| | - Mary C. Whitman
- F.M. Kirby Neurobiology Center, Boston Children’s Hospital, Boston, MA USA ,Department of Ophthalmology, Boston Children’s Hospital, Boston, MA USA ,Department of Ophthalmology, Harvard Medical School, Boston, MA USA
| | - Sherin Shaaban
- F.M. Kirby Neurobiology Center, Boston Children’s Hospital, Boston, MA USA ,Department of Neurology, Boston Children’s Hospital, Boston, MA USA ,Department of Neurology, Harvard Medical School, Boston, MA USA ,Department of Pathology, University of Utah School of Medicine, Salt Lake City, UT USA
| | - Caroline D. Robson
- Division of Neuroradiology, Department of Radiology, Boston Children’s Hospital, Boston, MA USA ,Department of Radiology, Harvard Medical School, Boston, MA USA
| | - Sarah MacKinnon
- Department of Ophthalmology, Boston Children’s Hospital, Boston, MA USA ,Department of Ophthalmology, Harvard Medical School, Boston, MA USA
| | - Eleina M. England
- Center for Mendelian Genomics, Program in Medical and Population Genetics, Broad Institute of MIT and Harvard, Cambridge, MA USA ,Analytic and Translational Genetics Unit, Massachusetts General Hospital, Boston, MA USA ,Division of Genetics and Genomics, Boston Children’s Hospital, Boston, MA USA
| | - Hugh J. McMillan
- Division of Neurology, Department of Pediatrics, Children’s Hospital of Eastern Ontario, Ottawa, ON Canada
| | - Christopher Kelly
- Pediatric Ophthalmology and Physician Informatics, MultiCare Health System, Tacoma, WA USA
| | - Brandon M. Pratt
- F.M. Kirby Neurobiology Center, Boston Children’s Hospital, Boston, MA USA ,Department of Neurology, Boston Children’s Hospital, Boston, MA USA ,Department of Neurology, Harvard Medical School, Boston, MA USA
| | | | - Anne O’Donnell-Luria
- Center for Mendelian Genomics, Program in Medical and Population Genetics, Broad Institute of MIT and Harvard, Cambridge, MA USA ,Analytic and Translational Genetics Unit, Massachusetts General Hospital, Boston, MA USA ,Division of Genetics and Genomics, Boston Children’s Hospital, Boston, MA USA
| | - Daniel G. MacArthur
- Center for Mendelian Genomics, Program in Medical and Population Genetics, Broad Institute of MIT and Harvard, Cambridge, MA USA ,Analytic and Translational Genetics Unit, Massachusetts General Hospital, Boston, MA USA ,Centre for Population Genomics, Garvan Institute of Medical Research and UNSW, Sydney, NSW Australia ,Murdoch Children’s Research Institute, Parkville, VIC Australia
| | - Kym M. Boycott
- Children’s Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, ON Canada ,Department of Genetics, Children’s Hospital of Eastern Ontario, Ottawa, ON Canada
| | - David G. Hunter
- Department of Ophthalmology, Boston Children’s Hospital, Boston, MA USA ,Department of Ophthalmology, Harvard Medical School, Boston, MA USA
| | - Elizabeth C. Engle
- F.M. Kirby Neurobiology Center, Boston Children’s Hospital, Boston, MA USA ,Department of Neurology, Boston Children’s Hospital, Boston, MA USA ,Department of Neurology, Harvard Medical School, Boston, MA USA ,Broad Institute of MIT and Harvard, Cambridge, MA USA ,Howard Hughes Medical Institute, Chevy Chase, MD USA ,Department of Ophthalmology, Boston Children’s Hospital, Boston, MA USA ,Department of Ophthalmology, Harvard Medical School, Boston, MA USA
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25
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Vala M, Bujak Ł, García Marín A, Holanová K, Henrichs V, Braun M, Lánský Z, Piliarik M. Nanoscopic Structural Fluctuations of Disassembling Microtubules Revealed by Label-Free Super-Resolution Microscopy. SMALL METHODS 2021; 5:e2000985. [PMID: 34927839 DOI: 10.1002/smtd.202000985] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 12/22/2020] [Indexed: 06/14/2023]
Abstract
Microtubules are cytoskeletal polymers of tubulin dimers assembled into protofilaments that constitute nanotubes undergoing periods of assembly and disassembly. Static electron micrographs suggest a structural transition of straight protofilaments into curved ones occurring at the tips of disassembling microtubules. However, these structural transitions have never been observed and the process of microtubule disassembly thus remains unclear. Here, label-free optical microscopy capable of selective imaging of the transient structural changes of protofilaments at the tip of a disassembling microtubule is introduced. Upon induced disassembly, the transition of ordered protofilaments into a disordered conformation is resolved at the tip of the microtubule. Imaging the unbinding of individual tubulin oligomers from the microtubule tip reveals transient pauses and relapses in the disassembly, concurrent with increased organization of protofilament segments at the microtubule tip. These findings show that microtubule disassembly is a discrete process and suggest a stochastic mechanism of switching from the disassembly to the assembly phase.
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Affiliation(s)
- Milan Vala
- Institute of Photonics and Electronics of the Czech Academy of Sciences, Chaberská 1014/57, Prague, 182 51, Czech Republic
| | - Łukasz Bujak
- Institute of Photonics and Electronics of the Czech Academy of Sciences, Chaberská 1014/57, Prague, 182 51, Czech Republic
| | - Antonio García Marín
- Institute of Photonics and Electronics of the Czech Academy of Sciences, Chaberská 1014/57, Prague, 182 51, Czech Republic
| | - Kristýna Holanová
- Institute of Photonics and Electronics of the Czech Academy of Sciences, Chaberská 1014/57, Prague, 182 51, Czech Republic
| | - Verena Henrichs
- Institute of Biotechnology of the Czech Academy of Sciences, BIOCEV, Průmyslová 595, Vestec, 252 50, Czech Republic
| | - Marcus Braun
- Institute of Biotechnology of the Czech Academy of Sciences, BIOCEV, Průmyslová 595, Vestec, 252 50, Czech Republic
| | - Zdeněk Lánský
- Institute of Biotechnology of the Czech Academy of Sciences, BIOCEV, Průmyslová 595, Vestec, 252 50, Czech Republic
| | - Marek Piliarik
- Institute of Photonics and Electronics of the Czech Academy of Sciences, Chaberská 1014/57, Prague, 182 51, Czech Republic
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26
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Ayyappan S, Dharan PS, Krishnan A, Marira RR, Lambert M, Manna TK, Vijayan V. SxIP binding disrupts the constitutive homodimer interface of EB1 and stabilizes EB1 monomer. Biophys J 2021; 120:2019-2029. [PMID: 33737159 DOI: 10.1016/j.bpj.2021.03.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 02/16/2021] [Accepted: 03/01/2021] [Indexed: 11/16/2022] Open
Abstract
SxIP is a microtubule tip localizing signal found in many +TIP proteins that bind to the hydrophobic cavity of the C-terminal domain of end binding protein 1 (EB1) and then positively regulate the microtubule plus-end tracking of EBs. However, the exact mechanism of microtubule activation of EBs in the presence of SxIP signaling motif is not known. Here, we studied the effect of SxIP peptide on the native conformation of EB1 in solution. Using various NMR experiments, we found that SxIP peptide promoted the dissociation of natively formed EB1 dimer. We also discovered that I224A mutation of EB1 resulted in an unfolded C-terminal domain, which upon binding with the SxIP motif folded to its native structure. Molecular dynamics simulations also confirmed the relative structural stability of EB1 monomer in the SxIP bound state. Residual dipolar couplings and heteronuclear NOE analysis suggested that the binding of SxIP peptide at the C-terminal domain of EB1 decreased the dynamics and conformational flexibility of the N-terminal domain involved in EB1-microtubule interaction. The SxIP-induced disruption of the dimeric interactions in EB1, coupled with the reduction in conformational flexibility of the N-terminal domain of EB1, might facilitate the microtubule association of EB1.
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Affiliation(s)
- Shine Ayyappan
- School of Chemistry, Indian Institute of Science Education and Research, Thiruvananthapuram, Kerala, India
| | - Pooja S Dharan
- School of Chemistry, Indian Institute of Science Education and Research, Thiruvananthapuram, Kerala, India
| | - Arya Krishnan
- School of Biology, Indian Institute of Science Education and Research, Thiruvananthapuram, Kerala, India
| | - Renjith R Marira
- School of Biology, Indian Institute of Science Education and Research, Thiruvananthapuram, Kerala, India
| | - Mahil Lambert
- School of Chemistry, Indian Institute of Science Education and Research, Thiruvananthapuram, Kerala, India
| | - Tapas K Manna
- School of Biology, Indian Institute of Science Education and Research, Thiruvananthapuram, Kerala, India
| | - Vinesh Vijayan
- School of Chemistry, Indian Institute of Science Education and Research, Thiruvananthapuram, Kerala, India.
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27
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Chen J, Yu Q, Patterson E, Sayer C, Powles S. Dinitroaniline Herbicide Resistance and Mechanisms in Weeds. FRONTIERS IN PLANT SCIENCE 2021; 12:634018. [PMID: 33841462 PMCID: PMC8027333 DOI: 10.3389/fpls.2021.634018] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Accepted: 03/08/2021] [Indexed: 05/08/2023]
Abstract
Dinitroanilines are microtubule inhibitors, targeting tubulin proteins in plants and protists. Dinitroaniline herbicides, such as trifluralin, pendimethalin and oryzalin, have been used as pre-emergence herbicides for weed control for decades. With widespread resistance to post-emergence herbicides in weeds, the use of pre-emergence herbicides such as dinitroanilines has increased, in part, due to relatively slow evolution of resistance in weeds to these herbicides. Target-site resistance (TSR) to dinitroaniline herbicides due to point mutations in α-tubulin genes has been confirmed in a few weedy plant species (e.g., Eleusine indica, Setaria viridis, and recently in Lolium rigidum). Of particular interest is the resistance mutation Arg-243-Met identified from dinitroaniline-resistant L. rigidum that causes helical growth when plants are homozygous for the mutation. The recessive nature of the TSR, plus possible fitness cost for some resistance mutations, likely slows resistance evolution. Furthermore, non-target-site resistance (NTSR) to dinitroanilines has been rarely reported and only confirmed in Lolium rigidum due to enhanced herbicide metabolism (metabolic resistance). A cytochrome P450 gene (CYP81A10) has been recently identified in L. rigidum that confers resistance to trifluralin. Moreover, TSR and NTSR have been shown to co-exist in the same weedy species, population, and plant. The implication of knowledge and information on TSR and NTSR in management of dinitroaniline resistance is discussed.
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Affiliation(s)
- Jinyi Chen
- Australian Herbicide Resistance Initiative (AHRI), School of Agriculture and Environment, University of Western Australia (UWA), Perth, WA, Australia
- Department of Plant, Soil, and Microbial Sciences, Michigan State University, East Lansing, MI, United States
| | - Qin Yu
- Australian Herbicide Resistance Initiative (AHRI), School of Agriculture and Environment, University of Western Australia (UWA), Perth, WA, Australia
- *Correspondence: Qin Yu,
| | - Eric Patterson
- Department of Plant, Soil, and Microbial Sciences, Michigan State University, East Lansing, MI, United States
| | - Chad Sayer
- Nufarm Limited, Melbourne, VIC, Australia
| | - Stephen Powles
- Australian Herbicide Resistance Initiative (AHRI), School of Agriculture and Environment, University of Western Australia (UWA), Perth, WA, Australia
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28
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Abstract
Since their discovery more than 100 years ago, the viruses that infect bacteria (bacteriophages) have been widely studied as model systems. Largely overlooked, however, have been "jumbo phages," with genome sizes ranging from 200 to 500 kbp. Jumbo phages generally have large virions with complex structures and a broad host spectrum. While the majority of jumbo phage genes are poorly functionally characterized, recent work has discovered many unique biological features, including a conserved tubulin homolog that coordinates a proteinaceous nucleus-like compartment that houses and segregates phage DNA. The tubulin spindle displays dynamic instability and centers the phage nucleus within the bacterial host during phage infection for optimal reproduction. The shell provides robust physical protection for the enclosed phage genomes against attack from DNA-targeting bacterial immune systems, thereby endowing jumbo phages with broad resistance. In this review, we focus on the current knowledge of the cytoskeletal elements and the specialized nuclear compartment derived from jumbo phages, and we highlight their importance in facilitating spatial and temporal organization over the viral life cycle. Additionally, we discuss the evolutionary relationships between jumbo phages and eukaryotic viruses, as well as the therapeutic potential and drawbacks of jumbo phages as antimicrobial agents in phage therapy.
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29
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Manka SW, Moores CA. Pseudo-repeats in doublecortin make distinct mechanistic contributions to microtubule regulation. EMBO Rep 2020; 21:e51534. [PMID: 33051979 PMCID: PMC7726794 DOI: 10.15252/embr.202051534] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 09/17/2020] [Accepted: 09/18/2020] [Indexed: 11/16/2022] Open
Abstract
Doublecortin (DCX) is a neuronal microtubule-associated protein (MAP) indispensable for brain development. Its flexibly linked doublecortin (DC) domains-NDC and CDC-mediate microtubule (MT) nucleation and stabilization, but it is unclear how. Using high-resolution time-resolved cryo-EM, we mapped NDC and CDC interactions with tubulin at different MT polymerization stages and studied their functional effects on MT dynamics using TIRF microscopy. Although coupled, each DC repeat within DCX appears to have a distinct role in MT nucleation and stabilization: CDC is a conformationally plastic module that appears to facilitate MT nucleation and stabilize tubulin-tubulin contacts in the nascent MT lattice, while NDC appears to be favored along the mature lattice, providing MT stabilization. Our structures of MT-bound DC domains also explain in unprecedented detail the DCX mutation-related brain defects observed in the clinic. This modular composition of DCX reflects a common design principle among MAPs where pseudo-repeats of tubulin/MT binding elements chaperone or stabilize distinct conformational transitions to regulate distinct stages of MT dynamic instability.
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Affiliation(s)
- Szymon W Manka
- Institute of Structural and Molecular BiologyDepartment of Biological Sciences, BirkbeckUniversity of LondonLondonUK
| | - Carolyn A Moores
- Institute of Structural and Molecular BiologyDepartment of Biological Sciences, BirkbeckUniversity of LondonLondonUK
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30
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Boiarska Z, Passarella D. Microtubule-targeting agents and neurodegeneration. Drug Discov Today 2020; 26:604-615. [PMID: 33279455 DOI: 10.1016/j.drudis.2020.11.033] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 11/17/2020] [Accepted: 11/28/2020] [Indexed: 11/25/2022]
Abstract
The association of microtubule (MT) breakdown with neurodegeneration and neurotoxicity has provided an emerging therapeutic approach for neurodegenerative diseases. Tubulin binders are able to modulate MT dynamics and, as a result, are of particular interest both as potential therapeutics and experimental tools used to validate this strategy. Here, we provide a comprehensive overview of current knowledge and recent advancements regarding MT-targeting approaches for neurodegeneration and evaluate the potential application of MT-targeting agents (MTAs) based on available preclinical and clinical data.
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Affiliation(s)
- Zlata Boiarska
- Dipartimento di Chimica, Università degli Studi di Milano, Via Golgi 19, 20133 Milano, Italy
| | - Daniele Passarella
- Dipartimento di Chimica, Università degli Studi di Milano, Via Golgi 19, 20133 Milano, Italy.
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31
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Principal Postulates of Centrosomal Biology. Version 2020. Cells 2020; 9:cells9102156. [PMID: 32987651 PMCID: PMC7598677 DOI: 10.3390/cells9102156] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 09/10/2020] [Accepted: 09/21/2020] [Indexed: 12/13/2022] Open
Abstract
The centrosome, which consists of two centrioles surrounded by pericentriolar material, is a unique structure that has retained its main features in organisms of various taxonomic groups from unicellular algae to mammals over one billion years of evolution. In addition to the most noticeable function of organizing the microtubule system in mitosis and interphase, the centrosome performs many other cell functions. In particular, centrioles are the basis for the formation of sensitive primary cilia and motile cilia and flagella. Another principal function of centrosomes is the concentration in one place of regulatory proteins responsible for the cell's progression along the cell cycle. Despite the existing exceptions, the functioning of the centrosome is subject to general principles, which are discussed in this review.
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32
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Dynamic and asymmetric fluctuations in the microtubule wall captured by high-resolution cryoelectron microscopy. Proc Natl Acad Sci U S A 2020; 117:16976-16984. [PMID: 32636254 DOI: 10.1073/pnas.2001546117] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Microtubules are tubular polymers with essential roles in numerous cellular activities. Structures of microtubules have been captured at increasing resolution by cryo-EM. However, dynamic properties of the microtubule are key to its function, and this behavior has proved difficult to characterize at a structural level due to limitations in existing structure determination methods. We developed a high-resolution cryo-EM refinement method that divides an imaged microtubule into its constituent protofilaments, enabling deviations from helicity and other sources of heterogeneity to be quantified and corrected for at the single-subunit level. We demonstrate that this method improves the resolution of microtubule 3D reconstructions and substantially reduces anisotropic blurring artifacts, compared with methods that utilize helical symmetry averaging. Moreover, we identified an unexpected, discrete behavior of the m-loop, which mediates lateral interactions between neighboring protofilaments and acts as a flexible hinge between them. The hinge angle adopts preferred values corresponding to distinct conformations of the m-loop that are incompatible with helical symmetry. These hinge angles fluctuate in a stochastic manner, and perfectly cylindrical microtubule conformations are thus energetically and entropically penalized. The hinge angle can diverge further from helical symmetry at the microtubule seam, generating a subpopulation of highly distorted microtubules. However, the seam-distorted subpopulation disappears in the presence of Taxol, a microtubule stabilizing agent. These observations provide clues into the structural origins of microtubule flexibility and dynamics and highlight the role of structural polymorphism in defining microtubule behavior.
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33
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Roll-Mecak A. The Tubulin Code in Microtubule Dynamics and Information Encoding. Dev Cell 2020; 54:7-20. [PMID: 32634400 PMCID: PMC11042690 DOI: 10.1016/j.devcel.2020.06.008] [Citation(s) in RCA: 128] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 05/08/2020] [Accepted: 06/03/2020] [Indexed: 01/05/2023]
Abstract
Microtubules are non-covalent mesoscale polymers central to the eukaryotic cytoskeleton. Microtubule structure, dynamics, and mechanics are modulated by a cell's choice of tubulin isoforms and post-translational modifications, a "tubulin code," which is thought to support the diverse morphology and dynamics of microtubule arrays across various cell types, cell cycle, and developmental stages. We give a brief historical overview of research into tubulin diversity and highlight recent progress toward uncovering the mechanistic underpinnings of the tubulin code. As a large number of essential pathways converge upon the microtubule cytoskeleton, understanding how cells utilize tubulin diversity is crucial to understanding cellular physiology and disease.
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Affiliation(s)
- Antonina Roll-Mecak
- Cell Biology and Biophysics Unit, National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA; Biochemistry and Biophysics Center, National Heart Lung and Blood Institute, Bethesda, MD 20892, USA.
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34
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Abstract
Several types of mammalian sensory receptor cells possess modified cilia which may play a primary role in stimulus detection. Axonemes and basal apparatus from other types of cilia and flagella have been isolated, characterized and compared in detail. In this communication we report results of what may be the first attempt to isolate and characterize such structures from a sensory cilium, the bovine retinal rod outer segment.Bovine eyes were obtained from a nearby abattoir, the retinas were removed and swirled vigorously in a cold solution of 50% sucrose, 5 mM Tris, 2 mM MgCl2, pH 7.5, to detach outer segments. The suspension was then filtered through cheesecloth and the filtrate was centrifuged at 20,000 rpm for 1 hr. Rod outer segments were collected from the solution surface, diluted, layered onto a continuous sucrose gradient (25-38% sucrose in Tris MgCl2 buffer) and centrifuged for 3-12 hrs. at 10,000 rpm.
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35
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Chakraborty S, Jasnin M, Baumeister W. Three-dimensional organization of the cytoskeleton: A cryo-electron tomography perspective. Protein Sci 2020; 29:1302-1320. [PMID: 32216120 PMCID: PMC7255506 DOI: 10.1002/pro.3858] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 03/17/2020] [Accepted: 03/20/2020] [Indexed: 01/01/2023]
Abstract
Traditionally, structures of cytoskeletal components have been studied ex situ, that is, with biochemically purified materials. There are compelling reasons to develop approaches to study them in situ in their native functional context. In recent years, cryo-electron tomography emerged as a powerful method for visualizing the molecular organization of unperturbed cellular landscapes with the potential to attain near-atomic resolution. Here, we review recent works on the cytoskeleton using cryo-electron tomography, demonstrating the power of in situ studies. We also highlight the potential of this method in addressing important questions pertinent to the field of cytoskeletal biomechanics.
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Affiliation(s)
- Saikat Chakraborty
- Department of Molecular Structural BiologyMax Planck Institute of BiochemistryMartinsriedGermany
| | - Marion Jasnin
- Department of Molecular Structural BiologyMax Planck Institute of BiochemistryMartinsriedGermany
| | - Wolfgang Baumeister
- Department of Molecular Structural BiologyMax Planck Institute of BiochemistryMartinsriedGermany
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36
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Michaels TC, Feng S, Liang H, Mahadevan L. Mechanics and kinetics of dynamic instability. eLife 2020; 9:54077. [PMID: 32392128 PMCID: PMC7213977 DOI: 10.7554/elife.54077] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2019] [Accepted: 04/04/2020] [Indexed: 11/13/2022] Open
Abstract
During dynamic instability, self-assembling microtubules (MTs) stochastically alternate between phases of growth and shrinkage. This process is driven by the presence of two distinct states of MT subunits, GTP- and GDP-bound tubulin dimers, that have different structural properties. Here, we use a combination of analysis and computer simulations to study the mechanical and kinetic regulation of dynamic instability in three-dimensional (3D) self-assembling MTs. Our model quantifies how the 3D structure and kinetics of the distinct states of tubulin dimers determine the mechanical stability of MTs. We further show that dynamic instability is influenced by the presence of quenched disorder in the state of the tubulin subunit as reflected in the fraction of non-hydrolysed tubulin. Our results connect the 3D geometry, kinetics and statistical mechanics of these tubular assemblies within a single framework, and may be applicable to other self-assembled systems where these same processes are at play.
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Affiliation(s)
- Thomas Ct Michaels
- Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, United States
| | - Shuo Feng
- Department of Modern Mechanics, University of Science and Technology of China, Hefei, China.,IAT Chungu Joint Laboratory for Additive Manufacturing, Anhui Chungu 3D Institute of Intelligent Equipment and Industrial Technology, Wuhu, China
| | - Haiyi Liang
- Department of Modern Mechanics, University of Science and Technology of China, Hefei, China.,IAT Chungu Joint Laboratory for Additive Manufacturing, Anhui Chungu 3D Institute of Intelligent Equipment and Industrial Technology, Wuhu, China
| | - L Mahadevan
- Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, United States.,Department of Physics, Harvard University, Cambridge, United States.,Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, United States
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37
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Varikoti RA, Macke AC, Speck V, Ross JL, Dima RI. Molecular investigations into the unfoldase action of severing enzymes on microtubules. Cytoskeleton (Hoboken) 2020; 77:214-228. [DOI: 10.1002/cm.21606] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Revised: 03/05/2020] [Accepted: 03/10/2020] [Indexed: 12/20/2022]
Affiliation(s)
| | - Amanda C. Macke
- Department of Chemistry University of Cincinnati Cincinnati Ohio USA
| | - Virginia Speck
- Department of Chemistry University of Cincinnati Cincinnati Ohio USA
| | | | - Ruxandra I. Dima
- Department of Chemistry University of Cincinnati Cincinnati Ohio USA
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38
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Horníková L, Bruštíková K, Forstová J. Microtubules in Polyomavirus Infection. Viruses 2020; 12:E121. [PMID: 31963741 PMCID: PMC7019765 DOI: 10.3390/v12010121] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 01/15/2020] [Accepted: 01/16/2020] [Indexed: 12/12/2022] Open
Abstract
Microtubules, part of the cytoskeleton, are indispensable for intracellular movement, cell division, and maintaining cell shape and polarity. In addition, microtubules play an important role in viral infection. In this review, we summarize the role of the microtubules' network during polyomavirus infection. Polyomaviruses usurp microtubules and their motors to travel via early and late acidic endosomes to the endoplasmic reticulum. As shown for SV40, kinesin-1 and microtubules are engaged in the release of partially disassembled virus from the endoplasmic reticulum to the cytosol, and dynein apparently assists in the further disassembly of virions prior to their translocation to the cell nucleus-the place of their replication. Polyomavirus gene products affect the regulation of microtubule dynamics. Early T antigens destabilize microtubules and cause aberrant mitosis. The role of these activities in tumorigenesis has been documented. However, its importance for productive infection remains elusive. On the other hand, in the late phase of infection, the major capsid protein, VP1, of the mouse polyomavirus, counteracts T-antigen-induced destabilization. It physically binds microtubules and stabilizes them. The interaction results in the G2/M block of the cell cycle and prolonged S phase, which is apparently required for successful completion of the viral replication cycle.
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Affiliation(s)
| | | | - Jitka Forstová
- Department of Genetics and Microbiology, Faculty of Science, Charles University, BIOCEV, 25250 Vestec, Czech Republic; (L.H.); (K.B.)
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39
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Khalifa AAZ, Ichikawa M, Dai D, Kubo S, Black CS, Peri K, McAlear TS, Veyron S, Yang SK, Vargas J, Bechstedt S, Trempe JF, Bui KH. The inner junction complex of the cilia is an interaction hub that involves tubulin post-translational modifications. eLife 2020; 9:e52760. [PMID: 31951202 PMCID: PMC6994238 DOI: 10.7554/elife.52760] [Citation(s) in RCA: 187] [Impact Index Per Article: 46.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Accepted: 01/16/2020] [Indexed: 12/11/2022] Open
Abstract
Microtubules are cytoskeletal structures involved in stability, transport and organization in the cell. The building blocks, the α- and β-tubulin heterodimers, form protofilaments that associate laterally into the hollow microtubule. Microtubule also exists as highly stable doublet microtubules in the cilia where stability is needed for ciliary beating and function. The doublet microtubule maintains its stability through interactions at its inner and outer junctions where its A- and B-tubules meet. Here, using cryo-electron microscopy, bioinformatics and mass spectrometry of the doublets of Chlamydomonas reinhardtii and Tetrahymena thermophila, we identified two new inner junction proteins, FAP276 and FAP106, and an inner junction-associated protein, FAP126, thus presenting the complete answer to the inner junction identity and localization. Our structural study of the doublets shows that the inner junction serves as an interaction hub that involves tubulin post-translational modifications. These interactions contribute to the stability of the doublet and hence, normal ciliary motility.
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Affiliation(s)
- Ahmad Abdelzaher Zaki Khalifa
- Department of Anatomy and Cell BiologyMcGill UniversityQuébecCanada
- Centre de Recherche en Biologie Structurale - FRQSMcGill UniversityQuébecCanada
| | | | - Daniel Dai
- Department of Anatomy and Cell BiologyMcGill UniversityQuébecCanada
- Centre de Recherche en Biologie Structurale - FRQSMcGill UniversityQuébecCanada
| | - Shintaroh Kubo
- Centre de Recherche en Biologie Structurale - FRQSMcGill UniversityQuébecCanada
- Department of Biophysics, Graduate School of ScienceKyoto UniversityKyotoJapan
| | - Corbin Steven Black
- Department of Anatomy and Cell BiologyMcGill UniversityQuébecCanada
- Centre de Recherche en Biologie Structurale - FRQSMcGill UniversityQuébecCanada
| | - Katya Peri
- Department of Anatomy and Cell BiologyMcGill UniversityQuébecCanada
| | - Thomas S McAlear
- Department of Anatomy and Cell BiologyMcGill UniversityQuébecCanada
- Centre de Recherche en Biologie Structurale - FRQSMcGill UniversityQuébecCanada
| | - Simon Veyron
- Centre de Recherche en Biologie Structurale - FRQSMcGill UniversityQuébecCanada
- Department of Pharmacology & TherapeuticsMcGill UniversityMontréalCanada
| | - Shun Kai Yang
- Department of Anatomy and Cell BiologyMcGill UniversityQuébecCanada
- Centre de Recherche en Biologie Structurale - FRQSMcGill UniversityQuébecCanada
| | - Javier Vargas
- Department of Anatomy and Cell BiologyMcGill UniversityQuébecCanada
- Centre de Recherche en Biologie Structurale - FRQSMcGill UniversityQuébecCanada
| | - Susanne Bechstedt
- Department of Anatomy and Cell BiologyMcGill UniversityQuébecCanada
- Centre de Recherche en Biologie Structurale - FRQSMcGill UniversityQuébecCanada
| | - Jean-François Trempe
- Centre de Recherche en Biologie Structurale - FRQSMcGill UniversityQuébecCanada
- Department of Pharmacology & TherapeuticsMcGill UniversityMontréalCanada
| | - Khanh Huy Bui
- Department of Anatomy and Cell BiologyMcGill UniversityQuébecCanada
- Centre de Recherche en Biologie Structurale - FRQSMcGill UniversityQuébecCanada
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40
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O V SS, Palaparthi S, Pidaparti R. Mimicking Sub-Structures Self-Organization in Microtubules. Biomimetics (Basel) 2019; 4:biomimetics4040071. [PMID: 31635308 PMCID: PMC6963431 DOI: 10.3390/biomimetics4040071] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Revised: 09/19/2019] [Accepted: 10/15/2019] [Indexed: 01/25/2023] Open
Abstract
Microtubules (MTs) are highly dynamic polymers distributed in the cytoplasm of a biological cell. Alpha and beta globular proteins constituting the heterodimer building blocks combine to form these tubules through polymerization, controlled by the concentration of Guanosine-triphosphate (GTPs) and other Microtubule Associated Proteins (MAPs). MTs play a crucial role in many intracellular processes, predominantly in mitosis, organelle transport and cell locomotion. Current research in this area is focused on understanding the exclusive behaviors of self-organization and their association with different MAPs through organized laboratory experiments. However, the intriguing intelligence behind these tiny machines resulting in complex self-organizing structures is mostly unexplored. In this study, we propose a novel swarm engineering framework in modeling rules for these systems, by combining the principles of design with swarm intelligence. The proposed framework was simulated on a game engine and these simulations demonstrated self-organization of rings and protofilaments in MTs. Analytics from these simulations assisted in understanding the influence of GTPs on protofilament formation. Also, results showed that the population density of GTPs rather than their bonding probabilities played a crucial role in polymerization in forming microtubule substructures.
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Affiliation(s)
- Sanjay Sarma O V
- College of Engineering, University of Georgia, Athens, GA 30602, USA.
| | - Sruthi Palaparthi
- Department of Computer Science, University of Georgia, Athens, GA 30602, USA.
| | - Ramana Pidaparti
- College of Engineering, University of Georgia, Athens, GA 30602, USA.
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41
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Reid TA, Coombes C, Mukherjee S, Goldblum RR, White K, Parmar S, McClellan M, Zanic M, Courtemanche N, Gardner MK. Structural state recognition facilitates tip tracking of EB1 at growing microtubule ends. eLife 2019; 8:48117. [PMID: 31478831 PMCID: PMC6742484 DOI: 10.7554/elife.48117] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Accepted: 08/23/2019] [Indexed: 11/13/2022] Open
Abstract
The microtubule binding protein EB1 specifically targets the growing ends of microtubules in cells, where EB1 facilitates the interactions of cellular proteins with microtubule plus-ends. Microtubule end targeting of EB1 has been attributed to high-affinity binding of EB1 to GTP-tubulin that is present at growing microtubule ends. However, our 3D single-molecule diffusion simulations predicted a ~ 6000% increase in EB1 arrivals to open, tapered microtubule tip structures relative to closed lattice conformations. Using quantitative fluorescence, single-molecule, and electron microscopy experiments, we found that the binding of EB1 onto opened, structurally disrupted microtubules was dramatically increased relative to closed, intact microtubules, regardless of hydrolysis state. Correspondingly, in cells, the blunting of growing microtubule plus-ends by Vinblastine was correlated with reduced EB1 targeting. Together, our results suggest that microtubule structural recognition, based on a fundamental diffusion-limited binding model, facilitates the tip tracking of EB1 at growing microtubule ends.
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Affiliation(s)
- Taylor A Reid
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, United States
| | - Courtney Coombes
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, United States
| | - Soumya Mukherjee
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, United States
| | - Rebecca R Goldblum
- Medical Scientist Training Program, University of Minnesota, Minneapolis, United States.,Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, United States
| | - Kyle White
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, United States
| | - Sneha Parmar
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, United States
| | - Mark McClellan
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, United States
| | - Marija Zanic
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, United States
| | - Naomi Courtemanche
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, United States
| | - Melissa K Gardner
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, United States
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42
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Hervy J, Bicout DJ. Dynamical decoration of stabilized-microtubules by Tau-proteins. Sci Rep 2019; 9:12473. [PMID: 31462746 PMCID: PMC6713733 DOI: 10.1038/s41598-019-48790-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Accepted: 08/12/2019] [Indexed: 11/19/2022] Open
Abstract
Tau is a microtubule-associated protein that regulates axonal transport, stabilizes and spatially organizes microtubules in parallel networks. The Tau-microtubule pair is crucial for maintaining the architecture and integrity of axons. Therefore, it is essential to understand how these two entities interact to ensure and modulate the normal axonal functions. Based on evidence from several published experiments, we have developed a two-dimensional model that describes the interaction between a population of Tau proteins and a stabilized microtubule at the scale of the tubulin dimers (binding sites) as an adsorption-desorption dynamical process in which Tau can bind on the microtubule outer surface via two distinct modes: a longitudinal (along a protofilament) and lateral (across adjacent protofilaments) modes. Such a process yields a dynamical distribution of Tau molecules on the microtubule surface referred to as microtubule decoration that we have characterized at the equilibrium using two observables: the total microtubule surface coverage with Tau's and the distribution of nearest neighbors Tau's. Using both analytical and numerical approaches, we have derived expressions and computed these observables as a function of key parameters controlling the binding reaction: the stoichiometries of the Taus in the two binding modes, the associated dissociation constants and the ratio of the Tau concentration to that of microtubule tubulin dimers.
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Affiliation(s)
- Jordan Hervy
- Institut Laue-Langevin, 71 Avenue des Martyrs, 38042, Grenoble, France
- Laboratory of Physics and Modelling of Condensed Matter, Grenoble Alpes University, CNRS, Grenoble, France
| | - Dominique J Bicout
- Institut Laue-Langevin, 71 Avenue des Martyrs, 38042, Grenoble, France.
- EPSP, TIMC Laboratory, UMR CNRS 5525 Grenoble Alpes University, VetAgro Sup, Grenoble, France.
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43
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Duan YT, Sangani CB, Liu W, Soni KV, Yao Y. New Promises to Cure Cancer and Other Genetic Diseases/Disorders: Epi-drugs Through Epigenetics. Curr Top Med Chem 2019; 19:972-994. [DOI: 10.2174/1568026619666190603094439] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2019] [Revised: 05/05/2019] [Accepted: 05/27/2019] [Indexed: 12/13/2022]
Abstract
All the heritable alterations in gene expression and chromatin structure due to chemical modifications that do not involve changes in the primary gene nucleotide sequence are referred to as epigenetics. DNA methylation, histone modifications, and non-coding RNAs are distinct types of epigenetic inheritance. Epigenetic patterns have been linked to the developmental stages, environmental exposure, and diet. Therapeutic strategies are now being developed to target human diseases such as cancer with mutations in epigenetic regulatory genes using specific inhibitors. Within the past two decades, seven epigenetic drugs have received regulatory approval and many others show their candidature in clinical trials. The current article represents a review of epigenetic heritance, diseases connected with epigenetic alterations and regulatory approved epigenetic drugs as future medicines.
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Affiliation(s)
- Yong-Tao Duan
- Henan Provincial Key Laboratory of Children's Genetics and Metabolic Diseases, Zhengzhou Children's Hospital, Zhengzhou University, Zhengzhou 450018, China
| | - Chetan B. Sangani
- Shri Maneklal M. Patel Institute of Sciences and Research, Kadi Sarva Vishwavidyalaya University, Gandhinagar, Gujarat, 362024, India
| | - Wei Liu
- Henan Provincial Key Laboratory of Children's Genetics and Metabolic Diseases, Zhengzhou Children's Hospital, Zhengzhou University, Zhengzhou 450018, China
| | - Kunjal V. Soni
- Shri Maneklal M. Patel Institute of Sciences and Research, Kadi Sarva Vishwavidyalaya University, Gandhinagar, Gujarat, 362024, India
| | - Yongfang Yao
- Collaborative Innovation Center of New Drug Research and Safety Evaluation, Zhengzhou University, Zhengzhou, 450001, China
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44
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Brändén G, Hammarin G, Harimoorthy R, Johansson A, Arnlund D, Malmerberg E, Barty A, Tångefjord S, Berntsen P, DePonte DP, Seuring C, White TA, Stellato F, Bean R, Beyerlein KR, Chavas LMG, Fleckenstein H, Gati C, Ghoshdastider U, Gumprecht L, Oberthür D, Popp D, Seibert M, Tilp T, Messerschmidt M, Williams GJ, Loh ND, Chapman HN, Zwart P, Liang M, Boutet S, Robinson RC, Neutze R. Coherent diffractive imaging of microtubules using an X-ray laser. Nat Commun 2019; 10:2589. [PMID: 31197138 PMCID: PMC6565740 DOI: 10.1038/s41467-019-10448-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Accepted: 05/02/2019] [Indexed: 01/09/2023] Open
Abstract
X-ray free electron lasers (XFELs) create new possibilities for structural studies of biological objects that extend beyond what is possible with synchrotron radiation. Serial femtosecond crystallography has allowed high-resolution structures to be determined from micro-meter sized crystals, whereas single particle coherent X-ray imaging requires development to extend the resolution beyond a few tens of nanometers. Here we describe an intermediate approach: the XFEL imaging of biological assemblies with helical symmetry. We collected X-ray scattering images from samples of microtubules injected across an XFEL beam using a liquid microjet, sorted these images into class averages, merged these data into a diffraction pattern extending to 2 nm resolution, and reconstructed these data into a projection image of the microtubule. Details such as the 4 nm tubulin monomer became visible in this reconstruction. These results illustrate the potential of single-molecule X-ray imaging of biological assembles with helical symmetry at room temperature.
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Affiliation(s)
- Gisela Brändén
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530, Gothenburg, Sweden.
| | - Greger Hammarin
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530, Gothenburg, Sweden
| | - Rajiv Harimoorthy
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530, Gothenburg, Sweden
| | - Alexander Johansson
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530, Gothenburg, Sweden
| | - David Arnlund
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530, Gothenburg, Sweden
| | - Erik Malmerberg
- Molecular Biophysics and Integrated Bio-Imaging Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, 94720, Berkeley, CA, USA
| | - Anton Barty
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany
| | - Stefan Tångefjord
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530, Gothenburg, Sweden
| | - Peter Berntsen
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530, Gothenburg, Sweden
| | - Daniel P DePonte
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Carolin Seuring
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany.,The Hamburg Center for Ultrafast Imaging, 22761, Hamburg, Germany
| | - Thomas A White
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany
| | - Francesco Stellato
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany
| | - Richard Bean
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany
| | - Kenneth R Beyerlein
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany
| | - Leonard M G Chavas
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany
| | - Holger Fleckenstein
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany
| | - Cornelius Gati
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany
| | - Umesh Ghoshdastider
- Institute of Molecular and Cell Biology, Biopolis, A*STAR (Agency for Science, Technology and Research), 138673, Singapore, Singapore
| | - Lars Gumprecht
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany
| | - Dominik Oberthür
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany
| | - David Popp
- Institute of Molecular and Cell Biology, Biopolis, A*STAR (Agency for Science, Technology and Research), 138673, Singapore, Singapore
| | - Marvin Seibert
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Thomas Tilp
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany
| | - Marc Messerschmidt
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Garth J Williams
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - N Duane Loh
- Department of Physics, National University of Singapore, 117551, Singapore, Singapore
| | - Henry N Chapman
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany.,The Hamburg Center for Ultrafast Imaging, 22761, Hamburg, Germany.,Department of Physics, University of Hamburg, 22761, Hamburg, Germany
| | - Peter Zwart
- Molecular Biophysics and Integrated Bio-Imaging Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, 94720, Berkeley, CA, USA
| | - Mengning Liang
- Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany.,Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Sébastien Boutet
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Robert C Robinson
- Institute of Molecular and Cell Biology, Biopolis, A*STAR (Agency for Science, Technology and Research), 138673, Singapore, Singapore.,Department of Biochemistry, National University of Singapore, 117597, Singapore, Singapore.,Research Institute for Interdisciplinary Science, Okayama University, Okayama, 700-8530, Japan
| | - Richard Neutze
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530, Gothenburg, Sweden.
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45
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Manka SW, Moores CA. Microtubule structure by cryo-EM: snapshots of dynamic instability. Essays Biochem 2018; 62:737-751. [PMID: 30315096 PMCID: PMC6281474 DOI: 10.1042/ebc20180031] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Revised: 09/14/2018] [Accepted: 09/19/2018] [Indexed: 01/24/2023]
Abstract
The development of cryo-electron microscopy (cryo-EM) allowed microtubules to be captured in their solution-like state, enabling decades of insight into their dynamic mechanisms and interactions with binding partners. Cryo-EM micrographs provide 2D visualization of microtubules, and these 2D images can also be used to reconstruct the 3D structure of the polymer and any associated binding partners. In this way, the binding sites for numerous components of the microtubule cytoskeleton-including motor domains from many kinesin motors, and the microtubule-binding domains of dynein motors and an expanding collection of microtubule associated proteins-have been determined. The effects of various microtubule-binding drugs have also been studied. High-resolution cryo-EM structures have also been used to probe the molecular basis of microtubule dynamic instability, driven by the GTPase activity of β-tubulin. These studies have shown the conformational changes in lattice-confined tubulin dimers in response to steps in the tubulin GTPase cycle, most notably lattice compaction at the longitudinal inter-dimer interface. Although work is ongoing to define a complete structural model of dynamic instability, attention has focused on the role of gradual destabilization of lateral contacts between tubulin protofilaments, particularly at the microtubule seam. Furthermore, lower resolution cryo-electron tomography 3D structures are shedding light on the heterogeneity of microtubule ends and how their 3D organization contributes to dynamic instability. The snapshots of these polymers captured using cryo-EM will continue to provide critical insights into their dynamics, interactions with cellular components, and the way microtubules contribute to cellular functions in diverse physiological contexts.
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Affiliation(s)
- Szymon W Manka
- Institute of Structural and Molecular Biology, Department of Biological Sciences, Birkbeck, University of London, London, U.K.
| | - Carolyn A Moores
- Institute of Structural and Molecular Biology, Department of Biological Sciences, Birkbeck, University of London, London, U.K
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46
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Abstract
The cytoskeleton is crucially important for the assembly of cell-cell junctions and the homeostatic regulation of their functions. Junctional proteins act, in turn, as anchors for cytoskeletal filaments, and as regulators of cytoskeletal dynamics and signalling proteins. The cross-talk between junctions and the cytoskeleton is critical for the morphogenesis and physiology of epithelial and other tissues, but is not completely understood. Microtubules are implicated in the delivery of junctional proteins to cell-cell contact sites, in the differentiation and spatial organization of the cytoplasm, and in the stabilization of the barrier and adhesive functions of junctions. Here we focus on the relationships between microtubules and junctions of vertebrate epithelial cells. We highlight recent discoveries on the molecular underpinnings of microtubule-junction interactions, and report new data about the interaction of cingulin and paracingulin with microtubules. We also propose a possible new role of junctions as “molecular sinks” for microtubule-associated signalling proteins.
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Affiliation(s)
- Ekaterina Vasileva
- a Department of Cell Biology, Faculty of Sciences and Institute for Genetics and Genomics in Geneva (iGE3) , University of Geneva , Geneva , Switzerland
| | - Sandra Citi
- a Department of Cell Biology, Faculty of Sciences and Institute for Genetics and Genomics in Geneva (iGE3) , University of Geneva , Geneva , Switzerland
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47
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Ti SC, Alushin GM, Kapoor TM. Human β-Tubulin Isotypes Can Regulate Microtubule Protofilament Number and Stability. Dev Cell 2018; 47:175-190.e5. [PMID: 30245156 DOI: 10.1016/j.devcel.2018.08.014] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Revised: 06/28/2018] [Accepted: 08/20/2018] [Indexed: 10/28/2022]
Abstract
Cell biological studies have shown that protofilament number, a fundamental feature of microtubules, can correlate with the expression of different tubulin isotypes. However, it is not known if tubulin isotypes directly control this basic microtubule property. Here, we report high-resolution cryo-EM reconstructions (3.5-3.65 Å) of purified human α1B/β3 and α1B/β2B microtubules and find that the β-tubulin isotype can determine protofilament number. Comparisons of atomic models of 13- and 14-protofilament microtubules reveal how tubulin subunit plasticity, manifested in "accordion-like" distributed structural changes, can accommodate distinct lattice organizations. Furthermore, compared to α1B/β3 microtubules, α1B/β2B filaments are more stable to passive disassembly and against depolymerization by MCAK or chTOG, microtubule-associated proteins with distinct mechanisms of action. Mixing tubulin isotypes in different proportions results in microtubules with protofilament numbers and stabilities intermediate to those of isotypically pure filaments. Together, our findings indicate that microtubule protofilament number and stability can be controlled through β-tubulin isotype composition.
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Affiliation(s)
- Shih-Chieh Ti
- Laboratory of Chemistry and Cell Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Gregory M Alushin
- Laboratory of Structural Biophysics and Mechanobiology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.
| | - Tarun M Kapoor
- Laboratory of Chemistry and Cell Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.
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48
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Chaaban S, Jariwala S, Hsu CT, Redemann S, Kollman JM, Müller-Reichert T, Sept D, Bui KH, Brouhard GJ. The Structure and Dynamics of C. elegans Tubulin Reveals the Mechanistic Basis of Microtubule Growth. Dev Cell 2018; 47:191-204.e8. [PMID: 30245157 DOI: 10.1016/j.devcel.2018.08.023] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Revised: 07/06/2018] [Accepted: 08/23/2018] [Indexed: 01/04/2023]
Abstract
The dynamic instability of microtubules is a conserved and fundamental mechanism in eukaryotes. Yet microtubules from different species diverge in their growth rates, lattice structures, and responses to GTP hydrolysis. Therefore, we do not know what limits microtubule growth, what determines microtubule structure, or whether the mechanisms of dynamic instability are universal. Here, we studied microtubules from the nematode C. elegans, which have strikingly fast growth rates and non-canonical lattices in vivo. Using a reconstitution approach, we discovered that C. elegans microtubules combine intrinsically fast growth with very frequent catastrophes. We solved the structure of C. elegans microtubules to 4.8 Å and discovered sequence divergence in the lateral contact loops, one of which is ordered in C. elegans but unresolved in other species. We provide direct evidence that C. elegans tubulin has a higher free energy in solution and propose a model wherein the ordering of lateral contact loops activates tubulin for growth.
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Affiliation(s)
- Sami Chaaban
- Department of Biology, 1205 Avenue Docteur Penfield, Montréal, QC H3A 1B1, Canada
| | - Shashank Jariwala
- Department of Computational Medicine and Bioinformatics, 100 Washtenaw Avenue, Ann Arbor, MI 48109, USA
| | - Chieh-Ting Hsu
- Department of Biology, 1205 Avenue Docteur Penfield, Montréal, QC H3A 1B1, Canada
| | - Stefanie Redemann
- Experimental Center, Technische Universität Dresden, Faculty of Medicine, Fiedlerstraße 42, 01307 Dresden, Germany; Center for Membrane & Cell Physiology, University of Virginia and Department of Molecular Physiology & Biological Physics, 480 Ray C. Hung Drive, Charlottesville, VA 22903, USA
| | - Justin M Kollman
- Department of Biochemistry, 1959 NE Pacific Street, Seattle, WA 98195, USA
| | - Thomas Müller-Reichert
- Experimental Center, Technische Universität Dresden, Faculty of Medicine, Fiedlerstraße 42, 01307 Dresden, Germany
| | - David Sept
- Department of Biomedical Engineering, 2200 Bonisteel Boulevard, Ann Arbor, MI 48109, USA
| | - Khanh Huy Bui
- Department of Anatomy and Cell Biology, 3640 Rue University, Montréal, QC H3A 0C7, Canada
| | - Gary J Brouhard
- Department of Biology, 1205 Avenue Docteur Penfield, Montréal, QC H3A 1B1, Canada.
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49
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Atherton J, Stouffer M, Francis F, Moores CA. Microtubule architecture in vitro and in cells revealed by cryo-electron tomography. ACTA CRYSTALLOGRAPHICA SECTION D-STRUCTURAL BIOLOGY 2018; 74:572-584. [PMID: 29872007 PMCID: PMC6096491 DOI: 10.1107/s2059798318001948] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Accepted: 02/01/2018] [Indexed: 01/03/2023]
Abstract
Electron microscopy is a key methodology for studying microtubule structure and organization. Here, the results of cryo-electron tomography experiments on in vitro-polymerized microtubules and comparisons with microtubule ultrastructure in cells are described. The microtubule cytoskeleton is involved in many vital cellular processes. Microtubules act as tracks for molecular motors, and their polymerization and depolymerization can be harnessed to generate force. The structures of microtubules provide key information about the mechanisms by which their cellular roles are accomplished and the physiological context in which these roles are performed. Cryo-electron microscopy allows the visualization of in vitro-polymerized microtubules and has provided important insights into their overall morphology and the influence of a range of factors on their structure and dynamics. Cryo-electron tomography can be used to determine the unique three-dimensional structure of individual microtubules and their ends. Here, a previous cryo-electron tomography study of in vitro-polymerized GMPCPP-stabilized microtubules is revisited, the findings are compared with new tomograms of dynamic in vitro and cellular microtubules, and the information that can be extracted from such data is highlighted. The analysis shows the surprising structural heterogeneity of in vitro-polymerized microtubules. Lattice defects can be observed both in vitro and in cells. The shared ultrastructural properties in these different populations emphasize the relevance of three-dimensional structures of in vitro microtubules for understanding microtubule cellular functions.
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Affiliation(s)
- Joseph Atherton
- Institute of Structural and Molecular Biology, Birkbeck College, Malet Street, London WC1E 7HX, England
| | | | - Fiona Francis
- INSERM UMR-S 839, 17 Rue du Fer à Moulin, 75005 Paris, France
| | - Carolyn A Moores
- Institute of Structural and Molecular Biology, Birkbeck College, Malet Street, London WC1E 7HX, England
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50
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Aher A, Akhmanova A. Tipping microtubule dynamics, one protofilament at a time. Curr Opin Cell Biol 2018; 50:86-93. [PMID: 29573640 DOI: 10.1016/j.ceb.2018.02.015] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2018] [Revised: 02/19/2018] [Accepted: 02/28/2018] [Indexed: 01/10/2023]
Abstract
Microtubules are polymeric tubes that switch between phases of growth and shortening, and this property is essential to drive key cellular processes. Microtubules are composed of protofilaments formed by longitudinally arranged tubulin dimers. Microtubule dynamics can be affected by structural perturbations at the plus end, such as end tapering, and targeting only a small subset of protofilaments can alter the dynamics of the whole microtubule. Microtubule lattice plasticity, including compaction along the longitudinal axis upon GTP hydrolysis and tubulin dimer loss and reinsertion along microtubule shafts can also affect microtubule dynamics or mechanics. Microtubule behaviour can be fine-tuned by post-translational modifications and tubulin isotypes, which together support the diversity of microtubule functions within and across various cell types or cell cycle and developmental stages.
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Affiliation(s)
- Amol Aher
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Anna Akhmanova
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
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