1
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Exploring the dynamics of flagellar dynein within the axoneme with Fluctuating Finite Element Analysis. Q Rev Biophys 2020; 53:e9. [PMID: 32772965 DOI: 10.1017/s0033583520000062] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Flagellar dyneins are the molecular motors responsible for producing the propagating bending motions of cilia and flagella. They are located within a densely packed and highly organised super-macromolecular cytoskeletal structure known as the axoneme. Using the mesoscale simulation technique Fluctuating Finite Element Analysis (FFEA), which represents proteins as viscoelastic continuum objects subject to explicit thermal noise, we have quantified the constraints on the range of molecular conformations that can be explored by dynein-c within the crowded architecture of the axoneme. We subsequently assess the influence of crowding on the 3D exploration of microtubule-binding sites, and specifically on the axial step length. Our calculations combine experimental information on the shape, flexibility and environment of dynein-c from three distinct sources; negative stain electron microscopy, cryo-electron microscopy (cryo-EM) and cryo-electron tomography (cryo-ET). Our FFEA simulations show that the super-macromolecular organisation of multiple protein complexes into higher-order structures can have a significant influence on the effective flexibility of the individual molecular components, and may, therefore, play an important role in the physical mechanisms underlying their biological function.
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2
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Markus SM, Marzo MG, McKenney RJ. New insights into the mechanism of dynein motor regulation by lissencephaly-1. eLife 2020; 9:59737. [PMID: 32692650 PMCID: PMC7373426 DOI: 10.7554/elife.59737] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Accepted: 07/13/2020] [Indexed: 12/20/2022] Open
Abstract
Lissencephaly (‘smooth brain’) is a severe brain disease associated with numerous symptoms, including cognitive impairment, and shortened lifespan. The main causative gene of this disease – lissencephaly-1 (LIS1) – has been a focus of intense scrutiny since its first identification almost 30 years ago. LIS1 is a critical regulator of the microtubule motor cytoplasmic dynein, which transports numerous cargoes throughout the cell, and is a key effector of nuclear and neuronal transport during brain development. Here, we review the role of LIS1 in cellular dynein function and discuss recent key findings that have revealed a new mechanism by which this molecule influences dynein-mediated transport. In addition to reconciling prior observations with this new model for LIS1 function, we also discuss phylogenetic data that suggest that LIS1 may have coevolved with an autoinhibitory mode of cytoplasmic dynein regulation.
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Affiliation(s)
- Steven M Markus
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, United States
| | - Matthew G Marzo
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, United States
| | - Richard J McKenney
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, United States
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3
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Johnson CM, Fenn JD, Brown A, Jung P. Dynamic catch-bonding generates the large stall forces of cytoplasmic dynein. Phys Biol 2020; 17:046004. [PMID: 32369788 DOI: 10.1088/1478-3975/ab907d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Cytoplasmic dynein is an important molecular motor involved in the transport of vesicular and macromolecular cargo along microtubules in cells, often in conjunction with kinesin motors. Dynein is larger and more complex than kinesin and the mechanism and regulation of its movement is currently the subject of intense research. While it was believed for a long time that dynein motors are relatively weak in terms of the force they can generate, recent studies have shown that interactions with regulatory proteins confer large stall forces comparable to those of kinesin. This paper reports on a theoretical study which suggests that these large stall forces may be the result of an emergent, ATP-dependent, bistability resulting in a dynamic catch-bonding behavior that can cause the motor to switch between high and low load-force states.
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Affiliation(s)
- Christopher M Johnson
- Department of Physics and Astronomy, Ohio University, Athens, OH 45701, United States of America
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4
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Hanson BS, Iida S, Read DJ, Harlen OG, Kurisu G, Nakamura H, Harris SA. Continuum mechanical parameterisation of cytoplasmic dynein from atomistic simulation. Methods 2020; 185:39-48. [PMID: 32007556 DOI: 10.1016/j.ymeth.2020.01.021] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Revised: 01/28/2020] [Accepted: 01/28/2020] [Indexed: 01/08/2023] Open
Abstract
Cytoplasmic dynein is responsible for intra-cellular transport in eukaryotic cells. Using Fluctuating Finite Element Analysis (FFEA), a novel algorithm that represents proteins as continuum viscoelastic solids subject to thermal noise, we are building computational tools to study the mechanics of these molecular machines. Here we present a methodology for obtaining the material parameters required to represent the flexibility of cytoplasmic dynein within FFEA from atomistic molecular dynamics (MD) simulations, and show that this continuum representation is sufficient to capture the principal dynamic properties of the motor.
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Affiliation(s)
- Benjamin S Hanson
- School of Physics & Astronomy, University of Leeds, Leeds LS2 9JT, UK
| | - Shinji Iida
- Institute for Protein Research, Osaka University, 3-2 Yamadoaka, Suita, Osaka 565-0871, Japan
| | - Daniel J Read
- School of Mathematics, University of Leeds, Leeds LS2 9JT, UK
| | - Oliver G Harlen
- School of Mathematics, University of Leeds, Leeds LS2 9JT, UK
| | - Genji Kurisu
- Institute for Protein Research, Osaka University, 3-2 Yamadoaka, Suita, Osaka 565-0871, Japan
| | - Haruki Nakamura
- Institute for Protein Research, Osaka University, 3-2 Yamadoaka, Suita, Osaka 565-0871, Japan
| | - Sarah A Harris
- School of Physics & Astronomy, University of Leeds, Leeds LS2 9JT, UK; Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK.
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5
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A model for the chemomechanical coupling of the mammalian cytoplasmic dynein molecular motor. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2019; 48:609-619. [PMID: 31278451 DOI: 10.1007/s00249-019-01386-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 06/17/2019] [Accepted: 07/01/2019] [Indexed: 01/07/2023]
Abstract
Available single-molecule data have shown that some mammalian cytoplasmic dynein dimers move on microtubules with a constant step size of about 8.2 nm. Here, a model is presented for the chemomechanical coupling of these mammalian cytoplasmic dynein dimers. In contrast to the previous models, a peculiar feature of the current model is that the rate constants of ATPase activity are independent of the external force. Based on this model, analytical studies of the motor dynamics are presented. With only four adjustable parameters, the theoretical results reproduce quantitatively diverse available single-molecule data on the force dependence of stepping ratio, velocity, mean dwell time, and dwell-time distribution between two mechanical steps. Predicted results are also provided for the force dependence of the number of ATP molecules consumed per mechanical step, indicating that under no or low force the motors exhibit a tight chemomechanical coupling, and as the force increases the number of ATPs consumed per step increases greatly.
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6
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Sosnowski P, Urnavicius L, Boland A, Fagiewicz R, Busselez J, Papai G, Schmidt H. The CryoEM structure of the Saccharomyces cerevisiae ribosome maturation factor Rea1. eLife 2018; 7:39163. [PMID: 30460895 PMCID: PMC6286127 DOI: 10.7554/elife.39163] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 11/08/2018] [Indexed: 11/29/2022] Open
Abstract
The biogenesis of 60S ribosomal subunits is initiated in the nucleus where rRNAs and proteins form pre-60S particles. These pre-60S particles mature by transiently interacting with various assembly factors. The ~5000 amino-acid AAA+ ATPase Rea1 (or Midasin) generates force to mechanically remove assembly factors from pre-60S particles, which promotes their export to the cytosol. Here we present three Rea1 cryoEM structures. We visualise the Rea1 engine, a hexameric ring of AAA+ domains, and identify an α-helical bundle of AAA2 as a major ATPase activity regulator. The α-helical bundle interferes with nucleotide-induced conformational changes that create a docking site for the substrate binding MIDAS domain on the AAA +ring. Furthermore, we reveal the architecture of the Rea1 linker, which is involved in force generation and extends from the AAA+ ring. The data presented here provide insights into the mechanism of one of the most complex ribosome maturation factors.
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Affiliation(s)
- Piotr Sosnowski
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Centre National de la Recherche Scientifique, UMR7104, Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U964, Illkirch, France.,Université de Strasbourg, Illkirch, France
| | - Linas Urnavicius
- Division of Structural Studies, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Andreas Boland
- Division of Structural Studies, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Robert Fagiewicz
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Centre National de la Recherche Scientifique, UMR7104, Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U964, Illkirch, France.,Université de Strasbourg, Illkirch, France
| | - Johan Busselez
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Centre National de la Recherche Scientifique, UMR7104, Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U964, Illkirch, France.,Université de Strasbourg, Illkirch, France
| | - Gabor Papai
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Centre National de la Recherche Scientifique, UMR7104, Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U964, Illkirch, France.,Université de Strasbourg, Illkirch, France
| | - Helgo Schmidt
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Centre National de la Recherche Scientifique, UMR7104, Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U964, Illkirch, France.,Université de Strasbourg, Illkirch, France
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7
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Barsegov V, Ross JL, Dima RI. Dynamics of microtubules: highlights of recent computational and experimental investigations. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:433003. [PMID: 28812545 DOI: 10.1088/1361-648x/aa8670] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Microtubules are found in most eukaryotic cells, with homologs in eubacteria and archea, and they have functional roles in mitosis, cell motility, intracellular transport, and the maintenance of cell shape. Numerous efforts have been expended over the last two decades to characterize the interactions between microtubules and the wide variety of microtubule associated proteins that control their dynamic behavior in cells resulting in microtubules being assembled and disassembled where and when they are required by the cell. We present the main findings regarding microtubule polymerization and depolymerization and review recent work about the molecular motors that modulate microtubule dynamics by inducing either microtubule depolymerization or severing. We also discuss the main experimental and computational approaches used to quantify the thermodynamics and mechanics of microtubule filaments.
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Affiliation(s)
- Valeri Barsegov
- Department of Chemistry, University of Massachusetts, Lowell, MA 01854, United States of America
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8
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Šarlah A, Vilfan A. Minimum requirements for motility of a processive motor protein. PLoS One 2017; 12:e0185948. [PMID: 29016643 PMCID: PMC5634618 DOI: 10.1371/journal.pone.0185948] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Accepted: 09/21/2017] [Indexed: 11/19/2022] Open
Abstract
Motor proteins generally have a two-way coupling between the ATP hydrolysis site, the lever movement and the binding affinity for their track, which allows them to perform efficient stepping. Here we explore the minimal requirements for directed motility based on simpler schemes in which the binding/unbinding from the track is decoupled from the ATPase cycle. We show that a directed power stroke alone is not sufficient for motility, but combined with an asymmetry in force-induced unbinding rates it can generate stepping. The energetic efficiency of such stepping is limited to approximately 20%. We conclude that the allosteric coupling between the ATP hydrolysis and the track binding is not strictly necessary for motility, but it greatly improves its efficiency.
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Affiliation(s)
- Andreja Šarlah
- Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana, Slovenia
- * E-mail: (AŠ); (AV)
| | - Andrej Vilfan
- J. Stefan Institute, Ljubljana, Slovenia
- * E-mail: (AŠ); (AV)
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9
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Schroeder CM, Vale RD. Assembly and activation of dynein-dynactin by the cargo adaptor protein Hook3. J Cell Biol 2017; 214:309-18. [PMID: 27482052 PMCID: PMC4970328 DOI: 10.1083/jcb.201604002] [Citation(s) in RCA: 90] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Accepted: 07/07/2016] [Indexed: 11/22/2022] Open
Abstract
Metazoan dynein moves processively with the aid of dynactin and the endosomal cargo adaptor Hook3. A structure–function study of Hook3 reveals how it assembles dynein with dynactin and suggests that an additional step of allosteric activation is required beyond complex assembly. Metazoan cytoplasmic dynein moves processively along microtubules with the aid of dynactin and an adaptor protein that joins dynein and dynactin into a stable ternary complex. Here, we examined how Hook3, a cargo adaptor involved in Golgi and endosome transport, forms a motile dynein–dynactin complex. We show that the conserved Hook domain interacts directly with the dynein light intermediate chain 1 (LIC1). By solving the crystal structure of the Hook domain and using structure-based mutagenesis, we identify two conserved surface residues that are each critical for LIC1 binding. Hook proteins with mutations in these residues fail to form a stable dynein–dynactin complex, revealing a crucial role for LIC1 in this interaction. We also identify a region of Hook3 specifically required for an allosteric activation of processive motility. Our work reveals the structural details of Hook3’s interaction with dynein and offers insight into how cargo adaptors form processive dynein–dynactin motor complexes.
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Affiliation(s)
- Courtney M Schroeder
- The Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158 Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158
| | - Ronald D Vale
- The Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158 Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158
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10
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Steinman JB, Santarossa CC, Miller RM, Yu LS, Serpinskaya AS, Furukawa H, Morimoto S, Tanaka Y, Nishitani M, Asano M, Zalyte R, Ondrus AE, Johnson AG, Ye F, Nachury MV, Fukase Y, Aso K, Foley MA, Gelfand VI, Chen JK, Carter AP, Kapoor TM. Chemical structure-guided design of dynapyrazoles, cell-permeable dynein inhibitors with a unique mode of action. eLife 2017; 6. [PMID: 28524820 PMCID: PMC5478271 DOI: 10.7554/elife.25174] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Accepted: 05/17/2017] [Indexed: 12/11/2022] Open
Abstract
Cytoplasmic dyneins are motor proteins in the AAA+ superfamily that transport cellular cargos toward microtubule minus-ends. Recently, ciliobrevins were reported as selective cell-permeable inhibitors of cytoplasmic dyneins. As is often true for first-in-class inhibitors, the use of ciliobrevins has in part been limited by low potency. Moreover, suboptimal chemical properties, such as the potential to isomerize, have hindered efforts to improve ciliobrevins. Here, we characterized the structure of ciliobrevins and designed conformationally constrained isosteres. These studies identified dynapyrazoles, inhibitors more potent than ciliobrevins. At single-digit micromolar concentrations dynapyrazoles block intraflagellar transport in the cilium and lysosome motility in the cytoplasm, processes that depend on cytoplasmic dyneins. Further, we find that while ciliobrevins inhibit both dynein's microtubule-stimulated and basal ATPase activity, dynapyrazoles strongly block only microtubule-stimulated activity. Together, our studies suggest that chemical-structure-based analyses can lead to inhibitors with improved properties and distinct modes of inhibition. DOI:http://dx.doi.org/10.7554/eLife.25174.001
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Affiliation(s)
- Jonathan B Steinman
- Laboratory of Chemistry and Cell Biology, Rockefeller University, New York, United States
| | - Cristina C Santarossa
- Laboratory of Chemistry and Cell Biology, Rockefeller University, New York, United States
| | - Rand M Miller
- Laboratory of Chemistry and Cell Biology, Rockefeller University, New York, United States
| | - Lola S Yu
- Laboratory of Chemistry and Cell Biology, Rockefeller University, New York, United States
| | - Anna S Serpinskaya
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Hideki Furukawa
- Tri-Institutitional Therapeutics Discovery Institute, New York, United States
| | - Sachie Morimoto
- Tri-Institutitional Therapeutics Discovery Institute, New York, United States
| | - Yuta Tanaka
- Tri-Institutitional Therapeutics Discovery Institute, New York, United States
| | | | - Moriteru Asano
- Tri-Institutitional Therapeutics Discovery Institute, New York, United States
| | - Ruta Zalyte
- Medical Research Council Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Alison E Ondrus
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, United States
| | - Alex G Johnson
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, United States
| | - Fan Ye
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, United States
| | - Maxence V Nachury
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, United States
| | - Yoshiyuki Fukase
- Tri-Institutitional Therapeutics Discovery Institute, New York, United States
| | - Kazuyoshi Aso
- Tri-Institutitional Therapeutics Discovery Institute, New York, United States
| | - Michael A Foley
- Tri-Institutitional Therapeutics Discovery Institute, New York, United States
| | - Vladimir I Gelfand
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - James K Chen
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, United States
| | - Andrew P Carter
- Medical Research Council Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Tarun M Kapoor
- Laboratory of Chemistry and Cell Biology, Rockefeller University, New York, United States
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11
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Schmidt H, Carter AP. Review: Structure and mechanism of the dynein motor ATPase. Biopolymers 2016; 105:557-67. [PMID: 27062277 PMCID: PMC4879348 DOI: 10.1002/bip.22856] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Revised: 03/31/2016] [Accepted: 04/01/2016] [Indexed: 12/21/2022]
Abstract
Dyneins are multiprotein complexes that move cargo along microtubules in the minus end direction. The largest individual component of the dynein complex is the heavy chain. Its C-terminal 3500 amino-acid residues form the motor domain, which hydrolyses ATP in its ring of AAA+ (ATPases associated with diverse cellular activities) domains to generate the force for movement. The production of force is synchronized with cycles of microtubule binding and release, another important prerequisite for efficient motility along the microtubule. Although the large scale conformational changes that lead to force production and microtubule affinity regulation are well established, it has been largely enigmatic how ATP-hydrolysis in the AAA+ ring causes these rearrangements. The past five years have seen a surge of high resolution information on the dynein motor domain that finally allowed unprecedented insights into this important open question. This review, part of the "ATP and GTP hydrolysis in Biology" special issue, will summarize our current understanding of the dynein motor mechanism with a special emphasis on the recently obtained crystal and EM structures. © 2016 Wiley Periodicals, Inc. Biopolymers 105: 557-567, 2016.
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Affiliation(s)
- Helgo Schmidt
- Division of Structural Studies, Medical Research Council Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK
| | - Andrew P Carter
- Division of Structural Studies, Medical Research Council Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK
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12
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Bhabha G, Johnson GT, Schroeder CM, Vale RD. How Dynein Moves Along Microtubules. Trends Biochem Sci 2015; 41:94-105. [PMID: 26678005 DOI: 10.1016/j.tibs.2015.11.004] [Citation(s) in RCA: 102] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Revised: 11/05/2015] [Accepted: 11/10/2015] [Indexed: 01/20/2023]
Abstract
Cytoplasmic dynein, a member of the AAA (ATPases Associated with diverse cellular Activities) family of proteins, drives the processive movement of numerous intracellular cargos towards the minus end of microtubules. Here, we summarize the structural and motile properties of dynein and highlight features that distinguish this motor from kinesin-1 and myosin V, two well-studied transport motors. Integrating information from recent crystal and cryoelectron microscopy structures, as well as high-resolution single-molecule studies, we also discuss models for how dynein biases its movement in one direction along a microtubule track, and present a movie that illustrates these principles.
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Affiliation(s)
- Gira Bhabha
- Department of Cellular and Molecular Pharmacology and the Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA, USA
| | - Graham T Johnson
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, CA, USA; California Institute for Quantitative Biosciences (QB3), University of California, San Francisco, CA, USA
| | - Courtney M Schroeder
- Department of Cellular and Molecular Pharmacology and the Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA, USA
| | - Ronald D Vale
- Department of Cellular and Molecular Pharmacology and the Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA, USA.
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13
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Lammers LG, Markus SM. The dynein cortical anchor Num1 activates dynein motility by relieving Pac1/LIS1-mediated inhibition. J Cell Biol 2015; 211:309-22. [PMID: 26483554 PMCID: PMC4621840 DOI: 10.1083/jcb.201506119] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Accepted: 09/02/2015] [Indexed: 12/31/2022] Open
Abstract
Upon offloading to Num1 cortical receptor sites in budding yeast, cytoplasmic dynein motility is switched “on” by a mechanism that likely involves Num1-mediated dissociation of the Pac1 inhibitor, a homologue of human LIS1. Cortically anchored dynein orients the spindle through interactions with astral microtubules. In budding yeast, dynein is offloaded to Num1 receptors from microtubule plus ends. Rather than walking toward minus ends, dynein remains associated with plus ends due in part to its association with Pac1/LIS1, an inhibitor of dynein motility. The mechanism by which dynein is switched from “off” at the plus ends to “on” at the cell cortex remains unknown. Here, we show that overexpression of the coiled-coil domain of Num1 specifically depletes dynein–dynactin–Pac1/LIS1 complexes from microtubule plus ends and reduces dynein-Pac1/LIS1 colocalization. Depletion of dynein from plus ends requires its microtubule-binding domain, suggesting that motility is required. An enhanced Pac1/LIS1 affinity mutant of dynein or overexpression of Pac1/LIS1 rescues dynein plus end depletion. Live-cell imaging reveals minus end–directed dynein–dynactin motility along microtubules upon overexpression of the coiled-coil domain of Num1, an event that is not observed in wild-type cells. Our findings indicate that dynein activity is directly switched “on” by Num1, which induces Pac1/LIS1 removal.
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Affiliation(s)
- Lindsay G Lammers
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523
| | - Steven M Markus
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523
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