1
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Xu J, Elshazly AM, Gewirtz DA. The Cytoprotective, Cytotoxic and Nonprotective Functional Forms of Autophagy Induced by Microtubule Poisons in Tumor Cells—Implications for Autophagy Modulation as a Therapeutic Strategy. Biomedicines 2022; 10:biomedicines10071632. [PMID: 35884937 PMCID: PMC9312878 DOI: 10.3390/biomedicines10071632] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 06/30/2022] [Accepted: 07/01/2022] [Indexed: 12/12/2022] Open
Abstract
Microtubule poisons, as is the case with other antitumor drugs, routinely promote autophagy in tumor cells. However, the nature and function of the autophagy, in terms of whether it is cytoprotective, cytotoxic or nonprotective, cannot be predicted; this likely depends on both the type of drug studied as well as the tumor cell under investigation. In this article, we explore the literature relating to the spectrum of microtubule poisons and the nature of the autophagy induced. We further speculate as to whether autophagy inhibition could be a practical strategy for improving the response to cancer therapy involving these drugs that have microtubule function as a primary target.
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Affiliation(s)
- Jingwen Xu
- School of Pharmacy, Guangdong Pharmaceutical University, Guangzhou 510006, China;
| | - Ahmed M. Elshazly
- Massey Cancer Center, Department of Pharmacology and Toxicology, Virginia Commonwealth University, 401 College St., Richmond, VA 23298, USA;
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Kafrelsheikh University, Kafrelsheikh 33516, Egypt
| | - David A. Gewirtz
- Massey Cancer Center, Department of Pharmacology and Toxicology, Virginia Commonwealth University, 401 College St., Richmond, VA 23298, USA;
- Correspondence:
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2
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Bidirectional flow of MHD nanofluid with Hall current and Cattaneo-Christove heat flux toward the stretching surface. PLoS One 2022; 17:e0264208. [PMID: 35421096 PMCID: PMC9009632 DOI: 10.1371/journal.pone.0264208] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2021] [Accepted: 02/05/2022] [Indexed: 12/19/2022] Open
Abstract
Vacuum pump oil (VPO) is used as a lubricant in pumps of different machines. The rate of heat transport is a fundamental requirement of all phenomena. To enhance the rate of heat transmission and reduce the amount of energy consumed as a result of high temperatures. For this reason, the vacuum pump oil (VPO) is taken as a base fluid and Fe3O4 is the nanoparticles suspended in VPO. That’s why, the present study inspected the consequence of Hall current, Joule heating effect and variable thickness on these three-dimensional magnetohydrodynamics bidirectional flow of nanoliquid past on a stretchable sheet. Further, the Cattaneo-Christove heat flux and radiation impacts are also considered. The VPO−Fe3O4 nanofluid model is composed of momentum equations in x−direction, y−direction and temperature equations. The leading higher-order non-linear PDEs of the current study have been changed into non-linear ODEs with the implementation of appropriate similarity transformations. The procedure of the homotopy analysis method is hired on the resulting higher-order non-linear ODEs along with boundary conditions for the analytical solution. The significance of distinct flow parameters on the velocities in x−direction, y−direction and temperature profiles of the nanofluid have been encountered and briefly explained in a graphical form. Some important findings of the present modelling are that with the increment of nanoparticles volume fraction the nanofluid velocities in x−direction and y−direction are increased. It is also detected that higher estimations of magnetic field parameter, Prandtl number and thermal relaxation time parameter declined the nanofluid temperature. During this examination of the model, it is found that the Fe3O4-Vacuum pump oil (VPO) nanofluid enhanced the rate of heat transfer. Also, the vacuum pump oil (VPO) has many industrial and engineering applications. The current study will help to improve the rate of heat transmission by taking this into account due to which working machines will do better performance and the loss of useful energy will be decayed. Lastly, the skin friction coefficient and Nusselt number are also illustrated in a tabular form. Some major findings according to the numerical computation of the problem are that the enhancing estimations of magnetic parameter, nanoparticles volume fraction and wall thickness parameter augmented the skin friction coefficient in x−direction and Nusselt number. The reduction in skin friction coefficient of the nanofluid in y−direction is examined for Hall current and shape parameter.
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3
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Chang X, Liu Z, Cao S, Bian J, Zheng D, Wang N, Guan Q, Wu Y, Zhang W, Li Z, Zuo D. Novel microtubule inhibitor SQ overcomes multidrug resistance in MCF-7/ADR cells by inhibiting BCRP function and mediating apoptosis. Toxicol Appl Pharmacol 2022; 436:115883. [PMID: 35031325 DOI: 10.1016/j.taap.2022.115883] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Revised: 01/04/2022] [Accepted: 01/09/2022] [Indexed: 11/15/2022]
Abstract
The occurrence of multidrug resistance (MDR) is one of the impediments in the clinical treatment of breast cancer, and MDR breast cancer has abnormally high breast cancer resistance protein (BCRP/ABCG2) expression. However, there are currently no clinical drugs that inhibit this target. Our previous study found that 2-Methoxy-5((3,4,5-trimethosyphenyl)seleninyl) phenol (SQ0814061/SQ), a small molecule drug with low toxicity to normal tissues, could target microtubules, inhibit the proliferation of breast cancer, and reduce its migration and invasion abilities. However, the effect and the underlying mechanism of SQ on MDR breast cancers are still unknown. Therefore, in this study, we investigated the effect of SQ on adriamycin-resistant MCF-7 (MCF-7/ADR) cells and explored the underlying mechanism. The MTT assay showed that SQ had potent cytotoxicity to MCF-7/ADR cells. In particular, the results of western blot and flow cytometry proved that SQ could effectively inhibit the expression of BCRP in MCF-7/ADR cells to decrease its drug delivery activity. In addition, SQ could block the cell cycle at G2/M phase in parental and MCF-7/ADR cells, thereby mediating cell apoptosis, which was related with the inhibition of PI3K-Akt-MDM2 pathway. Taken together, our findings indicate that SQ overcomes multidrug resistance in MCF-7/ADR cells by inhibiting BCRP function and mediating apoptosis through PI3K-Akt-MDM2 pathway inhibition.
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Affiliation(s)
- Xing Chang
- Department of Pharmacology, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang 110016, China
| | - Zi Liu
- Department of Pharmacology, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang 110016, China
| | - Simeng Cao
- Department of Pharmacology, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang 110016, China
| | - Jiang Bian
- Department of Pharmacology, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang 110016, China
| | - Dayong Zheng
- Department of Pharmacology, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang 110016, China; School of Pharmacy, North China University of Science and Technology, 21 Bohai Road, Caofeidian District, Tangshan 063210, China
| | - Nuo Wang
- Department of Pharmacology, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang 110016, China
| | - Qi Guan
- Key Laboratory of Structure-Based Drug Design and Discovery, Ministry of Education, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang 110016, China
| | - Yingliang Wu
- Department of Pharmacology, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang 110016, China
| | - Weige Zhang
- Key Laboratory of Structure-Based Drug Design and Discovery, Ministry of Education, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang 110016, China.
| | - Zengqiang Li
- Department of Pharmacology, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang 110016, China.
| | - Daiying Zuo
- Department of Pharmacology, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenhe District, Shenyang 110016, China.
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4
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Goldblum RR, McClellan M, White K, Gonzalez SJ, Thompson BR, Vang HX, Cohen H, Higgins L, Markowski TW, Yang TY, Metzger JM, Gardner MK. Oxidative stress pathogenically remodels the cardiac myocyte cytoskeleton via structural alterations to the microtubule lattice. Dev Cell 2021; 56:2252-2266.e6. [PMID: 34343476 DOI: 10.1016/j.devcel.2021.07.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Revised: 04/07/2021] [Accepted: 07/09/2021] [Indexed: 11/19/2022]
Abstract
In the failing heart, the cardiac myocyte microtubule network is remodeled, which contributes to cellular contractile failure and patient death. However, the origins of this deleterious cytoskeletal reorganization are unknown. We now find that oxidative stress, a condition characteristic of heart failure, leads to cysteine oxidation of microtubules. Our electron and fluorescence microscopy experiments revealed regions of structural damage within the microtubule lattice that occurred at locations of oxidized tubulin. The incorporation of GTP-tubulin into these damaged, oxidized regions led to stabilized "hot spots" within the microtubule lattice, which suppressed the shortening of dynamic microtubules. Thus, oxidative stress may act inside of cardiac myocytes to facilitate a pathogenic shift from a sparse microtubule network into a dense, aligned network. Our results demonstrate how a disease condition characterized by oxidative stress can trigger a molecular oxidation event, which likely contributes to a toxic cellular-scale transformation of the cardiac myocyte microtubule network.
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Affiliation(s)
- Rebecca R Goldblum
- Medical Scientist Training Program, University of Minnesota, Minneapolis, MN, USA; Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN, USA
| | - Mark McClellan
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN, USA
| | - Kyle White
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN, USA
| | - Samuel J Gonzalez
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN, USA
| | - Brian R Thompson
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, Minneapolis, MN, USA
| | - Hluechy X Vang
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, Minneapolis, MN, USA
| | - Houda Cohen
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, Minneapolis, MN, USA
| | - LeeAnn Higgins
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN, USA
| | - Todd W Markowski
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN, USA
| | - Tzu-Yi Yang
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN, USA
| | - Joseph M Metzger
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, Minneapolis, MN, USA
| | - Melissa K Gardner
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN, USA.
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5
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Estévez-Gallego J, Josa-Prado F, Ku S, Buey RM, Balaguer FA, Prota AE, Lucena-Agell D, Kamma-Lorger C, Yagi T, Iwamoto H, Duchesne L, Barasoain I, Steinmetz MO, Chrétien D, Kamimura S, Díaz JF, Oliva MA. Structural model for differential cap maturation at growing microtubule ends. eLife 2020; 9:50155. [PMID: 32151315 PMCID: PMC7064335 DOI: 10.7554/elife.50155] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Accepted: 01/25/2020] [Indexed: 11/13/2022] Open
Abstract
Microtubules (MTs) are hollow cylinders made of tubulin, a GTPase responsible for essential functions during cell growth and division, and thus, key target for anti-tumor drugs. In MTs, GTP hydrolysis triggers structural changes in the lattice, which are responsible for interaction with regulatory factors. The stabilizing GTP-cap is a hallmark of MTs and the mechanism of the chemical-structural link between the GTP hydrolysis site and the MT lattice is a matter of debate. We have analyzed the structure of tubulin and MTs assembled in the presence of fluoride salts that mimic the GTP-bound and GDP•Pi transition states. Our results challenge current models because tubulin does not change axial length upon GTP hydrolysis. Moreover, analysis of the structure of MTs assembled in the presence of several nucleotide analogues and of taxol allows us to propose that previously described lattice expansion could be a post-hydrolysis stage involved in Pi release.
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Affiliation(s)
- Juan Estévez-Gallego
- Structural and Chemical Biology Department, Centro de Investigaciones Biológicas, CSIC, Madrid, Spain
| | - Fernando Josa-Prado
- Structural and Chemical Biology Department, Centro de Investigaciones Biológicas, CSIC, Madrid, Spain
| | - Siou Ku
- Univ Rennes, CNRS, IGDR (Institut de Génétique et Développement de Rennes) - UMR 6290, Rennes, France
| | - Ruben M Buey
- Structural and Chemical Biology Department, Centro de Investigaciones Biológicas, CSIC, Madrid, Spain.,Departamento de Microbiología y Genética, Universidad de Salamanca-Campus Miguel de Unamuno, Salamanca, Spain
| | - Francisco A Balaguer
- Structural and Chemical Biology Department, Centro de Investigaciones Biológicas, CSIC, Madrid, Spain
| | - Andrea E Prota
- Division of Biology and Chemistry, Laboratory of Biomolecular Research, Paul Scherrer Institut, Villigen, Switzerland
| | - Daniel Lucena-Agell
- Structural and Chemical Biology Department, Centro de Investigaciones Biológicas, CSIC, Madrid, Spain
| | | | - Toshiki Yagi
- Department of Life Sciences, Faculty of Life and Environmental Sciences, Prefectural University of Hiroshima, Hiroshima, Japan
| | - Hiroyuki Iwamoto
- Diffraction and Scattering Division, Japan Synchrotron Radiation Research Institute, Hyogo, Japan
| | - Laurence Duchesne
- Univ Rennes, CNRS, IGDR (Institut de Génétique et Développement de Rennes) - UMR 6290, Rennes, France
| | - Isabel Barasoain
- Structural and Chemical Biology Department, Centro de Investigaciones Biológicas, CSIC, Madrid, Spain
| | - Michel O Steinmetz
- Division of Biology and Chemistry, Laboratory of Biomolecular Research, Paul Scherrer Institut, Villigen, Switzerland.,University of Basel, Biozentrum, Basel, Switzerland
| | - Denis Chrétien
- Univ Rennes, CNRS, IGDR (Institut de Génétique et Développement de Rennes) - UMR 6290, Rennes, France
| | - Shinji Kamimura
- Department of Biological Sciences, Faculty of Science and Engineering, Chuo University, Tokyo, Japan
| | - J Fernando Díaz
- Structural and Chemical Biology Department, Centro de Investigaciones Biológicas, CSIC, Madrid, Spain
| | - Maria A Oliva
- Structural and Chemical Biology Department, Centro de Investigaciones Biológicas, CSIC, Madrid, Spain
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6
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Jonasson EM, Mauro AJ, Li C, Labuz EC, Mahserejian SM, Scripture JP, Gregoretti IV, Alber M, Goodson HV. Behaviors of individual microtubules and microtubule populations relative to critical concentrations: dynamic instability occurs when critical concentrations are driven apart by nucleotide hydrolysis. Mol Biol Cell 2019; 31:589-618. [PMID: 31577530 PMCID: PMC7202068 DOI: 10.1091/mbc.e19-02-0101] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The concept of critical concentration (CC) is central to understanding the behavior of microtubules (MTs) and other cytoskeletal polymers. Traditionally, these polymers are understood to have one CC, measured in multiple ways and assumed to be the subunit concentration necessary for polymer assembly. However, this framework does not incorporate dynamic instability (DI), and there is work indicating that MTs have two CCs. We use our previously established simulations to confirm that MTs have (at least) two experimentally relevant CCs and to clarify the behavior of individuals and populations relative to the CCs. At free subunit concentrations above the lower CC (CCElongation), growth phases of individual filaments can occur transiently; above the higher CC (CCNetAssembly), the population’s polymer mass will increase persistently. Our results demonstrate that most experimental CC measurements correspond to CCNetAssembly, meaning that “typical” DI occurs below the concentration traditionally considered necessary for polymer assembly. We report that [free tubulin] at steady state does not equal CCNetAssembly, but instead approaches CCNetAssembly asymptotically as [total tubulin] increases, and depends on the number of stable MT nucleation sites. We show that the degree of separation between CCElongation and CCNetAssembly depends on the rate of nucleotide hydrolysis. This clarified framework helps explain and unify many experimental observations.
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Affiliation(s)
- Erin M Jonasson
- Department of Chemistry and Biochemistry.,Department of Natural Sciences, Saint Martin's University, Lacey, WA 98503
| | - Ava J Mauro
- Department of Chemistry and Biochemistry.,Department of Applied and Computational Mathematics and Statistics, and.,Department of Mathematics and Statistics, University of Massachusetts Amherst, Amherst, MA 01003
| | - Chunlei Li
- Department of Applied and Computational Mathematics and Statistics, and
| | | | | | | | | | - Mark Alber
- Department of Applied and Computational Mathematics and Statistics, and.,Department of Mathematics, University of California, Riverside, Riverside, CA 92521
| | - Holly V Goodson
- Department of Chemistry and Biochemistry.,Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556
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7
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Mauro AJ, Jonasson EM, Goodson HV. Relationship between dynamic instability of individual microtubules and flux of subunits into and out of polymer. Cytoskeleton (Hoboken) 2019; 76:495-516. [PMID: 31403242 DOI: 10.1002/cm.21557] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 07/03/2019] [Accepted: 07/31/2019] [Indexed: 12/28/2022]
Abstract
Behaviors of dynamic polymers such as microtubules and actin are frequently assessed at one or both of the following scales: (a) net assembly or disassembly of bulk polymer, (b) growth and shortening of individual filaments. Previous work has derived various forms of an equation to relate the rate of change in bulk polymer mass (i.e., flux of subunits into and out of polymer, often abbreviated as "J") to individual filament behaviors. However, these versions of the "J equation" differ in the variables used to quantify individual filament behavior, which correspond to different experimental approaches. For example, some variants of the J equation use dynamic instability parameters, obtained by following particular individual filaments for long periods of time. Another form of the equation uses measurements from many individuals followed over short time steps. We use a combination of derivations and computer simulations that mimic experiments to (a) relate the various forms of the J equation to each other, (b) determine conditions under which these J equation forms are and are not equivalent, and (c) identify aspects of the measurements that can affect the accuracy of each form of the J equation. Improved understanding of the J equation and its connections to experimentally measurable quantities will contribute to efforts to build a multiscale understanding of steady-state polymer behavior.
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Affiliation(s)
- Ava J Mauro
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana
| | - Erin M Jonasson
- Department of Natural Sciences, Saint Martin's University, Lacey, Washington
| | - Holly V Goodson
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana
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8
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Lawrence EJ, Zanic M. Rescuing microtubules from the brink of catastrophe: CLASPs lead the way. Curr Opin Cell Biol 2019; 56:94-101. [PMID: 30453184 PMCID: PMC6370552 DOI: 10.1016/j.ceb.2018.10.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Revised: 10/12/2018] [Accepted: 10/31/2018] [Indexed: 01/11/2023]
Abstract
Microtubules are cytoskeletal polymers that dynamically remodel to perform essential cellular functions. Individual microtubules alternate between phases of growth and shrinkage via sudden transitions called catastrophe and rescue, driven by losing and regaining a stabilizing cap at the dynamic microtubule end. New in vitro studies now show that a conserved family of CLASP proteins specifically modulate microtubule catastrophe and rescue transitions. Further, recent cryo-electron microscopy approaches have elucidated new structural features of the stabilizing cap. Together, these new advances provide a clearer view on the complexity of the microtubule end and its regulation.
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Affiliation(s)
- E J Lawrence
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, United States
| | - M Zanic
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, United States; Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN 37240, United States; Department of Biochemistry, Vanderbilt University, Nashville, TN 37240, United States.
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9
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Denarier E, Brousse C, Sissoko A, Andrieux A, Boscheron C. A neurodevelopmental TUBB2B β-tubulin mutation impairs Bim1 (yeast EB1)-dependent spindle positioning. Biol Open 2019; 8:bio.038620. [PMID: 30674462 PMCID: PMC6361202 DOI: 10.1242/bio.038620] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Malformations of the human cerebral cortex can be caused by mutations in tubulins that associate to compose microtubules. Cerebral cortical folding relies on neuronal migration and on progenitor proliferation partly dictated by microtubule-dependent mitotic spindle positioning. A single amino acid change, F265L, in the conserved TUBB2B β-tubulin gene has been identified in patients with abnormal cortex formation. A caveat for studying this mutation in mammalian cells is that nine genes encode β-tubulin in human. Here, we generate a yeast strain expressing F265L tubulin mutant as the sole source of β-tubulin. The F265L mutation does not preclude expression of a stable β-tubulin protein which is incorporated into microtubules. However, impaired cell growth was observed at high temperatures along with altered microtubule dynamics and stability. In addition, F265L mutation produces a highly specific mitotic spindle positioning defect related to Bim1 (yeast EB1) dysfunction. Indeed, F265L cells display an abnormal Bim1 recruitment profile at microtubule plus-ends. These results indicate that the F265L β-tubulin mutation affects microtubule plus-end complexes known to be important for microtubule dynamics and for microtubule function during mitotic spindle positioning.
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Affiliation(s)
- Eric Denarier
- Univ. Grenoble Alpes, Grenoble Institut des Neurosciences, GIN, F-38000, Grenoble, France.,Institut National de la Santé et de la Recherche Médicale (INSERM), U1216, F-38000, Grenoble, France.,Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Biosciences and Biotechnology Institute of Grenoble, Grenoble, France
| | - Carine Brousse
- Institut National de la Transfusion Sanguine (INTS), F-75015 Paris, France
| | | | - Annie Andrieux
- Univ. Grenoble Alpes, Grenoble Institut des Neurosciences, GIN, F-38000, Grenoble, France.,Institut National de la Santé et de la Recherche Médicale (INSERM), U1216, F-38000, Grenoble, France.,Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Biosciences and Biotechnology Institute of Grenoble, Grenoble, France
| | - Cécile Boscheron
- Univ. Grenoble Alpes, Grenoble Institut des Neurosciences, GIN, F-38000, Grenoble, France .,Institut National de la Santé et de la Recherche Médicale (INSERM), U1216, F-38000, Grenoble, France.,Institut de Biologie Structurale (IBS) , F-38000 Grenoble, France
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10
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Aparna JS, Padinhateeri R, Das D. Signatures of a macroscopic switching transition for a dynamic microtubule. Sci Rep 2017; 7:45747. [PMID: 28374844 PMCID: PMC5379563 DOI: 10.1038/srep45747] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Accepted: 03/02/2017] [Indexed: 11/17/2022] Open
Abstract
Characterising complex kinetics of non-equilibrium self-assembly of bio-filaments is of general interest. Dynamic instability in microtubules, consisting of successive catastrophes and rescues, is observed to occur as a result of the non-equilibrium conversion of GTP-tubulin to GDP-tubulin. We study this phenomenon using a model for microtubule kinetics with GTP/GDP state-dependent polymerisation, depolymerisation and hydrolysis of subunits. Our results reveal a sharp switch-like transition in the mean velocity of the filaments, from a growth phase to a shrinkage phase, with an associated co-existence of the two phases. This transition is reminiscent of the discontinuous phase transition across the liquid-gas boundary. We probe the extent of discontinuity in the transition quantitatively using characteristic signatures such as bimodality in velocity distribution, variance and Binder cumulant, and also hysteresis behaviour of the system. We further investigate ageing behaviour in catastrophes of the filament, and find that the multi-step nature of catastrophes is intensified in the vicinity of the switching transition. This assumes importance in the context of Microtubule Associated Proteins which have the potential of altering kinetic parameter values.
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Affiliation(s)
- J S Aparna
- Centre for Research in Nanotechnology and Sciences, Indian Institute of Technology Bombay, Mumbai, India
| | - Ranjith Padinhateeri
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Dibyendu Das
- Department of Physics, Indian Institute of Technology Bombay, Mumbai, India
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11
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Ko HR, Hwang I, Ahn SY, Chang YS, Park WS, Ahn JY. Neuron-specific expression of p48 Ebp1 during murine brain development and its contribution to CNS axon regeneration. BMB Rep 2017; 50:126-131. [PMID: 27916024 PMCID: PMC5422024 DOI: 10.5483/bmbrep.2017.50.3.190] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Indexed: 01/06/2023] Open
Abstract
P48 Ebp1 is expressed in rapidly proliferating cells such as cancer cells and accelerates cell growth and survival. However, its expression pattern and role in central nervous system development have not been studied. Here, we demonstrated the spatiotemporal expression pattern of p48 Ebp1 during embryonic development and the postnatal period. During embryonic development, p48 Ebp1 was highly expressed in the brain. Expression gradually decreased after birth but was still more abundant than p42 expression after birth. Strikingly, we found that p48 Ebp1 was expressed in a cell type specific manner in neurons but not astrocytes. Moreover, p48 Ebp1 physically interacted with beta tubulin but not alpha tubulin. This fits with its accumulation in distal microtubule growth cone regions. Furthermore, in injured hippocampal slices, p48 Ebp1 introduction promoted axon regeneration. Thus, we speculate that p48 Ebp1 might contribute to microtubule dynamics acting as an MAP and promotes CNS axon regeneration. [BMB Reports 2017; 50(3): 126-131].
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Affiliation(s)
- Hyo Rim Ko
- Department of Molecular Cell Biology, Center for Molecular Medicine, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon 16419, Korea
| | - Inwoo Hwang
- Department of Molecular Cell Biology, Center for Molecular Medicine, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon 16419, Korea
| | - So Yoon Ahn
- Department of Pediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul 06351; Stem Cell and Regenerative Medicine Institute, Samsung Medical Center, Seoul 06351, Korea
| | - Yun Sil Chang
- Department of Pediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul 06351; Stem Cell and Regenerative Medicine Institute, Samsung Medical Center, Seoul 06351; Department of Health Sciences and Technology, SAIHST, Sungkyunkwan University, Seoul 06351, Korea
| | - Won Soon Park
- Department of Pediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul 06351; Stem Cell and Regenerative Medicine Institute, Samsung Medical Center, Seoul 06351; Department of Health Sciences and Technology, SAIHST, Sungkyunkwan University, Seoul 06351, Korea
| | - Jee-Yin Ahn
- Department of Molecular Cell Biology, Center for Molecular Medicine, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon 16419; Department of Health Sciences and Technology, SAIHST, Sungkyunkwan University, Seoul 06351, Korea
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12
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Guesdon A, Bazile F, Buey RM, Mohan R, Monier S, García RR, Angevin M, Heichette C, Wieneke R, Tampé R, Duchesne L, Akhmanova A, Steinmetz MO, Chrétien D. EB1 interacts with outwardly curved and straight regions of the microtubule lattice. Nat Cell Biol 2016; 18:1102-8. [PMID: 27617931 DOI: 10.1038/ncb3412] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Accepted: 08/18/2016] [Indexed: 12/16/2022]
Abstract
EB1 is a microtubule plus-end tracking protein that recognizes GTP-tubulin dimers in microtubules and thus represents a unique probe to investigate the architecture of the GTP cap of growing microtubule ends. Here, we conjugated EB1 to gold nanoparticles (EB1-gold) and imaged by cryo-electron tomography its interaction with dynamic microtubules assembled in vitro from purified tubulin. EB1-gold forms comets at the ends of microtubules assembled in the presence of GTP, and interacts with the outer surface of curved and straight tubulin sheets as well as closed regions of the microtubule lattice. Microtubules assembled in the presence of GTP, different GTP analogues or cell extracts display similarly curved sheets at their growing ends, which gradually straighten as their protofilament number increases until they close into a tube. Together, our data provide unique structural information on the interaction of EB1 with growing microtubule ends. They further offer insights into the conformational changes that tubulin dimers undergo during microtubule assembly and the architecture of the GTP-cap region.
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Affiliation(s)
- Audrey Guesdon
- Institute of Genetics and Development of Rennes, UMR6290 CNRS, University of Rennes 1, Campus Universitaire de Beaulieu, 35042 Rennes Cédex, France
| | - Franck Bazile
- Institute of Genetics and Development of Rennes, UMR6290 CNRS, University of Rennes 1, Campus Universitaire de Beaulieu, 35042 Rennes Cédex, France
| | - Rubén M Buey
- Laboratory of Biomolecular Research, Department of Biology and Chemistry, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.,Metabolic Engineering Group, Department of Microbiology and Genetics, University of Salamanca, Campus Miguel de Unamuno s/n, 37007 Salamanca, Spain
| | - Renu Mohan
- Cell Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Solange Monier
- Institute of Genetics and Development of Rennes, UMR6290 CNRS, University of Rennes 1, Campus Universitaire de Beaulieu, 35042 Rennes Cédex, France
| | - Ruddi Rodríguez García
- Cell Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Morgane Angevin
- Institute of Genetics and Development of Rennes, UMR6290 CNRS, University of Rennes 1, Campus Universitaire de Beaulieu, 35042 Rennes Cédex, France
| | - Claire Heichette
- Institute of Genetics and Development of Rennes, UMR6290 CNRS, University of Rennes 1, Campus Universitaire de Beaulieu, 35042 Rennes Cédex, France
| | - Ralph Wieneke
- Institute of Biochemistry, Biocenter, and Cluster of Excellence-Macromolecular Complexes, Goethe-University Frankfurt, Max-von-Laue Strasse 9, 60438 Frankfurt am Main, Germany
| | - Robert Tampé
- Institute of Biochemistry, Biocenter, and Cluster of Excellence-Macromolecular Complexes, Goethe-University Frankfurt, Max-von-Laue Strasse 9, 60438 Frankfurt am Main, Germany
| | - Laurence Duchesne
- Institute of Genetics and Development of Rennes, UMR6290 CNRS, University of Rennes 1, Campus Universitaire de Beaulieu, 35042 Rennes Cédex, France
| | - Anna Akhmanova
- Cell Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Michel O Steinmetz
- Laboratory of Biomolecular Research, Department of Biology and Chemistry, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - Denis Chrétien
- Institute of Genetics and Development of Rennes, UMR6290 CNRS, University of Rennes 1, Campus Universitaire de Beaulieu, 35042 Rennes Cédex, France.,Microscopy Rennes Imaging Centre, and Biosit, UMS3480 CNRS, University of Rennes 1, Campus Santé de Villejean, 35043 Rennes Cédex, France
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13
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Brouhard GJ. Dynamic instability 30 years later: complexities in microtubule growth and catastrophe. Mol Biol Cell 2016; 26:1207-10. [PMID: 25823928 PMCID: PMC4454169 DOI: 10.1091/mbc.e13-10-0594] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Microtubules are not like other polymers. Whereas polymers such as F-actin will grow continuously as long as the subunit concentration is high enough, a steadily growing microtubule can suddenly shrink even when there is ample αβ-tubulin around. This remarkable behavior was discovered in 1984 when Tim Mitchison and Marc Kirschner deduced that microtubules switch from growth to shrinkage when they lose their GTP caps. Here, I review the canonical explanation of dynamic instability that was fleshed out in the years after its discovery. Many aspects of this explanation have been recently subverted, particularly those related to how GTP-tubulin forms polymers and why GTP hydrolysis disrupts them. I describe these developments and speculate on how our explanation of dynamic instability can be changed to accommodate them.
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Affiliation(s)
- Gary J Brouhard
- Department of Biology, McGill University, Montréal, QC H3A 1B1, Canada
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14
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Duellberg C, Cade NI, Holmes D, Surrey T. The size of the EB cap determines instantaneous microtubule stability. eLife 2016; 5. [PMID: 27050486 PMCID: PMC4829430 DOI: 10.7554/elife.13470] [Citation(s) in RCA: 98] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 02/23/2016] [Indexed: 12/24/2022] Open
Abstract
The function of microtubules relies on their ability to switch between phases of growth and shrinkage. A nucleotide-dependent stabilising cap at microtubule ends is thought to be lost before this switch can occur; however, the nature and size of this protective cap are unknown. Using a microfluidics-assisted multi-colour TIRF microscopy assay with close-to-nm and sub-second precision, we measured the sizes of the stabilizing cap of individual microtubules. We find that the protective caps are formed by the extended binding regions of EB proteins. Cap lengths vary considerably and longer caps are more stable. Nevertheless, the trigger of instability lies in a short region at the end of the cap, as a quantitative model of cap stability demonstrates. Our study establishes the spatial and kinetic characteristics of the protective cap and provides an insight into the molecular mechanism by which its loss leads to the switch from microtubule growth to shrinkage. DOI:http://dx.doi.org/10.7554/eLife.13470.001 Much like the skeleton supports the human body, a structure called the cytoskeleton provides support and structure to cells. Part of this cytoskeleton is made up of small tubes called microtubules that – unlike bones – can shrink and grow very quickly. This allows the cell to change shape, move and split into two new cells. Exactly how the microtubules switch between growing and shrinking was not clear. One suggestion is that a protective cap at the end of microtubule allows it to keep growing and prevents it from shrinking. However, the nature and size of this cap have been debated. Now, Duellberg et al. have measured the caps of microtubules with high precision by combining the techniques of microfluidics, TIRF microscopy and recently developed image analysis tools. This revealed that the cap sizes change, with longer caps being more stable. In addition, proteins called end-binding proteins can destabilize the cap by binding to it. This allows microtubules to switch from a growing to a shrinking state more often. Future work could now investigate how changes in cap length cause the microtubules to switch from growing to shrinking. It also remains to be seen whether other proteins also influence the cap to control this switching behaviour. DOI:http://dx.doi.org/10.7554/eLife.13470.002
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Affiliation(s)
- Christian Duellberg
- Lincoln's Inn Fields Laboratory, The Francis Crick Institute, London, United Kingdom
| | - Nicholas I Cade
- Lincoln's Inn Fields Laboratory, The Francis Crick Institute, London, United Kingdom
| | - David Holmes
- London Centre of Nanotechnology, London, United Kingdom
| | - Thomas Surrey
- Lincoln's Inn Fields Laboratory, The Francis Crick Institute, London, United Kingdom
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15
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Ti SC, Pamula MC, Howes SC, Duellberg C, Cade NI, Kleiner RE, Forth S, Surrey T, Nogales E, Kapoor TM. Mutations in Human Tubulin Proximal to the Kinesin-Binding Site Alter Dynamic Instability at Microtubule Plus- and Minus-Ends. Dev Cell 2016; 37:72-84. [PMID: 27046833 PMCID: PMC4832424 DOI: 10.1016/j.devcel.2016.03.003] [Citation(s) in RCA: 81] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Revised: 02/12/2016] [Accepted: 03/04/2016] [Indexed: 01/10/2023]
Abstract
The assembly of microtubule-based cellular structures depends on regulated tubulin polymerization and directional transport. Here, we purify and characterize tubulin heterodimers that have human β-tubulin isotype III (TUBB3), as well as heterodimers with one of two β-tubulin mutations (D417H or R262H). Both point mutations are proximal to the kinesin-binding site and have been linked to an ocular motility disorder in humans. Compared to wild-type, microtubules with these mutations have decreased catastrophe frequencies and increased average lifetimes of plus- and minus-end-stabilizing caps. Importantly, the D417H mutation does not alter microtubule lattice structure or Mal3 binding to growing filaments. Instead, this mutation reduces the affinity of tubulin for TOG domains and colchicine, suggesting that the distribution of tubulin heterodimer conformations is changed. Together, our findings reveal how residues on the surface of microtubules, distal from the GTP-hydrolysis site and inter-subunit contacts, can alter polymerization dynamics at the plus- and minus-ends of microtubules.
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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
| | - Melissa C Pamula
- Laboratory of Chemistry and Cell Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Stuart C Howes
- Biophysics Graduate Group, University of California, Berkeley, CA 94720, USA
| | - Christian Duellberg
- The Francis Crick Institute, Lincoln's Inn Fields Laboratory, 44 Lincoln's Inn Fields, London WC2A 3LY, UK
| | - Nicholas I Cade
- The Francis Crick Institute, Lincoln's Inn Fields Laboratory, 44 Lincoln's Inn Fields, London WC2A 3LY, UK
| | - Ralph E Kleiner
- Laboratory of Chemistry and Cell Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Scott Forth
- Laboratory of Chemistry and Cell Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Thomas Surrey
- The Francis Crick Institute, Lincoln's Inn Fields Laboratory, 44 Lincoln's Inn Fields, London WC2A 3LY, UK
| | - Eva Nogales
- Life Sciences Division, Lawrence Berkeley National Lab, Berkeley, CA 94720, USA; Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California Berkeley, Berkeley, CA 94720, 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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16
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Abstract
Microtubule dynamics are fundamental for many aspects of cell physiology, but their mechanistic underpinnings remain unclear despite 40 years of intense research. In recent years, the continued union of reconstitution biochemistry, structural biology, and modeling has yielded important discoveries that deepen our understanding of microtubule dynamics. These studies, which we review here, underscore the importance of GTP hydrolysis-induced changes in tubulin structure as microtubules assemble, and highlight the fact that each aspect of microtubule behavior is the output of complex, multi-step processes. Although this body of work moves us closer to appreciating the key features of microtubule biochemistry that drive dynamic instability, the divide between our understanding of microtubules in isolation versus within the cellular milieu remains vast. Bridging this gap will serve as fertile grounds of cytoskeleton-focused research for many years to come.
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Affiliation(s)
- Ryoma Ohi
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Marija Zanic
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA; Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee, USA
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17
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Statistical mechanics provides novel insights into microtubule stability and mechanism of shrinkage. PLoS Comput Biol 2015; 11:e1004099. [PMID: 25692909 PMCID: PMC4333834 DOI: 10.1371/journal.pcbi.1004099] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Accepted: 12/21/2014] [Indexed: 01/11/2023] Open
Abstract
Microtubules are nano-machines that grow and shrink stochastically, making use of the coupling between chemical kinetics and mechanics of its constituent protofilaments (PFs). We investigate the stability and shrinkage of microtubules taking into account inter-protofilament interactions and bending interactions of intrinsically curved PFs. Computing the free energy as a function of PF tip position, we show that the competition between curvature energy, inter-PF interaction energy and entropy leads to a rich landscape with a series of minima that repeat over a length-scale determined by the intrinsic curvature. Computing Langevin dynamics of the tip through the landscape and accounting for depolymerization, we calculate the average unzippering and shrinkage velocities of GDP protofilaments and compare them with the experimentally known results. Our analysis predicts that the strength of the inter-PF interaction (E(s)(m)) has to be comparable to the strength of the curvature energy (E(b)(m)) such that E(s)(m) - E(b)(m) ≈ 1kBT, and questions the prevalent notion that unzippering results from the domination of bending energy of curved GDP PFs. Our work demonstrates how the shape of the free energy landscape is crucial in explaining the mechanism of MT shrinkage where the unzippered PFs will fluctuate in a set of partially peeled off states and subunit dissociation will reduce the length.
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18
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Yan S, Zhang H, Hou G, Ahmed S, Williams JC, Polenova T. Internal dynamics of dynactin CAP-Gly is regulated by microtubules and plus end tracking protein EB1. J Biol Chem 2014; 290:1607-22. [PMID: 25451937 DOI: 10.1074/jbc.m114.603118] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
CAP-Gly domain of dynactin, a microtubule-associated activator of dynein motor, participates in multiple cellular processes, and its point mutations are associated with neurodegenerative diseases. Recently, we have demonstrated that conformational plasticity is an intrinsic property of CAP-Gly. To understand its origin, we addressed internal dynamics of CAP-Gly assembled on polymeric microtubules, bound to end-binding protein EB1 and free, by magic angle spinning NMR and molecular dynamics simulations. The analysis of residue-specific dynamics of CAP-Gly on time scales spanning nano- through milliseconds reveals its unusually high mobility, both free and assembled on polymeric microtubules. On the contrary, CAP-Gly bound to EB1 is significantly more rigid. Molecular dynamics simulations indicate that these motions are strongly temperature-dependent, and loop regions are surprisingly mobile. These findings establish the connection between conformational plasticity and internal dynamics in CAP-Gly, which is essential for the biological functions of CAP-Gly and its ability to bind to polymeric microtubules and multiple binding partners. In this work, we establish an approach, for the first time, to probe atomic resolution dynamic profiles of a microtubule-associated protein assembled on polymeric microtubules. More broadly, the methodology established here can be applied for atomic resolution analysis of dynamics in other microtubule-associated protein assemblies, including but not limited to dynactin, dynein, and kinesin motors assembled on microtubules.
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Affiliation(s)
- Si Yan
- From the Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716 and
| | - Huilan Zhang
- From the Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716 and
| | - Guangjin Hou
- From the Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716 and
| | - Shubbir Ahmed
- the Department of Molecular Medicine, Beckman Research Institute of City of Hope, Duarte, California 91010
| | - John C Williams
- the Department of Molecular Medicine, Beckman Research Institute of City of Hope, Duarte, California 91010
| | - Tatyana Polenova
- From the Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716 and
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19
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Coombes CE, Yamamoto A, Kenzie MR, Odde DJ, Gardner MK. Evolving tip structures can explain age-dependent microtubule catastrophe. Curr Biol 2013; 23:1342-8. [PMID: 23831290 DOI: 10.1016/j.cub.2013.05.059] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2012] [Revised: 05/22/2013] [Accepted: 05/30/2013] [Indexed: 11/27/2022]
Abstract
Microtubules are key structural and transport elements in cells. The dynamics at microtubule ends are characterized by periods of slow growth, followed by stochastic switching events termed "catastrophes," in which microtubules suddenly undergo rapid shortening. Growing microtubules are thought to be protected from catastrophe by a GTP-tubulin "cap": GTP-tubulin subunits add to the tips of growing microtubules but are subsequently hydrolyzed to GDP-tubulin subunits once they are incorporated into the microtubule lattice. Loss of the GTP-tubulin cap exposes GDP-tubulin subunits at the microtubule tip, resulting in a catastrophe event. However, the mechanistic basis for sudden loss of the GTP cap, leading to catastrophe, is not known. To investigate microtubule catastrophe events, we performed 3D mechanochemical simulations that account for interactions between neighboring protofilaments. We found that there are two separate factors that contribute to catastrophe events in the 3D simulation: the GTP-tubulin cap size, which settles into a steady-state value that depends on the free tubulin concentration during microtubule growth, and the structure of the microtubule tip. Importantly, 3D simulations predict, and both fluorescence and electron microscopy experiments confirm, that microtubule tips become more tapered as the microtubule grows. This effect destabilizes the tip and ultimately contributes to microtubule catastrophe. Thus, the likelihood of a catastrophe event may be intimately linked to the aging physical structure of the growing microtubule tip. These results have important consequences for catastrophe regulation in cells, as microtubule-associated proteins could promote catastrophe events in part by modifying microtubule tip structures.
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Affiliation(s)
- Courtney E Coombes
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, MN 55455, USA
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20
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Hanazono Y, Takeda K, Yohda M, Miki K. Structural Studies on the Oligomeric Transition of a Small Heat Shock Protein, StHsp14.0. J Mol Biol 2012; 422:100-8. [DOI: 10.1016/j.jmb.2012.05.017] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Revised: 05/11/2012] [Accepted: 05/14/2012] [Indexed: 10/28/2022]
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21
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Maurer S, Fourniol F, Bohner G, Moores C, Surrey T. EBs recognize a nucleotide-dependent structural cap at growing microtubule ends. Cell 2012; 149:371-82. [PMID: 22500803 PMCID: PMC3368265 DOI: 10.1016/j.cell.2012.02.049] [Citation(s) in RCA: 275] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 12/19/2011] [Accepted: 02/10/2012] [Indexed: 11/24/2022]
Abstract
Growing microtubule ends serve as transient binding platforms for essential proteins that regulate microtubule dynamics and their interactions with cellular substructures. End-binding proteins (EBs) autonomously recognize an extended region at growing microtubule ends with unknown structural characteristics and then recruit other factors to the dynamic end structure. Using cryo-electron microscopy, subnanometer single-particle reconstruction, and fluorescence imaging, we present a pseudoatomic model of how the calponin homology (CH) domain of the fission yeast EB Mal3 binds to the end regions of growing microtubules. The Mal3 CH domain bridges protofilaments except at the microtubule seam. By binding close to the exchangeable GTP-binding site, the CH domain is ideally positioned to sense the microtubule's nucleotide state. The same microtubule-end region is also a stabilizing structural cap protecting the microtubule from depolymerization. This insight supports a common structural link between two important biological phenomena, microtubule dynamic instability and end tracking.
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Affiliation(s)
- Sebastian P. Maurer
- Cancer Research UK London Research Institute, Lincoln's Inn Fields Laboratories, 44 Lincoln's Inn Fields, London WC2A 3LY, UK
- European Molecular Biology Laboratory, Cell Biology and Biophysics Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Franck J. Fourniol
- Cancer Research UK London Research Institute, Lincoln's Inn Fields Laboratories, 44 Lincoln's Inn Fields, London WC2A 3LY, UK
| | - Gergő Bohner
- Cancer Research UK London Research Institute, Lincoln's Inn Fields Laboratories, 44 Lincoln's Inn Fields, London WC2A 3LY, UK
| | - Carolyn A. Moores
- Institute of Structural and Molecular Biology, Birkbeck College, London WC1E 7HX, UK
| | - Thomas Surrey
- Cancer Research UK London Research Institute, Lincoln's Inn Fields Laboratories, 44 Lincoln's Inn Fields, London WC2A 3LY, UK
- European Molecular Biology Laboratory, Cell Biology and Biophysics Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany
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22
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Padinhateeri R, Kolomeisky AB, Lacoste D. Random hydrolysis controls the dynamic instability of microtubules. Biophys J 2012; 102:1274-83. [PMID: 22455910 DOI: 10.1016/j.bpj.2011.12.059] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2011] [Revised: 10/15/2011] [Accepted: 12/01/2011] [Indexed: 01/20/2023] Open
Abstract
Uncovering mechanisms that control the dynamics of microtubules is fundamental for our understanding of multiple cellular processes such as chromosome separation and cell motility. Building on previous theoretical work on the dynamic instability of microtubules, we propose here a stochastic model that includes all relevant biochemical processes that affect the dynamics of microtubule plus-end, namely, the binding of GTP-bound monomers, unbinding of GTP- and GDP-bound monomers, and hydrolysis of GTP monomers. The inclusion of dissociation processes, present in our approach but absent from many previous studies, is essential to guarantee the thermodynamic consistency of the model. Our theoretical method allows us to compute all dynamic properties of microtubules explicitly. Using experimentally determined rates, it is found that the cap size is ∼3.6 layers, an estimate that is compatible with several experimental observations. In the end, our model provides a comprehensive description of the dynamic instability of microtubules that includes not only the statistics of catastrophes but also the statistics of rescues.
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Affiliation(s)
- Ranjith Padinhateeri
- Department of Biosciences and Bioengineering and Wadhwani Research Centre for Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India
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23
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Gardner MK, Zanic M, Gell C, Bormuth V, Howard J. Depolymerizing kinesins Kip3 and MCAK shape cellular microtubule architecture by differential control of catastrophe. Cell 2012; 147:1092-103. [PMID: 22118464 DOI: 10.1016/j.cell.2011.10.037] [Citation(s) in RCA: 136] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2011] [Revised: 07/11/2011] [Accepted: 10/26/2011] [Indexed: 10/15/2022]
Abstract
Microtubules are dynamic filaments whose ends alternate between periods of slow growth and rapid shortening as they explore intracellular space and move organelles. A key question is how regulatory proteins modulate catastrophe, the conversion from growth to shortening. To study this process, we reconstituted microtubule dynamics in the absence and presence of the kinesin-8 Kip3 and the kinesin-13 MCAK. Surprisingly, we found that, even in the absence of the kinesins, the microtubule catastrophe frequency depends on the age of the microtubule, indicating that catastrophe is a multistep process. Kip3 slowed microtubule growth in a length-dependent manner and increased the rate of aging. In contrast, MCAK eliminated the aging process. Thus, both kinesins are catastrophe factors; Kip3 mediates fine control of microtubule length by narrowing the distribution of maximum lengths prior to catastrophe, whereas MCAK promotes rapid restructuring of the microtubule cytoskeleton by making catastrophe a first-order random process.
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Affiliation(s)
- Melissa K Gardner
- Department of Genetics, University of Minnesota, Minneapolis, MN 55455, USA
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24
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Gardner MK, Charlebois BD, Jánosi IM, Howard J, Hunt AJ, Odde DJ. Rapid microtubule self-assembly kinetics. Cell 2011; 146:582-92. [PMID: 21854983 DOI: 10.1016/j.cell.2011.06.053] [Citation(s) in RCA: 153] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2010] [Revised: 05/26/2011] [Accepted: 06/30/2011] [Indexed: 12/18/2022]
Abstract
Microtubule assembly is vital for many fundamental cellular processes. Current models for microtubule assembly kinetics assume that the subunit dissociation rate from a microtubule tip is independent of free subunit concentration. Total-Internal-Reflection-Fluorescence (TIRF) microscopy experiments and data from a laser tweezers assay that measures in vitro microtubule assembly with nanometer resolution, provides evidence that the subunit dissociation rate from a microtubule tip increases as the free subunit concentration increases. These data are consistent with a two-dimensional model for microtubule assembly, and are explained by a shift in microtubule tip structure from a relatively blunt shape at low free concentrations to relatively tapered at high free concentrations. We find that because both the association and the dissociation rates increase at higher free subunit concentrations, the kinetics of microtubule assembly are an order-of-magnitude higher than currently estimated in the literature.
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Affiliation(s)
- Melissa K Gardner
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455, USA
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25
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Macroscopic simulations of microtubule dynamics predict two steady-state processes governing array morphology. Comput Biol Chem 2011; 35:269-81. [PMID: 22000798 DOI: 10.1016/j.compbiolchem.2011.06.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Revised: 05/10/2011] [Accepted: 06/17/2011] [Indexed: 01/21/2023]
Abstract
Microtubule polymers typically function through their collective organization into a patterned array. The formation of the pattern, whether it is a relatively simple astral array or a highly complex mitotic spindle, relies on controlled microtubule nucleation and the basal dynamics parameters governing polymer growth and shortening. We have investigated the interaction between the microtubule nucleation and dynamics parameters, using macroscopic Monte Carlo simulations, to determine how these parameters contribute to the underlying microtubule array morphology (i.e. polymer density and length distribution). In addition to the well-characterized steady state achieved between free tubulin subunits and microtubule polymer, we propose that microtubule nucleation and extinction constitute a second, interdependent steady state process. Our simulation studies show that the magnitude of both nucleation and extinction additively impacts the final steady state free subunit concentration. We systematically varied individual microtubule dynamics parameters to survey the effects on array morphology and find specific sensitivity to perturbations of catastrophe frequency. Altering the cellular context for the microtubule array, we find that nucleation template number plays a defining role in shaping the microtubule length distribution and polymer density.
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26
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Structural insight into the inhibition of tubulin by vinca domain peptide ligands. EMBO Rep 2008; 9:1101-6. [PMID: 18787557 DOI: 10.1038/embor.2008.171] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2008] [Revised: 08/06/2008] [Accepted: 08/06/2008] [Indexed: 11/08/2022] Open
Abstract
The tubulin vinca domain is the target of widely different microtubule inhibitors that interfere with the binding of vinblastine. Although all these ligands inhibit the hydrolysis of GTP, they affect nucleotide exchange to variable extents. The structures of two vinca domain antimitotic peptides--phomopsin A and soblidotin (a dolastatin 10 analogue)--bound to tubulin in a complex with a stathmin-like domain show that their sites partly overlap with that of vinblastine and extend the definition of the vinca domain. The structural data, together with the biochemical results from the ligands we studied, highlight two main contributors in nucleotide exchange: the flexibility of the tubulin subunits' arrangement at their interfaces and the residues in the carboxy-terminal part of the beta-tubulin H6-H7 loop. The structures also highlight common features of the mechanisms by which vinca domain ligands favour curved tubulin assemblies and destabilize microtubules.
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27
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Nogales E, Wang HW. Structural mechanisms underlying nucleotide-dependent self-assembly of tubulin and its relatives. Curr Opin Struct Biol 2006; 16:221-9. [PMID: 16549346 DOI: 10.1016/j.sbi.2006.03.005] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2006] [Revised: 02/07/2006] [Accepted: 03/10/2006] [Indexed: 10/24/2022]
Abstract
The alphabeta-tubulin dimer assembles into microtubules, essential polymers in all eukaryotic cells. Microtubules are highly dynamic, a property that derives from tubulin's GTPase activity. Both the bacterial homolog, FtsZ, and the recently discovered bacterial tubulins from Prosthecobacter self-assemble in a nucleotide-dependent manner into protofilaments similar to those that form the microtubule wall. A number of structural studies of alphabeta-tubulin, gamma-tubulin (the isoform involved in microtubule nucleation), FtsZ and bacterial tubulin, in a variety of nucleotide and polymerization states, have been reported in the past few years. These studies have revealed the similarities and differences between these structures and their possible functional implications. In particular, a two-state mechanism has been proposed for the recycling of alphabeta-tubulin during the microtubule disassembly-assembly cycle; this mechanism may be unique to eukaryotic dimeric tubulin and the microtubule structure.
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Affiliation(s)
- Eva Nogales
- Howard Hughes Medical Institute, Molecular and Cell Biology Department, University of California Berkeley and Lawrence Berkeley National Laboratory, 355 LSA, University of California Berkeley, Berkeley, CA 94720-3200, USA.
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Deymier PA, Yang Y, Hoying J. Effect of tubulin diffusion on polymerization of microtubules. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2005; 72:021906. [PMID: 16196603 DOI: 10.1103/physreve.72.021906] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2005] [Revised: 05/02/2005] [Indexed: 05/04/2023]
Abstract
The dynamics of microtubules (MT's) growing from a nucleation center is simulated with a kinetic Monte Carlo model that includes tubulin diffusion. In the limit of fast diffusion (homogeneous tubulin concentration), MT growth is synchronous and bounded. The microtubules form an aster with a monotonously decreasing long-time distribution of lengths. Slow tubulin diffusion leads to rapid dephasing in the growth dynamics, unbounded growth of some MT's, spatial inhomogeneities, and morphological change toward a morphology with bounded short MT's located in the nucleation center and unbounded long MT's with narrowly distributed lengths. The transition from unbounded to bounded growth is driven by the competition between the reaction rate of the tubulin assembly and the tubulin's diffusion rate. While the present study reports the effect of the tubulin diffusion coefficient on the transition, the results of the simulations are qualitatively comparable to the morphological and dynamical changes of centrosome-nucleated MT's from interphase to mitosis in cellular systems where the transition is regulated by the reaction rates.
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Affiliation(s)
- P A Deymier
- Department of Materials Science and Engineering, The University of Arizona, Tucson, Arizona 85721, USA
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29
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Maiato H, Sampaio P, Sunkel CE. Microtubule-associated proteins and their essential roles during mitosis. ACTA ACUST UNITED AC 2005; 241:53-153. [PMID: 15548419 DOI: 10.1016/s0074-7696(04)41002-x] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Microtubules play essential roles during mitosis, including chromosome capture, congression, and segregation. In addition, microtubules are also required for successful cytokinesis. At the heart of these processes is the ability of microtubules to do work, a property that derives from their intrinsic dynamic behavior. However, if microtubule dynamics were not properly regulated, it is certain that microtubules alone could not accomplish any of these tasks. In vivo, the regulation of microtubule dynamics is the responsibility of microtubule-associated proteins. Among these, we can distinguish several classes according to their function: (1) promotion and stabilization of microtubule polymerization, (2) destabilization or severance of microtubules, (3) functioning as linkers between various structures, or (4) motility-related functions. Here we discuss how the various properties of microtubule-associated proteins can be used to assemble an efficient mitotic apparatus capable of ensuring the bona fide transmission of the genetic information in animal cells.
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Affiliation(s)
- Hélder Maiato
- Instituto de Biologia Molecular e Celular, Universidade do Porto, 4150-180 Porto, Portugal
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30
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Gigant B, Martin-Barbey C, Curmi PA, Sobel A, Knossow M. [The stathmin-tubulin interaction and the regulation of the microtubule assembly]. PATHOLOGIE-BIOLOGIE 2003; 51:33-8. [PMID: 12628290 DOI: 10.1016/s0369-8114(02)00324-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Stathmin family proteins interact with tubulin and negatively regulate its assembly in microtubules. One stathmin molecule forms a complex with two alphabeta tubulin heterodimers in an interaction that is weakened upon stathmin phosphorylation. The X-ray structure of crystals of the complex reveals a head-to-tail arrangement of the two tubulins which are connected by a long stathmin alpha helix. By holding tubulins in a curved complex that is not incorporated in microtubules, stathmin lowers the pool of "assembly competent" tubulin. An alternate mechanism has been also proposed to account for the stathmin action in vivo; it involves a direct interaction of stathmin with microtubule (+) ends. More experiments are needed to evaluate the relative contribution of this alternative mechanism to the regulation of tubulin assembly by stathmin.
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Affiliation(s)
- B Gigant
- Laboratoire d'Enzymologie et Biochimie Structurales, UPR 9063, Centre National de la Recherche Scientifique, Bâtiment 34, 1, avenue de la Terrasse, 91198 cedex, Gif-sur-Yvette, France.
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31
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Leguy R, Melki R, Pantaloni D, Carlier MF. Monomeric gamma -tubulin nucleates microtubules. J Biol Chem 2000; 275:21975-80. [PMID: 10764751 DOI: 10.1074/jbc.m000688200] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
gamma-Tubulin is required for nucleation and polarized organization of microtubules in vivo. The mechanism of microtubule nucleation by gamma-tubulin and the role of associated proteins is not understood. Here we show that in vitro translated monomeric gamma-tubulin nucleates microtubules by lowering the size of the nucleus from seven to three tubulin subunits. In capping the minus end with high affinity (10(10) m(-1)) and a binding stoichiometry of one molecule of gamma-tubulin/microtubule, gamma-tubulin establishes the critical concentration of the plus end in the medium and prevents minus end growth. gamma-Tubulin interacts strongly with beta-tubulin. A structural model accounts for these results.
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Affiliation(s)
- R Leguy
- Dynamique du Cytosquelette, Laboratoire d'Enzymologie et Biochimie Structurales, CNRS, 91198 Gif-sur-Yvette, France
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32
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Abstract
FtsZ forms a cytokinetic ring, designated the Z ring, that directs cytokinesis in prokaryotes. It has limited sequence similarity to eukaryotic tubulins and, like tubulin, it has GTPase activity and the ability to assemble into various structures including protofilaments, bundles and minirings. By using both electron microscopy and sedimentation, we demonstrate that FtsZ from Escherichia coli undergoes a strictly GTP-dependent polymerization and the polymers disappear as the GTP is consumed. Thus, FtsZ polymerization, like that of tubulin, is dynamic and regulated by GTP hydrolysis. These results provide the basis for the dynamics of the Z ring and favor a model in which the Z ring is formed by a nucleation event.
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Affiliation(s)
- A Mukherjee
- Department of Microbiology, Molecular Genetics and Immunology, University of Kansas Medical Center, Kansas City 66160, USA
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33
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Carlier MF, Didry D, Pantaloni D. Hydrolysis of GTP associated with the formation of tubulin oligomers is involved in microtubule nucleation. Biophys J 1997; 73:418-27. [PMID: 9199805 PMCID: PMC1180942 DOI: 10.1016/s0006-3495(97)78081-0] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Hydrolysis of GTP is known to accompany microtubule assembly. Here we show that hydrolysis of GTP is also associated with the formation of linear oligomers of tubulin, which are precursors (prenuclei) in microtubule assembly. The hydrolysis of GTP on these linear oligomers inhibits the lateral association of GTP-tubulin that leads to the formation of a bidimensional lattice. Therefore GTP hydrolysis interferes with the nucleation of microtubules. Linear oligomers are also formed in mixtures of GTP-tubulin and GDP-tubulin. The hydrolysis of GTP associated with heterologous interactions between GTP-tubulin and GDP-tubulin in the cooligomer takes place at a threefold faster rate than upon homologous interactions between GTP-tubulins. The implication of these results in a model of vectorial GTP hydrolysis in microtubule assembly is discussed.
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Affiliation(s)
- M F Carlier
- Laboratoire d'Enzymologie et Biochimie Structurale, CNRS, Gif-sur-Yvetta, France.
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34
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Abstract
Cell duplication is characteristic of life. The coordination of cell growth with cell duplication and, specifically, the ordered steps necessary for this process are termed the cell cycle. Central to this process is the faithful replication and segregation of the chromosomes. The cycle consists of four phases: G1, where the decision to enter the cell cycle, which is known as Start, is made; S phase, during which the DNA is replicated; G2, during which controls assuring the completion of S phase operate; and M, or the mitotic phase, which is characterized by chromosome segregation, nuclear division, and cytokinesis. The budding yeast Saccharomyces cerevisiae has been developed into a model genetic system for the study of the cell division cycle (Hartwell et al. ["73] Genetics, 74:267-286). Here I review the basic processes by which chromosomes are segregated, with an emphasis on the physical structures fundamental to this process.
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Affiliation(s)
- S G Sobel
- Department of Cell Biology, Yale University, New Haven, Connecticut 06536-0812, USA
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35
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Symmons MF, Martin SR, Bayley PM. Dynamic properties of nucleated microtubules: GTP utilisation in the subcritical concentration regime. J Cell Sci 1996; 109 ( Pt 11):2755-66. [PMID: 8937993 DOI: 10.1242/jcs.109.11.2755] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Microtubule assembly kinetics have been studied quantitatively under solution conditions supporting microtubule dynamic instability. Purified GTP-tubulin (Tu-GTP) and covalently cross-linked short microtubule seeds (EGS-seeds; Koshland et al. (1988) Nature 331, 499) were used with and without biotinylation. Under sub-critical concentration conditions ([Tu-GTP] < 5.3 microM), significant microtubule growth of limited length was observed on a proportion of the EGS-seeds by immuno-electron microscopy. A sensitive fluorescence assay for microtubule GDP production was developed for parallel assessment of GTP utilisation. This revealed a correlation between the detected microtubule growth and the production of tubulin-GDP, deriving from the shortening phase of the dynamic microtubules. This correlation was confirmed by the action of nocodazole, a specific inhibitor of microtubule assembly, that was found to abolish the GDP release. The variation of the GDP release with tubulin concentration (Jh(c) plot) was determined below the critical concentration (Cc). The GDP production observed was consistent with the elongation of the observed seeded microtubules with an apparent rate constant of 1.5 × 10(6) M-1 second-1 above a threshold of approximately 1 microM tubulin. The form of this Jh(c) plot for elongation below Cc is reproduced by the Lateral Cap model for microtubule dynamic instability adapted for seeded assembly. The behaviour of the system is contrasted with that previously studied in the absence of detectable microtubule elongation (Caplow and Shanks (1990) J. Biol. Chem. 265, 8935–8941). The approach provides a means of monitoring microtubule dynamics at concentrations inaccessible to optical microscopy, and shows that essentially the same dynamic mechanisms apply at all concentrations. Numerical simulation of the subcritical concentration regime shows dynamic growth features applicable to the initiation of microtubule growth in vivo.
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Affiliation(s)
- M F Symmons
- Division of Physical Biochemistry, National Institute for Medical Research, London, UK
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36
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Flyvbjerg H, Holy TE, Leibler S. Microtubule dynamics: Caps, catastrophes, and coupled hydrolysis. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 1996; 54:5538-5560. [PMID: 9965740 DOI: 10.1103/physreve.54.5538] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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37
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Abstract
BACKGROUND Microtubules polymerized from pure tubulin show the unusual property of dynamic instability, in which both growing and shrinking polymers coexist at steady state. Shortly after its addition to a microtubule end, a tubulin subunit hydrolyzes its bound GTP. Studies with non-hydrolyzable analogs have shown that GTP hydrolysis is not required for microtubule assembly, but is essential for generating a dynamic polymer, in which the subunits at the growing tip have bound GTP and those in the bulk of the polymer have bound GDP. It has been suggested that loss of the 'GTP cap' through dissociation or hydrolysis exposes the unstable GDP core, leading to rapid depolymerization. However, evidence for a stabilizing cap has been very difficult to obtain. RESULTS We developed an assay to determine the minimum GTP cap necessary to stabilize a microtubule from shrinking. Assembly of a small number of subunits containing a slowly hydrolyzed GTP analog (GMPCPP) onto the end of dynamic microtubules stabilized the polymer to dilution. By labeling the subunits with rhodamine, we measured the size of the cap and found that as few as 40 subunits were sufficient to stabilize a microtubule. CONCLUSIONS On the basis of statistical arguments, in which the proportion of stabilized microtubules is compared to the probability that when 40 GMPCPP-tubulin subunits have polymerized onto a microtubule end, all protofilaments have added at least one GMPCPP-tubulin subunit, our measurements of cap size support a model in which a single GTP subunit at the end of each of the 13 protofilaments of a microtubule is sufficient for stabilization. Depolymerization of a microtubule may be initiated by an exposed tubulin-GDP subunit at even a single position. These results have implications for the structure of microtubules and their means of regulation.
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Affiliation(s)
- D N Drechsel
- Department of Biochemistry and Biophysics, University of California, San Francisco 94143-0448, USA
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38
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Vasquez RJ, Gard DL, Cassimeris L. XMAP from Xenopus eggs promotes rapid plus end assembly of microtubules and rapid microtubule polymer turnover. J Cell Biol 1994; 127:985-93. [PMID: 7962080 PMCID: PMC2200056 DOI: 10.1083/jcb.127.4.985] [Citation(s) in RCA: 186] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
We have used video-enhanced DIC microscopy to examine the effects of XMAP, a Mr 215,000 microtubule-associated protein from Xenopus eggs (Gard, D.L., and M. W. Kirschner. 1987. J. Cell Biol. 105:2203-2215), on the dynamic instability of microtubules nucleated from axoneme fragments in vitro. Our results indicate that XMAP substantially alters the parameters of microtubule assembly at plus ends. Specifically, addition of 0.2 microM XMAP resulted in (a) 7-10-fold increase in elongation velocity, (b) approximately threefold increase in shortening velocity, and (c) near elimination of rescue (the switch from rapid shortening to elongation). Thus, addition of XMAP resulted in the assembly of longer, but more dynamic, microtubules from the plus ends of axonemes which upon catastrophe disassembled back to the axoneme nucleation site. In agreement with previous observations (Gard, D.L., and M. W. Kirschner. 1987. J. Cell Biol. 105:2203-2215), the effects of XMAP on the minus end were much less dramatic, with only a 1.5-3-fold increase in elongation velocity. These results indicate that XMAP, unlike brain MAPs, promotes both polymer assembly and turnover, and suggests that the interaction of XMAP with tubulin and the function of XMAP in vivo may differ from previously characterized MAPs.
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Affiliation(s)
- R J Vasquez
- Department of Molecular Biology, Lehigh University, Bethlehem, Pennsylvania 18015
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39
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Martin SR, Schilstra MJ, Bayley PM. Dynamic instability of microtubules: Monte Carlo simulation and application to different types of microtubule lattice. Biophys J 1993; 65:578-96. [PMID: 8218889 PMCID: PMC1225761 DOI: 10.1016/s0006-3495(93)81091-9] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Dynamic instability is the term used to describe the transition of an individual microtubule, apparently at random, between extended periods of slow growth and brief periods of rapid shortening. The typical sawtooth growth and shortening transition behavior has been successfully simulated numerically for the 13-protofilament microtubule A-lattice by a lateral cap model (Bayley, P. M., M. J. Schilstra, and S. R. Martin. 1990. J. Cell Sci. 95:33-48). This kinetic model is now extended systematically to other related lattice geometries, namely the 13-protofilament B-lattice and the 14-protofilament A-lattice, which contain structural "seams". The treatment requires the assignment of the free energies of specific protein-protein interactions in terms of the basic microtubule lattice. It is seen that dynamic instability is not restricted to the helically symmetric 13-protofilament A-lattice but is potentially a feature of all A- and B-lattices, irrespective of protofilament number. The advantages of this general energetic approach are that it allows a consistent treatment to be made for both ends of any microtubule lattice. Important features are the predominance of longitudinal interactions between tubulin molecules within the same protofilament and the implication of a relatively favorable interaction of tubulin-GDP with the growing microtubule end. For the three lattices specifically considered, the treatment predicts the dependence of the transition behavior upon tubulin concentration as a cooperative process, in good agreement with recent experimental observations. The model rationalizes the dynamic properties in terms of a metastable microtubule lattice of tubulin-GDP, stabilized by the kinetic process of tubulin-GTP addition. It provides a quantitative basis for the consideration of in vitro microtubule behaviour under both steady-state and non-steady-state conditions, for comparison with experimental data on the dilution-induced disassembly of microtubules. Similarly, the effects of small tubulin-binding molecules such as GDP and nonhydrolyzable GTP analogues are readily treated. An extension of the model allows a detailed quantitative examination of possible modes of substoichiometric action of a number of antimitotic drugs relevant to cancer chemotherapy.
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Affiliation(s)
- S R Martin
- Division of Physical Biochemistry, National Institute for Medical Research, Mill Hill, London, England
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40
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Trinczek B, Marx A, Mandelkow EM, Murphy DB, Mandelkow E. Dynamics of microtubules from erythrocyte marginal bands. Mol Biol Cell 1993; 4:323-35. [PMID: 8485321 PMCID: PMC300930 DOI: 10.1091/mbc.4.3.323] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Microtubules can adjust their length by the mechanism of dynamic instability, that is by switching between phases of growth and shrinkage. Thus far this phenomenon has been studied with microtubules that contain several components, that is, a mixture of tubulin isoforms, with or without a mixture of microtubule-associated proteins (MAPs), which can act as regulators of dynamic instability. Here we concentrate on the influence of the tubulin component. We have studied MAP-free microtubules from the marginal band of avian erythrocytes and compared them with mammalian brain microtubules. The erythrocyte system was selected because it represents a naturally stable aggregate of microtubules; second, the tubulin is largely homogeneous, in contrast to brain tubulin. Qualitatively, erythrocyte microtubules show similar features as brain microtubules, but they were found to be much less dynamic. The critical concentration of elongation, and the rates of association and dissociation of tubulin are all lower than with brain microtubules. Catastrophes are rare, rescues frequent, and shrinkage slow. This means that dynamic instability can be controlled by the tubulin isotype, independently of MAPs. Moreover, the extent of dynamic behavior is highly dependent on buffer conditions. In particular, dynamic instability is strongly enhanced in phosphate buffer, both for erythrocyte marginal band and brain microtubules. The lower stability in phosphate buffer argues against the hypothesis that a cap of tubulin.GDP.Pi subunits stabilizes microtubules. The difference in dynamics between tubulin isotypes and between the two ends of microtubules is preserved in the different buffer systems.
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Affiliation(s)
- B Trinczek
- Max-Planck-Unit for Structural Molecular Biology, Hamburg, Germany
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41
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Mandelkow EM, Mandelkow E. Microtubule oscillations. CELL MOTILITY AND THE CYTOSKELETON 1992; 22:235-44. [PMID: 1516147 DOI: 10.1002/cm.970220403] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- E M Mandelkow
- Max-Planck-Unit for Structural Molecular Biology, DESY, Hamburg, Germany
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42
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Affiliation(s)
- J R McIntosh
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder 80309-0347
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43
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Mandelkow EM, Mandelkow E, Milligan RA. Microtubule dynamics and microtubule caps: a time-resolved cryo-electron microscopy study. J Cell Biol 1991; 114:977-91. [PMID: 1874792 PMCID: PMC2289108 DOI: 10.1083/jcb.114.5.977] [Citation(s) in RCA: 469] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Microtubules display the unique property of dynamic instability characterized by phase changes between growth and shrinkage, even in constant environmental conditions. The phases can be synchronized, leading to bulk oscillations of microtubules. To study the structural basis of dynamic instability we have examined growing, shrinking, and oscillating microtubules by time-resolved cryo-EM. In particular we have addressed three questions which are currently a matter of debate: (a) What is the relationship between microtubules, tubulin subunits, and tubulin oligomers in microtubule dynamics?; (b) How do microtubules shrink? By release of subunits or via oligomers?; and (c) Is there a conformational change at microtubule ends during the transitions from growth to shrinkage and vice versa? The results show that (a) oscillating microtubules coexist with a substantial fraction of oligomers, even at a maximum of microtubule assembly; (b) microtubules disassemble primarily into oligomers; and (c) the ends of growing microtubules have straight protofilaments, shrinking microtubules have protofilaments coiled inside out. This is interpreted as a transition from a tense to a relaxed conformation which could be used to perform work, as suggested by some models of poleward chromosome movement during anaphase.
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Affiliation(s)
- E M Mandelkow
- Max-Planck-Unit for Structural Molecular Biology, Hamburg, Germany
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44
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Burns RG. Assembly of chick brain MAP2-tubulin microtubule protein. Characterization of the protein and the MAP2-dependent addition of tubulin dimers. Biochem J 1991; 277 ( Pt 1):231-8. [PMID: 1854335 PMCID: PMC1151214 DOI: 10.1042/bj2770231] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The principle proteins present in twice-cycled chick brain microtubule protein were characterized. The protein consists of a stoichiometric mixture of MAP2 and tubulin, together with a number of minor components. Its composition remains unaltered after a third cycle of assembly in a buffer supplemented with 67 mM-NaCl, with the exception of the phosphorylation of MAP2 to a low level (congruent to 1 mol.mol-1). The inclusion of 67 mM-NaCl dissociates the MAP2-tubulin oligomers, and restricts the assembly to the MAP2-dependent addition and loss of tubulin dimers, such that the assembly kinetics approximate to a simple pseudo-first-order reaction. The assembled microtubules exhibit dynamic instability, with no evidence for end-to-end annealing.
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Affiliation(s)
- R G Burns
- Biophysics Section, Blackett Laboratory, Imperial College of Science, Technology and Medicine, London, U.K
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45
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Burns RG. Kinetics of GTP hydrolysis during the assembly of chick brain MAP2-tubulin microtubule protein. Biochem J 1991; 277 ( Pt 1):239-43. [PMID: 1854336 PMCID: PMC1151215 DOI: 10.1042/bj2770239] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The kinetics of GTP hydrolysis during microtubule assembly have been examined using chick brain MAP2-tubulin microtubule protein in a NaCl-supplemented buffer. The elongating microtubules terminate in a 'GTP cap', since the kinetics of GTP hydrolysis are slower than those of subunit addition. GTP hydrolysis is (a) stoichiometric, (b) occurs as a vectorial wave as the initial rate of hydrolysis is proportional to the molar concentration of microtubule ends and not to the initial rate of subunit addition, and (c) either does not occur, or occurs only at a much lower rate, in the terminal subunits.
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Affiliation(s)
- R G Burns
- Biophysics Section, Blackett Laboratory, Imperial College of Science, Technology and Medicine, London, U.K
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46
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Symmons MF, Burns RG. Assembly of chick brain MAP2-tubulin microtubule protein. Analysis of tubulin subunit flux rates by immunofluorescence microscopy. Biochem J 1991; 277 ( Pt 1):245-53. [PMID: 1854337 PMCID: PMC1151216 DOI: 10.1042/bj2770245] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
A filter-based immunofluorescence-microscopy method for obtaining microtubule lengths has been developed and evaluated. Kinetic constants and mean lengths obtained show close agreement with those obtained by complementary methods applied to chick brain MAP2-tubulin microtubule protein in NaCl-supplemented buffer. The filter-based method has been used to estimate tubulin subunit flux (Jon) resulting from isothermal dilution of microtubule populations to various free tubulin concentrations, (c). This experimental Jon(c) plot is significantly different from that predicted by a variety of theoretical models, but is consistent with a 'lateral cap' model of dynamic instability [Bayley, Schilstra & Martin (1990) J. Cell. Sci. 95, 33-48] adapted to accommodate the observed vectorial GTP hydrolysis.
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Affiliation(s)
- M F Symmons
- Biophysics Section, Blackett Laboratory, Imperial College of Science, Technology and Medicine, London, U.K
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47
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Beck KA, Keen JH. Self-association of the plasma membrane-associated clathrin assembly protein AP-2. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(20)64341-1] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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48
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Regulation of tubulin levels and microtubule assembly in Saccharomyces cerevisiae: consequences of altered tubulin gene copy number. Mol Cell Biol 1990. [PMID: 2204811 DOI: 10.1128/mcb.10.10.5286] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Microtubule organization in the cytoplasm is in part a function of the number and length of the assembled polymers. The intracellular concentration of tubulin could specify those parameters. Saccharomyces cerevisiae strains constructed with moderately decreased or increased copy numbers of tubulin genes provide an opportunity to study the cellular response to a steady-state change in tubulin concentration. We found no evidence of a mechanism for adjusting tubulin concentrations upward from a deficit, nor did we find a need for such a mechanism: cells with no more than 50% of the wild-type tubulin level were normal with respect to a series of microtubule-dependent properties. Strains with increased copies of both alpha- and beta-tubulin genes, or of alpha-tubulin genes alone, apparently did down regulate their tubulin levels. As a result, they contained greater than normal concentrations of tubulin but much less than predicted from the increase in gene number. Some of this down regulation occurred at the level of protein. These strains were also phenotypically normal. Cells could contain excess alpha-tubulin protein without detectable consequences, but perturbations resulting in excess beta-tubulin genes may have affected microtubule-dependent functions. All of the observed regulation of levels of tubulin can be explained as a response to toxicity associated with excess tubulin proteins, especially if beta-tubulin is much more toxic than alpha-tubulin.
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Burns RG, Surridge C. Analysis of beta-tubulin sequences reveals highly conserved, coordinated amino acid substitutions. Evidence that these 'hot spots' are directly involved in the conformational change required for dynamic instability. FEBS Lett 1990; 271:1-8. [PMID: 2226794 DOI: 10.1016/0014-5793(90)80359-q] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Vertebrate beta-tubulins have been classified into six classes on the basis of their C-terminal sequences [(1987) J. Cell Biol. 105, 1707-1720]. In particular, the sequences starting at residue 430 differ between isotypes of the same animal but are conserved between species. We extend this analysis and show that there are three 'hot spots', at residues 35, 55-57 and 124 which exhibit intra-species heterogeneity but inter-species conservation. There is a remarkable correlation between the identity of these residues and the C-terminal sequences, and suggests that the vertebrate beta-tubulins fall into three broad types. This correlation extends to those non-vertebrate organisms which have the Type 1 C-terminal sequence. We propose that these three 'hot spots' and the C-terminal peptide interact in the tertiary structure. We have also noted that the C-terminal peptide almost always contains a single phenylalanine or tyrosine residue, and that there is a strong correlation between this residue and the amino acids at positions 217/218, in both the vertebrate and non-vertebrate sequences. We propose that the C-terminal aromatic amino acid interacts with residues 217/218 in the tertiary structure. Analysis of conditions which stabilise microtubules and/or lower the steady state critical concentration strongly suggests that these two sets of coordinated amino acid substitutions are directly involved in effecting the conformational change associated with GTP hydrolysis which results in dynamic instability. We propose that there is an interaction between the highly acidic sequence between residue 430 and the aromatic amino acid (termed peptide A) and conserved basic amino acids located close to the 'hot spots'. We suggest that this interaction is altered in response to the assembly-dependent GTP hydrolysis, with the consequential increase in the subunit dissociation rate constant.
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Affiliation(s)
- R G Burns
- Blackett Laboratory, Imperial College of Science, Technology and Medicine, London, UK
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Katz W, Weinstein B, Solomon F. Regulation of tubulin levels and microtubule assembly in Saccharomyces cerevisiae: consequences of altered tubulin gene copy number. Mol Cell Biol 1990; 10:5286-94. [PMID: 2204811 PMCID: PMC361216 DOI: 10.1128/mcb.10.10.5286-5294.1990] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Microtubule organization in the cytoplasm is in part a function of the number and length of the assembled polymers. The intracellular concentration of tubulin could specify those parameters. Saccharomyces cerevisiae strains constructed with moderately decreased or increased copy numbers of tubulin genes provide an opportunity to study the cellular response to a steady-state change in tubulin concentration. We found no evidence of a mechanism for adjusting tubulin concentrations upward from a deficit, nor did we find a need for such a mechanism: cells with no more than 50% of the wild-type tubulin level were normal with respect to a series of microtubule-dependent properties. Strains with increased copies of both alpha- and beta-tubulin genes, or of alpha-tubulin genes alone, apparently did down regulate their tubulin levels. As a result, they contained greater than normal concentrations of tubulin but much less than predicted from the increase in gene number. Some of this down regulation occurred at the level of protein. These strains were also phenotypically normal. Cells could contain excess alpha-tubulin protein without detectable consequences, but perturbations resulting in excess beta-tubulin genes may have affected microtubule-dependent functions. All of the observed regulation of levels of tubulin can be explained as a response to toxicity associated with excess tubulin proteins, especially if beta-tubulin is much more toxic than alpha-tubulin.
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Affiliation(s)
- W Katz
- Department of Biology, Massachusetts Institute of Technology, Cambridge 02139
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