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Dey S, Kumar N, Balakrishnan S, Koushika SP, Ghosh-Roy A. KLP-7/Kinesin-13 orchestrates axon-dendrite checkpoints for polarized trafficking in neurons. Mol Biol Cell 2024; 35:ar115. [PMID: 38985513 PMCID: PMC7616348 DOI: 10.1091/mbc.e23-08-0335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Revised: 06/27/2024] [Accepted: 07/03/2024] [Indexed: 07/12/2024] Open
Abstract
The polarized nature of neurons depends on their microtubule dynamics and orientation determined by both microtubule-stabilizing and destabilizing factors. The role of destabilizing factors in developing and maintaining neuronal polarity is unclear. We investigated the function of KLP-7, a microtubule depolymerizing motor of the Kinesin-13 family, in axon-dendrite compartmentalization using PVD neurons in Caenorhabditis elegans. Loss of KLP-7 caused a mislocalization of axonal proteins, including RAB-3, SAD-1, and their motor UNC-104, to dendrites. This is rescued by cell-autonomous expression of the KLP-7 or colchicine treatment, indicating the involvement of KLP-7-dependent microtubule depolymerization. The high mobility of KLP-7 is correlated to increased microtubule dynamics in the dendrites, which restricts the enrichment of UNC-44, an integral component of Axon Initial Segment (AIS) in these processes. Due to the loss of KLP-7, ectopic enrichment of UNC-44 in the dendrite potentially redirects axonal traffic into dendrites that include plus-end out microtubules, axonal motors, and cargoes. These observations indicate that KLP-7-mediated depolymerization defines the microtubule dynamics conducive to the specific enrichment of AIS components in dendrites. This further compartmentalizes dendritic and axonal microtubules, motors, and cargoes, thereby influencing neuronal polarity.
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Affiliation(s)
- Swagata Dey
- Cellular and Molecular Neuroscience, National Brain Research Centre, Manesar, Gurugram, Haryana 122052, India
| | - Nitish Kumar
- Cellular and Molecular Neuroscience, National Brain Research Centre, Manesar, Gurugram, Haryana 122052, India
| | - Supraja Balakrishnan
- Cellular and Molecular Neuroscience, National Brain Research Centre, Manesar, Gurugram, Haryana 122052, India
| | - Sandhya P. Koushika
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, Maharashtra 400005, India
| | - Anindya Ghosh-Roy
- Cellular and Molecular Neuroscience, National Brain Research Centre, Manesar, Gurugram, Haryana 122052, India
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2
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Sahayaraj AE, Abdul Vahid A, Dhara A, Babu AT, Vijayan V. Role of G326 in Determining the Aggregation Propensity of R3 Tau Repeat: Insights from Studies on R1R3 Tau Construct. J Phys Chem B 2024; 128:4325-4335. [PMID: 38676652 DOI: 10.1021/acs.jpcb.4c00123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/29/2024]
Abstract
The Microtubule-binding repeat region (MTBR) of Tau has been studied extensively due to its pathological implications in neurodegenerative diseases like Alzheimer's disease. The pathological property of MTBR is mainly due to the R3 repeat's high propensity for self-aggregation, highlighting the critical molecular grammar of the repeat. Utilizing the R1R3 construct (WT) and its G326E mutant (EE), we determine the distinct characteristics of various peptide segments that modulate the aggregation propensity of the R3 repeat using NMR spectroscopy. Through time-dependent experiments, we have identified 317KVTSKCGS324 in R3 repeat as the aggregation initiating motif (AIM) due to its role at the initial stages of aggregation. The G326E mutation induces changes in conformation and dynamics at the AIM, thereby effectively abrogating the aggregation propensity of the R1R3 construct. We further corroborate our findings through MD simulations and propose that AIM is a robust site of interest for tauopathy drug design.
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Affiliation(s)
- Allwin Ebenezer Sahayaraj
- School of Chemistry, IISER-Thiruvananthapuram, Maruthamala PO, Thiruvananthapuram, Kerala 695551, India
| | - Arshad Abdul Vahid
- School of Chemistry, IISER-Thiruvananthapuram, Maruthamala PO, Thiruvananthapuram, Kerala 695551, India
| | - Asmita Dhara
- School of Chemistry, IISER-Thiruvananthapuram, Maruthamala PO, Thiruvananthapuram, Kerala 695551, India
| | - Ann Teres Babu
- School of Chemistry, IISER-Thiruvananthapuram, Maruthamala PO, Thiruvananthapuram, Kerala 695551, India
| | - Vinesh Vijayan
- School of Chemistry, IISER-Thiruvananthapuram, Maruthamala PO, Thiruvananthapuram, Kerala 695551, India
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3
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Cario A, Berger CL. Tau, microtubule dynamics, and axonal transport: New paradigms for neurodegenerative disease. Bioessays 2023; 45:e2200138. [PMID: 37489532 PMCID: PMC10630968 DOI: 10.1002/bies.202200138] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 05/04/2023] [Accepted: 05/23/2023] [Indexed: 07/26/2023]
Abstract
The etiology of Tauopathies, a diverse class of neurodegenerative diseases associated with the Microtubule Associated Protein (MAP) Tau, is usually described by a common mechanism in which Tau dysfunction results in the loss of axonal microtubule stability. Here, we reexamine and build upon the canonical disease model to encompass other Tau functions. In addition to regulating microtubule dynamics, Tau acts as a modulator of motor proteins, a signaling hub, and a scaffolding protein. This diverse array of functions is related to the dynamic nature of Tau isoform expression, post-translational modification (PTM), and conformational flexibility. Thus, there is no single mechanism that can describe Tau dysfunction. The effects of specific pathogenic mutations or aberrant PTMs need to be examined on all of the various functions of Tau in order to understand the unique etiology of each disease state.
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Affiliation(s)
- Alisa Cario
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT 05405
| | - Christopher L. Berger
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT 05405
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4
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Rosito M, Sanchini C, Gosti G, Moreno M, De Panfilis S, Giubettini M, Debellis D, Catalano F, Peruzzi G, Marotta R, Indrieri A, De Leonibus E, De Stefano ME, Ragozzino D, Ruocco G, Di Angelantonio S, Bartolini F. Microglia reactivity entails microtubule remodeling from acentrosomal to centrosomal arrays. Cell Rep 2023; 42:112104. [PMID: 36787220 PMCID: PMC10423306 DOI: 10.1016/j.celrep.2023.112104] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 12/02/2022] [Accepted: 01/27/2023] [Indexed: 02/15/2023] Open
Abstract
Microglia reactivity entails a large-scale remodeling of cellular geometry, but the behavior of the microtubule cytoskeleton during these changes remains unexplored. Here we show that activated microglia provide an example of microtubule reorganization from a non-centrosomal array of parallel and stable microtubules to a radial array of more dynamic microtubules. While in the homeostatic state, microglia nucleate microtubules at Golgi outposts, and activating signaling induces recruitment of nucleating material nearby the centrosome, a process inhibited by microtubule stabilization. Our results demonstrate that a hallmark of microglia reactivity is a striking remodeling of the microtubule cytoskeleton and suggest that while pericentrosomal microtubule nucleation may serve as a distinct marker of microglia activation, inhibition of microtubule dynamics may provide a different strategy to reduce microglia reactivity in inflammatory disease.
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Affiliation(s)
- Maria Rosito
- Center for Life Nano- & Neuro-Science, Istituto Italiano di Tecnologia, 00161 Rome, Italy; Department of Physiology and Pharmacology, Sapienza University, 00185 Rome, Italy
| | - Caterina Sanchini
- Center for Life Nano- & Neuro-Science, Istituto Italiano di Tecnologia, 00161 Rome, Italy; Department of Physiology and Pharmacology, Sapienza University, 00185 Rome, Italy
| | - Giorgio Gosti
- Center for Life Nano- & Neuro-Science, Istituto Italiano di Tecnologia, 00161 Rome, Italy; Soft and Living Matter Laboratory, Institute of Nanotechnology, Consiglio Nazionale delle Ricerche, 00185 Rome, Italy
| | - Manuela Moreno
- Department of Physiology and Pharmacology, Sapienza University, 00185 Rome, Italy
| | - Simone De Panfilis
- Center for Life Nano- & Neuro-Science, Istituto Italiano di Tecnologia, 00161 Rome, Italy
| | | | - Doriana Debellis
- Electron Microscopy Facility, Istituto Italiano di Tecnologia, 16163 Genova, Italy
| | - Federico Catalano
- Electron Microscopy Facility, Istituto Italiano di Tecnologia, 16163 Genova, Italy
| | - Giovanna Peruzzi
- Center for Life Nano- & Neuro-Science, Istituto Italiano di Tecnologia, 00161 Rome, Italy
| | - Roberto Marotta
- Electron Microscopy Facility, Istituto Italiano di Tecnologia, 16163 Genova, Italy
| | - Alessia Indrieri
- Telethon Institute of Genetics and Medicine, 80078 Pozzuoli, Italy; Institute for Genetic and Biomedical Research, National Research Council, 20090 Milan, Italy
| | - Elvira De Leonibus
- Telethon Institute of Genetics and Medicine, 80078 Pozzuoli, Italy; Institute of Biochemistry and Cellular Biology, National Research Council, 00015 Rome, Italy
| | - Maria Egle De Stefano
- Department of Biology and Biotechnologies "Charles Darwin", Sapienza University, 00185 Rome, Italy
| | - Davide Ragozzino
- Department of Physiology and Pharmacology, Sapienza University, 00185 Rome, Italy; Santa Lucia Foundation (IRCCS Fondazione Santa Lucia), 00179 Rome, Italy
| | - Giancarlo Ruocco
- Center for Life Nano- & Neuro-Science, Istituto Italiano di Tecnologia, 00161 Rome, Italy; Department of Physics, Sapienza University, 00185 Rome, Italy
| | - Silvia Di Angelantonio
- Center for Life Nano- & Neuro-Science, Istituto Italiano di Tecnologia, 00161 Rome, Italy; Department of Physiology and Pharmacology, Sapienza University, 00185 Rome, Italy; D-Tails s.r.l, 00165 Rome, Italy.
| | - Francesca Bartolini
- Department of Pathology and Cell Biology, Columbia University Medical Center, New York, NY 10032, USA.
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Miryala CSJ, Holland ED, Dent EW. Contributions of microtubule dynamics and transport to presynaptic and postsynaptic functions. Mol Cell Neurosci 2022; 123:103787. [PMID: 36252720 PMCID: PMC9838116 DOI: 10.1016/j.mcn.2022.103787] [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: 08/29/2022] [Revised: 10/07/2022] [Accepted: 10/11/2022] [Indexed: 11/27/2022] Open
Abstract
Microtubules (MT) are elongated, tubular, cytoskeletal structures formed from polymerization of tubulin dimers. They undergo continuous cycles of polymerization and depolymerization, primarily at their plus ends, termed dynamic instability. Although this is an intrinsic property of MTs, there are a myriad of MT-associated proteins that function in regulating MT dynamic instability and other dynamic processes that shape the MT array. Additionally, MTs assemble into long, semi-rigid structures which act as substrates for long-range, motor-driven transport of many different types of cargoes throughout the cell. Both MT dynamics and motor-based transport play important roles in the function of every known type of cell. Within the last fifteen years many groups have shown that MT dynamics and transport play ever-increasing roles in the neuronal function of mature neurons. Not only are neurons highly polarized cells, but they also connect with one another through synapses to form complex networks. Here we will focus on exciting studies that have illuminated how MTs function both pre-synaptically in axonal boutons and post-synaptically in dendritic spines. It is becoming clear that MT dynamics and transport both serve important functions in synaptic plasticity. Thus, it is not surprising that disruption of MTs, either through hyperstabilization or destabilization, has profound consequences for learning and memory. Together, the studies described here suggest that MT dynamics and transport play key roles in synaptic function and when disrupted result in compromised learning and memory.
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Affiliation(s)
- Chandra S. J. Miryala
- Department of Neuroscience, University of Wisconsin, School of Medicine and Public Health, Madison, WI 53705
| | - Elizabeth D. Holland
- Neuroscience Training Program, University of Wisconsin-Madison, Madison, WI 53705
| | - Erik W. Dent
- Department of Neuroscience, University of Wisconsin, School of Medicine and Public Health, Madison, WI 53705,Corresponding Author: Department of Neuroscience, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI 53705,
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6
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Thyagarajan P, Feng C, Lee D, Shorey M, Rolls MM. Microtubule polarity is instructive for many aspects of neuronal polarity. Dev Biol 2022; 486:56-70. [PMID: 35341730 PMCID: PMC9058238 DOI: 10.1016/j.ydbio.2022.03.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 03/04/2022] [Accepted: 03/22/2022] [Indexed: 11/25/2022]
Abstract
Many neurons in bilaterian animals are polarized with functionally distinct axons and dendrites. Microtubule polarity, microtubule stability, and the axon initial segment (AIS) have all been shown to influence polarized transport in neurons. Each of these cytoskeletal cues could act independently to control axon and dendrite identity, or there could be a hierarchy in which one acts upstream of the others. Here we test the hypothesis that microtubule polarity acts as a master regulator of neuronal polarity by using a Drosophila genetic background in which some dendrites have normal minus-end-out microtubule polarity and others have the axonal plus-end-out polarity. In these mosaic dendrite arbors, we found that ribosomes, which are more abundant in dendrites than axons, were reduced in plus-end-out dendrites, while an axonal cargo was increased. In addition, we determined that microtubule stability was different in plus-end-out and minus-end-out dendrites, with plus-end-out ones having more stable microtubules like axons. Similarly, we found that ectopic diffusion barriers, like those at the AIS, formed at the base of dendrites with plus-end-out regions. Thus, changes in microtubule polarity were sufficient to rearrange other cytoskeletal features associated with neuronal polarization. However, overall neuron shape was maintained with only subtle changes in branching in mosaic arbors. We conclude that microtubule polarity can act upstream of many aspects of intracellular neuronal polarization, but shape is relatively resilient to changes in microtubule polarity in vivo.
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Affiliation(s)
- Pankajam Thyagarajan
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Chengye Feng
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA, 16802, USA
| | - David Lee
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Matthew Shorey
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Melissa M Rolls
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA, 16802, USA.
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7
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Peña-Ortega F, Robles-Gómez ÁA, Xolalpa-Cueva L. Microtubules as Regulators of Neural Network Shape and Function: Focus on Excitability, Plasticity and Memory. Cells 2022; 11:cells11060923. [PMID: 35326374 PMCID: PMC8946818 DOI: 10.3390/cells11060923] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2022] [Revised: 02/09/2022] [Accepted: 02/17/2022] [Indexed: 12/19/2022] Open
Abstract
Neuronal microtubules (MTs) are complex cytoskeletal protein arrays that undergo activity-dependent changes in their structure and function as a response to physiological demands throughout the lifespan of neurons. Many factors shape the allostatic dynamics of MTs and tubulin dimers in the cytosolic microenvironment, such as protein–protein interactions and activity-dependent shifts in these interactions that are responsible for their plastic capabilities. Recently, several findings have reinforced the role of MTs in behavioral and cognitive processes in normal and pathological conditions. In this review, we summarize the bidirectional relationships between MTs dynamics, neuronal processes, and brain and behavioral states. The outcomes of manipulating the dynamicity of MTs by genetic or pharmacological approaches on neuronal morphology, intrinsic and synaptic excitability, the state of the network, and behaviors are heterogeneous. We discuss the critical position of MTs as responders and adaptative elements of basic neuronal function whose impact on brain function is not fully understood, and we highlight the dilemma of artificially modulating MT dynamics for therapeutic purposes.
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8
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Localisation of S100 Protein and Acetylated Tubulin in Sheep Pancreas. FOLIA VETERINARIA 2021. [DOI: 10.2478/fv-2021-0012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Abstract
The pancreas plays a critical role in the control of nutritional homeostasis. It consists of two major parts, the exocrine pancreas, and the endocrine pancreas. In the present study S100 protein and acetylated α-tubulin were used to identify positive structures in both the exocrine and endocrine part of the ovine pancreas. In the exocrine part of the pancreas, a positive reaction to S100 protein was confined to centroacinar cells, intercalated, and intralobular ducts cells. In addition, the S100 protein was localized in the Schwann cells of nerve fibres. On the pancreatic islets, the S100 protein has been observed in Schwann cells of nerve axons, where they form a fine envelope that invests the islet surface. Inside the pancreatic islets, the Schwann cells positive for S100 protein envelope the endocrine cells of the islets. The difference in positivity of the S100 protein was found in relation to the endocrine cells. The relationship between endocrine cell positivity and positive exocrine duct cells was discussed. Acetylated α-tubulin (AT) was restricted to axons of the nerve fibres and was located within the connective tissue accompanying intralobular and inter-lobular ducts, and between secretory acini in close contact with secretory cells.
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9
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Moutin MJ, Bosc C, Peris L, Andrieux A. Tubulin post-translational modifications control neuronal development and functions. Dev Neurobiol 2020; 81:253-272. [PMID: 33325152 PMCID: PMC8246997 DOI: 10.1002/dneu.22774] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 05/26/2020] [Accepted: 07/14/2020] [Indexed: 12/22/2022]
Abstract
Microtubules (MTs) are an essential component of the neuronal cytoskeleton; they are involved in various aspects of neuron development, maintenance, and functions including polarization, synaptic plasticity, and transport. Neuronal MTs are highly heterogeneous due to the presence of multiple tubulin isotypes and extensive post‐translational modifications (PTMs). These PTMs—most notably detyrosination, acetylation, and polyglutamylation—have emerged as important regulators of the neuronal microtubule cytoskeleton. With this review, we summarize what is currently known about the impact of tubulin PTMs on microtubule dynamics, neuronal differentiation, plasticity, and transport as well as on brain function in normal and pathological conditions, in particular during neuro‐degeneration. The main therapeutic approaches to neuro‐diseases based on the modulation of tubulin PTMs are also summarized. Overall, the review indicates how tubulin PTMs can generate a large number of functionally specialized microtubule sub‐networks, each of which is crucial to specific neuronal features.
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Affiliation(s)
- Marie-Jo Moutin
- Grenoble Institut Neurosciences, University Grenoble Alpes, Inserm, U1216, CEA, CNRS, Grenoble, France
| | - Christophe Bosc
- Grenoble Institut Neurosciences, University Grenoble Alpes, Inserm, U1216, CEA, CNRS, Grenoble, France
| | - Leticia Peris
- Grenoble Institut Neurosciences, University Grenoble Alpes, Inserm, U1216, CEA, CNRS, Grenoble, France
| | - Annie Andrieux
- Grenoble Institut Neurosciences, University Grenoble Alpes, Inserm, U1216, CEA, CNRS, Grenoble, France
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10
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Taran AS, Shuvalova LD, Lagarkova MA, Alieva IB. Huntington's Disease-An Outlook on the Interplay of the HTT Protein, Microtubules and Actin Cytoskeletal Components. Cells 2020; 9:E1514. [PMID: 32580314 PMCID: PMC7348758 DOI: 10.3390/cells9061514] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 06/17/2020] [Accepted: 06/17/2020] [Indexed: 12/13/2022] Open
Abstract
Huntington's disease is a severe and currently incurable neurodegenerative disease. An autosomal dominant mutation in the Huntingtin gene (HTT) causes an increase in the polyglutamine fragment length at the protein N-terminus. The consequence of the mutation is the death of neurons, mostly striatal neurons, leading to the occurrence of a complex of motor, cognitive and emotional-volitional personality sphere disorders in carriers. Despite intensive studies, the functions of both mutant and wild-type huntingtin remain poorly understood. Surprisingly, there is the selective effect of the mutant form of HTT even on nervous tissue, whereas the protein is expressed ubiquitously. Huntingtin plays a role in cell physiology and affects cell transport, endocytosis, protein degradation and other cellular and molecular processes. Our experimental data mining let us conclude that a significant part of the Huntingtin-involved cellular processes is mediated by microtubules and other cytoskeletal cell structures. The review attempts to look at unresolved issues in the study of the huntingtin and its mutant form, including their functions affecting microtubules and other components of the cell cytoskeleton.
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Affiliation(s)
- Aleksandra S. Taran
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, 1–73, Leninsky Gory, 119992 Moscow, Russia; (A.S.T.); (L.D.S.)
| | - Lilia D. Shuvalova
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, 1–73, Leninsky Gory, 119992 Moscow, Russia; (A.S.T.); (L.D.S.)
- Federal Research and Clinical Center of Physical-Chemical Medicine of Federal Medical Biological Agency, 1a Malaya Pirogovskaya St., 119435 Moscow, Russia
| | - Maria A. Lagarkova
- Federal Research and Clinical Center of Physical-Chemical Medicine of Federal Medical Biological Agency, 1a Malaya Pirogovskaya St., 119435 Moscow, Russia
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Federal Research and Clinical Center of Physical-Chemical Medicine of Federal Medical Biological Agency, 1a Malaya Pirogovskaya St., 119435 Moscow, Russia
| | - Irina B. Alieva
- Federal Research and Clinical Center of Physical-Chemical Medicine of Federal Medical Biological Agency, 1a Malaya Pirogovskaya St., 119435 Moscow, Russia
- A.N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 1–40, Leninsky Gory, 119992 Moscow, Russia
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11
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McElmurry K, Stone JE, Ma D, Lamoureux P, Zhang Y, Steidemann M, Fix L, Huang F, Miller KE, Suter DM. Dynein-mediated microtubule translocation powering neurite outgrowth in chick and Aplysia neurons requires microtubule assembly. J Cell Sci 2020; 133:133/8/jcs232983. [PMID: 32332091 DOI: 10.1242/jcs.232983] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2019] [Accepted: 03/02/2020] [Indexed: 12/22/2022] Open
Abstract
Previously, we have shown that bulk microtubule (MT) movement correlates with neurite elongation, and blocking either dynein activity or MT assembly inhibits both processes. However, whether the contributions of MT dynamics and dynein activity to neurite elongation are separate or interdependent is unclear. Here, we investigated the underlying mechanism by testing the roles of dynein and MT assembly in neurite elongation of Aplysia and chick neurites using time-lapse imaging, fluorescent speckle microscopy, super-resolution imaging and biophysical analysis. Pharmacologically inhibiting either dynein activity or MT assembly reduced neurite elongation rates as well as bulk and individual MT anterograde translocation. Simultaneously suppressing both processes did not have additive effects, suggesting a shared mechanism of action. Single-molecule switching nanoscopy revealed that inhibition of MT assembly decreased the association of dynein with MTs. Finally, inhibiting MT assembly prevented the rise in tension induced by dynein inhibition. Taken together, our results suggest that MT assembly is required for dynein-driven MT translocation and neurite outgrowth.
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Affiliation(s)
- Kristi McElmurry
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - Jessica E Stone
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - Donghan Ma
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA
| | - Phillip Lamoureux
- Department of Integrative Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Yueyun Zhang
- Department of Statistics, Purdue University, West Lafayette, IN 47904, USA
| | - Michelle Steidemann
- Department of Pharmacology & Toxicology, Michigan State University, East Lansing, MI 48824, USA
| | - Lucas Fix
- Department of Integrative Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Fang Huang
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA.,Purdue Institute of Inflammation, Immunology and Infectious Disease, Purdue University, West Lafayette, IN 47907, USA.,Purdue Institute for Integrative Neuroscience, Purdue University, West Lafayette, IN 47907, USA
| | - Kyle E Miller
- Department of Integrative Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Daniel M Suter
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA .,Purdue Institute for Integrative Neuroscience, Purdue University, West Lafayette, IN 47907, USA.,Bindley Bioscience Center, Purdue University, West Lafayette, IN 47907, USA.,Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, USA
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12
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Vargas EJM, Matamoros AJ, Qiu J, Jan CH, Wang Q, Gorczyca D, Han TW, Weissman JS, Jan YN, Banerjee S, Song Y. The microtubule regulator ringer functions downstream from the RNA repair/splicing pathway to promote axon regeneration. Genes Dev 2020; 34:194-208. [PMID: 31919191 PMCID: PMC7000917 DOI: 10.1101/gad.331330.119] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Accepted: 12/10/2019] [Indexed: 12/17/2022]
Abstract
In this study, Vargas et al. set out to elucidate the downstream effectors of the Rtca-mediated RNA repair/splicing pathway. Using genome-wide transcriptome analysis, the authors demonstrate that the microtubule-associated protein (MAP) tubulin polymerization-promoting protein (TPPP) ringer functions downstream from and is suppressed by Rtca via Xbp1-dependent transcription. Ringer cell-autonomously promotes axon regeneration in the peripheral and central nervous system. Promoting axon regeneration in the central and peripheral nervous system is of clinical importance in neural injury and neurodegenerative diseases. Both pro- and antiregeneration factors are being identified. We previously reported that the Rtca mediated RNA repair/splicing pathway restricts axon regeneration by inhibiting the nonconventional splicing of Xbp1 mRNA under cellular stress. However, the downstream effectors remain unknown. Here, through transcriptome profiling, we show that the tubulin polymerization-promoting protein (TPPP) ringmaker/ringer is dramatically increased in Rtca-deficient Drosophila sensory neurons, which is dependent on Xbp1. Ringer is expressed in sensory neurons before and after injury, and is cell-autonomously required for axon regeneration. While loss of ringer abolishes the regeneration enhancement in Rtca mutants, its overexpression is sufficient to promote regeneration both in the peripheral and central nervous system. Ringer maintains microtubule stability/dynamics with the microtubule-associated protein futsch/MAP1B, which is also required for axon regeneration. Furthermore, ringer lies downstream from and is negatively regulated by the microtubule-associated deacetylase HDAC6, which functions as a regeneration inhibitor. Taken together, our findings suggest that ringer acts as a hub for microtubule regulators that relays cellular status information, such as cellular stress, to the integrity of microtubules in order to instruct neuroregeneration.
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Affiliation(s)
- Ernest J Monahan Vargas
- Raymond G. Perelman Center for Cellular and Molecular Therapeutics, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, USA.,Cell and Molecular Biology Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Andrew J Matamoros
- Raymond G. Perelman Center for Cellular and Molecular Therapeutics, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, USA.,Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Jingyun Qiu
- Raymond G. Perelman Center for Cellular and Molecular Therapeutics, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, USA.,Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Calvin H Jan
- Department of Cellular and Molecular Pharmacology, University of California at San Francisco, San Francisco, California 94158, USA.,Howard Hughes Medical Institute, University of California at San Francisco, San Francisco, California 94158, USA
| | - Qin Wang
- Raymond G. Perelman Center for Cellular and Molecular Therapeutics, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, USA.,Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - David Gorczyca
- Howard Hughes Medical Institute, University of California at San Francisco, San Francisco, California 94158, USA.,Department of Physiology, University of California at San Francisco, San Francisco, California 94158, USA.,Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California 94158, USA
| | - Tina W Han
- Howard Hughes Medical Institute, University of California at San Francisco, San Francisco, California 94158, USA.,Department of Physiology, University of California at San Francisco, San Francisco, California 94158, USA.,Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California 94158, USA
| | - Jonathan S Weissman
- Department of Cellular and Molecular Pharmacology, University of California at San Francisco, San Francisco, California 94158, USA.,Howard Hughes Medical Institute, University of California at San Francisco, San Francisco, California 94158, USA
| | - Yuh Nung Jan
- Howard Hughes Medical Institute, University of California at San Francisco, San Francisco, California 94158, USA.,Department of Physiology, University of California at San Francisco, San Francisco, California 94158, USA.,Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California 94158, USA
| | - Swati Banerjee
- Department of Cellular and Integrative Physiology, Long School of Medicine, University of Texas Health Science Center, San Antonio, Texas 78229, USA
| | - Yuanquan Song
- Raymond G. Perelman Center for Cellular and Molecular Therapeutics, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, USA.,Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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13
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Fawcett JW. The Struggle to Make CNS Axons Regenerate: Why Has It Been so Difficult? Neurochem Res 2019; 45:144-158. [PMID: 31388931 PMCID: PMC6942574 DOI: 10.1007/s11064-019-02844-y] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Revised: 07/09/2019] [Accepted: 07/19/2019] [Indexed: 12/12/2022]
Abstract
Axon regeneration in the CNS is inhibited by many extrinsic and intrinsic factors. Because these act in parallel, no single intervention has been sufficient to enable full regeneration of damaged axons in the adult mammalian CNS. In the external environment, NogoA and CSPGs are strongly inhibitory to the regeneration of adult axons. CNS neurons lose intrinsic regenerative ability as they mature: embryonic but not mature neurons can grow axons for long distances when transplanted into the adult CNS, and regeneration fails with maturity in in vitro axotomy models. The causes of this loss of regeneration include partitioning of neurons into axonal and dendritic fields with many growth-related molecules directed specifically to dendrites and excluded from axons, changes in axonal signalling due to changes in expression and localization of receptors and their ligands, changes in local translation of proteins in axons, and changes in cytoskeletal dynamics after injury. Also with neuronal maturation come epigenetic changes in neurons, with many of the transcription factor binding sites that drive axon growth-related genes becoming inaccessible. The overall aim for successful regeneration is to ensure that the right molecules are expressed after axotomy and to arrange for them to be transported to the right place in the neuron, including the damaged axon tip.
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Affiliation(s)
- James W Fawcett
- John Van Geest Centre for Brain Repair, University of Cambridge, Robinson Way, Cambridge, CB2 0PY, UK.
- Centre of Reconstructive Neuroscience, Institute for Experimental Medicine ASCR, Prague, Czech Republic.
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14
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Logan CM, Menko AS. Microtubules: Evolving roles and critical cellular interactions. Exp Biol Med (Maywood) 2019; 244:1240-1254. [PMID: 31387376 DOI: 10.1177/1535370219867296] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Microtubules are cytoskeletal elements known as drivers of directed cell migration, vesicle and organelle trafficking, and mitosis. In this review, we discuss new research in the lens that has shed light into further roles for stable microtubules in the process of development and morphogenesis. In the lens, as well as other systems, distinct roles for characteristically dynamic microtubules and stabilized populations are coming to light. Understanding the mechanisms of microtubule stabilization and the associated microtubule post-translational modifications is an evolving field of study. Appropriate cellular homeostasis relies on not only one cytoskeletal element, but also rather an interaction between cytoskeletal proteins as well as other cellular regulators. Microtubules are key integrators with actin and intermediate filaments, as well as cell–cell junctional proteins and other cellular regulators including myosin and RhoGTPases to maintain this balance.Impact statementThe role of microtubules in cellular functioning is constantly expanding. In this review, we examine new and exciting fields of discovery for microtubule’s involvement in morphogenesis, highlight our evolving understanding of differential roles for stabilized versus dynamic subpopulations, and further understanding of microtubules as a cellular integrator.
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Affiliation(s)
- Caitlin M Logan
- Pathology Anatomy and Cell Biology Department, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - A Sue Menko
- Pathology Anatomy and Cell Biology Department, Thomas Jefferson University, Philadelphia, PA 19107, USA
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15
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Baas PW, Qiang L. Tau: It's Not What You Think. Trends Cell Biol 2019; 29:452-461. [PMID: 30929793 PMCID: PMC6527491 DOI: 10.1016/j.tcb.2019.02.007] [Citation(s) in RCA: 70] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2019] [Revised: 02/12/2019] [Accepted: 02/21/2019] [Indexed: 12/12/2022]
Abstract
Tau is a multifunctional microtubule-associated protein in the neuron. For decades, tau's main function in neurons has been broadly accepted as stabilizing microtubules in the axon; however, this conclusion was reached mainly on the basis of studies performed in vitro and on ectopic expression of tau in non-neuronal cells. The idea has become so prevailing that some disease researchers are even seeking to use microtubule-stabilizing drugs to treat diseases in which tau dissociates from microtubules. Recent work suggests that tau is not a stabilizer of microtubules in the axon, but rather enables axonal microtubules to have long labile domains, in part by outcompeting genuine stabilizers. This new perspective on tau challenges long-standing dogma.
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Affiliation(s)
- Peter W Baas
- Drexel University College of Medicine, Department of Neurobiology and Anatomy, 2900 Queen Lane, Philadelphia, PA 19129, USA.
| | - Liang Qiang
- Drexel University College of Medicine, Department of Neurobiology and Anatomy, 2900 Queen Lane, Philadelphia, PA 19129, USA
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16
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Mitotic Motor KIFC1 Is an Organizer of Microtubules in the Axon. J Neurosci 2019; 39:3792-3811. [PMID: 30804089 DOI: 10.1523/jneurosci.3099-18.2019] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 01/30/2019] [Accepted: 02/18/2019] [Indexed: 11/21/2022] Open
Abstract
KIFC1 (also called HSET or kinesin-14a) is best known as a multifunctional motor protein essential for mitosis. The present studies are the first to explore KIFC1 in terminally postmitotic neurons. Using RNA interference to partially deplete KIFC1 from rat neurons (from animals of either gender) in culture, pharmacologic agents that inhibit KIFC1, and expression of mutant KIFC1 constructs, we demonstrate critical roles for KIFC1 in regulating axonal growth and retraction as well as growth cone morphology. Experimental manipulations of KIFC1 elicit morphological changes in the axon as well as changes in the organization, distribution, and polarity orientation of its microtubules. Together, the results indicate a mechanism by which KIFC1 binds to microtubules in the axon and slides them into alignment in an ATP-dependent fashion and then cross-links them in an ATP-independent fashion to oppose their subsequent sliding by other motors.SIGNIFICANCE STATEMENT Here, we establish that KIFC1, a molecular motor well characterized in mitosis, is robustly expressed in neurons, where it has profound influence on the organization of microtubules in a number of different functional contexts. KIFC1 may help answer long-standing questions in cellular neuroscience such as, mechanistically, how growth cones stall and how axonal microtubules resist forces that would otherwise cause the axon to retract. Knowledge about KIFC1 may help researchers to devise strategies for treating disorders of the nervous system involving axonal retraction given that KIFC1 is expressed in adult neurons as well as developing neurons.
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17
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Knockdown of Fidgetin Improves Regeneration of Injured Axons by a Microtubule-Based Mechanism. J Neurosci 2019; 39:2011-2024. [PMID: 30647150 DOI: 10.1523/jneurosci.1888-18.2018] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 11/21/2018] [Accepted: 12/24/2018] [Indexed: 12/16/2022] Open
Abstract
Fidgetin is a microtubule-severing protein that pares back the labile domains of microtubules in the axon. Experimental depletion of fidgetin results in elongation of the labile domains of microtubules and faster axonal growth. To test whether fidgetin knockdown assists axonal regeneration, we plated dissociated adult rat DRGs transduced using AAV5-shRNA-fidgetin on a laminin substrate with spots of aggrecan, a growth-inhibitory chondroitin sulfate proteoglycan. This cell culture assay mimics the glial scar formed after CNS injury. Aggrecan is more concentrated at the edge of the spot, such that axons growing from within the spot toward the edge encounter a concentration gradient that causes growth cones to become dystrophic and axons to retract or curve back on themselves. Fidgetin knockdown resulted in faster-growing axons on both laminin and aggrecan and enhanced crossing of axons from laminin onto aggrecan. Strikingly, axons from within the spot grew more avidly against the inhibitory aggrecan concentration gradient to cross onto laminin, without retracting or curving back. We also tested whether depleting fidgetin improves axonal regeneration in vivo after a dorsal root crush in adult female rats. Whereas control DRG neurons failed to extend axons across the dorsal root entry zone after injury, DRG neurons in which fidgetin was knocked down displayed enhanced regeneration of axons across the dorsal root entry zone into the spinal cord. Collectively, these results establish fidgetin as a novel therapeutic target to augment nerve regeneration and provide a workflow template by which microtubule-related targets can be compared in the future.SIGNIFICANCE STATEMENT Here we establish a workflow template from cell culture to animals in which microtubule-based treatments can be tested and compared with one another for their effectiveness in augmenting regeneration of injured axons relevant to spinal cord injury. The present work uses a viral transduction approach to knock down fidgetin from rat neurons, which coaxes nerve regeneration by elevating microtubule mass in their axons. Unlike previous strategies using microtubule-stabilizing drugs, fidgetin knockdown adds microtubule mass that is labile (rather than stable), thereby better recapitulating the growth status of a developing axon.
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18
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Chakrabarty N, Dubey P, Tang Y, Ganguly A, Ladt K, Leterrier C, Jung P, Roy S. Processive flow by biased polymerization mediates the slow axonal transport of actin. J Cell Biol 2019; 218:112-124. [PMID: 30401699 PMCID: PMC6314539 DOI: 10.1083/jcb.201711022] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2017] [Revised: 09/02/2018] [Accepted: 10/25/2018] [Indexed: 12/15/2022] Open
Abstract
Classic pulse-chase studies have shown that actin is conveyed in slow axonal transport, but the mechanistic basis for this movement is unknown. Recently, we reported that axonal actin was surprisingly dynamic, with focal assembly/disassembly events ("actin hotspots") and elongating polymers along the axon shaft ("actin trails"). Using a combination of live imaging, superresolution microscopy, and modeling, in this study, we explore how these dynamic structures can lead to processive transport of actin. We found relatively more actin trails elongated anterogradely as well as an overall slow, anterogradely biased flow of actin in axon shafts. Starting with first principles of monomer/filament assembly and incorporating imaging data, we generated a quantitative model simulating axonal hotspots and trails. Our simulations predict that the axonal actin dynamics indeed lead to a slow anterogradely biased flow of the population. Collectively, the data point to a surprising scenario where local assembly and biased polymerization generate the slow axonal transport of actin without involvement of microtubules (MTs) or MT-based motors. Mechanistically distinct from polymer sliding, this might be a general strategy to convey highly dynamic cytoskeletal cargoes.
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Affiliation(s)
- Nilaj Chakrabarty
- Department of Physics and Astronomy, Neuroscience Program and Quantitative Biology Institute, Ohio University, Athens, OH
| | - Pankaj Dubey
- Department of Pathology and Laboratory Medicine, University of Wisconsin-Madison, Madison, WI
| | - Yong Tang
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA
| | - Archan Ganguly
- Department of Neurosciences, University of California, San Diego, La Jolla, CA
| | - Kelsey Ladt
- Department of Neurosciences, University of California, San Diego, La Jolla, CA
| | - Christophe Leterrier
- Aix-Marseille Université, Centre National de la Recherche Scientifique, Institut Neurophysiopathol, NeuroCyto, Marseille, France
| | - Peter Jung
- Department of Physics and Astronomy, Neuroscience Program and Quantitative Biology Institute, Ohio University, Athens, OH
| | - Subhojit Roy
- Department of Pathology and Laboratory Medicine, University of Wisconsin-Madison, Madison, WI
- Department of Neuroscience, University of Wisconsin-Madison, Madison, WI
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19
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Kahn OI, Schätzle P, van de Willige D, Tas RP, Lindhout FW, Portegies S, Kapitein LC, Hoogenraad CC. APC2 controls dendrite development by promoting microtubule dynamics. Nat Commun 2018; 9:2773. [PMID: 30018294 PMCID: PMC6050278 DOI: 10.1038/s41467-018-05124-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2017] [Accepted: 06/12/2018] [Indexed: 12/12/2022] Open
Abstract
Mixed polarity microtubule organization is the signature characteristic of vertebrate dendrites. Oppositely oriented microtubules form the basis for selective cargo trafficking in neurons, however the mechanisms that establish and maintain this organization are unclear. Here, we show that APC2, the brain-specific homolog of tumor-suppressor protein adenomatous polyposis coli (APC), promotes dynamics of minus-end-out microtubules in dendrites. We found that APC2 localizes as distinct clusters along microtubule bundles in dendrites and that this localization is driven by LC8-binding and two separate microtubule-interacting domains. Depletion of APC2 reduces the plus end dynamics of minus-end-out oriented microtubules, increases microtubule sliding, and causes defects in dendritic morphology. We propose a model in which APC2 regulates dendrite development by promoting dynamics of minus-end-out microtubules.
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Affiliation(s)
- Olga I Kahn
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 CH, Utrecht, The Netherlands
| | - Philipp Schätzle
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 CH, Utrecht, The Netherlands
| | - Dieudonnée van de Willige
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 CH, Utrecht, The Netherlands
| | - Roderick P Tas
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 CH, Utrecht, The Netherlands
| | - Feline W Lindhout
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 CH, Utrecht, The Netherlands
| | - Sybren Portegies
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 CH, Utrecht, The Netherlands
| | - Lukas C Kapitein
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 CH, Utrecht, The Netherlands
| | - Casper C Hoogenraad
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 CH, Utrecht, The Netherlands.
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20
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Tau Does Not Stabilize Axonal Microtubules but Rather Enables Them to Have Long Labile Domains. Curr Biol 2018; 28:2181-2189.e4. [PMID: 30008334 DOI: 10.1016/j.cub.2018.05.045] [Citation(s) in RCA: 135] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Revised: 04/16/2018] [Accepted: 05/16/2018] [Indexed: 11/22/2022]
Abstract
It is widely believed that tau stabilizes microtubules in the axon [1-3] and, hence, that disease-induced loss of tau from axonal microtubules leads to their destabilization [3-5]. An individual microtubule in the axon has a stable domain and a labile domain [6-8]. We found that tau is more abundant on the labile domain, which is inconsistent with tau's proposed role as a microtubule stabilizer. When tau is experimentally depleted from cultured rat neurons, the labile microtubule mass of the axon drops considerably, the remaining labile microtubule mass becomes less labile, and the stable microtubule mass increases. MAP6 (also called stable tubule-only polypeptide), which is normally enriched on the stable domain [9], acquires a broader distribution across the microtubule when tau is depleted, providing a potential explanation for the increase in stable microtubule mass. When MAP6 is depleted, the labile microtubule mass becomes even more labile, indicating that, unlike tau, MAP6 is a genuine stabilizer of axonal microtubules. We conclude that tau is not a stabilizer of axonal microtubules but is enriched on the labile domain of the microtubule to promote its assembly while limiting the binding to it of genuine stabilizers, such as MAP6. This enables the labile domain to achieve great lengths without being stabilized. These conclusions are contrary to tau dogma.
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21
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Kath C, Goni-Oliver P, Müller R, Schultz C, Haucke V, Eickholt B, Schmoranzer J. PTEN suppresses axon outgrowth by down-regulating the level of detyrosinated microtubules. PLoS One 2018; 13:e0193257. [PMID: 29617365 PMCID: PMC5884485 DOI: 10.1371/journal.pone.0193257] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Accepted: 02/07/2018] [Indexed: 11/19/2022] Open
Abstract
Inhibition of the phospholipid phosphatase and tumor suppressor PTEN leads to excessive polarized cell growth during directed cell migration and neurite outgrowth. These processes require the precise regulation of both the actin and microtubule cytoskeleton. While PTEN is known to regulate actin dynamics through phospholipid modulation, whether and how PTEN regulates microtubule dynamics is unknown. Here, we show that depletion of PTEN leads to elevated levels of stable and post-translationally modified (detyrosinated) microtubules in fibroblasts and developing neurons. Further, PTEN depletion enhanced axon outgrowth, which was rescued by reducing the level of detyrosinated microtubules. These data demonstrate a novel role of PTEN in regulating the microtubule cytoskeleton. They further show a novel function of detyrosinated microtubules in axon outgrowth. Specifically, PTEN suppresses axon outgrowth by down-regulating the level of detyrosinated microtubules. Our results suggest that PTEN's role in preventing excessive cell growth in cancerous and neurodevelopmental phenotypes is partially exerted by stabilization and detyrosination of the microtubule cytoskeleton.
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Affiliation(s)
- Christina Kath
- Charité –Universtiätsmedizin, Virchowweg 6, Berlin, Germany
- Leibniz Institute for Molecular Pharmacology, Robert-Roessle-Strasse 10, Berlin, Germany
| | | | - Rainer Müller
- European Molecular Biology Laboratory, Meyerhofstraße 1, Heidelberg, Germany
| | - Carsten Schultz
- European Molecular Biology Laboratory, Meyerhofstraße 1, Heidelberg, Germany
| | - Volker Haucke
- Leibniz Institute for Molecular Pharmacology, Robert-Roessle-Strasse 10, Berlin, Germany
| | | | - Jan Schmoranzer
- Charité –Universtiätsmedizin, Virchowweg 6, Berlin, Germany
- Leibniz Institute for Molecular Pharmacology, Robert-Roessle-Strasse 10, Berlin, Germany
- * E-mail:
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22
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Mondal P, Das G, Khan J, Pradhan K, Ghosh S. Crafting of Neuroprotective Octapeptide from Taxol-Binding Pocket of β-Tubulin. ACS Chem Neurosci 2018; 9:615-625. [PMID: 29155559 DOI: 10.1021/acschemneuro.7b00457] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Microtubules play a crucial role in maintaining the shape and function of neurons. During progression of Alzheimer's disease (AD), severe destabilization of microtubules occurs, which leads to the permanent disruption of signal transduction processes and memory loss. Thus, microtubule stabilization is one of the key requirements for the treatment of AD. Taxol, a microtubule stabilizing anticancer drug, has been considered as a potential anti-AD drug but was never tested in AD patients, likely because of its' toxic nature and poor brain exposure. However, other microtubule-targeting agents such as epothilone D (BMS-241027) and TPI-287 (abeotaxane) and NAP peptide (davunetide) have entered in AD clinical programs. Therefore, the taxol binding pocket of tubulin could be a potential site for designing of mild and noncytotoxic microtubule stabilizing molecules. Here, we adopted an innovative strategy for the development of a peptide based microtubule stabilizer, considering the taxol binding pocket of β-tubulin, by using alanine scanning mutagenesis technique. This approach lead us to a potential octapeptide, which strongly binds to the taxol pocket of β-tubulin, serves as an excellent microtubule stabilizer, increases the expression of acetylated tubulin, and acts as an Aβ aggregation inhibitor and neuroprotective agent. Further, results revealed that this peptide is nontoxic against both PC12 derived neurons and primary cortical neurons. We believe that our strategy and discovery of peptide-based microtubule stabilizer will open the door for the development of potential anti-AD therapeutics in near future.
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Affiliation(s)
- Prasenjit Mondal
- Organic & Medicinal Chemistry Division, CSIR-Indian Institute of Chemical Biology, 4, Raja S. C. Mullick Road, Jadavpur, Kolkata, 700032 West Bengal, India
- Academy of Scientific and Innovative Research (AcSIR), CSIR-Indian Institute of Chemical Biology Campus, 4 Raja S. C. Mullick Road, Kolkata 700032, India
| | - Gaurav Das
- Organic & Medicinal Chemistry Division, CSIR-Indian Institute of Chemical Biology, 4, Raja S. C. Mullick Road, Jadavpur, Kolkata, 700032 West Bengal, India
- Academy of Scientific and Innovative Research (AcSIR), CSIR-Indian Institute of Chemical Biology Campus, 4 Raja S. C. Mullick Road, Kolkata 700032, India
| | - Juhee Khan
- Organic & Medicinal Chemistry Division, CSIR-Indian Institute of Chemical Biology, 4, Raja S. C. Mullick Road, Jadavpur, Kolkata, 700032 West Bengal, India
- Academy of Scientific and Innovative Research (AcSIR), CSIR-Indian Institute of Chemical Biology Campus, 4 Raja S. C. Mullick Road, Kolkata 700032, India
| | - Krishnangsu Pradhan
- Organic & Medicinal Chemistry Division, CSIR-Indian Institute of Chemical Biology, 4, Raja S. C. Mullick Road, Jadavpur, Kolkata, 700032 West Bengal, India
| | - Surajit Ghosh
- Organic & Medicinal Chemistry Division, CSIR-Indian Institute of Chemical Biology, 4, Raja S. C. Mullick Road, Jadavpur, Kolkata, 700032 West Bengal, India
- Academy of Scientific and Innovative Research (AcSIR), CSIR-Indian Institute of Chemical Biology Campus, 4 Raja S. C. Mullick Road, Kolkata 700032, India
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23
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Lehigh KM, West KM, Ginty DD. Retrogradely Transported TrkA Endosomes Signal Locally within Dendrites to Maintain Sympathetic Neuron Synapses. Cell Rep 2017; 19:86-100. [PMID: 28380365 DOI: 10.1016/j.celrep.2017.03.028] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 02/10/2017] [Accepted: 03/07/2017] [Indexed: 11/17/2022] Open
Abstract
Sympathetic neurons require NGF from their target fields for survival, axonal target innervation, dendritic growth and formation, and maintenance of synaptic inputs from preganglionic neurons. Target-derived NGF signals are propagated retrogradely, from distal axons to somata of sympathetic neurons via TrkA signaling endosomes. We report that a subset of TrkA endosomes that are transported from distal axons to cell bodies translocate into dendrites, where they are signaling competent and move bidirectionally, in close proximity to synaptic protein clusters. Using a strategy for spatially confined inhibition of TrkA kinase activity, we found that distal-axon-derived TrkA signaling endosomes are necessary within sympathetic neuron dendrites for maintenance of synapses. Thus, TrkA signaling endosomes have unique functions in different cellular compartments. Moreover, target-derived NGF mediates circuit formation and synapse maintenance through TrkA endosome signaling within dendrites to promote aggregation of postsynaptic protein complexes.
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Affiliation(s)
- Kathryn M Lehigh
- Department of Neurobiology, Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA; Neuroscience Training Program, Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Katherine M West
- Department of Neurobiology, Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - David D Ginty
- Department of Neurobiology, Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA.
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24
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25
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Dent EW. Of microtubules and memory: implications for microtubule dynamics in dendrites and spines. Mol Biol Cell 2017; 28:1-8. [PMID: 28035040 PMCID: PMC5221613 DOI: 10.1091/mbc.e15-11-0769] [Citation(s) in RCA: 97] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Revised: 10/20/2016] [Accepted: 10/26/2016] [Indexed: 12/25/2022] Open
Abstract
Microtubules (MTs) are cytoskeletal polymers composed of repeating subunits of tubulin that are ubiquitously expressed in eukaryotic cells. They undergo a stochastic process of polymerization and depolymerization from their plus ends termed dynamic instability. MT dynamics is an ongoing process in all cell types and has been the target for the development of several useful anticancer drugs, which compromise rapidly dividing cells. Recent studies also suggest that MT dynamics may be particularly important in neurons, which develop a highly polarized morphology, consisting of a single axon and multiple dendrites that persist throughout adulthood. MTs are especially dynamic in dendrites and have recently been shown to polymerize directly into dendritic spines, the postsynaptic compartment of excitatory neurons in the CNS. These transient polymerization events into dendritic spines have been demonstrated to play important roles in synaptic plasticity in cultured neurons. Recent studies also suggest that MT dynamics in the adult brain function in the essential process of learning and memory and may be compromised in degenerative diseases, such as Alzheimer's disease. This raises the possibility of targeting MT dynamics in the design of new therapeutic agents.
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Affiliation(s)
- Erik W Dent
- Department of Neuroscience, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI 53705
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26
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Dynamic Palmitoylation Targets MAP6 to the Axon to Promote Microtubule Stabilization during Neuronal Polarization. Neuron 2017; 94:809-825.e7. [PMID: 28521134 DOI: 10.1016/j.neuron.2017.04.042] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 02/19/2017] [Accepted: 04/27/2017] [Indexed: 11/22/2022]
Abstract
Microtubule-associated proteins (MAPs) are main candidates to stabilize neuronal microtubules, playing an important role in establishing axon-dendrite polarity. However, how MAPs are selectively targeted to specific neuronal compartments remains poorly understood. Here, we show specific localization of microtubule-associated protein 6 (MAP6)/stable tubule-only polypeptide (STOP) throughout neuronal maturation and its role in axonal development. In unpolarized neurons, MAP6 is present at the Golgi complex and in secretory vesicles. As neurons mature, MAP6 is translocated to the proximal axon, where it binds and stabilizes microtubules. Further, we demonstrate that dynamic palmitoylation, mediated by the family of α/β Hydrolase domain-containing protein 17 (ABHD17A-C) depalmitoylating enzymes, controls shuttling of MAP6 between membranes and microtubules and is required for MAP6 retention in axons. We propose a model in which MAP6's palmitoylation mediates microtubule stabilization, allows efficient organelle trafficking, and controls axon maturation in vitro and in situ.
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27
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Lin S, Sterling NA, Junker IP, Helm CT, Smith GM. Effects of αTAT1 and HDAC5 on axonal regeneration in adult neurons. PLoS One 2017; 12:e0177496. [PMID: 28505206 PMCID: PMC5432171 DOI: 10.1371/journal.pone.0177496] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Accepted: 04/27/2017] [Indexed: 12/28/2022] Open
Abstract
The role of posttranslational modifications in axonal injury and regeneration has been widely studied but there has been little consensus over the mechanism by which each modification affects adult axonal growth. Acetylation is known to play an important role in a variety of neuronal functions and its homeostasis is controlled by two enzyme families: the Histone Deacetylases (HDACs) and Histone Acetyl Transferases (HATs). Recent studies show that HDAC5 deacetylates microtubules in the axonal cytoplasm as part of an injury-induced regeneration response, but little is known about how acetylation of microtubules plays a role. Alpha-tubulin acetyl transferase (αTAT1) is a microtubule specific acetyl transferase that binds to microtubules and directly affects microtubule stability in cells. We hypothesize that increasing tubulin acetylation may play an important role in increasing the rate of axonal growth. In this study, we infected cultured adult DRG neurons with αTAT1 and αTAT1-D157N, a catalytically inactive mutant, and HDAC5, using lentiviruses. We found that αTAT1 significantly increases tubulin acetylation in 293T cells and DRG neurons but αTAT1-D157N does not. Furthermore, in neurons infected with αTAT1, a significant increase in acetylated tubulin was detected towards the distal portion of the axon but this increase was not detected in neurons infected with αTAT1-D157N. However, we found a significant increase in axon lengths of DRG neurons after αTAT1 and αTAT1-D157N infection, but no effect on axon lengths after infection with HDAC5. Our results suggest that while αTAT1 may play a role in axon growth in vitro, the increase is not directly due to acetylation of axonal microtubules. Our results also show that HDAC5 overexpression in the axonal cytoplasm does not play a crucial role in axonal regeneration of cultured DRG neurons. We expressed these genes in DRG neurons in adult rats and performed a sciatic nerve crush. We found that axons did not regenerate any better when infected with any of the constructs compared with control animals. Thus, while αTAT1 may be important for axonal growth in vitro, neither αTAT1 nor HDAC5 had an effect in vivo on the regeneration of sciatic nerves.
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Affiliation(s)
- Shen Lin
- Center for Neural Repair and Rehabilitation, Department of Neuroscience, Shriners Hospitals for Pediatric Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania, United States of America
- * E-mail:
| | - Noelle A. Sterling
- Center for Neural Repair and Rehabilitation, Department of Neuroscience, Shriners Hospitals for Pediatric Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Ian P. Junker
- Center for Neural Repair and Rehabilitation, Department of Neuroscience, Shriners Hospitals for Pediatric Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Courtney T. Helm
- Center for Neural Repair and Rehabilitation, Department of Neuroscience, Shriners Hospitals for Pediatric Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - George M. Smith
- Center for Neural Repair and Rehabilitation, Department of Neuroscience, Shriners Hospitals for Pediatric Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania, United States of America
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Baas PW, Rao AN, Matamoros AJ, Leo L. Stability properties of neuronal microtubules. Cytoskeleton (Hoboken) 2016; 73:442-60. [PMID: 26887570 PMCID: PMC5541393 DOI: 10.1002/cm.21286] [Citation(s) in RCA: 184] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Revised: 02/02/2016] [Accepted: 02/12/2016] [Indexed: 01/12/2023]
Abstract
Neurons are terminally differentiated cells that use their microtubule arrays not for cell division but rather as architectural elements required for the elaboration of elongated axons and dendrites. In addition to acting as compression-bearing struts that provide for the shape of the neuron, microtubules also act as directional railways for organelle transport. The stability properties of neuronal microtubules are commonly discussed in the biomedical literature as crucial to the development and maintenance of the nervous system, and have recently gained attention as central to the etiology of neurodegenerative diseases. Drugs that affect microtubule stability are currently under investigation as potential therapies for disease and injury of the nervous system. There is often a lack of consistency, however, in how the issue of microtubule stability is discussed in the literature, and this can affect the design and interpretation of experiments as well as potential therapeutic regimens. Neuronal microtubules are considered to be more stable than microtubules in dividing cells. On average, this is true, but in addition to an abundant stable microtubule fraction in neurons, there is also an abundant labile microtubule fraction. Both are functionally important. Individual microtubules consist of domains that differ in their stability properties, and these domains can also differ markedly in their composition as well as how they interact with various microtubule-related proteins in the neuron. Myriad proteins and pathways have been discussed as potential contributors to microtubule stability in neurons. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Peter W Baas
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania, USA.
| | - Anand N Rao
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania, USA
| | - Andrew J Matamoros
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania, USA
| | - Lanfranco Leo
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania, USA
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Dendrites In Vitro and In Vivo Contain Microtubules of Opposite Polarity and Axon Formation Correlates with Uniform Plus-End-Out Microtubule Orientation. J Neurosci 2016; 36:1071-85. [PMID: 26818498 DOI: 10.1523/jneurosci.2430-15.2016] [Citation(s) in RCA: 135] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
UNLABELLED In cultured vertebrate neurons, axons have a uniform arrangement of microtubules with plus-ends distal to the cell body (plus-end-out), whereas dendrites contain mixed polarity orientations with both plus-end-out and minus-end-out oriented microtubules. Rather than non-uniform microtubules, uniparallel minus-end-out microtubules are the signature of dendrites in Drosophila and Caenorhabditis elegans neurons. To determine whether mixed microtubule organization is a conserved feature of vertebrate dendrites, we used live-cell imaging to systematically analyze microtubule plus-end orientations in primary cultures of rat hippocampal and cortical neurons, dentate granule cells in mouse organotypic slices, and layer 2/3 pyramidal neurons in the somatosensory cortex of living mice. In vitro and in vivo, all microtubules had a plus-end-out orientation in axons, whereas microtubules in dendrites had mixed orientations. When dendritic microtubules were severed by laser-based microsurgery, we detected equal numbers of plus- and minus-end-out microtubule orientations throughout the dendritic processes. In dendrites, the minus-end-out microtubules were generally more stable and comparable with plus-end-out microtubules in axons. Interestingly, at early stages of neuronal development in nonpolarized cells, newly formed neurites already contained microtubules of opposite polarity, suggesting that the establishment of uniform plus-end-out microtubules occurs during axon formation. We propose a model in which the selective formation of uniform plus-end-out microtubules in the axon is a critical process underlying neuronal polarization. SIGNIFICANCE STATEMENT Live-cell imaging was used to systematically analyze microtubule organization in primary cultures of rat hippocampal neurons, dentate granule cells in mouse organotypic slices, and layer 2/3 pyramidal neuron in somatosensory cortex of living mice. In vitro and in vivo, all microtubules have a plus-end-out orientation in axons, whereas microtubules in dendrites have mixed orientations. Interestingly, newly formed neurites of nonpolarized neurons already contain mixed microtubules, and the specific organization of uniform plus-end-out microtubules only occurs during axon formation. Based on these findings, the authors propose a model in which the selective formation of uniform plus-end-out microtubules in the axon is a critical process underlying neuronal polarization.
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Yau KW, Schätzle P, Tortosa E, Pagès S, Holtmaat A, Kapitein LC, Hoogenraad CC. Dendrites In Vitro and In Vivo Contain Microtubules of Opposite Polarity and Axon Formation Correlates with Uniform Plus-End-Out Microtubule Orientation. J Neurosci 2016. [PMID: 26818498 DOI: 10.1523/jneurosci.2430-15.20166] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/23/2023] Open
Abstract
UNLABELLED In cultured vertebrate neurons, axons have a uniform arrangement of microtubules with plus-ends distal to the cell body (plus-end-out), whereas dendrites contain mixed polarity orientations with both plus-end-out and minus-end-out oriented microtubules. Rather than non-uniform microtubules, uniparallel minus-end-out microtubules are the signature of dendrites in Drosophila and Caenorhabditis elegans neurons. To determine whether mixed microtubule organization is a conserved feature of vertebrate dendrites, we used live-cell imaging to systematically analyze microtubule plus-end orientations in primary cultures of rat hippocampal and cortical neurons, dentate granule cells in mouse organotypic slices, and layer 2/3 pyramidal neurons in the somatosensory cortex of living mice. In vitro and in vivo, all microtubules had a plus-end-out orientation in axons, whereas microtubules in dendrites had mixed orientations. When dendritic microtubules were severed by laser-based microsurgery, we detected equal numbers of plus- and minus-end-out microtubule orientations throughout the dendritic processes. In dendrites, the minus-end-out microtubules were generally more stable and comparable with plus-end-out microtubules in axons. Interestingly, at early stages of neuronal development in nonpolarized cells, newly formed neurites already contained microtubules of opposite polarity, suggesting that the establishment of uniform plus-end-out microtubules occurs during axon formation. We propose a model in which the selective formation of uniform plus-end-out microtubules in the axon is a critical process underlying neuronal polarization. SIGNIFICANCE STATEMENT Live-cell imaging was used to systematically analyze microtubule organization in primary cultures of rat hippocampal neurons, dentate granule cells in mouse organotypic slices, and layer 2/3 pyramidal neuron in somatosensory cortex of living mice. In vitro and in vivo, all microtubules have a plus-end-out orientation in axons, whereas microtubules in dendrites have mixed orientations. Interestingly, newly formed neurites of nonpolarized neurons already contain mixed microtubules, and the specific organization of uniform plus-end-out microtubules only occurs during axon formation. Based on these findings, the authors propose a model in which the selective formation of uniform plus-end-out microtubules in the axon is a critical process underlying neuronal polarization.
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Affiliation(s)
- Kah Wai Yau
- Cell Biology, Faculty of Science, Utrecht University, 3584 CH, Utrecht, The Netherlands, and
| | - Philipp Schätzle
- Cell Biology, Faculty of Science, Utrecht University, 3584 CH, Utrecht, The Netherlands, and
| | - Elena Tortosa
- Cell Biology, Faculty of Science, Utrecht University, 3584 CH, Utrecht, The Netherlands, and
| | - Stéphane Pagès
- Department of Basic Neurosciences, Faculty of Medicine and the Center for Neuroscience, University of Geneva, 1211 Geneva, Switzerland
| | - Anthony Holtmaat
- Department of Basic Neurosciences, Faculty of Medicine and the Center for Neuroscience, University of Geneva, 1211 Geneva, Switzerland
| | - Lukas C Kapitein
- Cell Biology, Faculty of Science, Utrecht University, 3584 CH, Utrecht, The Netherlands, and
| | - Casper C Hoogenraad
- Cell Biology, Faculty of Science, Utrecht University, 3584 CH, Utrecht, The Netherlands, and
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Parésys L, Hoffmann K, Froger N, Bianchi M, Villey I, Baulieu EE, Fuchs E. Effects of the Synthetic Neurosteroid: 3β-Methoxypregnenolone (MAP4343) on Behavioral and Physiological Alterations Provoked by Chronic Psychosocial Stress in Tree Shrews. Int J Neuropsychopharmacol 2015; 19:pyv119. [PMID: 26476437 PMCID: PMC4851265 DOI: 10.1093/ijnp/pyv119] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Accepted: 10/14/2015] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND Most currently available active antidepressant drugs are selective serotonin/noradrenaline reuptake inhibitors. However, as their clinical efficacy is not immediate, long-term administration is often accompanied by substantial side effects, and numerous patients remain non- or partial responders. We have recently found that the synthetic neurosteroid derivative 3β-methoxypregnenolone, which binds to the microtubule-associated protein-2, can provide a novel therapeutic approach in experimental model of depressive disorders in rats. To further validate the antidepressant-like efficacy of 3β-methoxypregnenolone, we investigated effects of a longer treatment (4-week oral administration; 50mg/kg/d) in a nonrodent species, the tree shrew, exposed to psychosocial stress that elicits close-to-human alterations observed in patients with depressive disorders. METHODS During the experimental period, physiological parameters were registered, including core body temperature and electroencephalogram, while animals were videotaped to analyze their avoidance behavior. Morning urine samples were collected for measurements of cortisol and noradrenaline levels. RESULTS We found that treatment with 3β-methoxypregnenolone abolished stress-triggered avoidance behavior and prevented hormone hypersecretion, hypothermia, and sleep disturbances, further suggesting its antidepressant-like efficacy. Comparative treatment with fluoxetine also prevented some of the physiological alterations, while the hypersecretion of cortisol and sleep disturbances were not or partially restored by fluoxetine, suggesting a better efficacy of 3β-methoxypregnenolone. Alpha-tubulin isoforms were measured in hippocampi: we found that 3β-methoxypregnenolone reversed the specific decrease in acetylation of α-tubulin induced by psychosocial stress, while it did not modify the psychosocial stress-elicited reduction of tyrosinated α-tubulin. CONCLUSIONS Taken together, these data strongly suggest a potent antidepressant-like effect of 3β-methoxypregnenolone on translational parameters.
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Affiliation(s)
| | | | - Nicolas Froger
- MAPREG SAS, Le Kremlin-Bicêtre, France (Drs Parésys, Froger, Bianchi, Villey, and Baulieu); German Primate Center, Göttingen, Germany (Drs Hoffmann and Fuchs).
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32
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Namba T, Funahashi Y, Nakamuta S, Xu C, Takano T, Kaibuchi K. Extracellular and Intracellular Signaling for Neuronal Polarity. Physiol Rev 2015; 95:995-1024. [PMID: 26133936 DOI: 10.1152/physrev.00025.2014] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Neurons are one of the highly polarized cells in the body. One of the fundamental issues in neuroscience is how neurons establish their polarity; therefore, this issue fascinates many scientists. Cultured neurons are useful tools for analyzing the mechanisms of neuronal polarization, and indeed, most of the molecules important in their polarization were identified using culture systems. However, we now know that the process of neuronal polarization in vivo differs in some respects from that in cultured neurons. One of the major differences is their surrounding microenvironment; neurons in vivo can be influenced by extrinsic factors from the microenvironment. Therefore, a major question remains: How are neurons polarized in vivo? Here, we begin by reviewing the process of neuronal polarization in culture conditions and in vivo. We also survey the molecular mechanisms underlying neuronal polarization. Finally, we introduce the theoretical basis of neuronal polarization and the possible involvement of neuronal polarity in disease and traumatic brain injury.
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Affiliation(s)
- Takashi Namba
- Department of Cell Pharmacology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Yasuhiro Funahashi
- Department of Cell Pharmacology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Shinichi Nakamuta
- Department of Cell Pharmacology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Chundi Xu
- Department of Cell Pharmacology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Tetsuya Takano
- Department of Cell Pharmacology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Kozo Kaibuchi
- Department of Cell Pharmacology, Nagoya University Graduate School of Medicine, Nagoya, Japan
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33
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Gory-Fauré S, Windscheid V, Brocard J, Montessuit S, Tsutsumi R, Denarier E, Fukata Y, Bosc C, Delaroche J, Collomb N, Fukata M, Martinou JC, Pernet-Gallay K, Andrieux A. Non-microtubular localizations of microtubule-associated protein 6 (MAP6). PLoS One 2014; 9:e114905. [PMID: 25526643 PMCID: PMC4272302 DOI: 10.1371/journal.pone.0114905] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Accepted: 11/11/2014] [Indexed: 01/29/2023] Open
Abstract
MAP6 proteins (MAP6s), which include MAP6-N (also called Stable Tubule Only Polypeptide, or STOP) and MAP6d1 (MAP6 domain-containing protein 1, also called STOP-Like protein 21 kD, or SL21), bind to and stabilize microtubules. MAP6 deletion in mice severely alters integrated brain functions and is associated with synaptic defects, suggesting that MAP6s may also have alternative cellular roles. MAP6s reportedly associate with the Golgi apparatus through palmitoylation of their N-terminal domain, and specific isoforms have been shown to bind actin. Here, we use heterologous systems to investigate several biochemical properties of MAP6 proteins. We demonstrate that the three N-terminal cysteines of MAP6d1 are palmitoylated by a subset of DHHC-type palmitoylating enzymes. Analysis of the subcellular localization of palmitoylated MAP6d1, including electron microscopic analysis, reveals possible localization to the Golgi and the plasma membrane but no association with the endoplasmic reticulum. Moreover, we observed localization of MAP6d1 to mitochondria, which requires the N-terminus of the protein but does not require palmitoylation. We show that endogenous MAP6d1 localized at mitochondria in mature mice neurons as well as at the outer membrane and in the intermembrane space of purified mouse mitochondria. Last, we found that MAP6d1 can multimerize via a microtubule-binding module. Interestingly, most of these properties of MAP6d1 are shared by MAP6-N. Together, these results describe several properties of MAP6 proteins, including their intercellular localization and multimerization activity, which may be relevant to neuronal differentiation and synaptic functions.
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Affiliation(s)
- Sylvie Gory-Fauré
- Inserm, U836, Physiopathologie du cytosquelette, BP170, Grenoble, France
- University Grenoble Alpes, Grenoble Institut des Neurosciences, BP170, Grenoble, France
- * E-mail: (SGF); (AA)
| | - Vanessa Windscheid
- Inserm, U836, Physiopathologie du cytosquelette, BP170, Grenoble, France
- University Grenoble Alpes, Grenoble Institut des Neurosciences, BP170, Grenoble, France
| | - Jacques Brocard
- Inserm, U836, Physiopathologie du cytosquelette, BP170, Grenoble, France
- University Grenoble Alpes, Grenoble Institut des Neurosciences, BP170, Grenoble, France
| | - Sylvie Montessuit
- Department of Cell Biology, University of Geneva, Sciences III, Geneva, Switzerland
| | - Ryouhei Tsutsumi
- Division of Membrane Physiology, Department of Cell Physiology, National Institute for Physiological Sciences, Aichi, Japan
| | - Eric Denarier
- Inserm, U836, Physiopathologie du cytosquelette, BP170, Grenoble, France
- University Grenoble Alpes, Grenoble Institut des Neurosciences, BP170, Grenoble, France
- Commissariat à l'énergie atomique, Institut de Recherches en Technologies et Sciences pour le Vivant, Groupe Physiopathologie du Cytosquelette, Grenoble, France
| | - Yuko Fukata
- Division of Membrane Physiology, Department of Cell Physiology, National Institute for Physiological Sciences, Aichi, Japan
| | - Christophe Bosc
- Inserm, U836, Physiopathologie du cytosquelette, BP170, Grenoble, France
- University Grenoble Alpes, Grenoble Institut des Neurosciences, BP170, Grenoble, France
| | - Julie Delaroche
- Inserm, U836, Physiopathologie du cytosquelette, BP170, Grenoble, France
- University Grenoble Alpes, Grenoble Institut des Neurosciences, BP170, Grenoble, France
| | - Nora Collomb
- Inserm, U836, Physiopathologie du cytosquelette, BP170, Grenoble, France
- University Grenoble Alpes, Grenoble Institut des Neurosciences, BP170, Grenoble, France
| | - Masaki Fukata
- Division of Membrane Physiology, Department of Cell Physiology, National Institute for Physiological Sciences, Aichi, Japan
| | - Jean-Claude Martinou
- Department of Cell Biology, University of Geneva, Sciences III, Geneva, Switzerland
| | - Karin Pernet-Gallay
- Inserm, U836, Physiopathologie du cytosquelette, BP170, Grenoble, France
- University Grenoble Alpes, Grenoble Institut des Neurosciences, BP170, Grenoble, France
| | - Annie Andrieux
- Inserm, U836, Physiopathologie du cytosquelette, BP170, Grenoble, France
- University Grenoble Alpes, Grenoble Institut des Neurosciences, BP170, Grenoble, France
- Commissariat à l'énergie atomique, Institut de Recherches en Technologies et Sciences pour le Vivant, Groupe Physiopathologie du Cytosquelette, Grenoble, France
- * E-mail: (SGF); (AA)
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Lacroix B, Maddox AS. Microtubule dynamics followed through cell differentiation and tissue biogenesis in C. elegans. WORM 2014; 3:e967611. [PMID: 26430551 DOI: 10.4161/21624046.2014.967611] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Revised: 09/08/2014] [Accepted: 09/15/2014] [Indexed: 01/27/2023]
Abstract
Microtubules (MTs) are cytoskeletal filaments essential for many processes in eukaryotic cells. Assembled of tubulin subunits, MTs are dynamic structures that undergo successive and stochastic phases of polymerization and depolymerization, a behavior called dynamic instability. Dynamic instability has been extensively studied in cultured cells and in vitro using cytoplasmic extracts or reconstituted MTs. However, how MTs behave in intact tissues and how their dynamics are affected by or affect tissue function are poorly understood. Recent advances in high-resolution live imaging have helped overcome technical limitation in order to visualize MTs in intact living organisms including Drosophila or Caenorhabditis elegans. We recently took advantage of the well-characterized development, small size and transparency of C. elegans to monitor MT dynamics throughout tissue biogenesis with high spatial and temporal resolution. Using the sex myoblast lineage that generates the egg-laying muscles from 2 mitotic precursors, we identified selective dynamics in precursor versus differentiated cells, and molecular regulation of MT dynamics changes that occur during cell differentiation. We discuss here how this approach led to novel insights into the regulation of MTs dynamics and organization in vivo.
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Affiliation(s)
- Benjamin Lacroix
- Institut Jacques Monod; CNRS; University Paris Diderot ; Paris, France
| | - Amy S Maddox
- Department of Biology; University of North Carolina at Chapel Hill ; Chapel Hill, NC USA
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35
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Kahn OI, Sharma V, González-Billault C, Baas PW. Effects of kinesin-5 inhibition on dendritic architecture and microtubule organization. Mol Biol Cell 2014; 26:66-77. [PMID: 25355946 PMCID: PMC4279230 DOI: 10.1091/mbc.e14-08-1313] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Inhibition of kinesin-5, a molecular motor protein best known for its essential role in mitosis, has notable effects on the morphology and microtubule organization of dendrites of terminally postmitotic neurons. Kinesin-5 acts as a brake that can limit the capacity of other motor proteins to influence microtubule organization and distribution. Kinesin-5 is a slow homotetrameric motor protein best known for its essential role in the mitotic spindle, where it limits the rate at which faster motors can move microtubules. In neurons, experimental suppression of kinesin-5 causes the axon to grow faster by increasing the mobility of microtubules in the axonal shaft and the invasion of microtubules into the growth cone. Does kinesin-5 act differently in dendrites, given that they have a population of minus end–distal microtubules not present in axons? Using rodent primary neurons in culture, we found that inhibition of kinesin-5 during various windows of time produces changes in dendritic morphology and microtubule organization. Specifically, dendrites became shorter and thinner and contained a greater proportion of minus end–distal microtubules, suggesting that kinesin-5 acting normally restrains the number of minus end–distal microtubules that are transported into dendrites. Additional data indicate that, in neurons, CDK5 is the kinase responsible for phosphorylating kinesin-5 at Thr-926, which is important for kinesin-5 to associate with microtubules. We also found that kinesin-5 associates preferentially with microtubules rich in tyrosinated tubulin. This is consistent with an observed accumulation of kinesin-5 on dendritic microtubules, as they are known to be less detyrosinated than axonal microtubules.
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Affiliation(s)
- Olga I Kahn
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129
| | - Vandana Sharma
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129
| | - Christian González-Billault
- Department of Biology and Institute for Cell Dynamics and Biotechnology (ICDB), Faculty of Sciences, Universidad de Chile, 7800024 Nunoa, Santiago, Chile
| | - Peter W Baas
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129
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36
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In situ imaging in C. elegans reveals developmental regulation of microtubule dynamics. Dev Cell 2014; 29:203-16. [PMID: 24780738 DOI: 10.1016/j.devcel.2014.03.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Revised: 12/12/2013] [Accepted: 03/13/2014] [Indexed: 11/20/2022]
Abstract
Microtubules (MTs) are cytoskeletal polymers that undergo dynamic instability, the stochastic transition between growth and shrinkage phases. MT dynamics are required for diverse cellular processes and, while intrinsic to tubulin, are highly regulated. However, little is known about how MT dynamics facilitate or are regulated by tissue biogenesis and differentiation. We imaged MT dynamics in a smooth muscle-like lineage in intact developing Caenorhabditis elegans. All aspects of MT dynamics change significantly as stem-like precursors exit mitosis and, secondarily, as they differentiate. We found that suppression, but not enhancement, of dynamics perturbs differentiated muscle function in vivo. Distinct ensembles of MT-associated proteins are specifically required for tissue biogenesis versus tissue function. A CLASP family MT stabilizer and the depolymerizing kinesin MCAK are differentially required for MT dynamics in the precursor or differentiated cells, respectively. All of these multidimensional phenotypic comparisons were facilitated by a data display method called the diamond graph.
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37
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Fan Y, Wali G, Sutharsan R, Bellette B, Crane DI, Sue CM, Mackay-Sim A. Low dose tubulin-binding drugs rescue peroxisome trafficking deficit in patient-derived stem cells in Hereditary Spastic Paraplegia. Biol Open 2014; 3:494-502. [PMID: 24857849 PMCID: PMC4058084 DOI: 10.1242/bio.20147641] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Hereditary Spastic Paraplegia (HSP) is a genetically heterogeneous group of disorders, diagnosed by progressive gait disturbances with muscle weakness and spasticity, for which there are no treatments targeted at the underlying pathophysiology. Mutations in spastin are a common cause of HSP. Spastin is a microtubule-severing protein whose mutation in mouse causes defective axonal transport. In human patient-derived olfactory neurosphere-derived (ONS) cells, spastin mutations lead to lower levels of acetylated α-tubulin, a marker of stabilised microtubules, and to slower speed of peroxisome trafficking. Here we screened multiple concentrations of four tubulin-binding drugs for their ability to rescue levels of acetylated α-tubulin in patient-derived ONS cells. Drug doses that restored acetylated α-tubulin to levels in control-derived ONS cells were then selected for their ability to rescue peroxisome trafficking deficits. Automated microscopic screening identified very low doses of the four drugs (0.5 nM taxol, 0.5 nM vinblastine, 2 nM epothilone D, 10 µM noscapine) that rescued acetylated α-tubulin in patient-derived ONS cells. These same doses rescued peroxisome trafficking deficits, restoring peroxisome speeds to untreated control cell levels. These results demonstrate a novel approach for drug screening based on high throughput automated microscopy for acetylated α-tubulin followed by functional validation of microtubule-based peroxisome transport. From a clinical perspective, all the drugs tested are used clinically, but at much higher doses. Importantly, epothilone D and noscapine can enter the central nervous system, making them potential candidates for future clinical trials.
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Affiliation(s)
- Yongjun Fan
- National Centre for Adult Stem Cell Research, Eskitis Institute for Drug Discovery, Griffith University, Brisbane, QLD 4111, Australia
| | - Gautam Wali
- National Centre for Adult Stem Cell Research, Eskitis Institute for Drug Discovery, Griffith University, Brisbane, QLD 4111, Australia
| | - Ratneswary Sutharsan
- National Centre for Adult Stem Cell Research, Eskitis Institute for Drug Discovery, Griffith University, Brisbane, QLD 4111, Australia
| | - Bernadette Bellette
- National Centre for Adult Stem Cell Research, Eskitis Institute for Drug Discovery, Griffith University, Brisbane, QLD 4111, Australia
| | - Denis I Crane
- National Centre for Adult Stem Cell Research, Eskitis Institute for Drug Discovery, Griffith University, Brisbane, QLD 4111, Australia
| | - Carolyn M Sue
- Kolling Institute for Medical Research, University of Sydney, Sydney, NSW 2065, Australia
| | - Alan Mackay-Sim
- National Centre for Adult Stem Cell Research, Eskitis Institute for Drug Discovery, Griffith University, Brisbane, QLD 4111, Australia
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Abstract
The proper formation and morphogenesis of dendrites is fundamental to the establishment of neural circuits in the brain. Following cell cycle exit and migration, neurons undergo organized stages of dendrite morphogenesis, which include dendritic arbor growth and elaboration followed by retraction and pruning. Although these developmental stages were characterized over a century ago, molecular regulators of dendrite morphogenesis have only recently been defined. In particular, studies in Drosophila and mammalian neurons have identified numerous cell-intrinsic drivers of dendrite morphogenesis that include transcriptional regulators, cytoskeletal and motor proteins, secretory and endocytic pathways, cell cycle-regulated ubiquitin ligases, and components of other signaling cascades. Here, we review cell-intrinsic drivers of dendrite patterning and discuss how the characterization of such crucial regulators advances our understanding of normal brain development and pathogenesis of diverse cognitive disorders.
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Affiliation(s)
- Sidharth V Puram
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
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Lefèvre J, Savarin P, Gans P, Hamon L, Clément MJ, David MO, Bosc C, Andrieux A, Curmi PA. Structural basis for the association of MAP6 protein with microtubules and its regulation by calmodulin. J Biol Chem 2013; 288:24910-22. [PMID: 23831686 DOI: 10.1074/jbc.m113.457267] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Microtubules are highly dynamic αβ-tubulin polymers. In vitro and in living cells, microtubules are most often cold- and nocodazole-sensitive. When present, the MAP6/STOP family of proteins protects microtubules from cold- and nocodazole-induced depolymerization but the molecular and structure determinants by which these proteins stabilize microtubules remain under debate. We show here that a short protein fragment from MAP6-N, which encompasses its Mn1 and Mn2 modules (MAP6(90-177)), recapitulates the function of the full-length MAP6-N protein toward microtubules, i.e. its ability to stabilize microtubules in vitro and in cultured cells in ice-cold conditions or in the presence of nocodazole. We further show for the first time, using biochemical assays and NMR spectroscopy, that these effects result from the binding of MAP6(90-177) to microtubules with a 1:1 MAP6(90-177):tubulin heterodimer stoichiometry. NMR data demonstrate that the binding of MAP6(90-177) to microtubules involve its two Mn modules but that a single one is also able to interact with microtubules in a closely similar manner. This suggests that the Mn modules represent each a full microtubule binding domain and that MAP6 proteins may stabilize microtubules by bridging tubulin heterodimers from adjacent protofilaments or within a protofilament. Finally, we demonstrate that Ca(2+)-calmodulin competes with microtubules for MAP6(90-177) binding and that the binding mode of MAP6(90-177) to microtubules and Ca(2+)-calmodulin involves a common stretch of amino acid residues on the MAP6(90-177) side. This result accounts for the regulation of microtubule stability in cold condition by Ca(2+)-calmodulin.
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Affiliation(s)
- Julien Lefèvre
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR829, Laboratoire Structure-Activité des Biomolécules Normales et Pathologiques, Université Evry-Val d'Essonne, Evry 91025, France.
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40
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Baas PW, Ahmad FJ. Beyond taxol: microtubule-based treatment of disease and injury of the nervous system. ACTA ACUST UNITED AC 2013; 136:2937-51. [PMID: 23811322 DOI: 10.1093/brain/awt153] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Contemporary research has revealed a great deal of information on the behaviours of microtubules that underlie critical events in the lives of neurons. Microtubules in the neuron undergo dynamic assembly and disassembly, bundling and splaying, severing, and rapid transport as well as integration with other cytoskeletal elements such as actin filaments. These various behaviours are regulated by signalling pathways that affect microtubule-related proteins such as molecular motor proteins and microtubule severing enzymes, as well as a variety of proteins that promote the assembly, stabilization and bundling of microtubules. In recent years, translational neuroscientists have earmarked microtubules as a promising target for therapy of injury and disease of the nervous system. Proof-of-principle has come mainly from studies using taxol and related drugs to pharmacologically stabilize microtubules in animal models of nerve injury and disease. However, concerns persist that the negative consequences of abnormal microtubule stabilization may outweigh the positive effects. Other potential approaches include microtubule-active drugs with somewhat different properties, but also expanding the therapeutic toolkit to include intervention at the level of microtubule regulatory proteins.
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Affiliation(s)
- Peter W Baas
- 1 Drexel University College of Medicine, Philadelphia, PA, USA
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41
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Asthana J, Kapoor S, Mohan R, Panda D. Inhibition of HDAC6 deacetylase activity increases its binding with microtubules and suppresses microtubule dynamic instability in MCF-7 cells. J Biol Chem 2013; 288:22516-26. [PMID: 23798680 DOI: 10.1074/jbc.m113.489328] [Citation(s) in RCA: 81] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The post-translational modification of tubulin appears to be a highly controlled mechanism that regulates microtubule functioning. Acetylation of the ε-amino group of Lys-40 of α-tubulin marks stable microtubules, although the causal relationship between tubulin acetylation and microtubule stability has remained poorly understood. HDAC6, the tubulin deacetylase, plays a key role in maintaining typical distribution of acetylated microtubules in cells. Here, by using tubastatin A, an HDAC6-specific inhibitor, and siRNA-mediated depletion of HDAC6, we have explored whether tubulin acetylation has a role in regulating microtubule stability. We found that whereas both pharmacological inhibition of HDAC6 as well as its depletion enhance microtubule acetylation, only pharmacological inhibition of HDAC6 activity leads to an increase in microtubule stability against cold and nocodazole-induced depolymerizing conditions. Tubastatin A treatment suppressed the dynamics of individual microtubules in MCF-7 cells and delayed the reassembly of depolymerized microtubules. Interestingly, both the localization of HDAC6 on microtubules and the amount of HDAC6 associated with polymeric fraction of tubulin were found to increase in the tubastatin A-treated cells compared with the control cells, suggesting that the pharmacological inhibition of HDAC6 enhances the binding of HDAC6 to microtubules. The evidence presented in this study indicated that the increased binding of HDAC6, rather than the acetylation per se, causes microtubule stability. The results are in support of a hypothesis that in addition to its deacetylase function, HDAC6 might function as a MAP that regulates microtubule dynamics under certain conditions.
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Affiliation(s)
- Jayant Asthana
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai 400076, India
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42
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Abstract
Microtubules are nearly uniformly oriented in the axons of vertebrate neurons but are non-uniformly oriented in their dendrites. Studies to date suggest a scenario for establishing these microtubule patterns whereby microtubules are transported into the axon and nascent dendrites with plus-ends-leading, and then additional microtubules of the opposite orientation are transported into the developing dendrites. Here, we used contemporary tools to confirm that depletion of kinesin-6 (also called CHO1/MKLP1 or kif23) from rat sympathetic neurons causes a reduction in the appearance of minus-end-distal microtubules in developing dendrites, which in turn causes them to assume an axon-like morphology. Interestingly, we observed a similar phenomenon when we depleted kinesin-12 (also called kif15 or HKLP2). Both motors are best known for their participation in mitosis in other cell types, and both are enriched in the cell body and dendrites of neurons. Unlike kinesin-12, which is present throughout the neuron, kinesin-6 is barely detectable in the axon. Accordingly, depletion of kinesin-6, unlike depletion of kinesin-12, has no effect on axonal branching or navigation. Interestingly, depletion of either motor results in faster growing axons with greater numbers of mobile microtubules. Based on these observations, we posit a model whereby these two motors generate forces that attenuate the transport of microtubules with plus-ends-leading from the cell body into the axon. Some of these microtubules are not only prevented from moving into the axon but are driven with minus-ends-leading into developing dendrites. In this manner, these so-called "mitotic" motors coregulate the microtubule patterns of axons and dendrites.
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Baas PW, Lin S. Hooks and comets: The story of microtubule polarity orientation in the neuron. Dev Neurobiol 2011; 71:403-18. [PMID: 21557497 DOI: 10.1002/dneu.20818] [Citation(s) in RCA: 155] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
It is widely believed that signature patterns of microtubule polarity orientation within axons and dendrites underlie compositional and morphological differences that distinguish these neuronal processes from one another. Axons of vertebrate neurons display uniformly plus-end-distal microtubules, whereas their dendrites display non-uniformly oriented microtubules. Recent studies on insect neurons suggest that it is the minus-end-distal microtubules that are the critical feature of the dendritic microtubule array, whether or not they are accompanied by plus-end-distal microtubules. Discussed in this article are the history of these findings, their implications for the regulation of neuronal polarity across the animal kingdom, and potential mechanisms by which neurons establish the distinct microtubule polarity patterns that define axons and dendrites.
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Affiliation(s)
- Peter W Baas
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129, USA.
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Schuster M, Kilaru S, Fink G, Collemare J, Roger Y, Steinberg G. Kinesin-3 and dynein cooperate in long-range retrograde endosome motility along a nonuniform microtubule array. Mol Biol Cell 2011; 22:3645-57. [PMID: 21832152 PMCID: PMC3183019 DOI: 10.1091/mbc.e11-03-0217] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The polarity of microtubules (MTs) determines the motors for intracellular motility, with kinesins moving to plus ends and dynein to minus ends. In elongated cells of Ustilago maydis, dynein is thought to move early endosomes (EEs) toward the septum (retrograde), whereas kinesin-3 transports them to the growing cell tip (anterograde). Occasionally, EEs run up to 90 μm in one direction. The underlying MT array consists of unipolar MTs at both cell ends and antipolar bundles in the middle region of the cell. Cytoplasmic MT-organizing centers, labeled with a γ-tubulin ring complex protein, are distributed along the antipolar MTs but are absent from the unipolar regions. Dynein colocalizes with EEs for 10-20 μm after they have left the cell tip. Inactivation of temperature-sensitive dynein abolishes EE motility within the unipolar MT array, whereas long-range motility is not impaired. In contrast, kinesin-3 is continuously present, and its inactivation stops long-range EE motility. This indicates that both motors participate in EE motility, with dynein transporting the organelles through the unipolar MT array near the cell ends, and kinesin-3 taking over at the beginning of the medial antipolar MT array. The cooperation of both motors mediates EE movements over the length of the entire cell.
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Affiliation(s)
- Martin Schuster
- Department of Biosciences, University of Exeter, Exeter EX4 4QD, United Kingdom
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45
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Sudo H, Baas PW. Strategies for diminishing katanin-based loss of microtubules in tauopathic neurodegenerative diseases. Hum Mol Genet 2010; 20:763-78. [PMID: 21118899 DOI: 10.1093/hmg/ddq521] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
It is commonly stated that microtubules gradually disintegrate as tau becomes dissociated from them in tauopathies such as Alzheimer's disease. However, there has been no compelling evidence to date that such disintegration is due to depolymerization of microtubules from their ends. In recent studies, we have shown that neurons contain sufficient levels of the microtubule-severing protein termed katanin to completely break down the axonal microtubule array if not somehow attenuated. The presence of tau on axonal microtubules renders them notably less sensitive to katanin, prompting us to posit that microtubule disintegration in tauopathies may result from elevated severing of the microtubules as they lose tau. In support of this hypothesis, we demonstrate here that pathogenic tau mutants that bind less strongly to microtubules than wild-type tau provide correspondingly less protection against katanin-based severing. Using cultured rat hippocampal neurons, we pursued two potential therapies for fortifying axonal microtubules against excess severing by katanin, under conditions of tau depletion. We found that either deacetylating the microtubules via overexpression of HDAC6 or treating the neurons with NAP, a microtubule-interacting neuroprotective peptide, resulted in notable protection of the microtubules against katanin-based loss. In both cases, we found that these treatments also diminished the characteristic increase in axonal branching that normally accompanies tau depletion, an effect that is also known to be directly related to the severing of microtubules. These observations may be useful in developing therapeutic regimes for preserving microtubules against loss in the axons of patients suffering from tauopathies.
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Affiliation(s)
- Haruka Sudo
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, 2900 W. Queen Lane, Philadelphia, PA 19129, USA
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46
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Acetylation of microtubules influences their sensitivity to severing by katanin in neurons and fibroblasts. J Neurosci 2010; 30:7215-26. [PMID: 20505088 DOI: 10.1523/jneurosci.0048-10.2010] [Citation(s) in RCA: 134] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Here we investigated whether the sensitivity of microtubules to severing by katanin is regulated by acetylation of the microtubules. During interphase, fibroblasts display long microtubules with discrete regions rich in acetylated tubulin. Overexpression of katanin for short periods of time produced breaks preferentially in these regions. In fibroblasts with experimentally enhanced or diminished microtubule acetylation, the sensitivity of the microtubules to severing by katanin was increased or decreased, respectively. In neurons, microtubules are notably more acetylated in axons than in dendrites. Experimental manipulation of microtubule acetylation in neurons yielded similar results on dendrites as observed on fibroblasts. However, under these experimental conditions, axonal microtubules were not appreciably altered with regard to their sensitivity to katanin. We hypothesized that this may be attributable to the effects of tau on the axonal microtubules, and this was validated by studies in which overexpression of tau caused microtubules in dendrites and fibroblasts to be more resistant to severing by katanin in a manner that was not dependent on the acetylation state of the microtubules. Interestingly, none of these various findings apply to spastin, because the severing of microtubules by spastin does not appear to be strongly influenced by either the acetylation state of the microtubules or tau. We conclude that sensitivity to microtubule severing by katanin is regulated by a balance of factors, including the acetylation state of the microtubules and the binding of tau to the microtubules. In the neuron, this contributes to regional differences in the microtubule arrays of axons and dendrites.
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Quantitative Analysis of MAP-Mediated Regulation of Microtubule Dynamic Instability In Vitro. Methods Cell Biol 2010; 95:481-503. [DOI: 10.1016/s0091-679x(10)95024-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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48
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Hammond JW, Huang CF, Kaech S, Jacobson C, Banker G, Verhey KJ. Posttranslational modifications of tubulin and the polarized transport of kinesin-1 in neurons. Mol Biol Cell 2009; 21:572-83. [PMID: 20032309 PMCID: PMC2820422 DOI: 10.1091/mbc.e09-01-0044] [Citation(s) in RCA: 221] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
During the development of neuronal polarity, the Kinesin-1 motor translocates preferentially to the axon. We show that Kinesin-1 selectivity does not depend on differences between axons and dendrites in microtubule stability or tubulin acetylation, but is likely specified by other tubulin posttranslational modifications. Polarized transport by microtubule-based motors is critical for neuronal development and function. Selective translocation of the Kinesin-1 motor domain is the earliest known marker of axonal identity, occurring before morphological differentiation. Thus, Kinesin-1–mediated transport may contribute to axonal specification. We tested whether posttranslational modifications of tubulin influence the ability of Kinesin-1 motors to distinguish microtubule tracks during neuronal development. We detected no difference in microtubule stability between axons and minor neurites in polarized stage 3 hippocampal neurons. In contrast, microtubule modifications were enriched in a subset of neurites in unpolarized stage 2 cells and the developing axon in polarized stage 3 cells. This enrichment correlated with the selective accumulation of constitutively active Kinesin-1 motors. Increasing tubulin acetylation, without altering the levels of other tubulin modifications, did not alter the selectivity of Kinesin-1 accumulation in polarized cells. However, globally enhancing tubulin acetylation, detyrosination, and polyglutamylation by Taxol treatment or inhibition of glycogen synthase kinase 3β decreased the selectivity of Kinesin-1 translocation and led to the formation of multiple axons. Although microtubule acetylation enhances the motility of Kinesin-1, the preferential translocation of Kinesin-1 on axonal microtubules in polarized neuronal cells is not determined by acetylation alone but is probably specified by a combination of tubulin modifications.
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Affiliation(s)
- Jennetta W Hammond
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
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49
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Bisig CG, Chesta ME, Zampar GG, Purro SA, Santander VS, Arce CA. Lack of stabilized microtubules as a result of the absence of major maps in CAD cells does not preclude neurite formation. FEBS J 2009; 276:7110-23. [DOI: 10.1111/j.1742-4658.2009.07422.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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50
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Kollins KM, Bell RL, Butts M, Withers GS. Dendrites differ from axons in patterns of microtubule stability and polymerization during development. Neural Dev 2009; 4:26. [PMID: 19602271 PMCID: PMC2717962 DOI: 10.1186/1749-8104-4-26] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2009] [Accepted: 07/14/2009] [Indexed: 11/10/2022] Open
Abstract
Background Dendrites differ from axons in patterns of growth and development, as well as in morphology. Given that microtubules are key structural elements in cells, we assessed patterns of microtubule stability and polymerization during hippocampal neuron development in vitro to determine if these aspects of microtubule organization could distinguish axons from dendrites. Results Quantitative ratiometric immunocytochemistry identified significant differences in microtubule stability between axons and dendrites. Most notably, regardless of developmental stage, there were high levels of dynamic microtubules throughout the dendritic arbor, whereas dynamic microtubules were predominantly concentrated in the distal end of axons. Analysis of microtubule polymerization using green fluorescent protein-tagged EB1 showed both developmental and regional differences in microtubule polymerization between axons and dendrites. Early in development (for example, 1 to 2 days in vitro), polymerization events were distributed equally in both the anterograde and retrograde directions throughout the length of both axons and dendrites. As development progressed, however, polymerization became biased, with a greater number of polymerization events in distal than in proximal and middle regions. While polymerization occurred almost exclusively in the anterograde direction for axons, both anterograde and retrograde polymerization was observed in dendrites. This is in agreement with predicted differences in microtubule polarity within these compartments, although fewer retrograde events were observed in dendrites than expected. Conclusion Both immunocytochemical and live imaging analyses showed that newly formed microtubules predominated at the distal end of axons and dendrites, suggesting a common mechanism that incorporates increased microtubule polymerization at growing process tips. Dendrites had more immature, dynamic microtubules throughout the entire arbor than did axons, however. Identifying these differences in microtubule stability and polymerization is a necessary first step toward understanding how they are developmentally regulated, and may reveal novel mechanisms underlying neuron maturation and dendritic plasticity that extend beyond the initial specification of polarity.
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