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Cepkenovic B, Friedland F, Noetzel E, Maybeck V, Offenhäusser A. Single-neuron mechanical perturbation evokes calcium plateaus that excite and modulate the network. Sci Rep 2023; 13:20669. [PMID: 38001109 PMCID: PMC10673841 DOI: 10.1038/s41598-023-47090-z] [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: 03/24/2023] [Accepted: 11/08/2023] [Indexed: 11/26/2023] Open
Abstract
Mechanical stimulation is a promising means to non-invasively excite and modulate neuronal networks with a high spatial resolution. Despite the thorough characterization of the initiation mechanism, whether or how mechanical responses disperse into non-target areas remains to be discovered. Our in vitro study demonstrates that a single-neuron deformation evokes responses that propagate to about a third of the untouched neighbors. The responses develop via calcium influx through mechanosensitive channels and regeneratively propagate through the neuronal ensemble via gap junctions. Although independent of action potentials and synapses, mechanical responses reliably evoke membrane depolarizations capable of inducing action potentials both in the target and neighbors. Finally, we show that mechanical stimulation transiently potentiates the responding assembly for further inputs, as both gain and excitability are transiently increased exclusively in neurons that respond to a neighbor's mechanical stimulation. The findings indicate a biological component affecting the spatial resolution of mechanostimulation and point to a cross-talk in broad-network mechanical stimulations. Since giga-seal formation in patch-clamp produces a similar mechanical stimulus on the neuron, our findings inform which neuroscientific questions could be reliably tackled with patch-clamp and what recovery post-gigaseal formation is necessary.
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Affiliation(s)
- Bogdana Cepkenovic
- Institute of Biological Information Processing: Bioelectronics (IBI-3), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße 1, 52428, Jülich, Germany
- RWTH Aachen University, Templergraben 55, 52062, Aachen, Germany
| | - Florian Friedland
- Institute of Biological Information Processing: Mechanobiology (IBI-2), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße 1, 52428, Jülich, Germany
| | - Erik Noetzel
- Institute of Biological Information Processing: Mechanobiology (IBI-2), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße 1, 52428, Jülich, Germany
| | - Vanessa Maybeck
- Institute of Biological Information Processing: Bioelectronics (IBI-3), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße 1, 52428, Jülich, Germany.
| | - Andreas Offenhäusser
- Institute of Biological Information Processing: Bioelectronics (IBI-3), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße 1, 52428, Jülich, Germany
- RWTH Aachen University, Templergraben 55, 52062, Aachen, Germany
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2
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Holland SM, Gallo G. Actin cytoskeletal dynamics do not impose an energy drain on growth cone bioenergetics. J Cell Sci 2023; 136:jcs261356. [PMID: 37534394 PMCID: PMC10445737 DOI: 10.1242/jcs.261356] [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: 05/23/2023] [Accepted: 07/26/2023] [Indexed: 08/04/2023] Open
Abstract
The regulation of the intracellular level of ATP is a fundamental aspect of bioenergetics. Actin cytoskeletal dynamics have been reported to be an energetic drain in developing neurons and platelets. We addressed the role of actin dynamics in primary embryonic chicken neurons using luciferase assays, and by measurement of the ATP/ADP ratio using the ratiometric reporter PercevalHR and the ATP level using the ratiometric reporter mRuby-iATPSnFR. None of the methods revealed an effect of suppressing actin dynamics on the decline in the neuronal ATP level or the ATP/ADP ratio following shutdown of ATP production. Similarly, we find that treatments that elevate or suppress actin dynamics do not alter the ATP/ADP ratio in growth cones, the subcellular domain with the highest actin dynamics in developing neurons. Collectively, the data indicate that actin cytoskeletal dynamics are not a significant energy drain in developing neurons and that the ATP/ADP ratio is maintained when energy utilization varies. Discrepancies between prior work and the current data are discussed with emphasis on methodology and interpretation of the data.
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Affiliation(s)
- Sabrina M. Holland
- Lewis Katz School of Medicine at Temple University, Department of Neural Sciences, Shriners Pediatric Research Center, 3500 North Broad St, Philadelphia, PA 19140, USA
| | - Gianluca Gallo
- Lewis Katz School of Medicine at Temple University, Department of Neural Sciences, Shriners Pediatric Research Center, 3500 North Broad St, Philadelphia, PA 19140, USA
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3
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Ayad MA, Mahon T, Patel M, Cararo-Lopes MM, Hacihaliloglu I, Firestein BL, Boustany NN. Förster resonance energy transfer efficiency of the vinculin tension sensor in cultured primary cortical neuronal growth cones. NEUROPHOTONICS 2022; 9:025002. [PMID: 35651869 PMCID: PMC9150715 DOI: 10.1117/1.nph.9.2.025002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Accepted: 04/05/2022] [Indexed: 06/15/2023]
Abstract
Significance: Interaction of neurons with their extracellular environment and the mechanical forces at focal adhesions and synaptic junctions play important roles in neuronal development. Aim: To advance studies of mechanotransduction, we demonstrate the use of the vinculin tension sensor (VinTS) in primary cultures of cortical neurons. VinTS consists of TS module (TSMod), a Förster resonance energy transfer (FRET)-based tension sensor, inserted between vinculin's head and tail. FRET efficiency decreases with increased tension across vinculin. Approach: Primary cortical neurons cultured on glass coverslips coated with poly-d-lysine and laminin were transfected with plasmids encoding untargeted TSMod, VinTS, or tail-less vinculinTS (VinTL) lacking the actin-binding domain. The neurons were imaged between day in vitro (DIV) 5 to 8. We detail the image processing steps for calculation of FRET efficiency and use this system to investigate the expression and FRET efficiency of VinTS in growth cones. Results: The distribution of fluorescent constructs was similar within growth cones at DIV 5 to 8. The mean FRET efficiency of TSMod ( 28.5 ± 3.6 % ) in growth cones was higher than the mean FRET efficiency of VinTS ( 24.6 ± 2 % ) and VinTL ( 25.8 ± 1.8 % ) ( p < 10 - 6 ). While small, the difference between the FRET efficiency of VinTS and VinTL was statistically significant ( p < 10 - 3 ), suggesting that vinculin is under low tension in growth cones. Two-hour treatment with the Rho-associated kinase inhibitor Y-27632 did not affect the mean FRET efficiency. Growth cones exhibited dynamic changes in morphology as observed by time-lapse imaging. VinTS FRET efficiency showed greater variance than TSMod FRET efficiency as a function of time, suggesting a greater dependence of VinTS FRET efficiency on growth cone dynamics compared with TSMod. Conclusions: The results demonstrate the feasibility of using VinTS to probe the function of vinculin in neuronal growth cones and provide a foundation for studies of mechanotransduction in neurons using this tension probe.
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Affiliation(s)
- Marina A. Ayad
- Rutgers University, Department of Biomedical Engineering, Piscataway, New Jersey, United States
| | - Timothy Mahon
- Rutgers University, Department of Biomedical Engineering, Piscataway, New Jersey, United States
| | - Mihir Patel
- Rutgers University, Department of Cell Biology and Neuroscience, Piscataway, New Jersey, United States
| | - Marina M. Cararo-Lopes
- Rutgers University, Department of Cell Biology and Neuroscience, Piscataway, New Jersey, United States
| | - Ilker Hacihaliloglu
- Rutgers University, Department of Biomedical Engineering, Piscataway, New Jersey, United States
| | - Bonnie L. Firestein
- Rutgers University, Department of Cell Biology and Neuroscience, Piscataway, New Jersey, United States
| | - Nada N. Boustany
- Rutgers University, Department of Biomedical Engineering, Piscataway, New Jersey, United States
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4
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Lilienberg J, Hegyi Z, Szabó E, Hathy E, Málnási-Csizmadia A, Réthelyi JM, Apáti Á, Homolya L. Pharmacological Modulation of Neurite Outgrowth in Human Neural Progenitor Cells by Inhibiting Non-muscle Myosin II. Front Cell Dev Biol 2021; 9:719636. [PMID: 34604221 PMCID: PMC8484915 DOI: 10.3389/fcell.2021.719636] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 08/27/2021] [Indexed: 12/31/2022] Open
Abstract
Studies on neural development and neuronal regeneration after injury are mainly based on animal models. The establishment of pluripotent stem cell (PSC) technology, however, opened new perspectives for better understanding these processes in human models by providing unlimited cell source for hard-to-obtain human tissues. Here, we aimed at identifying the molecular factors that confine and modulate an early step of neural regeneration, the formation of neurites in human neural progenitor cells (NPCs). Enhanced green fluorescent protein (eGFP) was stably expressed in NPCs differentiated from human embryonic and induced PSC lines, and the neurite outgrowth was investigated under normal and injury-related conditions using a high-content screening system. We found that inhibitors of the non-muscle myosin II (NMII), blebbistatin and its novel, non-toxic derivatives, initiated extensive neurite outgrowth in human NPCs. The extracellular matrix components strongly influenced the rate of neurite formation but NMII inhibitors were able to override the inhibitory effect of a restrictive environment. Non-additive stimulatory effect on neurite generation was also detected by the inhibition of Rho-associated, coiled-coil-containing protein kinase 1 (ROCK1), the upstream regulator of NMII. In contrast, inhibition of c-Jun N-terminal kinases (JNKs) had only a negligible effect, suggesting that the ROCK1 signal is dominantly manifested by actomyosin activity. In addition to providing a reliable cell-based in vitro model for identifying intrinsic mechanisms and environmental factors responsible for impeded axonal regeneration in humans, our results demonstrate that NMII and ROCK1 are important pharmacological targets for the augmentation of neural regeneration at the progenitor level. These studies may open novel perspectives for development of more effective pharmacological treatments and cell therapies for various neurodegenerative disorders.
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Affiliation(s)
- Julianna Lilienberg
- Institute of Enzymology, Research Centre for Natural Sciences, Budapest, Hungary
| | - Zoltán Hegyi
- Institute of Enzymology, Research Centre for Natural Sciences, Budapest, Hungary
| | - Eszter Szabó
- Institute of Enzymology, Research Centre for Natural Sciences, Budapest, Hungary
| | - Edit Hathy
- Molecular Psychiatry and in vitro Disease Modelling Research Group, National Brain Research Project, Hungarian Academy of Sciences and Semmelweis University, Budapest, Hungary
| | - András Málnási-Csizmadia
- MTA-ELTE Motor Pharmacology Research Group, Eötvös Loránd University, Budapest, Hungary.,Motorpharma, Ltd., Budapest, Hungary
| | - János M Réthelyi
- Molecular Psychiatry and in vitro Disease Modelling Research Group, National Brain Research Project, Hungarian Academy of Sciences and Semmelweis University, Budapest, Hungary.,Department of Psychiatry and Psychotherapy, Semmelweis University, Budapest, Hungary
| | - Ágota Apáti
- Institute of Enzymology, Research Centre for Natural Sciences, Budapest, Hungary
| | - László Homolya
- Institute of Enzymology, Research Centre for Natural Sciences, Budapest, Hungary
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5
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Liaci C, Camera M, Caslini G, Rando S, Contino S, Romano V, Merlo GR. Neuronal Cytoskeleton in Intellectual Disability: From Systems Biology and Modeling to Therapeutic Opportunities. Int J Mol Sci 2021; 22:ijms22116167. [PMID: 34200511 PMCID: PMC8201358 DOI: 10.3390/ijms22116167] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 05/25/2021] [Accepted: 06/04/2021] [Indexed: 02/06/2023] Open
Abstract
Intellectual disability (ID) is a pathological condition characterized by limited intellectual functioning and adaptive behaviors. It affects 1–3% of the worldwide population, and no pharmacological therapies are currently available. More than 1000 genes have been found mutated in ID patients pointing out that, despite the common phenotype, the genetic bases are highly heterogeneous and apparently unrelated. Bibliomic analysis reveals that ID genes converge onto a few biological modules, including cytoskeleton dynamics, whose regulation depends on Rho GTPases transduction. Genetic variants exert their effects at different levels in a hierarchical arrangement, starting from the molecular level and moving toward higher levels of organization, i.e., cell compartment and functions, circuits, cognition, and behavior. Thus, cytoskeleton alterations that have an impact on cell processes such as neuronal migration, neuritogenesis, and synaptic plasticity rebound on the overall establishment of an effective network and consequently on the cognitive phenotype. Systems biology (SB) approaches are more focused on the overall interconnected network rather than on individual genes, thus encouraging the design of therapies that aim to correct common dysregulated biological processes. This review summarizes current knowledge about cytoskeleton control in neurons and its relevance for the ID pathogenesis, exploiting in silico modeling and translating the implications of those findings into biomedical research.
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Affiliation(s)
- Carla Liaci
- Department of Molecular Biotechnology and Health Sciences, University of Torino, Via Nizza 52, 10126 Torino, Italy; (C.L.); (M.C.); (G.C.); (S.R.)
| | - Mattia Camera
- Department of Molecular Biotechnology and Health Sciences, University of Torino, Via Nizza 52, 10126 Torino, Italy; (C.L.); (M.C.); (G.C.); (S.R.)
| | - Giovanni Caslini
- Department of Molecular Biotechnology and Health Sciences, University of Torino, Via Nizza 52, 10126 Torino, Italy; (C.L.); (M.C.); (G.C.); (S.R.)
| | - Simona Rando
- Department of Molecular Biotechnology and Health Sciences, University of Torino, Via Nizza 52, 10126 Torino, Italy; (C.L.); (M.C.); (G.C.); (S.R.)
| | - Salvatore Contino
- Department of Engineering, University of Palermo, Viale delle Scienze Ed. 8, 90128 Palermo, Italy;
| | - Valentino Romano
- Department of Biological, Chemical and Pharmaceutical Sciences and Technologies (STEBICEF), University of Palermo, Viale delle Scienze Ed. 16, 90128 Palermo, Italy;
| | - Giorgio R. Merlo
- Department of Molecular Biotechnology and Health Sciences, University of Torino, Via Nizza 52, 10126 Torino, Italy; (C.L.); (M.C.); (G.C.); (S.R.)
- Correspondence: ; Tel.: +39-0116706449; Fax: +39-0116706432
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6
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Pinto-Costa R, Sousa MM. Microtubules, actin and cytolinkers: how to connect cytoskeletons in the neuronal growth cone. Neurosci Lett 2021; 747:135693. [PMID: 33529653 DOI: 10.1016/j.neulet.2021.135693] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Revised: 01/12/2021] [Accepted: 01/16/2021] [Indexed: 01/20/2023]
Abstract
Cytolinkers ensure the integration of the different cytoskeleton components in the neuronal growth cone during development and in the course of axon regeneration. In neurons, an integrated skeleton guarantees appropriate function, and connectivity of high order circuits. Over the past years, several cytoskeleton regulatory proteins with actin-microtubule crosslinking activity have been identified. In neurons, the importance of spectrins, formins and other cytolinkers capable of coupling actin and microtubules has been extensively highlighted during axon outgrowth and guidance. In this Review, we discuss the current knowledge on cytolinkers specifically expressed in the neuronal growth cone of developing and regenerating axons.
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Affiliation(s)
- Rita Pinto-Costa
- Nerve Regeneration Group, i3S-Instituto de Investigação e Inovação em Saúde and IBMC-Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135, Porto, Portugal
| | - Monica Mendes Sousa
- Nerve Regeneration Group, i3S-Instituto de Investigação e Inovação em Saúde and IBMC-Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135, Porto, Portugal.
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7
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Gallo G. The bioenergetics of neuronal morphogenesis and regeneration: Frontiers beyond the mitochondrion. Dev Neurobiol 2020; 80:263-276. [PMID: 32750228 DOI: 10.1002/dneu.22776] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 07/29/2020] [Accepted: 07/29/2020] [Indexed: 12/27/2022]
Abstract
The formation of axons and dendrites during development, and their regeneration following injury, are energy intensive processes. The underlying assembly and dynamics of the cytoskeleton, axonal transport mechanisms, and extensive signaling networks all rely on ATP and GTP consumption. Cellular ATP is generated through oxidative phosphorylation (OxP) in mitochondria, glycolysis and "regenerative" kinase systems. Recent investigations have focused on the role of the mitochondrion in axonal development and regeneration emphasizing the importance of this organelle and OxP in axon development and regeneration. In contrast, the understanding of alternative sources of ATP in neuronal morphogenesis and regeneration remains largely unexplored. This review focuses on the current state of the field of neuronal bioenergetics underlying morphogenesis and regeneration and considers the literature on the bioenergetics of non-neuronal cell motility to emphasize the potential contributions of non-mitochondrial energy sources.
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Affiliation(s)
- Gianluca Gallo
- Department of Anatomy and Cell Biology, Lewis Katz School of Medicine, Shriners Hospitals Pediatric Research Center, Temple University, Philadelphia, PA, USA
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8
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Mikhaylova M, Rentsch J, Ewers H. Actomyosin Contractility in the Generation and Plasticity of Axons and Dendritic Spines. Cells 2020; 9:cells9092006. [PMID: 32882840 PMCID: PMC7565476 DOI: 10.3390/cells9092006] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 08/19/2020] [Accepted: 08/25/2020] [Indexed: 12/15/2022] Open
Abstract
Actin and non-muscle myosins have long been known to play important roles in growth cone steering and neurite outgrowth. More recently, novel functions for non-muscle myosin have been described in axons and dendritic spines. Consequently, possible roles of actomyosin contraction in organizing and maintaining structural properties of dendritic spines, the size and location of axon initial segment and axonal diameter are emerging research topics. In this review, we aim to summarize recent findings involving myosin localization and function in these compartments and to discuss possible roles for actomyosin in their function and the signaling pathways that control them.
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Affiliation(s)
- Marina Mikhaylova
- RG Optobiology, Institute of Biology, Humboldt Universität zu Berlin, 10115 Berlin, Germany
- DFG Emmy Noether Group ‘Neuronal Protein Transport’, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
- Correspondence: (M.M.); (H.E.); Tel.: +49-4074-1055-815 (M.M.); +49-30-838-60644 (H.E.)
| | - Jakob Rentsch
- Institut für Chemie und Biochemie, Freie Universität Berlin, 14195 Berlin, Germany;
| | - Helge Ewers
- Institut für Chemie und Biochemie, Freie Universität Berlin, 14195 Berlin, Germany;
- Correspondence: (M.M.); (H.E.); Tel.: +49-4074-1055-815 (M.M.); +49-30-838-60644 (H.E.)
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9
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Costa AR, Sousa MM. Non-Muscle Myosin II in Axonal Cell Biology: From the Growth Cone to the Axon Initial Segment. Cells 2020; 9:cells9091961. [PMID: 32858875 PMCID: PMC7563147 DOI: 10.3390/cells9091961] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 08/21/2020] [Accepted: 08/21/2020] [Indexed: 12/14/2022] Open
Abstract
By binding to actin filaments, non-muscle myosin II (NMII) generates actomyosin networks that hold unique contractile properties. Their dynamic nature is essential for neuronal biology including the establishment of polarity, growth cone formation and motility, axon growth during development (and axon regeneration in the adult), radial and longitudinal axonal tension, and synapse formation and function. In this review, we discuss the current knowledge on the spatial distribution and function of the actomyosin cytoskeleton in different axonal compartments. We highlight some of the apparent contradictions and open questions in the field, including the role of NMII in the regulation of axon growth and regeneration, the possibility that NMII structural arrangement along the axon shaft may control both radial and longitudinal contractility, and the mechanism and functional purpose underlying NMII enrichment in the axon initial segment. With the advances in live cell imaging and super resolution microscopy, it is expected that in the near future the spatial distribution of NMII in the axon, and the mechanisms by which it participates in axonal biology will be further untangled.
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10
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Conventional and Non-Conventional Roles of Non-Muscle Myosin II-Actin in Neuronal Development and Degeneration. Cells 2020; 9:cells9091926. [PMID: 32825197 PMCID: PMC7566000 DOI: 10.3390/cells9091926] [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: 07/20/2020] [Revised: 08/12/2020] [Accepted: 08/13/2020] [Indexed: 12/13/2022] Open
Abstract
Myosins are motor proteins that use chemical energy to produce mechanical forces driving actin cytoskeletal dynamics. In the brain, the conventional non-muscle myosin II (NMII) regulates actin filament cytoskeletal assembly and contractile forces during structural remodeling of axons and dendrites, contributing to morphology, polarization, and migration of neurons during brain development. NMII isoforms also participate in neurotransmission and synaptic plasticity by driving actin cytoskeletal dynamics during synaptic vesicle release and retrieval, and formation, maturation, and remodeling of dendritic spines. NMIIs are expressed differentially in cerebral non-neuronal cells, such as microglia, astrocytes, and endothelial cells, wherein they play key functions in inflammation, myelination, and repair. Besides major efforts to understand the physiological functions and regulatory mechanisms of NMIIs in the nervous system, their contributions to brain pathologies are still largely unclear. Nonetheless, genetic mutations or deregulation of NMII and its regulatory effectors are linked to autism, schizophrenia, intellectual disability, and neurodegeneration, indicating non-conventional roles of NMIIs in cellular mechanisms underlying neurodevelopmental and neurodegenerative disorders. Here, we summarize the emerging biological roles of NMIIs in the brain, and discuss how actomyosin signaling contributes to dysfunction of neurons and glial cells in the context of neurological disorders. This knowledge is relevant for a deep understanding of NMIIs on the pathogenesis and therapeutics of neuropsychiatric and neurodegenerative diseases.
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11
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Extremely Low Forces Induce Extreme Axon Growth. J Neurosci 2020; 40:4997-5007. [PMID: 32444384 DOI: 10.1523/jneurosci.3075-19.2020] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Revised: 04/16/2020] [Accepted: 04/21/2020] [Indexed: 12/27/2022] Open
Abstract
Stretch-growth has been defined as a process that extends axons via the application of mechanical forces. In the present article, we used a protocol based on magnetic nanoparticles (NPs) for labeling the entire axon tract of hippocampal neurons, and an external magnetic field gradient to generate a dragging force. We found that the application of forces below 10 pN induces growth at a rate of 0.66 ± 0.02 µm h-1 pN-1 Calcium imaging confirmed the strong increase in elongation rate, in comparison with the condition of tip-growth. Enhanced growth in stretched axons was also accompanied by endoplasmic reticulum (ER) accumulation and, accordingly, it was blocked by an inhibition of translation. Stretch-growth was also found to stimulate axonal branching, glutamatergic synaptic transmission, and neuronal excitability. Moreover, stretched axons showed increased microtubule (MT) density and MT assembly was key to sustaining stretch-growth, suggesting a possible role of tensile forces in MT translocation/assembly. Additionally, our data showed that stretched axons do not respond to BDNF signaling, suggesting interference between the two pathways. As these extremely low mechanical forces are physiologically relevant, stretch-growth could be an important endogenous mechanism of axon growth, with a potential for designing novel strategies for axonal regrowth.SIGNIFICANCE STATEMENT Axon growth involves motion, and motion is driven by forces. The growth cone (GC) itself can generate very low intracellular forces by inducing a drastic cytoskeleton remodeling, in response to signaling molecules. Here, we investigated the key role of intracellular force as an endogenous regulator of axon outgrowth, which it has been neglected for decades because of the lack of methodologies to investigate the topic. Our results indicate a critical role of force in promoting axon growth by facilitating microtubule (MT) polymerization.
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12
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Neurite regrowth stimulation by a red-light spot focused on the neuronal cell soma following blue light-induced retraction. Sci Rep 2019; 9:18210. [PMID: 31796850 PMCID: PMC6890775 DOI: 10.1038/s41598-019-54687-w] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Accepted: 11/18/2019] [Indexed: 11/13/2022] Open
Abstract
The interaction of light with biological tissues has been considered for various therapeutic applications. Light-induced neurite growth has the potential to be a clinically useful technique for neuron repair. However, most previous studies used either a large illumination area to accelerate overall neurite growth or employed a light spot to guide a growing neurite. It is not clear if optical stimulation can induce the regrowth of a retracted neurite. In the present work, we used blue light (wavelength: 473 nm) to cause neurite retraction, and we proved that using a red-light (wavelength: 650 nm) spot to illuminate the soma near the junction of the retracted neurite could induce neurite regrowth. As a comparison, we found that green light (wavelength 550 nm) had a 62% probability of inducing neurite regrowth, while red light had a 75% probability of inducing neurite regrowth at the same power level. Furthermore, the neurite regrowth length induced by red light was increased by the pre-treatment with inhibitors of myosin functions. We also observed actin propagation from the soma to the tip of the re-growing neurite following red-light stimulation of the soma. The red light-induced extension and regrowth were abrogated in the calcium-free medium. These results suggest that illumination with a red-light spot on the soma may trigger the regrowth of a neurite after the retraction caused by blue-light illumination.
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13
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Abstract
Neurons develop polarity by the formation of specialized dendritic and axonal structural compartments. A new report now provides evidence that reveals how neurons regulate the initiation and further maintenance of axonal growth, challenging our currently held view of RhoA function in axogenesis.
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Affiliation(s)
- Anton Omelchenko
- Department of Cell Biology and Neuroscience, Rutgers, The State University of New Jersey, 604 Allison Road, Piscataway, NJ 08854, USA
| | - Bonnie L Firestein
- Department of Cell Biology and Neuroscience, Rutgers, The State University of New Jersey, 604 Allison Road, Piscataway, NJ 08854, USA.
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14
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Dupraz S, Hilton BJ, Husch A, Santos TE, Coles CH, Stern S, Brakebusch C, Bradke F. RhoA Controls Axon Extension Independent of Specification in the Developing Brain. Curr Biol 2019; 29:3874-3886.e9. [PMID: 31679934 DOI: 10.1016/j.cub.2019.09.040] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 08/22/2019] [Accepted: 09/16/2019] [Indexed: 12/22/2022]
Abstract
The specification of an axon and its subsequent outgrowth are key steps during neuronal polarization, a prerequisite to wire the brain. The Rho-guanosine triphosphatase (GTPase) RhoA is believed to be a central player in these processes. However, its physiological role has remained undefined. Here, genetic loss- and gain-of-function experiments combined with time-lapse microscopy, cell culture, and in vivo analysis show that RhoA is not involved in axon specification but confines the initiation of neuronal polarization and axon outgrowth during development. Biochemical analysis and super-resolution microscopy together with molecular and pharmacological manipulations reveal that RhoA restrains axon growth by activating myosin-II-mediated actin arc formation in the growth cone to prevent microtubules from protruding toward the leading edge. Through this mechanism, RhoA regulates the duration of axon growth and pause phases, thus controlling the tightly timed extension of developing axons. Thereby, this work unravels physiologically relevant players coordinating actin-microtubule interactions during axon growth.
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Affiliation(s)
- Sebastian Dupraz
- Axonal Growth and Regeneration Group, German Center for Neurodegenerative Diseases (DZNE), Venusberg-Campus 1, Building 99, 53127 Bonn, Germany
| | - Brett J Hilton
- Axonal Growth and Regeneration Group, German Center for Neurodegenerative Diseases (DZNE), Venusberg-Campus 1, Building 99, 53127 Bonn, Germany
| | - Andreas Husch
- Axonal Growth and Regeneration Group, German Center for Neurodegenerative Diseases (DZNE), Venusberg-Campus 1, Building 99, 53127 Bonn, Germany
| | - Telma E Santos
- Axonal Growth and Regeneration Group, German Center for Neurodegenerative Diseases (DZNE), Venusberg-Campus 1, Building 99, 53127 Bonn, Germany
| | - Charlotte H Coles
- Axonal Growth and Regeneration Group, German Center for Neurodegenerative Diseases (DZNE), Venusberg-Campus 1, Building 99, 53127 Bonn, Germany
| | - Sina Stern
- Axonal Growth and Regeneration Group, German Center for Neurodegenerative Diseases (DZNE), Venusberg-Campus 1, Building 99, 53127 Bonn, Germany
| | - Cord Brakebusch
- Biotech Research & Innovation Centre, University of Copenhagen, Ole Maaløes Vej 5, 2200 Copenhagen, Denmark
| | - Frank Bradke
- Axonal Growth and Regeneration Group, German Center for Neurodegenerative Diseases (DZNE), Venusberg-Campus 1, Building 99, 53127 Bonn, Germany.
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15
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Sato Y, Kamijo K, Tsutsumi M, Murakami Y, Takahashi M. Nonmuscle myosin IIA and IIB differently suppress microtubule growth to stabilize cell morphology. J Biochem 2019; 167:25-39. [DOI: 10.1093/jb/mvz082] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Accepted: 09/22/2019] [Indexed: 12/21/2022] Open
Abstract
Abstract
Precise regulation of cytoskeletal dynamics is important in many fundamental cellular processes such as cell shape determination. Actin and microtubule (MT) cytoskeletons mutually regulate their stability and dynamics. Nonmuscle myosin II (NMII) is a candidate protein that mediates the actin–MT crosstalk. NMII regulates the stability and dynamics of actin filaments to control cell morphology. Additionally, previous reports suggest that NMII-dependent cellular contractility regulates MT dynamics, and MTs also control cell morphology; however, the detailed mechanism whereby NMII regulates MT dynamics and the relationship among actin dynamics, MT dynamics and cell morphology remain unclear. The present study explores the roles of two well-characterized NMII isoforms, NMIIA and NMIIB, on the regulation of MT growth dynamics and cell morphology. We performed RNAi and drug experiments and demonstrated the NMII isoform-specific mechanisms—NMIIA-dependent cellular contractility upregulates the expression of some mammalian diaphanous-related formin (mDia) proteins that suppress MT dynamics; NMIIB-dependent inhibition of actin depolymerization suppresses MT growth independently of cellular contractility. The depletion of either NMIIA or NMIIB resulted in the increase in cellular morphological dynamicity, which was alleviated by the perturbation of MT dynamics. Thus, the NMII-dependent control of cell morphology significantly relies on MT dynamics.
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Affiliation(s)
- Yuta Sato
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Kita 13, Nishi 8, Kita-ku, Sapporo Hokkaido, Japan
| | - Keiju Kamijo
- Division of Anatomy and Cell Biology, Faculty of Medicine, Tohoku Medical and Pharmaceutical University, 1-15-1 Fukumuro, Miyagino-ku, Sendai Miyagi, Japan
| | - Motosuke Tsutsumi
- Research Institute for Electronic Science, Hokkaido University, Kita 20, Nishi 10, Kita-ku, Sapporo Hokkaido, Japan
| | - Yota Murakami
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Kita 13, Nishi 8, Kita-ku, Sapporo Hokkaido, Japan
- Department of Chemistry, Faculty of Science, Hokkaido University, Kita 10, Nishi 8, Kita-ku, Sapporo Hokkaido, Japan
| | - Masayuki Takahashi
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Kita 13, Nishi 8, Kita-ku, Sapporo Hokkaido, Japan
- Department of Chemistry, Faculty of Science, Hokkaido University, Kita 10, Nishi 8, Kita-ku, Sapporo Hokkaido, Japan
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16
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Berger SL, Leo-Macias A, Yuen S, Khatri L, Pfennig S, Zhang Y, Agullo-Pascual E, Caillol G, Zhu MS, Rothenberg E, Melendez-Vasquez CV, Delmar M, Leterrier C, Salzer JL. Localized Myosin II Activity Regulates Assembly and Plasticity of the Axon Initial Segment. Neuron 2018; 97:555-570.e6. [PMID: 29395909 PMCID: PMC5805619 DOI: 10.1016/j.neuron.2017.12.039] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 08/24/2017] [Accepted: 12/22/2017] [Indexed: 01/08/2023]
Abstract
The axon initial segment (AIS) is the site of action potential generation and a locus of activity-dependent homeostatic plasticity. A multimeric complex of sodium channels, linked via a cytoskeletal scaffold of ankyrin G and beta IV spectrin to submembranous actin rings, mediates these functions. The mechanisms that specify the AIS complex to the proximal axon and underlie its plasticity remain poorly understood. Here we show phosphorylated myosin light chain (pMLC), an activator of contractile myosin II, is highly enriched in the assembling and mature AIS, where it associates with actin rings. MLC phosphorylation and myosin II contractile activity are required for AIS assembly, and they regulate the distribution of AIS components along the axon. pMLC is rapidly lost during depolarization, destabilizing actin and thereby providing a mechanism for activity-dependent structural plasticity of the AIS. Together, these results identify pMLC/myosin II activity as a common link between AIS assembly and plasticity.
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Affiliation(s)
- Stephen L Berger
- Neuroscience Institute and Department of Neuroscience and Physiology, NYU School of Medicine, New York, NY 10016, USA
| | | | - Stephanie Yuen
- Neuroscience Institute and Department of Neuroscience and Physiology, NYU School of Medicine, New York, NY 10016, USA
| | - Latika Khatri
- Neuroscience Institute and Department of Neuroscience and Physiology, NYU School of Medicine, New York, NY 10016, USA
| | - Sylvia Pfennig
- Neuroscience Institute and Department of Neuroscience and Physiology, NYU School of Medicine, New York, NY 10016, USA
| | - Yanqing Zhang
- Neuroscience Institute and Department of Neuroscience and Physiology, NYU School of Medicine, New York, NY 10016, USA
| | | | - Ghislaine Caillol
- Aix Marseille Université, CNRS, INP UMR7051, 13344 Cedex 15, Marseille, France
| | - Min-Sheng Zhu
- Model Animal Research Center and MOE Key Laboratory of Model Animal and Disease Study, Nanjing University, Nanjing 210061, China
| | - Eli Rothenberg
- Department of Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, NY 10016, USA
| | - Carmen V Melendez-Vasquez
- Department of Biological Sciences, Hunter College, New York, NY 10065, USA; Department of Molecular, Cellular, and Developmental Biology, The Graduate Center, The City University of New York, NY 10016, USA
| | - Mario Delmar
- Division of Cardiology, NYU School of Medicine, New York, NY 10016, USA
| | | | - James L Salzer
- Neuroscience Institute and Department of Neuroscience and Physiology, NYU School of Medicine, New York, NY 10016, USA.
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17
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Sherman SP, Bang AG. High-throughput screen for compounds that modulate neurite growth of human induced pluripotent stem cell-derived neurons. Dis Model Mech 2018; 11:dmm.031906. [PMID: 29361516 PMCID: PMC5894944 DOI: 10.1242/dmm.031906] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Accepted: 12/29/2017] [Indexed: 01/01/2023] Open
Abstract
Development of technology platforms to perform compound screens of human induced pluripotent stem cell (hiPSC)-derived neurons with relatively high throughput is essential to realize their potential for drug discovery. Here, we demonstrate the feasibility of high-throughput screening of hiPSC-derived neurons using a high-content, image-based approach focused on neurite growth, a process that is fundamental to formation of neural networks and nerve regeneration. From a collection of 4421 bioactive small molecules, we identified 108 hit compounds, including 37 approved drugs, that target molecules or pathways known to regulate neurite growth, as well as those not previously associated with this process. These data provide evidence that many pathways and targets known to play roles in neurite growth have similar activities in hiPSC-derived neurons that can be identified in an unbiased phenotypic screen. The data also suggest that hiPSC-derived neurons provide a useful system to study the mechanisms of action and off-target activities of the approved drugs identified as hits, leading to a better understanding of their clinical efficacy and toxicity, especially in the context of specific human genetic backgrounds. Finally, the hit set we report constitutes a sublibrary of approved drugs and tool compounds that modulate neurites. This sublibrary will be invaluable for phenotypic analyses and interrogation of hiPSC-based disease models as probes for defining phenotypic differences and cellular vulnerabilities in patient versus control cells, as well as for investigations of the molecular mechanisms underlying human neurite growth in development and maintenance of neuronal networks, and nerve regeneration. Summary: High-throughput, small molecule screening of hiPSC-derived neurons using a high-content, image-based approach focused on neurite growth identified hit compounds, including approved drugs, which target molecules or pathways known to regulate neurite growth.
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Affiliation(s)
- Sean P Sherman
- Conrad Prebys Center for Chemical Genomics, Sanford Burnham Prebys Medical Discovery Institute La Jolla, CA 92037, USA
| | - Anne G Bang
- Conrad Prebys Center for Chemical Genomics, Sanford Burnham Prebys Medical Discovery Institute La Jolla, CA 92037, USA
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18
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Evans MD, Tufo C, Dumitrescu AS, Grubb MS. Myosin II activity is required for structural plasticity at the axon initial segment. Eur J Neurosci 2017; 46:1751-1757. [PMID: 28452088 PMCID: PMC5573965 DOI: 10.1111/ejn.13597] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Revised: 03/29/2017] [Accepted: 04/20/2017] [Indexed: 12/21/2022]
Abstract
In neurons, axons possess a molecularly defined and highly organised proximal region – the axon initial segment (AIS) – that is a key regulator of both electrical excitability and cellular polarity. Despite existing as a large, dense structure with specialised cytoskeletal architecture, the AIS is surprisingly plastic, with sustained alterations in neuronal activity bringing about significant alterations to its position, length or molecular composition. However, although the upstream activity‐dependent signalling pathways that lead to such plasticity have begun to be elucidated, the downstream mechanisms that produce structural changes at the AIS are completely unknown. Here, we use dissociated cultures of rat hippocampus to show that two forms of AIS plasticity in dentate granule cells – long‐term relocation, and more rapid shortening – are completely blocked by treatment with blebbistatin, a potent and selective myosin II ATPase inhibitor. These data establish a link between myosin II and AIS function, and suggest that myosin II's primary role at the structure may be to effect activity‐dependent morphological alterations.
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Affiliation(s)
- Mark D Evans
- Centre for Developmental Neurobiology, King's College London, London, SE1 1UL, UK
| | - Candida Tufo
- Centre for Developmental Neurobiology, King's College London, London, SE1 1UL, UK
| | - Adna S Dumitrescu
- Centre for Developmental Neurobiology, King's College London, London, SE1 1UL, UK
| | - Matthew S Grubb
- Centre for Developmental Neurobiology, King's College London, London, SE1 1UL, UK.,FENS-Kavli Network of Excellence, Europe-wide
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19
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Recho P, Jerusalem A, Goriely A. Growth, collapse, and stalling in a mechanical model for neurite motility. Phys Rev E 2016; 93:032410. [PMID: 27078393 DOI: 10.1103/physreve.93.032410] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2015] [Indexed: 06/05/2023]
Abstract
Neurites, the long cellular protrusions that form the routes of the neuronal network, are capable of actively extending during early morphogenesis or regenerating after trauma. To perform this task, they rely on their cytoskeleton for mechanical support. In this paper, we present a three-component active gel model that describes neurites in the three robust mechanical states observed experimentally: collapsed, static, and motile. These states arise from an interplay between the physical forces driven by the growth of the microtubule-rich inner core of the neurite and the acto-myosin contractility of its surrounding cortical membrane. In particular, static states appear as a mechanical balance between traction and compression of these two parallel structures. The model predicts how the response of a neurite to a towing force depends on the force magnitude and recovers the response of neurites to several drug treatments that modulate the cytoskeleton active and passive properties.
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Affiliation(s)
- Pierre Recho
- Mathematical Institute, University of Oxford, Oxford OX26GG, United Kingdom
| | - Antoine Jerusalem
- Department of Engineering Science, University of Oxford, Oxford OX13PJ, United Kingdom
| | - Alain Goriely
- Mathematical Institute, University of Oxford, Oxford OX26GG, United Kingdom
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20
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Harada S, Matsuura W, Takano M, Tokuyama S. Withdrawal: Proteomic Profiling in the Spinal Cord and Sciatic Nerve in a Global Cerebral Ischemia-Induced Mechanical Allodynia Mouse Model. Biol Pharm Bull 2016; 39:230-8. [DOI: 10.1248/bpb.b15-00647] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Shinichi Harada
- Department of Clinical Pharmacy, School of Pharmaceutical Sciences, Kobe Gakuin University
| | - Wataru Matsuura
- Department of Clinical Pharmacy, School of Pharmaceutical Sciences, Kobe Gakuin University
| | - Masaoki Takano
- Department of Life Sciences Pharmacy, School of Pharmaceutical Sciences, Kobe Gakuin University
| | - Shogo Tokuyama
- Department of Clinical Pharmacy, School of Pharmaceutical Sciences, Kobe Gakuin University
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21
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Turney SG, Ahmed M, Chandrasekar I, Wysolmerski RB, Goeckeler ZM, Rioux RM, Whitesides GM, Bridgman PC. Nerve growth factor stimulates axon outgrowth through negative regulation of growth cone actomyosin restraint of microtubule advance. Mol Biol Cell 2016; 27:500-17. [PMID: 26631553 PMCID: PMC4751601 DOI: 10.1091/mbc.e15-09-0636] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Revised: 11/23/2015] [Accepted: 11/24/2015] [Indexed: 01/19/2023] Open
Abstract
Nerve growth factor (NGF) promotes growth, differentiation, and survival of sensory neurons in the mammalian nervous system. Little is known about how NGF elicits faster axon outgrowth or how growth cones integrate and transform signal input to motor output. Using cultured mouse dorsal root ganglion neurons, we found that myosin II (MII) is required for NGF to stimulate faster axon outgrowth. From experiments inducing loss or gain of function of MII, specific MII isoforms, and vinculin-dependent adhesion-cytoskeletal coupling, we determined that NGF causes decreased vinculin-dependent actomyosin restraint of microtubule advance. Inhibition of MII blocked NGF stimulation, indicating the central role of restraint in directed outgrowth. The restraint consists of myosin IIB- and IIA-dependent processes: retrograde actin network flow and transverse actin bundling, respectively. The processes differentially contribute on laminin-1 and fibronectin due to selective actin tethering to adhesions. On laminin-1, NGF induced greater vinculin-dependent adhesion-cytoskeletal coupling, which slowed retrograde actin network flow (i.e., it regulated the molecular clutch). On fibronectin, NGF caused inactivation of myosin IIA, which negatively regulated actin bundling. On both substrates, the result was the same: NGF-induced weakening of MII-dependent restraint led to dynamic microtubules entering the actin-rich periphery more frequently, giving rise to faster elongation.
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Affiliation(s)
- Stephen G Turney
- Center for Brain Science and Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138
| | - Mostafa Ahmed
- Department of Neuroscience, Washington University School of Medicine, St. Louis, MO 63110
| | - Indra Chandrasekar
- Department of Neuroscience, Washington University School of Medicine, St. Louis, MO 63110
| | - Robert B Wysolmerski
- Department of Neurobiology and Anatomy, West Virginia University School of Medicine, Morgantown, WV 26506
| | - Zoe M Goeckeler
- Department of Neurobiology and Anatomy, West Virginia University School of Medicine, Morgantown, WV 26506
| | - Robert M Rioux
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138
| | - George M Whitesides
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138
| | - Paul C Bridgman
- Department of Neuroscience, Washington University School of Medicine, St. Louis, MO 63110
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22
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Athamneh AIM, Suter DM. Quantifying mechanical force in axonal growth and guidance. Front Cell Neurosci 2015; 9:359. [PMID: 26441530 PMCID: PMC4584967 DOI: 10.3389/fncel.2015.00359] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Accepted: 08/27/2015] [Indexed: 11/17/2022] Open
Abstract
Mechanical force plays a fundamental role in neuronal development, physiology, and regeneration. In particular, research has shown that force is involved in growth cone-mediated axonal growth and guidance as well as stretch-induced elongation when an organism increases in size after forming initial synaptic connections. However, much of the details about the exact role of force in these fundamental processes remain unknown. In this review, we highlight: (1) standing questions concerning the role of mechanical force in axonal growth and guidance; and (2) different experimental techniques used to quantify forces in axons and growth cones. We believe that satisfying answers to these questions will require quantitative information about the relationship between elongation, forces, cytoskeletal dynamics, axonal transport, signaling, substrate adhesion, and stiffness contributing to directional growth advance. Furthermore, we address why a wide range of force values have been reported in the literature, and what these values mean in the context of neuronal mechanics. We hope that this review will provide a guide for those interested in studying the role of force in development and regeneration of neuronal networks.
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Affiliation(s)
- Ahmad I M Athamneh
- Bindley Bioscience Center, Birck Nanotechnology Center, Department of Biological Sciences, Purdue University West Lafayette, IN, USA
| | - Daniel M Suter
- Bindley Bioscience Center, Birck Nanotechnology Center, Department of Biological Sciences, Purdue University West Lafayette, IN, USA
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23
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Abstract
Neurons are highly polarized cells with structurally and functionally distinct processes called axons and dendrites. This polarization underlies the directional flow of information in the central nervous system, so the establishment and maintenance of neuronal polarization is crucial for correct development and function. Great progress in our understanding of how neurons establish their polarity has been made through the use of cultured hippocampal neurons, while recent technological advances have enabled in vivo analysis of axon specification and elongation. This short review and accompanying poster highlight recent advances in this fascinating field, with an emphasis on the signaling mechanisms underlying axon and dendrite specification in vitro and in vivo.
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Affiliation(s)
- Tetsuya Takano
- Department of Cell Pharmacology, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Chundi Xu
- Department of Cell Pharmacology, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Yasuhiro Funahashi
- Department of Cell Pharmacology, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Takashi Namba
- Department of Cell Pharmacology, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Kozo Kaibuchi
- Department of Cell Pharmacology, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
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24
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Jalilian I, Heu C, Cheng H, Freittag H, Desouza M, Stehn JR, Bryce NS, Whan RM, Hardeman EC, Fath T, Schevzov G, Gunning PW. Cell elasticity is regulated by the tropomyosin isoform composition of the actin cytoskeleton. PLoS One 2015; 10:e0126214. [PMID: 25978408 PMCID: PMC4433179 DOI: 10.1371/journal.pone.0126214] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Accepted: 03/31/2015] [Indexed: 02/07/2023] Open
Abstract
The actin cytoskeleton is the primary polymer system within cells responsible for regulating cellular stiffness. While various actin binding proteins regulate the organization and dynamics of the actin cytoskeleton, the proteins responsible for regulating the mechanical properties of cells are still not fully understood. In the present study, we have addressed the significance of the actin associated protein, tropomyosin (Tpm), in influencing the mechanical properties of cells. Tpms belong to a multi-gene family that form a co-polymer with actin filaments and differentially regulate actin filament stability, function and organization. Tpm isoform expression is highly regulated and together with the ability to sort to specific intracellular sites, result in the generation of distinct Tpm isoform-containing actin filament populations. Nanomechanical measurements conducted with an Atomic Force Microscope using indentation in Peak Force Tapping in indentation/ramping mode, demonstrated that Tpm impacts on cell stiffness and the observed effect occurred in a Tpm isoform-specific manner. Quantitative analysis of the cellular filamentous actin (F-actin) pool conducted both biochemically and with the use of a linear detection algorithm to evaluate actin structures revealed that an altered F-actin pool does not absolutely predict changes in cell stiffness. Inhibition of non-muscle myosin II revealed that intracellular tension generated by myosin II is required for the observed increase in cell stiffness. Lastly, we show that the observed increase in cell stiffness is partially recapitulated in vivo as detected in epididymal fat pads isolated from a Tpm3.1 transgenic mouse line. Together these data are consistent with a role for Tpm in regulating cell stiffness via the generation of specific populations of Tpm isoform-containing actin filaments.
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Affiliation(s)
- Iman Jalilian
- Oncology Research Unit, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia
| | - Celine Heu
- Oncology Research Unit, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia
- Biomedical Imaging facility, UNSW Australia, Sydney, NSW 2052, Australia
| | - Hong Cheng
- Neurodegeneration and Repair Unit, School of Medical Sciences, UNSW Australia, Sydney NSW 2052, Australia
| | - Hannah Freittag
- Neurodegeneration and Repair Unit, School of Medical Sciences, UNSW Australia, Sydney NSW 2052, Australia
| | - Melissa Desouza
- Oncology Research Unit, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia
| | - Justine R. Stehn
- Oncology Research Unit, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia
| | - Nicole S. Bryce
- Oncology Research Unit, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia
| | - Renee M. Whan
- Biomedical Imaging facility, UNSW Australia, Sydney, NSW 2052, Australia
| | - Edna C. Hardeman
- Neuromuscular and Regenerative Medicine Unit, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia
| | - Thomas Fath
- Neurodegeneration and Repair Unit, School of Medical Sciences, UNSW Australia, Sydney NSW 2052, Australia
| | - Galina Schevzov
- Oncology Research Unit, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia
| | - Peter W. Gunning
- Oncology Research Unit, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia
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25
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Abstract
Neurons begin their life as simple spheres, but can ultimately assume an elaborate morphology with numerous, highly arborized dendrites, and long axons. This is achieved via an astounding developmental progression which is dependent upon regulated assembly and dynamics of the cellular cytoskeleton. As neurites emerge out of the soma, neurons break their spherical symmetry and begin to acquire the morphological features that define their structure and function. Neurons regulate their cytoskeleton to achieve changes in cell shape, velocity, and direction as they migrate, extend neurites, and polarize. Of particular importance, the organization and dynamics of actin and microtubules directs the migration and morphogenesis of neurons. This review focuses on the regulation of intrinsic properties of the actin and microtubule cytoskeletons and how specific cytoskeletal structures and dynamics are associated with the earliest phase of neuronal morphogenesis—neuritogenesis.
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26
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Roland AB, Ricobaraza A, Carrel D, Jordan BM, Rico F, Simon A, Humbert-Claude M, Ferrier J, McFadden MH, Scheuring S, Lenkei Z. Cannabinoid-induced actomyosin contractility shapes neuronal morphology and growth. eLife 2014; 3:e03159. [PMID: 25225054 PMCID: PMC4179426 DOI: 10.7554/elife.03159] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Accepted: 09/09/2014] [Indexed: 12/23/2022] Open
Abstract
Endocannabinoids are recently recognized regulators of brain development, but molecular effectors downstream of type-1 cannabinoid receptor (CB1R)-activation remain incompletely understood. We report atypical coupling of neuronal CB1Rs, after activation by endo- or exocannabinoids such as the marijuana component ∆(9)-tetrahydrocannabinol, to heterotrimeric G12/G13 proteins that triggers rapid and reversible non-muscle myosin II (NM II) dependent contraction of the actomyosin cytoskeleton, through a Rho-GTPase and Rho-associated kinase (ROCK). This induces rapid neuronal remodeling, such as retraction of neurites and axonal growth cones, elevated neuronal rigidity, and reshaping of somatodendritic morphology. Chronic pharmacological inhibition of NM II prevents cannabinoid-induced reduction of dendritic development in vitro and leads, similarly to blockade of endocannabinoid action, to excessive growth of corticofugal axons into the sub-ventricular zone in vivo. Our results suggest that CB1R can rapidly transform the neuronal cytoskeleton through actomyosin contractility, resulting in cellular remodeling events ultimately able to affect the brain architecture and wiring.
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Affiliation(s)
- Alexandre B Roland
- Brain Plasticity Unit, ESPCI-ParisTech, CNRS UMR8249, Paris, France
- FAS Center for Systems Biology, Harvard University, Cambridge, United States
| | - Ana Ricobaraza
- Brain Plasticity Unit, ESPCI-ParisTech, CNRS UMR8249, Paris, France
| | - Damien Carrel
- Brain Plasticity Unit, ESPCI-ParisTech, CNRS UMR8249, Paris, France
| | - Benjamin M Jordan
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, United States
| | - Felix Rico
- U1006 INSERM, Aix-Marseille Université, Parc Scientifique et Technologique de Luminy, Marseille, France
| | - Anne Simon
- Brain Plasticity Unit, ESPCI-ParisTech, CNRS UMR8249, Paris, France
| | | | - Jeremy Ferrier
- Brain Plasticity Unit, ESPCI-ParisTech, CNRS UMR8249, Paris, France
| | | | - Simon Scheuring
- U1006 INSERM, Aix-Marseille Université, Parc Scientifique et Technologique de Luminy, Marseille, France
| | - Zsolt Lenkei
- Brain Plasticity Unit, ESPCI-ParisTech, CNRS UMR8249, Paris, France
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27
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Matsumoto Y, Inden M, Tamura A, Hatano R, Tsukita S, Asano S. Ezrin mediates neuritogenesis via down-regulation of RhoA activity in cultured cortical neurons. PLoS One 2014; 9:e105435. [PMID: 25144196 PMCID: PMC4140760 DOI: 10.1371/journal.pone.0105435] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Accepted: 07/18/2014] [Indexed: 01/06/2023] Open
Abstract
Neuronal morphogenesis is implicated in neuronal function and development with rearrangement of cytoskeletal organization. Ezrin, a member of Ezrin/Radixin/Moesin (ERM) proteins links between membrane proteins and actin cytoskeleton, and contributes to maintenance of cellular function and morphology. In cultured hippocampal neurons, suppression of both radixin and moesin showed deficits in growth cone morphology and neurite extensions. Down-regulation of ezrin using siRNA caused impairment of netrin-1-induced axon outgrowth in cultured cortical neurons. However, roles of ezrin in the neuronal morphogenesis of the cultured neurons have been poorly understood. In this report, we performed detailed studies on the roles of ezrin in the cultured cortical neurons prepared from the ezrin knockdown (Vil2kd/kd) mice embryo that showed a very small amount of ezrin expression compared with the wild-type (Vil2+/+) neurons. Ezrin was mainly expressed in cell body in the cultured cortical neurons. We demonstrated that the cultured cortical neurons prepared from the Vil2kd/kd mice embryo exhibited impairment of neuritogenesis. Moreover, we observed increased RhoA activity and phosphorylation of myosin light chain 2 (MLC2), as a downstream effector of RhoA in the Vil2kd/kd neurons. In addition, inhibition of Rho kinase and myosin II rescued the impairment of neuritogenesis in the Vil2kd/kd neurons. These data altogether suggest a novel role of ezrin in the neuritogenesis of the cultured cortical neurons through down-regulation of RhoA activity.
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Affiliation(s)
- Yosuke Matsumoto
- Department of Molecular Physiology, College of Pharmaceutical Sciences, Ritsumeikan University, Kusatsu, Shiga, Japan
| | - Masatoshi Inden
- Laboratory of Medical Therapeutics and Molecular Therapeutics, Gifu Pharmaceutical University, Gifu, Japan
| | - Atsushi Tamura
- Laboratory of Biological Science, Graduate School of Frontier Biosciences and Graduate School of Medicine, Osaka University, Suita, Osaka, Japan
| | - Ryo Hatano
- Department of Molecular Physiology, College of Pharmaceutical Sciences, Ritsumeikan University, Kusatsu, Shiga, Japan
| | - Sachiko Tsukita
- Laboratory of Biological Science, Graduate School of Frontier Biosciences and Graduate School of Medicine, Osaka University, Suita, Osaka, Japan
| | - Shinji Asano
- Department of Molecular Physiology, College of Pharmaceutical Sciences, Ritsumeikan University, Kusatsu, Shiga, Japan
- * E-mail:
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Cytoskeletal and signaling mechanisms of neurite formation. Cell Tissue Res 2014; 359:267-78. [PMID: 25080065 DOI: 10.1007/s00441-014-1955-0] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Accepted: 07/01/2014] [Indexed: 10/25/2022]
Abstract
The formation of a neurite, the basis for axons and dendrites, begins with the concerted accumulation and organization of actin and microtubules. Whereas much is known about the proteins that play a role in these processes, because they perform similar functions in axon branching and filopodia formation, much remains to be discovered concerning the interaction of these individual cytoskeletal regulators during neurite formation. Here, we review the literature regarding various models of filopodial formation and the way in which proteins that control actin organization and polymerization induce neurite formation. Although several different regulators of actin polymerization are involved in neurite initiation, redundancy occurs between these regulators, as the effects of the loss of a single regulator can be mitigated by the addition of neurite-promoting substrates and proteins. Similar to actin dynamics, both microtubule stabilizing and destabilizing proteins play a role in neurite initiation. Furthermore, interactions between the actin and microtubule cytoskeleton are required for neurite formation. Several lines of evidence indicate that the interactions between these two components of the cytoskeleton are needed for force generation and for the localization of microtubules at sites of nascent neurites. The general theme that emerges is the existence of several central regulatory pathways on which extracellular cues converge to control and organize both actin and microtubules to induce the formation of neurites.
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Ferraz-Nogueira JP, Díez-Guerra FJ, Llopis J. Visualization of phosphatidic acid fluctuations in the plasma membrane of living cells. PLoS One 2014; 9:e102526. [PMID: 25025521 PMCID: PMC4099201 DOI: 10.1371/journal.pone.0102526] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2014] [Accepted: 06/18/2014] [Indexed: 11/19/2022] Open
Abstract
We developed genetically-encoded fluorescent sensors based on Förster Resonance Energy Transfer to monitor phosphatidic acid (PA) fluctuations in the plasma membrane using Spo20 as PA-binding motif. Basal PA levels and phospholipase D activity varied in different cell types. In addition, stimuli that activate PA phosphatases, leading to lower PA levels, increased lamellipodia and filopodia formation. Lower PA levels were observed in the leading edge than in the trailing edge of migrating HeLa cells. In MSC80 and OLN93 cells, which are stable cell lines derived from Schwann cells and oligodendrocytes, respectively, a higher ratio of diacylglycerol to PA levels was demonstrated in the membrane processes involved in myelination, compared to the cell body. We propose that the PA sensors reported here are valuable tools to unveil the role of PA in a variety of intracellular signaling pathways.
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Affiliation(s)
- José P. Ferraz-Nogueira
- Centro Regional de Investigaciones Biomédicas and Facultad de Medicina de Albacete, Universidad de Castilla-La Mancha, Albacete, Spain,
| | - F. Javier Díez-Guerra
- Centro de Biología Molecular Severo Ochoa and Departamento de Biología Molecular, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Spain
| | - Juan Llopis
- Centro Regional de Investigaciones Biomédicas and Facultad de Medicina de Albacete, Universidad de Castilla-La Mancha, Albacete, Spain,
- * E-mail:
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30
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Sur S, Newcomb CJ, Webber MJ, Stupp SI. Tuning supramolecular mechanics to guide neuron development. Biomaterials 2013; 34:4749-57. [PMID: 23562052 PMCID: PMC3635952 DOI: 10.1016/j.biomaterials.2013.03.025] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Accepted: 03/10/2013] [Indexed: 12/30/2022]
Abstract
The mechanical properties of the extracellular matrix (ECM) are known to influence neuronal differentiation and maturation, though the mechanism by which neuronal cells respond to these biophysical cues is not completely understood. Here we design ECM mimics using self-assembled peptide nanofibers, in which fiber rigidity is tailored by supramolecular interactions, in order to investigate the relationship between matrix stiffness and morphological development of hippocampal neurons. We observe that development of neuronal polarity is accelerated on soft nanofiber substrates, and results from the dynamics of neuronal processes. While the total neurite outgrowth of non-polar neurons remains conserved, weaker adhesion of neurites to soft PA substrate facilitates easier retraction, thus enhancing the frequency of "extension-retraction" events. We hypothesize that higher neurite motility enhances the probability of one neurite to reach a critical length relative to others, thereby initiating the developmental sequence of axon differentiation. Our results suggest that substrate stiffness can influence neuronal development by regulating its dynamics, thus providing useful information on scaffold design for applications in neural regeneration.
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Affiliation(s)
- Shantanu Sur
- The Institute for BioNanotechnology in Medicine, Northwestern University, Chicago, IL, 60611
| | - Christina J. Newcomb
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208
| | - Matthew J. Webber
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, 60208
| | - Samuel I. Stupp
- The Institute for BioNanotechnology in Medicine, Northwestern University, Chicago, IL, 60611
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208
- Department of Chemistry, Northwestern University, Evanston, IL, 60208
- Department of Medicine, Northwestern University, Chicago, IL, 60611
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Albus CA, Rishal I, Fainzilber M. Cell length sensing for neuronal growth control. Trends Cell Biol 2013; 23:305-10. [PMID: 23511112 DOI: 10.1016/j.tcb.2013.02.001] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Revised: 02/03/2013] [Accepted: 02/11/2013] [Indexed: 11/27/2022]
Abstract
Neurons exhibit great size differences, and must coordinate biosynthesis rates in cell bodies with the growth needs of different lengths of axons. Classically, axon growth has been viewed mainly as a consequence of extrinsic influences. However, recent publications have proposed at least two different intrinsic axon growth-control mechanisms. We suggest that these mechanisms form part of a continuum of axon growth-control mechanisms, wherein initial growth rates are pre-programmed by transcription factor levels, and subsequent elongating growth is dependent on feedback from intrinsic length-sensing enabled by bidirectional motor-dependent oscillating signals. This model might explain intrinsic limits on elongating neuronal growth and provides a mechanistic framework for determining the connections between genome expression and cellular growth rates in neurons.
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Affiliation(s)
- Christin A Albus
- Department of Biological Chemistry, Weizmann Institute of Science, 76100 Rehovot, Israel
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Rishal I, Kam N, Perry RBT, Shinder V, Fisher EMC, Schiavo G, Fainzilber M. A motor-driven mechanism for cell-length sensing. Cell Rep 2013; 1:608-16. [PMID: 22773964 PMCID: PMC3389498 DOI: 10.1016/j.celrep.2012.05.013] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Size homeostasis is fundamental in cell biology, but it is not clear how large cells such as neurons can assess their own size or length. We examined a role for molecular motors in intracellular length sensing. Computational simulations suggest that spatial information can be encoded by the frequency of an oscillating retrograde signal arising from a composite negative feedback loop between bidirectional motor-dependent signals. The model predicts that decreasing either or both anterograde or retrograde signals should increase cell length, and this prediction was confirmed upon application of siRNAs for specific kinesin and/or dynein heavy chains in adult sensory neurons. Heterozygous dynein heavy chain 1 mutant sensory neurons also exhibited increased lengths both in vitro and during embryonic development. Moreover, similar length increases were observed in mouse embryonic fibroblasts upon partial downregulation of dynein heavy chain 1. Thus, molecular motors critically influence cell-length sensing and growth control.
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Affiliation(s)
- Ida Rishal
- Department of Biological Chemistry, Weizmann Institute of Science, 76100 Rehovot, Israel
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33
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Gallo G. Mechanisms underlying the initiation and dynamics of neuronal filopodia: from neurite formation to synaptogenesis. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2013; 301:95-156. [PMID: 23317818 DOI: 10.1016/b978-0-12-407704-1.00003-8] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Filopodia are finger-like cellular protrusions found throughout the metazoan kingdom and perform fundamental cellular functions during development and cell migration. Neurons exhibit a wide variety of extremely complex morphologies. In the nervous system, filopodia underlie many major morphogenetic events. Filopodia have roles spanning the initiation and guidance of neuronal processes, axons and dendrites to the formation of synaptic connections. This chapter addresses the mechanisms of the formation and dynamics of neuronal filopodia. Some of the major lessons learned from the study of neuronal filopodia are (1) there are multiple mechanisms that can regulate filopodia in a context-dependent manner, (2) that filopodia are specialized subcellular domains, (3) that filopodia exhibit dynamic membrane recycling which also controls aspects of filopodial dynamics, (4) that neuronal filopodia contain machinery for the orchestration of the actin and microtubule cytoskeleton, and (5) localized protein synthesis contributes to neuronal filopodial dynamics.
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Affiliation(s)
- Gianluca Gallo
- Shriners Hospitals Pediatric Research Center, Center for Neural Repair and Rehabilitation, Department of Anatomy and Cell Biology, Temple University, Philadelphia, PA, USA.
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34
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Plosa EJ, Gooding KA, Zent R, Prince LS. Nonmuscle myosin II regulation of lung epithelial morphology. Dev Dyn 2012; 241:1770-81. [PMID: 22972683 DOI: 10.1002/dvdy.23866] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/28/2012] [Indexed: 11/07/2022] Open
Abstract
BACKGROUND The regulation of epithelial cell shape and orientation during lung branching morphogenesis is not clearly understood. Nonmuscle myosins regulate cell size, morphology, and planar cell polarity. Here, we test the hypothesis that nonmuscle myosin II (NM II) regulates lung epithelial morphology in a spatially restricted manner. RESULTS Epithelial cell orientation at airway tips in fetal mouse lungs underwent a significant transformation at embryonic day (E) E17. Treatment of E15 lung explants with the NM II inhibitor blebbistatin increased airway branching, epithelial cell size, and the degree of anisotropy in epithelial cells lining the airway stalks. In cultured MLE-12 lung epithelial cells, blebbistatin increased cell velocity, but left the migratory response to FGF-10 unchanged. CONCLUSIONS In the developing lung, NM II acts to constrain cell morphology and orientation, but may be suppressed at sites of branching and cell migration. The regulation of epithelial orientation may therefore undergo dynamic variations from E15 to E17.
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Affiliation(s)
- Erin J Plosa
- Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
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35
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Greif KF, Asabere N, Lutz GJ, Gallo G. Synaptotagmin-1 promotes the formation of axonal filopodia and branches along the developing axons of forebrain neurons. Dev Neurobiol 2012; 73:27-44. [PMID: 22589224 DOI: 10.1002/dneu.22033] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2012] [Revised: 04/29/2012] [Accepted: 05/08/2012] [Indexed: 01/01/2023]
Abstract
Synaptotagmin-1 (syt1) is a Ca(2+)-binding protein that functions in regulation of synaptic vesicle exocytosis at the synapse. Syt1 is expressed in many types of neurons well before synaptogenesis begins both in vivo and in vitro. To determine if expression of syt1 has a functional role in neuronal development before synapse formation, we examined the effects of syt1 overexpression and knockdown on the growth and branching of the axons of cultured primary embryonic day 8 chicken forebrain neurons. In vivo these neurons express syt1, and most have not yet extended axons. We present evidence that syt1 plays a role in regulating axon branching, while not regulating overall axon length. To study the effects of overexpression of syt1, we used adenovirus-mediated infection to introduce a syt1-YFP construct, or control GFP construct, into neurons. Syt1 levels were reduced using RNA interference. Overexpression of syt1 increased the formation of axonal filopodia and branches. Conversely, knockdown of syt1 decreased the number of axonal filopodia and branches. Time-lapse analysis of filopodial dynamics in syt1-overexpressing cells demonstrated that elevation of syt1 levels increased both the frequency of filopodial initiation and their lifespan. Taken together these data indicate that syt1 regulates the formation of axonal filopodia and branches before engaging in its conventional functions at the synapse.
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Affiliation(s)
- Karen F Greif
- Department of Biology, Bryn Mawr College, Bryn Mawr, Pennsylvania 19010, USA.
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36
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Yu H, Wang N, Ju X, Yang Y, Sun D, Lai M, Cui L, Sheikh MA, Zhang J, Wang X, Zhu X. PtdIns (3,4,5) P3 recruitment of Myo10 is essential for axon development. PLoS One 2012; 7:e36988. [PMID: 22590642 PMCID: PMC3349655 DOI: 10.1371/journal.pone.0036988] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2012] [Accepted: 04/11/2012] [Indexed: 02/03/2023] Open
Abstract
Myosin X (Myo10) with pleckstrin homology (PH) domains is a motor protein acting in filopodium initiation and extension. However, its potential role has not been fully understood, especially in neuronal development. In the present study the preferential accumulation of Myo10 in axon tips has been revealed in primary culture of hippocampal neurons with the aid of immunofluorescence from anti-Myo10 antibody in combination with anti-Tuj1 antibody as specific marker. Knocking down Myo10 gene transcription impaired outgrowth of axon with loss of Tau-1-positive phenotype. Interestingly, inhibition of actin polymerization by cytochalasin D rescued the defect of axon outgrowth. Furthermore, ectopic expression of Myo10 with enhanced green fluorescence protein (EGFP) labeled Myo10 mutants induced multiple axon-like neurites in a motor-independent way. Mechanism studies demonstrated that the recruitment of Myo10 through its PH domain to phosphatidylinositol (3,4,5)-trisphosphate (PtdIns (3,4,5) P3) was essential for axon formation. In addition, in vivo studies confirmed that Myo10 was required for neuronal morphological transition during radial neuronal migration in the developmental neocortex.
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Affiliation(s)
- Huali Yu
- Key Laboratory of Molecular Epigenetics of Ministry of Education, Institute of Cytology and Genetics, Northeast Normal University, Changchun, China
| | - Nannan Wang
- Key Laboratory of Molecular Epigenetics of Ministry of Education, Institute of Cytology and Genetics, Northeast Normal University, Changchun, China
| | - Xingda Ju
- Key Laboratory of Molecular Epigenetics of Ministry of Education, Institute of Cytology and Genetics, Northeast Normal University, Changchun, China
| | - Yan Yang
- Key Laboratory of Molecular Epigenetics of Ministry of Education, Institute of Cytology and Genetics, Northeast Normal University, Changchun, China
| | - Dong Sun
- Key Laboratory of Molecular Epigenetics of Ministry of Education, Institute of Cytology and Genetics, Northeast Normal University, Changchun, China
| | - Mingming Lai
- Key Laboratory of Molecular Epigenetics of Ministry of Education, Institute of Cytology and Genetics, Northeast Normal University, Changchun, China
| | - Lei Cui
- Key Laboratory of Molecular Epigenetics of Ministry of Education, Institute of Cytology and Genetics, Northeast Normal University, Changchun, China
| | - Muhammad Abid Sheikh
- Key Laboratory of Molecular Epigenetics of Ministry of Education, Institute of Cytology and Genetics, Northeast Normal University, Changchun, China
| | - Jianhua Zhang
- Key Laboratory of Molecular Epigenetics of Ministry of Education, Institute of Cytology and Genetics, Northeast Normal University, Changchun, China
| | - Xingzhi Wang
- Key Laboratory of Molecular Epigenetics of Ministry of Education, Institute of Cytology and Genetics, Northeast Normal University, Changchun, China
| | - Xiaojuan Zhu
- Key Laboratory of Molecular Epigenetics of Ministry of Education, Institute of Cytology and Genetics, Northeast Normal University, Changchun, China
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Abstract
During development, axons are guided to their appropriate targets by a variety of guidance factors. On arriving at their synaptic targets, or while en route, axons form branches. Branches generated de novo from the main axon are termed collateral branches. The generation of axon collateral branches allows individual neurons to make contacts with multiple neurons within a target and with multiple targets. In the adult nervous system, the formation of axon collateral branches is associated with injury and disease states and may contribute to normally occurring plasticity. Collateral branches are initiated by actin filament– based axonal protrusions that subsequently become invaded by microtubules, thereby allowing the branch to mature and continue extending. This article reviews the current knowledge of the cellular mechanisms of the formation of axon collateral branches. The major conclusions of this review are (1) the mechanisms of axon extension and branching are not identical; (2) active suppression of protrusive activity along the axon negatively regulates branching; (3) the earliest steps in the formation of axon branches involve focal activation of signaling pathways within axons, which in turn drive the formation of actin-based protrusions; and (4) regulation of the microtubule array by microtubule-associated and severing proteins underlies the development of branches. Linking the activation of signaling pathways to specific proteins that directly regulate the axonal cytoskeleton underlying the formation of collateral branches remains a frontier in the field.
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Affiliation(s)
- Gianluca Gallo
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, 2900 Queen Lane, Philadelphia, Pennsylvania 19129, USA.
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38
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Neukirchen D, Bradke F. Neuronal polarization and the cytoskeleton. Semin Cell Dev Biol 2011; 22:825-33. [DOI: 10.1016/j.semcdb.2011.08.007] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2011] [Revised: 07/29/2011] [Accepted: 08/16/2011] [Indexed: 12/26/2022]
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40
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Suter DM, Miller KE. The emerging role of forces in axonal elongation. Prog Neurobiol 2011; 94:91-101. [PMID: 21527310 DOI: 10.1016/j.pneurobio.2011.04.002] [Citation(s) in RCA: 171] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2010] [Revised: 03/18/2011] [Accepted: 04/06/2011] [Indexed: 11/26/2022]
Abstract
An understanding of how axons elongate is needed to develop rational strategies to treat neurological diseases and nerve injury. Growth cone-mediated neuronal elongation is currently viewed as occurring through cytoskeletal dynamics involving the polymerization of actin and tubulin subunits at the tip of the axon. However, recent work suggests that axons and growth cones also generate forces (through cytoskeletal dynamics, kinesin, dynein, and myosin), forces induce axonal elongation, and axons lengthen by stretching. This review highlights results from various model systems (Drosophila, Aplysia, Xenopus, chicken, mouse, rat, and PC12 cells), supporting a role for forces, bulk microtubule movements, and intercalated mass addition in the process of axonal elongation. We think that a satisfying answer to the question, "How do axons grow?" will come by integrating the best aspects of biophysics, genetics, and cell biology.
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Affiliation(s)
- Daniel M Suter
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907-2054, United States.
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41
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AMP-activated protein kinase (AMPK) activity is not required for neuronal development but regulates axogenesis during metabolic stress. Proc Natl Acad Sci U S A 2011; 108:5849-54. [PMID: 21436046 DOI: 10.1073/pnas.1013660108] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Mammalian brain connectivity requires the coordinated production and migration of billions of neurons and the formation of axons and dendrites. The LKB1/Par4 kinase is required for axon formation during cortical development in vivo partially through its ability to activate SAD-A/B kinases. LKB1 is a master kinase phosphorylating and activating at least 11 other serine/threonine kinases including the metabolic sensor AMP-activated protein kinase (AMPK), which defines this branch of the kinome. A recent study using a gene-trap allele of the β1 regulatory subunit of AMPK suggested that AMPK catalytic activity is required for proper brain development including neurogenesis and neuronal survival. We used a genetic loss-of-function approach producing AMPKα1/α2-null cortical neurons to demonstrate that AMPK catalytic activity is not required for cortical neurogenesis, neuronal migration, polarization, or survival. However, we found that application of metformin or AICAR, potent AMPK activators, inhibit axogenesis and axon growth in an AMPK-dependent manner. We show that inhibition of axon growth mediated by AMPK overactivation requires TSC1/2-mediated inhibition of the mammalian target of rapamycin (mTOR) signaling pathway. Our results demonstrate that AMPK catalytic activity is not required for early neural development in vivo but its overactivation during metabolic stress impairs neuronal polarization in a mTOR-dependent manner.
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42
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Myers KA, Applegate KT, Danuser G, Fischer RS, Waterman CM. Distinct ECM mechanosensing pathways regulate microtubule dynamics to control endothelial cell branching morphogenesis. ACTA ACUST UNITED AC 2011; 192:321-34. [PMID: 21263030 PMCID: PMC3172168 DOI: 10.1083/jcb.201006009] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The compliance and dimensionality of the ECM regulate distinct changes in microtubule growth speed and growth persistence. During angiogenesis, cytoskeletal dynamics that mediate endothelial cell branching morphogenesis during vascular guidance are thought to be regulated by physical attributes of the extracellular matrix (ECM) in a process termed mechanosensing. Here, we tested the involvement of microtubules in linking mechanosensing to endothelial cell branching morphogenesis. We used a recently developed microtubule plus end–tracking program to show that specific parameters of microtubule assembly dynamics, growth speed and growth persistence, are globally and regionally modified by, and contribute to, ECM mechanosensing. We demonstrated that engagement of compliant two-dimensional or three-dimensional ECMs induces local differences in microtubule growth speed that require myosin II contractility. Finally, we found that microtubule growth persistence is modulated by myosin II–mediated compliance mechanosensing when cells are cultured on two-dimensional ECMs, whereas three-dimensional ECM engagement makes microtubule growth persistence insensitive to changes in ECM compliance. Thus, compliance and dimensionality ECM mechanosensing pathways independently regulate specific and distinct microtubule dynamics parameters in endothelial cells to guide branching morphogenesis in physically complex ECMs.
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Affiliation(s)
- Kenneth A Myers
- Cell Biology and Physiology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
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43
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Abstract
The assembly of functional neuronal networks in the developing animal relies on the polarization of neurons, i.e., the formation of a single axon and multiple dendrites. Breaking the symmetry of neurons depends on cytoskeletal rearrangements. In particular, axon specification requires local dynamic instability of actin and stabilization of microtubules. The polarized cytoskeleton also provides the basis for selective trafficking and retention of cellular components in the future somatodendritic or axonal compartments. Hence, these mechanisms are not only essential to achieve neuronal polarization, but also to maintain it. Different extracellular and intracellular signals converge on the regulation of the cytoskeleton. Most notably, Rho GTPases, PI3K, Ena/VASP, cofilin and SAD kinases are major intracellular regulators of neuronal polarity. Analyzing polarity signals under physiological conditions will provide a better understanding of how neurons can be induced to repolarize under pathological conditions, i.e., to regenerate their axons after central nervous system (CNS) injury.
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Affiliation(s)
- Sabina Tahirovic
- Max Planck Institute of Neurobiology, Axonal Growth and Regeneration, Am Klopferspitz 18, 82152 Martinsried, Germany
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44
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Bridgman PC. Myosin motor proteins in the cell biology of axons and other neuronal compartments. Results Probl Cell Differ 2010; 48:91-105. [PMID: 19554282 DOI: 10.1007/400_2009_10] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Most neurons of both the central and peripheral nervous systems express multiple members of the myosin superfamily that include nonmuscle myosin II, and a number of classes of unconventional myosins. Several classes of unconventional myosins found in neurons have been shown to play important roles in transport processes. A general picture of the myosin-dependent transport processes in neurons is beginning to emerge, although much more work still needs to be done to fully define these roles and establish the importance of myosin for axonal transport. Myosins appear to contribute to three types of transport processes in neurons; recycling of receptors or other membrane components, dynamic tethering of vesicular components, and transport or tethering of protein translational machinery including mRNA. Defects in one or more of these functions have potential to contribute to disease processes.
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Affiliation(s)
- Paul C Bridgman
- Department of Anatomy and Neurobiology, Box 8108, Washington University School of Medicine, 660 Euclid Avenue, St. Louis, MO 63110, USA.
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45
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Seabrooke S, Qiu X, Stewart BA. Nonmuscle Myosin II helps regulate synaptic vesicle mobility at the Drosophila neuromuscular junction. BMC Neurosci 2010; 11:37. [PMID: 20233422 PMCID: PMC2853426 DOI: 10.1186/1471-2202-11-37] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2009] [Accepted: 03/16/2010] [Indexed: 11/22/2022] Open
Abstract
Background Although the mechanistic details of the vesicle transport process from the cell body to the nerve terminal are well described, the mechanisms underlying vesicle traffic within nerve terminal boutons is relatively unknown. The actin cytoskeleton has been implicated but exactly how actin or actin-binding proteins participate in vesicle movement is not clear. Results In the present study we have identified Nonmuscle Myosin II as a candidate molecule important for synaptic vesicle traffic within Drosophila larval neuromuscular boutons. Nonmuscle Myosin II was found to be localized at the Drosophila larval neuromuscular junction; genetics and pharmacology combined with the time-lapse imaging technique FRAP were used to reveal a contribution of Nonmuscle Myosin II to synaptic vesicle movement. FRAP analysis showed that vesicle dynamics were highly dependent on the expression level of Nonmuscle Myosin II. Conclusion Our results provide evidence that Nonmuscle Myosin II is present presynaptically, is important for synaptic vesicle mobility and suggests a role for Nonmuscle Myosin II in shuttling vesicles at the Drosophila neuromuscular junction. This work begins to reveal the process by which synaptic vesicles traverse within the bouton.
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Affiliation(s)
- Sara Seabrooke
- Department of Biology, University of Toronto, Mississauga, ON L5L 1C6, Canada
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46
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Jiang XS, Wassif CA, Backlund PS, Song L, Holtzclaw LA, Li Z, Yergey AL, Porter FD. Activation of Rho GTPases in Smith-Lemli-Opitz syndrome: pathophysiological and clinical implications. Hum Mol Genet 2010; 19:1347-57. [PMID: 20067919 DOI: 10.1093/hmg/ddq011] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Smith-Lemli-Opitz syndrome (SLOS) is a malformation syndrome with neurocognitive deficits due to mutations of DHCR7 that impair the reduction of 7-dehydrocholesterol to cholesterol. To investigate the pathological processes underlying the neurocognitive deficits, we compared protein expression in Dhcr7(+/+) and Dhcr7(Delta3-5/Delta3-5) brain tissue. One of the proteins identified was cofilin-1, an actin depolymerizing factor which regulates neuronal dendrite and axon formation. Differential expression of cofilin-1 was due to increased phosphorylation. Phosphorylation of cofilin-1 is regulated by Rho GTPases through Rho-Rock-Limk-Cofilin-1 and Rac/Cdc42-Pak-Limk-Cofilin-1 pathways. Pull-down assays were used to demonstrate increased activation of RhoA, Rac1 and Cdc42 in Dhcr7(Delta3-5/Delta3-5) brains. Consistent with increased activation of these Rho GTPases, we observed increased phosphorylation of both Limk and Pak in mutant brain tissue. Altered Rho/Rac signaling impairs normal dendritic and axonal formation, and mutations in genes encoding regulators and effectors of the Rho GTPases underlie other human mental retardation syndromes. Thus, we hypothesized that aberrant activation of Rho/Rac could have functional consequences for dendrite and axonal growth. In vitro analysis of Dhcr7(Delta3-5/Delta3-5) hippocampal neurons demonstrated both axonal and dendritic abnormalities. Developmental abnormalities of neuronal process formation may contribute to the neurocognitive deficits found in SLOS and may represent a potential target for therapeutic intervention.
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Affiliation(s)
- Xiao-Sheng Jiang
- Section on Molecular Dysmorphology, Program in Developmental Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health, National Institutes of Health, Bethesda, MD 20892, USA
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47
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Abstract
Actin filaments are thin polymers of the 42 kD protein actin. In mature axons a network of subaxolemmal actin filaments provide stability for membrane integrity and a substrate for short distance transport of cargos. In developing neurons dynamic regulation of actin polymerization and organization mediates axonal morphogenesis and axonal pathfinding to synaptic targets. Other changes in axonal shape, collateral branching, branch retraction, and axonal regeneration, also depend on actin filament dynamics. Actin filament organization is regulated by a diversity of actin-binding proteins (ABP). ABP are the focus of complex extrinsic and intrinsic signaling pathways, and many neurological pathologies and dysfunctions arise from defective regulation of ABP function.
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Affiliation(s)
- Paul C Letourneau
- Department of Neuroscience, 6-145 Jackson Hall, University of Minnesota, Minneapolis, MN 55455, USA.
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