1
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Gallo G. The Axonal Actin Filament Cytoskeleton: Structure, Function, and Relevance to Injury and Degeneration. Mol Neurobiol 2024:10.1007/s12035-023-03879-7. [PMID: 38216856 DOI: 10.1007/s12035-023-03879-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Accepted: 12/13/2023] [Indexed: 01/14/2024]
Abstract
Early investigations of the neuronal actin filament cytoskeleton gave rise to the notion that, although growth cones exhibit high levels of actin filaments, the axon shaft exhibits low levels of actin filaments. With the development of new tools and imaging techniques, the axonal actin filament cytoskeleton has undergone a renaissance and is now an active field of research. This article reviews the current state of knowledge about the actin cytoskeleton of the axon shaft. The best understood forms of actin filament organization along axons are axonal actin patches and a submembranous system of rings that endow the axon with protrusive competency and structural integrity, respectively. Additional forms of actin filament organization along the axon have also been described and their roles are being elucidated. Extracellular signals regulate the axonal actin filament cytoskeleton and our understanding of the signaling mechanisms involved is being elaborated. Finally, recent years have seen advances in our perspective on how the axonal actin cytoskeleton is impacted by, and contributes to, axon injury and degeneration. The work to date has opened new venues and future research will undoubtedly continue to provide a richer understanding of the axonal actin filament cytoskeleton.
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Affiliation(s)
- Gianluca Gallo
- Department of Neural Sciences, Shriners Pediatric Research Center, Lewis Katz School of Medicine at Temple University, 3500 North Broad St, Philadelphia, PA, 19140, USA.
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2
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Smith G, Sweeney ST, O’Kane CJ, Prokop A. How neurons maintain their axons long-term: an integrated view of axon biology and pathology. Front Neurosci 2023; 17:1236815. [PMID: 37564364 PMCID: PMC10410161 DOI: 10.3389/fnins.2023.1236815] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Accepted: 07/06/2023] [Indexed: 08/12/2023] Open
Abstract
Axons are processes of neurons, up to a metre long, that form the essential biological cables wiring nervous systems. They must survive, often far away from their cell bodies and up to a century in humans. This requires self-sufficient cell biology including structural proteins, organelles, and membrane trafficking, metabolic, signalling, translational, chaperone, and degradation machinery-all maintaining the homeostasis of energy, lipids, proteins, and signalling networks including reactive oxygen species and calcium. Axon maintenance also involves specialised cytoskeleton including the cortical actin-spectrin corset, and bundles of microtubules that provide the highways for motor-driven transport of components and organelles for virtually all the above-mentioned processes. Here, we aim to provide a conceptual overview of key aspects of axon biology and physiology, and the homeostatic networks they form. This homeostasis can be derailed, causing axonopathies through processes of ageing, trauma, poisoning, inflammation or genetic mutations. To illustrate which malfunctions of organelles or cell biological processes can lead to axonopathies, we focus on axonopathy-linked subcellular defects caused by genetic mutations. Based on these descriptions and backed up by our comprehensive data mining of genes linked to neural disorders, we describe the 'dependency cycle of local axon homeostasis' as an integrative model to explain why very different causes can trigger very similar axonopathies, providing new ideas that can drive the quest for strategies able to battle these devastating diseases.
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Affiliation(s)
- Gaynor Smith
- Cardiff University, School of Medicine, College of Biomedical and Life Sciences, Cardiff, United Kingdom
| | - Sean T. Sweeney
- Department of Biology, University of York and York Biomedical Research Institute, York, United Kingdom
| | - Cahir J. O’Kane
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Andreas Prokop
- Manchester Academic Health Science Centre, Faculty of Biology, Medicine and Health, School of Biology, The University of Manchester, Manchester, United Kingdom
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3
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Alfadil E, Bradke F. Moving through the crowd. Where are we at understanding physiological axon growth? Semin Cell Dev Biol 2023; 140:63-71. [PMID: 35817655 DOI: 10.1016/j.semcdb.2022.07.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Revised: 07/01/2022] [Accepted: 07/04/2022] [Indexed: 01/28/2023]
Abstract
Axon growth enables the rapid wiring of the central nervous system. Understanding this process is a prerequisite to retriggering it under pathological conditions, such as a spinal cord injury, to elicit axon regeneration. The last decades saw progress in understanding the mechanisms underlying axon growth. Most of these studies employed cultured neurons grown on flat surfaces. Only recently studies on axon growth were performed in 3D. In these studies, physiological environments exposed more complex and dynamic aspects of axon development. Here, we describe current views on axon growth and highlight gaps in our knowledge. We discuss how axons interact with the extracellular matrix during development and the role of the growth cone and its cytoskeleton within. Finally, we propose that the time is ripe to study axon growth in a more physiological setting. This will help us uncover the physiologically relevant mechanisms underlying axon growth, and how they can be reactivated to induce axon regeneration.
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Affiliation(s)
- Eissa Alfadil
- Laboratory of Axon Growth and Regeneration, Deutsches Zentrum für Neurodegenerative Erkrankungen (DZNE), Venusberg-Campus 1, Building 99, 53127, Bonn, Germany.
| | - Frank Bradke
- Laboratory of Axon Growth and Regeneration, Deutsches Zentrum für Neurodegenerative Erkrankungen (DZNE), Venusberg-Campus 1, Building 99, 53127, Bonn, Germany
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4
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Cakir Z, Lord SJ, Zhou Y, Jang GM, Polacco BJ, Eckhardt M, Jimenez-Morales D, Newton BW, Orr AL, Johnson JR, da Cruz A, Mullins RD, Krogan NJ, Mahley RW, Swaney DL. Quantitative Proteomic Analysis Reveals apoE4-Dependent Phosphorylation of the Actin-Regulating Protein VASP. Mol Cell Proteomics 2023; 22:100541. [PMID: 37019383 PMCID: PMC10196575 DOI: 10.1016/j.mcpro.2023.100541] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Revised: 02/03/2023] [Accepted: 03/24/2023] [Indexed: 04/05/2023] Open
Abstract
Apolipoprotein (apo) E4 is the major genetic risk factor for Alzheimer's disease. While neurons generally produce a minority of the apoE in the central nervous system, neuronal expression of apoE increases dramatically in response to stress and is sufficient to drive pathology. Currently, the molecular mechanisms of how apoE4 expression may regulate pathology are not fully understood. Here, we expand upon our previous studies measuring the impact of apoE4 on protein abundance to include the analysis of protein phosphorylation and ubiquitylation signaling in isogenic Neuro-2a cells expressing apoE3 or apoE4. ApoE4 expression resulted in a dramatic increase in vasodilator-stimulated phosphoprotein (VASP) S235 phosphorylation in a protein kinase A (PKA)-dependent manner. This phosphorylation disrupted VASP interactions with numerous actin cytoskeletal and microtubular proteins. Reduction of VASP S235 phosphorylation via PKA inhibition resulted in a significant increase in filopodia formation and neurite outgrowth in apoE4-expressing cells, exceeding levels observed in apoE3-expressing cells. Our results highlight the pronounced and diverse impact of apoE4 on multiple modes of protein regulation and identify protein targets to restore apoE4-related cytoskeletal defects.
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Affiliation(s)
- Zeynep Cakir
- Quantitative Biosciences Institute (QBI), University of California San Francisco, San Francisco, California, USA; Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, California, USA; Gladstone Institute of Data Science and Biotechnology, Gladstone Institutes, San Francisco, California, USA
| | - Samuel J Lord
- Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, California, USA; Howard Hughes Medical Institute, San Francisco, California, USA
| | - Yuan Zhou
- Quantitative Biosciences Institute (QBI), University of California San Francisco, San Francisco, California, USA; Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, California, USA; Gladstone Institute of Data Science and Biotechnology, Gladstone Institutes, San Francisco, California, USA
| | - Gwendolyn M Jang
- Quantitative Biosciences Institute (QBI), University of California San Francisco, San Francisco, California, USA; Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, California, USA; Gladstone Institute of Data Science and Biotechnology, Gladstone Institutes, San Francisco, California, USA
| | - Benjamin J Polacco
- Quantitative Biosciences Institute (QBI), University of California San Francisco, San Francisco, California, USA; Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, California, USA; Gladstone Institute of Data Science and Biotechnology, Gladstone Institutes, San Francisco, California, USA
| | - Manon Eckhardt
- Quantitative Biosciences Institute (QBI), University of California San Francisco, San Francisco, California, USA; Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, California, USA; Gladstone Institute of Data Science and Biotechnology, Gladstone Institutes, San Francisco, California, USA
| | - David Jimenez-Morales
- Quantitative Biosciences Institute (QBI), University of California San Francisco, San Francisco, California, USA; Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, California, USA; Gladstone Institute of Data Science and Biotechnology, Gladstone Institutes, San Francisco, California, USA
| | - Billy W Newton
- Quantitative Biosciences Institute (QBI), University of California San Francisco, San Francisco, California, USA; Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, California, USA; Gladstone Institute of Data Science and Biotechnology, Gladstone Institutes, San Francisco, California, USA
| | - Adam L Orr
- Gladstone Institute of Neurological Disease, Gladstone Institutes, San Francisco, California, USA
| | - Jeffrey R Johnson
- Quantitative Biosciences Institute (QBI), University of California San Francisco, San Francisco, California, USA; Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, California, USA; Gladstone Institute of Data Science and Biotechnology, Gladstone Institutes, San Francisco, California, USA
| | | | - R Dyche Mullins
- Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, California, USA; Howard Hughes Medical Institute, San Francisco, California, USA
| | - Nevan J Krogan
- Quantitative Biosciences Institute (QBI), University of California San Francisco, San Francisco, California, USA; Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, California, USA; Gladstone Institute of Data Science and Biotechnology, Gladstone Institutes, San Francisco, California, USA
| | - Robert W Mahley
- Gladstone Institute of Neurological Disease, Gladstone Institutes, San Francisco, California, USA; Departments of Pathology and Medicine, University of California San Francisco, San Francisco, California, USA
| | - Danielle L Swaney
- Quantitative Biosciences Institute (QBI), University of California San Francisco, San Francisco, California, USA; Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, California, USA; Gladstone Institute of Data Science and Biotechnology, Gladstone Institutes, San Francisco, California, USA.
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5
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Gu X, Jia C, Wang J. Advances in Understanding the Molecular Mechanisms of Neuronal Polarity. Mol Neurobiol 2023; 60:2851-2870. [PMID: 36738353 DOI: 10.1007/s12035-023-03242-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 01/22/2023] [Indexed: 02/05/2023]
Abstract
The establishment and maintenance of neuronal polarity are important for neural development and function. Abnormal neuronal polarity establishment commonly leads to a variety of neurodevelopmental disorders. Over the past three decades, with the continuous development and improvement of biological research methods and techniques, we have made tremendous progress in the understanding of the molecular mechanisms of neuronal polarity establishment. The activity of positive and negative feedback signals and actin waves are both essential in this process. They drive the directional transport and aggregation of key molecules of neuronal polarity, promote the spatiotemporal regulation of ordered and coordinated interactions of actin filaments and microtubules, stimulate the specialization and growth of axons, and inhibit the formation of multiple axons. In this review, we focus on recent advances in these areas, in particular the important findings about neuronal polarity in two classical models, in vitro primary hippocampal/cortical neurons and in vivo cortical pyramidal neurons, and discuss our current understanding of neuronal polarity..
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Affiliation(s)
- Xi Gu
- Fujian Key Laboratory for Translational Research in Cancer and Neurodegenerative Diseases, Institute for Translational Medicine, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China.
| | - Chunhong Jia
- Department of Pediatrics, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, China.
| | - Junhao Wang
- Fujian Key Laboratory for Translational Research in Cancer and Neurodegenerative Diseases, Institute for Translational Medicine, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China
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6
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Septins mediate a microtubule-actin crosstalk that enables actin growth on microtubules. Proc Natl Acad Sci U S A 2022; 119:e2202803119. [PMID: 36475946 PMCID: PMC9897426 DOI: 10.1073/pnas.2202803119] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Cellular morphogenesis and processes such as cell division and migration require the coordination of the microtubule and actin cytoskeletons. Microtubule-actin crosstalk is poorly understood and largely regarded as the capture and regulation of microtubules by actin. Septins are filamentous guanosine-5'-triphosphate (GTP) binding proteins, which comprise the fourth component of the cytoskeleton along microtubules, actin, and intermediate filaments. Here, we report that septins mediate microtubule-actin crosstalk by coupling actin polymerization to microtubule lattices. Superresolution and platinum replica electron microscopy (PREM) show that septins localize to overlapping microtubules and actin filaments in the growth cones of neurons and non-neuronal cells. We demonstrate that recombinant septin complexes directly crosslink microtubules and actin filaments into hybrid bundles. In vitro reconstitution assays reveal that microtubule-bound septins capture and align stable actin filaments with microtubules. Strikingly, septins enable the capture and polymerization of growing actin filaments on microtubule lattices. In neuronal growth cones, septins are required for the maintenance of the peripheral actin network that fans out from microtubules. These findings show that septins directly mediate microtubule interactions with actin filaments, and reveal a mechanism of microtubule-templated actin growth with broader significance for the self-organization of the cytoskeleton and cellular morphogenesis.
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7
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Fuchs J, Eickholt BJ. Precursor types predict the stability of neuronal branches. J Cell Sci 2021; 134:273430. [PMID: 34766183 PMCID: PMC8714070 DOI: 10.1242/jcs.258983] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 11/03/2021] [Indexed: 11/20/2022] Open
Abstract
Branches are critical for neuron function, generating the morphological complexity required for functional networks. They emerge from different, well-described, cytoskeletal precursor structures that elongate to branches. While branches are thought to be maintained by shared cytoskeletal regulators, our data from mouse hippocampal neurons indicate that the precursor structures trigger alternative branch maintenance mechanisms with differing stabilities. Whereas branches originating from lamellipodia or growth cone splitting events collapse soon after formation, branches emerging from filopodia persist. Furthermore, compared to other developing neurites, axons stabilise all branches and preferentially initiate branches from filopodia. These differences explain the altered stability of branches we observe in neurons lacking the plasma membrane protein phospholipid phosphatase-related protein 3 (PLPPR3, also known as PRG2) and in neurons treated with netrin-1. Rather than altering branch stability directly, PLPPR3 and netrin-1 boost a 'filopodia branch programme' on axons, thereby indirectly initiating more long-lived branches. In summary, we propose that studies on branching should distinguish overall stabilising effects from effects on precursor types, ideally using multifactorial statistical models, as exemplified in this study.
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Affiliation(s)
- Joachim Fuchs
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Institute of Molecular Biology and Biochemistry, Virchowweg 6, 10117 Berlin, Germany
| | - Britta J Eickholt
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Institute of Molecular Biology and Biochemistry, Virchowweg 6, 10117 Berlin, Germany
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8
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Bamburg JR, Minamide LS, Wiggan O, Tahtamouni LH, Kuhn TB. Cofilin and Actin Dynamics: Multiple Modes of Regulation and Their Impacts in Neuronal Development and Degeneration. Cells 2021; 10:cells10102726. [PMID: 34685706 PMCID: PMC8534876 DOI: 10.3390/cells10102726] [Citation(s) in RCA: 48] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 10/06/2021] [Accepted: 10/07/2021] [Indexed: 02/06/2023] Open
Abstract
Proteins of the actin depolymerizing factor (ADF)/cofilin family are ubiquitous among eukaryotes and are essential regulators of actin dynamics and function. Mammalian neurons express cofilin-1 as the major isoform, but ADF and cofilin-2 are also expressed. All isoforms bind preferentially and cooperatively along ADP-subunits in F-actin, affecting the filament helical rotation, and when either alone or when enhanced by other proteins, promotes filament severing and subunit turnover. Although self-regulating cofilin-mediated actin dynamics can drive motility without post-translational regulation, cells utilize many mechanisms to locally control cofilin, including cooperation/competition with other proteins. Newly identified post-translational modifications function with or are independent from the well-established phosphorylation of serine 3 and provide unexplored avenues for isoform specific regulation. Cofilin modulates actin transport and function in the nucleus as well as actin organization associated with mitochondrial fission and mitophagy. Under neuronal stress conditions, cofilin-saturated F-actin fragments can undergo oxidative cross-linking and bundle together to form cofilin-actin rods. Rods form in abundance within neurons around brain ischemic lesions and can be rapidly induced in neurites of most hippocampal and cortical neurons through energy depletion or glutamate-induced excitotoxicity. In ~20% of rodent hippocampal neurons, rods form more slowly in a receptor-mediated process triggered by factors intimately connected to disease-related dementias, e.g., amyloid-β in Alzheimer’s disease. This rod-inducing pathway requires a cellular prion protein, NADPH oxidase, and G-protein coupled receptors, e.g., CXCR4 and CCR5. Here, we will review many aspects of cofilin regulation and its contribution to synaptic loss and pathology of neurodegenerative diseases.
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Affiliation(s)
- James R. Bamburg
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA; (L.S.M.); (O.W.); (L.H.T.); (T.B.K.)
- Correspondence: ; Tel.: +1-970-988-9120; Fax: +1-970-491-0494
| | - Laurie S. Minamide
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA; (L.S.M.); (O.W.); (L.H.T.); (T.B.K.)
| | - O’Neil Wiggan
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA; (L.S.M.); (O.W.); (L.H.T.); (T.B.K.)
| | - Lubna H. Tahtamouni
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA; (L.S.M.); (O.W.); (L.H.T.); (T.B.K.)
- Department of Biology and Biotechnology, The Hashemite University, Zarqa 13115, Jordan
| | - Thomas B. Kuhn
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA; (L.S.M.); (O.W.); (L.H.T.); (T.B.K.)
- Department of Chemistry and Biochemistry, University of Alaska, Fairbanks, AK 99775, USA
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9
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Namme JN, Bepari AK, Takebayashi H. Cofilin Signaling in the CNS Physiology and Neurodegeneration. Int J Mol Sci 2021; 22:ijms221910727. [PMID: 34639067 PMCID: PMC8509315 DOI: 10.3390/ijms221910727] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Revised: 09/26/2021] [Accepted: 09/29/2021] [Indexed: 12/18/2022] Open
Abstract
All eukaryotic cells are composed of the cytoskeleton, which plays crucial roles in coordinating diverse cellular functions such as cell division, morphology, migration, macromolecular stabilization, and protein trafficking. The cytoskeleton consists of microtubules, intermediate filaments, and actin filaments. Cofilin, an actin-depolymerizing protein, is indispensable for regulating actin dynamics in the central nervous system (CNS) development and function. Cofilin activities are spatiotemporally orchestrated by numerous extra- and intra-cellular factors. Phosphorylation at Ser-3 by kinases attenuate cofilin’s actin-binding activity. In contrast, dephosphorylation at Ser-3 enhances cofilin-induced actin depolymerization. Cofilin functions are also modulated by various binding partners or reactive oxygen species. Although the mechanism of cofilin-mediated actin dynamics has been known for decades, recent research works are unveiling the profound impacts of cofilin dysregulation in neurodegenerative pathophysiology. For instance, oxidative stress-induced increase in cofilin dephosphorylation is linked to the accumulation of tau tangles and amyloid-beta plaques in Alzheimer’s disease. In Parkinson’s disease, cofilin activation by silencing its upstream kinases increases α-synuclein-fibril entry into the cell. This review describes the molecular mechanism of cofilin-mediated actin dynamics and provides an overview of cofilin’s importance in CNS physiology and pathophysiology.
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Affiliation(s)
- Jannatun Nayem Namme
- Department of Pharmaceutical Sciences, North South University, Dhaka 1229, Bangladesh;
| | - Asim Kumar Bepari
- Department of Pharmaceutical Sciences, North South University, Dhaka 1229, Bangladesh;
- Correspondence: (A.K.B.); (H.T.)
| | - Hirohide Takebayashi
- Division of Neurobiology and Anatomy, Graduate School of Medical and Dental Sciences, Niigata University, Niigata 951-8510, Japan
- Correspondence: (A.K.B.); (H.T.)
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10
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Studying Neuronal Biology Using Spinning Disc Confocal Microscopy. Methods Mol Biol 2021. [PMID: 34028722 DOI: 10.1007/978-1-0716-1402-0_14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/07/2023]
Abstract
Cytoskeletal integrity is essential for neuronal complexity and functionality. Certain inherited neurological diseases are associated with mutated genes that directly or indirectly compromise cytoskeletal stability. While the large size and complexity of the neurons grown in culture poses certain challenges for imaging, live-cell imaging is an excellent approach to determine the morphological consequences of such mutants. This protocol details the use of spinning disk confocal microscopy and image analysis tools to evaluate branching and neurite length of healthy iPSC-derived glutamatergic neurons that express specific fluorescent proteins. The protocols can be adapted to neuronal cell lines of choice by the investigator.
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Weaver CJ, Poulain FE. From whole organism to ultrastructure: progress in axonal imaging for decoding circuit development. Development 2021; 148:271122. [PMID: 34328171 DOI: 10.1242/dev.199717] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Since the pioneering work of Ramón y Cajal, scientists have sought to unravel the complexities of axon development underlying neural circuit formation. Micrometer-scale axonal growth cones navigate to targets that are often centimeters away. To reach their targets, growth cones react to dynamic environmental cues that change in the order of seconds to days. Proper axon growth and guidance are essential to circuit formation, and progress in imaging has been integral to studying these processes. In particular, advances in high- and super-resolution microscopy provide the spatial and temporal resolution required for studying developing axons. In this Review, we describe how improved microscopy has revolutionized our understanding of axonal development. We discuss how novel technologies, specifically light-sheet and super-resolution microscopy, led to new discoveries at the cellular scale by imaging axon outgrowth and circuit wiring with extreme precision. We next examine how advanced microscopy broadened our understanding of the subcellular dynamics driving axon growth and guidance. We finally assess the current challenges that the field of axonal biology still faces for imaging axons, and examine how future technology could meet these needs.
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Affiliation(s)
- Cory J Weaver
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA
| | - Fabienne E Poulain
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA
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12
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Avila Ponce de León MA, Félix B, Othmer HG. A phosphoinositide-based model of actin waves in frustrated phagocytosis. J Theor Biol 2021; 527:110764. [PMID: 34029577 DOI: 10.1016/j.jtbi.2021.110764] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 05/05/2021] [Accepted: 05/07/2021] [Indexed: 12/21/2022]
Abstract
Phagocytosis is a complex process by which phagocytes such as lymphocytes or macrophages engulf and destroy foreign bodies called pathogens in a tissue. The process is triggered by the detection of antibodies that trigger signaling mechanisms that control the changes of the cellular cytoskeleton needed for engulfment of the pathogen. A mathematical model of the entire process would be extremely complicated, because the signaling and cytoskeletal changes produce large mechanical deformations of the cell. Recent experiments have used a confinement technique that leads to a process called frustrated phagocytosis, in which the membrane does not deform, but rather, signaling triggers actin waves that propagate along the boundary of the cell. This eliminates the large-scale deformations and facilitates modeling of the wave dynamics. Herein we develop a model of the actin dynamics observed in frustrated phagocytosis and show that it can replicate the experimental observations. We identify the key components that control the actin waves and make a number of experimentally-testable predictions. In particular, we predict that diffusion coefficients of membrane-bound species must be larger behind the wavefront to replicate the internal structure of the waves. Our model is a first step toward a more complete model of phagocytosis, and provides insights into circular dorsal ruffles as well.
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Affiliation(s)
| | - Bryan Félix
- School of Mathematics, University of Minnesota, Minneapolis, MN, USA
| | - Hans G Othmer
- School of Mathematics, University of Minnesota, Minneapolis, MN, USA.
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13
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Deletion of the Actin-Associated Tropomyosin Tpm3 Leads to Reduced Cell Complexity in Cultured Hippocampal Neurons-New Insights into the Role of the C-Terminal Region of Tpm3.1. Cells 2021; 10:cells10030715. [PMID: 33807093 PMCID: PMC8005004 DOI: 10.3390/cells10030715] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 03/15/2021] [Accepted: 03/17/2021] [Indexed: 12/20/2022] Open
Abstract
Tropomyosins (Tpms) have been described as master regulators of actin, with Tpm3 products shown to be involved in early developmental processes, and the Tpm3 isoform Tpm3.1 controlling changes in the size of neuronal growth cones and neurite growth. Here, we used primary mouse hippocampal neurons of C57/Bl6 wild type and Bl6Tpm3flox transgenic mice to carry out morphometric analyses in response to the absence of Tpm3 products, as well as to investigate the effect of C-terminal truncation on the ability of Tpm3.1 to modulate neuronal morphogenesis. We found that the knock-out of Tpm3 leads to decreased neurite length and complexity, and that the deletion of two amino acid residues at the C-terminus of Tpm3.1 leads to more detrimental changes in neurite morphology than the deletion of six amino acid residues. We also found that Tpm3.1 that lacks the 6 C-terminal amino acid residues does not associate with stress fibres, does not segregate to the tips of neurites, and does not impact the amount of the filamentous actin pool at the axonal growth cones, as opposed to Tpm3.1, which lacks the two C-terminal amino acid residues. Our study provides further insight into the role of both Tpm3 products and the C-terminus of Tpm3.1, and it forms the basis for future studies that aim to identify the molecular mechanisms underlying Tpm3.1 targeting to different subcellular compartments.
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14
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Braïni C, Bugnicourt G, Villard C. Neuronal growth from a volume perspective. Phys Biol 2021; 18:016007. [PMID: 33147573 DOI: 10.1088/1478-3975/abc79c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Microfluidic-based fluorescent exclusion method allows to tackle the issue of neuronal growth from a volume perspective. Based on this technology, we studied the two main actin-rich structures accompanying the early stages of neuron development, i.e. growth cones, located at the tip of growing neuronal processes, and propagative actin waves. Our work reveals that growth cones tend to loose volume during their forward motion, as do actin waves during their journey from the cell body to the tip of neuronal processes, before the total transfer of their remaining volume to the growth cone. Actin waves seem thus to supply material to increasingly distant growth cones as neurons develop. In addition, our work may suggest the existence of a membrane recycling phenomena associated to actin waves as a pulsatile anterograde source of material and by a continuous retrograde transport.
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Affiliation(s)
- Céline Braïni
- Physico-Chimie Curie, CNRS UMR 168, Université PSL, Sorbonne Université, Paris, France
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15
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Wilkes OR, Moore AW. Distinct Microtubule Organizing Center Mechanisms Combine to Generate Neuron Polarity and Arbor Complexity. Front Cell Neurosci 2020; 14:594199. [PMID: 33328893 PMCID: PMC7711044 DOI: 10.3389/fncel.2020.594199] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Accepted: 11/02/2020] [Indexed: 01/15/2023] Open
Abstract
Dendrite and axon arbor wiring patterns determine the connectivity and computational characteristics of a neuron. The identities of these dendrite and axon arbors are created by differential polarization of their microtubule arrays, and their complexity and pattern are generated by the extension and organization of these arrays. We describe how several molecularly distinct microtubule organizing center (MTOC) mechanisms function during neuron differentiation to generate and arrange dendrite and axon microtubules. The temporal and spatial organization of these MTOCs generates, patterns, and diversifies arbor wiring.
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Affiliation(s)
- Oliver R Wilkes
- Laboratory for Neurodiversity, RIKEN Center for Brain Science, Wako-shi, Japan.,Department of Cellular and Molecular Biology, Institute for Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Adrian W Moore
- Laboratory for Neurodiversity, RIKEN Center for Brain Science, Wako-shi, Japan
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16
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Huang YA, Hsu CH, Chiu HC, Hsi PY, Ho CT, Lo WL, Hwang E. Actin waves transport RanGTP to the neurite tip to regulate non-centrosomal microtubules in neurons. J Cell Sci 2020; 133:jcs241992. [PMID: 32253322 DOI: 10.1242/jcs.241992] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Accepted: 03/17/2020] [Indexed: 12/18/2022] Open
Abstract
Microtubules (MTs) are the most abundant cytoskeleton in neurons, and control multiple facets of their development. While the MT-organizing center (MTOC) in mitotic cells is typically located at the centrosome, the MTOC in neurons switches to non-centrosomal sites. A handful of cellular components have been shown to promote non-centrosomal MT (ncMT) formation in neurons, yet the regulation mechanism remains unknown. Here, we demonstrate that the small GTPase Ran is a key regulator of ncMTs in neurons. Using an optogenetic tool that enables light-induced local production of RanGTP, we demonstrate that RanGTP promotes ncMT plus-end growth along the neurite. Additionally, we discovered that actin waves drive the anterograde transport of RanGTP. Pharmacological disruption of actin waves abolishes the enrichment of RanGTP and reduces growing ncMT plus-ends at the neurite tip. These observations identify a novel regulation mechanism for ncMTs and pinpoint an indirect connection between the actin and MT cytoskeletons in neurons.
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Affiliation(s)
- Yung-An Huang
- Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan 30068
| | - Chih-Hsuan Hsu
- Institute of Molecular Medicine and Bioengineering, National Chiao Tung University, Hsinchu, Taiwan 30068
| | - Ho-Chieh Chiu
- Institute of Molecular Medicine and Bioengineering, National Chiao Tung University, Hsinchu, Taiwan 30068
| | - Pei-Yu Hsi
- Institute of Molecular Medicine and Bioengineering, National Chiao Tung University, Hsinchu, Taiwan 30068
| | - Chris T Ho
- Institute of Molecular Medicine and Bioengineering, National Chiao Tung University, Hsinchu, Taiwan 30068
| | - Wei-Lun Lo
- Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan 30068
| | - Eric Hwang
- Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan 30068
- Institute of Molecular Medicine and Bioengineering, National Chiao Tung University, Hsinchu, Taiwan 30068
- Institute of Bioinformatics and Systems Biology, National Chiao Tung University, Hsinchu, Taiwan 30068
- Center for Intelligent Drug Systems and Smart Bio-devices (IDS2B), National Chiao Tung University, Hsinchu, Taiwan 30068
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17
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Radler MR, Suber A, Spiliotis ET. Spatial control of membrane traffic in neuronal dendrites. Mol Cell Neurosci 2020; 105:103492. [PMID: 32294508 DOI: 10.1016/j.mcn.2020.103492] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Revised: 03/24/2020] [Accepted: 04/01/2020] [Indexed: 02/06/2023] Open
Abstract
Neuronal dendrites are highly branched and specialized compartments with distinct structures and secretory organelles (e.g., spines, Golgi outposts), and a unique cytoskeletal organization that includes microtubules of mixed polarity. Dendritic membranes are enriched with proteins, which specialize in the formation and function of the post-synaptic membrane of the neuronal synapse. How these proteins partition preferentially in dendrites, and how they traffic in a manner that is spatiotemporally accurate and regulated by synaptic activity are long-standing questions of neuronal cell biology. Recent studies have shed new insights into the spatial control of dendritic membrane traffic, revealing new classes of proteins (e.g., septins) and cytoskeleton-based mechanisms with dendrite-specific functions. Here, we review these advances by revisiting the fundamental mechanisms that control membrane traffic at the levels of protein sorting and motor-driven transport on microtubules and actin filaments. Overall, dendrites possess unique mechanisms for the spatial control of membrane traffic, which might have specialized and co-evolved with their highly arborized morphology.
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Affiliation(s)
- Megan R Radler
- Department of Biology, Drexel University, 3245 Chestnut St, Philadelphia, PA 19104, USA
| | - Ayana Suber
- Department of Biology, Drexel University, 3245 Chestnut St, Philadelphia, PA 19104, USA
| | - Elias T Spiliotis
- Department of Biology, Drexel University, 3245 Chestnut St, Philadelphia, PA 19104, USA.
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18
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Meka DP, Scharrenberg R, Calderon de Anda F. Emerging roles of the centrosome in neuronal development. Cytoskeleton (Hoboken) 2020; 77:84-96. [DOI: 10.1002/cm.21593] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Revised: 12/16/2019] [Accepted: 01/04/2020] [Indexed: 12/24/2022]
Affiliation(s)
- Durga Praveen Meka
- RG Neuronal Development, Center for Molecular Neurobiology Hamburg (ZMNH)University Medical Center Hamburg‐Eppendorf Hamburg Germany
| | - Robin Scharrenberg
- RG Neuronal Development, Center for Molecular Neurobiology Hamburg (ZMNH)University Medical Center Hamburg‐Eppendorf Hamburg Germany
| | - Froylan Calderon de Anda
- RG Neuronal Development, Center for Molecular Neurobiology Hamburg (ZMNH)University Medical Center Hamburg‐Eppendorf Hamburg Germany
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19
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Venkatesh K, Mathew A, Koushika SP. Role of actin in organelle trafficking in neurons. Cytoskeleton (Hoboken) 2020; 77:97-109. [DOI: 10.1002/cm.21580] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 10/14/2019] [Accepted: 11/05/2019] [Indexed: 01/29/2023]
Affiliation(s)
- Keertana Venkatesh
- Department of Biological SciencesTata Institute of Fundamental Research Mumbai India
| | - Amal Mathew
- Department of Biological SciencesTata Institute of Fundamental Research Mumbai India
| | - Sandhya P. Koushika
- Department of Biological SciencesTata Institute of Fundamental Research Mumbai India
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20
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Much More Than a Scaffold: Cytoskeletal Proteins in Neurological Disorders. Cells 2020; 9:cells9020358. [PMID: 32033020 PMCID: PMC7072452 DOI: 10.3390/cells9020358] [Citation(s) in RCA: 63] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Revised: 01/27/2020] [Accepted: 01/29/2020] [Indexed: 02/08/2023] Open
Abstract
Recent observations related to the structure of the cytoskeleton in neurons and novel cytoskeletal abnormalities involved in the pathophysiology of some neurological diseases are changing our view on the function of the cytoskeletal proteins in the nervous system. These efforts allow a better understanding of the molecular mechanisms underlying neurological diseases and allow us to see beyond our current knowledge for the development of new treatments. The neuronal cytoskeleton can be described as an organelle formed by the three-dimensional lattice of the three main families of filaments: actin filaments, microtubules, and neurofilaments. This organelle organizes well-defined structures within neurons (cell bodies and axons), which allow their proper development and function through life. Here, we will provide an overview of both the basic and novel concepts related to those cytoskeletal proteins, which are emerging as potential targets in the study of the pathophysiological mechanisms underlying neurological disorders.
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21
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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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22
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Locally Activating TrkB Receptor Generates Actin Waves and Specifies Axonal Fate. Cell Chem Biol 2019; 26:1652-1663.e4. [PMID: 31678045 DOI: 10.1016/j.chembiol.2019.10.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 08/26/2019] [Accepted: 10/10/2019] [Indexed: 01/15/2023]
Abstract
Actin waves are filamentous actin (F-actin)-rich structures that initiate in the somato-neuritic area and move toward neurite ends. The upstream cues that initiate actin waves are poorly understood. Here, using an optogenetic approach (Opto-cytTrkB), we found that local activation of the TrkB receptor around the neurite end initiates actin waves and triggers neurite elongation. During actin wave generation, locally activated TrkB signaling in the distal neurite was functionally connected with preferentially localized Rac1 and its signaling pathways in the proximal region. Moreover, TrkB activity changed the location of ankyrinG--the master organizer of the axonal initial segment-and initiated the stimulated neurite to acquire axonal characteristics. Taken together, these findings suggest that local Opto-cytTrkB activation switches the fate from minor to major axonal neurite during neuronal polarization by generating actin waves.
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23
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Meka DP, Scharrenberg R, Zhao B, Kobler O, König T, Schaefer I, Schwanke B, Klykov S, Richter M, Eggert D, Windhorst S, Dotti CG, Kreutz MR, Mikhaylova M, Calderon de Anda F. Radial somatic F-actin organization affects growth cone dynamics during early neuronal development. EMBO Rep 2019; 20:e47743. [PMID: 31650708 PMCID: PMC6893363 DOI: 10.15252/embr.201947743] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Revised: 09/06/2019] [Accepted: 09/27/2019] [Indexed: 11/16/2022] Open
Abstract
The centrosome is thought to be the major neuronal microtubule‐organizing center (MTOC) in early neuronal development, producing microtubules with a radial organization. In addition, albeit in vitro, recent work showed that isolated centrosomes could serve as an actin‐organizing center, raising the possibility that neuronal development may, in addition, require a centrosome‐based actin radial organization. Here, we report, using super‐resolution microscopy and live‐cell imaging of cultured rodent neurons, F‐actin organization around the centrosome with dynamic F‐actin aster‐like structures with F‐actin fibers extending and retracting actively. Photoactivation/photoconversion experiments and molecular manipulations of F‐actin stability reveal a robust flux of somatic F‐actin toward the cell periphery. Finally, we show that somatic F‐actin intermingles with centrosomal PCM‐1 (pericentriolar material 1 protein) satellites. Knockdown of PCM‐1 and disruption of centrosomal activity not only affect F‐actin dynamics near the centrosome but also in distal growth cones. Collectively, the data show a radial F‐actin organization during early neuronal development, which might be a cellular mechanism for providing peripheral regions with a fast and continuous source of actin polymers, hence sustaining initial neuronal development.
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Affiliation(s)
- Durga Praveen Meka
- RG Neuronal Development, Center for Molecular Neurobiology Hamburg (ZMNH), University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Robin Scharrenberg
- RG Neuronal Development, Center for Molecular Neurobiology Hamburg (ZMNH), University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Bing Zhao
- RG Neuronal Development, Center for Molecular Neurobiology Hamburg (ZMNH), University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Oliver Kobler
- Combinatorial Neuroimaging Core Facility (CNI), Leibniz Institute for Neurobiology, Magdeburg, Germany
| | - Theresa König
- RG Neuronal Development, Center for Molecular Neurobiology Hamburg (ZMNH), University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Irina Schaefer
- RG Neuronal Development, Center for Molecular Neurobiology Hamburg (ZMNH), University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Birgit Schwanke
- RG Neuronal Development, Center for Molecular Neurobiology Hamburg (ZMNH), University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Sergei Klykov
- Emmy-Noether Group "Neuronal Protein Transport", Center for Molecular Neurobiology (ZMNH), University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Melanie Richter
- RG Neuronal Development, Center for Molecular Neurobiology Hamburg (ZMNH), University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Dennis Eggert
- Max Planck Institute for the Structure and Dynamics of Matter, Hamburg, Germany.,Heinrich Pette Institute-Leibniz Institute for Experimental Virology, Hamburg, Germany
| | - Sabine Windhorst
- Department of Biochemistry and Signal Transduction, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Carlos G Dotti
- Centro de Biología Molecular "Severo Ochoa", CSIC-UAM, Madrid, Spain
| | - Michael R Kreutz
- RG Neuroplasticity, Leibniz Institute for Neurobiology, Magdeburg, Germany.,Leibniz Guest Group "Dendritic Organelles and Synaptic Function", Center for Molecular Neurobiology (ZMNH), University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Marina Mikhaylova
- Emmy-Noether Group "Neuronal Protein Transport", Center for Molecular Neurobiology (ZMNH), University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Froylan Calderon de Anda
- RG Neuronal Development, Center for Molecular Neurobiology Hamburg (ZMNH), University Medical Center Hamburg-Eppendorf, Hamburg, Germany
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24
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Reshetniak S, Rizzoli SO. Interrogating Synaptic Architecture: Approaches for Labeling Organelles and Cytoskeleton Components. Front Synaptic Neurosci 2019; 11:23. [PMID: 31507402 PMCID: PMC6716447 DOI: 10.3389/fnsyn.2019.00023] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Accepted: 08/02/2019] [Indexed: 01/06/2023] Open
Abstract
Synaptic transmission has been studied for decades, as a fundamental step in brain function. The structure of the synapse, and its changes during activity, turned out to be key aspects not only in the transfer of information between neurons, but also in cognitive processes such as learning and memory. The overall synaptic morphology has traditionally been studied by electron microscopy, which enables the visualization of synaptic structure in great detail. The changes in the organization of easily identified structures, such as the presynaptic active zone, or the postsynaptic density, are optimally studied via electron microscopy. However, few reliable methods are available for labeling individual organelles or protein complexes in electron microscopy. For such targets one typically relies either on combination of electron and fluorescence microscopy, or on super-resolution fluorescence microscopy. This review focuses on approaches and techniques used to specifically reveal synaptic organelles and protein complexes, such as cytoskeletal assemblies. We place the strongest emphasis on methods detecting the targets of interest by affinity binding, and we discuss the advantages and limitations of each method.
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Affiliation(s)
- Sofiia Reshetniak
- Institute for Neuro- and Sensory Physiology, Center for Biostructural Imaging of Neurodegeneration (BIN), University Medical Center Göttingen, Göttingen, Germany
- International Max Planck Research School for Molecular Biology, Göttingen, Germany
| | - Silvio O. Rizzoli
- Institute for Neuro- and Sensory Physiology, Center for Biostructural Imaging of Neurodegeneration (BIN), University Medical Center Göttingen, Göttingen, Germany
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25
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The Development of Neuronal Polarity: A Retrospective View. J Neurosci 2019; 38:1867-1873. [PMID: 29467146 DOI: 10.1523/jneurosci.1372-16.2018] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 01/04/2018] [Accepted: 01/05/2018] [Indexed: 11/21/2022] Open
Abstract
In 1988, Carlos Dotti, Chris Sullivan, and I published a paper on the establishment of polarity by hippocampal neurons in culture, which continues to be frequently cited 30 years later (Dotti et al., 1988). By following individual neurons from the time of plating until they had formed well developed axonal and dendritic arbors, we identified the five stages of development that lead to the mature expression of neuronal polarity. We were surprised to find that, before axon formation, the cells pass through a multipolar phase, in which several, apparently identical short neurites undergo periods of extension and retraction. Then one of these neurites begins a period of prolonged growth, becoming the definitive axon; the remaining neurites subsequently become dendrites. This observation suggested that any of the initial neurites were capable of becoming axons, a hypothesis confirmed by later work. In this Progressions article, I will try to recall the circumstances that led to this work, recapture some of the challenges we faced in conducting these experiments, and consider why some of today's neuroscientists still find this paper relevant.
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26
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Zhang Y, Nichols EL, Zellmer AM, Guldner IH, Kankel C, Zhang S, Howard SS, Smith CJ. Generating intravital super-resolution movies with conventional microscopy reveals actin dynamics that construct pioneer axons. Development 2019; 146:dev.171512. [PMID: 30760484 PMCID: PMC6432666 DOI: 10.1242/dev.171512] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Accepted: 02/04/2019] [Indexed: 01/06/2023]
Abstract
Super-resolution microscopy is broadening our in-depth understanding of cellular structure. However, super-resolution approaches are limited, for numerous reasons, from utilization in longer-term intravital imaging. We devised a combinatorial imaging technique that combines deconvolution with stepwise optical saturation microscopy (DeSOS) to circumvent this issue and image cells in their native physiological environment. Other than a traditional confocal or two-photon microscope, this approach requires no additional hardware. Here, we provide an open-access application to obtain DeSOS images from conventional microscope images obtained at low excitation powers. We show that DeSOS can be used in time-lapse imaging to generate super-resolution movies in zebrafish. DeSOS was also validated in live mice. These movies uncover that actin structures dynamically remodel to produce a single pioneer axon in a ‘top-down’ scaffolding event. Further, we identify an F-actin population – stable base clusters – that orchestrate that scaffolding event. We then identify that activation of Rac1 in pioneer axons destabilizes stable base clusters and disrupts pioneer axon formation. The ease of acquisition and processing with this approach provides a universal technique for biologists to answer questions in living animals. Summary: Actin dynamics are examined in zebrafish axons using DeSOS, a new super-resolution technique combining deconvolution with stepwise optical saturation microscopy that allows detailed intravital imaging of cells in their native environments.
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Affiliation(s)
- Yide Zhang
- Department of Electrical Engineering, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Evan L Nichols
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA.,Center for Stem Cells and Regenerative Medicine, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Abigail M Zellmer
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Ian H Guldner
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA.,Mike and Josie Harper Cancer Research Institute, University of Notre Dame, Notre Dame, IN 46556, USA.,Indiana University Melvin and Bren Simon Cancer Center, Indianapolis, IN 46202, USA
| | - Cody Kankel
- Center for Research Computing. University of Notre Dame, Notre Dame, IN 46556, USA
| | - Siyuan Zhang
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA.,Mike and Josie Harper Cancer Research Institute, University of Notre Dame, Notre Dame, IN 46556, USA.,Indiana University Melvin and Bren Simon Cancer Center, Indianapolis, IN 46202, USA
| | - Scott S Howard
- Department of Electrical Engineering, University of Notre Dame, Notre Dame, IN 46556, USA .,Mike and Josie Harper Cancer Research Institute, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Cody J Smith
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA .,Center for Stem Cells and Regenerative Medicine, University of Notre Dame, Notre Dame, IN 46556, USA
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27
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Coudrier E, Iuliano O. [An unconventional myosin controls the axon formation]. Med Sci (Paris) 2019; 35:16-18. [PMID: 30672453 DOI: 10.1051/medsci/2018315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Evelyne Coudrier
- Institut Curie, PSL Research University, CNRS, UMR 144, 26 rue d'Ulm, 75005 Paris, France
| | - Olga Iuliano
- Université Paul Sabatier UMR5169 (MINDING), Toulouse, France
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28
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Woeste MA, Stern S, Raju DN, Grahn E, Dittmann D, Gutbrod K, Dörmann P, Hansen JN, Schonauer S, Marx CE, Hamzeh H, Körschen HG, Aerts JMFG, Bönigk W, Endepols H, Sandhoff R, Geyer M, Berger TK, Bradke F, Wachten D. Species-specific differences in nonlysosomal glucosylceramidase GBA2 function underlie locomotor dysfunction arising from loss-of-function mutations. J Biol Chem 2019; 294:3853-3871. [PMID: 30662006 DOI: 10.1074/jbc.ra118.006311] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 01/16/2019] [Indexed: 11/06/2022] Open
Abstract
The nonlysosomal glucosylceramidase β2 (GBA2) catalyzes the hydrolysis of glucosylceramide to glucose and ceramide. Mutations in the human GBA2 gene have been associated with hereditary spastic paraplegia (HSP), autosomal-recessive cerebellar ataxia (ARCA), and the Marinesco-Sjögren-like syndrome. However, the underlying molecular mechanisms are ill-defined. Here, using biochemistry, immunohistochemistry, structural modeling, and mouse genetics, we demonstrate that all but one of the spastic gait locus #46 (SPG46)-connected mutations cause a loss of GBA2 activity. We demonstrate that GBA2 proteins form oligomeric complexes and that protein-protein interactions are perturbed by some of these mutations. To study the pathogenesis of GBA2-related HSP and ARCA in vivo, we investigated GBA2-KO mice as a mammalian model system. However, these mice exhibited a high phenotypic variance and did not fully resemble the human phenotype, suggesting that mouse and human GBA2 differ in function. Whereas some GBA2-KO mice displayed a strong locomotor defect, others displayed only mild alterations of the gait pattern and no signs of cerebellar defects. On a cellular level, inhibition of GBA2 activity in isolated cerebellar neurons dramatically affected F-actin dynamics and reduced neurite outgrowth, which has been associated with the development of neurological disorders. Our results shed light on the molecular mechanism underlying the pathogenesis of GBA2-related HSP and ARCA and reveal species-specific differences in GBA2 function in vivo.
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Affiliation(s)
- Marina A Woeste
- From the Institute of Innate Immunity, University Hospital, University of Bonn, 53127 Bonn, Germany
| | - Sina Stern
- the German Center for Neurodegenerative Diseases (DZNE), 53127 Bonn, Germany
| | - Diana N Raju
- From the Institute of Innate Immunity, University Hospital, University of Bonn, 53127 Bonn, Germany
| | - Elena Grahn
- the Center of Advanced European Studies and Research (Caesar), 53175 Bonn, Germany
| | - Dominik Dittmann
- From the Institute of Innate Immunity, University Hospital, University of Bonn, 53127 Bonn, Germany
| | - Katharina Gutbrod
- the Institute of Molecular Physiology and Biotechnology of Plants, University of Bonn, 53115 Bonn, Germany
| | - Peter Dörmann
- the Institute of Molecular Physiology and Biotechnology of Plants, University of Bonn, 53115 Bonn, Germany
| | - Jan N Hansen
- From the Institute of Innate Immunity, University Hospital, University of Bonn, 53127 Bonn, Germany
| | - Sophie Schonauer
- the Center of Advanced European Studies and Research (Caesar), 53175 Bonn, Germany
| | - Carina E Marx
- the Center of Advanced European Studies and Research (Caesar), 53175 Bonn, Germany
| | - Hussein Hamzeh
- the Center of Advanced European Studies and Research (Caesar), 53175 Bonn, Germany
| | - Heinz G Körschen
- the Center of Advanced European Studies and Research (Caesar), 53175 Bonn, Germany
| | - Johannes M F G Aerts
- the Leiden Institute of Chemistry, Leiden University, 2333 CD Leiden, The Netherlands
| | - Wolfgang Bönigk
- the Center of Advanced European Studies and Research (Caesar), 53175 Bonn, Germany
| | - Heike Endepols
- the Institute of Radiochemistry and Experimental Molecular Imaging (IREMB) and Department of Nuclear Medicine, University Hospital of Cologne, 50937 Cologne, Germany
| | - Roger Sandhoff
- the Department of Cellular and Molecular Pathology, German Cancer Research Center, Heidelberg, Germany.,the Lipid Pathobiochemistry Group, German Cancer Research Center, 69120 Heidelberg, Germany, and
| | - Matthias Geyer
- the Institute of Structural Biology, University Hospital, University of Bonn, 53127 Bonn, Germany
| | - Thomas K Berger
- the Center of Advanced European Studies and Research (Caesar), 53175 Bonn, Germany
| | - Frank Bradke
- the German Center for Neurodegenerative Diseases (DZNE), 53127 Bonn, Germany
| | - Dagmar Wachten
- From the Institute of Innate Immunity, University Hospital, University of Bonn, 53127 Bonn, Germany, .,the Center of Advanced European Studies and Research (Caesar), 53175 Bonn, Germany
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29
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McGregor CE, English AW. The Role of BDNF in Peripheral Nerve Regeneration: Activity-Dependent Treatments and Val66Met. Front Cell Neurosci 2019; 12:522. [PMID: 30687012 PMCID: PMC6336700 DOI: 10.3389/fncel.2018.00522] [Citation(s) in RCA: 86] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 12/14/2018] [Indexed: 11/29/2022] Open
Abstract
Despite the ability of peripheral nerves to spontaneously regenerate after injury, recovery is generally very poor. The neurotrophins have emerged as an important modulator of axon regeneration, particularly brain derived neurotrophic factor (BDNF). BDNF regulation and signaling, as well as its role in activity-dependent treatments including electrical stimulation, exercise, and optogenetic stimulation are discussed here. The importance of a single nucleotide polymorphism in the BDNF gene, Val66Met, which is present in 30% of the human population and may hinder the efficacy of these treatments in enhancing regeneration after injury is considered. Preliminary data are presented on the effectiveness of one such activity-dependent treatment, electrical stimulation, in enhancing axon regeneration in mice expressing the met allele of the Val66Met polymorphism.
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Affiliation(s)
- Claire Emma McGregor
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, United States
| | - Arthur W English
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, United States
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30
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Won SJ, Minnella AM, Wu L, Eun CH, Rome E, Herson PS, Shaw AE, Bamburg JR, Swanson RA. Cofilin-actin rod formation in neuronal processes after brain ischemia. PLoS One 2018; 13:e0198709. [PMID: 30325927 PMCID: PMC6191105 DOI: 10.1371/journal.pone.0198709] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Accepted: 10/03/2018] [Indexed: 12/19/2022] Open
Abstract
Functional impairment after brain ischemia results in part from loss of neuronal spines and dendrites, independent of neuronal death. Cofilin-actin rods are covalently linked aggregates of cofilin-1 and actin that form in neuronal processes (neurites) under conditions of ATP depletion and oxidative stress, and which cause neurite degeneration if not disassembled. ATP depletion and oxidative stress occur with differing severity, duration, and time course in different ischemic conditions. Here we evaluated four mouse models of brain ischemia to define the conditions that drive formation of cofilin-actin rods. Three of the models provide early reperfusion: transient middle cerebral artery occlusion (MCAo), transient bilateral common carotid artery occlusion (CCAo), and cardiac arrest / cardiopulmonary resuscitation (CA/CPR). Early reperfusion restores ATP generating capacity, but also induces oxidative stress. The fourth model, photothrombotic cortical infarction, does not provide reperfusion. Cofilin-actin rods were formed in each of these models, but with differing patterns. Where acute reperfusion occurred, rod formation was maximal within 4 hours after reperfusion. Where infarction occurred, rods continued to form for at least 24 hours after ischemic onset, and extended into the adjacent non-ischemic tissue. Interventions that limit cofilin-actin rod formation may help to preserve integrity of neuronal processes in permanent ischemia.
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Affiliation(s)
- Seok Joon Won
- Dept. of Neurology, University of California San Francisco and San Francisco Veterans Affairs Medical Center, San Francisco, CA, United States of America
| | - Angela M. Minnella
- Dept. of Neurology, University of California San Francisco and San Francisco Veterans Affairs Medical Center, San Francisco, CA, United States of America
| | - Long Wu
- Dept. of Neurology, University of California San Francisco and San Francisco Veterans Affairs Medical Center, San Francisco, CA, United States of America
| | - Claire H. Eun
- Dept. of Neurology, University of California San Francisco and San Francisco Veterans Affairs Medical Center, San Francisco, CA, United States of America
| | - Eric Rome
- Dept. of Neurology, University of California San Francisco and San Francisco Veterans Affairs Medical Center, San Francisco, CA, United States of America
| | - Paco S. Herson
- Neuronal Injury Program, Department of Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, CO, United States of America
- Department of Pharmacology, University of Colorado Anschutz Medical Campus, Aurora, CO, United States of America
| | - Alisa E. Shaw
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, United States of America
| | - James R. Bamburg
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, United States of America
| | - Raymond A. Swanson
- Dept. of Neurology, University of California San Francisco and San Francisco Veterans Affairs Medical Center, San Francisco, CA, United States of America
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31
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Nithianandam V, Chien CT. Actin blobs prefigure dendrite branching sites. J Cell Biol 2018; 217:3731-3746. [PMID: 30042190 PMCID: PMC6168249 DOI: 10.1083/jcb.201711136] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Revised: 03/28/2018] [Accepted: 07/09/2018] [Indexed: 02/08/2023] Open
Abstract
Nithianandam and Chien show via in vivo imaging that a dynamic population of F-actin termed actin blobs propagates bidirectionally in dendrites and stalls at future branching sites. The F-actin–severing protein Tsr/cofilin is a regulator of actin blob dynamics and dendrite branching. The actin cytoskeleton provides structural stability and adaptability to the cell. Neuronal dendrites frequently undergo morphological changes by emanating, elongating, and withdrawing branches. However, the knowledge about actin dynamics in dendrites during these processes is limited. By performing in vivo imaging of F-actin markers, we found that F-actin was highly dynamic and heterogeneously distributed in dendritic shafts with enrichment at terminal dendrites. A dynamic F-actin population that we named actin blobs propagated bidirectionally at an average velocity of 1 µm/min. Interestingly, these actin blobs stalled at sites where new dendrites would branch out in minutes. Overstabilization of F-actin by the G15S mutant abolished actin blobs and dendrite branching. We identified the F-actin–severing protein Tsr/cofilin as a regulator of dynamic actin blobs and branching activity. Hence, actin blob localization at future branching sites represents a dendrite-branching mechanism to account for highly diversified dendritic morphology.
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Affiliation(s)
- Vanitha Nithianandam
- Molecular and Cell Biology, Taiwan International Graduate Program, Academia Sinica and Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan.,Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
| | - Cheng-Ting Chien
- Molecular and Cell Biology, Taiwan International Graduate Program, Academia Sinica and Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan .,Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
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32
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Gangatharan G, Schneider-Maunoury S, Breau MA. Role of mechanical cues in shaping neuronal morphology and connectivity. Biol Cell 2018; 110:125-136. [PMID: 29698566 DOI: 10.1111/boc.201800003] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Accepted: 04/09/2018] [Indexed: 02/06/2023]
Abstract
Neuronal circuits, the functional building blocks of the nervous system, assemble during development through a series of dynamic processes including the migration of neurons to their final position, the growth and navigation of axons and their synaptic connection with target cells. While the role of chemical cues in guiding neuronal migration and axonal development has been extensively analysed, the contribution of mechanical inputs, such as forces and stiffness, has received far less attention. In this article, we review the in vitro and more recent in vivo studies supporting the notion that mechanical signals are critical for multiple aspects of neuronal circuit assembly, from the emergence of axons to the formation of functional synapses. By combining live imaging approaches with tools designed to measure and manipulate the mechanical environment of neurons, the emerging field of neuromechanics will add a new paradigm in our understanding of neuronal development and potentially inspire novel regenerative therapies.
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Affiliation(s)
- Girisaran Gangatharan
- Sorbonne Université, CNRS UMR 7622, Laboratoire de Biologie du Développement-Institut de Biologie Paris Seine (LBD-IBPS), INSERM, Paris, 75005, France
| | - Sylvie Schneider-Maunoury
- Sorbonne Université, CNRS UMR 7622, Laboratoire de Biologie du Développement-Institut de Biologie Paris Seine (LBD-IBPS), INSERM, Paris, 75005, France
| | - Marie Anne Breau
- Sorbonne Université, CNRS UMR 7622, Laboratoire de Biologie du Développement-Institut de Biologie Paris Seine (LBD-IBPS), INSERM, Paris, 75005, France.,Sorbonne Université, CNRS UMR 8237, Laboratoire Jean Perrin, Paris, 75005, France
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33
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Papandréou MJ, Leterrier C. The functional architecture of axonal actin. Mol Cell Neurosci 2018; 91:151-159. [PMID: 29758267 DOI: 10.1016/j.mcn.2018.05.003] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Revised: 05/10/2018] [Accepted: 05/11/2018] [Indexed: 11/17/2022] Open
Abstract
The cytoskeleton builds and supports the complex architecture of neurons. It orchestrates the specification, growth, and compartmentation of the axon: axon initial segment, axonal shaft, presynapses. The cytoskeleton must then maintain this intricate architecture for the whole life of its host, but also drive its adaptation to new network demands and changing physiological conditions. Microtubules are readily visible inside axon shafts by electron microscopy, whereas axonal actin study has long been focused on dynamic structures of the axon such as growth cones. Super-resolution microscopy and live-cell imaging have recently revealed new actin-based structures in mature axons: rings, hotspots and trails. This has caused renewed interest for axonal actin, with efforts underway to understand the precise organization and cellular functions of these assemblies. Actin is also present in presynapses, where its arrangement is still poorly defined, and its functions vigorously debated. Here we review the organization of axonal actin, focusing on recent advances and current questions in this rejuvenated field.
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34
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Inner Workings: Uncovering the neuron's internal skeleton. Proc Natl Acad Sci U S A 2018; 113:13931-13933. [PMID: 27930346 DOI: 10.1073/pnas.1617651113] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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35
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Iuliano O, Yoshimura A, Prospéri MT, Martin R, Knölker HJ, Coudrier E. Myosin 1b promotes axon formation by regulating actin wave propagation and growth cone dynamics. J Cell Biol 2018; 217:2033-2046. [PMID: 29588377 PMCID: PMC5987710 DOI: 10.1083/jcb.201703205] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Revised: 12/20/2017] [Accepted: 03/02/2018] [Indexed: 02/06/2023] Open
Abstract
Single-headed myosin 1 has been identified in neurons, but its function in these cells is still unclear. We demonstrate that depletion of myosin 1b (Myo1b), inhibition of its motor activity, or its binding to phosphoinositides impairs the formation of the axon, whereas overexpression of Myo1b increases the number of axon-like structures. Myo1b is associated with growth cones and actin waves, two major contributors to neuronal symmetry breaking. We show that Myo1b controls the dynamics of the growth cones and the anterograde propagation of the actin waves. By coupling the membrane to the actin cytoskeleton, Myo1b regulates the size of the actin network as well as the stability and size of filopodia in the growth cones. Our data provide the first evidence that a myosin 1 plays a major role in neuronal symmetry breaking and argue for a mechanical control of the actin cytoskeleton both in actin waves and in the growth cones by this myosin.
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Affiliation(s)
- Olga Iuliano
- Institut Curie, Paris Sciences et Lettres Research University, Centre National de la Recherche Scientifique, UMR 144, Paris, France
| | - Azumi Yoshimura
- Institut Curie, Paris Sciences et Lettres Research University, Centre National de la Recherche Scientifique, UMR 144, Paris, France
| | - Marie-Thérèse Prospéri
- Institut Curie, Paris Sciences et Lettres Research University, Centre National de la Recherche Scientifique, UMR 144, Paris, France
| | - René Martin
- Department of Chemistry, Technische Univesität Dresden, Dresden, Germany
| | | | - Evelyne Coudrier
- Institut Curie, Paris Sciences et Lettres Research University, Centre National de la Recherche Scientifique, UMR 144, Paris, France
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36
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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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37
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Mortal S, Iseppon F, Perissinotto A, D'Este E, Cojoc D, Napolitano LMR, Torre V. Actin Waves Do Not Boost Neurite Outgrowth in the Early Stages of Neuron Maturation. Front Cell Neurosci 2017; 11:402. [PMID: 29326552 PMCID: PMC5741660 DOI: 10.3389/fncel.2017.00402] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Accepted: 12/01/2017] [Indexed: 11/27/2022] Open
Abstract
During neurite development, Actin Waves (AWs) emerge at the neurite base and move up to its tip, causing a transient retraction of the Growth Cone (GC). Many studies have shown that AWs are linked to outbursts of neurite growth and, therefore, contribute to the fast elongation of the nascent axon. Using long term live cell-imaging, we show that AWs do not boost neurite outgrowth and that neurites without AWs can elongate for several hundred microns. Inhibition of Myosin II abolishes the transient GC retraction and strongly modifies the AWs morphology. Super-resolution nanoscopy shows that Myosin IIB shapes the growth cone-like AWs structure and is differently distributed in AWs and GCs. Interestingly, depletion of membrane cholesterol and inhibition of Rho GTPases decrease AWs frequency and velocity. Our results indicate that Myosin IIB, membrane tension, and small Rho GTPases are important players in the regulation of the AW dynamics. Finally, we suggest a role for AWs in maintaining the GCs active during environmental exploration.
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Affiliation(s)
- Simone Mortal
- Neurobiology Department, International School for Advanced Studies, Trieste, Italy
| | - Federico Iseppon
- Neurobiology Department, International School for Advanced Studies, Trieste, Italy
| | - Andrea Perissinotto
- Neurobiology Department, International School for Advanced Studies, Trieste, Italy
| | - Elisa D'Este
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Dan Cojoc
- Optical Manipulation Lab, Istituto Officina dei Materiali (CNR), Trieste, Italy
| | - Luisa M R Napolitano
- Neurobiology Department, International School for Advanced Studies, Trieste, Italy
| | - Vincent Torre
- Neurobiology Department, International School for Advanced Studies, Trieste, Italy
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38
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Oscillatory fungal cell growth. Fungal Genet Biol 2017; 110:10-14. [PMID: 29229585 DOI: 10.1016/j.fgb.2017.12.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2017] [Revised: 11/26/2017] [Accepted: 12/06/2017] [Indexed: 12/20/2022]
Abstract
Cells are dynamic systems, the state of which undergoes constant alteration that results in morphological changes and movement. Many dynamic cellular processes that appear continuous are driven by underlying mechanisms that oscillate with distinct periods. For example eukaryotic cells do not grow continuously, but rather by pulsed extension of the periphery. Stepwise cell extension at the hyphal tips of several filamentous fungi was discovered 20 years ago, but only a few molecular details of the mechanism have been clarified since then. A recent study has provided evidence for correlations among intracellular Ca2+ levels, actin assembly, exocytosis and cell extension in growing hyphal tips. This suggests that pulsed Ca2+ influxes coordinate the temporal control of actin assembly and exocytosis, which results in stepwise cell extension. The coordinated oscillation of these machineries are likely to be ubiquitous among all eukaryotes. Indeed, intracellular Ca2+ levels and/or actin polymerization oscillate in mammalian and plant cells. This review summarizes the mechanisms of oscillation in several systems.
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39
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40
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Establishing Neuronal Polarity with Environmental and Intrinsic Mechanisms. Neuron 2017; 96:638-650. [DOI: 10.1016/j.neuron.2017.10.021] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Revised: 10/14/2017] [Accepted: 10/15/2017] [Indexed: 12/31/2022]
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41
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Actin Waves: Origin of Cell Polarization and Migration? Trends Cell Biol 2017; 27:515-526. [DOI: 10.1016/j.tcb.2017.02.003] [Citation(s) in RCA: 83] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 01/26/2017] [Accepted: 02/07/2017] [Indexed: 01/22/2023]
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42
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Zhao H, Alam A, San CY, Eguchi S, Chen Q, Lian Q, Ma D. Molecular mechanisms of brain-derived neurotrophic factor in neuro-protection: Recent developments. Brain Res 2017; 1665:1-21. [PMID: 28396009 DOI: 10.1016/j.brainres.2017.03.029] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Revised: 03/02/2017] [Accepted: 03/28/2017] [Indexed: 12/13/2022]
Abstract
Neuronal cell injury, as a consequence of acute or chronic neurological trauma, is a significant cause of mortality around the world. On a molecular level, the condition is characterized by widespread cell death and poor regeneration, which can result in severe morbidity in survivors. Potential therapeutics are of major interest, with a promising candidate being brain-derived neurotrophic factor (BDNF), a ubiquitous agent in the brain which has been associated with neural development and may facilitate protective and regenerative effects following injury. This review summarizes the available information on the potential benefits of BDNF and the molecular mechanisms involved in several pathological conditions, including hypoxic brain injury, stroke, Alzheimer's disease and Parkinson's disease. It further explores the methods in which BDNF can be applied in clinical and therapeutic settings, and the potential challenges to overcome.
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Affiliation(s)
- Hailin Zhao
- Anaesthetics, Pain Medicine and Intensive Care, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, Chelsea & Westminster Hospital, London, UK
| | - Azeem Alam
- Anaesthetics, Pain Medicine and Intensive Care, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, Chelsea & Westminster Hospital, London, UK
| | - Chun-Yin San
- Anaesthetics, Pain Medicine and Intensive Care, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, Chelsea & Westminster Hospital, London, UK
| | - Shiori Eguchi
- Anaesthetics, Pain Medicine and Intensive Care, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, Chelsea & Westminster Hospital, London, UK
| | - Qian Chen
- Anaesthetics, Pain Medicine and Intensive Care, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, Chelsea & Westminster Hospital, London, UK; Department of Anaesthesiology, Southwest Hospital, Third Military Medical University, Chongqing, China
| | - Qingquan Lian
- Department of Anesthesiology, Second Affiliated Hospital, Wenzhou Medical University, Wenzhou, China.
| | - Daqing Ma
- Anaesthetics, Pain Medicine and Intensive Care, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, Chelsea & Westminster Hospital, London, UK.
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43
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Tomba C, Braïni C, Bugnicourt G, Cohen F, Friedrich BM, Gov NS, Villard C. Geometrical Determinants of Neuronal Actin Waves. Front Cell Neurosci 2017; 11:86. [PMID: 28424590 PMCID: PMC5372798 DOI: 10.3389/fncel.2017.00086] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Accepted: 03/13/2017] [Indexed: 11/19/2022] Open
Abstract
Hippocampal neurons produce in their early stages of growth propagative, actin-rich dynamical structures called actin waves. The directional motion of actin waves from the soma to the tip of neuronal extensions has been associated with net forward growth, and ultimately with the specification of neurites into axon and dendrites. Here, geometrical cues are used to control actin wave dynamics by constraining neurons on adhesive stripes of various widths. A key observable, the average time between the production of consecutive actin waves, or mean inter-wave interval (IWI), was identified. It scales with the neurite width, and more precisely with the width of the proximal segment close to the soma. In addition, the IWI is independent of the total number of neurites. These two results suggest a mechanistic model of actin wave production, by which the material conveyed by actin waves is assembled in the soma until it reaches the threshold leading to the initiation and propagation of a new actin wave. Based on these observations, we formulate a predictive theoretical description of actin wave-driven neuronal growth and polarization, which consistently accounts for different sets of experiments.
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Affiliation(s)
- Caterina Tomba
- Université Grenoble Alpes, Centre National de la Recherche Scientifique (CNRS), Institut NéelGrenoble, France.,Université Grenoble Alpes, Centre National de la Recherche Scientifique (CNRS), Laboratoire des Technologies de la Microélectronique, CEA-LETIGrenoble, France
| | - Céline Braïni
- Université Grenoble Alpes, Centre National de la Recherche Scientifique (CNRS), Institut NéelGrenoble, France.,Laboratoire PhysicoChimie Curie, Institut Curie, Pierre-Gilles de Gennes Institute for Microfluidics, CNRS, PSL Research UniversityParis, France
| | - Ghislain Bugnicourt
- Université Grenoble Alpes, Centre National de la Recherche Scientifique (CNRS), Institut NéelGrenoble, France
| | - Floriane Cohen
- Laboratoire PhysicoChimie Curie, Institut Curie, Pierre-Gilles de Gennes Institute for Microfluidics, CNRS, PSL Research UniversityParis, France
| | - Benjamin M Friedrich
- Biological Algorithms Group, Center for Advancing Electronics Dresden, Technische Universität DresdenDresden, Germany
| | - Nir S Gov
- Department of Chemical Physics, Weizmann Institute of ScienceRehovot, Israel
| | - Catherine Villard
- Université Grenoble Alpes, Centre National de la Recherche Scientifique (CNRS), Institut NéelGrenoble, France.,Laboratoire PhysicoChimie Curie, Institut Curie, Pierre-Gilles de Gennes Institute for Microfluidics, CNRS, PSL Research UniversityParis, France
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44
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Neuronal polarization: From spatiotemporal signaling to cytoskeletal dynamics. Mol Cell Neurosci 2017; 84:11-28. [PMID: 28363876 DOI: 10.1016/j.mcn.2017.03.008] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Revised: 03/24/2017] [Accepted: 03/26/2017] [Indexed: 12/20/2022] Open
Abstract
Neuronal polarization establishes distinct molecular structures to generate a single axon and multiple dendrites. Studies over the past years indicate that this efficient separation is brought about by a network of feedback loops. Axonal growth seems to play a major role in fueling those feedback loops and thereby stabilizing neuronal polarity. Indeed, various effectors involved in feedback loops are pivotal for axonal growth by ultimately acting on the actin and microtubule cytoskeleton. These effectors have key roles in interconnecting actin and microtubule dynamics - a mechanism crucial to commanding the growth of axons. We propose a model connecting signaling with cytoskeletal dynamics and neurite growth to better describe the underlying processes involved in neuronal polarization. We will discuss the current views on feedback loops and highlight the current limits of our understanding.
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45
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Armijo-Weingart L, Gallo G. It takes a village to raise a branch: Cellular mechanisms of the initiation of axon collateral branches. Mol Cell Neurosci 2017; 84:36-47. [PMID: 28359843 DOI: 10.1016/j.mcn.2017.03.007] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Revised: 01/03/2017] [Accepted: 03/01/2017] [Indexed: 12/14/2022] Open
Abstract
The formation of axon collateral branches from the pre-existing shafts of axons is an important aspect of neurodevelopment and the response of the nervous system to injury. This article provides an overview of the role of the cytoskeleton and signaling mechanisms in the formation of axon collateral branches. Both the actin filament and microtubule components of the cytoskeleton are required for the formation of axon branches. Recent work has begun to shed light on how these two elements of the cytoskeleton are integrated by proteins that functionally or physically link the cytoskeleton. While a number of signaling pathways have been determined as having a role in the formation of axon branches, the complexity of the downstream mechanisms and links to specific signaling pathways remain to be fully determined. The regulation of intra-axonal protein synthesis and organelle function are also emerging as components of signal-induced axon branching. Although much has been learned in the last couple of decades about the mechanistic basis of axon branching we can look forward to continue elucidating this complex biological phenomenon with the aim of understanding how multiple signaling pathways, cytoskeletal regulators and organelles are coordinated locally along the axon to give rise to a branch.
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Affiliation(s)
- Lorena Armijo-Weingart
- Shriners Pediatric Research Center, Temple University, Department of Anatomy and Cell Biology, 3500 North Broad St, Philadelphia, PA 19140, United States
| | - Gianluca Gallo
- Shriners Pediatric Research Center, Temple University, Department of Anatomy and Cell Biology, 3500 North Broad St, Philadelphia, PA 19140, United States.
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Qu Y, Hahn I, Webb SED, Pearce SP, Prokop A. Periodic actin structures in neuronal axons are required to maintain microtubules. Mol Biol Cell 2016; 28:296-308. [PMID: 27881663 PMCID: PMC5231898 DOI: 10.1091/mbc.e16-10-0727] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Revised: 11/09/2016] [Accepted: 11/15/2016] [Indexed: 12/31/2022] Open
Abstract
Drosophila genetics is combined with high-resolution microscopy and a number of functional readouts to demonstrate key factors required for the presence of regularly spaced rings of cortical actin in axons. The data suggest important roles for the actin rings in microtubule regulation, most likely by sustaining their polymerization. Axons are cable-like neuronal processes wiring the nervous system. They contain parallel bundles of microtubules as structural backbones, surrounded by regularly spaced actin rings termed the periodic membrane skeleton (PMS). Despite being an evolutionarily conserved, ubiquitous, highly ordered feature of axons, the function of PMS is unknown. Here we studied PMS abundance, organization, and function, combining versatile Drosophila genetics with superresolution microscopy and various functional readouts. Analyses with 11 actin regulators and three actin-targeting drugs suggest that PMS contains short actin filaments that are depolymerization resistant and sensitive to spectrin, adducin, and nucleator deficiency, consistent with microscopy-derived models proposing PMS as specialized cortical actin. Upon actin removal, we observed gaps in microtubule bundles, reduced microtubule polymerization, and reduced axon numbers, suggesting a role of PMS in microtubule organization. These effects become strongly enhanced when carried out in neurons lacking the microtubule-stabilizing protein Short stop (Shot). Combining the aforementioned actin manipulations with Shot deficiency revealed a close correlation between PMS abundance and microtubule regulation, consistent with a model in which PMS-dependent microtubule polymerization contributes to their maintenance in axons. We discuss potential implications of this novel PMS function along axon shafts for axon maintenance and regeneration.
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Affiliation(s)
- Yue Qu
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Ines Hahn
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Stephen E D Webb
- Rutherford Appleton Laboratory, Science and Technology Facilities Council, Didcot OX11 0QX, United Kingdom
| | - Simon P Pearce
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom.,School of Mathematics, University of Manchester, Manchester M13 9PL, United Kingdom
| | - Andreas Prokop
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
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Pacheco A, Gallo G. Actin filament-microtubule interactions in axon initiation and branching. Brain Res Bull 2016; 126:300-310. [PMID: 27491623 DOI: 10.1016/j.brainresbull.2016.07.013] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Revised: 07/28/2016] [Accepted: 07/30/2016] [Indexed: 10/21/2022]
Abstract
Neurons begin life as spherical cells. A major hallmark of neuronal development is the formation of elongating processes from the cell body which subsequently differentiate into dendrites and the axon. The formation and later development of neuronal processes is achieved through the concerted organization of actin filaments and microtubules. Here, we review the literature regarding recent advances in the understanding of cytoskeletal interactions in neurons focusing on the initiation of processes from neuronal cell bodies and the collateral branching of axons. The complex crosstalk between cytoskeletal elements is mediated by a cohort of proteins that either bind both cytoskeletal systems or allow one to regulate the other. Recent studies have highlighted the importance of microtubule plus-tip proteins in the regulation of the dynamics and organization of actin filaments, while also providing a mechanism for the subcellular capture and guidance of microtubule tips by actin filaments. Although the understanding of cytoskeletal crosstalk and interactions in neuronal morphogenesis has advanced significantly in recent years the appreciation of the neuron as an integrated cytoskeletal system remains a frontier.
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Affiliation(s)
- Almudena Pacheco
- Temple University, Lewis Kats School of Medicine, Shriners Hospitals Pediatric Research Center, Department of Anatomy and Cell Biology, 3500 North Broad Street, Philadelphia, PA 19140, United States
| | - Gianluca Gallo
- Temple University, Lewis Kats School of Medicine, Shriners Hospitals Pediatric Research Center, Department of Anatomy and Cell Biology, 3500 North Broad Street, Philadelphia, PA 19140, United States.
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Brettle M, Patel S, Fath T. Tropomyosins in the healthy and diseased nervous system. Brain Res Bull 2016; 126:311-323. [PMID: 27298153 DOI: 10.1016/j.brainresbull.2016.06.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Revised: 06/09/2016] [Accepted: 06/10/2016] [Indexed: 12/25/2022]
Abstract
Regulation of the actin cytoskeleton is dependent on a plethora of actin-associated proteins in all eukaryotic cells. The family of tropomyosins plays a key role in controlling the function of several of these actin-associated proteins and their access to actin filaments. In order to understand the regulation of the actin cytoskeleton in highly dynamic subcellular compartments of neurons such as growth cones of developing neurons and the synaptic compartment of mature neurons, it is pivotal to decipher the functional role of tropomyosins in the nervous system. In this review, we will discuss the current understanding and recent findings on the regulation of the actin cytoskeleton by tropomyosins and potential implication that this has for the dysregulation of the actin cytoskeleton in neurological diseases.
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Affiliation(s)
- Merryn Brettle
- Neurodegeneration and Repair Unit, School of Medical Sciences, University of New South Wales, 2052 Sydney, New South Wales, Australia
| | - Shrujna Patel
- Neurodegeneration and Repair Unit, School of Medical Sciences, University of New South Wales, 2052 Sydney, New South Wales, Australia
| | - Thomas Fath
- Neurodegeneration and Repair Unit, School of Medical Sciences, University of New South Wales, 2052 Sydney, New South Wales, Australia.
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49
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Abstract
The growth and migration of neurons require continuous remodelling of the neuronal cytoskeleton, providing a versatile cellular framework for force generation and guided movement, in addition to structural support. Actin filaments and microtubules are central to the dynamic action of the cytoskeleton and rapid advances in imaging technologies are enabling ever more detailed visualisation of the dynamic intracellular networks that they form. However, these filaments do not act individually and an expanding body of evidence emphasises the importance of actin-microtubule crosstalk in orchestrating cytoskeletal dynamics. Here, we summarise our current understanding of the structure and dynamics of actin and microtubules in isolation, before reviewing both the mechanisms and the molecular players involved in mediating actin-microtubule crosstalk in neurons.
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Affiliation(s)
- Charlotte H Coles
- Laboratory for Axon Growth and Regeneration, German Center for Neurodegenerative Diseases (DZNE), Ludwig-Erhard-Allee 2, 53175, Bonn, Germany.
| | - Frank Bradke
- Laboratory for Axon Growth and Regeneration, German Center for Neurodegenerative Diseases (DZNE), Ludwig-Erhard-Allee 2, 53175, Bonn, Germany.
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50
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Leite SC, Sousa MM. The neuronal and actin commitment: Why do neurons need rings? Cytoskeleton (Hoboken) 2016; 73:424-34. [DOI: 10.1002/cm.21273] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Revised: 01/07/2016] [Accepted: 01/07/2016] [Indexed: 12/17/2022]
Affiliation(s)
- Sérgio Carvalho Leite
- Nerve Regeneration Group, IBMC - Instituto De Biologia Molecular E Celular; Porto Portugal
- Instituto De Investigação E Inovação Em Saúde, Universidade Do Porto; Porto Portugal
- ICBAS, Universidade Do Porto; Porto Portugal
| | - Mónica Mendes Sousa
- Nerve Regeneration Group, IBMC - Instituto De Biologia Molecular E Celular; Porto Portugal
- Instituto De Investigação E Inovação Em Saúde, Universidade Do Porto; Porto Portugal
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