1
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Fang HY, Forghani R, Clarke A, McQueen PG, Chandrasekaran A, O’Neill KM, Losert W, Papoian GA, Giniger E. Enabled primarily controls filopodial morphology, not actin organization, in the TSM1 growth cone in Drosophila. Mol Biol Cell 2023; 34:ar83. [PMID: 37223966 PMCID: PMC10398877 DOI: 10.1091/mbc.e23-01-0003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Revised: 05/18/2023] [Accepted: 05/19/2023] [Indexed: 05/25/2023] Open
Abstract
Ena/VASP proteins are processive actin polymerases that are required throughout animal phylogeny for many morphogenetic processes, including axon growth and guidance. Here we use in vivo live imaging of morphology and actin distribution to determine the role of Ena in promoting the growth of the TSM1 axon of the Drosophila wing. Altering Ena activity causes stalling and misrouting of TSM1. Our data show that Ena has a substantial impact on filopodial morphology in this growth cone but exerts only modest effects on actin distribution. This is in contrast to the main regulator of Ena, Abl tyrosine kinase, which was shown previously to have profound effects on actin and only mild effects on TSM1 growth cone morphology. We interpret these data as suggesting that the primary role of Ena in this axon may be to link actin to the morphogenetic processes of the plasma membrane, rather than to regulate actin organization itself. These data also suggest that a key role of Ena, acting downstream of Abl, may be to maintain consistent organization and reliable evolution of growth cone structure, even as Abl activity varies in response to guidance cues in the environment.
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Affiliation(s)
- Hsiao Yu Fang
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892
| | - Rameen Forghani
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892
| | - Akanni Clarke
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892
| | - Philip G. McQueen
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892
| | - Aravind Chandrasekaran
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20752
| | - Kate M. O’Neill
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892
- Institute for Physical Sciences and Department of Physics, University of Maryland, College Park, MD 20752
| | - Wolfgang Losert
- Institute for Physical Sciences and Department of Physics, University of Maryland, College Park, MD 20752
| | - Garegin A. Papoian
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20752
| | - Edward Giniger
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892
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2
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Schneider F, Metz I, Rust MB. Regulation of actin filament assembly and disassembly in growth cone motility and axon guidance. Brain Res Bull 2023; 192:21-35. [PMID: 36336143 DOI: 10.1016/j.brainresbull.2022.10.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 10/26/2022] [Accepted: 10/28/2022] [Indexed: 11/06/2022]
Abstract
Directed outgrowth of axons is fundamental for the establishment of neuronal networks. Axon outgrowth is guided by growth cones, highly motile structures enriched in filamentous actin (F-actin) located at the axons' distal tips. Growth cones exploit F-actin-based protrusions to scan the environment for guidance cues, and they contain the sensory apparatus to translate guidance cue information into intracellular signaling cascades. These cascades act upstream of actin-binding proteins (ABP) and thereby control assembly and disassembly of F-actin. Spatiotemporally controlled F-actin dis-/assembly in growth cones steers the axon towards attractants and away from repellents, and it thereby navigates the axon through the developing nervous system. Hence, ABP that control F-actin dynamics emerged as critical regulators of neuronal network formation. In the present review article, we will summarize and discuss current knowledge of the mechanisms that control remodeling of the actin cytoskeleton in growth cones, focusing on recent progress in the field. Further, we will introduce tools and techniques that allow to study actin regulatory mechanism in growth cones.
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Affiliation(s)
- Felix Schneider
- Molecular Neurobiology Group, Institute of Physiological Chemistry, Philipps-University of Marburg, 35032 Marburg, Germany; DFG Research Training Group 'Membrane Plasticity in Tissue Development and Remodeling', GRK 2213, Philipps-University of Marburg, 35032 Marburg, Germany; Molecular Urooncology, Department of Urology, University Hospital Heidelberg, 69120 Heidelberg, Germany
| | - Isabell Metz
- Molecular Neurobiology Group, Institute of Physiological Chemistry, Philipps-University of Marburg, 35032 Marburg, Germany; DFG Research Training Group 'Membrane Plasticity in Tissue Development and Remodeling', GRK 2213, Philipps-University of Marburg, 35032 Marburg, Germany
| | - Marco B Rust
- Molecular Neurobiology Group, Institute of Physiological Chemistry, Philipps-University of Marburg, 35032 Marburg, Germany; DFG Research Training Group 'Membrane Plasticity in Tissue Development and Remodeling', GRK 2213, Philipps-University of Marburg, 35032 Marburg, Germany; Center for Mind, Brain and Behavior (CMBB), University of Marburg and Justus-Liebig-University Giessen, 35032 Marburg, Germany.
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3
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Qu Y, Alves‐Silva J, Gupta K, Hahn I, Parkin J, Sánchez‐Soriano N, Prokop A. Re-evaluating the actin-dependence of spectraplakin functions during axon growth and maintenance. Dev Neurobiol 2022; 82:288-307. [PMID: 35333003 PMCID: PMC9320987 DOI: 10.1002/dneu.22873] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 01/30/2022] [Accepted: 03/07/2022] [Indexed: 11/11/2022]
Abstract
Axons are the long and slender processes of neurons constituting the biological cables that wire the nervous system. The growth and maintenance of axons require loose microtubule bundles that extend through their entire length. Understanding microtubule regulation is therefore an essential aspect of axon biology. Key regulators of neuronal microtubules are the spectraplakins, a well-conserved family of cytoskeletal cross-linkers that underlie neuropathies in mouse and humans. Spectraplakin deficiency in mouse or Drosophila causes severe decay of microtubule bundles and reduced axon growth. The underlying mechanisms are best understood for Drosophila's spectraplakin Short stop (Shot) and believed to involve cytoskeletal cross-linkage: Shot's binding to microtubules and Eb1 via its C-terminus has been thoroughly investigated, whereas its F-actin interaction via N-terminal calponin homology (CH) domains is little understood. Here, we have gained new understanding by showing that the F-actin interaction must be finely balanced: altering the properties of F-actin networks or deleting/exchanging Shot's CH domains induces changes in Shot function-with a Lifeact-containing Shot variant causing remarkable remodeling of neuronal microtubules. In addition to actin-microtubule (MT) cross-linkage, we find strong indications that Shot executes redundant MT bundle-promoting roles that are F-actin-independent. We argue that these likely involve the neuronal Shot-PH isoform, which is characterized by a large, unexplored central plakin repeat region (PRR) similarly existing also in mammalian spectraplakins.
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Affiliation(s)
- Yue Qu
- Manchester Academic Health Science CentreFaculty of BiologyMedicine and HealthSchool of Biology, The University of ManchesterManchesterUK
- Present address:
Division of Nutritional Sciences, College of Human Ecology, Cornell University, Ithaca, USA
| | - Juliana Alves‐Silva
- Manchester Academic Health Science CentreFaculty of BiologyMedicine and HealthSchool of Biology, The University of ManchesterManchesterUK
- Present address:
Departamento de Morfologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Kriti Gupta
- Department of Molecular Physiology & Cell SignallingInstitute of SystemsMolecular & Integrative BiologyUniversity of LiverpoolLiverpoolUK
| | - Ines Hahn
- Manchester Academic Health Science CentreFaculty of BiologyMedicine and HealthSchool of Biology, The University of ManchesterManchesterUK
| | - Jill Parkin
- Manchester Academic Health Science CentreFaculty of BiologyMedicine and HealthSchool of Biology, The University of ManchesterManchesterUK
| | - Natalia Sánchez‐Soriano
- Department of Molecular Physiology & Cell SignallingInstitute of SystemsMolecular & Integrative BiologyUniversity of LiverpoolLiverpoolUK
| | - Andreas Prokop
- Manchester Academic Health Science CentreFaculty of BiologyMedicine and HealthSchool of Biology, The University of ManchesterManchesterUK
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4
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Grintsevich EE, Ahmed G, Ginosyan AA, Wu H, Rich SK, Reisler E, Terman JR. Profilin and Mical combine to impair F-actin assembly and promote disassembly and remodeling. Nat Commun 2021; 12:5542. [PMID: 34545088 PMCID: PMC8452626 DOI: 10.1038/s41467-021-25781-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Accepted: 08/24/2021] [Indexed: 11/30/2022] Open
Abstract
Cellular events require the spatiotemporal interplay between actin assembly and actin disassembly. Yet, how different factors promote the integration of these two opposing processes is unclear. In particular, cellular monomeric (G)-actin is complexed with profilin, which inhibits spontaneous actin nucleation but fuels actin filament (F-actin) assembly by elongation-promoting factors (formins, Ena/VASP). In contrast, site-specific F-actin oxidation by Mical promotes F-actin disassembly and release of polymerization-impaired Mical-oxidized (Mox)-G-actin. Here we find that these two opposing processes connect with one another to orchestrate actin/cellular remodeling. Specifically, we find that profilin binds Mox-G-actin, yet these complexes do not fuel elongation factors’-mediated F-actin assembly, but instead inhibit polymerization and promote further Mox-F-actin disassembly. Using Drosophila as a model system, we show that similar profilin–Mical connections occur in vivo – where they underlie F-actin/cellular remodeling that accompanies Semaphorin–Plexin cellular/axon repulsion. Thus, profilin and Mical combine to impair F-actin assembly and promote F-actin disassembly, while concomitantly facilitating cellular remodeling and plasticity. Actin-based structures in cells and tissues are built and maintained through a poorly understood balance between assembly and disassembly. Here, our findings provide insights into how factors known to promote these opposing effects dynamically integrate to shape cells and tissue systems.
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Affiliation(s)
- Elena E Grintsevich
- Department of Chemistry and Biochemistry, University of California, Los Angeles (UCLA), Los Angeles, CA, 90095, USA. .,Department of Chemistry and Biochemistry, California State University, Long Beach (CSULB), Long Beach, CA, 90840, USA.
| | - Giasuddin Ahmed
- Departments of Neuroscience and Pharmacology, The University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Anush A Ginosyan
- Department of Chemistry and Biochemistry, University of California, Los Angeles (UCLA), Los Angeles, CA, 90095, USA
| | - Heng Wu
- Departments of Neuroscience and Pharmacology, The University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Shannon K Rich
- Departments of Neuroscience and Pharmacology, The University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Emil Reisler
- Department of Chemistry and Biochemistry, University of California, Los Angeles (UCLA), Los Angeles, CA, 90095, USA. .,Molecular Biology Institute, UCLA, Los Angeles, CA, 90095, USA.
| | - Jonathan R Terman
- Departments of Neuroscience and Pharmacology, The University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA.
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5
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Yaniv SP, Meltzer H, Alyagor I, Schuldiner O. Developmental axon regrowth and primary neuron sprouting utilize distinct actin elongation factors. J Cell Biol 2021; 219:151569. [PMID: 32191286 PMCID: PMC7199854 DOI: 10.1083/jcb.201903181] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2019] [Revised: 11/06/2019] [Accepted: 02/14/2020] [Indexed: 01/23/2023] Open
Abstract
Intrinsic neurite growth potential is a key determinant of neuronal regeneration efficiency following injury. The stereotypical remodeling of Drosophila γ-neurons includes developmental regrowth of pruned axons to form adult specific connections, thereby offering a unique system to uncover growth potential regulators. Motivated by the dynamic expression in remodeling γ-neurons, we focus here on the role of actin elongation factors as potential regulators of developmental axon regrowth. We found that regrowth in vivo requires the actin elongation factors Ena and profilin, but not the formins that are expressed in γ-neurons. In contrast, primary γ-neuron sprouting in vitro requires profilin and the formin DAAM, but not Ena. Furthermore, we demonstrate that DAAM can compensate for the loss of Ena in vivo. Similarly, DAAM mutants express invariably high levels of Ena in vitro. Thus, we show that different linear actin elongation factors function in distinct contexts even within the same cell type and that they can partially compensate for each other.
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Affiliation(s)
- Shiri P Yaniv
- Department of Molecular Cell Biology, Weizmann Institute of Sciences, Rehovot, Israel
| | - Hagar Meltzer
- Department of Molecular Cell Biology, Weizmann Institute of Sciences, Rehovot, Israel
| | - Idan Alyagor
- Department of Molecular Cell Biology, Weizmann Institute of Sciences, Rehovot, Israel
| | - Oren Schuldiner
- Department of Molecular Cell Biology, Weizmann Institute of Sciences, Rehovot, Israel
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6
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Gau D, Vignaud L, Allen A, Guo Z, Sahel J, Boone D, Koes D, Guillonneau X, Roy P. Disruption of profilin1 function suppresses developmental and pathological retinal neovascularization. J Biol Chem 2020; 295:9618-9629. [PMID: 32444495 PMCID: PMC7363146 DOI: 10.1074/jbc.ra120.012613] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 05/20/2020] [Indexed: 12/18/2022] Open
Abstract
Angiogenesis-mediated neovascularization in the eye is usually associated with visual complications. Pathological angiogenesis is particularly prominent in the retina in the settings of proliferative diabetic retinopathy, in which it can lead to permanent loss of vision. In this study, by bioinformatics analyses, we provide evidence for elevated expression of actin-binding protein PFN1 (profilin1) in the retinal vascular endothelial cells (VECs) of individuals with proliferative diabetic retinopathy, findings further supported by gene expression analyses for PFN1 in experimentally induced abnormal retinal neovascularization in an oxygen-induced retinopathy murine model. We observed that in a conditional knockout mouse model, postnatal deletion of the Pfn1 gene in VECs leads to defects in tip cell activity (marked by impaired filopodial protrusions) and reduced vascular sprouting, resulting in hypovascularization during developmental angiogenesis in the retina. Consistent with these findings, an investigative small molecule compound targeting the PFN1-actin interaction reduced random motility, proliferation, and cord morphogenesis of retinal VECs in vitro and experimentally induced abnormal retinal neovascularization in vivo In summary, these findings provide the first direct in vivo evidence that PFN1 is required for formation of actin-based protrusive structures and developmental angiogenesis in the retina. The proof of concept of susceptibility of abnormal angiogenesis to small molecule intervention of PFN1-actin interaction reported here lays a conceptual foundation for targeting PFN1 as a possible strategy in angiogenesis-dependent retinal diseases.
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Affiliation(s)
- David Gau
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Lucile Vignaud
- Institut de la Vision, Sorbonne Université, INSERM, Paris, France
| | - Abigail Allen
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Zhijian Guo
- Department of Nephrology, Southern Medical University, Guangzhou, China
| | - Jose Sahel
- Institut de la Vision, Sorbonne Université, INSERM, Paris, France,Department of Ophthalmology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA
| | - David Boone
- Department of Biomedical Informatics, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - David Koes
- Department of Computational Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | | | - Partha Roy
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, USA .,Department of Pathology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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7
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Clarke A, McQueen PG, Fang HY, Kannan R, Wang V, McCreedy E, Wincovitch S, Giniger E. Abl signaling directs growth of a pioneer axon in Drosophila by shaping the intrinsic fluctuations of actin. Mol Biol Cell 2020; 31:466-477. [PMID: 31967946 PMCID: PMC7185895 DOI: 10.1091/mbc.e19-10-0564] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The fundamental problem in axon growth and guidance is understanding how cytoplasmic signaling modulates the cytoskeleton to produce directed growth cone motility. Live imaging of the TSM1 axon of the developing Drosophila wing has shown that the essential role of the core guidance signaling molecule, Abelson (Abl) tyrosine kinase, is to modulate the organization and spatial localization of actin in the advancing growth cone. Here, we dissect in detail the properties of that actin organization and its consequences for growth cone morphogenesis and motility. We show that advance of the actin mass in the distal axon drives the forward motion of the dynamic filopodial domain that defines the growth cone. We further show that Abl regulates both the width of the actin mass and its internal organization, spatially biasing the intrinsic fluctuations of actin to achieve net advance of the actin, and thus of the dynamic filopodial domain of the growth cone, while maintaining the essential coherence of the actin mass itself. These data suggest a model whereby guidance signaling systematically shapes the intrinsic, stochastic fluctuations of actin in the growth cone to produce axon growth and guidance.
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Affiliation(s)
- Akanni Clarke
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892.,Department of Biochemistry and Molecular Medicine, George Washington University School of Medicine/National Institutes of Health Graduate Partnerships Program, Washington, DC 20037
| | - Philip G McQueen
- Center for Information Technology, National Institutes of Health, Bethesda, MD 20892
| | - Hsiao Yu Fang
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892
| | - Ramakrishnan Kannan
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892
| | - Victor Wang
- Center for Information Technology, National Institutes of Health, Bethesda, MD 20892
| | - Evan McCreedy
- Center for Information Technology, National Institutes of Health, Bethesda, MD 20892
| | - Stephen Wincovitch
- National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892
| | - Edward Giniger
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892
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8
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Drosophila Atg9 regulates the actin cytoskeleton via interactions with profilin and Ena. Cell Death Differ 2019; 27:1677-1692. [PMID: 31740789 DOI: 10.1038/s41418-019-0452-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 10/25/2019] [Accepted: 10/29/2019] [Indexed: 12/16/2022] Open
Abstract
Autophagy ensures the turnover of cytoplasm and requires the coordinated action of Atg proteins, some of which also have moonlighting functions in higher eukaryotes. Here we show that the transmembrane protein Atg9 is required for female fertility, and its loss leads to defects in actin cytoskeleton organization in the ovary and enhances filopodia formation in neurons in Drosophila. Atg9 localizes to the plasma membrane anchor points of actin cables and is also important for the integrity of the cortical actin network. Of note, such phenotypes are not seen in other Atg mutants, suggesting that these are independent of autophagy defects. Mechanistically, we identify the known actin regulators profilin and Ena/VASP as novel binding partners of Atg9 based on microscopy, biochemical, and genetic interactions. Accordingly, the localization of both profilin and Ena depends on Atg9. Taken together, our data identify a new and unexpected role for Atg9 in actin cytoskeleton regulation.
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9
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Hahn I, Voelzmann A, Liew YT, Costa-Gomes B, Prokop A. The model of local axon homeostasis - explaining the role and regulation of microtubule bundles in axon maintenance and pathology. Neural Dev 2019; 14:11. [PMID: 31706327 PMCID: PMC6842214 DOI: 10.1186/s13064-019-0134-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Accepted: 10/02/2019] [Indexed: 12/20/2022] Open
Abstract
Axons are the slender, cable-like, up to meter-long projections of neurons that electrically wire our brains and bodies. In spite of their challenging morphology, they usually need to be maintained for an organism's lifetime. This makes them key lesion sites in pathological processes of ageing, injury and neurodegeneration. The morphology and physiology of axons crucially depends on the parallel bundles of microtubules (MTs), running all along to serve as their structural backbones and highways for life-sustaining cargo transport and organelle dynamics. Understanding how these bundles are formed and then maintained will provide important explanations for axon biology and pathology. Currently, much is known about MTs and the proteins that bind and regulate them, but very little about how these factors functionally integrate to regulate axon biology. As an attempt to bridge between molecular mechanisms and their cellular relevance, we explain here the model of local axon homeostasis, based on our own experiments in Drosophila and published data primarily from vertebrates/mammals as well as C. elegans. The model proposes that (1) the physical forces imposed by motor protein-driven transport and dynamics in the confined axonal space, are a life-sustaining necessity, but pose a strong bias for MT bundles to become disorganised. (2) To counterbalance this risk, MT-binding and -regulating proteins of different classes work together to maintain and protect MT bundles as necessary transport highways. Loss of balance between these two fundamental processes can explain the development of axonopathies, in particular those linking to MT-regulating proteins, motors and transport defects. With this perspective in mind, we hope that more researchers incorporate MTs into their work, thus enhancing our chances of deciphering the complex regulatory networks that underpin axon biology and pathology.
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Affiliation(s)
- Ines Hahn
- Manchester Academic Health Science Centre, Faculty of Biology, Medicine and Health, The University of Manchester, School of Biology, Manchester, UK
| | - André Voelzmann
- Manchester Academic Health Science Centre, Faculty of Biology, Medicine and Health, The University of Manchester, School of Biology, Manchester, UK
| | - Yu-Ting Liew
- Manchester Academic Health Science Centre, Faculty of Biology, Medicine and Health, The University of Manchester, School of Biology, Manchester, UK
| | - Beatriz Costa-Gomes
- Manchester Academic Health Science Centre, Faculty of Biology, Medicine and Health, The University of Manchester, School of Biology, Manchester, UK
| | - Andreas Prokop
- Manchester Academic Health Science Centre, Faculty of Biology, Medicine and Health, The University of Manchester, School of Biology, Manchester, UK.
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10
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Ren Y, He Y, Brown S, Zbornik E, Mlodzianoski MJ, Ma D, Huang F, Mattoo S, Suter DM. A single tyrosine phosphorylation site in cortactin is important for filopodia formation in neuronal growth cones. Mol Biol Cell 2019; 30:1817-1833. [PMID: 31116646 PMCID: PMC6727743 DOI: 10.1091/mbc.e18-04-0202] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Cortactin is a Src tyrosine phosphorylation substrate that regulates multiple actin-related cellular processes. While frequently studied in nonneuronal cells, the functions of cortactin in neuronal growth cones are not well understood. We recently reported that cortactin mediates the effects of Src tyrosine kinase in regulating actin organization and dynamics in both lamellipodia and filopodia of Aplysia growth cones. Here, we identified a single cortactin tyrosine phosphorylation site (Y499) to be important for the formation of filopodia. Overexpression of a 499F phospho-deficient cortactin mutant decreased filopodia length and density, whereas overexpression of a 499E phospho-mimetic mutant increased filopodia length. Using an antibody against cortactin pY499, we showed that tyrosine-phosphorylated cortactin is enriched along the leading edge. The leading edge localization of phosphorylated cortactin is Src2-dependent, F-actin-independent, and important for filopodia formation. In vitro kinase assays revealed that Src2 phosphorylates cortactin at Y499, although Y505 is the preferred site in vitro. Finally, we provide evidence that Arp2/3 complex acts downstream of phosphorylated cortactin to regulate density but not length of filopodia. In conclusion, we have characterized a tyrosine phosphorylation site in Aplysia cortactin that plays a major role in the Src/cortactin/Arp2/3 signaling pathway controlling filopodia formation.
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Affiliation(s)
- Yuan Ren
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907
| | - Yingpei He
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907
| | - Sherlene Brown
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907
| | - Erica Zbornik
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907
| | - Michael J Mlodzianoski
- Department of Weldon School of Biomedical Engineering, Purdue Institutes of Inflammation, Immunology and Infectious Disease, Purdue University, West Lafayette, IN 47907
| | - Donghan Ma
- Department of Weldon School of Biomedical Engineering, Purdue Institutes of Inflammation, Immunology and Infectious Disease, Purdue University, West Lafayette, IN 47907
| | - Fang Huang
- Department of Weldon School of Biomedical Engineering, Purdue Institutes of Inflammation, Immunology and Infectious Disease, Purdue University, West Lafayette, IN 47907.,Department of Inflammation, Immunology and Infectious Disease, Purdue University, West Lafayette, IN 47907.,Department of Integrative Neuroscience, Purdue University, West Lafayette, IN 47907
| | - Seema Mattoo
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907.,Department of Inflammation, Immunology and Infectious Disease, Purdue University, West Lafayette, IN 47907
| | - Daniel M Suter
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907.,Department of Integrative Neuroscience, Purdue University, West Lafayette, IN 47907.,Department of Bindley Bioscience Center, Purdue University, West Lafayette, IN 47907.,Department of Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907
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11
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Multiple roles of the actin and microtubule-regulating formins in the developing brain. Neurosci Res 2019; 138:59-69. [DOI: 10.1016/j.neures.2018.09.008] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Revised: 08/22/2018] [Accepted: 08/23/2018] [Indexed: 01/08/2023]
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12
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Deng X, Tu Z, Xiong M, Tembo K, Zhou L, Liu P, Pan S, Xiong J, Yang X, Leng J, Zhang Q, Xiao R, Zhang Q. Wnt5a and CCL25 promote adult T-cell acute lymphoblastic leukemia cell migration, invasion and metastasis. Oncotarget 2018; 8:39033-39047. [PMID: 28380463 PMCID: PMC5503593 DOI: 10.18632/oncotarget.16559] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Accepted: 02/27/2017] [Indexed: 01/10/2023] Open
Abstract
Adult T-cell acute lymphoblastic leukemia (T-ALL) is a refractory leukemia. We previously showed that CCL25/CCR9 promotes T-ALL metastasis. In the present study, we assessed the effects of CCL25 on Wnt expression and the effects of Wnt5a and CCL25 on PI3K/Akt and RhoA activation. Transwell assays and mouse xenograft experiments were utilized to assess the effects of Wnt5a and CCL25 on MOLT4 cell invasion, migration and metastasis. The effects of Wnt5a on MOLT4 cell actin polarization and pseudopodium formation were examined using laser scanning confocal microscopy and scanning electron microscopy. CCL25 induced Wnt5a expression in MOLT4 cells by promoting protein kinase C (PKC) expression and activation. Wnt5a promoted MOLT4 cell migration, invasion, actin polarization, and lamellipodium and filopodia formation via PI3K/Akt-RhoA pathway activation. These effects were rescued by PI3K/Akt or RhoA knockdown or inhibition. Additionally, Wnt5a in cooperation with CCL25 promoted MOLT4 cell mouse liver metastasis and stimulated RhoA activation. These results show that CCL25/CCR9 upregulates Wnt5a by promoting PKC expression and activation in MOLT4 cells. This in turn promotes cell migration and invasion via PI3K/Akt-RhoA signaling, enhancing cell polarization and pseudopodium formation. These findings indicate that the PI3K/Akt-RhoA pathway is likely responsible for Wnt5a-induced adult T-ALL cell migration and invasion.
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Affiliation(s)
- Xinzhou Deng
- Department of Immunology, School of Basic Medical Sciences, Wuhan University, Wuhan, Hubei, China.,Department of Clinical Oncology, Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei, China
| | - Zhenbo Tu
- Department of Immunology, School of Basic Medical Sciences, Wuhan University, Wuhan, Hubei, China
| | - Meng Xiong
- Department of Immunology, School of Basic Medical Sciences, Wuhan University, Wuhan, Hubei, China
| | - Kingsley Tembo
- Department of Immunology, School of Basic Medical Sciences, Wuhan University, Wuhan, Hubei, China
| | - Lu Zhou
- Department of Hematology, Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei, China
| | - Pan Liu
- Department of Immunology, School of Basic Medical Sciences, Wuhan University, Wuhan, Hubei, China
| | - Shan Pan
- Department of Immunology, School of Basic Medical Sciences, Wuhan University, Wuhan, Hubei, China
| | - Jie Xiong
- Department of Immunology, School of Basic Medical Sciences, Wuhan University, Wuhan, Hubei, China
| | - Xiangyong Yang
- Department of Biochemical Engineering, Hubei University of Technology Engineering and Technology College, Wuhan, Hubei, China
| | - Jun Leng
- Department of Immunology, School of Basic Medical Sciences, Wuhan University, Wuhan, Hubei, China
| | - Qian Zhang
- Department of Hematology, Zhongnan Hospital of Wuhan University, Wuhan, Hubei, China
| | - Ruijing Xiao
- Department of Immunology, School of Basic Medical Sciences, Wuhan University, Wuhan, Hubei, China
| | - Qiuping Zhang
- Department of Immunology, School of Basic Medical Sciences, Wuhan University, Wuhan, Hubei, China.,Hubei Provincial Key Laboratory of Developmentally Originated Disease, Wuhan, Hubei, China
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13
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Luo J, Liu Y, Nässel DR. Transcriptional Reorganization of Drosophila Motor Neurons and Their Muscular Junctions toward a Neuroendocrine Phenotype by the bHLH Protein Dimmed. Front Mol Neurosci 2017; 10:260. [PMID: 28855860 PMCID: PMC5557793 DOI: 10.3389/fnmol.2017.00260] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Accepted: 07/31/2017] [Indexed: 01/13/2023] Open
Abstract
Neuroendocrine cells store and secrete bulk amounts of neuropeptides, and display morphological and molecular characteristics distinct from neurons signaling with classical neurotransmitters. In Drosophila the transcription factor Dimmed (Dimm), is a prime organizer of neuroendocrine capacity in a majority of the peptidergic neurons. These neurons display large cell bodies and extensive axon terminations that commonly do not form regular synapses. We ask which molecular compartments of a neuron are affected by Dimm to generate these morphological features. Thus, we ectopically expressed Dimm in glutamatergic, Dimm-negative, motor neurons and analyzed their characteristics in the central nervous system and the neuromuscular junction. Ectopic Dimm results in motor neurons with enlarged cell bodies, diminished dendrites, larger axon terminations and boutons, as well as reduced expression of synaptic proteins both pre and post-synaptically. Furthermore, the neurons display diminished vesicular glutamate transporter, and signaling components known to sustain interactions between the developing axon termination and muscle, such as wingless and frizzled are down regulated. Ectopic co-expression of Dimm and the insulin receptor augments most of the above effects on the motor neurons. In summary, ectopic Dimm expression alters the glutamatergic motor neuron phenotype toward a neuroendocrine one, both pre- and post-synaptically. Thus, Dimm is a key organizer of both secretory capacity and morphological features characteristic of neuroendocrine cells, and this transcription factor affects also post-synaptic proteins.
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Affiliation(s)
- Jiangnan Luo
- Department of Zoology, Stockholm UniversityStockholm, Sweden
| | - Yiting Liu
- Department of Zoology, Stockholm UniversityStockholm, Sweden
| | - Dick R Nässel
- Department of Zoology, Stockholm UniversityStockholm, Sweden
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14
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Szikora S, Földi I, Tóth K, Migh E, Vig A, Bugyi B, Maléth J, Hegyi P, Kaltenecker P, Sanchez-Soriano N, Mihály J. The formin DAAM is required for coordination of the actin and microtubule cytoskeleton in axonal growth cones. J Cell Sci 2017; 130:2506-2519. [PMID: 28606990 DOI: 10.1242/jcs.203455] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Accepted: 06/05/2017] [Indexed: 01/10/2023] Open
Abstract
Directed axonal growth depends on correct coordination of the actin and microtubule cytoskeleton in the growth cone. However, despite the relatively large number of proteins implicated in actin-microtubule crosstalk, the mechanisms whereby actin polymerization is coupled to microtubule stabilization and advancement in the peripheral growth cone remained largely unclear. Here, we identified the formin Dishevelled-associated activator of morphogenesis (DAAM) as a novel factor playing a role in concerted regulation of actin and microtubule remodeling in Drosophilamelanogaster primary neurons. In vitro, DAAM binds to F-actin as well as to microtubules and has the ability to crosslink the two filament systems. Accordingly, DAAM associates with the neuronal cytoskeleton, and a significant fraction of DAAM accumulates at places where the actin filaments overlap with that of microtubules. Loss of DAAM affects growth cone and microtubule morphology, and several aspects of microtubule dynamics; and biochemical and cellular assays revealed a microtubule stabilization activity and binding to the microtubule tip protein EB1. Together, these data suggest that, besides operating as an actin assembly factor, DAAM is involved in linking actin remodeling in filopodia to microtubule stabilization during axonal growth.
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Affiliation(s)
- Szilárd Szikora
- Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, MTA-SZBK NAP B Axon Growth and Regeneration Group, Temesvári krt. 62, Szeged H-6726, Hungary
| | - István Földi
- Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, MTA-SZBK NAP B Axon Growth and Regeneration Group, Temesvári krt. 62, Szeged H-6726, Hungary
| | - Krisztina Tóth
- Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, MTA-SZBK NAP B Axon Growth and Regeneration Group, Temesvári krt. 62, Szeged H-6726, Hungary
| | - Ede Migh
- Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, MTA-SZBK NAP B Axon Growth and Regeneration Group, Temesvári krt. 62, Szeged H-6726, Hungary
| | - Andrea Vig
- University of Pécs, Medical School, Department of Biophysics, Szigeti str. 12, Pécs H-7624, Hungary
| | - Beáta Bugyi
- University of Pécs, Medical School, Department of Biophysics, Szigeti str. 12, Pécs H-7624, Hungary.,Szentágothai Research Center, Ifjúság str. 34, Pécs H-7624, Hungary
| | - József Maléth
- MTA-SZTE Translational Gastroenterology Research Group, First Department of Internal Medicine, Szeged H-6720, Hungary
| | - Péter Hegyi
- MTA-SZTE Translational Gastroenterology Research Group, First Department of Internal Medicine, Szeged H-6720, Hungary.,Institute for Translational Medicine, Department of Pathophysiology, University of Pécs, Pécs H-7624, Hungary
| | - Péter Kaltenecker
- Institute for Translational Medicine, Department of Cellular and Molecular Physiology, University of Liverpool, Liverpool L69 3BX, UK
| | - Natalia Sanchez-Soriano
- Institute for Translational Medicine, Department of Cellular and Molecular Physiology, University of Liverpool, Liverpool L69 3BX, UK
| | - József Mihály
- Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, MTA-SZBK NAP B Axon Growth and Regeneration Group, Temesvári krt. 62, Szeged H-6726, Hungary
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15
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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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16
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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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17
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Aradhya R, Zmojdzian M, Da Ponte JP, Jagla K. Muscle niche-driven Insulin-Notch-Myc cascade reactivates dormant Adult Muscle Precursors in Drosophila. eLife 2015; 4. [PMID: 26650355 PMCID: PMC4749548 DOI: 10.7554/elife.08497] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2015] [Accepted: 10/28/2015] [Indexed: 01/25/2023] Open
Abstract
How stem cells specified during development keep their non-differentiated quiescent state, and how they are reactivated, remain poorly understood. Here, we applied a Drosophila model to follow in vivo behavior of adult muscle precursors (AMPs), the transient fruit fly muscle stem cells. We report that emerging AMPs send out thin filopodia that make contact with neighboring muscles. AMPs keep their filopodia-based association with muscles throughout their dormant state but also when they start to proliferate, suggesting that muscles could play a role in AMP reactivation. Indeed, our genetic analyses indicate that muscles send inductive dIlp6 signals that switch the Insulin pathway ON in closely associated AMPs. This leads to the activation of Notch, which regulates AMP proliferation via dMyc. Altogether, we report that Drosophila AMPs display homing behavior to muscle niche and that the niche-driven Insulin-Notch-dMyc cascade plays a key role in setting the activated state of AMPs. DOI:http://dx.doi.org/10.7554/eLife.08497.001 Muscles experience wear and tear over our lifetimes and therefore need to be regularly repaired and replenished by new cells. These cells are produced by stem cells, which often reside in a special microenvironment called the stem cell niche. This niche may also contain support cells that produce signals to attract stem cells and then maintain them in a dormant state. When the muscle is damaged, its resident stem cells are activated so that they divide to produce new cells. Understanding how this happens is an important goal for regenerative medicine, but many of the details remain unclear. In fruit flies, stem cells called adult muscle precursor cells (or AMPs for short) lie dormant in the embryo and larva, but are then activated to form the muscles of the adult fly. These cells share many features with the muscle stem cells of mammals, which prompted Aradhya, Zmojdzian et al. to use them as a model to investigate how stem cells find their niche and are later activated. For the experiments, the AMPs in fruit fly larvae were labelled with a fluorescent protein. Aradhya, Zmojdzian et al. observed that these cells produce long extensions that connect them to each other, to nearby muscle and to nerve cells. During development, these extensions are gradually lost until they contact only the muscles that are closest to the AMPs, which indicates that these muscles provide a niche for the AMPs and are perhaps involved in their activation. Further experiments show that neighbouring muscles do indeed help to activate AMPs, as they produce a signal that activates a cell communication system called the insulin pathway inside the AMPs. Insulin signalling – which is sensitive to the availability of nutrients in the body – turns on another signalling pathway, called Notch, that then stimulate the AMPs to divide. Aradhya, Zmojdzian et al. propose that this signalling cascade might help to ensure that AMPs are only activated at the right time in development. The next step is to find out whether stem cells in human muscles are activated in a similar way. DOI:http://dx.doi.org/10.7554/eLife.08497.002
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Affiliation(s)
- Rajaguru Aradhya
- Génétique Reproduction et Développement, INSERM U1103, CNRS UMR6293, Clermont-Ferrand, France
| | - Monika Zmojdzian
- Génétique Reproduction et Développement, INSERM U1103, CNRS UMR6293, Clermont-Ferrand, France
| | - Jean Philippe Da Ponte
- Génétique Reproduction et Développement, INSERM U1103, CNRS UMR6293, Clermont-Ferrand, France
| | - Krzysztof Jagla
- Génétique Reproduction et Développement, INSERM U1103, CNRS UMR6293, Clermont-Ferrand, France
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18
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The Formin DAAM Functions as Molecular Effector of the Planar Cell Polarity Pathway during Axonal Development in Drosophila. J Neurosci 2015; 35:10154-67. [PMID: 26180192 DOI: 10.1523/jneurosci.3708-14.2015] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Recent studies established that the planar cell polarity (PCP) pathway is critical for various aspects of nervous system development and function, including axonal guidance. Although it seems clear that PCP signaling regulates actin dynamics, the mechanisms through which this occurs remain elusive. Here, we establish a functional link between the PCP system and one specific actin regulator, the formin DAAM, which has previously been shown to be required for embryonic axonal morphogenesis and filopodia formation in the growth cone. We show that dDAAM also plays a pivotal role during axonal growth and guidance in the adult Drosophila mushroom body, a brain center for learning and memory. By using a combination of genetic and biochemical assays, we demonstrate that Wnt5 and the PCP signaling proteins Frizzled, Strabismus, and Dishevelled act in concert with the small GTPase Rac1 to activate the actin assembly functions of dDAAM essential for correct targeting of mushroom body axons. Collectively, these data suggest that dDAAM is used as a major molecular effector of the PCP guidance pathway. By uncovering a signaling system from the Wnt5 guidance cue to an actin assembly factor, we propose that the Wnt5/PCP navigation system is linked by dDAAM to the regulation of the growth cone actin cytoskeleton, and thereby growth cone behavior, in a direct way.
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19
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He Y, Ren Y, Wu B, Decourt B, Lee AC, Taylor A, Suter DM. Src and cortactin promote lamellipodia protrusion and filopodia formation and stability in growth cones. Mol Biol Cell 2015. [PMID: 26224308 PMCID: PMC4569314 DOI: 10.1091/mbc.e15-03-0142] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
How Src tyrosine kinase and cortactin control actin organization and dynamics in neuronal growth cones is not well understood. Using multiple high-resolution imaging techniques, this study shows that Src and cortactin control the persistence of lamellipodial protrusion as well as the formation, stability, and elongation of filopodia in growth cones. Src tyrosine kinases have been implicated in axonal growth and guidance; however, the underlying cellular mechanisms are not well understood. Specifically, it is unclear which aspects of actin organization and dynamics are regulated by Src in neuronal growth cones. Here, we investigated the function of Src2 and one of its substrates, cortactin, in lamellipodia and filopodia of Aplysia growth cones. We found that up-regulation of Src2 activation state or cortactin increased lamellipodial length, protrusion time, and actin network density, whereas down-regulation had opposite effects. Furthermore, Src2 or cortactin up-regulation increased filopodial density, length, and protrusion time, whereas down-regulation promoted lateral movements of filopodia. Fluorescent speckle microscopy revealed that rates of actin assembly and retrograde flow were not affected in either case. In summary, our results support a model in which Src and cortactin regulate growth cone motility by increasing actin network density and protrusion persistence of lamellipodia by controlling the state of actin-driven protrusion versus retraction. In addition, both proteins promote the formation and stability of actin bundles in filopodia.
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Affiliation(s)
- Yingpei He
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907
| | - Yuan Ren
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907
| | - Bingbing Wu
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907
| | - Boris Decourt
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907
| | - Aih Cheun Lee
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907
| | - Aaron Taylor
- Bindley Bioscience Center, Purdue University, West Lafayette, IN 47907
| | - Daniel M Suter
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907 Bindley Bioscience Center, Purdue University, West Lafayette, IN 47907 )
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20
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Haralalka S, Shelton C, Cartwright HN, Guo F, Trimble R, Kumar RP, Abmayr SM. Live imaging provides new insights on dynamic F-actin filopodia and differential endocytosis during myoblast fusion in Drosophila. PLoS One 2014; 9:e114126. [PMID: 25474591 PMCID: PMC4256407 DOI: 10.1371/journal.pone.0114126] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Accepted: 10/28/2014] [Indexed: 11/29/2022] Open
Abstract
The process of myogenesis includes the recognition, adhesion, and fusion of committed myoblasts into multinucleate syncytia. In the larval body wall muscles of Drosophila, this elaborate process is initiated by Founder Cells and Fusion-Competent Myoblasts (FCMs), and cell adhesion molecules Kin-of-IrreC (Kirre) and Sticks-and-stones (Sns) on their respective surfaces. The FCMs appear to provide the driving force for fusion, via the assembly of protrusions associated with branched F-actin and the WASp, SCAR and Arp2/3 pathways. In the present study, we utilize the dorsal pharyngeal musculature that forms in the Drosophila embryo as a model to explore myoblast fusion and visualize the fusion process in live embryos. These muscles rely on the same cell types and genes as the body wall muscles, but are amenable to live imaging since they do not undergo extensive morphogenetic movement during formation. Time-lapse imaging with F-actin and membrane markers revealed dynamic FCM-associated actin-enriched protrusions that rapidly extend and retract into the myotube from different sites within the actin focus. Ultrastructural analysis of this actin-enriched area showed that they have two morphologically distinct structures: wider invasions and/or narrow filopodia that contain long linear filaments. Consistent with this, formin Diaphanous (Dia) and branched actin nucleator, Arp3, are found decorating the filopodia or enriched at the actin focus, respectively, indicating that linear actin is present along with branched actin at sites of fusion in the FCM. Gain-of-function Dia and loss-of-function Arp3 both lead to fusion defects, a decrease of F-actin foci and prominent filopodia from the FCMs. We also observed differential endocytosis of cell surface components at sites of fusion, with actin reorganizing factors, WASp and SCAR, and Kirre remaining on the myotube surface and Sns preferentially taken up with other membrane proteins into early endosomes and lysosomes in the myotube.
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Affiliation(s)
- Shruti Haralalka
- Stowers Institute for Medical Research, Kansas City, Missouri, 64110, United States of America
| | - Claude Shelton
- Stowers Institute for Medical Research, Kansas City, Missouri, 64110, United States of America
| | - Heather N. Cartwright
- Stowers Institute for Medical Research, Kansas City, Missouri, 64110, United States of America
| | - Fengli Guo
- Stowers Institute for Medical Research, Kansas City, Missouri, 64110, United States of America
| | - Rhonda Trimble
- Stowers Institute for Medical Research, Kansas City, Missouri, 64110, United States of America
| | - Ram P. Kumar
- Stowers Institute for Medical Research, Kansas City, Missouri, 64110, United States of America
| | - Susan M. Abmayr
- Stowers Institute for Medical Research, Kansas City, Missouri, 64110, United States of America
- Department of Anatomy and Cell Biology, University of Kansas School of Medicine, Kansas City, Kansas, 66160, United States of America
- * E-mail:
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21
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Prokop A, Sánchez-Soriano N, Gonçalves-Pimentel C, Molnár I, Kalmár T, Mihály J. DAAM family members leading a novel path into formin research. Commun Integr Biol 2014. [DOI: 10.4161/cib.16511] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
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22
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Nowotarski SH, McKeon N, Moser RJ, Peifer M. The actin regulators Enabled and Diaphanous direct distinct protrusive behaviors in different tissues during Drosophila development. Mol Biol Cell 2014; 25:3147-65. [PMID: 25143400 PMCID: PMC4196866 DOI: 10.1091/mbc.e14-05-0951] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Actin-based protrusions are important for signaling and migration during development and homeostasis. Gain- and loss-of-function and quantitative approaches are used to define differential roles for the actin elongation factors Diaphanous and Enabled in regulating distinct protrusive behaviors in different tissues during Drosophila morphogenesis. Actin-based protrusions are important for signaling and migration during development and homeostasis. Defining how different tissues in vivo craft diverse protrusive behaviors using the same genomic toolkit of actin regulators is a current challenge. The actin elongation factors Diaphanous and Enabled both promote barbed-end actin polymerization and can stimulate filopodia in cultured cells. However, redundancy in mammals and Diaphanous’ role in cytokinesis limited analysis of whether and how they regulate protrusions during development. We used two tissues driving Drosophila dorsal closure—migratory leading-edge (LE) and nonmigratory amnioserosal (AS) cells—as models to define how cells shape distinct protrusions during morphogenesis. We found that nonmigratory AS cells produce filopodia that are morphologically and dynamically distinct from those of LE cells. We hypothesized that differing Enabled and/or Diaphanous activity drives these differences. Combining gain- and loss-of-function with quantitative approaches revealed that Diaphanous and Enabled each regulate filopodial behavior in vivo and defined a quantitative “fingerprint”—the protrusive profile—which our data suggest is characteristic of each actin regulator. Our data suggest that LE protrusiveness is primarily Enabled driven, whereas Diaphanous plays the primary role in the AS, and reveal each has roles in dorsal closure, but its robustness ensures timely completion in their absence.
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Affiliation(s)
- Stephanie H Nowotarski
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Natalie McKeon
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Rachel J Moser
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Mark Peifer
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599 Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
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23
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Shields AR, Spence AC, Yamashita YM, Davies EL, Fuller MT. The actin-binding protein profilin is required for germline stem cell maintenance and germ cell enclosure by somatic cyst cells. Development 2014; 141:73-82. [PMID: 24346697 DOI: 10.1242/dev.101931] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Specialized microenvironments, or niches, provide signaling cues that regulate stem cell behavior. In the Drosophila testis, the JAK-STAT signaling pathway regulates germline stem cell (GSC) attachment to the apical hub and somatic cyst stem cell (CySC) identity. Here, we demonstrate that chickadee, the Drosophila gene that encodes profilin, is required cell autonomously to maintain GSCs, possibly facilitating localization or maintenance of E-cadherin to the GSC-hub cell interface. Germline specific overexpression of Adenomatous Polyposis Coli 2 (APC2) rescued GSC loss in chic hypomorphs, suggesting an additive role of APC2 and F-actin in maintaining the adherens junctions that anchor GSCs to the niche. In addition, loss of chic function in the soma resulted in failure of somatic cyst cells to maintain germ cell enclosure and overproliferation of transit-amplifying spermatogonia.
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Affiliation(s)
- Alicia R Shields
- Department of Genetics, Stanford University, School of Medicine, Stanford, CA 94305, USA
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24
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Colombo A, Palma K, Armijo L, Mione M, Signore IA, Morales C, Guerrero N, Meynard MM, Pérez R, Suazo J, Marcelain K, Briones L, Härtel S, Wilson SW, Concha ML. Daam1a mediates asymmetric habenular morphogenesis by regulating dendritic and axonal outgrowth. Development 2013; 140:3997-4007. [PMID: 24046318 PMCID: PMC3775416 DOI: 10.1242/dev.091934] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Although progress has been made in resolving the genetic pathways that specify neuronal asymmetries in the brain, little is known about genes that mediate the development of structural asymmetries between neurons on left and right. In this study, we identify daam1a as an asymmetric component of the signalling pathways leading to asymmetric morphogenesis of the habenulae in zebrafish. Daam1a is a member of the Formin family of actin-binding proteins and the extent of Daam1a expression in habenular neuron dendrites mirrors the asymmetric growth of habenular neuropil between left and right. Local loss and gain of Daam1a function affects neither cell number nor subtype organisation but leads to a decrease or increase of neuropil, respectively. Daam1a therefore plays a key role in the asymmetric growth of habenular neuropil downstream of the pathways that specify asymmetric cellular domains in the habenulae. In addition, Daam1a mediates the development of habenular efferent connectivity as local loss and gain of Daam1a function impairs or enhances, respectively, the growth of habenular neuron terminals in the interpeduncular nucleus. Abrogation of Daam1a disrupts the growth of both dendritic and axonal processes and results in disorganised filamentous actin and α-tubulin. Our results indicate that Daam1a plays a key role in asymmetric habenular morphogenesis mediating the growth of dendritic and axonal processes in dorsal habenular neurons.
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Affiliation(s)
- Alicia Colombo
- Institute of Biomedical Sciences, Facultad de Medicina, Universidad de Chile, Independencia 1027, Santiago 8380453, Chile
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Prokop A. The intricate relationship between microtubules and their associated motor proteins during axon growth and maintenance. Neural Dev 2013; 8:17. [PMID: 24010872 PMCID: PMC3846809 DOI: 10.1186/1749-8104-8-17] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Accepted: 08/14/2013] [Indexed: 12/15/2022] Open
Abstract
The hallmarks of neurons are their slender axons which represent the longest cellular processes of animals and which act as the cables that electrically wire the brain, and the brain to the body. Axons extend along reproducible paths during development and regeneration, and they have to be maintained for the lifetime of an organism. Both axon extension and maintenance essentially depend on the microtubule (MT) cytoskeleton. For this, MTs organize into parallel bundles that are established through extension at the leading axon tips within growth cones, and these bundles then form the architectural backbones, as well as the highways for axonal transport essential for supply and intracellular communication. Axon transport over these enormous distances takes days or even weeks and is a substantial logistical challenge. It is performed by kinesins and dynein/dynactin, which are molecular motors that form close functional links to the MTs they walk along. The intricate machinery which regulates MT dynamics, axonal transport and the motors is essential for nervous system development and function, and its investigation has huge potential to bring urgently required progress in understanding the causes of many developmental and degenerative brain disorders. During the last years new explanations for the highly specific properties of axonal MTs and for their close functional links to motor proteins have emerged, and it has become increasingly clear that motors play active roles also in regulating axonal MT networks. Here, I will provide an overview of these new developments.
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Affiliation(s)
- Andreas Prokop
- Faculty of Life Sciences, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK.
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Prokop A, Beaven R, Qu Y, Sánchez-Soriano N. Using fly genetics to dissect the cytoskeletal machinery of neurons during axonal growth and maintenance. J Cell Sci 2013; 126:2331-41. [PMID: 23729743 DOI: 10.1242/jcs.126912] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The extension of long slender axons is a key process of neuronal circuit formation, both during brain development and regeneration. For this, growth cones at the tips of axons are guided towards their correct target cells by signals. Growth cone behaviour downstream of these signals is implemented by their actin and microtubule cytoskeleton. In the first part of this Commentary, we discuss the fundamental roles of the cytoskeleton during axon growth. We present the various classes of actin- and microtubule-binding proteins that regulate the cytoskeleton, and highlight the important gaps in our understanding of how these proteins functionally integrate into the complex machinery that implements growth cone behaviour. Deciphering such machinery requires multidisciplinary approaches, including genetics and the use of simple model organisms. In the second part of this Commentary, we discuss how the application of combinatorial genetics in the versatile genetic model organism Drosophila melanogaster has started to contribute to the understanding of actin and microtubule regulation during axon growth. Using the example of dystonin-linked neuron degeneration, we explain how knowledge acquired by studying axonal growth in flies can also deliver new understanding in other aspects of neuron biology, such as axon maintenance in higher animals and humans.
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Affiliation(s)
- Andreas Prokop
- Faculty of Life Sciences, The University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK.
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27
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Drosophila Psidin regulates olfactory neuron number and axon targeting through two distinct molecular mechanisms. J Neurosci 2013; 32:16080-94. [PMID: 23152593 DOI: 10.1523/jneurosci.3116-12.2012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The formation of neuronal circuits is a key process of development, laying foundations for behavior. The cellular mechanisms regulating circuit development are not fully understood. Here, we reveal Psidin as an intracellular regulator of Drosophila olfactory system formation. We show that Psidin is required in several classes of olfactory receptor neurons (ORNs) for survival and subsequently for axon guidance. During axon guidance, Psidin functions as an actin regulator and antagonist of Tropomyosin. Accordingly, Psidin-deficient primary neurons in culture display growth cones with significantly smaller lamellipodia. This lamellipodial phenotype, as well as the mistargeting defects in vivo, is suppressed by parallel removal of Tropomyosin. In contrast, Psidin functions as the noncatalytic subunit of the N-acetyltransferase complex B (NatB) to maintain the number of ORNs. Psidin physically binds the catalytic NatB subunit CG14222 (dNAA20) and functionally interacts with it in vivo. We define the dNAA20 interaction domain within Psidin and identify a conserved serine as a candidate for phosphorylation-mediated regulation of NatB complex formation. A phosphomimetic mutation of this serine showed severely reduced binding to dNAA20 in vitro. In vivo, it fully rescued the targeting defect but not the reduction in neuron numbers. In addition, we show that a different amino acid point mutation shows exactly the opposite effect by rescuing only the cell number but not the axon targeting defect. Together, our data suggest that Psidin plays two independent developmental roles via the acquisition of separate signaling pathways, both of which contribute to the formation of olfactory circuits.
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Gallo G. Mechanisms underlying the initiation and dynamics of neuronal filopodia: from neurite formation to synaptogenesis. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2013; 301:95-156. [PMID: 23317818 DOI: 10.1016/b978-0-12-407704-1.00003-8] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Filopodia are finger-like cellular protrusions found throughout the metazoan kingdom and perform fundamental cellular functions during development and cell migration. Neurons exhibit a wide variety of extremely complex morphologies. In the nervous system, filopodia underlie many major morphogenetic events. Filopodia have roles spanning the initiation and guidance of neuronal processes, axons and dendrites to the formation of synaptic connections. This chapter addresses the mechanisms of the formation and dynamics of neuronal filopodia. Some of the major lessons learned from the study of neuronal filopodia are (1) there are multiple mechanisms that can regulate filopodia in a context-dependent manner, (2) that filopodia are specialized subcellular domains, (3) that filopodia exhibit dynamic membrane recycling which also controls aspects of filopodial dynamics, (4) that neuronal filopodia contain machinery for the orchestration of the actin and microtubule cytoskeleton, and (5) localized protein synthesis contributes to neuronal filopodial dynamics.
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Affiliation(s)
- Gianluca Gallo
- Shriners Hospitals Pediatric Research Center, Center for Neural Repair and Rehabilitation, Department of Anatomy and Cell Biology, Temple University, Philadelphia, PA, USA.
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Spectraplakins promote microtubule-mediated axonal growth by functioning as structural microtubule-associated proteins and EB1-dependent +TIPs (tip interacting proteins). J Neurosci 2012; 32:9143-58. [PMID: 22764224 DOI: 10.1523/jneurosci.0416-12.2012] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The correct outgrowth of axons is essential for the development and regeneration of nervous systems. Axon growth is primarily driven by microtubules. Key regulators of microtubules in this context are the spectraplakins, a family of evolutionarily conserved actin-microtubule linkers. Loss of function of the mouse spectraplakin ACF7 or of its close Drosophila homolog Short stop/Shot similarly cause severe axon shortening and microtubule disorganization. How spectraplakins perform these functions is not known. Here we show that axonal growth-promoting roles of Shot require interaction with EB1 (End binding protein) at polymerizing plus ends of microtubules. We show that binding of Shot to EB1 requires SxIP motifs in Shot's C-terminal tail (Ctail), mutations of these motifs abolish Shot functions in axonal growth, loss of EB1 function phenocopies Shot loss, and genetic interaction studies reveal strong functional links between Shot and EB1 in axonal growth and microtubule organization. In addition, we report that Shot localizes along microtubule shafts and stabilizes them against pharmacologically induced depolymerization. This function is EB1-independent but requires net positive charges within Ctail which essentially contribute to the microtubule shaft association of Shot. Therefore, spectraplakins are true members of two important classes of neuronal microtubule regulating proteins: +TIPs (tip interacting proteins; plus end regulators) and structural MAPs (microtubule-associated proteins). From our data we deduce a model that relates the different features of the spectraplakin C terminus to the two functions of Shot during axonal growth.
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Yang C, Svitkina T. Filopodia initiation: focus on the Arp2/3 complex and formins. Cell Adh Migr 2012; 5:402-8. [PMID: 21975549 DOI: 10.4161/cam.5.5.16971] [Citation(s) in RCA: 138] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Filopodia are long, slender, actin-rich cellular protrusions, which recently have become a focus of cell biology research because of their proposed roles as sensory and exploratory organelles that allow for "intelligent" cell behavior. Actin nucleation, elongation and bundling are believed to be essential for filopodia formation and functions. However, the identity of actin filament nucleators responsible for the initiation of filopodia remains controversial. Two alternative models, the convergent elongation and tip nucleation, emphasize two different actin filament nucleators, the Arp2/3 complex or formins, respectively, as key players during filopodia initiation. Although these two models in principle are not mutually exclusive, it is important to understand which of them is actually employed by cells. In this review, we discuss the existing evidence regarding the relative roles of the Arp2/3 complex and formins in filopodia initiation.
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Affiliation(s)
- Changsong Yang
- Department of Biology; University of Pennsylvania; Philadelphia, PA, USA
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Prokop A, Küppers-Munther B, Sánchez-Soriano N. Using Primary Neuron Cultures of Drosophila to Analyze Neuronal Circuit Formation and Function. NEUROMETHODS 2012. [DOI: 10.1007/978-1-61779-830-6_10] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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32
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Schevzov G, Curthoys NM, Gunning PW, Fath T. Functional diversity of actin cytoskeleton in neurons and its regulation by tropomyosin. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2012; 298:33-94. [PMID: 22878104 DOI: 10.1016/b978-0-12-394309-5.00002-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Neurons comprise functionally, molecularly, and spatially distinct subcellular compartments which include the soma, dendrites, axon, branches, dendritic spines, and growth cones. In this chapter, we detail the remarkable ability of the neuronal cytoskeleton to exquisitely regulate all these cytoplasmic distinct partitions, with particular emphasis on the microfilament system and its plethora of associated proteins. Importance will be given to the family of actin-associated proteins, tropomyosin, in defining distinct actin filament populations. The ability of tropomyosin isoforms to regulate the access of actin-binding proteins to the filaments is believed to define the structural diversity and dynamics of actin filaments and ultimately be responsible for the functional outcome of these filaments.
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Affiliation(s)
- Galina Schevzov
- Oncology Research Unit, Department of Pharmacology, School of Medical Sciences, University of New South Wales, Kensington, Australia
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Stephan R, Gohl C, Fleige A, Klämbt C, Bogdan S. Membrane-targeted WAVE mediates photoreceptor axon targeting in the absence of the WAVE complex in Drosophila. Mol Biol Cell 2011; 22:4079-92. [PMID: 21900504 PMCID: PMC3204070 DOI: 10.1091/mbc.e11-02-0121] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
A tight spatial-temporal coordination of F-actin dynamics is crucial for a large variety of cellular processes that shape cells. The Abelson interactor (Abi) has a conserved role in Arp2/3-dependent actin polymerization, regulating Wiskott-Aldrich syndrome protein (WASP) and WASP family verprolin-homologous protein (WAVE). In this paper, we report that Abi exerts nonautonomous control of photoreceptor axon targeting in the Drosophila visual system through WAVE. In abi mutants, WAVE is unstable but restored by reexpression of Abi, confirming that Abi controls the integrity of the WAVE complex in vivo. Remarkably, expression of a membrane-tethered WAVE protein rescues the axonal projection defects of abi mutants in the absence of the other subunits of the WAVE complex, whereas cytoplasmic WAVE only slightly affects the abi mutant phenotype. Thus complex formation not only stabilizes WAVE, but also provides further membrane-recruiting signals, resulting in an activation of WAVE.
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Affiliation(s)
- Raiko Stephan
- Institut für Neurobiologie, Universität Münster, 48149 Münster, Germany
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Prokop A, Sánchez-Soriano N, Gonçalves-Pimentel C, Molnár I, Kalmár T, Mihály J. DAAM family members leading a novel path into formin research. Commun Integr Biol 2011; 4:538-42. [PMID: 22046456 DOI: 10.4161/cib.4.5.16511] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Accepted: 05/17/2011] [Indexed: 11/19/2022] Open
Abstract
Formins are an important and evolutionarily well conserved class of actin binding proteins with essential biological functions. Although their molecular roles in actin regulation have been clearly demonstrated in vitro, their functions at the cellular or organism levels are still poorly understood. To illustrate this problem, but also to demonstrate potential ways forward, we focus here on the DAAM group of formins. In vertebrates, DAAM group members have been demonstrated to be important regulators of cellular and tissue morphogenesis but, as for all formins, the molecular mechanisms underlying these morphogenetic functions remain to be uncovered. The genome of the fruitfly Drosophila encodes a single DAAM gene that is evolutionarily highly conserved. Recent work on dDAAM has already provided a unique combination of observations and experimental opportunities unrivalled by any other Drosophila formin. These comprise in vitro actin polymerisation assays, subcellular studies in culture and in vivo, and a range of developmental phenotypes revealing a role in tracheal morphogenesis, axonal growth and muscle organization. At all these levels, future work on dDAAM will capitalize on the power of fly genetics, raising unique opportunities to advance our understanding of dDAAM at the systems level, with obvious implications for other formins.
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Affiliation(s)
- Andreas Prokop
- Faculty of Life Sciences; Wellcome Trust Centre for Cell-Matrix Research; Michael Smith Building; Manchester, UK
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