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Malkin J, O'Donnell C, Houghton CJ, Aitchison L. Signatures of Bayesian inference emerge from energy-efficient synapses. eLife 2024; 12:RP92595. [PMID: 39106188 DOI: 10.7554/elife.92595] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/09/2024] Open
Abstract
Biological synaptic transmission is unreliable, and this unreliability likely degrades neural circuit performance. While there are biophysical mechanisms that can increase reliability, for instance by increasing vesicle release probability, these mechanisms cost energy. We examined four such mechanisms along with the associated scaling of the energetic costs. We then embedded these energetic costs for reliability in artificial neural networks (ANNs) with trainable stochastic synapses, and trained these networks on standard image classification tasks. The resulting networks revealed a tradeoff between circuit performance and the energetic cost of synaptic reliability. Additionally, the optimised networks exhibited two testable predictions consistent with pre-existing experimental data. Specifically, synapses with lower variability tended to have (1) higher input firing rates and (2) lower learning rates. Surprisingly, these predictions also arise when synapse statistics are inferred through Bayesian inference. Indeed, we were able to find a formal, theoretical link between the performance-reliability cost tradeoff and Bayesian inference. This connection suggests two incompatible possibilities: evolution may have chanced upon a scheme for implementing Bayesian inference by optimising energy efficiency, or alternatively, energy-efficient synapses may display signatures of Bayesian inference without actually using Bayes to reason about uncertainty.
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Affiliation(s)
- James Malkin
- Faculty of Engineering, University of Bristol, Bristol, United Kingdom
| | - Cian O'Donnell
- Faculty of Engineering, University of Bristol, Bristol, United Kingdom
- Intelligent Systems Research Centre, School of Computing, Engineering, and Intelligent Systems, Ulster University, Derry/Londonderry, United Kingdom
| | - Conor J Houghton
- Faculty of Engineering, University of Bristol, Bristol, United Kingdom
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2
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Parkes M, Landers NL, Gramlich MW. Recently recycled synaptic vesicles use multi-cytoskeletal transport and differential presynaptic capture probability to establish a retrograde net flux during ISVE in central neurons. Front Cell Dev Biol 2023; 11:1286915. [PMID: 38020880 PMCID: PMC10657820 DOI: 10.3389/fcell.2023.1286915] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Accepted: 10/18/2023] [Indexed: 12/01/2023] Open
Abstract
Presynapses locally recycle synaptic vesicles to efficiently communicate information. During use and recycling, proteins on the surface of synaptic vesicles break down and become less efficient. In order to maintain efficient presynaptic function and accommodate protein breakdown, new proteins are regularly produced in the soma and trafficked to presynaptic locations where they replace older protein-carrying vesicles. Maintaining a balance of new proteins and older proteins is thus essential for presynaptic maintenance and plasticity. While protein production and turnover have been extensively studied, it is still unclear how older synaptic vesicles are trafficked back to the soma for recycling in order to maintain balance. In the present study, we use a combination of fluorescence microscopy, hippocampal cell cultures, and computational analyses to determine the mechanisms that mediate older synaptic vesicle trafficking back to the soma. We show that synaptic vesicles, which have recently undergone exocytosis, can differentially utilize either the microtubule or the actin cytoskeleton networks. We show that axonally trafficked vesicles traveling with higher speeds utilize the microtubule network and are less likely to be captured by presynapses, while slower vesicles utilize the actin network and are more likely to be captured by presynapses. We also show that retrograde-driven vesicles are less likely to be captured by a neighboring presynapse than anterograde-driven vesicles. We show that the loss of synaptic vesicle with bound molecular motor myosin V is the mechanism that differentiates whether vesicles will utilize the microtubule or actin networks. Finally, we present a theoretical framework of how our experimentally observed retrograde vesicle trafficking bias maintains the balance with previously observed rates of new vesicle trafficking from the soma.
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Bertin F, Jara-Wilde J, Auer B, Köhler-Solís A, González-Silva C, Thomas U, Sierralta J. Drosophila Atlastin regulates synaptic vesicle mobilization independent of bone morphogenetic protein signaling. Biol Res 2023; 56:49. [PMID: 37710314 PMCID: PMC10503011 DOI: 10.1186/s40659-023-00462-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Accepted: 09/01/2023] [Indexed: 09/16/2023] Open
Abstract
BACKGROUND The endoplasmic reticulum (ER) contacts endosomes in all parts of a motor neuron, including the axon and presynaptic terminal, to move structural proteins, proteins that send signals, and lipids over long distances. Atlastin (Atl), a large GTPase, is required for membrane fusion and the structural dynamics of the ER tubules. Atl mutations are the second most common cause of Hereditary Spastic Paraplegia (HSP), which causes spasticity in both sexes' lower extremities. Through an unknown mechanism, Atl mutations stimulate the BMP (bone morphogenetic protein) pathway in vertebrates and Drosophila. Synaptic defects are caused by atl mutations, which affect the abundance and distribution of synaptic vesicles (SV) in the bouton. We hypothesize that BMP signaling, does not cause Atl-dependent SV abnormalities in Drosophila. RESULTS We show that atl knockdown in motor neurons (Atl-KD) increases synaptic and satellite boutons in the same way that constitutively activating the BMP-receptor Tkv (thick veins) (Tkv-CA) increases the bouton number. The SV proteins Cysteine string protein (CSP) and glutamate vesicular transporter are reduced in Atl-KD and Tkv-CA larvae. Reducing the activity of the BMP receptor Wishful thinking (wit) can rescue both phenotypes. Unlike Tkv-CA larvae, Atl-KD larvae display altered activity-dependent distributions of CSP staining. Furthermore, Atl-KD larvae display an increased FM 1-43 unload than Control and Tkv-CA larvae. As decreasing wit function does not reduce the phenotype, our hypothesis that BMP signaling is not involved is supported. We also found that Rab11/CSP colocalization increased in Atl-KD larvae, which supports the concept that late recycling endosomes regulate SV movements. CONCLUSIONS Our findings reveal that Atl modulates neurotransmitter release in motor neurons via SV distribution independently of BMP signaling, which could explain the observed SV accumulation and synaptic dysfunction. Our data suggest that Atl is involved in membrane traffic as well as formation and/or recycling of the late endosome.
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Affiliation(s)
- Francisca Bertin
- Biomedical Neuroscience Institute (BNI), Santiago, Chile
- Department of Neuroscience, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Jorge Jara-Wilde
- SCIAN-Lab, Biomedical Neuroscience Institute (BNI), Santiago, Chile
- Department of Computational Sciences, Faculty of Physical and Mathematical Sciences, Universidad de Chile, Santiago, Chile
| | - Benedikt Auer
- Laboratory of Neuronal and Synaptic Signals, Department of Cellular Neuroscience, Leibniz Institute for Neurobiology, Magdeburg, Germany
| | - Andrés Köhler-Solís
- Biomedical Neuroscience Institute (BNI), Santiago, Chile
- Department of Neuroscience, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Carolina González-Silva
- Biomedical Neuroscience Institute (BNI), Santiago, Chile
- Department of Neuroscience, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Ulrich Thomas
- Functional Genetics of the Synapse, Department of Cellular Neuroscience, Leibniz Institute for Neurobiology, 39118, Magdeburg, Germany
| | - Jimena Sierralta
- Biomedical Neuroscience Institute (BNI), Santiago, Chile.
- Department of Neuroscience, Faculty of Medicine, Universidad de Chile, Santiago, Chile.
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Gromova KV, Thies E, Janiesch PC, Lützenkirchen FP, Zhu Y, Stajano D, Dürst CD, Schweizer M, Konietzny A, Mikhaylova M, Gee CE, Kneussel M. The kinesin Kif21b binds myosin Va and mediates changes in actin dynamics underlying homeostatic synaptic downscaling. Cell Rep 2023; 42:112743. [PMID: 37418322 DOI: 10.1016/j.celrep.2023.112743] [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: 12/13/2022] [Revised: 05/15/2023] [Accepted: 06/19/2023] [Indexed: 07/09/2023] Open
Abstract
Homeostatic synaptic plasticity adjusts the strength of synapses to restrain neuronal activity within a physiological range. Postsynaptic guanylate kinase-associated protein (GKAP) controls the bidirectional synaptic scaling of AMPA receptors (AMPARs); however, mechanisms by which chronic activity triggers cytoskeletal remodeling to downscale synaptic transmission are barely understood. Here, we report that the microtubule-dependent kinesin motor Kif21b binds GKAP and likewise is located in dendritic spines in a myosin Va- and neuronal-activity-dependent manner. Kif21b depletion unexpectedly alters actin dynamics in spines, and adaptation of actin turnover following chronic activity is lost in Kif21b-knockout neurons. Consistent with a role of the kinesin in regulating actin dynamics, Kif21b overexpression promotes actin polymerization. Moreover, Kif21b controls GKAP removal from spines and the decrease of GluA2-containing AMPARs from the neuronal surface, thereby inducing homeostatic synaptic downscaling. Our data highlight a critical role of Kif21b at the synaptic actin cytoskeleton underlying homeostatic scaling of neuronal firing.
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Affiliation(s)
- Kira V Gromova
- Department of Molecular Neurogenetics, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany.
| | - Edda Thies
- Department of Molecular Neurogenetics, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
| | - Philipp C Janiesch
- Department of Molecular Neurogenetics, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
| | - Felix P Lützenkirchen
- Department of Molecular Neurogenetics, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
| | - Yipeng Zhu
- Department of Molecular Neurogenetics, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
| | - Daniele Stajano
- Department of Molecular Neurogenetics, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
| | - Céline D Dürst
- Department of Synaptic Physiology, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
| | - Michaela Schweizer
- Core Facility Morphology, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
| | - Anja Konietzny
- RG Neuronal Protein Transport, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
| | - Marina Mikhaylova
- RG Neuronal Protein Transport, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany; RG Optobiology, Institute of Biology, Humboldt Universität zu Berlin, 10099 Berlin, Germany
| | - Christine E Gee
- Department of Synaptic Physiology, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
| | - Matthias Kneussel
- Department of Molecular Neurogenetics, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany; Hamburg Center of Neuroscience, HCNS, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany.
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Miryala CSJ, Holland ED, Dent EW. Contributions of microtubule dynamics and transport to presynaptic and postsynaptic functions. Mol Cell Neurosci 2022; 123:103787. [PMID: 36252720 PMCID: PMC9838116 DOI: 10.1016/j.mcn.2022.103787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Revised: 10/07/2022] [Accepted: 10/11/2022] [Indexed: 11/27/2022] Open
Abstract
Microtubules (MT) are elongated, tubular, cytoskeletal structures formed from polymerization of tubulin dimers. They undergo continuous cycles of polymerization and depolymerization, primarily at their plus ends, termed dynamic instability. Although this is an intrinsic property of MTs, there are a myriad of MT-associated proteins that function in regulating MT dynamic instability and other dynamic processes that shape the MT array. Additionally, MTs assemble into long, semi-rigid structures which act as substrates for long-range, motor-driven transport of many different types of cargoes throughout the cell. Both MT dynamics and motor-based transport play important roles in the function of every known type of cell. Within the last fifteen years many groups have shown that MT dynamics and transport play ever-increasing roles in the neuronal function of mature neurons. Not only are neurons highly polarized cells, but they also connect with one another through synapses to form complex networks. Here we will focus on exciting studies that have illuminated how MTs function both pre-synaptically in axonal boutons and post-synaptically in dendritic spines. It is becoming clear that MT dynamics and transport both serve important functions in synaptic plasticity. Thus, it is not surprising that disruption of MTs, either through hyperstabilization or destabilization, has profound consequences for learning and memory. Together, the studies described here suggest that MT dynamics and transport play key roles in synaptic function and when disrupted result in compromised learning and memory.
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Affiliation(s)
- Chandra S. J. Miryala
- Department of Neuroscience, University of Wisconsin, School of Medicine and Public Health, Madison, WI 53705
| | - Elizabeth D. Holland
- Neuroscience Training Program, University of Wisconsin-Madison, Madison, WI 53705
| | - Erik W. Dent
- Department of Neuroscience, University of Wisconsin, School of Medicine and Public Health, Madison, WI 53705,Corresponding Author: Department of Neuroscience, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI 53705,
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6
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Taipala E, Pfitzer JC, Hellums M, Reed MN, Gramlich MW. rTg(TauP301L)4510 mice exhibit increased VGlut1 in hippocampal presynaptic glutamatergic vesicles and increased extracellular glutamate release. Front Synaptic Neurosci 2022; 14:925546. [PMID: 35989711 PMCID: PMC9383415 DOI: 10.3389/fnsyn.2022.925546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Accepted: 07/01/2022] [Indexed: 11/13/2022] Open
Abstract
The molecular pathways that contribute to the onset of symptoms in tauopathy models, including Alzheimer’s disease (AD), are difficult to distinguish because multiple changes can happen simultaneously at different stages of disease progression. Understanding early synaptic alterations and their supporting molecular pathways is essential to develop better pharmacological targets to treat AD. Here, we focus on an early onset rTg(TauP301L)4510 tauopathy mouse model that exhibits hyperexcitability in hippocampal neurons of adult mice that is correlated with presynaptic changes and increased extracellular glutamate levels. However, it is not clear if increased extracellular glutamate is caused by presynaptic changes alone, or if presynaptic changes are a contributing factor among other factors. To determine whether pathogenic tau alters presynaptic function and glutamate release, we studied cultured hippocampal neurons at 14–18 days in vitro (DIV) from animals of both sexes to measure presynaptic changes in tauP301L positive mice. We observed that presynaptic vesicles exhibit increased vesicular glutamate transporter 1 (VGlut1) using immunohistochemistry of fixed cells and an established pH-sensitive green fluorescent protein approach. We show that tauP301L positive neurons exhibit a 40% increase in VGlut1 per vesicle compared to tauP301L negative littermates. Further, we use the extracellular glutamate reporter iGluSnFR to show that increased VGlut1 per vesicle directly translates into a 40% increase in extracellular glutamate. Together, these results show that increased extracellular glutamate levels observed in tauP301L mice are not caused by increased vesicle exocytosis probability but rather are directly related to increased VGlut1 transporters per synaptic vesicle.
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Affiliation(s)
- Erika Taipala
- Department of Physics, Auburn University, Auburn, AL, United States
| | | | - Morgan Hellums
- Department of Physics, Auburn University, Auburn, AL, United States
| | - Miranda N. Reed
- Harrison School of Pharmacy, Auburn University, Auburn, AL, United States
| | - Michael W. Gramlich
- Department of Physics, Auburn University, Auburn, AL, United States
- *Correspondence: Michael W. Gramlich,
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7
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Park C, Jung S, Park H. Single vesicle tracking for studying synaptic vesicle dynamics in small central synapses. Curr Opin Neurobiol 2022; 76:102596. [PMID: 35803103 DOI: 10.1016/j.conb.2022.102596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Revised: 04/20/2022] [Accepted: 05/27/2022] [Indexed: 11/26/2022]
Abstract
Sustained neurotransmission is driven by a continuous supply of synaptic vesicles to the release sites and modulated by synaptic vesicle dynamics. However, synaptic vesicle dynamics in synapses remain elusive because of technical limitations. Recent advances in fluorescence imaging techniques have enabled the tracking of single synaptic vesicles in small central synapses in living neurons. Single vesicle tracking has uncovered a wealth of new information about synaptic vesicle dynamics both within and outside presynaptic terminals, showing that single vesicle tracking is an effective tool for studying synaptic vesicle dynamics. Particularly, single vesicle tracking with high spatiotemporal resolution has revealed the dependence of synaptic vesicle dynamics on the location, stages of recycling, and neuronal activity. This review summarizes the recent findings from single synaptic vesicle tracking in small central synapses and their implications in synaptic transmission and pathogenic mechanisms of neurodegenerative diseases.
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Affiliation(s)
- Chungwon Park
- Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, 999077, Hong Kong
| | - Sangyong Jung
- Institute of Molecular and Cell Biology (IMCB), Agency for Science, Technology and Research (A∗STAR), 11 Biopolis Way, 138667, Singapore; Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, 119077, Singapore
| | - Hyokeun Park
- Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, 999077, Hong Kong; Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, 999077, Hong Kong; State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, 999077, Hong Kong.
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8
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Birdsall V, Kirwan K, Zhu M, Imoto Y, Wilson SM, Watanabe S, Waites CL. Axonal transport of Hrs is activity dependent and facilitates synaptic vesicle protein degradation. Life Sci Alliance 2022; 5:5/10/e202000745. [PMID: 35636965 PMCID: PMC9152131 DOI: 10.26508/lsa.202000745] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2020] [Revised: 05/18/2022] [Accepted: 05/19/2022] [Indexed: 11/29/2022] Open
Abstract
This study describes an activity-dependent mechanism for transporting ESCRT-0 protein Hrs to synaptic vesicle (SV) pools, facilitating SV protein degradation in response to increased neuronal firing. Turnover of synaptic vesicle (SV) proteins is vital for the maintenance of healthy and functional synapses. SV protein turnover is driven by neuronal activity in an endosomal sorting complex required for transport (ESCRT)-dependent manner. Here, we characterize a critical step in this process: axonal transport of ESCRT-0 component Hrs, necessary for sorting proteins into the ESCRT pathway and recruiting downstream ESCRT machinery to catalyze multivesicular body (MVB) formation. We find that neuronal activity stimulates the formation of presynaptic endosomes and MVBs, as well as the motility of Hrs+ vesicles in axons and their delivery to SV pools. Hrs+ vesicles co-transport ESCRT-0 component STAM1 and comprise a subset of Rab5+ vesicles, likely representing pro-degradative early endosomes. Furthermore, we identify kinesin motor protein KIF13A as essential for the activity-dependent transport of Hrs to SV pools and the degradation of SV membrane proteins. Together, these data demonstrate a novel activity- and KIF13A-dependent mechanism for mobilizing axonal transport of ESCRT machinery to facilitate the degradation of SV membrane proteins.
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Affiliation(s)
- Veronica Birdsall
- Neurobiology and Behavior PhD Program, Columbia University, New York, NY, USA
| | - Konner Kirwan
- Neurobiology and Behavior PhD Program, Columbia University, New York, NY, USA
| | - Mei Zhu
- Department of Pathology and Cell Biology, Columbia University Medical Center, New York, NY, USA
| | - Yuuta Imoto
- Department of Cell Biology, Johns Hopkins University, Baltimore, MD, USA
| | - Scott M Wilson
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Shigeki Watanabe
- Department of Cell Biology, Johns Hopkins University, Baltimore, MD, USA.,Solomon H Snyder Department of Neuroscience, Johns Hopkins University, Baltimore, MD, USA
| | - Clarissa L Waites
- Department of Pathology and Cell Biology, Columbia University Medical Center, New York, NY, USA .,Department of Neuroscience, Columbia University, New York, NY, USA
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9
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An SJ, Stagi M, Gould TJ, Wu Y, Mlodzianoski M, Rivera-Molina F, Toomre D, Strittmatter SM, De Camilli P, Bewersdorf J, Zenisek D. Multimodal imaging of synaptic vesicles with a single probe. CELL REPORTS METHODS 2022; 2:100199. [PMID: 35497490 PMCID: PMC9046237 DOI: 10.1016/j.crmeth.2022.100199] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 02/11/2022] [Accepted: 03/28/2022] [Indexed: 05/17/2023]
Abstract
A complete understanding of synaptic-vesicle recycling requires the use of multiple microscopy methods to obtain complementary information. However, many currently available probes are limited to a specific microscopy modality, which necessitates the use of multiple probes and labeling paradigms. Given the complexity of vesicle populations and recycling pathways, having new single-vesicle probes that could be used for multiple microscopy techniques would complement existing sets of tools for studying vesicle function. Here, we present a probe based on the membrane-binding C2 domain of cytosolic phospholipase A2 (cPLA2) that fulfills this need. By conjugating the C2 domain with different detectable tags, we demonstrate that a single, modular probe can allow synaptic vesicles to be imaged at multiple levels of spatial and temporal resolution. Moreover, as a general endocytic marker, the C2 domain may also be used to study membrane recycling in many cell types.
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Affiliation(s)
- Seong J. An
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Massimiliano Stagi
- Program in Cellular Neuroscience, Neurodegeneration & Repair, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, USA
- Kavli Institute of Neuroscience, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Molecular Physiology & Cell Signalling, Institute of Systems, Molecular & Integrative Biology, University of Liverpool, Liverpool 69 3BX, UK
| | - Travis J. Gould
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Physics and Astronomy, Bates College, Lewiston, ME 04240, USA
| | - Yumei Wu
- Program in Cellular Neuroscience, Neurodegeneration & Repair, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA
- Kavli Institute of Neuroscience, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Michael Mlodzianoski
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Biomedical Engineering, Yale University School of Medicine, New Haven, CT 06510, USA
- Kavli Institute of Neuroscience, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Felix Rivera-Molina
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Derek Toomre
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Stephen M. Strittmatter
- Program in Cellular Neuroscience, Neurodegeneration & Repair, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, USA
- Kavli Institute of Neuroscience, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Pietro De Camilli
- Program in Cellular Neuroscience, Neurodegeneration & Repair, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA
- Kavli Institute of Neuroscience, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Joerg Bewersdorf
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Biomedical Engineering, Yale University School of Medicine, New Haven, CT 06510, USA
- Kavli Institute of Neuroscience, Yale University School of Medicine, New Haven, CT 06510, USA
| | - David Zenisek
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06510, USA
- Program in Cellular Neuroscience, Neurodegeneration & Repair, Yale University School of Medicine, New Haven, CT 06510, USA
- Kavli Institute of Neuroscience, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT 06510, USA
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10
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Lamb R, Dhar B, Cherra SJ. PXF-1 promotes synapse development at the neuromuscular junction in Caenorhabditis elegans. Front Mol Neurosci 2022; 15:945680. [PMID: 36311020 PMCID: PMC9606220 DOI: 10.3389/fnmol.2022.945680] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Accepted: 09/27/2022] [Indexed: 11/30/2022] Open
Abstract
Guanine nucleotide exchange factors (GEFs) are a family of proteins that modulate small G protein signaling. Mutations in a subfamily of GEFs that act on Rap, known as RapGEFs, have been associated with neurological disorders, and knockout mice display impairments in neuronal activity. However, the precise functions of RapGEFs in the nervous system remain unclear. Here, we have used the Caenorhabditis elegans neuromuscular junction, to investigate how the RapGEF homolog, PXF-1, regulates synaptic function. We found that loss of function mutations in pxf-1 reduced cholinergic activity at the neuromuscular junction. We observed that PXF-1 is expressed in the nervous system, and its expression in neurons is sufficient to promote synaptic activity. In pxf-1 mutant animals, there is a reduction in the levels of synaptic vesicles in cholinergic motor neurons but no change in the overall synapse numbers. In addition to synaptic vesicles proteins, we also found that filamentous actin, a scaffold for nascent synapses, was reduced at developing cholinergic synapses in pxf-1 mutant animals. Our studies indicate that PXF-1 regulates neuromuscular function by promoting the formation of actin filaments to support the development of motor neuron synapses.
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Affiliation(s)
- Reagan Lamb
- Department of Neuroscience, University of Kentucky College of Medicine, Lexington, KY, United States
| | - Bithika Dhar
- Department of Neuroscience, University of Kentucky College of Medicine, Lexington, KY, United States
| | - Salvatore J Cherra
- Department of Neuroscience, University of Kentucky College of Medicine, Lexington, KY, United States
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11
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Super-resolution microscopy: a closer look at synaptic dysfunction in Alzheimer disease. Nat Rev Neurosci 2021; 22:723-740. [PMID: 34725519 DOI: 10.1038/s41583-021-00531-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/27/2021] [Indexed: 11/08/2022]
Abstract
The synapse has emerged as a critical neuronal structure in the degenerative process of Alzheimer disease (AD), in which the pathogenic signals of two key players - amyloid-β (Aβ) and tau - converge, thereby causing synaptic dysfunction and cognitive deficits. The synapse presents a dynamic, confined microenvironment in which to explore how key molecules travel, localize, interact and assume different levels of organizational complexity, thereby affecting neuronal function. However, owing to their small size and the diffraction-limited resolution of conventional light microscopic approaches, investigating synaptic structure and dynamics has been challenging. Super-resolution microscopy (SRM) techniques have overcome the resolution barrier and are revolutionizing our quantitative understanding of biological systems in unprecedented spatio-temporal detail. Here we review critical new insights provided by SRM into the molecular architecture and dynamic organization of the synapse and, in particular, the interactions between Aβ and tau in this compartment. We further highlight how SRM can transform our understanding of the molecular pathological mechanisms that underlie AD. The application of SRM for understanding the roles of synapses in AD pathology will provide a stepping stone towards a broader understanding of dysfunction in other subcellular compartments and at cellular and circuit levels in this disease.
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12
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Real-time three-dimensional tracking of single vesicles reveals abnormal motion and pools of synaptic vesicles in neurons of Huntington's disease mice. iScience 2021; 24:103181. [PMID: 34703988 PMCID: PMC8521108 DOI: 10.1016/j.isci.2021.103181] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 08/30/2021] [Accepted: 09/23/2021] [Indexed: 11/23/2022] Open
Abstract
Although defective synaptic transmission was suggested to play a role in neurodegenerative diseases, the dynamics and vesicle pools of synaptic vesicles during neurodegeneration remain elusive. Here, we performed real-time three-dimensional tracking of single synaptic vesicles in cortical neurons from a mouse model of Huntington's disease (HD). Vesicles in HD neurons had a larger net displacement and radius of gyration compared with wild-type neurons. Vesicles with high release probability (Pr) were interspersed with low-Pr vesicles in HD neurons, whereas high-Pr vesicles were closer to fusion sites than low-Pr in wild-type neurons. Non-releasing vesicles in HD neurons had an abnormally high prevalence of irregular oscillatory motion. These abnormal dynamics and vesicle pools were rescued by overexpressing Rab11, and the abnormal irregular oscillatory motion was rescued by jasplakinolide. Our studies reveal the abnormal dynamics and pools of synaptic vesicles in the early stages of HD, suggesting a possible pathogenic mechanism of neurodegenerative diseases.
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13
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O'Neil SD, Rácz B, Brown WE, Gao Y, Soderblom EJ, Yasuda R, Soderling SH. Action potential-coupled Rho GTPase signaling drives presynaptic plasticity. eLife 2021; 10:63756. [PMID: 34269176 PMCID: PMC8285108 DOI: 10.7554/elife.63756] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Accepted: 07/06/2021] [Indexed: 12/30/2022] Open
Abstract
In contrast to their postsynaptic counterparts, the contributions of activity-dependent cytoskeletal signaling to presynaptic plasticity remain controversial and poorly understood. To identify and evaluate these signaling pathways, we conducted a proteomic analysis of the presynaptic cytomatrix using in vivo biotin identification (iBioID). The resultant proteome was heavily enriched for actin cytoskeleton regulators, including Rac1, a Rho GTPase that activates the Arp2/3 complex to nucleate branched actin filaments. Strikingly, we find Rac1 and Arp2/3 are closely associated with synaptic vesicle membranes in adult mice. Using three independent approaches to alter presynaptic Rac1 activity (genetic knockout, spatially restricted inhibition, and temporal optogenetic manipulation), we discover that this pathway negatively regulates synaptic vesicle replenishment at both excitatory and inhibitory synapses, bidirectionally sculpting short-term synaptic depression. Finally, we use two-photon fluorescence lifetime imaging to show that presynaptic Rac1 activation is coupled to action potentials by voltage-gated calcium influx. Thus, this study uncovers a previously unrecognized mechanism of actin-regulated short-term presynaptic plasticity that is conserved across excitatory and inhibitory terminals. It also provides a new proteomic framework for better understanding presynaptic physiology, along with a blueprint of experimental strategies to isolate the presynaptic effects of ubiquitously expressed proteins.
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Affiliation(s)
| | - Bence Rácz
- Department of Anatomy and Histology, University of Veterinary Medicine, Budapest, Hungary
| | - Walter Evan Brown
- Department of Cell Biology, Duke University Medical Center, Durham, United States
| | - Yudong Gao
- Department of Cell Biology, Duke University Medical Center, Durham, United States
| | - Erik J Soderblom
- Department of Cell Biology, Duke University Medical Center, Durham, United States.,Proteomics and Metabolomics Shared Resource and Center for Genomic and Computational Biology, Duke University Medical Center, Durham, United States
| | - Ryohei Yasuda
- Max Planck Florida Institute for Neuroscience, Jupiter, United States
| | - Scott H Soderling
- Department of Neurobiology, Duke University Medical Center, Durham, United States.,Department of Cell Biology, Duke University Medical Center, Durham, United States
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14
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Aiken J, Holzbaur ELF. Cytoskeletal regulation guides neuronal trafficking to effectively supply the synapse. Curr Biol 2021; 31:R633-R650. [PMID: 34033795 DOI: 10.1016/j.cub.2021.02.024] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The development and proper function of the brain requires the formation of highly complex neuronal circuitry. These circuits are shaped from synaptic connections between neurons and must be maintained over a lifetime. The formation and continued maintenance of synapses requires accurate trafficking of presynaptic and postsynaptic components along the axon and dendrite, respectively, necessitating deliberate and specialized delivery strategies to replenish essential synaptic components. Maintenance of synaptic transmission also requires readily accessible energy stores, produced in part by localized mitochondria, that are tightly regulated with activity level. In this review, we focus on recent developments in our understanding of the cytoskeletal environment of axons and dendrites, examining how local regulation of cytoskeletal dynamics and organelle trafficking promotes synapse-specific delivery and plasticity. These new insights shed light on the complex and coordinated role that cytoskeletal elements play in establishing and maintaining neuronal circuitry.
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Affiliation(s)
- Jayne Aiken
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Erika L F Holzbaur
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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15
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Maschi D, Gramlich MW, Klyachko VA. Myosin V Regulates Spatial Localization of Different Forms of Neurotransmitter Release in Central Synapses. Front Synaptic Neurosci 2021; 13:650334. [PMID: 33935678 PMCID: PMC8081987 DOI: 10.3389/fnsyn.2021.650334] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Accepted: 03/03/2021] [Indexed: 11/18/2022] Open
Abstract
Synaptic active zone (AZ) contains multiple specialized release sites for vesicle fusion. The utilization of release sites is regulated to determine spatiotemporal organization of the two main forms of synchronous release, uni-vesicular (UVR) and multi-vesicular (MVR). We previously found that the vesicle-associated molecular motor myosin V regulates temporal utilization of release sites by controlling vesicle anchoring at release sites in an activity-dependent manner. Here we show that acute inhibition of myosin V shifts preferential location of vesicle docking away from AZ center toward periphery, and results in a corresponding spatial shift in utilization of release sites during UVR. Similarly, inhibition of myosin V also reduces preferential utilization of central release sites during MVR, leading to more spatially distributed and temporally uniform MVR that occurs farther away from the AZ center. Using a modeling approach, we provide a conceptual framework that unites spatial and temporal functions of myosin V in vesicle release by controlling the gradient of release site release probability across the AZ, which in turn determines the spatiotemporal organization of both UVR and MVR. Thus myosin V regulates both temporal and spatial utilization of release sites during two main forms of synchronous release.
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Affiliation(s)
- Dario Maschi
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, United States
| | | | - Vitaly A Klyachko
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, United States
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16
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Voorn RA, Vogl C. Molecular Assembly and Structural Plasticity of Sensory Ribbon Synapses-A Presynaptic Perspective. Int J Mol Sci 2020; 21:E8758. [PMID: 33228215 PMCID: PMC7699581 DOI: 10.3390/ijms21228758] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Revised: 11/16/2020] [Accepted: 11/17/2020] [Indexed: 12/13/2022] Open
Abstract
In the mammalian cochlea, specialized ribbon-type synapses between sensory inner hair cells (IHCs) and postsynaptic spiral ganglion neurons ensure the temporal precision and indefatigability of synaptic sound encoding. These high-through-put synapses are presynaptically characterized by an electron-dense projection-the synaptic ribbon-which provides structural scaffolding and tethers a large pool of synaptic vesicles. While advances have been made in recent years in deciphering the molecular anatomy and function of these specialized active zones, the developmental assembly of this presynaptic interaction hub remains largely elusive. In this review, we discuss the dynamic nature of IHC (pre-) synaptogenesis and highlight molecular key players as well as the transport pathways underlying this process. Since developmental assembly appears to be a highly dynamic process, we further ask if this structural plasticity might be maintained into adulthood, how this may influence the functional properties of a given IHC synapse and how such plasticity could be regulated on the molecular level. To do so, we take a closer look at other ribbon-bearing systems, such as retinal photoreceptors and pinealocytes and aim to infer conserved mechanisms that may mediate these phenomena.
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MESH Headings
- Alcohol Oxidoreductases/genetics
- Alcohol Oxidoreductases/metabolism
- Animals
- Co-Repressor Proteins/genetics
- Co-Repressor Proteins/metabolism
- Cytoskeletal Proteins/genetics
- Cytoskeletal Proteins/metabolism
- Cytoskeleton/metabolism
- Cytoskeleton/ultrastructure
- Gene Expression Regulation, Developmental
- Hair Cells, Auditory, Inner/metabolism
- Hair Cells, Auditory, Inner/ultrastructure
- Hair Cells, Auditory, Outer/metabolism
- Hair Cells, Auditory, Outer/ultrastructure
- Hair Cells, Vestibular/metabolism
- Hair Cells, Vestibular/ultrastructure
- Mechanotransduction, Cellular
- Mice
- Nerve Tissue Proteins/genetics
- Nerve Tissue Proteins/metabolism
- Neuronal Plasticity/genetics
- Neuropeptides/genetics
- Neuropeptides/metabolism
- Rats
- Synapses/metabolism
- Synapses/ultrastructure
- Synaptic Transmission/genetics
- Synaptic Vesicles/metabolism
- Synaptic Vesicles/ultrastructure
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Affiliation(s)
- Roos Anouk Voorn
- Presynaptogenesis and Intracellular Transport in Hair Cells Junior Research Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Goettingen, 37075 Goettingen, Germany;
- Göttingen Graduate Center for Neurosciences, Biophysics and Molecular Biosciences, 37075 Goettingen, Germany
- Collaborative Research Center 889 “Cellular Mechanisms of Sensory Processing”, 37075 Goettingen, Germany
| | - Christian Vogl
- Presynaptogenesis and Intracellular Transport in Hair Cells Junior Research Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Goettingen, 37075 Goettingen, Germany;
- Collaborative Research Center 889 “Cellular Mechanisms of Sensory Processing”, 37075 Goettingen, Germany
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17
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Chenouard N, Xuan F, Tsien RW. Synaptic vesicle traffic is supported by transient actin filaments and regulated by PKA and NO. Nat Commun 2020; 11:5318. [PMID: 33087709 PMCID: PMC7578807 DOI: 10.1038/s41467-020-19120-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Accepted: 09/25/2020] [Indexed: 11/10/2022] Open
Abstract
Synaptic vesicles (SVs) can be pooled across multiple synapses, prompting questions about their dynamic allocation for neurotransmission and plasticity. We find that the axonal traffic of recycling vesicles is not supported by ubiquitous microtubule-based motility but relies on actin instead. Vesicles freed from synaptic clusters undergo ~1 µm bouts of active transport, initiated by nearby elongation of actin filaments. Long distance translocation arises when successive bouts of active transport were linked by periods of free diffusion. The availability of SVs for active transport can be promptly increased by protein kinase A, a key player in neuromodulation. Vesicle motion is in turn impeded by shutting off axonal actin polymerization, mediated by nitric oxide-cyclic GMP signaling leading to inhibition of RhoA. These findings provide a potential framework for coordinating post-and pre-synaptic strength, using retrograde regulation of axonal actin dynamics to mobilize and recruit presynaptic SV resources.
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Affiliation(s)
- Nicolas Chenouard
- NYU Neuroscience Institute and Department of Neuroscience and Physiology, NYU Langone Medical Center, New York, NY, 10016, USA.,Univ. Bordeaux, CNRS, Interdisciplinary Institute for Neuroscience, IINS, UMR 5297, F-33000, Bordeaux, France
| | - Feng Xuan
- NYU Neuroscience Institute and Department of Neuroscience and Physiology, NYU Langone Medical Center, New York, NY, 10016, USA.,Interdepartmental Neuroscience Program, Northwestern University, Evanston, IL, 60208, USA
| | - Richard W Tsien
- NYU Neuroscience Institute and Department of Neuroscience and Physiology, NYU Langone Medical Center, New York, NY, 10016, USA. .,Center for Neural Science, New York University, New York, NY, 10003, USA.
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18
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Frank M, Citarella CG, Quinones GB, Bentley M. A novel labeling strategy reveals that myosin Va and myosin Vb bind the same dendritically polarized vesicle population. Traffic 2020; 21:689-701. [PMID: 32959500 DOI: 10.1111/tra.12764] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 09/17/2020] [Accepted: 09/17/2020] [Indexed: 12/14/2022]
Abstract
Neurons are specialized cells with a polarized geometry and several distinct subdomains that require specific complements of proteins. Delivery of transmembrane proteins requires vesicle transport, which is mediated by molecular motor proteins. The myosin V family of motor proteins mediates transport to the barbed end of actin filaments, and little is known about the vesicles bound by myosin V in neurons. We developed a novel strategy to visualize myosin V-labeled vesicles in cultured hippocampal neurons and systematically characterized the vesicle populations labeled by myosin Va and Vb. We find that both myosins bind vesicles that are polarized to the somatodendritic domain where they undergo bidirectional long-range transport. A series of two-color imaging experiments showed that myosin V specifically colocalized with two different vesicle populations: vesicles labeled with the transferrin receptor and vesicles labeled by low-density lipoprotein receptor. Finally, coexpression with Kinesin-3 family members found that myosin V binds vesicles concurrently with KIF13A or KIF13B, supporting the hypothesis that coregulation of kinesins and myosin V on vesicles is likely to play an important role in neuronal vesicle transport. We anticipate that this new assay will be applicable in a broad range of cell types to determine the function of myosin V motor proteins.
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Affiliation(s)
- Madeline Frank
- Department of Biological Sciences and the Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York, USA
| | - Clara G Citarella
- Department of Biological Sciences and the Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York, USA
| | - Geraldine B Quinones
- Department of Biological Sciences and the Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York, USA
| | - Marvin Bentley
- Department of Biological Sciences and the Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York, USA
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19
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Gramlich MW, Klyachko VA. Nanoscale Organization of Vesicle Release at Central Synapses. Trends Neurosci 2020; 42:425-437. [PMID: 31176424 DOI: 10.1016/j.tins.2019.03.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Revised: 02/20/2019] [Accepted: 03/01/2019] [Indexed: 11/28/2022]
Abstract
Presynaptic boutons support neurotransmitter release with nanoscale precision at sub-millisecond timescales. Studies over the past two decades have revealed a rich tapestry of molecular players governing synaptic vesicle fusion at highly specialized release sites in the active zone (AZ). However, the spatiotemporal organization of release at active synapses remains elusive, in part owing to the extremely small size of the AZ and the limited resolution of conventional approaches. Recent advances in fluorescence nanoscopy have revolutionized direct investigation of presynaptic release organization and dynamics. We discuss here recent nanoscopy-based studies of the molecular architecture, the spatial organization and dynamic regulation of release sites, and the mechanisms of release site replenishment. These findings have uncovered previously unknown levels of structural and functional organization at central synapses, with important implications for synaptic transmission and plasticity.
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Affiliation(s)
- Michael W Gramlich
- Department of Cell Biology and Physiology, Department of Biomedical Engineering, Washington University School of Medicine, St. Louis, MO, USA; Present address: Department of Physics, Auburn University, Auburn, AL, USA
| | - Vitaly A Klyachko
- Department of Cell Biology and Physiology, Department of Biomedical Engineering, Washington University School of Medicine, St. Louis, MO, USA.
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20
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Costa AR, Sousa SC, Pinto-Costa R, Mateus JC, Lopes CD, Costa AC, Rosa D, Machado D, Pajuelo L, Wang X, Zhou FQ, Pereira AJ, Sampaio P, Rubinstein BY, Mendes Pinto I, Lampe M, Aguiar P, Sousa MM. The membrane periodic skeleton is an actomyosin network that regulates axonal diameter and conduction. eLife 2020; 9:55471. [PMID: 32195665 PMCID: PMC7105375 DOI: 10.7554/elife.55471] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Accepted: 03/19/2020] [Indexed: 02/06/2023] Open
Abstract
Neurons have a membrane periodic skeleton (MPS) composed of actin rings interconnected by spectrin. Here, combining chemical and genetic gain- and loss-of-function assays, we show that in rat hippocampal neurons the MPS is an actomyosin network that controls axonal expansion and contraction. Using super-resolution microscopy, we analyzed the localization of axonal non-muscle myosin II (NMII). We show that active NMII light chains are colocalized with actin rings and organized in a circular periodic manner throughout the axon shaft. In contrast, NMII heavy chains are mostly positioned along the longitudinal axonal axis, being able to crosslink adjacent rings. NMII filaments can play contractile or scaffolding roles determined by their position relative to actin rings and activation state. We also show that MPS destabilization through NMII inactivation affects axonal electrophysiology, increasing action potential conduction velocity. In summary, our findings open new perspectives on axon diameter regulation, with important implications in neuronal biology.
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Affiliation(s)
- Ana Rita Costa
- Nerve Regeneration Group, Porto, Portugal.,i3S- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
| | - Sara C Sousa
- Nerve Regeneration Group, Porto, Portugal.,i3S- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.,ICBAS- Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
| | - Rita Pinto-Costa
- Nerve Regeneration Group, Porto, Portugal.,i3S- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
| | - José C Mateus
- i3S- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.,ICBAS- Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal.,Neuroengineering and Computational Neuroscience Group, INEB- Instituto de Engenharia Biomédica, Universidade do Porto, Porto, Portugal
| | - Cátia Df Lopes
- i3S- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.,Neuroengineering and Computational Neuroscience Group, INEB- Instituto de Engenharia Biomédica, Universidade do Porto, Porto, Portugal
| | - Ana Catarina Costa
- Nerve Regeneration Group, Porto, Portugal.,i3S- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.,ICBAS- Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal.,Neuroengineering and Computational Neuroscience Group, INEB- Instituto de Engenharia Biomédica, Universidade do Porto, Porto, Portugal
| | - David Rosa
- Nerve Regeneration Group, Porto, Portugal.,i3S- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
| | - Diana Machado
- Nerve Regeneration Group, Porto, Portugal.,i3S- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
| | - Luis Pajuelo
- Nerve Regeneration Group, Porto, Portugal.,i3S- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
| | - Xuewei Wang
- Department of Orthopaedic Surgery, Johns Hopkins University School of Medicine; The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, United States
| | - Feng-Quan Zhou
- Department of Orthopaedic Surgery, Johns Hopkins University School of Medicine; The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, United States
| | - António J Pereira
- i3S- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.,Chromosome Instability and Dynamics Group, Porto, Portugal
| | - Paula Sampaio
- i3S- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.,Advanced Light Microscopy, IBMC- Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
| | | | | | - Marko Lampe
- Advanced Light Microscopy Facility, EMBL, Heidelberg, Germany
| | - Paulo Aguiar
- i3S- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.,Neuroengineering and Computational Neuroscience Group, INEB- Instituto de Engenharia Biomédica, Universidade do Porto, Porto, Portugal
| | - Monica M Sousa
- Nerve Regeneration Group, Porto, Portugal.,i3S- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
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21
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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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22
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Zhang XM, François U, Silm K, Angelo MF, Fernandez-Busch MV, Maged M, Martin C, Bernard V, Cordelières FP, Deshors M, Pons S, Maskos U, Bemelmans AP, Wojcik SM, El Mestikawy S, Humeau Y, Herzog E. A proline-rich motif on VGLUT1 reduces synaptic vesicle super-pool and spontaneous release frequency. eLife 2019; 8:50401. [PMID: 31663854 PMCID: PMC6861006 DOI: 10.7554/elife.50401] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Accepted: 10/27/2019] [Indexed: 12/29/2022] Open
Abstract
Glutamate secretion at excitatory synapses is tightly regulated to allow for the precise tuning of synaptic strength. Vesicular Glutamate Transporters (VGLUT) accumulate glutamate into synaptic vesicles (SV) and thereby regulate quantal size. Further, the number of release sites and the release probability of SVs maybe regulated by the organization of active-zone proteins and SV clusters. In the present work, we uncover a mechanism mediating an increased SV clustering through the interaction of VGLUT1 second proline-rich domain, endophilinA1 and intersectin1. This strengthening of SV clusters results in a combined reduction of axonal SV super-pool size and miniature excitatory events frequency. Our findings support a model in which clustered vesicles are held together through multiple weak interactions between Src homology three and proline-rich domains of synaptic proteins. In mammals, VGLUT1 gained a proline-rich sequence that recruits endophilinA1 and turns the transporter into a regulator of SV organization and spontaneous release.
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Affiliation(s)
- Xiao Min Zhang
- Interdisciplinary Institute for Neuroscience, Université de Bordeaux, Bordeaux, France.,Interdisciplinary Institute for Neuroscience CNRS UMR 5297, Bordeaux, France.,Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Urielle François
- Interdisciplinary Institute for Neuroscience, Université de Bordeaux, Bordeaux, France.,Interdisciplinary Institute for Neuroscience CNRS UMR 5297, Bordeaux, France
| | - Kätlin Silm
- Neuroscience Paris Seine NPS, Université Pierre et Marie Curie INSERM U1130 CNRS UMR8246, Paris, France
| | - Maria Florencia Angelo
- Interdisciplinary Institute for Neuroscience, Université de Bordeaux, Bordeaux, France.,Interdisciplinary Institute for Neuroscience CNRS UMR 5297, Bordeaux, France
| | - Maria Victoria Fernandez-Busch
- Interdisciplinary Institute for Neuroscience, Université de Bordeaux, Bordeaux, France.,Interdisciplinary Institute for Neuroscience CNRS UMR 5297, Bordeaux, France
| | - Mona Maged
- Interdisciplinary Institute for Neuroscience, Université de Bordeaux, Bordeaux, France.,Interdisciplinary Institute for Neuroscience CNRS UMR 5297, Bordeaux, France
| | - Christelle Martin
- Interdisciplinary Institute for Neuroscience, Université de Bordeaux, Bordeaux, France.,Interdisciplinary Institute for Neuroscience CNRS UMR 5297, Bordeaux, France
| | - Véronique Bernard
- Neuroscience Paris Seine NPS, Université Pierre et Marie Curie INSERM U1130 CNRS UMR8246, Paris, France
| | - Fabrice P Cordelières
- Bordeaux Imaging Center, Université de Bordeaux, CNRS UMS 3420, INSERM US4, Bordeaux, France
| | - Melissa Deshors
- Interdisciplinary Institute for Neuroscience, Université de Bordeaux, Bordeaux, France.,Interdisciplinary Institute for Neuroscience CNRS UMR 5297, Bordeaux, France
| | - Stéphanie Pons
- Institut Pasteur, CNRS UMR 3571, Unité NISC, Paris, France
| | - Uwe Maskos
- Institut Pasteur, CNRS UMR 3571, Unité NISC, Paris, France
| | - Alexis Pierre Bemelmans
- Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Direction de laRecherche Fondamentale (DRF), Institut de Biologie François Jacob (IBFJ), MolecularImaging Research Center (MIRCen), Fontenay-aux-Roses, France
| | - Sonja M Wojcik
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Salah El Mestikawy
- Neuroscience Paris Seine NPS, Université Pierre et Marie Curie INSERM U1130 CNRS UMR8246, Paris, France.,Department of Psychiatry, Douglas Mental Health University Institute, McGill University, Montreal, Canada
| | - Yann Humeau
- Interdisciplinary Institute for Neuroscience, Université de Bordeaux, Bordeaux, France.,Interdisciplinary Institute for Neuroscience CNRS UMR 5297, Bordeaux, France
| | - Etienne Herzog
- Interdisciplinary Institute for Neuroscience, Université de Bordeaux, Bordeaux, France.,Interdisciplinary Institute for Neuroscience CNRS UMR 5297, Bordeaux, France
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23
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Konietzny A, González-Gallego J, Bär J, Perez-Alvarez A, Drakew A, Demmers JAA, Dekkers DHW, Hammer JA, Frotscher M, Oertner TG, Wagner W, Kneussel M, Mikhaylova M. Myosin V regulates synaptopodin clustering and localization in the dendrites of hippocampal neurons. J Cell Sci 2019; 132:jcs.230177. [PMID: 31371487 PMCID: PMC6737913 DOI: 10.1242/jcs.230177] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Accepted: 07/19/2019] [Indexed: 01/15/2023] Open
Abstract
The spine apparatus (SA) is an endoplasmic reticulum-related organelle that is present in a subset of dendritic spines in cortical and pyramidal neurons, and plays an important role in Ca2+ homeostasis and dendritic spine plasticity. The protein synaptopodin is essential for the formation of the SA and is widely used as a maker for this organelle. However, it is still unclear which factors contribute to its localization at selected synapses, and how it triggers local SA formation. In this study, we characterized development, localization and mobility of synaptopodin clusters in hippocampal primary neurons, as well as the molecular dynamics within these clusters. Interestingly, synaptopodin at the shaft-associated clusters is less dynamic than at spinous clusters. We identify the actin-based motor proteins myosin V (herein referring to both the myosin Va and Vb forms) and VI as novel interaction partners of synaptopodin, and demonstrate that myosin V is important for the formation and/or maintenance of the SA. We found no evidence of active microtubule-based transport of synaptopodin. Instead, new clusters emerge inside spines, which we interpret as the SA being assembled on-site.
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Affiliation(s)
- Anja Konietzny
- DFG Emmy Noether Group 'Neuronal Protein Transport', Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
| | - Judit González-Gallego
- DFG Emmy Noether Group 'Neuronal Protein Transport', Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
| | - Julia Bär
- DFG Emmy Noether Group 'Neuronal Protein Transport', Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
| | - Alberto Perez-Alvarez
- Institute for Synaptic Physiology, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
| | - Alexander Drakew
- Institute of Structural Neurobiology, Center for Molecular Neurobiology Hamburg, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany.,Institute of Clinical Neuroanatomy, Faculty of Medicine, Theodor-Stern-Kai 7, 60590 Frankfurt, Germany
| | | | - Dick H W Dekkers
- Center for Proteomics, Erasmus MC, 3000 CA Rotterdam, The Netherlands
| | - John A Hammer
- Cell Biology and Physiology Center, National Heart, Lung Blood Institute, National Institutes of Health, Bethesda, MD 20814, USA
| | - Michael Frotscher
- Institute of Structural Neurobiology, Center for Molecular Neurobiology Hamburg, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
| | - Thomas G Oertner
- Institute for Synaptic Physiology, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
| | - Wolfgang Wagner
- Department of Molecular Neurogenetics, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
| | - Matthias Kneussel
- Department of Molecular Neurogenetics, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
| | - Marina Mikhaylova
- DFG Emmy Noether Group 'Neuronal Protein Transport', Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
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24
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Chakrabarty N, Jung P. Stochastic models of polymerization-based axonal actin transport. Phys Biol 2019; 16:056001. [PMID: 31195374 DOI: 10.1088/1478-3975/ab29cd] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Recent advances in live cell imaging of F-actin structures, combined with pulse-chase imaging and computational modeling have suggested that actin is transported along the axon via biased polymerization of metastable actin fibers (actin trails). This mechanism is distinct from motor driven polymer transport, such as for neurofilaments and can be best described as molecular hitchhiking, where G-actin molecules are intermittently incorporated into actin fibers which grow preferentially in the anterograde direction. In this paper, we discuss how various axonal and actin trail parameters like axon diameter, trail nucleation rates, basal G-actin concentration, and trail length influence the transport rate. These predictions can help guide future experiments to verify this novel protein transport mechanism. We introduce a simplified, analytically solvable model of actin transport which relates these parameters to experimentally measurable quantities. We also discuss why a simple diffusion-based transport mechanism cannot explain bulk actin transport in the axon.
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Affiliation(s)
- Nilaj Chakrabarty
- Department of Physics and Astronomy, Neuroscience Program and Quantitative Biology Institute, Athens, OH 45701, United States of America
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25
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van Bommel B, Konietzny A, Kobler O, Bär J, Mikhaylova M. F-actin patches associated with glutamatergic synapses control positioning of dendritic lysosomes. EMBO J 2019; 38:e101183. [PMID: 31267565 PMCID: PMC6669925 DOI: 10.15252/embj.2018101183] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Revised: 05/27/2019] [Accepted: 05/29/2019] [Indexed: 12/31/2022] Open
Abstract
Organelle positioning within neurites is required for proper neuronal function. In dendrites, with their complex cytoskeletal organization, transport of organelles is guided by local specializations of the microtubule and actin cytoskeleton, and by coordinated activity of different motor proteins. Here, we focus on the actin cytoskeleton in the dendritic shaft and describe dense structures consisting of longitudinal and branched actin filaments. These actin patches are devoid of microtubules and are frequently located at the base of spines, or form an actin mesh around excitatory shaft synapses. Using lysosomes as an example, we demonstrate that the presence of actin patches has a strong impact on dendritic organelle transport, as lysosomes frequently stall at these locations. We provide mechanistic insights on this pausing behavior, demonstrating that actin patches form a physical barrier for kinesin-driven cargo. In addition, we identify myosin Va as an active tether which mediates long-term stalling. This correlation between the presence of actin meshes and halting of organelles could be a generalized principle by which synapses control organelle trafficking.
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Affiliation(s)
- Bas van Bommel
- DFG Emmy Noether Group "Neuronal Protein Transport", Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Anja Konietzny
- DFG Emmy Noether Group "Neuronal Protein Transport", Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Oliver Kobler
- Combinatorial Neuroimaging Core Facility (CNI), Leibniz Institute for Neurobiology, Magdeburg, Germany
| | - Julia Bär
- DFG Emmy Noether Group "Neuronal Protein Transport", Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Marina Mikhaylova
- DFG Emmy Noether Group "Neuronal Protein Transport", Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
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26
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Maschi D, Gramlich MW, Klyachko VA. Myosin V functions as a vesicle tether at the plasma membrane to control neurotransmitter release in central synapses. eLife 2018; 7:e39440. [PMID: 30320552 PMCID: PMC6209431 DOI: 10.7554/elife.39440] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2018] [Accepted: 10/11/2018] [Indexed: 12/21/2022] Open
Abstract
Synaptic vesicle fusion occurs at specialized release sites at the active zone. How refilling of release sites with new vesicles is regulated in central synapses remains poorly understood. Using nanoscale-resolution detection of individual release events in rat hippocampal synapses we found that inhibition of myosin V, the predominant vesicle-associated motor, strongly reduced refilling of the release sites during repetitive stimulation. Single-vesicle tracking revealed that recycling vesicles continuously shuttle between a plasma membrane pool and an inner pool. Vesicle retention at the membrane pool was regulated by neural activity in a myosin V dependent manner. Ultrastructural measurements of vesicle occupancy at the plasma membrane together with analyses of single-vesicle trajectories during vesicle shuttling between the pools suggest that myosin V acts as a vesicle tether at the plasma membrane, rather than a motor transporting vesicles to the release sites, or directly regulating vesicle exocytosis.
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Affiliation(s)
- Dario Maschi
- Department of Cell Biology and PhysiologyWashington UniversityMissouriUnited States
- Department of Biomedical EngineeringWashington UniversityMissouriUnited States
| | - Michael W Gramlich
- Department of Cell Biology and PhysiologyWashington UniversityMissouriUnited States
- Department of Biomedical EngineeringWashington UniversityMissouriUnited States
| | - Vitaly A Klyachko
- Department of Cell Biology and PhysiologyWashington UniversityMissouriUnited States
- Department of Biomedical EngineeringWashington UniversityMissouriUnited States
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27
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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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28
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Activity-Dependence of Synaptic Vesicle Dynamics. J Neurosci 2017; 37:10597-10610. [PMID: 28954868 DOI: 10.1523/jneurosci.0383-17.2017] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Revised: 08/08/2017] [Accepted: 08/15/2017] [Indexed: 11/21/2022] Open
Abstract
The proper function of synapses relies on efficient recycling of synaptic vesicles. The small size of synaptic boutons has hampered efforts to define the dynamical states of vesicles during recycling. Moreover, whether vesicle motion during recycling is regulated by neural activity remains largely unknown. We combined nanoscale-resolution tracking of individual synaptic vesicles in cultured hippocampal neurons from rats of both sexes with advanced motion analyses to demonstrate that the majority of recently endocytosed vesicles undergo sequences of transient dynamical states including epochs of directed, diffusional, and stalled motion. We observed that vesicle motion is modulated in an activity-dependent manner, with dynamical changes apparent in ∼20% of observed boutons. Within this subpopulation of boutons, 35% of observed vesicles exhibited acceleration and 65% exhibited deceleration, accompanied by corresponding changes in directed motion. Individual vesicles observed in the remaining ∼80% of boutons did not exhibit apparent dynamical changes in response to stimulation. More quantitative transient motion analyses revealed that the overall reduction of vesicle mobility, and specifically of the directed motion component, is the predominant activity-evoked change across the entire bouton population. Activity-dependent modulation of vesicle mobility may represent an important mechanism controlling vesicle availability and neurotransmitter release.SIGNIFICANCE STATEMENT Mechanisms governing synaptic vesicle dynamics during recycling remain poorly understood. Using nanoscale resolution tracking of individual synaptic vesicles in hippocampal synapses and advanced motion analysis tools we demonstrate that synaptic vesicles undergo complex sets of dynamical states that include epochs of directed, diffusive, and stalled motion. Most importantly, our analyses revealed that vesicle motion is modulated in an activity-dependent manner apparent as the reduction in overall vesicle mobility in response to stimulation. These results define the vesicle dynamical states during recycling and reveal their activity-dependent modulation. Our study thus provides fundamental new insights into the principles governing synaptic function.
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29
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Heissler SM, Chinthalapudi K, Sellers JR. Kinetic signatures of myosin-5B, the motor involved in microvillus inclusion disease. J Biol Chem 2017; 292:18372-18385. [PMID: 28882893 DOI: 10.1074/jbc.m117.801456] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 08/29/2017] [Indexed: 11/06/2022] Open
Abstract
Myosin-5B is a ubiquitous molecular motor that transports cargo vesicles of the endomembrane system in intracellular recycling pathways. Myosin-5B malfunction causes the congenital enteropathy microvillus inclusion disease, underlining its importance in cellular homeostasis. Here we describe the interaction of myosin-5B with F-actin, nucleotides, and the pyrazolopyrimidine compound myoVin-1. We show that single-headed myosin-5B is an intermediate duty ratio motor with a kinetic ATPase cycle that is rate-limited by the release of phosphate. The presence of a second head generates strain and gating in the myosin-5B dimer that alters the kinetic signature by reducing the actin-activated ADP release rate to become rate-limiting. This kinetic transition into a high-duty ratio motor is a prerequisite for the proposed transport function of myosin-5B in cellular recycling pathways. Moreover, we show that the small molecule compound myoVin-1 inhibits the enzymatic and functional activity of myosin-5B in vitro Partial inhibition of the actin-activated steady-state ATPase activity and sliding velocity suggests that caution should be used when probing the effect of myoVin-1 on myosin-5-dependent transport processes in cells.
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Affiliation(s)
- Sarah M Heissler
- From the Laboratory of Molecular Physiology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892-8015 and
| | - Krishna Chinthalapudi
- the Cell Adhesion Laboratory, Department of Integrative Structural and Computational Biology, Scripps Research Institute, Jupiter, Florida 33458
| | - James R Sellers
- From the Laboratory of Molecular Physiology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892-8015 and
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30
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Nirschl JJ, Ghiretti AE, Holzbaur ELF. The impact of cytoskeletal organization on the local regulation of neuronal transport. Nat Rev Neurosci 2017; 18:585-597. [PMID: 28855741 DOI: 10.1038/nrn.2017.100] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Neurons are akin to modern cities in that both are dependent on robust transport mechanisms. Like the best mass transit systems, trafficking in neurons must be tailored to respond to local requirements. Neurons depend on both high-speed, long-distance transport and localized dynamics to correctly deliver cargoes and to tune synaptic responses. Here, we focus on the mechanisms that provide localized regulation of the transport machinery, including the cytoskeleton and molecular motors, to yield compartment-specific trafficking in the axon initial segment, axon terminal, dendrites and spines. The synthesis of these mechanisms provides a sophisticated and responsive transit system for the cell.
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Affiliation(s)
- Jeffrey J Nirschl
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, 638A Clinical Research Building, 415 Curie Boulevard, Philadelphia, Pennsylvania 19104, USA
| | - Amy E Ghiretti
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, 638A Clinical Research Building, 415 Curie Boulevard, Philadelphia, Pennsylvania 19104, USA
| | - Erika L F Holzbaur
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, 638A Clinical Research Building, 415 Curie Boulevard, Philadelphia, Pennsylvania 19104, USA
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