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Song SH, Augustine GJ. A role for synapsin tetramerization in synaptic vesicle clustering. J Physiol 2024. [PMID: 38979871 DOI: 10.1113/jp286177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2024] [Accepted: 06/06/2024] [Indexed: 07/10/2024] Open
Abstract
Although synapsins have long been proposed to be key regulators of synaptic vesicle (SV) clustering, their mechanism of action has remained mysterious and somewhat controversial. Here, we review synapsins and their associations with each other and with SVs. We highlight the recent hypothesis that synapsin tetramerization is a mechanism for SV clustering. This hypothesis, which aligns with numerous experimental results, suggests that the larger size of synapsin tetramers, in comparison to dimers, allows tetramers to form optimal bridges between SVs that overcome the repulsive force associated with the negatively charged membrane of SVs and allow synapsins to form a reserve pool of SVs within presynaptic terminals.
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Affiliation(s)
| | - George J Augustine
- Temasek Life sciences Laboratory, Singapore
- Department of Physiology, National University of Singapore, Singapore
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2
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Longfield SF, Gormal RS, Feller M, Parutto P, Reingruber J, Wallis TP, Joensuu M, Augustine GJ, Martínez-Mármol R, Holcman D, Meunier FA. Synapsin 2a tetramerisation selectively controls the presynaptic nanoscale organisation of reserve synaptic vesicles. Nat Commun 2024; 15:2217. [PMID: 38472171 PMCID: PMC10933366 DOI: 10.1038/s41467-024-46256-1] [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: 03/22/2023] [Accepted: 02/21/2024] [Indexed: 03/14/2024] Open
Abstract
Neurotransmitter release relies on the regulated fusion of synaptic vesicles (SVs) that are tightly packed within the presynaptic bouton of neurons. The mechanism by which SVs are clustered at the presynapse, while preserving their ability to dynamically recycle to support neuronal communication, remains unknown. Synapsin 2a (Syn2a) tetramerization has been suggested as a potential clustering mechanism. Here, we used Dual-pulse sub-diffractional Tracking of Internalised Molecules (DsdTIM) to simultaneously track single SVs from the recycling and the reserve pools, in live hippocampal neurons. The reserve pool displays a lower presynaptic mobility compared to the recycling pool and is also present in the axons. Triple knockout of Synapsin 1-3 genes (SynTKO) increased the mobility of reserve pool SVs. Re-expression of wild-type Syn2a (Syn2aWT), but not the tetramerization-deficient mutant K337Q (Syn2aK337Q), fully rescued these effects. Single-particle tracking revealed that Syn2aK337QmEos3.1 exhibited altered activity-dependent presynaptic translocation and nanoclustering. Therefore, Syn2a tetramerization controls its own presynaptic nanoclustering and thereby contributes to the dynamic immobilisation of the SV reserve pool.
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Affiliation(s)
- Shanley F Longfield
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Rachel S Gormal
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Matis Feller
- Group of Data Modelling and Computational Biology, IBENS, Ecole Normale Superieure, 75005, Paris, France
| | - Pierre Parutto
- Group of Data Modelling and Computational Biology, IBENS, Ecole Normale Superieure, 75005, Paris, France
| | - Jürgen Reingruber
- Group of Data Modelling and Computational Biology, IBENS, Ecole Normale Superieure, 75005, Paris, France
| | - Tristan P Wallis
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Merja Joensuu
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia
- Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, QLD 4072, Australia
| | | | - Ramón Martínez-Mármol
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia
| | - David Holcman
- Group of Data Modelling and Computational Biology, IBENS, Ecole Normale Superieure, 75005, Paris, France
- Department of Applied Mathematics and Theoretical Physics (DAMPT) visitor, University of Cambridge, and Churchill College, CB30DS, Cambridge, UK
| | - Frédéric A Meunier
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia.
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD 4072, Australia.
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Alfken J, Neuhaus C, Major A, Taskina A, Hoffmann C, Ganzella M, Petrovic A, Zwicker D, Fernández-Busnadiego R, Jahn R, Milovanovic D, Salditt T. Vesicle condensation induced by synapsin: condensate size, geometry, and vesicle shape deformations. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2024; 47:8. [PMID: 38270681 PMCID: PMC11233366 DOI: 10.1140/epje/s10189-023-00404-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Accepted: 12/28/2023] [Indexed: 01/26/2024]
Abstract
We study the formation of vesicle condensates induced by the protein synapsin, as a cell-free model system mimicking vesicle pool formation in the synapse. The system can be considered as an example of liquid-liquid phase separation (LLPS) in biomolecular fluids, where one phase is a complex fluid itself consisting of vesicles and a protein network. We address the pertinent question why the LLPS is self-limiting and stops at a certain size, i.e., why macroscopic phase separation is prevented. Using fluorescence light microscopy, we observe different morphologies of the condensates (aggregates) depending on the protein-to-lipid ratio. Cryogenic electron microscopy then allows us to resolve individual vesicle positions and shapes in a condensate and notably the size and geometry of adhesion zones between vesicles. We hypothesize that the membrane tension induced by already formed adhesion zones then in turn limits the capability of vesicles to bind additional vesicles, resulting in a finite condensate size. In a simple numerical toy model we show that this effect can be accounted for by redistribution of effective binding particles on the vesicle surface, accounting for the synapsin-induced adhesion zone.
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Affiliation(s)
- Jette Alfken
- Institut für Röntgenphysik, Georg-August-Universität, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany
| | - Charlotte Neuhaus
- Institut für Röntgenphysik, Georg-August-Universität, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany
| | - András Major
- Institut für Röntgenphysik, Georg-August-Universität, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany
| | - Alyona Taskina
- Institut für Röntgenphysik, Georg-August-Universität, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany
- Theorie Biologischer Flüssigkeiten, Max-Planck-Institut für Dynamik und Selbstorganisation, Am Fassberg 11, 37077, Göttingen, Germany
| | - Christian Hoffmann
- Molekulare Neurowissenschaften, Deutsches Zentrum für Neurodegenerative Erkrankungen (DZNE), Charitéplatz 1, 10117, Berlin, Germany
| | - Marcelo Ganzella
- Labor für Neurobiologie, Max-Planck-Institut für multidisziplinäre Naturwissenschaften, Am Fassberg 11, 37077, Göttingen, Germany
| | - Arsen Petrovic
- Institut für Neuropathologie, Universitätsmedizin Göttingen, Justus-von-Liebig-Weg 11, 37077, Göttingen, Germany
| | - David Zwicker
- Theorie Biologischer Flüssigkeiten, Max-Planck-Institut für Dynamik und Selbstorganisation, Am Fassberg 11, 37077, Göttingen, Germany
| | - Rubén Fernández-Busnadiego
- Institut für Neuropathologie, Universitätsmedizin Göttingen, Justus-von-Liebig-Weg 11, 37077, Göttingen, Germany
| | - Reinhard Jahn
- Labor für Neurobiologie, Max-Planck-Institut für multidisziplinäre Naturwissenschaften, Am Fassberg 11, 37077, Göttingen, Germany
| | - Dragomir Milovanovic
- Molekulare Neurowissenschaften, Deutsches Zentrum für Neurodegenerative Erkrankungen (DZNE), Charitéplatz 1, 10117, Berlin, Germany
| | - Tim Salditt
- Institut für Röntgenphysik, Georg-August-Universität, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany.
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Phosphatidylserine in the Nervous System: Cytoplasmic Regulator of the AKT and PKC Signaling Pathways and Extracellular "Eat-Me" Signal in Microglial Phagocytosis. Mol Neurobiol 2023; 60:1050-1066. [PMID: 36401705 DOI: 10.1007/s12035-022-03133-6] [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: 07/25/2022] [Accepted: 11/08/2022] [Indexed: 11/21/2022]
Abstract
Phosphatidylserine (PtdSer) is an important anionic phospholipid found in eukaryotic cells and has been proven to serve as a beneficial factor in the treatment of neurodegenerative diseases. PtdSer resides in the inner leaflet of the plasma membrane, where it is involved in regulating the AKT and PKC signaling pathways; however, it becomes exposed to the extracellular leaflet during neurodevelopmental processes and neurodegenerative diseases, participating in microglia-mediated synaptic and neuronal phagocytosis. In this paper, we review several characteristics of PtdSer, including the synthesis and translocation of PtdSer, the functions of cytoplasmic and exposed PtdSer, and different PtdSer-detection materials used to further understand the role of PtdSer in the nervous system.
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Yan P, Liu H, Zhou T, Sun P, Wang Y, Wang X, Zhang L, Wang T, Dong J, Zhu J, Lv L, Li W, Qi S, Liang Y, Kong E. Crosstalk of Synapsin1 palmitoylation and phosphorylation controls the dynamicity of synaptic vesicles in neurons. Cell Death Dis 2022; 13:786. [PMID: 36097267 PMCID: PMC9468182 DOI: 10.1038/s41419-022-05235-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Revised: 08/30/2022] [Accepted: 09/05/2022] [Indexed: 01/21/2023]
Abstract
The dynamics of synaptic vesicles (SVs) within presynaptic domains are tightly controlled by synapsin1 phosphorylation; however, the mechanism underlying the anchoring of synapsin1 with F-actin or SVs is not yet fully understood. Here, we found that Syn1 is modified with protein palmitoylation, and examining the roles of Syn1 palmitoylation in neurons led us to uncover that Syn1 palmitoylation is negatively regulated by its phosphorylation; together, they manipulate the clustering and redistribution of SVs. Using the combined approaches of electron microscopy and genetics, we revealed that Syn1 palmitoylation is vital for its binding with F-actin but not SVs. Inhibition of Syn1 palmitoylation causes defects in SVs clustering and a reduced number of total SVs in vivo. We propose a model in which SVs redistribution is triggered by upregulated Syn1 phosphorylation and downregulated Syn1 palmitoylation, and they reversibly promote SVs clustering. The crosstalk of Syn1 palmitoylation and phosphorylation thereby bidirectionally manipulates SVs dynamics in neurons.
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Affiliation(s)
- Peipei Yan
- grid.412990.70000 0004 1808 322XThe Second Affiliated Hospital of Xinxiang Medical University, Xinxiang, China ,grid.412990.70000 0004 1808 322XInstitute of Psychiatry and Neuroscience, Xinxiang key laboratory of protein palmitoylation and major human diseases, Xinxiang Medical University, Xinxiang, China
| | - Huicong Liu
- grid.412990.70000 0004 1808 322XThe Second Affiliated Hospital of Xinxiang Medical University, Xinxiang, China ,grid.412990.70000 0004 1808 322XInstitute of Psychiatry and Neuroscience, Xinxiang key laboratory of protein palmitoylation and major human diseases, Xinxiang Medical University, Xinxiang, China
| | - Tao Zhou
- grid.412990.70000 0004 1808 322XInstitute of Psychiatry and Neuroscience, Xinxiang key laboratory of protein palmitoylation and major human diseases, Xinxiang Medical University, Xinxiang, China
| | - Pu Sun
- grid.412990.70000 0004 1808 322XInstitute of Psychiatry and Neuroscience, Xinxiang key laboratory of protein palmitoylation and major human diseases, Xinxiang Medical University, Xinxiang, China
| | - Yilin Wang
- grid.412990.70000 0004 1808 322XInstitute of Psychiatry and Neuroscience, Xinxiang key laboratory of protein palmitoylation and major human diseases, Xinxiang Medical University, Xinxiang, China
| | - Xibin Wang
- grid.412990.70000 0004 1808 322XInstitute of Psychiatry and Neuroscience, Xinxiang key laboratory of protein palmitoylation and major human diseases, Xinxiang Medical University, Xinxiang, China
| | - Lin Zhang
- grid.412990.70000 0004 1808 322XInstitute of Psychiatry and Neuroscience, Xinxiang key laboratory of protein palmitoylation and major human diseases, Xinxiang Medical University, Xinxiang, China
| | - Tian Wang
- grid.412990.70000 0004 1808 322XInstitute of Psychiatry and Neuroscience, Xinxiang key laboratory of protein palmitoylation and major human diseases, Xinxiang Medical University, Xinxiang, China
| | - Jing Dong
- grid.412990.70000 0004 1808 322XInstitute of Psychiatry and Neuroscience, Xinxiang key laboratory of protein palmitoylation and major human diseases, Xinxiang Medical University, Xinxiang, China
| | - Jiangli Zhu
- grid.13291.380000 0001 0807 1581Department of Urology, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University and National Collaborative Innovation Center, 610041 Chengdu, China
| | - Luxian Lv
- grid.412990.70000 0004 1808 322XThe Second Affiliated Hospital of Xinxiang Medical University, Xinxiang, China
| | - Wenqiang Li
- grid.412990.70000 0004 1808 322XThe Second Affiliated Hospital of Xinxiang Medical University, Xinxiang, China
| | - Shiqian Qi
- grid.13291.380000 0001 0807 1581Department of Urology, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University and National Collaborative Innovation Center, 610041 Chengdu, China
| | - Yinming Liang
- grid.412990.70000 0004 1808 322XLaboratory of Genetic Regulators in the Immune System, Henan Key Laboratory of Immunology and Targeted Therapy, School of Laboratory Medicine, Xinxiang Medical University, Xinxiang, China
| | - Eryan Kong
- grid.412990.70000 0004 1808 322XThe Second Affiliated Hospital of Xinxiang Medical University, Xinxiang, China ,grid.412990.70000 0004 1808 322XInstitute of Psychiatry and Neuroscience, Xinxiang key laboratory of protein palmitoylation and major human diseases, Xinxiang Medical University, Xinxiang, China
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Mir S, Ashraf S, Saeed M, Rahman AU, Ul-Haq Z. Protonation states at different pH, conformational changes and impact of glycosylation in synapsin Ia. Phys Chem Chem Phys 2021; 23:16718-16729. [PMID: 34318818 DOI: 10.1039/d1cp00531f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Synapsin I (SynI) is the most abundant brain phosphoprotein present at presynaptic terminals that regulates neurotransmitter release, clustering of synaptic vesicles (SVs) at active zones, and stimulates synaptogenesis and neurite outgrowth. Earlier studies have established that SynI displays pH-dependent tethering of SVs to actin filaments and exhibits a maximum binding around neutral pH, however, the effect of pH shift from acidic to basic on the conformational stability of SynI has not been explored yet. Another important aspect of SynIa is its O-GlcNAcylation (O-GlcNac) at the Thr87 position, which is responsible for the positive regulation of synaptic plasticity linked to learning and memory in mice. Furthermore, reduced levels of O-GlcNAc have been observed in Alzheimer's disease, suggesting a possible link to deficits in synaptic plasticity. In this study, the effect of pH and glycosylation on the structure and functional stability of SynIa is determined through molecular dynamics (MD) simulation approach. The 3D structure of SynIa was established via threading-based homology modeling methods. It was observed that the structure of SynIa adopts extended conformational changes as the pH shifts from acidic to basic, resulting in a compact conformation at pH 8.0. Moreover, the results obtained by comparing the glycosylated and unglycosylated protein indicated that the glycan moiety imparts stability to the protein by forming intramolecular hydrogen bond interactions with the protein residues. The results indicate that although O-GlcNAc moieties do not induce a significant change in SynIa structure they minimize protein dynamics, likely leading to enhanced protein stability.
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Affiliation(s)
- Sonia Mir
- H.E.J., Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 75270, Pakistan.
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Longhena F, Faustini G, Brembati V, Pizzi M, Benfenati F, Bellucci A. An updated reappraisal of synapsins: structure, function and role in neurological and psychiatric disorders. Neurosci Biobehav Rev 2021; 130:33-60. [PMID: 34407457 DOI: 10.1016/j.neubiorev.2021.08.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 07/29/2021] [Accepted: 08/09/2021] [Indexed: 01/02/2023]
Abstract
Synapsins (Syns) are phosphoproteins strongly involved in neuronal development and neurotransmitter release. Three distinct genes SYN1, SYN2 and SYN3, with elevated evolutionary conservation, have been described to encode for Synapsin I, Synapsin II and Synapsin III, respectively. Syns display a series of common features, but also exhibit distinctive localization, expression pattern, post-translational modifications (PTM). These characteristics enable their interaction with other synaptic proteins, membranes and cytoskeletal components, which is essential for the proper execution of their multiple functions in neuronal cells. These include the control of synapse formation and growth, neuron maturation and renewal, as well as synaptic vesicle mobilization, docking, fusion, recycling. Perturbations in the balanced expression of Syns, alterations of their PTM, mutations and polymorphisms of their encoding genes induce severe dysregulations in brain networks functions leading to the onset of psychiatric or neurological disorders. This review presents what we have learned since the discovery of Syn I in 1977, providing the state of the art on Syns structure, function, physiology and involvement in central nervous system disorders.
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Affiliation(s)
- Francesca Longhena
- Division of Pharmacology, Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, 25123, Brescia, Italy.
| | - Gaia Faustini
- Division of Pharmacology, Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, 25123, Brescia, Italy.
| | - Viviana Brembati
- Division of Pharmacology, Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, 25123, Brescia, Italy.
| | - Marina Pizzi
- Division of Pharmacology, Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, 25123, Brescia, Italy.
| | - Fabio Benfenati
- Italian Institute of Technology, Via Morego 30, Genova, Italy; IRCSS Policlinico San Martino Hospital, Largo Rosanna Benzi 10, 16132, Genova, Italy.
| | - Arianna Bellucci
- Division of Pharmacology, Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, 25123, Brescia, Italy; Laboratory for Preventive and Personalized Medicine, Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, 25123, Brescia, Italy.
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Zhang M, Augustine GJ. Synapsins and the Synaptic Vesicle Reserve Pool: Floats or Anchors? Cells 2021; 10:cells10030658. [PMID: 33809712 PMCID: PMC8002314 DOI: 10.3390/cells10030658] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Revised: 03/08/2021] [Accepted: 03/11/2021] [Indexed: 11/24/2022] Open
Abstract
In presynaptic terminals, synaptic vesicles (SVs) are found in a discrete cluster that includes a reserve pool that is mobilized during synaptic activity. Synapsins serve as a key protein for maintaining SVs within this reserve pool, but the mechanism that allows synapsins to do this is unclear. This mechanism is likely to involve synapsins either cross-linking SVs, thereby anchoring SVs to each other, or creating a liquid phase that allows SVs to float within a synapsin droplet. Here, we summarize what is known about the role of synapsins in clustering of SVs and evaluate experimental evidence supporting these two models.
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Giving names to the actors of synaptic transmission: The long journey from synaptic vesicles to neural plasticity. ADVANCES IN PHARMACOLOGY 2021; 90:19-37. [PMID: 33706933 DOI: 10.1016/bs.apha.2020.09.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/29/2023]
Abstract
More than a scientific paper or a review article, this is a remembrance of a unique time of science and life that the authors spent in Paul Greengard's laboratory at the Rockefeller University in New York in the 1980s and 1990s, forming the so-called synaptic vesicle group. It was a time in which the molecular mechanisms of synaptic transmission and the nature of the organelles in charge of storing and releasing neurotransmitter were just beginning to be understood. It was an exciting time in which the protein composition of synaptic vesicles started to be identified. It turned out that the interactions of synaptic vesicle proteins with the cytoskeleton and the presynaptic membrane and their modulation by protein phosphorylation represented an essential network regulating the efficiency of neurotransmitter release and thereby synaptic strength and plasticity. This is also a description of the distinct scientific journeys that the three authors took on going back to Europe and how they were strongly influenced by the generous and outstanding mentorship of Paul Greengard, his genuine interest in their lives and careers and the life-long friendship with him.
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Abstract
Emerging evidence indicates that liquid-liquid phase separation, the formation of a condensed molecular assembly within another diluted aqueous solution, is a means for cells to organize highly condensed biological assemblies (also known as biological condensates or membraneless compartments) with very broad functions and regulatory properties in different subcellular regions. Molecular machineries dictating synaptic transmissions in both presynaptic boutons and postsynaptic densities of neuronal synapses may be such biological condensates. Here we review recent developments showing how phase separation can build dense synaptic molecular clusters, highlight unique features of such condensed clusters in the context of synaptic development and signaling, discuss how aberrant phase-separation-mediated synaptic assembly formation may contribute to dysfunctional signaling in psychiatric disorders, and present some challenges and opportunities of phase separation in synaptic biology.
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Heroin Cue-Evoked Astrocytic Structural Plasticity at Nucleus Accumbens Synapses Inhibits Heroin Seeking. Biol Psychiatry 2019; 86:811-819. [PMID: 31495448 PMCID: PMC6823145 DOI: 10.1016/j.biopsych.2019.06.026] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Revised: 06/06/2019] [Accepted: 06/19/2019] [Indexed: 12/11/2022]
Abstract
BACKGROUND Opioid addiction is a critical medical and societal problem characterized by vulnerability to relapse. Glutamatergic synapses in the nucleus accumbens regulate the motivation to relapse to opioid use, and downregulation of glutamate transporters on astroglial processes adjacent to accumbens synapses contributes to heroin seeking induced by cues. However, it is not known how astroglial processes themselves respond to heroin cues or if changes in astroglial morphology are necessary for heroin seeking. METHODS Male Sprague Dawley rats (n = 62) were trained to self-administer heroin or sucrose and were reinstated by heroin-conditioned or sucrose-conditioned cues. Astroglial proximity to accumbens synapses was estimated using a confocal-based strategy, and the association between digitally isolated astroglia and the presynaptic marker synapsin I was quantified. To determine the functional consequence of astroglial morphological plasticity on cued heroin seeking, a morpholino antisense strategy was used to knock down expression of the actin binding protein ezrin, which is expressed almost exclusively in peripheral astroglial processes in the adult rat brain. RESULTS After heroin extinction, there was an enduring reduction in synaptic proximity by astroglia. Synaptic proximity was restored during 15 minutes of cued heroin seeking but returned to extinction levels by 120 minutes. Extinction from sucrose self-administration and reinstated sucrose seeking induced no changes in astroglial synaptic association. Ezrin knockdown reduced astroglial association with synapses and potentiated cued heroin seeking. CONCLUSIONS Cue-induced heroin seeking transiently increased synaptic proximity of accumbens astrocytes. Surprisingly, the reassociation of astroglia with synapses was compensatory, and preventing cue-induced morphological plasticity in astrocytes potentiated heroin seeking.
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Mertens R, Melchert S, Gitler D, Schou MB, Saether SG, Vaaler A, Piepgras J, Kochova E, Benfenati F, Ahnert-Hilger G, Ruprecht K, Höltje M. Epitope specificity of anti-synapsin autoantibodies: Differential targeting of synapsin I domains. PLoS One 2018; 13:e0208636. [PMID: 30543686 PMCID: PMC6292584 DOI: 10.1371/journal.pone.0208636] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2018] [Accepted: 11/20/2018] [Indexed: 01/07/2023] Open
Abstract
OBJECTIVE To identify the specific domains of the presynaptic protein synapsin targeted by recently described autoantibodies to synapsin. METHODS Sera of 20 and CSF of two patients with different psychiatric and neurological disorders previously tested positive for immunoglobulin (Ig)G antibodies to full-length synapsin were screened for IgG against synapsin I domains using HEK293 cells transfected with constructs encoding different domains of rat synapsin Ia. Additionally, IgG subclasses were determined using full-length synapsin Ia. Serum and CSF from one patient were also screened for IgA autoantibodies to synapsin I domains. Sera from nine and CSF from two healthy subjects were analyzed as controls. RESULTS IgG in serum from 12 of 20 IgG synapsin full-length positive patients, but from none of the healthy controls, bound to synapsin domains. Of these 12 sera, six bound to the A domain, five to the D domain, and one to the B- (and possibly A-), D-, and E-domains of synapsin I. IgG antibodies to the D-domain were also detected in one of the CSF samples. Determination of IgG subclasses detected IgG1 in two sera and one CSF, IgG2 in none of the samples, IgG3 in two sera, and IgG4 in eight sera. One patient known to be positive for IgA antibodies to full-length synapsin had IgA antibodies to the D-domain in serum and CSF. CONCLUSIONS Anti-synapsin autoantibodies preferentially bind to either the A- or the D-domain of synapsin I.
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Affiliation(s)
- Robert Mertens
- Institute of Integrative Neuroanatomy, Charité –Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Sarah Melchert
- Institute of Integrative Neuroanatomy, Charité –Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Daniel Gitler
- Department of Physiology and Cell Biology, Faculty of Health Sciences and Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Morten Brix Schou
- Department of Psychiatry, St. Olav’s University Hospital, Trondheim, Norway
- Department of Mental Health, Norwegian University of Science and Technology, Trondheim, Norway
| | - Sverre Georg Saether
- Department of Psychiatry, St. Olav’s University Hospital, Trondheim, Norway
- Department of Mental Health, Norwegian University of Science and Technology, Trondheim, Norway
| | - Arne Vaaler
- Department of Psychiatry, St. Olav’s University Hospital, Trondheim, Norway
- Department of Mental Health, Norwegian University of Science and Technology, Trondheim, Norway
| | - Johannes Piepgras
- Institute of Integrative Neuroanatomy, Charité –Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Elena Kochova
- Institute of Integrative Neuroanatomy, Charité –Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Fabio Benfenati
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Genova, Italy
| | - Gudrun Ahnert-Hilger
- Institute of Integrative Neuroanatomy, Charité –Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Klemens Ruprecht
- Department of Neurology, Charité –Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Markus Höltje
- Institute of Integrative Neuroanatomy, Charité –Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
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13
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Song SH, Augustine GJ. Synapsin Isoforms and Synaptic Vesicle Trafficking. Mol Cells 2015; 38:936-40. [PMID: 26627875 PMCID: PMC4673407 DOI: 10.14348/molcells.2015.0233] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Revised: 11/09/2015] [Accepted: 11/10/2015] [Indexed: 11/27/2022] Open
Abstract
Synapsins were the first presynaptic proteins identified and have served as the flagship of the presynaptic protein field. Here we review recent studies demonstrating that different members of the synapsin family play different roles at presynaptic terminals employing different types of synaptic vesicles. The structural underpinnings for these functions are just beginning to be understood and should provide a focus for future efforts.
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Affiliation(s)
- Sang-Ho Song
- Lee Kong Chian School of Medicine,
Singapore 637553,
Singapore
- Institute of Molecular and Cell Biology,
Singapore 138673,
Singapore
| | - George J. Augustine
- Lee Kong Chian School of Medicine,
Singapore 637553,
Singapore
- Institute of Molecular and Cell Biology,
Singapore 138673,
Singapore
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14
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Qin Z, Kaufman RS, Khoury RN, Khoury MK, Aswad DW. Isoaspartate accumulation in mouse brain is associated with altered patterns of protein phosphorylation and acetylation, some of which are highly sex-dependent. PLoS One 2013; 8:e80758. [PMID: 24224061 PMCID: PMC3818261 DOI: 10.1371/journal.pone.0080758] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Accepted: 10/14/2013] [Indexed: 12/05/2022] Open
Abstract
Isoaspartate (isoAsp) formation is a major source of protein damage that is kept in check by the repair function of protein L-isoaspartyl methyltransferase (PIMT). Mice deficient in PIMT accumulate isoAsp-containing proteins, resulting in cognitive deficits, abnormal neuronal physiology and cytoarchitecture, and fatal epileptic seizures 30–60 days after birth. Synapsins I and II, dynamin-1, collapsin response mediator protein 2 (CRMP2), and α/β-tubulin are major targets of PIMT in brain. To investigate links between isoAsp accumulation and the neurological phenotype of the KO mice, we used Western blotting to compare patterns of in vivo phosphorylation or acetylation of the major PIMT targets listed above. Phosphorylations of synapsins I and II at Ser-9 were increased in female KO vs. WT mice, and acetylation of tubulin at Lys-40 was decreased in male KO vs. WT mice. Average levels of dynamin-1 phosphorylation at Ser-778 and Ser-795 were higher in male KO vs. WT mice, but the statistical significance (P>0.1) was low. No changes in phosphorylation were found in synapsins I and II at Ser-603, in CRMP2 at Ser-522 or Thr-514, in DARPP-32 at Thr-34, or in PDK1 at Ser-241. General levels of phosphorylation assessed with Pro-Q Diamond stain, or an anti-phosphotyrosine antibody, appeared similar in the WT and KO mice. We conclude that isoAsp accumulation is associated with altered functional status of several neuronal proteins that are highly susceptible to this type of damage. We also uncovered unexpected differences in how male and female mice respond to isoAsp accumulation in the brain.
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Affiliation(s)
- Zhenxia Qin
- Department of Molecular Biology & Biochemistry, University of California Irvine, Irvine, California, United States of America
| | - Rachel S. Kaufman
- Department of Molecular Biology & Biochemistry, University of California Irvine, Irvine, California, United States of America
| | - Rana N. Khoury
- Department of Molecular Biology & Biochemistry, University of California Irvine, Irvine, California, United States of America
| | - Mitri K. Khoury
- Department of Molecular Biology & Biochemistry, University of California Irvine, Irvine, California, United States of America
| | - Dana W. Aswad
- Department of Molecular Biology & Biochemistry, University of California Irvine, Irvine, California, United States of America
- * E-mail:
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15
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Giannandrea M, Guarnieri FC, Gehring NH, Monzani E, Benfenati F, Kulozik AE, Valtorta F. Nonsense-mediated mRNA decay and loss-of-function of the protein underlie the X-linked epilepsy associated with the W356× mutation in synapsin I. PLoS One 2013; 8:e67724. [PMID: 23818987 PMCID: PMC3688603 DOI: 10.1371/journal.pone.0067724] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Accepted: 05/21/2013] [Indexed: 11/22/2022] Open
Abstract
Synapsins are a family of neuronal phosphoproteins associated with the cytosolic surface of synaptic vesicles. Experimental evidence suggests a role for synapsins in synaptic vesicle clustering and recycling at the presynaptic terminal, as well as in neuronal development and synaptogenesis. Synapsin knock-out (Syn1(-/-) ) mice display an epileptic phenotype and mutations in the SYN1 gene have been identified in individuals affected by epilepsy and/or autism spectrum disorder. We investigated the impact of the c.1067G>A nonsense transition, the first mutation described in a family affected by X-linked syndromic epilepsy, on the expression and functional properties of the synapsin I protein. We found that the presence of a premature termination codon in the human SYN1 transcript renders it susceptible to nonsense-mediated mRNA decay (NMD). Given that the NMD efficiency is highly variable among individuals and cell types, we investigated also the effects of expression of the mutant protein and found that it is expressed at lower levels compared to wild-type synapsin I, forms perinuclear aggregates and is unable to reach presynaptic terminals in mature hippocampal neurons grown in culture. Taken together, these data indicate that in patients carrying the W356× mutation the function of synapsin I is markedly impaired, due to both the strongly decreased translation and the altered function of the NMD-escaped protein, and support the value of Syn1(-/-) mice as an experimental model mimicking the human pathology.
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MESH Headings
- Animals
- Blotting, Northern
- Cells, Cultured
- Codon, Nonsense
- Epilepsy/genetics
- Epilepsy/metabolism
- Female
- Gene Expression
- Genetic Diseases, X-Linked/genetics
- Genetic Diseases, X-Linked/metabolism
- HeLa Cells
- Hippocampus/cytology
- Hippocampus/metabolism
- Humans
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Microscopy, Fluorescence
- Microtubule-Associated Proteins/metabolism
- Neurons/metabolism
- Nonsense Mediated mRNA Decay
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Rats
- Rats, Sprague-Dawley
- Synapsins/genetics
- Synapsins/metabolism
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Affiliation(s)
- Maila Giannandrea
- Division of Neuroscience, San Raffaele Scientific Institute and Vita-Salute University, Milan, Italy
| | - Fabrizia C. Guarnieri
- Division of Neuroscience, San Raffaele Scientific Institute and Vita-Salute University, Milan, Italy
| | | | - Elena Monzani
- Division of Neuroscience, San Raffaele Scientific Institute and Vita-Salute University, Milan, Italy
| | - Fabio Benfenati
- Department of Neuroscience and Brain Technologies, The Italian Institute of Technology, Genoa, Italy
- Department of Experimental Medicine, University of Genoa, Genoa, Italy
| | - Andreas E. Kulozik
- Department of Pediatric Oncology, Hematology and Immunology, University of Heidelberg Medical Center and Molecular Medicine Partnership Unit, EMBL and University of Heidelberg, Heidelberg, Germany
| | - Flavia Valtorta
- Division of Neuroscience, San Raffaele Scientific Institute and Vita-Salute University, Milan, Italy
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16
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Messa M, Congia S, Defranchi E, Valtorta F, Fassio A, Onofri F, Benfenati F. Tyrosine phosphorylation of synapsin I by Src regulates synaptic-vesicle trafficking. J Cell Sci 2010; 123:2256-65. [PMID: 20530578 DOI: 10.1242/jcs.068445] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Synapsins are synaptic vesicle (SV)-associated phosphoproteins involved in the regulation of neurotransmitter release. Synapsins reversibly tether SVs to the cytoskeleton and their phosphorylation by serine/threonine kinases increases SV availability for exocytosis by impairing their association with SVs and/or actin. We recently showed that synapsin I, through SH3- or SH2-mediated interactions, activates Src and is phosphorylated by the same kinase at Tyr301. Here, we demonstrate that, in contrast to serine phosphorylation, Src-mediated tyrosine phosphorylation of synapsin I increases its binding to SVs and actin, and increases the formation of synapsin dimers, which are both potentially involved in SV clustering. Synapsin I phosphorylation by Src affected SV dynamics and was physiologically regulated in brain slices in response to depolarization. Expression of the non-phosphorylatable (Y301F) synapsin I mutant in synapsin-I-knockout neurons increased the sizes of the readily releasable and recycling pools of SVs with respect to the wild-type form, which is consistent with an increased availability of recycled SVs for exocytosis. The data provide a mechanism for the effects of Src on SV trafficking and indicate that tyrosine phosphorylation of synapsins, unlike serine phosphorylation, stimulates the reclustering of recycled SVs and their recruitment to the reserve pool.
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Affiliation(s)
- Mirko Messa
- Department of Experimental Medicine, University of Genova and Istituto Nazionale di Neuroscienze, Viale Benedetto XV 3, 161632 Genova, Italy
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17
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The highly conserved synapsin domain E mediates synapsin dimerization and phospholipid vesicle clustering. Biochem J 2010; 426:55-64. [PMID: 19922412 DOI: 10.1042/bj20090762] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Synapsins are abundant SV (synaptic vesicle)-associated phosphoproteins that regulate synapse formation and function. The highly conserved C-terminal domain E was shown to contribute to several synapsin functions, ranging from formation of the SV reserve pool to regulation of the kinetics of exocytosis and SV cycling, although the molecular mechanisms underlying these effects are unknown. In the present study, we used a synthetic 25-mer peptide encompassing the most conserved region of domain E (Pep-E) to analyse the role of domain E in regulating the interactions between synapsin I and liposomes mimicking the phospholipid composition of SVs (SV-liposomes) and other pre-synaptic protein partners. In affinity-chromatography and cross-linking assays, Pep-E bound to endogenous and purified exogenous synapsin I and strongly inhibited synapsin dimerization, indicating a role in synapsin oligomerization. Consistently, Pep-E (but not its scrambled version) counteracted the ability of holo-synapsin I to bind and coat phospholipid membranes, as analysed by AFM (atomic force microscopy) topographical scanning, and significantly decreased the clustering of SV-liposomes induced by holo-synapsin I in FRET (Förster resonance energy transfer) assays, suggesting a causal relationship between synapsin oligomerization and vesicle clustering. Either Pep-E or a peptide derived from domain C was necessary and sufficient to inhibit both dimerization and vesicle clustering, indicating the participation of both domains in these activities of synapsin I. The results provide a molecular explanation for the effects of domain E in nerve terminal physiology and suggest that its effects on the size and integrity of SV pools are contributed by the regulation of synapsin dimerization and SV clustering.
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18
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John JPP, Sunyer B, Höger H, Pollak A, Lubec G. Hippocampal synapsin isoform levels are linked to spatial memory enhancement by SGS742. Hippocampus 2009; 19:731-8. [PMID: 19140176 DOI: 10.1002/hipo.20553] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Synapsins are essential proteins for synaptic plasticity and there is no information available for their role in cognitive enhancement (CE) of spatial memory formation. It was therefore the aim of the study to link individual synapsin proteins and their isoforms to spatial memory formation enhanced by SGS742 in the mouse. Extracted hippocampal proteins from a cognitive study treating OF1 mice with the cognitive enhancer SGS742 and tested in the Morris water maze, were run on two-dimensional gel electrophoresis. Subsequently, protein spots were unambiguously identified by qQ-TOF mass spectrometry. Quantification of proteins from four groups (NaCl-treated mice, SGS742-treated mice, SGS742-treated yoked controls, and NaCl-treated yoked controls) was carried out according to an in-gel stable isotope labeling method. A total of 17 protein spots representing synapsin isoforms were identified and quantified. Using quantification of individual synapsin isoforms showed that these can be clearly assigned to CE by the GABAB antagonist SGS742. Quantitative determination of individual synapsin isoform showed an increase in SGS742-treated mice (mean+/-SD) of ratios between light and heavy stable isotope labeled synapsin protein (SGS742 vs. controls: 2.19+/-0.41 for synapsin Ia, and 1.41+/-0.81 for synapsin IIa). Synapsins Ib and IIb were not linked to CE. The NaCl-treated controls and the use of yoked controls that were ruling out swimming- and stress-mediated changes of synapsins, unequivocally allow to propose a role for synapsins Ia and IIa in the mechanism of CE of spatial memory formation.
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19
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An Exonic Insertion Encodes an Alanine Stretch in Porcine Synapsin I. Biochem Genet 2009; 47:812-6. [DOI: 10.1007/s10528-009-9279-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2009] [Accepted: 05/28/2009] [Indexed: 10/20/2022]
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20
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Evergren E, Benfenati F, Shupliakov O. The synapsin cycle: a view from the synaptic endocytic zone. J Neurosci Res 2008; 85:2648-56. [PMID: 17455288 DOI: 10.1002/jnr.21176] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Although the synapsin phosphoproteins were discovered more than 30 years ago and are known to play important roles in neurotransmitter release and synaptogenesis, a complete picture of their functions within the nerve terminal is lacking. It has been shown that these proteins play an important role in the clustering of synaptic vesicles (SVs) at active zones and function as modulators of synaptic strength by acting at both pre- and postdocking levels. Recent studies have demonstrated that synapsins migrate to the endocytic zone of central synapses during neurotransmitter release, which suggests that there are additional functions for these proteins in SV recycling.
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Affiliation(s)
- E Evergren
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
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21
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Awizio AK, Onofri F, Benfenati F, Bonaccurso E. Influence of synapsin I on synaptic vesicles: an analysis by force-volume mode of the atomic force microscope and dynamic light scattering. Biophys J 2007; 93:1051-60. [PMID: 17483172 PMCID: PMC1913160 DOI: 10.1529/biophysj.107.104406] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Synaptic vesicles (SVs) are small neuronal organelles that store neurotransmitters and release them by exocytosis into the synaptic cleft for signal transmission between nerve cells. They consist of a highly curved membrane composed of different lipids containing several proteins with specific functions. A family of abundant extrinsic SV proteins, the synapsins, interact with SV proteins and phospholipids and play an important role in the regulation of SV trafficking and stability. We investigated the interactions of one these proteins with the SV membrane using atomic force microscope and dynamic light scattering. We examined SVs isolated from rat forebrain both under native conditions and after depletion of endogenous synapsin I. We used the atomic force microscope in two modes: imaging mode for characterizing the shape and size of SVs, and force-volume mode for characterizing their stiffness. Synapsin-depleted SVs were larger in size and showed a higher tendency to aggregate than native vesicles, although their stiffness was not significantly different. Because synapsins are believed to cross-link SV to each other and to the actin cytoskeleton, we also measured the SV aggregation kinetics induced by synapsin I by dynamic light scattering and atomic force microscopy and found that the addition of synapsin I promotes a rapid aggregation of SVs. The data indicate that synapsin directly affects SV stability and aggregation state and support the physiological role of synapsins in the assembly and regulation of SV pools within nerve terminals.
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22
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Onofri F, Messa M, Matafora V, Bonanno G, Corradi A, Bachi A, Valtorta F, Benfenati F. Synapsin phosphorylation by SRC tyrosine kinase enhances SRC activity in synaptic vesicles. J Biol Chem 2007; 282:15754-67. [PMID: 17400547 DOI: 10.1074/jbc.m701051200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Synapsins are synaptic vesicle-associated phosphoproteins implicated in the regulation of neurotransmitter release. Synapsin I is the major binding protein for the SH3 domain of the kinase c-Src in synaptic vesicles. Its binding leads to stimulation of synaptic vesicle-associated c-Src activity. We investigated the mechanism and role of Src activation by synapsins on synaptic vesicles. We found that synapsin is tyrosine phosphorylated by c-Src in vitro and on intact synaptic vesicles independently of its phosphorylation state on serine. Mass spectrometry revealed a single major phosphorylation site at Tyr(301), which is highly conserved in all synapsin isoforms and orthologues. Synapsin tyrosine phosphorylation triggered its binding to the SH2 domains of Src or Fyn. However, synapsin selectively activated and was phosphorylated by Src, consistent with the specific enrichment of c-Src in synaptic vesicles over Fyn or n-Src. The activity of Src on synaptic vesicles was controlled by the amount of vesicle-associated synapsin, which is in turn dependent on synapsin serine phosphorylation. Synaptic vesicles depleted of synapsin in vitro or derived from synapsin null mice exhibited greatly reduced Src activity and tyrosine phosphorylation of other synaptic vesicle proteins. Disruption of the Src-synapsin interaction by internalization of either the Src SH3 or SH2 domains into synaptosomes decreased synapsin tyrosine phosphorylation and concomitantly increased neurotransmitter release in response to Ca(2+)-ionophores. We conclude that synapsin is an endogenous substrate and activator of synaptic vesicle-associated c-Src and that regulation of Src activity on synaptic vesicles participates in the regulation of neurotransmitter release by synapsin.
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Affiliation(s)
- Franco Onofri
- Department of Experimental Medicine, University of Genova, 16132 Genova, Italy
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23
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Zhu C, Wu LQ, Wang X, Lee JH, English DS, Ghodssi R, Raghavan SR, Payne GF. Reversible vesicle restraint in response to spatiotemporally controlled electrical signals: a bridge between electrical and chemical signaling modes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:286-91. [PMID: 17190516 DOI: 10.1021/la061421i] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Microelectronic devices employ electrons for signaling whereas the nervous system signals using ions and chemicals. Bridging these signaling differences would benefit applications that range from biosensing to neuroprosthetics. Here, we report the use of localized electrical signals to perform an operation common to chemical signaling in the nervous system. Specifically, we employ electrical signals to restrain vesicles reversibly. We perform this operation using the stimuli-responsive aminopolysaccharide chitosan that is able to electrodeposit onto cathode surfaces in response to localized electrical stimuli. We show that surfactant-vesicles and liposomes can be co-deposited with chitosan and are entrapped (i.e., restrained) within the deposited film's matrix. Vesicle co-deposition could be controlled spatially and temporally using microfabricated wafers with independent electrode addresses. Finally, we show that vesicles restrained within the deposited chitosan matrix can be mobilized under mildly acidic conditions (pH <6.5) that resolubilize chitosan. Potentially, the ability to restrain and mobilize chemical signals that are segregated within vesicles may allow microfluidic systems to access the rich diversity offered by chemical signaling.
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Affiliation(s)
- Chao Zhu
- Center for Biosystems Research, University of Maryland Biotechnology Institute, College Park, Maryland 20742, USA
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24
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Zhu C, Lee JH, Raghavan SR, Payne GF. Bioinspired vesicle restraint and mobilization using a biopolymer scaffold. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:2951-5. [PMID: 16548539 DOI: 10.1021/la053475i] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Biology employs vesicles to package molecules (e.g., neurotransmitters) for their targeted delivery in response to specific spatiotemporal stimuli. Biology is also capable of employing localized stimuli to exert an additional control on vesicle trafficking; intact vesicles can be restrained (or mobilized) by association with (or release from) a cytoskeletal scaffold. We mimic these capabilities by tethering vesicles to a biopolymer scaffold that can undergo (i) stimuli-responsive network formation (for vesicle restraint) and (ii) enzyme-catalyzed network cleavage (for vesicle mobilization). Specifically, we use the aminopolysaccharide chitosan as our scaffold and graft a small number of hydrophobic moieties onto its backbone. These grafted hydrophobes can insert into the bilayer to tether vesicles to the scaffold. Under acidic conditions, the vesicles are not restrained by the hydrophobically modified chitosan (hm-chitosan) because this scaffold is soluble. Increasing the pH to neutral or basic conditions allows chitosan to form interpolymer associations that yield a strong, insoluble restraining network. Enzymatic hydrolysis of this scaffold by chitosanase cleaves the network and mobilizes intact vesicles. Potentially, this approach will provide a controllable means to store and liberate vesicle-based reagents/therapeutics for microfluidic/medical applications.
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Affiliation(s)
- Chao Zhu
- Center for Biosystems Research, University of Maryland Biotechnology Institute, College Park, Maryland 20742, USA
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25
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Blencowe A, Hayes W. Development and application of diazirines in biological and synthetic macromolecular systems. SOFT MATTER 2005; 1:178-205. [PMID: 32646075 DOI: 10.1039/b501989c] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Many different reagents and methodologies have been utilised for the modification of synthetic and biological macromolecular systems. In addition, an area of intense research at present is the construction of hybrid biosynthetic polymers, comprised of biologically active species immobilised or complexed with synthetic polymers. One of the most useful and widely applicable techniques available for functionalisation of macromolecular systems involves indiscriminate carbene insertion processes. The highly reactive and non-specific nature of carbenes has enabled a multitude of macromolecular structures to be functionalised without the need for specialised reagents or additives. The use of diazirines as stable carbene precursors has increased dramatically over the past twenty years and these reagents are fast becoming the most popular photophors for photoaffinity labelling and biological applications in which covalent modification of macromolecular structures is the basis to understanding structure-activity relationships. This review reports the synthesis and application of a diverse range of diazirines in macromolecular systems.
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Affiliation(s)
- Anton Blencowe
- School of Chemistry, The University of Reading, Whiteknights, Reading, Berkshire, UKRG6 6AD.
| | - Wayne Hayes
- School of Chemistry, The University of Reading, Whiteknights, Reading, Berkshire, UKRG6 6AD.
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26
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Lane-Guermonprez L, Morot-Gaudry-Talarmain Y, Meunier FM, O'Regan S, Onofri F, Le Caer JP, Benfenati F. Synapsin associates with cyclophilin B in an ATP- and cyclosporin A-dependent manner. J Neurochem 2005; 93:1401-11. [PMID: 15935056 DOI: 10.1111/j.1471-4159.2005.03125.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Immunophilins are ubiquitous enzymes responsible for proline isomerisation during protein synthesis and for the chaperoning of several membrane proteins. These activities can be blocked by the immunosuppressants cyclosporin A, FK506 and rapamycin. It has been shown that all three immunosuppressants have neurotrophic activity and can modulate neurotransmitter release, but the molecular basis of these effects is currently unknown. Here, we show that synapsin I, a synaptic vesicle-associated protein, can be purified from Torpedo cholinergic synaptosomes through its affinity to cyclophilin B, an immunophilin that is particularly abundant in brain. The interaction is direct and conserved in mammals, and shows a dissociation constant of about 0.5 microM in vitro. The binding between the two proteins can be disrupted by cyclosporin A and inhibited by physiological concentrations of ATP. Furthermore, cyclophilin B co-localizes with synapsin I in rat synaptic vesicle fractions and its levels in synaptic vesicle-containing fractions are decreased in synapsin knockout mice. These results suggest that immunophilins are involved in the complex protein networks operating at the presynaptic level and implicate the interaction between cyclophilin B and synapsins in presynaptic function.
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Affiliation(s)
- Lydie Lane-Guermonprez
- Laboratoire de Neurobiologie Cellulaire et Moléculaire, CNRS UPR 9040, Gif sur Yvette Cedex, France
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27
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Pera I, Stark R, Kappl M, Butt HJ, Benfenati F. Using the atomic force microscope to study the interaction between two solid supported lipid bilayers and the influence of synapsin I. Biophys J 2005; 87:2446-55. [PMID: 15454442 PMCID: PMC1304665 DOI: 10.1529/biophysj.104.044214] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
To measure the interaction between two lipid bilayers with an atomic force microscope one solid supported bilayer was formed on a planar surface by spontaneous vesicle fusion. To spontaneously adsorb lipid bilayers also on the atomic force microscope tip, the tips were first coated with gold and a monolayer of mercapto undecanol. Calculations indicate that long-chain hydroxyl terminated alkyl thiols tend to enhance spontaneous vesicle fusion because of an increased van der Waals attraction as compared to short-chain thiols. Interactions measured between dioleoylphosphatidylcholine, dioleoylphosphatidylserine, and dioleoyloxypropyl trimethylammonium chloride showed the electrostatic double-layer force plus a shorter-range repulsion which decayed exponentially with a decay length of 0.7 nm for dioleoylphosphatidylcholine, 1.2 nm for dioleoylphosphatidylserine, and 0.8 nm for dioleoyloxypropyl trimethylammonium chloride. The salt concentration drastically changed the interaction between dioleoyloxypropyl trimethylammonium chloride bilayers. As an example for the influence of proteins on bilayer-bilayer interaction, the influence of the synaptic vesicle-associated, phospholipid binding protein synapsin I was studied. Synapsin I increased membrane stability so that the bilayers could not be penetrated with the tip.
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Affiliation(s)
- Ioana Pera
- Max-Planck-Institute for Polymer Research, D-55128 Mainz, Germany
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28
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Abstract
Membrane vesicle cycling is orchestrated through the combined actions of proteins and lipids. At neuronal synapses, this orchestration must meet the stringent demands of speed, fidelity and sustainability of the synaptic vesicle cycle that mediates neurotransmission. Historically, the lion's share of the attention has been focused on the proteins that are involved in this cycle; but, in recent years, it has become clear that the previously unheralded plasma membrane and vesicle lipids are also key regulators of this cycle. This article reviews recent insights into the roles of lipid-modifying enzymes and lipids in the acute modulation of neurotransmission.
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Affiliation(s)
- Jeffrey Rohrbough
- Department of Biological Sciences, Vanderbilt Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, Tennessee 37235-1634, USA
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29
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Giovedì S, Darchen F, Valtorta F, Greengard P, Benfenati F. Synapsin is a novel Rab3 effector protein on small synaptic vesicles. II. Functional effects of the Rab3A-synapsin I interaction. J Biol Chem 2004; 279:43769-79. [PMID: 15265868 DOI: 10.1074/jbc.m404168200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Synapsins, a family of neuron-specific phosphoproteins that play an important role in the regulation of synaptic vesicle trafficking and neurotransmitter release, were recently demonstrated to interact with the synaptic vesicle-associated small G protein Rab3A within nerve terminals (Giovedi, S., Vaccaro, P., Valtorta, F., Darchen, F., Greengard, P., Cesareni, G., and Benfenati, F. (2004) J. Biol. Chem. 279, 43760-43768). We have analyzed the functional consequences of this interaction on the biological activities of both proteins and on their subcellular distribution within nerve terminals. The presence of synapsin I stimulated GTP binding and GTPase activity of both purified and endogenous synaptic vesicle-associated Rab3A. Conversely, Rab3A inhibited synapsin I binding to F-actin, as well as synapsin-induced actin bundling and vesicle clustering. Moreover, the amount of Rab3A associated with synaptic vesicles was decreased in synapsin knockout mice, and the presence of synapsin I prevented RabGDI-induced Rab3A dissociation from synaptic vesicles. The results indicate that an interaction between synapsin I and Rab3A exists on synaptic vesicles that modulates the functional properties of both proteins. Given the well recognized importance of both synapsins and Rab3A in synaptic vesicles exocytosis, this interaction is likely to play a major role in the modulation of neurotransmitter release.
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Affiliation(s)
- Silvia Giovedì
- Department of Experimental Medicine, Section of Human Physiology, University of Genova, Via Benedetto XV, 16132, Italy
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Guo SG, Zhang W, Jiang T, Dai M, Zhang LF, Meng YC, Zhao LY, Niu JZ. Influence of serum collected from rat perfused with compound Biejiaruangan drug on hepatic stellate cells. World J Gastroenterol 2004; 10:1487-94. [PMID: 15133859 PMCID: PMC4656290 DOI: 10.3748/wjg.v10.i10.1487] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
AIM: To observe the effect of compound Biejiaruangan decoction (CBJRGC) (composite prescription of Carapax trionycis for softening the liver) on proliferation, activation, excretion of collagen and cytokine of hepatic stellate cells (HSCs) and to find the mechanism of prevention and treatment of hepatic fibrosis by CBJRGC.
METHODS: Using MTT, immunohistochemistry and image analysis technology, the related indexes for proliferation, activation, excretion of collagen and cytokine of hepatic stellate cells were detected in 24 h, 48 h, and 72 h after adminstration of different dosages of CBJRGC.
RESULTS: Statistical analysis showed that serum collected from rat perfused with CBJRGC could restrain the proliferation of HSC in 48 h and 72 h especially in high and medium dosage groups, markedly decrease the expression of desmin, synapsin and platelet derived growth factor (PDGF) in HSC in 24 h, 48 h and 72 h, as well as the expression of α-SMA, collagen III, TIMP and TGFβ1 in 48 h and 72 h, decrease the excretion of collagen I in 72 h. CBJRGC serum had no significant effect on collagens I, III and TIMP in 24 h.
CONCLUSION: CBJRGC serum has a good curative effect on hepatic fibrosis. Its main mechanism may be related to the following factors. The drug serum can restrain the proliferation and activation of HSC, decrease the number of activated HSC and the total number of HSC, the excretion of collagens I, III, enhance the degradation of collagen and restore the balance of synthesis and degradation of collagen, inhibit the expression of transforming growth factor β1 (TGFβ1) and platelet derived growth factor (PDGF) in HSC, block and delay the process of hepatic fibrosis. Synapsin is a new marker of activation of HSC, which provides a theoretical and testing basis for neural regulation in the developing process of hepatic fibrosis.
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Affiliation(s)
- Shun-Gen Guo
- Laboratory of Cell and Biochemistry, Beijing University of Traditional Chinese Medicine, Beijing 100029, China.
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Hurley SL, Brown DL, Cheetham JJ. Cytoskeletal interactions of synapsin I in non-neuronal cells. Biochem Biophys Res Commun 2004; 317:16-23. [PMID: 15047142 DOI: 10.1016/j.bbrc.2004.03.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2003] [Indexed: 01/21/2023]
Abstract
Synapsin I is a neuronal phosphoprotein involved in the localization and stabilization of synaptic vesicles. Recently, synapsin I has been detected in several non-neuronal cell lines, but its function in these cells is unclear. To determine the localization of synapsin I in non-neuronal cells, it was transiently expressed in HeLa and NIH/3T3 cells as an enhanced green fluorescent protein fusion protein. Synapsin I-enhanced green fluorescent protein colocalized with F-actin in both cell lines, particularly with microspikes and membrane ruffles. It did not colocalize with microtubules or vimentin and it did not cause major alterations in cytoskeletal organization. Synapsin Ia-enhanced green fluorescent protein colocalized with microtubule bundles in taxol-treated HeLa cells and with F-actin spots at the plasma membrane in cells treated with cytochalasin B. It did not noticeably affect F-actin reassembly following drug removal. Synapsin Ia-enhanced green fluorescent protein remained colocalized with F-actin in cells treated with nocodazole, and it did not affect reassembly of microtubules following drug removal. These results demonstrate that synapsin I interacts with F-actin in non-neuronal cells and suggest that synapsin I may have a role in regions where actin is highly dynamic.
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Affiliation(s)
- Sandra L Hurley
- Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, Ont, Canada K1S 5B6
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Cheetham JJ, Murray J, Ruhkalova M, Cuccia L, McAloney R, Ingold KU, Johnston LJ. Interaction of synapsin I with membranes. Biochem Biophys Res Commun 2003; 309:823-9. [PMID: 13679047 DOI: 10.1016/j.bbrc.2003.08.082] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The synapsins (I, II, and III) comprise a family of peripheral membrane proteins that are involved in both regulation of neurotransmitter release and synaptogenesis. Synapsins are concentrated at presynaptic nerve terminals and are associated with the cytoplasmic surface of synaptic vesicles. Membrane-binding of synapsins involves interaction with both protein and lipid components of synaptic vesicles. Synapsin I binds rapidly and with high affinity to liposomes containing anionic lipids. The binding of bovine synapsin I to liposomes was studied using fluoresceinphosphatidyl-ethanolamine (FPE) to measure membrane electrostatic potential. Synapsin binding to liposomes caused a rapid increase in FPE fluorescence, indicating an increase in positive charge at the membrane surface. Synapsin I binding to monolayers resulted in a substantial increase in monolayer surface pressure. At higher initial surface pressures, the synapsin-induced increase in monolayer surface pressure is dependent on the presence of anionic lipids in the monolayer. Synapsin I also induced rapid aggregation of liposomes, but did not induce leakage of entrapped carboxyfluorescein, while other aggregation-inducing agents promoted extensive leakage. These results are in agreement with the presence of amphipathic stretches of amino acids in synapsin I that exhibit both electrostatic and hydrophobic interactions with membranes, and offer a molecular explanation for the high affinity binding of synapsin I to liposomes and for stabilization of membranes by synapsin I.
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Affiliation(s)
- James J Cheetham
- Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, Ont., Canada K1S 5B6.
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Cole NB, Murphy DD, Grider T, Rueter S, Brasaemle D, Nussbaum RL. Lipid droplet binding and oligomerization properties of the Parkinson's disease protein alpha-synuclein. J Biol Chem 2002; 277:6344-52. [PMID: 11744721 DOI: 10.1074/jbc.m108414200] [Citation(s) in RCA: 349] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
alpha-Synuclein is a major component of the fibrillary lesion known as Lewy bodies and Lewy neurites that are the pathologic hallmarks of Parkinson's disease (PD). In addition, point mutations in the alpha-synuclein gene imply alpha-synuclein dysfunction in the pathology of inherited forms of PD. alpha-Synuclein is a member of a family of proteins found primarily in the brain and is concentrated within presynaptic terminals. Here, we address the localization and membrane binding characteristics of wild type and PD mutants of alpha-synuclein in cultured cells. In cells treated with high concentrations of fatty acids, wild type alpha-synuclein accumulated on phospholipid monolayers surrounding triglyceride-rich lipid droplets and was able to protect stored triglycerides from hydrolysis. PD mutant synucleins showed variable distributions on lipid droplets and were less effective in regulating triglyceride turnover. Chemical cross-linking demonstrated that synuclein formed small oligomers within cells, primarily dimers and trimers, that preferentially associated with lipid droplets and cell membranes. Our results suggest that the initial phases of synuclein aggregation may occur on the surfaces of membranes and that pathological conditions that induce cross-linking of synuclein may enhance the propensity for subsequent synuclein aggregation.
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Affiliation(s)
- Nelson B Cole
- Genetic Disease Research Branch, National Human Genome Research Institute, National Institutes of Health Bethesda, Maryland 20982, USA.
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