1
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Hoffmann C, Milovanovic D. Dipping contacts - a novel type of contact site at the interface between membraneless organelles and membranes. J Cell Sci 2023; 136:jcs261413. [PMID: 38149872 PMCID: PMC10785658 DOI: 10.1242/jcs.261413] [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: 12/28/2023] Open
Abstract
Liquid-liquid phase separation is a major mechanism for organizing macromolecules, particularly proteins with intrinsically disordered regions, in compartments not limited by a membrane or a scaffold. The cell can therefore be perceived as a complex emulsion containing many of these membraneless organelles, also referred to as biomolecular condensates, together with numerous membrane-bound organelles. It is currently unclear how such a complex concoction operates to allow for intracellular trafficking, signaling and metabolic processes to occur with high spatiotemporal precision. Based on experimental observations of synaptic vesicle condensates - a membraneless organelle that is in fact packed with membranes - we present here the framework of dipping contacts: a novel type of contact site between membraneless organelles and membranes. In this Hypothesis, we propose that our framework of dipping contacts can serve as a foundation to investigate the interface that couples the diffusion and material properties of condensates to biochemical processes occurring in membranes. The identity and regulation of this interface is especially critical in the case of neurodegenerative diseases, where aberrant inclusions of misfolded proteins and damaged organelles underlie cellular pathology.
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Affiliation(s)
- Christian Hoffmann
- Laboratory of Molecular Neuroscience, German Center for Neurodegenerative Diseases (DZNE), 10117 Berlin, Germany
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA 02543, USA
| | - Dragomir Milovanovic
- Laboratory of Molecular Neuroscience, German Center for Neurodegenerative Diseases (DZNE), 10117 Berlin, Germany
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA 02543, USA
- National Center for X-ray Tomography, Advanced Light Source, Berkeley, CA 94720, USA
- Einstein Center for Neuroscience, Charité-Universitätsmedizin Berlin, Freie Universität Berlin, Humboldt-Universität Berlin and Berlin Institute of Health, 10117 Berlin, Germany
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2
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Hoffmann C, Rentsch J, Tsunoyama TA, Chhabra A, Aguilar Perez G, Chowdhury R, Trnka F, Korobeinikov AA, Shaib AH, Ganzella M, Giannone G, Rizzoli SO, Kusumi A, Ewers H, Milovanovic D. Synapsin condensation controls synaptic vesicle sequestering and dynamics. Nat Commun 2023; 14:6730. [PMID: 37872159 PMCID: PMC10593750 DOI: 10.1038/s41467-023-42372-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Accepted: 10/09/2023] [Indexed: 10/25/2023] Open
Abstract
Neuronal transmission relies on the regulated secretion of neurotransmitters, which are packed in synaptic vesicles (SVs). Hundreds of SVs accumulate at synaptic boutons. Despite being held together, SVs are highly mobile, so that they can be recruited to the plasma membrane for their rapid release during neuronal activity. However, how such confinement of SVs corroborates with their motility remains unclear. To bridge this gap, we employ ultrafast single-molecule tracking (SMT) in the reconstituted system of native SVs and in living neurons. SVs and synapsin 1, the most highly abundant synaptic protein, form condensates with liquid-like properties. In these condensates, synapsin 1 movement is slowed in both at short (i.e., 60-nm) and long (i.e., several hundred-nm) ranges, suggesting that the SV-synapsin 1 interaction raises the overall packing of the condensate. Furthermore, two-color SMT and super-resolution imaging in living axons demonstrate that synapsin 1 drives the accumulation of SVs in boutons. Even the short intrinsically-disordered fragment of synapsin 1 was sufficient to restore the native SV motility pattern in synapsin triple knock-out animals. Thus, synapsin 1 condensation is sufficient to guarantee reliable confinement and motility of SVs, allowing for the formation of mesoscale domains of SVs at synapses in vivo.
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Affiliation(s)
- Christian Hoffmann
- Laboratory of Molecular Neuroscience, German Center for Neurodegenerative Diseases (DZNE), 10117, Berlin, Germany
| | - Jakob Rentsch
- Institute of Chemistry and Biochemistry, Freie Universität Berlin, 14195, Berlin, Germany
| | - Taka A Tsunoyama
- Membrane Cooperativity Unit, Okinawa Institute of Science and Technology Graduate University (OIST); Onna-son, Okinawa, 904-0495, Japan
| | - Akshita Chhabra
- Laboratory of Molecular Neuroscience, German Center for Neurodegenerative Diseases (DZNE), 10117, Berlin, Germany
| | - Gerard Aguilar Perez
- Laboratory of Molecular Neuroscience, German Center for Neurodegenerative Diseases (DZNE), 10117, Berlin, Germany
| | - Rajdeep Chowdhury
- University Medical Center Göttingen, Institute for Neuro- and Sensory Physiology, Germany; Biostructural Imaging of Neurodegeneration (BIN) Center, Göttingen, Germany; Excellence Cluster Multiscale Bioimaging, 37073, Göttingen, Germany
| | - Franziska Trnka
- Laboratory of Molecular Neuroscience, German Center for Neurodegenerative Diseases (DZNE), 10117, Berlin, Germany
| | - Aleksandr A Korobeinikov
- Laboratory of Molecular Neuroscience, German Center for Neurodegenerative Diseases (DZNE), 10117, Berlin, Germany
| | - Ali H Shaib
- University Medical Center Göttingen, Institute for Neuro- and Sensory Physiology, Germany; Biostructural Imaging of Neurodegeneration (BIN) Center, Göttingen, Germany; Excellence Cluster Multiscale Bioimaging, 37073, Göttingen, Germany
| | - Marcelo Ganzella
- Department of Neurobiology, Max Planck Institute for Multidisciplinary Sciences, 37077, Göttingen, Germany
| | - Gregory Giannone
- Interdisciplinary Institute for Neuroscience, University of Bordeaux, UMR 5297, F-33000, Bordeaux, France
| | - Silvio O Rizzoli
- University Medical Center Göttingen, Institute for Neuro- and Sensory Physiology, Germany; Biostructural Imaging of Neurodegeneration (BIN) Center, Göttingen, Germany; Excellence Cluster Multiscale Bioimaging, 37073, Göttingen, Germany
| | - Akihiro Kusumi
- Membrane Cooperativity Unit, Okinawa Institute of Science and Technology Graduate University (OIST); Onna-son, Okinawa, 904-0495, Japan
| | - Helge Ewers
- Institute of Chemistry and Biochemistry, Freie Universität Berlin, 14195, Berlin, Germany
| | - Dragomir Milovanovic
- Laboratory of Molecular Neuroscience, German Center for Neurodegenerative Diseases (DZNE), 10117, Berlin, Germany.
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3
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Yoshida T, Takenaka KI, Sakamoto H, Kojima Y, Sakano T, Shibayama K, Nakamura K, Hanawa-Suetsugu K, Mori Y, Hirabayashi Y, Hirose K, Takamori S. Compartmentalization of soluble endocytic proteins in synaptic vesicle clusters by phase separation. iScience 2023; 26:106826. [PMID: 37250768 PMCID: PMC10209458 DOI: 10.1016/j.isci.2023.106826] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 04/10/2023] [Accepted: 05/02/2023] [Indexed: 05/31/2023] Open
Abstract
Synaptic vesicle (SV) clusters, which reportedly result from synapsin's capacity to undergo liquid-liquid phase separation (LLPS), constitute the structural basis for neurotransmission. Although these clusters contain various endocytic accessory proteins, how endocytic proteins accumulate in SV clusters remains unknown. Here, we report that endophilin A1 (EndoA1), the endocytic scaffold protein, undergoes LLPS under physiologically relevant concentrations at presynaptic terminals. On heterologous expression, EndoA1 facilitates the formation of synapsin condensates and accumulates in SV-like vesicle clusters via synapsin. Moreover, EndoA1 condensates recruit endocytic proteins such as dynamin 1, amphiphysin, and intersectin 1, none of which are recruited in vesicle clusters by synapsin. In cultured neurons, like synapsin, EndoA1 is compartmentalized in SV clusters through LLPS, exhibiting activity-dependent dispersion/reassembly cycles. Thus, beyond its essential function in SV endocytosis, EndoA1 serves an additional structural function by undergoing LLPS, thereby accumulating various endocytic proteins in dynamic SV clusters in concert with synapsin.
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Affiliation(s)
- Tomofumi Yoshida
- Laboratory of Neural Membrane Biology, Graduate School of Brain Science, Doshisha University, Kyoto 610-0394, Japan
| | - Koh-ichiro Takenaka
- Laboratory of Neural Membrane Biology, Graduate School of Brain Science, Doshisha University, Kyoto 610-0394, Japan
| | - Hirokazu Sakamoto
- Department of Pharmacology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Yusuke Kojima
- Department of Pharmacology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Takumi Sakano
- Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, Tokyo 113-0033, Japan
| | - Koyo Shibayama
- Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, Tokyo 113-0033, Japan
| | - Koki Nakamura
- Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, Tokyo 113-0033, Japan
| | - Kyoko Hanawa-Suetsugu
- Laboratory of Neural Membrane Biology, Graduate School of Brain Science, Doshisha University, Kyoto 610-0394, Japan
| | - Yasunori Mori
- Laboratory of Neural Membrane Biology, Graduate School of Brain Science, Doshisha University, Kyoto 610-0394, Japan
| | - Yusuke Hirabayashi
- Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, Tokyo 113-0033, Japan
| | - Kenzo Hirose
- Department of Pharmacology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
- International Research Center for Neurointelligence (WPI-IRCN), The University of Tokyo, Tokyo 113-0033, Japan
| | - Shigeo Takamori
- Laboratory of Neural Membrane Biology, Graduate School of Brain Science, Doshisha University, Kyoto 610-0394, Japan
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4
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Sansevrino R, Hoffmann C, Milovanovic D. Condensate biology of synaptic vesicle clusters. Trends Neurosci 2023; 46:293-306. [PMID: 36725404 DOI: 10.1016/j.tins.2023.01.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 12/20/2022] [Accepted: 01/10/2023] [Indexed: 01/31/2023]
Abstract
Neuronal communication crucially relies on exocytosis of neurotransmitters from synaptic vesicles (SVs) which are clustered at synapses. To ensure reliable neurotransmitter release, synapses need to maintain an adequate pool of SVs at all times. Decades of research have established that SVs are clustered by synapsin 1, an abundant SV-associated phosphoprotein. The classical view postulates that SVs are crosslinked in a scaffold of protein-protein interactions between synapsins and their binding partners. Recent studies have shown that synapsins cluster SVs via liquid-liquid phase separation (LLPS), thus providing a new framework for the organization of the synapse. We discuss the evidence for phase separation of SVs, emphasizing emerging questions related to its regulation, specificity, and reversibility.
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Affiliation(s)
- Roberto Sansevrino
- Laboratory of Molecular Neuroscience, German Center for Neurodegenerative Diseases (DZNE), 10117 Berlin, Germany
| | - Christian Hoffmann
- Laboratory of Molecular Neuroscience, German Center for Neurodegenerative Diseases (DZNE), 10117 Berlin, Germany
| | - Dragomir Milovanovic
- Laboratory of Molecular Neuroscience, German Center for Neurodegenerative Diseases (DZNE), 10117 Berlin, Germany.
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5
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Mougios N, Opazo F, Rizzoli SO, Reshetniak S. Trafficking proteins show limited differences in mobility across different postsynaptic spines. iScience 2023; 26:105971. [PMID: 36718370 PMCID: PMC9883188 DOI: 10.1016/j.isci.2023.105971] [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: 10/31/2022] [Revised: 11/24/2022] [Accepted: 01/10/2023] [Indexed: 01/14/2023] Open
Abstract
The function of the postsynaptic compartment is based on the presence and activity of postsynaptic receptors, whose dynamics are controlled by numerous scaffolding, signaling and trafficking proteins. Although the receptors and the scaffolding proteins have received substantial attention, the trafficking proteins have not been investigated extensively. Their mobility rates are unknown, and it is unclear how the postsynaptic environment affects their dynamics. To address this, we analyzed several trafficking proteins (α-synuclein, amphiphysin, calmodulin, doc2a, dynamin, and endophilin), estimating their movement rates in the dendritic shaft, as well as in morphologically distinct "mushroom" and "stubby" postsynapse types. The diffusion parameters were surprisingly similar across dendritic compartments, and a few differences between proteins became evident only in the presence of a synapse neck. We conclude that the movement of trafficking proteins is not strongly affected by the postsynaptic compartment, in stark contrast to the presynapse, which regulates strongly the movement of such proteins.
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Affiliation(s)
- Nikolaos Mougios
- Institute of Neuro- and Sensory Physiology, University Medical Center Göttingen, 37073 Göttingen, Germany,Center for Biostructural Imaging of Neurodegeneration (BIN), University of Göttingen Medical Center, 37075 Göttingen, Germany
| | - Felipe Opazo
- Institute of Neuro- and Sensory Physiology, University Medical Center Göttingen, 37073 Göttingen, Germany,Center for Biostructural Imaging of Neurodegeneration (BIN), University of Göttingen Medical Center, 37075 Göttingen, Germany,NanoTag Biotechnologies GmbH, Göttingen, Germany
| | - Silvio O. Rizzoli
- Institute of Neuro- and Sensory Physiology, University Medical Center Göttingen, 37073 Göttingen, Germany,Center for Biostructural Imaging of Neurodegeneration (BIN), University of Göttingen Medical Center, 37075 Göttingen, Germany,Corresponding author
| | - Sofiia Reshetniak
- Institute of Neuro- and Sensory Physiology, University Medical Center Göttingen, 37073 Göttingen, Germany,Corresponding author
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6
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Brodin L, Milovanovic D, Rizzoli SO, Shupliakov O. α-Synuclein in the Synaptic Vesicle Liquid Phase: Active Player or Passive Bystander? Front Mol Biosci 2022; 9:891508. [PMID: 35664678 PMCID: PMC9159372 DOI: 10.3389/fmolb.2022.891508] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Accepted: 04/26/2022] [Indexed: 12/15/2022] Open
Abstract
The protein α-synuclein, which is well-known for its links to Parkinson’s Disease, is associated with synaptic vesicles (SVs) in nerve terminals. Despite intensive studies, its precise physiological function remains elusive. Accumulating evidence indicates that liquid-liquid phase separation takes part in the assembly and/or maintenance of different synaptic compartments. The current review discusses recent data suggesting α-synuclein as a component of the SV liquid phase. We also consider possible implications of these data for disease.
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Affiliation(s)
- Lennart Brodin
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
- *Correspondence: Lennart Brodin, ; Oleg Shupliakov,
| | - Dragomir Milovanovic
- Laboratory of Molecular Neuroscience, German Center for Neurodegenerative Diseases (DZNE), Berlin, Germany
| | - Silvio O. Rizzoli
- Institute of Neuro- and Sensory Physiology, University Medical Center Göttingen, Göttingen, Germany
| | - Oleg Shupliakov
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
- Institute of Translational Biomedicine, St. Petersburg University, St. Petersburg, Russia
- *Correspondence: Lennart Brodin, ; Oleg Shupliakov,
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7
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Abstract
Fundamental discoveries have shaped our molecular understanding of presynaptic processes, such as neurotransmitter release, active zone organization and mechanisms of synaptic vesicle (SV) recycling. However, certain regulatory steps still remain incompletely understood. Protein liquid-liquid phase separation (LLPS) and its role in SV clustering and active zone regulation now introduce a new perception of how the presynapse and its different compartments are organized. This article highlights the newly emerging concept of LLPS at the synapse, providing a systematic overview on LLPS tendencies of over 500 presynaptic proteins, spotlighting individual proteins and discussing recent progress in the field. Newly discovered LLPS systems like ELKS/liprin-alpha and Eps15/FCho are put into context, and further LLPS candidate proteins, including epsin1, dynamin, synaptojanin, complexin and rabphilin-3A, are highlighted.
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Affiliation(s)
- Janin Lautenschläger
- Department of Clinical Neurosciences, Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, UK
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8
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Sertel SM, Blumenstein W, Mandad S, Shomroni O, Salinas G, Rizzoli SO. Differences in synaptic vesicle pool behavior between male and female hippocampal cultured neurons. Sci Rep 2021; 11:17374. [PMID: 34462487 PMCID: PMC8405817 DOI: 10.1038/s41598-021-96846-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Accepted: 08/17/2021] [Indexed: 12/15/2022] Open
Abstract
A strong focus on sex-related differences has arisen recently in neurobiology, but most investigations focus on brain function in vivo, ignoring common experimental models like cultured neurons. A few studies have addressed morphological differences between male and female neurons in culture, but very few works focused on functional aspects, and especially on presynaptic function. To fill this gap, we studied here functional parameters of synaptic vesicle recycling in hippocampal cultures from male and female rats, which are a standard model system for many laboratories. We found that, although the total vesicle pools are similar, the recycling pool of male synapses was larger, and was more frequently used. This was in line with the observation that the male synapses engaged in stronger local translation. Nevertheless, the general network activity of the neurons was similar, and only small differences could be found when stimulating the cultures. We also found only limited differences in several other assays. We conclude that, albeit these cultures are similar in behavior, future studies of synapse behavior in culture should take the sex of the animals into account.
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Affiliation(s)
- Sinem M Sertel
- Institute for Neuro- and Sensory Physiology, University Medical Center Göttingen, 37075, Göttingen, Germany. .,Cluster of Excellence "Multiscale Bioimaging: From Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, 37073, Göttingen, Germany.
| | - Wiebke Blumenstein
- Institute for Neuro- and Sensory Physiology, University Medical Center Göttingen, 37075, Göttingen, Germany.,Cluster of Excellence "Multiscale Bioimaging: From Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, 37073, Göttingen, Germany
| | - Sunit Mandad
- Institute for Neuro- and Sensory Physiology, University Medical Center Göttingen, 37075, Göttingen, Germany.,Cluster of Excellence "Multiscale Bioimaging: From Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, 37073, Göttingen, Germany
| | - Orr Shomroni
- NGS-Integrative Genomics Core Unit Göttingen (NIG), Institute of Human Genetics, University Medical Center Göttingen, 37077, Göttingen, Germany
| | - Gabriela Salinas
- NGS-Integrative Genomics Core Unit Göttingen (NIG), Institute of Human Genetics, University Medical Center Göttingen, 37077, Göttingen, Germany
| | - Silvio O Rizzoli
- Institute for Neuro- and Sensory Physiology, University Medical Center Göttingen, 37075, Göttingen, Germany. .,Cluster of Excellence "Multiscale Bioimaging: From Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, 37073, Göttingen, Germany.
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9
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Hoffmann C, Sansevrino R, Morabito G, Logan C, Vabulas RM, Ulusoy A, Ganzella M, Milovanovic D. Synapsin Condensates Recruit alpha-Synuclein. J Mol Biol 2021; 433:166961. [PMID: 33774037 DOI: 10.1016/j.jmb.2021.166961] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Revised: 03/07/2021] [Accepted: 03/19/2021] [Indexed: 12/24/2022]
Abstract
Neurotransmission relies on the tight spatial and temporal regulation of the synaptic vesicle (SV) cycle. Nerve terminals contain hundreds of SVs that form tight clusters. These clusters represent a distinct liquid phase in which one component of the phase are SVs and the other synapsin 1, a highly abundant synaptic protein. Another major family of disordered proteins at the presynapse includes synucleins, most notably α-synuclein. The precise physiological role of α-synuclein in synaptic physiology remains elusive, albeit its role has been implicated in nearly all steps of the SV cycle. To determine the effect of α-synuclein on the synapsin phase, we employ the reconstitution approach using natively purified SVs from rat brains and the heterologous cell system to generate synapsin condensates. We demonstrate that synapsin condensates recruit α-synuclein, and while enriched into these synapsin condensates, α-synuclein still maintains its high mobility. The presence of SVs enhances the rate of synapsin/α-synuclein condensation, suggesting that SVs act as catalyzers for the formation of synapsin condensates. Notably, at physiological salt and protein concentrations, α-synuclein alone is not able to cluster isolated SVs. Excess of α-synuclein disrupts the kinetics of synapsin/SV condensate formation, indicating that the molar ratio between synapsin and α-synuclein is important in assembling the functional condensates of SVs. Understanding the molecular mechanism of α-synuclein interactions at the nerve terminals is crucial for clarifying the pathogenesis of synucleinopathies, where α-synuclein, synaptic proteins and lipid organelles all accumulate as insoluble intracellular inclusions.
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Affiliation(s)
- Christian Hoffmann
- Laboratory of Molecular Neuroscience, German Center for Neurodegenerative Diseases (DZNE), 10117 Berlin, Germany
| | - Roberto Sansevrino
- Laboratory of Molecular Neuroscience, German Center for Neurodegenerative Diseases (DZNE), 10117 Berlin, Germany
| | - Giuseppe Morabito
- Laboratory of Molecular Neuroscience, German Center for Neurodegenerative Diseases (DZNE), 10117 Berlin, Germany
| | - Chinyere Logan
- Laboratory of Molecular Neuroscience, German Center for Neurodegenerative Diseases (DZNE), 10117 Berlin, Germany
| | - R Martin Vabulas
- Charité - Universitätsmedizin Berlin, Institute of Biochemistry, 10117 Berlin, Germany
| | - Ayse Ulusoy
- Laboratory of Neuroprotective Mechanisms, German Center for Neurodegenerative Diseases (DZNE), 53127 Bonn, Germany
| | - Marcelo Ganzella
- Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Dragomir Milovanovic
- Laboratory of Molecular Neuroscience, German Center for Neurodegenerative Diseases (DZNE), 10117 Berlin, Germany.
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10
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Jähne S, Mikulasch F, Heuer HGH, Truckenbrodt S, Agüi-Gonzalez P, Grewe K, Vogts A, Rizzoli SO, Priesemann V. Presynaptic activity and protein turnover are correlated at the single-synapse level. Cell Rep 2021; 34:108841. [PMID: 33730575 DOI: 10.1016/j.celrep.2021.108841] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 12/18/2020] [Accepted: 02/17/2021] [Indexed: 11/15/2022] Open
Abstract
Synaptic transmission relies on the continual exocytosis and recycling of synaptic vesicles. Aged vesicle proteins are prevented from recycling and are eventually degraded. This implies that active synapses would lose vesicles and vesicle-associated proteins over time, unless the supply correlates to activity, to balance the losses. To test this hypothesis, we first model the quantitative relation between presynaptic spike rate and vesicle turnover. The model predicts that the vesicle supply needs to increase with the spike rate. To follow up this prediction, we measure protein turnover in individual synapses of cultured hippocampal neurons by combining nanoscale secondary ion mass spectrometry (nanoSIMS) and fluorescence microscopy. We find that turnover correlates with activity at the single-synapse level, but not with other parameters such as the abundance of synaptic vesicles or postsynaptic density proteins. We therefore suggest that the supply of newly synthesized proteins to synapses is closely connected to synaptic activity.
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Affiliation(s)
- Sebastian Jähne
- Department of Neuro- and Sensory Physiology, University Medical Center Göttingen, Humboldtallee 23, 37073 Göttingen, Germany.
| | - Fabian Mikulasch
- Max-Planck-Institute for Dynamics and Self-Organization, Am Faßberg 17, 37077 Göttingen, Germany
| | - Helge G H Heuer
- Max-Planck-Institute for Dynamics and Self-Organization, Am Faßberg 17, 37077 Göttingen, Germany; Faculty of Physics, Georg-August-University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Sven Truckenbrodt
- Department of Neuro- and Sensory Physiology, University Medical Center Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | - Paola Agüi-Gonzalez
- Department of Neuro- and Sensory Physiology, University Medical Center Göttingen, Humboldtallee 23, 37073 Göttingen, Germany; Center for Biostructural Imaging of Neurodegeneration (BIN), von Siebold Str. 3a, 37075 Göttingen, Germany; Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, 37073 Göttingen, Germany
| | - Katharina Grewe
- Department of Neuro- and Sensory Physiology, University Medical Center Göttingen, Humboldtallee 23, 37073 Göttingen, Germany; Center for Biostructural Imaging of Neurodegeneration (BIN), von Siebold Str. 3a, 37075 Göttingen, Germany; Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, 37073 Göttingen, Germany
| | - Angela Vogts
- NanoSIMS lab, Leibniz Institute for Baltic Sea Research Warnemünde (IOW), Seestraße 15, 18119 Rostock, Germany
| | - Silvio O Rizzoli
- Department of Neuro- and Sensory Physiology, University Medical Center Göttingen, Humboldtallee 23, 37073 Göttingen, Germany; Center for Biostructural Imaging of Neurodegeneration (BIN), von Siebold Str. 3a, 37075 Göttingen, Germany; Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, 37073 Göttingen, Germany.
| | - Viola Priesemann
- Max-Planck-Institute for Dynamics and Self-Organization, Am Faßberg 17, 37077 Göttingen, Germany; Faculty of Physics, Georg-August-University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany; Bernstein-Center for Computational Neuroscience, Heinrich-Düker-Weg 12, 37073 Göttingen, Germany.
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11
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The vesicle cluster as a major organizer of synaptic composition in the short-term and long-term. Curr Opin Cell Biol 2021; 71:63-68. [PMID: 33706235 DOI: 10.1016/j.ceb.2021.02.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Revised: 01/22/2021] [Accepted: 02/04/2021] [Indexed: 01/29/2023]
Abstract
For decades, the synaptic vesicle cluster has been thought of as a storage space for synaptic vesicles, whose obvious function is to provide vesicles for the depolarization-induced release of neurotransmitters; however, reports over the last few years indicate that the synaptic vesicle cluster probably plays a much broader and more fundamental role in synaptic biology. Various experiments suggest that the cluster is able to regulate protein distribution and mobility in the synapse; moreover, it probably regulates cytoskeleton architecture, mediates the selective removal of synaptic components from the bouton, and controls the responses of the presynapse to plasticity. Here we discuss these features of the vesicle cluster and conclude that it serves as a key organizer of synaptic composition and dynamics.
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12
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Perego E, Reshetniak S, Lorenz C, Hoffmann C, Milovanović D, Rizzoli SO, Köster S. A minimalist model to measure interactions between proteins and synaptic vesicles. Sci Rep 2020; 10:21086. [PMID: 33273508 PMCID: PMC7713060 DOI: 10.1038/s41598-020-77887-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 11/17/2020] [Indexed: 02/03/2023] Open
Abstract
Protein dynamics in the synaptic bouton are still not well understood, despite many quantitative studies of synaptic structure and function. The complexity of the synaptic environment makes investigations of presynaptic protein mobility challenging. Here, we present an in vitro approach to create a minimalist model of the synaptic environment by patterning synaptic vesicles (SVs) on glass coverslips. We employed fluorescence correlation spectroscopy (FCS) to measure the mobility of monomeric enhanced green fluorescent protein (mEGFP)-tagged proteins in the presence of the vesicle patterns. We observed that the mobility of all eleven measured proteins is strongly reduced in the presence of the SVs, suggesting that they all bind to the SVs. The mobility observed in these conditions is within the range of corresponding measurements in synapses of living cells. Overall, our simple, but robust, approach should enable numerous future studies of organelle-protein interactions in general.
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Affiliation(s)
- Eleonora Perego
- Institute for X-Ray Physics, University of Göttingen, 37077, Göttingen, Germany
| | - Sofiia Reshetniak
- Institute for Neuro- and Sensory Physiology, Center for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, 37075, Göttingen, Germany
| | - Charlotta Lorenz
- Institute for X-Ray Physics, University of Göttingen, 37077, Göttingen, Germany
| | - Christian Hoffmann
- Laboratory of Molecular Neuroscience, German Center for Neurodegenerative Diseases (DZNE), 10117, Berlin, Germany
| | - Dragomir Milovanović
- Laboratory of Molecular Neuroscience, German Center for Neurodegenerative Diseases (DZNE), 10117, Berlin, Germany
| | - Silvio O Rizzoli
- Institute for Neuro- and Sensory Physiology, Center for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, 37075, Göttingen, Germany.,Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, 37073, Göttingen, Germany
| | - Sarah Köster
- Institute for X-Ray Physics, University of Göttingen, 37077, Göttingen, Germany. .,Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, 37073, Göttingen, Germany.
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13
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Reshetniak S, Ußling JE, Perego E, Rammner B, Schikorski T, Fornasiero EF, Truckenbrodt S, Köster S, Rizzoli SO. A comparative analysis of the mobility of 45 proteins in the synaptic bouton. EMBO J 2020; 39:e104596. [PMID: 32627850 PMCID: PMC7429486 DOI: 10.15252/embj.2020104596] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 05/20/2020] [Accepted: 05/29/2020] [Indexed: 02/01/2023] Open
Abstract
Many proteins involved in synaptic transmission are well known, and their features, as their abundance or spatial distribution, have been analyzed in systematic studies. This has not been the case, however, for their mobility. To solve this, we analyzed the motion of 45 GFP‐tagged synaptic proteins expressed in cultured hippocampal neurons, using fluorescence recovery after photobleaching, particle tracking, and modeling. We compared synaptic vesicle proteins, endo‐ and exocytosis cofactors, cytoskeleton components, and trafficking proteins. We found that movement was influenced by the protein association with synaptic vesicles, especially for membrane proteins. Surprisingly, protein mobility also correlated significantly with parameters as the protein lifetimes, or the nucleotide composition of their mRNAs. We then analyzed protein movement thoroughly, taking into account the spatial characteristics of the system. This resulted in a first visualization of overall protein motion in the synapse, which should enable future modeling studies of synaptic physiology.
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Affiliation(s)
- Sofiia Reshetniak
- Institute for Neuro- and Sensory Physiology and Biostructural Imaging of Neurodegeneration (BIN) Center, University Medical Center Göttingen, Göttingen, Germany.,International Max Planck Research School for Molecular Biology, Göttingen, Germany
| | - Jan-Eike Ußling
- Institute for Neuro- and Sensory Physiology and Biostructural Imaging of Neurodegeneration (BIN) Center, University Medical Center Göttingen, Göttingen, Germany
| | - Eleonora Perego
- Institute for X-Ray Physics, University of Göttingen, Göttingen, Germany
| | - Burkhard Rammner
- Institute for Neuro- and Sensory Physiology and Biostructural Imaging of Neurodegeneration (BIN) Center, University Medical Center Göttingen, Göttingen, Germany
| | - Thomas Schikorski
- Department of Neuroscience, Universidad Central del Caribe, Bayamon, PR, USA
| | - Eugenio F Fornasiero
- Institute for Neuro- and Sensory Physiology and Biostructural Imaging of Neurodegeneration (BIN) Center, University Medical Center Göttingen, Göttingen, Germany
| | - Sven Truckenbrodt
- Institute for Neuro- and Sensory Physiology and Biostructural Imaging of Neurodegeneration (BIN) Center, University Medical Center Göttingen, Göttingen, Germany.,International Max Planck Research School for Molecular Biology, Göttingen, Germany
| | - Sarah Köster
- Institute for X-Ray Physics, University of Göttingen, Göttingen, Germany.,Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Göttingen, Germany
| | - Silvio O Rizzoli
- Institute for Neuro- and Sensory Physiology and Biostructural Imaging of Neurodegeneration (BIN) Center, University Medical Center Göttingen, Göttingen, Germany.,Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Göttingen, Germany
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14
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Pechstein A, Tomilin N, Fredrich K, Vorontsova O, Sopova E, Evergren E, Haucke V, Brodin L, Shupliakov O. Vesicle Clustering in a Living Synapse Depends on a Synapsin Region that Mediates Phase Separation. Cell Rep 2020; 30:2594-2602.e3. [DOI: 10.1016/j.celrep.2020.01.092] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Revised: 08/15/2019] [Accepted: 01/24/2020] [Indexed: 12/28/2022] Open
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15
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Two Pathways for the Activity-Dependent Growth and Differentiation of Synaptic Boutons in Drosophila. eNeuro 2019; 6:ENEURO.0060-19.2019. [PMID: 31387877 PMCID: PMC6709223 DOI: 10.1523/eneuro.0060-19.2019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Revised: 07/15/2019] [Accepted: 07/26/2019] [Indexed: 11/21/2022] Open
Abstract
Synapse formation can be promoted by intense activity. At the Drosophila larval neuromuscular junction (NMJ), new synaptic boutons can grow acutely in response to patterned stimulation. We combined confocal imaging with electron microscopy and tomography to investigate the initial stages of growth and differentiation of new presynaptic boutons at the Drosophila NMJ. We found that the new boutons can form rapidly in intact larva in response to intense crawling activity, and we observed two different patterns of bouton formation and maturation. The first pathway involves the growth of filopodia followed by a formation of boutons that are initially devoid of synaptic vesicles (SVs) but filled with filamentous matrix. The second pathway involves rapid budding of synaptic boutons packed with SVs, and these more mature boutons are sometimes capable of exocytosis/endocytosis. We demonstrated that intense activity predominantly promotes the second pathway, i.e., budding of more mature boutons filled with SVs. We also showed that this pathway depends on synapsin (Syn), a neuronal protein which reversibly associates with SVs and mediates their clustering via a protein kinase A (PKA)-dependent mechanism. Finally, we took advantage of the temperature-sensitive mutant sei to demonstrate that seizure activity can promote very rapid budding of new boutons filled with SVs, and this process occurs at scale of minutes. Altogether, these results demonstrate that intense activity acutely and selectively promotes rapid budding of new relatively mature presynaptic boutons filled with SVs, and that this process is regulated via a PKA/Syn-dependent pathway.
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16
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Somasundaram A, Taraska JW. Local protein dynamics during microvesicle exocytosis in neuroendocrine cells. Mol Biol Cell 2018; 29:1891-1903. [PMID: 29874123 PMCID: PMC6085826 DOI: 10.1091/mbc.e17-12-0716] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Calcium-triggered exocytosis is key to many physiological processes, including neurotransmitter and hormone release by neurons and endocrine cells. Dozens of proteins regulate exocytosis, yet the temporal and spatial dynamics of these factors during vesicle fusion remain unclear. Here we use total internal reflection fluorescence microscopy to visualize local protein dynamics at single sites of exocytosis of small synaptic-like microvesicles in live cultured neuroendocrine PC12 cells. We employ two-color imaging to simultaneously observe membrane fusion (using vesicular acetylcholine ACh transporter tagged to pHluorin) and the dynamics of associated proteins at the moments surrounding exocytosis. Our experiments show that many proteins, including the SNAREs syntaxin1 and VAMP2, the SNARE modulator tomosyn, and Rab proteins, are preclustered at fusion sites and rapidly lost at fusion. The ATPase N-ethylmaleimide–sensitive factor is locally recruited at fusion. Interestingly, the endocytic Bin-Amphiphysin-Rvs domain–containing proteins amphiphysin1, syndapin2, and endophilins are dynamically recruited to fusion sites and slow the loss of vesicle membrane-bound cargo from fusion sites. A similar effect on vesicle membrane protein dynamics was seen with the overexpression of the GTPases dynamin1 and dynamin2. These results suggest that proteins involved in classical clathrin-mediated endocytosis can regulate exocytosis of synaptic-like microvesicles. Our findings provide insights into the dynamics, assembly, and mechanistic roles of many key factors of exocytosis and endocytosis at single sites of microvesicle fusion in live cells.
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Affiliation(s)
- Agila Somasundaram
- Laboratory of Molecular Biophysics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
| | - Justin W Taraska
- Laboratory of Molecular Biophysics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
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17
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Milovanovic D, De Camilli P. Synaptic Vesicle Clusters at Synapses: A Distinct Liquid Phase? Neuron 2017; 93:995-1002. [PMID: 28279363 DOI: 10.1016/j.neuron.2017.02.013] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 02/06/2017] [Accepted: 02/06/2017] [Indexed: 11/17/2022]
Abstract
Phase separation in the cytoplasm is emerging as a major principle in intracellular organization. In this process, sets of macromolecules assemble themselves into liquid compartments that are distinct from the surrounding medium but are not delimited by membrane boundaries. Here, we discuss how phase separation, in which a component of one of the two phases is vesicles rather than macromolecules, could underlie the formation of synaptic vesicle (SV) clusters in proximity to presynaptic sites. The organization of SVs into a liquid phase could explain how SVs remain tightly clustered without being stably bound to a scaffold so that they can be efficiently recruited to release site by active zone components.
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Affiliation(s)
- Dragomir Milovanovic
- Departments of Neuroscience and Cell Biology, Program in Cellular Neuroscience, Neurodegeneration and Repair, Kavli Institute for Neuroscience, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Pietro De Camilli
- Departments of Neuroscience and Cell Biology, Program in Cellular Neuroscience, Neurodegeneration and Repair, Kavli Institute for Neuroscience, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06520, USA.
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18
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Winther ÅME, Vorontsova O, Rees KA, Näreoja T, Sopova E, Jiao W, Shupliakov O. An Endocytic Scaffolding Protein together with Synapsin Regulates Synaptic Vesicle Clustering in the Drosophila Neuromuscular Junction. J Neurosci 2015; 35:14756-70. [PMID: 26538647 PMCID: PMC6605226 DOI: 10.1523/jneurosci.1675-15.2015] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Revised: 09/16/2015] [Accepted: 09/25/2015] [Indexed: 11/21/2022] Open
Abstract
Many endocytic proteins accumulate in the reserve pool of synaptic vesicles (SVs) in synapses and relocalize to the endocytic periactive zone during neurotransmitter release. Currently little is known about their functions outside the periactive zone. Here we show that in the Drosophila neuromuscular junction (NMJ), the endocytic scaffolding protein Dap160 colocalizes during the SV cycle and forms a functional complex with the SV-associated phosphoprotein synapsin, previously implicated in SV clustering. This direct interaction is strongly enhanced under phosphorylation-promoting conditions and is essential for proper localization of synapsin at NMJs. In a dap160 rescue mutant lacking the interaction between Dap160 and synapsin, perturbed reclustering of SVs during synaptic activity is observed. Our data indicate that in addition to the function in endocytosis, Dap160 is a component of a network of protein-protein interactions that serves for clustering of SVs in conjunction with synapsin. During the SV cycle, Dap160 interacts with synapsin dispersed from SVs and helps direct synapsin back to vesicles. The proteins function in synergy to achieve efficient clustering of SVs in the reserve pool. SIGNIFICANCE STATEMENT We provide the first evidence for the function of the SH3 domain interaction in synaptic vesicle (SV) organization at the synaptic active zone. Using Drosophila neuromuscular junction as a model synapse, we describe the molecular mechanism that enables the protein implicated in SV clustering, synapsin, to return to the pool of vesicles during neurotransmitter release. We also identify the endocytic scaffolding complex that includes Dap160 as a regulator of the events linking exocytosis and endocytosis in synapses.
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Affiliation(s)
- Åsa M E Winther
- Department of Neuroscience, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Olga Vorontsova
- Department of Neuroscience, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Kathryn A Rees
- Department of Neuroscience, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Tuomas Näreoja
- Department of Neuroscience, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Elena Sopova
- Department of Neuroscience, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Wei Jiao
- Department of Neuroscience, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Oleg Shupliakov
- Department of Neuroscience, Karolinska Institutet, 171 77 Stockholm, Sweden
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19
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Morton A, Marland JRK, Cousin MA. Synaptic vesicle exocytosis and increased cytosolic calcium are both necessary but not sufficient for activity-dependent bulk endocytosis. J Neurochem 2015; 134:405-15. [PMID: 25913068 PMCID: PMC4950031 DOI: 10.1111/jnc.13132] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Revised: 03/23/2015] [Accepted: 03/30/2015] [Indexed: 01/22/2023]
Abstract
Activity‐dependent bulk endocytosis (ADBE) is the dominant synaptic vesicle (SV) endocytosis mode in central nerve terminals during intense neuronal activity. By definition this mode is triggered by neuronal activity; however, key questions regarding its mechanism of activation remain unaddressed. To determine the basic requirements for ADBE triggering in central nerve terminals, we decoupled SV fusion events from activity‐dependent calcium influx using either clostridial neurotoxins or buffering of intracellular calcium. ADBE was monitored both optically and morphologically by observing uptake of the fluid phase markers tetramethylrhodamine‐dextran and horse radish peroxidase respectively. Ablation of SV fusion with tetanus toxin resulted in the arrest of ADBE, but had no effect on other calcium‐dependent events such as activity‐dependent dynamin I dephosphorylation, indicating that SV exocytosis is necessary for triggering. Furthermore, the calcium chelator EGTA abolished ADBE while leaving SV exocytosis intact, demonstrating that ADBE is triggered by intracellular free calcium increases outside the active zone. Activity‐dependent dynamin I dephosphorylation was also arrested in EGTA‐treated neurons, consistent with its proposed role in triggering ADBE. Thus, SV fusion and increased cytoplasmic free calcium are both necessary but not sufficient individually to trigger ADBE.![]() Activity‐dependent bulk endocytosis (ADBE) is the dominant synaptic vesicle (SV) endocytosis mode in central nerve terminals during intense neuronal activity. To determine the minimal requirements for ADBE triggering, we decoupled SV fusion events from activity‐dependent calcium influx using either clostridial neurotoxins or buffering of intracellular calcium. We found that SV fusion and increased cytoplasmic free calcium are both necessary but not sufficient to trigger ADBE.
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Affiliation(s)
- Andrew Morton
- Centre for Integrative Physiology, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland
| | - Jamie R K Marland
- Centre for Integrative Physiology, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland
| | - Michael A Cousin
- Centre for Integrative Physiology, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland
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20
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Kokotos AC, Cousin MA. Synaptic vesicle generation from central nerve terminal endosomes. Traffic 2014; 16:229-40. [PMID: 25346420 DOI: 10.1111/tra.12235] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Revised: 10/15/2014] [Accepted: 10/20/2014] [Indexed: 01/01/2023]
Abstract
Central nerve terminals contain a small number of synaptic vesicles (SVs) that must sustain the fidelity of neurotransmission across a wide range of stimulation intensities. For this to be achieved, nerve terminals integrate a number of complementary endocytosis modes whose activation spans the breadth of these neuronal stimulation patterns. Two such modes are ultrafast endocytosis and activity-dependent bulk endocytosis, which are triggered by stimuli at either end of the physiological range. Both endocytosis modes generate endosomes directly from the nerve terminal plasma membrane, before the subsequent production of SVs from these structures. This review will discuss the current knowledge relating to the molecular mechanisms involved in the generation of SVs from nerve terminal endosomes, how this relates to other mechanisms of SV production and the functional role of such SVs.
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Affiliation(s)
- Alexandros C Kokotos
- Centre for Integrative Physiology, George Square, University of Edinburgh, Edinburgh, EH8 9XD, UK
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21
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Wilhelm BG, Mandad S, Truckenbrodt S, Kröhnert K, Schäfer C, Rammner B, Koo SJ, Claßen GA, Krauss M, Haucke V, Urlaub H, Rizzoli SO. Composition of isolated synaptic boutons reveals the amounts of vesicle trafficking proteins. Science 2014; 344:1023-8. [PMID: 24876496 DOI: 10.1126/science.1252884] [Citation(s) in RCA: 503] [Impact Index Per Article: 50.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Synaptic vesicle recycling has long served as a model for the general mechanisms of cellular trafficking. We used an integrative approach, combining quantitative immunoblotting and mass spectrometry to determine protein numbers; electron microscopy to measure organelle numbers, sizes, and positions; and super-resolution fluorescence microscopy to localize the proteins. Using these data, we generated a three-dimensional model of an "average" synapse, displaying 300,000 proteins in atomic detail. The copy numbers of proteins involved in the same step of synaptic vesicle recycling correlated closely. In contrast, copy numbers varied over more than three orders of magnitude between steps, from about 150 copies for the endosomal fusion proteins to more than 20,000 for the exocytotic ones.
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Affiliation(s)
- Benjamin G Wilhelm
- Department of Neuro- and Sensory Physiology, University of Göttingen Medical Center, European Neuroscience Institute, Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain, Göttingen, Germany. International Max Planck Research School Neurosciences, 37077 Göttingen, Germany
| | - Sunit Mandad
- Bioanalytical Mass Spectrometry Group, Max-Planck-Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Sven Truckenbrodt
- Department of Neuro- and Sensory Physiology, University of Göttingen Medical Center, European Neuroscience Institute, Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain, Göttingen, Germany. International Max Planck Research School Molecular Biology, 37077 Göttingen, Germany
| | - Katharina Kröhnert
- Department of Neuro- and Sensory Physiology, University of Göttingen Medical Center, European Neuroscience Institute, Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain, Göttingen, Germany
| | - Christina Schäfer
- Department of Neuro- and Sensory Physiology, University of Göttingen Medical Center, European Neuroscience Institute, Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain, Göttingen, Germany
| | - Burkhard Rammner
- Department of Neuro- and Sensory Physiology, University of Göttingen Medical Center, European Neuroscience Institute, Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain, Göttingen, Germany
| | - Seong Joo Koo
- Leibniz Institut für Molekulare Pharmakologie, Department of Molecular Pharmacology and Cell Biology, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Gala A Claßen
- Leibniz Institut für Molekulare Pharmakologie, Department of Molecular Pharmacology and Cell Biology, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Michael Krauss
- Leibniz Institut für Molekulare Pharmakologie, Department of Molecular Pharmacology and Cell Biology, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Volker Haucke
- Leibniz Institut für Molekulare Pharmakologie, Department of Molecular Pharmacology and Cell Biology, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Henning Urlaub
- Bioanalytical Mass Spectrometry Group, Max-Planck-Institute for Biophysical Chemistry, 37077 Göttingen, Germany. Bioanalytics, Department of Clinical Chemistry, University Medical Center Göttingen, 37075 Göttingen, Germany
| | - Silvio O Rizzoli
- Department of Neuro- and Sensory Physiology, University of Göttingen Medical Center, European Neuroscience Institute, Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain, Göttingen, Germany.
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22
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Abstract
Synaptic vesicle recycling is one of the best-studied cellular pathways. Many of the proteins involved are known, and their interactions are becoming increasingly clear. However, as for many other pathways, it is still difficult to understand synaptic vesicle recycling as a whole. While it is generally possible to point out how synaptic reactions take place, it is not always easy to understand what triggers or controls them. Also, it is often difficult to understand how the availability of the reaction partners is controlled: how the reaction partners manage to find each other in the right place, at the right time. I present here an overview of synaptic vesicle recycling, discussing the mechanisms that trigger different reactions, and those that ensure the availability of reaction partners. A central argument is that synaptic vesicles bind soluble cofactor proteins, with low affinity, and thus control their availability in the synapse, forming a buffer for cofactor proteins. The availability of cofactor proteins, in turn, regulates the different synaptic reactions. Similar mechanisms, in which one of the reaction partners buffers another, may apply to many other processes, from the biogenesis to the degradation of the synaptic vesicle.
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Affiliation(s)
- Silvio O Rizzoli
- Department of Neuro- and Sensory Physiology, University Medical Center Göttingen European Neuroscience Institute, Göttingen, Germany
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23
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Barth J, Volknandt W. Proteomic investigations of the synaptic vesicle interactome. Expert Rev Proteomics 2014; 8:211-20. [DOI: 10.1586/epr.11.7] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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24
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A local, periactive zone endocytic machinery at photoreceptor synapses in close vicinity to synaptic ribbons. J Neurosci 2013; 33:10278-300. [PMID: 23785143 DOI: 10.1523/jneurosci.5048-12.2013] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Photoreceptor ribbon synapses are continuously active synapses with large active zones that contain synaptic ribbons. Synaptic ribbons are anchored to the active zones and are associated with large numbers of synaptic vesicles. The base of the ribbon that is located close to L-type voltage-gated Ca(2+) channels is a hotspot of exocytosis. The continuous exocytosis at the ribbon synapse needs to be balanced by compensatory endocytosis. Recent analyses indicated that vesicle recycling at the synaptic ribbon is also an important determinant of synaptic signaling at the photoreceptor synapse. To get insights into mechanisms of vesicle recycling at the photoreceptor ribbon synapse, we performed super-resolution structured illumination microscopy and immunogold electron microscopy to localize major components of the endocytotic membrane retrieval machinery in the photoreceptor synapse of the mouse retina. We found dynamin, syndapin, amphiphysin, and calcineurin, a regulator of activity-dependent endocytosis, to be highly enriched around the active zone and the synaptic ribbon. We present evidence for two clathrin heavy chain variants in the photoreceptor terminal; one is enriched around the synaptic ribbon, whereas the other is localized in the entry region of the terminal. The focal enrichment of endocytic proteins around the synaptic ribbon is consistent with a focal uptake of endocytic markers at that site. This endocytic activity functionally depends on dynamin. These data propose that the presynaptic periactive zone surrounding the synaptic ribbon complex is a hotspot of endocytosis in photoreceptor ribbon synapses.
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25
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Ovsepian SV, Antyborzec I, O'Leary VB, Zaborszky L, Herms J, Oliver Dolly J. Neurotrophin receptor p75 mediates the uptake of the amyloid beta (Aβ) peptide, guiding it to lysosomes for degradation in basal forebrain cholinergic neurons. Brain Struct Funct 2013; 219:1527-41. [PMID: 23716278 DOI: 10.1007/s00429-013-0583-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2012] [Accepted: 05/15/2013] [Indexed: 12/12/2022]
Abstract
A fascinating yet perhaps overlooked trait of the p75 neurotrophin receptor (p75(NTR)) is its ability to bind ligands with no obvious neurotrophic function. Using cultured basal forebrain (BF) neurons, this study demonstrates selective internalization of amyloid β (Aβ) 1-42 in conjunction with p75(NTR) (labelled with IgG192-Cy3) by cholinergic cells. Active under resting conditions, this process was enhanced by high K(+) stimulation and was insensitive to inhibitors of regulated synaptic activity-tetrodotoxin or botulinum neurotoxins (BoNT type/A and/B). Blockade of sarco-endoplasmic reticulum (SERCA) Ca(2+) ATPase with thapsigargin and CPA or chelation of Ca(2+) with EGTA-AM strongly suppressed the endocytosis of p75(NTR), implicating the role of ER released Ca(2+). The uptake of IgG192-Cy3 was also reduced by T-type Ca(2+) channel blocker mibefradil but not Cd(2+), an indiscriminate blocker of high voltage-activated Ca(2+) currents. A strong co-localization of IgG192-Cy3 with late endosome (Rab7) or lysosome (Lamp1) qualifier proteins suggest these compartments as the primary destination for internalized IgG192 and Aβ. Selective uptake and labeling of BF cholinergic cells with IgG192-Cy3 injected into the prefrontal cortex was verified also in vivo. The significance of these findings in relation to Aβ clearance in the cerebral cortex and pathophysiology of Alzheimer's disease is discussed.
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Affiliation(s)
- Saak V Ovsepian
- International Centre for Neurotherapeutics, Dublin City University, Glasnevin, Dublin 9, Republic of Ireland,
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26
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Adaptor protein complexes 1 and 3 are essential for generation of synaptic vesicles from activity-dependent bulk endosomes. J Neurosci 2012; 32:6014-23. [PMID: 22539861 DOI: 10.1523/jneurosci.6305-11.2012] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Activity-dependent bulk endocytosis is the dominant synaptic vesicle retrieval mode during high intensity stimulation in central nerve terminals. A key event in this endocytosis mode is the generation of new vesicles from bulk endosomes, which replenish the reserve vesicle pool. We have identified an essential requirement for both adaptor protein complexes 1 and 3 in this process by employing morphological and optical tracking of bulk endosome-derived synaptic vesicles in rat primary neuronal cultures. We show that brefeldin A inhibits synaptic vesicle generation from bulk endosomes and that both brefeldin A knockdown and shRNA knockdown of either adaptor protein 1 or 3 subunits inhibit reserve pool replenishment from bulk endosomes. Conversely, no plasma membrane function was found for adaptor protein 1 or 3 in either bulk endosome formation or clathrin-mediated endocytosis. Simultaneous knockdown of both adaptor proteins 1 and 3 indicated that they generated the same population of synaptic vesicles. Thus, adaptor protein complexes 1 and 3 play an essential dual role in generation of synaptic vesicles during activity-dependent bulk endocytosis.
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The reserve pool of synaptic vesicles acts as a buffer for proteins involved in synaptic vesicle recycling. Proc Natl Acad Sci U S A 2011; 108:17183-8. [PMID: 21903923 DOI: 10.1073/pnas.1112690108] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Presynaptic nerve terminals contain between several hundred vesicles (for example in small CNS synapses) and several tens of thousands (as in neuromuscular junctions). Although it has long been assumed that such high numbers of vesicles are required to sustain neurotransmission during conditions of high demand, we found that activity in vivo requires the recycling of only a few percent of the vesicles. However, the maintenance of large amounts of reserve vesicles in many evolutionarily distinct species suggests that they are relevant for synaptic function. We suggest here that these vesicles constitute buffers for soluble accessory proteins involved in vesicle recycling, preventing their loss into the axon. Supporting this hypothesis, we found that vesicle clusters contain a large variety of proteins needed for vesicle recycling, but without an obvious function within the clusters. Disrupting the clusters by application of black widow spider venom resulted in the diffusion of numerous soluble proteins into the axons. Prolonged stimulation and ionomycin application had a similar effect, suggesting that calcium influx causes the unbinding of soluble proteins from vesicles. Confirming this hypothesis, we found that isolated synaptic vesicles in vitro sequestered soluble proteins from the cytosol in a process that was inhibited by calcium addition. We conclude that the reserve vesicles support neurotransmission indirectly, ensuring that soluble recycling proteins are delivered upon demand during synaptic activity.
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Synaptogyrin-dependent modulation of synaptic neurotransmission in Caenorhabditis elegans. Neuroscience 2011; 190:75-88. [DOI: 10.1016/j.neuroscience.2011.05.069] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2010] [Revised: 05/20/2011] [Accepted: 05/28/2011] [Indexed: 01/31/2023]
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Shupliakov O, Haucke V, Pechstein A. How synapsin I may cluster synaptic vesicles. Semin Cell Dev Biol 2011; 22:393-9. [DOI: 10.1016/j.semcdb.2011.07.006] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2011] [Accepted: 07/13/2011] [Indexed: 12/14/2022]
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Sundborger A, Soderblom C, Vorontsova O, Evergren E, Hinshaw JE, Shupliakov O. An endophilin-dynamin complex promotes budding of clathrin-coated vesicles during synaptic vesicle recycling. J Cell Sci 2011; 124:133-43. [PMID: 21172823 DOI: 10.1242/jcs.072686] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Clathrin-mediated vesicle recycling in synapses is maintained by a unique set of endocytic proteins and interactions. We show that endophilin localizes in the vesicle pool at rest and in spirals at the necks of clathrin-coated pits (CCPs) during activity in lamprey synapses. Endophilin and dynamin colocalize at the base of the clathrin coat. Protein spirals composed of these proteins on lipid tubes in vitro have a pitch similar to the one observed at necks of CCPs in living synapses, and lipid tubules are thinner than those formed by dynamin alone. Tubulation efficiency and the amount of dynamin recruited to lipid tubes are dramatically increased in the presence of endophilin. Blocking the interactions of the endophilin SH3 domain in situ reduces dynamin accumulation at the neck and prevents the formation of elongated necks observed in the presence of GTPγS. Therefore, endophilin recruits dynamin to a restricted part of the CCP neck, forming a complex, which promotes budding of new synaptic vesicles.
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Affiliation(s)
- Anna Sundborger
- Department of Neuroscience, DBRM, Karolinska Institutet, 17177 Stockholm, Sweden
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31
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Reichert S, Welker P, Calderón M, Khandare J, Mangoldt D, Licha K, Kainthan RK, Brooks DE, Haag R. Size-dependant cellular uptake of dendritic polyglycerol. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2011; 7:820-829. [PMID: 21337511 DOI: 10.1002/smll.201002220] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Indexed: 05/28/2023]
Abstract
To study the mechanism of cellular internalization, hyperbranched polyether derivatives consisting of amino-bearing hyperbranched polyglycerols (HPGs) of varied molecular mass and size range are designed and synthesized. HPGs were further fluorescently labelled by conjugating maleimido indocarbocyanine dye (ICC-mal). The conjugates are characterized by UV-vis spectroscopy, fluorescence profile, zeta potential, and dynamic light scattering. The uptake mechanism is studied by fluorescence-activated cell sorting (FACS) analysis, fluorescence spectroscopy, and confocal microscopy with human lung cancer cells A549, human epidermoid carcinoma cells A431, and human umbilical vein endothelial cells (HUVEC) cells. For the first time, the results suggest that the higher-molecular-weight HPGs (40-870 kDa) predominantly accumulate in the cytoplasm much better than their low-molecular-weight counterparts (2-20 kDa). The HPG nanocarriers discussed here have many biomedical implications, particularly for delivering drugs to the targeted site.
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Affiliation(s)
- Stephanie Reichert
- Department of Biology, Chemistry, and Pharmacy, Freie Universität Berlin, Takustrasse 3, 14195 Berlin, Germany
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32
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Bai J, Hu Z, Dittman JS, Pym ECG, Kaplan JM. Endophilin functions as a membrane-bending molecule and is delivered to endocytic zones by exocytosis. Cell 2010; 143:430-41. [PMID: 21029864 DOI: 10.1016/j.cell.2010.09.024] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2010] [Revised: 06/02/2010] [Accepted: 09/07/2010] [Indexed: 12/11/2022]
Abstract
Two models have been proposed for endophilin function in synaptic vesicle (SV) endocytosis. The scaffolding model proposes that endophilin's SH3 domain recruits essential endocytic proteins, whereas the membrane-bending model proposes that the BAR domain induces positively curved membranes. We show that mutations disrupting the scaffolding function do not impair endocytosis, whereas those disrupting membrane bending cause significant defects. By anchoring endophilin to the plasma membrane, we show that endophilin acts prior to scission to promote endocytosis. Despite acting at the plasma membrane, the majority of endophilin is targeted to the SV pool. Photoactivation studies suggest that the soluble pool of endophilin at synapses is provided by unbinding from the adjacent SV pool and that the unbinding rate is regulated by exocytosis. Thus, endophilin participates in an association-dissociation cycle with SVs that parallels the cycle of exo- and endocytosis. This endophilin cycle may provide a mechanism for functionally coupling endocytosis and exocytosis.
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Affiliation(s)
- Jihong Bai
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA
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33
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Vos M, Lauwers E, Verstreken P. Synaptic mitochondria in synaptic transmission and organization of vesicle pools in health and disease. Front Synaptic Neurosci 2010; 2:139. [PMID: 21423525 PMCID: PMC3059669 DOI: 10.3389/fnsyn.2010.00139] [Citation(s) in RCA: 177] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2010] [Accepted: 08/09/2010] [Indexed: 12/21/2022] Open
Abstract
Cell types rich in mitochondria, including neurons, display a high energy demand and a need for calcium buffering. The importance of mitochondria for proper neuronal function is stressed by the occurrence of neurological defects in patients suffering from a great variety of diseases caused by mutations in mitochondrial genes. Genetic and pharmacological evidence also reveal a role of these organelles in various aspects of neuronal physiology and in the pathogenesis of neurodegenerative disorders. Yet the mechanisms by which mitochondria can affect neurotransmission largely remain to be elucidated. In this review we focus on experimental data that suggest a critical function of synaptic mitochondria in the function and organization of synaptic vesicle pools, and in neurotransmitter release during intense neuronal activity. We discuss how calcium handling, ATP production and other mitochondrial mechanisms may influence synaptic vesicle pool organization and synaptic function. Given the link between synaptic mitochondrial function and neuronal communication, efforts toward better understanding mitochondrial biology may lead to novel therapeutic approaches of neurological disorders including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and psychiatric disorders that are at least in part caused by mitochondrial deficits.
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Affiliation(s)
- Melissa Vos
- Department of Molecular and Developmental Genetics VIB, Leuven, Belgium
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Pechstein A, Shupliakov O. Taking a back seat: synaptic vesicle clustering in presynaptic terminals. Front Synaptic Neurosci 2010; 2:143. [PMID: 21423529 PMCID: PMC3059686 DOI: 10.3389/fnsyn.2010.00143] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2010] [Accepted: 08/23/2010] [Indexed: 11/13/2022] Open
Abstract
Central inter-neuronal synapses employ various molecular mechanisms to sustain neurotransmitter release during phases of high-frequency synaptic activity. One of the features ensuring this property is the presence of a pool of synaptic vesicles (SVs) in the presynaptic terminal. At rest and low rates of stimulation, most of the vesicles composing this pool remain in a tight cluster. They are actively utilized when neurons fire action potentials at higher rates and the capability of the recycling machinery is limited. In addition, SV clusters are capable of migrating between release sites and reassemble into clusters at neighboring active zones (AZs). Within the cluster, thin "tethers" interconnect SVs. These dynamic filamentous structures are reorganized during stimulation thereby releasing SVs from the cluster. So far, one protein family, the synapsins, which bind actin filaments and vesicles in a phosphorylation-dependent manner, has been implicated in SV clustering in vertebrate synapses. As evident from recent studies, many endocytic proteins reside in the SV cluster in addition to synapsin. Here we discuss alternative possible mechanisms involved in the organization of this population of SVs. We propose a model in which synapsins together with other synaptic proteins, a large proportion of which is involved in SV recycling, form a dynamic proteinaceous "matrix" which limits the mobility of SVs. Actin filaments, however, do not seem to contribute to SV crosslinking within the SV cluster, but instead they are present peripherally to it, at sites of neurotransmitter release, and at sites of SV recycling.
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Affiliation(s)
- Arndt Pechstein
- Department of Neuroscience, Developmental Biology for Regenerative Medicine, Karolinska Institutet Stockholm, Sweden
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35
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Salinas S, Schiavo G, Kremer EJ. A hitchhiker's guide to the nervous system: the complex journey of viruses and toxins. Nat Rev Microbiol 2010; 8:645-55. [PMID: 20706281 DOI: 10.1038/nrmicro2395] [Citation(s) in RCA: 130] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
To reach the central nervous system (CNS), pathogens have to circumvent the wall of tightly sealed endothelial cells that compose the blood-brain barrier. Neuronal projections that connect to peripheral cells and organs are the Achilles heels in CNS isolation. Some viruses and bacterial toxins interact with membrane receptors that are present at nerve terminals to enter the axoplasm. Pathogens can then be mistaken for cargo and recruit trafficking components, allowing them to undergo long-range axonal transport to neuronal cell bodies. In this Review, we highlight the strategies used by pathogens to exploit axonal transport during CNS invasion.
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Affiliation(s)
- Sara Salinas
- Institut de Génétique Moléculaire de Montpellier, CNRS UMR 5535, 34293 Montpellier Cedex 5, France.
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Zefirov AL, Grigor'ev PN. Sensitivity of intracellular calcium-binding sites for exo- and endocytosis of synaptic vesicles to Sr, Ba, and Mg ions. ACTA ACUST UNITED AC 2010; 40:389-96. [PMID: 20339941 DOI: 10.1007/s11055-010-9269-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2008] [Indexed: 11/28/2022]
Abstract
Experiments on frog cutaneous-thoracic muscle preparations using electrophysiological (intra- and extracellular recording of postsynaptic signals) and optical (confocal microscopy with the fluorescent endocytic stain FM 1-43) methods were performed to study neurotransmitter secretion and the processes of exo- and endocytosis of synaptic vesicles in motor nerve endings on substitution of extracellular Ca ions with other alkaline earth metals (Sr, Ba, or Mg). Massive asynchronous exocytosis was induced by high-potassium solution, while synchronous exocytosis was induced by prolonged high-frequency stimulation of the motor nerve. The calcium-binding site for asynchronous exocytosis was found to be sensitive to Sr, Ba, and Mg ions, while the site for synchronous exocytosis was only sensitive to Sr ions. During stimulation of both asynchronous and synchronous exocytosis, the calcium-binding site for endocytosis was sensitive to Sr and Ba ions and had the lowest affinity for Sr ions. These experiments led to the conclusion that different intracellular calcium-binding sites exist for the exocytosis and endocytosis of synaptic vesicles and that they have different sensitivities for alkaline earth metals.
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Affiliation(s)
- A L Zefirov
- Kazan State Medical University, Kazan, Russia.
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Regulation of synaptic vesicle recycling by complex formation between intersectin 1 and the clathrin adaptor complex AP2. Proc Natl Acad Sci U S A 2010; 107:4206-11. [PMID: 20160082 DOI: 10.1073/pnas.0911073107] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Clathrin-mediated synaptic vesicle (SV) recycling involves the spatiotemporally controlled assembly of clathrin coat components at phosphatidylinositiol (4, 5)-bisphosphate [PI(4,5)P(2)]-enriched membrane sites within the periactive zone. Such spatiotemporal control is needed to coordinate SV cargo sorting with clathrin/AP2 recruitment and to restrain membrane fission and synaptojanin-mediated uncoating until membrane deformation and clathrin coat assembly are completed. The molecular events underlying these control mechanisms are unknown. Here we show that the endocytic SH3 domain-containing accessory protein intersectin 1 scaffolds the endocytic process by directly associating with the clathrin adaptor AP2. Acute perturbation of the intersectin 1-AP2 interaction in lamprey synapses in situ inhibits the onset of SV recycling. Structurally, complex formation can be attributed to the direct association of hydrophobic peptides within the intersectin 1 SH3A-B linker region with the "side sites" of the AP2 alpha- and beta-appendage domains. AP2 appendage association of the SH3A-B linker region inhibits binding of the inositol phosphatase synaptojanin 1 to intersectin 1. These data identify the intersectin-AP2 complex as an important regulator of clathrin-mediated SV recycling in synapses.
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38
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Synaptic and endosomal localization of active gamma-secretase in rat brain. PLoS One 2010; 5:e8948. [PMID: 20126630 PMCID: PMC2812513 DOI: 10.1371/journal.pone.0008948] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2009] [Accepted: 01/05/2010] [Indexed: 12/02/2022] Open
Abstract
Background A key player in the development of Alzheimer's disease (AD) is the γ-secretase complex consisting of at least four components: presenilin, nicastrin, Aph-1 and Pen-2. γ-Secretase is crucial for the generation of the neurotoxic amyloid β-peptide (Aβ) but also takes part in the processing of many other substrates. In cell lines, active γ-secretase has been found to localize primarily to the Golgi apparatus, endosomes and plasma membranes. However, no thorough studies have been performed to show the subcellular localization of the active γ-secretase in the affected organ of AD, namely the brain. Principal Findings We show by subcellular fractionation of rat brain that high γ-secretase activity, as assessed by production of Aβ40, is present in an endosome- and plasma membrane-enriched fraction of an iodixanol gradient. We also prepared crude synaptic vesicles as well as synaptic membranes and both fractions showed high Aβ40 production and contained high amounts of the γ-secretase components. Further purification of the synaptic vesicles verified the presence of the γ-secretase components in these compartments. The localization of an active γ-secretase in synapses and endosomes was confirmed in rat brain sections and neuronal cultures by using a biotinylated γ-secretase inhibitor together with confocal microscopy. Significance The information about the subcellular localization of γ-secretase in brain is important for the understanding of the molecular mechanisms of AD. Furthermore, the identified fractions can be used as sources for highly active γ-secretase.
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Abstract
During neurotransmitter release, SVs (synaptic vesicles) fuse at the active zone and are recovered predominantly via clathrin-mediated endocytosis at the presynaptic compartment surrounding the site of release, referred to as the periactive zone. Exo- and endo-cytosis in synapses are tightly temporarily and spatially coupled to sustain synaptic transmission. The molecular mechanisms linking these two cellular events, which take place in separate compartments of the nerve terminal, remain largely enigmatic. Several lines of evidence indicate that multiple factors may be involved in exocytic–endocytic coupling including SV integral membrane proteins, SV membrane lipids and the membrane-associated actin cytoskeleton. A number of recent studies also indicate that multimodular adaptor proteins shuttling between the active and periactive zones aid the dynamic assembly of macromolecular protein complexes that execute the exo- and endo-cytic limbs of the SV cycle. Here, we discuss recent evidence implicating the multidomain scaffolding and adaptor protein ITSN1 (intersectin 1) as a central regulator of SV cycling.
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40
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Abstract
Central nerve terminals release neurotransmitter in response to a wide variety of stimuli. Because maintenance of neurotransmitter release is dependent on the continual supply of synaptic vesicles (SVs), nerve terminals possess an array of endocytosis modes to retrieve and recycle SV membrane and proteins. During mild stimulation conditions, single SV retrieval modes such as clathrin-mediated endocytosis predominate. However, during increased neuronal activity, additional SV retrieval capacity is required, which is provided by activity-dependent bulk endocytosis (ADBE). ADBE is the dominant SV retrieval mechanism during elevated neuronal activity. It is a high capacity SV retrieval mode that is immediately triggered during such stimulation conditions. This review will summarize the current knowledge regarding the molecular mechanism of ADBE, including molecules required for its triggering and subsequent steps, including SV budding from bulk endosomes. The molecular relationship between ADBE and the SV reserve pool will also be discussed. It is becoming clear that an understanding of the molecular physiology of ADBE will be of critical importance in attempts to modulate both normal and abnormal synaptic function during intense neuronal activity.
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Affiliation(s)
- Emma L. Clayton
- Membrane Biology Group, Centre for Integrative Physiology, George Square, University of Edinburgh, EH8 9XD, Scotland, U.K
| | - Michael A. Cousin
- Membrane Biology Group, Centre for Integrative Physiology, George Square, University of Edinburgh, EH8 9XD, Scotland, U.K
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41
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Abstract
Exocytosis and endocytosis of synaptic vesicles are tightly coordinated to maintain a steady supply of new vesicles during periods of extended neuronal stimulation. Yao et al. (2009) now report that a synaptic vesicle membrane protein named Flower promotes endocytosis at neuromuscular junctions in the fruit fly Drosophila.
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Affiliation(s)
- Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, D-37075 Göttingen, Germany.
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42
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Davanger S, Manahan-Vaughan D, Mulle C, Storm-Mathisen J, Ottersen OP. Protein trafficking, targeting, and interaction at the glutamate synapse. Neuroscience 2008; 158:1-3. [PMID: 19027053 DOI: 10.1016/j.neuroscience.2008.11.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- S Davanger
- Institute of Basic Medical Sciences, Department of Anatomy, University of Oslo, P.O. Box 1105 Blindern, 0317 Oslo, Norway.
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