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Saenz J, Khezerlou E, Aggarwal M, Shaikh A, Ganti N, Herborg F, Pan PY. Parkinson's disease gene, Synaptojanin1, dysregulates the surface maintenance of the dopamine transporter. NPJ Parkinsons Dis 2024; 10:148. [PMID: 39117637 PMCID: PMC11310474 DOI: 10.1038/s41531-024-00769-0] [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: 03/06/2024] [Accepted: 07/29/2024] [Indexed: 08/10/2024] Open
Abstract
Missense mutations of PARK20/SYNJ1 (synaptojanin1/Synj1) were found in complex forms of familial Parkinsonism. However, the Synj1-regulated molecular and cellular changes associated with dopaminergic dysfunction remain unknown. We now report a fast depletion of evoked dopamine and impaired maintenance of the axonal dopamine transporter (DAT) in the Synj1 haploinsufficient (Synj1+/-) neurons. While Synj1 has been traditionally known to facilitate the endocytosis of synaptic vesicles, we provide in vitro and in vivo evidence demonstrating that Synj1 haploinsufficiency results in an increase of total DAT but a reduction of the surface DAT. Synj1+/- neurons exhibit maladaptive DAT trafficking, which could contribute to the altered DA release. We showed that the loss of surface DAT is associated with the impaired 5'-phosphatase activity and the hyperactive PI(4,5)P2-PKCβ pathway downstream of Synj1 deficiency. Thus, our findings provided important mechanistic insight for Synj1-regulated DAT trafficking integral to dysfunctional DA signaling, which might be relevant to early Parkinsonism.
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Affiliation(s)
- Jacqueline Saenz
- Department of Neuroscience and Cell Biology, Rutgers University Robert Wood Johnson Medical School, 675 Hoes Lane West, Piscataway, NJ, 08854, USA
- Rutgers Graduate School of Biomedical Sciences, Molecular Biosciences Graduate Program, 675 Hoes Lane West, Piscataway, NJ, 08854, USA
| | - Elnaz Khezerlou
- Department of Neuroscience and Cell Biology, Rutgers University Robert Wood Johnson Medical School, 675 Hoes Lane West, Piscataway, NJ, 08854, USA
| | - Meha Aggarwal
- Department of Neuroscience and Cell Biology, Rutgers University Robert Wood Johnson Medical School, 675 Hoes Lane West, Piscataway, NJ, 08854, USA
| | - Amina Shaikh
- Department of Neuroscience and Cell Biology, Rutgers University Robert Wood Johnson Medical School, 675 Hoes Lane West, Piscataway, NJ, 08854, USA
| | - Naga Ganti
- Department of Neuroscience and Cell Biology, Rutgers University Robert Wood Johnson Medical School, 675 Hoes Lane West, Piscataway, NJ, 08854, USA
| | - Freja Herborg
- Department of Neuroscience, University of Copenhagen, Blegdamsvej 3, DK-2200, Copenhagen, Denmark
| | - Ping-Yue Pan
- Department of Neuroscience and Cell Biology, Rutgers University Robert Wood Johnson Medical School, 675 Hoes Lane West, Piscataway, NJ, 08854, USA.
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2
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Small C, Harper C, Jiang A, Kontaxi C, Pronot M, Yak N, Malapaka A, Davenport EC, Wallis TP, Gormal RS, Joensuu M, Martínez-Mármol R, Cousin MA, Meunier FA. SV2A controls the surface nanoclustering and endocytic recruitment of Syt1 during synaptic vesicle recycling. J Neurochem 2024. [PMID: 39091022 DOI: 10.1111/jnc.16186] [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: 02/12/2024] [Revised: 07/04/2024] [Accepted: 07/06/2024] [Indexed: 08/04/2024]
Abstract
Following exocytosis, the recapture of plasma membrane-stranded vesicular proteins into recycling synaptic vesicles (SVs) is essential for sustaining neurotransmission. Surface clustering of vesicular proteins has been proposed to act as a 'pre-assembly' mechanism for endocytosis that ensures high-fidelity retrieval of SV cargo. Here, we used single-molecule imaging to examine the nanoclustering of synaptotagmin-1 (Syt1) and synaptic vesicle protein 2A (SV2A) in hippocampal neurons. Syt1 forms surface nanoclusters through the interaction of its C2B domain with SV2A, which are sensitive to mutations in this domain (Syt1K326A/K328A) and SV2A knockdown. SV2A co-clustering with Syt1 is reduced by blocking SV2A's cognate interaction with Syt1 (SV2AT84A). Surprisingly, impairing SV2A-Syt1 nanoclustering enhanced the plasma membrane recruitment of key endocytic protein dynamin-1, causing accelerated Syt1 endocytosis, altered intracellular sorting and decreased trafficking of Syt1 to Rab5-positive endocytic compartments. Therefore, SV2A and Syt1 are segregated from the endocytic machinery in surface nanoclusters, limiting dynamin recruitment and negatively regulating Syt1 entry into recycling SVs.
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Affiliation(s)
- Christopher Small
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, the University of Queensland, Brisbane, Queensland, Australia
| | - Callista Harper
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
- Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, UK
- Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK
| | - Anmin Jiang
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, the University of Queensland, Brisbane, Queensland, Australia
| | - Christiana Kontaxi
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
- Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, UK
- Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK
| | - Marie Pronot
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
- Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, UK
- Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK
| | - Nyakuoy Yak
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, the University of Queensland, Brisbane, Queensland, Australia
| | - Anusha Malapaka
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, the University of Queensland, Brisbane, Queensland, Australia
| | - Elizabeth C Davenport
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
- Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, UK
- Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK
| | - Tristan P Wallis
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, the University of Queensland, Brisbane, Queensland, Australia
| | - Rachel S Gormal
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, the University of Queensland, Brisbane, Queensland, Australia
| | - Merja Joensuu
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, the University of Queensland, Brisbane, Queensland, Australia
| | - Ramón Martínez-Mármol
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, the University of Queensland, Brisbane, Queensland, Australia
| | - Michael A Cousin
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
- Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, UK
- Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK
| | - Frédéric A Meunier
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, the University of Queensland, Brisbane, Queensland, Australia
- School of Biomedical Sciences, the University of Queensland, Brisbane, Queensland, Australia
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3
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Asmerian H, Alberts J, Sanetra AM, Diaz AJ, Silm K. Role of adaptor protein complexes in generating functionally distinct synaptic vesicle pools. J Physiol 2024. [PMID: 39034608 DOI: 10.1113/jp286179] [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: 04/24/2024] [Accepted: 07/05/2024] [Indexed: 07/23/2024] Open
Abstract
The synaptic vesicle (SV) cycle ensures the release of neurotransmitters and the replenishment of SVs to sustain neuronal activity. Multiple endocytosis and sorting pathways contribute to the recapture of the SV membrane and proteins after fusion. Adaptor protein (AP) complexes are among the critical components of the SV retrieval machinery. The canonical clathrin adaptor AP2 ensures the replenishment of most SVs across many neuronal populations. An alternative AP1/AP3-dependent process mediates the formation of a subset of SVs that differ from AP2 vesicles in molecular composition and respond preferentially during higher frequency firing. Furthermore, recent studies show that vesicular transporters for different neurotransmitters depend to a different extent on the AP3 pathway and this affects the release properties of the respective neurotransmitters. This review focuses on the current understanding of the AP-dependent molecular and functional diversity among SVs. We also discuss the contribution of these pathways to the regulation of neurotransmitter release across neuronal populations.
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Affiliation(s)
- Hrach Asmerian
- Center for Neural Science and Medicine, Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- Board of Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- Department of Neurology, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Jacob Alberts
- Center for Neural Science and Medicine, Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- Board of Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- Department of Neurology, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Anna M Sanetra
- Center for Neural Science and Medicine, Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- Board of Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- Department of Neurology, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Alexia J Diaz
- Center for Neural Science and Medicine, Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- Board of Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- Department of Neurology, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Katlin Silm
- Center for Neural Science and Medicine, Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- Board of Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- Department of Neurology, Cedars-Sinai Medical Center, Los Angeles, CA, USA
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4
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Saenz J, Khezerlou E, Aggarwal M, Shaikh A, Ganti N, Herborg F, Pan PY. Parkinson's disease gene, Synaptojanin1, dysregulates the surface maintenance of the dopamine transporter. RESEARCH SQUARE 2024:rs.3.rs-4021466. [PMID: 38559229 PMCID: PMC10980101 DOI: 10.21203/rs.3.rs-4021466/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Missense mutations of PARK20/SYNJ1 (synaptojanin1/Synj1) have been linked to complex forms of familial parkinsonism, however, the molecular and cellular changes associated with dopaminergic dysfunction remains unknown. We now report fast depletion of evoked dopamine (DA) and altered maintenance of the axonal dopamine transporter (DAT) in the Synj1+/- neurons. While Synj1 has been traditionally known to facilitate the endocytosis of synaptic vesicles, we demonstrated that axons of cultured Synj1+/- neurons exhibit an increase of total DAT but a reduction of the surface DAT, which could be exacerbated by neuronal activity. We revealed that the loss of surface DAT is specifically associated with the impaired 5'-phosphatase activity of Synj1 and the hyperactive downstream PI(4,5)P2-PKCβ pathway. Thus, our findings provided important mechanistic insight for Synj1-regulated DAT trafficking integral to dysfunctional DA signaling in early parkinsonism.
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Affiliation(s)
- Jacqueline Saenz
- Department of Neuroscience and Cell Biology, Rutgers University Robert Wood Johnson Medical School, 675 Hoes Lane West, Piscataway, NJ 08854, USA
- Rutgers Graduate School of Biomedical Sciences, Molecular Biosciences Graduate Program, 675 Hoes Lane West, Piscataway, NJ 08854, USA
| | - Elnaz Khezerlou
- Department of Neuroscience and Cell Biology, Rutgers University Robert Wood Johnson Medical School, 675 Hoes Lane West, Piscataway, NJ 08854, USA
| | - Meha Aggarwal
- Department of Neuroscience and Cell Biology, Rutgers University Robert Wood Johnson Medical School, 675 Hoes Lane West, Piscataway, NJ 08854, USA
| | - Amina Shaikh
- Department of Neuroscience and Cell Biology, Rutgers University Robert Wood Johnson Medical School, 675 Hoes Lane West, Piscataway, NJ 08854, USA
| | - Naga Ganti
- Department of Neuroscience and Cell Biology, Rutgers University Robert Wood Johnson Medical School, 675 Hoes Lane West, Piscataway, NJ 08854, USA
| | - Freja Herborg
- Department of Neuroscience, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen, Denmark
| | - Ping-Yue Pan
- Department of Neuroscience and Cell Biology, Rutgers University Robert Wood Johnson Medical School, 675 Hoes Lane West, Piscataway, NJ 08854, USA
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5
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Bolz S, Kaempf N, Puchkov D, Krauss M, Russo G, Soykan T, Schmied C, Lehmann M, Müller R, Schultz C, Perrais D, Maritzen T, Haucke V. Synaptotagmin 1-triggered lipid signaling facilitates coupling of exo- and endocytosis. Neuron 2023; 111:3765-3774.e7. [PMID: 37738980 DOI: 10.1016/j.neuron.2023.08.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 06/16/2023] [Accepted: 08/16/2023] [Indexed: 09/24/2023]
Abstract
Exocytosis and endocytosis are essential physiological processes and are of prime importance for brain function. Neurotransmission depends on the Ca2+-triggered exocytosis of synaptic vesicles (SVs). In neurons, exocytosis is spatiotemporally coupled to the retrieval of an equal amount of membrane and SV proteins by compensatory endocytosis. How exocytosis and endocytosis are balanced to maintain presynaptic membrane homeostasis and, thereby, sustain brain function is essentially unknown. We combine mouse genetics with optical imaging to show that the SV calcium sensor Synaptotagmin 1 couples exocytic SV fusion to the endocytic retrieval of SV membranes by promoting the local activity-dependent formation of the signaling lipid phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) at presynaptic sites. Interference with these mechanisms impairs PI(4,5)P2-triggered SV membrane retrieval but not exocytic SV fusion. Our findings demonstrate that the coupling of SV exocytosis and endocytosis involves local Synaptotagmin 1-induced lipid signaling to maintain presynaptic membrane homeostasis in central nervous system neurons.
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Affiliation(s)
- Svenja Bolz
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Robert-Rössle-Str. 10, 13125 Berlin, Germany
| | - Natalie Kaempf
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Robert-Rössle-Str. 10, 13125 Berlin, Germany
| | - Dmytro Puchkov
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Robert-Rössle-Str. 10, 13125 Berlin, Germany
| | - Michael Krauss
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Robert-Rössle-Str. 10, 13125 Berlin, Germany
| | - Giulia Russo
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Robert-Rössle-Str. 10, 13125 Berlin, Germany
| | - Tolga Soykan
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Robert-Rössle-Str. 10, 13125 Berlin, Germany
| | - Christopher Schmied
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Robert-Rössle-Str. 10, 13125 Berlin, Germany
| | - Martin Lehmann
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Robert-Rössle-Str. 10, 13125 Berlin, Germany
| | - Rainer Müller
- European Molecular Biology Laboratory (EMBL), Cell Biology and Biophysics Unit, 69117 Heidelberg, Germany
| | - Carsten Schultz
- European Molecular Biology Laboratory (EMBL), Cell Biology and Biophysics Unit, 69117 Heidelberg, Germany; Department of Chemical Physiology & Biochemistry, Oregon Health & Science University (OHSU), Portland, OR 97239, USA
| | - David Perrais
- University of Bordeaux, CNRS, Interdisciplinary Institute for Neuroscience, UMR 5297, 33000 Bordeaux, France
| | - Tanja Maritzen
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Robert-Rössle-Str. 10, 13125 Berlin, Germany; Department of Nanophysiology, University of Kaiserslautern-Landau, 67663 Kaiserslautern, Germany
| | - Volker Haucke
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Robert-Rössle-Str. 10, 13125 Berlin, Germany; Faculty of Biology, Chemistry, Pharmacy, Freie Universität Berlin, 14195 Berlin, Germany; NeuroCure Cluster of Excellence, Charité Universitätsmedizin Berlin, 10117 Berlin, Germany.
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6
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Cocaine-regulated trafficking of dopamine transporters in cultured neurons revealed by a pH sensitive reporter. iScience 2022; 26:105782. [PMID: 36594015 PMCID: PMC9804146 DOI: 10.1016/j.isci.2022.105782] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Revised: 11/07/2022] [Accepted: 12/07/2022] [Indexed: 12/14/2022] Open
Abstract
Cocaine acts by inhibiting plasma membrane dopamine transporter (DAT) function and altering its surface expression. The precise manner and mechanism by which cocaine regulates DAT trafficking, especially at neuronal processes, are poorly understood. In this study, we engineered and validated the use of DAT-pHluorin for studying DAT localization and its dynamic trafficking at neuronal processes of cultured mouse midbrain neurons. We demonstrate that unlike neuronal soma and dendrites, which contain a majority of the DATs in weakly acidic intracellular compartments, axonal DATs at both shafts and boutons are primarily (75%) localized to the plasma membrane, whereas large varicosities contain abundant intracellular DAT within acidic intracellular structures. We also demonstrate that cocaine exposure leads to a Synaptojanin1-sensitive DAT internalization process followed by membrane reinsertion that lasts for days. Thus, our study reveals the previously unknown dynamics and molecular regulation for cocaine-regulated DAT trafficking in neuronal processes.
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7
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Ponterio G, Faustini G, El Atiallah I, Sciamanna G, Meringolo M, Tassone A, Imbriani P, Cerri S, Martella G, Bonsi P, Bellucci A, Pisani A. Alpha-Synuclein is Involved in DYT1 Dystonia Striatal Synaptic Dysfunction. Mov Disord 2022; 37:949-961. [PMID: 35420219 PMCID: PMC9323501 DOI: 10.1002/mds.29024] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Revised: 02/24/2022] [Accepted: 03/19/2022] [Indexed: 12/26/2022] Open
Abstract
Background The neuronal protein alpha‐synuclein (α‐Syn) is crucially involved in Parkinson's disease pathophysiology. Intriguingly, torsinA (TA), the protein causative of DYT1 dystonia, has been found to accumulate in Lewy bodies and to interact with α‐Syn. Both proteins act as molecular chaperones and control synaptic machinery. Despite such evidence, the role of α‐Syn in dystonia has never been investigated. Objective We explored whether α‐Syn and N‐ethylmaleimide sensitive fusion attachment protein receptor proteins (SNAREs), that are known to be modulated by α‐Syn, may be involved in DYT1 dystonia synaptic dysfunction. Methods We used electrophysiological and biochemical techniques to study synaptic alterations in the dorsal striatum of the Tor1a+/Δgag mouse model of DYT1 dystonia. Results In the Tor1a+/Δgag DYT1 mutant mice, we found a significant reduction of α‐Syn levels in whole striata, mainly involving glutamatergic corticostriatal terminals. Strikingly, the striatal levels of the vesicular SNARE VAMP‐2, a direct α‐Syn interactor, and of the transmembrane SNARE synaptosome‐associated protein 23 (SNAP‐23), that promotes glutamate synaptic vesicles release, were markedly decreased in mutant mice. Moreover, we detected an impairment of miniature glutamatergic postsynaptic currents (mEPSCs) recorded from striatal spiny neurons, in parallel with a decreased asynchronous release obtained by measuring quantal EPSCs (qEPSCs), which highlight a robust alteration in release probability. Finally, we also observed a significant reduction of TA striatal expression in α‐Syn null mice. Conclusions Our data demonstrate an unprecedented relationship between TA and α‐Syn, and reveal that α‐Syn and SNAREs alterations characterize the synaptic dysfunction underlying DYT1 dystonia. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson Movement Disorder Society.
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Affiliation(s)
- Giulia Ponterio
- Laboratory of Neurophysiology and Plasticity, IRCCS Fondazione Santa Lucia, Rome, Italy
| | - Gaia Faustini
- Division of Pharmacology, Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
| | - Ilham El Atiallah
- Laboratory of Neurophysiology and Plasticity, IRCCS Fondazione Santa Lucia, Rome, Italy.,Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy
| | - Giuseppe Sciamanna
- Laboratory of Neurophysiology and Plasticity, IRCCS Fondazione Santa Lucia, Rome, Italy.,UniCamillus-Saint Camillus International University of Health Sciences, Rome, Italy
| | - Maria Meringolo
- Laboratory of Neurophysiology and Plasticity, IRCCS Fondazione Santa Lucia, Rome, Italy
| | - Annalisa Tassone
- Laboratory of Neurophysiology and Plasticity, IRCCS Fondazione Santa Lucia, Rome, Italy
| | - Paola Imbriani
- Laboratory of Neurophysiology and Plasticity, IRCCS Fondazione Santa Lucia, Rome, Italy
| | | | - Giuseppina Martella
- Laboratory of Neurophysiology and Plasticity, IRCCS Fondazione Santa Lucia, Rome, Italy
| | - Paola Bonsi
- Laboratory of Neurophysiology and Plasticity, IRCCS Fondazione Santa Lucia, Rome, Italy
| | - Arianna Bellucci
- Division of Pharmacology, Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
| | - Antonio Pisani
- IRCCS Fondazione Mondino, Pavia, Italy.,Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy
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8
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Sasaki-Hamada S, Sanai E, Kanemaru M, Kamanaka G, Oka JI. Long-term exposure to high glucose induces changes in the expression of AMPA receptor subunits and glutamate transmission in primary cultured cortical neurons. Biochem Biophys Res Commun 2022; 589:48-54. [PMID: 34891041 DOI: 10.1016/j.bbrc.2021.11.108] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Revised: 11/25/2021] [Accepted: 11/30/2021] [Indexed: 12/14/2022]
Abstract
Hyperglycemia, which occurs under the diabetic conditions, induces serious diabetic complications. Diabetic encephalopathy has been defined as one of the major complications of diabetes, and is characterized by neurochemical and neurodegenerative changes. However, little is known about the effect of long-term exposure to high glucose on neuronal cells. In the present study, we showed that exposure to glutamate (100 mM) for 7 days induced toxicity in primary cortical neurons using the MTT assay. Additionally, high glucose increased the sensitivity of AMPA- or NMDA-induced neurotoxicity, and decreased extracellular glutamate levels in primary cortical neurons. In Western blot analyses, the protein levels of the GluA1 and GluA2 subunits of the AMPA receptor as well as synaptophysin in neurons treated with high glucose were significantly increased compared with the control (25 mM glucose). Therefore, long-term exposure to high glucose induced neuronal death through the disruption of glutamate homeostasis.
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Affiliation(s)
- Sachie Sasaki-Hamada
- Laboratory of Pharmacology, Faculty of Pharmaceutical Sciences, Tokyo University of Science, Chiba, 278-8510, Japan; Department of Physiology, School of Allied Health Sciences, Kitasato University, Sagamihara, 252-0373, Japan.
| | - Emi Sanai
- Laboratory of Pharmacology, Faculty of Pharmaceutical Sciences, Tokyo University of Science, Chiba, 278-8510, Japan
| | - Mariko Kanemaru
- Laboratory of Pharmacology, Faculty of Pharmaceutical Sciences, Tokyo University of Science, Chiba, 278-8510, Japan
| | - Gaku Kamanaka
- Laboratory of Pharmacology, Faculty of Pharmaceutical Sciences, Tokyo University of Science, Chiba, 278-8510, Japan
| | - Jun-Ichiro Oka
- Laboratory of Pharmacology, Faculty of Pharmaceutical Sciences, Tokyo University of Science, Chiba, 278-8510, Japan.
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9
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López-Hernández T, Takenaka KI, Mori Y, Kongpracha P, Nagamori S, Haucke V, Takamori S. Clathrin-independent endocytic retrieval of SV proteins mediated by the clathrin adaptor AP-2 at mammalian central synapses. eLife 2022; 11:e71198. [PMID: 35014951 PMCID: PMC8752090 DOI: 10.7554/elife.71198] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Accepted: 12/28/2021] [Indexed: 12/25/2022] Open
Abstract
Neurotransmission is based on the exocytic fusion of synaptic vesicles (SVs) followed by endocytic membrane retrieval and the reformation of SVs. Conflicting models have been proposed regarding the mechanisms of SV endocytosis, most notably clathrin/adaptor protein complex 2 (AP-2)-mediated endocytosis and clathrin-independent ultrafast endocytosis. Partitioning between these pathways has been suggested to be controlled by temperature and stimulus paradigm. We report on the comprehensive survey of six major SV proteins to show that SV endocytosis in mouse hippocampal neurons at physiological temperature occurs independent of clathrin while the endocytic retrieval of a subset of SV proteins including the vesicular transporters for glutamate and GABA depend on sorting by the clathrin adaptor AP-2. Our findings highlight a clathrin-independent role of the clathrin adaptor AP-2 in the endocytic retrieval of select SV cargos from the presynaptic cell surface and suggest a revised model for the endocytosis of SV membranes at mammalian central synapses.
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Affiliation(s)
| | - Koh-ichiro Takenaka
- Laboratory of Neural Membrane Biology, Graduate School of Brain Science, Doshisha UniversityKyotoJapan
| | - Yasunori Mori
- Laboratory of Neural Membrane Biology, Graduate School of Brain Science, Doshisha UniversityKyotoJapan
| | - Pornparn Kongpracha
- Department of Laboratory Medicine, The Jikei University School of MedicineTokyoJapan
| | - Shushi Nagamori
- Department of Laboratory Medicine, The Jikei University School of MedicineTokyoJapan
| | - Volker Haucke
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP)BerlinGermany
| | - Shigeo Takamori
- Laboratory of Neural Membrane Biology, Graduate School of Brain Science, Doshisha UniversityKyotoJapan
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10
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Egashira Y, Katsurabayashi S, Takamori S. Quantitative Analysis of Presynaptic Vesicle Luminal pH in Cultured Neurons. Methods Mol Biol 2022; 2417:45-58. [PMID: 35099790 DOI: 10.1007/978-1-0716-1916-2_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Newly generated synaptic vesicles (SVs) are re-acidified by the activity of the vacuolar-type H+-ATPases. Since H+ gradient across SV membrane drives neurotransmitter uptake into SVs, precise measurements of steady-state vesicular pH and dynamics of re-acidification process will provide important information concerning the H+-driven neurotransmitter uptake. Indeed, we recently demonstrated distinct features of steady state and dynamics of vesicular pH between glutamatergic vesicles and GABAergic vesicles in cultured hippocampal neurons. In this article, we focus on an experimental protocol and setup required to determine steady-state luminal pH of SVs in living neurons. This protocol is composed of efficient expression of a pH-sensitive fluorescent protein in the lumen of SVs in cultured neurons, and recordings of its fluorescence changes under a conventional fluorescent microscope during local applications of acidic buffer and ionophores-containing solution at a given pH. The method described here can be easily applied for measuring luminal pH of different types of secretory organelles and other acidic organelles such as lysosomes and endosomes in cultured cell preparations.
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Affiliation(s)
- Yoshihiro Egashira
- Laboratory of Neural Membrane Biology, Graduate School of Brain Science, Doshisha University, Kyoto, Japan.
- Department of Physiology, Faculty of Medicine, Osaka Medical and Pharmaceutical University, Osaka, Japan.
| | - Shutaro Katsurabayashi
- Department of Neuropharmacology, Faculty of Pharmaceutical Sciences, Fukuoka University, Fukuoka, Japan
| | - Shigeo Takamori
- Laboratory of Neural Membrane Biology, Graduate School of Brain Science, Doshisha University, Kyoto, Japan.
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11
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Pulido C, Ryan TA. Synaptic vesicle pools are a major hidden resting metabolic burden of nerve terminals. SCIENCE ADVANCES 2021; 7:eabi9027. [PMID: 34860552 PMCID: PMC8641928 DOI: 10.1126/sciadv.abi9027] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Accepted: 10/14/2021] [Indexed: 05/15/2023]
Abstract
The brain is a metabolically fragile organ as compromises in fuel availability rapidly degrade cognitive function. Nerve terminals are likely loci of this vulnerability as they do not store sufficient ATP molecules, needing to synthesize them during activity or suffer acute degradation in performance. The ability of on-demand ATP synthesis to satisfy activity-driven ATP hydrolysis will depend additionally on the magnitude of local resting metabolic processes. We show here that synaptic vesicle (SV) pools are a major source of presynaptic basal energy consumption. This basal metabolic processes arises from SV-resident V-ATPases compensating for a hidden resting H+ efflux from the SV lumen. We show that this steady-state H+ efflux (i) is mediated by vesicular neurotransmitter transporters, (ii) is independent of the SV cycle, (iii) accounts for up to 44% of the resting synaptic energy consumption, and (iv) contributes substantially to nerve terminal intolerance of fuel deprivation.
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Affiliation(s)
- Camila Pulido
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
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12
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Cousin MA. Synaptophysin-dependent synaptobrevin-2 trafficking at the presynapse-Mechanism and function. J Neurochem 2021; 159:78-89. [PMID: 34468992 DOI: 10.1111/jnc.15499] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Revised: 08/26/2021] [Accepted: 08/28/2021] [Indexed: 12/30/2022]
Abstract
Synaptobrevin-2 (Syb2) is a soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) that is essential for neurotransmitter release. It is the most numerous protein on a synaptic vesicle (SV) and drives SV fusion via interactions with its cognate SNARE partners on the presynaptic plasma membrane. Synaptophysin (Syp) is the second most abundant protein on SVs; however, in contrast to Syb2, it has no obligatory role in neurotransmission. Syp interacts with Syb2 on SVs, and the molecular nature of its interaction with Syb2 and its physiological role has been debated for decades. However, recent studies have revealed that the sole physiological role of Syp at the presynapse is to ensure the efficient retrieval of Syb2 during SV endocytosis. In this review, current theories surrounding the role of Syp in Syb2 trafficking will be discussed, in addition to the debate regarding the molecular nature of their interaction. A unifying model is presented that describes how Syp controls Syb2 function as part of an integrated mechanism involving key molecular players such as intersectin-1 and AP180/CALM. Finally, key future questions surrounding the role of Syp-dependent Syb2 trafficking will be posed, with respect to brain function in health and disease.
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Affiliation(s)
- Michael A Cousin
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, Scotland, UK.,Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, Scotland, UK.,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, Scotland, UK
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13
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Almeida RG, Williamson JM, Madden ME, Early JJ, Voas MG, Talbot WS, Bianco IH, Lyons DA. Myelination induces axonal hotspots of synaptic vesicle fusion that promote sheath growth. Curr Biol 2021; 31:3743-3754.e5. [PMID: 34270947 PMCID: PMC8445327 DOI: 10.1016/j.cub.2021.06.036] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Revised: 05/17/2021] [Accepted: 06/11/2021] [Indexed: 02/08/2023]
Abstract
Myelination of axons by oligodendrocytes enables fast saltatory conduction. Oligodendrocytes are responsive to neuronal activity, which has been shown to induce changes to myelin sheaths, potentially to optimize conduction and neural circuit function. However, the cellular bases of activity-regulated myelination in vivo are unclear, partly due to the difficulty of analyzing individual myelinated axons over time. Activity-regulated myelination occurs in specific neuronal subtypes and can be mediated by synaptic vesicle fusion, but several questions remain: it is unclear whether vesicular fusion occurs stochastically along axons or in discrete hotspots during myelination and whether vesicular fusion regulates myelin targeting, formation, and/or growth. It is also unclear why some neurons, but not others, exhibit activity-regulated myelination. Here, we imaged synaptic vesicle fusion in individual neurons in living zebrafish and documented robust vesicular fusion along axons during myelination. Surprisingly, we found that axonal vesicular fusion increased upon and required myelination. We found that axonal vesicular fusion was enriched in hotspots, namely the heminodal non-myelinated domains into which sheaths grew. Blocking vesicular fusion reduced the stable formation and growth of myelin sheaths, and chemogenetically stimulating neuronal activity promoted sheath growth. Finally, we observed high levels of axonal vesicular fusion only in neuronal subtypes that exhibit activity-regulated myelination. Our results identify a novel "feedforward" mechanism whereby the process of myelination promotes the neuronal activity-regulated signal, vesicular fusion that, in turn, consolidates sheath growth along specific axons selected for myelination.
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Affiliation(s)
- Rafael G Almeida
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.
| | - Jill M Williamson
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - Megan E Madden
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - Jason J Early
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - Matthew G Voas
- Department of Developmental Biology, Stanford University, Stanford, CA, USA; National Cancer Institute, Frederick, MD, USA
| | - William S Talbot
- Department of Developmental Biology, Stanford University, Stanford, CA, USA
| | - Isaac H Bianco
- Department of Neuroscience, Physiology and Pharmacology, UCL, London, UK
| | - David A Lyons
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.
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14
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Zhou JW, Zhao M, Rang WL, Zhang XY, Liu ZM, Zhang LR, Wang TX, Wu CT, Cheng XR, Zhou WX. Proteome Profiling Identified Amyloid-β Protein Precursor as a Novel Binding Partner and Modulator of VGLUT1. J Alzheimers Dis 2021; 81:981-1038. [PMID: 33896843 DOI: 10.3233/jad-210117] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND The toxicity of excessive glutamate release has been implicated in various acute and chronic neurodegenerative conditions. Vesicular glutamate transporters (VGLUTs) are the major mediators for the uptake of glutamate into synaptic vesicles. However, the dynamics and mechanism of this process in glutamatergic neurons are still largely unknown. OBJECTIVE This study aimed to investigate the candidate protein partners of VGLUT1 and their regulatory roles in the vesicles in rat brain. METHODS Pull down assay, co-immunoprecipitation assay, or split-ubiquitin membrane yeast two hybrid screening coupled with nanoRPLC-MS/MS were used to identify the candidate protein partners of VGLUT1 in the vesicles in rat brain. The in vitro and in vivo models were used to test effects of AβPP, Atp6ap2, Gja1, and Synataxin on VGLUT1 expression. RESULTS A total of 255 and 225 proteins and 172 known genes were identified in the pull down assay, co-immunoprecipitation assay, or split-ubiquitin yeast two-hybrid screening respectively. The physiological interactions of SV2A, Syntaxin 12, Gja1, AβPP, and Atp6ap2 to VGLUT1 were further confirmed. Knockdown of Atp6ap2, Gja1, and Synataxin increased VGLUT1 mRNA expression and only knockdown of AβPP increased both mRNA and protein levels of VGLUT1 in PC12 cells. The regulatory function of AβPP on VGLUT1 expression was further confirmed in the in vitro and in vivo models. CONCLUSION These results elucidate that the AβPP and VGLUT1 interacts at vesicular level and AβPP plays a role in the regulation of VGLUT1 expression which is essential for maintaining vesicular activities.
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Affiliation(s)
- Jin-Wu Zhou
- School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
| | - Man Zhao
- Department of Blood Transfusion, Chinese PLA General Hospital, Beijing, China
| | - Wen-Liang Rang
- Department of Experimental Hematology, Beijing Institute of Radiation Medicine, Beijing, China
| | - Xiao-Yan Zhang
- State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, Beijing, China
| | - Zhen-Ming Liu
- State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, Beijing, China
| | - Liang-Ren Zhang
- State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, Beijing, China
| | - Tong-Xing Wang
- Beijing Institute of Pharmacology and Toxicology, Beijing, China
| | - Chu-Tse Wu
- School of Chemical Engineering and Technology, Tianjin University, Tianjin, China.,Department of Experimental Hematology, Beijing Institute of Radiation Medicine, Beijing, China
| | - Xiao-Rui Cheng
- Beijing Institute of Pharmacology and Toxicology, Beijing, China.,State Key Laboratory of Toxicology and Medical Countermeasures, Beijing, China
| | - Wen-Xia Zhou
- Beijing Institute of Pharmacology and Toxicology, Beijing, China.,State Key Laboratory of Toxicology and Medical Countermeasures, Beijing, China
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15
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Combining Single Molecule Super-Resolution Imaging Techniques to Unravel the Nanoscale Organization of the Presynapse. Methods Mol Biol 2020. [PMID: 33222141 DOI: 10.1007/978-1-0716-1044-2_18] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2023]
Abstract
The fusion of synaptic vesicles with the plasma membrane underpins neurotransmission. A number of presynaptic proteins play a critical role in overcoming the energy barrier inherent to the fusion of the negatively charged vesicular and plasma membranes. Emerging concepts suggest that this process is hierarchical and dependent on rapid and transient reorganization of proteins in and out of small nanoclusters located in the active zones of nerve terminals. Examining the nanoscale organization of presynaptic molecules requires super-resolution microscopy to overcome the limits of conventional light microscopy. In this chapter, we describe three super-resolution techniques that allow for the examination of the nanoscale organization of proteins within live hippocampal nerve terminals. We used (1) single-particle tracking photoactivated localization microscopy (sptPALM) to resolve the mobility and clustering of syntaxin1A (STX1A), (2) universal Point Accumulation Imaging in Nanoscale Topography (uPAINT) to study the mobility of a pool of vesicular-associated membrane protein 2 (VAMP2) transiting on the plasma membrane, and (3) subdiffractional Tracking of Internalized Molecules (sdTIM) to track VAMP2-positive recycling synaptic vesicles in conjunction with Cholera Toxin subunit B (CTB), which has recently been shown to be trafficked retrogradely from the presynapse to the cell body via signaling endosomes.
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16
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An Epilepsy-Associated SV2A Mutation Disrupts Synaptotagmin-1 Expression and Activity-Dependent Trafficking. J Neurosci 2020; 40:4586-4595. [PMID: 32341095 DOI: 10.1523/jneurosci.0210-20.2020] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 03/05/2020] [Accepted: 03/27/2020] [Indexed: 01/28/2023] Open
Abstract
The epilepsy-linked gene SV2A, has a number of potential roles in the synaptic vesicle (SV) life cycle. However, how loss of SV2A function translates into presynaptic dysfunction and ultimately seizure activity is still undetermined. In this study, we examined whether the first SV2A mutation identified in human disease (R383Q) could provide information regarding which SV2A-dependent events are critical in the translation to epilepsy. We utilized a molecular replacement strategy in which exogenous SV2A was expressed in mouse neuronal cultures of either sex, which had been depleted of endogenous SV2A to mimic the homozygous human condition. We found that the R383Q mutation resulted in a mislocalization of SV2A from SVs to the plasma membrane, but had no effect on its activity-dependent trafficking. This SV2A mutant displayed reduced mobility when stranded on the plasma membrane and reduced binding to its interaction partner synaptotagmin-1 (Syt1). Furthermore, the R383Q mutant failed to rescue reduced expression and dysfunctional activity-dependent trafficking of Syt1 in the absence of endogenous SV2A. This suggests that the inability to control Syt1 expression and trafficking at the presynapse may be key in the transition from loss of SV2A function to seizure activity.SIGNIFICANCE STATEMENT SV2A is a synaptic vesicle (SV) protein, the absence or dysfunction of which is linked to epilepsy. However, the series of molecular events that result in this neurological disorder is still undetermined. We demonstrate here that the first human mutation in SV2A identified in an individual with epilepsy displays reduced binding to synaptotagmin-1 (Syt1), an SV protein essential for synchronous neurotransmitter release. Furthermore, this mutant cannot correct alterations in both Syt1 expression and trafficking when expressed in the absence of endogenous SV2A (to mimic the homozygous human condition). This suggests that the inability to control Syt1 expression and trafficking may be key in the transition from loss of SV2A function to seizure activity.
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17
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Eriksen J, Li F, Edwards RH. The mechanism and regulation of vesicular glutamate transport: Coordination with the synaptic vesicle cycle. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183259. [PMID: 32147354 DOI: 10.1016/j.bbamem.2020.183259] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Revised: 03/02/2020] [Accepted: 03/02/2020] [Indexed: 01/30/2023]
Abstract
The transport of classical neurotransmitters into synaptic vesicles generally relies on a H+ electrochemical gradient (∆μH+). Synaptic vesicle uptake of glutamate depends primarily on the electrical component ∆ψ as the driving force, rather than the chemical component ∆pH. However, the vesicular glutamate transporters (VGLUTs) belong to the solute carrier 17 (SLC17) family, which includes closely related members that function as H+ cotransporters. Recent work has also shown that the VGLUTs undergo allosteric regulation by H+ and Cl-, and exhibit an associated Cl- conductance. These properties appear to coordinate VGLUT activity with the large ionic shifts that accompany the rapid recycling of synaptic vesicles driven by neural activity. Recent structural information also suggests common mechanisms that underlie the apparently divergent function of SLC17 family members, and that confer allosteric regulation.
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Affiliation(s)
- Jacob Eriksen
- Department of Physiology, UCSF School of Medicine, United States of America; Department of Neurology, UCSF School of Medicine, United States of America
| | - Fei Li
- Department of Physiology, UCSF School of Medicine, United States of America; Department of Neurology, UCSF School of Medicine, United States of America
| | - Robert H Edwards
- Department of Physiology, UCSF School of Medicine, United States of America; Department of Neurology, UCSF School of Medicine, United States of America.
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18
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Zhang XM, François U, Silm K, Angelo MF, Fernandez-Busch MV, Maged M, Martin C, Bernard V, Cordelières FP, Deshors M, Pons S, Maskos U, Bemelmans AP, Wojcik SM, El Mestikawy S, Humeau Y, Herzog E. A proline-rich motif on VGLUT1 reduces synaptic vesicle super-pool and spontaneous release frequency. eLife 2019; 8:50401. [PMID: 31663854 PMCID: PMC6861006 DOI: 10.7554/elife.50401] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Accepted: 10/27/2019] [Indexed: 12/29/2022] Open
Abstract
Glutamate secretion at excitatory synapses is tightly regulated to allow for the precise tuning of synaptic strength. Vesicular Glutamate Transporters (VGLUT) accumulate glutamate into synaptic vesicles (SV) and thereby regulate quantal size. Further, the number of release sites and the release probability of SVs maybe regulated by the organization of active-zone proteins and SV clusters. In the present work, we uncover a mechanism mediating an increased SV clustering through the interaction of VGLUT1 second proline-rich domain, endophilinA1 and intersectin1. This strengthening of SV clusters results in a combined reduction of axonal SV super-pool size and miniature excitatory events frequency. Our findings support a model in which clustered vesicles are held together through multiple weak interactions between Src homology three and proline-rich domains of synaptic proteins. In mammals, VGLUT1 gained a proline-rich sequence that recruits endophilinA1 and turns the transporter into a regulator of SV organization and spontaneous release.
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Affiliation(s)
- Xiao Min Zhang
- Interdisciplinary Institute for Neuroscience, Université de Bordeaux, Bordeaux, France.,Interdisciplinary Institute for Neuroscience CNRS UMR 5297, Bordeaux, France.,Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Urielle François
- Interdisciplinary Institute for Neuroscience, Université de Bordeaux, Bordeaux, France.,Interdisciplinary Institute for Neuroscience CNRS UMR 5297, Bordeaux, France
| | - Kätlin Silm
- Neuroscience Paris Seine NPS, Université Pierre et Marie Curie INSERM U1130 CNRS UMR8246, Paris, France
| | - Maria Florencia Angelo
- Interdisciplinary Institute for Neuroscience, Université de Bordeaux, Bordeaux, France.,Interdisciplinary Institute for Neuroscience CNRS UMR 5297, Bordeaux, France
| | - Maria Victoria Fernandez-Busch
- Interdisciplinary Institute for Neuroscience, Université de Bordeaux, Bordeaux, France.,Interdisciplinary Institute for Neuroscience CNRS UMR 5297, Bordeaux, France
| | - Mona Maged
- Interdisciplinary Institute for Neuroscience, Université de Bordeaux, Bordeaux, France.,Interdisciplinary Institute for Neuroscience CNRS UMR 5297, Bordeaux, France
| | - Christelle Martin
- Interdisciplinary Institute for Neuroscience, Université de Bordeaux, Bordeaux, France.,Interdisciplinary Institute for Neuroscience CNRS UMR 5297, Bordeaux, France
| | - Véronique Bernard
- Neuroscience Paris Seine NPS, Université Pierre et Marie Curie INSERM U1130 CNRS UMR8246, Paris, France
| | - Fabrice P Cordelières
- Bordeaux Imaging Center, Université de Bordeaux, CNRS UMS 3420, INSERM US4, Bordeaux, France
| | - Melissa Deshors
- Interdisciplinary Institute for Neuroscience, Université de Bordeaux, Bordeaux, France.,Interdisciplinary Institute for Neuroscience CNRS UMR 5297, Bordeaux, France
| | - Stéphanie Pons
- Institut Pasteur, CNRS UMR 3571, Unité NISC, Paris, France
| | - Uwe Maskos
- Institut Pasteur, CNRS UMR 3571, Unité NISC, Paris, France
| | - Alexis Pierre Bemelmans
- Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Direction de laRecherche Fondamentale (DRF), Institut de Biologie François Jacob (IBFJ), MolecularImaging Research Center (MIRCen), Fontenay-aux-Roses, France
| | - Sonja M Wojcik
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Salah El Mestikawy
- Neuroscience Paris Seine NPS, Université Pierre et Marie Curie INSERM U1130 CNRS UMR8246, Paris, France.,Department of Psychiatry, Douglas Mental Health University Institute, McGill University, Montreal, Canada
| | - Yann Humeau
- Interdisciplinary Institute for Neuroscience, Université de Bordeaux, Bordeaux, France.,Interdisciplinary Institute for Neuroscience CNRS UMR 5297, Bordeaux, France
| | - Etienne Herzog
- Interdisciplinary Institute for Neuroscience, Université de Bordeaux, Bordeaux, France.,Interdisciplinary Institute for Neuroscience CNRS UMR 5297, Bordeaux, France
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19
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Silliman K. Population structure, genetic connectivity, and adaptation in the Olympia oyster ( Ostrea lurida) along the west coast of North America. Evol Appl 2019; 12:923-939. [PMID: 31080505 PMCID: PMC6503834 DOI: 10.1111/eva.12766] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Revised: 11/28/2018] [Accepted: 12/02/2018] [Indexed: 01/02/2023] Open
Abstract
Effective management of threatened and exploited species requires an understanding of both the genetic connectivity among populations and local adaptation. The Olympia oyster (Ostrea lurida), patchily distributed from Baja California to the central coast of Canada, has a long history of population declines due to anthropogenic stressors. For such coastal marine species, population structure could follow a continuous isolation-by-distance model, contain regional blocks of genetic similarity separated by barriers to gene flow, or be consistent with a null model of no population structure. To distinguish between these hypotheses in O. lurida, 13,424 single nucleotide polymorphisms (SNPs) were used to characterize rangewide population structure, genetic connectivity, and adaptive divergence. Samples were collected across the species range on the west coast of North America, from southern California to Vancouver Island. A conservative approach for detecting putative loci under selection identified 235 SNPs across 129 GBS loci, which were functionally annotated and analyzed separately from the remaining neutral loci. While strong population structure was observed on a regional scale in both neutral and outlier markers, neutral markers had greater power to detect fine-scale structure. Geographic regions of reduced gene flow aligned with known marine biogeographic barriers, such as Cape Mendocino, Monterey Bay, and the currents around Cape Flattery. The outlier loci identified as under putative selection included genes involved in developmental regulation, sensory information processing, energy metabolism, immune response, and muscle contraction. These loci are excellent candidates for future research and may provide targets for genetic monitoring programs. Beyond specific applications for restoration and management of the Olympia oyster, this study lends to the growing body of evidence for both population structure and adaptive differentiation across a range of marine species exhibiting the potential for panmixia. Computational notebooks are available to facilitate reproducibility and future open-sourced research on the population structure of O. lurida.
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20
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Silm K, Yang J, Marcott PF, Asensio CS, Eriksen J, Guthrie DA, Newman AH, Ford CP, Edwards RH. Synaptic Vesicle Recycling Pathway Determines Neurotransmitter Content and Release Properties. Neuron 2019; 102:786-800.e5. [PMID: 31003725 PMCID: PMC6541489 DOI: 10.1016/j.neuron.2019.03.031] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Revised: 01/28/2019] [Accepted: 03/19/2019] [Indexed: 01/03/2023]
Abstract
In contrast to temporal coding by synaptically acting neurotransmitters such as glutamate, neuromodulators such as monoamines signal changes in firing rate. The two modes of signaling have been thought to reflect differences in release by different cells. We now find that midbrain dopamine neurons release glutamate and dopamine with different properties that reflect storage in different synaptic vesicles. The vesicles differ in release probability, coupling to presynaptic Ca2+ channels and frequency dependence. Although previous work has attributed variation in these properties to differences in location or cytoskeletal association of synaptic vesicles, the release of different transmitters shows that intrinsic differences in vesicle identity drive different modes of release. Indeed, dopamine but not glutamate vesicles depend on the adaptor protein AP-3, revealing an unrecognized linkage between the pathway of synaptic vesicle recycling and the properties of exocytosis. Storage of the two transmitters in different vesicles enables the transmission of distinct signals.
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Affiliation(s)
- Kätlin Silm
- Departments of Neurology and Physiology, Graduate Programs in Neuroscience and Cell Biology, Kavli Institute for Fundamental Neuroscience, Weill Institute for the Neurosciences, UCSF School of Medicine, San Francisco, CA 94143, USA
| | - Jing Yang
- Departments of Neurology and Physiology, Graduate Programs in Neuroscience and Cell Biology, Kavli Institute for Fundamental Neuroscience, Weill Institute for the Neurosciences, UCSF School of Medicine, San Francisco, CA 94143, USA
| | - Pamela F Marcott
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Cedric S Asensio
- Departments of Neurology and Physiology, Graduate Programs in Neuroscience and Cell Biology, Kavli Institute for Fundamental Neuroscience, Weill Institute for the Neurosciences, UCSF School of Medicine, San Francisco, CA 94143, USA
| | - Jacob Eriksen
- Departments of Neurology and Physiology, Graduate Programs in Neuroscience and Cell Biology, Kavli Institute for Fundamental Neuroscience, Weill Institute for the Neurosciences, UCSF School of Medicine, San Francisco, CA 94143, USA
| | - Daryl A Guthrie
- Medicinal Chemistry Section, Molecular Targets and Medications Discovery Branch, National Institutes of Drug Abuse - Intramural Research Program, Baltimore, MD 21224, USA
| | - Amy H Newman
- Medicinal Chemistry Section, Molecular Targets and Medications Discovery Branch, National Institutes of Drug Abuse - Intramural Research Program, Baltimore, MD 21224, USA
| | - Christopher P Ford
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA; Department of Pharmacology, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Robert H Edwards
- Departments of Neurology and Physiology, Graduate Programs in Neuroscience and Cell Biology, Kavli Institute for Fundamental Neuroscience, Weill Institute for the Neurosciences, UCSF School of Medicine, San Francisco, CA 94143, USA.
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21
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Chanaday NL, Kavalali ET. Presynaptic origins of distinct modes of neurotransmitter release. Curr Opin Neurobiol 2018; 51:119-126. [PMID: 29597140 PMCID: PMC6066415 DOI: 10.1016/j.conb.2018.03.005] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Revised: 02/22/2018] [Accepted: 03/12/2018] [Indexed: 11/17/2022]
Abstract
Presynaptic nerve terminals release neurotransmitter synchronously, asynchronously or spontaneously. During synchronous neurotransmission release is precisely coupled to action potentials, in contrast, asynchronous release events show only loose temporal coupling to presynaptic activity whereas spontaneous neurotransmission occurs independent of presynaptic activity. The mechanisms that give rise to this diversity in neurotransmitter release modes are poorly understood. Recent studies have described several presynaptic molecular pathways controlling synaptic vesicle pool segregation and recycling, which in turn may dictate distinct modes of neurotransmitter release. In this article, we review this recent work regarding neurotransmitter release modes and their relationship to synaptic vesicle pool dynamics as well as the molecular machinery that establishes synaptic vesicle pool identity.
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Affiliation(s)
- Natali L Chanaday
- Department of Neuroscience, the University of Texas Southwestern Medical Center, Dallas, TX 75390-9111, USA
| | - Ege T Kavalali
- Department of Neuroscience, the University of Texas Southwestern Medical Center, Dallas, TX 75390-9111, USA.
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22
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Chanaday NL, Kavalali ET. Optical detection of three modes of endocytosis at hippocampal synapses. eLife 2018; 7:36097. [PMID: 29683423 PMCID: PMC5959719 DOI: 10.7554/elife.36097] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Accepted: 04/20/2018] [Indexed: 12/23/2022] Open
Abstract
Coupling of synaptic vesicle fusion and retrieval constitutes a core mechanism ensuring maintenance of presynaptic function. Recent studies using fast-freeze electron microscopy and capacitance measurements reported an ultrafast mode of endocytosis operating at physiological temperatures. Here, using rat hippocampal neurons, we optically monitored single synaptic vesicle endocytosis with high time resolution using the vesicular glutamate transporter, synaptophysin and the V0a1 subunit of the vacuolar ATPase as probes. In this setting, we could distinguish three components of retrieval operating at ultrafast (~150-250 ms, ~20% of events), fast (~5-12 s, ~40% of events) and ultraslow speeds (>20 s, ~40% of events). While increasing Ca2+ slowed the fast events, increasing temperature accelerated their time course. In contrast, the kinetics of ultrafast events were only mildly affected by these manipulations. These results suggest that synaptic vesicle proteins can be retrieved with ultrafast kinetics, although a majority of evoked fusion events are coupled to slower retrieval mechanisms.
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Affiliation(s)
- Natali L Chanaday
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, United States
| | - Ege T Kavalali
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, United States
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23
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Lou X. Sensing Exocytosis and Triggering Endocytosis at Synapses: Synaptic Vesicle Exocytosis-Endocytosis Coupling. Front Cell Neurosci 2018; 12:66. [PMID: 29593500 PMCID: PMC5861208 DOI: 10.3389/fncel.2018.00066] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Accepted: 02/26/2018] [Indexed: 12/29/2022] Open
Abstract
The intact synaptic structure is critical for information processing in neural circuits. During synaptic transmission, rapid vesicle exocytosis increases the size of never terminals and endocytosis counteracts the increase. Accumulating evidence suggests that SV exocytosis and endocytosis are tightly connected in time and space during SV recycling, and this process is essential for synaptic function and structural stability. Research in the past has illustrated the molecular details of synaptic vesicle (SV) exocytosis and endocytosis; however, the mechanisms that timely connect these two fundamental events are poorly understood at central synapses. Here we discuss recent progress in SV recycling and summarize several emerging mechanisms by which synapses can “sense” the occurrence of exocytosis and timely initiate compensatory endocytosis. They include Ca2+ sensing, SV proteins sensing, and local membrane stress sensing. In addition, the spatial organization of endocytic zones adjacent to active zones provides a structural basis for efficient coupling between SV exocytosis and endocytosis. Through linking different endocytosis pathways with SV fusion, these mechanisms ensure necessary plasticity and robustness of nerve terminals to meet diverse physiological needs.
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Affiliation(s)
- Xuelin Lou
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI, United States
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Mori Y, Takamori S. Molecular Signatures Underlying Synaptic Vesicle Cargo Retrieval. Front Cell Neurosci 2018; 11:422. [PMID: 29379416 PMCID: PMC5770824 DOI: 10.3389/fncel.2017.00422] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2017] [Accepted: 12/15/2017] [Indexed: 12/31/2022] Open
Abstract
Efficient retrieval of the synaptic vesicle (SV) membrane from the presynaptic plasma membrane, a process called endocytosis, is crucial for the fidelity of neurotransmission, particularly during sustained neural activity. Although multiple modes of endocytosis have been identified, it is clear that the efficient retrieval of the major SV cargos into newly formed SVs during any of these modes is fundamental for synaptic transmission. It is currently believed that SVs are eventually reformed via a clathrin-dependent pathway. Various adaptor proteins recognize SV cargos and link them to clathrin, ensuring the efficient retrieval of the cargos into newly formed SVs. Here, we summarize our current knowledge of the molecular signatures within individual SV cargos that underlie efficient retrieval into SV membranes, as well as discuss possible contributions of the mechanisms under physiological conditions.
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Affiliation(s)
- Yasunori Mori
- Laboratory of Neural Membrane Biology, Graduate School of Brain Science, Doshisha University, Kyoto, Japan
| | - Shigeo Takamori
- Laboratory of Neural Membrane Biology, Graduate School of Brain Science, Doshisha University, Kyoto, Japan
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Collado-Alsina A, Hofmann F, Sánchez-Prieto J, Torres M. Altered Synaptic Membrane Retrieval after Strong Stimulation of Cerebellar Granule Neurons in Cyclic GMP-Dependent Protein Kinase II (cGKII) Knockout Mice. Int J Mol Sci 2017; 18:ijms18112281. [PMID: 29084181 PMCID: PMC5713251 DOI: 10.3390/ijms18112281] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 10/23/2017] [Accepted: 10/25/2017] [Indexed: 01/26/2023] Open
Abstract
The nitric oxide (NO)/cyclic guanosine monophosphate (cGMP)/cGMP-dependent protein kinase (cGK) signaling pathway regulates the clustering and the recruitment of proteins and vesicles to the synapse, thereby adjusting the exoendocytic cycle to the intensity of activity. Accordingly, this pathway can accelerate endocytosis following large-scale exocytosis, and pre-synaptic cGK type II (cGKII) plays a major role in this process, controlling the homeostatic balance of vesicle exocytosis and endocytosis. We have studied synaptic vesicle recycling in cerebellar granule cells from mice lacking cGKII under strong and sustained stimulation, combining imaging techniques and ultrastructural analyses. The ultrastructure of synapses in the adult mouse cerebellar cortex was also examined in these animals. The lack of cGKII provokes structural changes to synapses in cultured cells and in the cerebellar cortex. Moreover, endocytosis is slowed down in a subset of boutons in these cells when they are stimulated strongly. In addition, from the results obtained with the selective inhibitor of cGKs, KT5823, it can be concluded that cGKI also regulates some aspects of vesicle cycling. Overall, these results confirm the importance of the cGMP pathway in the regulation of vesicle cycling following strong stimulation of cerebellar granule cells.
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Affiliation(s)
- Andrea Collado-Alsina
- Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense, 28040 Madrid, Spain.
- Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), 28040 Madrid, Spain.
| | - Franz Hofmann
- FOR 923, Institut für Pharmakologie und Toxikologie, Technische Universität München, Biedersteiner Str. 29, 80802 Munich, Germany.
| | - José Sánchez-Prieto
- Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense, 28040 Madrid, Spain.
- Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), 28040 Madrid, Spain.
| | - Magdalena Torres
- Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense, 28040 Madrid, Spain.
- Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), 28040 Madrid, Spain.
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Li H, Santos MS, Park CK, Dobry Y, Voglmaier SM. VGLUT2 Trafficking Is Differentially Regulated by Adaptor Proteins AP-1 and AP-3. Front Cell Neurosci 2017; 11:324. [PMID: 29123471 PMCID: PMC5662623 DOI: 10.3389/fncel.2017.00324] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2017] [Accepted: 09/28/2017] [Indexed: 01/25/2023] Open
Abstract
Release of the major excitatory neurotransmitter glutamate by synaptic vesicle exocytosis depends on glutamate loading into synaptic vesicles by vesicular glutamate transporters (VGLUTs). The two principal isoforms, VGLUT1 and 2, exhibit a complementary pattern of expression in adult brain that broadly distinguishes cortical (VGLUT1) and subcortical (VGLUT2) systems, and correlates with distinct physiological properties in synapses expressing these isoforms. Differential trafficking of VGLUT1 and 2 has been suggested to underlie their functional diversity. Increasing evidence suggests individual synaptic vesicle proteins use specific sorting signals to engage specialized biochemical mechanisms to regulate their recycling. We observed that VGLUT2 recycles differently in response to high frequency stimulation than VGLUT1. Here we further explore the trafficking of VGLUT2 using a pHluorin-based reporter, VGLUT2-pH. VGLUT2-pH exhibits slower rates of both exocytosis and endocytosis than VGLUT1-pH. VGLUT2-pH recycling is slower than VGLUT1-pH in both hippocampal neurons, which endogenously express mostly VGLUT1, and thalamic neurons, which endogenously express mostly VGLUT2, indicating that protein identity, not synaptic vesicle membrane or neuronal cell type, controls sorting. We characterize sorting signals in the C-terminal dileucine-like motif, which plays a crucial role in VGLUT2 trafficking. Disruption of this motif abolishes synaptic targeting of VGLUT2 and essentially eliminates endocytosis of the transporter. Mutational and biochemical analysis demonstrates that clathrin adaptor proteins (APs) interact with VGLUT2 at the dileucine-like motif. VGLUT2 interacts with AP-2, a well-studied adaptor protein for clathrin mediated endocytosis. In addition, VGLUT2 also interacts with the alternate adaptors, AP-1 and AP-3. VGLUT2 relies on distinct recycling mechanisms from VGLUT1. Abrogation of these differences by pharmacological and molecular inhibition reveals that these mechanisms are dependent on the adaptor proteins AP-1 and AP-3. Further, shRNA-mediated knockdown reveals differential roles for AP-1 and AP-3 in VGLUT2 recycling.
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Affiliation(s)
- Haiyan Li
- Department of Psychiatry, School of Medicine, Weill Institute for Neurosciences, Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, CA, United States
| | - Magda S Santos
- Department of Psychiatry, School of Medicine, Weill Institute for Neurosciences, Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, CA, United States
| | - Chihyung K Park
- Department of Psychiatry, School of Medicine, Weill Institute for Neurosciences, Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, CA, United States
| | - Yuriy Dobry
- Department of Psychiatry, School of Medicine, Weill Institute for Neurosciences, Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, CA, United States
| | - Susan M Voglmaier
- Department of Psychiatry, School of Medicine, Weill Institute for Neurosciences, Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, CA, United States
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Kaempf N, Maritzen T. Safeguards of Neurotransmission: Endocytic Adaptors as Regulators of Synaptic Vesicle Composition and Function. Front Cell Neurosci 2017; 11:320. [PMID: 29085282 PMCID: PMC5649181 DOI: 10.3389/fncel.2017.00320] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Accepted: 09/26/2017] [Indexed: 11/13/2022] Open
Abstract
Communication between neurons relies on neurotransmitters which are released from synaptic vesicles (SVs) upon Ca2+ stimuli. To efficiently load neurotransmitters, sense the rise in intracellular Ca2+ and fuse with the presynaptic membrane, SVs need to be equipped with a stringently controlled set of transmembrane proteins. In fact, changes in SV protein composition quickly compromise neurotransmission and most prominently give rise to epileptic seizures. During exocytosis SVs fully collapse into the presynaptic membrane and consequently have to be replenished to sustain neurotransmission. Therefore, surface-stranded SV proteins have to be efficiently retrieved post-fusion to be used for the generation of a new set of fully functional SVs, a process in which dedicated endocytic sorting adaptors play a crucial role. The question of how the precise reformation of SVs is achieved is intimately linked to how SV membranes are retrieved. For a long time both processes were believed to be two sides of the same coin since Clathrin-mediated endocytosis (CME), the proposed predominant SV recycling mode, will jointly retrieve SV membranes and proteins. However, with the recent proposal of Clathrin-independent SV recycling pathways SV membrane retrieval and SV reformation turn into separable events. This review highlights the progress made in unraveling the molecular mechanisms mediating the high-fidelity retrieval of SV proteins and discusses how the gathered knowledge about SV protein recycling fits in with the new notions of SV membrane endocytosis.
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Affiliation(s)
- Natalie Kaempf
- Molecular Physiology and Cell Biology Section, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Tanja Maritzen
- Molecular Physiology and Cell Biology Section, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany
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Abstract
Synaptic vesicle recycling is essential for sustained and reliable neurotransmission. A key component of synaptic vesicle recycling is the synaptic vesicle biogenesis process that is observed in synapses and that maintains the molecular identity of synaptic vesicles. However, the mechanisms by which synaptic vesicles are retrieved and reconstituted after fusion remain unclear. The complex molecular composition of synaptic vesicles renders their rapid biogenesis a daunting task. Therefore, in this context, kiss-and-run type transient fusion of synaptic vesicles with the plasma membrane without loss of their membrane composition and molecular identity remains a viable hypothesis that can account for the fidelity of the synaptic vesicle cycle. In this article, we discuss the biological implications of this problem as well as its possible molecular solutions.
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Affiliation(s)
- Natali L Chanaday
- Department of Neuroscience, University of Texas Southwestern Medical Centre, Dallas, TX, 75390-9111, USA
| | - Ege T Kavalali
- Department of Neuroscience, University of Texas Southwestern Medical Centre, Dallas, TX, 75390-9111, USA
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Cousin MA. Integration of Synaptic Vesicle Cargo Retrieval with Endocytosis at Central Nerve Terminals. Front Cell Neurosci 2017; 11:234. [PMID: 28824381 PMCID: PMC5541026 DOI: 10.3389/fncel.2017.00234] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Accepted: 07/25/2017] [Indexed: 12/12/2022] Open
Abstract
Central nerve terminals contain a limited number of synaptic vesicles (SVs) which mediate the essential process of neurotransmitter release during their activity-dependent fusion. The rapid and accurate formation of new SVs with the appropriate cargo is essential to maintain neurotransmission in mammalian brain. Generating SVs containing the correct SV cargo with the appropriate stoichiometry is a significant challenge, especially when multiple modes of endocytosis exist in central nerve terminals, which occur at different locations within the nerve terminals. These endocytosis modes include ultrafast endocytosis, clathrin-mediated endocytosis (CME) and activity-dependent bulk endocytosis (ADBE) which are triggered by specific patterns of neuronal activity. This review article will assess the evidence for the role of classical adaptor protein complexes in SV retrieval, discuss the role of monomeric adaptors and how interactions between specific SV cargoes can facilitate retrieval. In addition it will consider the evidence for preassembled plasma membrane cargo complexes and their role in facilitating these endocytosis modes. Finally it will present a unifying model for cargo retrieval at the presynapse, which integrates endocytosis modes in time and space.
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Affiliation(s)
- Michael A Cousin
- Centre for Integrative Physiology, University of EdinburghEdinburgh, United Kingdom
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Yue HY, Bieberich E, Xu J. Promotion of endocytosis efficiency through an ATP-independent mechanism at rat calyx of Held terminals. J Physiol 2017; 595:5265-5284. [PMID: 28555839 DOI: 10.1113/jp274275] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2017] [Accepted: 05/15/2017] [Indexed: 01/14/2023] Open
Abstract
KEY POINTS At rat calyx of Held terminals, ATP was required not only for slow endocytosis, but also for rapid phase of compensatory endocytosis. An ATP-independent form of endocytosis was recruited to accelerate membrane retrieval at increased activity and temperature. ATP-independent endocytosis primarily involved retrieval of pre-existing membrane, which depended on Ca2+ and the activity of neutral sphingomyelinase but not clathrin-coated pit maturation. ATP-independent endocytosis represents a non-canonical mechanism that can efficiently retrieve membrane at physiological conditions without competing for the limited ATP at elevated neuronal activity. ABSTRACT Neurotransmission relies on membrane endocytosis to maintain vesicle supply and membrane stability. Endocytosis has been generally recognized as a major ATP-dependent function, which efficiently retrieves more membrane at elevated neuronal activity when ATP consumption within nerve terminals increases drastically. This paradox raises the interesting question of whether increased activity recruits ATP-independent mechanism(s) to accelerate endocytosis at the same time as preserving ATP availability for other tasks. To address this issue, we studied ATP requirement in three typical forms of endocytosis at rat calyx of Held terminals by whole-cell membrane capacitance measurements. At room temperature, blocking ATP hydrolysis effectively abolished slow endocytosis and rapid endocytosis but only partially inhibited excess endocytosis following intense stimulation. The ATP-independent endocytosis occurred at calyces from postnatal days 8-15, suggesting its existence before and after hearing onset. This endocytosis was not affected by a reduction of exocytosis using the light chain of botulinum toxin C, nor by block of clathrin-coat maturation. It was abolished by EGTA, which preferentially blocked endocytosis of retrievable membrane pre-existing at the surface, and was impaired by oxidation of cholesterol and inhibition of neutral sphingomyelinase. ATP-independent endocytosis became more significant at 34-35°C, and recovered membrane by an amount that, on average, was close to exocytosis. The results of the present study suggest that activity and temperature recruit ATP-independent endocytosis of pre-existing membrane (in addition to ATP-dependent endocytosis) to efficiently retrieve membrane at nerve terminals. This less understood endocytosis represents a non-canonical mechanism regulated by lipids such as cholesterol and sphingomyelinase.
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Affiliation(s)
- Hai-Yuan Yue
- Departments of Neuroscience and Regenerative Medicine, Augusta University, USA
| | - Erhard Bieberich
- Departments of Neuroscience and Regenerative Medicine, Augusta University, USA
| | - Jianhua Xu
- Departments of Neuroscience and Regenerative Medicine, Augusta University, USA.,Department of Neurology, Medical College of Georgia, Augusta University, USA
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Poon VY, Gu M, Ji F, VanDongen AM, Fivaz M. miR-27b shapes the presynaptic transcriptome and influences neurotransmission by silencing the polycomb group protein Bmi1. BMC Genomics 2016; 17:777. [PMID: 27716060 PMCID: PMC5050705 DOI: 10.1186/s12864-016-3139-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2016] [Accepted: 09/28/2016] [Indexed: 12/02/2022] Open
Abstract
Background MicroRNAs (miRNAs) are short non-coding RNAs that are emerging as important post-transcriptional regulators of neuronal and synaptic development. The precise impact of miRNAs on presynaptic function and neurotransmission remains, however, poorly understood. Results Here, we identify miR-27b—an abundant neuronal miRNA implicated in neurological disorders—as a global regulator of the presynaptic transcriptome. miR-27b influences the expression of three quarters of genes associated with presynaptic function in cortical neurons. Contrary to expectation, a large majority of these genes are up-regulated by miR-27b. This stimulatory effect is mediated by miR-27b-directed silencing of several transcriptional repressors that cooperate to suppress the presynaptic transcriptome. The strongest repressive activity appears to be mediated by Bmi1, a component of the polycomb repressive complex implicated in self-renewal of neural stem cells. miR-27b knockdown leads to reduced synaptogenesis and to a marked decrease in neural network activity, which is fully restored by RNAi-mediated silencing of Bmi1. Conclusions We conclude that silencing of Bmi1 by miR-27b relieves repression of the presynaptic transcriptome and supports neurotransmission in cortical networks. These results expand the repressive activity of Bmi1 to genes involved in synaptic function and identify a unique post-transcriptional circuitry that stimulates expression of synaptic genes and promotes synapse differentiation. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-3139-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Vivian Y Poon
- Program in Neuroscience and Behavioral Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Minxia Gu
- Program in Neuroscience and Behavioral Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Fang Ji
- Program in Neuroscience and Behavioral Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Antonius M VanDongen
- Program in Neuroscience and Behavioral Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Marc Fivaz
- Program in Neuroscience and Behavioral Disorders, Duke-NUS Medical School, Singapore, Singapore. .,Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.
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Modes and mechanisms of synaptic vesicle recycling. Curr Opin Neurobiol 2016; 39:17-23. [DOI: 10.1016/j.conb.2016.03.005] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Revised: 03/02/2016] [Accepted: 03/07/2016] [Indexed: 11/30/2022]
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Okamoto Y, Lipstein N, Hua Y, Lin KH, Brose N, Sakaba T, Midorikawa M. Distinct modes of endocytotic presynaptic membrane and protein uptake at the calyx of Held terminal of rats and mice. eLife 2016; 5. [PMID: 27154627 PMCID: PMC4927297 DOI: 10.7554/elife.14643] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Accepted: 05/06/2016] [Indexed: 11/15/2022] Open
Abstract
Neurotransmitter is released at synapses by fusion of synaptic vesicles with the plasma membrane. To sustain synaptic transmission, compensatory retrieval of membranes and vesicular proteins is essential. We combined capacitance measurements and pH-imaging via pH-sensitive vesicular protein marker (anti-synaptotagmin2-cypHer5E), and compared the retrieval kinetics of membranes and vesicular proteins at the calyx of Held synapse. Membrane and Syt2 were retrieved with a similar time course when slow endocytosis was elicited. When fast endocytosis was elicited, Syt2 was still retrieved together with the membrane, but endocytosed organelle re-acidification was slowed down, which provides strong evidence for two distinct endocytotic pathways. Strikingly, CaM inhibitors or the inhibition of the Ca2+-calmodulin-Munc13-1 signaling pathway only impaired the uptake of Syt2 while leaving membrane retrieval intact, indicating different recycling mechanisms for membranes and vesicle proteins. Our data identify a novel mechanism of stimulus- and Ca2+-dependent regulation of coordinated endocytosis of synaptic membranes and vesicle proteins. DOI:http://dx.doi.org/10.7554/eLife.14643.001 Nerve cells release chemicals called neurotransmitters to communicate with each other. The neurotransmitters are packaged inside membrane-encased sacs called vesicles that fuse with the cell’s membrane and release their contents into the space between the nerve cells. The vesicle membrane (which also has proteins embedded in it) can then be retrieved into the cell, and recycled to make new vesicles ready to release more neurotransmitters. Recycling vesicle components requires highly coordinated mechanisms that regulate how much membrane and vesicle protein is retrieved from the cell membrane. Researchers interested in these processes have often studied them at a part of the brainstem of mammals known as the calyx of Held. However, many of the details about how vesicle proteins are recycled remained unclear. Okamoto et al. have now measured vesicle membrane and protein retrieval at the same time and in the same cell at the calyx of Held from rats and mice. The cell surface area was also measured, and the experiments focused on a fluorescently tagged version of a vesicle protein called Synaptotagmin2 that could be tracked under a microscope. Okamoto et al. found that, in weakly active nerve cells, the vesicle membrane and Synaptotagmin2 were retrieved together at a slow rate. The process was faster in more active nerve cells, and Synaptotagmin2 was still retrieved with the membrane but it appeared to be stored first in larger sacs. This suggests that membrane and vesicle proteins may be retrieved via two distinct modes depending on the activity strength. The results of further experiments went on to suggest that vesicle membranes might be recycled in a different way from vesicle proteins. Finally, Okamoto et al. also found a signaling pathway that couples the uptake of vesicle membrane with uptake of Synaptotagmin2. Future studies could now explore how these processes work in other types of nerve cell. DOI:http://dx.doi.org/10.7554/eLife.14643.002
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Affiliation(s)
- Yuji Okamoto
- Graduate School of Brain Science, Doshisha University, Kyoto, Japan
| | - Noa Lipstein
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Yunfeng Hua
- Department of Connectomics, Max Planck Institute of Brain Research, Frankfurt, Germany.,Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany
| | - Kun-Han Lin
- Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Takeshi Sakaba
- Graduate School of Brain Science, Doshisha University, Kyoto, Japan
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Gordon SL, Harper CB, Smillie KJ, Cousin MA. A Fine Balance of Synaptophysin Levels Underlies Efficient Retrieval of Synaptobrevin II to Synaptic Vesicles. PLoS One 2016; 11:e0149457. [PMID: 26871701 PMCID: PMC4752265 DOI: 10.1371/journal.pone.0149457] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Accepted: 01/31/2016] [Indexed: 12/25/2022] Open
Abstract
Synaptobrevin II (sybII) is a vesicular soluble NSF attachment protein receptor (SNARE) protein that is essential for neurotransmitter release, and thus its correct trafficking to synaptic vesicles (SVs) is critical to render them fusion competent. The SV protein synaptophysin binds to sybII and facilitates its retrieval to SVs during endocytosis. Synaptophysin and sybII are the two most abundant proteins on SVs, being present in a 1:2 ratio. Synaptophysin and sybII are proposed to form a large multimeric complex, and the copy number of the proteins in this complex is also in a 1:2 ratio. We investigated the importance of this ratio between these proteins for the localisation and trafficking of sybII in central neurons. SybII was overexpressed in mouse hippocampal neurons at either 1.6 or 2.15–2.35-fold over endogenous protein levels, in the absence or presence of varying levels of synaptophysin. In the absence of exogenous synaptophysin, exogenous sybII was dispersed along the axon, trapped on the plasma membrane and retrieved slowly during endocytosis. Co-expression of exogenous synaptophysin rescued all of these defects. Importantly, the expression of synaptophysin at nerve terminals in a 1:2 ratio with sybII was sufficient to fully rescue normal sybII trafficking. These results demonstrate that the balance between synaptophysin and sybII levels is critical for the correct targeting of sybII to SVs and suggests that small alterations in synaptophysin levels might affect the localisation of sybII and subsequent presynaptic performance.
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Affiliation(s)
- Sarah L. Gordon
- Florey Institute of Neuroscience and Mental Health, The University of Melbourne, 30 Royal Parade, Parkville, 3052, Victoria, Australia
- * E-mail: (SG); (MC)
| | - Callista B. Harper
- Centre for Integrative Physiology, George Square, University of Edinburgh, EH8 9XD Edinburgh, United Kingdom
| | - Karen J. Smillie
- Centre for Integrative Physiology, George Square, University of Edinburgh, EH8 9XD Edinburgh, United Kingdom
| | - Michael A. Cousin
- Centre for Integrative Physiology, George Square, University of Edinburgh, EH8 9XD Edinburgh, United Kingdom
- * E-mail: (SG); (MC)
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Gordon SL, Cousin MA. The iTRAPs: Guardians of Synaptic Vesicle Cargo Retrieval During Endocytosis. Front Synaptic Neurosci 2016; 8:1. [PMID: 26903854 PMCID: PMC4746236 DOI: 10.3389/fnsyn.2016.00001] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Accepted: 01/25/2016] [Indexed: 11/30/2022] Open
Abstract
The reformation of synaptic vesicles (SVs) during endocytosis is essential for the maintenance of neurotransmission in central nerve terminals. Newly formed SVs must be generated with the correct protein cargo in the correct stoichiometry to be functional for exocytosis. Classical clathrin adaptor protein complexes play a key role in sorting and clustering synaptic vesicle cargo in this regard. However it is becoming increasingly apparent that additional “fail-safe” mechanisms exist to ensure the accurate retrieval of essential cargo molecules. For example, the monomeric adaptor proteins AP180/CALM and stonin-2 are required for the efficient retrieval of synaptobrevin II (sybII) and synaptotagmin-1 respectively. Furthermore, recent studies have revealed that sybII and synaptotagmin-1 interact with other SV cargoes to ensure a high fidelity of retrieval. These cargoes are synaptophysin (for sybII) and SV2A (for synaptotagmin-1). In this review, we summarize current knowledge regarding the retrieval mechanisms for both sybII and synaptotagmin-1 during endocytosis. We also define and set criteria for a new functional group of SV molecules that facilitate the retrieval of their interaction partners. We have termed these molecules intrinsic trafficking partners (iTRAPs) and we discuss how the function of this group impacts on presynaptic performance in both health and disease.
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Affiliation(s)
- Sarah L Gordon
- Florey Institute of Neuroscience and Mental Health, The University of Melbourne Parkville, VIC, Australia
| | - Michael A Cousin
- Centre for Integrative Physiology, University of Edinburgh Edinburgh, UK
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Nicholson-Fish JC, Kokotos AC, Gillingwater TH, Smillie KJ, Cousin MA. VAMP4 Is an Essential Cargo Molecule for Activity-Dependent Bulk Endocytosis. Neuron 2015; 88:973-984. [PMID: 26607000 PMCID: PMC4678114 DOI: 10.1016/j.neuron.2015.10.043] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Revised: 09/22/2015] [Accepted: 10/15/2015] [Indexed: 11/23/2022]
Abstract
The accurate formation of synaptic vesicles (SVs) and incorporation of their protein cargo during endocytosis is critical for the maintenance of neurotransmission. During intense neuronal activity, a transient and acute accumulation of SV cargo occurs at the plasma membrane. Activity-dependent bulk endocytosis (ADBE) is the dominant SV endocytosis mode under these conditions; however, it is currently unknown how ADBE mediates cargo retrieval. We examined the retrieval of different SV cargo molecules during intense stimulation using a series of genetically encoded pH-sensitive reporters in neuronal cultures. The retrieval of only one reporter, VAMP4-pHluorin, was perturbed by inhibiting ADBE. This selective recovery was confirmed by the enrichment of endogenous VAMP4 in purified bulk endosomes formed by ADBE. VAMP4 was also essential for ADBE, with a cytoplasmic di-leucine motif being critical for this role. Therefore, VAMP4 is the first identified ADBE cargo and is essential for this endocytosis mode to proceed. VAMP4 is the first identified ADBE cargo VAMP4 is essential for ADBE Most synaptic vesicle cargoes are not selectively recovered by ADBE
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Affiliation(s)
- Jessica C Nicholson-Fish
- Centre for Integrative Physiology, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, Scotland
| | - Alexandros C Kokotos
- Centre for Integrative Physiology, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, Scotland
| | - Thomas H Gillingwater
- Centre for Integrative Physiology, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, Scotland
| | - Karen J Smillie
- Centre for Integrative Physiology, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, Scotland.
| | - Michael A Cousin
- Centre for Integrative Physiology, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, Scotland.
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