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Zhang C, Tong F, Zhou B, He M, Liu S, Zhou X, Ma Q, Feng T, Du WJ, Yang H, Xu H, Xiao L, Xu ZZ, Zhu C, Wu R, Wang YQ, Han Q. TMC6 functions as a GPCR-like receptor to sense noxious heat via Gαq signaling. Cell Discov 2024; 10:66. [PMID: 38886367 DOI: 10.1038/s41421-024-00678-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Accepted: 04/08/2024] [Indexed: 06/20/2024] Open
Abstract
Thermosensation is vital for the survival, propagation, and adaption of all organisms, but its mechanism is not fully understood yet. Here, we find that TMC6, a membrane protein of unknown function, is highly expressed in dorsal root ganglion (DRG) neurons and functions as a Gαq-coupled G protein-coupled receptor (GPCR)-like receptor to sense noxious heat. TMC6-deficient mice display a substantial impairment in noxious heat sensation while maintaining normal perception of cold, warmth, touch, and mechanical pain. Further studies show that TMC6 interacts with Gαq via its intracellular C-terminal region spanning Ser780 to Pro810. Specifically disrupting such interaction using polypeptide in DRG neurons, genetically ablating Gαq, or pharmacologically blocking Gαq-coupled GPCR signaling can replicate the phenotype of TMC6 deficient mice regarding noxious heat sensation. Noxious heat stimulation triggers intracellular calcium release from the endoplasmic reticulum (ER) of TMC6- but not control vector-transfected HEK293T cell, which can be significantly inhibited by blocking PLC or IP3R. Consistently, noxious heat-induced intracellular Ca2+ release from ER and action potentials of DRG neurons largely reduced when ablating TMC6 or blocking Gαq/PLC/IP3R signaling pathway as well. In summary, our findings indicate that TMC6 can directly function as a Gαq-coupled GPCR-like receptor sensing noxious heat.
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Affiliation(s)
- Chen Zhang
- Shanghai Stomatological Hospital & School of Stomatology, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Department of Integrative Medicine and Neurobiology, School of Basic Medical Science, Fudan University, Shanghai, China
| | - Fang Tong
- Shanghai Stomatological Hospital & School of Stomatology, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Department of Integrative Medicine and Neurobiology, School of Basic Medical Science, Fudan University, Shanghai, China
| | - Bin Zhou
- Shanghai Stomatological Hospital & School of Stomatology, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Department of Integrative Medicine and Neurobiology, School of Basic Medical Science, Fudan University, Shanghai, China
| | - Mingdong He
- Shanghai Stomatological Hospital & School of Stomatology, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Department of Integrative Medicine and Neurobiology, School of Basic Medical Science, Fudan University, Shanghai, China
| | - Shuai Liu
- Shanghai Stomatological Hospital & School of Stomatology, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Department of Integrative Medicine and Neurobiology, School of Basic Medical Science, Fudan University, Shanghai, China
| | - Xiaomeng Zhou
- Shanghai Stomatological Hospital & School of Stomatology, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Department of Integrative Medicine and Neurobiology, School of Basic Medical Science, Fudan University, Shanghai, China
| | - Qiang Ma
- School of Brain Science and Brain Medicine, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Tianyu Feng
- Shanghai Stomatological Hospital & School of Stomatology, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Department of Integrative Medicine and Neurobiology, School of Basic Medical Science, Fudan University, Shanghai, China
| | - Wan-Jie Du
- Shanghai Stomatological Hospital & School of Stomatology, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Department of Integrative Medicine and Neurobiology, School of Basic Medical Science, Fudan University, Shanghai, China
| | - Huan Yang
- Shanghai Stomatological Hospital & School of Stomatology, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Department of Integrative Medicine and Neurobiology, School of Basic Medical Science, Fudan University, Shanghai, China
| | - Hao Xu
- Shanghai Stomatological Hospital & School of Stomatology, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Department of Integrative Medicine and Neurobiology, School of Basic Medical Science, Fudan University, Shanghai, China
| | - Lei Xiao
- Shanghai Stomatological Hospital & School of Stomatology, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Department of Integrative Medicine and Neurobiology, School of Basic Medical Science, Fudan University, Shanghai, China
| | - Zhen-Zhong Xu
- School of Brain Science and Brain Medicine, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Cheng Zhu
- Tianjin Key Laboratory of Function and Application of Biological Macromolecular Structures, School of Life Sciences, Tianjin University, Tianjin, China
| | - Ruiqi Wu
- Shanghai Stomatological Hospital & School of Stomatology, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Department of Integrative Medicine and Neurobiology, School of Basic Medical Science, Fudan University, Shanghai, China.
| | - Yan-Qing Wang
- Shanghai Stomatological Hospital & School of Stomatology, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Department of Integrative Medicine and Neurobiology, School of Basic Medical Science, Fudan University, Shanghai, China.
| | - Qingjian Han
- Shanghai Stomatological Hospital & School of Stomatology, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Department of Integrative Medicine and Neurobiology, School of Basic Medical Science, Fudan University, Shanghai, China.
- Shanghai Key Laboratory of Craniomaxillofacial Development and Diseases, Fudan University, Shanghai, China.
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2
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Mao F, Yang W. How Merkel cells transduce mechanical stimuli: A biophysical model of Merkel cells. PLoS Comput Biol 2023; 19:e1011720. [PMID: 38117763 PMCID: PMC10732429 DOI: 10.1371/journal.pcbi.1011720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2023] [Accepted: 11/27/2023] [Indexed: 12/22/2023] Open
Abstract
Merkel cells combine with Aβ afferents, producing slowly adapting type 1(SA1) responses to mechanical stimuli. However, how Merkel cells transduce mechanical stimuli into neural signals to Aβ afferents is still unclear. Here we develop a biophysical model of Merkel cells for mechanical transduction by incorporating main ingredients such as Ca2+ and K+ voltage-gated channels, Piezo2 channels, internal Ca2+ stores, neurotransmitters release, and cell deformation. We first validate our model with several experiments. Then we reveal that Ca2+ and K+ channels on the plasma membrane shape the depolarization of membrane potentials, further regulating the Ca2+ transients in the cells. We also show that Ca2+ channels on the plasma membrane mainly inspire the Ca2+ transients, while internal Ca2+ stores mainly maintain the Ca2+ transients. Moreover, we show that though Piezo2 channels are rapidly adapting mechanical-sensitive channels, they are sufficient to inspire sustained Ca2+ transients in Merkel cells, which further induce the release of neurotransmitters for tens of seconds. Thus our work provides a model that captures the membrane potentials and Ca2+ transients features of Merkel cells and partly explains how Merkel cells transduce the mechanical stimuli by Piezo2 channels.
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Affiliation(s)
- Fangtao Mao
- Research Center for Humanoid Sensing, Intelligent Perception Research Institute of Zhejiang Lab, Hangzhou, Zhejiang, China
| | - Wenzhen Yang
- Research Center for Humanoid Sensing, Intelligent Perception Research Institute of Zhejiang Lab, Hangzhou, Zhejiang, China
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3
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Bonnycastle K, Dobson KL, Blumrich EM, Gajbhiye A, Davenport EC, Pronot M, Steinruecke M, Trost M, Gonzalez-Sulser A, Cousin MA. Reversal of cell, circuit and seizure phenotypes in a mouse model of DNM1 epileptic encephalopathy. Nat Commun 2023; 14:5285. [PMID: 37648685 PMCID: PMC10468497 DOI: 10.1038/s41467-023-41035-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Accepted: 08/17/2023] [Indexed: 09/01/2023] Open
Abstract
Dynamin-1 is a large GTPase with an obligatory role in synaptic vesicle endocytosis at mammalian nerve terminals. Heterozygous missense mutations in the dynamin-1 gene (DNM1) cause a novel form of epileptic encephalopathy, with pathogenic mutations clustering within regions required for its essential GTPase activity. We reveal the most prevalent pathogenic DNM1 mutation, R237W, disrupts dynamin-1 enzyme activity and endocytosis when overexpressed in central neurons. To determine how this mutation impacted cell, circuit and behavioural function, we generated a mouse carrying the R237W mutation. Neurons from heterozygous mice display dysfunctional endocytosis, in addition to altered excitatory neurotransmission and seizure-like phenotypes. Importantly, these phenotypes are corrected at the cell, circuit and in vivo level by the drug, BMS-204352, which accelerates endocytosis. Here, we demonstrate a credible link between dysfunctional endocytosis and epileptic encephalopathy, and importantly reveal that synaptic vesicle recycling may be a viable therapeutic target for monogenic intractable epilepsies.
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Affiliation(s)
- Katherine Bonnycastle
- Centre for Discovery Brain Sciences, Hugh Robson Building, George Square, University of Edinburgh, EH8 9XD, Edinburgh, Scotland, UK.
- Simons Initiative for the Developing Brain, Hugh Robson Building, George Square, University of Edinburgh, EH8 9XD, Edinburgh, Scotland, UK.
- Muir Maxwell Epilepsy Centre, Hugh Robson Building, George Square, University of Edinburgh, EH8 9XD, Edinburgh, Scotland, UK.
- Service de Génétique Médicale, Centre Hospitalier Universitaire (CHU) Sainte-Justine, Université de Montréal, Montreal, QC, Canada.
| | - Katharine L Dobson
- Centre for Discovery Brain Sciences, Hugh Robson Building, George Square, University of Edinburgh, EH8 9XD, Edinburgh, Scotland, UK
- Simons Initiative for the Developing Brain, Hugh Robson Building, George Square, University of Edinburgh, EH8 9XD, Edinburgh, Scotland, UK
- Muir Maxwell Epilepsy Centre, Hugh Robson Building, George Square, University of Edinburgh, EH8 9XD, Edinburgh, Scotland, UK
| | - Eva-Maria Blumrich
- Centre for Discovery Brain Sciences, Hugh Robson Building, George Square, University of Edinburgh, EH8 9XD, Edinburgh, Scotland, UK
- Simons Initiative for the Developing Brain, Hugh Robson Building, George Square, University of Edinburgh, EH8 9XD, Edinburgh, Scotland, UK
- Muir Maxwell Epilepsy Centre, Hugh Robson Building, George Square, University of Edinburgh, EH8 9XD, Edinburgh, Scotland, UK
| | - Akshada Gajbhiye
- Newcastle University Biosciences Institute, Faculty of Medical Sciences, NE2 4HH, Newcastle upon Tyne, UK
| | - Elizabeth C Davenport
- Centre for Discovery Brain Sciences, Hugh Robson Building, George Square, University of Edinburgh, EH8 9XD, Edinburgh, Scotland, UK
- Simons Initiative for the Developing Brain, Hugh Robson Building, George Square, University of Edinburgh, EH8 9XD, Edinburgh, Scotland, UK
- Muir Maxwell Epilepsy Centre, Hugh Robson Building, George Square, University of Edinburgh, EH8 9XD, Edinburgh, Scotland, UK
| | - Marie Pronot
- Centre for Discovery Brain Sciences, Hugh Robson Building, George Square, University of Edinburgh, EH8 9XD, Edinburgh, Scotland, UK
- Simons Initiative for the Developing Brain, Hugh Robson Building, George Square, University of Edinburgh, EH8 9XD, Edinburgh, Scotland, UK
- Muir Maxwell Epilepsy Centre, Hugh Robson Building, George Square, University of Edinburgh, EH8 9XD, Edinburgh, Scotland, UK
| | - Moritz Steinruecke
- Centre for Discovery Brain Sciences, Hugh Robson Building, George Square, University of Edinburgh, EH8 9XD, Edinburgh, Scotland, UK
- Simons Initiative for the Developing Brain, Hugh Robson Building, George Square, University of Edinburgh, EH8 9XD, Edinburgh, Scotland, UK
- Muir Maxwell Epilepsy Centre, Hugh Robson Building, George Square, University of Edinburgh, EH8 9XD, Edinburgh, Scotland, UK
| | - Matthias Trost
- Newcastle University Biosciences Institute, Faculty of Medical Sciences, NE2 4HH, Newcastle upon Tyne, UK
| | - Alfredo Gonzalez-Sulser
- Centre for Discovery Brain Sciences, Hugh Robson Building, George Square, University of Edinburgh, EH8 9XD, Edinburgh, Scotland, UK
- Simons Initiative for the Developing Brain, Hugh Robson Building, George Square, University of Edinburgh, EH8 9XD, Edinburgh, Scotland, UK
- Muir Maxwell Epilepsy Centre, Hugh Robson Building, George Square, University of Edinburgh, EH8 9XD, Edinburgh, Scotland, UK
| | - Michael A Cousin
- Centre for Discovery Brain Sciences, Hugh Robson Building, George Square, University of Edinburgh, EH8 9XD, Edinburgh, Scotland, UK.
- Simons Initiative for the Developing Brain, Hugh Robson Building, George Square, University of Edinburgh, EH8 9XD, Edinburgh, Scotland, UK.
- Muir Maxwell Epilepsy Centre, Hugh Robson Building, George Square, University of Edinburgh, EH8 9XD, Edinburgh, Scotland, UK.
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4
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Heitmann T, Barrow JC. The Role of Inositol Hexakisphosphate Kinase in the Central Nervous System. Biomolecules 2023; 13:1317. [PMID: 37759717 PMCID: PMC10526494 DOI: 10.3390/biom13091317] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Revised: 08/23/2023] [Accepted: 08/26/2023] [Indexed: 09/29/2023] Open
Abstract
Inositol is a unique biological small molecule that can be phosphorylated or even further pyrophosphorylated on each of its six hydroxyl groups. These numerous phosphorylation states of inositol along with the kinases and phosphatases that interconvert them comprise the inositol phosphate signaling pathway. Inositol hexakisphosphate kinases, or IP6Ks, convert the fully mono-phosphorylated inositol to the pyrophosphate 5-IP7 (also denoted IP7). There are three isoforms of IP6K: IP6K1, 2, and 3. Decades of work have established a central role for IP6Ks in cell signaling. Genetic and pharmacologic manipulation of IP6Ks in vivo and in vitro has shown their importance in metabolic disease, chronic kidney disease, insulin signaling, phosphate homeostasis, and numerous other cellular and physiologic processes. In addition to these peripheral processes, a growing body of literature has shown the role of IP6Ks in the central nervous system (CNS). IP6Ks have a key role in synaptic vesicle regulation, Akt/GSK3 signaling, neuronal migration, cell death, autophagy, nuclear translocation, and phosphate homeostasis. IP6Ks' regulation of these cellular processes has functional implications in vivo in behavior and CNS anatomy.
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Affiliation(s)
- Tyler Heitmann
- Department of Pharmacology and Molecular Sciences, School of Medicine, Johns Hopkins University, 725 North Wolfe Street Suite 300, Baltimore, MD 21205, USA
- The Lieber Institute for Brain Development, 855 North Wolfe Street Suite 300, Baltimore, MD 21205, USA
| | - James C. Barrow
- Department of Pharmacology and Molecular Sciences, School of Medicine, Johns Hopkins University, 725 North Wolfe Street Suite 300, Baltimore, MD 21205, USA
- The Lieber Institute for Brain Development, 855 North Wolfe Street Suite 300, Baltimore, MD 21205, USA
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5
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Blumrich EM, Nicholson-Fish JC, Pronot M, Davenport EC, Kurian D, Cole A, Smillie KJ, Cousin MA. Phosphatidylinositol 4-kinase IIα is a glycogen synthase kinase 3-regulated interaction hub for activity-dependent bulk endocytosis. Cell Rep 2023; 42:112633. [PMID: 37314927 DOI: 10.1016/j.celrep.2023.112633] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 04/04/2023] [Accepted: 05/25/2023] [Indexed: 06/16/2023] Open
Abstract
Phosphatidylinositol 4-kinase IIα (PI4KIIα) generates essential phospholipids and is a cargo for endosomal adaptor proteins. Activity-dependent bulk endocytosis (ADBE) is the dominant synaptic vesicle endocytosis mode during high neuronal activity and is sustained by glycogen synthase kinase 3β (GSK3β) activity. We reveal the GSK3β substrate PI4KIIα is essential for ADBE via its depletion in primary neuronal cultures. Kinase-dead PI4KIIα rescues ADBE in these neurons but not a phosphomimetic form mutated at the GSK3β site, Ser-47. Ser-47 phosphomimetic peptides inhibit ADBE in a dominant-negative manner, confirming that Ser-47 phosphorylation is essential for ADBE. Phosphomimetic PI4KIIα interacts with a specific cohort of presynaptic molecules, two of which, AGAP2 and CAMKV, are also essential for ADBE when depleted in neurons. Thus, PI4KIIα is a GSK3β-dependent interaction hub that silos essential ADBE molecules for liberation during neuronal activity.
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Affiliation(s)
- Eva-Maria Blumrich
- Centre for Discovery Brain Sciences, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland EH8 9XD, UK; Muir Maxwell Epilepsy Centre, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland EH8 9XD, UK; Simons Initiative for the Developing Brain, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland EH8 9XD, UK
| | - Jessica C Nicholson-Fish
- Centre for Discovery Brain Sciences, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland EH8 9XD, UK
| | - Marie Pronot
- Centre for Discovery Brain Sciences, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland EH8 9XD, UK; Muir Maxwell Epilepsy Centre, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland EH8 9XD, UK; Simons Initiative for the Developing Brain, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland EH8 9XD, UK
| | - Elizabeth C Davenport
- Centre for Discovery Brain Sciences, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland EH8 9XD, UK; Muir Maxwell Epilepsy Centre, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland EH8 9XD, UK; Simons Initiative for the Developing Brain, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland EH8 9XD, UK
| | - Dominic Kurian
- The Roslin Institute, University of Edinburgh, Easter Bush, Midlothian, Scotland EH25 9RG, UK
| | - Adam Cole
- Neurosignalling and Mood Disorders Group, The Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, NSW 2010, Australia
| | - Karen J Smillie
- Centre for Discovery Brain Sciences, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland EH8 9XD, UK; Muir Maxwell Epilepsy Centre, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland EH8 9XD, UK.
| | - Michael A Cousin
- Centre for Discovery Brain Sciences, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland EH8 9XD, UK; Muir Maxwell Epilepsy Centre, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland EH8 9XD, UK; Simons Initiative for the Developing Brain, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland EH8 9XD, UK.
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6
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Malagon G, Myeong J, Klyachko VA. Two forms of asynchronous release with distinctive spatiotemporal dynamics in central synapses. eLife 2023; 12:e84041. [PMID: 37166282 PMCID: PMC10174687 DOI: 10.7554/elife.84041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2022] [Accepted: 04/24/2023] [Indexed: 05/12/2023] Open
Abstract
Asynchronous release is a ubiquitous form of neurotransmitter release that persists for tens to hundreds of milliseconds after an action potential. How asynchronous release is organized and regulated at the synaptic active zone (AZ) remains debatable. Using nanoscale-precision imaging of individual release events in rat hippocampal synapses, we observed two spatially distinct subpopulations of asynchronous events, ~75% of which occurred inside the AZ and with a bias towards the AZ center, while ~25% occurred outside of the functionally defined AZ, that is, ectopically. The two asynchronous event subpopulations also differed from each other in temporal properties, with ectopic events occurring at significantly longer time intervals from synchronous events than the asynchronous events inside the AZ. Both forms of asynchronous release did not, to a large extent, utilize the same release sites as synchronous events. The two asynchronous event subpopulations also differ from synchronous events in some aspects of exo-endocytosis coupling, particularly in the contribution from the fast calcium-dependent endocytosis. These results identify two subpopulations of asynchronous release events with distinctive organization and spatiotemporal dynamics.
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Affiliation(s)
- Gerardo Malagon
- Department of Cell Biology and Physiology, Washington University School of MedicineSt LouisUnited States
| | - Jongyun Myeong
- Department of Cell Biology and Physiology, Washington University School of MedicineSt LouisUnited States
| | - Vitaly A Klyachko
- Department of Cell Biology and Physiology, Washington University School of MedicineSt LouisUnited States
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7
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Kontaxi C, Ivanova D, Davenport EC, Kind PC, Cousin MA. Epilepsy-Related CDKL5 Deficiency Slows Synaptic Vesicle Endocytosis in Central Nerve Terminals. J Neurosci 2023; 43:2002-2020. [PMID: 36759195 PMCID: PMC10027047 DOI: 10.1523/jneurosci.1537-22.2023] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 12/20/2022] [Accepted: 01/09/2023] [Indexed: 02/11/2023] Open
Abstract
Cyclin-dependent kinase-like 5 (CDKL5) deficiency disorder (CDD) is a severe early-onset epileptic encephalopathy resulting mainly from de novo mutations in the X-linked CDKL5 gene. To determine whether loss of presynaptic CDKL5 function contributes to CDD, we examined synaptic vesicle (SV) recycling in primary hippocampal neurons generated from Cdkl5 knockout rat males. Using a genetically encoded reporter, we revealed that CDKL5 is selectively required for efficient SV endocytosis. We showed that CDKL5 kinase activity is both necessary and sufficient for optimal SV endocytosis, since kinase-inactive mutations failed to correct endocytosis in Cdkl5 knockout neurons, whereas the isolated CDKL5 kinase domain fully restored SV endocytosis kinetics. Finally, we demonstrated that CDKL5-mediated phosphorylation of amphiphysin 1, a putative presynaptic target, is not required for CDKL5-dependent control of SV endocytosis. Overall, our findings reveal a key presynaptic role for CDKL5 kinase activity and enhance our insight into how its dysfunction may culminate in CDD.SIGNIFICANCE STATEMENT Loss of cyclin-dependent kinase like 5 (CDKL5) function is a leading cause of monogenic childhood epileptic encephalopathy. However, information regarding its biological role is scarce. In this study, we reveal a selective presynaptic role for CDKL5 in synaptic vesicle endocytosis and that its protein kinase activity is both necessary and sufficient for this role. The isolated protein kinase domain is sufficient to correct this loss of function, which may facilitate future gene therapy strategies if presynaptic dysfunction is proven to be central to the disorder. It also reveals that a CDKL5-specific substrate is located at the presynapse, the phosphorylation of which is required for optimal SV endocytosis.
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Affiliation(s)
- Christiana Kontaxi
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH8 9XD, United Kingdom
- Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, EH8 9XD, United Kingdom
- Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, EH8 9XD, United Kingdom
| | - Daniela Ivanova
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH8 9XD, United Kingdom
- Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, EH8 9XD, United Kingdom
- Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, EH8 9XD, United Kingdom
| | - Elizabeth C Davenport
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH8 9XD, United Kingdom
- Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, EH8 9XD, United Kingdom
- Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, EH8 9XD, United Kingdom
| | - Peter C Kind
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH8 9XD, United Kingdom
- Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, EH8 9XD, United Kingdom
- Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, EH8 9XD, United Kingdom
| | - Michael A Cousin
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH8 9XD, United Kingdom
- Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, EH8 9XD, United Kingdom
- Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, EH8 9XD, United Kingdom
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8
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Biasetti L, Rey S, Fowler M, Ratnayaka A, Fennell K, Smith C, Marshall K, Hall C, Vargas-Caballero M, Serpell L, Staras K. Elevated amyloid beta disrupts the nanoscale organization and function of synaptic vesicle pools in hippocampal neurons. Cereb Cortex 2023; 33:1263-1276. [PMID: 35368053 PMCID: PMC9930632 DOI: 10.1093/cercor/bhac134] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 02/02/2022] [Accepted: 03/07/2022] [Indexed: 11/14/2022] Open
Abstract
Alzheimer's disease is linked to increased levels of amyloid beta (Aβ) in the brain, but the mechanisms underlying neuronal dysfunction and neurodegeneration remain enigmatic. Here, we investigate whether organizational characteristics of functional presynaptic vesicle pools, key determinants of information transmission in the central nervous system, are targets for elevated Aβ. Using an optical readout method in cultured hippocampal neurons, we show that acute Aβ42 treatment significantly enlarges the fraction of functional vesicles at individual terminals. We observe the same effect in a chronically elevated Aβ transgenic model (APPSw,Ind) using an ultrastructure-function approach that provides detailed information on nanoscale vesicle pool positioning. Strikingly, elevated Aβ is correlated with excessive accumulation of recycled vesicles near putative endocytic sites, which is consistent with deficits in vesicle retrieval pathways. Using the glutamate reporter, iGluSnFR, we show that there are parallel functional consequences, where ongoing information signaling capacity is constrained. Treatment with levetiracetam, an antiepileptic that dampens synaptic hyperactivity, partially rescues these transmission defects. Our findings implicate organizational and dynamic features of functional vesicle pools as targets in Aβ-driven synaptic impairment, suggesting that interventions to relieve the overloading of vesicle retrieval pathways might have promising therapeutic value.
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Affiliation(s)
- Luca Biasetti
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Brighton, BN1 9QG, United Kingdom
| | - Stephanie Rey
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Brighton, BN1 9QG, United Kingdom
- National Physical Laboratory, Middlesex, TW11 0LW, United Kingdom
| | - Milena Fowler
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Brighton, BN1 9QG, United Kingdom
| | - Arjuna Ratnayaka
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Brighton, BN1 9QG, United Kingdom
- Faculty of Medicine, University of Southampton, SO17 1BJ, United Kingdom
| | - Kate Fennell
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Brighton, BN1 9QG, United Kingdom
| | - Catherine Smith
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Brighton, BN1 9QG, United Kingdom
| | - Karen Marshall
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Brighton, BN1 9QG, United Kingdom
| | - Catherine Hall
- Sussex Neuroscience, School of Psychology, University of Sussex, Brighton, BN1 9QH, United Kingdom
| | - Mariana Vargas-Caballero
- School of Biological Sciences, University of Southampton, Highfield Campus, Southampton SO17 1BJ, United Kingdom
| | - Louise Serpell
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Brighton, BN1 9QG, United Kingdom
| | - Kevin Staras
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Brighton, BN1 9QG, United Kingdom
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9
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Wu XS, Wu LG. Multiple Modes of Fusion and Retrieval at the Calyx of Held Synapse. ADVANCES IN NEUROBIOLOGY 2023; 33:43-62. [PMID: 37615863 DOI: 10.1007/978-3-031-34229-5_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Abstract
Neurotransmitter in vesicles is released through a fusion pore when vesicles fuse with the plasma membrane. Subsequent retrieval of the fused vesicle membrane is the key step in recycling exocytosed vesicles. Application of advanced electrophysiological techniques to a large nerve terminal, the calyx of Held, has led to recordings of endocytosis, individual vesicle fusion and retrieval, and the kinetics of the fusion pore opening process and the fission pore closure process. These studies have revealed three kinetically different forms of endocytosis-rapid, slow, and bulk-and two forms of fusion-full collapse and kiss-and-run. Calcium influx triggers all kinetically distinguishable forms of endocytosis at calyces by activation of calmodulin/calcineurin signaling pathway and protein kinase C, which may dephosphorylate and phosphorylate endocytic proteins. Polymerized actin may provide mechanical forces to bend the membrane, forming membrane pits, the precursor for generating vesicles. These research advancements are reviewed in this chapter.
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Affiliation(s)
- Xin-Sheng Wu
- National Institute of Neurological Disorders and Stroke, Bethesda, MD, USA.
| | - Ling-Gang Wu
- National Institute of Neurological Disorders and Stroke, Bethesda, MD, USA.
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10
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Park HG, Kim YD, Cho E, Lu TY, Yao CK, Lee J, Lee S. Vav independently regulates synaptic growth and plasticity through distinct actin-based processes. J Cell Biol 2022; 221:213401. [PMID: 35976098 PMCID: PMC9388202 DOI: 10.1083/jcb.202203048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Revised: 07/23/2022] [Accepted: 08/03/2022] [Indexed: 11/22/2022] Open
Abstract
Modulation of presynaptic actin dynamics is fundamental to synaptic growth and functional plasticity; yet the underlying molecular and cellular mechanisms remain largely unknown. At Drosophila NMJs, the presynaptic Rac1-SCAR pathway mediates BMP-induced receptor macropinocytosis to inhibit BMP growth signaling. Here, we show that the Rho-type GEF Vav acts upstream of Rac1 to inhibit synaptic growth through macropinocytosis. We also present evidence that Vav-Rac1-SCAR signaling has additional roles in tetanus-induced synaptic plasticity. Presynaptic inactivation of Vav signaling pathway components, but not regulators of macropinocytosis, impairs post-tetanic potentiation (PTP) and enhances synaptic depression depending on external Ca2+ concentration. Interfering with the Vav-Rac1-SCAR pathway also impairs mobilization of reserve pool (RP) vesicles required for tetanus-induced synaptic plasticity. Finally, treatment with an F-actin–stabilizing drug completely restores RP mobilization and plasticity defects in Vav mutants. We propose that actin-regulatory Vav-Rac1-SCAR signaling independently regulates structural and functional presynaptic plasticity by driving macropinocytosis and RP mobilization, respectively.
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Affiliation(s)
- Hyun Gwan Park
- Department of Brain and Cognitive Sciences, Seoul National University, Seoul, Korea.,Department of Cell and Developmental Biology and Dental Research Institute, Seoul National University, Seoul, Korea
| | - Yeongjin David Kim
- Department of Brain and Cognitive Sciences, Seoul National University, Seoul, Korea.,Department of Cell and Developmental Biology and Dental Research Institute, Seoul National University, Seoul, Korea
| | - Eunsang Cho
- Department of Brain and Cognitive Sciences, Seoul National University, Seoul, Korea.,Department of Cell and Developmental Biology and Dental Research Institute, Seoul National University, Seoul, Korea
| | - Ting-Yi Lu
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Chi-Kuang Yao
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Jihye Lee
- Department of Oral Pathology, School of Dentistry, Pusan National University, Yangsan, Korea
| | - Seungbok Lee
- Department of Brain and Cognitive Sciences, Seoul National University, Seoul, Korea.,Department of Cell and Developmental Biology and Dental Research Institute, Seoul National University, Seoul, Korea
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11
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Monitoring cell membrane recycling dynamics of proteins using whole-cell fluorescence recovery after photobleaching of pH-sensitive genetic tags. Nat Protoc 2022; 17:3056-3079. [PMID: 36064755 DOI: 10.1038/s41596-022-00732-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2021] [Accepted: 06/07/2022] [Indexed: 11/08/2022]
Abstract
Population behavior of signaling molecules on the cell surface is key to their adaptive function. Live imaging of proteins tagged with fluorescent molecules has been an essential tool in understanding this behavior. Typically, genetic or chemical tags are used to target molecules present throughout the cell, whereas antibody-based tags label the externally exposed molecular domains only. Both approaches could potentially overlook the intricate process of in-out membrane recycling in which target molecules appear or disappear on the cell surface. This limitation is overcome by using a pH-sensitive fluorescent tag, such as Super-Ecliptic pHluorin (SEP), because its emission depends on whether it resides inside or outside the cell. Here we focus on the main glial glutamate transporter GLT1 and describe a genetic design that equips GLT1 molecules with SEP without interfering with the transporter's main function. Expressing GLT1-SEP in astroglia in cultures or in hippocampal slices enables monitoring of the real-time dynamics of the cell-surface and cytosolic fractions of the transporter in living cells. Whole-cell fluorescence recovery after photobleaching and quantitative image-kinetic analysis of the resulting time-lapse images enables assessment of the rate of GLT1-SEP recycling on the cell surface, a fundamental trafficking parameter unattainable previously. The present protocol takes 15-20 d to set up cell preparations, and 2-3 d to carry out live cell experiments and data analyses. The protocol can be adapted to study different membrane molecules of interest, particularly those proteins whose lifetime on the cell surface is critical to their adaptive function.
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12
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Montenegro‐Venegas C, Guhathakurta D, Pina‐Fernandez E, Andres‐Alonso M, Plattner F, Gundelfinger ED, Fejtova A. Bassoon controls synaptic vesicle release via regulation of presynaptic phosphorylation and
cAMP. EMBO Rep 2022; 23:e53659. [PMID: 35766170 PMCID: PMC9346490 DOI: 10.15252/embr.202153659] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Revised: 05/23/2022] [Accepted: 06/01/2022] [Indexed: 11/11/2022] Open
Abstract
Neuronal presynaptic terminals contain hundreds of neurotransmitter‐filled synaptic vesicles (SVs). The morphologically uniform SVs differ in their release competence segregating into functional pools that differentially contribute to neurotransmission. The presynaptic scaffold bassoon is required for neurotransmission, but the underlying molecular mechanisms are unknown. We report that glutamatergic synapses lacking bassoon feature decreased SV release competence and increased resting pool of SVs as assessed by imaging of SV release in cultured neurons. CDK5/calcineurin and cAMP/PKA presynaptic signalling are dysregulated, resulting in an aberrant phosphorylation of their downstream effectors synapsin1 and SNAP25, well‐known regulators of SV release competence. An acute pharmacological restoration of physiological CDK5 and cAMP/PKA activity fully normalises the SV pools in neurons lacking bassoon. Finally, we demonstrate that CDK5‐dependent regulation of PDE4 activity interacts with cAMP/PKA signalling and thereby controls SV release competence. These data reveal that bassoon organises SV pools in glutamatergic synapses via regulation of presynaptic phosphorylation and cAMP homeostasis and indicate a role of CDK5/PDE4/cAMP axis in the control of neurotransmitter release.
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Affiliation(s)
- Carolina Montenegro‐Venegas
- Department of Neurochemistry and Molecular Biology Leibniz Institute for Neurobiology Magdeburg Germany
- Center for Behavioral Brain Sciences (CBBS) Magdeburg Germany
- Institute for Pharmacology and Toxicology, Medical Faculty Otto von Guericke University Magdeburg Germany
| | - Debarpan Guhathakurta
- Molecular Psychiatry, Department of Psychiatry and Psychotherapy Universitätsklinikum Erlangen, Friedrich‐Alexander‐Universität Erlangen‐Nürnberg Erlangen Germany
| | | | - Maria Andres‐Alonso
- RG Presynaptic Plasticity Leibniz Institute for Neurobiology Magdeburg Germany
| | | | - Eckart D Gundelfinger
- Department of Neurochemistry and Molecular Biology Leibniz Institute for Neurobiology Magdeburg Germany
- Center for Behavioral Brain Sciences (CBBS) Magdeburg Germany
- Institute for Pharmacology and Toxicology, Medical Faculty Otto von Guericke University Magdeburg Germany
| | - Anna Fejtova
- Department of Neurochemistry and Molecular Biology Leibniz Institute for Neurobiology Magdeburg Germany
- Molecular Psychiatry, Department of Psychiatry and Psychotherapy Universitätsklinikum Erlangen, Friedrich‐Alexander‐Universität Erlangen‐Nürnberg Erlangen Germany
- RG Presynaptic Plasticity Leibniz Institute for Neurobiology Magdeburg Germany
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13
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Li H, Datunashvili M, Reyes RC, Voglmaier SM. Inositol hexakisphosphate kinases differentially regulate trafficking of vesicular glutamate transporters 1 and 2. Front Cell Neurosci 2022; 16:926794. [PMID: 35936490 PMCID: PMC9355605 DOI: 10.3389/fncel.2022.926794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2022] [Accepted: 06/27/2022] [Indexed: 11/16/2022] Open
Abstract
Inositol pyrophosphates have been implicated in cellular signaling and membrane trafficking, including synaptic vesicle (SV) recycling. Inositol hexakisphosphate kinases (IP6Ks) and their product, diphosphoinositol pentakisphosphate (PP-IP5 or IP7), directly and indirectly regulate proteins important in vesicle recycling by the activity-dependent bulk endocytosis pathway (ADBE). In the present study, we show that two isoforms, IP6K1 and IP6K3, are expressed in axons. The role of the kinases in SV recycling are investigated using pharmacologic inhibition, shRNA knockdown, and IP6K1 and IP6K3 knockout mice. Live-cell imaging experiments use optical reporters of SV recycling based on vesicular glutamate transporter isoforms, VGLUT1- and VGLUT2-pHluorins (pH), which recycle differently. VGLUT1-pH recycles by classical AP-2 dependent endocytosis under moderate stimulation conditions, while VGLUT2-pH recycles using AP-1 and AP-3 adaptor proteins as well. Using a short stimulus to release the readily releasable pool (RRP), we show that IP6K1 KO increases exocytosis of both VGLUT1-and VGLUT2-pH, while IP6K3 KO decreases the amount of both transporters in the RRP. In electrophysiological experiments we measure glutamate signaling with short stimuli and under the intense stimulation conditions that trigger bulk endocytosis. IP6K1 KO increases synaptic facilitation and IP6K3 KO decreases facilitation compared to wild type in CA1 hippocampal Schaffer collateral synapses. After intense stimulation, the rate of endocytosis of VGLUT2-pH, but not VGLUT1-pH, is increased by knockout, knockdown, and pharmacologic inhibition of IP6Ks. Thus IP6Ks differentially affect the endocytosis of two SV protein cargos that use different endocytic pathways. However, while IP6K1 KO and IP6K3 KO exert similar effects on endocytosis after stimulation, the isoforms exert different effects on exocytosis earlier in the stimulus and on the early phase of glutamate release. Taken together, the data indicate a role for IP6Ks both in exocytosis early in the stimulation period and in endocytosis, particularly under conditions that may utilize AP-1/3 adaptors.
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14
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Shi B, Jin YH, Wu LG. Dynamin 1 controls vesicle size and endocytosis at hippocampal synapses. Cell Calcium 2022; 103:102564. [PMID: 35220002 PMCID: PMC9009158 DOI: 10.1016/j.ceca.2022.102564] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 01/27/2022] [Accepted: 02/15/2022] [Indexed: 11/16/2022]
Abstract
Following calcium-triggered vesicle exocytosis, endocytosis regenerates vesicles to maintain exocytosis and thus synaptic transmission, which underlies neuronal circuit activities. Although most molecules involved in endocytosis have been identified, it remains rather poorly understood how endocytic machinery regulates vesicle size. Vesicle size, together with the transmitter concentration inside the vesicle, determines the amount of transmitter the vesicle can release, the quantal size, that may control the strength of synaptic transmission. Here, we report that, surprisingly, knockout of the GTPase dynamin 1, the most abundant brain dynamin isoform known to catalyze fission of the membrane pit's neck (the last step of endocytosis), not only significantly slowed endocytosis but also increased the synaptic vesicle diameter by as much as ∼40-64% at cultured hippocampal synapses. Furthermore, dynamin 1 knockout increased the size of membrane pits, the precursor for endocytic vesicle formation. These results suggest an important function of dynamin other than its well-known fission function - control of vesicle size at the pit formation stage.
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Affiliation(s)
- Bo Shi
- National Institute of Neurological Disorders and Stroke, 35 Convent Dr., Bethesda, MD 20892 United States; Biological Sciences Graduate Program, College of Computer, Mathematical, and Natural Sciences, University of Maryland, College Park, MD 20740 United States
| | - Ying-Hui Jin
- National Institute of Neurological Disorders and Stroke, 35 Convent Dr., Bethesda, MD 20892 United States; Department of Critical Care Medicine, Nanfang Hospital, Southern Medical University, 1838 North Guangzhou Ave, Guangzhou 510515, China
| | - Ling-Gang Wu
- National Institute of Neurological Disorders and Stroke, 35 Convent Dr., Bethesda, MD 20892 United States.
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15
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FMRP Sustains Presynaptic Function via Control of Activity-Dependent Bulk Endocytosis. J Neurosci 2022; 42:1618-1628. [PMID: 34996816 PMCID: PMC8883869 DOI: 10.1523/jneurosci.0852-21.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 12/22/2021] [Accepted: 12/23/2021] [Indexed: 11/21/2022] Open
Abstract
Synaptic vesicle (SV) recycling is essential for the maintenance of neurotransmission, with a number of neurodevelopmental disorders linked to defects in this process. Fragile X syndrome (FXS) results from a loss of fragile X mental retardation protein (FMRP) encoded by the FMR1 gene. Hyperexcitability of neuronal circuits is a key feature of FXS, therefore we investigated whether SV recycling was affected by the absence of FMRP during increased neuronal activity. We revealed that primary neuronal cultures from male Fmr1 knock-out (KO) rats display a specific defect in activity-dependent bulk endocytosis (ADBE). ADBE is dominant during intense neuronal activity, and this defect resulted in an inability of Fmr1 KO neurons to sustain SV recycling during trains of high-frequency stimulation. Using a molecular replacement strategy, we also revealed that a human FMRP mutant that cannot bind BK channels failed to correct ADBE dysfunction in KO neurons, however this dysfunction was corrected by BK channel agonists. Therefore, FMRP performs a key role in sustaining neurotransmitter release via selective control of ADBE, suggesting intervention via this endocytosis mode may correct the hyperexcitability observed in FXS.SIGNIFICANCE STATEMENT Loss of fragile X mental retardation protein (FMRP) results in fragile X syndrome (FXS), however whether its loss has a direct role in neurotransmitter release remains a matter of debate. We demonstrate that neurons lacking FMRP display a specific defect in a mechanism that sustains neurotransmitter release during intense neuronal firing, called activity-dependent bulk endocytosis (ADBE). This discovery provides key insights into mechanisms of brain communication that occur because of loss of FMRP function. Importantly it also reveals ADBE as a potential therapeutic target to correct the circuit hyperexcitability observed in FXS.
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16
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Clayton EL, Bonnycastle K, Isaacs AM, Cousin MA, Schorge S. A novel synaptopathy-defective synaptic vesicle protein trafficking in the mutant CHMP2B mouse model of frontotemporal dementia. J Neurochem 2022; 160:412-425. [PMID: 34855215 DOI: 10.1111/jnc.15551] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 11/10/2021] [Accepted: 11/18/2021] [Indexed: 12/13/2022]
Abstract
Mutations in the ESCRT-III subunit CHMP2B cause frontotemporal dementia (FTD) and lead to impaired endolysosomal trafficking and lysosomal storage pathology in neurons. We investigated the effect of mutant CHMP2B on synaptic pathology, as ESCRT function was recently implicated in the degradation of synaptic vesicle (SV) proteins. We report here that expression of C-terminally truncated mutant CHMP2B results in a novel synaptopathy. This unique synaptic pathology is characterised by selective retention of presynaptic SV trafficking proteins in aged mutant CHMP2B transgenic mice, despite significant loss of postsynaptic proteins. Furthermore, ultrastructural analysis of primary cortical cultures from transgenic CHMP2B mice revealed a significant increase in the number of presynaptic endosomes, while neurons expressing mutant CHMP2B display defective SV recycling and alterations to functional SV pools. Therefore, we reveal how mutations in CHMP2B affect specific presynaptic proteins and SV recycling, identifying CHMP2B FTD as a novel synaptopathy. This novel synaptopathic mechanism of impaired SV physiology may be a key early event in multiple forms of FTD, since proteins that mediate the most common genetic forms of FTD all localise at the presynapse.
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Affiliation(s)
- Emma L Clayton
- Department of Pharmacology, UCL School of Pharmacy, London, UK
- Currently at UK Dementia Research Institute at King's College London, London, UK
| | - Katherine Bonnycastle
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, Scotland
- Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, Scotland
- Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, Scotland
| | - Adrian M Isaacs
- UK Dementia Research Institute at UCL, London, UK
- Department of Neurodegenerative Disease, UCL Queen Square Institute of Neurology, London, UK
| | - Michael A Cousin
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, Scotland
- Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, Scotland
- Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, Scotland
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17
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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: 39] [Impact Index Per Article: 13.0] [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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18
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Kesharwani A, Schwarz K, Dembla E, Dembla M, Schmitz F. Early Changes in Exo- and Endocytosis in the EAE Mouse Model of Multiple Sclerosis Correlate with Decreased Synaptic Ribbon Size and Reduced Ribbon-Associated Vesicle Pools in Rod Photoreceptor Synapses. Int J Mol Sci 2021; 22:ijms221910789. [PMID: 34639129 PMCID: PMC8509850 DOI: 10.3390/ijms221910789] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 09/29/2021] [Accepted: 10/01/2021] [Indexed: 12/17/2022] Open
Abstract
Multiple sclerosis (MS) is an inflammatory disease of the central nervous system that finally leads to demyelination. Demyelinating optic neuritis is a frequent symptom in MS. Recent studies also revealed synapse dysfunctions in MS patients and MS mouse models. We previously reported alterations of photoreceptor ribbon synapses in the experimental auto-immune encephalomyelitis (EAE) mouse model of MS. In the present study, we found that the previously observed decreased imunosignals of photoreceptor ribbons in early EAE resulted from a decrease in synaptic ribbon size, whereas the number/density of ribbons in photoreceptor synapses remained unchanged. Smaller photoreceptor ribbons are associated with fewer docked and ribbon-associated vesicles. At a functional level, depolarization-evoked exocytosis as monitored by optical recording was diminished even as early as on day 7 after EAE induction. Moreover compensatory, post-depolarization endocytosis was decreased. Decreased post-depolarization endocytosis in early EAE correlated with diminished synaptic enrichment of dynamin3. In contrast, basal endocytosis in photoreceptor synapses of resting non-depolarized retinal slices was increased in early EAE. Increased basal endocytosis correlated with increased de-phosphorylation of dynamin1. Thus, multiple endocytic pathways in photoreceptor synapse are differentially affected in early EAE and likely contribute to the observed synapse pathology in early EAE.
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Affiliation(s)
- Ajay Kesharwani
- Department of Neuroanatomy, Institute of Anatomy and Cell Biology, Medical School, Saarland University, 66421 Homburg, Germany; (K.S.); (E.D.); (M.D.); (F.S.)
- Correspondence:
| | - Karin Schwarz
- Department of Neuroanatomy, Institute of Anatomy and Cell Biology, Medical School, Saarland University, 66421 Homburg, Germany; (K.S.); (E.D.); (M.D.); (F.S.)
| | - Ekta Dembla
- Department of Neuroanatomy, Institute of Anatomy and Cell Biology, Medical School, Saarland University, 66421 Homburg, Germany; (K.S.); (E.D.); (M.D.); (F.S.)
- Department of Ophthalmology, Duke University School of Medicine, Durham, NC 27710, USA
| | - Mayur Dembla
- Department of Neuroanatomy, Institute of Anatomy and Cell Biology, Medical School, Saarland University, 66421 Homburg, Germany; (K.S.); (E.D.); (M.D.); (F.S.)
- Department of Ophthalmology, Duke University School of Medicine, Durham, NC 27710, USA
| | - Frank Schmitz
- Department of Neuroanatomy, Institute of Anatomy and Cell Biology, Medical School, Saarland University, 66421 Homburg, Germany; (K.S.); (E.D.); (M.D.); (F.S.)
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19
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Subrahmanyam R, Dwivedi D, Rashid Z, Bonnycastle K, Cousin MA, Chattarji S. Reciprocal regulation of spontaneous synaptic vesicle fusion by Fragile X mental retardation protein and group I metabotropic glutamate receptors. J Neurochem 2021; 158:1094-1109. [PMID: 34327719 DOI: 10.1111/jnc.15484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Revised: 06/21/2021] [Accepted: 07/22/2021] [Indexed: 11/29/2022]
Abstract
Fragile X mental retardation protein (FMRP) is a neuronal protein mediating multiple functions, with its absence resulting in one of the most common monogenic causes of autism, Fragile X syndrome (FXS). Analyses of FXS pathophysiology have identified a range of aberrations in synaptic signaling pathways and plasticity associated with group I metabotropic glutamate (mGlu) receptors. These studies, however, have mostly focused on the post-synaptic functions of FMRP and mGlu receptor activation, and relatively little is known about their presynaptic effects. Neurotransmitter release is mediated via multiple forms of synaptic vesicle (SV) fusion, each of which contributes to specific neuronal functions. The impacts of mGlu receptor activation and loss of FMRP on these SV fusion events remain unexplored. Here we combined electrophysiological and fluorescence imaging analyses on primary hippocampal cultures prepared from an Fmr1 knockout (KO) rat model. Compared to wild-type (WT) hippocampal neurons, KO neurons displayed an increase in the frequency of spontaneous excitatory post-synaptic currents (sEPSCs), as well as spontaneous SV fusion events. Pharmacological activation of mGlu receptors in WT neurons caused a similar increase in spontaneous SV fusion and sEPSC frequency. Notably, this increase in SV fusion was not observed when spontaneous activity was blocked using the sodium channel antagonist tetrodotoxin. Importantly, the effect of mGlu receptor activation on spontaneous SV fusion was occluded in Fmr1 KO neurons. Together, our results reveal that FMRP represses spontaneous presynaptic SV fusion, whereas mGlu receptor activation increases this event. This reciprocal control appears to be mediated via their regulation of intrinsic neuronal excitability.
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Affiliation(s)
- Rohini Subrahmanyam
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bengaluru, India
| | - Deepanjali Dwivedi
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bengaluru, India
| | - Zubin Rashid
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bengaluru, India
| | - Katherine Bonnycastle
- Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK.,The Patrick Wild Centre, University of Edinburgh, Edinburgh, UK.,Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - Michael A Cousin
- Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK.,The Patrick Wild Centre, University of Edinburgh, Edinburgh, UK.,Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - Sumantra Chattarji
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bengaluru, India.,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK.,The Patrick Wild Centre, University of Edinburgh, Edinburgh, UK.,Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.,Centre for Brain Development and Repair, Institute for Stem Cell Biology and Regenerative Medicine, Bengaluru, India
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20
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Ivanova D, Dobson KL, Gajbhiye A, Davenport EC, Hacker D, Ultanir SK, Trost M, Cousin MA. Control of synaptic vesicle release probability via VAMP4 targeting to endolysosomes. SCIENCE ADVANCES 2021; 7:7/18/eabf3873. [PMID: 33931449 PMCID: PMC8087399 DOI: 10.1126/sciadv.abf3873] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 03/11/2021] [Indexed: 05/03/2023]
Abstract
Synaptic vesicle (SV) release probability (Pr), determines the steady state and plastic control of neurotransmitter release. However, how diversity in SV composition arises and regulates the Pr of individual SVs is not understood. We found that modulation of the copy number of the noncanonical vesicular SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor), vesicle-associated membrane protein 4 (VAMP4), on SVs is key for regulating Pr. Mechanistically, this is underpinned by its reduced ability to form an efficient SNARE complex with canonical plasma membrane SNAREs. VAMP4 has unusually high synaptic turnover and is selectively sorted to endolysosomes during activity-dependent bulk endocytosis. Disruption of endolysosomal trafficking and function markedly increased the abundance of VAMP4 in the SV pool and inhibited SV fusion. Together, our results unravel a new mechanism for generating SV heterogeneity and control of Pr through coupling of SV recycling to a major clearing system that regulates protein homeostasis.
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Affiliation(s)
- Daniela Ivanova
- Centre for Discovery Brain Sciences, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland.
- Muir Maxwell Epilepsy Centre, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland
- Simons Initiative for the Developing Brain, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland
| | - Katharine L Dobson
- Centre for Discovery Brain Sciences, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland
- Muir Maxwell Epilepsy Centre, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland
- Simons Initiative for the Developing Brain, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland
| | - Akshada Gajbhiye
- Newcastle University Biosciences Institute, Faculty of Medical Sciences, Newcastle upon Tyne NE2 4HH, UK
| | - Elizabeth C Davenport
- Centre for Discovery Brain Sciences, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland
- Muir Maxwell Epilepsy Centre, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland
- Simons Initiative for the Developing Brain, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland
| | - Daniela Hacker
- Centre for Discovery Brain Sciences, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland
- Muir Maxwell Epilepsy Centre, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland
- Simons Initiative for the Developing Brain, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland
| | - Sila K Ultanir
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Matthias Trost
- Newcastle University Biosciences Institute, Faculty of Medical Sciences, Newcastle upon Tyne NE2 4HH, UK
| | - Michael A Cousin
- Centre for Discovery Brain Sciences, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland.
- Muir Maxwell Epilepsy Centre, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland
- Simons Initiative for the Developing Brain, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland
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21
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Orlando M, Schmitz D, Rosenmund C, Herman MA. Calcium-Independent Exo-endocytosis Coupling at Small Central Synapses. Cell Rep 2020; 29:3767-3774.e3. [PMID: 31851910 DOI: 10.1016/j.celrep.2019.11.060] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 10/08/2019] [Accepted: 11/14/2019] [Indexed: 12/27/2022] Open
Abstract
At presynaptic terminals, neurotransmitters are released by synaptic vesicle exocytosis at the active zone. In order to maintain efficient neurotransmission and proper synaptic structure, sites of vesicle fusion must be cleared rapidly by endocytosis. Therefore, the coupling of exo- and endocytosis is crucial. Despite many years of research, the exact molecular and biophysical requirements for the coupling of exo- and endocytosis remain unclear. We investigate whether endocytosis can be triggered in a calcium-independent fashion by evoking calcium-independent exocytosis using a hypertonic sucrose solution. We demonstrate that endocytosis can be triggered, in the absence of calcium influx, in a clathrin-independent manner that relies on actin polymerization. Our findings point to a central role of membrane tension dependent on actin for efficient coupling of exo- and endocytosis.
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Affiliation(s)
- Marta Orlando
- Charité-Universitätsmedizin Berlin, corporate member of Freie Universitäts Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of Health, NeuroCure Cluster of Excellence, Institut für Neurophysiologie, Charitéplatz 1, 10117 Berlin, Germany
| | - Dietmar Schmitz
- Charité-Universitätsmedizin Berlin, corporate member of Freie Universitäts Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of Health, NeuroCure Cluster of Excellence, German Center for Neurodegenerative Diseases (DZNE), Charitéplatz 1, 10117 Berlin, Germany; Einstein Center for Neurosciences (ECN), 10117 Berlin, Germany; Bernstein Center for Computational Neuroscience (BCCN) Berlin, 10115 Berlin, Germany; Max-Delbruck-Centrum (MDC) for Molecular Medicine, 13125 Berlin, Germany
| | - Christian Rosenmund
- Charité-Universitätsmedizin Berlin, corporate member of Freie Universitäts Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of Health, NeuroCure Cluster of Excellence, Institut für Neurophysiologie, Charitéplatz 1, 10117 Berlin, Germany; Einstein Center for Neurosciences (ECN), 10117 Berlin, Germany.
| | - Melissa A Herman
- Charité-Universitätsmedizin Berlin, corporate member of Freie Universitäts Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of Health, NeuroCure Cluster of Excellence, Institut für Neurophysiologie, Charitéplatz 1, 10117 Berlin, Germany.
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22
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Nosov G, Kahms M, Klingauf J. The Decade of Super-Resolution Microscopy of the Presynapse. Front Synaptic Neurosci 2020; 12:32. [PMID: 32848695 PMCID: PMC7433402 DOI: 10.3389/fnsyn.2020.00032] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Accepted: 07/21/2020] [Indexed: 01/05/2023] Open
Abstract
The presynaptic compartment of the chemical synapse is a small, yet extremely complex structure. Considering its size, most methods of optical microscopy are not able to resolve its nanoarchitecture and dynamics. Thus, its ultrastructure could only be studied by electron microscopy. In the last decade, new methods of optical superresolution microscopy have emerged allowing the study of cellular structures and processes at the nanometer scale. While this is a welcome addition to the experimental arsenal, it has necessitated careful analysis and interpretation to ensure the data obtained remains artifact-free. In this article we review the application of nanoscopic techniques to the study of the synapse and the progress made over the last decade with a particular focus on the presynapse. We find to our surprise that progress has been limited, calling for imaging techniques and probes that allow dense labeling, multiplexing, longer imaging times, higher temporal resolution, while at least maintaining the spatial resolution achieved thus far.
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Affiliation(s)
- Georgii Nosov
- Institute of Medical Physics and Biophysics, University of Münster, Münster, Germany.,CIM-IMPRS Graduate Program in Münster, Münster, Germany
| | - Martin Kahms
- Institute of Medical Physics and Biophysics, University of Münster, Münster, Germany
| | - Jurgen Klingauf
- Institute of Medical Physics and Biophysics, University of Münster, Münster, Germany
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23
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Kotova A, Timonina K, Zoidl GR. Endocytosis of Connexin 36 is Mediated by Interaction with Caveolin-1. Int J Mol Sci 2020; 21:E5401. [PMID: 32751343 PMCID: PMC7432810 DOI: 10.3390/ijms21155401] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2020] [Revised: 07/25/2020] [Accepted: 07/28/2020] [Indexed: 12/22/2022] Open
Abstract
The gap junctional protein connexin 36 (Cx36) has been co-purified with the lipid raft protein caveolin-1 (Cav-1). The relevance of an interaction between the two proteins is unknown. In this study, we explored the significance of Cav-1 interaction in the context of intracellular and membrane transport of Cx36. Coimmunoprecipitation assays and Förster resonance energy transfer analysis (FRET) were used to confirm the interaction between the two proteins in the Neuro 2a cell line. We found that the Cx36 and Cav-1 interaction was dependent on the intracellular calcium levels. By employing different microscopy techniques, we demonstrated that Cav-1 enhances the vesicular transport of Cx36. Pharmacological interventions coupled with cell surface biotinylation assays and FRET analysis revealed that Cav-1 regulates membrane localization of Cx36. Our data indicate that the interaction between Cx36 and Cav-1 plays a role in the internalization of Cx36 by a caveolin-dependent pathway.
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Affiliation(s)
- Anna Kotova
- Department of Biology, York University, Toronto, ON M3J 1P3, Canada; (A.K.); (K.T.)
| | - Ksenia Timonina
- Department of Biology, York University, Toronto, ON M3J 1P3, Canada; (A.K.); (K.T.)
| | - Georg R. Zoidl
- Department of Biology, York University, Toronto, ON M3J 1P3, Canada; (A.K.); (K.T.)
- Department of Psychology, York University, Toronto, ON M3J 1P3, Canada
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24
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Activity and Cytosolic Na + Regulate Synaptic Vesicle Endocytosis. J Neurosci 2020; 40:6112-6120. [PMID: 32605936 DOI: 10.1523/jneurosci.0119-20.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Revised: 06/18/2020] [Accepted: 06/24/2020] [Indexed: 11/21/2022] Open
Abstract
Retrieval of synaptic vesicles via endocytosis is essential for maintaining sustained synaptic transmission, especially for neurons that fire action potentials at high frequencies. However, how neuronal activity regulates synaptic vesicle recycling is largely unknown. Here we report that Na+ substantially accumulated in the mouse calyx of Held terminals of either sex during repetitive high-frequency spiking. Elevated presynaptic Na+ accelerated both slow and rapid forms of endocytosis and facilitated endocytosis overshoot, but did not affect the readily releasable pool size, Ca2+ influx, or exocytosis. To examine whether this facilitation of endocytosis is related to the Na+-dependent vesicular content change, we dialyzed glutamate into the presynaptic cytosol or blocked the vesicular glutamate uptake with bafilomycin and found that the rate of endocytosis was not affected by regulating the vesicular glutamate content. Endocytosis is critically dependent on intracellular Ca2+, and the activity of Na+/Ca2+ exchanger (NCX) may be altered when the Na+ gradient is changed. However, neither NCX inhibitor nor change of extracellular Na+ concentration affected the endocytosis rate. Moreover, two-photon Ca2+ imaging showed that presynaptic Na+ did not affect the action potential-evoked intracellular Ca2+ transient and decay. Therefore, we revealed a novel mechanism of cytosolic Na+ in accelerating vesicle endocytosis. During high-frequency synaptic transmission, when large numbers of synaptic vesicles were fused, the rapid buildup of presynaptic cytosolic Na+ promoted vesicle recycling and sustained synaptic transmission.SIGNIFICANCE STATEMENT High-frequency firing neurons are widely distributed in the CNS. A large number of synaptic vesicles are released during high-frequency synaptic transmission; accordingly, synaptic vesicles need to be recycled rapidly to replenish the vesicle pool. Synaptic vesicle exocytosis and endocytosis are tightly coupled, and their coupling is essential for synaptic function and structural stability. We showed here that intracellular Na+ concentration at the calyx of Held terminal increased rapidly during spike activity and the increased Na+ accelerated endocytosis. Thus, when large numbers of synaptic vesicles are released during high-frequency synaptic transmission, Na+ accumulated in terminals and facilitated vesicle recycling. These findings represent a novel cellular mechanism that supports reliable synaptic transmission at high frequency in the CNS.
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25
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Park SJ, Park H, Kim MG, Zhang S, Park SE, Kim S, Chung C. Inositol Pyrophosphate Metabolism Regulates Presynaptic Vesicle Cycling at Central Synapses. iScience 2020; 23:101000. [PMID: 32252022 PMCID: PMC7132149 DOI: 10.1016/j.isci.2020.101000] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 02/17/2020] [Accepted: 03/18/2020] [Indexed: 11/27/2022] Open
Abstract
The coordination of synaptic vesicle exocytosis and endocytosis supports neurotransmitter release from presynaptic terminals. Although inositol pyrophosphates, such as 5-diphosphoinositol pentakisphosphate (5-IP7), are versatile signaling metabolites in many biological events, physiological actions of 5-IP7 on synaptic membrane vesicle trafficking remain unclear. Here, we investigated the role of 5-IP7 in synaptic transmission in hippocampal brain slices from inositol hexakisphosphate kinase 1 (Ip6k1)-knockout mice. We found that presynaptic release probability was significantly increased in Ip6k1-knockout neurons, implying enhanced activity-dependent synaptic vesicle exocytosis. Expression of wild-type but not catalytically inactive IP6K1 in the Ip6k1-knockout hippocampus restored the altered presynaptic release probability. Moreover, Ip6k1-knockout neurons were insensitive to folimycin, a vacuolar ATPase inhibitor, and dynasore, a dynamin inhibitor, suggesting marked impairment in synaptic endocytosis during exocytosis. Our findings collectively establish that IP6K1 and its product, 5-IP7, act as key physiological determinants for inhibition of presynaptic vesicle exocytosis and stimulation of endocytosis at central synapses. Excitatory synaptic vesicle release is increased in Ip6k1-KO hippocampal neurons Wild-type IP6K1 restores presynaptic functions and plasticity of KO neurons Catalytically inactive mutant IP6K1 fails to rescue defective presynaptic release Synaptic endocytosis during exocytosis is severely impaired in Ip6k1-KO neurons
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Affiliation(s)
- Seung Ju Park
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Hoyong Park
- Department of Biological Sciences, Konkuk University, Seoul 05029, Korea
| | - Min-Gyu Kim
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Seungjae Zhang
- Department of Biological Sciences, Konkuk University, Seoul 05029, Korea
| | - Seung Eun Park
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Seyun Kim
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea; KAIST Institute for the BioCentury, KAIST, Daejeon 34141, Korea.
| | - ChiHye Chung
- Department of Biological Sciences, Konkuk University, Seoul 05029, Korea.
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26
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Loss of huntingtin function slows synaptic vesicle endocytosis in striatal neurons from the httQ140/Q140 mouse model of Huntington's disease. Neurobiol Dis 2020; 134:104637. [DOI: 10.1016/j.nbd.2019.104637] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Revised: 08/23/2019] [Accepted: 10/09/2019] [Indexed: 12/13/2022] Open
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27
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The landscape of multiscale transcriptomic networks and key regulators in Parkinson's disease. Nat Commun 2019; 10:5234. [PMID: 31748532 PMCID: PMC6868244 DOI: 10.1038/s41467-019-13144-y] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2019] [Accepted: 10/21/2019] [Indexed: 12/21/2022] Open
Abstract
Genetic and genomic studies have advanced our knowledge of inherited Parkinson’s disease (PD), however, the etiology and pathophysiology of idiopathic PD remain unclear. Herein, we perform a meta-analysis of 8 PD postmortem brain transcriptome studies by employing a multiscale network biology approach to delineate the gene-gene regulatory structures in the substantia nigra and determine key regulators of the PD transcriptomic networks. We identify STMN2, which encodes a stathmin family protein and is down-regulated in PD brains, as a key regulator functionally connected to known PD risk genes. Our network analysis predicts a function of human STMN2 in synaptic trafficking, which is validated in Stmn2-knockdown mouse dopaminergic neurons. Stmn2 reduction in the mouse midbrain causes dopaminergic neuron degeneration, phosphorylated α-synuclein elevation, and locomotor deficits. Our integrative analysis not only begins to elucidate the global landscape of PD transcriptomic networks but also pinpoints potential key regulators of PD pathogenic pathways. Parkinson’s disease (PD) is characterized by neurodegeneration associated with loss of dopaminergic (DA) neurons and deposition of Lewy bodies. Here, Wang et al. use co-expression network analysis to pinpoint disease pathways and propose reduced expression of STMN2 as a cause of presynaptic function loss in PD.
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28
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Protein Kinase C and Calmodulin Serve As Calcium Sensors for Calcium-Stimulated Endocytosis at Synapses. J Neurosci 2019; 39:9478-9490. [PMID: 31628181 DOI: 10.1523/jneurosci.0182-19.2019] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Revised: 08/27/2019] [Accepted: 10/07/2019] [Indexed: 02/04/2023] Open
Abstract
Calcium influx triggers and facilitates endocytosis, which recycles vesicles and thus sustains synaptic transmission. Despite decades of studies, the underlying calcium sensor remained not well understood. Here, we examined two calcium binding proteins, protein kinase C (PKC) and calmodulin. Whether PKC is involved in endocytosis was unclear; whether calmodulin acts as a calcium sensor for endocytosis was neither clear, although calmodulin involvement in endocytosis had been suggested. We generated PKC (α or β-isoform) and calmodulin (calmodulin 2 gene) knock-out mice of either sex and measured endocytosis with capacitance measurements, pHluorin imaging and electron microscopy. We found that these knock-outs inhibited slow (∼10-30 s) and rapid (<∼3 s) endocytosis at large calyx-type calyces, and inhibited slow endocytosis and bulk endocytosis (forming large endosome-like structures) at small conventional hippocampal synapses, suggesting the involvement of PKC and calmodulin in three most common forms of endocytosis-the slow, rapid and bulk endocytosis. Inhibition of slow endocytosis in PKC or calmodulin 2 knock-out hippocampal synapses was rescued by overexpressing wild-type PKC or calmodulin, but not calcium-binding-deficient PKC or calmodulin mutant, respectively, suggesting that calcium stimulates endocytosis by binding with its calcium sensor PKC and calmodulin. PKC and calmodulin 2 knock-out inhibited calcium-dependent vesicle mobilization to the readily releasable pool, suggesting that PKC and calmodulin may mediate calcium-dependent facilitation of vesicle mobilization. These findings shed light on the molecular signaling link among calcium, endocytosis and vesicle mobilization that are crucial in maintaining synaptic transmission and neuronal network activity.SIGNIFICANCE STATEMENT Vesicle fusion releases neurotransmitters to mediate synaptic transmission. To sustain synaptic transmission, fused vesicles must be retrieved via endocytosis. Accumulating evidence suggests that calcium influx triggers synaptic vesicle endocytosis. However, how calcium triggers endocytosis is not well understood. Using genetic tools together with capacitance measurements, optical imaging and electron microscopy, we identified two calcium sensors, including protein kinase C (α and β isoforms) and calmodulin, for the most commonly observed forms of endocytosis: slow, rapid, and bulk. We also found that these two proteins are involved in calcium-dependent vesicle mobilization to the readily releasable pool. These results provide the molecular signaling link among calcium, endocytosis, and vesicle mobilization that are essential in sustaining synaptic transmission and neuronal network activity.
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29
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Kokotos AC, Harper CB, Marland JRK, Smillie KJ, Cousin MA, Gordon SL. Synaptophysin sustains presynaptic performance by preserving vesicular synaptobrevin-II levels. J Neurochem 2019; 151:28-37. [PMID: 31216055 PMCID: PMC6851701 DOI: 10.1111/jnc.14797] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 05/24/2019] [Accepted: 06/01/2019] [Indexed: 01/01/2023]
Abstract
The two most abundant molecules on synaptic vesicles (SVs) are synaptophysin and synaptobrevin‐II (sybII). SybII is essential for SV fusion, whereas synaptophysin is proposed to control the trafficking of sybII after SV fusion and its retrieval during endocytosis. Despite controlling key aspects of sybII packaging into SVs, the absence of synaptophysin results in negligible effects on neurotransmission. We hypothesised that this apparent absence of effect may be because of the abundance of sybII on SVs, with the impact of inefficient sybII retrieval only revealed during periods of repeated SV turnover. To test this hypothesis, we subjected primary cultures of synaptophysin knockout neurons to repeated trains of neuronal activity, while monitoring SV fusion events and levels of vesicular sybII. We identified a significant decrease in both the number of SV fusion events (monitored using the genetically encoded reporter vesicular glutamate transporter‐pHluorin) and vesicular sybII levels (via both immunofluorescence and Western blotting) using this protocol. This revealed that synaptophysin is essential to sustain both parameters during periods of repetitive SV turnover. This was confirmed by the rescue of presynaptic performance by the expression of exogenous synaptophysin. Importantly, the expression of exogenous sybII also fully restored SV fusion events in synaptophysin knockout neurons. The ability of additional copies of sybII to fully rescue presynaptic performance in these knockout neurons suggests that the principal role of synaptophysin is to mediate the efficient retrieval of sybII to sustain neurotransmitter release. ![]()
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Affiliation(s)
- Alexandros C Kokotos
- Centre for Discovery Brain Sciences, Hugh Robson Building, University of Edinburgh, George Square, Edinburgh, Scotland, UK, EH8 9XD.,Muir Maxwell Epilepsy Centre, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland, UK, EH8 9XD
| | - Callista B Harper
- Centre for Discovery Brain Sciences, Hugh Robson Building, University of Edinburgh, George Square, Edinburgh, Scotland, UK, EH8 9XD.,Muir Maxwell Epilepsy Centre, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland, UK, EH8 9XD.,Simons Initiative for the Developing Brain, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland, UK, EH8 9XD
| | - Jamie R K Marland
- Centre for Discovery Brain Sciences, Hugh Robson Building, University of Edinburgh, George Square, Edinburgh, Scotland, UK, EH8 9XD
| | - Karen J Smillie
- Centre for Discovery Brain Sciences, Hugh Robson Building, University of Edinburgh, George Square, Edinburgh, Scotland, UK, EH8 9XD.,Muir Maxwell Epilepsy Centre, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland, UK, EH8 9XD
| | - Michael A Cousin
- Centre for Discovery Brain Sciences, Hugh Robson Building, University of Edinburgh, George Square, Edinburgh, Scotland, UK, EH8 9XD.,Muir Maxwell Epilepsy Centre, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland, UK, EH8 9XD.,Simons Initiative for the Developing Brain, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland, UK, EH8 9XD
| | - Sarah L Gordon
- The Florey Institute of Neuroscience and Mental Health, and Melbourne Dementia Research Centre, The Florey Institute for Neuroscience and Mental Health, The University of Melbourne, Victoria, Australia
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30
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Ibata K, Kono M, Narumi S, Motohashi J, Kakegawa W, Kohda K, Yuzaki M. Activity-Dependent Secretion of Synaptic Organizer Cbln1 from Lysosomes in Granule Cell Axons. Neuron 2019; 102:1184-1198.e10. [PMID: 31072786 DOI: 10.1016/j.neuron.2019.03.044] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2019] [Revised: 03/18/2019] [Accepted: 03/27/2019] [Indexed: 12/18/2022]
Abstract
Synapse formation is achieved by various synaptic organizers. Although this process is highly regulated by neuronal activity, the underlying molecular mechanisms remain largely unclear. Here we show that Cbln1, a synaptic organizer of the C1q family, is released from lysosomes in axons but not dendrites of cerebellar granule cells in an activity- and Ca2+-dependent manner. Exocytosed Cbln1 was retained on axonal surfaces by binding to its presynaptic receptor neurexin. Cbln1 further diffused laterally along the axonal surface and accumulated at boutons by binding postsynaptic δ2 glutamate receptors. Cbln1 exocytosis was insensitive to tetanus neurotoxin, accompanied by cathepsin B release, and decreased by disrupting lysosomes. Furthermore, overexpression of lysosomal sialidase Neu1 not only inhibited Cbln1 and cathepsin B exocytosis in vitro but also reduced axonal bouton formation in vivo. Our findings imply that co-release of Cbln1 and cathepsin B from lysosomes serves as a new mechanism of activity-dependent coordinated synapse modification.
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Affiliation(s)
- Keiji Ibata
- Department of Physiology, Keio University School of Medicine, Tokyo 160-8582, Japan; Department of Physiology, St. Marianna University School of Medicine, Kanagawa 216-8511, Japan
| | - Maya Kono
- Department of Physiology, Keio University School of Medicine, Tokyo 160-8582, Japan; Department of Neurosurgery, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Sakae Narumi
- Department of Physiology, St. Marianna University School of Medicine, Kanagawa 216-8511, Japan
| | - Junko Motohashi
- Department of Physiology, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Wataru Kakegawa
- Department of Physiology, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Kazuhisa Kohda
- Department of Physiology, St. Marianna University School of Medicine, Kanagawa 216-8511, Japan
| | - Michisuke Yuzaki
- Department of Physiology, Keio University School of Medicine, Tokyo 160-8582, Japan.
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31
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Vásquez-Navarrete J, Martínez AD, Ory S, Baéz-Matus X, González-Jamett AM, Brauchi S, Caviedes P, Cárdenas AM. RCAN1 Knockdown Reverts Defects in the Number of Calcium-Induced Exocytotic Events in a Cellular Model of Down Syndrome. Front Cell Neurosci 2018; 12:189. [PMID: 30034324 PMCID: PMC6043644 DOI: 10.3389/fncel.2018.00189] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Accepted: 06/12/2018] [Indexed: 12/15/2022] Open
Abstract
In humans, Down Syndrome (DS) is a condition caused by partial or full trisomy of chromosome 21. Genes present in the DS critical region can result in excess gene dosage, which at least partially can account for DS phenotype. Although regulator of calcineurin 1 (RCAN1) belongs to this region and its ectopic overexpression in neurons impairs transmitter release, synaptic plasticity, learning and memory, the relative contribution of RCAN1 in a context of DS has yet to be clarified. In the present work, we utilized an in vitro model of DS, the CTb neuronal cell line derived from the brain cortex of a trisomy 16 (Ts16) fetal mouse, which reportedly exhibits acetylcholine release impairments compared to CNh cells (a neuronal cell line established from a normal littermate). We analyzed single exocytotic events by using total internal reflection fluorescence microscopy (TIRFM) and the vesicular acetylcholine transporter fused to the pH-sensitive green fluorescent protein (VAChT-pHluorin) as a reporter. Our analyses showed that, compared with control CNh cells, the trisomic CTb cells overexpress RCAN1, and they display a reduced number of Ca2+-induced exocytotic events. Remarkably, RCAN1 knockdown increases the extent of exocytosis at levels comparable to those of CNh cells. These results support a critical contribution of RCAN1 to the exocytosis process in the trisomic condition.
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Affiliation(s)
- Jacqueline Vásquez-Navarrete
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Agustín D Martínez
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Stéphane Ory
- Centre National de la Recherche Scientifique (CNRS UPR 3212), Institut des Neurosciences Cellulaires et Intégratives (INCI), Strasbourg, France
| | - Ximena Baéz-Matus
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Arlek M González-Jamett
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Sebastián Brauchi
- Department of Physiology, Faculty of Medicine, Universidad Austral de Chile, Valdivia, Chile
| | - Pablo Caviedes
- Programa de Farmacología Molecular y Clínica, ICBM, Facultad de Medicina, Universidad de Chile, Santiago, Chile.,Centro de Biotecnología y Bioingeniería (CeBiB), Departamento de Ingeniería Química, Biotecnología y Materiales, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Santiago, Chile
| | - Ana M Cárdenas
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
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32
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Gan Q, Watanabe S. Synaptic Vesicle Endocytosis in Different Model Systems. Front Cell Neurosci 2018; 12:171. [PMID: 30002619 PMCID: PMC6031744 DOI: 10.3389/fncel.2018.00171] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Accepted: 06/01/2018] [Indexed: 11/13/2022] Open
Abstract
Neurotransmission in complex animals depends on a choir of functionally distinct synapses releasing neurotransmitters in a highly coordinated manner. During synaptic signaling, vesicles fuse with the plasma membrane to release their contents. The rate of vesicle fusion is high and can exceed the rate at which synaptic vesicles can be re-supplied by distant sources. Thus, local compensatory endocytosis is needed to replenish the synaptic vesicle pools. Over the last four decades, various experimental methods and model systems have been used to study the cellular and molecular mechanisms underlying synaptic vesicle cycle. Clathrin-mediated endocytosis is thought to be the predominant mechanism for synaptic vesicle recycling. However, recent studies suggest significant contribution from other modes of endocytosis, including fast compensatory endocytosis, activity-dependent bulk endocytosis, ultrafast endocytosis, as well as kiss-and-run. Currently, it is not clear whether a universal model of vesicle recycling exist for all types of synapses. It is possible that each synapse type employs a particular mode of endocytosis. Alternatively, multiple modes of endocytosis operate at the same synapse, and the synapse toggles between different modes depending on its activity level. Here we compile review and research articles based on well-characterized model systems: frog neuromuscular junctions, C. elegans neuromuscular junctions, Drosophila neuromuscular junctions, lamprey reticulospinal giant axons, goldfish retinal ribbon synapses, the calyx of Held, and rodent hippocampal synapses. We will compare these systems in terms of their known modes and kinetics of synaptic vesicle endocytosis, as well as the underlying molecular machineries. We will also provide the future development of this field.
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Affiliation(s)
- Quan Gan
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Shigeki Watanabe
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD, United States.,Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, United States
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Jeans AF, van Heusden FC, Al-Mubarak B, Padamsey Z, Emptage NJ. Homeostatic Presynaptic Plasticity Is Specifically Regulated by P/Q-type Ca 2+ Channels at Mammalian Hippocampal Synapses. Cell Rep 2018; 21:341-350. [PMID: 29020622 PMCID: PMC5643522 DOI: 10.1016/j.celrep.2017.09.061] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Revised: 08/11/2017] [Accepted: 09/19/2017] [Indexed: 11/17/2022] Open
Abstract
Voltage-dependent Ca2+ channels (VGCC) represent the principal source of Ca2+ ions driving evoked neurotransmitter release at presynaptic boutons. In mammals, presynaptic Ca2+ influx is mediated mainly via P/Q-type and N-type VGCC, which differ in their properties. Changes in their relative contributions tune neurotransmission both during development and in Hebbian plasticity. However, whether this represents a functional motif also present in other forms of activity-dependent regulation is unknown. Here, we study the role of VGCC in homeostatic plasticity (HSP) in mammalian hippocampal neurons using optical techniques. We find that changes in evoked Ca2+ currents specifically through P/Q-type, but not N-type, VGCC mediate bidirectional homeostatic regulation of both neurotransmitter release efficacy and the size of the major synaptic vesicle pools. Selective dependence of HSP on P/Q-type VGCC in mammalian terminals has important implications for phenotypes associated with P/Q-type channelopathies, including migraine and epilepsy. P/Q-type VGCC regulate homeostatic synaptic plasticity (HSP) in mammals Changes in synaptic vesicle pool sizes during HSP are also mediated via P/Q-type VGCC Expression of HSP is independent of N-type VGCC regulation P/Q-type regulation of HSP may explain phenotypes of P/Q-type channelopathies
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Affiliation(s)
- Alexander F Jeans
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK.
| | - Fran C van Heusden
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK
| | - Bashayer Al-Mubarak
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK; Department of Genetics, King Faisal Specialist Hospital and Research Center, PO Box 3354, Riyadh 11211, Saudi Arabia
| | - Zahid Padamsey
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK
| | - Nigel J Emptage
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK.
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Chang HF, Mannebach S, Beck A, Ravichandran K, Krause E, Frohnweiler K, Fecher-Trost C, Schirra C, Pattu V, Flockerzi V, Rettig J. Cytotoxic granule endocytosis depends on the Flower protein. J Cell Biol 2018; 217:667-683. [PMID: 29288152 PMCID: PMC5800809 DOI: 10.1083/jcb.201706053] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 11/09/2017] [Accepted: 11/29/2017] [Indexed: 12/23/2022] Open
Abstract
Cytotoxic T lymphocytes (CTLs) kill target cells by the regulated release of cytotoxic substances from granules at the immunological synapse. To kill multiple target cells, CTLs use endocytosis of membrane components of cytotoxic granules. We studied the potential calcium dependence of endocytosis in mouse CTLs on Flower, which mediates the calcium dependence of synaptic vesicle endocytosis in Drosophila melanogaster Flower is predominantly localized on intracellular vesicles that move to the synapse on target cell contact. Endocytosis is entirely blocked at an early stage in Flower-deficient CTLs and is rescued to wild-type level by reintroducing Flower or by raising extracellular calcium. A Flower mutant lacking binding sites for the endocytic adaptor AP-2 proteins fails to rescue endocytosis, indicating that Flower interacts with proteins of the endocytic machinery to mediate granule endocytosis. Thus, our data identify Flower as a key protein mediating granule endocytosis.
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Affiliation(s)
- Hsin-Fang Chang
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
| | - Stefanie Mannebach
- Department of Experimental and Clinical Pharmacology and Toxicology and Preclinical Center for Molecular Signaling, Saarland University, Homburg, Germany
| | - Andreas Beck
- Department of Experimental and Clinical Pharmacology and Toxicology and Preclinical Center for Molecular Signaling, Saarland University, Homburg, Germany
- Center of Human and Molecular Biology, Saarland University, Homburg, Germany
| | - Keerthana Ravichandran
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
| | - Elmar Krause
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
| | - Katja Frohnweiler
- Department of Experimental and Clinical Pharmacology and Toxicology and Preclinical Center for Molecular Signaling, Saarland University, Homburg, Germany
| | - Claudia Fecher-Trost
- Department of Experimental and Clinical Pharmacology and Toxicology and Preclinical Center for Molecular Signaling, Saarland University, Homburg, Germany
| | - Claudia Schirra
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
| | - Varsha Pattu
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
| | - Veit Flockerzi
- Department of Experimental and Clinical Pharmacology and Toxicology and Preclinical Center for Molecular Signaling, Saarland University, Homburg, Germany
| | - Jens Rettig
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
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Maritzen T, Haucke V. Coupling of exocytosis and endocytosis at the presynaptic active zone. Neurosci Res 2018; 127:45-52. [DOI: 10.1016/j.neures.2017.09.013] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Revised: 07/13/2017] [Accepted: 08/25/2017] [Indexed: 01/08/2023]
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Ventimiglia D, Bargmann CI. Diverse modes of synaptic signaling, regulation, and plasticity distinguish two classes of C. elegans glutamatergic neurons. eLife 2017; 6:31234. [PMID: 29160768 PMCID: PMC5705214 DOI: 10.7554/elife.31234] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Accepted: 11/20/2017] [Indexed: 11/13/2022] Open
Abstract
Synaptic vesicle release properties vary between neuronal cell types, but in most cases the molecular basis of this heterogeneity is unknown. Here, we compare in vivo synaptic properties of two neuronal classes in the C. elegans central nervous system, using VGLUT-pHluorin to monitor synaptic vesicle exocytosis and retrieval in intact animals. We show that the glutamatergic sensory neurons AWCON and ASH have distinct synaptic dynamics associated with tonic and phasic synaptic properties, respectively. Exocytosis in ASH and AWCON is differentially affected by SNARE-complex regulators that are present in both neurons: phasic ASH release is strongly dependent on UNC-13, whereas tonic AWCON release relies upon UNC-18 and on the protein kinase C homolog PKC-1. Strong stimuli that elicit high calcium levels increase exocytosis and retrieval rates in AWCON, generating distinct tonic and evoked synaptic modes. These results highlight the differential deployment of shared presynaptic proteins in neuronal cell type-specific functions.
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Affiliation(s)
- Donovan Ventimiglia
- Lulu and Anthony Wang Laboratory of Neural Circuits and Behavior, The Rockefeller University, New York, United States
| | - Cornelia I Bargmann
- Lulu and Anthony Wang Laboratory of Neural Circuits and Behavior, The Rockefeller University, New York, United States
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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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Villarreal S, Lee SH, Wu LG. Measuring Synaptic Vesicle Endocytosis in Cultured Hippocampal Neurons. J Vis Exp 2017. [PMID: 28892038 DOI: 10.3791/55862] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
During endocytosis, fused synaptic vesicles are retrieved at nerve terminals, allowing for vesicle recycling and thus the maintenance of synaptic transmission during repetitive nerve firing. Impaired endocytosis in pathological conditions leads to decreases in synaptic strength and brain functions. Here, we describe methods used to measure synaptic vesicle endocytosis at the mammalian hippocampal synapse in neuronal culture. We monitored synaptic vesicle protein endocytosis by fusing a synaptic vesicular membrane protein, including synaptophysin and VAMP2/synaptobrevin, at the vesicular lumenal side, with pHluorin, a pH-sensitive green fluorescent protein that increases its fluorescence intensity as the pH increases. During exocytosis, vesicular lumen pH increases, whereas during endocytosis vesicular lumen pH is re-acidified. Thus, an increase of pHluorin fluorescence intensity indicates fusion, whereas a decrease indicates endocytosis of the labelled synaptic vesicle protein. In addition to using the pHluorin imaging method to record endocytosis, we monitored vesicular membrane endocytosis by electron microscopy (EM) measurements of Horseradish peroxidase (HRP) uptake by vesicles. Finally, we monitored the formation of nerve terminal membrane pits at various times after high potassium-induced depolarization. The time course of HRP uptake and membrane pit formation indicates the time course of endocytosis.
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Affiliation(s)
| | - Sung Hoon Lee
- National Institute of Neurological Disorders and Stroke; College of Pharmacy, Chung-ang University;
| | - Ling-Gang Wu
- National Institute of Neurological Disorders and Stroke
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40
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Yao CK, Liu YT, Lee IC, Wang YT, Wu PY. A Ca2+ channel differentially regulates Clathrin-mediated and activity-dependent bulk endocytosis. PLoS Biol 2017; 15:e2000931. [PMID: 28414717 PMCID: PMC5393565 DOI: 10.1371/journal.pbio.2000931] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 03/21/2017] [Indexed: 11/19/2022] Open
Abstract
Clathrin-mediated endocytosis (CME) and activity-dependent bulk endocytosis (ADBE) are two predominant forms of synaptic vesicle (SV) endocytosis, elicited by moderate and strong stimuli, respectively. They are tightly coupled with exocytosis for sustained neurotransmission. However, the underlying mechanisms are ill defined. We previously reported that the Flower (Fwe) Ca2+ channel present in SVs is incorporated into the periactive zone upon SV fusion, where it triggers CME, thus coupling exocytosis to CME. Here, we show that Fwe also promotes ADBE. Intriguingly, the effects of Fwe on CME and ADBE depend on the strength of the stimulus. Upon mild stimulation, Fwe controls CME independently of Ca2+ channeling. However, upon strong stimulation, Fwe triggers a Ca2+ influx that initiates ADBE. Moreover, knockout of rodent fwe in cultured rat hippocampal neurons impairs but does not completely abolish CME, similar to the loss of Drosophila fwe at the neuromuscular junction, suggesting that Fwe plays a regulatory role in regulating CME across species. In addition, the function of Fwe in ADBE is conserved at mammalian central synapses. Hence, Fwe exerts different effects in response to different stimulus strengths to control two major modes of endocytosis.
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Affiliation(s)
- Chi-Kuang Yao
- Institute of Biological Chemistry, Academia Sinica, Nankang, Taipei, Taiwan
- Neuroscience Program in Academia Sinica, Academia Sinica, Nankang, Taipei, Taiwan
- Institute of Biochemical Sciences, College of Life Science, National Taiwan University, Taipei, Taiwan
- * E-mail:
| | - Yu-Tzu Liu
- Institute of Biological Chemistry, Academia Sinica, Nankang, Taipei, Taiwan
| | - I-Chi Lee
- Institute of Biological Chemistry, Academia Sinica, Nankang, Taipei, Taiwan
| | - You-Tung Wang
- Institute of Biological Chemistry, Academia Sinica, Nankang, Taipei, Taiwan
| | - Ping-Yen Wu
- Institute of Biological Chemistry, Academia Sinica, Nankang, Taipei, Taiwan
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41
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Rampérez A, Sánchez-Prieto J, Torres M. Brefeldin A sensitive mechanisms contribute to endocytotic membrane retrieval and vesicle recycling in cerebellar granule cells. J Neurochem 2017; 141:662-675. [PMID: 28295320 DOI: 10.1111/jnc.14017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 02/22/2017] [Accepted: 03/01/2017] [Indexed: 11/26/2022]
Abstract
The recycling of synaptic vesicle (SV) proteins and transmitter release occur at multiple sites along the axon. These processes are sensitive to inhibition of the small GTP binding protein ARF1, which regulates the adaptor protein 1 and 3 complex (AP-1/AP-3). As the axon matures, SV recycling becomes restricted to the presynaptic bouton, and its machinery undergoes a complex process of maturation. We used the styryl dye FM1-43 to highlight differences in the efficiency of membrane recycling at different sites in cerebellar granule cells cultured for 7 days in vitro. We used Brefeldin A (BFA) to inhibit AP-1/AP-3-mediated recycling and to test the contribution of this pathway to the heterogeneity of the responses when these cells are strongly stimulated. Combining imaging techniques and ultrastructural analyses, we found a significant decrease in the density of functional boutons and an increase in the presence of endosome-like structures within the boutons of cells incubated with BFA prior to FM1-43 loading. Such effects were not observed when BFA was added 5 min after the end of the loading step, when endocytosis was almost fully completed. In this situation, vesicles were found closer to the active zone (AZ) in boutons exposed to BFA. Together, these data suggest that the AP-1/AP-3 pathway contributes to SV recycling, affecting different steps in all boutons but not equally, and thus being partly responsible for the heterogeneity of the different recycling efficiencies. Cover Image for this issue: doi. 10.1111/jnc.13801.
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Affiliation(s)
- Alberto Rampérez
- Departamento de Bioquímica y Biología Molecular, Facultad de Veterinaria, Universidad Complutense, Madrid, Spain.,Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid, Spain
| | - José Sánchez-Prieto
- Departamento de Bioquímica y Biología Molecular, Facultad de Veterinaria, Universidad Complutense, Madrid, Spain.,Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid, Spain
| | - Magdalena Torres
- Departamento de Bioquímica y Biología Molecular, Facultad de Veterinaria, Universidad Complutense, Madrid, Spain.,Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid, Spain
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Kabayama H, Tokushige N, Takeuchi M, Kabayama M, Fukuda M, Mikoshiba K. Parkin promotes proteasomal degradation of synaptotagmin IV by accelerating polyubiquitination. Mol Cell Neurosci 2017; 80:89-99. [PMID: 28254618 DOI: 10.1016/j.mcn.2017.02.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Revised: 02/02/2017] [Accepted: 02/15/2017] [Indexed: 12/25/2022] Open
Abstract
Parkin is an E3 ubiquitin ligase whose mutations cause autosomal recessive juvenile Parkinson's disease (PD). Unlike the human phenotype, parkin knockout (KO) mice show no apparent dopamine neuron degeneration, although they demonstrate reduced expression and activity of striatal mitochondrial proteins believed to be necessary for neuronal survival. Instead, parkin-KO mice show reduced striatal evoked dopamine release, abnormal synaptic plasticity, and non-motor symptoms, all of which appear to mimic the preclinical features of Parkinson's disease. Extensive studies have screened candidate synaptic proteins responsible for reduced evoked dopamine release, and synaptotagmin XI (Syt XI), an isoform of Syt family regulating membrane trafficking, has been identified as a substrate of parkin in humans. However, its expression level is unaltered in the striatum of parkin-KO mice. Thus, the target(s) of parkin and the molecular mechanisms underlying the impaired dopamine release in parkin-KO mice remain unknown. In this study, we focused on Syt IV because of its highly homology to Syt XI, and because they share an evolutionarily conserved lack of Ca2+-binding capacity; thus, Syt IV plays an inhibitory role in Ca2+-dependent neurotransmitter release in PC12 cells and neurons in various brain regions. We found that a proteasome inhibitor increased Syt IV protein, but not Syt XI protein, in neuron-like, differentiated PC12 cells, and that parkin interacted with and polyubiquitinated Syt IV, thereby accelerating its protein turnover. Parkin overexpression selectively degraded Syt IV protein, but not Syt I protein (indispensable for Ca2+-dependent exocytosis), thus enhancing depolarization-dependent exocytosis. Furthermore, in parkin-KO mice, the level of striatal Syt IV protein was increased. Our data indicate a crucial role for parkin in the proteasomal degradation of Syt IV, and provide a potential mechanism of parkin-regulated, evoked neurotransmitter release.
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Affiliation(s)
- Hiroyuki Kabayama
- Laboratory for Developmental Neurobiology, Brain Science Institute, Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
| | - Naoko Tokushige
- Laboratory for Developmental Neurobiology, Brain Science Institute, Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Makoto Takeuchi
- Laboratory for Developmental Neurobiology, Brain Science Institute, Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Miyuki Kabayama
- Division of Functional Morphology, Department of Basic Veterinary Medicine, School of Veterinary Medicine, Nippon Veterinary and Life Science University, 1-7-1 Kyonantyo, Musashino, Tokyo 180-8602, Japan
| | - Mitsunori Fukuda
- Laboratory of Membrane Trafficking Mechanisms, Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Aobayama, Aoba-ku, Sendai, Miyagi 980-8578, Japan
| | - Katsuhiko Mikoshiba
- Laboratory for Developmental Neurobiology, Brain Science Institute, Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
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Abstract
The maintenance of pH in the intracellular compartments is essential for the viability of cells. Several genetically encoded fluorescent pH sensors have been developed for noninvasive in vivo analysis. Here, we describe the methods using PEpHluorin (plant-solubility-modified ecliptic pHluorin) and PRpHluorin (plant-solubility-modified ratiometric pHluorin) as pH sensors for in vivo visualization and quantification organelle pH of in plant secretory pathway.
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Affiliation(s)
- Jinbo Shen
- School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China.
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44
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Nakahata Y, Eto K, Murakoshi H, Watanabe M, Kuriu T, Hirata H, Moorhouse AJ, Ishibashi H, Nabekura J. Activation-Dependent Rapid Postsynaptic Clustering of Glycine Receptors in Mature Spinal Cord Neurons. eNeuro 2017; 4:ENEURO.0194-16.2017. [PMID: 28197549 PMCID: PMC5292596 DOI: 10.1523/eneuro.0194-16.2017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 01/05/2017] [Accepted: 01/17/2017] [Indexed: 12/02/2022] Open
Abstract
Inhibitory synapses are established during development but continue to be generated and modulated in strength in the mature nervous system. In the spinal cord and brainstem, presynaptically released inhibitory neurotransmitter dominantly switches from GABA to glycine during normal development in vivo. While presynaptic mechanisms of the shift of inhibitory neurotransmission are well investigated, the contribution of postsynaptic neurotransmitter receptors to this shift is not fully elucidated. Synaptic clustering of glycine receptors (GlyRs) is regulated by activation-dependent depolarization in early development. However, GlyR activation induces hyperpolarization after the first postnatal week, and little is known whether and how presynaptically released glycine regulates postsynaptic receptors in a depolarization-independent manner in mature developmental stage. Here we developed spinal cord neuronal culture of rodents using chronic strychnine application to investigate whether initial activation of GlyRs in mature stage could change postsynaptic localization of GlyRs. Immunocytochemical analyses demonstrate that chronic blockade of GlyR activation until mature developmental stage resulted in smaller clusters of postsynaptic GlyRs that could be enlarged upon receptor activation for 1 h in the mature stage. Furthermore, live cell-imaging techniques show that GlyR activation decreases its lateral diffusion at synapses, and this phenomenon is dependent on PKC, but neither Ca2+ nor CaMKII activity. These results suggest that the GlyR activation can regulate receptor diffusion and cluster size at inhibitory synapses in mature stage, providing not only new insights into the postsynaptic mechanism of shifting inhibitory neurotransmission but also the inhibitory synaptic plasticity in mature nervous system.
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Affiliation(s)
- Yoshihisa Nakahata
- Division of Homeostatic Development, Department of Developmental Physiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
- Department of Physiological Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
| | - Kei Eto
- Division of Homeostatic Development, Department of Developmental Physiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
- Department of Physiological Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
| | - Hideji Murakoshi
- Department of Physiological Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
- Supportive Center for Brain Research, National Institute for Physiological Science, Okazaki 444-8585, Japan
- PRESTO, Japan Science and Technology Agency (JST), Kawaguchi 332-0012, Japan
| | - Miho Watanabe
- Department of Neurophysiology, Hamamatsu University School of Medicine, Hamamatsu 431-3192, Japan
| | - Toshihiko Kuriu
- Department of Neurophysiology, Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, Tokushima 769-2193, Japan
| | - Hiromi Hirata
- PRESTO, Japan Science and Technology Agency (JST), Kawaguchi 332-0012, Japan
- Division of Molecular and Developmental Biology, National Institute of Genetics, Mishima 411-8540, Japan
- Department of Genetics, The Graduate University for Advanced Studies (SOKENDAI), Mishima 411-8540, Japan
- Department of Chemistry and Biological Science, Graduate School of Science and Engineering, Aoyama Gakuin University, Sagamihara 252-5258, Japan
| | - Andrew J. Moorhouse
- Department of Physiology, School of Medical Sciences, University of New South Wales, Sydney 2052, Australia
| | - Hitoshi Ishibashi
- Division of Homeostatic Development, Department of Developmental Physiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
- Department of Physiological Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
- Department of Physiology, Kitasato University School of Allied Health Sciences, Sagamihara 252-0373, Japan
| | - Junichi Nabekura
- Division of Homeostatic Development, Department of Developmental Physiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
- Department of Physiological Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
- CREST, Japan Science and Technology Agency (JST), Kawaguchi 332-0012, Japan
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45
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Shang S, Zhu F, Liu B, Chai Z, Wu Q, Hu M, Wang Y, Huang R, Zhang X, Wu X, Sun L, Wang Y, Wang L, Xu H, Teng S, Liu B, Zheng L, Zhang C, Zhang F, Feng X, Zhu D, Wang C, Liu T, Zhu MX, Zhou Z. Intracellular TRPA1 mediates Ca2+ release from lysosomes in dorsal root ganglion neurons. J Cell Biol 2016; 215:369-381. [PMID: 27799370 PMCID: PMC5100290 DOI: 10.1083/jcb.201603081] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Revised: 08/16/2016] [Accepted: 10/04/2016] [Indexed: 11/22/2022] Open
Abstract
Transient receptor potential A1 (TRPA1) is a nonselective cation channel implicated in thermosensation and inflammatory pain. In this study, we show that TRPA1 (activated by allyl isothiocyanate, acrolein, and 4-hydroxynonenal) elevates the intracellular Ca2+ concentration ([Ca2+]i) in dorsal root ganglion (DRG) neurons in the presence and absence of extracellular Ca2+ Pharmacological and immunocytochemical analyses revealed the presence of TRPA1 channels both on the plasma membrane and in endolysosomes. Confocal line-scan imaging demonstrated Ca2+ signals elicited from individual endolysosomes ("lysosome Ca2+ sparks") by TRPA1 activation. In physiological solutions, the TRPA1-mediated endolysosomal Ca2+ release contributed to ∼40% of the overall [Ca2+]i rise and directly triggered vesicle exocytosis and calcitonin gene-related peptide release, which greatly enhanced the excitability of DRG neurons. Thus, in addition to working via Ca2+ influx, TRPA1 channels trigger vesicle release in sensory neurons by releasing Ca2+ from lysosome-like organelles.
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Affiliation(s)
- Shujiang Shang
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China.,Laboratory Animal Center, Peking University, Beijing 100871, China.,School of Life Science, Peking University, Beijing 100871, China
| | - Feipeng Zhu
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Bin Liu
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Zuying Chai
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Qihui Wu
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Meiqin Hu
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Yuan Wang
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Rong Huang
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Xiaoyu Zhang
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Xi Wu
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Lei Sun
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Yeshi Wang
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Li Wang
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Huadong Xu
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Sasa Teng
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Bing Liu
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Lianghong Zheng
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Chen Zhang
- School of Life Science, Peking University, Beijing 100871, China
| | - Fukang Zhang
- Institute for Biomedical Science of Pain, Capital Medical University, Beijing 100069, China
| | - Xinghua Feng
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, TX 77030
| | - Desheng Zhu
- Laboratory Animal Center, Peking University, Beijing 100871, China
| | - Changhe Wang
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Tao Liu
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Michael X Zhu
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, TX 77030
| | - Zhuan Zhou
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
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46
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Lampe M, Vassilopoulos S, Merrifield C. Clathrin coated pits, plaques and adhesion. J Struct Biol 2016; 196:48-56. [DOI: 10.1016/j.jsb.2016.07.009] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Revised: 07/11/2016] [Accepted: 07/13/2016] [Indexed: 11/27/2022]
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Epsin1 modulates synaptic vesicle retrieval capacity at CNS synapses. Sci Rep 2016; 6:31997. [PMID: 27557559 PMCID: PMC4997357 DOI: 10.1038/srep31997] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Accepted: 08/01/2016] [Indexed: 11/08/2022] Open
Abstract
Synaptic vesicle retrieval is an essential process for continuous maintenance of neural information flow after synaptic transmission. Epsin1, originally identified as an EPS15-interacting protein, is a major component of clathrin-mediated endocytosis. However, the role of Epsin1 in synaptic vesicle endocytosis at CNS synapses remains elusive. Here, we showed significantly altered synaptic vesicle endocytosis in neurons transfected with shRNA targeting Epsin1 during/after neural activity. Endocytosis was effectively restored by introducing shRNA-insensitive Epsin1 into Epsin1-depleted neurons. Domain studies performed on neurons in which domain deletion mutants of Epsin1 were introduced after Epsin1 knockdown revealed that ENTH, CLAP, and NPFs are essential for synaptic vesicle endocytosis, whereas UIMs are not. Strikingly, the efficacy of the rate of synaptic vesicle retrieval (the "endocytic capacity") was significantly decreased in the absence of Epsin1. Thus, Epsin1 is required for proper synaptic vesicle retrieval and modulates the endocytic capacity of synaptic vesicles.
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Cano R, Tabares L. The Active and Periactive Zone Organization and the Functional Properties of Small and Large Synapses. Front Synaptic Neurosci 2016; 8:12. [PMID: 27252645 PMCID: PMC4877509 DOI: 10.3389/fnsyn.2016.00012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 05/09/2016] [Indexed: 12/29/2022] Open
Abstract
The arrival of an action potential (AP) at a synaptic terminal elicits highly synchronized quanta release. Repetitive APs produce successive synaptic vesicle (SV) fusions that require management of spent SV components in the presynaptic membrane with minimum disturbance of the secretory apparatus. To this end, the synaptic machinery is structured accordingly to the strength and the range of frequencies at which each particular synapse operates. This results in variations in the number and dimension of Active Zones (AZs), amount and distribution of SVs, and probably, in the primary endocytic mechanisms they use. Understanding better how these structural differences determine the functional response in each case has been a matter of long-term interest. Here we review the structural and functional properties of three distinct types of synapses: the neuromuscular junction (NMJ; a giant, highly reliable synapse that must exocytose a large number of quanta with each stimulus to guarantee excitation of the postsynaptic cell), the hippocampal excitatory small synapse (which most often has a single release site and a relatively small pool of vesicles), and the cerebellar mossy fiber-granule cell synapse (which possesses hundreds of release sites and is able to translocate, dock and prime vesicles at high speed). We will focus on how the release apparatus is organized in each case, the relative amount of vesicular membrane that needs to be accommodated within the periAZ upon stimulation, the different mechanisms for retrieving the excess of membrane and finally, how these factors may influence the functioning of the release sites.
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Affiliation(s)
- Raquel Cano
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville Seville, Spain
| | - Lucia Tabares
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville Seville, Spain
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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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50
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Fast, Temperature-Sensitive and Clathrin-Independent Endocytosis at Central Synapses. Neuron 2016; 90:492-8. [PMID: 27146271 DOI: 10.1016/j.neuron.2016.03.013] [Citation(s) in RCA: 97] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Revised: 02/29/2016] [Accepted: 03/15/2016] [Indexed: 11/24/2022]
Abstract
The fusion of neurotransmitter-filled vesicles during synaptic transmission is balanced by endocytotic membrane retrieval. Despite extensive research, the speed and mechanisms of synaptic vesicle endocytosis have remained controversial. Here, we establish low-noise time-resolved membrane capacitance measurements that allow monitoring changes in surface membrane area elicited by single action potentials and stronger stimuli with high-temporal resolution at physiological temperature in individual bona-fide mature central synapses. We show that single action potentials trigger very rapid endocytosis, retrieving presynaptic membrane with a time constant of 470 ms. This fast endocytosis is independent of clathrin but mediated by dynamin and actin. In contrast, stronger stimuli evoke a slower mode of endocytosis that is clathrin, dynamin, and actin dependent. Furthermore, the speed of endocytosis is highly temperature dependent with a Q10 of ∼3.5. These results demonstrate that distinct molecular modes of endocytosis with markedly different kinetics operate at central synapses.
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