1
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Afuwape OAT, Chanaday NL, Kasap M, Monteggia LM, Kavalali ET. Persistence of quantal synaptic vesicle recycling in virtual absence of dynamins. J Physiol 2024. [PMID: 39141823 DOI: 10.1113/jp286711] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2024] [Accepted: 07/23/2024] [Indexed: 08/16/2024] Open
Abstract
Dynamins are GTPases required for pinching vesicles off the plasma membrane once a critical curvature is reached during endocytosis. Here, we probed dynamin function in central synapses by depleting all three dynamin isoforms in postnatal hippocampal neurons down to negligible levels. We found a decrease in the propensity of evoked neurotransmission as well as a reduction in synaptic vesicle numbers. Recycling of synaptic vesicles during spontaneous or low levels of evoked activity were largely impervious to dynamin depletion, while retrieval of synaptic vesicle components at higher levels of activity was partially arrested. These results suggest the existence of balancing dynamin-independent mechanisms for synaptic vesicle recycling at central synapses. Classical dynamin-dependent mechanisms are not essential for retrieval of synaptic vesicle proteins after quantal single synaptic vesicle fusion, but they become more relevant for membrane retrieval during intense, sustained neuronal activity. KEY POINTS: Loss of dynamin 2 does not impair synaptic transmission. Loss of all three dynamin isoforms mostly affects evoked neurotransmission. Excitatory synapse function is more susceptible to dynamin loss. Spontaneous neurotransmission is only mildly affected by loss of dynamins. Single synaptic vesicle endocytosis is largely dynamin independent.
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Affiliation(s)
- Olusoji A T Afuwape
- Department of Neurosurgery, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Natali L Chanaday
- Department of Physiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA
| | - Merve Kasap
- U.S. Food and Drug Administration, The Center for Drug Evaluation and Research (CDER), Silver Spring, Maryland, USA
| | - Lisa M Monteggia
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee, USA
- Vanderbilt Brain Institute, Vanderbilt University, Nashville, Tennessee, USA
| | - Ege T Kavalali
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee, USA
- Vanderbilt Brain Institute, Vanderbilt University, Nashville, Tennessee, USA
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2
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Asmerian H, Alberts J, Sanetra AM, Diaz AJ, Silm K. Role of adaptor protein complexes in generating functionally distinct synaptic vesicle pools. J Physiol 2024. [PMID: 39034608 DOI: 10.1113/jp286179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2024] [Accepted: 07/05/2024] [Indexed: 07/23/2024] Open
Abstract
The synaptic vesicle (SV) cycle ensures the release of neurotransmitters and the replenishment of SVs to sustain neuronal activity. Multiple endocytosis and sorting pathways contribute to the recapture of the SV membrane and proteins after fusion. Adaptor protein (AP) complexes are among the critical components of the SV retrieval machinery. The canonical clathrin adaptor AP2 ensures the replenishment of most SVs across many neuronal populations. An alternative AP1/AP3-dependent process mediates the formation of a subset of SVs that differ from AP2 vesicles in molecular composition and respond preferentially during higher frequency firing. Furthermore, recent studies show that vesicular transporters for different neurotransmitters depend to a different extent on the AP3 pathway and this affects the release properties of the respective neurotransmitters. This review focuses on the current understanding of the AP-dependent molecular and functional diversity among SVs. We also discuss the contribution of these pathways to the regulation of neurotransmitter release across neuronal populations.
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Affiliation(s)
- Hrach Asmerian
- Center for Neural Science and Medicine, Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- Board of Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- Department of Neurology, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Jacob Alberts
- Center for Neural Science and Medicine, Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- Board of Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- Department of Neurology, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Anna M Sanetra
- Center for Neural Science and Medicine, Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- Board of Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- Department of Neurology, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Alexia J Diaz
- Center for Neural Science and Medicine, Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- Board of Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- Department of Neurology, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Katlin Silm
- Center for Neural Science and Medicine, Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- Board of Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- Department of Neurology, Cedars-Sinai Medical Center, Los Angeles, CA, USA
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3
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Kim SR, Eom Y, Lee SH. Comprehensive analysis of sex differences in the function and ultrastructure of hippocampal presynaptic terminals. Neurochem Int 2023; 169:105570. [PMID: 37451344 DOI: 10.1016/j.neuint.2023.105570] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Revised: 05/08/2023] [Accepted: 07/04/2023] [Indexed: 07/18/2023]
Abstract
Sex differences in the brain, encompassing variations in specific brain structures, size, cognitive function, and synaptic connections, have been identified across numerous species. While previous research has explored sex differences in postsynaptic structures, synaptic plasticity, and hippocampus-dependent functions, the hippocampal presynaptic terminals remain largely uninvestigated. The hippocampus is a critical structure responsible for multiple brain functions. This study examined presynaptic differences in cultured hippocampal neurons derived from male and female mice using a combination of biochemical assays, functional analyses measuring exocytosis and endocytosis of synaptic vesicle proteins, ultrastructural analyses via electron microscopy, and presynaptic Ca2+-specific optical probes. Our findings revealed that female neurons exhibited a higher number of synaptic vesicles at presynaptic terminals compared to male neurons. However, no significant differences were observed in presynaptic protein expression, presynaptic terminal ultrastructure, synaptic vesicle exocytosis and endocytosis, or presynaptic Ca2+ alterations between male and female neurons.
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Affiliation(s)
- Sung Rae Kim
- College of Pharmacy, Chung-Ang University, Seoul 06974, Republic of Korea; Brain Research Core Facilities of Korea Brain Research Institute (KBRI), Daegu 41068, Republic of Korea.
| | - Yunkyung Eom
- College of Pharmacy, Chung-Ang University, Seoul 06974, Republic of Korea.
| | - Sung Hoon Lee
- College of Pharmacy, Chung-Ang University, Seoul 06974, Republic of Korea.
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4
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Ng XY, Wu Y, Lin Y, Yaqoob SM, Greene LE, De Camilli P, Cao M. Mutations in Parkinsonism-linked endocytic proteins synaptojanin1 and auxilin have synergistic effects on dopaminergic axonal pathology. NPJ Parkinsons Dis 2023; 9:26. [PMID: 36792618 PMCID: PMC9932162 DOI: 10.1038/s41531-023-00465-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Accepted: 01/20/2023] [Indexed: 02/17/2023] Open
Abstract
Parkinson's disease (PD) is a neurodegenerative disorder characterized by defective dopaminergic (DAergic) input to the striatum. Mutations in two genes encoding synaptically enriched clathrin-uncoating factors, synaptojanin 1 (SJ1) and auxilin, have been implicated in atypical Parkinsonism. SJ1 knock-in (SJ1-KIRQ) mice carrying a disease-linked mutation display neurological manifestations reminiscent of Parkinsonism. Here we report that auxilin knockout (Aux-KO) mice display dystrophic changes of a subset of nigrostriatal DAergic terminals similar to those of SJ1-KIRQ mice. Furthermore, Aux-KO/SJ1-KIRQ double mutant mice have shorter lifespan and more severe synaptic defects than single mutant mice. These include increase in dystrophic striatal nerve terminals positive for DAergic markers and for the PD risk protein SV2C, as well as adaptive changes in striatal interneurons. The synergistic effect of the two mutations demonstrates a special lability of DAergic neurons to defects in clathrin uncoating, with implications for PD pathogenesis in at least some forms of this condition.
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Affiliation(s)
- Xin Yi Ng
- Programme in Neuroscience and Behavioural Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Yumei Wu
- Departments of Neuroscience and Cell Biology, Howard Hughes Medical Institute, Program in Cellular Neuroscience, Neurodegeneration and Repair, Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, CT, 06510, USA
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD, USA
| | - Youneng Lin
- Programme in Neuroscience and Behavioural Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Sidra Mohamed Yaqoob
- Programme in Neuroscience and Behavioural Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Lois E Greene
- Laboratory of Cell Biology, NHLBI, National Institutes of Health, Bethesda, MD, USA
| | - Pietro De Camilli
- Departments of Neuroscience and Cell Biology, Howard Hughes Medical Institute, Program in Cellular Neuroscience, Neurodegeneration and Repair, Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, CT, 06510, USA
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD, USA
| | - Mian Cao
- Programme in Neuroscience and Behavioural Disorders, Duke-NUS Medical School, Singapore, Singapore.
- Department of Physiology, National University of Singapore, Singapore, Singapore.
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5
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Wu X, Qiu H, Zhang M. Interactions between Membraneless Condensates and Membranous Organelles at the Presynapse: A Phase Separation View of Synaptic Vesicle Cycle. J Mol Biol 2023; 435:167629. [PMID: 35595170 DOI: 10.1016/j.jmb.2022.167629] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Revised: 05/03/2022] [Accepted: 05/04/2022] [Indexed: 02/04/2023]
Abstract
Action potential-induced neurotransmitter release in presynaptic boutons involves coordinated actions of a large list of proteins that are associated directly or indirectly with membrane structures including synaptic vesicles and plasma membranes. These proteins are often highly abundant in different synaptic bouton sub-compartments, and they rarely act alone. Instead, these proteins interact with each other forming intricate and distinct molecular complexes. Many of these complexes form condensed clusters on membrane surfaces. This review summarizes findings in recent years showing that many of presynaptic protein complex assemblies are formed via phase separation. These protein condensates extensively interact with lipid membranes via distinct modes, forming various mesoscale structures by different mode of organizations between membraneless condensates and membranous organelles. We discuss that such mesoscale interactions could have deep implications on mobilization, exocytosis, and retrieval of synaptic vesicles.
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Affiliation(s)
- Xiandeng Wu
- Division of Life Science, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Hua Qiu
- Division of Life Science, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Mingjie Zhang
- Greater Bay Biomedical Innocenter, Shenzhen Bay Laboratory, Shenzhen 518036, China; School of Life Sciences, Southern University of Science and Technology, Shenzhen 518055, China.
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6
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Chung GHC, Lorvellec M, Gissen P, Pichaud F, Burden JJ, Stefan CJ. The ultrastructural organization of endoplasmic reticulum-plasma membrane contacts is conserved in epithelial cells. Mol Biol Cell 2022; 33:ar113. [PMID: 35947498 PMCID: PMC9635291 DOI: 10.1091/mbc.e21-11-0534-t] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Contacts between the endoplasmic reticulum and the plasma membrane (ER-PM contacts) have important roles in membrane lipid and calcium dynamics, yet their organization in polarized epithelial cells has not been thoroughly described. Here we examine ER-PM contacts in hepatocytes in mouse liver using electron microscopy, providing the first comprehensive ultrastructural study of ER-PM contacts in a mammalian epithelial tissue. Our quantitative analyses reveal strikingly distinct ER-PM contact architectures spatially linked to apical, lateral, and basal PM domains. Notably, we find that an extensive network of ER-PM contacts exists at lateral PM domains that form intercellular junctions between hepatocytes. Moreover, the spatial organization of ER-PM contacts is conserved in epithelial spheroids, suggesting that ER-PM contacts may serve conserved roles in epithelial cell architecture. Consistent with this notion, we show that ORP5 activity at ER-PM contacts modulates the apical-basolateral aspect ratio in HepG2 cells. Thus ER-PM contacts have a conserved distribution and crucial roles in PM domain architecture across epithelial cell types.
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Affiliation(s)
- Gary Hong Chun Chung
- Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK
| | - Maëlle Lorvellec
- Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK
- NIHR Great Ormond Street Hospital Biomedical Research Centre, University College London, London WC1N 1EH, UK
| | - Paul Gissen
- Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK
- NIHR Great Ormond Street Hospital Biomedical Research Centre, University College London, London WC1N 1EH, UK
| | - Franck Pichaud
- Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK
| | - Jemima J Burden
- Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK
| | - Christopher J Stefan
- Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK
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7
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Heuser JE. The Structural Basis of Long-Term Potentiation in Hippocampal Synapses, Revealed by Electron Microscopy Imaging of Lanthanum-Induced Synaptic Vesicle Recycling. Front Cell Neurosci 2022; 16:920360. [PMID: 35978856 PMCID: PMC9376242 DOI: 10.3389/fncel.2022.920360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Accepted: 05/05/2022] [Indexed: 11/29/2022] Open
Abstract
Hippocampal neurons in dissociated cell cultures were exposed to the trivalent cation lanthanum for short periods (15–30 min) and prepared for electron microscopy (EM), to evaluate the stimulatory effects of this cation on synaptic ultrastructure. Not only were characteristic ultrastructural changes of exaggerated synaptic vesicle turnover seen within the presynapses of these cultures—including synaptic vesicle depletion and proliferation of vesicle-recycling structures—but the overall architecture of a large proportion of the synapses in the cultures was dramatically altered, due to large postsynaptic “bulges” or herniations into the presynapses. Moreover, in most cases, these postsynaptic herniations or protrusions produced by lanthanum were seen by EM to distort or break or “perforate” the so-called postsynaptic densities (PSDs) that harbor receptors and recognition molecules essential for synaptic function. These dramatic EM observations lead us to postulate that such PSD breakages or “perforations” could very possibly create essential substrates or “tags” for synaptic growth, simply by creating fragmented free edges around the PSDs, into which new receptors and recognition molecules could be recruited more easily, and thus, they could represent the physical substrate for the important synaptic growth process known as “long-term potentiation” (LTP). All of this was created simply in hippocampal dissociated cell cultures, and simply by pushing synaptic vesicle recycling way beyond its normal limits with the trivalent cation lanthanum, but we argued in this report that such fundamental changes in synaptic architecture—given that they can occur at all—could also occur at the extremes of normal neuronal activity, which are presumed to lead to learning and memory.
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8
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An SJ, Stagi M, Gould TJ, Wu Y, Mlodzianoski M, Rivera-Molina F, Toomre D, Strittmatter SM, De Camilli P, Bewersdorf J, Zenisek D. Multimodal imaging of synaptic vesicles with a single probe. CELL REPORTS METHODS 2022; 2:100199. [PMID: 35497490 PMCID: PMC9046237 DOI: 10.1016/j.crmeth.2022.100199] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 02/11/2022] [Accepted: 03/28/2022] [Indexed: 05/17/2023]
Abstract
A complete understanding of synaptic-vesicle recycling requires the use of multiple microscopy methods to obtain complementary information. However, many currently available probes are limited to a specific microscopy modality, which necessitates the use of multiple probes and labeling paradigms. Given the complexity of vesicle populations and recycling pathways, having new single-vesicle probes that could be used for multiple microscopy techniques would complement existing sets of tools for studying vesicle function. Here, we present a probe based on the membrane-binding C2 domain of cytosolic phospholipase A2 (cPLA2) that fulfills this need. By conjugating the C2 domain with different detectable tags, we demonstrate that a single, modular probe can allow synaptic vesicles to be imaged at multiple levels of spatial and temporal resolution. Moreover, as a general endocytic marker, the C2 domain may also be used to study membrane recycling in many cell types.
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Affiliation(s)
- Seong J. An
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Massimiliano Stagi
- Program in Cellular Neuroscience, Neurodegeneration & Repair, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, USA
- Kavli Institute of Neuroscience, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Molecular Physiology & Cell Signalling, Institute of Systems, Molecular & Integrative Biology, University of Liverpool, Liverpool 69 3BX, UK
| | - Travis J. Gould
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Physics and Astronomy, Bates College, Lewiston, ME 04240, USA
| | - Yumei Wu
- Program in Cellular Neuroscience, Neurodegeneration & Repair, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA
- Kavli Institute of Neuroscience, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Michael Mlodzianoski
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Biomedical Engineering, Yale University School of Medicine, New Haven, CT 06510, USA
- Kavli Institute of Neuroscience, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Felix Rivera-Molina
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Derek Toomre
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Stephen M. Strittmatter
- Program in Cellular Neuroscience, Neurodegeneration & Repair, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, USA
- Kavli Institute of Neuroscience, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Pietro De Camilli
- Program in Cellular Neuroscience, Neurodegeneration & Repair, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA
- Kavli Institute of Neuroscience, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Joerg Bewersdorf
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Biomedical Engineering, Yale University School of Medicine, New Haven, CT 06510, USA
- Kavli Institute of Neuroscience, Yale University School of Medicine, New Haven, CT 06510, USA
| | - David Zenisek
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06510, USA
- Program in Cellular Neuroscience, Neurodegeneration & Repair, Yale University School of Medicine, New Haven, CT 06510, USA
- Kavli Institute of Neuroscience, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT 06510, USA
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9
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Yang S, Park D, Manning L, Hill SE, Cao M, Xuan Z, Gonzalez I, Dong Y, Clark B, Shao L, Okeke I, Almoril-Porras A, Bai J, De Camilli P, Colón-Ramos DA. Presynaptic autophagy is coupled to the synaptic vesicle cycle via ATG-9. Neuron 2022; 110:824-840.e10. [PMID: 35065714 PMCID: PMC9017068 DOI: 10.1016/j.neuron.2021.12.031] [Citation(s) in RCA: 35] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 10/20/2021] [Accepted: 12/20/2021] [Indexed: 01/01/2023]
Abstract
Autophagy is a cellular degradation pathway essential for neuronal health and function. Autophagosome biogenesis occurs at synapses, is locally regulated, and increases in response to neuronal activity. The mechanisms that couple autophagosome biogenesis to synaptic activity remain unknown. In this study, we determine that trafficking of ATG-9, the only transmembrane protein in the core autophagy pathway, links the synaptic vesicle cycle with autophagy. ATG-9-positive vesicles in C. elegans are generated from the trans-Golgi network via AP-3-dependent budding and delivered to presynaptic sites. At presynaptic sites, ATG-9 undergoes exo-endocytosis in an activity-dependent manner. Mutations that disrupt endocytosis, including a lesion in synaptojanin 1 associated with Parkinson's disease, result in abnormal ATG-9 accumulation at clathrin-rich synaptic foci and defects in activity-induced presynaptic autophagy. Our findings uncover regulated key steps of ATG-9 trafficking at presynaptic sites and provide evidence that ATG-9 exo-endocytosis couples autophagosome biogenesis at presynaptic sites with the activity-dependent synaptic vesicle cycle.
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Affiliation(s)
- Sisi Yang
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and of Cell Biology, Yale University School of Medicine, 260 Whitney Avenue, YSB C167, New Haven, CT 06511, USA
| | - Daehun Park
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and of Cell Biology, Yale University School of Medicine, 260 Whitney Avenue, YSB C167, New Haven, CT 06511, USA; Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA; Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD 20815, USA
| | - Laura Manning
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and of Cell Biology, Yale University School of Medicine, 260 Whitney Avenue, YSB C167, New Haven, CT 06511, USA
| | - Sarah E Hill
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and of Cell Biology, Yale University School of Medicine, 260 Whitney Avenue, YSB C167, New Haven, CT 06511, USA
| | - Mian Cao
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and of Cell Biology, Yale University School of Medicine, 260 Whitney Avenue, YSB C167, New Haven, CT 06511, USA; Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA; Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD 20815, USA
| | - Zhao Xuan
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and of Cell Biology, Yale University School of Medicine, 260 Whitney Avenue, YSB C167, New Haven, CT 06511, USA
| | - Ian Gonzalez
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and of Cell Biology, Yale University School of Medicine, 260 Whitney Avenue, YSB C167, New Haven, CT 06511, USA
| | - Yongming Dong
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Benjamin Clark
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and of Cell Biology, Yale University School of Medicine, 260 Whitney Avenue, YSB C167, New Haven, CT 06511, USA
| | - Lin Shao
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and of Cell Biology, Yale University School of Medicine, 260 Whitney Avenue, YSB C167, New Haven, CT 06511, USA
| | - Ifechukwu Okeke
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and of Cell Biology, Yale University School of Medicine, 260 Whitney Avenue, YSB C167, New Haven, CT 06511, USA
| | - Agustin Almoril-Porras
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and of Cell Biology, Yale University School of Medicine, 260 Whitney Avenue, YSB C167, New Haven, CT 06511, USA
| | - Jihong Bai
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Pietro De Camilli
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and of Cell Biology, Yale University School of Medicine, 260 Whitney Avenue, YSB C167, New Haven, CT 06511, USA; Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA; Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, CT 06510, USA; Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD 20815, USA
| | - Daniel A Colón-Ramos
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Departments of Neuroscience and of Cell Biology, Yale University School of Medicine, 260 Whitney Avenue, YSB C167, New Haven, CT 06511, USA; Instituto de Neurobiología José del Castillo, Recinto de Ciencias Médicas, Universidad de Puerto Rico, 201 Boulevard del Valle, San Juan, PR 00901, USA; Wu Tsai Institute, Yale University, New Haven, CT 06510, USA.
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10
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Stepinac E, Landrein N, Skwarzyńska D, Wójcik P, Lesigang J, Lučić I, He CY, Bonhivers M, Robinson DR, Dong G. Structural studies of the shortest extended synaptotagmin with only two C2 domains from Trypanosoma brucei. iScience 2021; 24:102422. [PMID: 33997700 PMCID: PMC8093936 DOI: 10.1016/j.isci.2021.102422] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 04/03/2021] [Accepted: 04/08/2021] [Indexed: 11/25/2022] Open
Abstract
Extended synaptotagmins (E-Syts) localize at membrane contact sites between the endoplasmic reticulum (ER) and the plasma membrane to mediate inter-membrane lipid transfer and control plasma membrane lipid homeostasis. All known E-Syts contain an N-terminal transmembrane (TM) hairpin, a central synaptotagmin-like mitochondrial lipid-binding protein (SMP) domain, and three or five C2 domains at their C termini. Here we report an uncharacterized E-Syt from the protist parasite Trypanosoma brucei, namely, TbE-Syt. TbE-Syt contains only two C2 domains (C2A and C2B), making it the shortest E-Syt known by now. We determined a 1.5-Å-resolution crystal structure of TbE-Syt-C2B and revealed that it binds lipids via both Ca2+- and PI(4,5)P2-dependent means. In contrast, TbE-Syt-C2A lacks the Ca2+-binding site but may still interact with lipids via a basic surface patch. Our studies suggest a mechanism for how TbE-Syt tethers the ER membrane tightly to the plasma membrane to transfer lipids between the two organelles. We identified a new type of extended synaptotagmin (E-Syt) in Trypanosoma brucei TbE-Syt is the shortest known E-Syt with only two C2 domains, C2A and C2B TbE-Syt-C2B binds lipids via both Ca2+- and PI(4,5)P2-dependent means Unlike all other known E-Syts, TbE-Syt-C2A and C2B are connected by a flexible loop
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Affiliation(s)
- Emma Stepinac
- Max Perutz Labs, Vienna Biocenter, Center for Medical Biochemistry, Medical University of Vienna, 1030 Vienna, Austria
| | - Nicolas Landrein
- University of Bordeaux, CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, 33000 Bordeaux, France
| | - Daria Skwarzyńska
- Max Perutz Labs, Vienna Biocenter, Center for Medical Biochemistry, Medical University of Vienna, 1030 Vienna, Austria.,Silesian University of Technology, Gliwice, Poland
| | - Patrycja Wójcik
- Max Perutz Labs, Vienna Biocenter, Center for Medical Biochemistry, Medical University of Vienna, 1030 Vienna, Austria.,Silesian University of Technology, Gliwice, Poland
| | - Johannes Lesigang
- Max Perutz Labs, Vienna Biocenter, Center for Medical Biochemistry, Medical University of Vienna, 1030 Vienna, Austria
| | - Iva Lučić
- Max Perutz Labs, Vienna Biocenter, Center for Medical Biochemistry, Medical University of Vienna, 1030 Vienna, Austria
| | - Cynthia Y He
- Department of Biological Sciences, Center for BioImaging Sciences, National University of Singapore, Singapore, Singapore
| | - Mélanie Bonhivers
- University of Bordeaux, CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, 33000 Bordeaux, France
| | - Derrick R Robinson
- University of Bordeaux, CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, 33000 Bordeaux, France
| | - Gang Dong
- Max Perutz Labs, Vienna Biocenter, Center for Medical Biochemistry, Medical University of Vienna, 1030 Vienna, Austria
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11
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Altered Fast Synaptic Transmission in a Mouse Model of DNM1-Associated Developmental Epileptic Encephalopathy. eNeuro 2021; 8:ENEURO.0269-20.2020. [PMID: 33372033 PMCID: PMC7986544 DOI: 10.1523/eneuro.0269-20.2020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 12/01/2020] [Accepted: 12/07/2020] [Indexed: 12/05/2022] Open
Abstract
Developmental epileptic encephalopathies (DEEs) are severe seizure disorders that occur in infants and young children, characterized by developmental delay, cognitive decline, and early mortality. Recent efforts have identified a wide variety of genetic variants that cause DEEs. Among these, variants in the DNM1 gene have emerged as definitive causes of DEEs, including infantile spasms and Lennox–Gastaut syndrome. A mouse model of Dnm1-associated DEE, known as “Fitful” (Dnm1Ftfl), recapitulates key features of the disease, including spontaneous seizures, early lethality, and neuronal degeneration. Previous work showed that DNM1 is a key regulator of synaptic vesicle (SV) endocytosis and synaptic transmission and suggested that inhibitory neurotransmission may be more reliant on DNM1 function than excitatory transmission. The Dnm1Ftfl variant is thought to encode a dominant negative DNM1 protein; however, the effects of the Dnm1Ftfl variant on synaptic transmission are largely unknown. To understand these synaptic effects, we recorded from pairs of cultured mouse cortical neurons and characterized all four major connection types [excitation of excitation (E-E), inhibition of inhibition (I-I), E-I, I-E]. Miniature and spontaneous EPSCs and IPSCs were larger, but less frequent, at all Dnm1Ftfl synaptic types, and Dnm1Ftfl neurons had reduced expression of excitatory and inhibitory SV markers. Baseline evoked transmission, however, was reduced only at inhibitory synapses onto excitatory neurons, because of a smaller pool of releasable SVs. In addition to these synaptic alterations, Dnm1Ftfl neurons degenerated later in development, although their activity levels were reduced, suggesting that Dnm1Ftfl may impair synaptic transmission and neuronal health through distinct mechanisms.
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12
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Zou L, Zhang X, Xiong M, Meng L, Tian Y, Pan L, Yuan X, Chen G, Wang Z, Bu L, Yao Z, Zhang Z, Ye K, Zhang Z. Asparagine endopeptidase cleaves synaptojanin 1 and triggers synaptic dysfunction in Parkinson's disease. Neurobiol Dis 2021; 154:105326. [PMID: 33677035 DOI: 10.1016/j.nbd.2021.105326] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 02/02/2021] [Accepted: 03/02/2021] [Indexed: 10/22/2022] Open
Abstract
Parkinson's disease (PD) is one of the most common neurodegenerative diseases, which is characterized by the loss of dopaminergic neurons in the nigrostriatal pathway. Synaptic dysfunction impairs dopamine turnover and contributes to the degeneration of dopaminergic neurons. However, the molecular mechanisms underlying synaptic dysfunction and dopaminergic neuronal vulnerability in PD are not clear. Here, we report that synaptojanin 1 (SYNJ1), a polyphosphoinositide phosphatase concentrated at nerve terminals, is a substrate of a cysteine proteinase, asparagine endopeptidase (AEP). SYNJ1 is cleaved by the cysteine proteinase AEP at N599 in the brains of PD patients. AEP-mediated cleavage of SYNJ1 disrupts neuronal phosphoinositide homeostasis and causes synaptic dysfunction. Overexpression of the AEP-generated fragments of SYNJ1 triggers synaptic dysfunction and the degeneration of dopaminergic neurons, inducing motor defects in the α-synuclein transgenic mice. Blockage of AEP-mediated cleavage of SYJN1 alleviates the pathological and behavioral defects in a mouse model of PD. Our results demonstrate that the fragmentation of SYNJ1 by AEP mediates synaptic dysfunction and dopaminergic neuronal degeneration in PD.
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Affiliation(s)
- Li Zou
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan 430060, China
| | - Xingyu Zhang
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan 430060, China
| | - Min Xiong
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan 430060, China
| | - Lanxia Meng
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan 430060, China
| | - Ye Tian
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan 430060, China
| | - Lina Pan
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan 430060, China
| | - Xin Yuan
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan 430060, China
| | - Guiqin Chen
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan 430060, China; Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Zhihao Wang
- Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Lihong Bu
- PET-CT/MRI Center, Faculty of Radiology and Nuclear Medicine, Renmin Hospital of Wuhan University, Wuhan 430060, China
| | - Zhaohui Yao
- Department of Geriatrics, Renmin Hospital of Wuhan University, Wuhan 430060, China
| | - Zhaohui Zhang
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan 430060, China
| | - Keqiang Ye
- Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Zhentao Zhang
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan 430060, China.
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13
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Tu C, Du Z, Zhang H, Feng Y, Qi Y, Zheng Y, Liu J, Wang J. Endocytic pathway inhibition attenuates extracellular vesicle-induced reduction of chemosensitivity to bortezomib in multiple myeloma cells. Am J Cancer Res 2021; 11:2364-2380. [PMID: 33500730 PMCID: PMC7797667 DOI: 10.7150/thno.47996] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2020] [Accepted: 11/18/2020] [Indexed: 12/16/2022] Open
Abstract
Extracellular vesicles (EVs), including exosomes and microvesicles, derived from bone marrow stromal cells (BMSCs) have been demonstrated as key factors in the progression and drug resistance of multiple myeloma (MM). EV uptake involves a variety of mechanisms which largely depend on the vesicle origin and recipient cell type. The aim of the present study was to identify the mechanisms involved in the uptake of BMSC-derived small EVs (sEVs) by MM cells, and to evaluate the anti-MM effect of targeting this process. Methods: Human BMSC-derived sEVs were identified by transmission electron microscopy, nanoparticle tracking analysis, and western blot. The effects of chemical inhibitors and shRNA-mediated knockdown of endocytosis-associated genes on sEV uptake and cell apoptosis were analyzed by flow cytometry. The anti-MM effect of blocking sEV uptake was evaluated in vitro and in a xenograft MM mouse model. Results: sEVs derived from BMSC were taken up by MM cells in a time- and dose-dependent manner, and subsequently promoted MM cell cycling and reduced their chemosensitivity to bortezomib. Chemical endocytosis inhibitors targeting heparin sulphate proteoglycans, actin, tyrosine kinase, dynamin-2, sodium/proton exchangers, or phosphoinositide 3-kinases significantly reduced MM cell internalization of BMSC-derived sEVs. Moreover, shRNA-mediated knockdown of endocytosis-associated proteins, including caveolin-1, flotillin-1, clathrin heavy chain, and dynamin-2 in MM cells suppressed sEV uptake. Furthermore, an endocytosis inhibitor targeting dynamin-2 preferentially suppressed the uptake of sEV by primary MM cells ex vivo and enhanced the anti-MM effects of bortezomib in vitro and in a mouse model. Conclusion: Clathrin- and caveolin-dependent endocytosis and macropinocytosis are the predominant routes of sEV-mediated communication between BMSCs and MM cells, and inhibiting endocytosis attenuates sEV-induced reduction of chemosensitivity to bortezomib, and thus enhances its anti-MM properties.
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14
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Arriagada-Diaz J, Prado-Vega L, Cárdenas Díaz AM, Ardiles AO, Gonzalez-Jamett AM. Dynamin Superfamily at Pre- and Postsynapses: Master Regulators of Synaptic Transmission and Plasticity in Health and Disease. Neuroscientist 2020; 28:41-58. [PMID: 33300419 DOI: 10.1177/1073858420974313] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Dynamin superfamily proteins (DSPs) comprise a large group of GTP-ases that orchestrate membrane fusion and fission, and cytoskeleton remodeling in different cell-types. At the central nervous system, they regulate synaptic vesicle recycling and signaling-receptor turnover, allowing the maintenance of synaptic transmission. In the presynapses, these GTP-ases control the recycling of synaptic vesicles influencing the size of the ready-releasable pool and the release of neurotransmitters from nerve terminals, whereas in the postsynapses, they are involved in AMPA-receptor trafficking to and from postsynaptic densities, supporting excitatory synaptic plasticity, and consequently learning and memory formation. In agreement with these relevant roles, an important number of neurological disorders are associated with mutations and/or dysfunction of these GTP-ases. Along the present review we discuss the importance of DSPs at synapses and their implication in different neuropathological contexts.
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Affiliation(s)
- Jorge Arriagada-Diaz
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile.,Programa de Magister en Ciencias, mención Neurociencia, Universidad de Valparaíso, Valparaíso, Chile
| | - Lorena Prado-Vega
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile.,Programa de Magister en Ciencias, mención Neurociencia, Universidad de Valparaíso, Valparaíso, Chile
| | - Ana M Cárdenas Díaz
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Alvaro O Ardiles
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile.,Centro de Neurología Traslacional, Facultad de Medicina, Universidad de Valparaíso, Valparaíso, Chile.,Centro Interdisciplinario de Estudios en Salud, Facultad de Medicina, Universidad de Valparaíso, Viña del Mar, Chile
| | - Arlek M Gonzalez-Jamett
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
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15
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Nath VR, Mishra S, Basak B, Trivedi D, Raghu P. Extended synaptotagmin regulates membrane contact site structure and lipid transfer function in vivo. EMBO Rep 2020; 21:e50264. [PMID: 32716137 DOI: 10.15252/embr.202050264] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 06/12/2020] [Accepted: 06/22/2020] [Indexed: 12/20/2022] Open
Abstract
Inter-organelle communication between closely apposed membranes is proposed at membrane contact sites (MCS). However, the regulation of MCS structure and their functional relevance in vivo remain debated. The extended synaptotagmins (Esyt) are evolutionarily conserved proteins proposed to function at MCS. However, loss of all three Esyts in yeast or mammals shows minimal phenotypes questioning the functional importance of Esyt. We report that in Drosophila photoreceptors, MCS number is regulated by PLCβ activity. Photoreceptors of a null allele of Drosophila extended synaptotagmin (dEsyt) show loss of ER-PM MCS. Loss of dEsyt results in mislocalization of RDGB, an MCS localized lipid transfer protein, required for photoreceptor structure and function, ultimately leading to retinal degeneration. dEsyt depletion enhanced the retinal degeneration, reduced light responses and slower rates of plasma membrane PIP2 resynthesis seen in rdgB mutants. Thus, dEsyt function and PLCβ signaling regulate ER-PM MCS structure and lipid transfer in Drosophila photoreceptors.
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Affiliation(s)
- Vaisaly R Nath
- National Centre for Biological Sciences-TIFR, Bangalore, India.,School of Biotechnology, Amrita Vishwa Vidyapeetham, Amritapuri, Kollam, Kerala, India
| | - Shirish Mishra
- National Centre for Biological Sciences-TIFR, Bangalore, India
| | - Bishal Basak
- National Centre for Biological Sciences-TIFR, Bangalore, India
| | - Deepti Trivedi
- National Centre for Biological Sciences-TIFR, Bangalore, India
| | - Padinjat Raghu
- National Centre for Biological Sciences-TIFR, Bangalore, India
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16
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Bonnycastle K, Davenport EC, Cousin MA. Presynaptic dysfunction in neurodevelopmental disorders: Insights from the synaptic vesicle life cycle. J Neurochem 2020; 157:179-207. [PMID: 32378740 DOI: 10.1111/jnc.15035] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 04/14/2020] [Accepted: 04/22/2020] [Indexed: 12/11/2022]
Abstract
The activity-dependent fusion, retrieval and recycling of synaptic vesicles is essential for the maintenance of neurotransmission. Until relatively recently it was believed that most mutations in genes that were essential for this process would be incompatible with life, because of this fundamental role. However, an ever-expanding number of mutations in this very cohort of genes are being identified in individuals with neurodevelopmental disorders, including autism, intellectual disability and epilepsy. This article will summarize the current state of knowledge linking mutations in presynaptic genes to neurodevelopmental disorders by sequentially covering the various stages of the synaptic vesicle life cycle. It will also discuss how perturbations of specific stages within this recycling process could translate into human disease. Finally, it will also provide perspectives on the potential for future therapy that are targeted to presynaptic function.
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Affiliation(s)
- Katherine Bonnycastle
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.,Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, UK.,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK
| | - Elizabeth C Davenport
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.,Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, UK.,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK
| | - Michael A Cousin
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.,Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, UK.,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK
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17
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Cherian I, Venkatesh T, Paul PM. In silico prediction of UCLH1 disease-causing SNPs and its effects on protein stability. GENE REPORTS 2020. [DOI: 10.1016/j.genrep.2020.100677] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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18
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Absence of Sac2/INPP5F enhances the phenotype of a Parkinson's disease mutation of synaptojanin 1. Proc Natl Acad Sci U S A 2020; 117:12428-12434. [PMID: 32424101 PMCID: PMC7275725 DOI: 10.1073/pnas.2004335117] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Extensive genetic studies have identified numerous genes whose mutations results on Parkinson’s disease (PD), including synaptojanin 1 (SJ1/Park20), a nerve terminal enriched protein that includes an inositol 4-phosphatase domain (Sac domain). In addition, many PD candidate genes have been identified by genome-wide association studies, but for most of these genes, the link to PD remains hypothetical. One such gene is Sac2/INPP5F, which, interestingly, also includes an inositol 4-phosphatase domain. While Sac2KO mice do not show obvious defects, we show a striking synthetic effect in mice of the KO of Sac2 and the Sac domain mutation of SJ1 found in PD patients. These findings support a synergistic role of SJ1 and Sac2 on a PI4P pool whose dysfunction results in PD. Numerous genes whose mutations cause, or increase the risk of, Parkinson’s disease (PD) have been identified. An inactivating mutation (R258Q) in the Sac inositol phosphatase domain of synaptojanin 1 (SJ1/PARK20), a phosphoinositide phosphatase implicated in synaptic vesicle recycling, results in PD. The gene encoding Sac2/INPP5F, another Sac domain-containing protein, is located within a PD risk locus identified by genome-wide association studies. Knock-In mice carrying the SJ1 patient mutation (SJ1RQKI) exhibit PD features, while Sac2 knockout mice (Sac2KO) do not have obvious neurologic defects. We report a “synthetic” effect of the SJ1 mutation and the KO of Sac2 in mice. Most mice with both mutations died perinatally. The occasional survivors had stunted growth, died within 3 wk, and showed abnormalities of striatal dopaminergic nerve terminals at an earlier stage than SJ1RQKI mice. The abnormal accumulation of endocytic factors observed at synapses of cultured SJ1RQKI neurons was more severe in double-mutant neurons. Our results suggest that SJ1 and Sac2 have partially overlapping functions and are consistent with a potential role of Sac2 as a PD risk gene.
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19
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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: 11] [Impact Index Per Article: 2.8] [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.
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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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20
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Yang Y, Li T, Li Z, Liu N, Yan Y, Liu B. Role of Mitophagy in Cardiovascular Disease. Aging Dis 2020; 11:419-437. [PMID: 32257551 PMCID: PMC7069452 DOI: 10.14336/ad.2019.0518] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Accepted: 05/18/2019] [Indexed: 12/17/2022] Open
Abstract
Cardiovascular disease is the leading cause of mortality worldwide, and mitochondrial dysfunction is the primary contributor to these disorders. Recent studies have elaborated on selective autophagy-mitophagy, which eliminates damaged and dysfunctional mitochondria, stabilizes mitochondrial structure and function, and maintains cell survival and growth. Numerous recent studies have reported that mitophagy plays an important role in the pathogenesis of various cardiovascular diseases. This review summarizes the mechanisms underlying mitophagy and advancements in studies on the role of mitophagy in cardiovascular disease.
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Affiliation(s)
- Yibo Yang
- Department of Cardiology, The Second Hospital of Jilin University, Changchun 130041, China
| | - Tianyi Li
- Department of Cardiology, The Second Hospital of Jilin University, Changchun 130041, China
| | - Zhibo Li
- Department of Cardiology, The Second Hospital of Jilin University, Changchun 130041, China
| | - Ning Liu
- Department of Cardiology, The Second Hospital of Jilin University, Changchun 130041, China
| | - Youyou Yan
- Department of Cardiology, The Second Hospital of Jilin University, Changchun 130041, China
| | - Bin Liu
- Department of Cardiology, The Second Hospital of Jilin University, Changchun 130041, China
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21
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Cheung G, Cousin MA. Synaptic vesicle generation from activity-dependent bulk endosomes requires a dephosphorylation-dependent dynamin-syndapin interaction. J Neurochem 2019; 151:570-583. [PMID: 31479508 PMCID: PMC6899846 DOI: 10.1111/jnc.14862] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 07/24/2019] [Accepted: 08/28/2019] [Indexed: 12/13/2022]
Abstract
Activity‐dependent bulk endocytosis generates synaptic vesicles (SVs) during intense neuronal activity via a two‐step process. First, bulk endosomes are formed direct from the plasma membrane from which SVs are then generated. SV generation from bulk endosomes requires the efflux of previously accumulated calcium and activation of the protein phosphatase calcineurin. However, it is still unknown how calcineurin mediates SV generation. We addressed this question using a series of acute interventions that decoupled the generation of SVs from bulk endosomes in rat primary neuronal culture. This was achieved by either disruption of protein–protein interactions via delivery of competitive peptides, or inhibition of enzyme activity by known inhibitors. SV generation was monitored using either a morphological horseradish peroxidase assay or an optical assay that monitors the replenishment of the reserve SV pool. We found that SV generation was inhibited by, (i) peptides that disrupt calcineurin interactions, (ii) an inhibitor of dynamin I GTPase activity and (iii) peptides that disrupt the phosphorylation‐dependent dynamin I–syndapin I interaction. Peptides that disrupted syndapin I interactions with eps15 homology domain‐containing proteins had no effect. This revealed that (i) calcineurin must be localized at bulk endosomes to mediate its effect, (ii) dynamin I GTPase activity is essential for SV fission and (iii) the calcineurin‐dependent interaction between dynamin I and syndapin I is essential for SV generation. We therefore propose that a calcineurin‐dependent dephosphorylation cascade that requires both dynamin I GTPase and syndapin I lipid‐deforming activity is essential for SV generation from bulk endosomes. ![]()
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Affiliation(s)
- Giselle Cheung
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - Michael A Cousin
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.,Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, UK.,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK
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22
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Watanabe S, Mamer LE, Raychaudhuri S, Luvsanjav D, Eisen J, Trimbuch T, Söhl-Kielczynski B, Fenske P, Milosevic I, Rosenmund C, Jorgensen EM. Synaptojanin and Endophilin Mediate Neck Formation during Ultrafast Endocytosis. Neuron 2019; 98:1184-1197.e6. [PMID: 29953872 DOI: 10.1016/j.neuron.2018.06.005] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Revised: 05/12/2018] [Accepted: 06/04/2018] [Indexed: 11/19/2022]
Abstract
Ultrafast endocytosis generates vesicles from the plasma membrane as quickly as 50 ms in hippocampal neurons following synaptic vesicle fusion. The molecular mechanism underlying the rapid maturation of these endocytic pits is not known. Here we demonstrate that synaptojanin-1, and its partner endophilin-A, function in ultrafast endocytosis. In the absence of synaptojanin or endophilin, the membrane is rapidly invaginated, but pits do not become constricted at the base. The 5-phosphatase activity of synaptojanin is involved in formation of the neck, but 4-phosphatase is not required. Nevertheless, these pits are eventually cleaved into vesicles; within a 30-s interval, synaptic endosomes form and are resolved by clathrin-mediated budding. Then synaptojanin and endophilin function at a second step to aid with the removal of clathrin coats from the regenerated vesicles. These data together suggest that synaptojanin and endophilin can mediate membrane remodeling on a millisecond timescale during ultrafast endocytosis.
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Affiliation(s)
- Shigeki Watanabe
- Department of Neurophysiology, NeuroCure Cluster of Excellence, Charité-Universitätsmedizin Berlin, Berlin, Germany; Department of Cell Biology, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA; Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA.
| | - Lauren Elizabeth Mamer
- Department of Neurophysiology, NeuroCure Cluster of Excellence, Charité-Universitätsmedizin Berlin, Berlin, Germany; The Ohio State University College of Medicine, The Ohio State University, Columbus, OH 43210, USA
| | - Sumana Raychaudhuri
- Department of Cell Biology, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA
| | - Delgermaa Luvsanjav
- Department of Cell Biology, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA
| | - Julia Eisen
- Barnard College of Columbia University, New York, NY, USA
| | - Thorsten Trimbuch
- Department of Neurophysiology, NeuroCure Cluster of Excellence, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Berit Söhl-Kielczynski
- Department of Neurophysiology, NeuroCure Cluster of Excellence, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Pascal Fenske
- Department of Neurophysiology, NeuroCure Cluster of Excellence, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Ira Milosevic
- Synaptic Vesicle Dynamics, European Neuroscience Institute, University Medical Center Göttingen, 37077 Göttingen, Germany
| | - Christian Rosenmund
- Department of Neurophysiology, NeuroCure Cluster of Excellence, Charité-Universitätsmedizin Berlin, Berlin, Germany.
| | - Erik M Jorgensen
- Department of Neurophysiology, NeuroCure Cluster of Excellence, Charité-Universitätsmedizin Berlin, Berlin, Germany; Department of Biology and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT 84112-0840, USA.
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23
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Ackermann F, Schink KO, Bruns C, Izsvák Z, Hamra FK, Rosenmund C, Garner CC. Critical role for Piccolo in synaptic vesicle retrieval. eLife 2019; 8:46629. [PMID: 31074746 PMCID: PMC6541439 DOI: 10.7554/elife.46629] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Accepted: 05/09/2019] [Indexed: 12/30/2022] Open
Abstract
Loss of function of the active zone protein Piccolo has recently been linked to a disease, Pontocerebellar Hypoplasia type 3, which causes brain atrophy. Here, we address how Piccolo inactivation in rat neurons adversely affects synaptic function and thus may contribute to neuronal loss. Our analysis shows that Piccolo is critical for the recycling and maintenance of synaptic vesicles. We find that boutons lacking Piccolo have deficits in the Rab5/EEA1 dependent formation of early endosomes and thus the recycling of SVs. Mechanistically, impaired Rab5 function was caused by reduced synaptic recruitment of Pra1, known to interact selectively with the zinc finger domains of Piccolo. Importantly, over-expression of GTPase deficient Rab5 or the Znf1 domain of Piccolo restores the size and recycling of SV pools. These data provide a molecular link between the active zone and endosome sorting at synapses providing hints to how Piccolo contributes to developmental and psychiatric disorders.
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Affiliation(s)
- Frauke Ackermann
- German Center for Neurodegenerative Diseases e.V. (DZNE), Charité Medical University, Berlin, Germany
| | - Kay Oliver Schink
- Center for Cancer Biomedicine, University of Oslo, Norwegian Radium Hospital, Oslo, Norway
| | - Christine Bruns
- German Center for Neurodegenerative Diseases e.V. (DZNE), Charité Medical University, Berlin, Germany
| | - Zsuzsanna Izsvák
- Max-Delbrück Center for Molecular Medicine in the Helmholtz Society, Berlin, Germany
| | - F Kent Hamra
- Department of Obstetrics and Gynecology, University of Texas Southwestern, Dallas, United States
| | - Christian Rosenmund
- NeuroCure Cluster of Excellence, Neuroscience Research Center, Charité Medical University, Berlin, Germany
| | - Craig Curtis Garner
- German Center for Neurodegenerative Diseases e.V. (DZNE), Charité Medical University, Berlin, Germany
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Rampérez A, Bartolomé-Martín D, García-Pascual A, Sánchez-Prieto J, Torres M. Photoconversion of FM1-43 Reveals Differences in Synaptic Vesicle Recycling and Sensitivity to Pharmacological Disruption of Actin Dynamics in Individual Synapses. ACS Chem Neurosci 2019; 10:2045-2059. [PMID: 30763065 DOI: 10.1021/acschemneuro.8b00712] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The cycling of synaptic vesicles ensures that neurons can communicate adequately through their synapses on repeated occasions when activity is sustained, and several steps in this cycle are modulated by actin. The effects of pharmacological stabilization of actin with jasplakinolide or its depolymerization with latrunculin A was assessed on the synaptic vesicle cycle at individual boutons of cerebellar granule cells, using FM1-43 imaging to track vesicle recycling and its photoconversion to specifically label recycled organelles. Remarkable differences in the recycling capacity of individual boutons are evident, and their dependence on the actin cytoskeleton for recycling is clear. Disrupting actin dynamics causes a loss of functional boutons, and while this indicates that exo/endocytotic cycling in boutons is fully dependent on such events, this dependence is only partial in other boutons. Indeed, exocytosis and vesicle trafficking are impaired significantly by stabilizing or depolymerizing actin, whereas repositioning recycled vesicles at the active zone seems to be dependent on actin polymerization alone. These findings support the hypothesis that different steps of synaptic vesicle cycling depend on actin dynamics and that such dependence varies among individual boutons.
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Affiliation(s)
- Alberto Rampérez
- Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid 28040, Spain
| | - David Bartolomé-Martín
- Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid 28040, Spain
| | - Angeles García-Pascual
- Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid 28040, Spain
| | - Jose Sánchez-Prieto
- Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid 28040, Spain
| | - Magdalena Torres
- Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid 28040, Spain
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25
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Yu SC, Jánosi B, Liewald JF, Wabnig S, Gottschalk A. Endophilin A and B Join Forces With Clathrin to Mediate Synaptic Vesicle Recycling in Caenorhabditis elegans. Front Mol Neurosci 2018; 11:196. [PMID: 29962934 PMCID: PMC6010539 DOI: 10.3389/fnmol.2018.00196] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 05/17/2018] [Indexed: 01/24/2023] Open
Abstract
Synaptic vesicle (SV) recycling enables ongoing transmitter release, even during prolonged activity. SV membrane and proteins are retrieved by ultrafast endocytosis and new SVs are formed from synaptic endosomes (large vesicles—LVs). Many proteins contribute to SV recycling, e.g., endophilin, synaptojanin, dynamin and clathrin, while the site of action of these proteins (at the plasma membrane (PM) vs. at the endosomal membrane) is only partially understood. Here, we investigated the roles of endophilin A (UNC-57), endophilin-related protein (ERP-1, homologous to human endophilin B1) and of clathrin, in SV recycling at the cholinergic neuromuscular junction (NMJ) of C. elegans. erp-1 mutants exhibited reduced transmission and a progressive reduction in optogenetically evoked muscle contraction, indicative of impaired SV recycling. This was confirmed by electrophysiology, where particularly endophilin A (UNC-57), but also endophilin B (ERP-1) mutants exhibited reduced transmission. By optogenetic and electrophysiological analysis, phenotypes in the unc-57; erp-1 double mutant are largely dominated by the unc-57 mutation, arguing for partially redundant functions of endophilins A and B, but also hinting at a back-up mechanism for neuronal endocytosis. By electron microscopy (EM), we observed that unc-57 and erp-1; unc-57 double mutants showed increased numbers of synaptic endosomes of large size, assigning a role for both proteins at the endosome, because endosomal disintegration into new SVs, but not formation of endosomes were hampered. Accordingly, only low amounts of SVs were present. Also erp-1 mutants show reduced SV numbers (but no increase in LVs), thus ERP-1 contributes to SV formation. We analyzed temperature-sensitive mutants of clathrin heavy chain (chc-1), as well as erp-1; chc-1 and unc-57; chc-1 double mutants. SV recycling phenotypes were obvious from optogenetic stimulation experiments. By EM, chc-1 mutants showed formation of numerous and large endosomes, arguing that clathrin, as shown for mammalian synapses, acts at the endosome in formation of new SVs. Without endophilins, clathrin formed endosomes at the PM, while endophilins A and B compensated for the loss of clathrin at the PM, under conditions of high SV turnover.
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Affiliation(s)
- Szi-Chieh Yu
- Buchmann Institute of Molecular Life Sciences (BMLS), Goethe University, Frankfurt, Germany.,Institute of Biophysical Chemistry, Department of Biochemistry, Chemistry and Pharmacy, Goethe University, Frankfurt, Germany
| | - Barbara Jánosi
- Buchmann Institute of Molecular Life Sciences (BMLS), Goethe University, Frankfurt, Germany.,Institute of Biophysical Chemistry, Department of Biochemistry, Chemistry and Pharmacy, Goethe University, Frankfurt, Germany
| | - Jana F Liewald
- Buchmann Institute of Molecular Life Sciences (BMLS), Goethe University, Frankfurt, Germany.,Institute of Biophysical Chemistry, Department of Biochemistry, Chemistry and Pharmacy, Goethe University, Frankfurt, Germany
| | - Sebastian Wabnig
- Buchmann Institute of Molecular Life Sciences (BMLS), Goethe University, Frankfurt, Germany.,Institute of Biophysical Chemistry, Department of Biochemistry, Chemistry and Pharmacy, Goethe University, Frankfurt, Germany
| | - Alexander Gottschalk
- Buchmann Institute of Molecular Life Sciences (BMLS), Goethe University, Frankfurt, Germany.,Institute of Biophysical Chemistry, Department of Biochemistry, Chemistry and Pharmacy, Goethe University, Frankfurt, Germany.,Cluster of Excellence Frankfurt, Macromolecular Complexes (CEF-MC), Goethe University, Frankfurt, Germany
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26
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Lou X. Sensing Exocytosis and Triggering Endocytosis at Synapses: Synaptic Vesicle Exocytosis-Endocytosis Coupling. Front Cell Neurosci 2018; 12:66. [PMID: 29593500 PMCID: PMC5861208 DOI: 10.3389/fncel.2018.00066] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Accepted: 02/26/2018] [Indexed: 12/29/2022] Open
Abstract
The intact synaptic structure is critical for information processing in neural circuits. During synaptic transmission, rapid vesicle exocytosis increases the size of never terminals and endocytosis counteracts the increase. Accumulating evidence suggests that SV exocytosis and endocytosis are tightly connected in time and space during SV recycling, and this process is essential for synaptic function and structural stability. Research in the past has illustrated the molecular details of synaptic vesicle (SV) exocytosis and endocytosis; however, the mechanisms that timely connect these two fundamental events are poorly understood at central synapses. Here we discuss recent progress in SV recycling and summarize several emerging mechanisms by which synapses can “sense” the occurrence of exocytosis and timely initiate compensatory endocytosis. They include Ca2+ sensing, SV proteins sensing, and local membrane stress sensing. In addition, the spatial organization of endocytic zones adjacent to active zones provides a structural basis for efficient coupling between SV exocytosis and endocytosis. Through linking different endocytosis pathways with SV fusion, these mechanisms ensure necessary plasticity and robustness of nerve terminals to meet diverse physiological needs.
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Affiliation(s)
- Xuelin Lou
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI, United States
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27
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Milosevic I. Revisiting the Role of Clathrin-Mediated Endoytosis in Synaptic Vesicle Recycling. Front Cell Neurosci 2018; 12:27. [PMID: 29467622 PMCID: PMC5807904 DOI: 10.3389/fncel.2018.00027] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Accepted: 01/17/2018] [Indexed: 12/11/2022] Open
Abstract
Without robust mechanisms to efficiently form new synaptic vesicles (SVs), the tens to hundreds of SVs typically present at the neuronal synapse would be rapidly used up, even at modest levels of neuronal activity. SV recycling is thus critical for synaptic physiology and proper function of sensory and nervous systems. Yet, more than four decades after it was originally proposed that the SVs are formed and recycled locally at the presynaptic terminals, the mechanisms of endocytic processes at the synapse are heavily debated. Clathrin-mediated endocytosis, a type of endocytosis that capitalizes on the clathrin coat, a number of adaptor and accessory proteins, and the GTPase dynamin, is well understood, while the contributions of clathrin-independent fast endocytosis, kiss-and-run, bulk endocytosis and ultrafast endocytosis are still being evaluated. This review article revisits and summarizes the current knowledge on the SV reformation with a focus on clathrin-mediated endocytosis, and it discusses the modes of SV formation from endosome-like structures at the synapse. Given the importance of this topic, future advances in this active field are expected to contribute to better comprehension of neurotransmission, and to have general implications for neuroscience and medicine.
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Affiliation(s)
- Ira Milosevic
- Synaptic Vesicle Dynamics Group, European Neuroscience Institute (ENI), University Medical Center Göttingen (UMG), Göttingen, Germany
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28
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Wall MJ, Corrêa SAL. The mechanistic link between Arc/Arg3.1 expression and AMPA receptor endocytosis. Semin Cell Dev Biol 2017; 77:17-24. [PMID: 28890421 DOI: 10.1016/j.semcdb.2017.09.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 09/06/2017] [Accepted: 09/06/2017] [Indexed: 02/06/2023]
Abstract
The activity-regulated cytoskeleton associated protein (Arc/Arg3.1) plays a key role in determining synaptic strength through facilitation of AMPA receptor (AMPAR) endocytosis. Although there is considerable data on the mechanism by which Arc induction controls synaptic plasticity and learning behaviours, several key mechanistic questions remain. Here we review data on the link between Arc expression and the clathrin-mediated endocytic pathway which internalises AMPARs and discuss the significance of Arc binding to the clathrin adaptor protein 2 (AP-2) and to endophilin/dynamin. We consider which AMPAR subunits are selected for Arc-mediated internalisation, implications for synaptic function and consider Arc as a therapeutic target.
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Affiliation(s)
- Mark J Wall
- School of Life Sciences, University of Warwick, United Kingdom.
| | - Sonia A L Corrêa
- School of Pharmacy and Medical Sciences, Faculty of Life Sciences, University of Bradford, United Kingdom.
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29
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Parkinson Sac Domain Mutation in Synaptojanin 1 Impairs Clathrin Uncoating at Synapses and Triggers Dystrophic Changes in Dopaminergic Axons. Neuron 2017; 93:882-896.e5. [PMID: 28231468 DOI: 10.1016/j.neuron.2017.01.019] [Citation(s) in RCA: 119] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Revised: 11/22/2016] [Accepted: 01/20/2017] [Indexed: 01/10/2023]
Abstract
Synaptojanin 1 (SJ1) is a major presynaptic phosphatase that couples synaptic vesicle endocytosis to the dephosphorylation of PI(4,5)P2, a reaction needed for the shedding of endocytic factors from their membranes. While the role of SJ1's 5-phosphatase module in this process is well recognized, the contribution of its Sac phosphatase domain, whose preferred substrate is PI4P, remains unclear. Recently a homozygous mutation in its Sac domain was identified in early-onset parkinsonism patients. We show that mice carrying this mutation developed neurological manifestations similar to those of human patients. Synapses of these mice displayed endocytic defects and a striking accumulation of clathrin-coated intermediates, strongly implicating Sac domain's activity in endocytic protein dynamics. Mutant brains had elevated auxilin (PARK19) and parkin (PARK2) levels. Moreover, dystrophic axonal terminal changes were selectively observed in dopaminergic axons in the dorsal striatum. These results strengthen evidence for a link between synaptic endocytic dysfunction and Parkinson's disease.
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30
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Abstract
Epileptic encephalopathies account for a large proportion of the intractable early-onset epilepsies and are characterized by frequent seizures and poor developmental outcome. The epileptic encephalopathies can be loosely divided into two related groups of named syndromes. The first comprises epilepsies where continuous EEG changes directly result in cognitive and developmental dysfunction. The second includes patients where cognitive impairment is present at seizure onset and is due to the underlying etiology but the epileptic activity may then worsen the cognitive abilities over time. Recent, large-scale exome studies have begun to establish the genetic architecture of the epileptic encephalopathies, resulting in a re-consideration of the boundaries of these named syndromes. The emergence of this genetic architecture has lead to three main pathophysiological concepts to provide a mechanistic framework for these disorders. In this article, we will review the classic syndromes, the most significant genetic findings, and relate both to the pathophysiological understanding of epileptic encephalopathies.
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31
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Ubiquitin C-terminal hydrolase L1 (UCH-L1): structure, distribution and roles in brain function and dysfunction. Biochem J 2017; 473:2453-62. [PMID: 27515257 PMCID: PMC4980807 DOI: 10.1042/bcj20160082] [Citation(s) in RCA: 153] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2016] [Accepted: 04/29/2016] [Indexed: 12/13/2022]
Abstract
Ubiquitin C-terminal hydrolase L1 (UCH-L1) is an extremely abundant protein in the brain where, remarkably, it is estimated to make up 1–5% of total neuronal protein. Although it comprises only 223 amino acids it has one of the most complicated 3D knotted structures yet discovered. Beyond its expression in neurons UCH-L1 has only very limited expression in other healthy tissues but it is highly expressed in several forms of cancer. Although UCH-L1 is classed as a deubiquitinating enzyme (DUB) the direct functions of UCH-L1 remain enigmatic and a wide array of alternative functions has been proposed. UCH-L1 is not essential for neuronal development but it is absolutely required for the maintenance of axonal integrity and UCH-L1 dysfunction is implicated in neurodegenerative disease. Here we review the properties of UCH-L1, and how understanding its complex structure can provide new insights into its roles in neuronal function and pathology.
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32
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Li YC, Kavalali ET. Synaptic Vesicle-Recycling Machinery Components as Potential Therapeutic Targets. Pharmacol Rev 2017; 69:141-160. [PMID: 28265000 DOI: 10.1124/pr.116.013342] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Presynaptic nerve terminals are highly specialized vesicle-trafficking machines. Neurotransmitter release from these terminals is sustained by constant local recycling of synaptic vesicles independent from the neuronal cell body. This independence places significant constraints on maintenance of synaptic protein complexes and scaffolds. Key events during the synaptic vesicle cycle-such as exocytosis and endocytosis-require formation and disassembly of protein complexes. This extremely dynamic environment poses unique challenges for proteostasis at synaptic terminals. Therefore, it is not surprising that subtle alterations in synaptic vesicle cycle-associated proteins directly or indirectly contribute to pathophysiology seen in several neurologic and psychiatric diseases. In contrast to the increasing number of examples in which presynaptic dysfunction causes neurologic symptoms or cognitive deficits associated with multiple brain disorders, synaptic vesicle-recycling machinery remains an underexplored drug target. In addition, irrespective of the involvement of presynaptic function in the disease process, presynaptic machinery may also prove to be a viable therapeutic target because subtle alterations in the neurotransmitter release may counter disease mechanisms, correct, or compensate for synaptic communication deficits without the need to interfere with postsynaptic receptor signaling. In this article, we will overview critical properties of presynaptic release machinery to help elucidate novel presynaptic avenues for the development of therapeutic strategies against neurologic and neuropsychiatric disorders.
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Affiliation(s)
- Ying C Li
- Departments of Neuroscience (Y.C.L., E.T.K.) and Physiology (E.T.K.), University of Texas Southwestern Medical Center, Dallas, Texas
| | - Ege T Kavalali
- Departments of Neuroscience (Y.C.L., E.T.K.) and Physiology (E.T.K.), University of Texas Southwestern Medical Center, Dallas, Texas
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33
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Dalmau J, Geis C, Graus F. Autoantibodies to Synaptic Receptors and Neuronal Cell Surface Proteins in Autoimmune Diseases of the Central Nervous System. Physiol Rev 2017; 97:839-887. [PMID: 28298428 PMCID: PMC5539405 DOI: 10.1152/physrev.00010.2016] [Citation(s) in RCA: 340] [Impact Index Per Article: 48.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Investigations in the last 10 years have revealed a new category of neurological diseases mediated by antibodies against cell surface and synaptic proteins. There are currently 16 such diseases all characterized by autoantibodies against neuronal proteins involved in synaptic signaling and plasticity. In clinical practice these findings have changed the diagnostic and treatment approach to potentially lethal, but now treatable, neurological and psychiatric syndromes previously considered idiopathic or not even suspected to be immune-mediated. Studies show that patients' antibodies can impair the surface dynamics of the target receptors eliminating them from synapses (e.g., NMDA receptor), block the function of the antigens without changing their synaptic density (e.g., GABAb receptor), interfere with synaptic protein-protein interactions (LGI1, Caspr2), alter synapse formation (e.g., neurexin-3α), or by unclear mechanisms associate to a new form of tauopathy (IgLON5). Here we first trace the process of discovery of these diseases, describing the triggers and symptoms related to each autoantigen, and then review in detail the structural and functional alterations caused by the autoantibodies with special emphasis in those (NMDA receptor, amphiphysin) that have been modeled in animals.
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Affiliation(s)
- Josep Dalmau
- Institut d'Investigacions Biomèdiques August Pi i Sunyer, Hospital Clínic, Universitat de Barcelona, Barcelona, Spain; Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania; Institució Catalana de Recerca i Estudis Avançats, Barcelona, Spain; Hans-Berger Department of Neurology, Jena University Hospital, Jena, Germany; Servei de Neurologia, Hospital Clínic, Universitat de Barcelona, Barcelona, Spain
| | - Christian Geis
- Institut d'Investigacions Biomèdiques August Pi i Sunyer, Hospital Clínic, Universitat de Barcelona, Barcelona, Spain; Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania; Institució Catalana de Recerca i Estudis Avançats, Barcelona, Spain; Hans-Berger Department of Neurology, Jena University Hospital, Jena, Germany; Servei de Neurologia, Hospital Clínic, Universitat de Barcelona, Barcelona, Spain
| | - Francesc Graus
- Institut d'Investigacions Biomèdiques August Pi i Sunyer, Hospital Clínic, Universitat de Barcelona, Barcelona, Spain; Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania; Institució Catalana de Recerca i Estudis Avançats, Barcelona, Spain; Hans-Berger Department of Neurology, Jena University Hospital, Jena, Germany; Servei de Neurologia, Hospital Clínic, Universitat de Barcelona, Barcelona, Spain
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Xie Z, Long J, Liu J, Chai Z, Kang X, Wang C. Molecular Mechanisms for the Coupling of Endocytosis to Exocytosis in Neurons. Front Mol Neurosci 2017; 10:47. [PMID: 28348516 PMCID: PMC5346583 DOI: 10.3389/fnmol.2017.00047] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2016] [Accepted: 02/10/2017] [Indexed: 11/13/2022] Open
Abstract
Neuronal communication and brain function mainly depend on the fundamental biological events of neurotransmission, including the exocytosis of presynaptic vesicles (SVs) for neurotransmitter release and the subsequent endocytosis for SV retrieval. Neurotransmitters are released through the Ca2+- and SNARE-dependent fusion of SVs with the presynaptic plasma membrane. Following exocytosis, endocytosis occurs immediately to retrieve SV membrane and fusion machinery for local recycling and thus maintain the homeostasis of synaptic structure and sustained neurotransmission. Apart from the general endocytic machinery, recent studies have also revealed the involvement of SNARE proteins (synaptobrevin, SNAP25 and syntaxin), synaptophysin, Ca2+/calmodulin, and members of the synaptotagmin protein family (Syt1, Syt4, Syt7 and Syt11) in the balance and tight coupling of exo-endocytosis in neurons. Here, we provide an overview of recent progress in understanding how these neuron-specific adaptors coordinate to ensure precise and efficient endocytosis during neurotransmission.
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Affiliation(s)
- Zhenli Xie
- Center for Mitochondrial Biology and Medicine, The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong UniversityXi'an, China; Frontier Institute of Science and Technology, Xi'an Jiaotong UniversityXi'an, China; State Key Laboratory of Membrane Biology, Peking UniversityBeijing, China; Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, Peking UniversityBeijing, China
| | - Jiangang Long
- Center for Mitochondrial Biology and Medicine, The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong UniversityXi'an, China; Frontier Institute of Science and Technology, Xi'an Jiaotong UniversityXi'an, China
| | - Jiankang Liu
- Center for Mitochondrial Biology and Medicine, The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong UniversityXi'an, China; Frontier Institute of Science and Technology, Xi'an Jiaotong UniversityXi'an, China
| | - Zuying Chai
- State Key Laboratory of Membrane Biology, Peking UniversityBeijing, China; Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, Peking UniversityBeijing, China
| | - Xinjiang Kang
- State Key Laboratory of Membrane Biology, Peking UniversityBeijing, China; Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, Peking UniversityBeijing, China; College of Life Sciences, Liaocheng UniversityLiaocheng, China; Key Laboratory of Medical Electrophysiology, Ministry of Education of China, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical UniversityLuzhou, China
| | - Changhe Wang
- Center for Mitochondrial Biology and Medicine, The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong UniversityXi'an, China; Frontier Institute of Science and Technology, Xi'an Jiaotong UniversityXi'an, China; State Key Laboratory of Membrane Biology, Peking UniversityBeijing, China; Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, Peking UniversityBeijing, China
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35
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Sheehan P, Waites CL. Coordination of synaptic vesicle trafficking and turnover by the Rab35 signaling network. Small GTPases 2017; 10:54-63. [PMID: 28129039 PMCID: PMC6343537 DOI: 10.1080/21541248.2016.1270392] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Rab35 and the Rab35 network of GAPs, GEFs, and effectors are important regulators of membrane trafficking for a variety of cellular processes, from cytokinesis and phagocytosis to neurite outgrowth. In the past five years, components of this signaling network have also been implicated as critical mediators of synaptic vesicle (SV) recycling and protein homeostasis. Recent studies by several groups, including our own, have demonstrated that Rab35-mediated endosomal sorting is required for the degradation of SV proteins via the ESCRT pathway, thereby eliminating old or damaged proteins from the SV pool. This sorting process is regulated by Rab35 activation in response to neuronal activity, and potentially by an antagonistic signaling relationship between Rab35 and the small GTPase Arf6 that directs SVs into distinct recycling pathways depending on neuronal activity levels. Furthermore, mutations in genes encoding Rab35 regulatory proteins are emerging as causative factors in human neurologic and neurodegenerative diseases, consistent with their important roles in synaptic and neuronal health. Here, we review these recent findings and offer our perspective on how the Rab35 signaling network functions to maintain neurotransmission and synaptic fitness.
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Affiliation(s)
- Patricia Sheehan
- a Department of Pathology and Cell Biology , Columbia University Medical Center , New York , NY , USA
| | - Clarissa L Waites
- a Department of Pathology and Cell Biology , Columbia University Medical Center , New York , NY , USA.,b Department of Neuroscience , Columbia University Medical Center , New York , NY , USA
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36
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Abstract
The epileptic encephalopathies are severe and often treatment-resistant conditions that are associated with a progressive disturbance of brain function, resulting in a broad range of neurological and non-neurological comorbidities. The concept of epileptic encephalopathies entails that the encephalopathy aspect of the overall condition is primarily driven by the epileptic activity of the disease, which often manifests as specific and pathological features on the electroencephalogram. Genetic factors in epileptic encephalopathies are increasingly recognized. As of 2016, more than 30 genes have been securely implicated as causative genes for genetic epileptic encephalopathies. Even though the traditional concept of epileptic encephalopathies entails that the progressive disturbance of brain dysfunction is primarily due to the abnormal hypersynchronous activity that underlies the seizure disorders, this strict concept rarely holds true for patients with identified genetic etiologies. More commonly, an underlying genetic etiology is thought to predispose both to the neurodevelopmental comorbidities and to the seizure phenotype with a complex interaction between both. In this chapter, we will elucidate to what extent neurodegeneration rather than epilepsy-related regression is a feature of the common epileptic encephalopathies, drawing parallels between two relatively separate fields of neurogenetic research.
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37
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Siao W, Wang P, Voigt B, Hussey PJ, Baluska F. Arabidopsis SYT1 maintains stability of cortical endoplasmic reticulum networks and VAP27-1-enriched endoplasmic reticulum-plasma membrane contact sites. JOURNAL OF EXPERIMENTAL BOTANY 2016; 67:6161-6171. [PMID: 27811083 PMCID: PMC5100027 DOI: 10.1093/jxb/erw381] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Arabidopsis synaptotagmin 1 (SYT1) is localized on the endoplasmic reticulum-plasma membrane (ER-PM) contact sites in leaf and root cells. The ER-PM localization of Arabidopsis SYT1 resembles that of the extended synaptotagmins (E-SYTs) in animal cells. In mammals, E-SYTs have been shown to regulate calcium signaling, lipid transfer, and endocytosis. Arabidopsis SYT1 was reported to be essential for maintaining cell integrity and virus movement. This study provides detailed insight into the subcellular localization of SYT1 and VAP27-1, another ER-PM-tethering protein. SYT1 and VAP27-1 were shown to be localized on distinct ER-PM contact sites. The VAP27-1-enriched ER-PM contact sites (V-EPCSs) were always in contact with the SYT1-enriched ER-PM contact sites (S-EPCSs). The V-EPCSs still existed in the leaf epidermal cells of the SYT1 null mutant; however, they were less stable than those in the wild type. The polygonal networks of cortical ER disassembled and the mobility of VAP27-1 protein on the ER-PM contact sites increased in leaf cells of the SYT1 null mutant. These results suggest that SYT1 is responsible for stabilizing the ER network and V-EPCSs.
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Affiliation(s)
- Wei Siao
- Institute of Cellular and Molecular Botany, University of Bonn, Kirschallee 1, D-53115 Bonn, Germany
| | - Pengwei Wang
- Department of Biosciences, Durham University, South Road, Durham DH1 3LE, UK
| | - Boris Voigt
- Institute of Cellular and Molecular Botany, University of Bonn, Kirschallee 1, D-53115 Bonn, Germany
| | - Patrick J Hussey
- Department of Biosciences, Durham University, South Road, Durham DH1 3LE, UK
| | - Frantisek Baluska
- Institute of Cellular and Molecular Botany, University of Bonn, Kirschallee 1, D-53115 Bonn, Germany
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Murdoch JD, Rostosky CM, Gowrisankaran S, Arora AS, Soukup SF, Vidal R, Capece V, Freytag S, Fischer A, Verstreken P, Bonn S, Raimundo N, Milosevic I. Endophilin-A Deficiency Induces the Foxo3a-Fbxo32 Network in the Brain and Causes Dysregulation of Autophagy and the Ubiquitin-Proteasome System. Cell Rep 2016; 17:1071-1086. [PMID: 27720640 PMCID: PMC5080600 DOI: 10.1016/j.celrep.2016.09.058] [Citation(s) in RCA: 86] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Revised: 06/24/2016] [Accepted: 09/19/2016] [Indexed: 12/21/2022] Open
Abstract
Endophilin-A, a well-characterized endocytic adaptor essential for synaptic vesicle recycling, has recently been linked to neurodegeneration. We report here that endophilin-A deficiency results in impaired movement, age-dependent ataxia, and neurodegeneration in mice. Transcriptional analysis of endophilin-A mutant mice, complemented by proteomics, highlighted ataxia- and protein-homeostasis-related genes and revealed upregulation of the E3-ubiquitin ligase FBXO32/atrogin-1 and its transcription factor FOXO3A. FBXO32 overexpression triggers apoptosis in cultured cells and neurons but, remarkably, coexpression of endophilin-A rescues it. FBXO32 interacts with all three endophilin-A proteins. Similarly to endophilin-A, FBXO32 tubulates membranes and localizes on clathrin-coated structures. Additionally, FBXO32 and endophilin-A are necessary for autophagosome formation, and both colocalize transiently with autophagosomes. Our results point to a role for endophilin-A proteins in autophagy and protein degradation, processes that are impaired in their absence, potentially contributing to neurodegeneration and ataxia. Endophilin-A is needed for autophagosome formation in mammalian neurons and brain Absence of endophilin-A upregulates the E3-ubiquitin ligase FBXO32 FBXO32-endophilin-A interaction maintains neuronal health and protein homeostasis Endophilin-A KO mice show age-dependent ataxia, motor impairments, and neurodegeneration
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Affiliation(s)
- John D Murdoch
- European Neuroscience Institute (ENI), 37077 Göttingen, Germany; Institute of Cellular Biochemistry, University Medical Center Göttingen (UMG), 37073 Göttingen, Germany
| | | | | | | | - Sandra-Fausia Soukup
- VIB Center for Brain & Disease Research, 3000 Leuven, Belgium; KU Leuven Department of Human Genetics, Leuven Institute for Neurodegenerative Disease (LIND), 3000 Leuven, Belgium
| | - Ramon Vidal
- Computational Systems Biology, German Center for Neurodegenerative Diseases (DZNE), 37077 Göttingen, Germany
| | - Vincenzo Capece
- Computational Systems Biology, German Center for Neurodegenerative Diseases (DZNE), 37077 Göttingen, Germany
| | - Siona Freytag
- European Neuroscience Institute (ENI), 37077 Göttingen, Germany
| | - Andre Fischer
- Epigenetics and Systems Medicine in Neurodegenerative Diseases, German Center for Neurodegenerative Diseases (DZNE), 37077 Göttingen, Germany; Department of Psychiatry and Psychotherapy, University Medical Center Göttingen, 37077 Göttingen, Germany
| | - Patrik Verstreken
- VIB Center for Brain & Disease Research, 3000 Leuven, Belgium; KU Leuven Department of Human Genetics, Leuven Institute for Neurodegenerative Disease (LIND), 3000 Leuven, Belgium
| | - Stefan Bonn
- Computational Systems Biology, German Center for Neurodegenerative Diseases (DZNE), 37077 Göttingen, Germany
| | - Nuno Raimundo
- Institute of Cellular Biochemistry, University Medical Center Göttingen (UMG), 37073 Göttingen, Germany.
| | - Ira Milosevic
- European Neuroscience Institute (ENI), 37077 Göttingen, Germany.
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Dynamin 1 isoform roles in a mouse model of severe childhood epileptic encephalopathy. Neurobiol Dis 2016; 95:1-11. [PMID: 27363778 DOI: 10.1016/j.nbd.2016.06.014] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Revised: 06/23/2016] [Accepted: 06/26/2016] [Indexed: 01/05/2023] Open
Abstract
Dynamin 1 is a large neuron-specific GTPase involved in the endocytosis and recycling of pre-synaptic membranes and synaptic vesicles. Mutations in the gene encoding dynamin 1 (DNM1) underlie two epileptic encephalopathy syndromes, Lennox-Gastaut Syndrome and Infantile Spasms. Mice homozygous for the Dnm1 "fitful" mutation, a non-synonymous coding variant in an alternatively spliced exon of Dnm1 (exon 10a; isoform designation: Dnm1a(Ftfl)) have an epileptic encephalopathy-like disorder including lethal early onset seizures, locomotor and neurosensory deficits. Although fitful heterozygotes have milder recurrent seizures later in life, suggesting an additive or semi-dominant mechanism, the molecular etiology must also consider the fact that Dnm1a(Ftfl) exerts a dominant negative effect on endocytosis in vitro. Another complication is that the fitful mutation induces alterations in the relative abundance of Dnm1 splice variants; mutants have a downregulation of Dnm1a and an upregulation of Dnm1b, changes which may contribute to the epileptic pathology. To examine whether Dnm1a loss of function, Dnm1a(Ftfl) dominance or compensation by Dnm1b is the most critical for severe seizures, we studied alternate isoform-specific mutant mice. Mice lacking Dnm1 exon 10a or Dnm1 exon 10b have neither spontaneous seizures nor other overt abnormalities, suggesting that in normal conditions the major role of each isoform is redundant. However, in the presence of Dnm1a(Ftfl) only exon 10a deleted mice experience severe seizures. These results reveal functional differences between Dnm1a and Dnm1b isoforms in the presence of a challenge, i.e. toxic Dnm1(Ftfl), while reinforcing its effect explicitly in this model of severe pediatric epilepsy.
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Sclip A, Bacaj T, Giam LR, Südhof TC. Extended Synaptotagmin (ESyt) Triple Knock-Out Mice Are Viable and Fertile without Obvious Endoplasmic Reticulum Dysfunction. PLoS One 2016; 11:e0158295. [PMID: 27348751 PMCID: PMC4922586 DOI: 10.1371/journal.pone.0158295] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Accepted: 06/13/2016] [Indexed: 01/15/2023] Open
Abstract
Extended synaptotagmins (ESyts) are endoplasmic reticulum (ER) proteins composed of an N-terminal transmembrane region, a central SMP-domain, and five (ESyt1) or three C-terminal cytoplasmic C2-domains (ESyt2 and ESyt3). ESyts bind phospholipids in a Ca2+-dependent manner via their C2-domains, are localized to ER-plasma membrane contact sites, and may catalyze lipid exchange between the plasma membrane and the ER via their SMP-domains. However, the overall function of ESyts has remained enigmatic. Here, we generated triple constitutive and conditional knock-out mice that lack all three ESyt isoforms; in addition, we produced knock-in mice that express mutant ESyt1 or ESyt2 carrying inactivating substitutions in the Ca2+-binding sites of their C2A-domains. Strikingly, all ESyt mutant mice, even those lacking all ESyts, were apparently normal and survived and bred in a manner indistinguishable from control mice. ESyt mutant mice displayed no major changes in brain morphology or synaptic protein composition, and exhibited no large alterations in stress responses. Thus, in mice ESyts do not perform an essential role in basic cellular functions, suggesting that these highly conserved proteins may perform a specialized role that may manifest only during specific, as yet untested challenges.
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Affiliation(s)
- Alessandra Sclip
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA, 94305–5453, United States of America
- Howard Hughes Medical Institute, Stanford University Medical School, 265 Campus Drive, Stanford, CA, United States of America
| | - Taulant Bacaj
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA, 94305–5453, United States of America
| | - Louise R. Giam
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA, 94305–5453, United States of America
| | - Thomas C. Südhof
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA, 94305–5453, United States of America
- Howard Hughes Medical Institute, Stanford University Medical School, 265 Campus Drive, Stanford, CA, United States of America
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Mahapatra S, Lou X. Dynamin-1 deletion enhances post-tetanic potentiation and quantal size after tetanic stimulation at the calyx of Held. J Physiol 2016; 595:193-206. [PMID: 27229184 DOI: 10.1113/jp271937] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Accepted: 05/18/2016] [Indexed: 01/09/2023] Open
Abstract
KEY POINTS Post-tetanic potentiation (PTP) is attributed mainly to an increase in release probability (Pr ) and/or readily-releasable pool (RRP) in many synapses, but the role of endocytosis in PTP is unknown. Using the calyx of Held synapse from tissue-specific dynamin-1 knockout (cKO) mice (P16-20), we report that cKO synapses show enhanced PTP compared to control. We found significant increases in both spontaneous excitatory postsynaptic current (spEPSC) amplitude and RRP size (estimated by a train of 30 APs at 100 Hz) in cKO over control during PTP. Actin depolymerization blocks the increase in spEPSC amplitude in both control and cKO, and it abolishes the enhancement of PTP in cKO. PTP is sensitive to the PKC inhibitor GF109203X in both control and cKO. We conclude that an activity-dependent quantal size increase contributes to the enhancement of PTP in cKO over control and an altered endocytosis affects short-term plasticity through quantal size changes. ABSTRACT High-frequency stimulation leads to post-tetanic potentiation (PTP) at many types of synapses. Previous studies suggest that PTP results primarily from a protein kinase C (PKC)-dependent increase in release probability (Pr ) and/or readily-releasable pool (RRP) of synaptic vesicles (SVs), but the role of SV endocytosis in PTP is unknown. Using the mature calyx of Held (P16-20), we report that tissue-specific ablation of dynamin-1 (cKO), an endocytic protein crucial for SV regeneration, enhances PTP in cKO over control. To explore the mechanism of this enhancement, we estimated the changes in paired-pulse ratios (PPRs) and RRP size during PTP. RRP was estimated by the back-extrapolation of cumulative EPSC amplitudes during a train of 30 action potentials at 100 Hz (termed RRPtrain ). We found an increase in RRPtrain during PTP in both control and cKO, but no significant changes in the PPR. Moreover, the amplitude and frequency of spontaneous excitatory postsynaptic currents (spEPSCs) increased during PTP in both control and cKO; however, the spEPSC amplitude in cKO during PTP was significantly larger than in control. Actin depolymerization reagent latrunculin-B (Lat-B) abolished the activity-dependent increase in spEPSC amplitude in both control and cKO, but selectively blocked the enhancement of PTP in cKO, without affecting PTP in control. PKC inhibitor GF109203X nearly abolished PTP in both control and cKO. These data suggest that the quantal size increase contributes to the enhancement of PTP in dynamin-1 cKO, and this change depends on strong synaptic activity and actin polymerization.
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Affiliation(s)
- Satyajit Mahapatra
- Department of Neuroscience, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Xuelin Lou
- Department of Neuroscience, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, 53706, USA
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Gallo A, Vannier C, Galli T. Endoplasmic Reticulum-Plasma Membrane Associations:Structures and Functions. Annu Rev Cell Dev Biol 2016; 32:279-301. [PMID: 27298092 DOI: 10.1146/annurev-cellbio-111315-125024] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Inside eukaryotic cells, membrane contact sites (MCSs), regions where two membrane-bound organelles are apposed at less than 30 nm, generate regions of important lipid and calcium exchange. This review principally focuses on the structure and the function of MCSs between the endoplasmic reticulum (ER) and the plasma membrane (PM). Here we describe how tethering structures form and maintain these junctions and, in some instances, participate in their function. We then discuss recent insights into the mechanisms by which specific classes of proteins mediate nonvesicular lipid exchange between the ER and PM and how such phenomena, already known to be crucial for maintaining organelle identity, are also emerging as regulators of cell growth and development.
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Affiliation(s)
- Alessandra Gallo
- Membrane Traffic in Health & Disease Group (INSERM ERL U950), F-75013 Paris, France;
| | - Christian Vannier
- Membrane Traffic in Health & Disease Group (INSERM ERL U950), F-75013 Paris, France;
| | - Thierry Galli
- Membrane Traffic in Health & Disease Group (INSERM ERL U950), F-75013 Paris, France;
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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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Tissue-specific dynamin-1 deletion at the calyx of Held decreases short-term depression through a mechanism distinct from vesicle resupply. Proc Natl Acad Sci U S A 2016; 113:E3150-8. [PMID: 27185948 DOI: 10.1073/pnas.1520937113] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Dynamin is a large GTPase with a crucial role in synaptic vesicle regeneration. Acute dynamin inhibition impairs neurotransmitter release, in agreement with the protein's established role in vesicle resupply. Here, using tissue-specific dynamin-1 knockout [conditional knockout (cKO)] mice at a fast central synapse that releases neurotransmitter at high rates, we report that dynamin-1 deletion unexpectedly leads to enhanced steady-state neurotransmission and consequently less synaptic depression during brief periods of high-frequency stimulation. These changes are also accompanied by increased transmission failures. Interestingly, synaptic vesicle resupply and several other synaptic properties remain intact, including basal neurotransmission, presynaptic Ca(2+) influx, initial release probability, and postsynaptic receptor saturation and desensitization. However, acute application of Latrunculin B, a reagent known to induce actin depolymerization and impair bulk and ultrafast endocytosis, has a stronger effect on steady-state depression in cKO than in control and brings the depression down to a control level. The slow phase of presynaptic capacitance decay following strong stimulation is impaired in cKO; the rapid capacitance changes immediately after strong depolarization are also different between control and cKO and sensitive to Latrunculin B. These data raise the possibility that, in addition to its established function in regenerating synaptic vesicles, the endocytosis protein dynamin-1 may have an impact on short-term synaptic depression. This role comes into play primarily during brief high-frequency stimulation.
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Judson MC, Wallace ML, Sidorov MS, Burette AC, Gu B, van Woerden GM, King IF, Han JE, Zylka MJ, Elgersma Y, Weinberg RJ, Philpot BD. GABAergic Neuron-Specific Loss of Ube3a Causes Angelman Syndrome-Like EEG Abnormalities and Enhances Seizure Susceptibility. Neuron 2016; 90:56-69. [PMID: 27021170 DOI: 10.1016/j.neuron.2016.02.040] [Citation(s) in RCA: 114] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Revised: 01/17/2016] [Accepted: 02/24/2016] [Indexed: 11/19/2022]
Abstract
Loss of maternal UBE3A causes Angelman syndrome (AS), a neurodevelopmental disorder associated with severe epilepsy. We previously implicated GABAergic deficits onto layer (L) 2/3 pyramidal neurons in the pathogenesis of neocortical hyperexcitability, and perhaps epilepsy, in AS model mice. Here we investigate consequences of selective Ube3a loss from either GABAergic or glutamatergic neurons, focusing on the development of hyperexcitability within L2/3 neocortex and in broader circuit and behavioral contexts. We find that GABAergic Ube3a loss causes AS-like increases in neocortical EEG delta power, enhances seizure susceptibility, and leads to presynaptic accumulation of clathrin-coated vesicles (CCVs)-all without decreasing GABAergic inhibition onto L2/3 pyramidal neurons. Conversely, glutamatergic Ube3a loss fails to yield EEG abnormalities, seizures, or associated CCV phenotypes, despite impairing tonic inhibition onto L2/3 pyramidal neurons. These results substantiate GABAergic Ube3a loss as the principal cause of circuit hyperexcitability in AS mice, lending insight into ictogenic mechanisms in AS.
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Affiliation(s)
- Matthew C Judson
- Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC 27599, USA; Carolina Institute for Developmental Disabilities, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Michael L Wallace
- Curriculum in Neurobiology, University of North Carolina, Chapel Hill, NC 27599, USA; Carolina Institute for Developmental Disabilities, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Michael S Sidorov
- Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC 27599, USA; Carolina Institute for Developmental Disabilities, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Alain C Burette
- Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Bin Gu
- Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC 27599, USA; Carolina Institute for Developmental Disabilities, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Geeske M van Woerden
- Department of Neuroscience, Erasmus Medical Center, Wytemaweg 80, 3015 CN Rotterdam, the Netherlands; ENCORE Center for Neurodevelopmental Disorders, Erasmus Medical Center, Wytemaweg 80, 3015 CN Rotterdam, the Netherlands
| | - Ian F King
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599, USA
| | - Ji Eun Han
- Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Mark J Zylka
- Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC 27599, USA; Curriculum in Neurobiology, University of North Carolina, Chapel Hill, NC 27599, USA; Carolina Institute for Developmental Disabilities, University of North Carolina, Chapel Hill, NC 27599, USA; Neuroscience Center, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599, USA
| | - Ype Elgersma
- Department of Neuroscience, Erasmus Medical Center, Wytemaweg 80, 3015 CN Rotterdam, the Netherlands; ENCORE Center for Neurodevelopmental Disorders, Erasmus Medical Center, Wytemaweg 80, 3015 CN Rotterdam, the Netherlands
| | - Richard J Weinberg
- Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC 27599, USA; Curriculum in Neurobiology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Benjamin D Philpot
- Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC 27599, USA; Curriculum in Neurobiology, University of North Carolina, Chapel Hill, NC 27599, USA; Carolina Institute for Developmental Disabilities, University of North Carolina, Chapel Hill, NC 27599, USA; Neuroscience Center, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599, USA.
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46
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Jacob J. Cortical interneuron dysfunction in epilepsy associated with autism spectrum disorders. Epilepsia 2015; 57:182-93. [DOI: 10.1111/epi.13272] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/05/2015] [Indexed: 12/30/2022]
Affiliation(s)
- John Jacob
- Nuffield Department of Clinical Neurosciences; John Radcliffe Hospital; Oxford United Kingdom
- Department of Neurology; Milton Keynes Hospital; Buckinghamshire United Kingdom
- Department of Neurology; John Radcliffe Hospital; Oxford United Kingdom
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47
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Ubiquitin-Synaptobrevin Fusion Protein Causes Degeneration of Presynaptic Motor Terminals in Mice. J Neurosci 2015; 35:11514-31. [PMID: 26290230 DOI: 10.1523/jneurosci.5288-14.2015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Protein aggregates containing ubiquitin (Ub) are commonly observed in neurodegenerative disorders, implicating the involvement of the ubiquitin proteasome system (UPS) in their pathogenesis. Here, we aimed to generate a mouse model for monitoring UPS function using a green fluorescent protein (GFP)-based substrate that carries a "noncleavable" N-terminal ubiquitin moiety (Ub(G76V)). We engineered transgenic mice expressing a fusion protein, consisting of the following: (1) Ub(G76V), GFP, and a synaptic vesicle protein synaptobrevin-2 (Ub(G76V)-GFP-Syb2); (2) GFP-Syb2; or (3) Ub(G76V)-GFP-Syntaxin1, all under the control of a neuron-specific Thy-1 promoter. As expected, Ub(G76V)-GFP-Syb2, GFP-Syb2, and Ub(G76V)-GFP-Sytaxin1 were highly expressed in neurons, such as motoneurons and motor nerve terminals of the neuromuscular junction (NMJ). Surprisingly, Ub(G76V)-GFP-Syb2 mice developed progressive adult-onset degeneration of motor nerve terminals, whereas GFP-Syb2 and Ub(G76V)-GFP-Syntaxin1 mice were normal. The degeneration of nerve terminals in Ub(G76V)-GFP-Syb2 mice was preceded by a progressive impairment of synaptic transmission at the NMJs. Biochemical analyses demonstrated that Ub(G76V)-GFP-Syb2 interacted with SNAP-25 and Syntaxin1, the SNARE partners of synaptobrevin. Ultrastructural analyses revealed a marked reduction in synaptic vesicle density, accompanying an accumulation of tubulovesicular structures at presynaptic nerve terminals. These morphological defects were largely restricted to motor nerve terminals, as the ultrastructure of motoneuron somata appeared to be normal at the stages when synaptic nerve terminals degenerated. Furthermore, synaptic vesicle endocytosis and membrane trafficking were impaired in Ub(G76V)-GFP-Syb2 mice. These findings indicate that Ub(G76V)-GFP-Syb2 may compete with endogenous synaptobrevin, acting as a gain-of-function mutation that impedes SNARE function, resulting in the depletion of synaptic vesicles and degeneration of the nerve terminals. SIGNIFICANCE STATEMENT Degeneration of motor nerve terminals occurs in amyotrophic lateral sclerosis (ALS) patients as well as in mouse models of ALS, leading to progressive paralysis. What causes a motor nerve terminal to degenerate remains unknown. Here we report on transgenic mice expressing a ubiquitinated synaptic vesicle protein (Ub(G76V)-GFP-Syb2) that develop progressive degeneration of motor nerve terminals. These mice may serve as a model for further elucidating the underlying cellular and molecular mechanisms of presynaptic nerve terminal degeneration.
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Cao X, Choi S, Maléth JJ, Park S, Ahuja M, Muallem S. The ER/PM microdomain, PI(4,5)P₂ and the regulation of STIM1-Orai1 channel function. Cell Calcium 2015; 58:342-8. [PMID: 25843208 PMCID: PMC4564333 DOI: 10.1016/j.ceca.2015.03.003] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2015] [Revised: 03/06/2015] [Accepted: 03/09/2015] [Indexed: 12/18/2022]
Abstract
All forms of cell signaling occur in discreet cellular microdomains in which the ER is the main participant and include microdomains formed by the ER with lysosomes, endosomes, the nucleus, mitochondria and the plasma membrane. In the microdomains the two opposing organelles transfer and exchange constituents including lipids and ions. As is the case for other forms of signaling pathways, many components of the receptor-evoked Ca(2+) signal are clustered at the ER/PM microdomain, including the Orai1-STIM1 complex. This review discusses recent advances in understanding the molecular components that tether the ER and plasma membrane to form the ER/PM microdomains in which PI(4,5)P2 is enriched, and how dynamic targeting of the Orai1-STIM1 complex to PI(4,5)P2-poor and PI(4,5)P2-rich microdomains controls the activity of Orai1 and its regulation by Ca(2+) that is mediated by SARAF.
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Affiliation(s)
- Xu Cao
- Epithelial Signaling and Transport Section, Molecular Physiology and Therapeutics Branch, NIDCR, NIH, Bethesda, MD 20892, United States
| | - Seok Choi
- Department of Physiology, College of Medicine, Chosun University, 501-375, Republic of Korea
| | - Jozsef J Maléth
- First Department of Medicine, University of Szeged, Szeged H-6725, Hungary
| | - Seonghee Park
- Department of Physiology, School of Medicine, Ewha Womans University, 911-1 Mok-6-dong, Yang Chun-gu, Seoul 158-710, Republic of Korea
| | - Malini Ahuja
- Epithelial Signaling and Transport Section, Molecular Physiology and Therapeutics Branch, NIDCR, NIH, Bethesda, MD 20892, United States
| | - Shmuel Muallem
- Epithelial Signaling and Transport Section, Molecular Physiology and Therapeutics Branch, NIDCR, NIH, Bethesda, MD 20892, United States.
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Koo SJ, Kochlamazashvili G, Rost B, Puchkov D, Gimber N, Lehmann M, Tadeus G, Schmoranzer J, Rosenmund C, Haucke V, Maritzen T. Vesicular Synaptobrevin/VAMP2 Levels Guarded by AP180 Control Efficient Neurotransmission. Neuron 2015; 88:330-44. [PMID: 26412491 DOI: 10.1016/j.neuron.2015.08.034] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Revised: 07/17/2015] [Accepted: 08/19/2015] [Indexed: 01/01/2023]
Abstract
Neurotransmission depends on synaptic vesicle (SV) exocytosis driven by soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex formation of vesicular synaptobrevin/VAMP2 (Syb2). Exocytic fusion is followed by endocytic SV membrane retrieval and the high-fidelity reformation of SVs. Syb2 is the most abundant SV protein with 70 copies per SV, yet, one to three Syb2 molecules appear to be sufficient for basal exocytosis. Here we demonstrate that loss of the Syb2-specific endocytic adaptor AP180 causes a moderate activity-dependent reduction of vesicular Syb2 levels, defects in SV reformation, and a corresponding impairment of neurotransmission that lead to excitatory/inhibitory imbalance, epileptic seizures, and premature death. Further reduction of Syb2 levels in AP180(-/-)/Syb2(+/-) mice results in perinatal lethality, whereas Syb2(+/-) mice partially phenocopy loss of AP180, indicating that reduced vesicular Syb2 levels underlie the observed defects in neurotransmission. Thus, a large vesicular Syb2 pool maintained by AP180 is crucial to sustain efficient neurotransmission and SV reformation.
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Affiliation(s)
- Seong Joo Koo
- Leibniz-Institut für Molekulare Pharmakologie, Robert-Roessle-Straße 10, 13125 Berlin, Germany
| | - Gaga Kochlamazashvili
- Leibniz-Institut für Molekulare Pharmakologie, Robert-Roessle-Straße 10, 13125 Berlin, Germany
| | - Benjamin Rost
- NeuroCure Cluster of Excellence, Charité Universitätsmedizin Berlin, Virchowweg 6, 10117 Berlin, Germany
| | - Dmytro Puchkov
- Leibniz-Institut für Molekulare Pharmakologie, Robert-Roessle-Straße 10, 13125 Berlin, Germany
| | - Niclas Gimber
- Leibniz-Institut für Molekulare Pharmakologie, Robert-Roessle-Straße 10, 13125 Berlin, Germany
| | - Martin Lehmann
- Leibniz-Institut für Molekulare Pharmakologie, Robert-Roessle-Straße 10, 13125 Berlin, Germany; Freie Universität Berlin, Faculty of Biology, Chemistry and Pharmacy, 14195 Berlin, Germany
| | - Georgi Tadeus
- Leibniz-Institut für Molekulare Pharmakologie, Robert-Roessle-Straße 10, 13125 Berlin, Germany
| | - Jan Schmoranzer
- Leibniz-Institut für Molekulare Pharmakologie, Robert-Roessle-Straße 10, 13125 Berlin, Germany; Freie Universität Berlin, Faculty of Biology, Chemistry and Pharmacy, 14195 Berlin, Germany
| | - Christian Rosenmund
- NeuroCure Cluster of Excellence, Charité Universitätsmedizin Berlin, Virchowweg 6, 10117 Berlin, Germany
| | - Volker Haucke
- Leibniz-Institut für Molekulare Pharmakologie, Robert-Roessle-Straße 10, 13125 Berlin, Germany; Freie Universität Berlin, Faculty of Biology, Chemistry and Pharmacy, 14195 Berlin, Germany; NeuroCure Cluster of Excellence, Charité Universitätsmedizin Berlin, Virchowweg 6, 10117 Berlin, Germany.
| | - Tanja Maritzen
- Leibniz-Institut für Molekulare Pharmakologie, Robert-Roessle-Straße 10, 13125 Berlin, Germany.
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Asinof SK, Sukoff Rizzo SJ, Buckley AR, Beyer BJ, Letts VA, Frankel WN, Boumil RM. Independent Neuronal Origin of Seizures and Behavioral Comorbidities in an Animal Model of a Severe Childhood Genetic Epileptic Encephalopathy. PLoS Genet 2015; 11:e1005347. [PMID: 26125563 PMCID: PMC4488318 DOI: 10.1371/journal.pgen.1005347] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Accepted: 06/09/2015] [Indexed: 01/01/2023] Open
Abstract
The childhood epileptic encephalopathies (EE’s) are seizure disorders that broadly impact development including cognitive, sensory and motor progress with severe consequences and comorbidities. Recently, mutations in DNM1 (dynamin 1) have been implicated in two EE syndromes, Lennox-Gastaut Syndrome and Infantile Spasms. Dnm1 encodes dynamin 1, a large multimeric GTPase necessary for activity-dependent membrane recycling in neurons, including synaptic vesicle endocytosis. Dnm1Ftfl or “fitful” mice carry a spontaneous mutation in the mouse ortholog of DNM1 and recapitulate many of the disease features associated with human DNM1 patients, providing a relevant disease model of human EE’s. In order to examine the cellular etiology of seizures and behavioral and neurological comorbidities, we engineered a conditional Dnm1Ftfl mouse model of DNM1 EE. Observations of Dnm1Ftfl/flox mice in combination with various neuronal subpopulation specific cre strains demonstrate unique seizure phenotypes and clear separation of major neurobehavioral comorbidities from severe seizures associated with the germline model. This demonstration of pleiotropy suggests that treating seizures per se may not prevent severe comorbidity observed in EE associated with dynamin-1 mutations, and is likely to have implications for other genetic forms of EE. Childhood epilepsy syndromes, such as the early epileptic encephalopathies (EE’s) encompass seizure disorders that manifest early and negatively impact or completely block developmental progression. Recently, mutations in DNM1 (dynamin 1) have been implicated in two EE syndromes, Lennox-Gastaut Syndrome and Infantile Spasms. Dynamin 1 is a large multimeric protein that is critical for electro-chemical communication between neurons. To understand the relationship between severe seizures and the cognitive and behavioral developmental outcomes in DNM1 patients, we focus on “fitful” mice that carry a mutation in the dynamin 1 gene. Fitful mice have an EE disorder that is highly reminiscent of the documented human patients. Here, we describe genetic manipulations in the mice that allow us to determine that the seizure activity has independent cellular origins from the developmental and behavioral consequences. This separation confirms that the seizures do not cause the severe developmental delay and abnormal behaviors in this animal model and further suggests that any treatments aimed at controlling the seizures per se may not be effective for some of the most acute neurobehavioral symptoms in these patients.
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Affiliation(s)
- Samuel K. Asinof
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
| | | | - Alexandra R. Buckley
- Biomedical Sciences Graduate Program, University of California, San Diego, San Diego, California, United States of America
| | - Barbara J. Beyer
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
| | - Verity A. Letts
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
| | - Wayne N. Frankel
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
| | - Rebecca M. Boumil
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
- * E-mail:
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