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Vlasova AD, Bukhalovich SM, Bagaeva DF, Polyakova AP, Ilyinsky NS, Nesterov SV, Tsybrov FM, Bogorodskiy AO, Zinovev EV, Mikhailov AE, Vlasov AV, Kuklin AI, Borshchevskiy VI, Bamberg E, Uversky VN, Gordeliy VI. Intracellular microbial rhodopsin-based optogenetics to control metabolism and cell signaling. Chem Soc Rev 2024; 53:3327-3349. [PMID: 38391026 DOI: 10.1039/d3cs00699a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2024]
Abstract
Microbial rhodopsin (MRs) ion channels and pumps have become invaluable optogenetic tools for neuroscience as well as biomedical applications. Recently, MR-optogenetics expanded towards subcellular organelles opening principally new opportunities in optogenetic control of intracellular metabolism and signaling via precise manipulations of organelle ion gradients using light. This new optogenetic field expands the opportunities for basic and medical studies of cancer, cardiovascular, and metabolic disorders, providing more detailed and accurate control of cell physiology. This review summarizes recent advances in studies of the cellular metabolic processes and signaling mediated by optogenetic tools targeting mitochondria, endoplasmic reticulum (ER), lysosomes, and synaptic vesicles. Finally, we discuss perspectives of such an optogenetic approach in both fundamental and applied research.
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Affiliation(s)
- Anastasiia D Vlasova
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Siarhei M Bukhalovich
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Diana F Bagaeva
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Aleksandra P Polyakova
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Nikolay S Ilyinsky
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Semen V Nesterov
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Fedor M Tsybrov
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Andrey O Bogorodskiy
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Egor V Zinovev
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Anatolii E Mikhailov
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Alexey V Vlasov
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
- Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna, Russia
| | - Alexander I Kuklin
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
- Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna, Russia
| | - Valentin I Borshchevskiy
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
- Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna, Russia
| | - Ernst Bamberg
- Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - Vladimir N Uversky
- Department of Molecular Medicine and Byrd Alzheimer's Research Institute, Morsani College of Medicine, University of South Florida, Tampa, FL, USA.
| | - Valentin I Gordeliy
- Institut de Biologie Structurale Jean-Pierre Ebel, Université Grenoble Alpes-Commissariat à l'Energie Atomique et aux Energies Alternatives-CNRS, 38027 Grenoble, France.
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Wu Z, Kusick GF, Berns MMM, Raychaudhuri S, Itoh K, Walter AM, Chapman ER, Watanabe S. Synaptotagmin 7 docks synaptic vesicles to support facilitation and Doc2α-triggered asynchronous release. eLife 2024; 12:RP90632. [PMID: 38536730 PMCID: PMC10972563 DOI: 10.7554/elife.90632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/11/2024] Open
Abstract
Despite decades of intense study, the molecular basis of asynchronous neurotransmitter release remains enigmatic. Synaptotagmin (syt) 7 and Doc2 have both been proposed as Ca2+ sensors that trigger this mode of exocytosis, but conflicting findings have led to controversy. Here, we demonstrate that at excitatory mouse hippocampal synapses, Doc2α is the major Ca2+ sensor for asynchronous release, while syt7 supports this process through activity-dependent docking of synaptic vesicles. In synapses lacking Doc2α, asynchronous release after single action potentials is strongly reduced, while deleting syt7 has no effect. However, in the absence of syt7, docked vesicles cannot be replenished on millisecond timescales. Consequently, both synchronous and asynchronous release depress from the second pulse onward during repetitive activity. By contrast, synapses lacking Doc2α have normal activity-dependent docking, but continue to exhibit decreased asynchronous release after multiple stimuli. Moreover, disruption of both Ca2+ sensors is non-additive. These findings result in a new model whereby syt7 drives activity-dependent docking, thus providing synaptic vesicles for synchronous (syt1) and asynchronous (Doc2 and other unidentified sensors) release during ongoing transmission.
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Affiliation(s)
- Zhenyong Wu
- Department of Neuroscience, University of Wisconsin-MadisonMadisonUnited States
- Howard Hughes Medical InstituteMadisonUnited States
| | - Grant F Kusick
- Department of Cell Biology, Johns Hopkins University, School of MedicineBaltimoreUnited States
- Biochemistry, Cellular and Molecular Biology Graduate Program, Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Manon MM Berns
- Department of Neuroscience, University of CopenhagenCopenhagenDenmark
| | - Sumana Raychaudhuri
- Department of Cell Biology, Johns Hopkins University, School of MedicineBaltimoreUnited States
| | - Kie Itoh
- Department of Cell Biology, Johns Hopkins University, School of MedicineBaltimoreUnited States
| | - Alexander M Walter
- Department of Neuroscience, University of CopenhagenCopenhagenDenmark
- Molecular and Theoretical Neuroscience, Leibniz-Institut für Molekulare Pharmakologie, FMP im CharitéCrossOverBerlinGermany
| | - Edwin R Chapman
- Department of Neuroscience, University of Wisconsin-MadisonMadisonUnited States
- Howard Hughes Medical InstituteMadisonUnited States
| | - Shigeki Watanabe
- Department of Cell Biology, Johns Hopkins University, School of MedicineBaltimoreUnited States
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of MedicineBaltimoreUnited States
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Kim J, Bustamante E, Sotonyi P, Maxwell ND, Parameswaran P, Kent JK, Wetsel WC, Soderblom EJ, Rácz B, Soderling SH. Presynaptic Rac1 in the hippocampus selectively regulates working memory. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.18.585488. [PMID: 38562715 PMCID: PMC10983896 DOI: 10.1101/2024.03.18.585488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
One of the most extensively studied members of the Ras superfamily of small GTPases, Rac1 is an intracellular signal transducer that remodels actin and phosphorylation signaling networks. Previous studies have shown that Rac1-mediated signaling is associated with hippocampal-dependent working memory and longer-term forms of learning and memory and that Rac1 can modulate forms of both pre- and postsynaptic plasticity. How these different cognitive functions and forms of plasticity mediated by Rac1 are linked, however, is unclear. Here, we show that spatial working memory is selectively impaired following the expression of a genetically encoded Rac1-inhibitor at presynaptic terminals, while longer-term cognitive processes are affected by Rac1 inhibition at postsynaptic sites. To investigate the regulatory mechanisms of this presynaptic process, we leveraged new advances in mass spectrometry to identify the proteomic and post-translational landscape of presynaptic Rac1 signaling. We identified serine/threonine kinases and phosphorylated cytoskeletal signaling and synaptic vesicle proteins enriched with active Rac1. The phosphorylated sites in these proteins are at positions likely to have regulatory effects on synaptic vesicles. Consistent with this, we also report changes in the distribution and morphology of synaptic vesicles and in postsynaptic ultrastructure following presynaptic Rac1 inhibition. Overall, this study reveals a previously unrecognized presynaptic role of Rac1 signaling in cognitive processes and provides insights into its potential regulatory mechanisms.
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Affiliation(s)
- Jaebin Kim
- Department of Cell Biology, Duke University Medical School, Durham, North Carolina, USA
| | - Edwin Bustamante
- Department of Cell Biology, Duke University Medical School, Durham, North Carolina, USA
| | - Peter Sotonyi
- Department of Anatomy and Histology, University of Veterinary Medicine, Budapest, Hungary
| | - Nicholas D Maxwell
- Department of Cell Biology, Duke University Medical School, Durham, North Carolina, USA
| | - Pooja Parameswaran
- Department of Cell Biology, Duke University Medical School, Durham, North Carolina, USA
| | - Julie K Kent
- Department of Cell Biology, Duke University Medical School, Durham, North Carolina, USA
| | - William C Wetsel
- Department of Cell Biology, Duke University Medical School, Durham, North Carolina, USA
- Mouse Behavioral and Neuroendocrine Analysis Core Facility, Duke University Medical School, Durham, North Carolina, USA
- Department of Neurobiology, Duke University Medical School, Durham, North Carolina, USA
| | - Erik J Soderblom
- Department of Cell Biology, Duke University Medical School, Durham, North Carolina, USA
- Mouse Behavioral and Neuroendocrine Analysis Core Facility, Duke University Medical School, Durham, North Carolina, USA
| | - Bence Rácz
- Department of Anatomy and Histology, University of Veterinary Medicine, Budapest, Hungary
| | - Scott H Soderling
- Department of Cell Biology, Duke University Medical School, Durham, North Carolina, USA
- Department of Neurobiology, Duke University Medical School, Durham, North Carolina, USA
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Lebowitz JJ, Kissiwaa SA, Engeln KA, Bowman AM, Williams JT, Jackman SL. Synaptotagmin-7 Counteracts Short-Term Depression during Phasic Dopamine Release. eNeuro 2024; 11:ENEURO.0501-23.2024. [PMID: 38365841 PMCID: PMC10932592 DOI: 10.1523/eneuro.0501-23.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Revised: 01/02/2024] [Accepted: 01/17/2024] [Indexed: 02/18/2024] Open
Abstract
Dopamine neurons switch from tonic pacemaker activity to high-frequency bursts in response to salient stimuli. These bursts lead to superlinear increases in dopamine release, and the degree of this increase is highly dependent on firing frequency. The superlinearity and frequency dependence of dopamine release implicate short-term plasticity processes. The presynaptic Ca2+-sensor synaptotagmin-7 (SYT7) has suitable properties to mediate such short-term plasticity and has been implicated in regulating dopamine release from somatodendritic compartments. Here, we use a genetically encoded dopamine sensor and whole-cell electrophysiology in Syt7 KO mice to determine how SYT7 contributes to both axonal and somatodendritic dopamine release. We find that SYT7 mediates a hidden component of facilitation of release from dopamine terminals that can be unmasked by lowering initial release probability or by predepressing synapses with low-frequency stimulation. Depletion of SYT7 increased short-term depression and reduced release during stimulations that mimic in vivo firing. Recordings of D2-mediated inhibitory postsynaptic currents in the substantia nigra pars compacta (SNc) confirmed a similar role for SYT7 in somatodendritic release. Our results indicate that SYT7 drives short-term facilitation of dopamine release, which may explain the frequency dependence of dopamine signaling seen in vivo.
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Affiliation(s)
- Joseph J Lebowitz
- Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239-3098
| | - Sarah A Kissiwaa
- Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239-3098
| | - Kim A Engeln
- Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239-3098
| | - Anna M Bowman
- Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239-3098
| | - John T Williams
- Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239-3098
| | - Skyler L Jackman
- Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239-3098
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5
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Neher E. Interpretation of presynaptic phenotypes of synaptic plasticity in terms of a two-step priming process. J Gen Physiol 2024; 156:e202313454. [PMID: 38112713 PMCID: PMC10730358 DOI: 10.1085/jgp.202313454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2023] Open
Abstract
Studies on synaptic proteins involved in neurotransmitter release often aim at distinguishing between their roles in vesicle priming (the docking of synaptic vesicles to the plasma membrane and the assembly of a release machinery) as opposed to the process of vesicle fusion. This has traditionally been done by estimating two parameters, the size of the pool of fusion-competent vesicles (the readily releasable pool, RRP) and the probability that such vesicles are released by an action potential, with the aim of determining how these parameters are affected by molecular perturbations. Here, it is argued that the assumption of a homogeneous RRP may be too simplistic and may blur the distinction between vesicle priming and fusion. Rather, considering priming as a dynamic and reversible multistep process allows alternative interpretations of mutagenesis-induced changes in synaptic transmission and suggests mechanisms for variability in synaptic strength and short-term plasticity among synapses, as well as for interactions between short- and long-term plasticity. In many cases, assigned roles of proteins or causes for observed phenotypes are shifted from fusion- to priming-related when considering multistep priming. Activity-dependent enhancement of priming is an essential element in this alternative view and its variation among synapse types can explain why some synapses show depression and others show facilitation at low to intermediate stimulation frequencies. Multistep priming also suggests a mechanism for frequency invariance of steady-state release, which can be observed in some synapses involved in sensory processing.
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Affiliation(s)
- Erwin Neher
- Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
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6
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Courtney KC, Mandal T, Mehta N, Wu L, Li Y, Das D, Cui Q, Chapman ER. Synaptotagmin-7 outperforms synaptotagmin-1 to promote the formation of large, stable fusion pores via robust membrane penetration. Nat Commun 2023; 14:7761. [PMID: 38012142 PMCID: PMC10681989 DOI: 10.1038/s41467-023-42497-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Accepted: 10/11/2023] [Indexed: 11/29/2023] Open
Abstract
Synaptotagmin-1 and synaptotagmin-7 are two prominent calcium sensors that regulate exocytosis in neuronal and neuroendocrine cells. Upon binding calcium, both proteins partially penetrate lipid bilayers that bear anionic phospholipids, but the specific underlying mechanisms that enable them to trigger exocytosis remain controversial. Here, we examine the biophysical properties of these two synaptotagmin isoforms and compare their interactions with phospholipid membranes. We discover that synaptotagmin-1-membrane interactions are greatly influenced by membrane order; tight packing of phosphatidylserine inhibits binding due to impaired membrane penetration. In contrast, synaptotagmin-7 exhibits robust membrane binding and penetration activity regardless of phospholipid acyl chain structure. Thus, synaptotagmin-7 is a super-penetrator. We exploit these observations to specifically isolate and examine the role of membrane penetration in synaptotagmin function. Using nanodisc-black lipid membrane electrophysiology, we demonstrate that membrane penetration is a critical component that underlies how synaptotagmin proteins regulate reconstituted, exocytic fusion pores in response to calcium.
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Affiliation(s)
- Kevin C Courtney
- Howard Hughes Medical Institute and the Department of Neuroscience, University of Wisconsin, 1111 Highland Avenue, Madison, WI, 53705, USA
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV, 26506, USA
| | - Taraknath Mandal
- Department of Chemistry, Boston University, Boston, MA, 02215, USA
- Department of Physics, Indian Institute of Technology - Kanpur, Kanpur, 208016, India
| | - Nikunj Mehta
- Howard Hughes Medical Institute and the Department of Neuroscience, University of Wisconsin, 1111 Highland Avenue, Madison, WI, 53705, USA
| | - Lanxi Wu
- Howard Hughes Medical Institute and the Department of Neuroscience, University of Wisconsin, 1111 Highland Avenue, Madison, WI, 53705, USA
| | - Yueqi Li
- Howard Hughes Medical Institute and the Department of Neuroscience, University of Wisconsin, 1111 Highland Avenue, Madison, WI, 53705, USA
- Center for Bioanalytical Chemistry, University of Science and Technology of China, Hefei, 230026, China
| | - Debasis Das
- Howard Hughes Medical Institute and the Department of Neuroscience, University of Wisconsin, 1111 Highland Avenue, Madison, WI, 53705, USA
- Department of Biological Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Navy Nagar, Colaba, Mumbai, 400005, India
| | - Qiang Cui
- Department of Chemistry, Boston University, Boston, MA, 02215, USA
| | - Edwin R Chapman
- Howard Hughes Medical Institute and the Department of Neuroscience, University of Wisconsin, 1111 Highland Avenue, Madison, WI, 53705, USA.
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7
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Jusyte M, Blaum N, Böhme MA, Berns MMM, Bonard AE, Vámosi ÁB, Pushpalatha KV, Kobbersmed JRL, Walter AM. Unc13A dynamically stabilizes vesicle priming at synaptic release sites for short-term facilitation and homeostatic potentiation. Cell Rep 2023; 42:112541. [PMID: 37243591 DOI: 10.1016/j.celrep.2023.112541] [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: 11/08/2022] [Revised: 03/10/2023] [Accepted: 05/03/2023] [Indexed: 05/29/2023] Open
Abstract
Presynaptic plasticity adjusts neurotransmitter (NT) liberation. Short-term facilitation (STF) tunes synapses to millisecond repetitive activation, while presynaptic homeostatic potentiation (PHP) of NT release stabilizes transmission over minutes. Despite different timescales of STF and PHP, our analysis of Drosophila neuromuscular junctions reveals functional overlap and shared molecular dependence on the release-site protein Unc13A. Mutating Unc13A's calmodulin binding domain (CaM-domain) increases baseline transmission while blocking STF and PHP. Mathematical modeling suggests that Ca2+/calmodulin/Unc13A interaction plastically stabilizes vesicle priming at release sites and that CaM-domain mutation causes constitutive stabilization, thereby blocking plasticity. Labeling the functionally essential Unc13A MUN domain reveals higher STED microscopy signals closer to release sites following CaM-domain mutation. Acute phorbol ester treatment similarly enhances NT release and blocks STF/PHP in synapses expressing wild-type Unc13A, while CaM-domain mutation occludes this, indicating common downstream effects. Thus, Unc13A regulatory domains integrate signals across timescales to switch release-site participation for synaptic plasticity.
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Affiliation(s)
- Meida Jusyte
- Molecular and Theoretical Neuroscience, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany; Einstein Center for Neurosciences Berlin, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Natalie Blaum
- Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark
| | - Mathias A Böhme
- Molecular and Theoretical Neuroscience, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany; Rudolf Schönheimer Institute of Biochemistry, Division of General Biochemistry, Medical Faculty, Leipzig University, Leipzig, Germany
| | - Manon M M Berns
- Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark
| | - Alix E Bonard
- Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark
| | - Ábel B Vámosi
- Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark
| | | | - Janus R L Kobbersmed
- Department of Mathematical Sciences, University of Copenhagen, Copenhagen, Denmark; Center of Functionally Integrative Neuroscience, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Alexander M Walter
- Molecular and Theoretical Neuroscience, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany; Einstein Center for Neurosciences Berlin, Charité Universitätsmedizin Berlin, Berlin, Germany; Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark.
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8
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Caballero-Florán RN, Bendahmane M, Gupta JP, Chen X, Wu X, Morales A, Anantharam A, Jenkins PM. Synaptotagmin-7 facilitates acetylcholine release in splanchnic nerve-chromaffin cell synapses during nerve activity. Neurosci Lett 2023; 800:137129. [PMID: 36796621 PMCID: PMC10145958 DOI: 10.1016/j.neulet.2023.137129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Revised: 01/23/2023] [Accepted: 02/11/2023] [Indexed: 02/16/2023]
Abstract
Disturbances that threaten homeostasis elicit activation of the sympathetic nervous system (SNS) and the adrenal medulla. The effectors discharge as a unit to drive global and immediate changes in whole-body physiology. Descending sympathetic information is conveyed to the adrenal medulla via preganglionic splanchnic fibers. These fibers pass into the gland and synapse onto chromaffin cells, which synthesize, store, and secrete catecholamines and vasoactive peptides. While the importance of the sympatho-adrenal branch of the autonomic nervous system has been appreciated for many decades, the mechanisms underlying transmission between presynaptic splanchnic neurons and postsynaptic chromaffin cells have remained obscure. In contrast to chromaffin cells, which have enjoyed sustained attention as a model system for exocytosis, even the Ca2+ sensors that are expressed within splanchnic terminals have not yet been identified. This study shows that a ubiquitous Ca2+-binding protein, synaptotagmin-7 (Syt7), is expressed within the fibers that innervate the adrenal medulla, and that its absence can alter synaptic transmission in the preganglionic terminals of chromaffin cells. The prevailing impact in synapses that lack Syt7 is a decrease in synaptic strength and neuronal short-term plasticity. Evoked excitatory postsynaptic currents (EPSCs) in Syt7 KO preganglionic terminals are smaller in amplitude than in wild-type synapses stimulated in an identical manner. Splanchnic inputs also display robust short-term presynaptic facilitation, which is compromised in the absence of Syt7. These data reveal, for the first time, a role for any synaptotagmin at the splanchnic-chromaffin cell synapse. They also suggest that Syt7 has actions at synaptic terminals that are conserved across central and peripheral branches of the nervous system.
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Affiliation(s)
- René N Caballero-Florán
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109, United States
| | - Mounir Bendahmane
- Department of Neuroscience, University of Toledo, Toledo, OH 43614, United States
| | - Julie P Gupta
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109, United States
| | - Xiaohuan Chen
- Department of Neuroscience, University of Toledo, Toledo, OH 43614, United States
| | - Xiaojun Wu
- Department of Neuroscience, University of Toledo, Toledo, OH 43614, United States
| | - Alina Morales
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109, United States; Department of Neuroscience, University of Toledo, Toledo, OH 43614, United States
| | - Arun Anantharam
- Department of Neuroscience, University of Toledo, Toledo, OH 43614, United States.
| | - Paul M Jenkins
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109, United States; Department of Psychiatry, University of Michigan Medical School, Ann Arbor, MI 48109, United States.
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9
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Suo H, Xiao N, Wang K. Potential roles of synaptotagmin family members in cancers: Recent advances and prospects. Front Med (Lausanne) 2022; 9:968081. [PMID: 36004367 PMCID: PMC9393329 DOI: 10.3389/fmed.2022.968081] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Accepted: 07/18/2022] [Indexed: 11/16/2022] Open
Abstract
With the continuous development of bioinformatics and public database, more and more genes that play a role in cancers have been discovered. Synaptotagmins (SYTs) are abundant, evolutionarily conserved integral membrane proteins composed of a short N-terminus, a variable linker domain, a single transmembrane domain, and two C2 domains, and they constitute a family of 17 isoforms. The synaptotagmin family members are known to regulate calcium-dependent membrane fusion events. Some SYTs play roles in hormone secretion or neurotransmitter release or both, and much evidence supports SYTs as Ca2+ sensors of exocytosis. Since 5 years ago, an increasing number of studies have found that SYTs also played important roles in the occurrence and development of lung cancer, gastric cancer, colon cancer, and other cancers. Down-regulation of SYTs inhibited cell proliferation, migration, and invasion of cancer cells, but promoted cell apoptosis. Growth of peritoneal nodules is inhibited and survival is prolonged in mice administrated with siSYTs intraperitoneally. Therefore, most studies have found SYTs serve as an oncogene after overexpression and may become potential prognostic biomarkers for multiple cancers. This article provides an overview of recent studies that focus on SYT family members’ roles in cancers and highlights the advances that have been achieved.
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Affiliation(s)
- Huandan Suo
- Department of Surgery, The First Affiliated Hospital of China Medical University, Shenyang, China
| | - Nan Xiao
- Department of Gastrointestinal Surgery, The First Affiliated Hospital of China Medical University, Shenyang, China
| | - Kewei Wang
- Department of Gastrointestinal Surgery, The First Affiliated Hospital of China Medical University, Shenyang, China
- *Correspondence: Kewei Wang,
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10
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Hanuscheck N, Thalman C, Domingues M, Schmaul S, Muthuraman M, Hetsch F, Ecker M, Endle H, Oshaghi M, Martino G, Kuhlmann T, Bozek K, van Beers T, Bittner S, von Engelhardt J, Vogt J, Vogelaar CF, Zipp F. Interleukin-4 receptor signaling modulates neuronal network activity. J Exp Med 2022; 219:213227. [PMID: 35587822 PMCID: PMC9123307 DOI: 10.1084/jem.20211887] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Revised: 12/13/2021] [Accepted: 04/29/2022] [Indexed: 11/25/2022] Open
Abstract
Evidence is emerging that immune responses not only play a part in the central nervous system (CNS) in diseases but may also be relevant for healthy conditions. We discovered a major role for the interleukin-4 (IL-4)/IL-4 receptor alpha (IL-4Rα) signaling pathway in synaptic processes, as indicated by transcriptome analysis in IL-4Rα–deficient mice and human neurons with/without IL-4 treatment. Moreover, IL-4Rα is expressed presynaptically, and locally available IL-4 regulates synaptic transmission. We found reduced synaptic vesicle pools, altered postsynaptic currents, and a higher excitatory drive in cortical networks of IL-4Rα–deficient neurons. Acute effects of IL-4 treatment on postsynaptic currents in wild-type neurons were mediated via PKCγ signaling release and led to increased inhibitory activity supporting the findings in IL-4Rα–deficient neurons. In fact, the deficiency of IL-4Rα resulted in increased network activity in vivo, accompanied by altered exploration and anxiety-related learning behavior; general learning and memory was unchanged. In conclusion, neuronal IL-4Rα and its presynaptic prevalence appear relevant for maintaining homeostasis of CNS synaptic function.
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Affiliation(s)
- Nicholas Hanuscheck
- Department of Neurology, Focus Program Translational Neuroscience and Immunotherapy, Rhine Main Neuroscience Network (rmn2), University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Carine Thalman
- Department of Neurology, Focus Program Translational Neuroscience and Immunotherapy, Rhine Main Neuroscience Network (rmn2), University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Micaela Domingues
- Department of Neurology, Focus Program Translational Neuroscience and Immunotherapy, Rhine Main Neuroscience Network (rmn2), University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Samantha Schmaul
- Department of Neurology, Focus Program Translational Neuroscience and Immunotherapy, Rhine Main Neuroscience Network (rmn2), University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Muthuraman Muthuraman
- Department of Neurology, Focus Program Translational Neuroscience and Immunotherapy, Rhine Main Neuroscience Network (rmn2), University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Florian Hetsch
- Institute for Pathophysiology, Focus Program Translational Neuroscience, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Manuela Ecker
- Department of Neurology, Focus Program Translational Neuroscience and Immunotherapy, Rhine Main Neuroscience Network (rmn2), University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Heiko Endle
- Department of Molecular and Translational Neuroscience, Cluster of Excellence-Cellular Stress Response in Aging-Associated Diseases and Center of Molecular Medicine Cologne, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Mohammadsaleh Oshaghi
- Department of Neurology, Focus Program Translational Neuroscience and Immunotherapy, Rhine Main Neuroscience Network (rmn2), University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Gianvito Martino
- Neuroimmunology Unit, Institute of Experimental Neurology, Division of Neuroscience, IRCCS San Raffaele Scientific Institute and Vita Salute San Raffaele University, Milan, Italy
| | - Tanja Kuhlmann
- Institute for Neuropathology, University Hospital Münster, Münster, Germany
| | - Katarzyna Bozek
- Center for Molecular Medicine, Faculty of Medicine and University Hospital Cologne; University of Cologne, Cologne, Germany
| | - Tim van Beers
- Molecular Cell Biology, Institute I of Anatomy, University of Cologne, Cologne, Germany
| | - Stefan Bittner
- Department of Neurology, Focus Program Translational Neuroscience and Immunotherapy, Rhine Main Neuroscience Network (rmn2), University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Jakob von Engelhardt
- Institute for Pathophysiology, Focus Program Translational Neuroscience, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Johannes Vogt
- Department of Neurology, Focus Program Translational Neuroscience and Immunotherapy, Rhine Main Neuroscience Network (rmn2), University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany.,Department of Molecular and Translational Neuroscience, Cluster of Excellence-Cellular Stress Response in Aging-Associated Diseases and Center of Molecular Medicine Cologne, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Christina Francisca Vogelaar
- Department of Neurology, Focus Program Translational Neuroscience and Immunotherapy, Rhine Main Neuroscience Network (rmn2), University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Frauke Zipp
- Department of Neurology, Focus Program Translational Neuroscience and Immunotherapy, Rhine Main Neuroscience Network (rmn2), University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
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11
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Kusick GF, Ogunmowo TH, Watanabe S. Transient docking of synaptic vesicles: Implications and mechanisms. Curr Opin Neurobiol 2022; 74:102535. [PMID: 35398664 PMCID: PMC9167714 DOI: 10.1016/j.conb.2022.102535] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Revised: 02/19/2022] [Accepted: 03/06/2022] [Indexed: 02/03/2023]
Abstract
As synaptic vesicles fuse, they must continually be replaced with new docked, fusion-competent vesicles to sustain neurotransmission. It has long been appreciated that vesicles are recruited to docking sites in an activity-dependent manner. However, once entering the sites, vesicles were thought to be stably docked, awaiting calcium signals. Based on recent data from electrophysiology, electron microscopy, biochemistry, and computer simulations, a picture emerges in which vesicles can rapidly and reversibly transit between docking and undocking during activity. This "transient docking" can account for many aspects of synaptic physiology. In this review, we cover recent evidence for transient docking, physiological processes at the synapse that it may support, and progress on the underlying mechanisms. We also discuss an open question: what determines for how long and whether vesicles stay docked, or eventually undock?
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Affiliation(s)
- Grant F Kusick
- Department of Cell Biology, Johns Hopkins University, School of Medicine, 725 N Wolfe St., Baltimore, MD 21287, USA; Biochemistry, Cellular and Molecular Biology Graduate Program, Johns Hopkins University, School of Medicine, 1830 E. Monument St., Baltimore, MD 21287, USA. https://twitter.com/@ultrafastgrant
| | - Tyler H Ogunmowo
- Department of Cell Biology, Johns Hopkins University, School of Medicine, 725 N Wolfe St., Baltimore, MD 21287, USA; Biochemistry, Cellular and Molecular Biology Graduate Program, Johns Hopkins University, School of Medicine, 1830 E. Monument St., Baltimore, MD 21287, USA. https://twitter.com/@unculturedTy
| | - Shigeki Watanabe
- Department of Cell Biology, Johns Hopkins University, School of Medicine, 725 N Wolfe St., Baltimore, MD 21287, USA; Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, School of Medicine, 725 N Wolfe St., Baltimore, MD 21287, USA.
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12
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Henry D, Joselevitch C, Matthews GG, Wollmuth LP. Expression and distribution of synaptotagmin family members in the zebrafish retina. J Comp Neurol 2022; 530:705-728. [PMID: 34468021 PMCID: PMC8792163 DOI: 10.1002/cne.25238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 08/21/2021] [Accepted: 08/24/2021] [Indexed: 11/10/2022]
Abstract
Synaptotagmins belong to a large family of proteins. Although various synaptotagmins have been implicated as Ca2+ sensors for vesicle replenishment and release at conventional synapses, their roles at retinal ribbon synapses remain incompletely understood. Zebrafish is a widely used experimental model for retinal research. We therefore investigated the homology between human, rat, mouse, and zebrafish synaptotagmins 1-10 using a bioinformatics approach. We also characterized the expression and distribution of various synaptotagmin (syt) genes in the zebrafish retina using RT-PCR, qPCR, and in situhybridization, focusing on the family members whose products likely underlie Ca2+ -dependent exocytosis in the central nervous system (synaptotagmins 1, 2, 5, and 7). Most zebrafish synaptotagmins are well conserved and can be grouped in the same classes as mammalian synaptotagmins, based on crucial amino acid residues needed for coordinating Ca2+ binding and determining phospholipid binding affinity. The only exception is synaptotagmin 1b, which lacks 34 amino acid residues in the C2B domain and is therefore unlikely to bind Ca2+ there. Additionally, the products of zebrafish syt5a and syt5b genes share identity with mammalian class 1 and 5 synaptotagmins. Zebrafish syt1, syt2, syt5, and syt7 paralogues are found in the zebrafish brain, eye, and retina, excepting syt1b, which is only present in the brain. The complementary expression pattern of the remaining paralogues in the retina suggests that syt1a and syt5a may underlie synchronous release and syt7a and syt7b may mediate asynchronous release or other Ca2+ -dependent processes in different retinal neurons.
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Affiliation(s)
- Diane Henry
- Department of Neurobiology & Behavior, Stony Brook University, Stony Brook, NY 11794-5230,Center for Nervous System Disorders, Stony Brook University, Stony Brook, NY 11794-5230
| | - Christina Joselevitch
- Department of Neurobiology & Behavior, Stony Brook University, Stony Brook, NY 11794-5230,Center for Nervous System Disorders, Stony Brook University, Stony Brook, NY 11794-5230
| | - Gary G. Matthews
- Department of Neurobiology & Behavior, Stony Brook University, Stony Brook, NY 11794-5230,Center for Nervous System Disorders, Stony Brook University, Stony Brook, NY 11794-5230
| | - Lonnie P. Wollmuth
- Department of Neurobiology & Behavior, Stony Brook University, Stony Brook, NY 11794-5230,Department of Biochemistry & Cell Biology, Stony Brook University, Stony Brook, NY 11794-5230,Center for Nervous System Disorders, Stony Brook University, Stony Brook, NY 11794-5230
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13
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Ivanova D, Cousin MA. Synaptic Vesicle Recycling and the Endolysosomal System: A Reappraisal of Form and Function. Front Synaptic Neurosci 2022; 14:826098. [PMID: 35280702 PMCID: PMC8916035 DOI: 10.3389/fnsyn.2022.826098] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 02/03/2022] [Indexed: 12/15/2022] Open
Abstract
The endolysosomal system is present in all cell types. Within these cells, it performs a series of essential roles, such as trafficking and sorting of membrane cargo, intracellular signaling, control of metabolism and degradation. A specific compartment within central neurons, called the presynapse, mediates inter-neuronal communication via the fusion of neurotransmitter-containing synaptic vesicles (SVs). The localized recycling of SVs and their organization into functional pools is widely assumed to be a discrete mechanism, that only intersects with the endolysosomal system at specific points. However, evidence is emerging that molecules essential for endolysosomal function also have key roles within the SV life cycle, suggesting that they form a continuum rather than being isolated processes. In this review, we summarize the evidence for key endolysosomal molecules in SV recycling and propose an alternative model for membrane trafficking at the presynapse. This includes the hypotheses that endolysosomal intermediates represent specific functional SV pools, that sorting of cargo to SVs is mediated via the endolysosomal system and that manipulation of this process can result in both plastic changes to neurotransmitter release and pathophysiology via neurodegeneration.
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Affiliation(s)
- Daniela Ivanova
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom
- Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, United Kingdom
- Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, United Kingdom
- *Correspondence: Daniela Ivanova,
| | - Michael A. Cousin
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom
- Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, United Kingdom
- Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, United Kingdom
- Michael A. Cousin,
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14
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Deutschmann AU, Kirkland JM, Briand LA. Adolescent social isolation induced alterations in nucleus accumbens glutamate signalling. Addict Biol 2022; 27:e13077. [PMID: 34278652 PMCID: PMC9206853 DOI: 10.1111/adb.13077] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 05/20/2021] [Accepted: 06/28/2021] [Indexed: 01/03/2023]
Abstract
Exposure to adversity during early childhood and adolescence increases an individual's vulnerability to developing substance use disorder. Despite the knowledge of this vulnerability, the mechanisms underlying it are still poorly understood. Excitatory afferents to the nucleus accumbens (NAc) mediate responses to both stressful and rewarding stimuli. Understanding how adolescent social isolation alters these afferents could inform the development of targeted interventions both before and after drug use. Here, we used social isolation rearing as a model of early life adversity which we have previously demonstrated increases vulnerability to cocaine addiction-like behaviour. The current study examined the effect of social isolation rearing on presynaptic glutamatergic transmission in NAc medium spiny neurons in both male and female mice. We show that social isolation rearing alters presynaptic plasticity in the NAc by decreasing the paired-pulse ratio and the size of the readily releasable pool of glutamate. Optogenetically activating the glutamatergic input from the ventral hippocampus to the NAc is sufficient to recapitulate the decreases in paired-pulse ratio and readily releasable pool size seen following electrical stimulation of all NAc afferents. Further, optogenetically inhibiting the ventral hippocampal afferent during electrical stimulation eliminates the effect of early life adversity on the paired-pulse ratio or readily releasable pool size. In summary, we demonstrate that social isolation rearing leads to alterations in glutamate transmission driven by projections from the ventral hippocampus. These data suggest that targeting the circuit from the ventral hippocampus to the nucleus accumbens could provide a means to reverse stress-induced plasticity.
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Affiliation(s)
| | | | - Lisa A. Briand
- Department of Psychology, Temple University,Neuroscience Program, Temple University
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15
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Mirabella F, Desiato G, Mancinelli S, Fossati G, Rasile M, Morini R, Markicevic M, Grimm C, Amegandjin C, Termanini A, Peano C, Kunderfranco P, di Cristo G, Zerbi V, Menna E, Lodato S, Matteoli M, Pozzi D. Prenatal interleukin 6 elevation increases glutamatergic synapse density and disrupts hippocampal connectivity in offspring. Immunity 2021; 54:2611-2631.e8. [PMID: 34758338 PMCID: PMC8585508 DOI: 10.1016/j.immuni.2021.10.006] [Citation(s) in RCA: 52] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 04/24/2021] [Accepted: 10/07/2021] [Indexed: 02/07/2023]
Abstract
Early prenatal inflammatory conditions are thought to be a risk factor for different neurodevelopmental disorders. Maternal interleukin-6 (IL-6) elevation during pregnancy causes abnormal behavior in offspring, but whether these defects result from altered synaptic developmental trajectories remains unclear. Here we showed that transient IL-6 elevation via injection into pregnant mice or developing embryos enhanced glutamatergic synapses and led to overall brain hyperconnectivity in offspring into adulthood. IL-6 activated synaptogenesis gene programs in glutamatergic neurons and required the transcription factor STAT3 and expression of the RGS4 gene. The STAT3-RGS4 pathway was also activated in neonatal brains during poly(I:C)-induced maternal immune activation, which mimics viral infection during pregnancy. These findings indicate that IL-6 elevation at early developmental stages is sufficient to exert a long-lasting effect on glutamatergic synaptogenesis and brain connectivity, providing a mechanistic framework for the association between prenatal inflammatory events and brain neurodevelopmental disorders.
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Affiliation(s)
- Filippo Mirabella
- Department of Biomedical Sciences, Humanitas University, Via Rita Levi Montalcini 4, 20090 Pieve Emanuele, Milan, Italy; IRCCS Humanitas Research Hospital, via Manzoni 56, 20089 Rozzano, Milan, Italy
| | - Genni Desiato
- IRCCS Humanitas Research Hospital, via Manzoni 56, 20089 Rozzano, Milan, Italy; Institute of Neuroscience - National Research Council, 20139 Milan, Italy
| | - Sara Mancinelli
- IRCCS Humanitas Research Hospital, via Manzoni 56, 20089 Rozzano, Milan, Italy
| | - Giuliana Fossati
- IRCCS Humanitas Research Hospital, via Manzoni 56, 20089 Rozzano, Milan, Italy
| | - Marco Rasile
- Department of Biomedical Sciences, Humanitas University, Via Rita Levi Montalcini 4, 20090 Pieve Emanuele, Milan, Italy
| | - Raffaella Morini
- IRCCS Humanitas Research Hospital, via Manzoni 56, 20089 Rozzano, Milan, Italy
| | - Marija Markicevic
- Neuroscience Center Zürich, ETH Zürich and University of Zürich, Zürich 8057, Switzerland
| | - Christina Grimm
- Neuroscience Center Zürich, ETH Zürich and University of Zürich, Zürich 8057, Switzerland
| | - Clara Amegandjin
- Department of Neurosciences, Université de Montréal, Montréal, QC, Canada; CHU Sainte-Justine Research Center, Montréal, QC, Canada
| | - Alberto Termanini
- Bioinformatic Unit, Humanitas Clinical and Research Center, 20089 Rozzano, Milan, Italy
| | - Clelia Peano
- Institute of Genetic and Biomedical Research, UoS Milan, National Research Council, 20089 Rozzano, Milan, Italy; Genomic Unit, Humanitas Clinical and Research Center, 20089 Rozzano, Milan, Italy
| | - Paolo Kunderfranco
- Bioinformatic Unit, Humanitas Clinical and Research Center, 20089 Rozzano, Milan, Italy
| | - Graziella di Cristo
- Department of Neurosciences, Université de Montréal, Montréal, QC, Canada; CHU Sainte-Justine Research Center, Montréal, QC, Canada
| | - Valerio Zerbi
- Neuroscience Center Zürich, ETH Zürich and University of Zürich, Zürich 8057, Switzerland; Neural Control of Movement Lab, Department of Health Sciences and Technology, ETH Zürich, Zürich 8057, Switzerland
| | - Elisabetta Menna
- IRCCS Humanitas Research Hospital, via Manzoni 56, 20089 Rozzano, Milan, Italy; Institute of Neuroscience - National Research Council, 20139 Milan, Italy
| | - Simona Lodato
- Department of Biomedical Sciences, Humanitas University, Via Rita Levi Montalcini 4, 20090 Pieve Emanuele, Milan, Italy; IRCCS Humanitas Research Hospital, via Manzoni 56, 20089 Rozzano, Milan, Italy
| | - Michela Matteoli
- IRCCS Humanitas Research Hospital, via Manzoni 56, 20089 Rozzano, Milan, Italy; Institute of Neuroscience - National Research Council, 20139 Milan, Italy.
| | - Davide Pozzi
- Department of Biomedical Sciences, Humanitas University, Via Rita Levi Montalcini 4, 20090 Pieve Emanuele, Milan, Italy; IRCCS Humanitas Research Hospital, via Manzoni 56, 20089 Rozzano, Milan, Italy.
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16
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Tanaka M, Sakaba T, Miki T. Quantal analysis estimates docking site occupancy determining short-term depression at hippocampal glutamatergic synapses. J Physiol 2021; 599:5301-5327. [PMID: 34705277 DOI: 10.1113/jp282235] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 10/20/2021] [Indexed: 12/23/2022] Open
Abstract
Before fusion, synaptic vesicles (SVs) pause at discrete release/docking sites. During repetitive stimulation, the probability of site occupancy changes following SV fusion and replenishment. The occupancy probability is considered to be one of the crucial determinants of synaptic strength, but it is difficult to estimate separately because it usually blends with other synaptic parameters. Thus, the contribution of site occupancy to synaptic function, particularly to synaptic depression, remains elusive. Here, we directly estimated the occupancy probability at the hippocampal mossy fibre-CA3 interneuron synapse showing synaptic depression, using statistics of counts of vesicular events detected by deconvolution. We found that this synapse had a particularly high occupancy (∼0.85) with a high release probability of a docked SV (∼0.8) under 3 mm external calcium conditions. Analyses of quantal amplitudes and SV counts indicated that quantal size reduction decreased the amplitudes of all responses in a train to a similar degree, whereas release/docking site number was unchanged during trains, suggesting that quantal size and release/docking site number had little influence on the extent of synaptic depression. Model simulations revealed that the initial occupancy with high release probability and slow replenishment determined the time course of synaptic depression. Consistently, decreasing external calcium concentration reduced both the occupancy and release probability, and the reductions in turn produced less depression. Based on these results, we suggest that the occupancy probability is a crucial determinant of short-term synaptic depression at glutamatergic synapses in the hippocampus. KEY POINTS: The occupancy probability of a release/docking site by a synaptic vesicle at presynaptic terminals is considered to be one of the crucial determinants of synaptic strength, but it is difficult to estimate separately from other synaptic parameters. Here, we directly estimate the occupancy probability at the hippocampal mossy fibre-interneuron synapse using statistics of vesicular events detected by deconvolution. We show that the synapses have particularly high occupancy (0.85) with high release probability (0.8) under high external calcium concentration ([Ca2+ ]o ) conditions, and that both parameter values change with [Ca2+ ]o , shaping synaptic depression. Analyses of the quantal amplitudes and synaptic vesicle counts suggest that quantal sizes and release/docking site number have little influence on the extent of synaptic depression. The results suggest that the occupancy probability is a crucial determinant of short-term synaptic depression at glutamatergic synapses in the hippocampus.
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Affiliation(s)
- Mamoru Tanaka
- Graduate School of Brain Science, Doshisha University, Kyoto, Japan
| | - Takeshi Sakaba
- Graduate School of Brain Science, Doshisha University, Kyoto, Japan
| | - Takafumi Miki
- Graduate School of Brain Science, Doshisha University, Kyoto, Japan.,Organization for Research Initiatives and Development, Doshisha University, Kyoto, Japan
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17
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Eshra A, Schmidt H, Eilers J, Hallermann S. Calcium dependence of neurotransmitter release at a high fidelity synapse. eLife 2021; 10:70408. [PMID: 34612812 PMCID: PMC8494478 DOI: 10.7554/elife.70408] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2021] [Accepted: 08/24/2021] [Indexed: 11/15/2022] Open
Abstract
The Ca2+-dependence of the priming, fusion, and replenishment of synaptic vesicles are fundamental parameters controlling neurotransmitter release and synaptic plasticity. Despite intense efforts, these important steps in the synaptic vesicles’ cycle remain poorly understood due to the technical challenge in disentangling vesicle priming, fusion, and replenishment. Here, we investigated the Ca2+-sensitivity of these steps at mossy fiber synapses in the rodent cerebellum, which are characterized by fast vesicle replenishment mediating high-frequency signaling. We found that the basal free Ca2+ concentration (<200 nM) critically controls action potential-evoked release, indicating a high-affinity Ca2+ sensor for vesicle priming. Ca2+ uncaging experiments revealed a surprisingly shallow and non-saturating relationship between release rate and intracellular Ca2+ concentration up to 50 μM. The rate of vesicle replenishment during sustained elevated intracellular Ca2+ concentration exhibited little Ca2+-dependence. Finally, quantitative mechanistic release schemes with five Ca2+ binding steps incorporating rapid vesicle replenishment via parallel or sequential vesicle pools could explain our data. We thus show that co-existing high- and low-affinity Ca2+ sensors mediate priming, fusion, and replenishment of synaptic vesicles at a high-fidelity synapse.
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Affiliation(s)
- Abdelmoneim Eshra
- Carl-Ludwig-Institute for Physiology, Medical Faculty, University of Leipzig, Leipzig, Germany
| | - Hartmut Schmidt
- Carl-Ludwig-Institute for Physiology, Medical Faculty, University of Leipzig, Leipzig, Germany
| | - Jens Eilers
- Carl-Ludwig-Institute for Physiology, Medical Faculty, University of Leipzig, Leipzig, Germany
| | - Stefan Hallermann
- Carl-Ludwig-Institute for Physiology, Medical Faculty, University of Leipzig, Leipzig, Germany
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18
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Weyrer C, Turecek J, Harrison B, Regehr WG. Introduction of synaptotagmin 7 promotes facilitation at the climbing fiber to Purkinje cell synapse. Cell Rep 2021; 36:109719. [PMID: 34551307 PMCID: PMC9152841 DOI: 10.1016/j.celrep.2021.109719] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 06/29/2021] [Accepted: 08/25/2021] [Indexed: 11/15/2022] Open
Abstract
Synaptotagmin 7 (Syt7) is a high-affinity calcium sensor that is implicated in multiple aspects of synaptic transmission. Here, we study the influence of Syt7 on the climbing fiber (CF) to Purkinje cell (PC) synapse. We find that small facilitation and prominent calcium-dependent recovery from depression at this synapse do not rely on Syt7 and that Syt7 is not normally present in CFs. We expressed Syt7 in CFs to assess the consequences of introducing Syt7 to a synapse that normally lacks Syt7. Syt7 expression does not promote asynchronous release or accelerate recovery from depression. Syt7 decreases the excitatory postsynaptic current (EPSC) magnitude, consistent with a decrease in the initial probability of release (PR). Syt7 also increases synaptic facilitation to such a large extent that it could not arise solely as an indirect consequence of decreased PR. Thus, the primary consequence of Syt7 expression in CFs, which normally lack Syt7, is to promote synaptic facilitation.
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Affiliation(s)
- Christopher Weyrer
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA; Department of Physiology, Development, and Neuroscience, University of Cambridge, Cambridge CB2 3EG, UK
| | - Josef Turecek
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Bailey Harrison
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Wade G Regehr
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA.
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19
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Vevea JD, Kusick GF, Courtney KC, Chen E, Watanabe S, Chapman ER. Synaptotagmin 7 is targeted to the axonal plasma membrane through γ-secretase processing to promote synaptic vesicle docking in mouse hippocampal neurons. eLife 2021; 10:e67261. [PMID: 34543184 PMCID: PMC8452306 DOI: 10.7554/elife.67261] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 08/27/2021] [Indexed: 12/28/2022] Open
Abstract
Synaptotagmin 7 (SYT7) has emerged as a key regulator of presynaptic function, but its localization and precise role in the synaptic vesicle cycle remain the subject of debate. Here, we used iGluSnFR to optically interrogate glutamate release, at the single-bouton level, in SYT7KO-dissociated mouse hippocampal neurons. We analyzed asynchronous release, paired-pulse facilitation, and synaptic vesicle replenishment and found that SYT7 contributes to each of these processes to different degrees. 'Zap-and-freeze' electron microscopy revealed that a loss of SYT7 diminishes docking of synaptic vesicles after a stimulus and inhibits the recovery of depleted synaptic vesicles after a stimulus train. SYT7 supports these functions from the axonal plasma membrane, where its localization and stability require both γ-secretase-mediated cleavage and palmitoylation. In summary, SYT7 is a peripheral membrane protein that controls multiple modes of synaptic vesicle (SV) exocytosis and plasticity, in part, through enhancing activity-dependent docking of SVs.
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Affiliation(s)
- Jason D Vevea
- Department of Neuroscience, University of Wisconsin-MadisonMadisonUnited States
- Howard Hughes Medical InstituteMadisonUnited States
| | - Grant F Kusick
- Department of Cell Biology, Johns Hopkins University, School of MedicineBaltimoreUnited States
- Biochemistry, Cellular and Molecular Biology Graduate Program, Johns Hopkins University, School of MedicineBaltimoreUnited States
| | - Kevin C Courtney
- Department of Neuroscience, University of Wisconsin-MadisonMadisonUnited States
- Howard Hughes Medical InstituteMadisonUnited States
| | - Erin Chen
- Department of Cell Biology, Johns Hopkins University, School of MedicineBaltimoreUnited States
| | - Shigeki Watanabe
- Department of Cell Biology, Johns Hopkins University, School of MedicineBaltimoreUnited States
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, School of MedicineBaltimoreUnited States
| | - Edwin R Chapman
- Department of Neuroscience, University of Wisconsin-MadisonMadisonUnited States
- Howard Hughes Medical InstituteMadisonUnited States
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20
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Hays CL, Sladek AL, Thoreson WB. Resting and stimulated mouse rod photoreceptors show distinct patterns of vesicle release at ribbon synapses. J Gen Physiol 2021; 152:211528. [PMID: 33175961 PMCID: PMC7664508 DOI: 10.1085/jgp.202012716] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 10/01/2020] [Accepted: 10/19/2020] [Indexed: 01/04/2023] Open
Abstract
The vertebrate visual system can detect and transmit signals from single photons. To understand how single-photon responses are transmitted, we characterized voltage-dependent properties of glutamate release in mouse rods. We measured presynaptic glutamate transporter anion current and found that rates of synaptic vesicle release increased with voltage-dependent Ca2+ current. Ca2+ influx and release rate also rose with temperature, attaining a rate of ∼11 vesicles/s/ribbon at -40 mV (35°C). By contrast, spontaneous release events at hyperpolarized potentials (-60 to -70 mV) were univesicular and occurred at random intervals. However, when rods were voltage clamped at -40 mV for many seconds to simulate maintained darkness, release occurred in coordinated bursts of 17 ± 7 quanta (mean ± SD; n = 22). Like fast release evoked by brief depolarizing stimuli, these bursts involved vesicles in the readily releasable pool of vesicles and were triggered by the opening of nearby ribbon-associated Ca2+ channels. Spontaneous release rates were elevated and bursts were absent after genetic elimination of the Ca2+ sensor synaptotagmin 1 (Syt1). This study shows that at the resting potential in darkness, rods release glutamate-filled vesicles from a pool at the base of synaptic ribbons at low rates but in Syt1-dependent bursts. The absence of bursting in cones suggests that this behavior may have a role in transmitting scotopic responses.
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Affiliation(s)
- Cassandra L Hays
- Cellular and Integrative Physiology, College of Medicine, University of Nebraska Medical Center, Omaha, NE.,Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, College of Medicine, University of Nebraska Medical Center, Omaha, NE
| | - Asia L Sladek
- Pharmacology and Experimental Neuroscience, College of Medicine, University of Nebraska Medical Center, Omaha, NE
| | - Wallace B Thoreson
- Pharmacology and Experimental Neuroscience, College of Medicine, University of Nebraska Medical Center, Omaha, NE.,Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, College of Medicine, University of Nebraska Medical Center, Omaha, NE
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21
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Xue R, Meng H, Yin J, Xia J, Hu Z, Liu H. The Role of Calmodulin vs. Synaptotagmin in Exocytosis. Front Mol Neurosci 2021; 14:691363. [PMID: 34421537 PMCID: PMC8375295 DOI: 10.3389/fnmol.2021.691363] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Accepted: 07/19/2021] [Indexed: 12/04/2022] Open
Abstract
Exocytosis is a Ca2+-regulated process that requires the participation of Ca2+ sensors. In the 1980s, two classes of Ca2+-binding proteins were proposed as putative Ca2+ sensors: EF-hand protein calmodulin, and the C2 domain protein synaptotagmin. In the next few decades, numerous studies determined that in the final stage of membrane fusion triggered by a micromolar boost in the level of Ca2+, the low affinity Ca2+-binding protein synaptotagmin, especially synaptotagmin 1 and 2, acts as the primary Ca2+ sensor, whereas calmodulin is unlikely to be functional due to its high Ca2+ affinity. However, in the meantime emerging evidence has revealed that calmodulin is involved in the earlier exocytotic steps prior to fusion, such as vesicle trafficking, docking and priming by acting as a high affinity Ca2+ sensor activated at submicromolar level of Ca2+. Calmodulin directly interacts with multiple regulatory proteins involved in the regulation of exocytosis, including VAMP, myosin V, Munc13, synapsin, GAP43 and Rab3, and switches on key kinases, such as type II Ca2+/calmodulin-dependent protein kinase, to phosphorylate a series of exocytosis regulators, including syntaxin, synapsin, RIM and Ca2+ channels. Moreover, calmodulin interacts with synaptotagmin through either direct binding or indirect phosphorylation. In summary, calmodulin and synaptotagmin are Ca2+ sensors that play complementary roles throughout the process of exocytosis. In this review, we discuss the complementary roles that calmodulin and synaptotagmin play as Ca2+ sensors during exocytosis.
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Affiliation(s)
- Renhao Xue
- Shanghai Key Laboratory of Maternal Fetal Medicine, Clinical and Translational Research Center of Shanghai First Maternity & Infant Hospital, School of Life Sciences and Technology, Tongji University, Shanghai, China
| | - Hao Meng
- Guangzhou Laboratory, Guangzhou, China.,Bioland Laboratory, Guangzhou Regenerative Medicine and Health Guangdong Laboratory, Guangzhou, China
| | - Jiaxiang Yin
- Guangzhou Laboratory, Guangzhou, China.,Bioland Laboratory, Guangzhou Regenerative Medicine and Health Guangdong Laboratory, Guangzhou, China
| | - Jingyao Xia
- Clem Jones Centre for Ageing Dementia Research (CJCADR), Queensland Brain Institute, The University of Queensland, Brisbane, QLD, Australia
| | - Zhitao Hu
- Clem Jones Centre for Ageing Dementia Research (CJCADR), Queensland Brain Institute, The University of Queensland, Brisbane, QLD, Australia
| | - Huisheng Liu
- Guangzhou Laboratory, Guangzhou, China.,Bioland Laboratory, Guangzhou Regenerative Medicine and Health Guangdong Laboratory, Guangzhou, China
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22
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Mori Y, Takenaka KI, Fukazawa Y, Takamori S. The endosomal Q-SNARE, Syntaxin 7, defines a rapidly replenishing synaptic vesicle recycling pool in hippocampal neurons. Commun Biol 2021; 4:981. [PMID: 34408265 PMCID: PMC8373932 DOI: 10.1038/s42003-021-02512-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2020] [Accepted: 08/02/2021] [Indexed: 12/12/2022] Open
Abstract
Upon the arrival of repetitive stimulation at the presynaptic terminals of neurons, replenishment of readily releasable synaptic vesicles (SVs) with vesicles in the recycling pool is important for sustained neurotransmitter release. Kinetics of replenishment and the available pool size define synaptic performance. However, whether all SVs in the recycling pool are recruited for release with equal probability and speed is unknown. Here, based on comprehensive optical imaging of various presynaptic endosomal SNARE proteins in cultured hippocampal neurons, all of which are implicated in organellar membrane fusion in non-neuronal cells, we show that part of the recycling pool bearing the endosomal Q-SNARE, syntaxin 7 (Stx7), is preferentially mobilized for release during high-frequency repetitive stimulation. Recruitment of the SV pool marked with an Stx7-reporter requires actin polymerization, as well as activation of the Ca2+/calmodulin signaling pathway, reminiscent of rapidly replenishing SVs characterized previously in calyx of Held synapses. Furthermore, disruption of Stx7 function by overexpressing its N-terminal domain selectively abolished this pool. Thus, our data indicate that endosomal membrane fusion involving Stx7 forms rapidly replenishing vesicles essential for synaptic responses to high-frequency repetitive stimulation, and also highlight functional diversities of endosomal SNAREs in generating distinct exocytic vesicles in the presynaptic terminals. Yasunori Mori et al. find that a subset of neurotransmitter-bearing synaptic vesicles are marked for release by the endosomal Q-SNARE protein Stx7. They show that Stx7 function is necessary for the rapid replenishment of synaptic vesicles that is needed to sustain synaptic transmission during high-frequency stimulation.
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Affiliation(s)
- Yasunori Mori
- Laboratory of Neural Membrane Biology, Graduate School of Brain Science, Doshisha University, Kyoto, Japan. .,Department of Biochemistry, Faculty of Medicine, University of Yamanashi, Yamanashi, Japan.
| | - Koh-Ichiro Takenaka
- Laboratory of Neural Membrane Biology, Graduate School of Brain Science, Doshisha University, Kyoto, Japan
| | - Yugo Fukazawa
- Division of Brain Structure and Function, Research Center for Child Mental Development, Life Science Innovation Center, School of Medical Science, University of Fukui, Fukui, Japan
| | - Shigeo Takamori
- Laboratory of Neural Membrane Biology, Graduate School of Brain Science, Doshisha University, Kyoto, Japan.
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23
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Wang QW, Wang YH, Wang B, Chen Y, Lu SY, Yao J. Synaptotagmin-7-mediated activation of spontaneous NMDAR currents is disrupted in bipolar disorder susceptibility variants. PLoS Biol 2021; 19:e3001323. [PMID: 34228711 PMCID: PMC8284830 DOI: 10.1371/journal.pbio.3001323] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Revised: 07/16/2021] [Accepted: 06/15/2021] [Indexed: 11/19/2022] Open
Abstract
Synaptotagmin-7 (Syt7) plays direct or redundant Ca2+ sensor roles in multiple forms of vesicle exocytosis in synapses. Here, we show that Syt7 is a redundant Ca2+ sensor with Syt1/Doc2 to drive spontaneous glutamate release, which functions uniquely to activate the postsynaptic GluN2B-containing NMDARs that significantly contribute to mental illness. In mouse hippocampal neurons lacking Syt1/Doc2, Syt7 inactivation largely diminishes spontaneous release. Using 2 approaches, including measuring Ca2+ dose response and substituting extracellular Ca2+ with Sr2+, we detect that Syt7 directly triggers spontaneous release via its Ca2+ binding motif to activate GluN2B-NMDARs. Furthermore, modifying the localization of Syt7 in the active zone still allows Syt7 to drive spontaneous release, but the GluN2B-NMDAR activity is abolished. Finally, Syt7 SNPs identified in bipolar disorder patients destroy the function of Syt7 in spontaneous release in patient iPSC-derived and mouse hippocampal neurons. Therefore, Syt7 could contribute to neuropsychiatric disorders through driving spontaneous glutamate release.
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Affiliation(s)
- Qiu-Wen Wang
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, Beijing, China
| | - Ying-Han Wang
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, Beijing, China
| | - Bing Wang
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, Beijing, China
| | - Yun Chen
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, Beijing, China
| | - Si-Yao Lu
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, Beijing, China
| | - Jun Yao
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, Beijing, China
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24
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Silva M, Tran V, Marty A. Calcium-dependent docking of synaptic vesicles. Trends Neurosci 2021; 44:579-592. [PMID: 34049722 DOI: 10.1016/j.tins.2021.04.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Revised: 02/23/2021] [Accepted: 04/09/2021] [Indexed: 10/21/2022]
Abstract
The concentration of calcium ions in presynaptic terminals regulates transmitter release, but underlying mechanisms have remained unclear. Here we review recent studies that shed new light on this issue. Fast-freezing electron microscopy and total internal reflection fluorescence microscopy studies reveal complex calcium-dependent vesicle movements including docking on a millisecond time scale. Recordings from so-called 'simple synapses' indicate that calcium not only triggers exocytosis, but also modifies synaptic strength by controlling a final, rapid vesicle maturation step before release. Molecular studies identify several calcium-sensitive domains on Munc13 and on synaptotagmin-1 that are likely involved in bringing the vesicular and plasma membranes closer together in response to calcium elevation. Together, these results suggest that calcium-dependent vesicle docking occurs in a wide range of time domains and plays a crucial role in several phenomena including synaptic facilitation, post-tetanic potentiation, and neuromodulator-induced potentiation.
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Affiliation(s)
- Melissa Silva
- Université de Paris, SPPIN-Saints Pères Paris Institute for the Neurosciences, CNRS, F-75006 Paris, France
| | - Van Tran
- Université de Paris, SPPIN-Saints Pères Paris Institute for the Neurosciences, CNRS, F-75006 Paris, France
| | - Alain Marty
- Université de Paris, SPPIN-Saints Pères Paris Institute for the Neurosciences, CNRS, F-75006 Paris, France.
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25
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van Westen R, Poppinga J, Díez Arazola R, Toonen RF, Verhage M. Neuromodulator release in neurons requires two functionally redundant calcium sensors. Proc Natl Acad Sci U S A 2021; 118:e2012137118. [PMID: 33903230 PMCID: PMC8106342 DOI: 10.1073/pnas.2012137118] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Neuropeptides and neurotrophic factors secreted from dense core vesicles (DCVs) control many brain functions, but the calcium sensors that trigger their secretion remain unknown. Here, we show that in mouse hippocampal neurons, DCV fusion is strongly and equally reduced in synaptotagmin-1 (Syt1)- or Syt7-deficient neurons, but combined Syt1/Syt7 deficiency did not reduce fusion further. Cross-rescue, expression of Syt1 in Syt7-deficient neurons, or vice versa, completely restored fusion. Hence, both sensors are rate limiting, operating in a single pathway. Overexpression of either sensor in wild-type neurons confirmed this and increased fusion. Syt1 traveled with DCVs and was present on fusing DCVs, but Syt7 supported fusion largely from other locations. Finally, the duration of single DCV fusion events was reduced in Syt1-deficient but not Syt7-deficient neurons. In conclusion, two functionally redundant calcium sensors drive neuromodulator secretion in an expression-dependent manner. In addition, Syt1 has a unique role in regulating fusion pore duration.
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Affiliation(s)
- Rhodé van Westen
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands
- Department of Clinical Genetics, Amsterdam University Medical Centers, 1081 HV Amsterdam, The Netherlands
| | - Josse Poppinga
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands
| | - Rocío Díez Arazola
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands
| | - Ruud F Toonen
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands;
| | - Matthijs Verhage
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands;
- Department of Clinical Genetics, Amsterdam University Medical Centers, 1081 HV Amsterdam, The Netherlands
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26
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Bourgeois-Jaarsma Q, Miaja Hernandez P, Groffen AJ. Ca 2+ sensor proteins in spontaneous release and synaptic plasticity: Limited contribution of Doc2c, rabphilin-3a and synaptotagmin 7 in hippocampal glutamatergic neurons. Mol Cell Neurosci 2021; 112:103613. [PMID: 33753311 DOI: 10.1016/j.mcn.2021.103613] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 03/09/2021] [Accepted: 03/13/2021] [Indexed: 11/28/2022] Open
Abstract
Presynaptic neurotransmitter release is strictly regulated by SNARE proteins, Ca2+ and a number of Ca2+ sensors including synaptotagmins (Syts) and Double C2 domain proteins (Doc2s). More than seventy years after the original description of spontaneous release, the mechanism that regulates this process is still poorly understood. Syt-1, Syt7 and Doc2 proteins contribute predominantly, but not exclusively, to synchronous, asynchronous and spontaneous phases of release. The proteins share a conserved tandem C2 domain architecture, but are functionally diverse in their subcellular location, Ca2+-binding properties and protein interactions. In absence of Syt-1, Doc2a and -b, neurons still exhibit spontaneous vesicle fusion which remains Ca2+-sensitive, suggesting the existence of additional sensors. Here, we selected Doc2c, rabphilin-3a and Syt-7 as three potential Ca2+ sensors for their sequence homology with Syt-1 and Doc2b. We genetically ablated each candidate gene in absence of Doc2a and -b and investigated spontaneous and evoked release in glutamatergic hippocampal neurons, cultured either in networks or on microglial islands (autapses). The removal of Doc2c had no effect on spontaneous or evoked release. Syt-7 removal also did not affect spontaneous release, although it altered short-term plasticity by accentuating short-term depression. The removal of rabphilin caused an increased spontaneous release frequency in network cultures, an effect that was not observed in autapses. Taken together, we conclude that Doc2c and Syt-7 do not affect spontaneous release of glutamate in hippocampal neurons, while our results suggest a possible regulatory role of rabphilin-3a in neuronal networks. These findings importantly narrow down the repertoire of synaptic Ca2+ sensors that may be implicated in the spontaneous release of glutamate.
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Affiliation(s)
- Quentin Bourgeois-Jaarsma
- Department of Functional Genomics, Faculty of Science, Center for Neurogenomics and Cognitive Research, VU University, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands
| | - Pablo Miaja Hernandez
- Department of Functional Genomics, Faculty of Science, Center for Neurogenomics and Cognitive Research, VU University, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands
| | - Alexander J Groffen
- Department of Functional Genomics, Faculty of Science, Center for Neurogenomics and Cognitive Research, VU University, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands; Department of Clinical Genetics, VU Medical Center, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands.
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27
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Tawfik B, Martins JS, Houy S, Imig C, Pinheiro PS, Wojcik SM, Brose N, Cooper BH, Sørensen JB. Synaptotagmin-7 places dense-core vesicles at the cell membrane to promote Munc13-2- and Ca 2+-dependent priming. eLife 2021; 10:64527. [PMID: 33749593 PMCID: PMC8012061 DOI: 10.7554/elife.64527] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Accepted: 03/19/2021] [Indexed: 12/17/2022] Open
Abstract
Synaptotagmins confer calcium-dependence to the exocytosis of secretory vesicles, but how coexpressed synaptotagmins interact remains unclear. We find that synaptotagmin-1 and synaptotagmin-7 when present alone act as standalone fast and slow Ca2+-sensors for vesicle fusion in mouse chromaffin cells. When present together, synaptotagmin-1 and synaptotagmin-7 are found in largely non-overlapping clusters on dense-core vesicles. Synaptotagmin-7 stimulates Ca2+-dependent vesicle priming and inhibits depriming, and it promotes ubMunc13-2- and phorbolester-dependent priming, especially at low resting calcium concentrations. The priming effect of synaptotagmin-7 increases the number of vesicles fusing via synaptotagmin-1, while negatively affecting their fusion speed, indicating both synergistic and competitive interactions between synaptotagmins. Synaptotagmin-7 places vesicles in close membrane apposition (<6 nm); without it, vesicles accumulate out of reach of the fusion complex (20-40 nm). We suggest that a synaptotagmin-7-dependent movement toward the membrane is involved in Munc13-2/phorbolester/Ca2+-dependent priming as a prelude to fast and slow exocytosis triggering.
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Affiliation(s)
- Bassam Tawfik
- Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark
| | - Joana S Martins
- Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark
| | - Sébastien Houy
- Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark
| | - Cordelia Imig
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Paulo S Pinheiro
- Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark.,Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal
| | - Sonja M Wojcik
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Benjamin H Cooper
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
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28
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Function of Drosophila Synaptotagmins in membrane trafficking at synapses. Cell Mol Life Sci 2021; 78:4335-4364. [PMID: 33619613 PMCID: PMC8164606 DOI: 10.1007/s00018-021-03788-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 01/29/2021] [Accepted: 02/09/2021] [Indexed: 12/13/2022]
Abstract
The Synaptotagmin (SYT) family of proteins play key roles in regulating membrane trafficking at neuronal synapses. Using both Ca2+-dependent and Ca2+-independent interactions, several SYT isoforms participate in synchronous and asynchronous fusion of synaptic vesicles (SVs) while preventing spontaneous release that occurs in the absence of stimulation. Changes in the function or abundance of the SYT1 and SYT7 isoforms alter the number and route by which SVs fuse at nerve terminals. Several SYT family members also regulate trafficking of other subcellular organelles at synapses, including dense core vesicles (DCV), exosomes, and postsynaptic vesicles. Although SYTs are linked to trafficking of multiple classes of synaptic membrane compartments, how and when they interact with lipids, the SNARE machinery and other release effectors are still being elucidated. Given mutations in the SYT family cause disorders in both the central and peripheral nervous system in humans, ongoing efforts are defining how these proteins regulate vesicle trafficking within distinct neuronal compartments. Here, we review the Drosophila SYT family and examine their role in synaptic communication. Studies in this invertebrate model have revealed key similarities and several differences with the predicted activity of their mammalian counterparts. In addition, we highlight the remaining areas of uncertainty in the field and describe outstanding questions on how the SYT family regulates membrane trafficking at nerve terminals.
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29
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Abstract
Mammalian central synapses of diverse functions contribute to highly complex brain organization, but the molecular basis of synaptic diversity remains open. This is because current synapse proteomics are restricted to the “average” composition of abundant synaptic proteins. Here, we demonstrate a subcellular proteomic workflow that can identify and quantify the deep proteome of synaptic vesicles, including previously missing proteins present in a small percentage of central synapses. This synaptic vesicle proteome revealed many proteins of physiological and pathological relevance, particularly in the low-abundance range, thus providing a resource for future investigations on diversified synaptic functions and neuronal dysfunctions. Current proteomic studies clarified canonical synaptic proteins that are common to many types of synapses. However, proteins of diversified functions in a subset of synapses are largely hidden because of their low abundance or structural similarities to abundant proteins. To overcome this limitation, we have developed an “ultra-definition” (UD) subcellular proteomic workflow. Using purified synaptic vesicle (SV) fraction from rat brain, we identified 1,466 proteins, three times more than reported previously. This refined proteome includes all canonical SV proteins, as well as numerous proteins of low abundance, many of which were hitherto undetected. Comparison of UD quantifications between SV and synaptosomal fractions has enabled us to distinguish SV-resident proteins from potential SV-visitor proteins. We found 134 SV residents, of which 86 are present in an average copy number per SV of less than one, including vesicular transporters of nonubiquitous neurotransmitters in the brain. We provide a fully annotated resource of all categorized SV-resident and potential SV-visitor proteins, which can be utilized to drive novel functional studies, as we characterized here Aak1 as a regulator of synaptic transmission. Moreover, proteins in the SV fraction are associated with more than 200 distinct brain diseases. Remarkably, a majority of these proteins was found in the low-abundance proteome range, highlighting its pathological significance. Our deep SV proteome will provide a fundamental resource for a variety of future investigations on the function of synapses in health and disease.
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30
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Wang QW, Lu SY, Liu YN, Chen Y, Wei H, Shen W, Chen YF, Fu CL, Wang YH, Dai A, Huang X, Gage FH, Xu Q, Yao J. Synaptotagmin-7 deficiency induces mania-like behavioral abnormalities through attenuating GluN2B activity. Proc Natl Acad Sci U S A 2020; 117:31438-31447. [PMID: 33229564 PMCID: PMC7733786 DOI: 10.1073/pnas.2016416117] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Synaptotagmin-7 (Syt7) probably plays an important role in bipolar-like behavioral abnormalities in mice; however, the underlying mechanisms for this have remained elusive. Unlike antidepressants that cause mood overcorrection in bipolar depression, N-methyl-d-aspartate receptor (NMDAR)-targeted drugs show moderate clinical efficacy, for unexplained reasons. Here we identified Syt7 single nucleotide polymorphisms (SNPs) in patients with bipolar disorder and demonstrated that mice lacking Syt7 or expressing the SNPs showed GluN2B-NMDAR dysfunction, leading to antidepressant behavioral consequences and avoidance of overcorrection by NMDAR antagonists. In human induced pluripotent stem cell (iPSC)-derived and mouse hippocampal neurons, Syt7 and GluN2B-NMDARs were localized to the peripheral synaptic region, and Syt7 triggered multiple forms of glutamate release to efficiently activate the juxtaposed GluN2B-NMDARs. Thus, while Syt7 deficiency and SNPs induced GluN2B-NMDAR dysfunction in mice, patient iPSC-derived neurons showed Syt7 deficit-induced GluN2B-NMDAR hypoactivity that was rescued by Syt7 overexpression. Therefore, Syt7 deficits induced mania-like behaviors in mice by attenuating GluN2B activity, which enabled NMDAR antagonists to avoid mood overcorrection.
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Affiliation(s)
- Qiu-Wen Wang
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, 100084 Beijing, China
| | - Si-Yao Lu
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, 100084 Beijing, China
| | - Yao-Nan Liu
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, 100084 Beijing, China
| | - Yun Chen
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, 100084 Beijing, China
| | - Hui Wei
- State Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences Chinese Academy of Medical Sciences and Peking Union Medical College, Neuroscience Center, Chinese Academy of Medical Sciences, 100005 Beijing, China
| | - Wei Shen
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, 100084 Beijing, China
| | - Yan-Fen Chen
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, 100084 Beijing, China
| | - Chong-Lei Fu
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, 100084 Beijing, China
| | - Ying-Han Wang
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, 100084 Beijing, China
| | - Anbang Dai
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, 100084 Beijing, China
| | - Xuan Huang
- Medical Research Center, Beijing Chao-Yang Hospital, Capital Medical University, 100020 Beijing, China
| | - Fred H Gage
- Laboratory of Genetics, The Salk Institute for Biological Studies, La Jolla, CA 92037
| | - Qi Xu
- State Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences Chinese Academy of Medical Sciences and Peking Union Medical College, Neuroscience Center, Chinese Academy of Medical Sciences, 100005 Beijing, China;
| | - Jun Yao
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, 100084 Beijing, China;
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31
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Wolfes AC, Dean C. The diversity of synaptotagmin isoforms. Curr Opin Neurobiol 2020; 63:198-209. [PMID: 32663762 DOI: 10.1016/j.conb.2020.04.006] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2020] [Revised: 04/07/2020] [Accepted: 04/10/2020] [Indexed: 12/20/2022]
Abstract
The synaptotagmin family of molecules is known for regulating calcium-dependent membrane fusion events. Mice and humans express 17 synaptotagmin isoforms, where most studies have focused on isoforms 1, 2, and 7, which are involved in synaptic vesicle exocytosis. Recent work has highlighted how brain function relies on additional isoforms, with roles in postsynaptic receptor endocytosis, vesicle trafficking, membrane repair, synaptic plasticity, and protection against neurodegeneration, for example, in addition to the traditional concept of synaptotagmin-mediated neurotransmitter release - in neurons as well as glia, and at different timepoints. In fact, it is not uncommon for the same isoform to feature several splice isoforms, form homo- and heterodimers, and function in different subcellular locations and cell types. This review aims to highlight the diversity of synaptotagmins, offers a concise summary of key findings on all isoforms, and discusses different ways of grouping these.
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Affiliation(s)
- Anne C Wolfes
- Department of Brain Sciences, Division of Neuroscience, Imperial College London, Hammersmith Hospital Campus, Du Cane Road, London, W12 0NN, UK; UK Dementia Research Institute at Imperial College, London, UK
| | - Camin Dean
- German Center for Neurodegenerative Diseases, Charité University of Medicine - Berlin, 10117 Berlin, Germany.
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32
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Direct imaging of rapid tethering of synaptic vesicles accompanying exocytosis at a fast central synapse. Proc Natl Acad Sci U S A 2020; 117:14493-14502. [PMID: 32513685 DOI: 10.1073/pnas.2000265117] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
A high rate of synaptic vesicle (SV) release is required at cerebellar mossy fiber terminals for rapid information processing. As the number of release sites is limited, fast SV reloading is necessary to achieve sustained release. However, rapid reloading has not been observed directly. Here, we visualize SV movements near presynaptic membrane using total internal reflection fluorescence (TIRF) microscopy. Upon stimulation, SVs appeared in the TIRF-field and became tethered to the presynaptic membrane with unexpectedly rapid time course, almost as fast as SVs disappeared due to release. However, such stimulus-induced tethering was abolished by inhibiting exocytosis, suggesting that the tethering is tightly coupled to preceding exocytosis. The newly tethered vesicles became fusion competent not immediately but only 300 ms to 400 ms after tethering. Together with model simulations, we propose that rapid tethering leads to an immediate filling of vacated spaces and release sites within <100 nm of the active zone by SVs, which serve as precursors of readily releasable vesicles, thereby shortening delays during sustained activity.
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33
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Guan Z, Quiñones-Frías MC, Akbergenova Y, Littleton JT. Drosophila Synaptotagmin 7 negatively regulates synaptic vesicle release and replenishment in a dosage-dependent manner. eLife 2020; 9:e55443. [PMID: 32343229 PMCID: PMC7224696 DOI: 10.7554/elife.55443] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Accepted: 04/28/2020] [Indexed: 01/03/2023] Open
Abstract
Synchronous neurotransmitter release is triggered by Ca2+ binding to the synaptic vesicle protein Synaptotagmin 1, while asynchronous fusion and short-term facilitation is hypothesized to be mediated by plasma membrane-localized Synaptotagmin 7 (SYT7). We generated mutations in Drosophila Syt7 to determine if it plays a conserved role as the Ca2+ sensor for these processes. Electrophysiology and quantal imaging revealed evoked release was elevated 2-fold. Syt7 mutants also had a larger pool of readily-releasable vesicles, faster recovery following stimulation, and intact facilitation. Syt1/Syt7 double mutants displayed more release than Syt1 mutants alone, indicating SYT7 does not mediate the residual asynchronous release remaining in the absence of SYT1. SYT7 localizes to an internal membrane tubular network within the peri-active zone, but does not enrich at active zones. These findings indicate the two Ca2+ sensor model of SYT1 and SYT7 mediating all phases of neurotransmitter release and facilitation is not applicable at Drosophila synapses.
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Affiliation(s)
- Zhuo Guan
- The Picower Institute for Learning and Memory, Department of Biology and Department of Brain and Cognitive Sciences, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Monica C Quiñones-Frías
- The Picower Institute for Learning and Memory, Department of Biology and Department of Brain and Cognitive Sciences, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Yulia Akbergenova
- The Picower Institute for Learning and Memory, Department of Biology and Department of Brain and Cognitive Sciences, Massachusetts Institute of TechnologyCambridgeUnited States
| | - J Troy Littleton
- The Picower Institute for Learning and Memory, Department of Biology and Department of Brain and Cognitive Sciences, Massachusetts Institute of TechnologyCambridgeUnited States
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Huson V, Regehr WG. Diverse roles of Synaptotagmin-7 in regulating vesicle fusion. Curr Opin Neurobiol 2020; 63:42-52. [PMID: 32278209 DOI: 10.1016/j.conb.2020.02.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Revised: 02/12/2020] [Accepted: 02/13/2020] [Indexed: 11/18/2022]
Abstract
Synaptotagmin 7 (Syt7) is a multifunctional calcium sensor expressed throughout the body. Its high calcium affinity makes it well suited to act in processes triggered by modest calcium increases within cells. In synaptic transmission, Syt7 has been shown to mediate asynchronous neurotransmitter release, facilitation, and vesicle replenishment. In this review we provide an update on recent developments, and the newly emerging roles of Syt7 in frequency invariant synaptic transmission and in suppressing spontaneous release. Additionally, we discuss Syt7's regulation of membrane fusion in non-neuronal cells, and its involvement in disease. How such diversity of functions is regulated remains an open question. We discuss several potential factors including temperature, presynaptic calcium signals, the localization of Syt7, and its interaction with other Syt isoforms.
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Xing Y, Chen J, Hilley H, Steele H, Yang J, Han L. Molecular Signature of Pruriceptive MrgprA3 + Neurons. J Invest Dermatol 2020; 140:2041-2050. [PMID: 32234460 DOI: 10.1016/j.jid.2020.03.935] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Revised: 03/12/2020] [Accepted: 03/13/2020] [Indexed: 02/07/2023]
Abstract
Itch, initiated by the activation of sensory neurons, is associated frequently with dermatological diseases. MrgprA3+ sensory neurons have been identified as one of the major itch-sensing neuronal populations. Mounting evidence has demonstrated that peripheral pathological conditions induce physiological regulation of sensory neurons, which is critical for the maintenance of chronic itch sensation. However, the underlying molecular mechanisms are not clear. Here, we performed RNA sequencing of genetically labeled MrgprA3+ neurons under both naïve and allergic contact dermatitis conditions. Our results revealed the unique molecular signature of itch-sensing neurons and the distinct transcriptional profile changes that result in response to dermatitis. We found enrichment of nine Mrgpr family members and two histamine receptors in MrgprA3+ neurons, suggesting that MrgprA3+ neurons are a direct neuronal target for histamine and Mrgpr agonists. In addition, PTPN6 and PCDH12 were identified as highly selective markers of MrgprA3+ neurons. We also discovered that MrgprA3+ neurons respond to skin dermatitis in a way that is unique from other sensory neurons by regulating a combination of transcriptional factors, ion channels, and key molecules involved in synaptic transmission. These results significantly increase our knowledge of itch transmission and uncover potential targets for combating itch.
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Affiliation(s)
- Yanyan Xing
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Junyu Chen
- Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Henry Hilley
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Haley Steele
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Jingjing Yang
- Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Liang Han
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA.
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36
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Bridi MS, Shin S, Huang S, Kirkwood A. Dynamic Recovery from Depression Enables Rate Encoding in Inhibitory Synapses. iScience 2020; 23:100940. [PMID: 32163896 PMCID: PMC7066227 DOI: 10.1016/j.isci.2020.100940] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Revised: 07/18/2019] [Accepted: 02/21/2020] [Indexed: 12/25/2022] Open
Abstract
Parvalbumin-expressing fast-spiking interneurons (PV-INs) control network firing and the gain of cortical response to sensory stimulation. Crucial for these functions, PV-INs can sustain high-frequency firing with no accommodation. However, PV-INs also exhibit short-term depression (STD) during sustained activation, largely due to the depletion of synaptic resources (vesicles). In most synapses the rate of replenishment of depleted vesicles is constant, determining an inverse relationship between depression levels and the activation rate, which theoretically, severely limits rate-coding capabilities. We examined STD of the PV-IN to pyramidal cell synapse in the mouse visual cortex and found that in these synapses the recovery from depression is not constant but increases linearly with the frequency of use. By combining modeling, dynamic clamp, and optogenetics, we demonstrated that this recovery enables PV-INs to reduce pyramidal cell firing in a linear manner, which theoretically is crucial for controlling the gain of cortical visual responses. Recovery rate from depression in inhibitory synapses from PV-INs is use dependent Dynamic recovery from depression enables rate coding in inhibitory inputs PV-IN synapses reduce pyramidal firing in a frequency-dependent manner
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Affiliation(s)
- Morgan S Bridi
- Program in Neuroscience, Hussman Institute for Autism, Baltimore, MD 21201, USA
| | - Sangyep Shin
- Program in Neuroscience, Hussman Institute for Autism, Baltimore, MD 21201, USA
| | - Shiyong Huang
- Program in Neuroscience, Hussman Institute for Autism, Baltimore, MD 21201, USA; The Mind/Brain Institute, Johns Hopkins University, Baltimore, MD 21218, USA.
| | - Alfredo Kirkwood
- The Mind/Brain Institute, Johns Hopkins University, Baltimore, MD 21218, USA; Department of Neuroscience, Johns Hopkins University, Baltimore, MD 21205, USA.
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Kobbersmed JR, Grasskamp AT, Jusyte M, Böhme MA, Ditlevsen S, Sørensen JB, Walter AM. Rapid regulation of vesicle priming explains synaptic facilitation despite heterogeneous vesicle:Ca 2+ channel distances. eLife 2020; 9:51032. [PMID: 32077852 PMCID: PMC7145420 DOI: 10.7554/elife.51032] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Accepted: 02/14/2020] [Indexed: 12/27/2022] Open
Abstract
Chemical synaptic transmission relies on the Ca2+-induced fusion of transmitter-laden vesicles whose coupling distance to Ca2+ channels determines synaptic release probability and short-term plasticity, the facilitation or depression of repetitive responses. Here, using electron- and super-resolution microscopy at the Drosophila neuromuscular junction we quantitatively map vesicle:Ca2+ channel coupling distances. These are very heterogeneous, resulting in a broad spectrum of vesicular release probabilities within synapses. Stochastic simulations of transmitter release from vesicles placed according to this distribution revealed strong constraints on short-term plasticity; particularly facilitation was difficult to achieve. We show that postulated facilitation mechanisms operating via activity-dependent changes of vesicular release probability (e.g. by a facilitation fusion sensor) generate too little facilitation and too much variance. In contrast, Ca2+-dependent mechanisms rapidly increasing the number of releasable vesicles reliably reproduce short-term plasticity and variance of synaptic responses. We propose activity-dependent inhibition of vesicle un-priming or release site activation as novel facilitation mechanisms. Cells in the nervous system of all animals communicate by releasing and sensing chemicals at contact points named synapses. The ‘talking’ (or pre-synaptic) cell stores the chemicals close to the synapse, in small spheres called vesicles. When the cell is activated, calcium ions flow in and interact with the release-ready vesicles, which then spill the chemicals into the synapse. In turn, the ‘listening’ (or post-synaptic) cell can detect the chemicals and react accordingly. When the pre-synaptic cell is activated many times in a short period, it can release a greater quantity of chemicals, allowing a bigger reaction in the post-synaptic cell. This phenomenon is known as facilitation, but it is still unclear how exactly it can take place. This is especially the case when many of the vesicles are not ready to respond, for example when they are too far from where calcium flows into the cell. Computer simulations have been created to model facilitation but they have assumed that all vesicles are placed at the same distance to the calcium entry point: Kobbersmed et al. now provide evidence that this assumption is incorrect. Two high-resolution imaging techniques were used to measure the actual distances between the vesicles and the calcium source in the pre-synaptic cells of fruit flies: this showed that these distances are quite variable – some vesicles sit much closer to the source than others. This information was then used to create a new computer model to simulate facilitation. The results from this computing work led Kobbersmed et al. to suggest that facilitation may take place because a calcium-based mechanism in the cell increases the number of vesicles ready to release their chemicals. This new model may help researchers to better understand how the cells in the nervous system work. Ultimately, this can guide experiments to investigate what happens when information processing at synapses breaks down, for example in diseases such as epilepsy.
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Affiliation(s)
- Janus Rl Kobbersmed
- Department of Mathematical Sciences, University of Copenhagen, København, Denmark.,Department of Neuroscience, University of Copenhagen, København, Denmark
| | - Andreas T Grasskamp
- Molecular and Theoretical Neuroscience, Leibniz-Forschungsinstitut für Molekulare Pharmakologie, FMP im CharitéCrossOver, Berlin, Germany
| | - Meida Jusyte
- Molecular and Theoretical Neuroscience, Leibniz-Forschungsinstitut für Molekulare Pharmakologie, FMP im CharitéCrossOver, Berlin, Germany.,Einstein Center for Neuroscience, Berlin, Germany
| | - Mathias A Böhme
- Molecular and Theoretical Neuroscience, Leibniz-Forschungsinstitut für Molekulare Pharmakologie, FMP im CharitéCrossOver, Berlin, Germany
| | - Susanne Ditlevsen
- Department of Mathematical Sciences, University of Copenhagen, København, Denmark
| | | | - Alexander M Walter
- Molecular and Theoretical Neuroscience, Leibniz-Forschungsinstitut für Molekulare Pharmakologie, FMP im CharitéCrossOver, Berlin, Germany.,Einstein Center for Neuroscience, Berlin, Germany
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38
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Synaptotagmin-7 is a key factor for bipolar-like behavioral abnormalities in mice. Proc Natl Acad Sci U S A 2020; 117:4392-4399. [PMID: 32041882 DOI: 10.1073/pnas.1918165117] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The pathogenesis of bipolar disorder (BD) has remained enigmatic, largely because genetic animal models based on identified susceptible genes have often failed to show core symptoms of spontaneous mood cycling. However, pedigree and induced pluripotent stem cell (iPSC)-based analyses have implicated that dysfunction in some key signaling cascades might be crucial for the disease pathogenesis in a subpopulation of BD patients. We hypothesized that the behavioral abnormalities of patients and the comorbid metabolic abnormalities might share some identical molecular mechanism. Hence, we investigated the expression of insulin/synapse dually functioning genes in neurons derived from the iPSCs of BD patients and the behavioral phenotype of mice with these genes silenced in the hippocampus. By these means, we identified synaptotagmin-7 (Syt7) as a candidate risk factor for behavioral abnormalities. We then investigated Syt7 knockout (KO) mice and observed nocturnal manic-like and diurnal depressive-like behavioral fluctuations in a majority of these animals, analogous to the mood cycling symptoms of BD. We treated the Syt7 KO mice with clinical BD drugs including olanzapine and lithium, and found that the drug treatments could efficiently regulate the behavioral abnormalities of the Syt7 KO mice. To further verify whether Syt7 deficits existed in BD patients, we investigated the plasma samples of 20 BD patients and found that the Syt7 mRNA level was significantly attenuated in the patient plasma compared to the healthy controls. We therefore concluded that Syt7 is likely a key factor for the bipolar-like behavioral abnormalities.
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Wesseling JF. Considerations for Measuring Activity-Dependence of Recruitment of Synaptic Vesicles to the Readily Releasable Pool. Front Synaptic Neurosci 2019; 11:32. [PMID: 31824292 PMCID: PMC6879548 DOI: 10.3389/fnsyn.2019.00032] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Accepted: 11/06/2019] [Indexed: 11/29/2022] Open
Abstract
The connection strength of most chemical synapses changes dynamically during normal use as a function of the recent history of activity. The phenomenon is known as short-term synaptic plasticity or synaptic dynamics, and is thought to be involved in processing and filtering information as it is transmitted across the synaptic cleft. Multiple presynaptic mechanisms have been implicated, but large gaps remain in our understanding of how the mechanisms are modulated and how they interact. One important factor is the timing of recruitment of synaptic vesicles to a readily-releasable pool. A number of studies have concluded that activity and/or residual Ca2+ can accelerate the mechanism, but alternative explanations for some of the evidence have emerged. Here I review the methodology that we have developed for isolating the recruitment and the dependence on activity from other kinds of mechanisms that are activated concurrently.
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Affiliation(s)
- John F Wesseling
- CSIC/Instituto de Neurociencias, Universidad Miguel Hernández, Alicante, Spain
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40
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Wu HK, Zhang Y, Cao CM, Hu X, Fang M, Yao Y, Jin L, Chen G, Jiang P, Zhang S, Song R, Peng W, Liu F, Guo J, Tang L, He Y, Shan D, Huang J, Zhou Z, Wang DW, Lv F, Xiao RP. Glucose-Sensitive Myokine/Cardiokine MG53 Regulates Systemic Insulin Response and Metabolic Homeostasis. Circulation 2019; 139:901-914. [PMID: 30586741 DOI: 10.1161/circulationaha.118.037216] [Citation(s) in RCA: 74] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
BACKGROUND Mitsugumin 53 (MG53 or TRIM72), a striated muscle-specific E3 ligase, promotes ubiquitin-dependent degradation of the insulin receptor and insulin receptor substrate-1 and subsequently induces insulin resistance, resulting in metabolic syndrome and type 2 diabetes mellitus (T2DM). However, it is unknown how MG53 from muscle regulates systemic insulin response and energy metabolism. Increasing evidence demonstrates that muscle secretes proteins as myokines or cardiokines that regulate systemic metabolic processes. We hypothesize that MG53 may act as a myokine/cardiokine, contributing to interorgan regulation of insulin sensitivity and metabolic homeostasis. METHODS Using perfused rodent hearts or skeletal muscle, we investigated whether high glucose, high insulin, or their combination (conditions mimicking metabolic syndrome or T2DM) alters MG53 protein concentration in the perfusate. We also measured serum MG53 levels in rodents and humans in the presence or absence of metabolic diseases, particularly T2DM. The effects of circulating MG53 on multiorgan insulin response were evaluated by systemic delivery of recombinant MG53 protein to mice. Furthermore, the potential involvement of circulating MG53 in the pathogenesis of T2DM was assessed by neutralizing blood MG53 with monoclonal antibodies in diabetic db/db mice. Finally, to delineate the mechanism underlying the action of extracellular MG53 on insulin signaling, we analyzed the potential interaction of MG53 with extracellular domain of insulin receptor using coimmunoprecipitation and surface plasmon resonance assays. RESULTS Here, we demonstrate that MG53 is a glucose-sensitive myokine/cardiokine that governs the interorgan regulation of insulin sensitivity. First, high glucose or high insulin induces MG53 secretion from isolated rodent hearts and skeletal muscle. Second, hyperglycemia is accompanied by increased circulating MG53 in humans and rodents with diabetes mellitus. Third, systemic delivery of recombinant MG53 or cardiac-specific overexpression of MG53 causes systemic insulin resistance and metabolic syndrome in mice, whereas neutralizing circulating MG53 with monoclonal antibodies has therapeutic effects in T2DM db/db mice. Mechanistically, MG53 binds to the extracellular domain of the insulin receptor and acts as an allosteric blocker. CONCLUSIONS Thus, MG53 has dual actions as a myokine/cardiokine and an E3 ligase, synergistically inhibiting the insulin signaling pathway. Targeting circulating MG53 opens a new therapeutic avenue for T2DM and its complications.
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Affiliation(s)
- Hong-Kun Wu
- State Key Laboratory of Membrane Biology, Institute of Molecular Medicine (H.-K.W., Y.Z., C.-M.C., X.H., M.F., Y.Y., L.J., G.C., P.J., S.Z., R.S., W.P., F.L., J.G., L.T., Y.H., D.S., Z.Z., F.L., R.-P.X.)
| | - Yan Zhang
- State Key Laboratory of Membrane Biology, Institute of Molecular Medicine (H.-K.W., Y.Z., C.-M.C., X.H., M.F., Y.Y., L.J., G.C., P.J., S.Z., R.S., W.P., F.L., J.G., L.T., Y.H., D.S., Z.Z., F.L., R.-P.X.)
| | - Chun-Mei Cao
- State Key Laboratory of Membrane Biology, Institute of Molecular Medicine (H.-K.W., Y.Z., C.-M.C., X.H., M.F., Y.Y., L.J., G.C., P.J., S.Z., R.S., W.P., F.L., J.G., L.T., Y.H., D.S., Z.Z., F.L., R.-P.X.)
| | - Xinli Hu
- State Key Laboratory of Membrane Biology, Institute of Molecular Medicine (H.-K.W., Y.Z., C.-M.C., X.H., M.F., Y.Y., L.J., G.C., P.J., S.Z., R.S., W.P., F.L., J.G., L.T., Y.H., D.S., Z.Z., F.L., R.-P.X.)
| | - Meng Fang
- State Key Laboratory of Membrane Biology, Institute of Molecular Medicine (H.-K.W., Y.Z., C.-M.C., X.H., M.F., Y.Y., L.J., G.C., P.J., S.Z., R.S., W.P., F.L., J.G., L.T., Y.H., D.S., Z.Z., F.L., R.-P.X.)
| | - Yuan Yao
- State Key Laboratory of Membrane Biology, Institute of Molecular Medicine (H.-K.W., Y.Z., C.-M.C., X.H., M.F., Y.Y., L.J., G.C., P.J., S.Z., R.S., W.P., F.L., J.G., L.T., Y.H., D.S., Z.Z., F.L., R.-P.X.)
| | - Li Jin
- State Key Laboratory of Membrane Biology, Institute of Molecular Medicine (H.-K.W., Y.Z., C.-M.C., X.H., M.F., Y.Y., L.J., G.C., P.J., S.Z., R.S., W.P., F.L., J.G., L.T., Y.H., D.S., Z.Z., F.L., R.-P.X.)
| | - Gengjia Chen
- State Key Laboratory of Membrane Biology, Institute of Molecular Medicine (H.-K.W., Y.Z., C.-M.C., X.H., M.F., Y.Y., L.J., G.C., P.J., S.Z., R.S., W.P., F.L., J.G., L.T., Y.H., D.S., Z.Z., F.L., R.-P.X.)
| | - Peng Jiang
- State Key Laboratory of Membrane Biology, Institute of Molecular Medicine (H.-K.W., Y.Z., C.-M.C., X.H., M.F., Y.Y., L.J., G.C., P.J., S.Z., R.S., W.P., F.L., J.G., L.T., Y.H., D.S., Z.Z., F.L., R.-P.X.)
| | - Shuo Zhang
- State Key Laboratory of Membrane Biology, Institute of Molecular Medicine (H.-K.W., Y.Z., C.-M.C., X.H., M.F., Y.Y., L.J., G.C., P.J., S.Z., R.S., W.P., F.L., J.G., L.T., Y.H., D.S., Z.Z., F.L., R.-P.X.)
| | - Ruisheng Song
- State Key Laboratory of Membrane Biology, Institute of Molecular Medicine (H.-K.W., Y.Z., C.-M.C., X.H., M.F., Y.Y., L.J., G.C., P.J., S.Z., R.S., W.P., F.L., J.G., L.T., Y.H., D.S., Z.Z., F.L., R.-P.X.)
| | - Wei Peng
- State Key Laboratory of Membrane Biology, Institute of Molecular Medicine (H.-K.W., Y.Z., C.-M.C., X.H., M.F., Y.Y., L.J., G.C., P.J., S.Z., R.S., W.P., F.L., J.G., L.T., Y.H., D.S., Z.Z., F.L., R.-P.X.)
| | - Fenghua Liu
- State Key Laboratory of Membrane Biology, Institute of Molecular Medicine (H.-K.W., Y.Z., C.-M.C., X.H., M.F., Y.Y., L.J., G.C., P.J., S.Z., R.S., W.P., F.L., J.G., L.T., Y.H., D.S., Z.Z., F.L., R.-P.X.)
| | - Jiaojiao Guo
- State Key Laboratory of Membrane Biology, Institute of Molecular Medicine (H.-K.W., Y.Z., C.-M.C., X.H., M.F., Y.Y., L.J., G.C., P.J., S.Z., R.S., W.P., F.L., J.G., L.T., Y.H., D.S., Z.Z., F.L., R.-P.X.)
| | - Lifei Tang
- State Key Laboratory of Membrane Biology, Institute of Molecular Medicine (H.-K.W., Y.Z., C.-M.C., X.H., M.F., Y.Y., L.J., G.C., P.J., S.Z., R.S., W.P., F.L., J.G., L.T., Y.H., D.S., Z.Z., F.L., R.-P.X.)
| | - Yanyun He
- State Key Laboratory of Membrane Biology, Institute of Molecular Medicine (H.-K.W., Y.Z., C.-M.C., X.H., M.F., Y.Y., L.J., G.C., P.J., S.Z., R.S., W.P., F.L., J.G., L.T., Y.H., D.S., Z.Z., F.L., R.-P.X.)
| | - Dan Shan
- State Key Laboratory of Membrane Biology, Institute of Molecular Medicine (H.-K.W., Y.Z., C.-M.C., X.H., M.F., Y.Y., L.J., G.C., P.J., S.Z., R.S., W.P., F.L., J.G., L.T., Y.H., D.S., Z.Z., F.L., R.-P.X.)
| | - Jin Huang
- Department of Internal Medicine, Tongji Medical College, Huazhong University of Science & Technology, Wuhan, China (J.H., D.W.)
| | - Zhuan Zhou
- State Key Laboratory of Membrane Biology, Institute of Molecular Medicine (H.-K.W., Y.Z., C.-M.C., X.H., M.F., Y.Y., L.J., G.C., P.J., S.Z., R.S., W.P., F.L., J.G., L.T., Y.H., D.S., Z.Z., F.L., R.-P.X.).,Beijing City Key Laboratory of Cardiometabolic Molecular Medicine (Z.Z., R.-P.X.).,Peking University, China. Peking-Tsinghua Center for Life Sciences, Beijing, China (Z.Z., R.-P.X.)
| | - Dao Wen Wang
- Department of Internal Medicine, Tongji Medical College, Huazhong University of Science & Technology, Wuhan, China (J.H., D.W.)
| | - Fengxiang Lv
- State Key Laboratory of Membrane Biology, Institute of Molecular Medicine (H.-K.W., Y.Z., C.-M.C., X.H., M.F., Y.Y., L.J., G.C., P.J., S.Z., R.S., W.P., F.L., J.G., L.T., Y.H., D.S., Z.Z., F.L., R.-P.X.)
| | - Rui-Ping Xiao
- State Key Laboratory of Membrane Biology, Institute of Molecular Medicine (H.-K.W., Y.Z., C.-M.C., X.H., M.F., Y.Y., L.J., G.C., P.J., S.Z., R.S., W.P., F.L., J.G., L.T., Y.H., D.S., Z.Z., F.L., R.-P.X.).,Beijing City Key Laboratory of Cardiometabolic Molecular Medicine (Z.Z., R.-P.X.).,Peking University, China. Peking-Tsinghua Center for Life Sciences, Beijing, China (Z.Z., R.-P.X.)
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Fritsche L, Teuber-Hanselmann S, Soub D, Harnisch K, Mairinger F, Junker A. MicroRNA profiles of MS gray matter lesions identify modulators of the synaptic protein synaptotagmin-7. Brain Pathol 2019; 30:524-540. [PMID: 31663645 PMCID: PMC8018161 DOI: 10.1111/bpa.12800] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Accepted: 10/24/2019] [Indexed: 12/11/2022] Open
Abstract
We established microRNA (miRNA) profiles in gray and white matter multiple sclerosis (MS) lesions and identified seven miRNAs which were significantly more upregulated in the gray matter lesions. Five of those seven miRNAs, miR‐330‐3p, miR‐4286, miR‐4488, let‐7e‐5p, miR‐432‐5p shared the common target synaptotagmin7 (Syt7). Immunohistochemistry and transcript analyses using nanostring technology revealed a maldistribution of Syt7, with Syt7 accumulation in neuronal soma and decreased expression in axonal structures. This maldistribution could be at least partially explained by an axonal Syt7 transport disturbance. Since Syt7 is a synapse‐associated molecule, this maldistribution could result in impairment of neuronal functions in MS patients. Thus, our results lead to the hypothesis that the overexpression of these five miRNAs in gray matter lesions is a cellular mechanism to reduce further endogenous neuronal Syt7 production. Therefore, miRNAs seem to play an important role as modulators of neuronal structures in MS.
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Affiliation(s)
- Lena Fritsche
- Institute of Neuropathology, University Hospital Essen, D-45147, Essen, Germany
| | | | - Daniel Soub
- Institute of Neuropathology, University Hospital Essen, D-45147, Essen, Germany
| | - Kim Harnisch
- Institute of Neuropathology, University Hospital Essen, D-45147, Essen, Germany
| | - Fabian Mairinger
- Institute of Pathology, University Hospital Essen, D-45147, Essen, Germany
| | - Andreas Junker
- Institute of Neuropathology, University Hospital Essen, D-45147, Essen, Germany
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Schmidt H. Control of Presynaptic Parallel Fiber Efficacy by Activity-Dependent Regulation of the Number of Occupied Release Sites. Front Syst Neurosci 2019; 13:30. [PMID: 31379524 PMCID: PMC6650762 DOI: 10.3389/fnsys.2019.00030] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Accepted: 07/01/2019] [Indexed: 11/13/2022] Open
Abstract
Parallel fiber (PF) synapses show pronounced and lasting facilitation during bursts of high-frequency activity. They typically connect to their target neurons via a single active zone (AZ), harboring few release sites (~2-8) with moderate initial vesicular release probability (~0.2-0.4). In light of these biophysical characteristics, it seems surprising that PF synapses can sustain facilitation during high-frequency periods of tens of action potentials (APs). Recent findings suggest an increase in the number of occupied release sites due to ultra-rapid (~180 s-1), Ca2+ dependent recruitment of synaptic vesicles (SVs) from replenishment sites as major presynaptic mechanism of this lasting facilitation. On the molecular level, Synaptotagmin 7 or Munc13s have been suggested to be involved in mediating facilitation at PF synapses. The recruitment of SVs from replenishment sites appears to be reversible on a slower time-scale, thereby, explaining that PF synapses rapidly depress and ultimately become silent during low-frequency activity. Hence, PF synapses show high-frequency facilitation (HFF) but low-frequency depression (LFD). This behavior is explained by regulation of the number of occupied release sites at the AZ by AP frequency.
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Affiliation(s)
- Hartmut Schmidt
- Carl-Ludwig Institute for Physiology, Medical Faculty, University of Leipzig, Leipzig, Germany
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Miki T. What We Can Learn From Cumulative Numbers of Vesicular Release Events. Front Cell Neurosci 2019; 13:257. [PMID: 31293386 PMCID: PMC6598442 DOI: 10.3389/fncel.2019.00257] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Accepted: 05/23/2019] [Indexed: 12/28/2022] Open
Abstract
Following action potential invasion in presynaptic terminals, synaptic vesicles are released in a stochastic manner at release sites (docking sites). Since neurotransmission occurs at frequencies up to 1 kHz, the mechanisms underlying consecutive vesicle releases at a docking site during high frequency bursts is a key factor for understanding the role and strength of the synapse. Particularly new vesicle recruitment at the docking site during neuronal activity is thought to be crucial for short-term plasticity. However current studies have not reached a unified docking site model for central synapses. Here I review newly developed analyses that can provide insight into docking site models. Quantal analysis using counts of vesicular release events provide a wealth of information not only to monitor the number of docking sites, but also to distinguish among docking site models. The stochastic properties of cumulative release number during bursts allow us to estimate the total number of releasable vesicles and to deduce the features of vesicle recruitment at docking sites and the change of release probability during bursts. This analytical method may contribute to a comprehensive understanding of release/replenishment mechanisms at a docking site.
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Affiliation(s)
- Takafumi Miki
- Graduate School of Brain Science, Doshisha University, Kyoto, Japan
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Barzilai-Tutsch H, Dewulf M, Lamaze C, Butler Browne G, Pines M, Halevy O. A promotive effect for halofuginone on membrane repair and synaptotagmin-7 levels in muscle cells of dysferlin-null mice. Hum Mol Genet 2019; 27:2817-2829. [PMID: 29771357 DOI: 10.1093/hmg/ddy185] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Accepted: 05/09/2018] [Indexed: 11/14/2022] Open
Abstract
In the absence of dysferlin, skeletal muscle cells fail to reseal properly after injury, resulting in slow progress of the dysferlinopathy muscular dystrophy (MD). Halofuginone, a leading agent in preventing fibrosis in MDs, was tested for its effects on membrane resealing post-injury. A hypo-osmotic shock assay on myotubes derived from wild-type (Wt) and dysferlin-null (dysf-/-) mice revealed that pre-treatment with halofuginone reduces the percentage of membrane-ruptured myotubes only in dysf-/- myotubes. In laser-induced injury of isolated myofibers, halofuginone decreased the amount of FM1-43 at the injury site of dysf-/- myofibers while having no effect on Wt myofibers. These results implicate halofuginone in ameliorating muscle-cell membrane integrity in dysf-/- mice. Halofuginone increased lysosome scattering across the cytosol of dysf-/- primary myoblasts, in a protein kinase/extracellular signal-regulated protein kinase and phosphoinositide 3 kinase/Akt-dependent manner, in agreement with an elevation in lysosomal exocytotic activity in these cells. A spatial- and age-dependent synaptotagmin-7 (Syt-7) expression pattern was shown in dysf-/- versus Wt mice, suggesting that these pattern alterations are related to the disease progress and that sytnaptotagmin-7 may be compensating for the lack of dysferlin at least with regard to membrane resealing post-injury. While halofuginone did not affect patch-repair-complex key proteins, it further enhanced Syt-7 levels and its spread across the cytosol in dysf-/- myofibers and muscle tissue, and increased its co-localization with lysosomes. Together, the data imply a novel role for halofuginone in membrane-resealing events with Syt-7 possibly taking part in these events.
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Affiliation(s)
- Hila Barzilai-Tutsch
- Department of Animal Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel
| | - Melissa Dewulf
- Membrane Dynamics and Mechanics of Intracellular Signaling Laboratory, Institut Curie-Centre de Recherche, PSL Research University, INSERM U1143, Centre national de la recherche scientifique, UMR 3666, Paris, France
| | - Christophe Lamaze
- Membrane Dynamics and Mechanics of Intracellular Signaling Laboratory, Institut Curie-Centre de Recherche, PSL Research University, INSERM U1143, Centre national de la recherche scientifique, UMR 3666, Paris, France
| | - Gillian Butler Browne
- Center for Research in Myology, CNRS FRE 3617, UPMC Univ Paris 06, UM76, INSERM U974, Sorbonne Universités, Paris, France
| | - Mark Pines
- The Volcani Center, Institute of Animal Science, Bet Dagan 52505, Israel
| | - Orna Halevy
- Department of Animal Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel
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Rozov A, Bolshakov AP, Valiullina-Rakhmatullina F. The Ever-Growing Puzzle of Asynchronous Release. Front Cell Neurosci 2019; 13:28. [PMID: 30809127 PMCID: PMC6379310 DOI: 10.3389/fncel.2019.00028] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 01/22/2019] [Indexed: 11/13/2022] Open
Abstract
Invasion of an action potential (AP) to presynaptic terminals triggers calcium dependent vesicle fusion in a relatively short time window, about a millisecond, after the onset of the AP. This allows fast and precise information transfer from neuron to neuron by means of synaptic transmission and phasic mediator release. However, at some synapses a single AP or a short burst of APs can generate delayed or asynchronous synaptic release lasting for tens or hundreds of milliseconds. Understanding the mechanisms underlying asynchronous release (AR) is important, since AR can better recruit extrasynaptic metabotropic receptors and maintain a high level of neurotransmitter in the extracellular space for a substantially longer period of time after presynaptic activity. Over the last decade substantial work has been done to identify the presynaptic calcium sensor that may be involved in AR. Several models have been suggested which may explain the long lasting presynaptic calcium elevation a prerequisite for prolonged delayed release. However, the presynaptic mechanisms underlying asynchronous vesicle release are still not well understood. In this review article, we provide an overview of the current state of knowledge on the molecular components involved in delayed vesicle fusion and in the maintenance of sufficient calcium concentration to trigger AR. In addition, we discuss possible alternative models that may explain intraterminal calcium dynamics underlying AR.
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Affiliation(s)
- Andrei Rozov
- Laboratory of Neurobiology, Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan, Russia.,Department of Physiology and Pathophysiology, University of Heidelberg, Heidelberg, Germany
| | - Alexey P Bolshakov
- Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences (RAS), Moscow, Russia.,Laboratory of Electrophysiology, Pirogov Russian National Research Medical University, Moscow, Russia
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Tran HT, Anderson LH, Knight JD. Membrane-Binding Cooperativity and Coinsertion by C2AB Tandem Domains of Synaptotagmins 1 and 7. Biophys J 2019; 116:1025-1036. [PMID: 30795874 DOI: 10.1016/j.bpj.2019.01.035] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Revised: 12/21/2018] [Accepted: 01/30/2019] [Indexed: 02/04/2023] Open
Abstract
Synaptotagmin-1 (Syt-1) and synaptotagmin-7 (Syt-7) contain analogous tandem C2 domains, C2A and C2B, which together sense Ca2+ to bind membranes and promote the stabilization of exocytotic fusion pores. Syt-1 triggers fast release of neurotransmitters, whereas Syt-7 functions in processes that involve lower Ca2+ concentrations such as hormone secretion. Syt-1 C2 domains are reported to bind membranes cooperatively, based on the observation that they penetrate farther into membranes as the C2AB tandem than as individual C2 domains. In contrast, we previously suggested that the two C2 domains of Syt-7 bind membranes independently, based in part on measurements of their liposome dissociation kinetics. Here, we investigated C2A-C2B interdomain cooperativity with Syt-1 and Syt-7 using directly comparable measurements. Equilibrium Ca2+ titrations demonstrate that the Syt-7 C2AB tandem binds liposomes lacking phosphatidylinositol-4,5-bisphosphate (PIP2) with greater Ca2+ sensitivity than either of its individual domains and binds to membranes containing PIP2 even in the absence of Ca2+. Stopped-flow kinetic measurements show differences in cooperativity between Syt-1 and Syt-7: Syt-1 C2AB dissociates from PIP2-free liposomes much more slowly than either of its individual C2 domains, indicating cooperativity, whereas the major population of Syt-7 C2AB has a dissociation rate comparable to its C2A domain, suggesting a lack of cooperativity. A minor subpopulation of Syt-7 C2AB dissociates at a slower rate, which could be due to a small cooperative component and/or liposome clustering. Measurements using an environment-sensitive fluorescent probe indicate that the Syt-7 C2B domain inserts deeply into membranes as part of the C2AB tandem, similar to the coinsertion previously reported for Syt-1. Overall, coinsertion of C2A and C2B domains is coupled to cooperative energetic effects in Syt-1 to a much greater extent than in Syt-7. The difference can be understood in terms of the relative contributions of C2A and C2B domains toward membrane binding in the two proteins.
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Affiliation(s)
- Hai T Tran
- Department of Chemistry, University of Colorado Denver, Denver, Colorado
| | - Lauren H Anderson
- Department of Chemistry, University of Colorado Denver, Denver, Colorado
| | - Jefferson D Knight
- Department of Chemistry, University of Colorado Denver, Denver, Colorado.
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Bornschein G, Schmidt H. Synaptotagmin Ca 2+ Sensors and Their Spatial Coupling to Presynaptic Ca v Channels in Central Cortical Synapses. Front Mol Neurosci 2019; 11:494. [PMID: 30697148 PMCID: PMC6341215 DOI: 10.3389/fnmol.2018.00494] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Accepted: 12/21/2018] [Indexed: 11/21/2022] Open
Abstract
Ca2+ concentrations drop rapidly over a distance of a few tens of nanometers from an open voltage-gated Ca2+ channel (Cav), thereby, generating a spatially steep and temporally short-lived Ca2+ gradient that triggers exocytosis of a neurotransmitter filled synaptic vesicle. These non-steady state conditions make the Ca2+-binding kinetics of the Ca2+ sensors for release and their spatial coupling to the Cavs important parameters of synaptic efficacy. In the mammalian central nervous system, the main release sensors linking action potential mediated Ca2+ influx to synchronous release are Synaptotagmin (Syt) 1 and 2. We review here quantitative work focusing on the Ca2+ kinetics of Syt2-mediated release. At present similar quantitative detail is lacking for Syt1-mediated release. In addition to triggering release, Ca2+ remaining bound to Syt after the first of two successive high-frequency activations was found to be capable of facilitating release during the second activation. More recently, the Ca2+ sensor Syt7 was identified as additional facilitation sensor. We further review how several recent functional studies provided quantitative insights into the spatial topographical relationships between Syts and Cavs and identified mechanisms regulating the sensor-to-channel coupling distances at presynaptic active zones. Most synapses analyzed in matured cortical structures were found to operate at tight, nanodomain coupling. For fast signaling synapses a developmental switch from loose, microdomain to tight, nanodomain coupling was found. The protein Septin5 has been known for some time as a developmentally down-regulated “inhibitor” of tight coupling, while Munc13-3 was found only recently to function as a developmentally up-regulated mediator of tight coupling. On the other hand, a highly plastic synapse was found to operate at loose coupling in the matured hippocampus. Together these findings suggest that the coupling topography and its regulation is a specificity of the type of synapse. However, to definitely draw such conclusion our knowledge of functional active zone topographies of different types of synapses in different areas of the mammalian brain is too incomplete.
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Affiliation(s)
- Grit Bornschein
- Carl-Ludwig Institute for Physiology, Medical Faculty, University of Leipzig, Leipzig, Germany
| | - Hartmut Schmidt
- Carl-Ludwig Institute for Physiology, Medical Faculty, University of Leipzig, Leipzig, Germany
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He Y, Kulasiri D, Liang J. A mathematical model of synaptotagmin 7 revealing functional importance of short-term synaptic plasticity. Neural Regen Res 2019; 14:621-631. [PMID: 30632502 PMCID: PMC6352580 DOI: 10.4103/1673-5374.247466] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Synaptotagmin 7 (Syt7), a presynaptic calcium sensor, has a significant role in the facilitation in short-term synaptic plasticity: Syt7 knock out mice show a significant reduction in the facilitation. The functional importance of short-term synaptic plasticity such as facilitation is not well understood. In this study, we attempt to investigate the potential functional relationship between the short-term synaptic plasticity and postsynaptic response by developing a mathematical model that captures the responses of both wild-type and Syt7 knock-out mice. We then studied the model behaviours of wild-type and Syt7 knock-out mice in response to multiple input action potentials. These behaviors could establish functional importance of short-term plasticity in regulating the postsynaptic response and related synaptic properties. In agreement with previous modeling studies, we show that release sites are governed by non-uniform release probabilities of neurotransmitters. The structure of non-uniform release of neurotransmitters makes short-term synaptic plasticity to act as a high-pass filter. We also propose that Syt7 may be a modulator for the long-term changes of postsynaptic response that helps to train the target frequency of the filter. We have developed a mathematical model of short-term plasticity which explains the experimental data.
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Affiliation(s)
- Yao He
- Center for Advanced Computational Solutions (C-fACS), Lincoln University, Christchurch, New Zealand
| | - Don Kulasiri
- Center for Advanced Computational Solutions (C-fACS), Lincoln University, Christchurch, New Zealand
| | - Jingyi Liang
- Center for Advanced Computational Solutions (C-fACS), Lincoln University, Christchurch, New Zealand
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Neher E, Brose N. Dynamically Primed Synaptic Vesicle States: Key to Understand Synaptic Short-Term Plasticity. Neuron 2018; 100:1283-1291. [DOI: 10.1016/j.neuron.2018.11.024] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Revised: 10/26/2018] [Accepted: 11/13/2018] [Indexed: 01/09/2023]
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Presenilin-mediated cleavage of APP regulates synaptotagmin-7 and presynaptic plasticity. Nat Commun 2018; 9:4780. [PMID: 30429473 PMCID: PMC6235831 DOI: 10.1038/s41467-018-06813-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Accepted: 09/19/2018] [Indexed: 11/09/2022] Open
Abstract
Mutations of the intramembrane protease presenilin (PS) or of its main substrate, the amyloid precursor protein (APP), cause early-onset form of Alzheimer disease. PS and APP interact with proteins of the neurotransmitter release machinery without identified functional consequences. Here we report that genetic deletion of PS markedly decreases the presynaptic levels of the Ca2+ sensor synaptotagmin-7 (Syt7) leading to impaired synaptic facilitation and replenishment of synaptic vesicles. The regulation of Syt7 expression by PS occurs post-transcriptionally and depends on γ-secretase proteolytic activity. It requires the substrate APP as revealed by the combined genetic invalidation of APP and PS1, and in particular the APP-Cterminal fragments which interact with Syt7 and accumulate in synaptic terminals under pharmacological or genetic inhibition of γ-secretase. Thus, we uncover a role of PS in presynaptic mechanisms, through APP cleavage and regulation of Syt7, that highlights aberrant synaptic vesicle processing as a possible new pathway in AD. Mutations in presenilin, which cleaves amyloid precursor protein, cause familial Alzheimer’s Disease. Here, the authors show that loss of presenilin leads to loss of synaptotagmin 7, leading to impaired presynaptic release.
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