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Nair AG, Bollmohr N, Schökle L, Keim J, Melero JMM, Müller M. Presynaptic quantal size enhancement counteracts post-tetanic release depression. J Physiol 2024. [PMID: 39183664 DOI: 10.1113/jp286176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2024] [Accepted: 07/30/2024] [Indexed: 08/27/2024] Open
Abstract
Repetitive synaptic stimulation can induce different forms of synaptic plasticity but may also limit the robustness of synaptic transmission by exhausting key resources. Little is known about how synaptic transmission is stabilized after high-frequency stimulation. In the present study, we observed that tetanic stimulation of the Drosophila neuromuscular junction (NMJ) decreases quantal content, release-ready vesicle pool size and synaptic vesicle density for minutes after stimulation. This was accompanied by a pronounced increase in quantal size. Interestingly, action potential-evoked synaptic transmission remained largely unchanged. EPSC amplitude fluctuation analysis confirmed the post-tetanic increase in quantal size and the decrease in quantal content, suggesting that the quantal size increase counteracts release depression to maintain evoked transmission. The magnitude of the post-tetanic quantal size increase and release depression correlated with stimulation frequency and duration, indicating activity-dependent stabilization of synaptic transmission. The post-tetanic quantal size increase persisted after genetic ablation of the glutamate receptor subunits GluRIIA or GluRIIB, and glutamate receptor calcium permeability, as well as blockade of postsynaptic calcium channels. By contrast, it was strongly attenuated by pharmacological or presynaptic genetic perturbation of the GTPase dynamin. Similar observations were made after inhibition of the H+-ATPase, suggesting that the quantal size increase is presynaptically driven. Additionally, dynamin and H+-ATPase perturbation resulted in a post-tetanic decrease in evoked amplitudes. Finally, we observed an increase in synaptic vesicle diameter after tetanic stimulation. Thus, a presynaptically-driven quantal size increase, likely mediated by larger synaptic vesicles, counterbalances post-tetanic release depression, thereby conferring robustness to synaptic transmission on the minute time scale. KEY POINTS: Many synapses transmit robustly after sustained activity despite the limitation of key resources, such as release-ready synaptic vesicles. We report robust synaptic transmission after sustained high-frequency stimulation of the Drosophila neuromuscular junction despite a reduction in release-ready vesicle number. An increased postsynaptic response to individual vesicles, likely driven by an increase in vesicle size due to endocytosis defects, stabilizes synaptic efficacy for minutes after sustained activity. Our study provides novel insights into the mechanisms governing synaptic stability after sustained neural activity.
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Affiliation(s)
- Anu G Nair
- Department of Molecular Life Sciences, University of Zurich, Zurich, Switzerland
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
- Present address: Roche Pharma Research and Early Development, Basel, Switzerland
| | - Nasrin Bollmohr
- Department of Molecular Life Sciences, University of Zurich, Zurich, Switzerland
- Neuroscience Center Zurich, University of Zurich/ETH Zurich, Zurich, Switzerland
| | - Levin Schökle
- Department of Molecular Life Sciences, University of Zurich, Zurich, Switzerland
| | - Jennifer Keim
- Department of Molecular Life Sciences, University of Zurich, Zurich, Switzerland
- Present address: AbbVie AG, Cham, Switzerland
| | | | - Martin Müller
- Department of Molecular Life Sciences, University of Zurich, Zurich, Switzerland
- Neuroscience Center Zurich, University of Zurich/ETH Zurich, Zurich, Switzerland
- University Research Priority Program (URPP), Adaptive Brain Circuits in Development and Learning (AdaBD), University of Zurich, Zurich, Switzerland
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2
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Takács V, Bardóczi Z, Orosz Á, Major A, Tar L, Berki P, Papp P, Mayer MI, Sebők H, Zsolt L, Sos KE, Káli S, Freund TF, Nyiri G. Synaptic and dendritic architecture of different types of hippocampal somatostatin interneurons. PLoS Biol 2024; 22:e3002539. [PMID: 38470935 PMCID: PMC10959371 DOI: 10.1371/journal.pbio.3002539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2023] [Revised: 03/22/2024] [Accepted: 02/06/2024] [Indexed: 03/14/2024] Open
Abstract
GABAergic inhibitory neurons fundamentally shape the activity and plasticity of cortical circuits. A major subset of these neurons contains somatostatin (SOM); these cells play crucial roles in neuroplasticity, learning, and memory in many brain areas including the hippocampus, and are implicated in several neuropsychiatric diseases and neurodegenerative disorders. Two main types of SOM-containing cells in area CA1 of the hippocampus are oriens-lacunosum-moleculare (OLM) cells and hippocampo-septal (HS) cells. These cell types show many similarities in their soma-dendritic architecture, but they have different axonal targets, display different activity patterns in vivo, and are thought to have distinct network functions. However, a complete understanding of the functional roles of these interneurons requires a precise description of their intrinsic computational properties and their synaptic interactions. In the current study we generated, analyzed, and make available several key data sets that enable a quantitative comparison of various anatomical and physiological properties of OLM and HS cells in mouse. The data set includes detailed scanning electron microscopy (SEM)-based 3D reconstructions of OLM and HS cells along with their excitatory and inhibitory synaptic inputs. Combining this core data set with other anatomical data, patch-clamp electrophysiology, and compartmental modeling, we examined the precise morphological structure, inputs, outputs, and basic physiological properties of these cells. Our results highlight key differences between OLM and HS cells, particularly regarding the density and distribution of their synaptic inputs and mitochondria. For example, we estimated that an OLM cell receives about 8,400, whereas an HS cell about 15,600 synaptic inputs, about 16% of which are GABAergic. Our data and models provide insight into the possible basis of the different functionality of OLM and HS cell types and supply essential information for more detailed functional models of these neurons and the hippocampal network.
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Affiliation(s)
- Virág Takács
- Laboratory of Cerebral Cortex Research, HUN-REN Institute of Experimental Medicine, Budapest, Hungary
| | - Zsuzsanna Bardóczi
- Laboratory of Cerebral Cortex Research, HUN-REN Institute of Experimental Medicine, Budapest, Hungary
| | - Áron Orosz
- Laboratory of Cerebral Cortex Research, HUN-REN Institute of Experimental Medicine, Budapest, Hungary
- János Szentágothai Doctoral School of Neurosciences, Semmelweis University, Budapest, Hungary
| | - Abel Major
- Laboratory of Cerebral Cortex Research, HUN-REN Institute of Experimental Medicine, Budapest, Hungary
| | - Luca Tar
- Laboratory of Cerebral Cortex Research, HUN-REN Institute of Experimental Medicine, Budapest, Hungary
- Roska Tamás Doctoral School of Sciences and Technology, Pázmány Péter Catholic University, Budapest, Hungary
| | - Péter Berki
- Laboratory of Cerebral Cortex Research, HUN-REN Institute of Experimental Medicine, Budapest, Hungary
- János Szentágothai Doctoral School of Neurosciences, Semmelweis University, Budapest, Hungary
| | - Péter Papp
- Laboratory of Cerebral Cortex Research, HUN-REN Institute of Experimental Medicine, Budapest, Hungary
| | - Márton I. Mayer
- Laboratory of Cerebral Cortex Research, HUN-REN Institute of Experimental Medicine, Budapest, Hungary
- János Szentágothai Doctoral School of Neurosciences, Semmelweis University, Budapest, Hungary
| | - Hunor Sebők
- Laboratory of Cerebral Cortex Research, HUN-REN Institute of Experimental Medicine, Budapest, Hungary
| | - Luca Zsolt
- Laboratory of Cerebral Cortex Research, HUN-REN Institute of Experimental Medicine, Budapest, Hungary
| | - Katalin E. Sos
- Laboratory of Cerebral Cortex Research, HUN-REN Institute of Experimental Medicine, Budapest, Hungary
- János Szentágothai Doctoral School of Neurosciences, Semmelweis University, Budapest, Hungary
| | - Szabolcs Káli
- Laboratory of Cerebral Cortex Research, HUN-REN Institute of Experimental Medicine, Budapest, Hungary
| | - Tamás F. Freund
- Laboratory of Cerebral Cortex Research, HUN-REN Institute of Experimental Medicine, Budapest, Hungary
| | - Gábor Nyiri
- Laboratory of Cerebral Cortex Research, HUN-REN Institute of Experimental Medicine, Budapest, Hungary
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3
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Tabassum S, Misrani A, Huang HX, Zhang ZY, Li QW, Long C. Resveratrol Attenuates Chronic Unpredictable Mild Stress-Induced Alterations in the SIRT1/PGC1α/SIRT3 Pathway and Associated Mitochondrial Dysfunction in Mice. Mol Neurobiol 2023; 60:5102-5116. [PMID: 37256428 DOI: 10.1007/s12035-023-03395-8] [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: 11/18/2022] [Accepted: 05/18/2023] [Indexed: 06/01/2023]
Abstract
Environmental challenges, specifically chronic stress, have long been associated with neuropsychiatric disorders, including anxiety and depression. Sirtuin-1 (SIRT1) is a NAD+-dependent deacetylase that is widely distributed in the cortex and is involved in stress responses and neuropsychiatric disorders. Nevertheless, how chronic stress modulates the SIRT1 pathway and associated signaling remains unclear. In this study, we first explored the impact of chronic unpredictable mild stress (CUMS) on the SIRT1/PGC1α/SIRT3 pathway, on GABAergic mechanisms, and on mitophagy, autophagy and apoptosis in mice. We also asked whether activation of SIRT1 by resveratrol (RSV) can attenuate CUMS-induced molecular and behavioral alterations. Two-month-old C57/BL6J mice were subjected to three weeks of CUMS and one week of RSV treatment (30 mg/kg; i.p.) during the third week of CUMS. CUMS caused downregulation of the SIRT1/PGC1α/SIRT3 pathway leading to impaired mitochondrial morphology and function. CUMS also resulted in a reduction in numbers of parvalbumin-positive interneurons and increased oxidative stress leading to reduced expression of autophagy- and mitophagy-related proteins. Strikingly, activation of SIRT1 by RSV ameliorated expression of SIRT1/PGC1α/SIRT3, and also improved mitochondrial function, GABAergic mechanisms, mitophagy, autophagy and apoptosis. RSV also rescued CUMS-induced anxiety-like and depressive-like behavior in mice. Our results raise the compelling possibility that RSV treatment might be a viable therapeutic method of blocking stress-induced behavioral alterations.
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Affiliation(s)
- Sidra Tabassum
- South China Normal University-Panyu Central Hospital Joint Laboratory of Translational Medical Research, Panyu Central Hospital, Guangzhou, 511400, China
- School of Life Sciences, South China Normal University, Guangzhou, 510631, China
| | - Afzal Misrani
- South China Normal University-Panyu Central Hospital Joint Laboratory of Translational Medical Research, Panyu Central Hospital, Guangzhou, 511400, China
- School of Life Sciences, South China Normal University, Guangzhou, 510631, China
| | - Hui-Xian Huang
- South China Normal University-Panyu Central Hospital Joint Laboratory of Translational Medical Research, Panyu Central Hospital, Guangzhou, 511400, China
- School of Life Sciences, South China Normal University, Guangzhou, 510631, China
| | - Zai-Yong Zhang
- Department of Cardiology, Panyu Central Hospital, Guangzhou, 511400, China
- Cardiovascular Institute of Panyu District, Guangzhou, 511400, China
| | - Qiao-Wei Li
- Department of Neurology, Panyu District Central Hospital, Guangzhou, 511400, China
| | - Cheng Long
- South China Normal University-Panyu Central Hospital Joint Laboratory of Translational Medical Research, Panyu Central Hospital, Guangzhou, 511400, China.
- School of Life Sciences, South China Normal University, Guangzhou, 510631, China.
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Hao Y, Liu H, Zeng XT, Wang Y, Zeng WX, Qian KY, Li L, Chi MX, Gao S, Hu Z, Tong XJ. UNC-43/CaMKII-triggered anterograde signals recruit GABA ARs to mediate inhibitory synaptic transmission and plasticity at C. elegans NMJs. Nat Commun 2023; 14:1436. [PMID: 36918518 PMCID: PMC10015018 DOI: 10.1038/s41467-023-37137-0] [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: 07/17/2022] [Accepted: 02/28/2023] [Indexed: 03/16/2023] Open
Abstract
Disturbed inhibitory synaptic transmission has functional impacts on neurodevelopmental and psychiatric disorders. An essential mechanism for modulating inhibitory synaptic transmission is alteration of the postsynaptic abundance of GABAARs, which are stabilized by postsynaptic scaffold proteins and recruited by presynaptic signals. However, how GABAergic neurons trigger signals to transsynaptically recruit GABAARs remains elusive. Here, we show that UNC-43/CaMKII functions at GABAergic neurons to recruit GABAARs and modulate inhibitory synaptic transmission at C. elegans neuromuscular junctions. We demonstrate that UNC-43 promotes presynaptic MADD-4B/Punctin secretion and NRX-1α/Neurexin surface delivery. Together, MADD-4B and NRX-1α recruit postsynaptic NLG-1/Neuroligin and stabilize GABAARs. Further, the excitation of GABAergic neurons potentiates the recruitment of NLG-1-stabilized-GABAARs, which depends on UNC-43, MADD-4B, and NRX-1. These data all support that UNC-43 triggers MADD-4B and NRX-1α, which act as anterograde signals to recruit postsynaptic GABAARs. Thus, our findings elucidate a mechanism for pre- and postsynaptic communication and inhibitory synaptic transmission and plasticity.
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Affiliation(s)
- Yue Hao
- School of Life Science and Technology, ShanghaiTech University, Shanghai, 201210, China
- Institute of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China
- University of Chinese Academy of Sciences, Beijing, 100190, China
| | - Haowen Liu
- Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research (CJCADR), The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Xian-Ting Zeng
- School of Life Science and Technology, ShanghaiTech University, Shanghai, 201210, China
| | - Ya Wang
- College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, 430074, China
| | - Wan-Xin Zeng
- School of Life Science and Technology, ShanghaiTech University, Shanghai, 201210, China
- Institute of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China
- University of Chinese Academy of Sciences, Beijing, 100190, China
| | - Kang-Ying Qian
- School of Life Science and Technology, ShanghaiTech University, Shanghai, 201210, China
- Institute of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China
- University of Chinese Academy of Sciences, Beijing, 100190, China
| | - Lei Li
- Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research (CJCADR), The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Ming-Xuan Chi
- School of Life Science and Technology, ShanghaiTech University, Shanghai, 201210, China
| | - Shangbang Gao
- College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, 430074, China
| | - Zhitao Hu
- Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research (CJCADR), The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Xia-Jing Tong
- School of Life Science and Technology, ShanghaiTech University, Shanghai, 201210, China.
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5
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Naylor DE. In the fast lane: Receptor trafficking during status epilepticus. Epilepsia Open 2023; 8 Suppl 1:S35-S65. [PMID: 36861477 PMCID: PMC10173858 DOI: 10.1002/epi4.12718] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Accepted: 02/23/2023] [Indexed: 03/03/2023] Open
Abstract
Status epilepticus (SE) remains a significant cause of morbidity and mortality and often is refractory to standard first-line treatments. A rapid loss of synaptic inhibition and development of pharmacoresistance to benzodiazepines (BZDs) occurs early during SE, while NMDA and AMPA receptor antagonists remain effective treatments after BZDs have failed. Multimodal and subunit-selective receptor trafficking within minutes to an hour of SE involves GABA-A, NMDA, and AMPA receptors and contributes to shifts in the number and subunit composition of surface receptors with differential impacts on the physiology, pharmacology, and strength of GABAergic and glutamatergic currents at synaptic and extrasynaptic sites. During the first hour of SE, synaptic GABA-A receptors containing γ2 subunits move to the cell interior while extrasynaptic GABA-A receptors with δ subunits are preserved. Conversely, NMDA receptors containing N2B subunits are increased at synaptic and extrasynaptic sites, and homomeric GluA1 ("GluA2-lacking") calcium permeant AMPA receptor surface expression also is increased. Molecular mechanisms, largely driven by NMDA receptor or calcium permeant AMPA receptor activation early during circuit hyperactivity, regulate subunit-specific interactions with proteins involved with synaptic scaffolding, adaptin-AP2/clathrin-dependent endocytosis, endoplasmic reticulum (ER) retention, and endosomal recycling. Reviewed here is how SE-induced shifts in receptor subunit composition and surface representation increase the excitatory to inhibitory imbalance that sustains seizures and fuels excitotoxicity contributing to chronic sequela such as "spontaneous recurrent seizures" (SRS). A role for early multimodal therapy is suggested both for treatment of SE and for prevention of long-term comorbidities.
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Affiliation(s)
- David E Naylor
- VA Greater Los Angeles Healthcare System, Department of Neurology, David Geffen School of Medicine at UCLA, and The Lundquist Institute at Harbor-UCLA Medical Center, Los Angeles, California, USA
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6
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Lukacs IP, Francavilla R, Field M, Hunter E, Howarth M, Horie S, Plaha P, Stacey R, Livermore L, Ansorge O, Tamas G, Somogyi P. Differential effects of group III metabotropic glutamate receptors on spontaneous inhibitory synaptic currents in spine-innervating double bouquet and parvalbumin-expressing dendrite-targeting GABAergic interneurons in human neocortex. Cereb Cortex 2023; 33:2101-2142. [PMID: 35667019 PMCID: PMC9977385 DOI: 10.1093/cercor/bhac195] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2022] [Revised: 04/27/2022] [Accepted: 04/28/2022] [Indexed: 11/12/2022] Open
Abstract
Diverse neocortical GABAergic neurons specialize in synaptic targeting and their effects are modulated by presynaptic metabotropic glutamate receptors (mGluRs) suppressing neurotransmitter release in rodents, but their effects in human neocortex are unknown. We tested whether activation of group III mGluRs by L-AP4 changes GABAA receptor-mediated spontaneous inhibitory postsynaptic currents (sIPSCs) in 2 distinct dendritic spine-innervating GABAergic interneurons recorded in vitro in human neocortex. Calbindin-positive double bouquet cells (DBCs) had columnar "horsetail" axons descending through layers II-V innervating dendritic spines (48%) and shafts, but not somata of pyramidal and nonpyramidal neurons. Parvalbumin-expressing dendrite-targeting cell (PV-DTC) axons extended in all directions innervating dendritic spines (22%), shafts (65%), and somata (13%). As measured, 20% of GABAergic neuropil synapses innervate spines, hence DBCs, but not PV-DTCs, preferentially select spine targets. Group III mGluR activation paradoxically increased the frequency of sIPSCs in DBCs (to median 137% of baseline) but suppressed it in PV-DTCs (median 92%), leaving the amplitude unchanged. The facilitation of sIPSCs in DBCs may result from their unique GABAergic input being disinhibited via network effect. We conclude that dendritic spines receive specialized, diverse GABAergic inputs, and group III mGluRs differentially regulate GABAergic synaptic transmission to distinct GABAergic cell types in human cortex.
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Affiliation(s)
- Istvan P Lukacs
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
| | | | - Martin Field
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
| | - Emily Hunter
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
| | - Michael Howarth
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
| | - Sawa Horie
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
| | - Puneet Plaha
- Department of Neurosurgery, John Radcliffe Hospital, OUH NHS Foundation Trust, Oxford OX3 9DU, UK
| | - Richard Stacey
- Department of Neurosurgery, John Radcliffe Hospital, OUH NHS Foundation Trust, Oxford OX3 9DU, UK
| | - Laurent Livermore
- Department of Neurosurgery, John Radcliffe Hospital, OUH NHS Foundation Trust, Oxford OX3 9DU, UK
| | - Olaf Ansorge
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, UK
| | - Gabor Tamas
- Department of Physiology, Anatomy and Neuroscience, University of Szeged, 6726 Szeged, Hungary
| | - Peter Somogyi
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
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7
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Voltage-clamp evidence of GABA A receptor subunit-specific effects: pharmacodynamic fingerprint of chlornordiazepam, the major active metabolite of mexazolam, as compared to alprazolam, bromazepam, and zolpidem. Pharmacol Rep 2022; 74:956-968. [PMID: 36097257 DOI: 10.1007/s43440-022-00411-x] [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: 06/09/2022] [Revised: 08/25/2022] [Accepted: 08/26/2022] [Indexed: 10/14/2022]
Abstract
BACKGROUND Anxiolytic benzodiazepines, due to their clinical effectiveness, are one of the most prescribed drugs worldwide, despite being associated with sedative effects and impaired psychomotor and cognitive performance. Not every GABAA receptor functions in the same manner. Those containing α1 subunits are associated with sleep regulation and have a greater effect on the sedative-hypnotic benzodiazepines, whereas those containing α2 and/or α3 subunits are associated with anxiety phenomena and have a greater effect on the anxiolytic benzodiazepines. Therefore, characterization of the selectivity profile of anxiolytic drugs could translate into a significant clinical impact. METHODS The present study pharmacodynamically evaluated chlornordiazepam, the main active metabolite of mexazolam, upon GABAA receptors containing α2 and/or α3, anxiety-related, and those containing an α1 subunit, associated with sleep modulation. RESULTS As shown by whole-cell patch-clamp data, chlornordiazepam potentiated GABA-evoked current amplitude in α2 and α3 containing receptors without changing the current amplitude in α1 containing receptors. However, current decay time increased, particularly in GABAA receptors containing α1 subunits. In contrast, other anxiolytic benzodiazepines such as alprazolam, bromazepam, and zolpidem, all increased currents associated with GABAA receptors containing the α1 subunit. CONCLUSIONS This novel evidence demonstrates that mexazolam (through its main metabolite chlornordiazepam) has a "pharmacodynamic fingerprint" that correlates better with an anxiolytic profile and fewer sedative effects, when compared to alprazolam, bromazepam and zolpidem, explaining clinical trial outcomes with these drugs. This also highlights the relevance of the pharmacological selectivity over GABAA receptor subtypes in the selection of benzodiazepines, in addition to their clinical performance and pharmacokinetic characteristics.
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Imam N, Choudhury S, Heinze KG, Schindelin H. Differential modulation of collybistin conformational dynamics by the closely related GTPases Cdc42 and TC10. Front Synaptic Neurosci 2022; 14:959875. [PMID: 35989712 PMCID: PMC9386560 DOI: 10.3389/fnsyn.2022.959875] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Accepted: 07/06/2022] [Indexed: 11/13/2022] Open
Abstract
Interneuronal synaptic transmission relies on the proper spatial organization of presynaptic neurotransmitter release and its reception on the postsynaptic side by cognate neurotransmitter receptors. Neurotransmitter receptors are incorporated into and arranged within the plasma membrane with the assistance of scaffolding and adaptor proteins. At inhibitory GABAergic postsynapses, collybistin, a neuronal adaptor protein, recruits the scaffolding protein gephyrin and interacts with various neuronal factors including cell adhesion proteins of the neuroligin family, the GABA A receptor α2-subunit and the closely related small GTPases Cdc42 and TC10 (RhoQ). Most collybistin splice variants harbor an N-terminal SH3 domain and exist in an autoinhibited/closed state. Cdc42 and TC10, despite sharing 67.4% amino acid sequence identity, interact differently with collybistin. Here, we delineate the molecular basis of the collybistin conformational activation induced by TC10 with the aid of recently developed collybistin FRET sensors. Time-resolved fluorescence-based FRET measurements reveal that TC10 binds to closed/inactive collybistin leading to relief of its autoinhibition, contrary to Cdc42, which only interacts with collybistin when forced into an open state by the introduction of mutations destabilizing the closed state of collybistin. Taken together, our data describe a TC10-driven signaling mechanism in which collybistin switches from its autoinhibited closed state to an open/active state.
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Affiliation(s)
- Nasir Imam
- Institute of Structural Biology, Rudolf Virchow Center for Integrative and Translational Bioimaging, University of Würzburg, Würzburg, Germany
| | - Susobhan Choudhury
- Molecular Microscopy, Rudolf Virchow Center for Integrative and Translational Bioimaging, University of Würzburg, Würzburg, Germany
| | - Katrin G. Heinze
- Molecular Microscopy, Rudolf Virchow Center for Integrative and Translational Bioimaging, University of Würzburg, Würzburg, Germany
| | - Hermann Schindelin
- Institute of Structural Biology, Rudolf Virchow Center for Integrative and Translational Bioimaging, University of Würzburg, Würzburg, Germany
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9
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Why won't it stop? The dynamics of benzodiazepine resistance in status epilepticus. Nat Rev Neurol 2022; 18:428-441. [PMID: 35538233 DOI: 10.1038/s41582-022-00664-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/19/2022] [Indexed: 11/08/2022]
Abstract
Status epilepticus is a life-threatening neurological emergency that affects both adults and children. Approximately 36% of episodes of status epilepticus do not respond to the current preferred first-line treatment, benzodiazepines. The proportion of episodes that are refractory to benzodiazepines is higher in low-income and middle-income countries (LMICs) than in high-income countries (HICs). Evidence suggests that longer episodes of status epilepticus alter brain physiology, thereby contributing to the emergence of benzodiazepine resistance. Such changes include alterations in GABAA receptor function and in the transmembrane gradient for chloride, both of which erode the ability of benzodiazepines to enhance inhibitory synaptic signalling. Often, current management guidelines for status epilepticus do not account for these duration-related changes in pathophysiology, which might differentially impact individuals in LMICs, where the average time taken to reach medical attention is longer than in HICs. In this Perspective article, we aim to combine clinical insights and the latest evidence from basic science to inspire a new, context-specific approach to efficiently managing status epilepticus.
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10
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Barnes CL, Bonnéry D, Cardona A. Synaptic counts approximate synaptic contact area in Drosophila. PLoS One 2022; 17:e0266064. [PMID: 35377898 PMCID: PMC8979427 DOI: 10.1371/journal.pone.0266064] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Accepted: 03/12/2022] [Indexed: 11/19/2022] Open
Abstract
The pattern of synaptic connections among neurons defines the circuit structure, which constrains the computations that a circuit can perform. The strength of synaptic connections is costly to measure yet important for accurate circuit modeling. Synaptic surface area has been shown to correlate with synaptic strength, yet in the emerging field of connectomics, most studies rely instead on the counts of synaptic contacts between two neurons. Here we quantified the relationship between synaptic count and synaptic area as measured from volume electron microscopy of the larval Drosophila central nervous system. We found that the total synaptic surface area, summed across all synaptic contacts from one presynaptic neuron to a postsynaptic one, can be accurately predicted solely from the number of synaptic contacts, for a variety of neurotransmitters. Our findings support the use of synaptic counts for approximating synaptic strength when modeling neural circuits.
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Affiliation(s)
- Christopher L. Barnes
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Daniel Bonnéry
- Epidemiology and Modelling Group, Department of Plant Sciences, University of Cambridge, Cambridge, United Kingdom
| | - Albert Cardona
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
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11
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Beltrán-Matas P, Castilho Á, Tencer B, Veruki ML, Hartveit E. Inhibitory inputs to an inhibitory interneuron: Spontaneous postsynaptic currents and GABA A receptors of A17 amacrine cells in the rat retina. Eur J Neurosci 2022; 55:1442-1470. [PMID: 35236011 PMCID: PMC9314042 DOI: 10.1111/ejn.15634] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 02/25/2022] [Accepted: 02/26/2022] [Indexed: 11/29/2022]
Abstract
Amacrine cells constitute a large and heterogenous group of inhibitory interneurons in the retina. The A17 amacrine plays an important role for visual signaling in the rod pathway microcircuit of the mammalian retina. It receives excitatory input from rod bipolar cells and provides feedback inhibition to the same cells. However, from ultrastructural investigations, there is evidence for input to A17s from other types of amacrine cells, presumably inhibitory, but there is a lack of information about the identity and functional properties of the synaptic receptors and how inhibition contributes to the integrative properties of A17s. Here, we studied the biophysical and pharmacological properties of GABAergic spontaneous inhibitory postsynaptic currents (spIPSCs) and GABAA receptors of A17 amacrines, using whole-cell and outside-out patch recordings from rat retinal slices. The spIPSCs displayed fast onsets (10-90% rise time ~740 μs) and double-exponential decays (τfast ~4.5 ms [43% of amplitude]; τslow ~22 ms). Ultrafast application of brief pulses of GABA (3 mM) to patches evoked responses with deactivation kinetics best fitted by a triple-exponential function (τ1 ~5.3 ms [55% of amplitude]; τ2 ~48 ms [32% amplitude]; τ3 ~187 ms). Non-stationary noise analysis of spIPSCs and patch responses yielded single-channel conductances of ~21 and ~25 pS, respectively. Pharmacological analysis suggested that the spIPSCs are mediated by receptors with an α1βγ2 subunit composition and the somatic receptors have an α2βγ2 and/or α3βγ2 composition. These results demonstrate the presence of synaptic GABAA receptors on A17s, which may play an important role in signal integration in these cells.
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Affiliation(s)
| | - Áurea Castilho
- Department of Biomedicine, University of Bergen, Bergen, Norway
| | - Barbora Tencer
- Department of Biomedicine, University of Bergen, Bergen, Norway
| | | | - Espen Hartveit
- Department of Biomedicine, University of Bergen, Bergen, Norway
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12
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Janach GMS, Böhm M, Döhne N, Kim HR, Rosário M, Strauss U. Interferon-γ enhances neocortical synaptic inhibition by promoting membrane association and phosphorylation of GABA A receptors in a protein kinase C-dependent manner. Brain Behav Immun 2022; 101:153-164. [PMID: 34998939 DOI: 10.1016/j.bbi.2022.01.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 12/11/2021] [Accepted: 01/03/2022] [Indexed: 12/16/2022] Open
Abstract
Interferon-γ (IFN-γ), an important mediator of the antiviral immune response, can also act as a neuromodulator. CNS IFN-γ levels rise acutely in response to infection and therapeutically applied IFN-γ provokes CNS related side effects. Moreover, IFN-γ plays a key role in neurophysiological processes and a variety of chronic neurological and neuropsychiatric conditions. To close the gap between basic research, behavioral implications and clinical applicability, knowledge of the mechanism behind IFN-γ related changes in brain function is crucial. Here, we studied the underlying mechanism of acutely augmented neocortical inhibition by IFN-γ (1.000 IU ml-1) in layer 5 pyramidal neurons of male Wistar rats. We demonstrate postsynaptic mediation of IFN-γ augmented inhibition by pressure application of GABA and analysis of paired pulse ratios. IFN-γ increases membrane presence of GABAAR γ2, as quantified by cell surface biotinylation and functional synaptic GABAAR number, as determined by peak-scaled non-stationary noise analysis. The increase in functional receptor number was comparable to the increase in underlying miniature inhibitory postsynaptic current (mIPSC) amplitudes. Blockage of putative intracellular mediators, namely phosphoinositide 3-kinase and protein kinase C (PKC) by Wortmannin and Calphostin C, respectively, revealed PKC-dependency of the pro-inhibitory IFN-γ effect. This was corroborated by increased serine phosphorylation of P-serine PKC motifs on GABAAR γ2 upon IFN-γ application. GABAAR single channel conductance, intracellular chloride levels and GABAAR driving force are unlikely to contribute to the effect, as shown by single channel recordings and chloride imaging. The effect of IFN-γ on mIPSC amplitudes was similar in female and male rats, suggesting a gender-independent mechanism of action. Collectively, these results indicate a novel mechanism for the regulation of inhibition by IFN-γ, which could impact on neocortical function and therewith behavior.
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Affiliation(s)
- Gabriel M S Janach
- Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Cell Biology and Neurobiology, Charitéplatz 1, 10117 Berlin, Germany
| | - Maximilian Böhm
- Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Cell Biology and Neurobiology, Charitéplatz 1, 10117 Berlin, Germany
| | - Noah Döhne
- Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Cell Biology and Neurobiology, Charitéplatz 1, 10117 Berlin, Germany
| | - Ha-Rang Kim
- Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Cell Biology and Neurobiology, Charitéplatz 1, 10117 Berlin, Germany; CNRS, Interdisciplinary Institute for Neuroscience, UMR 5297, University of Bordeaux, Bordeaux, France
| | - Marta Rosário
- Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Cell Biology and Neurobiology, Charitéplatz 1, 10117 Berlin, Germany
| | - Ulf Strauss
- Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Cell Biology and Neurobiology, Charitéplatz 1, 10117 Berlin, Germany.
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13
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Systemic LPS-induced microglial activation results in increased GABAergic tone: A mechanism of protection against neuroinflammation in the medial prefrontal cortex in mice. Brain Behav Immun 2022; 99:53-69. [PMID: 34582995 DOI: 10.1016/j.bbi.2021.09.017] [Citation(s) in RCA: 37] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Revised: 09/19/2021] [Accepted: 09/21/2021] [Indexed: 02/01/2023] Open
Abstract
Neuroinflammation with excess microglial activation and synaptic dysfunction are early symptoms of most neurological diseases. However, how microglia-associated neuroinflammation regulates synaptic activity remains obscure. We report here that acute neuroinflammation induced by intraperitoneal injection of lipopolysaccharide (LPS) results in cell-type-specific increases in inhibitory postsynaptic currents in the glutamatergic, but not the GABAergic, neurons of medial prefrontal cortex (mPFC), coinciding with excessive microglial activation. LPS causes upregulation in levels of GABAAR subunits, glutamine synthetase and vesicular GABA transporter, and downregulation in brain-derived neurotrophic factor (BDNF) and its receptor, pTrkB. Blockage of microglial activation by minocycline ameliorates LPS-induced abnormal expression of GABA signaling-related proteins and activity of synaptic and network. Moreover, minocycline prevents the mice from LPS-induced aberrant behavior, such as a reduction in total distance and time spent in the centre in the open field test; decreases in entries into the open arm of elevated-plus maze and in consumption of sucrose; increased immobility in the tail suspension test. Furthermore, upregulation of GABA signaling by tiagabine also prevents LPS-induced microglial activation and aberrant behavior. This study illustrates a mode of bidirectional constitutive signaling between the neural and immune compartments of the brain, and suggests that the mPFC is an important area for brain-immune system communication. Moreover, the present study highlights GABAergic signaling as a key therapeutic target for mitigating neuroinflammation-induced abnormal synaptic activity in the mPFC, together with the associated behavioral abnormalities.
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14
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Garcia JD, Gookin SE, Crosby KC, Schwartz SL, Tiemeier E, Kennedy MJ, Dell'Acqua ML, Herson PS, Quillinan N, Smith KR. Stepwise disassembly of GABAergic synapses during pathogenic excitotoxicity. Cell Rep 2021; 37:110142. [PMID: 34936876 PMCID: PMC8824488 DOI: 10.1016/j.celrep.2021.110142] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Revised: 09/17/2021] [Accepted: 11/23/2021] [Indexed: 12/16/2022] Open
Abstract
GABAergic synaptic inhibition controls neuronal firing, excitability, and synaptic plasticity to regulate neuronal circuits. Following an acute excitotoxic insult, inhibitory synapses are eliminated, reducing synaptic inhibition, elevating circuit excitability, and contributing to the pathophysiology of brain injuries. However, mechanisms that drive inhibitory synapse disassembly and elimination are undefined. We find that inhibitory synapses are disassembled in a sequential manner following excitotoxicity: GABAARs undergo rapid nanoscale rearrangement and are dispersed from the synapse along with presynaptic active zone components, followed by the gradual removal of the gephyrin scaffold, prior to complete elimination of the presynaptic terminal. GABAAR nanoscale reorganization and synaptic declustering depends on calcineurin signaling, whereas disassembly of gephyrin relies on calpain activation, and blockade of both enzymes preserves inhibitory synapses after excitotoxic insult. Thus, inhibitory synapse disassembly occurs rapidly, with nanoscale precision, in a stepwise manner and most likely represents a critical step in the progression of hyperexcitability following excitotoxicity.
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Affiliation(s)
- Joshua D Garcia
- Department of Pharmacology, University of Colorado School of Medicine, Anschutz Medical Campus, 12800 East 19th Avenue, Aurora, CO 80045, USA
| | - Sara E Gookin
- Department of Pharmacology, University of Colorado School of Medicine, Anschutz Medical Campus, 12800 East 19th Avenue, Aurora, CO 80045, USA
| | - Kevin C Crosby
- Department of Pharmacology, University of Colorado School of Medicine, Anschutz Medical Campus, 12800 East 19th Avenue, Aurora, CO 80045, USA
| | - Samantha L Schwartz
- Department of Pharmacology, University of Colorado School of Medicine, Anschutz Medical Campus, 12800 East 19th Avenue, Aurora, CO 80045, USA
| | - Erika Tiemeier
- Department of Anesthesiology, Neuronal Injury Program, University of Colorado School of Medicine, Anschutz Medical Campus, 12801 East 17th Avenue, Aurora, CO 80045, USA
| | - Matthew J Kennedy
- Department of Pharmacology, University of Colorado School of Medicine, Anschutz Medical Campus, 12800 East 19th Avenue, Aurora, CO 80045, USA
| | - Mark L Dell'Acqua
- Department of Pharmacology, University of Colorado School of Medicine, Anschutz Medical Campus, 12800 East 19th Avenue, Aurora, CO 80045, USA
| | - Paco S Herson
- Department of Pharmacology, University of Colorado School of Medicine, Anschutz Medical Campus, 12800 East 19th Avenue, Aurora, CO 80045, USA; Department of Anesthesiology, Neuronal Injury Program, University of Colorado School of Medicine, Anschutz Medical Campus, 12801 East 17th Avenue, Aurora, CO 80045, USA
| | - Nidia Quillinan
- Department of Anesthesiology, Neuronal Injury Program, University of Colorado School of Medicine, Anschutz Medical Campus, 12801 East 17th Avenue, Aurora, CO 80045, USA
| | - Katharine R Smith
- Department of Pharmacology, University of Colorado School of Medicine, Anschutz Medical Campus, 12800 East 19th Avenue, Aurora, CO 80045, USA.
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15
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Maynard S, Rostaing P, Schaefer N, Gemin O, Candat A, Dumoulin A, Villmann C, Triller A, Specht CG. Identification of a stereotypic molecular arrangement of endogenous glycine receptors at spinal cord synapses. eLife 2021; 10:74441. [PMID: 34878402 PMCID: PMC8752092 DOI: 10.7554/elife.74441] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Accepted: 11/15/2021] [Indexed: 11/30/2022] Open
Abstract
Precise quantitative information about the molecular architecture of synapses is essential to understanding the functional specificity and downstream signaling processes at specific populations of synapses. Glycine receptors (GlyRs) are the primary fast inhibitory neurotransmitter receptors in the spinal cord and brainstem. These inhibitory glycinergic networks crucially regulate motor and sensory processes. Thus far, the nanoscale organization of GlyRs underlying the different network specificities has not been defined. Here, we have quantitatively characterized the molecular arrangement and ultra-structure of glycinergic synapses in spinal cord tissue using quantitative super-resolution correlative light and electron microscopy. We show that endogenous GlyRs exhibit equal receptor-scaffold occupancy and constant packing densities of about 2000 GlyRs µm-2 at synapses across the spinal cord and throughout adulthood, even though ventral horn synapses have twice the total copy numbers, larger postsynaptic domains, and more convoluted morphologies than dorsal horn synapses. We demonstrate that this stereotypic molecular arrangement is maintained at glycinergic synapses in the oscillator mouse model of the neuromotor disease hyperekplexia despite a decrease in synapse size, indicating that the molecular organization of GlyRs is preserved in this hypomorph. We thus conclude that the morphology and size of inhibitory postsynaptic specializations rather than differences in GlyR packing determine the postsynaptic strength of glycinergic neurotransmission in motor and sensory spinal cord networks.
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Affiliation(s)
- Stephanie Maynard
- Institut de Biologie de l'ENS (IBENS), PSL University, Paris, France
| | - Philippe Rostaing
- Institut de Biologie de l'ENS (IBENS), PSL University, Paris, France
| | - Natascha Schaefer
- Institute for Clinical Neurobiology, University of Wuerzburg, Wuerzburg, Germany
| | - Olivier Gemin
- Institut de Biologie de l'ENS (IBENS), PSL University, Paris, France
| | - Adrien Candat
- Institut de Biologie de l'ENS (IBENS), PSL University, Paris, France
| | - Andréa Dumoulin
- Institut de Biologie de l'ENS (IBENS), PSL University, Paris, France
| | - Carmen Villmann
- Institute for Clinical Neurobiology, University of Wuerzburg, Wuerzburg, Germany
| | - Antoine Triller
- Institut de Biologie de l'ENS (IBENS), PSL University, Paris, France
| | - Christian G Specht
- Diseases and Hormones of the Nervous System (DHNS), Inserm U1195, Université Paris-Saclay, Paris, France
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16
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Aguado-García A, Priego-Espinosa DA, Aldana A, Darszon A, Martínez-Mekler G. Mathematical model reveals that heterogeneity in the number of ion transporters regulates the fraction of mouse sperm capacitation. PLoS One 2021; 16:e0245816. [PMID: 34793454 PMCID: PMC8601445 DOI: 10.1371/journal.pone.0245816] [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: 12/26/2020] [Accepted: 10/20/2021] [Indexed: 12/03/2022] Open
Abstract
Capacitation is a complex maturation process mammalian sperm must undergo in the female genital tract to be able to fertilize an egg. This process involves, amongst others, physiological changes in flagellar beating pattern, membrane potential, intracellular ion concentrations and protein phosphorylation. Typically, in a capacitation medium, only a fraction of sperm achieve this state. The cause for this heterogeneous response is still not well understood and remains an open question. Here, one of our principal results is to develop a discrete regulatory network, with mostly deterministic dynamics in conjunction with some stochastic elements, for the main biochemical and biophysical processes involved in the early events of capacitation. The model criterion for capacitation requires the convergence of specific levels of a select set of nodes. Besides reproducing several experimental results and providing some insight on the network interrelations, the main contribution of the model is the suggestion that the degree of variability in the total amount and individual number of ion transporters among spermatozoa regulates the fraction of capacitated spermatozoa. This conclusion is consistent with recently reported experimental results. Based on this mathematical analysis, experimental clues are proposed for the control of capacitation levels. Furthermore, cooperative and interference traits that become apparent in the modelling among some components also call for future theoretical and experimental studies.
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Affiliation(s)
- Alejandro Aguado-García
- Instituto de Ciencias Básicas y Aplicadas, Universidad Autónoma del Estado de Morelos, Cuernavaca, Morelos, México
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México
| | | | - Andrés Aldana
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México
- Centro de Ciencias de la Complejidad, Universidad Nacional Autónoma de México, CDMX, México
| | - Alberto Darszon
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México
| | - Gustavo Martínez-Mekler
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México
- Centro de Ciencias de la Complejidad, Universidad Nacional Autónoma de México, CDMX, México
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17
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Tonotopic Specializations in Number, Size, and Reversal Potential of GABAergic Inputs Fine-Tune Temporal Coding at Avian Cochlear Nucleus. J Neurosci 2021; 41:8904-8916. [PMID: 34518306 DOI: 10.1523/jneurosci.0884-21.2021] [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: 04/23/2021] [Revised: 08/31/2021] [Accepted: 09/04/2021] [Indexed: 11/21/2022] Open
Abstract
GABAergic inhibition in neurons plays a critical role in determining the output of neural circuits. Neurons in avian nucleus magnocellularis (NM) use several tonotopic-region-dependent specializations to relay the timing information of sound in the auditory nerve to higher auditory nuclei. Previously, we showed that feedforward GABAergic inhibition in NM has a different dependence on the level of auditory nerve activity, with the low-frequency region having a low-threshold and linear relationship, while the high-frequency region has a high-threshold and step-like relationship. However, it remains unclear how the GABAergic synapses are tonotopically regulated and interact with other specializations of NM neurons. In this study, we examined GABAergic transmission in the NM of chickens of both sexes and explored its contributions to the temporal coding of sound at each tonotopic region. We found that the number and size of unitary GABAergic currents and their reversal potential were finely tuned at each tonotopic region in the NM. At the lower-frequency region, unitary GABAergic currents were larger in number but smaller in size. In addition, their reversal potential was close to the resting potential of neurons, which enabled reliable inhibition despite the smaller potassium conductance. At the higher-frequency region, on the other hand, unitary GABAergic currents were fewer, larger, and highly depolarizing, which enabled powerful inhibition via activating the large potassium conductance. Thus, we propose that GABAergic synapses are coordinated with the characteristics of excitatory synapses and postsynaptic neurons, ensuring the temporal coding for wide frequency and intensity ranges.SIGNIFICANCE STATEMENT We found in avian cochlear nucleus that the number and size of unitary GABAergic inputs differed among tonotopic regions and correlated to respective excitatory inputs; it was larger in number but smaller in size for neurons tuned to lower-frequency sound. Furthermore, GABAergic reversal potential also differed among the regions in accordance with the size of Kv1 current; it was less depolarized in the lower-frequency neurons with smaller Kv1 current. These differentiations of GABAergic transmission maximized the effects of inhibition at each tonotopic region, ensuring precise and reliable temporal coding across frequencies and intensities. Our results emphasize the importance of optimizing characteristics of GABAergic transmission within individual neurons for proper neural circuit function.
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18
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Metzdorf K, Fricke S, Balia MT, Korte M, Zagrebelsky M. Nogo-A Modulates the Synaptic Excitation of Hippocampal Neurons in a Ca 2+-Dependent Manner. Cells 2021; 10:cells10092299. [PMID: 34571950 PMCID: PMC8467072 DOI: 10.3390/cells10092299] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 08/27/2021] [Accepted: 08/30/2021] [Indexed: 11/16/2022] Open
Abstract
A tight regulation of the balance between inhibitory and excitatory synaptic transmission is a prerequisite for synaptic plasticity in neuronal networks. In this context, the neurite growth inhibitor membrane protein Nogo-A modulates synaptic plasticity, strength, and neurotransmitter receptor dynamics. However, the molecular mechanisms underlying these actions are unknown. We show that Nogo-A loss-of-function in primary mouse hippocampal cultures by application of a function-blocking antibody leads to higher excitation following a decrease in GABAARs at inhibitory and an increase in the GluA1, but not GluA2 AMPAR subunit at excitatory synapses. This unbalanced regulation of AMPAR subunits results in the incorporation of Ca2+-permeable GluA2-lacking AMPARs and increased intracellular Ca2+ levels due to a higher Ca2+ influx without affecting its release from the internal stores. Increased neuronal activation upon Nogo-A loss-of-function prompts the phosphorylation of the transcription factor CREB and the expression of c-Fos. These results contribute to the understanding of the molecular mechanisms underlying the regulation of the excitation/inhibition balance and thereby of plasticity in the brain.
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Affiliation(s)
- Kristin Metzdorf
- Division of Cellular Neurobiology, Zoological Institute, TU Braunschweig, D-38106 Braunschweig, Germany; (K.M.); (M.T.B.); (M.K.)
- Helmholtz Centre for Infection Research, AG NIND, Inhoffenstr. 7, D-38124 Braunschweig, Germany
| | - Steffen Fricke
- Division of Cell Physiology, Zoological Institute, TU Braunschweig, D-38106 Braunschweig, Germany;
| | - Maria Teresa Balia
- Division of Cellular Neurobiology, Zoological Institute, TU Braunschweig, D-38106 Braunschweig, Germany; (K.M.); (M.T.B.); (M.K.)
| | - Martin Korte
- Division of Cellular Neurobiology, Zoological Institute, TU Braunschweig, D-38106 Braunschweig, Germany; (K.M.); (M.T.B.); (M.K.)
- Helmholtz Centre for Infection Research, AG NIND, Inhoffenstr. 7, D-38124 Braunschweig, Germany
| | - Marta Zagrebelsky
- Division of Cellular Neurobiology, Zoological Institute, TU Braunschweig, D-38106 Braunschweig, Germany; (K.M.); (M.T.B.); (M.K.)
- Correspondence: ; Tel.: +49-(0)-531-3913225
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19
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Gemin O, Serna P, Zamith J, Assendorp N, Fossati M, Rostaing P, Triller A, Charrier C. Unique properties of dually innervated dendritic spines in pyramidal neurons of the somatosensory cortex uncovered by 3D correlative light and electron microscopy. PLoS Biol 2021; 19:e3001375. [PMID: 34428203 PMCID: PMC8415616 DOI: 10.1371/journal.pbio.3001375] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 09/03/2021] [Accepted: 07/29/2021] [Indexed: 01/04/2023] Open
Abstract
Pyramidal neurons (PNs) are covered by thousands of dendritic spines receiving excitatory synaptic inputs. The ultrastructure of dendritic spines shapes signal compartmentalization, but ultrastructural diversity is rarely taken into account in computational models of synaptic integration. Here, we developed a 3D correlative light-electron microscopy (3D-CLEM) approach allowing the analysis of specific populations of synapses in genetically defined neuronal types in intact brain circuits. We used it to reconstruct segments of basal dendrites of layer 2/3 PNs of adult mouse somatosensory cortex and quantify spine ultrastructural diversity. We found that 10% of spines were dually innervated and 38% of inhibitory synapses localized to spines. Using our morphometric data to constrain a model of synaptic signal compartmentalization, we assessed the impact of spinous versus dendritic shaft inhibition. Our results indicate that spinous inhibition is locally more efficient than shaft inhibition and that it can decouple voltage and calcium signaling, potentially impacting synaptic plasticity.
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Affiliation(s)
- Olivier Gemin
- Institut de Biologie de l’Ecole Normale Supérieure (IBENS), CNRS, INSERM, PSL Research University, Paris, France
| | - Pablo Serna
- Institut de Biologie de l’Ecole Normale Supérieure (IBENS), CNRS, INSERM, PSL Research University, Paris, France
- Laboratoire de Physique de l’Ecole Normale Supérieure, ENS, PSL Research University, CNRS, Sorbonne Université, Université Paris-Diderot, Sorbonne Paris Cité, Paris, France
| | - Joseph Zamith
- Institut de Biologie de l’Ecole Normale Supérieure (IBENS), CNRS, INSERM, PSL Research University, Paris, France
| | - Nora Assendorp
- Institut de Biologie de l’Ecole Normale Supérieure (IBENS), CNRS, INSERM, PSL Research University, Paris, France
| | - Matteo Fossati
- Institut de Biologie de l’Ecole Normale Supérieure (IBENS), CNRS, INSERM, PSL Research University, Paris, France
| | - Philippe Rostaing
- Institut de Biologie de l’Ecole Normale Supérieure (IBENS), CNRS, INSERM, PSL Research University, Paris, France
| | - Antoine Triller
- Institut de Biologie de l’Ecole Normale Supérieure (IBENS), CNRS, INSERM, PSL Research University, Paris, France
| | - Cécile Charrier
- Institut de Biologie de l’Ecole Normale Supérieure (IBENS), CNRS, INSERM, PSL Research University, Paris, France
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20
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Inhibitory control in neuronal networks relies on the extracellular matrix integrity. Cell Mol Life Sci 2021; 78:5647-5663. [PMID: 34128077 PMCID: PMC8257544 DOI: 10.1007/s00018-021-03861-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Revised: 05/11/2021] [Accepted: 05/19/2021] [Indexed: 11/14/2022]
Abstract
Inhibitory control is essential for the regulation of neuronal network activity, where excitatory and inhibitory synapses can act synergistically, reciprocally, and antagonistically. Sustained excitation-inhibition (E-I) balance, therefore, relies on the orchestrated adjustment of excitatory and inhibitory synaptic strength. While growing evidence indicates that the brain’s extracellular matrix (ECM) is a crucial regulator of excitatory synapse plasticity, it remains unclear whether and how the ECM contributes to inhibitory control in neuronal networks. Here we studied the simultaneous changes in excitatory and inhibitory connectivity after ECM depletion. We demonstrate that the ECM supports the maintenance of E-I balance by retaining inhibitory connectivity. Quantification of synapses and super-resolution microscopy showed that depletion of the ECM in mature neuronal networks preferentially decreases the density of inhibitory synapses and the size of individual inhibitory postsynaptic scaffolds. The reduction of inhibitory synapse density is partially compensated by the homeostatically increasing synaptic strength via the reduction of presynaptic GABAB receptors, as indicated by patch-clamp measurements and GABAB receptor expression quantifications. However, both spiking and bursting activity in neuronal networks is increased after ECM depletion, as indicated by multi-electrode recordings. With computational modelling, we determined that ECM depletion reduces the inhibitory connectivity to an extent that the inhibitory synapse scaling does not fully compensate for the reduced inhibitory synapse density. Our results indicate that the brain’s ECM preserves the balanced state of neuronal networks by supporting inhibitory control via inhibitory synapse stabilization, which expands the current understanding of brain activity regulation. ![]()
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21
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Yang X, Le Corronc H, Legendre P, Triller A, Specht CG. Differential regulation of glycinergic and GABAergic nanocolumns at mixed inhibitory synapses. EMBO Rep 2021; 22:e52154. [PMID: 34047007 PMCID: PMC8256292 DOI: 10.15252/embr.202052154] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 04/24/2021] [Accepted: 04/30/2021] [Indexed: 12/19/2022] Open
Abstract
Super‐resolution imaging has revealed that key synaptic proteins are dynamically organized within sub‐synaptic domains (SSDs). To examine how different inhibitory receptors are regulated, we carried out dual‐color direct stochastic optical reconstruction microscopy (dSTORM) of GlyRs and GABAARs at mixed inhibitory synapses in spinal cord neurons. We show that endogenous GlyRs and GABAARs as well as their common scaffold protein gephyrin form SSDs that align with pre‐synaptic RIM1/2, thus creating trans‐synaptic nanocolumns. Strikingly, GlyRs and GABAARs occupy different sub‐synaptic spaces, exhibiting only a partial overlap at mixed inhibitory synapses. When network activity is increased by 4‐aminopyridine treatment, the GABAAR copy numbers and the number of GABAAR SSDs are reduced, while GlyRs remain largely unchanged. This differential regulation is likely the result of changes in gephyrin phosphorylation that preferentially occurs outside of SSDs. The activity‐dependent regulation of GABAARs versus GlyRs suggests that different signaling pathways control the receptors' sub‐synaptic clustering. Taken together, our data reinforce the notion that the precise sub‐synaptic organization of GlyRs, GABAARs, and gephyrin has functional consequences for the plasticity of mixed inhibitory synapses.
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Affiliation(s)
- Xiaojuan Yang
- Institute of Biology of the École Normale Supérieure (IBENS), CNRS, Inserm, PSL Research University, Paris, France.,School of Psychology and Cognitive Science, East China Normal University, Shanghai, China
| | - Hervé Le Corronc
- Institute of Biology Paris Seine, Neuroscience Paris Seine, CNRS, Inserm, UPMC, Sorbonne University, Paris, France
| | - Pascal Legendre
- Institute of Biology Paris Seine, Neuroscience Paris Seine, CNRS, Inserm, UPMC, Sorbonne University, Paris, France
| | - Antoine Triller
- Institute of Biology of the École Normale Supérieure (IBENS), CNRS, Inserm, PSL Research University, Paris, France
| | - Christian G Specht
- Institute of Biology of the École Normale Supérieure (IBENS), CNRS, Inserm, PSL Research University, Paris, France.,Diseases and Hormones of the Nervous System (DHNS), Inserm, Université Paris-Saclay, Le Kremlin-Bicêtre, France
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22
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Shumate KM, Tas ST, Kavalali ET, Emeson RB. RNA editing-mediated regulation of calcium-dependent activator protein for secretion (CAPS1) localization and its impact on synaptic transmission. J Neurochem 2021; 158:182-196. [PMID: 33894004 DOI: 10.1111/jnc.15372] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Revised: 03/16/2021] [Accepted: 04/07/2021] [Indexed: 12/12/2022]
Abstract
Calcium-dependent activator protein for secretion 1 (CAPS1) is a SNARE accessory protein that facilitates formation of the SNARE complex to enable neurotransmitter release. Messenger RNAs encoding CAPS1 are subject to a site-specific adenosine-to-inosine (A-to-I) editing event resulting in a glutamate-to-glycine (E-to-G) substitution in the C-terminal domain of the encoded protein product. The C-terminal domain of CAPS1 is necessary for its synaptic enrichment and Cadps RNA editing has been shown previously to enhance the release of neuromodulatory transmitters. Using mutant mouse lines engineered to solely express CAPS1 protein isoforms encoded by either the non-edited or edited Cadps transcript, primary neuronal cultures from mouse hippocampus were used to explore the effect of Cadps editing on neurotransmission and CAPS1 synaptic localization at both glutamatergic and GABAergic synapses. While the editing of Cadps does not alter baseline evoked neurotransmission, it enhances short-term synaptic plasticity, specifically short-term depression, at inhibitory synapses. Cadps editing also alters spontaneous inhibitory neurotransmission. Neurons that solely express edited Cadps have a greater proportion of synapses that contain CAPS1 than neurons that solely express non-edited Cadps for both glutamatergic and GABAergic synapses. Editing of Cadps transcripts is regulated by neuronal activity, as global network stimulation increases the extent of transcripts edited in wild-type hippocampal neurons, whereas chronic network silencing decreases the level of Cadps editing. Taken together, these results provide key insights into the importance of Cadps editing in modulating its own synaptic localization, as well as the modulation of neurotransmission at inhibitory synapses in hippocampal neurons.
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Affiliation(s)
- Kayla M Shumate
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Sadik T Tas
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Ege T Kavalali
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA.,Training Program in Neuroscience, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Ronald B Emeson
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA.,Training Program in Neuroscience, Vanderbilt University School of Medicine, Nashville, TN, USA
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23
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Yiannakas A, Kolatt Chandran S, Kayyal H, Gould N, Khamaisy M, Rosenblum K. Parvalbumin interneuron inhibition onto anterior insula neurons projecting to the basolateral amygdala drives aversive taste memory retrieval. Curr Biol 2021; 31:2770-2784.e6. [PMID: 33930301 DOI: 10.1016/j.cub.2021.04.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 12/08/2020] [Accepted: 04/07/2021] [Indexed: 12/12/2022]
Abstract
Memory retrieval refers to the fundamental ability of organisms to make use of acquired, sometimes inconsistent, information about the world. Although memory acquisition has been studied extensively, the neurobiological mechanisms underlying memory retrieval remain largely unknown. Conditioned taste aversion (CTA) is a robust associative paradigm, through which animals can be trained to express aversion toward innately appetitive tastants. The anterior insula (aIC) is indispensable in the ability of mammals to retrieve associative information regarding tastants that have been previously linked with gastric malaise. Here, we show that CTA memory retrieval promotes cell-type-specific activation in the aIC. Using chemogenetic tools in the aIC, we found that CTA memory acquisition requires activation of excitatory neurons and inhibition of inhibitory neurons, whereas retrieval necessitates activation of both excitatory and inhibitory aIC circuits. CTA memory retrieval at the aIC activates parvalbumin (PV) interneurons and increases synaptic inhibition onto activated pyramidal neurons projecting to the basolateral amygdala (aIC-BLA). Unlike innately appetitive taste memory retrieval, CTA retrieval increases synaptic inhibition onto aIC-BLA-projecting neurons that is dependent on activity in aIC PV interneurons. PV aIC interneurons coordinate CTA memory retrieval and are necessary for its dominance when conflicting internal representations are encountered over time. The reinstatement of CTA memories following extinction is also dependent on activation of aIC PV interneurons, which increase the frequency of inhibition onto aIC-BLA-projecting neurons. This newly described interaction of PV and a subset of excitatory neurons can explain the coherency of aversive memory retrieval, an evolutionary pre-requisite for animal survival.
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Affiliation(s)
- Adonis Yiannakas
- Sagol Department of Neuroscience, University of Haifa, Mount Carmel, Haifa, Israel.
| | | | - Haneen Kayyal
- Sagol Department of Neuroscience, University of Haifa, Mount Carmel, Haifa, Israel
| | - Nathaniel Gould
- Sagol Department of Neuroscience, University of Haifa, Mount Carmel, Haifa, Israel
| | - Mohammad Khamaisy
- Sagol Department of Neuroscience, University of Haifa, Mount Carmel, Haifa, Israel
| | - Kobi Rosenblum
- Sagol Department of Neuroscience, University of Haifa, Mount Carmel, Haifa, Israel; Center for Gene Manipulation in the Brain, University of Haifa, Mount Carmel, Haifa, Israel.
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24
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Local miRNA-Dependent Translational Control of GABA AR Synthesis during Inhibitory Long-Term Potentiation. Cell Rep 2021; 31:107785. [PMID: 32579917 PMCID: PMC7486624 DOI: 10.1016/j.celrep.2020.107785] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Revised: 04/14/2020] [Accepted: 05/28/2020] [Indexed: 12/29/2022] Open
Abstract
Molecular mechanisms underlying plasticity at brain inhibitory synapses remain poorly characterized. Increased postsynaptic clustering of GABAA receptors (GABAARs) rapidly strengthens inhibition during inhibitory long-term potentiation (iLTP). However, it is unclear how synaptic GABAAR clustering is maintained to sustain iLTP. Here, we identify a role for miR376c in regulating the translation of mRNAs encoding the synaptic α1 and γ2 GABAAR subunits, GABRA1 and GABRG2, respectively. Following iLTP induction, transcriptional repression of miR376c is induced through a calcineurin-NFAT-HDAC signaling pathway and promotes increased translation and clustering of synaptic GABAARs. This pathway is essential for the long-term expression of iLTP and is blocked by miR376c overexpression, specifically impairing inhibitory synaptic strength. Finally, we show that local de novo synthesis of synaptic GABAARs occurs exclusively in dendrites and in a miR376c-dependent manner following iLTP. Together, this work describes a local post-transcriptional mechanism that regulates inhibitory synaptic plasticity via miRNA control of dendritic protein synthesis. Clustering of GABAARs at inhibitory synapses is crucial for synaptic inhibition. Rajgor et al. discover that synaptic GABAAR expression is controlled by their local translation, regulated by miR376c. During inhibitory synaptic potentiation, miR376c is downregulated, relieving its translational repression of GABAAR mRNAs and leading to de novo synthesis of dendritic GABAARs.
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25
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Karlocai MR, Heredi J, Benedek T, Holderith N, Lorincz A, Nusser Z. Variability in the Munc13-1 content of excitatory release sites. eLife 2021; 10:67468. [PMID: 33904397 PMCID: PMC8116053 DOI: 10.7554/elife.67468] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 04/26/2021] [Indexed: 01/15/2023] Open
Abstract
The molecular mechanisms underlying the diversity of cortical glutamatergic synapses are still incompletely understood. Here, we tested the hypothesis that presynaptic active zones (AZs) are constructed from molecularly uniform, independent release sites (RSs), the number of which scales linearly with the AZ size. Paired recordings between hippocampal CA1 pyramidal cells and fast-spiking interneurons in acute slices from adult mice followed by quantal analysis demonstrate large variability in the number of RSs (N) at these connections. High-resolution molecular analysis of functionally characterized synapses reveals variability in the content of one of the key vesicle priming factors – Munc13-1 – in AZs that possess the same N. Replica immunolabeling also shows a threefold variability in the total Munc13-1 content of AZs of identical size and a fourfold variability in the size and density of Munc13-1 clusters within the AZs. Our results provide evidence for quantitative molecular heterogeneity of RSs and support a model in which the AZ is built up from variable numbers of molecularly heterogeneous, but independent RSs.
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Affiliation(s)
- Maria Rita Karlocai
- Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Budapest, Hungary
| | - Judit Heredi
- Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Budapest, Hungary
| | - Tünde Benedek
- Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Budapest, Hungary
| | - Noemi Holderith
- Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Budapest, Hungary
| | - Andrea Lorincz
- Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Budapest, Hungary
| | - Zoltan Nusser
- Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Budapest, Hungary
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26
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Marshall P, Garton DR, Taira T, Võikar V, Vilenius C, Kulesskaya N, Rivera C, Andressoo JO. Elevated expression of endogenous glial cell line-derived neurotrophic factor impairs spatial memory performance and raises inhibitory tone in the hippocampus. Eur J Neurosci 2021; 53:2469-2482. [PMID: 33481269 DOI: 10.1111/ejn.15126] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 01/07/2021] [Accepted: 01/19/2021] [Indexed: 01/16/2023]
Abstract
Parvalbumin-positive interneurons (PV+) are a key component of inhibitory networks in the brain and are known to modulate memory and learning by shaping network activity. The mechanisms of PV+ neuron generation and maintenance are not fully understood, yet current evidence suggests that signalling via the glial cell line-derived neurotrophic factor (GDNF) receptor GFRα1 positively modulates the migration and differentiation of PV+ interneurons in the cortex. Whether GDNF also regulates PV+ cells in the hippocampus is currently unknown. In this study, we utilized a Gdnf "hypermorph" mouse model where GDNF is overexpressed from the native gene locus, providing greatly increased spatial and temporal specificity of protein expression over established models of ectopic expression. Gdnfwt/hyper mice demonstrated impairments in long-term memory performance in the Morris water maze test and an increase in inhibitory tone in the hippocampus measured electrophysiologically in acute brain slice preparations. Increased PV+ cell number was confirmed immunohistochemically in the hippocampus and in discrete cortical areas and an increase in epileptic seizure threshold was observed in vivo. The data consolidate prior evidence for the actions of GDNF as a regulator of PV+ cell development in the cortex and demonstrate functional effects upon network excitability via modulation of functional GABAergic signalling and under epileptic challenge.
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Affiliation(s)
- Pepin Marshall
- HiLIFE Neuroscience Centre, University of Helsinki, Helsinki, Finland
| | - Daniel R Garton
- Department of Pharmacology, Faculty of Medicine & Helsinki Institute of Life Science (HiLIFE) Helsinki, University of Helsinki, Helsinki, Finland
| | - Tomi Taira
- HiLIFE Neuroscience Centre, University of Helsinki, Helsinki, Finland.,Veterinary Biosciences, University of Helsinki, Helsinki, Finland
| | - Vootele Võikar
- HiLIFE Neuroscience Centre, University of Helsinki, Helsinki, Finland
| | - Carolina Vilenius
- HiLIFE Neuroscience Centre, University of Helsinki, Helsinki, Finland
| | | | - Claudio Rivera
- HiLIFE Neuroscience Centre, University of Helsinki, Helsinki, Finland.,Institut de Neurobiologie de la Méditerranée, INMED UMR901, Marseille, France
| | - Jaan-Olle Andressoo
- Department of Pharmacology, Faculty of Medicine & Helsinki Institute of Life Science (HiLIFE) Helsinki, University of Helsinki, Helsinki, Finland.,Karolinska Institute, Division of Neurogeriatrics, Department of Neurobiology, Care Sciences and Society (NVS), Stockholm, Sweden
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27
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Han W, Shepard RD, Lu W. Regulation of GABA ARs by Transmembrane Accessory Proteins. Trends Neurosci 2021; 44:152-165. [PMID: 33234346 PMCID: PMC7855156 DOI: 10.1016/j.tins.2020.10.011] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Revised: 09/08/2020] [Accepted: 10/20/2020] [Indexed: 12/13/2022]
Abstract
The vast majority of fast inhibitory transmission in the brain is mediated by GABA acting on GABAA receptors (GABAARs), which provides inhibitory balance to excitatory drive and controls neuronal output. GABAARs are also effectively targeted by clinically important drugs for treatment in a number of neurological disorders. It has long been hypothesized that function and pharmacology of GABAARs are determined by the channel pore-forming subunits. However, recent studies have provided new dimensions in studying GABAARs due to several transmembrane proteins that interact with GABAARs and modulate their trafficking and function. In this review, we summarize recent findings on these novel GABAAR transmembrane regulators and highlight a potential avenue to develop new GABAAR psychopharmacology by targeting these receptor-associated membrane proteins.
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Affiliation(s)
- Wenyan Han
- Synapse and Neural Circuit Research Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Ryan D Shepard
- Synapse and Neural Circuit Research Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Wei Lu
- Synapse and Neural Circuit Research Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.
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28
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OUP accepted manuscript. Microscopy (Oxf) 2021; 71:i72-i80. [DOI: 10.1093/jmicro/dfab048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Revised: 11/18/2021] [Accepted: 01/24/2022] [Indexed: 11/14/2022] Open
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29
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Schäfer J, Förster L, Mey I, Papadopoulos T, Brose N, Steinem C. Neuroligin-2 dependent conformational activation of collybistin reconstituted in supported hybrid membranes. J Biol Chem 2020; 295:18604-18613. [PMID: 33127642 PMCID: PMC7939476 DOI: 10.1074/jbc.ra120.015347] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 10/27/2020] [Indexed: 12/23/2022] Open
Abstract
The assembly of the postsynaptic transmitter sensing machinery at inhibitory nerve cell synapses requires the intimate interplay between cell adhesion proteins, scaffold and adaptor proteins, and γ-aminobutyric acid (GABA) or glycine receptors. We developed an in vitro membrane system to reconstitute this process, to identify the essential protein components, and to define their mechanism of action, with a specific focus on the mechanism by which the cytosolic C terminus of the synaptic cell adhesion protein Neuroligin-2 alters the conformation of the adaptor protein Collybistin-2 and thereby controls Collybistin-2-interactions with phosphoinositides (PtdInsPs) in the plasma membrane. Supported hybrid membranes doped with different PtdInsPs and 1,2-dioleoyl-sn-glycero-3-{[N-(5-amino-1-carboxypentyl)iminodiacetic acid]succinyl} nickel salt (DGS-NTA(Ni)) to allow for the specific adsorption of the His6-tagged intracellular domain of Neuroligin-2 (His-cytNL2) were prepared on hydrophobically functionalized silicon dioxide substrates via vesicle spreading. Two different collybistin variants, the WT protein (CB2SH3) and a mutant that adopts an intrinsically 'open' and activated conformation (CB2SH3/W24A-E262A), were bound to supported membranes in the absence or presence of His-cytNL2. The corresponding binding data, obtained by reflectometric interference spectroscopy, show that the interaction of the C terminus of Neuroligin-2 with Collybistin-2 induces a conformational change in Collybistin-2 that promotes its interaction with distinct membrane PtdInsPs.
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Affiliation(s)
- Jonas Schäfer
- Institute for Organic and Biomolecular Chemistry, Georg August University, Göttingen, Germany
| | - Lucas Förster
- Institute for Organic and Biomolecular Chemistry, Georg August University, Göttingen, Germany
| | - Ingo Mey
- Institute for Organic and Biomolecular Chemistry, Georg August University, Göttingen, Germany
| | | | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany.
| | - Claudia Steinem
- Institute for Organic and Biomolecular Chemistry, Georg August University, Göttingen, Germany; Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany.
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30
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Statistical Laws of Protein Motion in Neuronal Dendritic Trees. Cell Rep 2020; 33:108391. [PMID: 33207192 PMCID: PMC7672524 DOI: 10.1016/j.celrep.2020.108391] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Revised: 08/31/2020] [Accepted: 10/23/2020] [Indexed: 12/31/2022] Open
Abstract
Across their dendritic trees, neurons distribute thousands of protein species that are necessary for maintaining synaptic function and plasticity and that need to be produced continuously and trafficked to their final destination. As each dendritic branchpoint splits the protein flow, increasing branchpoints decreases the total protein number downstream. Consequently, a neuron needs to produce more proteins to maintain a minimal protein number at distal synapses. Combining in vitro experiments and a theoretical framework, we show that proteins that diffuse within the cell plasma membrane are, on average, 35% more effective at reaching downstream locations than proteins that diffuse in the cytoplasm. This advantage emerges from a bias for forward motion at branchpoints when proteins diffuse within the plasma membrane. Using 3D electron microscopy (EM) data, we show that pyramidal branching statistics and the diffusion lengths of common proteins fall into a region that minimizes the overall protein need. Surface proteins are more efficient at reaching distal sites than soluble proteins Daughter radius optimization reduces the number of proteins needed to populate dendrites Ratios of daughter radii at branchpoints are cell type specific Highly diffusive proteins incur a smaller extra cost for non-optimized radii
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31
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Absalom NL, Liao VWY, Kothur K, Indurthi DC, Bennetts B, Troedson C, Mohammad SS, Gupta S, McGregor IS, Bowen MT, Lederer D, Mary S, De Waele L, Jansen K, Gill D, Kurian MA, McTague A, Møller RS, Ahring PK, Dale RC, Chebib M. Gain-of-function GABRB3 variants identified in vigabatrin-hypersensitive epileptic encephalopathies. Brain Commun 2020; 2:fcaa162. [PMID: 33585817 PMCID: PMC7869430 DOI: 10.1093/braincomms/fcaa162] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Revised: 07/31/2020] [Accepted: 08/28/2020] [Indexed: 01/06/2023] Open
Abstract
Variants in the GABRB3 gene encoding the β3-subunit of the γ-aminobutyric acid type A ( receptor are associated with various developmental and epileptic encephalopathies. Typically, these variants cause a loss-of-function molecular phenotype whereby γ-aminobutyric acid has reduced inhibitory effectiveness leading to seizures. Drugs that potentiate inhibitory GABAergic activity, such as nitrazepam, phenobarbital or vigabatrin, are expected to compensate for this and thereby reduce seizure frequency. However, vigabatrin, a drug that inhibits γ-aminobutyric acid transaminase to increase tonic γ-aminobutyric acid currents, has mixed success in treating seizures in patients with GABRB3 variants: some patients experience seizure cessation, but there is hypersensitivity in some patients associated with hypotonia, sedation and respiratory suppression. A GABRB3 variant that responds well to vigabatrin involves a truncation variant (p.Arg194*) resulting in a clear loss-of-function. We hypothesized that patients with a hypersensitive response to vigabatrin may exhibit a different γ-aminobutyric acid A receptor phenotype. To test this hypothesis, we evaluated the phenotype of de novo variants in GABRB3 (p.Glu77Lys and p.Thr287Ile) associated with patients who are clinically hypersensitive to vigabatrin. We introduced the GABRB3 p.Glu77Lys and p.Thr287Ile variants into a concatenated synaptic and extrasynaptic γ-aminobutyric acid A receptor construct, to resemble the γ-aminobutyric acid A receptor expression by a patient heterozygous for the GABRB3 variant. The mRNA of these constructs was injected into Xenopus oocytes and activation properties of each receptor measured by two-electrode voltage clamp electrophysiology. Results showed an atypical gain-of-function molecular phenotype in the GABRB3 p.Glu77Lys and p.Thr287Ile variants characterized by increased potency of γ-aminobutyric acid A without change to the estimated maximum open channel probability, deactivation kinetics or absolute currents. Modelling of the activation properties of the receptors indicated that either variant caused increased chloride flux in response to low concentrations of γ-aminobutyric acid that mediate tonic currents. We therefore propose that the hypersensitivity reaction to vigabatrin is a result of GABRB3 variants that exacerbate GABAergic tonic currents and caution is required when prescribing vigabatrin. In contrast, drug strategies increasing tonic currents in loss-of-function variants are likely to be a safe and effective therapy. This study demonstrates that functional genomics can explain beneficial and adverse anti-epileptic drug effects, and propose that vigabatrin should be considered in patients with clear loss-of-function GABRB3 variants.
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Affiliation(s)
- Nathan L Absalom
- Faculty of Medicine and Health, School of Pharmacy, Brain and Mind Centre, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Vivian W Y Liao
- Faculty of Medicine and Health, School of Pharmacy, Brain and Mind Centre, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Kavitha Kothur
- Kids Neuroscience Centre at The Children’s Hospital at Westmead, Westmead, New South Wales 2145, Australia
| | - Dinesh C Indurthi
- Faculty of Medicine and Health, School of Pharmacy, Brain and Mind Centre, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Bruce Bennetts
- Department of Molecular Genetics, The Children’s Hospital at Westmead, Westmead, New South Wales 2145, Australia
- Discipline of Paediatrics and Adolescent Health, The Children's Hospital at Westmead Clinical School, The University of Sydney, 2145, Australia
| | - Christopher Troedson
- T.Y. Nelson Department of Neurology and Neurosurgery, The Children's Hospital at Westmead, Westmead, New South Wales 2145, Australia
| | - Shekeeb S Mohammad
- Kids Neuroscience Centre at The Children’s Hospital at Westmead, Westmead, New South Wales 2145, Australia
| | - Sachin Gupta
- T.Y. Nelson Department of Neurology and Neurosurgery, The Children's Hospital at Westmead, Westmead, New South Wales 2145, Australia
| | - Iain S McGregor
- Faculty of Science, Lambert Initiative for Cannabinoid Therapeutics, Brain and Mind Centre, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Michael T Bowen
- Faculty of Science, Lambert Initiative for Cannabinoid Therapeutics, Brain and Mind Centre, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Damien Lederer
- Institute of Pathology and Genetics, Center for Human Genetics, Gosselies 6041, Belgium
| | - Sandrine Mary
- Institute of Pathology and Genetics, Center for Human Genetics, Gosselies 6041, Belgium
| | - Liesbeth De Waele
- Department of Development and Regeneration, KULeuven, Leuven 3000, Belgium
| | - Katrien Jansen
- Department of Development and Regeneration, KULeuven, Leuven 3000, Belgium
| | - Deepak Gill
- Kids Neuroscience Centre at The Children’s Hospital at Westmead, Westmead, New South Wales 2145, Australia
| | - Manju A Kurian
- Molecular Neurosciences, UCL Great Ormond Street Institute of Child Health, London WC1E 6BT, UK
- Department of Neurology, Great Ormond Street Hospital for Children, London WC1N 3JH, UK
| | - Amy McTague
- Molecular Neurosciences, UCL Great Ormond Street Institute of Child Health, London WC1E 6BT, UK
- Department of Neurology, Great Ormond Street Hospital for Children, London WC1N 3JH, UK
| | - Rikke S Møller
- Department of Epilepsy Genetics and Personalized Medicine, Danish Epilepsy Centre, Dianalund 4293, Denmark
- Department of Regional Health Research, University of Southern Denmark, Odense 5230, Denmark
| | - Philip K Ahring
- Faculty of Medicine and Health, School of Pharmacy, Brain and Mind Centre, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Russell C Dale
- Kids Neuroscience Centre at The Children’s Hospital at Westmead, Westmead, New South Wales 2145, Australia
| | - Mary Chebib
- Faculty of Medicine and Health, School of Pharmacy, Brain and Mind Centre, The University of Sydney, Sydney, New South Wales 2006, Australia
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32
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Activity-Dependent Global Downscaling of Evoked Neurotransmitter Release across Glutamatergic Inputs in Drosophila. J Neurosci 2020; 40:8025-8041. [PMID: 32928887 DOI: 10.1523/jneurosci.0349-20.2020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 09/01/2020] [Accepted: 09/04/2020] [Indexed: 12/11/2022] Open
Abstract
Within mammalian brain circuits, activity-dependent synaptic adaptations, such as synaptic scaling, stabilize neuronal activity in the face of perturbations. Stability afforded through synaptic scaling involves uniform scaling of quantal amplitudes across all synaptic inputs formed on neurons, as well as on the postsynaptic side. It remains unclear whether activity-dependent uniform scaling also operates within peripheral circuits. We tested for such scaling in a Drosophila larval neuromuscular circuit, where the muscle receives synaptic inputs from different motoneurons. We used motoneuron-specific genetic manipulations to increase the activity of only one motoneuron and recordings of postsynaptic currents from inputs formed by the different motoneurons. We discovered an adaptation which caused uniform downscaling of evoked neurotransmitter release across all inputs through decreases in release probabilities. This "presynaptic downscaling" maintained the relative differences in neurotransmitter release across all inputs around a homeostatic set point, caused a compensatory decrease in synaptic drive to the muscle affording robust and stable muscle activity, and was induced within hours. Presynaptic downscaling was associated with an activity-dependent increase in Drosophila vesicular glutamate transporter expression. Activity-dependent uniform scaling can therefore manifest also on the presynaptic side to produce robust and stable circuit outputs. Within brain circuits, uniform downscaling on the postsynaptic side is implicated in sleep- and memory-related processes. Our results suggest that evaluation of such processes might be broadened to include uniform downscaling on the presynaptic side.SIGNIFICANCE STATEMENT To date, compensatory adaptations which stabilise target cell activity through activity-dependent global scaling have been observed only within central circuits, and on the postsynaptic side. Considering that maintenance of stable activity is imperative for the robust function of the nervous system as a whole, we tested whether activity-dependent global scaling could also manifest within peripheral circuits. We uncovered a compensatory adaptation which causes global scaling within a peripheral circuit and on the presynaptic side through uniform downscaling of evoked neurotransmitter release. Unlike in central circuits, uniform scaling maintains functionality over a wide, rather than a narrow, operational range, affording robust and stable activity. Activity-dependent global scaling therefore operates on both the presynaptic and postsynaptic sides to maintain target cell activity.
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33
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Nakamura Y, Morrow DH, Nathanson AJ, Henley JM, Wilkinson KA, Moss SJ. Phosphorylation on Ser-359 of the α2 subunit in GABA type A receptors down-regulates their density at inhibitory synapses. J Biol Chem 2020; 295:12330-12342. [PMID: 32620552 PMCID: PMC7458806 DOI: 10.1074/jbc.ra120.014303] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Revised: 06/25/2020] [Indexed: 11/06/2022] Open
Abstract
GABA type A receptors (GABAARs) mediate fast synaptic inhibition and are trafficked to functionally diverse synapses. However, the precise molecular mechanisms that regulate the synaptic targeting of these receptors are unclear. Whereas it has been previously shown that phosphorylation events in α4, β, and γ subunits of GABAARs govern their function and trafficking, phosphorylation of other subunits has not yet been demonstrated. Here, we show that the α2 subunit of GABAARs is phosphorylated at Ser-359 and enables dynamic regulation of GABAAR binding to the scaffolding proteins gephyrin and collybistin. We initially identified Ser-359 phosphorylation by MS analysis, and additional experiments revealed that it is regulated by the activities of cAMP-dependent protein kinase (PKA) and the protein phosphatase 1 (PP1) and/or PP2A. GST-based pulldowns and coimmunoprecipitation experiments demonstrate preferential binding of both gephyrin and collybistin to WT and an S359A phosphonull variant, but not to an S359D phosphomimetic variant. Furthermore, the decreased capacity of the α2 S359D variant to bind collybistin and gephyrin decreased the density of synaptic α2-containing GABAAR clusters and caused an absence of α2 enrichment in the axon initial segment. These results suggest that PKA-mediated phosphorylation and PP1/PP2A-dependent dephosphorylation of the α2 subunit play a role in the dynamic regulation of GABAAR accumulation at inhibitory synapses, thereby regulating the strength of synaptic inhibition. The MS data have been deposited to ProteomeXchange, with the data set identifier PXD019597.
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Affiliation(s)
- Yasuko Nakamura
- School of Biochemistry, Centre for Synaptic Plasticity, University of Bristol, Bristol, United Kingdom
| | - Danielle H. Morrow
- Department of Neuroscience, Tufts University, School of Medicine, Boston, Massachusetts, USA
| | - Anna J. Nathanson
- Department of Neuroscience, Tufts University, School of Medicine, Boston, Massachusetts, USA
| | - Jeremy M. Henley
- School of Biochemistry, Centre for Synaptic Plasticity, University of Bristol, Bristol, United Kingdom
| | - Kevin A. Wilkinson
- School of Biochemistry, Centre for Synaptic Plasticity, University of Bristol, Bristol, United Kingdom
| | - Stephen J. Moss
- Department of Neuroscience, Tufts University, School of Medicine, Boston, Massachusetts, USA,Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom,For correspondence: S. J. Moss,
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Fricke S, Metzdorf K, Ohm M, Haak S, Heine M, Korte M, Zagrebelsky M. Fast Regulation of GABA AR Diffusion Dynamics by Nogo-A Signaling. Cell Rep 2020; 29:671-684.e6. [PMID: 31618635 DOI: 10.1016/j.celrep.2019.09.015] [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] [Received: 03/18/2019] [Revised: 07/02/2019] [Accepted: 09/06/2019] [Indexed: 12/29/2022] Open
Abstract
Precisely controlling the excitatory and inhibitory balance is crucial for the stability and information-processing ability of neuronal networks. However, the molecular mechanisms maintaining this balance during ongoing sensory experiences are largely unclear. We show that Nogo-A signaling reciprocally regulates excitatory and inhibitory transmission. Loss of function for Nogo-A signaling through S1PR2 rapidly increases GABAAR diffusion, thereby decreasing their number at synaptic sites and the amplitude of GABAergic mIPSCs at CA3 hippocampal neurons. This increase in GABAAR diffusion rate is correlated with an increase in Ca2+ influx and requires the calcineurin-mediated dephosphorylation of the γ2 subunit at serine 327. These results suggest that Nogo-A signaling rapidly strengthens inhibitory GABAergic transmission by restricting the diffusion dynamics of GABAARs. Together with the observation that Nogo-A signaling regulates excitatory transmission in an opposite manner, these results suggest a crucial role for Nogo-A signaling in modulating the excitation and inhibition balance to restrict synaptic plasticity.
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Affiliation(s)
- Steffen Fricke
- Zoological Institute, Division of Cellular Neurobiology, TU Braunschweig, Braunschweig 38108, Germany
| | - Kristin Metzdorf
- Zoological Institute, Division of Cellular Neurobiology, TU Braunschweig, Braunschweig 38108, Germany
| | - Melanie Ohm
- Zoological Institute, Division of Cellular Neurobiology, TU Braunschweig, Braunschweig 38108, Germany
| | - Stefan Haak
- Zoological Institute, Division of Cellular Neurobiology, TU Braunschweig, Braunschweig 38108, Germany
| | - Martin Heine
- Molecular Physiology Group, Leibniz Institute of Neurobiology, Magdeburg 39118, Germany; Functional Neurobiology, Institute for Developmental Biology and Neurobiology, Johannes Gutenberg University, Mainz 55128, Germany
| | - Martin Korte
- Zoological Institute, Division of Cellular Neurobiology, TU Braunschweig, Braunschweig 38108, Germany; Helmholtz Centre for Infection Research, AG NIND, Inhoffenstr. 7, Braunschweig 38124, Germany
| | - Marta Zagrebelsky
- Zoological Institute, Division of Cellular Neurobiology, TU Braunschweig, Braunschweig 38108, Germany.
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Pizzarelli R, Griguoli M, Zacchi P, Petrini EM, Barberis A, Cattaneo A, Cherubini E. Tuning GABAergic Inhibition: Gephyrin Molecular Organization and Functions. Neuroscience 2020; 439:125-136. [PMID: 31356900 PMCID: PMC7351109 DOI: 10.1016/j.neuroscience.2019.07.036] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Revised: 07/16/2019] [Accepted: 07/17/2019] [Indexed: 01/15/2023]
Abstract
To be highly reliable, synaptic transmission needs postsynaptic receptors (Rs) in precise apposition to the presynaptic release sites. At inhibitory synapses, the postsynaptic protein gephyrin self-assembles to form a scaffold that anchors glycine and GABAARs to the cytoskeleton, thus ensuring the accurate accumulation of postsynaptic receptors at the right place. This protein undergoes several post-translational modifications which control protein-protein interaction and downstream signaling pathways. In addition, through the constant exchange of scaffolding elements and receptors in and out of synapses, gephyrin dynamically regulates synaptic strength and plasticity. The aim of the present review is to highlight recent findings on the functional role of gephyrin at GABAergic inhibitory synapses. We will discuss different approaches used to interfere with gephyrin in order to unveil its function. In addition, we will focus on the impact of gephyrin structure and distribution at the nanoscale level on the functional properties of inhibitory synapses as well as the implications of this scaffold protein in synaptic plasticity processes. Finally, we will emphasize how gephyrin genetic mutations or alterations in protein expression levels are implicated in several neuropathological disorders, including autism spectrum disorders, schizophrenia, temporal lobe epilepsy and Alzheimer's disease, all associated with severe deficits of GABAergic signaling. This article is part of a Special Issue entitled: Honoring Ricardo Miledi - outstanding neuroscientist of XX-XXI centuries.
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Affiliation(s)
- Rocco Pizzarelli
- European Brain Research Institute (EBRI), Fondazione Rita Levi-Montalcini, Roma, Italy
| | - Marilena Griguoli
- European Brain Research Institute (EBRI), Fondazione Rita Levi-Montalcini, Roma, Italy
| | - Paola Zacchi
- Department of Life Sciences, University of Trieste, Trieste, Italy
| | - Enrica Maria Petrini
- Fondazione Istituto Italiano di Tecnologia (IIT), Department of Neuroscience and Brain Technologies, Plasticity of inhibitory networks Unit, Genoa, Italy
| | - Andrea Barberis
- Fondazione Istituto Italiano di Tecnologia (IIT), Department of Neuroscience and Brain Technologies, Plasticity of inhibitory networks Unit, Genoa, Italy
| | - Antonino Cattaneo
- European Brain Research Institute (EBRI), Fondazione Rita Levi-Montalcini, Roma, Italy; Scuola Normale Superiore, Pisa, Italy
| | - Enrico Cherubini
- European Brain Research Institute (EBRI), Fondazione Rita Levi-Montalcini, Roma, Italy; Scuola Internazionale Superiore di Studi Avanzati, Trieste, Italy.
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36
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Li R, Wu B, He M, Zhang P, Zhang Q, Deng J, Yuan J, Chen Y. HAP1 Modulates Epileptic Seizures by Regulating GABA AR Function in Patients with Temporal Lobe Epilepsy and in the PTZ-Induced Epileptic Model. Neurochem Res 2020; 45:1997-2008. [PMID: 32419121 DOI: 10.1007/s11064-020-03052-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Revised: 04/13/2020] [Accepted: 05/06/2020] [Indexed: 01/03/2023]
Abstract
The number of γ-aminobutyric acid type A receptors (GABAARs) expressed on the surface membrane and at synaptic sites is implicated in the enhanced excitation of neuronal circuits and abnormal network oscillations in epilepsy. Huntingtin-associated protein 1 (HAP1), a key mediator of pathological alterations in protein trafficking, directly interacts with GABAARs and facilitates their recycling back to synapses after internalization from the surface; thus, HAP1 regulates the strength of inhibitory synaptic transmission. Here, we show that HAP1 modulates epileptic seizures by regulating GABAAR function in patients with temporal lobe epilepsy (TLE) and in the pentylenetetrazol (PTZ)-induced epileptic model. We demonstrate that GABAARβ2/3 and HAP1 expression are decreased and that the HAP1-GABAARβ2/3 complex is disrupted in the epileptic rat brain. We found that HAP1 upregulation exerts antiepileptic activity in the PTZ-induced seizure and that these changes are associated with increased surface GABAARβ2/3 expression and the amplitude of miniature inhibitory postsynaptic currents (mIPSCs). This study provides evidence that hippocampal HAP1 is linked to GABAARs in evoking seizures and suggests that this mechanism is involved in epileptic seizures in the brain, representing a potential therapeutic target for epilepsy.
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Affiliation(s)
- Rong Li
- Department of Neurology, Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400016, China
| | - Bing Wu
- Department of Neurology, Chongqing Key Laboratory of Neurology, First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Miaoqing He
- Center for Brain Disorders Research, Capital Medical University, Beijing, China.,Beijing Institute for Brain Disorders, Beijing, China
| | - Peng Zhang
- Department of Neurology, Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400016, China
| | - Qinbin Zhang
- Department of Neurology, Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400016, China
| | - Jing Deng
- Department of Neurology, Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400016, China
| | - Jinxian Yuan
- Department of Neurology, Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400016, China
| | - Yangmei Chen
- Department of Neurology, Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400016, China.
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Blanchard K, Zorrilla de San Martín J, Marty A, Llano I, Trigo FF. Differentially poised vesicles underlie fast and slow components of release at single synapses. J Gen Physiol 2020; 152:e201912523. [PMID: 32243497 PMCID: PMC7201884 DOI: 10.1085/jgp.201912523] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 03/12/2020] [Indexed: 12/25/2022] Open
Abstract
In several types of central mammalian synapses, sustained presynaptic stimulation leads to a sequence of two components of synaptic vesicle release, reflecting the consecutive contributions of a fast-releasing pool (FRP) and of a slow-releasing pool (SRP). Previous work has shown that following common depletion by a strong stimulation, FRP and SRP recover with different kinetics. However, it has remained unclear whether any manipulation could lead to a selective enhancement of either FRP or SRP. To address this question, we have performed local presynaptic calcium uncaging in single presynaptic varicosities of cerebellar interneurons. These varicosities typically form "simple synapses" onto postsynaptic interneurons, involving several (one to six) docking/release sites within a single active zone. We find that strong uncaging laser pulses elicit two phases of release with time constants of ∼1 ms (FRP release) and ∼20 ms (SRP release). When uncaging was preceded by action potential-evoked vesicular release, the extent of SRP release was specifically enhanced. We interpret this effect as reflecting an increased likelihood of two-step release (docking then release) following the elimination of docked synaptic vesicles by action potential-evoked release. In contrast, a subthreshold laser-evoked calcium elevation in the presynaptic varicosity resulted in an enhancement of the FRP release. We interpret this latter effect as reflecting an increased probability of occupancy of docking sites following subthreshold calcium increase. In conclusion, both fast and slow components of release can be specifically enhanced by certain presynaptic manipulations. Our results have implications for the mechanism of docking site replenishment and the regulation of synaptic responses, in particular following activation of ionotropic presynaptic receptors.
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Affiliation(s)
- Kris Blanchard
- Université de Paris, SPPIN - Saints-Pères Paris Institute for the Neurosciences, Centre National de la Recherche Scientifique, UMR 8003, Paris, France
| | - Javier Zorrilla de San Martín
- Université de Paris, SPPIN - Saints-Pères Paris Institute for the Neurosciences, Centre National de la Recherche Scientifique, UMR 8003, Paris, France
| | - Alain Marty
- Université de Paris, SPPIN - Saints-Pères Paris Institute for the Neurosciences, Centre National de la Recherche Scientifique, UMR 8003, Paris, France
| | - Isabel Llano
- Université de Paris, SPPIN - Saints-Pères Paris Institute for the Neurosciences, Centre National de la Recherche Scientifique, UMR 8003, Paris, France
| | - Federico F Trigo
- Université de Paris, SPPIN - Saints-Pères Paris Institute for the Neurosciences, Centre National de la Recherche Scientifique, UMR 8003, Paris, France
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38
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Woo J, Lee CJ. Sleep-enhancing Effects of Phytoncide Via Behavioral, Electrophysiological, and Molecular Modeling Approaches. Exp Neurobiol 2020; 29:120-129. [PMID: 32408402 PMCID: PMC7237266 DOI: 10.5607/en20013] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 04/24/2020] [Accepted: 04/27/2020] [Indexed: 12/16/2022] Open
Abstract
Sleep is indispensable for living animals to live and maintain a normal life. Due to the growing number of people suffering from sleep disorders such as insomnia, there have been increasing interests in environmentally friendly therapeutic approaches for sleep disorders to avoid any side effects of pharmacological treatment using synthetic hypnotics. It has been widely accepted that the various beneficial effects of forest, such as relieving stress and anxiety and enhancing immune system function, are caused by plant-derived products, also known as phytoncide. Recently, it has been reported that the sleep-enhancing effects of phytoncide are derived from pine trees such as (-)-α-pinene and 3-carene. These are the major constituents of pine tree that potentiate the inhibitory synaptic responses by acting as a positive modulator for GABAA-BZD receptor. In this review, we discuss the effects of phytoncide on sleep and review the latest approaches of sleep-related behavioral assay, electrophysiological recording, and molecular modeling technique.
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Affiliation(s)
- Junsung Woo
- Center for Cell and Gene Th erapy, Baylor College of Medicine, Houston, TX 77030, USA
| | - C Justin Lee
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon 34126, Korea
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39
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Hippocampal synaptic and membrane function in the DBA/2J-mdx mouse model of Duchenne muscular dystrophy. Mol Cell Neurosci 2020; 104:103482. [PMID: 32171922 DOI: 10.1016/j.mcn.2020.103482] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Revised: 03/09/2020] [Accepted: 03/10/2020] [Indexed: 12/14/2022] Open
Abstract
Dystrophin deficiency is associated with alterations in cell physiology. The functional consequences of dystrophin deficiency are particularly severe for muscle physiology, as observed in Duchenne muscle dystrophy (DMD). DMD is caused by the absence of a 427 kDa isoform of dystrophin. However, in addition to muscular dystrophy symptoms, DMD is frequently associated with memory and attention deficits and epilepsy. While this may be associated with a role for dystrophin in neuronal physiology, it is not clear what neuronal alterations are linked with DMD. Our work shows that CA1 pyramidal neurons from DBA/2J-mdx mice have increased afterhyperpolarization compared to WT controls. All the other electrotonic and electrogenic membrane properties were unaffected by this genotype. Finally, basal synaptic transmission, short-term and long-term synaptic plasticity at Schaffer collateral to CA1 glutamatergic synapses were unchanged between mdx and WT controls. These data show that the excitatory component of hippocampal activity is largely preserved in DBA/2J-mdx mice. Further studies, extending the investigation to the inhibitory GABAergic function, may provide a more complete picture of the functional, network alterations underlying impaired cognition in DMD. In addition, the investigation of changes in neuronal single conductance biophysical properties associated with this genotype, is required to identify the functional alterations associated with dystrophin deficiency and clarify its role in neuronal function.
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40
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Luo X, Guet-McCreight A, Villette V, Francavilla R, Marino B, Chamberland S, Skinner FK, Topolnik L. Synaptic Mechanisms Underlying the Network State-Dependent Recruitment of VIP-Expressing Interneurons in the CA1 Hippocampus. Cereb Cortex 2020; 30:3667-3685. [PMID: 32080739 DOI: 10.1093/cercor/bhz334] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Revised: 12/13/2019] [Indexed: 11/14/2022] Open
Abstract
Disinhibition is a widespread circuit mechanism for information selection and transfer. In the hippocampus, disinhibition of principal cells is provided by the interneuron-specific interneurons that express the vasoactive intestinal polypeptide (VIP-IS) and innervate selectively inhibitory interneurons. By combining optophysiological experiments with computational models, we determined the impact of synaptic inputs onto the network state-dependent recruitment of VIP-IS cells. We found that VIP-IS cells fire spikes in response to both the Schaffer collateral and the temporoammonic pathway activation. Moreover, by integrating their intrinsic and synaptic properties into computational models, we predicted recruitment of these cells between the rising phase and peak of theta oscillation and during ripples. Two-photon Ca2+-imaging in awake mice supported in part the theoretical predictions, revealing a significant speed modulation of VIP-IS cells and their preferential albeit delayed recruitment during theta-run epochs, with estimated firing at the rising phase and peak of the theta cycle. However, it also uncovered that VIP-IS cells are not activated during ripples. Thus, given the preferential theta-modulated firing of VIP-IS cells in awake hippocampus, we postulate that these cells may be important for information gating during spatial navigation and memory encoding.
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Affiliation(s)
- Xiao Luo
- Department of Biochemistry, Microbiology and Bio-informatics, Laval University, Québec, PQ, Canada.,Neuroscience Axis, CHU de Québec Research Center (CHUL), Québec, PQ, Canada
| | - Alexandre Guet-McCreight
- Krembil Research Institute, University Health Network, Toronto, ON, Canada.,Department of Physiology, University of Toronto, Toronto, ON, Canada
| | - Vincent Villette
- Department of Biochemistry, Microbiology and Bio-informatics, Laval University, Québec, PQ, Canada.,Neuroscience Axis, CHU de Québec Research Center (CHUL), Québec, PQ, Canada.,Institut de Biologie de l'ÉcoleNormale Supérieure (IBENS), École Normale Supérieure, CNRS, INSERM, PSL Research University, Paris, France
| | - Ruggiero Francavilla
- Department of Biochemistry, Microbiology and Bio-informatics, Laval University, Québec, PQ, Canada.,Neuroscience Axis, CHU de Québec Research Center (CHUL), Québec, PQ, Canada
| | - Beatrice Marino
- Department of Biochemistry, Microbiology and Bio-informatics, Laval University, Québec, PQ, Canada.,Neuroscience Axis, CHU de Québec Research Center (CHUL), Québec, PQ, Canada
| | - Simon Chamberland
- Department of Biochemistry, Microbiology and Bio-informatics, Laval University, Québec, PQ, Canada.,Neuroscience Axis, CHU de Québec Research Center (CHUL), Québec, PQ, Canada.,New York University Neuroscience Institute, New York, NY, USA
| | - Frances K Skinner
- Krembil Research Institute, University Health Network, Toronto, ON, Canada.,Departments of Medicine (Neurology) and Physiology, University of Toronto, Toronto, ON, Canada
| | - Lisa Topolnik
- Department of Biochemistry, Microbiology and Bio-informatics, Laval University, Québec, PQ, Canada.,Neuroscience Axis, CHU de Québec Research Center (CHUL), Québec, PQ, Canada
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Combining mGRASP and Optogenetics Enables High-Resolution Functional Mapping of Descending Cortical Projections. Cell Rep 2020; 24:1071-1080. [PMID: 30044974 PMCID: PMC6083038 DOI: 10.1016/j.celrep.2018.06.076] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Revised: 03/23/2018] [Accepted: 06/18/2018] [Indexed: 11/25/2022] Open
Abstract
We have applied optogenetics and mGRASP, a light microscopy technique that labels synaptic contacts, to map the number and strength of defined corticocollicular (CC) connections. Using mGRASP, we show that CC projections form small, medium, and large synapses, and both the number and the distribution of synapse size vary among the IC regions. Using optogenetics, we show that low-frequency stimulation of CC axons expressing channelrhodopsin produces prolonged elevations of the CC miniature EPSC (mEPSC) rate. Functional analysis of CC mEPSCs reveals small-, medium-, and large-amplitude events that mirror the synaptic distributions observed with mGRASP. Our results reveal that descending ipsilateral projections dominate CC feedback via an increased number of large synaptic contacts, especially onto the soma of IC neurons. This study highlights the feasibility of combining microscopy (i.e., mGRASP) and optogenetics to reveal synaptic weighting of defined projections at the level of single neurons, enabling functional connectomic mapping in diverse neural circuits. Optogenetic axonal stimulation causes prolonged increases in quantal synaptic release Quantal and anatomical measures of synapse strength directly correspond Strength and cellular location of cortical inputs to midbrain are region specific
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Chuang SH, Reddy DS. Isobolographic Analysis of Antiseizure Activity of the GABA Type A Receptor-Modulating Synthetic Neurosteroids Brexanolone and Ganaxolone with Tiagabine and Midazolam. J Pharmacol Exp Ther 2019; 372:285-298. [PMID: 31843812 DOI: 10.1124/jpet.119.261735] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Accepted: 12/13/2019] [Indexed: 12/11/2022] Open
Abstract
Epilepsy is often treated with a combination of antiepileptic drugs. Although neurosteroids are potent anticonvulsants, little is known about their combination potential for the treatment of refractory epilepsy. Here, we investigated the combination efficacy of neurosteroids allopregnanolone (AP, brexanolone) and ganaxolone (GX) with the GABA-reuptake inhibitor tiagabine (TG) or the benzodiazepine midazolam (MDZ) on tonic inhibition in dentate gyrus granule cells and seizure protection in the hippocampus kindling and 6-Hz seizure models. Isobolographic analysis indicated that combinations of GX and TG or AP and TG at three standard ratios (1:1, 3:1, and 1:3) displayed significant synergism in augmenting tonic inhibition. In pharmacological studies, GX, AP, and TG produced dose-dependent antiseizure effects in mice (ED50 = 1.46, 4.20, and 0.20 mg/kg, respectively). The combination of GX and TG at the fixed ratio of 1:1 exerted the greatest combination index (CI = 0.53), indicating strong synergistic interaction in seizure protection. In addition, combination regimens of AP and TG showed robust synergism for seizure protection (CI = 0.4). Finally, combination regimens of GX and MDZ elicited synergistic (CI = 0.6) responses for seizure protection. These results demonstrate striking synergism of neurosteroids and TG combination for seizure protection, likely because of their effects at extrasynaptic GABA type A (GABA-A) receptors from TG-induced elevation in GABA levels. Superadditive antiseizure activity of neurosteroid-MDZ combinations may stem from their actions at both synaptic and extrasynaptic GABA-A receptors. Together, these findings provide a potential mechanistic basis for combination potential of neurosteroids with TG or benzodiazepines for the management of refractory epilepsy, status epilepticus, and seizure disorders. SIGNIFICANCE STATEMENT: This paper investigates for the first time the potential synergistic interactions between two neurosteroids with anticonvulsant properties, allopregnanolone (brexanolone) and the very similar synthetic analog, ganaxolone, and two conventional antiepileptic drugs active at GABA type A receptors: the GABA-reuptake inhibitor tiagabine and a benzodiazepine, midazolam. The results demonstrate a synergistic protective effect of neurosteroid-tiagabine combinations, as well as neurosteroid-midazolam regimens in seizure models.
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Affiliation(s)
- Shu-Hui Chuang
- Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M University Health Science Center, Bryan, Texas
| | - Doodipala Samba Reddy
- Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M University Health Science Center, Bryan, Texas
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43
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Krajeski RN, Macey-Dare A, van Heusden F, Ebrahimjee F, Ellender TJ. Dynamic postnatal development of the cellular and circuit properties of striatal D1 and D2 spiny projection neurons. J Physiol 2019; 597:5265-5293. [PMID: 31531863 PMCID: PMC6900874 DOI: 10.1113/jp278416] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Accepted: 09/04/2019] [Indexed: 12/15/2022] Open
Abstract
KEY POINTS Imbalances in the activity of the D1-expressing direct pathway and D2-expressing indirect pathway striatal projection neurons (SPNs) are thought to contribute to many basal ganglia disorders, including early-onset neurodevelopmental disorders such as obsessive-compulsive disorder, attention deficit hyperactivity disorder and Tourette's syndrome. This study provides the first detailed quantitative investigation of development of D1 and D2 SPNs, including their cellular properties and connectivity within neural circuits, during the first postnatal weeks. This period is highly dynamic with many properties changing, but it is possible to make three main observations: many aspects of D1 and D2 SPNs progressively mature in parallel; there are notable exceptions when they diverge; and many of the defining properties of mature striatal SPNs and circuits are already established by the first and second postnatal weeks, suggesting guidance through intrinsic developmental programmes. These findings provide an experimental framework for future studies of striatal development in both health and disease. ABSTRACT Many basal ganglia neurodevelopmental disorders are thought to result from imbalances in the activity of the D1-expressing direct pathway and D2-expressing indirect pathway striatal projection neurons (SPNs). Insight into these disorders is reliant on our understanding of normal D1 and D2 SPN development. Here we provide the first detailed study and quantification of the striatal cellular and circuit changes occurring for both D1 and D2 SPNs in the first postnatal weeks using in vitro whole-cell patch-clamp electrophysiology. Characterization of their intrinsic electrophysiological and morphological properties, the excitatory long-range inputs coming from cortex and thalamus, as well their local gap junction and inhibitory synaptic connections reveals this period to be highly dynamic with numerous properties changing. However it is possible to make three main observations. Firstly, many aspects of SPNs mature in parallel, including intrinsic membrane properties, increases in dendritic arbours and spine densities, general synaptic inputs and expression of specific glutamate receptors. Secondly, there are notable exceptions, including a transient stronger thalamic innervation of D2 SPNs and stronger cortical NMDA receptor-mediated inputs to D1 SPNs, both in the second postnatal week. Thirdly, many of the defining properties of mature D1 and D2 SPNs and striatal circuits are already established by the first and second postnatal weeks, including different electrophysiological properties as well as biased local inhibitory connections between SPNs, suggesting this is guided through intrinsic developmental programmes. Together these findings provide an experimental framework for future studies of D1 and D2 SPN development in health and disease.
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Affiliation(s)
- Rohan N Krajeski
- Department of Pharmacology, University of Oxford, Oxford, OX1 3QT, UK
| | - Anežka Macey-Dare
- Department of Pharmacology, University of Oxford, Oxford, OX1 3QT, UK
| | - Fran van Heusden
- Department of Pharmacology, University of Oxford, Oxford, OX1 3QT, UK
| | - Farid Ebrahimjee
- Department of Pharmacology, University of Oxford, Oxford, OX1 3QT, UK
| | - Tommas J Ellender
- Department of Pharmacology, University of Oxford, Oxford, OX1 3QT, UK
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Distinct Nanoscale Calcium Channel and Synaptic Vesicle Topographies Contribute to the Diversity of Synaptic Function. Neuron 2019; 104:693-710.e9. [PMID: 31558350 DOI: 10.1016/j.neuron.2019.08.014] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 05/31/2019] [Accepted: 08/08/2019] [Indexed: 12/22/2022]
Abstract
The nanoscale topographical arrangement of voltage-gated calcium channels (VGCC) and synaptic vesicles (SVs) determines synaptic strength and plasticity, but whether distinct spatial distributions underpin diversity of synaptic function is unknown. We performed single bouton Ca2+ imaging, Ca2+ chelator competition, immunogold electron microscopic (EM) localization of VGCCs and the active zone (AZ) protein Munc13-1, at two cerebellar synapses. Unexpectedly, we found that weak synapses exhibited 3-fold more VGCCs than strong synapses, while the coupling distance was 5-fold longer. Reaction-diffusion modeling could explain both functional and structural data with two strikingly different nanotopographical motifs: strong synapses are composed of SVs that are tightly coupled (∼10 nm) to VGCC clusters, whereas at weak synapses VGCCs were excluded from the vicinity (∼50 nm) of docked vesicles. The distinct VGCC-SV topographical motifs also confer differential sensitivity to neuromodulation. Thus, VGCC-SV arrangements are not canonical, and their diversity could underlie functional heterogeneity across CNS synapses.
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Yang X, Specht CG. Subsynaptic Domains in Super-Resolution Microscopy: The Treachery of Images. Front Mol Neurosci 2019; 12:161. [PMID: 31312120 PMCID: PMC6614521 DOI: 10.3389/fnmol.2019.00161] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2019] [Accepted: 06/12/2019] [Indexed: 12/13/2022] Open
Abstract
The application of super-resolution optical microscopy to investigating synaptic structures has revealed a highly heterogeneous and variable intra-synaptic organization. Dense subsynaptic protein assemblies named subsynaptic domains or SSDs have been proposed as structural units that regulate the efficacy of neuronal transmission. However, an in-depth characterization of SSDs has been hampered by technical limitations of super-resolution microscopy of synapses, namely the stochasticity of the signals during the imaging procedures and the variability of the synaptic structures. Here, we synthetize the available evidence for the existence of SSDs at central synapses, as well as the possible functional relevance of SSDs. In particular, we discuss the possible regulation of co-transmission at mixed inhibitory synapses as a consequence of the subsynaptic distribution of glycine receptors (GlyRs) and GABAA receptors (GABAARs). LAY ABSTRACT Super-resolution imaging strategies bypass the resolution limit of conventional optical microscopy and have given new insights into the distribution of proteins at synapses in the central nervous system. Neurotransmitter receptors and scaffold proteins appear to occupy specialized locations within synapses that we refer to as subsynaptic domains or SSDs. Interestingly, these SSDs are highly dynamic and their formation seems to be related to the remodeling of synapses during synaptic plasticity. It was also shown that SSDs of pre-and post-synaptic proteins are aligned in so-called nanocolumns, highlighting the role of SSDs in the regulation of synaptic transmission. Despite recent advances, however, the detection of SSDs with super-resolution microscopy remains difficult due to the inherent technical limitations of these approaches that are discussed in this review article.
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Affiliation(s)
- Xiaojuan Yang
- École Normale Supérieure, PSL Research University, CNRS, Inserm, Institute of Biology (IBENS), Paris, France
| | - Christian G Specht
- École Normale Supérieure, PSL Research University, CNRS, Inserm, Institute of Biology (IBENS), Paris, France
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46
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Barberis A. Postsynaptic plasticity of GABAergic synapses. Neuropharmacology 2019; 169:107643. [PMID: 31108109 DOI: 10.1016/j.neuropharm.2019.05.020] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 05/14/2019] [Accepted: 05/16/2019] [Indexed: 12/18/2022]
Abstract
The flexibility of neuronal networks is believed to rely mainly on the plasticity of excitatory synapses. However, like their excitatory counterparts, inhibitory synapses also undergo several forms of synaptic plasticity. This review examines recent advances in the understanding of the molecular mechanisms leading to postsynaptic GABAergic plasticity. Specifically, modulation of GABAA receptor (GABAAR) number at postsynaptic sites plays a key role, with the interaction of GABAARs with the scaffold protein gephyrin and other postsynaptic scaffold/regulatory proteins having particular importance. Our understanding of these molecular interactions are progressing, based on recent insights into the processes of GABAAR lateral diffusion, gephyrin dynamics, and gephyrin nanoscale organization. This article is part of the special issue entitled 'Mobility and trafficking of neuronal membrane proteins'.
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Affiliation(s)
- Andrea Barberis
- Plasticity of Inhibitory Networks, Fondazione Istituto Italiano di Tecnologia, Via Morego 30, Genova, Italy.
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Kawaguchi Y, Otsuka T, Morishima M, Ushimaru M, Kubota Y. Control of excitatory hierarchical circuits by parvalbumin-FS basket cells in layer 5 of the frontal cortex: insights for cortical oscillations. J Neurophysiol 2019; 121:2222-2236. [PMID: 30995139 PMCID: PMC6620693 DOI: 10.1152/jn.00778.2018] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The cortex contains multiple neuron types with specific connectivity and functions. Recent progress has provided a better understanding of the interactions of these neuron types as well as their output organization particularly for the frontal cortex, with implications for the circuit mechanisms underlying cortical oscillations that have cognitive functions. Layer 5 pyramidal cells (PCs) in the frontal cortex comprise two major subtypes: crossed-corticostriatal (CCS) and corticopontine (CPn) cells. Functionally, CCS and CPn cells exhibit similar phase-dependent firing during gamma waves but participate in two distinct subnetworks that are linked unidirectionally from CCS to CPn cells. GABAergic parvalbumin-expressing fast-spiking (PV-FS) cells, necessary for gamma oscillation, innervate PCs, with stronger and global inhibition to somata and weaker and localized inhibitions to dendritic shafts/spines. While PV-FS cells form reciprocal connections with both CCS and CPn cells, the excitation from CPn to PV-FS cells exhibits short-term synaptic dynamics conducive for oscillation induction. The electrical coupling between PV-FS cells facilitates spike synchronization among PV-FS cells receiving common excitatory inputs from local PCs and inhibits other PV-FS cells via electrically communicated spike afterhyperpolarizations. These connectivity characteristics can promote synchronous firing in the local networks of CPn cells and firing of some CCS cells by anode-break excitation. Thus subsets of L5 CCS and CPn cells within different levels of connection hierarchy exhibit coordinated activity via their common connections with PV-FS cells, and the resulting PC output drives diverse neuronal targets in cortical layer 1 and the striatum with specific temporal precision, expanding the computational power of the cortical network.
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Affiliation(s)
- Yasuo Kawaguchi
- Division of Cerebral Circuitry, National Institute for Physiological Sciences , Okazaki , Japan.,Department of Physiological Sciences, SOKENDAI (Graduate University for Advanced Studies) , Okazaki , Japan
| | - Takeshi Otsuka
- Division of Cerebral Circuitry, National Institute for Physiological Sciences , Okazaki , Japan.,Department of Physiological Sciences, SOKENDAI (Graduate University for Advanced Studies) , Okazaki , Japan
| | - Mieko Morishima
- Division of Cerebral Circuitry, National Institute for Physiological Sciences , Okazaki , Japan.,Department of Physiological Sciences, SOKENDAI (Graduate University for Advanced Studies) , Okazaki , Japan
| | - Mika Ushimaru
- Department of Experimental Therapeutics, Institute for Advancement of Clinical and Translational Science, Kyoto University Hospital , Kyoto , Japan
| | - Yoshiyuki Kubota
- Division of Cerebral Circuitry, National Institute for Physiological Sciences , Okazaki , Japan.,Department of Physiological Sciences, SOKENDAI (Graduate University for Advanced Studies) , Okazaki , Japan
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48
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Modulation of inhibitory plasticity in basal ganglia output nuclei of patients with Parkinson's disease. Neurobiol Dis 2019; 124:46-56. [DOI: 10.1016/j.nbd.2018.10.020] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Revised: 10/17/2018] [Accepted: 10/31/2018] [Indexed: 01/07/2023] Open
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49
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Postsynaptic protein organization revealed by electron microscopy. Curr Opin Struct Biol 2019; 54:152-160. [PMID: 30904821 PMCID: PMC6753054 DOI: 10.1016/j.sbi.2019.02.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 02/02/2019] [Accepted: 02/18/2019] [Indexed: 11/21/2022]
Abstract
Neuronal synapses are key devices for transmitting and processing information in the nervous system. Synaptic plasticity, generally regarded as the cellular basis of learning and memory, involves changes of subcellular structures that take place at the nanoscale. High-resolution imaging methods, especially electron microscopy (EM), have allowed for quantitative analysis of such nanoscale structures in different types of synapses. In particular, the semi-ordered organization of neurotransmitter receptors and their interacting scaffolds in the postsynaptic density have been characterized for both excitatory and inhibitory synapses by studies using various EM techniques such as immuno-EM, electron tomography of high-pressure freezing and freeze-substituted samples, and cryo electron tomography. These techniques, in combination with new correlative approaches, will further facilitate our understanding of the molecular organization underlying diverse functions of neuronal synapses.
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Luque NR, Naveros F, Carrillo RR, Ros E, Arleo A. Spike burst-pause dynamics of Purkinje cells regulate sensorimotor adaptation. PLoS Comput Biol 2019; 15:e1006298. [PMID: 30860991 PMCID: PMC6430425 DOI: 10.1371/journal.pcbi.1006298] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 03/22/2019] [Accepted: 01/08/2019] [Indexed: 11/25/2022] Open
Abstract
Cerebellar Purkinje cells mediate accurate eye movement coordination. However, it remains unclear how oculomotor adaptation depends on the interplay between the characteristic Purkinje cell response patterns, namely tonic, bursting, and spike pauses. Here, a spiking cerebellar model assesses the role of Purkinje cell firing patterns in vestibular ocular reflex (VOR) adaptation. The model captures the cerebellar microcircuit properties and it incorporates spike-based synaptic plasticity at multiple cerebellar sites. A detailed Purkinje cell model reproduces the three spike-firing patterns that are shown to regulate the cerebellar output. Our results suggest that pauses following Purkinje complex spikes (bursts) encode transient disinhibition of target medial vestibular nuclei, critically gating the vestibular signals conveyed by mossy fibres. This gating mechanism accounts for early and coarse VOR acquisition, prior to the late reflex consolidation. In addition, properly timed and sized Purkinje cell bursts allow the ratio between long-term depression and potentiation (LTD/LTP) to be finely shaped at mossy fibre-medial vestibular nuclei synapses, which optimises VOR consolidation. Tonic Purkinje cell firing maintains the consolidated VOR through time. Importantly, pauses are crucial to facilitate VOR phase-reversal learning, by reshaping previously learnt synaptic weight distributions. Altogether, these results predict that Purkinje spike burst-pause dynamics are instrumental to VOR learning and reversal adaptation. Cerebellar Purkinje cells regulate accurate eye movement coordination. However, it remains unclear how cerebellar-dependent oculomotor adaptation depends on the interplay between Purkinje cell characteristic response patterns: tonic, high frequency bursting, and post-complex spike pauses. We explore the role of Purkinje spike burst-pause dynamics in VOR adaptation. A biophysical model of Purkinje cell is at the core of a spiking network model, which captures the cerebellar microcircuit properties and incorporates spike-based synaptic plasticity mechanisms at different cerebellar sites. We show that Purkinje spike burst-pause dynamics are critical for (1) gating the vestibular-motor response association during VOR acquisition; (2) mediating the LTD/LTP balance for VOR consolidation; (3) reshaping synaptic efficacy distributions for VOR phase-reversal adaptation; (4) explaining the reversal VOR gain discontinuities during sleeping.
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Affiliation(s)
- Niceto R. Luque
- Sorbonne Université, INSERM, CNRS, Institut de la Vision, Paris, France
- * E-mail: (NRL); (AA)
| | - Francisco Naveros
- Department of Computer Architecture and Technology, CITIC-University of Granada, Granada, Spain
| | - Richard R. Carrillo
- Department of Computer Architecture and Technology, CITIC-University of Granada, Granada, Spain
| | - Eduardo Ros
- Department of Computer Architecture and Technology, CITIC-University of Granada, Granada, Spain
| | - Angelo Arleo
- Sorbonne Université, INSERM, CNRS, Institut de la Vision, Paris, France
- * E-mail: (NRL); (AA)
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