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Rodriguez Gotor JJ, Mahfooz K, Perez-Otano I, Wesseling JF. Parallel processing of quickly and slowly mobilized reserve vesicles in hippocampal synapses. eLife 2024; 12:RP88212. [PMID: 38727712 PMCID: PMC11087054 DOI: 10.7554/elife.88212] [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] [Indexed: 05/12/2024] Open
Abstract
Vesicles within presynaptic terminals are thought to be segregated into a variety of readily releasable and reserve pools. The nature of the pools and trafficking between them is not well understood, but pools that are slow to mobilize when synapses are active are often assumed to feed pools that are mobilized more quickly, in a series. However, electrophysiological studies of synaptic transmission have suggested instead a parallel organization where vesicles within slowly and quickly mobilized reserve pools would separately feed independent reluctant- and fast-releasing subdivisions of the readily releasable pool. Here, we use FM-dyes to confirm the existence of multiple reserve pools at hippocampal synapses and a parallel organization that prevents intermixing between the pools, even when stimulation is intense enough to drive exocytosis at the maximum rate. The experiments additionally demonstrate extensive heterogeneity among synapses in the relative sizes of the slowly and quickly mobilized reserve pools, which suggests equivalent heterogeneity in the numbers of reluctant and fast-releasing readily releasable vesicles that may be relevant for understanding information processing and storage.
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Affiliation(s)
| | - Kashif Mahfooz
- Department of Pharmacology, University of OxfordOxfordUnited Kingdom
| | - Isabel Perez-Otano
- Instituto de Neurociencias de Alicante CSIC-UMHSan Juan de AlicanteSpain
| | - John F Wesseling
- Instituto de Neurociencias de Alicante CSIC-UMHSan Juan de AlicanteSpain
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2
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He K, Han Y, Li X, Hernandez RX, Riboul DV, Feghhi T, Justs KA, Mahneva O, Perry S, Macleod GT, Dickman D. Physiologic and Nanoscale Distinctions Define Glutamatergic Synapses in Tonic vs Phasic Neurons. J Neurosci 2023; 43:4598-4611. [PMID: 37221096 PMCID: PMC10286941 DOI: 10.1523/jneurosci.0046-23.2023] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Revised: 05/05/2023] [Accepted: 05/11/2023] [Indexed: 05/25/2023] Open
Abstract
Neurons exhibit a striking degree of functional diversity, each one tuned to the needs of the circuitry in which it is embedded. A fundamental functional dichotomy occurs in activity patterns, with some neurons firing at a relatively constant "tonic" rate, while others fire in bursts, a "phasic" pattern. Synapses formed by tonic versus phasic neurons are also functionally differentiated, yet the bases of their distinctive properties remain enigmatic. A major challenge toward illuminating the synaptic differences between tonic and phasic neurons is the difficulty in isolating their physiological properties. At the Drosophila neuromuscular junction, most muscle fibers are coinnervated by two motor neurons: the tonic "MN-Ib" and phasic "MN-Is." Here, we used selective expression of a newly developed botulinum neurotoxin transgene to silence tonic or phasic motor neurons in Drosophila larvae of either sex. This approach highlighted major differences in their neurotransmitter release properties, including probability, short-term plasticity, and vesicle pools. Furthermore, Ca2+ imaging demonstrated ∼2-fold greater Ca2+ influx at phasic neuron release sites relative to tonic, along with an enhanced synaptic vesicle coupling. Finally, confocal and super-resolution imaging revealed that phasic neuron release sites are organized in a more compact arrangement, with enhanced stoichiometry of voltage-gated Ca2+ channels relative to other active zone scaffolds. These data suggest that distinctions in active zone nano-architecture and Ca2+ influx collaborate to differentially tune glutamate release at tonic versus phasic synaptic subtypes.SIGNIFICANCE STATEMENT "Tonic" and "phasic" neuronal subtypes, based on differential firing properties, are common across many nervous systems. Using a recently developed approach to selectively silence transmission from one of these two neurons, we reveal specialized synaptic functional and structural properties that distinguish these specialized neurons. This study provides important insights into how input-specific synaptic diversity is achieved, which could have implications for neurologic disorders that involve changes in synaptic function.
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Affiliation(s)
- Kaikai He
- Department of Neurobiology, University of Southern California, Los Angeles, California 90089
- USC Neuroscience Graduate Program, Los Angeles, California 90089
| | - Yifu Han
- Department of Neurobiology, University of Southern California, Los Angeles, California 90089
- USC Neuroscience Graduate Program, Los Angeles, California 90089
| | - Xiling Li
- Department of Neurobiology, University of Southern California, Los Angeles, California 90089
- USC Neuroscience Graduate Program, Los Angeles, California 90089
| | - Roberto X Hernandez
- Integrative Biology and Neuroscience Graduate Program, Department of Biological Sciences, Florida Atlantic University, Boca Raton, Florida 33431
- International Max Planck Research School for Brain and Behavior, Jupiter, Florida 33458
| | - Danielle V Riboul
- Integrative Biology Graduate Program, Department of Biological Sciences, Florida Atlantic University, Boca Raton, Florida 33431
| | - Touhid Feghhi
- Department of Physics, Florida Atlantic University, Boca Raton, Florida 33431
| | - Karlis A Justs
- Integrative Biology and Neuroscience Graduate Program, Department of Biological Sciences, Florida Atlantic University, Boca Raton, Florida 33431
| | - Olena Mahneva
- Wilkes Honors College, Florida Atlantic University, Jupiter, Florida 33458
| | - Sarah Perry
- Department of Neurobiology, University of Southern California, Los Angeles, California 90089
| | - Gregory T Macleod
- Wilkes Honors College, Florida Atlantic University, Jupiter, Florida 33458
- Institute for Human Health and Disease Intervention, Florida Atlantic University, Jupiter, Florida 33458
| | - Dion Dickman
- Department of Neurobiology, University of Southern California, Los Angeles, California 90089
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3
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Zhou Q. Calcium Sensors of Neurotransmitter Release. ADVANCES IN NEUROBIOLOGY 2023; 33:119-138. [PMID: 37615865 DOI: 10.1007/978-3-031-34229-5_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Abstract
Calcium (Ca2+) plays a critical role in triggering all three primary modes of neurotransmitter release (synchronous, asynchronous, and spontaneous). Synaptotagmin1, a protein with two C2 domains, is the first isoform of the synaptotagmin family that was identified and demonstrated as the primary Ca2+ sensor for synchronous neurotransmitter release. Other isoforms of the synaptotagmin family as well as other C2 proteins such as the double C2 domain protein family were found to act as Ca2+ sensors for different modes of neurotransmitter release. Major recent advances and previous data suggest a new model, release-of-inhibition, for the initiation of Ca2+-triggered synchronous neurotransmitter release. Synaptotagmin1 binds Ca2+ via its two C2 domains and relieves a primed pre-fusion machinery. Before Ca2+ triggering, synaptotagmin1 interacts Ca2+ independently with partially zippered SNARE complexes, the plasma membrane, phospholipids, and other components to form a primed pre-fusion state that is ready for fast release. However, membrane fusion is inhibited until the arrival of Ca2+ reorients the Ca2+-binding loops of the C2 domain to perturb the lipid bilayers, help bridge the membranes, and/or induce membrane curvatures, which serves as a power stroke to activate fusion. This chapter reviews the evidence supporting these models and discusses the molecular interactions that may underlie these abilities.
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Affiliation(s)
- Qiangjun Zhou
- Department of Cell and Developmental Biology, Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN, USA.
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4
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Adeoye T, Shah SI, Demuro A, Rabson DA, Ullah G. Upregulated Ca 2+ Release from the Endoplasmic Reticulum Leads to Impaired Presynaptic Function in Familial Alzheimer's Disease. Cells 2022; 11:2167. [PMID: 35883609 PMCID: PMC9315668 DOI: 10.3390/cells11142167] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 06/28/2022] [Accepted: 07/02/2022] [Indexed: 12/10/2022] Open
Abstract
Neurotransmitter release from presynaptic terminals is primarily regulated by rapid Ca2+ influx through membrane-resident voltage-gated Ca2+ channels (VGCCs). Moreover, accumulating evidence indicates that the endoplasmic reticulum (ER) is extensively present in axonal terminals of neurons and plays a modulatory role in synaptic transmission by regulating Ca2+ levels. Familial Alzheimer's disease (FAD) is marked by enhanced Ca2+ release from the ER and downregulation of Ca2+ buffering proteins. However, the precise consequence of impaired Ca2+ signaling within the vicinity of VGCCs (active zone (AZ)) on exocytosis is poorly understood. Here, we perform in silico experiments of intracellular Ca2+ signaling and exocytosis in a detailed biophysical model of hippocampal synapses to investigate the effect of aberrant Ca2+ signaling on neurotransmitter release in FAD. Our model predicts that enhanced Ca2+ release from the ER increases the probability of neurotransmitter release in FAD. Moreover, over very short timescales (30-60 ms), the model exhibits activity-dependent and enhanced short-term plasticity in FAD, indicating neuronal hyperactivity-a hallmark of the disease. Similar to previous observations in AD animal models, our model reveals that during prolonged stimulation (~450 ms), pathological Ca2+ signaling increases depression and desynchronization with stimulus, causing affected synapses to operate unreliably. Overall, our work provides direct evidence in support of a crucial role played by altered Ca2+ homeostasis mediated by intracellular stores in FAD.
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Affiliation(s)
- Temitope Adeoye
- Department of Physics, University of South Florida, Tampa, FL 33620, USA; (T.A.); (S.I.S.); (D.A.R.)
| | - Syed I. Shah
- Department of Physics, University of South Florida, Tampa, FL 33620, USA; (T.A.); (S.I.S.); (D.A.R.)
| | - Angelo Demuro
- Department of Neurobiology and Behavior, University of California, Irvine, CA 92697, USA;
| | - David A. Rabson
- Department of Physics, University of South Florida, Tampa, FL 33620, USA; (T.A.); (S.I.S.); (D.A.R.)
| | - Ghanim Ullah
- Department of Physics, University of South Florida, Tampa, FL 33620, USA; (T.A.); (S.I.S.); (D.A.R.)
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Lopez-Manzaneda M, Fuentes-Moliz A, Tabares L. Presynaptic Mitochondria Communicate With Release Sites for Spatio-Temporal Regulation of Exocytosis at the Motor Nerve Terminal. Front Synaptic Neurosci 2022; 14:858340. [PMID: 35645766 PMCID: PMC9133601 DOI: 10.3389/fnsyn.2022.858340] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Accepted: 04/07/2022] [Indexed: 11/13/2022] Open
Abstract
Presynaptic Ca2+ regulation is critical for accurate neurotransmitter release, vesicle reloading of release sites, and plastic changes in response to electrical activity. One of the main players in the regulation of cytosolic Ca2+ in nerve terminals is mitochondria, which control the size and spread of the Ca2+ wave during sustained electrical activity. However, the role of mitochondria in Ca2+ signaling during high-frequency short bursts of action potentials (APs) is not well known. Here, we studied spatial and temporal relationships between mitochondrial Ca2+ (mCa2+) and exocytosis by live imaging and electrophysiology in adult motor nerve terminals of transgenic mice expressing synaptophysin-pHluorin (SypHy). Our results show that hot spots of exocytosis and mitochondria are organized in subsynaptic functional regions and that mitochondria start to uptake Ca2+ after a few APs. We also show that mitochondria contribute to the regulation of the mode of fusion (synchronous and asynchronous) and the kinetics of release and replenishment of the readily releasable pool (RRP) of vesicles. We propose that mitochondria modulate the timing and reliability of neurotransmission in motor nerve terminals during brief AP trains.
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6
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Three small vesicular pools in sequence govern synaptic response dynamics during action potential trains. Proc Natl Acad Sci U S A 2022; 119:2114469119. [PMID: 35101920 PMCID: PMC8812539 DOI: 10.1073/pnas.2114469119] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/08/2021] [Indexed: 11/30/2022] Open
Abstract
Short-term changes in the strength of synaptic connections underlie many brain functions. The strength of a synapse in response to subsequent stimulation is largely determined by the remaining number of synaptic vesicles available for release. We developed a methodological approach to measure the dynamics of various vesicle pools following synaptic activity. We find that the readily releasable pool, which comprises vesicles that are docked or tethered to release sites, is fed by a small-sized pool containing approximately one to four vesicles per release site at rest. This upstream pool is significantly depleted even after a short stimulation train. Therefore, regulation of the size of the upstream pool emerges as a key factor in determining synaptic strength during and after sustained stimulation. During prolonged trains of presynaptic action potentials (APs), synaptic release reaches a stable level that reflects the speed of replenishment of the readily releasable pool (RRP). Determining the size and filling dynamics of vesicular pools upstream of the RRP has been hampered by a lack of precision of synaptic output measurements during trains. Using the recent technique of tracking vesicular release in single active zone synapses, we now developed a method that allows the sizes of the RRP and upstream pools to be followed in time. We find that the RRP is fed by a small-sized pool containing approximately one to four vesicles per docking site at rest. This upstream pool is significantly depleted by short AP trains, and reaches a steady, depleted state for trains of >10 APs. We conclude that a small, highly dynamic vesicular pool upstream of the RRP potently controls synaptic strength during sustained stimulation.
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Benitez DP, Jiang S, Wood J, Wang R, Hall CM, Peerboom C, Wong N, Stringer KM, Vitanova KS, Smith VC, Joshi D, Saito T, Saido TC, Hardy J, Hanrieder J, De Strooper B, Salih DA, Tripathi T, Edwards FA, Cummings DM. Knock-in models related to Alzheimer's disease: synaptic transmission, plaques and the role of microglia. Mol Neurodegener 2021; 16:47. [PMID: 34266459 PMCID: PMC8281661 DOI: 10.1186/s13024-021-00457-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Accepted: 05/26/2021] [Indexed: 11/18/2022] Open
Abstract
Background Microglia are active modulators of Alzheimer’s disease but their role in relation to amyloid plaques and synaptic changes due to rising amyloid beta is unclear. We add novel findings concerning these relationships and investigate which of our previously reported results from transgenic mice can be validated in knock-in mice, in which overexpression and other artefacts of transgenic technology are avoided. Methods AppNL-F and AppNL-G-F knock-in mice expressing humanised amyloid beta with mutations in App that cause familial Alzheimer’s disease were compared to wild type mice throughout life. In vitro approaches were used to understand microglial alterations at the genetic and protein levels and synaptic function and plasticity in CA1 hippocampal neurones, each in relationship to both age and stage of amyloid beta pathology. The contribution of microglia to neuronal function was further investigated by ablating microglia with CSF1R inhibitor PLX5622. Results Both App knock-in lines showed increased glutamate release probability prior to detection of plaques. Consistent with results in transgenic mice, this persisted throughout life in AppNL-F mice but was not evident in AppNL-G-F with sparse plaques. Unlike transgenic mice, loss of spontaneous excitatory activity only occurred at the latest stages, while no change could be detected in spontaneous inhibitory synaptic transmission or magnitude of long-term potentiation. Also, in contrast to transgenic mice, the microglial response in both App knock-in lines was delayed until a moderate plaque load developed. Surviving PLX5266-depleted microglia tended to be CD68-positive. Partial microglial ablation led to aged but not young wild type animals mimicking the increased glutamate release probability in App knock-ins and exacerbated the App knock-in phenotype. Complete ablation was less effective in altering synaptic function, while neither treatment altered plaque load. Conclusions Increased glutamate release probability is similar across knock-in and transgenic mouse models of Alzheimer’s disease, likely reflecting acute physiological effects of soluble amyloid beta. Microglia respond later to increased amyloid beta levels by proliferating and upregulating Cd68 and Trem2. Partial depletion of microglia suggests that, in wild type mice, alteration of surviving phagocytic microglia, rather than microglial loss, drives age-dependent effects on glutamate release that become exacerbated in Alzheimer’s disease. Supplementary Information The online version contains supplementary material available at 10.1186/s13024-021-00457-0.
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Affiliation(s)
- Diana P Benitez
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Shenyi Jiang
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.,Ludwig Maximilians Universitat, Munich, Germany
| | - Jack Wood
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Rui Wang
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.,Institute for Synaptic Physiology, Center for Molecular Neurobiology (ZMNH), University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Chloe M Hall
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.,School of Pharmacy and Biomolecular Sciences, University of Brighton, Brighton, UK
| | - Carlijn Peerboom
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.,Cell Biology, Neurobiology and Biophysics, Biology Department, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands
| | - Natalie Wong
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Katie M Stringer
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.,Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Mölndal, Sweden
| | - Karina S Vitanova
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Victoria C Smith
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.,Centre for Doctoral Training at the Institute of Health Informatics, University College London, 222 Euston Road, London, NW1 2DA, UK
| | - Dhaval Joshi
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.,Department of Psychology, University of Cambridge, Cambridge, UK
| | - Takashi Saito
- Laboratory for Proteolytic Neuroscience, RIKEN Center for Brain Science, 2-1 Wako-shi, Saitama, 351-0198, Japan.,Department of Neurocognitive Science, Institute of Brain Science, Nagoya City, University Graduate School of Medical Sciences, Nagoya, Aichi, Japan
| | - Takaomi C Saido
- Laboratory for Proteolytic Neuroscience, RIKEN Center for Brain Science, 2-1 Wako-shi, Saitama, 351-0198, Japan
| | - John Hardy
- Dementia Research Institute, University College London, Gower Street, London, WC1E 6BT, UK.,Reta Lila Weston Institute, UCL Queen Square Institute of Neurology, 1 Wakefield Street, London, WC1N 1PJ, UK.,UCL Movement Disorders Centre, University College London, London, UK.,Institute for Advanced Study, The Hong Kong University of Science and Technology, Hong Kong, SAR, China
| | - Jörg Hanrieder
- Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Mölndal, Sweden.,Department of Neurodegenerative Disease, UCL Queen Square Institute of Neurology, Queen Square, London, WC1N 3BG, UK
| | - Bart De Strooper
- Dementia Research Institute, University College London, Gower Street, London, WC1E 6BT, UK.,VIB Center for Brain & Disease Research, 3000, Leuven, KU, Belgium.,Department of Neurosciences, Leuven Brain Institute, 3000, Leuven, Belgium
| | - Dervis A Salih
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.,Dementia Research Institute, University College London, Gower Street, London, WC1E 6BT, UK
| | - Takshashila Tripathi
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Frances A Edwards
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK. .,Institute of Healthy Ageing, University College London, Gower Street, London, WC1E 6BT, UK.
| | - Damian M Cummings
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK. .,Dementia Research Institute, University College London, Gower Street, London, WC1E 6BT, UK.
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8
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Xiong GJ, Cheng XT, Sun T, Xie Y, Huang N, Li S, Lin MY, Sheng ZH. Defects in syntabulin-mediated synaptic cargo transport associate with autism-like synaptic dysfunction and social behavioral traits. Mol Psychiatry 2021; 26:1472-1490. [PMID: 32332993 PMCID: PMC7584772 DOI: 10.1038/s41380-020-0713-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 03/05/2020] [Accepted: 03/10/2020] [Indexed: 01/09/2023]
Abstract
The formation and maintenance of synapses require long-distance delivery of newly synthesized synaptic proteins from the soma to distal synapses, raising the fundamental question of whether impaired transport is associated with neurodevelopmental disorders such as autism. We previously revealed that syntabulin acts as a motor adapter linking kinesin-1 motor and presynaptic cargos. Here, we report that defects in syntabulin-mediated transport and thus reduced formation and maturation of synapses are one of core synaptic mechanisms underlying autism-like synaptic dysfunction and social behavioral abnormalities. Syntabulin expression in the mouse brain peaks during the first 2 weeks of postnatal development and progressively declines during brain maturation. Neurons from conditional syntabulin-/- mice (stb cKO) display impaired transport of presynaptic cargos, reduced synapse density and active zones, and altered synaptic transmission and long-term plasticity. Intriguingly, stb cKO mice exhibit core autism-like traits, including defective social recognition and communication, increased stereotypic behavior, and impaired spatial learning and memory. These phenotypes establish a new mechanistic link between reduced transport of synaptic cargos and impaired maintenance of synaptic transmission and plasticity, contributing to autism-associated behavioral abnormalities. This notion is further confirmed by the human missense variant STB-R178Q, which is found in an autism patient and loses its adapter capacity for binding kinesin-1 motors. Expressing STB-R178Q fails to rescue reduced synapse formation and impaired synaptic transmission and plasticity in stb cKO neurons. Altogether, our study suggests that defects in syntabulin-mediated transport mechanisms underlie the synaptic dysfunction and behavioral abnormalities that bear similarities to autism.
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Affiliation(s)
- Gui-Jing Xiong
- Synaptic Function Section, The Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Room 2B-215, 35 Convent Drive, Bethesda, MD, 20892-3706, USA
| | - Xiu-Tang Cheng
- Synaptic Function Section, The Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Room 2B-215, 35 Convent Drive, Bethesda, MD, 20892-3706, USA
| | - Tao Sun
- Synaptic Function Section, The Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Room 2B-215, 35 Convent Drive, Bethesda, MD, 20892-3706, USA
| | - Yuxiang Xie
- Synaptic Function Section, The Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Room 2B-215, 35 Convent Drive, Bethesda, MD, 20892-3706, USA
| | - Ning Huang
- Synaptic Function Section, The Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Room 2B-215, 35 Convent Drive, Bethesda, MD, 20892-3706, USA
| | - Sunan Li
- Synaptic Function Section, The Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Room 2B-215, 35 Convent Drive, Bethesda, MD, 20892-3706, USA
| | - Mei-Yao Lin
- Synaptic Function Section, The Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Room 2B-215, 35 Convent Drive, Bethesda, MD, 20892-3706, USA
| | - Zu-Hang Sheng
- Synaptic Function Section, The Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Room 2B-215, 35 Convent Drive, Bethesda, MD, 20892-3706, USA.
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Ivanova D, Dobson KL, Gajbhiye A, Davenport EC, Hacker D, Ultanir SK, Trost M, Cousin MA. Control of synaptic vesicle release probability via VAMP4 targeting to endolysosomes. SCIENCE ADVANCES 2021; 7:7/18/eabf3873. [PMID: 33931449 PMCID: PMC8087399 DOI: 10.1126/sciadv.abf3873] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 03/11/2021] [Indexed: 05/03/2023]
Abstract
Synaptic vesicle (SV) release probability (Pr), determines the steady state and plastic control of neurotransmitter release. However, how diversity in SV composition arises and regulates the Pr of individual SVs is not understood. We found that modulation of the copy number of the noncanonical vesicular SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor), vesicle-associated membrane protein 4 (VAMP4), on SVs is key for regulating Pr. Mechanistically, this is underpinned by its reduced ability to form an efficient SNARE complex with canonical plasma membrane SNAREs. VAMP4 has unusually high synaptic turnover and is selectively sorted to endolysosomes during activity-dependent bulk endocytosis. Disruption of endolysosomal trafficking and function markedly increased the abundance of VAMP4 in the SV pool and inhibited SV fusion. Together, our results unravel a new mechanism for generating SV heterogeneity and control of Pr through coupling of SV recycling to a major clearing system that regulates protein homeostasis.
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Affiliation(s)
- Daniela Ivanova
- Centre for Discovery Brain Sciences, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland.
- Muir Maxwell Epilepsy Centre, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland
- Simons Initiative for the Developing Brain, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland
| | - Katharine L Dobson
- Centre for Discovery Brain Sciences, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland
- Muir Maxwell Epilepsy Centre, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland
- Simons Initiative for the Developing Brain, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland
| | - Akshada Gajbhiye
- Newcastle University Biosciences Institute, Faculty of Medical Sciences, Newcastle upon Tyne NE2 4HH, UK
| | - Elizabeth C Davenport
- Centre for Discovery Brain Sciences, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland
- Muir Maxwell Epilepsy Centre, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland
- Simons Initiative for the Developing Brain, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland
| | - Daniela Hacker
- Centre for Discovery Brain Sciences, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland
- Muir Maxwell Epilepsy Centre, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland
- Simons Initiative for the Developing Brain, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland
| | - Sila K Ultanir
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Matthias Trost
- Newcastle University Biosciences Institute, Faculty of Medical Sciences, Newcastle upon Tyne NE2 4HH, UK
| | - Michael A Cousin
- Centre for Discovery Brain Sciences, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland.
- Muir Maxwell Epilepsy Centre, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland
- Simons Initiative for the Developing Brain, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland
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10
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Li S, Raychaudhuri S, Lee SA, Brockmann MM, Wang J, Kusick G, Prater C, Syed S, Falahati H, Ramos R, Bartol TM, Hosy E, Watanabe S. Asynchronous release sites align with NMDA receptors in mouse hippocampal synapses. Nat Commun 2021; 12:677. [PMID: 33514725 PMCID: PMC7846561 DOI: 10.1038/s41467-021-21004-x] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Accepted: 01/08/2021] [Indexed: 01/30/2023] Open
Abstract
Neurotransmitter is released synchronously and asynchronously following an action potential. Our recent study indicates that the release sites of these two phases are segregated within an active zone, with asynchronous release sites enriched near the center in mouse hippocampal synapses. Here we demonstrate that synchronous and asynchronous release sites are aligned with AMPA receptor and NMDA receptor clusters, respectively. Computational simulations indicate that this spatial and temporal arrangement of release can lead to maximal membrane depolarization through AMPA receptors, alleviating the pore-blocking magnesium leading to greater activation of NMDA receptors. Together, these results suggest that release sites are likely organized to activate NMDA receptors efficiently.
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Affiliation(s)
- Shuo Li
- Department of Cell Biology, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
- Department of Biological and Molecular Biology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Sumana Raychaudhuri
- Department of Cell Biology, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
| | - Stephen Alexander Lee
- Neurobiology Course, The Marine Biological Laboratory, Woods Hole, MA, USA
- Department of Biomedical Engineering, Columbia University, New York, NY, USA
| | - Marisa M Brockmann
- Institute of Neurophysiology, Charité Universitätsmedizin, Berlin, Germany
| | - Jing Wang
- ThermoFisher Scientific, Hillsboro, OR, USA
| | - Grant Kusick
- Department of Cell Biology, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
- Biochemistry, Cellular and Molecular Biology Graduate Program, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
| | - Christine Prater
- Neurobiology Course, The Marine Biological Laboratory, Woods Hole, MA, USA
- Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, USA
| | - Sarah Syed
- Department of Cell Biology, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
| | - Hanieh Falahati
- Neurobiology Course, The Marine Biological Laboratory, Woods Hole, MA, USA
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT, USA
| | - Raul Ramos
- Neurobiology Course, The Marine Biological Laboratory, Woods Hole, MA, USA
- Department of Biology, Brandeis University, Waltham, MA, USA
| | - Tomas M Bartol
- Salk Institute for Biological Studies, La Jolla, CA, USA
| | - Eric Hosy
- Centre National de la Recherche Scientifique, Bordeaux, France
- Interdisciplinary Institute for Neuroscience, University of Bordeaux, Bordeaux, France
| | - Shigeki Watanabe
- Department of Cell Biology, Johns Hopkins University, School of Medicine, Baltimore, MD, USA.
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, School of Medicine, Baltimore, MD, USA.
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11
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Wang QW, Lu SY, Liu YN, Chen Y, Wei H, Shen W, Chen YF, Fu CL, Wang YH, Dai A, Huang X, Gage FH, Xu Q, Yao J. Synaptotagmin-7 deficiency induces mania-like behavioral abnormalities through attenuating GluN2B activity. Proc Natl Acad Sci U S A 2020; 117:31438-31447. [PMID: 33229564 PMCID: PMC7733786 DOI: 10.1073/pnas.2016416117] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Synaptotagmin-7 (Syt7) probably plays an important role in bipolar-like behavioral abnormalities in mice; however, the underlying mechanisms for this have remained elusive. Unlike antidepressants that cause mood overcorrection in bipolar depression, N-methyl-d-aspartate receptor (NMDAR)-targeted drugs show moderate clinical efficacy, for unexplained reasons. Here we identified Syt7 single nucleotide polymorphisms (SNPs) in patients with bipolar disorder and demonstrated that mice lacking Syt7 or expressing the SNPs showed GluN2B-NMDAR dysfunction, leading to antidepressant behavioral consequences and avoidance of overcorrection by NMDAR antagonists. In human induced pluripotent stem cell (iPSC)-derived and mouse hippocampal neurons, Syt7 and GluN2B-NMDARs were localized to the peripheral synaptic region, and Syt7 triggered multiple forms of glutamate release to efficiently activate the juxtaposed GluN2B-NMDARs. Thus, while Syt7 deficiency and SNPs induced GluN2B-NMDAR dysfunction in mice, patient iPSC-derived neurons showed Syt7 deficit-induced GluN2B-NMDAR hypoactivity that was rescued by Syt7 overexpression. Therefore, Syt7 deficits induced mania-like behaviors in mice by attenuating GluN2B activity, which enabled NMDAR antagonists to avoid mood overcorrection.
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Affiliation(s)
- Qiu-Wen Wang
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, 100084 Beijing, China
| | - Si-Yao Lu
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, 100084 Beijing, China
| | - Yao-Nan Liu
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, 100084 Beijing, China
| | - Yun Chen
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, 100084 Beijing, China
| | - Hui Wei
- State Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences Chinese Academy of Medical Sciences and Peking Union Medical College, Neuroscience Center, Chinese Academy of Medical Sciences, 100005 Beijing, China
| | - Wei Shen
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, 100084 Beijing, China
| | - Yan-Fen Chen
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, 100084 Beijing, China
| | - Chong-Lei Fu
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, 100084 Beijing, China
| | - Ying-Han Wang
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, 100084 Beijing, China
| | - Anbang Dai
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, 100084 Beijing, China
| | - Xuan Huang
- Medical Research Center, Beijing Chao-Yang Hospital, Capital Medical University, 100020 Beijing, China
| | - Fred H Gage
- Laboratory of Genetics, The Salk Institute for Biological Studies, La Jolla, CA 92037
| | - Qi Xu
- State Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences Chinese Academy of Medical Sciences and Peking Union Medical College, Neuroscience Center, Chinese Academy of Medical Sciences, 100005 Beijing, China;
| | - Jun Yao
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, IDG/McGovern Institute for Brain Research, School of Life Sciences, Tsinghua University, 100084 Beijing, China;
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12
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Huson V, Regehr WG. Diverse roles of Synaptotagmin-7 in regulating vesicle fusion. Curr Opin Neurobiol 2020; 63:42-52. [PMID: 32278209 DOI: 10.1016/j.conb.2020.02.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Revised: 02/12/2020] [Accepted: 02/13/2020] [Indexed: 11/18/2022]
Abstract
Synaptotagmin 7 (Syt7) is a multifunctional calcium sensor expressed throughout the body. Its high calcium affinity makes it well suited to act in processes triggered by modest calcium increases within cells. In synaptic transmission, Syt7 has been shown to mediate asynchronous neurotransmitter release, facilitation, and vesicle replenishment. In this review we provide an update on recent developments, and the newly emerging roles of Syt7 in frequency invariant synaptic transmission and in suppressing spontaneous release. Additionally, we discuss Syt7's regulation of membrane fusion in non-neuronal cells, and its involvement in disease. How such diversity of functions is regulated remains an open question. We discuss several potential factors including temperature, presynaptic calcium signals, the localization of Syt7, and its interaction with other Syt isoforms.
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13
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Schwarz Y, Oleinikov K, Schindeldecker B, Wyatt A, Weißgerber P, Flockerzi V, Boehm U, Freichel M, Bruns D. TRPC channels regulate Ca2+-signaling and short-term plasticity of fast glutamatergic synapses. PLoS Biol 2019; 17:e3000445. [PMID: 31536487 PMCID: PMC6773422 DOI: 10.1371/journal.pbio.3000445] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 10/01/2019] [Accepted: 08/29/2019] [Indexed: 11/18/2022] Open
Abstract
Transient receptor potential (TRP) proteins form Ca2+-permeable, nonselective cation channels, but their role in neuronal Ca2+ homeostasis is elusive. In the present paper, we show that TRPC channels potently regulate synaptic plasticity by changing the presynaptic Ca2+-homeostasis of hippocampal neurons. Specifically, loss of TRPC1/C4/C5 channels decreases basal-evoked secretion, reduces the pool size of readily releasable vesicles, and accelerates synaptic depression during high-frequency stimulation (HFS). In contrast, primary TRPC5 channel-expressing neurons, identified by a novel TRPC5–τ-green fluorescent protein (τGFP) knockin mouse line, show strong short-term enhancement (STE) of synaptic signaling during HFS, indicating a key role of TRPC5 in short-term plasticity. Lentiviral expression of either TRPC1 or TRPC5 turns classic synaptic depression of wild-type neurons into STE, demonstrating that TRPCs are instrumental in regulating synaptic plasticity. Presynaptic Ca2+ imaging shows that TRPC activity strongly boosts synaptic Ca2+ dynamics, showing that TRPC channels provide an additional presynaptic Ca2+ entry pathway, which efficiently regulates synaptic strength and plasticity. Transient receptor potential (TRP) proteins can form non-selective cation channels, but their role in synaptic transmission is poorly understood. This study shows that calcium-permeable TRPC channels provide an additional calcium entry pathway at presynaptic sites and are efficient regulators of synaptic strength and plasticity.
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Affiliation(s)
- Yvonne Schwarz
- Institute for Physiology, Saarland University, CIPMM, Homburg/Saar, Germany
| | | | | | - Amanda Wyatt
- Experimental and Clinical Pharmacology and Toxicology, PZMS, Saarland University, Homburg/Saar, Germany
| | - Petra Weißgerber
- Experimental and Clinical Pharmacology and Toxicology, PZMS, Saarland University, Homburg/Saar, Germany
| | - Veit Flockerzi
- Experimental and Clinical Pharmacology and Toxicology, PZMS, Saarland University, Homburg/Saar, Germany
| | - Ulrich Boehm
- Experimental and Clinical Pharmacology and Toxicology, PZMS, Saarland University, Homburg/Saar, Germany
| | - Marc Freichel
- Institute of Pharmacology, University of Heidelberg, Heidelberg, Germany
| | - Dieter Bruns
- Institute for Physiology, Saarland University, CIPMM, Homburg/Saar, Germany
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14
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Forte N, Binda F, Contestabile A, Benfenati F, Baldelli P. Synapsin I Synchronizes GABA Release in Distinct Interneuron Subpopulations. Cereb Cortex 2019; 30:1393-1406. [DOI: 10.1093/cercor/bhz174] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Revised: 07/02/2019] [Accepted: 07/03/2019] [Indexed: 01/28/2023] Open
Abstract
Abstract
Neurotransmitters can be released either synchronously or asynchronously with respect to action potential timing. Synapsins (Syns) are a family of synaptic vesicle (SV) phosphoproteins that assist gamma-aminobutyric acid (GABA) release and allow a physiological excitation/inhibition balance. Consistently, deletion of either or both Syn1 and Syn2 genes is epileptogenic. In this work, we have characterized the effect of SynI knockout (KO) in the regulation of GABA release dynamics. Using patch-clamp recordings in hippocampal slices, we demonstrate that the lack of SynI impairs synchronous GABA release via a reduction of the readily releasable SVs and, in parallel, increases asynchronous GABA release. The effects of SynI deletion on synchronous GABA release were occluded by ω-AgatoxinIVA, indicating the involvement of P/Q-type Ca2+channel-expressing neurons. Using in situ hybridization, we show that SynI is more expressed in parvalbumin (PV) interneurons, characterized by synchronous release, than in cholecystokinin or SOM interneurons, characterized by a more asynchronous release. Optogenetic activation of PV and SOM interneurons revealed a specific reduction of synchronous release in PV/SynIKO interneurons associated with an increased asynchronous release in SOM/SynIKO interneurons. The results demonstrate that SynI is differentially expressed in interneuron subpopulations, where it boosts synchronous and limits asynchronous GABA release.
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Affiliation(s)
- N Forte
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Largo Rosanna Benzi 10, 16132 Genova, Italy
- IRCSS, Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132 Genova, Italy
| | - F Binda
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Largo Rosanna Benzi 10, 16132 Genova, Italy
- IRCSS, Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132 Genova, Italy
| | - A Contestabile
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| | - F Benfenati
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Largo Rosanna Benzi 10, 16132 Genova, Italy
- IRCSS, Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132 Genova, Italy
| | - P Baldelli
- IRCSS, Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132 Genova, Italy
- Department of Experimental Medicine, University of Genova, Viale Benedetto XV, 3, 16132 Genova, Italy
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15
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Synaptotagmin-1 enables frequency coding by suppressing asynchronous release in a temperature dependent manner. Sci Rep 2019; 9:11341. [PMID: 31383906 PMCID: PMC6683208 DOI: 10.1038/s41598-019-47487-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Accepted: 07/17/2019] [Indexed: 01/08/2023] Open
Abstract
To support frequency-coded information transfer, mammalian synapses tightly synchronize neurotransmitter release to action potentials (APs). However, release desynchronizes during AP trains, especially at room temperature. Here we show that suppression of asynchronous release by Synaptotagmin-1 (Syt1), but not release triggering, is highly temperature sensitive, and enhances synchronous release during high-frequency stimulation. In Syt1-deficient synapses, asynchronous release increased with temperature, opposite to wildtype synapses. Mutations in Syt1 C2B-domain polybasic stretch (Syt1 K326Q,K327Q,K331Q) did not affect synchronization during sustained activity, while the previously observed reduced synchronous response to a single AP was confirmed. However, an inflexible linker between the C2-domains (Syt1 9Pro) reduced suppression, without affecting synchronous release upon a single AP. Syt1 9Pro expressing synapses showed impaired synchronization during AP trains, which was rescued by buffering global Ca2+ to prevent asynchronous release. Hence, frequency coding relies on Syt1's temperature sensitive suppression of asynchronous release, an aspect distinct from its known vesicle recruitment and triggering functions.
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16
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Salmasi M, Loebel A, Glasauer S, Stemmler M. Short-term synaptic depression can increase the rate of information transfer at a release site. PLoS Comput Biol 2019; 15:e1006666. [PMID: 30601804 PMCID: PMC6355030 DOI: 10.1371/journal.pcbi.1006666] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2018] [Revised: 01/31/2019] [Accepted: 11/23/2018] [Indexed: 11/18/2022] Open
Abstract
The release of neurotransmitters from synapses obeys complex and stochastic dynamics. Depending on the recent history of synaptic activation, many synapses depress the probability of releasing more neurotransmitter, which is known as synaptic depression. Our understanding of how synaptic depression affects the information efficacy, however, is limited. Here we propose a mathematically tractable model of both synchronous spike-evoked release and asynchronous release that permits us to quantify the information conveyed by a synapse. The model transits between discrete states of a communication channel, with the present state depending on many past time steps, emulating the gradual depression and exponential recovery of the synapse. Asynchronous and spontaneous releases play a critical role in shaping the information efficacy of the synapse. We prove that depression can enhance both the information rate and the information rate per unit energy expended, provided that synchronous spike-evoked release depresses less (or recovers faster) than asynchronous release. Furthermore, we explore the theoretical implications of short-term synaptic depression adapting on longer time scales, as part of the phenomenon of metaplasticity. In particular, we show that a synapse can adjust its energy expenditure by changing the dynamics of short-term synaptic depression without affecting the net information conveyed by each successful release. Moreover, the optimal input spike rate is independent of the amplitude or time constant of synaptic depression. We analyze the information efficacy of three types of synapses for which the short-term dynamics of both synchronous and asynchronous release have been experimentally measured. In hippocampal autaptic synapses, the persistence of asynchronous release during depression cannot compensate for the reduction of synchronous release, so that the rate of information transmission declines with synaptic depression. In the calyx of Held, the information rate per release remains constant despite large variations in the measured asynchronous release rate. Lastly, we show that dopamine, by controlling asynchronous release in corticostriatal synapses, increases the synaptic information efficacy in nucleus accumbens. Fatigue is an intrinsic property of living systems and synapses are no exception. Synaptic depression reduces the ability of synapses to release vesicles in response to an incoming action potential. Whether synaptic depression simply reflects the exhaustion of neuronal resources or whether it serves some additional function is still an open question. We ask how synaptic depression modulates the information transfer between neurons by keeping the synapse in an appropriate operating range. Using a tractable mathematical model for synaptic depression of both synchronous spike-evoked and asynchronous release of neurotransmitter, we derive a closed-form expression for the mutual information rate. Depression, it turns out, can both enhance or impair information transfer, depending on the relative level of depression for synchronous spike-evoked and asynchronous releases. We also study the compromise a synapse makes between its energy consumption and the rate of information transmission. Interestingly, we show that synaptic depression can regulate energy use without affecting the information (measured in bits) per synaptic release. By applying our mathematical framework to experimentally measured synapses, we show that some synapses can compensate for intrinsic variability in asynchronous release rates; moreover, we show how neuromodulators such as dopamine act to improve the information transmission rate.
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Affiliation(s)
- Mehrdad Salmasi
- Graduate School of Systemic Neurosciences, Ludwig-Maximilians-Universität, Munich, Germany.,Bernstein Center for Computational Neuroscience, Munich, Germany.,German Center for Vertigo and Balance Disorders, Ludwig-Maximilians-Universität, Munich, Germany
| | - Alex Loebel
- Bernstein Center for Computational Neuroscience, Munich, Germany.,Department of Biology II, Ludwig-Maximilians-Universität, Munich, Germany
| | - Stefan Glasauer
- Bernstein Center for Computational Neuroscience, Munich, Germany.,German Center for Vertigo and Balance Disorders, Ludwig-Maximilians-Universität, Munich, Germany.,Chair of Computational Neuroscience, Brandenburg University of Technology Cottbus-Senftenberg, Senftenberg, Germany
| | - Martin Stemmler
- Bernstein Center for Computational Neuroscience, Munich, Germany.,Department of Biology II, Ludwig-Maximilians-Universität, Munich, Germany
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17
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Chanaday NL, Kavalali ET. Presynaptic origins of distinct modes of neurotransmitter release. Curr Opin Neurobiol 2018; 51:119-126. [PMID: 29597140 PMCID: PMC6066415 DOI: 10.1016/j.conb.2018.03.005] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Revised: 02/22/2018] [Accepted: 03/12/2018] [Indexed: 11/17/2022]
Abstract
Presynaptic nerve terminals release neurotransmitter synchronously, asynchronously or spontaneously. During synchronous neurotransmission release is precisely coupled to action potentials, in contrast, asynchronous release events show only loose temporal coupling to presynaptic activity whereas spontaneous neurotransmission occurs independent of presynaptic activity. The mechanisms that give rise to this diversity in neurotransmitter release modes are poorly understood. Recent studies have described several presynaptic molecular pathways controlling synaptic vesicle pool segregation and recycling, which in turn may dictate distinct modes of neurotransmitter release. In this article, we review this recent work regarding neurotransmitter release modes and their relationship to synaptic vesicle pool dynamics as well as the molecular machinery that establishes synaptic vesicle pool identity.
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Affiliation(s)
- Natali L Chanaday
- Department of Neuroscience, the University of Texas Southwestern Medical Center, Dallas, TX 75390-9111, USA
| | - Ege T Kavalali
- Department of Neuroscience, the University of Texas Southwestern Medical Center, Dallas, TX 75390-9111, USA.
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18
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He E, Lozano MAG, Stringer S, Watanabe K, Sakamoto K, den Oudsten F, Koopmans F, Giamberardino SN, Hammerschlag A, Cornelisse LN, Li KW, van Weering J, Posthuma D, Smit AB, Sullivan PF, Verhage M. MIR137 schizophrenia-associated locus controls synaptic function by regulating synaptogenesis, synapse maturation and synaptic transmission. Hum Mol Genet 2018; 27:1879-1891. [PMID: 29635364 PMCID: PMC5961183 DOI: 10.1093/hmg/ddy089] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2017] [Revised: 02/15/2018] [Accepted: 02/17/2018] [Indexed: 02/06/2023] Open
Abstract
The MIR137 locus is a replicated genetic risk factor for schizophrenia. The risk-associated allele is reported to increase miR-137 expression and miR-137 overexpression alters synaptic transmission in mouse hippocampus. We investigated the cellular mechanisms underlying these observed effects in mouse hippocampal neurons in culture. First, we correlated the risk allele to expression of the genes in the MIR137 locus in human postmortem brain. Some evidence for increased MIR137HG expression was observed, especially in hippocampus of the disease-associated genotype. Second, in mouse hippocampal neurons, we confirmed previously observed changes in synaptic transmission upon miR-137 overexpression. Evoked synaptic transmission and spontaneous release were 50% reduced. We identified defects in release probability as the underlying cause. In contrast to previous observations, no evidence was obtained for selective synaptic vesicle docking defects. Instead, ultrastructural morphometry revealed multiple effects of miR-137 overexpression on docking, active zone length and total vesicle number. Moreover, proteomic analyses of neuronal protein showed that expression of Syt1 and Cplx1, previously reported as downregulated upon miR-137 overexpression, was unaltered. Immunocytochemistry of synapses overexpressing miR-137 showed normal Synaptotagmin1 and Complexin1 protein levels. Instead, our proteomic analyses revealed altered expression of genes involved in synaptogenesis. Concomitantly, synaptogenesis assays revealed 31% reduction in synapse formation. Taken together, these data show that miR-137 regulates synaptic function by regulating synaptogenesis, synaptic ultrastructure and synapse function. These effects are plausible contributors to the increased schizophrenia risk associated with miR-137 overexpression.
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Affiliation(s)
- Enqi He
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research (CNCR), Amsterdam Neuroscience, VU University Amsterdam and VU Medical Center, 1081 HV Amsterdam, The Netherlands
| | - Miguel A Gonzalez Lozano
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research (CNCR), Amsterdam Neuroscience, VU University Amsterdam and VU Medical Center, 1081 HV Amsterdam, The Netherlands
| | - Sven Stringer
- Department of Complex Trait Genetics, Center for Neurogenomics and Cognitive Research (CNCR), Amsterdam Neuroscience, VU University Amsterdam and VU Medical Center, 1081 HV Amsterdam, The Netherlands
| | - Kyoko Watanabe
- Department of Complex Trait Genetics, Center for Neurogenomics and Cognitive Research (CNCR), Amsterdam Neuroscience, VU University Amsterdam and VU Medical Center, 1081 HV Amsterdam, The Netherlands
| | - Kensuke Sakamoto
- Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Nobels väg 12A, 171 77 Stockholm, Sweden
- Department of Genetics, Center for Psychiatric Genomics, University of North Carolina at Chapel Hill, NC, USA
| | - Frank den Oudsten
- Department of Clinical Genetics, Center for Neurogenomics and Cognitive Research (CNCR), Amsterdam Neuroscience, VU University Amsterdam and VU Medical Center, 1081 HV Amsterdam, The Netherlands
| | - Frank Koopmans
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research (CNCR), Amsterdam Neuroscience, VU University Amsterdam and VU Medical Center, 1081 HV Amsterdam, The Netherlands
| | - Stephanie N Giamberardino
- Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Nobels väg 12A, 171 77 Stockholm, Sweden
- Department of Genetics, Center for Psychiatric Genomics, University of North Carolina at Chapel Hill, NC, USA
| | - Anke Hammerschlag
- Department of Complex Trait Genetics, Center for Neurogenomics and Cognitive Research (CNCR), Amsterdam Neuroscience, VU University Amsterdam and VU Medical Center, 1081 HV Amsterdam, The Netherlands
| | - L Niels Cornelisse
- Department of Clinical Genetics, Center for Neurogenomics and Cognitive Research (CNCR), Amsterdam Neuroscience, VU University Amsterdam and VU Medical Center, 1081 HV Amsterdam, The Netherlands
| | - Ka Wan Li
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research (CNCR), Amsterdam Neuroscience, VU University Amsterdam and VU Medical Center, 1081 HV Amsterdam, The Netherlands
| | - Jan van Weering
- Department of Clinical Genetics, Center for Neurogenomics and Cognitive Research (CNCR), Amsterdam Neuroscience, VU University Amsterdam and VU Medical Center, 1081 HV Amsterdam, The Netherlands
| | - Danielle Posthuma
- Department of Complex Trait Genetics, Center for Neurogenomics and Cognitive Research (CNCR), Amsterdam Neuroscience, VU University Amsterdam and VU Medical Center, 1081 HV Amsterdam, The Netherlands
| | - August B Smit
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research (CNCR), Amsterdam Neuroscience, VU University Amsterdam and VU Medical Center, 1081 HV Amsterdam, The Netherlands
| | - Patrick F Sullivan
- Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Nobels väg 12A, 171 77 Stockholm, Sweden
- Department of Genetics, Center for Psychiatric Genomics, University of North Carolina at Chapel Hill, NC, USA
| | - Matthijs Verhage
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research (CNCR), Amsterdam Neuroscience, VU University Amsterdam and VU Medical Center, 1081 HV Amsterdam, The Netherlands
- Department of Clinical Genetics, Center for Neurogenomics and Cognitive Research (CNCR), Amsterdam Neuroscience, VU University Amsterdam and VU Medical Center, 1081 HV Amsterdam, The Netherlands
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19
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Nieus T, D'Andrea V, Amin H, Di Marco S, Safaai H, Maccione A, Berdondini L, Panzeri S. State-dependent representation of stimulus-evoked activity in high-density recordings of neural cultures. Sci Rep 2018; 8:5578. [PMID: 29615719 PMCID: PMC5882875 DOI: 10.1038/s41598-018-23853-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Accepted: 03/21/2018] [Indexed: 01/01/2023] Open
Abstract
Neuronal responses to external stimuli vary from trial to trial partly because they depend on continuous spontaneous variations of the state of neural circuits, reflected in variations of ongoing activity prior to stimulus presentation. Understanding how post-stimulus responses relate to the pre-stimulus spontaneous activity is thus important to understand how state dependence affects information processing and neural coding, and how state variations can be discounted to better decode single-trial neural responses. Here we exploited high-resolution CMOS electrode arrays to record simultaneously from thousands of electrodes in in-vitro cultures stimulated at specific sites. We used information-theoretic analyses to study how ongoing activity affects the information that neuronal responses carry about the location of the stimuli. We found that responses exhibited state dependence on the time between the last spontaneous burst and the stimulus presentation and that the dependence could be described with a linear model. Importantly, we found that a small number of selected neurons carry most of the stimulus information and contribute to the state-dependent information gain. This suggests that a major value of large-scale recording is that it individuates the small subset of neurons that carry most information and that benefit the most from knowledge of its state dependence.
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Affiliation(s)
- Thierry Nieus
- NetS3 Laboratory, Neuroscience and Brain Technologies Department, Istituto Italiano di Tecnologia, Genova, Italy. .,Department of Biomedical and Clinical Sciences "Luigi Sacco", Università di Milano, Milano, Italy.
| | - Valeria D'Andrea
- Neural Computation Laboratory, Center for Neuroscience and Cognitive Systems @UniTn, Istituto Italiano di Tecnologia, Rovereto, Italy
| | - Hayder Amin
- NetS3 Laboratory, Neuroscience and Brain Technologies Department, Istituto Italiano di Tecnologia, Genova, Italy
| | - Stefano Di Marco
- NetS3 Laboratory, Neuroscience and Brain Technologies Department, Istituto Italiano di Tecnologia, Genova, Italy.,Scienze cliniche applicate e biotecnologiche, Università dell'Aquila, L'Aquila, Italy
| | - Houman Safaai
- Neural Computation Laboratory, Center for Neuroscience and Cognitive Systems @UniTn, Istituto Italiano di Tecnologia, Rovereto, Italy.,Department of Neurobiology, Harvard Medical School, 02115, Boston, Massachusetts, USA
| | - Alessandro Maccione
- NetS3 Laboratory, Neuroscience and Brain Technologies Department, Istituto Italiano di Tecnologia, Genova, Italy
| | - Luca Berdondini
- NetS3 Laboratory, Neuroscience and Brain Technologies Department, Istituto Italiano di Tecnologia, Genova, Italy
| | - Stefano Panzeri
- Neural Computation Laboratory, Center for Neuroscience and Cognitive Systems @UniTn, Istituto Italiano di Tecnologia, Rovereto, Italy.
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20
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Gioia DA, Alexander N, McCool BA. Ethanol Mediated Inhibition of Synaptic Vesicle Recycling at Amygdala Glutamate Synapses Is Dependent upon Munc13-2. Front Neurosci 2017; 11:424. [PMID: 28785200 PMCID: PMC5519577 DOI: 10.3389/fnins.2017.00424] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Accepted: 07/07/2017] [Indexed: 01/04/2023] Open
Abstract
Chronic exposure to alcohol produces adaptations within the basolateral amygdala (BLA) that are associated with the development of anxiety-like behaviors during withdrawal. In part, these adaptations are mediated by plasticity in glutamatergic synapses occurring through an AMPA receptor mediated form of post-synaptic facilitation in addition to a unique form of presynaptic facilitation. In comparison to the post-synaptic compartment, relatively less is understood about the mechanisms involved in the acute and chronic effects of ethanol in the presynaptic terminal. Previous research has demonstrated that glutamatergic terminals in the mouse BLA are sensitive to ethanol mediated inhibition of synaptic vesicle recycling in a strain-dependent fashion. Importantly, the strain-dependent differences in presynaptic ethanol sensitivity are in accordance with known strain-dependent differences in ethanol/anxiety interactions. In the present study, we have used a short-hairpin RNA to knockdown the expression of the presynaptic Munc13-2 protein in C57BL/6J mice, whose BLA glutamate terminals are normally ethanol-insensitive. We injected this shRNA, or a scrambled control virus, into the medial prefrontal cortex (mPFC) which sends dense projections to the BLA. Accordingly, this knockdown strategy reduces the expression of the Munc13-2 isoform in mPFC terminals within the BLA and alters presynaptic terminal function in C57BL/6J mice in a manner that phenocopies DBA/2J glutamate terminals which are normally ethanol-sensitive. Here, we provide evidence that manipulation of this single protein, Munc13-2, renders C57BL/6J terminals sensitive to ethanol mediated inhibition of synaptic vesicle recycling and post-tetanic potentiation. Furthermore, we found that this ethanol inhibition was dose dependent. Considering the important role of Munc13 proteins in synaptic plasticity, this study potentially identifies a molecular mechanism regulating the acute presynaptic effects of ethanol to the long lasting adaptations in the BLA that occur during chronic ethanol exposure.
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Affiliation(s)
- Dominic A Gioia
- Department of Physiology and Pharmacology, Wake Forest School of MedicineWinston Salem, NC, United States
| | - Nancy Alexander
- Department of Physiology and Pharmacology, Wake Forest School of MedicineWinston Salem, NC, United States
| | - Brian A McCool
- Department of Physiology and Pharmacology, Wake Forest School of MedicineWinston Salem, NC, United States
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21
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Harun R, Grassi CM, Munoz MJ, Wagner AK. Modeling Fast-scan Cyclic Voltammetry Data from Electrically Stimulated Dopamine Neurotransmission Data Using QNsim1.0. J Vis Exp 2017. [PMID: 28605373 DOI: 10.3791/55595] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Central dopaminergic (DAergic) pathways have an important role in a wide range of functions, such as attention, motivation, and movement. Dopamine (DA) is implicated in diseases and disorders including attention deficit hyperactivity disorder, Parkinson's disease, and traumatic brain injury. Thus, DA neurotransmission and the methods to study it are of intense scientific interest. In vivo fast-scan cyclic voltammetry (FSCV) is a method that allows for selectively monitoring DA concentration changes with fine temporal and spatial resolution. This technique is commonly used in conjunction with electrical stimulations of ascending DAergic pathways to control the impulse flow of dopamine neurotransmission. Although the stimulated DA neurotransmission paradigm can produce robust DA responses with clear morphologies, making them amenable for kinetic analysis, there is still much debate on how to interpret the responses in terms of their DA release and clearance components. To address this concern, a quantitative neurobiological (QN) framework of stimulated DA neurotransmission was recently developed to realistically model the dynamics of DA release and reuptake over the course of a stimulated DA response. The foundations of this model are based on experimental data from stimulated DA neurotransmission and on principles of neurotransmission adopted from various lines of research. The QN model implements 12 parameters related to stimulated DA release and reuptake dynamics to model DA responses. This work describes how to simulate DA responses using QNsim1.0 and also details principles that have been implemented to systematically discern alterations in the stimulated dopamine release and reuptake dynamics.
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Affiliation(s)
- Rashed Harun
- Center for Neuroscience, University of Pittsburgh; Department of Physical Medicine & Rehabilitation, University of Pittsburgh, School of Medicine; Safar Center for Resuscitation Research, University of Pittsburgh;
| | - Christine M Grassi
- Department of Physical Medicine & Rehabilitation, University of Pittsburgh, School of Medicine
| | - Miranda J Munoz
- Department of Physical Medicine & Rehabilitation, University of Pittsburgh, School of Medicine; Department of Biological Sciences, Mellon College of Science, Carnegie Mellon University
| | - Amy K Wagner
- Center for Neuroscience, University of Pittsburgh; Department of Physical Medicine & Rehabilitation, University of Pittsburgh, School of Medicine; Safar Center for Resuscitation Research, University of Pittsburgh
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22
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Li YC, Kavalali ET. Synaptic Vesicle-Recycling Machinery Components as Potential Therapeutic Targets. Pharmacol Rev 2017; 69:141-160. [PMID: 28265000 DOI: 10.1124/pr.116.013342] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Presynaptic nerve terminals are highly specialized vesicle-trafficking machines. Neurotransmitter release from these terminals is sustained by constant local recycling of synaptic vesicles independent from the neuronal cell body. This independence places significant constraints on maintenance of synaptic protein complexes and scaffolds. Key events during the synaptic vesicle cycle-such as exocytosis and endocytosis-require formation and disassembly of protein complexes. This extremely dynamic environment poses unique challenges for proteostasis at synaptic terminals. Therefore, it is not surprising that subtle alterations in synaptic vesicle cycle-associated proteins directly or indirectly contribute to pathophysiology seen in several neurologic and psychiatric diseases. In contrast to the increasing number of examples in which presynaptic dysfunction causes neurologic symptoms or cognitive deficits associated with multiple brain disorders, synaptic vesicle-recycling machinery remains an underexplored drug target. In addition, irrespective of the involvement of presynaptic function in the disease process, presynaptic machinery may also prove to be a viable therapeutic target because subtle alterations in the neurotransmitter release may counter disease mechanisms, correct, or compensate for synaptic communication deficits without the need to interfere with postsynaptic receptor signaling. In this article, we will overview critical properties of presynaptic release machinery to help elucidate novel presynaptic avenues for the development of therapeutic strategies against neurologic and neuropsychiatric disorders.
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Affiliation(s)
- Ying C Li
- Departments of Neuroscience (Y.C.L., E.T.K.) and Physiology (E.T.K.), University of Texas Southwestern Medical Center, Dallas, Texas
| | - Ege T Kavalali
- Departments of Neuroscience (Y.C.L., E.T.K.) and Physiology (E.T.K.), University of Texas Southwestern Medical Center, Dallas, Texas
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23
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Luo F, Südhof TC. Synaptotagmin-7-Mediated Asynchronous Release Boosts High-Fidelity Synchronous Transmission at a Central Synapse. Neuron 2017; 94:826-839.e3. [DOI: 10.1016/j.neuron.2017.04.020] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2016] [Revised: 03/31/2017] [Accepted: 04/13/2017] [Indexed: 11/17/2022]
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24
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Gioia DA, McCool B. Strain-Dependent Effects of Acute Alcohol on Synaptic Vesicle Recycling and Post-Tetanic Potentiation in Medial Glutamate Inputs to the Mouse Basolateral Amygdala. Alcohol Clin Exp Res 2017; 41:735-746. [PMID: 28118494 DOI: 10.1111/acer.13343] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 01/14/2017] [Indexed: 12/31/2022]
Abstract
BACKGROUND Inbred mouse strains are differentially sensitive to the acute effects of ethanol (EtOH) and are useful tools for examining how unique genomes differentially affect alcohol-related behaviors and physiology. DBA/2J mice have been shown to be sensitive to the acute anxiolytic effects of alcohol as well as the anxiogenic effects of withdrawal from chronic alcohol exposure, while B6 mice are resistant to both. Considering that the basolateral amygdala (BLA) is an important brain region for the acute and chronic effects of EtOH on fear and anxiety related behaviors, we hypothesized that there would be strain-dependent differences in the acute effects of EtOH in BLA slices. METHODS We utilized patch clamp electrophysiology in BLA coronal slices from 4 inbred mouse strains (A/J, BALBcJ, C57BL/6J, and DBA/2J) to examine how genetic background influences acute EtOH effects on synaptic vesicle recycling and post-tetanic potentiation (PTP) in response to low (2 Hz)- and high (40 Hz)-frequency stimulation. RESULTS We found that EtOH inhibited synaptic vesicle recycling in a strain- and stimulation frequency-dependent manner. Vesicle recycling in DBA/2J and BALBcJ cells was inhibited by acute EtOH during both low- and high-frequency stimulation, while recycling measured from A/J cells was sensitive only during high-frequency stimulation. Recycling at C57BL/6J synapses was insensitive to EtOH regardless of stimulation frequency. We additionally found that cells from DBA/2J and BALBcJ mice were sensitive to EtOH-mediated inhibition of PTP. CONCLUSIONS Acute EtOH application inhibited vesicle recycling and PTP at glutamatergic synapses in both a strain- and frequency-dependent fashion. Several presynaptic proteins that contribute to synaptic vesicle priming in addition to PTP have been implicated in alcohol-related behaviors, including Munc13, Munc18, and RIM proteins, making them potential candidates for the molecular mechanism controlling these effects.
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Affiliation(s)
- Dominic A Gioia
- Department of Physiology & Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Brian McCool
- Department of Physiology & Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina
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25
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Krächan EG, Fischer AU, Franke J, Friauf E. Synaptic reliability and temporal precision are achieved via high quantal content and effective replenishment: auditory brainstem versus hippocampus. J Physiol 2017; 595:839-864. [PMID: 27673320 PMCID: PMC5285727 DOI: 10.1113/jp272799] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Accepted: 09/07/2016] [Indexed: 12/11/2022] Open
Abstract
KEY POINTS Auditory brainstem neurons involved in sound source localization are equipped with several morphological and molecular features that enable them to compute interaural level and time differences. As sound source localization works continually, synaptic transmission between these neurons should be reliable and temporally precise, even during sustained periods of high-frequency activity. Using patch-clamp recordings in acute brain slices, we compared synaptic reliability and temporal precision in the seconds-minute range between auditory and two types of hippocampal synapses; the latter are less confronted with temporally precise high-frequency transmission than the auditory ones. We found striking differences in synaptic properties (e.g. continually high quantal content) that allow auditory synapses to reliably release vesicles at much higher rate than their hippocampal counterparts. Thus, they are indefatigable and also in a position to transfer information with exquisite temporal precision and their performance appears to be supported by very efficient replenishment mechanisms. ABSTRACT At early stations of the auditory pathway, information is encoded by precise signal timing and rate. Auditory synapses must maintain the relative timing of events with submillisecond precision even during sustained and high-frequency stimulation. In non-auditory brain regions, e.g. telencephalic ones, synapses are activated at considerably lower frequencies. Central to understanding the heterogeneity of synaptic systems is the elucidation of the physical, chemical and biological factors that determine synapse performance. In this study, we used slice recordings from three synapse types in the mouse auditory brainstem and hippocampus. Whereas the auditory brainstem nuclei experience high-frequency activity in vivo, the hippocampal circuits are activated at much lower frequencies. We challenged the synapses with sustained high-frequency stimulation (up to 200 Hz for 60 s) and found significant performance differences. Our results show that auditory brainstem synapses differ considerably from their hippocampal counterparts in several aspects, namely resistance to synaptic fatigue, low failure rate and exquisite temporal precision. Their high-fidelity performance supports the functional demands and appears to be due to the large size of the readily releasable pool and a high release probability, which together result in a high quantal content. In conjunction with very efficient vesicle replenishment mechanisms, these properties provide extremely rapid and temporally precise signalling required for neuronal communication at early stations of the auditory system, even during sustained activation in the minute range.
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Affiliation(s)
- Elisa G Krächan
- Animal Physiology Group, Department of BiologyUniversity of KaiserslauternD‐67663KaiserslauternGermany
| | - Alexander U Fischer
- Animal Physiology Group, Department of BiologyUniversity of KaiserslauternD‐67663KaiserslauternGermany
| | - Jürgen Franke
- Chair for Applied Mathematical Statistics, Department of MathematicsUniversity of KaiserslauternD‐67663KaiserslauternGermany
| | - Eckhard Friauf
- Animal Physiology Group, Department of BiologyUniversity of KaiserslauternD‐67663KaiserslauternGermany
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26
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Xie R, Manis PB. Synaptic transmission at the endbulb of Held deteriorates during age-related hearing loss. J Physiol 2016; 595:919-934. [PMID: 27618790 DOI: 10.1113/jp272683] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Accepted: 09/07/2016] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Synaptic transmission at the endbulb of Held was assessed by whole-cell patch clamp recordings from auditory neurons in mature (2-4 months) and aged (20-26 months) mice. Synaptic transmission is degraded in aged mice, which may contribute to the decline in neural processing of the central auditory system during age-related hearing loss. The changes in synaptic transmission in aged mice can be partially rescued by improving calcium buffering, or decreasing action potential-evoked calcium influx. These experiments suggest potential mechanisms, such as regulating intraterminal calcium, that could be manipulated to improve the fidelity of transmission at the aged endbulb of Held. ABSTRACT Age-related hearing loss (ARHL) is associated with changes to the auditory periphery that raise sensory thresholds and alter coding, and is accompanied by alterations in excitatory and inhibitory synaptic transmission, and intrinsic excitability in the circuits of the central auditory system. However, it remains unclear how synaptic transmission changes at the first central auditory synapses during ARHL. Using mature (2-4 months) and old (20-26 months) CBA/CaJ mice, we studied synaptic transmission at the endbulb of Held. Mature and old mice showed no difference in either spontaneous quantal synaptic transmission or low frequency evoked synaptic transmission at the endbulb of Held. However, when challenged with sustained high frequency stimulation, synapses in old mice exhibited increased asynchronous transmitter release and reduced synchronous release. This suggests that the transmission of temporally precise information is degraded at the endbulb during ARHL. Increasing intraterminal calcium buffering with EGTA-AM or decreasing calcium influx with ω-agatoxin IVA decreased the amount of asynchronous release and restored synchronous release in old mice. In addition, recovery from depression following high frequency trains was faster in old mice, but was restored to a normal time course by EGTA-AM treatment. These results suggest that intraterminal calcium in old endbulbs may rise to abnormally high levels during high rates of auditory nerve firing, or that calcium-dependent processes involved in release are altered with age. These observations suggest that ARHL is associated with a decrease in temporal precision of synaptic release at the first central auditory synapse, which may contribute to perceptual deficits in hearing.
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Affiliation(s)
- Ruili Xie
- Department of Neurosciences, University of Toledo, Toledo, OH, 43614-2598, USA
| | - Paul B Manis
- Department of Otolaryngology/Head and Neck Surgery, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599-7545, USA.,Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599-7070, USA
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27
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Jackson RE, Burrone J. Visualizing Presynaptic Calcium Dynamics and Vesicle Fusion with a Single Genetically Encoded Reporter at Individual Synapses. Front Synaptic Neurosci 2016; 8:21. [PMID: 27507942 PMCID: PMC4960916 DOI: 10.3389/fnsyn.2016.00021] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2016] [Accepted: 07/13/2016] [Indexed: 01/08/2023] Open
Abstract
Synaptic transmission depends on the influx of calcium into the presynaptic compartment, which drives neurotransmitter release. Genetically encoded reporters are widely used tools to understand these processes, particularly pHluorin-based reporters that report vesicle exocytosis and endocytosis through pH dependent changes in fluorescence, and genetically encoded calcium indicators (GECIs) that exhibit changes in fluorescence upon binding to calcium. The recent expansion of the color palette of available indicators has made it possible to image multiple probes simultaneously within a cell. We have constructed a single molecule reporter capable of concurrent imaging of both presynaptic calcium influx and exocytosis, by fusion of sypHy, the vesicle associated protein synaptophysin containing a GFP-based pHluorin sensor, with the red-shifted GECI R-GECO1. Due to the fixed stoichiometry of the two probes, the ratio of the two responses can also be measured, providing an all optical correlate of the calcium dependence of release. Here, we have characterized stimulus-evoked sypHy-RGECO responses of hippocampal synapses in vitro, exploring the effects of different stimulus strengths and frequencies as well as variations in external calcium concentrations. By combining live sypHy-RGECO imaging with post hoc fixation and immunofluorescence, we have also investigated correlations between structural and functional properties of synapses.
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Affiliation(s)
| | - Juan Burrone
- Centre for Developmental Neurobiology, King’s College LondonLondon, UK
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28
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Obrai S, Kumar R, Goyal M, Kaushal S. DFT studies of calcium(II), strontium(II) and barium(II) benzoates with N,N,N′,N′-Tetrakis(2-hydroxyethyl/propyl)ethylenediamine. J Mol Struct 2016. [DOI: 10.1016/j.molstruc.2016.02.021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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29
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Iremonger KJ, Bains JS. Asynchronous presynaptic glutamate release enhances neuronal excitability during the post-spike refractory period. J Physiol 2016; 594:1005-15. [PMID: 26662615 DOI: 10.1113/jp271485] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Accepted: 12/04/2015] [Indexed: 01/11/2023] Open
Abstract
KEY POINTS Many excitatory synapses in the brain release glutamate with both synchronous and asynchronous components. Immediately following an action potential, neurons display a reduced excitability due to the post-spike afterhyperpolarization (AHP). This gives rise to a relative refractory period. When an action potential is evoked by glutamate synaptic input possessing asynchronous release, the delayed glutamate release events act to depolarize the neuron during the AHP and overcome the relative refractory period. These results demonstrate a new role for asynchronous release in regulating post-spike excitability and the relative refractory period in central neurons. ABSTRACT Post-spike afterhyperpolarizations (AHPs) functionally inhibit neuronal excitability for tens to hundreds of milliseconds following each action potential. This imposes a relative refractory period during which synaptic excitation is less effective at evoking spikes. Here we asked whether some synapses have mechanisms in place that allow them to overcome the AHP and drive spiking in target cells during this period of reduced excitability. We examined glutamate synapses onto oxytocin and vasopressin neurons in the paraventricular nucleus of the hypothalamus. These synapses can display pronounced asynchronous glutamate release following a single presynaptic spike, with the time course of release being similar to that of the post-spike AHP. To test whether asynchronous release is more effective at overcoming the relative refractory period, we evoked a single action potential with either a brief synchronous depolarization or an asynchronous potential and then assessed excitability at multiple time points following the spike. Neurons receiving asynchronous depolarizing synaptic inputs had a shorter relative refractory period than those receiving synchronous depolarizations. Our data demonstrate that synapses releasing glutamate in an asynchronous and delayed manner are ideally adapted to counter the AHP. By effectively overcoming the relative refractory period, the kinetics of excitatory synaptic input can play an important role in controlling post-spike excitability.
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Affiliation(s)
- Karl J Iremonger
- Centre for Neuroendocrinology, Department of Physiology, University of Otago School of Medical Sciences, Dunedin, New Zealand
| | - Jaideep S Bains
- Hotchkiss Brain Institute & Department of Physiology and Pharmacology, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, T2N 4N1, Canada
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30
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Chamberland S, Tóth K. Functionally heterogeneous synaptic vesicle pools support diverse synaptic signalling. J Physiol 2015; 594:825-35. [PMID: 26614712 DOI: 10.1113/jp270194] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2015] [Accepted: 11/23/2015] [Indexed: 12/15/2022] Open
Abstract
Synaptic communication between neurons is a highly dynamic process involving specialized structures. At the level of the presynaptic terminal, neurotransmission is ensured by fusion of vesicles to the membrane, which releases neurotransmitter in the synaptic cleft. Depending on the level of activity experienced by the terminal, the spatiotemporal properties of calcium invasion will dictate the timing and the number of vesicles that need to be released. Diverse presynaptic firing patterns are translated to neurotransmitter release with a distinct temporal feature. Complex patterns of neurotransmitter release can be achieved when different vesicles respond to distinct calcium dynamics in the presynaptic terminal. Specific vesicles from different pools are recruited during various modes of release as the particular molecular composition of their membrane proteins define their functional properties. Such diversity endows the presynaptic terminal with the ability to respond to distinct physiological signals via the mobilization of specific subpopulation of vesicles. There are several mechanisms by which a diverse vesicle population could be generated in single presynaptic terminals, including distinct recycling pathways that utilize various adaptor proteins. Several additional factors could potentially contribute to the development of a heterogeneous vesicle pool such as specialized release sites, spatial segregation within the terminal and specialized delivery pathways. Among these factors molecular heterogeneity plays a central role in defining the functional properties of different subpopulations of vesicles.
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Affiliation(s)
- Simon Chamberland
- Quebec Mental Health Institute, Department of Psychiatry and Neuroscience, Université Laval, Quebec City, Quebec, Canada, G1J 2G3
| | - Katalin Tóth
- Quebec Mental Health Institute, Department of Psychiatry and Neuroscience, Université Laval, Quebec City, Quebec, Canada, G1J 2G3
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Loss of Local Astrocyte Support Disrupts Action Potential Propagation and Glutamate Release Synchrony from Unmyelinated Hippocampal Axon Terminals In Vitro. J Neurosci 2015; 35:11105-17. [PMID: 26245971 DOI: 10.1523/jneurosci.1289-15.2015] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Neuron-astrocyte interactions are critical for proper CNS development and function. Astrocytes secrete factors that are pivotal for synaptic development and function, neuronal metabolism, and neuronal survival. Our understanding of this relationship, however, remains incomplete due to technical hurdles that have prevented the removal of astrocytes from neuronal circuits without changing other important conditions. Here we overcame this obstacle by growing solitary rat hippocampal neurons on microcultures that were comprised of either an astrocyte bed (+astrocyte) or a collagen bed (-astrocyte) within the same culture dish. -Astrocyte autaptic evoked EPSCs, but not IPSCs, displayed an altered temporal profile, which included increased synaptic delay, increased time to peak, and severe glutamate release asynchrony, distinct from previously described quantal asynchrony. Although we observed minimal alteration of the somatically recorded action potential waveform, action potential propagation was altered. We observed a longer latency between somatic initiation and arrival at distal locations, which likely explains asynchronous EPSC peaks, and we observed broadening of the axonal spike, which likely underlies changes to evoked EPSC onset. No apparent changes in axon structure were observed, suggesting altered axonal excitability. In conclusion, we propose that local astrocyte support has an unappreciated role in maintaining glutamate release synchrony by disturbing axonal signal propagation. SIGNIFICANCE STATEMENT Certain glial cell types (oligodendrocytes, Schwann cells) facilitate the propagation of neuronal electrical signals, but a role for astrocytes has not been identified despite many other functions of astrocytes in supporting and modulating neuronal signaling. Under identical global conditions, we cultured neurons with or without local astrocyte support. Without local astrocytes, glutamate transmission was desynchronized by an alteration of the waveform and arrival time of axonal action potentials to synaptic terminals. GABA transmission was not disrupted. The disruption did not involve detectable morphological changes to axons of glutamate neurons. Our work identifies a developmental role for astrocytes in the temporal precision of excitatory signals.
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Shaping Neuronal Network Activity by Presynaptic Mechanisms. PLoS Comput Biol 2015; 11:e1004438. [PMID: 26372048 PMCID: PMC4570815 DOI: 10.1371/journal.pcbi.1004438] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Accepted: 06/23/2015] [Indexed: 02/06/2023] Open
Abstract
Neuronal microcircuits generate oscillatory activity, which has been linked to basic functions such as sleep, learning and sensorimotor gating. Although synaptic release processes are well known for their ability to shape the interaction between neurons in microcircuits, most computational models do not simulate the synaptic transmission process directly and hence cannot explain how changes in synaptic parameters alter neuronal network activity. In this paper, we present a novel neuronal network model that incorporates presynaptic release mechanisms, such as vesicle pool dynamics and calcium-dependent release probability, to model the spontaneous activity of neuronal networks. The model, which is based on modified leaky integrate-and-fire neurons, generates spontaneous network activity patterns, which are similar to experimental data and robust under changes in the model's primary gain parameters such as excitatory postsynaptic potential and connectivity ratio. Furthermore, it reliably recreates experimental findings and provides mechanistic explanations for data obtained from microelectrode array recordings, such as network burst termination and the effects of pharmacological and genetic manipulations. The model demonstrates how elevated asynchronous release, but not spontaneous release, synchronizes neuronal network activity and reveals that asynchronous release enhances utilization of the recycling vesicle pool to induce the network effect. The model further predicts a positive correlation between vesicle priming at the single-neuron level and burst frequency at the network level; this prediction is supported by experimental findings. Thus, the model is utilized to reveal how synaptic release processes at the neuronal level govern activity patterns and synchronization at the network level. The activity of neuronal networks underlies basic neural functions such as sleep, learning and sensorimotor gating. Computational models of neuronal networks have been developed to capture the complexity of the network activity and predict how neuronal networks generate spontaneous activity. However, most computational models do not simulate the intricate synaptic release process that governs the interaction between neurons and has been shown to significantly impact neuronal network activity and animal behavior, learning and memory. Our paper demonstrates the importance of simulating the elaborate synaptic release process to understand how neuronal networks generate spontaneous activity and respond to manipulations of the release process. The model provides mechanistic explanations and predictions for experimental pharmacological and genetic manipulations. Thus, the model presents a novel computational platform to understand how mechanistic changes in the synaptic release process modulate network oscillatory activity that might impact basic neural functions.
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33
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Saveliev A, Khuzakhmetova V, Samigullin D, Skorinkin A, Kovyazina I, Nikolsky E, Bukharaeva E. Bayesian analysis of the kinetics of quantal transmitter secretion at the neuromuscular junction. J Comput Neurosci 2015; 39:119-29. [PMID: 26129670 DOI: 10.1007/s10827-015-0567-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Revised: 06/15/2015] [Accepted: 06/19/2015] [Indexed: 11/29/2022]
Abstract
The timing of transmitter release from nerve endings is considered nowadays as one of the factors determining the plasticity and efficacy of synaptic transmission. In the neuromuscular junction, the moments of release of individual acetylcholine quanta are related to the synaptic delays of uniquantal endplate currents recorded under conditions of lowered extracellular calcium. Using Bayesian modelling, we performed a statistical analysis of synaptic delays in mouse neuromuscular junction with different patterns of rhythmic nerve stimulation and when the entry of calcium ions into the nerve terminal was modified. We have obtained a statistical model of the release timing which is represented as the summation of two independent statistical distributions. The first of these is the exponentially modified Gaussian distribution. The mixture of normal and exponential components in this distribution can be interpreted as a two-stage mechanism of early and late periods of phasic synchronous secretion. The parameters of this distribution depend on both the stimulation frequency of the motor nerve and the calcium ions' entry conditions. The second distribution was modelled as quasi-uniform, with parameters independent of nerve stimulation frequency and calcium entry. Two different probability density functions for the distribution of synaptic delays suggest at least two independent processes controlling the time course of secretion, one of them potentially involving two stages. The relative contribution of these processes to the total number of mediator quanta released depends differently on the motor nerve stimulation pattern and on calcium ion entry into nerve endings.
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Affiliation(s)
- Anatoly Saveliev
- Kazan Federal University, Kremlevskaya St. 18, Kazan, 420008, Russia
| | - Venera Khuzakhmetova
- Kazan Federal University, Kremlevskaya St. 18, Kazan, 420008, Russia.,Laboratory of the Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences, P.O. Box 30, Kazan, 420111, Russia
| | - Dmitry Samigullin
- Kazan Federal University, Kremlevskaya St. 18, Kazan, 420008, Russia.,Laboratory of the Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences, P.O. Box 30, Kazan, 420111, Russia.,Kazan National Research Technical University named after A. N. Tupolev, K. Marx St. 10, Kazan, 420111, Russia
| | - Andrey Skorinkin
- Kazan Federal University, Kremlevskaya St. 18, Kazan, 420008, Russia.,Laboratory of the Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences, P.O. Box 30, Kazan, 420111, Russia
| | - Irina Kovyazina
- Kazan Federal University, Kremlevskaya St. 18, Kazan, 420008, Russia.,Laboratory of the Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences, P.O. Box 30, Kazan, 420111, Russia
| | - Eugeny Nikolsky
- Kazan Federal University, Kremlevskaya St. 18, Kazan, 420008, Russia.,Laboratory of the Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences, P.O. Box 30, Kazan, 420111, Russia.,Kazan State Medical University, Butlerov St. 49, Kazan, 420012, Russia
| | - Ellya Bukharaeva
- Kazan Federal University, Kremlevskaya St. 18, Kazan, 420008, Russia. .,Laboratory of the Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences, P.O. Box 30, Kazan, 420111, Russia.
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PGC-1α provides a transcriptional framework for synchronous neurotransmitter release from parvalbumin-positive interneurons. J Neurosci 2015; 34:14375-87. [PMID: 25339750 DOI: 10.1523/jneurosci.1222-14.2014] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Accumulating evidence strongly implicates the transcriptional coactivator peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) in the pathophysiology of multiple neurological disorders, but the downstream gene targets of PGC-1α in the brain have remained enigmatic. Previous data demonstrate that PGC-1α is primarily concentrated in inhibitory neurons and that PGC-1α is required for the expression of the interneuron-specific Ca(2+)-binding protein parvalbumin (PV) throughout the cortex. To identify other possible transcriptional targets of PGC-1α in neural tissue, we conducted a microarray on neuroblastoma cells overexpressing PGC-1α, mined results for genes with physiological relevance to interneurons, and measured cortical gene and protein expression of these genes in mice with underexpression and overexpression of PGC-1α. We observed bidirectional regulation of novel PGC-1α-dependent transcripts spanning synaptic [synaptotagmin 2 (Syt2) and complexin 1 (Cplx1)], structural [neurofilament heavy chain (Nefh)], and metabolic [neutral cholesterol ester hydrolase 1 (Nceh1), adenylate kinase 1 (Ak1), inositol polyphosphate 5-phosphatase J (Inpp5j), ATP synthase mitochondrial F1 complex O subunit (Atp5o), phytanol-CoA-2hydroxylase (Phyh), and ATP synthase mitrochondrial F1 complex α subunit 1 (Atp5a1)] functions. The neuron-specific genes Syt2, Cplx1, and Nefh were developmentally upregulated in an expression pattern consistent with that of PGC-1α and were expressed in cortical interneurons. Conditional deletion of PGC-1α in PV-positive neurons significantly decreased cortical transcript expression of these genes, promoted asynchronous GABA release, and impaired long-term memory. Collectively, these data demonstrate that PGC-1α is required for normal PV-positive interneuron function and that loss of PGC-1α in this interneuron subpopulation could contribute to cortical dysfunction in disease states.
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Neurobiological model of stimulated dopamine neurotransmission to interpret fast-scan cyclic voltammetry data. Brain Res 2014; 1599:67-84. [PMID: 25527399 DOI: 10.1016/j.brainres.2014.12.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Revised: 12/05/2014] [Accepted: 12/06/2014] [Indexed: 11/22/2022]
Abstract
Fast-scan cyclic voltammetry (FSCV) is an electrochemical method that can assess real-time in vivo dopamine (DA) concentration changes to study the kinetics of DA neurotransmission. Electrical stimulation of dopaminergic (DAergic) pathways can elicit FSCV DA responses that largely reflect a balance of DA release and reuptake. Interpretation of these evoked DA responses requires a framework to discern the contribution of DA release and reuptake. The current, widely implemented interpretive framework for doing so is the Michaelis-Menten (M-M) model, which is grounded on two assumptions- (1) DA release rate is constant during stimulation, and (2) DA reuptake occurs through dopamine transporters (DAT) in a manner consistent with M-M enzyme kinetics. Though the M-M model can simulate evoked DA responses that rise convexly, response types that predominate in the ventral striatum, the M-M model cannot simulate dorsal striatal responses that rise concavely. Based on current neurotransmission principles and experimental FSCV data, we developed a novel, quantitative, neurobiological framework to interpret DA responses that assumes DA release decreases exponentially during stimulation and continues post-stimulation at a diminishing rate. Our model also incorporates dynamic M-M kinetics to describe DA reuptake as a process of decreasing reuptake efficiency. We demonstrate that this quantitative, neurobiological model is an extension of the traditional M-M model that can simulate heterogeneous regional DA responses following manipulation of stimulation duration, frequency, and DA pharmacology. The proposed model can advance our interpretive framework for future in vivo FSCV studies examining regional DA kinetics and their alteration by disease and DA pharmacology.
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36
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Weber JP, Toft-Bertelsen TL, Mohrmann R, Delgado-Martinez I, Sørensen JB. Synaptotagmin-7 is an asynchronous calcium sensor for synaptic transmission in neurons expressing SNAP-23. PLoS One 2014; 9:e114033. [PMID: 25422940 PMCID: PMC4244210 DOI: 10.1371/journal.pone.0114033] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Accepted: 11/03/2014] [Indexed: 12/25/2022] Open
Abstract
Synchronization of neurotransmitter release with the presynaptic action potential is essential for maintaining fidelity of information transfer in the central nervous system. However, synchronous release is frequently accompanied by an asynchronous release component that builds up during repetitive stimulation, and can even play a dominant role in some synapses. Here, we show that substitution of SNAP-23 for SNAP-25 in mouse autaptic glutamatergic hippocampal neurons results in asynchronous release and a higher frequency of spontaneous release events (mEPSCs). Use of neurons from double-knock-out (SNAP-25, synaptotagmin-7) mice in combination with viral transduction showed that SNAP-23-driven release is triggered by endogenous synaptotagmin-7. In the absence of synaptotagmin-7 release became even more asynchronous, and the spontaneous release rate increased even more, indicating that synaptotagmin-7 acts to synchronize release and suppress spontaneous release. However, compared to synaptotagmin-1, synaptotagmin-7 is a both leaky and asynchronous calcium sensor. In the presence of SNAP-25, consequences of the elimination of synaptotagmin-7 were small or absent, indicating that the protein pairs SNAP-25/synaptotagmin-1 and SNAP-23/synaptotagmin-7 might act as mutually exclusive calcium sensors. Expression of fusion proteins between pHluorin (pH-sensitive GFP) and synaptotagmin-1 or -7 showed that vesicles that fuse using the SNAP-23/synaptotagmin-7 combination contained synaptotagmin-1, while synaptotagmin-7 barely displayed activity-dependent trafficking between vesicle and plasma membrane, implying that it acts as a plasma membrane calcium sensor. Overall, these findings support the idea of alternative syt∶SNARE combinations driving release with different kinetics and fidelity.
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Affiliation(s)
- Jens P. Weber
- Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, Vrije Universiteit, Amsterdam, The Netherlands
| | - Trine L. Toft-Bertelsen
- Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Ralf Mohrmann
- Department of Physiology, University of Saarland, Homburg, Germany
| | | | - Jakob B. Sørensen
- Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
- Lundbeck Foundation Center for Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
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Park AJ, Havekes R, Choi JH, Luczak V, Nie T, Huang T, Abel T. A presynaptic role for PKA in synaptic tagging and memory. Neurobiol Learn Mem 2014; 114:101-112. [PMID: 24882624 DOI: 10.1016/j.nlm.2014.05.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Revised: 05/01/2014] [Accepted: 05/04/2014] [Indexed: 12/14/2022]
Abstract
Protein kinase A (PKA) and other signaling molecules are spatially restricted within neurons by A-kinase anchoring proteins (AKAPs). Although studies on compartmentalized PKA signaling have focused on postsynaptic mechanisms, presynaptically anchored PKA may contribute to synaptic plasticity and memory because PKA also regulates presynaptic transmitter release. Here, we examine this issue using genetic and pharmacological application of Ht31, a PKA anchoring disrupting peptide. At the hippocampal Schaffer collateral CA3-CA1 synapse, Ht31 treatment elicits a rapid decay of synaptic responses to repetitive stimuli, indicating a fast depletion of the readily releasable pool of synaptic vesicles. The interaction between PKA and proteins involved in producing this pool of synaptic vesicles is supported by biochemical assays showing that synaptic vesicle protein 2 (SV2), Rim1, and SNAP25 are components of a complex that interacts with cAMP. Moreover, acute treatment with Ht31 reduces the levels of SV2. Finally, experiments with transgenic mouse lines, which express Ht31 in excitatory neurons at the Schaffer collateral CA3-CA1 synapse, highlight a requirement for presynaptically anchored PKA in pathway-specific synaptic tagging and long-term contextual fear memory. These results suggest that a presynaptically compartmentalized PKA is critical for synaptic plasticity and memory by regulating the readily releasable pool of synaptic vesicles.
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Affiliation(s)
- Alan Jung Park
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104-6018, USA
| | - Robbert Havekes
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104-6018, USA
| | - Jennifer Hk Choi
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104-6018, USA
| | - Vince Luczak
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104-6018, USA
| | - Ting Nie
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104-6018, USA.,Department of Pediatrics, Emory University, VAMC, 1670 Clairmont Rd Atlanta, GA 30033, USA
| | - Ted Huang
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104-6018, USA
| | - Ted Abel
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104-6018, USA
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38
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Khuzakhmetova V, Samigullin D, Nurullin L, Vyskočil F, Nikolsky E, Bukharaeva E. Kinetics of neurotransmitter release in neuromuscular synapses of newborn and adult rats. Int J Dev Neurosci 2014; 34:9-18. [PMID: 24412779 DOI: 10.1016/j.ijdevneu.2013.12.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Revised: 12/24/2013] [Accepted: 12/28/2013] [Indexed: 01/02/2023] Open
Abstract
The kinetics of the phasic synchronous and delayed asynchronous release of acetylcholine quanta was studied at the neuromuscular junctions of aging rats from infant to mature animals at various frequencies of rhythmic stimulation of the motor nerve. We found that in infants 6 (P6) and 10 (P10) days after birth a strongly asynchronous phase of quantal release was observed, along with a reduced number of quanta compared to the synapses of adults. The rise time and decay of uni-quantal end-plate currents were significantly longer in infant synapses. The presynaptic immunostaining revealed that the area of the synapses in infants was significantly (up to six times) smaller than in mature junctions. The intensity of delayed asynchronous release in infants increased with the frequency of stimulation more than in adults. A blockade of the ryanodine receptors, which can contribute to the formation of delayed asynchronous release, had no effect on the kinetics of delayed secretion in the infants unlike synapses of adults. Therefore, high degree of asynchrony of quantal release in infants is not associated with the activity of ryanodine receptors and with the liberation of calcium ions from intracellular calcium stores.
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Affiliation(s)
- Venera Khuzakhmetova
- Kazan Institute of Biochemistry and Biophysics Kazan Scientific Center of the Russian Academy of Sciences, Post Box 30, 420111 Kazan, Russia
| | - Dmitry Samigullin
- Kazan Institute of Biochemistry and Biophysics Kazan Scientific Center of the Russian Academy of Sciences, Post Box 30, 420111 Kazan, Russia
| | - Leniz Nurullin
- Kazan Institute of Biochemistry and Biophysics Kazan Scientific Center of the Russian Academy of Sciences, Post Box 30, 420111 Kazan, Russia
| | - Frantisek Vyskočil
- Institute of Physiology, Academy of Sciences of the Czech Republic, Videnska 1083, 14200 Prague, Czech Republic; Department of Physiology, Faculty of Sciences, Charles University, Vinicna 7, Prague, Czech Republic
| | - Evgeny Nikolsky
- Kazan Institute of Biochemistry and Biophysics Kazan Scientific Center of the Russian Academy of Sciences, Post Box 30, 420111 Kazan, Russia; Kazan State Medical University, Butlerov st. 49, 420012 Kazan, Russia; Kazan Federal University, Kremlyovskaya st. 18, 420008 Kazan, Russia
| | - Ellya Bukharaeva
- Kazan Institute of Biochemistry and Biophysics Kazan Scientific Center of the Russian Academy of Sciences, Post Box 30, 420111 Kazan, Russia; Kazan State Medical University, Butlerov st. 49, 420012 Kazan, Russia; Kazan Federal University, Kremlyovskaya st. 18, 420008 Kazan, Russia.
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39
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Kaeser PS, Regehr WG. Molecular mechanisms for synchronous, asynchronous, and spontaneous neurotransmitter release. Annu Rev Physiol 2013; 76:333-63. [PMID: 24274737 DOI: 10.1146/annurev-physiol-021113-170338] [Citation(s) in RCA: 286] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Most neuronal communication relies upon the synchronous release of neurotransmitters, which occurs through synaptic vesicle exocytosis triggered by action potential invasion of a presynaptic bouton. However, neurotransmitters are also released asynchronously with a longer, variable delay following an action potential or spontaneously in the absence of action potentials. A compelling body of research has identified roles and mechanisms for synchronous release, but asynchronous release and spontaneous release are less well understood. In this review, we analyze how the mechanisms of the three release modes overlap and what molecular pathways underlie asynchronous and spontaneous release. We conclude that the modes of release have key fusion processes in common but may differ in the source of and necessity for Ca(2+) to trigger release and in the identity of the Ca(2+) sensor for release.
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Affiliation(s)
- Pascal S Kaeser
- Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115; ,
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40
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Jiang M, Yang M, Yin L, Zhang X, Shu Y. Developmental reduction of asynchronous GABA release from neocortical fast-spiking neurons. ACTA ACUST UNITED AC 2013; 25:258-70. [PMID: 23968835 DOI: 10.1093/cercor/bht236] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Delayed asynchronous release (AR) evoked by bursts of presynaptic action potentials (APs) occurs in certain types of hippocampal and neocortical inhibitory interneurons. Previous studies showed that AR provides long-lasting inhibition and desynchronizes the activity in postsynaptic cells. However, whether AR undergoes developmental change remains unknown. In this study, we performed whole-cell recording from fast-spiking (FS) interneurons and pyramidal cells (PCs) in prefrontal cortical slices obtained from juvenile and adult rats. In response to AP trains in FS neurons, AR occurred at their output synapses during both age periods, including FS autapses and FS-PC synapses; however, the AR strength was significantly weaker in adults than that in juveniles. Further experiments suggested that the reduction of AR in adult animals could be attributable to the rapid clearance of residual Ca(2+) from presynaptic terminals. Together, our results revealed that the AR strength was stronger at juvenile but weaker in adult, possibly resulting from changes in presynaptic Ca(2+) dynamics. AR changes may meet the needs of the neural network to generate different types of oscillations for cortical processing at distinct behavioral states.
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Affiliation(s)
- Man Jiang
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, P. R. China
| | - Mingpo Yang
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, P. R. China
| | - Luping Yin
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, P. R. China
| | - Xiaohui Zhang
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, P. R. China
| | - Yousheng Shu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, P. R. China
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Medrihan L, Cesca F, Raimondi A, Lignani G, Baldelli P, Benfenati F. Synapsin II desynchronizes neurotransmitter release at inhibitory synapses by interacting with presynaptic calcium channels. Nat Commun 2013; 4:1512. [PMID: 23443540 PMCID: PMC3586721 DOI: 10.1038/ncomms2515] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Accepted: 01/18/2013] [Indexed: 01/05/2023] Open
Abstract
In the central nervous system, most synapses show a fast mode of neurotransmitter release known as synchronous release followed by a phase of asynchronous release, which extends over tens of milliseconds to seconds. Synapsin II (SYN2) is a member of the multigene synapsin family (SYN1/2/3) of synaptic vesicle phosphoproteins that modulate synaptic transmission and plasticity, and are mutated in epileptic patients. Here we report that inhibitory synapses of the dentate gyrus of Syn II knockout mice display an upregulation of synchronous neurotransmitter release and a concomitant loss of delayed asynchronous release. Syn II promotes γ-aminobutyric acid asynchronous release in a Ca2+-dependent manner by a functional interaction with presynaptic Ca2+ channels, revealing a new role in synaptic transmission for synapsins. The arrival of action potentials at nerve terminals often leads to synchronous neurotransmitter release. Medrihan and colleagues use electrophysiology on mouse hippocampal neurons to show that the vesicle protein Synapsin II promotes GABAergic asynchronous release by interacting with calcium channels.
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Affiliation(s)
- Lucian Medrihan
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genoa, Italy.
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42
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Giachello CNG, Premoselli F, Montarolo PG, Ghirardi M. Pentylenetetrazol-induced epileptiform activity affects basal synaptic transmission and short-term plasticity in monosynaptic connections. PLoS One 2013; 8:e56968. [PMID: 23437283 PMCID: PMC3577694 DOI: 10.1371/journal.pone.0056968] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2012] [Accepted: 01/18/2013] [Indexed: 11/18/2022] Open
Abstract
Epileptic activity is generally induced in experimental models by local application of epileptogenic drugs, including pentylenetetrazol (PTZ), widely used on both vertebrate and invertebrate neurons. Despite the high prevalence of this neurological disorder and the extensive research on it, the cellular and molecular mechanisms underlying epileptogenesis still remain unclear. In this work, we examined PTZ-induced neuronal changes in Helix monosynaptic circuits formed in vitro, as a simpler experimental model to investigate the effects of epileptiform activity on both basal release and post-tetanic potentiation (PTP), a form of short-term plasticity. We observed a significant enhancement of basal synaptic strength, with kinetics resembling those of previously described use-dependent forms of plasticity, determined by changes in estimated quantal parameters, such as the readily releasable pool and the release probability. Moreover, these neurons exhibited a strong reduction in PTP expression and in its decay time constant, suggesting an impairment in the dynamic reorganization of synaptic vesicle pools following prolonged stimulation of synaptic transmission. In order to explain this imbalance, we determined whether epileptic activity is related to the phosphorylation level of synapsin, which is known to modulate synaptic plasticity. Using western blot and immunocytochemical staining we found a PTZ-dependent increase in synapsin phosphorylation at both PKA/CaMKI/IV and MAPK/Erk sites, both of which are important for modulating synaptic plasticity. Taken together, our findings suggest that prolonged epileptiform activity leads to an increase in the synapsin phosphorylation status, thereby contributing to an alteration of synaptic strength in both basal condition and tetanus-induced potentiation.
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43
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Catterall WA, Leal K, Nanou E. Calcium channels and short-term synaptic plasticity. J Biol Chem 2013; 288:10742-9. [PMID: 23400776 DOI: 10.1074/jbc.r112.411645] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Voltage-gated Ca(2+) channels in presynaptic nerve terminals initiate neurotransmitter release in response to depolarization by action potentials from the nerve axon. The strength of synaptic transmission is dependent on the third to fourth power of Ca(2+) entry, placing the Ca(2+) channels in a unique position for regulation of synaptic strength. Short-term synaptic plasticity regulates the strength of neurotransmission through facilitation and depression on the millisecond time scale and plays a key role in encoding information in the nervous system. Ca(V)2.1 channels are the major source of Ca(2+) entry for neurotransmission in the central nervous system. They are tightly regulated by Ca(2+), calmodulin, and related Ca(2+) sensor proteins, which cause facilitation and inactivation of channel activity. Emerging evidence reviewed here points to this mode of regulation of Ca(V)2.1 channels as a major contributor to short-term synaptic plasticity of neurotransmission and its diversity among synapses.
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Affiliation(s)
- William A Catterall
- Department of Pharmacology, University of Washington, Seattle, Washington 98195-7280, USA
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44
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Nikoletopoulou V, Tavernarakis N. Calcium homeostasis in aging neurons. Front Genet 2012; 3:200. [PMID: 23060904 PMCID: PMC3462315 DOI: 10.3389/fgene.2012.00200] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Accepted: 09/19/2012] [Indexed: 11/13/2022] Open
Abstract
The nervous system becomes increasingly vulnerable to insults and prone to dysfunction during aging. Age-related decline of neuronal function is manifested by the late onset of many neurodegenerative disorders, as well as by reduced signaling and processing capacity of individual neuron populations. Recent findings indicate that impairment of Ca(2+) homeostasis underlies the increased susceptibility of neurons to damage, associated with the aging process. However, the impact of aging on Ca(2+) homeostasis in neurons remains largely unknown. Here, we survey the molecular mechanisms that mediate neuronal Ca(2+) homeostasis and discuss the impact of aging on their efficacy. To address the question of how aging impinges on Ca(2+) homeostasis, we consider potential nodes through which mechanisms regulating Ca(2+) levels interface with molecular pathways known to influence the process of aging and senescent decline. Delineation of this crosstalk would facilitate the development of interventions aiming to fortify neurons against age-associated functional deterioration and death by augmenting Ca(2+) homeostasis.
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Affiliation(s)
- Vassiliki Nikoletopoulou
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology - Hellas Heraklion, Crete, Greece
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45
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Kasai H, Takahashi N, Tokumaru H. Distinct Initial SNARE Configurations Underlying the Diversity of Exocytosis. Physiol Rev 2012; 92:1915-64. [DOI: 10.1152/physrev.00007.2012] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The dynamics of exocytosis are diverse and have been optimized for the functions of synapses and a wide variety of cell types. For example, the kinetics of exocytosis varies by more than five orders of magnitude between ultrafast exocytosis in synaptic vesicles and slow exocytosis in large dense-core vesicles. However, in all cases, exocytosis is mediated by the same fundamental mechanism, i.e., the assembly of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins. It is often assumed that vesicles need to be docked at the plasma membrane and SNARE proteins must be preassembled before exocytosis is triggered. However, this model cannot account for the dynamics of exocytosis recently reported in synapses and other cells. For example, vesicles undergo exocytosis without prestimulus docking during tonic exocytosis of synaptic vesicles in the active zone. In addition, epithelial and hematopoietic cells utilize cAMP and kinases to trigger slow exocytosis of nondocked vesicles. In this review, we summarize the manner in which the diversity of exocytosis reflects the initial configurations of SNARE assembly, including trans-SNARE, binary-SNARE, unitary-SNARE, and cis-SNARE configurations. The initial SNARE configurations depend on the particular SNARE subtype (syntaxin, SNAP25, or VAMP), priming proteins (Munc18, Munc13, CAPS, complexin, or snapin), triggering proteins (synaptotagmins, Doc2, and various protein kinases), and the submembraneous cytomatrix, and they are the key to determining the kinetics of subsequent exocytosis. These distinct initial configurations will help us clarify the common SNARE assembly processes underlying exocytosis and membrane trafficking in eukaryotic cells.
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Affiliation(s)
- Haruo Kasai
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and Faculty of Pharmaceutical Sciences at Kagawa, Tokushima Bunri University, Kagawa, Japan
| | - Noriko Takahashi
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and Faculty of Pharmaceutical Sciences at Kagawa, Tokushima Bunri University, Kagawa, Japan
| | - Hiroshi Tokumaru
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and Faculty of Pharmaceutical Sciences at Kagawa, Tokushima Bunri University, Kagawa, Japan
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46
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Nguyen TH, Maucort G, Sullivan RKP, Schenning M, Lavidis NA, McCluskey A, Robinson PJ, Meunier FA. Actin- and dynamin-dependent maturation of bulk endocytosis restores neurotransmission following synaptic depletion. PLoS One 2012; 7:e36913. [PMID: 22629340 PMCID: PMC3358275 DOI: 10.1371/journal.pone.0036913] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2012] [Accepted: 04/09/2012] [Indexed: 11/18/2022] Open
Abstract
Bulk endocytosis contributes to the maintenance of neurotransmission at the amphibian neuromuscular junction by regenerating synaptic vesicles. How nerve terminals internalize adequate portions of the presynaptic membrane when bulk endocytosis is initiated before the end of a sustained stimulation is unknown. A maturation process, occurring at the end of the stimulation, is hypothesised to precisely restore the pools of synaptic vesicles. Using confocal time-lapse microscopy of FM1-43-labeled nerve terminals at the amphibian neuromuscular junction, we confirm that bulk endocytosis is initiated during a sustained tetanic stimulation and reveal that shortly after the end of the stimulation, nerve terminals undergo a maturation process. This includes a transient bulging of the plasma membrane, followed by the development of large intraterminal FM1-43-positive donut-like structures comprising large bulk membrane cisternae surrounded by recycling vesicles. The degree of bulging increased with stimulation frequency and the plasmalemma surface retrieved following the transient bulging correlated with the surface membrane internalized in bulk cisternae and recycling vesicles. Dyngo-4a, a potent dynamin inhibitor, did not block the initiation, but prevented the maturation of bulk endocytosis. In contrast, cytochalasin D, an inhibitor of actin polymerization, hindered both the initiation and maturation processes. Both inhibitors hampered the functional recovery of neurotransmission after synaptic depletion. Our data confirm that initiation of bulk endocytosis occurs during stimulation and demonstrates that a delayed maturation process controlled by actin and dynamin underpins the coupling between exocytosis and bulk endocytosis.
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Affiliation(s)
- Tam H. Nguyen
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia
| | - Guillaume Maucort
- School of Mathematics and Physics, The University of Queensland, Brisbane, Queensland, Australia
| | - Robert K. P. Sullivan
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia
- Centre for Microscopy and Microanalysis, The University of Queensland, Brisbane, Queensland, Australia
| | - Mitja Schenning
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia
- School of Biomedical Sciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Nickolas A. Lavidis
- School of Biomedical Sciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Adam McCluskey
- Chemistry, School of Environmental and Life Sciences, The University of Newcastle, Callaghan, Australia
| | - Phillip J. Robinson
- Cell Signalling Unit, Children's Medical Research Institute, The University of Sydney, Sydney, Australia
| | - Frederic A. Meunier
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia
- * E-mail:
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C-terminal complexin sequence is selectively required for clamping and priming but not for Ca2+ triggering of synaptic exocytosis. J Neurosci 2012; 32:2877-85. [PMID: 22357870 DOI: 10.1523/jneurosci.3360-11.2012] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Complexins are small soluble proteins that bind to assembling SNARE complexes during synaptic vesicle exocytosis, which in turn mediates neurotransmitter release. Complexins are required for clamping of spontaneous "mini " release and for the priming and synaptotagmin-dependent Ca(2+) triggering of evoked release. Mammalian genomes encode four complexins that are composed of an N-terminal unstructured sequence that activates synaptic exocytosis, an accessory α-helix that clamps exocytosis, an essential central α-helix that binds to assembling SNARE complexes and is required for all of its functions, and a long, apparently unstructured C-terminal sequence whose function remains unclear. Here, we used cultured mouse neurons to show that the C-terminal sequence of complexin-1 is not required for its synaptotagmin-activating function but is essential for its priming and clamping functions. Wild-type complexin-3 did not clamp exocytosis but nevertheless fully primed and activated exocytosis. Strikingly, exchanging the complexin-1 C terminus for the complexin-3 C terminus abrogated clamping, whereas exchanging the complexin-3 C terminus for the complexin-1 C terminus enabled clamping. Analysis of point mutations in the complexin-1 C terminus identified two single amino-acid substitutions that impaired clamping without altering the activation function of complexin-1. Examination of release induced by stimulus trains revealed that clamping-deficient C-terminal complexin mutants produced a modest relative increase in delayed release. Overall, our results show that the relatively large C-terminal complexin-1 sequence acts in priming and clamping synaptic exocytosis and demonstrate that the clamping function is not conserved in complexin-3, presumably because of its distinct C-terminal sequences.
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A mathematical model for astrocytes mediated LTP at single hippocampal synapses. J Comput Neurosci 2012; 33:341-70. [PMID: 22454034 DOI: 10.1007/s10827-012-0389-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2011] [Revised: 02/21/2012] [Accepted: 02/22/2012] [Indexed: 02/07/2023]
Abstract
Many contemporary studies have shown that astrocytes play a significant role in modulating both short and long form of synaptic plasticity. There are very few experimental models which elucidate the role of astrocyte over Long-term Potentiation (LTP). Recently, Perea and Araque (Science 317:1083-1086, 2007) demonstrated a role of astrocytes in induction of LTP at single hippocampal synapses. They suggested a purely pre-synaptic basis for induction of this N-methyl-D-Aspartate (NMDA) Receptor-independent LTP. Also, the mechanisms underlying this pre-synaptic induction were not investigated. Here, in this article, we propose a mathematical model for astrocyte modulated LTP which successfully imitates the experimental findings of Perea and Araque (Science 317:1083-1086, 2007). Our study suggests the role of retrograde messengers, possibly Nitric Oxide (NO), for this pre-synaptically modulated LTP.
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Samigullin DV, Khuzakhmetova VF, Tsentsevitsky AN, Bukharaeva EA. Presynaptic receptors regulating the time course of neurotransmitter release from vertebrate nerve endings. BIOCHEMISTRY MOSCOW SUPPLEMENT SERIES A-MEMBRANE AND CELL BIOLOGY 2012. [DOI: 10.1134/s1990747811060134] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Asynchronous Ca2+ current conducted by voltage-gated Ca2+ (CaV)-2.1 and CaV2.2 channels and its implications for asynchronous neurotransmitter release. Proc Natl Acad Sci U S A 2012; 109:E452-60. [PMID: 22308469 DOI: 10.1073/pnas.1121103109] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
We have identified an asynchronously activated Ca(2+) current through voltage-gated Ca(2+) (Ca(V))-2.1 and Ca(V)2.2 channels, which conduct P/Q- and N-type Ca(2+) currents that initiate neurotransmitter release. In nonneuronal cells expressing Ca(V)2.1 or Ca(V)2.2 channels and in hippocampal neurons, prolonged Ca(2+) entry activates a Ca(2+) current, I(Async), which is observed on repolarization and decays slowly with a half-time of 150-300 ms. I(Async) is not observed after L-type Ca(2+) currents of similar size conducted by Ca(V)1.2 channels. I(Async) is Ca(2+)-selective, and it is unaffected by changes in Na(+), K(+), Cl(-), or H(+) or by inhibitors of a broad range of ion channels. During trains of repetitive depolarizations, I(Async) increases in a pulse-wise manner, providing Ca(2+) entry that persists between depolarizations. In single-cultured hippocampal neurons, trains of depolarizations evoke excitatory postsynaptic currents that show facilitation followed by depression accompanied by asynchronous postsynaptic currents that increase steadily during the train in parallel with I(Async). I(Async) is much larger for slowly inactivating Ca(V)2.1 channels containing β(2a)-subunits than for rapidly inactivating channels containing β(1b)-subunits. I(Async) requires global rises in intracellular Ca(2+), because it is blocked when Ca(2+) is chelated by 10 mM EGTA in the patch pipette. Neither mutations that prevent Ca(2+) binding to calmodulin nor mutations that prevent calmodulin regulation of Ca(V)2.1 block I(Async). The rise of I(Async) during trains of stimuli, its decay after repolarization, its dependence on global increases of Ca(2+), and its enhancement by β(2a)-subunits all resemble asynchronous release, suggesting that I(Async) is a Ca(2+) source for asynchronous neurotransmission.
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