1
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Jackson MB, Chiang CW, Cheng J. Fusion pore flux controls the rise-times of quantal synaptic responses. J Gen Physiol 2024; 156:e202313484. [PMID: 38860965 PMCID: PMC11167452 DOI: 10.1085/jgp.202313484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 03/18/2024] [Accepted: 05/27/2024] [Indexed: 06/12/2024] Open
Abstract
The release of neurotransmitter from a single synaptic vesicle generates a quantal response, which at excitatory synapses in voltage-clamped neurons is referred to as a miniature excitatory postsynaptic current (mEPSC). We analyzed mEPSCs in cultured mouse hippocampal neurons and in HEK cells expressing postsynaptic proteins enabling them to receive synaptic inputs from cocultured neurons. mEPSC amplitudes and rise-times varied widely within and between cells. In neurons, mEPSCs with larger amplitudes had longer rise-times, and this correlation was stronger in neurons with longer mean rise-times. In HEK cells, this correlation was weak and unclear. Standard mechanisms thought to govern mEPSCs cannot account for these results. We therefore developed models to simulate mEPSCs and assess their dependence on different factors. Modeling indicated that longer diffusion times for transmitters released by larger vesicles to reach more distal receptors cannot account for the correlation between rise-time and amplitude. By contrast, incorporating the vesicle size dependence of fusion pore expulsion time recapitulated experimental results well. Larger vesicles produce mEPSCs with larger amplitudes and also take more time to lose their content. Thus, fusion pore flux directly contributes to mEPSC rise-time. Variations in fusion pores account for differences among neurons, between neurons and HEK cells, and the correlation between rise-time and the slope of rise-time versus amplitude plots. Plots of mEPSC amplitude versus rise-time are sensitive to otherwise inaccessible properties of a synapse and offer investigators a means of assessing the role of fusion pores in synaptic release.
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Affiliation(s)
- Meyer B. Jackson
- Department of Neuroscience, University of Wisconsin—Madison, Madison, WI, USA
| | - Chung-Wei Chiang
- Department of Neuroscience, University of Wisconsin—Madison, Madison, WI, USA
| | - Jinbo Cheng
- Department of Neuroscience, University of Wisconsin—Madison, Madison, WI, USA
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2
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Tian L, Zhang Y, Chen J, Liu X, Nie H, Li K, Liu H, Lai W, Shi Y, Xi Z, Lin B. Effects of nanoplastic exposure during pregnancy and lactation on neurodevelopment of rat offspring. JOURNAL OF HAZARDOUS MATERIALS 2024; 474:134800. [PMID: 38850955 DOI: 10.1016/j.jhazmat.2024.134800] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/25/2023] [Revised: 05/25/2024] [Accepted: 06/01/2024] [Indexed: 06/10/2024]
Abstract
Microplastics have emerged as a prominent global environmental contaminant, and they have been found in both human placenta and breast milk. However, the potential effects and mechanisms of maternal exposure to microplastics at various gestational stages on offspring neurodevelopment remain poorly understood. This investigation delves into the potential neurodevelopmental ramifications of maternal exposure to polystyrene nanoplastics (PS-NPs) during distinct phases of pregnancy and lactation. Targeted metabolomics shows that co-exposure during both pregnancy and lactation primarily engendered alterations in monoamine neurotransmitters within the cortex and amino acid neurotransmitters within the hippocampus. After prenatal exposure to PS-NPs, fetal rats showed appreciably diminished cortical thickness and heightened cortical cell proliferation. However, this exposure did not affect the neurodifferentiation of radial glial cells and intermediate progenitor cells. In addition, offspring are accompanied by disordered neocortical migration, typified by escalated superficial layer neurons proliferation and reduced deep layer neurons populations. Moreover, the hippocampal synapses showed significantly widened synaptic clefts and diminished postsynaptic density. Consequently, PS-NPs culminated in deficits in anxiolytic-like behaviors and spatial memory in adolescent offspring, aligning with concurrent neurotransmitter and synaptic alterations. In conclusion, this study elucidates the sensitive windows of early-life nanoplastic exposure and the consequential impact on offspring neurodevelopment.
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Affiliation(s)
- Lei Tian
- Tianjin Institute of Environmental and Operational Medicine, Tianjin 300050, China
| | - Yaping Zhang
- Tianjin Institute of Environmental and Operational Medicine, Tianjin 300050, China; School of Public Health and Management, Binzhou Medical University, Yantai 264003, China
| | - Jiang Chen
- Tianjin Institute of Environmental and Operational Medicine, Tianjin 300050, China; School of Public Health, North China University of Science and Technology, Tangshan 063200, China
| | - Xuan Liu
- Tianjin Institute of Environmental and Operational Medicine, Tianjin 300050, China
| | - Huipeng Nie
- Tianjin Institute of Environmental and Operational Medicine, Tianjin 300050, China
| | - Kang Li
- Tianjin Institute of Environmental and Operational Medicine, Tianjin 300050, China
| | - Huanliang Liu
- Tianjin Institute of Environmental and Operational Medicine, Tianjin 300050, China
| | - Wenqing Lai
- Tianjin Institute of Environmental and Operational Medicine, Tianjin 300050, China
| | - Yue Shi
- Tianjin Institute of Environmental and Operational Medicine, Tianjin 300050, China
| | - Zhuge Xi
- Tianjin Institute of Environmental and Operational Medicine, Tianjin 300050, China.
| | - Bencheng Lin
- Tianjin Institute of Environmental and Operational Medicine, Tianjin 300050, China.
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3
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Wang JZ, Hu P, Ma S. Mechanisms of stationary voltage fluctuation in the neuromuscular junction endplate and corresponding denoising paradigms. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2024; 53:299-310. [PMID: 39009693 DOI: 10.1007/s00249-024-01715-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Revised: 03/24/2024] [Accepted: 06/18/2024] [Indexed: 07/17/2024]
Abstract
The neuromuscular junction (NMJ) has an elaborate anatomy to ensure agile and accurate signal transmission. Based on our formerly obtained expressions of the thermal and conductance induced voltage fluctuations, in this paper, the mechanisms underlying the conductance-induced voltage fluctuation are characterized from two aspects: the scaling laws with respect to either of the two system-size factors, the number of receptors or the membrane area; and the "seesaw effect" with respect to the intensive parameter, the concentration of acetylcholine. According to these mechanisms, several aspects of the NMJ anatomy are explained from a denoising perspective. Finally, the power spectra of the two types of voltage fluctuations are characterized by their specific scaling laws, based on which we explain why the endplate noise has the low-frequency property that is described by the term "seashell sound".
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Affiliation(s)
- Jia-Zeng Wang
- School of Mathematics and Statistics, Beijing Technology and Business University, Beijing , 100048, PR China.
- Research Center for Statistical Science, Beijing Technology and Business University, Beijing, 100048, PR China.
| | - Pengkun Hu
- School of Mathematics and Statistics, Beijing Technology and Business University, Beijing , 100048, PR China
| | - Shu Ma
- School of Mathematics and Statistics, Beijing Technology and Business University, Beijing , 100048, PR China
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4
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Nowacka A, Getz AM, Bessa-Neto D, Choquet D. Activity-dependent diffusion trapping of AMPA receptors as a key step for expression of early LTP. Philos Trans R Soc Lond B Biol Sci 2024; 379:20230220. [PMID: 38853553 PMCID: PMC11343219 DOI: 10.1098/rstb.2023.0220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2024] [Revised: 04/10/2024] [Accepted: 04/11/2024] [Indexed: 06/11/2024] Open
Abstract
This review focuses on the activity-dependent diffusion trapping of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) as a crucial mechanism for the expression of early long-term potentiation (LTP), a process central to learning and memory. Despite decades of research, the precise mechanisms by which LTP induction leads to an increase in AMPAR responses at synapses have been elusive. We review the different hypotheses that have been put forward to explain the increased AMPAR responsiveness during LTP. We discuss the dynamic nature of AMPAR complexes, including their constant turnover and activity-dependent modifications that affect their synaptic accumulation. We highlight a hypothesis suggesting that AMPARs are diffusively trapped at synapses through activity-dependent interactions with protein-based binding slots in the post-synaptic density (PSD), offering a potential explanation for the increased synaptic strength during LTP. Furthermore, we outline the challenges still to be addressed before we fully understand the functional roles and molecular mechanisms of AMPAR dynamic nanoscale organization in LTP. This article is part of a discussion meeting issue 'Long-term potentiation: 50 years on'.
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Affiliation(s)
- Agata Nowacka
- University of Bordeaux, CNRS, Interdisciplinary Institute for Neuroscience, IINS, UMR 5297, BordeauxF-33000, France
| | - Angela M. Getz
- University of Bordeaux, CNRS, Interdisciplinary Institute for Neuroscience, IINS, UMR 5297, BordeauxF-33000, France
- University of Bordeaux, CNRS, INSERM, Bordeaux Imaging Center, BIC, UMS 3420, US 4, BordeauxF-33000, France
| | - Diogo Bessa-Neto
- University of Bordeaux, CNRS, Interdisciplinary Institute for Neuroscience, IINS, UMR 5297, BordeauxF-33000, France
| | - Daniel Choquet
- University of Bordeaux, CNRS, Interdisciplinary Institute for Neuroscience, IINS, UMR 5297, BordeauxF-33000, France
- University of Bordeaux, CNRS, INSERM, Bordeaux Imaging Center, BIC, UMS 3420, US 4, BordeauxF-33000, France
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5
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Harris KM, Kuwajima M, Flores JC, Zito K. Synapse-specific structural plasticity that protects and refines local circuits during LTP and LTD. Philos Trans R Soc Lond B Biol Sci 2024; 379:20230224. [PMID: 38853547 DOI: 10.1098/rstb.2023.0224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Accepted: 01/05/2024] [Indexed: 06/11/2024] Open
Abstract
Synapses form trillions of connections in the brain. Long-term potentiation (LTP) and long-term depression (LTD) are cellular mechanisms vital for learning that modify the strength and structure of synapses. Three-dimensional reconstruction from serial section electron microscopy reveals three distinct pre- to post-synaptic arrangements: strong active zones (AZs) with tightly docked vesicles, weak AZs with loose or non-docked vesicles, and nascent zones (NZs) with a postsynaptic density but no presynaptic vesicles. Importantly, LTP can be temporarily saturated preventing further increases in synaptic strength. At the onset of LTP, vesicles are recruited to NZs, converting them to AZs. During recovery of LTP from saturation (1-4 h), new NZs form, especially on spines where AZs are most enlarged by LTP. Sentinel spines contain smooth endoplasmic reticulum (SER), have the largest synapses and form clusters with smaller spines lacking SER after LTP recovers. We propose a model whereby NZ plasticity provides synapse-specific AZ expansion during LTP and loss of weak AZs that drive synapse shrinkage during LTD. Spine clusters become functionally engaged during LTP or disassembled during LTD. Saturation of LTP or LTD probably acts to protect recently formed memories from ongoing plasticity and may account for the advantage of spaced over massed learning. This article is part of a discussion meeting issue 'Long-term potentiation: 50 years on'.
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Affiliation(s)
- Kristen M Harris
- Department of Neuroscience and Center for Learning and Memory, The University of Texas at Austin , Austin, TX 78712, USA
| | - Masaaki Kuwajima
- Department of Neuroscience and Center for Learning and Memory, The University of Texas at Austin , Austin, TX 78712, USA
| | - Juan C Flores
- Center for Neuroscience, University of California , Davis, CA 95618, USA
| | - Karen Zito
- Center for Neuroscience, University of California , Davis, CA 95618, USA
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6
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Olah SS, Kareemo DJ, Buchta WC, Sinnen BL, Miller CN, Actor-Engel HS, Gookin SE, Winborn CS, Kleinjan MS, Crosby KC, Aoto J, Smith KR, Kennedy MJ. Acute reorganization of postsynaptic GABA A receptors reveals the functional impact of molecular nanoarchitecture at inhibitory synapses. Cell Rep 2023; 42:113331. [PMID: 37910506 PMCID: PMC10782565 DOI: 10.1016/j.celrep.2023.113331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Revised: 09/01/2023] [Accepted: 10/06/2023] [Indexed: 11/03/2023] Open
Abstract
Neurotransmitter receptors partition into nanometer-scale subdomains within the postsynaptic membrane that are precisely aligned with presynaptic neurotransmitter release sites. While spatial coordination between pre- and postsynaptic elements is observed at both excitatory and inhibitory synapses, the functional significance of this molecular architecture has been challenging to evaluate experimentally. Here we utilized an optogenetic clustering approach to acutely alter the nanoscale organization of the postsynaptic inhibitory scaffold gephyrin while monitoring synaptic function. Gephyrin clustering rapidly enlarged postsynaptic area, laterally displacing GABAA receptors from their normally precise apposition with presynaptic active zones. Receptor displacement was accompanied by decreased synaptic GABAA receptor currents even though presynaptic release probability and the overall abundance and function of synaptic GABAA receptors remained unperturbed. Thus, acutely repositioning neurotransmitter receptors within the postsynaptic membrane profoundly influences synaptic efficacy, establishing the functional importance of precision pre-/postsynaptic molecular coordination at inhibitory synapses.
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Affiliation(s)
- Samantha S Olah
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Dean J Kareemo
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - William C Buchta
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Brooke L Sinnen
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Carley N Miller
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Hannah S Actor-Engel
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Sara E Gookin
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Christina S Winborn
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Mason S Kleinjan
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Kevin C Crosby
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Jason Aoto
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Katharine R Smith
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Matthew J Kennedy
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA.
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7
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Srinivasan S, Daste S, Modi MN, Turner GC, Fleischmann A, Navlakha S. Effects of stochastic coding on olfactory discrimination in flies and mice. PLoS Biol 2023; 21:e3002206. [PMID: 37906721 PMCID: PMC10618007 DOI: 10.1371/journal.pbio.3002206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 08/21/2023] [Indexed: 11/02/2023] Open
Abstract
Sparse coding can improve discrimination of sensory stimuli by reducing overlap between their representations. Two factors, however, can offset sparse coding's benefits: similar sensory stimuli have significant overlap and responses vary across trials. To elucidate the effects of these 2 factors, we analyzed odor responses in the fly and mouse olfactory regions implicated in learning and discrimination-the mushroom body (MB) and the piriform cortex (PCx). We found that neuronal responses fall along a continuum from extremely reliable across trials to extremely variable or stochastic. Computationally, we show that the observed variability arises from noise within central circuits rather than sensory noise. We propose this coding scheme to be advantageous for coarse- and fine-odor discrimination. More reliable cells enable quick discrimination between dissimilar odors. For similar odors, however, these cells overlap and do not provide distinguishing information. By contrast, more unreliable cells are decorrelated for similar odors, providing distinguishing information, though these benefits only accrue with extended training with more trials. Overall, we have uncovered a conserved, stochastic coding scheme in vertebrates and invertebrates, and we identify a candidate mechanism, based on variability in a winner-take-all (WTA) inhibitory circuit, that improves discrimination with training.
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Affiliation(s)
- Shyam Srinivasan
- Kavli Institute for Brain and Mind, University of California, San Diego, California, United States of America
- Salk Institute for Biological Studies, La Jolla, California, United States of America
| | - Simon Daste
- Department of Neuroscience, Division of Biology and Medicine, Brown University, Providence, Rhode Island, United States of America
- Robert J. and Nancy D. Carney Institute for Brain Science, Brown University, Providence, Rhode Island, United States of America
| | - Mehrab N. Modi
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia, United States of America
| | - Glenn C. Turner
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia, United States of America
| | - Alexander Fleischmann
- Department of Neuroscience, Division of Biology and Medicine, Brown University, Providence, Rhode Island, United States of America
- Robert J. and Nancy D. Carney Institute for Brain Science, Brown University, Providence, Rhode Island, United States of America
| | - Saket Navlakha
- Simons Center for Quantitative Biology, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, United States of America
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8
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Misra S, Bland LC, Cardwell SG, Incorvia JAC, James CD, Kent AD, Schuman CD, Smith JD, Aimone JB. Probabilistic Neural Computing with Stochastic Devices. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2204569. [PMID: 36395387 DOI: 10.1002/adma.202204569] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 08/03/2022] [Indexed: 06/16/2023]
Abstract
The brain has effectively proven a powerful inspiration for the development of computing architectures in which processing is tightly integrated with memory, communication is event-driven, and analog computation can be performed at scale. These neuromorphic systems increasingly show an ability to improve the efficiency and speed of scientific computing and artificial intelligence applications. Herein, it is proposed that the brain's ubiquitous stochasticity represents an additional source of inspiration for expanding the reach of neuromorphic computing to probabilistic applications. To date, many efforts exploring probabilistic computing have focused primarily on one scale of the microelectronics stack, such as implementing probabilistic algorithms on deterministic hardware or developing probabilistic devices and circuits with the expectation that they will be leveraged by eventual probabilistic architectures. A co-design vision is described by which large numbers of devices, such as magnetic tunnel junctions and tunnel diodes, can be operated in a stochastic regime and incorporated into a scalable neuromorphic architecture that can impact a number of probabilistic computing applications, such as Monte Carlo simulations and Bayesian neural networks. Finally, a framework is presented to categorize increasingly advanced hardware-based probabilistic computing technologies.
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Affiliation(s)
- Shashank Misra
- Microsystems Engineering, Science and Applications, Sandia National Laboratories, Albuquerque, NM, 87123, USA
| | - Leslie C Bland
- Department of Physics, Temple University, Philadelphia, PA, 19122-1801, USA
| | - Suma G Cardwell
- Neural Exploration and Research Laboratory, Sandia National Laboratories, Albuquerque, NM, 87123, USA
| | - Jean Anne C Incorvia
- Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Conrad D James
- Microsystems Engineering, Science and Applications, Sandia National Laboratories, Albuquerque, NM, 87123, USA
| | - Andrew D Kent
- Department of Physics, New York University, New York, NY, 10003, USA
| | - Catherine D Schuman
- Department of Electrical Engineering and Computer Science, University of Tennessee, Knoxville, TN, 37996, USA
| | - J Darby Smith
- Neural Exploration and Research Laboratory, Sandia National Laboratories, Albuquerque, NM, 87123, USA
| | - James B Aimone
- Neural Exploration and Research Laboratory, Sandia National Laboratories, Albuquerque, NM, 87123, USA
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9
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Droogers WJ, MacGillavry HD. Plasticity of postsynaptic nanostructure. Mol Cell Neurosci 2023; 124:103819. [PMID: 36720293 DOI: 10.1016/j.mcn.2023.103819] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Revised: 01/19/2023] [Accepted: 01/23/2023] [Indexed: 01/31/2023] Open
Abstract
The postsynaptic density (PSD) of excitatory synapses is built from a wide variety of scaffolding proteins, receptors, and signaling molecules that collectively orchestrate synaptic transmission. Seminal work over the past decades has led to the identification and functional characterization of many PSD components. In contrast, we know far less about how these constituents are assembled within synapses, and how this organization contributes to synapse function. Notably, recent evidence from high-resolution microscopy studies and in silico models, highlights the importance of the precise subsynaptic structure of the PSD for controlling the strength of synaptic transmission. Even further, activity-driven changes in the distribution of glutamate receptors are acknowledged to contribute to long-term changes in synaptic efficacy. Thus, defining the mechanisms that drive structural changes within the PSD are important for a molecular understanding of synaptic transmission and plasticity. Here, we review the current literature on how the PSD is organized to mediate basal synaptic transmission and how synaptic activity alters the nanoscale organization of synapses to sustain changes in synaptic strength.
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Affiliation(s)
- W J Droogers
- Division of Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, 3584 CH, The Netherlands
| | - H D MacGillavry
- Division of Cell Biology, Neurobiology and Biophysics, Department of Biology, Faculty of Science, Utrecht University, 3584 CH, The Netherlands.
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10
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Tønnesen J, Hrabĕtová S, Soria FN. Local diffusion in the extracellular space of the brain. Neurobiol Dis 2023; 177:105981. [PMID: 36581229 DOI: 10.1016/j.nbd.2022.105981] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2022] [Revised: 12/23/2022] [Accepted: 12/25/2022] [Indexed: 12/27/2022] Open
Abstract
The brain extracellular space (ECS) is a vast interstitial reticulum of extreme morphological complexity, composed of narrow gaps separated by local expansions, enabling interconnected highways between neural cells. Constituting on average 20% of brain volume, the ECS is key for intercellular communication, and understanding its diffusional properties is of paramount importance for understanding the brain. Within the ECS, neuroactive substances travel predominantly by diffusion, spreading through the interstitial fluid and the extracellular matrix scaffold after being focally released. The nanoscale dimensions of the ECS render it unresolvable by conventional live tissue compatible imaging methods, and historically diffusion of tracers has been used to indirectly infer its structure. Novel nanoscopic imaging techniques now show that the ECS is a highly dynamic compartment, and that diffusivity in the ECS is more heterogeneous than anticipated, with great variability across brain regions and physiological states. Diffusion is defined primarily by the local ECS geometry, and secondarily by the viscosity of the interstitial fluid, including the obstructive and binding properties of the extracellular matrix. ECS volume fraction and tortuosity both strongly determine diffusivity, and each can be independently regulated e.g. through alterations in glial morphology and the extracellular matrix composition. Here we aim to provide an overview of our current understanding of the ECS and its diffusional properties. We highlight emerging technological advances to respectively interrogate and model diffusion through the ECS, and point out how these may contribute in resolving the remaining enigmas of the ECS.
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Affiliation(s)
- Jan Tønnesen
- Achucarro Basque Center for Neuroscience, Leioa, Spain; Department of Neuroscience, University of the Basque Country (UPV/EHU), Leioa, Spain; Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD 20815, USA
| | - Sabina Hrabĕtová
- Department of Cell Biology, State University of New York, Downstate Health Sciences University, Brooklyn, NY, USA; The Robert F. Furchgott Center for Neural and Behavioral Science, State University of New York Downstate Health Sciences University, Brooklyn, NY, USA
| | - Federico N Soria
- Achucarro Basque Center for Neuroscience, Leioa, Spain; Department of Neuroscience, University of the Basque Country (UPV/EHU), Leioa, Spain; Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD 20815, USA; Centro de Investigación Biomédica en Red Enfermedades Neurodegenerativas (CIBERNED), Spain.
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11
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Hao Y, Toulmé E, König B, Rosenmund C, Plested AJR. Targeted sensors for glutamatergic neurotransmission. eLife 2023; 12:e84029. [PMID: 36622100 PMCID: PMC9917459 DOI: 10.7554/elife.84029] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Accepted: 01/06/2023] [Indexed: 01/10/2023] Open
Abstract
Optical report of neurotransmitter release allows visualisation of excitatory synaptic transmission. Sensitive genetically-encoded fluorescent glutamate reporters operating with a range of affinities and emission wavelengths are available. However, without targeting to synapses, the specificity of the fluorescent signal is uncertain, compared to sensors directed at vesicles or other synaptic markers. We fused the state-of-the-art reporter iGluSnFR to glutamate receptor auxiliary proteins in order to target it to postsynaptic sites. Chimeras of Stargazin and gamma-8 that we named SnFR-γ2 and SnFR-γ8, were enriched at synapses, retained function and reported spontaneous glutamate release in rat hippocampal cells, with apparently diffraction-limited spatial precision. In autaptic mouse neurons cultured on astrocytic microislands, evoked neurotransmitter release could be quantitatively detected at tens of synapses in a field of view whilst evoked currents were recorded simultaneously. These experiments revealed a specific postsynaptic deficit from Stargazin overexpression, resulting in synapses with normal neurotransmitter release but without postsynaptic responses. This defect was reverted by delaying overexpression. By working at different calcium concentrations, we determined that SnFR-γ2 is a linear reporter of the global quantal parameters and short-term synaptic plasticity, whereas iGluSnFR is not. On average, half of iGluSnFR regions of interest (ROIs) showing evoked fluorescence changes had intense rundown, whereas less than 5% of SnFR-γ2 ROIs did. We provide an open-source analysis suite for extracting quantal parameters including release probability from fluorescence time series of individual and grouped synaptic responses. Taken together, postsynaptic targeting improves several properties of iGluSnFR and further demonstrates the importance of subcellular targeting for optogenetic actuators and reporters.
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Affiliation(s)
- Yuchen Hao
- Institute of Biology, Cellular Biophysics, Humboldt-Universität zu BerlinBerlinGermany
- Leibniz-Forschungsinstitut für Molekulare PharmakologieBerlinGermany
| | - Estelle Toulmé
- Institute for Neurophysiology, Charité - Universitätsmedizin BerlinBerlinGermany
| | - Benjamin König
- Institute of Biology, Cellular Biophysics, Humboldt-Universität zu BerlinBerlinGermany
- Leibniz-Forschungsinstitut für Molekulare PharmakologieBerlinGermany
| | - Christian Rosenmund
- Institute for Neurophysiology, Charité - Universitätsmedizin BerlinBerlinGermany
- NeuroCure Cluster of ExcellenceBerlinGermany
| | - Andrew JR Plested
- Institute of Biology, Cellular Biophysics, Humboldt-Universität zu BerlinBerlinGermany
- Leibniz-Forschungsinstitut für Molekulare PharmakologieBerlinGermany
- NeuroCure Cluster of ExcellenceBerlinGermany
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12
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Tanimura A, Shen W, Wokosin D, Surmeier DJ. Pathway-Specific Remodeling of Thalamostriatal Synapses in a Mouse Model of Parkinson's Disease. Mov Disord 2022; 37:1164-1174. [PMID: 35485341 PMCID: PMC9232945 DOI: 10.1002/mds.29030] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2022] [Accepted: 03/21/2022] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND The network pathophysiology underlying the motor symptoms of Parkinson's disease (PD) is poorly understood. In models of late-stage PD, there is significant cell-specific remodeling of corticostriatal, axospinous glutamatergic synapses on principal spiny projection neurons (SPNs). Neurons in the centrolateral nucleus (CLN) of the thalamus that relay cerebellar activity to the striatum also make axospinous synapses on SPNs, but the extent to which they are affected in PD has not been definitively characterized. OBJECTIVE To fill this gap, transgenic mice in which CLN neurons express Cre recombinase were used in conjunction with optogenetic and circuit mapping approaches to determine changes in the CLN projection to SPNs in a unilateral 6-hydroxydopamine (6-OHDA) model of late-stage PD. METHODS Adeno-associated virus vectors carrying Cre-dependent opsin expression constructs were stereotaxically injected into the CLN of Grp-KH288 mice in which CLN, but not parafascicular nucleus neurons, expressed Cre recombinase. The properties of this projection to identify direct pathway spiny projection neurons (dSPNs) and indirect pathway spiny projection neurons (iSPNs) were then studied in ex vivo brain slices of the dorsolateral striatum from control and 6-OHDA lesioned mice using anatomic, optogenetic, and electrophysiological approaches. RESULTS Optogenetically evoked excitatory synaptic currents in both iSPNs and dSPNs were reduced in lesioned mice; however, the reduction was significantly greater in dSPNs. In iSPNs, the reduction in evoked responses was attributable to synaptic pruning, because synaptic channelrhodopsin assisted circuit mapping (sCRACm) revealed fewer synapses per cell after lesioning. In contrast, sCRACm mapping of CLN inputs to dSPNs failed to detect any change in synapse abundance in lesioned mice. However, the ratio of currents through α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors to those through N-methyl-D-aspartate receptors was significantly reduced in dSPNs. Moreover, the distribution of currents evoked by optical stimulation of individual synapses shifted toward smaller amplitudes by lesioning, suggesting that they had undergone long-term depression. CONCLUSIONS Taken together, our results demonstrate that the CLN projection to the striatum undergoes a pathway-specific remodeling that could contribute to the circuit imbalance thought to drive the hypokinetic features of PD. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.
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Affiliation(s)
- Asami Tanimura
- Department of Neuroscience, Feinberg School of MedicineNorthwestern UniversityChicagoIllinoisUSA
- Department of BiomedicineAarhus UniversityAarhusDenmark
| | - Weixing Shen
- Department of Neuroscience, Feinberg School of MedicineNorthwestern UniversityChicagoIllinoisUSA
| | - David Wokosin
- Department of Neuroscience, Feinberg School of MedicineNorthwestern UniversityChicagoIllinoisUSA
| | - D. James Surmeier
- Department of Neuroscience, Feinberg School of MedicineNorthwestern UniversityChicagoIllinoisUSA
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13
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Re-examination of the determinants of synaptic strength from the perspective of superresolution imaging. Curr Opin Neurobiol 2022; 74:102540. [DOI: 10.1016/j.conb.2022.102540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 02/04/2022] [Accepted: 03/03/2022] [Indexed: 11/21/2022]
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14
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Wegner W, Steffens H, Gregor C, Wolf F, Willig KI. Environmental enrichment enhances patterning and remodeling of synaptic nanoarchitecture as revealed by STED nanoscopy. eLife 2022; 11:73603. [PMID: 35195066 PMCID: PMC8903838 DOI: 10.7554/elife.73603] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Accepted: 02/22/2022] [Indexed: 12/04/2022] Open
Abstract
Synaptic plasticity underlies long-lasting structural and functional changes to brain circuitry and its experience-dependent remodeling can be fundamentally enhanced by environmental enrichment. It is however unknown, whether and how the environmental enrichment alters the morphology and dynamics of individual synapses. Here, we present a virtually crosstalk-free two-color in vivo stimulated emission depletion (STED) microscope to simultaneously superresolve the dynamics of endogenous PSD95 of the post-synaptic density and spine geometry in the mouse cortex. In general, the spine head geometry and PSD95 assemblies were highly dynamic, their changes depended linearly on their original size but correlated only mildly. With environmental enrichment, the size distributions of PSD95 and spine head sizes were sharper than in controls, indicating that synaptic strength is set more uniformly. The topography of the PSD95 nanoorganization was more dynamic after environmental enrichment; changes in size were smaller but more correlated than in mice housed in standard cages. Thus, two-color in vivo time-lapse imaging of synaptic nanoorganization uncovers a unique synaptic nanoplasticity associated with the enhanced learning capabilities under environmental enrichment.
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Affiliation(s)
- Waja Wegner
- Center for Nanoscale Microscopy and Molecular Physiology of the Brain, University Medical Center Göttingen, Göttingen, Germany
| | - Heinz Steffens
- Center for Nanoscale Microscopy and Molecular Physiology of the Brain, University Medical Center Göttingen, Göttingen, Germany
| | - Carola Gregor
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Fred Wolf
- Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany
| | - Katrin I Willig
- Center for Nanoscale Microscopy and Molecular Physiology of the Brain, University Medical Center Göttingen, Göttingen, Germany
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15
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Rǎdulescu AR, Todd GC, Williams CL, Bennink BA, Lemus AA, Chesbro HE, Bourgeois JR, Kopec AM, Zuloaga DG, Scimemi A. Estimating the glutamate transporter surface density in distinct sub-cellular compartments of mouse hippocampal astrocytes. PLoS Comput Biol 2022; 18:e1009845. [PMID: 35120128 PMCID: PMC8849624 DOI: 10.1371/journal.pcbi.1009845] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 02/16/2022] [Accepted: 01/18/2022] [Indexed: 11/19/2022] Open
Abstract
Glutamate transporters preserve the spatial specificity of synaptic transmission by limiting glutamate diffusion away from the synaptic cleft, and prevent excitotoxicity by keeping the extracellular concentration of glutamate at low nanomolar levels. Glutamate transporters are abundantly expressed in astrocytes, and previous estimates have been obtained about their surface expression in astrocytes of the rat hippocampus and cerebellum. Analogous estimates for the mouse hippocampus are currently not available. In this work, we derive the surface density of astrocytic glutamate transporters in mice of different ages via quantitative dot blot. We find that the surface density of glial glutamate transporters is similar in 7-8 week old mice and rats. In mice, the levels of glutamate transporters increase until about 6 months of age and then begin to decline slowly. Our data, obtained from a combination of experimental and modeling approaches, point to the existence of stark differences in the density of expression of glutamate transporters across different sub-cellular compartments, indicating that the extent to which astrocytes limit extrasynaptic glutamate diffusion depends not only on their level of synaptic coverage, but also on the identity of the astrocyte compartment in contact with the synapse. Together, these findings provide information on how heterogeneity in the spatial distribution of glutamate transporters in the plasma membrane of hippocampal astrocytes my alter glutamate receptor activation out of the synaptic cleft.
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Affiliation(s)
- Anca R. Rǎdulescu
- Department of Mathematics, State University of New York at New Paltz, New Paltz, New York, United States of America
| | - Gabrielle C. Todd
- Department of Biology, State University of New York at Albany, Albany, New York, United States of America
| | - Cassandra L. Williams
- Department of Mathematics, State University of New York at New Paltz, New Paltz, New York, United States of America
| | - Benjamin A. Bennink
- Department of Biology, State University of New York at Albany, Albany, New York, United States of America
| | - Alex A. Lemus
- Department of Biology, State University of New York at Albany, Albany, New York, United States of America
| | - Haley E. Chesbro
- Department of Biology, State University of New York at Albany, Albany, New York, United States of America
| | - Justin R. Bourgeois
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, New York, United States of America
| | - Ashley M. Kopec
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, New York, United States of America
| | - Damian G. Zuloaga
- Department of Psychology, State University of New York at Albany, Albany, New York, United States of America
| | - Annalisa Scimemi
- Department of Biology, State University of New York at Albany, Albany, New York, United States of America
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16
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Guzikowski NJ, Kavalali ET. Nano-Organization at the Synapse: Segregation of Distinct Forms of Neurotransmission. Front Synaptic Neurosci 2022; 13:796498. [PMID: 35002671 PMCID: PMC8727373 DOI: 10.3389/fnsyn.2021.796498] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2021] [Accepted: 11/19/2021] [Indexed: 01/01/2023] Open
Abstract
Synapses maintain synchronous, asynchronous, and spontaneous modes of neurotransmission through distinct molecular and biochemical pathways. Traditionally a single synapse was assumed to have a homogeneous organization of molecular components both at the active zone and post-synaptically. However, recent advancements in experimental tools and the further elucidation of the physiological significance of distinct forms of release have challenged this notion. In comparison to rapid evoked release, the physiological significance of both spontaneous and asynchronous neurotransmission has only recently been considered in parallel with synaptic structural organization. Active zone nanostructure aligns with postsynaptic nanostructure creating a precise trans-synaptic alignment of release sites and receptors shaping synaptic efficacy, determining neurotransmission reliability, and tuning plasticity. This review will discuss how studies delineating synaptic nanostructure create a picture of a molecularly heterogeneous active zone tuned to distinct forms of release that may dictate diverse synaptic functional outputs.
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Affiliation(s)
- Natalie J Guzikowski
- Department of Pharmacology, Vanderbilt University, Nashville, TN, United States.,Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN, United States
| | - Ege T Kavalali
- Department of Pharmacology, Vanderbilt University, Nashville, TN, United States.,Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN, United States
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17
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Wichmann C, Kuner T. Heterogeneity of glutamatergic synapses: cellular mechanisms and network consequences. Physiol Rev 2022; 102:269-318. [PMID: 34727002 DOI: 10.1152/physrev.00039.2020] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Chemical synapses are commonly known as a structurally and functionally highly diverse class of cell-cell contacts specialized to mediate communication between neurons. They represent the smallest "computational" unit of the brain and are typically divided into excitatory and inhibitory as well as modulatory categories. These categories are subdivided into diverse types, each representing a different structure-function repertoire that in turn are thought to endow neuronal networks with distinct computational properties. The diversity of structure and function found among a given category of synapses is referred to as heterogeneity. The main building blocks for this heterogeneity are synaptic vesicles, the active zone, the synaptic cleft, the postsynaptic density, and glial processes associated with the synapse. Each of these five structural modules entails a distinct repertoire of functions, and their combination specifies the range of functional heterogeneity at mammalian excitatory synapses, which are the focus of this review. We describe synapse heterogeneity that is manifested on different levels of complexity ranging from the cellular morphology of the pre- and postsynaptic cells toward the expression of different protein isoforms at individual release sites. We attempt to define the range of structural building blocks that are used to vary the basic functional repertoire of excitatory synaptic contacts and discuss sources and general mechanisms of synapse heterogeneity. Finally, we explore the possible impact of synapse heterogeneity on neuronal network function.
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Affiliation(s)
- Carolin Wichmann
- Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience, InnerEarLab and Institute for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, Göttingen, Germany
| | - Thomas Kuner
- Department of Functional Neuroanatomy, Institute for Anatomy and Cell Biology, Heidelberg, Germany
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18
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Super-resolution microscopy: a closer look at synaptic dysfunction in Alzheimer disease. Nat Rev Neurosci 2021; 22:723-740. [PMID: 34725519 DOI: 10.1038/s41583-021-00531-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/27/2021] [Indexed: 11/08/2022]
Abstract
The synapse has emerged as a critical neuronal structure in the degenerative process of Alzheimer disease (AD), in which the pathogenic signals of two key players - amyloid-β (Aβ) and tau - converge, thereby causing synaptic dysfunction and cognitive deficits. The synapse presents a dynamic, confined microenvironment in which to explore how key molecules travel, localize, interact and assume different levels of organizational complexity, thereby affecting neuronal function. However, owing to their small size and the diffraction-limited resolution of conventional light microscopic approaches, investigating synaptic structure and dynamics has been challenging. Super-resolution microscopy (SRM) techniques have overcome the resolution barrier and are revolutionizing our quantitative understanding of biological systems in unprecedented spatio-temporal detail. Here we review critical new insights provided by SRM into the molecular architecture and dynamic organization of the synapse and, in particular, the interactions between Aβ and tau in this compartment. We further highlight how SRM can transform our understanding of the molecular pathological mechanisms that underlie AD. The application of SRM for understanding the roles of synapses in AD pathology will provide a stepping stone towards a broader understanding of dysfunction in other subcellular compartments and at cellular and circuit levels in this disease.
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19
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Abstract
Fluorescence imaging techniques play a pivotal role in our understanding of the nervous system. The emergence of various super-resolution microscopy methods and specialized fluorescent probes enables direct insight into neuronal structure and protein arrangements in cellular subcompartments with so far unmatched resolution. Super-resolving visualization techniques in neurons unveil a novel understanding of cytoskeletal composition, distribution, motility, and signaling of membrane proteins, subsynaptic structure and function, and neuron-glia interaction. Well-defined molecular targets in autoimmune and neurodegenerative disease models provide excellent starting points for in-depth investigation of disease pathophysiology using novel and innovative imaging methodology. Application of super-resolution microscopy in human brain samples and for testing clinical biomarkers is still in its infancy but opens new opportunities for translational research in neurology and neuroscience. In this review, we describe how super-resolving microscopy has improved our understanding of neuronal and brain function and dysfunction in the last two decades.
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Affiliation(s)
- Christian Werner
- Department of Biotechnology & Biophysics, Biocenter, University of Würzburg, 97074 Würzburg, Germany
| | - Markus Sauer
- Department of Biotechnology & Biophysics, Biocenter, University of Würzburg, 97074 Würzburg, Germany
| | - Christian Geis
- Section Translational Neuroimmunology, Department of Neurology, Jena University Hospital, Am Klinikum 1, 07747 Jena, Germany
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20
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The glutamatergic synapse: a complex machinery for information processing. Cogn Neurodyn 2021; 15:757-781. [PMID: 34603541 DOI: 10.1007/s11571-021-09679-w] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Revised: 03/04/2021] [Accepted: 04/16/2021] [Indexed: 10/21/2022] Open
Abstract
Being the most abundant synaptic type, the glutamatergic synapse is responsible for the larger part of the brain's information processing. Despite the conceptual simplicity of the basic mechanism of synaptic transmission, the glutamatergic synapse shows a large variation in the response to the presynaptic release of the neurotransmitter. This variability is observed not only among different synapses but also in the same single synapse. The synaptic response variability is due to several mechanisms of control of the information transferred among the neurons and suggests that the glutamatergic synapse is not a simple bridge for the transfer of information but plays an important role in its elaboration and management. The control of the synaptic information is operated at pre, post, and extrasynaptic sites in a sort of cooperation between the pre and postsynaptic neurons which also involves the activity of other neurons. The interaction between the different mechanisms of control is extremely complicated and its complete functionality is far from being fully understood. The present review, although not exhaustively, is intended to outline the most important of these mechanisms and their complexity, the understanding of which will be among the most intriguing challenges of future neuroscience.
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21
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Ramsey AM, Tang AH, LeGates TA, Gou XZ, Carbone BE, Thompson SM, Biederer T, Blanpied TA. Subsynaptic positioning of AMPARs by LRRTM2 controls synaptic strength. SCIENCE ADVANCES 2021; 7:7/34/eabf3126. [PMID: 34417170 PMCID: PMC8378824 DOI: 10.1126/sciadv.abf3126] [Citation(s) in RCA: 49] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Accepted: 06/30/2021] [Indexed: 05/07/2023]
Abstract
Recent evidence suggests that nano-organization of proteins within synapses may control the strength of communication between neurons in the brain. The unique subsynaptic distribution of glutamate receptors, which cluster in nanoalignment with presynaptic sites of glutamate release, supports this hypothesis. However, testing it has been difficult because mechanisms controlling subsynaptic organization remain unknown. Reasoning that transcellular interactions could position AMPA receptors (AMPARs), we targeted a key transsynaptic adhesion molecule implicated in controlling AMPAR number, LRRTM2, using engineered, rapid proteolysis. Severing the LRRTM2 extracellular domain led quickly to nanoscale declustering of AMPARs away from release sites, not prompting their escape from synapses until much later. This rapid remodeling of AMPAR position produced significant deficits in evoked, but not spontaneous, postsynaptic receptor activation. These results dissociate receptor numbers from their nanopositioning in determination of synaptic function and support the novel concept that adhesion molecules acutely position receptors to dynamically control synaptic strength.
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Affiliation(s)
- Austin M Ramsey
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
- Program in Neuroscience, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Ai-Hui Tang
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Tara A LeGates
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
- Program in Neuroscience, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | | | - Beatrice E Carbone
- Department of Neurology, Yale School of Medicine, New Haven, CT 06520, USA
| | - Scott M Thompson
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
- Program in Neuroscience, University of Maryland School of Medicine, Baltimore, MD 21201, USA
- Department of Psychiatry, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Thomas Biederer
- Department of Neurology, Yale School of Medicine, New Haven, CT 06520, USA
| | - Thomas A Blanpied
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
- Program in Neuroscience, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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22
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Wang JZ, Fan YH. Characterizing the voltage fluctuations driven by a cluster of ligand-gated channels. Phys Rev E 2021; 103:052401. [PMID: 34134193 DOI: 10.1103/physreve.103.052401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 04/09/2021] [Indexed: 11/07/2022]
Abstract
In this paper we present the properties of the voltage fluctuations driven by a cluster of ligand-gated channels. First, the second-order moment of the voltage is expressed in form of the integrated resistance and the random force. Then the power spectrum of the voltage noise is obtained analytically, and it is proved to have the 1/ω^{4}-form. Its mechanism lies in that the randomness of the voltage fluctuation is weaker than channel (conductance) noise, which can be approximately described by the Ornstein-Ulenbeck process.
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Affiliation(s)
- Jia-Zeng Wang
- School of Mathematics and Statistics, Beijing Technology and Business University, Beijing 100048, People's Republic of China
| | - Yan-Hua Fan
- School of Mathematics and Statistics, Beijing Technology and Business University, Beijing 100048, People's Republic of China
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23
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Shortened tethering filaments stabilize presynaptic vesicles in support of elevated release probability during LTP in rat hippocampus. Proc Natl Acad Sci U S A 2021; 118:2018653118. [PMID: 33875591 DOI: 10.1073/pnas.2018653118] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Long-term potentiation (LTP) is a cellular mechanism of learning and memory that results in a sustained increase in the probability of vesicular release of neurotransmitter. However, previous work in hippocampal area CA1 of the adult rat revealed that the total number of vesicles per synapse decreases following LTP, seemingly inconsistent with the elevated release probability. Here, electron-microscopic tomography (EMT) was used to assess whether changes in vesicle density or structure of vesicle tethering filaments at the active zone might explain the enhanced release probability following LTP. The spatial relationship of vesicles to the active zone varies with functional status. Tightly docked vesicles contact the presynaptic membrane, have partially formed SNARE complexes, and are primed for release of neurotransmitter upon the next action potential. Loosely docked vesicles are located within 8 nm of the presynaptic membrane where SNARE complexes begin to form. Nondocked vesicles comprise recycling and reserve pools. Vesicles are tethered to the active zone via filaments composed of molecules engaged in docking and release processes. The density of tightly docked vesicles was increased 2 h following LTP compared to control stimulation, whereas the densities of loosely docked or nondocked vesicles congregating within 45 nm above the active zones were unchanged. The tethering filaments on all vesicles were shorter and their attachment sites shifted closer to the active zone. These findings suggest that tethering filaments stabilize more vesicles in the primed state. Such changes would facilitate the long-lasting increase in release probability following LTP.
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24
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Chiang CW, Shu WC, Wan J, Weaver BA, Jackson MB. Recordings from neuron-HEK cell cocultures reveal the determinants of miniature excitatory postsynaptic currents. J Gen Physiol 2021; 153:211910. [PMID: 33755721 PMCID: PMC7992392 DOI: 10.1085/jgp.202012849] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Revised: 01/26/2021] [Accepted: 02/23/2021] [Indexed: 11/20/2022] Open
Abstract
Spontaneous exocytosis of single synaptic vesicles generates miniature synaptic currents, which provide a window into the dynamic control of synaptic transmission. To resolve the impact of different factors on the dynamics and variability of synaptic transmission, we recorded miniature excitatory postsynaptic currents (mEPSCs) from cocultures of mouse hippocampal neurons with HEK cells expressing the postsynaptic proteins GluA2, neuroligin 1, PSD-95, and stargazin. Synapses between neurons and these heterologous cells have a molecularly defined postsynaptic apparatus, while the compact morphology of HEK cells eliminates the distorting effect of dendritic filtering. HEK cells in coculture produced mEPSCs with a higher frequency, larger amplitude, and more rapid rise and decay than neurons from the same culture. However, mEPSC area indicated that nerve terminals in synapses with both neurons and HEK cells release similar populations of vesicles. Modulation by the glutamate receptor ligand aniracetam revealed receptor contributions to mEPSC shape. Dendritic cable effects account for the slower mEPSC rise in neurons, whereas the slower decay also depends on other factors. Lastly, expression of synaptobrevin transmembrane domain mutants in neurons slowed the rise of HEK cell mEPSCs, thus revealing the impact of synaptic fusion pores. In summary, we show that cocultures of neurons with heterologous cells provide a geometrically simplified and molecularly defined system to investigate the time course of synaptic transmission and to resolve the contribution of vesicles, fusion pores, dendrites, and receptors to this process.
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Affiliation(s)
- Chung-Wei Chiang
- Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, WI
| | - Wen-Chi Shu
- Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, WI
| | - Jun Wan
- Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, WI
| | - Beth A Weaver
- Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, WI
| | - Meyer B Jackson
- Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, WI
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25
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Becker MFP, Tetzlaff C. The biophysical basis underlying the maintenance of early phase long-term potentiation. PLoS Comput Biol 2021; 17:e1008813. [PMID: 33750943 PMCID: PMC8016278 DOI: 10.1371/journal.pcbi.1008813] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Revised: 04/01/2021] [Accepted: 02/17/2021] [Indexed: 11/18/2022] Open
Abstract
The maintenance of synaptic changes resulting from long-term potentiation (LTP) is essential for brain function such as memory and learning. Different LTP phases have been associated with diverse molecular processes and pathways, and the molecular underpinnings of LTP on the short, as well as long time scales, are well established. However, the principles on the intermediate time scale of 1-6 hours that mediate the early phase of LTP (E-LTP) remain elusive. We hypothesize that the interplay between specific features of postsynaptic receptor trafficking is responsible for sustaining synaptic changes during this LTP phase. We test this hypothesis by formalizing a biophysical model that integrates several experimentally-motivated mechanisms. The model captures a wide range of experimental findings and predicts that synaptic changes are preserved for hours when the receptor dynamics are shaped by the interplay of structural changes of the spine in conjunction with increased trafficking from recycling endosomes and the cooperative binding of receptors. Furthermore, our model provides several predictions to verify our findings experimentally.
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Affiliation(s)
- Moritz F. P. Becker
- III. Institute of Physics – Biophysics, Georg-August University, Göttingen, Germany
| | - Christian Tetzlaff
- III. Institute of Physics – Biophysics, Georg-August University, Göttingen, Germany
- Bernstein Center for Computational Neuroscience, Göttingen, Germany
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26
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Li X, Zhou H, Yang P, Shi HX, Xiong Y, Nie ZY, Yu JQ, Wang YA, Zhou R, Wang LY. Cyclin-dependent Kinase 5 Regulates Cortical Neurotransmission and Neural Circuits Associated with Motor Control in the Secondary Motor Cortex in the Mouse. Neuroscience 2020; 438:9-24. [PMID: 32353462 DOI: 10.1016/j.neuroscience.2020.04.031] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Revised: 04/17/2020] [Accepted: 04/20/2020] [Indexed: 11/17/2022]
Abstract
Cyclin-dependent kinase 5 (Cdk5) is a regulator of axon growth and radial neuronal migration in the developing mouse brain, and it plays critical roles in cortical structure formation and brain function. However, the function of Cdk5 in cortico-cortical and cortico-sensorimotor networks in the adult remains largely unknown. In this study, we investigated the function of Cdk5 in the rostral secondary motor cortex (M2) in the male mouse using CRISPR/Cas9 gene editing and somatic brain transgenesis, to produce M2-specific knockdown of Cdk5 in neurons in the male mouse. Mouse deficient in Cdk5 in the M2 exhibited a reduction in both the number of functional synapses and the total basal dendritic length, as well as motor dysfunction. Furthermore, whole-cell patch-clamp recordings in layer V green fluorescent protein (GFP)-tag pyramidal neurons revealed a decrease in the frequency and amplitude of miniature EPSCs and miniature IPSCs, as well as a reduction in the population synaptic responses (fEPSPs) in these mice. Specifically, retrograde labeling showed that Cdk5 knockdown in the M2 caused a reduction in long-range projections to the M2 from the thalamus/prefrontal cortex and claustrum. Collectively, our findings show a new regulatory role of Cdk5 in neural circuit maintenance, and that the changes in neural transmission and circuits in the mice with Cdk5 knockdown in the M2 likely contribute to the motor dysfunction in these animals.
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Affiliation(s)
- Xing Li
- Department of Pharmacology, Ningxia Medical University, 1160 Shengli Street, Yinchuan, Ningxia 750004, China
| | - Hu Zhou
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology and Toxicology, Beijing 100850, China
| | - Pei Yang
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology and Toxicology, Beijing 100850, China
| | - Hua-Xiang Shi
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology and Toxicology, Beijing 100850, China
| | - Ying Xiong
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology and Toxicology, Beijing 100850, China
| | - Zhi-Yong Nie
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology and Toxicology, Beijing 100850, China
| | - Jian-Qiang Yu
- Department of Pharmacology, Ningxia Medical University, 1160 Shengli Street, Yinchuan, Ningxia 750004, China
| | - Yong-An Wang
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology and Toxicology, Beijing 100850, China
| | - Ru Zhou
- Department of Pharmacology, Ningxia Medical University, 1160 Shengli Street, Yinchuan, Ningxia 750004, China.
| | - Li-Yun Wang
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology and Toxicology, Beijing 100850, China.
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Rusakov DA, Savtchenko LP, Latham PE. Noisy Synaptic Conductance: Bug or a Feature? Trends Neurosci 2020; 43:363-372. [PMID: 32459990 PMCID: PMC7902755 DOI: 10.1016/j.tins.2020.03.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2019] [Revised: 03/10/2020] [Accepted: 03/23/2020] [Indexed: 12/31/2022]
Abstract
More often than not, action potentials fail to trigger neurotransmitter release. And even when neurotransmitter is released, the resulting change in synaptic conductance is highly variable. Given the energetic cost of generating and propagating action potentials, and the importance of information transmission across synapses, this seems both wasteful and inefficient. However, synaptic noise arising from variable transmission can improve, in certain restricted conditions, information transmission. Under broader conditions, it can improve information transmission per release, a quantity that is relevant given the energetic constraints on computing in the brain. Here we discuss the role, both positive and negative, synaptic noise plays in information transmission and computation in the brain.
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Affiliation(s)
- Dmitri A Rusakov
- Queen Square UCL Institute of Neurology, University College London, Queen Square, London, WC1N 3BG, UK.
| | - Leonid P Savtchenko
- Queen Square UCL Institute of Neurology, University College London, Queen Square, London, WC1N 3BG, UK.
| | - Peter E Latham
- Gatsby Computational Neuroscience Unit, University College London, 25 Howland Street, London, W1T 4JG, UK.
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Heine M, Holcman D. Asymmetry Between Pre- and Postsynaptic Transient Nanodomains Shapes Neuronal Communication. Trends Neurosci 2020; 43:182-196. [DOI: 10.1016/j.tins.2020.01.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Revised: 01/12/2020] [Accepted: 01/13/2020] [Indexed: 10/25/2022]
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Ultrastructural and molecular features of excitatory and glutamatergic synapses. The auditory nerve synapses. VITAMINS AND HORMONES 2020; 114:23-51. [PMID: 32723545 DOI: 10.1016/bs.vh.2020.04.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Glutamatergic synapses mediate fast synaptic transmission in the central nervous system. New developments highlight the importance of the synapse structural and molecular remodeling during development, aging and in neurological disorders. This chapter summarizes key structural and molecular aspects of the presynaptic and postsynaptic components of glutamatergic synapses in the brain. In addition, this chapter describes how the structure of the postsynaptic density and ionotropic glutamate content contribute to the function of auditory nerve synapses in the lower auditory brainstem.
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Barros-Zulaica N, Rahmon J, Chindemi G, Perin R, Markram H, Muller E, Ramaswamy S. Estimating the Readily-Releasable Vesicle Pool Size at Synaptic Connections in the Neocortex. Front Synaptic Neurosci 2019; 11:29. [PMID: 31680928 PMCID: PMC6813366 DOI: 10.3389/fnsyn.2019.00029] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Accepted: 09/30/2019] [Indexed: 12/21/2022] Open
Abstract
Previous studies based on the 'Quantal Model' for synaptic transmission suggest that neurotransmitter release is mediated by a single release site at individual synaptic contacts in the neocortex. However, recent studies seem to contradict this hypothesis and indicate that multi-vesicular release (MVR) could better explain the synaptic response variability observed in vitro. In this study we present a novel method to estimate the number of release sites per synapse, also known as the size of the readily releasable pool (NRRP), from paired whole-cell recordings of connections between layer 5 thick tufted pyramidal cell (L5_TTPC) in the juvenile rat somatosensory cortex. Our approach extends the work of Loebel et al. (2009) by leveraging a recently published data-driven biophysical model of neocortical tissue. Using this approach, we estimated NRRP to be between two to three for synaptic connections between L5_TTPCs. To constrain NRRP values for other connections in the microcircuit, we developed and validated a generalization approach using published data on the coefficient of variation (CV) of the amplitudes of post-synaptic potentials (PSPs) from literature and comparing them against in silico experiments. Our study predicts that transmitter release at synaptic connections in the neocortex could be mediated by MVR and provides a data-driven approach to constrain the MVR model parameters in the microcircuit.
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Affiliation(s)
| | - John Rahmon
- Blue Brain Project, École Polytechnique Fédérale de Lausanne, Geneva, Switzerland
| | - Giuseppe Chindemi
- Blue Brain Project, École Polytechnique Fédérale de Lausanne, Geneva, Switzerland
| | - Rodrigo Perin
- Laboratory of Neural Microcircuitry, Brain Mind Institute, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Henry Markram
- Blue Brain Project, École Polytechnique Fédérale de Lausanne, Geneva, Switzerland.,Laboratory of Neural Microcircuitry, Brain Mind Institute, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Eilif Muller
- Blue Brain Project, École Polytechnique Fédérale de Lausanne, Geneva, Switzerland
| | - Srikanth Ramaswamy
- Blue Brain Project, École Polytechnique Fédérale de Lausanne, Geneva, Switzerland
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Soares C, Trotter D, Longtin A, Béïque JC, Naud R. Parsing Out the Variability of Transmission at Central Synapses Using Optical Quantal Analysis. Front Synaptic Neurosci 2019; 11:22. [PMID: 31474847 PMCID: PMC6702664 DOI: 10.3389/fnsyn.2019.00022] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Accepted: 07/31/2019] [Indexed: 12/11/2022] Open
Abstract
Properties of synaptic release dictates the core of information transfer in neural circuits. Despite decades of technical and theoretical advances, distinguishing bona fide information content from the multiple sources of synaptic variability remains a challenging problem. Here, we employed a combination of computational approaches with cellular electrophysiology, two-photon uncaging of MNI-Glutamate and imaging at single synapses. We describe and calibrate the use of the fluorescent glutamate sensor iGluSnFR and found that its kinetic profile is close to that of AMPA receptors, therefore providing several distinct advantages over slower methods relying on NMDA receptor activation (i.e., chemical or genetically encoded calcium indicators). Using an array of statistical methods, we further developed, and validated on surrogate data, an expectation-maximization algorithm that, by biophysically constraining release variability, extracts the quantal parameters n (maximum number of released vesicles) and p (unitary probability of release) from single-synapse iGluSnFR-mediated transients. Together, we present a generalizable mathematical formalism which, when applied to optical recordings, paves the way to an increasingly precise investigation of information transfer at central synapses.
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Affiliation(s)
- Cary Soares
- Department of Cellular and Molecular Medicine, uOttawa Brain and Mind Research Institute, Center for Neural Dynamics, University of Ottawa, Ottawa, ON, Canada
| | - Daniel Trotter
- Department of Physics, University of Ottawa, Ottawa, ON, Canada
| | - André Longtin
- Department of Cellular and Molecular Medicine, uOttawa Brain and Mind Research Institute, Center for Neural Dynamics, University of Ottawa, Ottawa, ON, Canada
- Department of Physics, University of Ottawa, Ottawa, ON, Canada
| | - Jean-Claude Béïque
- Department of Cellular and Molecular Medicine, uOttawa Brain and Mind Research Institute, Center for Neural Dynamics, University of Ottawa, Ottawa, ON, Canada
| | - Richard Naud
- Department of Cellular and Molecular Medicine, uOttawa Brain and Mind Research Institute, Center for Neural Dynamics, University of Ottawa, Ottawa, ON, Canada
- Department of Physics, University of Ottawa, Ottawa, ON, Canada
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Tottori T, Fujii M, Kuroda S. NMDAR-Mediated Ca 2+ Increase Shows Robust Information Transfer in Dendritic Spines. Biophys J 2019; 116:1748-1758. [PMID: 31023534 DOI: 10.1016/j.bpj.2019.03.030] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Revised: 03/11/2019] [Accepted: 03/28/2019] [Indexed: 01/21/2023] Open
Abstract
A dendritic spine is a small structure on the dendrites of a neuron that processes input timing information from other neurons. Tens of thousands of spines are present on a neuron. Why are spines so small and many? We addressed this issue by using the stochastic simulation model of N-methyl-D-aspartate receptor (NMDAR)-mediated Ca2+ increase. NMDAR-mediated Ca2+ increase codes the input timing information between prespiking and postspiking. We examined how much the input timing information is encoded by Ca2+ increase against presynaptic fluctuation. We found that the input timing information encoded in the cell volume (103μm3) largely decreases against the presynaptic fluctuation, whereas that in the spine volume (10-1μm3) slightly decreases. Therefore, the input timing information encoded in the spine volume is more robust against presynaptic fluctuation than that in the cell volume. We further examined the mechanism of the robust information transfer in the spine volume. We demonstrated that the condition for the robustness is that the stochastic NMDAR-mediated Ca2+ increase (intrinsic noise) becomes much larger than the presynaptic fluctuation (extrinsic noise). When the presynaptic fluctuation is large, the condition is satisfied in the spine volume but not in the cell volume. Moreover, we compared the input timing information encoded in many small spines with that encoded in a single large spine. We found that the input timing information encoded in many small spines are larger than that in a single large spine when presynaptic fluctuation is large because of their robustness. Thus, robustness is a functional reason why dendritic spines are so small and many.
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Affiliation(s)
- Takehiro Tottori
- Department of Bioinformatics and Systems Biology, Faculty of Science, University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Masashi Fujii
- Department of Bioinformatics and Systems Biology, Faculty of Science, University of Tokyo, Bunkyo-ku, Tokyo, Japan; Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo, Japan; Molecular Genetics Research Laboratory, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Shinya Kuroda
- Department of Bioinformatics and Systems Biology, Faculty of Science, University of Tokyo, Bunkyo-ku, Tokyo, Japan; Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo, Japan; Molecular Genetics Research Laboratory, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo, Japan; CREST, Japan Science and Technology Agency, Bunkyo-ku, Tokyo, Japan.
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33
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Gustafsson B, Ma R, Hanse E. The Small and Dynamic Pre-primed Pool at the Release Site; A Useful Concept to Understand Release Probability and Short-Term Synaptic Plasticity? Front Synaptic Neurosci 2019; 11:7. [PMID: 30899219 PMCID: PMC6416800 DOI: 10.3389/fnsyn.2019.00007] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Accepted: 02/20/2019] [Indexed: 11/23/2022] Open
Abstract
Advanced imaging techniques have revealed that synapses contain nanomodules in which pre- and post-synaptic molecules are brought together to form an integrated subsynaptic component for vesicle release and transmitter reception. Based on data from an electrophysiological study of ours in which release from synapses containing a single nanomodule was induced by brief 50 Hz trains using minimal stimulation, and on data from such imaging studies, we present a possible modus operandi of such a nanomodule. We will describe the techniques and tools used to obtain and analyze the electrophysiological data from single CA3–CA1 hippocampal synapses from the neonatal rat brain. This analysis leads to the proposal that a nanomodule, despite containing a number of release locations, operates as a single release site, releasing at most a single vesicle at a time. In this nanomodule there appears to be two separate sets of release locations, one set that is responsible for release in response to the first few action potentials and another set that produces the release thereafter. The data also suggest that vesicles at the first set of release locations are primed by synaptic inactivity lasting seconds, this synaptic inactivity also resulting in a large heterogeneity in the values for vesicle release probability among the synapses. The number of vesicles being primed at this set of release locations prior to the arrival of an action potential is small (0–3) and varies from train to train. Following the first action potential, this heterogeneity in vesicle release probability largely vanishes in a release-independent manner, shaping a variation in paired-pulse plasticity among the synapses. After the first few action potentials release is produced from the second set of release locations, and is given by vesicles that have been recruited after the onset of synaptic activity. This release depends on the number of such release locations and the recruitment to such a location. The initial heterogeneity in vesicle release probability, its disappearance after a single action potential, and variation in the recruitment to the second set of release locations are instrumental in producing the heterogeneity in short-term synaptic plasticity among these synapses, and can be seen as means to create differential dynamics within a synapse population.
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Affiliation(s)
- Bengt Gustafsson
- Department of Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Rong Ma
- Department of Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Eric Hanse
- Department of Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
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Buonarati OR, Hammes EA, Watson JF, Greger IH, Hell JW. Mechanisms of postsynaptic localization of AMPA-type glutamate receptors and their regulation during long-term potentiation. Sci Signal 2019; 12:12/562/eaar6889. [PMID: 30600260 PMCID: PMC7175813 DOI: 10.1126/scisignal.aar6889] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
l-Glutamate is the main excitatory neurotransmitter in the brain, with postsynaptic responses to its release predominantly mediated by AMPA-type glutamate receptors (AMPARs). A critical component of synaptic plasticity involves changes in the number of responding postsynaptic receptors, which are dynamically recruited to and anchored at postsynaptic sites. Emerging findings continue to shed new light on molecular mechanisms that mediate AMPAR postsynaptic trafficking and localization. Accordingly, unconventional secretory trafficking of AMPARs occurs in dendrites, from the endoplasmic reticulum (ER) through the ER-Golgi intermediary compartment directly to recycling endosomes, independent of the Golgi apparatus. Upon exocytosis, AMPARs diffuse in the plasma membrane to reach the postsynaptic site, where they are trapped to contribute to transmission. This trapping occurs through a combination of both intracellular interactions, such as TARP (transmembrane AMPAR regulatory protein) binding to α-actinin-stabilized PSD-95, and extracellular interactions through the receptor amino-terminal domain. These anchoring mechanisms may facilitate precise receptor positioning with respect to glutamate release sites to enable efficient synaptic transmission.
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Affiliation(s)
- Olivia R. Buonarati
- Department of Pharmacology, University of California, Davis, CA 95616-8636, USA
| | - Erik A. Hammes
- Department of Pharmacology, University of California, Davis, CA 95616-8636, USA
| | - Jake F. Watson
- Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
| | - Ingo H. Greger
- Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
| | - Johannes W. Hell
- Department of Pharmacology, University of California, Davis, CA 95616-8636, USA,Correspondence:
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35
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Individual synaptic vesicles mediate stimulated exocytosis from cochlear inner hair cells. Proc Natl Acad Sci U S A 2018; 115:12811-12816. [PMID: 30463957 PMCID: PMC6294930 DOI: 10.1073/pnas.1811814115] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Synaptic transmission is codetermined by presynaptic and postsynaptic neurons. Therefore, to understand how the inner hair cell (IHC) signals to spiral ganglion neurons at the first synapse in the auditory pathway, here we directly studied individual membrane fusion events by making cell-attached membrane capacitance recordings from IHCs, for which the quantal size is debated. The observed fusion steps in membrane capacitance are consistent with the quantal hypothesis of synaptic transmission in which individual synaptic vesicles undergo exocytosis independently from each other. This finding, in conjunction with previous work, raises the exciting possibility that action potential generation can be triggered by the release of a single vesicle at the IHC synapse. Spontaneous excitatory postsynaptic currents (sEPSCs) measured from the first synapse in the mammalian auditory pathway reach a large mean amplitude with a high level of variance (CV between 0.3 and 1). This has led some to propose that each inner hair cell (IHC) ribbon-type active zone (AZ), on average, releases ∼6 synaptic vesicles (SVs) per sEPSC in a coordinated manner. If true, then the predicted change in membrane capacitance (Cm) for such multivesicular fusion events would equate to ∼300 attofarads (aF). Here, we performed cell-attached Cm measurements to directly examine the size of fusion events at the basolateral membrane of IHCs where the AZs are located. The frequency of events depended on the membrane potential and the expression of Cav1.3, the principal Ca2+-channel type of IHCs. Fusion events averaged 40 aF, which equates to a normal-sized SV with an estimated diameter of 37 nm. The calculated SV volumes showed a high degree of variance (CV > 0.6). These results indicate that SVs fused individually with the plasma membrane during spontaneous and evoked release and SV volume may contribute more variability in EPSC amplitude than previously assumed.
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36
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Patriarchi T, Buonarati OR, Hell JW. Postsynaptic localization and regulation of AMPA receptors and Cav1.2 by β2 adrenergic receptor/PKA and Ca 2+/CaMKII signaling. EMBO J 2018; 37:e99771. [PMID: 30249603 PMCID: PMC6187224 DOI: 10.15252/embj.201899771] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2018] [Revised: 07/25/2018] [Accepted: 08/17/2018] [Indexed: 11/09/2022] Open
Abstract
The synapse transmits, processes, and stores data within its tiny space. Effective and specific signaling requires precise alignment of the relevant components. This review examines current insights into mechanisms of AMPAR and NMDAR localization by PSD-95 and their spatial distribution at postsynaptic sites to illuminate the structural and functional framework of postsynaptic signaling. It subsequently delineates how β2 adrenergic receptor (β2 AR) signaling via adenylyl cyclase and the cAMP-dependent protein kinase PKA is organized within nanodomains. Here, we discuss targeting of β2 AR, adenylyl cyclase, and PKA to defined signaling complexes at postsynaptic sites, i.e., AMPARs and the L-type Ca2+ channel Cav1.2, and other subcellular surface localizations, the role of A kinase anchor proteins, the physiological relevance of the spatial restriction of corresponding signaling, and their interplay with signal transduction by the Ca2+- and calmodulin-dependent kinase CaMKII How localized and specific signaling by cAMP occurs is a central cellular question. The dendritic spine constitutes an ideal paradigm for elucidating the dimensions of spatially restricted signaling because of their small size and defined protein composition.
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MESH Headings
- Animals
- Calcium Channels, L-Type/genetics
- Calcium Channels, L-Type/metabolism
- Calcium Signaling/physiology
- Calcium-Calmodulin-Dependent Protein Kinase Type 2/genetics
- Calcium-Calmodulin-Dependent Protein Kinase Type 2/metabolism
- Cyclic AMP-Dependent Protein Kinases/genetics
- Cyclic AMP-Dependent Protein Kinases/metabolism
- Humans
- Receptors, AMPA/genetics
- Receptors, AMPA/metabolism
- Receptors, Adrenergic, beta-2/genetics
- Receptors, Adrenergic, beta-2/metabolism
- Receptors, N-Methyl-D-Aspartate/genetics
- Receptors, N-Methyl-D-Aspartate/metabolism
- Synapses/genetics
- Synapses/metabolism
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Affiliation(s)
- Tommaso Patriarchi
- Department of Pharmacology, University of California, Davis, CA, USA
- Department of Biochemistry and Molecular Medicine, University of California, Davis, CA, USA
| | | | - Johannes W Hell
- Department of Pharmacology, University of California, Davis, CA, USA
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37
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Scheefhals N, MacGillavry HD. Functional organization of postsynaptic glutamate receptors. Mol Cell Neurosci 2018; 91:82-94. [PMID: 29777761 PMCID: PMC6276983 DOI: 10.1016/j.mcn.2018.05.002] [Citation(s) in RCA: 98] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Revised: 04/16/2018] [Accepted: 05/07/2018] [Indexed: 01/28/2023] Open
Abstract
Glutamate receptors are the most abundant excitatory neurotransmitter receptors in the brain, responsible for mediating the vast majority of excitatory transmission in neuronal networks. The AMPA- and NMDA-type ionotropic glutamate receptors (iGluRs) are ligand-gated ion channels that mediate the fast synaptic responses, while metabotropic glutamate receptors (mGluRs) are coupled to downstream signaling cascades that act on much slower timescales. These functionally distinct receptor sub-types are co-expressed at individual synapses, allowing for the precise temporal modulation of postsynaptic excitability and plasticity. Intriguingly, these receptors are differentially distributed with respect to the presynaptic release site. While iGluRs are enriched in the core of the synapse directly opposing the release site, mGluRs reside preferentially at the border of the synapse. As such, to understand the differential contribution of these receptors to synaptic transmission, it is important to not only consider their signaling properties, but also the mechanisms that control the spatial segregation of these receptor types within synapses. In this review, we will focus on the mechanisms that control the organization of glutamate receptors at the postsynaptic membrane with respect to the release site, and discuss how this organization could regulate synapse physiology.
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Affiliation(s)
- Nicky Scheefhals
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, The Netherlands
| | - Harold D MacGillavry
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, The Netherlands.
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38
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Nusser Z. Creating diverse synapses from the same molecules. Curr Opin Neurobiol 2018; 51:8-15. [DOI: 10.1016/j.conb.2018.01.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Accepted: 01/02/2018] [Indexed: 12/30/2022]
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39
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Haas KT, Compans B, Letellier M, Bartol TM, Grillo-Bosch D, Sejnowski TJ, Sainlos M, Choquet D, Thoumine O, Hosy E. Pre-post synaptic alignment through neuroligin-1 tunes synaptic transmission efficiency. eLife 2018; 7:e31755. [PMID: 30044218 PMCID: PMC6070337 DOI: 10.7554/elife.31755] [Citation(s) in RCA: 114] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 07/24/2018] [Indexed: 12/25/2022] Open
Abstract
The nanoscale organization of neurotransmitter receptors regarding pre-synaptic release sites is a fundamental determinant of the synaptic transmission amplitude and reliability. How modifications in the pre- and post-synaptic machinery alignments affects synaptic currents, has only been addressed with computer modelling. Using single molecule super-resolution microscopy, we found a strong spatial correlation between AMPA receptor (AMPAR) nanodomains and the post-synaptic adhesion protein neuroligin-1 (NLG1). Expression of a truncated form of NLG1 disrupted this correlation without affecting the intrinsic AMPAR organization, shifting the pre-synaptic release machinery away from AMPAR nanodomains. Electrophysiology in dissociated and organotypic hippocampal rodent cultures shows these treatments significantly decrease AMPAR-mediated miniature and EPSC amplitudes. Computer modelling predicts that ~100 nm lateral shift between AMPAR nanoclusters and glutamate release sites induces a significant reduction in AMPAR-mediated currents. Thus, our results suggest the synapses necessity to release glutamate precisely in front of AMPAR nanodomains, to maintain a high synaptic responses efficiency.
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Affiliation(s)
- Kalina T Haas
- Interdisciplinary Institute for NeuroscienceUniversity of Bordeaux, UMR 5297, F-33000BordeauxFrance
- Interdisciplinary Institute for NeuroscienceCNRS, UMR 5297, F-33000BordeauxFrance
| | - Benjamin Compans
- Interdisciplinary Institute for NeuroscienceUniversity of Bordeaux, UMR 5297, F-33000BordeauxFrance
- Interdisciplinary Institute for NeuroscienceCNRS, UMR 5297, F-33000BordeauxFrance
| | - Mathieu Letellier
- Interdisciplinary Institute for NeuroscienceUniversity of Bordeaux, UMR 5297, F-33000BordeauxFrance
- Interdisciplinary Institute for NeuroscienceCNRS, UMR 5297, F-33000BordeauxFrance
| | - Thomas M Bartol
- Howard Hughes Medical InstituteSalk Institute for Biological StudiesLa JollaUnited States
| | - Dolors Grillo-Bosch
- Interdisciplinary Institute for NeuroscienceUniversity of Bordeaux, UMR 5297, F-33000BordeauxFrance
- Interdisciplinary Institute for NeuroscienceCNRS, UMR 5297, F-33000BordeauxFrance
| | - Terrence J Sejnowski
- Howard Hughes Medical InstituteSalk Institute for Biological StudiesLa JollaUnited States
| | - Matthieu Sainlos
- Interdisciplinary Institute for NeuroscienceUniversity of Bordeaux, UMR 5297, F-33000BordeauxFrance
- Interdisciplinary Institute for NeuroscienceCNRS, UMR 5297, F-33000BordeauxFrance
| | - Daniel Choquet
- Interdisciplinary Institute for NeuroscienceUniversity of Bordeaux, UMR 5297, F-33000BordeauxFrance
- Interdisciplinary Institute for NeuroscienceCNRS, UMR 5297, F-33000BordeauxFrance
- Bordeaux Imaging CenterUMS 3420 CNRS, Université de Bordeaux, US4 INSERM, F-33000BordeauxFrance
| | - Olivier Thoumine
- Interdisciplinary Institute for NeuroscienceUniversity of Bordeaux, UMR 5297, F-33000BordeauxFrance
- Interdisciplinary Institute for NeuroscienceCNRS, UMR 5297, F-33000BordeauxFrance
| | - Eric Hosy
- Interdisciplinary Institute for NeuroscienceUniversity of Bordeaux, UMR 5297, F-33000BordeauxFrance
- Interdisciplinary Institute for NeuroscienceCNRS, UMR 5297, F-33000BordeauxFrance
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40
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Bourke AM, Bowen AB, Kennedy MJ. New approaches for solving old problems in neuronal protein trafficking. Mol Cell Neurosci 2018; 91:48-66. [PMID: 29649542 DOI: 10.1016/j.mcn.2018.04.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 04/05/2018] [Accepted: 04/06/2018] [Indexed: 11/16/2022] Open
Abstract
Fundamental cellular properties are determined by the repertoire and abundance of proteins displayed on the cell surface. As such, the trafficking mechanisms for establishing and maintaining the surface proteome must be tightly regulated for cells to respond appropriately to extracellular cues, yet plastic enough to adapt to ever-changing environments. Not only are the identity and abundance of surface proteins critical, but in many cases, their regulated spatial positioning within surface nanodomains can greatly impact their function. In the context of neuronal cell biology, surface levels and positioning of ion channels and neurotransmitter receptors play essential roles in establishing important properties, including cellular excitability and synaptic strength. Here we review our current understanding of the trafficking pathways that control the abundance and localization of proteins important for synaptic function and plasticity, as well as recent technological advances that are allowing the field to investigate protein trafficking with increasing spatiotemporal precision.
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Affiliation(s)
- Ashley M Bourke
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO, United States
| | - Aaron B Bowen
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO, United States
| | - Matthew J Kennedy
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO, United States.
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Gupta R. Self-crowding of AMPA receptors in the excitatory postsynaptic density can effectuate anomalous receptor sub-diffusion. PLoS Comput Biol 2018; 14:e1005984. [PMID: 29444074 PMCID: PMC5812565 DOI: 10.1371/journal.pcbi.1005984] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Accepted: 01/15/2018] [Indexed: 12/03/2022] Open
Abstract
AMPA receptors (AMPARs) and their associations with auxiliary transmembrane proteins are bulky structures with large steric-exclusion volumes. Hence, self-crowding of AMPARs, depending on the local density, may affect their lateral diffusion in the postsynaptic membrane as well as in the highly crowded postsynaptic density (PSD) at excitatory synapses. Earlier theoretical studies considered only the roles of transmembrane obstacles and the AMPAR-binding submembranous scaffold proteins in shaping receptor diffusion within PSD. Using lattice model of diffusion, the present study investigates the additional impacts of self-crowding on the anomalousity and effective diffusion coefficient (Deff) of AMPAR diffusion. A recursive algorithm for avoiding false self-blocking during diffusion simulation is also proposed. The findings suggest that high density of AMPARs in the obstacle-free membrane itself engenders strongly anomalous diffusion and severe decline in Deff. Adding transmembrane obstacles to the membrane accentuates the anomalousity arising from self-crowding due to the reduced free diffusion space. Contrarily, enhanced AMPAR-scaffold binding, either through increase in binding strength or scaffold density or both, ameliorates the anomalousity resulting from self-crowding. However, binding has differential impacts on Deff depending on the receptor density. Increase in binding causes consistent decrease in Deff for low and moderate receptor density. For high density, binding increases Deff as long as it reduces anomalousity associated with intense self-crowding. Given a sufficiently strong binding condition when diffusion acquires normal behavior, further increase in binding causes decrease in Deff. Supporting earlier experimental observations are mentioned and implications of present findings to the experimental observations on AMPAR diffusion are also drawn. The transmembrane AMPA receptors (AMPARs) prominently exhibit lateral diffusion in the postsynaptic membrane at excitatory synapses. Steric obstructions to AMPAR diffusion due to the crowd of other relatively static transmembrane proteins and binding of AMPARs to the submembranous scaffold proteins in the specialized region of postsynaptic density (PSD) are well known to retard receptor diffusion, which causes receptor trapping and accumulation within PSD. However, AMPARs are significantly bulky structures and may also obstruct their own diffusion paths in the presence of their high density. It is shown here that intense self-crowding of AMPARs may lead to highly obstructed and confined receptor diffusion even in the obstacle-free medium, and the presence of other obstacles further aggravates this effect. AMPAR-scaffold binding reduces confined diffusion arising from self-crowding and strong binding engenders normal diffusion even at high receptor density. However, it overall causes reduction in the effective diffusion coefficient of the receptor diffusion.
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Affiliation(s)
- Rahul Gupta
- School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi, India
- * E-mail:
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42
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The Altered Supramolecular Structure of Dopamine D2 Receptors in Disc1-deficient Mice. Sci Rep 2018; 8:1692. [PMID: 29374282 PMCID: PMC5785963 DOI: 10.1038/s41598-018-20090-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Accepted: 01/12/2018] [Indexed: 12/04/2022] Open
Abstract
Disc1 is a susceptibility gene for psychiatric disorders including schizophrenia. It has been suggested that excess transmission through dopamine type 2 receptors (D2Rs) in the striatum is an underlying mechanism of pathogenesis. In this study, we used super-resolution microscopy to study the distribution of D2Rs at the nanoscale in mice lacking exons 2 and 3 of Disc1 (Disc1-deficient mice). We found that D2Rs in the nucleus accumbens (NAc) of wild-type mice form nanoclusters (~ 20,000 nm2), and that Disc1-deficient mice have larger and more D2R nanoclusters than wild-type mice. Interestingly, administration of clozapine reduced the size and spatial distribution of the nanoclusters only in Disc1-deficient mice. Moreover, we observed that medium spiny neurons in the NAc of Disc1-deficient mice had reduced spine density on their dendrites than did wild-type mice, and this was also reversed by clozapine administration. The altered D2R nanoclusters might be morphological representations of the altered dopaminergic transmission in disease states such as schizophrenia.
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Szoboszlay M, Kirizs T, Nusser Z. Objective quantification of nanoscale protein distributions. Sci Rep 2017; 7:15240. [PMID: 29127366 PMCID: PMC5681686 DOI: 10.1038/s41598-017-15695-w] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Accepted: 11/01/2017] [Indexed: 01/13/2023] Open
Abstract
Nanoscale distribution of molecules within small subcellular compartments of neurons critically influences their functional roles. Although, numerous ways of analyzing the spatial arrangement of proteins have been described, a thorough comparison of their effectiveness is missing. Here we present an open source software, GoldExt, with a plethora of measures for quantification of the nanoscale distribution of proteins in subcellular compartments (e.g. synapses) of nerve cells. First, we compared the ability of five different measures to distinguish artificial uniform and clustered patterns from random point patterns. Then, the performance of a set of clustering algorithms was evaluated on simulated datasets with predefined number of clusters. Finally, we applied the best performing methods to experimental data, and analyzed the nanoscale distribution of different pre- and postsynaptic proteins, revealing random, uniform and clustered sub-synaptic distribution patterns. Our results reveal that application of a single measure is sufficient to distinguish between different distributions.
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Affiliation(s)
- Miklos Szoboszlay
- Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary.,János Szentágothai School of Neurosciences, Semmelweis University, Budapest, Hungary
| | - Tekla Kirizs
- Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary.,János Szentágothai School of Neurosciences, Semmelweis University, Budapest, Hungary
| | - Zoltan Nusser
- Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary.
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Tong XJ, López-Soto EJ, Li L, Liu H, Nedelcu D, Lipscombe D, Hu Z, Kaplan JM. Retrograde Synaptic Inhibition Is Mediated by α-Neurexin Binding to the α2δ Subunits of N-Type Calcium Channels. Neuron 2017; 95:326-340.e5. [PMID: 28669545 DOI: 10.1016/j.neuron.2017.06.018] [Citation(s) in RCA: 74] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Revised: 04/20/2017] [Accepted: 06/08/2017] [Indexed: 12/31/2022]
Abstract
The synaptic adhesion molecules Neurexin and Neuroligin alter the development and function of synapses and are linked to autism in humans. In C. elegans, post-synaptic Neurexin (NRX-1) and pre-synaptic Neuroligin (NLG-1) mediate a retrograde synaptic signal that inhibits acetylcholine (ACh) release at neuromuscular junctions. Here, we show that the retrograde signal decreases ACh release by inhibiting the function of pre-synaptic UNC-2/CaV2 calcium channels. Post-synaptic NRX-1 binds to an auxiliary subunit of pre-synaptic UNC-2/CaV2 channels (UNC-36/α2δ), decreasing UNC-36 abundance at pre-synaptic elements. Retrograde inhibition is mediated by a soluble form of NRX-1's ectodomain, which is released from the post-synaptic membrane by the SUP-17/ADAM10 protease. Mammalian Neurexin-1α binds α2δ-3 and decreases CaV2.2 current in transfected cells, whereas Neurexin-1α has no effect on CaV2.2 reconstituted with α2δ-1 and α2δ-2. Collectively, these results suggest that α-Neurexin binding to α2δ is a conserved mechanism for regulating synaptic transmission.
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Affiliation(s)
- Xia-Jing Tong
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Eduardo Javier López-Soto
- Department of Neuroscience and Brown Institute for Brain Science, Brown University, Providence, RI 02912, USA
| | - Lei Li
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Haowen Liu
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Daniel Nedelcu
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Diane Lipscombe
- Department of Neuroscience and Brown Institute for Brain Science, Brown University, Providence, RI 02912, USA
| | - Zhitao Hu
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Joshua M Kaplan
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA; Program in Neuroscience, Harvard Medical School, Boston, MA 02115, USA.
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Khan T, Bilgin BA, Akan OB. Diffusion-Based Model for Synaptic Molecular Communication Channel. IEEE Trans Nanobioscience 2017; 16:299-308. [PMID: 28541904 DOI: 10.1109/tnb.2017.2707482] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Computational methods have been extensively used to understand the underlying dynamics of molecular communication methods employed by nature. One very effective and popular approach is to utilize a Monte Carlo simulation. Although it is very reliable, this method can have a very high computational cost, which in some cases renders the simulation impractical. Therefore, in this paper, for the special case of an excitatory synaptic molecular communication channel, we present a novel mathematical model for the diffusion and binding of neurotransmitters that takes into account the effects of synaptic geometry in 3-D space and re-absorption of neurotransmitters by the transmitting neuron. Based on this model we develop a fast deterministic algorithm, which calculates expected value of the output of this channel, namely, the amplitude of excitatory postsynaptic potential (EPSP), for given synaptic parameters. We validate our algorithm by a Monte Carlo simulation, which shows total agreement between the results of the two methods. Finally, we utilize our model to quantify the effects of variation in synaptic parameters, such as position of release site, receptor density, size of postsynaptic density, diffusion coefficient, uptake probability, and number of neurotransmitters in a vesicle, on maximum number of bound receptors that directly affect the peak amplitude of EPSP.
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The number and distribution of AMPA receptor channels containing fast kinetic GluA3 and GluA4 subunits at auditory nerve synapses depend on the target cells. Brain Struct Funct 2017; 222:3375-3393. [PMID: 28397107 PMCID: PMC5676837 DOI: 10.1007/s00429-017-1408-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Accepted: 03/20/2017] [Indexed: 02/07/2023]
Abstract
The neurotransmitter receptor subtype, number, density, and distribution relative to the location of transmitter release sites are key determinants of signal transmission. AMPA-type ionotropic glutamate receptors (AMPARs) containing GluA3 and GluA4 subunits are prominently expressed in subsets of neurons capable of firing action potentials at high frequencies, such as auditory relay neurons. The auditory nerve (AN) forms glutamatergic synapses on two types of relay neurons, bushy cells (BCs) and fusiform cells (FCs) of the cochlear nucleus. AN-BC and AN-FC synapses have distinct kinetics; thus, we investigated whether the number, density, and localization of GluA3 and GluA4 subunits in these synapses are differentially organized using quantitative freeze-fracture replica immunogold labeling. We identify a positive correlation between the number of AMPARs and the size of AN-BC and AN-FC synapses. Both types of AN synapses have similar numbers of AMPARs; however, the AN-BC have a higher density of AMPARs than AN-FC synapses, because the AN-BC synapses are smaller. A higher number and density of GluA3 subunits are observed at AN-BC synapses, whereas a higher number and density of GluA4 subunits are observed at AN-FC synapses. The intrasynaptic distribution of immunogold labeling revealed that AMPAR subunits, particularly GluA3, are concentrated at the center of the AN-BC synapses. The central distribution of AMPARs is absent in GluA3-knockout mice, and gold particles are evenly distributed along the postsynaptic density. GluA4 gold labeling was homogenously distributed along both synapse types. Thus, GluA3 and GluA4 subunits are distributed at AN synapses in a target-cell-dependent manner.
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Walker AS, Neves G, Grillo F, Jackson RE, Rigby M, O'Donnell C, Lowe AS, Vizcay-Barrena G, Fleck RA, Burrone J. Distance-dependent gradient in NMDAR-driven spine calcium signals along tapering dendrites. Proc Natl Acad Sci U S A 2017; 114:E1986-E1995. [PMID: 28209776 PMCID: PMC5347575 DOI: 10.1073/pnas.1607462114] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Neurons receive a multitude of synaptic inputs along their dendritic arbor, but how this highly heterogeneous population of synaptic compartments is spatially organized remains unclear. By measuring N-methyl-d-aspartic acid receptor (NMDAR)-driven calcium responses in single spines, we provide a spatial map of synaptic calcium signals along dendritic arbors of hippocampal neurons and relate this to measures of synapse structure. We find that quantal NMDAR calcium signals increase in amplitude as they approach a thinning dendritic tip end. Based on a compartmental model of spine calcium dynamics, we propose that this biased distribution in calcium signals is governed by a gradual, distance-dependent decline in spine size, which we visualized using serial block-face scanning electron microscopy. Our data describe a cell-autonomous feature of principal neurons, where tapering dendrites show an inverse distribution of spine size and NMDAR-driven calcium signals along dendritic trees, with important implications for synaptic plasticity rules and spine function.
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Affiliation(s)
- Alison S Walker
- Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, United Kingdom
| | - Guilherme Neves
- Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, United Kingdom
| | - Federico Grillo
- Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, United Kingdom
| | - Rachel E Jackson
- Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, United Kingdom
| | - Mark Rigby
- Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, United Kingdom
| | - Cian O'Donnell
- Department of Computer Science, University of Bristol, Bristol BS8 1UB, United Kingdom
| | - Andrew S Lowe
- Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, United Kingdom
| | - Gema Vizcay-Barrena
- Centre for Ultrastructural Imaging, Kings College London, London SE1 1UL, United Kingdom
| | - Roland A Fleck
- Centre for Ultrastructural Imaging, Kings College London, London SE1 1UL, United Kingdom
| | - Juan Burrone
- Centre for Developmental Neurobiology, Kings College London, London SE1 1UL, United Kingdom;
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Sinnen BL, Bowen AB, Forte JS, Hiester BG, Crosby KC, Gibson ES, Dell'Acqua ML, Kennedy MJ. Optogenetic Control of Synaptic Composition and Function. Neuron 2017; 93:646-660.e5. [PMID: 28132827 DOI: 10.1016/j.neuron.2016.12.037] [Citation(s) in RCA: 93] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Revised: 10/22/2016] [Accepted: 12/22/2016] [Indexed: 10/20/2022]
Abstract
The molecular composition of the postsynaptic membrane is sculpted by synaptic activity. During synaptic plasticity at excitatory synapses, numerous structural, signaling, and receptor molecules concentrate at the postsynaptic density (PSD) to regulate synaptic strength. We developed an approach that uses light to tune the abundance of specific molecules in the PSD. We used this approach to investigate the relationship between the number of AMPA-type glutamate receptors in the PSD and synaptic strength. Surprisingly, adding more AMPA receptors to excitatory contacts had little effect on synaptic strength. Instead, we observed increased excitatory input through the apparent addition of new functional sites. Our data support a model where adding AMPA receptors is sufficient to activate synapses that had few receptors to begin with, but that additional remodeling events are required to strengthen established synapses. More broadly, this approach introduces the precise spatiotemporal control of optogenetics to the molecular control of synaptic function.
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Affiliation(s)
- Brooke L Sinnen
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Aaron B Bowen
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Jeffrey S Forte
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Brian G Hiester
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Kevin C Crosby
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Emily S Gibson
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Mark L Dell'Acqua
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Matthew J Kennedy
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA.
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49
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Gupta R, Reneaux M. Role of Heterogeneous Macromolecular Crowding and Geometrical Irregularity at Central Excitatory Synapses in Shaping Synaptic Transmission. PLoS One 2016; 11:e0167505. [PMID: 27907112 PMCID: PMC5131996 DOI: 10.1371/journal.pone.0167505] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 11/15/2016] [Indexed: 01/24/2023] Open
Abstract
Besides the geometrical tortousity due to the extrasynaptic structures, macromolecular crowding and geometrical irregularities constituting the cleft composition at central excitatory synapses has a major and direct role in retarding the glutamate diffusion within the cleft space. However, the cleft composition may not only coarsely reduce the overall diffusivity of the glutamate but may also lead to substantial spatial variation in the diffusivity across the cleft space. Decrease in the overall diffusivity of the glutamate may have straightforward consequences to the glutamate transients in the cleft. However, how spatial variation in the diffusivity may further affect glutamate transients is an intriguing aspect. Therefore, to understand the role of cleft heterogeneity, the present study adopts a novel approach of glutamate diffusion which considers a gamma statistical distribution of the diffusion coefficient of glutamate (Dglut) across the cleft space, such that its moments discernibly capture the dual impacts of the cleft composition, and further applies the framework of superstatistics. The findings reveal a power law behavior in the glutamate transients, akin to the long-range anomalous subdiffusion, which leads to slower decay profile of cleft glutamate at higher intensity of cleft heterogeneity. Moreover, increase in the cleft heterogeneity is seen to eventually cause slower-rising excitatory postsynaptic currents with higher amplitudes, lesser noise, and prolonged duration of charge transfer across the postsynaptic membrane. Further, with regard to the conventional standard diffusion approach, the study suggests that the effective Dglut essentially derives from the median of the Dglut distribution and does not necessarily need to be the mean Dglut. Together, the findings indicate a strong implication of cleft heterogeneity to the metabolically cost-effective tuning of synaptic response during the phenomenon of plasticity at individual synapses and also provide an additional factor of variability in transmission across identical synapses.
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Affiliation(s)
- Rahul Gupta
- School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi, India 110067
| | - Melissa Reneaux
- School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi, India 110067
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50
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Bird AD, Wall MJ, Richardson MJE. Bayesian Inference of Synaptic Quantal Parameters from Correlated Vesicle Release. Front Comput Neurosci 2016; 10:116. [PMID: 27932970 PMCID: PMC5122579 DOI: 10.3389/fncom.2016.00116] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Accepted: 10/28/2016] [Indexed: 11/13/2022] Open
Abstract
Synaptic transmission is both history-dependent and stochastic, resulting in varying responses to presentations of the same presynaptic stimulus. This complicates attempts to infer synaptic parameters and has led to the proposal of a number of different strategies for their quantification. Recently Bayesian approaches have been applied to make more efficient use of the data collected in paired intracellular recordings. Methods have been developed that either provide a complete model of the distribution of amplitudes for isolated responses or approximate the amplitude distributions of a train of post-synaptic potentials, with correct short-term synaptic dynamics but neglecting correlations. In both cases the methods provided significantly improved inference of model parameters as compared to existing mean-variance fitting approaches. However, for synapses with high release probability, low vesicle number or relatively low restock rate and for data in which only one or few repeats of the same pattern are available, correlations between serial events can allow for the extraction of significantly more information from experiment: a more complete Bayesian approach would take this into account also. This has not been possible previously because of the technical difficulty in calculating the likelihood of amplitudes seen in correlated post-synaptic potential trains; however, recent theoretical advances have now rendered the likelihood calculation tractable for a broad class of synaptic dynamics models. Here we present a compact mathematical form for the likelihood in terms of a matrix product and demonstrate how marginals of the posterior provide information on covariance of parameter distributions. The associated computer code for Bayesian parameter inference for a variety of models of synaptic dynamics is provided in the Supplementary Material allowing for quantal and dynamical parameters to be readily inferred from experimental data sets.
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Affiliation(s)
- Alex D Bird
- Theoretical Neuroscience Group, Warwick Systems Biology Centre, University of WarwickCoventry, UK; Ernst Strüngmann Institute for Neuroscience, Max Planck SocietyFrankfurt, Germany; Frankfurt Institute for Advanced StudiesFrankfurt, Germany
| | - Mark J Wall
- School of Life Sciences, University of Warwick Coventry, UK
| | - Magnus J E Richardson
- Theoretical Neuroscience Group, Warwick Systems Biology Centre, University of WarwickCoventry, UK; Warwick Mathematics Institute, University of WarwickCoventry, UK
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