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Chater TE, Eggl MF, Goda Y, Tchumatchenko T. Competitive processes shape multi-synapse plasticity along dendritic segments. Nat Commun 2024; 15:7572. [PMID: 39217140 PMCID: PMC11365941 DOI: 10.1038/s41467-024-51919-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Accepted: 08/21/2024] [Indexed: 09/04/2024] Open
Abstract
Neurons receive thousands of inputs onto their dendritic arbour, where individual synapses undergo activity-dependent plasticity. Long-lasting changes in postsynaptic strengths correlate with changes in spine head volume. The magnitude and direction of such structural plasticity - potentiation (sLTP) and depression (sLTD) - depend upon the number and spatial distribution of stimulated synapses. However, how neurons allocate resources to implement synaptic strength changes across space and time amongst neighbouring synapses remains unclear. Here we combined experimental and modelling approaches to explore the elementary processes underlying multi-spine plasticity. We used glutamate uncaging to induce sLTP at varying number of synapses sharing the same dendritic branch, and we built a model incorporating a dual role Ca2+-dependent component that induces spine growth or shrinkage. Our results suggest that competition among spines for molecular resources is a key driver of multi-spine plasticity and that spatial distance between simultaneously stimulated spines impacts the resulting spine dynamics.
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Affiliation(s)
- Thomas E Chater
- Laboratory for Synaptic Plasticity and Connectivity, RIKEN Center for Brain Science, Wako-shi, Saitama, Japan
- Department of Physiology, Keio University School of Medicine, Tokyo, Japan
| | - Maximilian F Eggl
- Institute of Experimental Epileptology and Cognition Research, University of Bonn Medical Center, Venusberg-Campus 1, 53127, Bonn, Germany
- Institute of Neuroscience, CSIC-UMH, Alicante, Spain
| | - Yukiko Goda
- Laboratory for Synaptic Plasticity and Connectivity, RIKEN Center for Brain Science, Wako-shi, Saitama, Japan.
- Synapse Biology Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Kunigami-gun, Okinawa, Japan.
| | - Tatjana Tchumatchenko
- Institute of Experimental Epileptology and Cognition Research, University of Bonn Medical Center, Venusberg-Campus 1, 53127, Bonn, Germany.
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Dittmer PJ, Dell’Acqua ML. L-type Ca 2+ channel activation of STIM1-Orai1 signaling remodels the dendritic spine ER to maintain long-term structural plasticity. Proc Natl Acad Sci U S A 2024; 121:e2407324121. [PMID: 39178228 PMCID: PMC11363309 DOI: 10.1073/pnas.2407324121] [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: 04/12/2024] [Accepted: 07/10/2024] [Indexed: 08/25/2024] Open
Abstract
Learning and memory require coordinated structural and functional plasticity at neuronal glutamatergic synapses located on dendritic spines. Here, we investigated how the endoplasmic reticulum (ER) controls postsynaptic Ca2+ signaling and long-term potentiation of dendritic spine size, i.e., sLTP that accompanies functional strengthening of glutamatergic synaptic transmission. In most ER-containing (ER+) spines, high-frequency optical glutamate uncaging (HFGU) induced long-lasting sLTP that was accompanied by a persistent increase in spine ER content downstream of a signaling cascade engaged by N-methyl-D-aspartate receptors (NMDARs), L-type Ca2+ channels (LTCCs), and Orai1 channels, the latter being activated by stromal interaction molecule 1 (STIM1) in response to ER Ca2+ release. In contrast, HFGU stimulation of ER-lacking (ER-) spines expressed only transient sLTP and exhibited weaker Ca2+ signals noticeably lacking Orai1 and ER contributions. Consistent with spine ER regulating structural metaplasticity, delivery of a second stimulus to ER- spines induced ER recruitment along with persistent sLTP, whereas ER+ spines showed no additional increases in size or ER content in response to sequential stimulation. Surprisingly, the physical interaction between STIM1 and Orai1 induced by ER Ca2+ release, but not the resulting Ca2+ entry through Orai1 channels, proved necessary for the persistent increases in both spine size and ER content required for expression of long-lasting late sLTP.
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Affiliation(s)
- Philip J. Dittmer
- Department of Pharmacology, School of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO80045
| | - Mark L. Dell’Acqua
- Department of Pharmacology, School of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO80045
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3
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Parkins EV, Gross C. Small Differences and Big Changes: The Many Variables of MicroRNA Expression and Function in the Brain. J Neurosci 2024; 44:e0365242024. [PMID: 39111834 PMCID: PMC11308354 DOI: 10.1523/jneurosci.0365-24.2024] [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: 02/24/2024] [Revised: 05/15/2024] [Accepted: 05/23/2024] [Indexed: 08/10/2024] Open
Abstract
MicroRNAs are emerging as crucial regulators within the complex, dynamic environment of the synapse, and they offer a promising new avenue for the treatment of neurological disease. These small noncoding RNAs modify gene expression in several ways, including posttranscriptional modulation via binding to complementary and semicomplementary sites on target mRNAs. This rapid, finely tuned regulation of gene expression is essential to meet the dynamic demands of the synapse. Here, we provide a detailed review of the multifaceted world of synaptic microRNA regulation. We discuss the many mechanisms by which microRNAs regulate gene expression at the synapse, particularly in the context of neuronal plasticity. We also describe the various factors, such as age, sex, and neurological disease, that can influence microRNA expression and activity in neurons. In summary, microRNAs play a crucial role in the intricate and quickly changing functional requirements of the synapse, and context is essential in the study of microRNAs and their potential therapeutic applications.
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Affiliation(s)
- Emma V Parkins
- University of Cincinnati Neuroscience Graduate Program, Cincinnati, Ohio 45229
- Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio 45229
| | - Christina Gross
- University of Cincinnati Neuroscience Graduate Program, Cincinnati, Ohio 45229
- Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio 45229
- Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio 45229
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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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Jabra S, Rietsche M, Muellerleile J, O'Leary A, Slattery DA, Deller T, Fellenz M. Sex- and cycle-dependent changes in spine density and size in hippocampal CA2 neurons. Sci Rep 2024; 14:12252. [PMID: 38806649 PMCID: PMC11133407 DOI: 10.1038/s41598-024-62951-x] [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: 02/27/2024] [Accepted: 05/22/2024] [Indexed: 05/30/2024] Open
Abstract
Sex hormones affect structural and functional plasticity in the rodent hippocampus. However, hormone levels not only differ between males and females, but also fluctuate across the female estrous cycle. While sex- and cycle-dependent differences in dendritic spine density and morphology have been found in the rodent CA1 region, but not in the CA3 or the dentate gyrus, comparable structural data on CA2, i.e. the hippocampal region involved in social recognition memory, is so far lacking. In this study, we, therefore, used wildtype male and female mice in diestrus or proestrus to analyze spines on dendritic segments from identified CA2 neurons. In basal stratum oriens, we found no differences in spine density, but a significant shift towards larger spine head areas in male mice compared to females. Conversely, in apical stratum radiatum diestrus females had a significantly higher spine density, and females in either cycle stage had a significant shift towards larger spine head areas as compared to males, with diestrus females showing the larger shift. Our results provide further evidence for the sexual dimorphism of hippocampal area CA2, and underscore the importance of considering not only the sex, but also the stage of the estrous cycle when interpreting morphological data.
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Affiliation(s)
- Sharif Jabra
- Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe University Frankfurt, Theodor-Stern-Kai 7, 60590, Frankfurt am Main, Germany
| | - Michael Rietsche
- Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe University Frankfurt, Theodor-Stern-Kai 7, 60590, Frankfurt am Main, Germany
| | - Julia Muellerleile
- Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe University Frankfurt, Theodor-Stern-Kai 7, 60590, Frankfurt am Main, Germany
| | - Aet O'Leary
- Department of Psychiatry, Psychosomatic Medicine and Psychotherapy, Goethe University Frankfurt, University Hospital, Heinrich-Hoffmann-Straße 10, 60528, Frankfurt am Main, Germany
| | - David A Slattery
- Department of Psychiatry, Psychosomatic Medicine and Psychotherapy, Goethe University Frankfurt, University Hospital, Heinrich-Hoffmann-Straße 10, 60528, Frankfurt am Main, Germany
| | - Thomas Deller
- Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe University Frankfurt, Theodor-Stern-Kai 7, 60590, Frankfurt am Main, Germany
| | - Meike Fellenz
- Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe University Frankfurt, Theodor-Stern-Kai 7, 60590, Frankfurt am Main, Germany.
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Falahati H, Wu Y, De Camilli P. Ectopic Reconstitution of a Spine-Apparatus Like Structure Provides Insight into Mechanisms Underlying Its Formation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.16.589782. [PMID: 38659799 PMCID: PMC11042382 DOI: 10.1101/2024.04.16.589782] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
The endoplasmic reticulum (ER) is a continuous cellular endomembrane network that displays focal specializations. Most notable examples of such specializations include the spine apparatus of neuronal dendrites, and the cisternal organelle of axonal initial segments. Both organelles exhibit stacks of smooth ER sheets with a narrow lumen and interconnected by a dense protein matrix. The actin-binding protein synaptopodin is required for their formation. Here, we report that expression in non-neuronal cells of a synaptopodin construct targeted to the ER is sufficient to generate stacked ER cisterns resembling the spine apparatus with molecular properties distinct from the surrounding ER. Cisterns within these stacks are connected to each other by an actin-based matrix that contains proteins also found at the spine apparatus of neuronal spines. These findings reveal a critical role of a synaptopodin-dependent actin matrix in generating cisternal stacks. These ectopically generated structures provide insight into spine apparatus morphogenesis.
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Affiliation(s)
- Hanieh Falahati
- HHMI; Departments of Neuroscience and Cell Biology; Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, 100 College Street, New Haven, 06511, CT, USA
| | - Yumei Wu
- HHMI; Departments of Neuroscience and Cell Biology; Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, 100 College Street, New Haven, 06511, CT, USA
| | - Pietro De Camilli
- HHMI; Departments of Neuroscience and Cell Biology; Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, 100 College Street, New Haven, 06511, CT, USA
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Glausier JR, Bouchet-Marquis C, Maier M, Banks-Tibbs T, Wu K, Ning J, Melchitzky D, Lewis DA, Freyberg Z. Characterization of the three-dimensional synaptic and mitochondrial nanoarchitecture within glutamatergic synaptic complexes in postmortem human brain via focused ion beam-scanning electron microscopy. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.26.582174. [PMID: 38463986 PMCID: PMC10925168 DOI: 10.1101/2024.02.26.582174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/12/2024]
Abstract
Glutamatergic synapses are the primary site of excitatory synaptic signaling and neural communication in the cerebral cortex. Electron microscopy (EM) studies in non-human model organisms have demonstrated that glutamate synaptic activity and functioning are directly reflected in quantifiable ultrastructural features. Thus, quantitative EM analysis of glutamate synapses in ex vivo preserved human brain tissue has the potential to provide novel insight into in vivo synaptic functioning. However, factors associated with the acquisition and preservation of human brain tissue have resulted in persistent concerns regarding the potential confounding effects of antemortem and postmortem biological processes on synaptic and sub-synaptic ultrastructural features. Thus, we sought to determine how well glutamate synaptic relationships and nanoarchitecture are preserved in postmortem human dorsolateral prefrontal cortex (DLPFC), a region that substantially differs in size and architecture from model systems. Focused ion beam-scanning electron microscopy (FIB-SEM), a powerful volume EM (VEM) approach, was employed to generate high-fidelity, fine-resolution, three-dimensional (3D) micrographic datasets appropriate for quantitative analyses. Using postmortem human DLPFC with a 6-hour postmortem interval, we optimized a tissue preservation and staining workflow that generated samples of excellent ultrastructural preservation and the high-contrast staining intensity required for FIB-SEM imaging. Quantitative analysis of sub-cellular, sub-synaptic and organelle components within glutamate axo-spinous synapses revealed that ultrastructural features of synaptic function and activity were well-preserved within and across individual synapses in postmortem human brain tissue. The synaptic, sub-synaptic and organelle measures were highly consistent with findings from experimental models that are free from antemortem or postmortem effects. Further, dense reconstruction of neuropil revealed a unique, ultrastructurally-complex, spiny dendritic shaft that exhibited features characteristic of neuronal processes with heightened synaptic communication, integration and plasticity. Altogether, our findings provide a critical proof-of-concept that ex vivo VEM analysis provides a valuable and informative means to infer in vivo functioning of human brain.
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Affiliation(s)
| | | | | | - Tabitha Banks-Tibbs
- Department of Psychiatry, University of Pittsburgh
- Department of Human Genetics, University of Pittsburgh
- College of Medicine, The Ohio State University
| | - Ken Wu
- Materials and Structural Analysis, Thermo Fisher Scientific
| | - Jiying Ning
- Department of Psychiatry, University of Pittsburgh
| | | | | | - Zachary Freyberg
- Department of Psychiatry, University of Pittsburgh
- Department of Cell Biology, University of Pittsburgh
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Mohrmann L, Seebach J, Missler M, Rohlmann A. Distinct Alterations in Dendritic Spine Morphology in the Absence of β-Neurexins. Int J Mol Sci 2024; 25:1285. [PMID: 38279285 PMCID: PMC10817056 DOI: 10.3390/ijms25021285] [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: 12/21/2023] [Revised: 01/12/2024] [Accepted: 01/18/2024] [Indexed: 01/28/2024] Open
Abstract
Dendritic spines are essential for synaptic function because they constitute the postsynaptic compartment of the neurons that receives the most excitatory input. The extracellularly shorter variant of the presynaptic cell adhesion molecules neurexins, β-neurexin, has been implicated in various aspects of synaptic function, including neurotransmitter release. However, its role in developing or stabilizing dendritic spines as fundamental computational units of excitatory synapses has remained unclear. Here, we show through morphological analysis that the deletion of β-neurexins in hippocampal neurons in vitro and in hippocampal tissue in vivo affects presynaptic dense-core vesicles, as hypothesized earlier, and, unexpectedly, alters the postsynaptic spine structure. Specifically, we observed that the absence of β-neurexins led to an increase in filopodial-like protrusions in vitro and more mature mushroom-type spines in the CA1 region of adult knockout mice. In addition, the deletion of β-neurexins caused alterations in the spine head dimension and an increase in spines with perforations of their postsynaptic density but no changes in the overall number of spines or synapses. Our results indicate that presynaptic β-neurexins play a role across the synaptic cleft, possibly by aligning with postsynaptic binding partners and glutamate receptors via transsynaptic columns.
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Affiliation(s)
| | | | - Markus Missler
- Institute of Anatomy and Molecular Neurobiology, University Münster, 48149 Münster, Germany; (L.M.); (J.S.)
| | - Astrid Rohlmann
- Institute of Anatomy and Molecular Neurobiology, University Münster, 48149 Münster, Germany; (L.M.); (J.S.)
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Tao-Cheng JH, Moreira SL, Winters CA, Reese TS, Dosemeci A. Modification of the synaptic cleft under excitatory conditions. Front Synaptic Neurosci 2023; 15:1239098. [PMID: 37840571 PMCID: PMC10568020 DOI: 10.3389/fnsyn.2023.1239098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Accepted: 09/14/2023] [Indexed: 10/17/2023] Open
Abstract
The synaptic cleft is the extracellular part of the synapse, bridging the pre- and postsynaptic membranes. The geometry and molecular organization of the cleft is gaining increased attention as an important determinant of synaptic efficacy. The present study by electron microscopy focuses on short-term morphological changes at the synaptic cleft under excitatory conditions. Depolarization of cultured hippocampal neurons with high K+ results in an increased frequency of synaptic profiles with clefts widened at the periphery (open clefts), typically exhibiting patches of membranes lined by postsynaptic density, but lacking associated presynaptic membranes (18.0% open clefts in high K+ compared to 1.8% in controls). Similarly, higher frequencies of open clefts were observed in adult brain upon a delay of perfusion fixation to promote excitatory/ischemic conditions. Inhibition of basal activity in cultured neurons through the application of TTX results in the disappearance of open clefts whereas application of NMDA increases their frequency (19.0% in NMDA vs. 5.3% in control and 2.6% in APV). Depletion of extracellular Ca2+ with EGTA also promotes an increase in the frequency of open clefts (16.6% in EGTA vs. 4.0% in controls), comparable to that by depolarization or NMDA, implicating dissociation of Ca2+-dependent trans-synaptic bridges. Dissociation of transsynaptic bridges under excitatory conditions may allow perisynaptic mobile elements, such as AMPA receptors to enter the cleft. In addition, peripheral opening of the cleft would facilitate neurotransmitter clearance and thus may have a homeostatic and/or protective function.
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Affiliation(s)
- Jung-Hwa Tao-Cheng
- NINDS Electron Microscopy Facility, National Institute of Neurological Diseases and Stroke, National Institutes of Health, Bethesda, MD, United States
| | - Sandra L. Moreira
- NINDS Electron Microscopy Facility, National Institute of Neurological Diseases and Stroke, National Institutes of Health, Bethesda, MD, United States
| | - Christine A. Winters
- Laboratory of Neurobiology, National Institute of Neurological Diseases and Stroke, National Institutes of Health, Bethesda, MD, United States
| | - Thomas S. Reese
- Laboratory of Neurobiology, National Institute of Neurological Diseases and Stroke, National Institutes of Health, Bethesda, MD, United States
| | - Ayse Dosemeci
- Laboratory of Neurobiology, National Institute of Neurological Diseases and Stroke, National Institutes of Health, Bethesda, MD, United States
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Mesa MH, Garcia GC, Hoerndli FJ, McCabe KJ, Rangamani P. Spine apparatus modulates Ca 2+ in spines through spatial localization of sources and sinks. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.22.558941. [PMID: 37790389 PMCID: PMC10542496 DOI: 10.1101/2023.09.22.558941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/05/2023]
Abstract
Dendritic spines are small protrusions on dendrites in neurons and serve as sites of postsynaptic activity. Some of these spines contain smooth endoplasmic reticulum (SER), and sometimes an even further specialized SER known as the spine apparatus (SA). In this work, we developed a stochastic spatial model to investigate the role of the SER and the SA in modulating Ca 2+ dynamics. Using this model, we investigated how ryanodine receptor (RyR) localization, spine membrane geometry, and SER geometry can impact Ca 2+ transients in the spine and in the dendrite. Our simulations found that RyR opening is dependent on where it is localized in the SER and on the SER geometry. In order to maximize Ca 2+ in the dendrites (for activating clusters of spines and spine-spine communication), a laminar SA was favorable with RyRs localized in the neck region, closer to the dendrite. We also found that the presence of the SER without the laminar structure, coupled with RyR localization at the head, leads to higher Ca 2+ presence in the spine. These predictions serve as design principles for understanding how spines with an ER can regulate Ca 2+ dynamics differently from spines without ER through a combination of geometry and receptor localization. Highlights 1RyR opening in dendritic spine ER is location dependent and spine geometry dependent. Ca 2+ buffers and SERCA can buffer against runaway potentiation of spines even when CICR is activated. RyRs located towards the ER neck allow for more Ca 2+ to reach the dendrites. RyRs located towards the spine head are favorable for increased Ca 2+ in spines.
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Xu Z, Foster JB, Lashley R, Wang X, Benson E, Kidd G, Lin CLG. Impact of a pyridazine derivative on tripartite synapse ultrastructure in hippocampus: a three-dimensional analysis. Front Cell Neurosci 2023; 17:1229731. [PMID: 37671169 PMCID: PMC10476950 DOI: 10.3389/fncel.2023.1229731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Accepted: 07/24/2023] [Indexed: 09/07/2023] Open
Abstract
Introduction We previously discovered a pyridazine derivative compound series that can improve cognitive functions in mouse models of Alzheimer's disease. One of the advanced compounds from this series, LDN/OSU-0215111-M3, was selected as the preclinical development candidate. This compound activates local protein translation at the perisynaptic astrocytic process (PAP) and enhances synaptic plasticity sequentially. While biochemical evidence supports the hypothesis that the compound enhances the structural plasticity of the tripartite synapse, its direct structural impact has not been investigated. Methods Volume electron microscopy was used to study the hippocampal tripartite synapse three-dimensional structure in 3-month-old wild-type FVB/NJ mice after LDN/OSU-0215111-M3 treatment. Results LDN/OSU-0215111-M3 increased the size of tertiary apical dendrites, the volume of mushroom spines, the proportion of mushroom spines containing spine apparatus, and alterations in the spine distribution across the surface area of tertiary dendrites. Compound also increased the number of the PAP interacting with the mushroom spines as well as the size of the PAP in contact with the spines. Furthermore, proteomic analysis of the isolated synaptic terminals indicated an increase in dendritic and synaptic proteins as well as suggested a possible involvement of the phospholipase D signaling pathway. To further validate that LDN/OSU-0215111-M3 altered synaptic function, electrophysiological studies showed increased long-term potentiation following compound treatment. Discussion This study provides direct evidence that pyridazine derivatives enhance the structural and functional plasticity of the tripartite synapse.
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Affiliation(s)
- Zan Xu
- Department of Neuroscience, College of Medicine, The Ohio State University, Columbus, OH, United States
| | - Joshua B. Foster
- Department of Neuroscience, College of Medicine, The Ohio State University, Columbus, OH, United States
| | - Rashelle Lashley
- Department of Neuroscience, College of Medicine, The Ohio State University, Columbus, OH, United States
| | - Xueqin Wang
- Department of Neuroscience, College of Medicine, The Ohio State University, Columbus, OH, United States
| | - Emily Benson
- Department of Neuroscience, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States
| | - Grahame Kidd
- Department of Neuroscience, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States
| | - Chien-liang Glenn Lin
- Department of Neuroscience, College of Medicine, The Ohio State University, Columbus, OH, United States
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Hu HT, Lin YJ, Wang UTT, Lee SP, Liou YH, Chen BC, Hsueh YP. Autism-related KLHL17 and SYNPO act in concert to control activity-dependent dendritic spine enlargement and the spine apparatus. PLoS Biol 2023; 21:e3002274. [PMID: 37651441 PMCID: PMC10499226 DOI: 10.1371/journal.pbio.3002274] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 09/13/2023] [Accepted: 07/24/2023] [Indexed: 09/02/2023] Open
Abstract
Dendritic spines, the tiny and actin-rich protrusions emerging from dendrites, are the subcellular locations of excitatory synapses in the mammalian brain that control synaptic activity and plasticity. Dendritic spines contain a specialized form of endoplasmic reticulum (ER), i.e., the spine apparatus, required for local calcium signaling and that is involved in regulating dendritic spine enlargement and synaptic plasticity. Many autism-linked genes have been shown to play critical roles in synaptic formation and plasticity. Among them, KLHL17 is known to control dendritic spine enlargement during development. As a brain-specific disease-associated gene, KLHL17 is expected to play a critical role in the brain, but it has not yet been well characterized. In this study, we report that KLHL17 expression in mice is strongly regulated by neuronal activity and KLHL17 modulates the synaptic distribution of synaptopodin (SYNPO), a marker of the spine apparatus. Both KLHL17 and SYNPO are F-actin-binding proteins linked to autism. SYNPO is known to maintain the structure of the spine apparatus in mature spines and contributes to synaptic plasticity. Our super-resolution imaging using expansion microscopy demonstrates that SYNPO is indeed embedded into the ER network of dendritic spines and that KLHL17 is closely adjacent to the ER/SYNPO complex. Using mouse genetic models, we further show that Klhl17 haploinsufficiency and knockout result in fewer dendritic spines containing ER clusters and an alteration of calcium events at dendritic spines. Accordingly, activity-dependent dendritic spine enlargement and neuronal activation (reflected by extracellular signal-regulated kinase (ERK) phosphorylation and C-FOS expression) are impaired. In addition, we show that the effect of disrupting the KLHL17 and SYNPO association is similar to the results of Klhl17 haploinsufficiency and knockout, further strengthening the evidence that KLHL17 and SYNPO act together to regulate synaptic plasticity. In conclusion, our findings unravel a role for KLHL17 in controlling synaptic plasticity via its regulation of SYNPO and synaptic ER clustering and imply that impaired synaptic plasticity contributes to the etiology of KLHL17-related disorders.
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Affiliation(s)
- Hsiao-Tang Hu
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
| | - Yung-Jui Lin
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
| | - Ueh-Ting Tim Wang
- Affiliated Senior High School of National Taiwan Normal University, Taipei, Taiwan
- Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
| | - Sue-Ping Lee
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
| | - Yae-Huei Liou
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
| | - Bi-Chang Chen
- Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
| | - Yi-Ping Hsueh
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
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Bell MK, Lee CT, Rangamani P. Spatiotemporal modelling reveals geometric dependence of AMPAR dynamics on dendritic spine morphology. J Physiol 2023; 601:3329-3350. [PMID: 36326020 DOI: 10.1113/jp283407] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Accepted: 11/01/2022] [Indexed: 08/02/2023] Open
Abstract
The modification of neural circuits depends on the strengthening and weakening of synaptic connections. Synaptic strength is often correlated to the density of the ionotropic, glutamatergic receptors, AMPARs, (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors) at the postsynaptic density (PSD). While AMPAR density is known to change based on complex biological signalling cascades, the effect of geometric factors such as dendritic spine shape, size and curvature remain poorly understood. In this work, we developed a deterministic, spatiotemporal model to study the dynamics of AMPARs during long-term potentiation (LTP). This model includes a minimal set of biochemical events that represent the upstream signalling events, trafficking of AMPARs to and from the PSD, lateral diffusion in the plane of the spine membrane, and the presence of an extrasynaptic AMPAR pool. Using idealized and realistic spine geometries, we show that the dynamics and increase of bound AMPARs at the PSD depends on a combination of endo- and exocytosis, membrane diffusion, the availability of free AMPARs and intracellular signalling interactions. We also found non-monotonic relationships between spine volume and the change in AMPARs at the PSD, suggesting that spines restrict changes in AMPARs to optimize resources and prevent runaway potentiation. KEY POINTS: Synaptic plasticity involves dynamic biochemical and physical remodelling of small protrusions called dendritic spines along the dendrites of neurons. Proper synaptic functionality within these spines requires changes in receptor number at the synapse, which has implications for downstream neural functions, such as learning and memory formation. In addition to being signalling subcompartments, spines also have unique morphological features that can play a role in regulating receptor dynamics on the synaptic surface. We have developed a spatiotemporal model that couples biochemical signalling and receptor trafficking modalities in idealized and realistic spine geometries to investigate the role of biochemical and biophysical factors in synaptic plasticity. Using this model, we highlight the importance of spine size and shape in regulating bound AMPA receptor dynamics that govern synaptic plasticity, and predict how spine shape might act to reset synaptic plasticity as a built-in resource optimization and regulation tool.
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Affiliation(s)
- Miriam K Bell
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, California, USA
| | - Christopher T Lee
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, California, USA
| | - Padmini Rangamani
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, California, USA
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14
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Konietzny A, Wegmann S, Mikhaylova M. The endoplasmic reticulum puts a new spin on synaptic tagging. Trends Neurosci 2023; 46:32-44. [PMID: 36428191 DOI: 10.1016/j.tins.2022.10.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Revised: 10/12/2022] [Accepted: 10/31/2022] [Indexed: 11/23/2022]
Abstract
The heterogeneity of the endoplasmic reticulum (ER) makes it a versatile platform for a broad range of homeostatic processes, ranging from calcium regulation to synthesis and trafficking of proteins and lipids. It is not surprising that neurons use this organelle to fine-tune synaptic properties and thereby provide specificity to synaptic inputs. In this review, we discuss the mechanisms that enable activity-dependent ER recruitment into dendritic spines, with a focus on molecular mechanisms that mediate transport and retention of the ER in spines. The role of calcium signaling in spine ER, synaptopodin 'tagging' of active synapses, and the formation of the spine apparatus (SA) are highlighted. Finally, we discuss the role of liquid-liquid phase separation as a possible driving force in these processes.
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Affiliation(s)
- Anja Konietzny
- AG Optobiology, Institute of Biology, Humboldt Universität zu Berlin, Berlin, Germany; Guest Group 'Neuronal Protein Transport', Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Susanne Wegmann
- German Center for Neurodegenerative Diseases (DZNE), Berlin, Germany
| | - Marina Mikhaylova
- AG Optobiology, Institute of Biology, Humboldt Universität zu Berlin, Berlin, Germany; Guest Group 'Neuronal Protein Transport', Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
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15
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Sun C, Schuman EM. Logistics of neuronal protein turnover: Numbers and mechanisms. Mol Cell Neurosci 2022; 123:103793. [PMID: 36396040 DOI: 10.1016/j.mcn.2022.103793] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 11/07/2022] [Accepted: 11/09/2022] [Indexed: 11/16/2022] Open
Abstract
Research in the past twenty years or so has revealed that neurons synthesize and degrade proteins at their synapses to enable synaptic proteome remodelling on demand and in real-time. Here we provide a quantitative overview of the decentralized neuronal protein-turnover logistics. We first analyse the huge neuronal protein turnover demand that arises from subcellular compartments outside the cell body, followed by an overview of key quantities and modulation strategies in neuronal protein turnover logistics. In the end, we briefly review recent progress in neuronal local protein synthesis and summarize diverse protein-degradation mechanisms that are found near synapses.
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Affiliation(s)
- Chao Sun
- Max Planck Institute for Brain Research, 60438 Frankfurt am Main, Germany
| | - Erin M Schuman
- Max Planck Institute for Brain Research, 60438 Frankfurt am Main, Germany.
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16
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Falahati H, Wu Y, Feuerer V, Simon HG, De Camilli P. Proximity proteomics of synaptopodin provides insight into the molecular composition of the spine apparatus of dendritic spines. Proc Natl Acad Sci U S A 2022; 119:e2203750119. [PMID: 36215465 PMCID: PMC9586327 DOI: 10.1073/pnas.2203750119] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Accepted: 09/02/2022] [Indexed: 02/03/2023] Open
Abstract
The spine apparatus is a specialized compartment of the neuronal smooth endoplasmic reticulum (ER) located in a subset of dendritic spines. It consists of stacks of ER cisterns that are interconnected by an unknown dense matrix and are continuous with each other and with the ER of the dendritic shaft. While this organelle was first observed over 60 y ago, its molecular organization remains a mystery. Here, we performed in vivo proximity proteomics to gain some insight into its molecular components. To do so, we used the only known spine apparatus-specific protein, synaptopodin, to target a biotinylating enzyme to this organelle. We validated the specific localization in dendritic spines of a small subset of proteins identified by this approach, and we further showed their colocalization with synaptopodin when expressed in nonneuronal cells. One such protein is Pdlim7, an actin binding protein not previously identified in spines. Pdlim7, which we found to interact with synaptopodin through multiple domains, also colocalizes with synaptopodin on the cisternal organelle, a peculiar stack of ER cisterns resembling the spine apparatus and found at axon initial segments of a subset of neurons. Moreover, Pdlim7 has an expression pattern similar to that of synaptopodin in the brain, highlighting a functional partnership between the two proteins. The components of the spine apparatus identified in this work will help elucidate mechanisms in the biogenesis and maintenance of this enigmatic structure with implications for the function of dendritic spines in physiology and disease.
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Affiliation(s)
- Hanieh Falahati
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT 06510
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510
- HHMI, Yale University School of Medicine, New Haven, CT 06510
- Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, New Haven, CT 06510
| | - Yumei Wu
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT 06510
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510
- HHMI, Yale University School of Medicine, New Haven, CT 06510
- Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, New Haven, CT 06510
| | - Vanessa Feuerer
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT 06510
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510
- HHMI, Yale University School of Medicine, New Haven, CT 06510
- Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, New Haven, CT 06510
| | - Hans-Georg Simon
- Department of Pediatrics, Feinberg School of Medicine, Northwestern University and Stanley Manne Children’s Research Institute, Chicago, IL 60611
| | - Pietro De Camilli
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT 06510
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510
- HHMI, Yale University School of Medicine, New Haven, CT 06510
- Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, New Haven, CT 06510
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17
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DeGiosio RA, Grubisha MJ, MacDonald ML, McKinney BC, Camacho CJ, Sweet RA. More than a marker: potential pathogenic functions of MAP2. Front Mol Neurosci 2022; 15:974890. [PMID: 36187353 PMCID: PMC9525131 DOI: 10.3389/fnmol.2022.974890] [Citation(s) in RCA: 42] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Accepted: 07/29/2022] [Indexed: 12/27/2022] Open
Abstract
Microtubule-associated protein 2 (MAP2) is the predominant cytoskeletal regulator within neuronal dendrites, abundant and specific enough to serve as a robust somatodendritic marker. It influences microtubule dynamics and microtubule/actin interactions to control neurite outgrowth and synaptic functions, similarly to the closely related MAP Tau. Though pathology of Tau has been well appreciated in the context of neurodegenerative disorders, the consequences of pathologically dysregulated MAP2 have been little explored, despite alterations in its immunoreactivity, expression, splicing and/or stability being observed in a variety of neurodegenerative and neuropsychiatric disorders including Huntington’s disease, prion disease, schizophrenia, autism, major depression and bipolar disorder. Here we review the understood structure and functions of MAP2, including in neurite outgrowth, synaptic plasticity, and regulation of protein folding/transport. We also describe known and potential mechanisms by which MAP2 can be regulated via post-translational modification. Then, we assess existing evidence of its dysregulation in various brain disorders, including from immunohistochemical and (phospho) proteomic data. We propose pathways by which MAP2 pathology could contribute to endophenotypes which characterize these disorders, giving rise to the concept of a “MAP2opathy”—a series of disorders characterized by alterations in MAP2 function.
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Affiliation(s)
- Rebecca A. DeGiosio
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA, United States
| | - Melanie J. Grubisha
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA, United States
| | - Matthew L. MacDonald
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA, United States
| | - Brandon C. McKinney
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA, United States
| | - Carlos J. Camacho
- Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, PA, United States
| | - Robert A. Sweet
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA, United States
- Department of Neurology, University of Pittsburgh, Pittsburgh, PA, United States
- *Correspondence: Robert A. Sweet
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18
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Gore A, Yurina A, Yukevich-Mussomeli A, Nahmani M. Synaptic spinules are reliable indicators of excitatory presynaptic bouton size and strength and are ubiquitous components of excitatory synapses in CA1 hippocampus. Front Synaptic Neurosci 2022; 14:968404. [PMID: 36032419 PMCID: PMC9403541 DOI: 10.3389/fnsyn.2022.968404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Accepted: 07/25/2022] [Indexed: 11/23/2022] Open
Abstract
Synaptic spinules are thin, finger-like projections from one neuron that become embedded within the presynaptic or postsynaptic compartments of another neuron. While spinules are conserved features of synapses across the animal kingdom, their specific function(s) remain unknown. Recent focused ion beam scanning electron microscopy (FIB-SEM) image volume analyses have demonstrated that spinules are embedded within ∼25% of excitatory boutons in primary visual cortex, yet the diversity of spinule sizes, origins, and ultrastructural relationships to their boutons remained unclear. To begin to uncover the function of synaptic spinules, we sought to determine the abundance, origins, and 3D ultrastructure of spinules within excitatory presynaptic spinule-bearing boutons (SBBs) in mammalian CA1 hippocampus and compare them with presynaptic boutons bereft of spinules (non-SBBs). Accordingly, we performed a comprehensive 3D analysis of every excitatory presynaptic bouton, their embedded spinules, and postsynaptic densities, within a 5 nm isotropic FIB-SEM image volume from CA1 hippocampus of an adult male rat. Surprisingly, we found that ∼74% of excitatory presynaptic boutons in this volume contained at least one spinule, suggesting they are fundamental components of excitatory synapses in CA1. In addition, we found that SBBs are 2.5-times larger and have 60% larger postsynaptic densities (PSDs) than non-SBBs. Moreover, synaptic spinules within SBBs are clearly differentiated into two groups: small clathrin-coated spinules, and 29-times larger spinules without clathrin. Together, these findings suggest that the presence of a spinule is a marker for stronger and more stable presynaptic boutons in CA1, and that synaptic spinules serve at least two separable and distinct functions.
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19
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Post-Synapses in the Brain: Role of Dendritic and Spine Structures. Biomedicines 2022; 10:biomedicines10081859. [PMID: 36009405 PMCID: PMC9405724 DOI: 10.3390/biomedicines10081859] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Revised: 06/26/2022] [Accepted: 07/22/2022] [Indexed: 02/07/2023] Open
Abstract
Brain synapses are neuronal structures of the greatest interest. For a long time, however, the knowledge about them was variable, and interest was mostly focused on their pre-synaptic portions, especially neurotransmitter release from axon terminals. In the present review interest is focused on post-synapses, the structures receiving and converting pre-synaptic messages. Upon further modulation, such messages are transferred to dendritic fibers. Dendrites are profoundly different from axons; they are shorter and of variable thickness. Their post-synapses are of two types. Those called flat/intended/aspines, integrated into dendritic fibers, are very frequent in inhibitory neurons. The spines, small and stemming protrusions, connected to dendritic fibers by their necks, are present in almost all excitatory neurons. Several structures and functions including the post-synaptic densities and associated proteins, the nanoscale mechanisms of compartmentalization, the cytoskeletons of actin and microtubules, are analogous in the two post-synaptic forms. However other properties, such as plasticity and its functions of learning and memory, are largely distinct. Several properties of spines, including emersion from dendritic fibers, growth, change in shape and decreases in size up to disappearance, are specific. Spinal heads correspond to largely independent signaling compartments. They are motile, their local signaling is fast, however transport through their thin necks is slow. When single spines are activated separately, their dendritic effects are often lacking; when multiple spines are activated concomitantly, their effects take place. Defects of post-synaptic responses, especially those of spines, take place in various brain diseases. Here alterations affecting symptoms and future therapy are shown to occur in neurodegenerative diseases and autism spectrum disorders.
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20
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Bell MK, Holst MV, Lee CT, Rangamani P. Dendritic spine morphology regulates calcium-dependent synaptic weight change. J Gen Physiol 2022; 154:e202112980. [PMID: 35819365 PMCID: PMC9280073 DOI: 10.1085/jgp.202112980] [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: 06/11/2021] [Revised: 05/28/2022] [Accepted: 06/07/2022] [Indexed: 01/14/2023] Open
Abstract
Dendritic spines act as biochemical computational units and must adapt their responses according to their activation history. Calcium influx acts as the first signaling step during postsynaptic activation and is a determinant of synaptic weight change. Dendritic spines also come in a variety of sizes and shapes. To probe the relationship between calcium dynamics and spine morphology, we used a stochastic reaction-diffusion model of calcium dynamics in idealized and realistic geometries. We show that despite the stochastic nature of the various calcium channels, receptors, and pumps, spine size and shape can modulate calcium dynamics and subsequently synaptic weight updates in a deterministic manner. Through a series of exhaustive simulations and analyses, we found that the calcium dynamics and synaptic weight change depend on the volume-to-surface area of the spine. The relationships between calcium dynamics and spine morphology identified in idealized geometries also hold in realistic geometries, suggesting that there are geometrically determined deterministic relationships that may modulate synaptic weight change.
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Affiliation(s)
- Miriam K. Bell
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA
| | - Maven V. Holst
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA
| | - Christopher T. Lee
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA
| | - Padmini Rangamani
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA
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21
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Dubes S, Soula A, Benquet S, Tessier B, Poujol C, Favereaux A, Thoumine O, Letellier M. miR
‐124‐dependent tagging of synapses by synaptopodin enables input‐specific homeostatic plasticity. EMBO J 2022; 41:e109012. [PMID: 35875872 PMCID: PMC9574720 DOI: 10.15252/embj.2021109012] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 06/11/2022] [Accepted: 06/27/2022] [Indexed: 12/26/2022] Open
Abstract
Homeostatic synaptic plasticity is a process by which neurons adjust their synaptic strength to compensate for perturbations in neuronal activity. Whether the highly diverse synapses on a neuron respond uniformly to the same perturbation remains unclear. Moreover, the molecular determinants that underlie synapse‐specific homeostatic synaptic plasticity are unknown. Here, we report a synaptic tagging mechanism in which the ability of individual synapses to increase their strength in response to activity deprivation depends on the local expression of the spine‐apparatus protein synaptopodin under the regulation of miR‐124. Using genetic manipulations to alter synaptopodin expression or regulation by miR‐124, we show that synaptopodin behaves as a “postsynaptic tag” whose translation is derepressed in a subpopulation of synapses and allows for nonuniform homeostatic strengthening and synaptic AMPA receptor stabilization. By genetically silencing individual connections in pairs of neurons, we demonstrate that this process operates in an input‐specific manner. Overall, our study shifts the current view that homeostatic synaptic plasticity affects all synapses uniformly to a more complex paradigm where the ability of individual synapses to undergo homeostatic changes depends on their own functional and biochemical state.
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Affiliation(s)
- Sandra Dubes
- University of Bordeaux CNRS Interdisciplinary Institute for Neuroscience UMR 5297 Bordeaux France
| | - Anaïs Soula
- University of Bordeaux CNRS Interdisciplinary Institute for Neuroscience UMR 5297 Bordeaux France
| | - Sébastien Benquet
- University of Bordeaux CNRS Interdisciplinary Institute for Neuroscience UMR 5297 Bordeaux France
| | - Béatrice Tessier
- University of Bordeaux CNRS Interdisciplinary Institute for Neuroscience UMR 5297 Bordeaux France
| | - Christel Poujol
- University of Bordeaux CNRS INSERM Bordeaux Imaging Center BIC UMS 3420, US 4 Bordeaux France
| | - Alexandre Favereaux
- University of Bordeaux CNRS Interdisciplinary Institute for Neuroscience UMR 5297 Bordeaux France
| | - Olivier Thoumine
- University of Bordeaux CNRS Interdisciplinary Institute for Neuroscience UMR 5297 Bordeaux France
| | - Mathieu Letellier
- University of Bordeaux CNRS Interdisciplinary Institute for Neuroscience UMR 5297 Bordeaux France
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22
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Khan S. Endoplasmic Reticulum in Metaplasticity: From Information Processing to Synaptic Proteostasis. Mol Neurobiol 2022; 59:5630-5655. [PMID: 35739409 DOI: 10.1007/s12035-022-02916-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Accepted: 06/05/2022] [Indexed: 11/29/2022]
Abstract
The ER (endoplasmic reticulum) is a Ca2+ reservoir and the unique protein-synthesizing machinery which is distributed throughout the neuron and composed of multiple different structural domains. One such domain is called EMC (endoplasmic reticulum membrane protein complex), pleiotropic nature in cellular functions. The ER/EMC position inside the neurons unmasks its contribution to synaptic plasticity via regulating various cellular processes from protein synthesis to Ca2+ signaling. Since presynaptic Ca2+ channels and postsynaptic ionotropic receptors are organized into the nanodomains, thus ER can be a crucial player in establishing TMNCs (transsynaptic molecular nanocolumns) to shape efficient neural communications. This review hypothesized that ER is not only involved in stress-mediated neurodegeneration but also axon regrowth, remyelination, neurotransmitter switching, information processing, and regulation of pre- and post-synaptic functions. Thus ER might not only be a protein-synthesizing and quality control machinery but also orchestrates plasticity of plasticity (metaplasticity) within the neuron to execute higher-order brain functions and neural repair.
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Affiliation(s)
- Shumsuzzaman Khan
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, USA.
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23
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Yang Y, Liu JJ. Structural LTP: Signal transduction, actin cytoskeleton reorganization, and membrane remodeling of dendritic spines. Curr Opin Neurobiol 2022; 74:102534. [DOI: 10.1016/j.conb.2022.102534] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2021] [Revised: 02/14/2022] [Accepted: 03/03/2022] [Indexed: 01/05/2023]
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24
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Harris KM, Hubbard DD, Kuwajima M, Abraham WC, Bourne JN, Bowden JB, Haessly A, Mendenhall JM, Parker PH, Shi B, Spacek J. Dendritic Spine Density Scales with Microtubule Number in Rat Hippocampal Dendrites. Neuroscience 2022; 489:84-97. [PMID: 35218884 PMCID: PMC9038701 DOI: 10.1016/j.neuroscience.2022.02.021] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Revised: 02/16/2022] [Accepted: 02/18/2022] [Indexed: 12/14/2022]
Abstract
Microtubules deliver essential resources to and from synapses. Three-dimensional reconstructions in rat hippocampus reveal a sampling bias regarding spine density that needs to be controlled for dendrite caliber and resource delivery based on microtubule number. The strength of this relationship varies across dendritic arbors, as illustrated for area CA1 and dentate gyrus. In both regions, proximal dendrites had more microtubules than distal dendrites. For CA1 pyramidal cells, spine density was greater on thicker than thinner dendrites in stratum radiatum, or on the more uniformly thin terminal dendrites in stratum lacunosum moleculare. In contrast, spine density was constant across the cone shaped arbor of tapering dendrites from dentate granule cells. These differences suggest that thicker dendrites supply microtubules to subsequent dendritic branches and local dendritic spines, whereas microtubules in thinner dendrites need only provide resources to local spines. Most microtubules ran parallel to dendrite length and associated with long, presumably stable mitochondria, which occasionally branched into lateral dendritic branches. Short, presumably mobile, mitochondria were tethered to microtubules that bent and appeared to direct them into a thin lateral branch. Prior work showed that dendritic segments with the same number of microtubules had elevated resources in subregions of their dendritic shafts where spine synapses had enlarged, and spine clusters had formed. Thus, additional microtubules were not required for redistribution of resources locally to growing spines or synapses. These results provide new understanding about the potential for microtubules to regulate resource delivery to and from dendritic branches and locally among dendritic spines.
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Affiliation(s)
- Kristen M Harris
- Department of Neuroscience, Center for Learning and Memory, University of Texas at Austin, Austin, TX, United States.
| | - Dusten D Hubbard
- Department of Neuroscience, Center for Learning and Memory, University of Texas at Austin, Austin, TX, United States
| | - Masaaki Kuwajima
- Department of Neuroscience, Center for Learning and Memory, University of Texas at Austin, Austin, TX, United States
| | - Wickliffe C Abraham
- Department of Neuroscience, Center for Learning and Memory, University of Texas at Austin, Austin, TX, United States
| | - Jennifer N Bourne
- Department of Neuroscience, Center for Learning and Memory, University of Texas at Austin, Austin, TX, United States
| | - Jared B Bowden
- Department of Neuroscience, Center for Learning and Memory, University of Texas at Austin, Austin, TX, United States
| | - Andrea Haessly
- Department of Neuroscience, Center for Learning and Memory, University of Texas at Austin, Austin, TX, United States
| | - John M Mendenhall
- Department of Neuroscience, Center for Learning and Memory, University of Texas at Austin, Austin, TX, United States
| | - Patrick H Parker
- Department of Neuroscience, Center for Learning and Memory, University of Texas at Austin, Austin, TX, United States
| | - Bitao Shi
- Department of Neuroscience, Center for Learning and Memory, University of Texas at Austin, Austin, TX, United States
| | - Josef Spacek
- Department of Neuroscience, Center for Learning and Memory, University of Texas at Austin, Austin, TX, United States
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25
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Chanaday NL, Kavalali ET. Role of the endoplasmic reticulum in synaptic transmission. Curr Opin Neurobiol 2022; 73:102538. [PMID: 35395547 PMCID: PMC9167765 DOI: 10.1016/j.conb.2022.102538] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Revised: 02/25/2022] [Accepted: 03/06/2022] [Indexed: 11/03/2022]
Abstract
Neurons possess a complex morphology spanning long distances and a large number of subcellular specializations such as presynaptic terminals and dendritic spines. This structural complexity is essential for maintenance of synaptic junctions and associated electrical as well as biochemical signaling events. Given the structural and functional complexity of neurons, neuronal endoplasmic reticulum is emerging as a key regulator of neuronal function, in particular synaptic signaling. Neuronal endoplasmic reticulum mediates calcium signaling, calcium and lipid homeostasis, vesicular trafficking, and proteostasis events that underlie autonomous functions of numerous subcellular compartments. However, based on its geometric complexity spanning the whole neuron, endoplasmic reticulum also integrates the activity of these autonomous compartments across the neuron and coordinates their interactions with the soma. In this article, we review recent work regarding neuronal endoplasmic reticulum function and its relationship to neurotransmission and plasticity.
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Affiliation(s)
- Natali L Chanaday
- Department of Pharmacology, School of Medicine, Vanderbilt University, Nashville, TN, 37240-7933, USA.
| | - Ege T Kavalali
- Department of Pharmacology, School of Medicine, Vanderbilt University, Nashville, TN, 37240-7933, USA; Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN, 37240-7933, USA.
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26
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Konietzny A, Grendel J, Kadek A, Bucher M, Han Y, Hertrich N, Dekkers DHW, Demmers JAA, Grünewald K, Uetrecht C, Mikhaylova M. Caldendrin and myosin V regulate synaptic spine apparatus localization via ER stabilization in dendritic spines. EMBO J 2022; 41:e106523. [PMID: 34935159 PMCID: PMC8844991 DOI: 10.15252/embj.2020106523] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Revised: 11/08/2021] [Accepted: 11/19/2021] [Indexed: 11/21/2022] Open
Abstract
Excitatory synapses of principal hippocampal neurons are frequently located on dendritic spines. The dynamic strengthening or weakening of individual inputs results in structural and molecular diversity of dendritic spines. Active spines with large calcium ion (Ca2+ ) transients are frequently invaded by a single protrusion from the endoplasmic reticulum (ER), which is dynamically transported into spines via the actin-based motor myosin V. An increase in synaptic strength correlates with stable anchoring of the ER, followed by the formation of an organelle referred to as the spine apparatus. Here, we show that myosin V binds the Ca2+ sensor caldendrin, a brain-specific homolog of the well-known myosin V interactor calmodulin. While calmodulin is an essential activator of myosin V motor function, we found that caldendrin acts as an inhibitor of processive myosin V movement. In mouse and rat hippocampal neurons, caldendrin regulates spine apparatus localization to a subset of dendritic spines through a myosin V-dependent pathway. We propose that caldendrin transforms myosin into a stationary F-actin tether that enables the localization of ER tubules and formation of the spine apparatus in dendritic spines.
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Affiliation(s)
- Anja Konietzny
- RG OptobiologyInstitute of BiologyHumboldt Universität zu BerlinBerlinGermany
- Guest Group Neuronal Protein TransportCenter for Molecular NeurobiologyZMNHUniversity Medical Center Hamburg‐EppendorfHamburgGermany
| | - Jasper Grendel
- RG OptobiologyInstitute of BiologyHumboldt Universität zu BerlinBerlinGermany
- Guest Group Neuronal Protein TransportCenter for Molecular NeurobiologyZMNHUniversity Medical Center Hamburg‐EppendorfHamburgGermany
| | - Alan Kadek
- Leibniz Institute for Experimental Virology (HPI)HamburgGermany
- European XFEL GmbHSchenefeldGermany
| | - Michael Bucher
- RG OptobiologyInstitute of BiologyHumboldt Universität zu BerlinBerlinGermany
- Guest Group Neuronal Protein TransportCenter for Molecular NeurobiologyZMNHUniversity Medical Center Hamburg‐EppendorfHamburgGermany
| | - Yuhao Han
- RG OptobiologyInstitute of BiologyHumboldt Universität zu BerlinBerlinGermany
- Guest Group Neuronal Protein TransportCenter for Molecular NeurobiologyZMNHUniversity Medical Center Hamburg‐EppendorfHamburgGermany
- Centre for Structural Systems BiologyHamburgGermany
| | - Nathalie Hertrich
- RG OptobiologyInstitute of BiologyHumboldt Universität zu BerlinBerlinGermany
- Guest Group Neuronal Protein TransportCenter for Molecular NeurobiologyZMNHUniversity Medical Center Hamburg‐EppendorfHamburgGermany
| | | | | | - Kay Grünewald
- Leibniz Institute for Experimental Virology (HPI)HamburgGermany
- Centre for Structural Systems BiologyHamburgGermany
- Department of ChemistryUniversity of HamburgHamburgGermany
| | - Charlotte Uetrecht
- Leibniz Institute for Experimental Virology (HPI)HamburgGermany
- European XFEL GmbHSchenefeldGermany
- Centre for Structural Systems BiologyHamburgGermany
| | - Marina Mikhaylova
- RG OptobiologyInstitute of BiologyHumboldt Universität zu BerlinBerlinGermany
- Guest Group Neuronal Protein TransportCenter for Molecular NeurobiologyZMNHUniversity Medical Center Hamburg‐EppendorfHamburgGermany
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27
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Sun C, Nold A, Fusco CM, Rangaraju V, Tchumatchenko T, Heilemann M, Schuman EM. The prevalence and specificity of local protein synthesis during neuronal synaptic plasticity. SCIENCE ADVANCES 2021; 7:eabj0790. [PMID: 34533986 PMCID: PMC8448450 DOI: 10.1126/sciadv.abj0790] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
To supply proteins to their vast volume, neurons localize mRNAs and ribosomes in dendrites and axons. While local protein synthesis is required for synaptic plasticity, the abundance and distribution of ribosomes and nascent proteins near synapses remain elusive. Here, we quantified the occurrence of local translation and visualized the range of synapses supplied by nascent proteins during basal and plastic conditions. We detected dendritic ribosomes and nascent proteins at single-molecule resolution using DNA-PAINT and metabolic labeling. Both ribosomes and nascent proteins positively correlated with synapse density. Ribosomes were detected at ~85% of synapses with ~2 translational sites per synapse; ~50% of the nascent protein was detected near synapses. The amount of locally synthesized protein detected at a synapse correlated with its spontaneous Ca2+ activity. A multifold increase in synaptic nascent protein was evident following both local and global plasticity at respective scales, albeit with substantial heterogeneity between neighboring synapses.
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Affiliation(s)
- Chao Sun
- Max Planck Institute for Brain Research, Frankfurt, Germany
| | - Andreas Nold
- Max Planck Institute for Brain Research, Frankfurt, Germany
- Institute of Experimental Epileptology and Cognition Research, Life and Brain Center, Universitätsklinikum Bonn, Venusberg-Campus 1, 53127 Bonn, Germany
| | | | | | - Tatjana Tchumatchenko
- Max Planck Institute for Brain Research, Frankfurt, Germany
- Institute of Experimental Epileptology and Cognition Research, Life and Brain Center, Universitätsklinikum Bonn, Venusberg-Campus 1, 53127 Bonn, Germany
| | - Mike Heilemann
- Institute of Physical and Theoretical Chemistry, Goethe University, Frankfurt, Germany
| | - Erin M. Schuman
- Max Planck Institute for Brain Research, Frankfurt, Germany
- Corresponding author.
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28
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Pulikkottil VV, Somashekar BP, Bhalla US. Computation, wiring, and plasticity in synaptic clusters. Curr Opin Neurobiol 2021; 70:101-112. [PMID: 34509808 DOI: 10.1016/j.conb.2021.08.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2021] [Revised: 07/28/2021] [Accepted: 08/09/2021] [Indexed: 01/19/2023]
Abstract
Synaptic clusters on dendrites are extraordinarily compact computational building blocks. They contribute to key local computations through biophysical and biochemical signaling that utilizes convergence in space and time as an organizing principle. However, these computations can only arise in very special contexts. Dendritic cluster computations, their highly organized input connectivity, and the mechanisms for their formation are closely linked, yet these have not been analyzed as parts of a single process. Here, we examine these linkages. The sheer density of axonal and dendritic arborizations means that there are far more potential connections (close enough for a spine to reach an axon) than actual ones. We see how dendritic clusters draw upon electrical, chemical, and mechano-chemical signaling to implement the rules for formation of connections and subsequent computations. Crucially, the same mechanisms that underlie their functions also underlie their formation.
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Affiliation(s)
| | - Bhanu Priya Somashekar
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, India
| | - Upinder S Bhalla
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, India.
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29
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Perez JD, Fusco CM, Schuman EM. A Functional Dissection of the mRNA and Locally Synthesized Protein Population in Neuronal Dendrites and Axons. Annu Rev Genet 2021; 55:183-207. [PMID: 34460296 DOI: 10.1146/annurev-genet-030321-054851] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Neurons are characterized by a complex morphology that enables the generation of subcellular compartments with unique biochemical and biophysical properties, such as dendrites, axons, and synapses. To sustain these different compartments and carry a wide array of elaborate operations, neurons express a diverse repertoire of gene products. Extensive regulation at both the messenger RNA (mRNA) and protein levels allows for the differentiation of subcellular compartments as well as numerous forms of plasticity in response to variable stimuli. Among the multiple mechanisms that control cellular functions, mRNA translation is manipulated by neurons to regulate where and when a protein emerges. Interestingly, transcriptomic and translatomic profiles of both dendrites and axons have revealed that the mRNA population only partially predicts the local protein population and that this relation significantly varies between different gene groups. Here, we describe the space that local translation occupies within the large molecular and regulatory complexity of neurons, in contrast to other modes of regulation. We then discuss the specialized organization of mRNAs within different neuronal compartments, as revealed by profiles of the local transcriptome. Finally, we discuss the features and functional implications of both locally correlated-and anticorrelated-mRNA-protein relations both under baseline conditions and during synaptic plasticity. Expected final online publication date for the Annual Review of Genetics, Volume 55 is November 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Julio D Perez
- Max Planck Institute for Brain Research, 60438 Frankfurt, Germany;
| | - Claudia M Fusco
- Max Planck Institute for Brain Research, 60438 Frankfurt, Germany;
| | - Erin M Schuman
- Max Planck Institute for Brain Research, 60438 Frankfurt, Germany;
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30
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Gemin O, Serna P, Zamith J, Assendorp N, Fossati M, Rostaing P, Triller A, Charrier C. Unique properties of dually innervated dendritic spines in pyramidal neurons of the somatosensory cortex uncovered by 3D correlative light and electron microscopy. PLoS Biol 2021; 19:e3001375. [PMID: 34428203 PMCID: PMC8415616 DOI: 10.1371/journal.pbio.3001375] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 09/03/2021] [Accepted: 07/29/2021] [Indexed: 01/04/2023] Open
Abstract
Pyramidal neurons (PNs) are covered by thousands of dendritic spines receiving excitatory synaptic inputs. The ultrastructure of dendritic spines shapes signal compartmentalization, but ultrastructural diversity is rarely taken into account in computational models of synaptic integration. Here, we developed a 3D correlative light-electron microscopy (3D-CLEM) approach allowing the analysis of specific populations of synapses in genetically defined neuronal types in intact brain circuits. We used it to reconstruct segments of basal dendrites of layer 2/3 PNs of adult mouse somatosensory cortex and quantify spine ultrastructural diversity. We found that 10% of spines were dually innervated and 38% of inhibitory synapses localized to spines. Using our morphometric data to constrain a model of synaptic signal compartmentalization, we assessed the impact of spinous versus dendritic shaft inhibition. Our results indicate that spinous inhibition is locally more efficient than shaft inhibition and that it can decouple voltage and calcium signaling, potentially impacting synaptic plasticity.
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Affiliation(s)
- Olivier Gemin
- Institut de Biologie de l’Ecole Normale Supérieure (IBENS), CNRS, INSERM, PSL Research University, Paris, France
| | - Pablo Serna
- Institut de Biologie de l’Ecole Normale Supérieure (IBENS), CNRS, INSERM, PSL Research University, Paris, France
- Laboratoire de Physique de l’Ecole Normale Supérieure, ENS, PSL Research University, CNRS, Sorbonne Université, Université Paris-Diderot, Sorbonne Paris Cité, Paris, France
| | - Joseph Zamith
- Institut de Biologie de l’Ecole Normale Supérieure (IBENS), CNRS, INSERM, PSL Research University, Paris, France
| | - Nora Assendorp
- Institut de Biologie de l’Ecole Normale Supérieure (IBENS), CNRS, INSERM, PSL Research University, Paris, France
| | - Matteo Fossati
- Institut de Biologie de l’Ecole Normale Supérieure (IBENS), CNRS, INSERM, PSL Research University, Paris, France
| | - Philippe Rostaing
- Institut de Biologie de l’Ecole Normale Supérieure (IBENS), CNRS, INSERM, PSL Research University, Paris, France
| | - Antoine Triller
- Institut de Biologie de l’Ecole Normale Supérieure (IBENS), CNRS, INSERM, PSL Research University, Paris, France
| | - Cécile Charrier
- Institut de Biologie de l’Ecole Normale Supérieure (IBENS), CNRS, INSERM, PSL Research University, Paris, France
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31
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Villalba RM, Behnke JA, Pare JF, Smith Y. Comparative Ultrastructural Analysis of Thalamocortical Innervation of the Primary Motor Cortex and Supplementary Motor Area in Control and MPTP-Treated Parkinsonian Monkeys. Cereb Cortex 2021; 31:3408-3425. [PMID: 33676368 PMCID: PMC8599722 DOI: 10.1093/cercor/bhab020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Revised: 12/29/2020] [Accepted: 01/19/2021] [Indexed: 12/15/2022] Open
Abstract
The synaptic organization of thalamic inputs to motor cortices remains poorly understood in primates. Thus, we compared the regional and synaptic connections of vGluT2-positive thalamocortical glutamatergic terminals in the supplementary motor area (SMA) and the primary motor cortex (M1) between control and MPTP-treated parkinsonian monkeys. In controls, vGluT2-containing fibers and terminal-like profiles invaded layer II-III and Vb of M1 and SMA. A significant reduction of vGluT2 labeling was found in layer Vb, but not in layer II-III, of parkinsonian animals, suggesting a potential thalamic denervation of deep cortical layers in parkinsonism. There was a significant difference in the pattern of synaptic connectivity in layers II-III, but not in layer Vb, between M1 and SMA of control monkeys. However, this difference was abolished in parkinsonian animals. No major difference was found in the proportion of perforated versus macular post-synaptic densities at thalamocortical synapses between control and parkinsonian monkeys in both cortical regions, except for a slight increase in the prevalence of perforated axo-dendritic synapses in the SMA of parkinsonian monkeys. Our findings suggest that disruption of the thalamic innervation of M1 and SMA may underlie pathophysiological changes of the motor thalamocortical loop in the state of parkinsonism.
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Affiliation(s)
- Rosa M Villalba
- Division of Neuropharmacology and Neurological Diseases, Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA
- UDALL Center for Excellence for Parkinson’s Disease, Emory University, Atlanta, GA 30329, USA
| | - Joseph A Behnke
- Division of Neuropharmacology and Neurological Diseases, Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA
- UDALL Center for Excellence for Parkinson’s Disease, Emory University, Atlanta, GA 30329, USA
| | - Jean-Francois Pare
- Division of Neuropharmacology and Neurological Diseases, Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA
- UDALL Center for Excellence for Parkinson’s Disease, Emory University, Atlanta, GA 30329, USA
| | - Yoland Smith
- Division of Neuropharmacology and Neurological Diseases, Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA
- UDALL Center for Excellence for Parkinson’s Disease, Emory University, Atlanta, GA 30329, USA
- Department of Neurology, School of Medicine, Emory University, Atlanta, GA 30329, USA
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32
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The importance of ultrastructural analysis of memory. Brain Res Bull 2021; 173:28-36. [PMID: 33984429 DOI: 10.1016/j.brainresbull.2021.04.019] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Revised: 04/19/2021] [Accepted: 04/22/2021] [Indexed: 11/22/2022]
Abstract
Plasticity of glutamatergic synapses in the hippocampus is believed to underlie learning and memory processes. Surprisingly, very few studies report long-lasting structural changes of synapses induced by behavioral training. It remains, therefore, unclear which synaptic changes in the hippocampus contribute to memory storage. Here, we systematically compare how long-term potentiation of synaptic transmission (LTP) (a primary form of synaptic plasticity and cellular model of memory) and behavioral training affect hippocampal glutamatergic synapses at the ultrastructural level enabled by electron microscopy. The review of the literature indicates that while LTP induces growth of dendritic spines and post-synaptic densities (PSD), that represent postsynaptic part of a glutamatergic synapse, after behavioral training there is transient (< 6 h) synaptogenesis and long-lasting (> 24 h) increase in PSD volume (without a significant change of dendritic spine volume), indicating that training-induced PSD growth may reflect long-term enhancement of synaptic functions. Additionally, formation of multi-innervated spines (MIS), is associated with long-term memory in aged mice and LTP-deficient mutant mice. Since volume of PSD, as well as atypical synapses, can be reliably observed only with electron microscopy, we argue that the ultrastructural level of analysis is required to reveal synaptic changes that are associated with long-term storage of information in the brain.
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33
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Obashi K, Taraska JW, Okabe S. The role of molecular diffusion within dendritic spines in synaptic function. J Gen Physiol 2021; 153:e202012814. [PMID: 33720306 PMCID: PMC7967910 DOI: 10.1085/jgp.202012814] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Accepted: 02/16/2021] [Indexed: 12/21/2022] Open
Abstract
Spines are tiny nanoscale protrusions from dendrites of neurons. In the cortex and hippocampus, most of the excitatory postsynaptic sites reside in spines. The bulbous spine head is connected to the dendritic shaft by a thin membranous neck. Because the neck is narrow, spine heads are thought to function as biochemically independent signaling compartments. Thus, dynamic changes in the composition, distribution, mobility, conformations, and signaling properties of molecules contained within spines can account for much of the molecular basis of postsynaptic function and regulation. A major factor in controlling these changes is the diffusional properties of proteins within this small compartment. Advances in measurement techniques using fluorescence microscopy now make it possible to measure molecular diffusion within single dendritic spines directly. Here, we review the regulatory mechanisms of diffusion in spines by local intra-spine architecture and discuss their implications for neuronal signaling and synaptic plasticity.
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Affiliation(s)
- Kazuki Obashi
- Biochemistry and Biophysics Center, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD
| | - Justin W. Taraska
- Biochemistry and Biophysics Center, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD
| | - Shigeo Okabe
- Department of Cellular Neurobiology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
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34
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Zhu Y, Uytiepo M, Bushong E, Haberl M, Beutter E, Scheiwe F, Zhang W, Chang L, Luu D, Chui B, Ellisman M, Maximov A. Nanoscale 3D EM reconstructions reveal intrinsic mechanisms of structural diversity of chemical synapses. Cell Rep 2021; 35:108953. [PMID: 33826888 PMCID: PMC8354523 DOI: 10.1016/j.celrep.2021.108953] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Revised: 01/21/2021] [Accepted: 03/15/2021] [Indexed: 10/25/2022] Open
Abstract
Chemical synapses of shared cellular origins have remarkably heterogeneous structures, but how this diversity is generated is unclear. Here, we use three-dimensional (3D) electron microscopy and artificial intelligence algorithms for image processing to reconstruct functional excitatory microcircuits in the mouse hippocampus and microcircuits in which neurotransmitter signaling is permanently suppressed with genetic tools throughout the lifespan. These nanoscale analyses reveal that experience is dispensable for morphogenesis of synapses with different geometric shapes and contents of membrane organelles and that arrangement of morphologically distinct connections in local networks is stochastic. Moreover, loss of activity increases the variability in sizes of opposed pre- and postsynaptic structures without disrupting their alignments, suggesting that inherently variable weights of naive connections become progressively matched with repetitive use. These results demonstrate that mechanisms for the structural diversity of neuronal synapses are intrinsic and provide insights into how circuits essential for memory storage assemble and integrate information.
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Affiliation(s)
- Yongchuan Zhu
- Department of Neuroscience, The Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Marco Uytiepo
- Department of Neuroscience, The Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Eric Bushong
- National Center for Microscopy and Imaging Research, University of California, San Diego, CA 92037, USA; Department of Neurosciences, University of California, San Diego, School of Medicine, La Jolla, CA 92037, USA
| | - Matthias Haberl
- National Center for Microscopy and Imaging Research, University of California, San Diego, CA 92037, USA; Department of Neurosciences, University of California, San Diego, School of Medicine, La Jolla, CA 92037, USA
| | - Elizabeth Beutter
- Department of Neuroscience, The Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Frederieke Scheiwe
- Department of Neuroscience, The Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Weiheng Zhang
- Department of Neuroscience, The Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Lyanne Chang
- Department of Neuroscience, The Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Danielle Luu
- Department of Neuroscience, The Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Brandon Chui
- Department of Neuroscience, The Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Mark Ellisman
- National Center for Microscopy and Imaging Research, University of California, San Diego, CA 92037, USA; Department of Neurosciences, University of California, San Diego, School of Medicine, La Jolla, CA 92037, USA.
| | - Anton Maximov
- Department of Neuroscience, The Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, CA 92037, USA.
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35
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Miry O, Li J, Chen L. The Quest for the Hippocampal Memory Engram: From Theories to Experimental Evidence. Front Behav Neurosci 2021; 14:632019. [PMID: 33519396 PMCID: PMC7843437 DOI: 10.3389/fnbeh.2020.632019] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2020] [Accepted: 12/17/2020] [Indexed: 11/18/2022] Open
Abstract
More than a century after Richard Semon's theoretical proposal of the memory engram, technological advancements have finally enabled experimental access to engram cells and their functional contents. In this review, we summarize theories and their experimental support regarding hippocampal memory engram formation and function. Specifically, we discuss recent advances in the engram field which help to reconcile two main theories for how the hippocampus supports memory formation: The Memory Indexing and Cognitive Map theories. We also highlight the latest evidence for engram allocation mechanisms through which memories can be linked or separately encoded. Finally, we identify unanswered questions for future investigations, through which a more comprehensive understanding of memory formation and retrieval may be achieved.
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Affiliation(s)
- Omid Miry
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA, United States
| | - Jie Li
- Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA, United States
| | - Lu Chen
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA, United States.,Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA, United States
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36
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Minehart JA, Speer CM. A Picture Worth a Thousand Molecules-Integrative Technologies for Mapping Subcellular Molecular Organization and Plasticity in Developing Circuits. Front Synaptic Neurosci 2021; 12:615059. [PMID: 33469427 PMCID: PMC7813761 DOI: 10.3389/fnsyn.2020.615059] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Accepted: 12/07/2020] [Indexed: 12/23/2022] Open
Abstract
A key challenge in developmental neuroscience is identifying the local regulatory mechanisms that control neurite and synaptic refinement over large brain volumes. Innovative molecular techniques and high-resolution imaging tools are beginning to reshape our view of how local protein translation in subcellular compartments drives axonal, dendritic, and synaptic development and plasticity. Here we review recent progress in three areas of neurite and synaptic study in situ-compartment-specific transcriptomics/translatomics, targeted proteomics, and super-resolution imaging analysis of synaptic organization and development. We discuss synergies between sequencing and imaging techniques for the discovery and validation of local molecular signaling mechanisms regulating synaptic development, plasticity, and maintenance in circuits.
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Affiliation(s)
| | - Colenso M. Speer
- Department of Biology, University of Maryland, College Park, MD, United States
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37
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TSUBOI M, HIRABAYASHI Y. New insights into the regulation of synaptic transmission and plasticity by the endoplasmic reticulum and its membrane contacts. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2021; 97:559-572. [PMID: 34897182 PMCID: PMC8687855 DOI: 10.2183/pjab.97.028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/11/2021] [Accepted: 10/18/2021] [Indexed: 06/14/2023]
Abstract
Mammalian neurons are highly compartmentalized yet very large cells. To provide each compartment with its distinct properties, metabolic homeostasis and molecular composition need to be precisely coordinated in a compartment-specific manner. Despite the importance of the endoplasmic reticulum (ER) as a platform for various biochemical reactions, such as protein synthesis, protein trafficking, and intracellular calcium control, the contribution of the ER to neuronal compartment-specific functions and plasticity remains elusive. Recent advances in the development of live imaging and serial scanning electron microscopy (sSEM) analysis have revealed that the neuronal ER is a highly dynamic organelle with compartment-specific structures. sSEM studies also revealed that the ER forms contacts with other membranes, such as the mitochondria and plasma membrane, although little is known about the functions of these ER-membrane contacts. In this review, we discuss the mechanisms and physiological roles of the ER structure and ER-mitochondria contacts in synaptic transmission and plasticity, thereby highlighting a potential link between organelle ultrastructure and neuronal functions.
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Affiliation(s)
- Masafumi TSUBOI
- Graduate School of Engineering, The University of Tokyo, Tokyo, Japan
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38
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Imig C, López-Murcia FJ, Maus L, García-Plaza IH, Mortensen LS, Schwark M, Schwarze V, Angibaud J, Nägerl UV, Taschenberger H, Brose N, Cooper BH. Ultrastructural Imaging of Activity-Dependent Synaptic Membrane-Trafficking Events in Cultured Brain Slices. Neuron 2020; 108:843-860.e8. [PMID: 32991831 PMCID: PMC7736621 DOI: 10.1016/j.neuron.2020.09.004] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 07/03/2020] [Accepted: 09/01/2020] [Indexed: 12/15/2022]
Abstract
Electron microscopy can resolve synapse ultrastructure with nanometer precision, but the capture of time-resolved, activity-dependent synaptic membrane-trafficking events has remained challenging, particularly in functionally distinct synapses in a tissue context. We present a method that combines optogenetic stimulation-coupled cryofixation ("flash-and-freeze") and electron microscopy to visualize membrane trafficking events and synapse-state-specific changes in presynaptic vesicle organization with high spatiotemporal resolution in synapses of cultured mouse brain tissue. With our experimental workflow, electrophysiological and "flash-and-freeze" electron microscopy experiments can be performed under identical conditions in artificial cerebrospinal fluid alone, without the addition of external cryoprotectants, which are otherwise needed to allow adequate tissue preservation upon freezing. Using this approach, we reveal depletion of docked vesicles and resolve compensatory membrane recycling events at individual presynaptic active zones at hippocampal mossy fiber synapses upon sustained stimulation.
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Affiliation(s)
- Cordelia Imig
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany.
| | - Francisco José López-Murcia
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Lydia Maus
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany; Georg August University School of Science, Georg August University Göttingen, 37073 Göttingen, Germany
| | - Inés Hojas García-Plaza
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany; Göttingen Graduate School for Neurosciences, Biophysics, and Molecular Biosciences, 37077 Göttingen, Germany
| | - Lena Sünke Mortensen
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Manuela Schwark
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Valentin Schwarze
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Julie Angibaud
- University of Bordeaux, CNRS, Interdisciplinary Institute for Neuroscience, IINS, UMR 5297, F-33000 Bordeaux, France
| | - U Valentin Nägerl
- University of Bordeaux, CNRS, Interdisciplinary Institute for Neuroscience, IINS, UMR 5297, F-33000 Bordeaux, France
| | - Holger Taschenberger
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany; Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" University of Göttingen, 37073 Göttingen, Germany.
| | - Benjamin H Cooper
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany.
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Gürth CM, Dankovich TM, Rizzoli SO, D'Este E. Synaptic activity and strength are reflected by changes in the post-synaptic secretory pathway. Sci Rep 2020; 10:20576. [PMID: 33239744 PMCID: PMC7688657 DOI: 10.1038/s41598-020-77260-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Accepted: 11/09/2020] [Indexed: 01/13/2023] Open
Abstract
Neurons are highly asymmetric cells that span long distances and need to react promptly to local demands. Consequently, neuronal secretory pathway elements are distributed throughout neurites, specifically in post-synaptic compartments, to enable local protein synthesis and delivery. Whether and how changes in local synaptic activity correlate to post-synaptic secretory elements is still unclear. To assess this, we used STED nanoscopy and automated quantitative image analysis of post-synaptic markers of the endoplasmic reticulum, ER-Golgi intermediate compartment, trans-Golgi network, and spine apparatus. We found that the distribution of these proteins was dependent on pre-synaptic activity, measured as the amount of recycling vesicles. Moreover, their abundance correlated to both pre- and post-synaptic markers of synaptic strength. Overall, the results suggest that in small, low-activity synapses the secretory pathway components are tightly clustered in the synaptic area, presumably to enable rapid local responses, while bigger synapses utilise secretory machinery components from larger, more diffuse areas.
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Affiliation(s)
- Clara-Marie Gürth
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077, Göttingen, Germany.,Department of Optical Nanoscopy, Max Planck Institute for Medical Research, Jahnstr. 29, 69120, Heidelberg, Germany
| | - Tal M Dankovich
- Institute for Neuro- and Sensory Physiology, University Medical Center Göttingen, Humboldtallee 23, 37073, Göttingen, Germany
| | - Silvio O Rizzoli
- Institute for Neuro- and Sensory Physiology, University Medical Center Göttingen, Humboldtallee 23, 37073, Göttingen, Germany
| | - Elisa D'Este
- Optical Microscopy Facility, Max Planck Institute for Medical Research, Jahnstr. 29, 69120, Heidelberg, Germany.
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40
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Jasinska M, Woznicka O, Jasek-Gajda E, Lis GJ, Pyza E, Litwin JA. Circadian Changes of Dendritic Spine Geometry in Mouse Barrel Cortex. Front Neurosci 2020; 14:578881. [PMID: 33117123 PMCID: PMC7550732 DOI: 10.3389/fnins.2020.578881] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 08/26/2020] [Indexed: 11/13/2022] Open
Abstract
The circadian rhythmicity changes the density and shape of dendritic spines in mouse somatosensory barrel cortex, influencing their stability and maturation. In this study, we analyzed the main geometric parameters of dendritic spines reflecting the strength of synapses located on these spines under light/dark (12:12) and constant darkness conditions, in order to distinguish between endogenously regulated and light-driven parameters. Using morphological analysis of serial electron micrographs, as well as three-dimensional reconstructions, we found that the light induces elongation of single-synapse spine necks and increases in the diameter of double-synapse spine necks, increasing and decreasing the isolation of synapses from the parent dendrite, respectively. During the subjective night of constant darkness, we observed an enlargement of postsynaptic density area in inhibitory synapses and an increase in the number of polyribosomes inside double-synapse spines. The results show that both endogenous effect (circadian clock/locomotor activity) and light affect the morphological parameters of single- and double-synapse spines in the somatosensory cortex: light reduces the efficiency of excitatory synapses on single-synapse spines, increases the effect of synaptic transmission in double-synapse spines, and additionally masks the endogenous clock-driven enlargement of inhibitory synapses located on double-synapse spines. This indicates a special role of double-synapse spines and their inhibitory synapses in the regulation of synaptic transmission during both circadian and diurnal cycles in the mouse somatosensory cortex.
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Affiliation(s)
- Malgorzata Jasinska
- Department of Histology, Jagiellonian University Medical College, Krakow, Poland
| | - Olga Woznicka
- Department of Cell Biology and Imaging, Institute of Zoology and Biomedical Research, Jagiellonian University, Krakow, Poland
| | - Ewa Jasek-Gajda
- Department of Histology, Jagiellonian University Medical College, Krakow, Poland
| | - Grzegorz J Lis
- Department of Histology, Jagiellonian University Medical College, Krakow, Poland
| | - Elzbieta Pyza
- Department of Cell Biology and Imaging, Institute of Zoology and Biomedical Research, Jagiellonian University, Krakow, Poland
| | - Jan A Litwin
- Department of Histology, Jagiellonian University Medical College, Krakow, Poland
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41
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Endoplasmic reticulum visits highly active spines and prevents runaway potentiation of synapses. Nat Commun 2020; 11:5083. [PMID: 33033259 PMCID: PMC7546627 DOI: 10.1038/s41467-020-18889-5] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 09/17/2020] [Indexed: 11/25/2022] Open
Abstract
In hippocampal pyramidal cells, a small subset of dendritic spines contain endoplasmic reticulum (ER). In large spines, ER frequently forms a spine apparatus, while smaller spines contain just a single tubule of smooth ER. Here we show that the ER visits dendritic spines in a non-random manner, targeting spines during periods of high synaptic activity. When we blocked ER motility using a dominant negative approach against myosin V, spine synapses became stronger compared to controls. We were not able to further potentiate these maxed-out synapses, but long-term depression (LTD) was readily induced by low-frequency stimulation. We conclude that the brief ER visits to active spines have the important function of preventing runaway potentiation of individual spine synapses, keeping most of them at an intermediate strength level from which both long-term potentiation (LTP) and LTD are possible. In hippocampal pyramidal cells, a subset of dendritic spines contain endoplasmic reticulum (ER). Here, the authors show that ER enters dendritic spines in a non-random manner, during high synaptic activity with the function of limiting synaptic strength.
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42
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Ostrovskaya OI, Cao G, Eroglu C, Harris KM. Developmental onset of enduring long-term potentiation in mouse hippocampus. Hippocampus 2020; 30:1298-1312. [PMID: 32894631 DOI: 10.1002/hipo.23257] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Revised: 07/18/2020] [Accepted: 08/13/2020] [Indexed: 11/10/2022]
Abstract
Analysis of long-term potentiation (LTP) provides a powerful window into cellular mechanisms of learning and memory. Prior work shows late LTP (L-LTP), lasting >3 hr, occurs abruptly at postnatal day 12 (P12) in the stratum radiatum of rat hippocampal area CA1. The goal here was to determine the developmental profile of synaptic plasticity leading to L-LTP in the mouse hippocampus. Two mouse strains and two mutations known to affect synaptic plasticity were chosen: C57BL/6J and Fmr1-/y on the C57BL/6J background, and 129SVE and Hevin-/- (Sparcl1-/- ) on the 129SVE background. Like rats, hippocampal slices from all of the mice showed test pulse-induced depression early during development that was gradually resolved with maturation by 5 weeks. All the mouse strains showed a gradual progression between P10-P35 in the expression of short-term potentiation (STP), lasting ≤1 hr. In the 129SVE mice, L-LTP onset (>25% of slices) occurred by 3 weeks, reliable L-LTP (>50% slices) was achieved by 4 weeks, and Hevin-/- advanced this profile by 1 week. In the C57BL/6J mice, L-LTP onset occurred significantly later, over 3-4 weeks, and reliability was not achieved until 5 weeks. Although some of the Fmr1-/y mice showed L-LTP before 3 weeks, reliable L-LTP also was not achieved until 5 weeks. L-LTP onset was not advanced in any of the mouse genotypes by multiple bouts of theta-burst stimulation at 90 or 180 min intervals. These findings show important species differences in the onset of STP and L-LTP, which occur at the same age in rats but are sequentially acquired in mice.
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Affiliation(s)
- Olga I Ostrovskaya
- Department of Neuroscience, Center for Learning and Memory, The University of Texas at Austin, Austin, Texas, USA
| | - Guan Cao
- Department of Neuroscience, Center for Learning and Memory, The University of Texas at Austin, Austin, Texas, USA
| | - Cagla Eroglu
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina, USA.,Department of Neurobiology Regeneration Next Initiative, Duke University Medical Center, Durham, North Carolina, USA
| | - Kristen M Harris
- Department of Neuroscience, Center for Learning and Memory, The University of Texas at Austin, Austin, Texas, USA
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43
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Lottes EN, Cox DN. Homeostatic Roles of the Proteostasis Network in Dendrites. Front Cell Neurosci 2020; 14:264. [PMID: 33013325 PMCID: PMC7461941 DOI: 10.3389/fncel.2020.00264] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 07/28/2020] [Indexed: 12/13/2022] Open
Abstract
Cellular protein homeostasis, or proteostasis, is indispensable to the survival and function of all cells. Distinct from other cell types, neurons are long-lived, exhibiting architecturally complex and diverse multipolar projection morphologies that can span great distances. These properties present unique demands on proteostatic machinery to dynamically regulate the neuronal proteome in both space and time. Proteostasis is regulated by a distributed network of cellular processes, the proteostasis network (PN), which ensures precise control of protein synthesis, native conformational folding and maintenance, and protein turnover and degradation, collectively safeguarding proteome integrity both under homeostatic conditions and in the contexts of cellular stress, aging, and disease. Dendrites are equipped with distributed cellular machinery for protein synthesis and turnover, including dendritically trafficked ribosomes, chaperones, and autophagosomes. The PN can be subdivided into an adaptive network of three major functional pathways that synergistically govern protein quality control through the action of (1) protein synthesis machinery; (2) maintenance mechanisms including molecular chaperones involved in protein folding; and (3) degradative pathways (e.g., Ubiquitin-Proteasome System (UPS), endolysosomal pathway, and autophagy. Perturbations in any of the three arms of proteostasis can have dramatic effects on neurons, especially on their dendrites, which require tightly controlled homeostasis for proper development and maintenance. Moreover, the critical importance of the PN as a cell surveillance system against protein dyshomeostasis has been highlighted by extensive work demonstrating that the aggregation and/or failure to clear aggregated proteins figures centrally in many neurological disorders. While these studies demonstrate the relevance of derangements in proteostasis to human neurological disease, here we mainly review recent literature on homeostatic developmental roles the PN machinery plays in the establishment, maintenance, and plasticity of stable and dynamic dendritic arbors. Beyond basic housekeeping functions, we consider roles of PN machinery in protein quality control mechanisms linked to dendritic plasticity (e.g., dendritic spine remodeling during LTP); cell-type specificity; dendritic morphogenesis; and dendritic pruning.
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Affiliation(s)
- Erin N Lottes
- Neuroscience Institute, Georgia State University, Atlanta, GA, United States
| | - Daniel N Cox
- Neuroscience Institute, Georgia State University, Atlanta, GA, United States
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44
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Harris KM. Structural LTP: from synaptogenesis to regulated synapse enlargement and clustering. Curr Opin Neurobiol 2020; 63:189-197. [PMID: 32659458 DOI: 10.1016/j.conb.2020.04.009] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Accepted: 04/30/2020] [Indexed: 02/09/2023]
Abstract
Nature teaches us that form precedes function, yet structure and function are intertwined. Such is the case with synapse structure, function, and plasticity underlying learning, especially in the hippocampus, a crucial brain region for memory formation. As the hippocampus matures, enduring changes in synapse structure produced by long-term potentiation (LTP) shift from synaptogenesis to synapse enlargement that is homeostatically balanced by stalled spine outgrowth and local spine clustering. Production of LTP leads to silent spine outgrowth at P15, and silent synapse enlargement in adult hippocampus at 2hours, but not at 5 or 30min following induction. Here we consider structural LTP in the context of developmental stage and variation in the availability of local resources of endosomes, smooth endoplasmic reticulum and polyribosomes. The emerging evidence supports a need for more nuanced analysis of synaptic plasticity in the context of subcellular resource availability and developmental stage.
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45
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Capillary-Based and Stokes-Based Trapping of Serial Sections for Scalable 3D-EM Connectomics. eNeuro 2020; 7:ENEURO.0328-19.2019. [PMID: 32094293 PMCID: PMC7174874 DOI: 10.1523/eneuro.0328-19.2019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Revised: 12/17/2019] [Accepted: 12/18/2019] [Indexed: 11/23/2022] Open
Abstract
Serial section electron microscopy (ssEM), a technique where volumes of tissue can be anatomically reconstructed by imaging consecutive tissue slices, has proven to be a powerful tool for the investigation of brain anatomy. Between the process of cutting the slices, or “sections,” and imaging them, however, handling 10°−106 delicate sections remains a bottleneck in ssEM, especially for batches in the “mesoscale” regime, i.e., 102–103 sections. We present a tissue section handling device that transports and positions sections, accurately and repeatability, for automated, robotic section pick-up and placement onto an imaging substrate. The device interfaces with a conventional ultramicrotomy diamond knife, accomplishing in-line, exact-constraint trapping of sections with 100-μm repeatability. An associated mathematical model includes capillary-based and Stokes-based forces, accurately describing observed behavior and fundamentally extends the modeling of water-air interface forces. Using the device, we demonstrate and describe the limits of reliable handling of hundreds of slices onto a variety of electron and light microscopy substrates without significant defects (n = 8 datasets composed of 126 serial sections in an automated fashion with an average loss rate and throughput of 0.50% and 63 s/section, respectively. In total, this work represents an automated mesoscale serial sectioning system for scalable 3D-EM connectomics.
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46
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Sanculi D, Pannoni KE, Bushong EA, Crump M, Sung M, Popat V, Zaher C, Hicks E, Song A, Mofakham N, Li P, Antzoulatos EG, Fioravante D, Ellisman MH, DeBello WM. Toric Spines at a Site of Learning. eNeuro 2020; 7:ENEURO.0197-19.2019. [PMID: 31822521 PMCID: PMC6944481 DOI: 10.1523/eneuro.0197-19.2019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Revised: 10/23/2019] [Accepted: 11/02/2019] [Indexed: 11/21/2022] Open
Abstract
We discovered a new type of dendritic spine. It is found on space-specific neurons in the barn owl inferior colliculus, a site of experience-dependent plasticity. Connectomic analysis revealed dendritic protrusions of unusual morphology including topological holes, hence termed "toric" spines (n = 76). More significantly, presynaptic terminals converging onto individual toric spines displayed numerous active zones (up to 49) derived from multiple axons (up to 11) with incoming trajectories distributed widely throughout 3D space. This arrangement is suited to integrate input sources. Dense reconstruction of two toric spines revealed that they were unconnected with the majority (∼84%) of intertwined axons, implying a high capacity for information storage. We developed an ex vivo slice preparation and provide the first published data on space-specific neuron intrinsic properties, including cellular subtypes with and without toric-like spines. We propose that toric spines are a cellular locus of sensory integration and behavioral learning.
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Affiliation(s)
- Daniel Sanculi
- Center for Neuroscience, University of California, Davis, CA 95618
| | | | - Eric A Bushong
- National Center for Molecular Imaging Research, University of California, La Jolla, CA 92093
| | - Michael Crump
- Center for Neuroscience, University of California, Davis, CA 95618
| | - Michelle Sung
- Center for Neuroscience, University of California, Davis, CA 95618
| | - Vyoma Popat
- Center for Neuroscience, University of California, Davis, CA 95618
| | - Camilia Zaher
- Center for Neuroscience, University of California, Davis, CA 95618
| | - Emma Hicks
- Center for Neuroscience, University of California, Davis, CA 95618
| | - Ashley Song
- Center for Neuroscience, University of California, Davis, CA 95618
| | - Nikan Mofakham
- Center for Neuroscience, University of California, Davis, CA 95618
| | - Peining Li
- Center for Neuroscience, University of California, Davis, CA 95618
| | | | | | - Mark H Ellisman
- National Center for Molecular Imaging Research, University of California, La Jolla, CA 92093
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47
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Affiliation(s)
- Kristen M Harris
- Department of Neuroscience, Center for Learning and Memory, University of Texas at Austin, Austin, Texas 78712
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48
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Kastellakis G, Poirazi P. Synaptic Clustering and Memory Formation. Front Mol Neurosci 2019; 12:300. [PMID: 31866824 PMCID: PMC6908852 DOI: 10.3389/fnmol.2019.00300] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Accepted: 11/25/2019] [Indexed: 01/12/2023] Open
Abstract
In the study of memory engrams, synaptic memory allocation is a newly emerged theme that focuses on how specific synapses are engaged in the storage of a given memory. Cumulating evidence from imaging and molecular experiments indicates that the recruitment of synapses that participate in the encoding and expression of memory is neither random nor uniform. A hallmark observation is the emergence of groups of synapses that share similar response properties and/or similar input properties and are located within a stretch of a dendritic branch. This grouping of synapses has been termed "synapse clustering" and has been shown to emerge in many different memory-related paradigms, as well as in in vitro studies. The clustering of synapses may emerge from synapses receiving similar input, or via many processes which allow for cross-talk between nearby synapses within a dendritic branch, leading to cooperative plasticity. Clustered synapses can act in concert to maximally exploit the nonlinear integration potential of the dendritic branches in which they reside. Their main contribution is to facilitate the induction of dendritic spikes and dendritic plateau potentials, which provide advanced computational and memory-related capabilities to dendrites and single neurons. This review focuses on recent evidence which investigates the role of synapse clustering in dendritic integration, sensory perception, learning, and memory as well as brain dysfunction. We also discuss recent theoretical work which explores the computational advantages provided by synapse clustering, leading to novel and revised theories of memory. As an eminent phenomenon during memory allocation, synapse clustering both shapes memory engrams and is also shaped by the parallel plasticity mechanisms upon which it relies.
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Affiliation(s)
| | - Panayiota Poirazi
- Institute of Molecular Biology and Biotechnology (IMBB), Foundation for Research and Technology Hellas (FORTH), Heraklion, Greece
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49
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Jasinska M, Jasek-Gajda E, Woznicka O, Lis GJ, Pyza E, Litwin JA. Circadian clock regulates the shape and content of dendritic spines in mouse barrel cortex. PLoS One 2019; 14:e0225394. [PMID: 31730670 PMCID: PMC6857954 DOI: 10.1371/journal.pone.0225394] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Accepted: 11/02/2019] [Indexed: 01/01/2023] Open
Abstract
Circadian rhythmicity affects neuronal activity induced changes in the density of synaptic contacts and dendritic spines, the most common location of synapses, in mouse somatosensory cortex. In the present study we analyzed morphology of single- and double-synapse spines under light/dark (12:12) and constant darkness conditions. Using serial electron micrographs we examined the shape of spines (stubby, thin, mushroom) and their content (smooth endoplasmic reticulum, spine apparatus), because these features are related to the maturation and stabilization of spines. We observed significant diurnal and circadian changes in the shape of spines that are differentially regulated: single-synapse spines remain under circadian clock regulation, while changes of double-synapse spines are driven by light. The thin and mushroom single-synapse spines, regardless of their content, are more stable comparing with the stubby single-synapse spines that show the greatest diversity. All types of double-synapse spines demonstrate a similar level of stability. In light/dark regime, formation of new mushroom single-synapse spines occurs, while under constant darkness new stubby single-synapse spines are formed. There are no shape preferences for new double-synapse spines. Diurnal and circadian alterations also concern spine content: both light exposure and the clock influence translocation of smooth endoplasmic reticulum from dendritic shaft to the spine. The increasing number of mushroom single-synapse spines and the presence of only those mushroom double-synapse spines that contain spine apparatus in the light phase indicates that the exposure to light, a stress factor for nocturnal animals, promotes enlargement and maturation of spines to increase synaptic strength and to enhance the effectiveness of neurotransmission.
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Affiliation(s)
- Malgorzata Jasinska
- Department of Histology, Jagiellonian University Medical College, Krakow, Poland
- * E-mail:
| | - Ewa Jasek-Gajda
- Department of Histology, Jagiellonian University Medical College, Krakow, Poland
| | - Olga Woznicka
- Department of Cell Biology and Imaging, Institute of Zoology and Biomedical Research, Jagiellonian University, Krakow, Poland
| | - Grzegorz J. Lis
- Department of Histology, Jagiellonian University Medical College, Krakow, Poland
| | - Elzbieta Pyza
- Department of Cell Biology and Imaging, Institute of Zoology and Biomedical Research, Jagiellonian University, Krakow, Poland
| | - Jan A. Litwin
- Department of Histology, Jagiellonian University Medical College, Krakow, Poland
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50
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Kulik YD, Watson DJ, Cao G, Kuwajima M, Harris KM. Structural plasticity of dendritic secretory compartments during LTP-induced synaptogenesis. eLife 2019; 8:e46356. [PMID: 31433297 PMCID: PMC6728136 DOI: 10.7554/elife.46356] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2019] [Accepted: 08/20/2019] [Indexed: 12/30/2022] Open
Abstract
Long-term potentiation (LTP), an increase in synaptic efficacy following high-frequency stimulation, is widely considered a mechanism of learning. LTP involves local remodeling of dendritic spines and synapses. Smooth endoplasmic reticulum (SER) and endosomal compartments could provide local stores of membrane and proteins, bypassing the distant Golgi apparatus. To test this hypothesis, effects of LTP were compared to control stimulation in rat hippocampal area CA1 at postnatal day 15 (P15). By two hours, small spines lacking SER increased after LTP, whereas large spines did not change in frequency, size, or SER content. Total SER volume decreased after LTP consistent with transfer of membrane to the added spines. Shaft SER remained more abundant in spiny than aspiny dendritic regions, apparently supporting the added spines. Recycling endosomes were elevated specifically in small spines after LTP. These findings suggest local secretory trafficking contributes to LTP-induced synaptogenesis and primes the new spines for future plasticity.
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Affiliation(s)
- Yelena D Kulik
- Center for Learning and Memory, Department of NeuroscienceThe University of Texas at AustinAustinUnited States
| | - Deborah J Watson
- Center for Learning and Memory, Department of NeuroscienceThe University of Texas at AustinAustinUnited States
| | - Guan Cao
- Center for Learning and Memory, Department of NeuroscienceThe University of Texas at AustinAustinUnited States
| | - Masaaki Kuwajima
- Center for Learning and Memory, Department of NeuroscienceThe University of Texas at AustinAustinUnited States
| | - Kristen M Harris
- Center for Learning and Memory, Department of NeuroscienceThe University of Texas at AustinAustinUnited States
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