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Gao Y, Shonai D, Trn M, Zhao J, Soderblom EJ, Garcia-Moreno SA, Gersbach CA, Wetsel WC, Dawson G, Velmeshev D, Jiang YH, Sloofman LG, Buxbaum JD, Soderling SH. Proximity analysis of native proteomes reveals phenotypic modifiers in a mouse model of autism and related neurodevelopmental conditions. Nat Commun 2024; 15:6801. [PMID: 39122707 PMCID: PMC11316102 DOI: 10.1038/s41467-024-51037-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: 02/20/2024] [Accepted: 07/23/2024] [Indexed: 08/12/2024] Open
Abstract
One of the main drivers of autism spectrum disorder is risk alleles within hundreds of genes, which may interact within shared but unknown protein complexes. Here we develop a scalable genome-editing-mediated approach to target 14 high-confidence autism risk genes within the mouse brain for proximity-based endogenous proteomics, achieving the identification of high-specificity spatial proteomes. The resulting native proximity proteomes are enriched for human genes dysregulated in the brain of autistic individuals, and reveal proximity interactions between proteins from high-confidence risk genes with those of lower-confidence that may provide new avenues to prioritize genetic risk. Importantly, the datasets are enriched for shared cellular functions and genetic interactions that may underlie the condition. We test this notion by spatial proteomics and CRISPR-based regulation of expression in two autism models, demonstrating functional interactions that modulate mechanisms of their dysregulation. Together, these results reveal native proteome networks in vivo relevant to autism, providing new inroads for understanding and manipulating the cellular drivers underpinning its etiology.
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Affiliation(s)
- Yudong Gao
- Department of Cell Biology, Duke University School of Medicine, Durham, NC, USA
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Daichi Shonai
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC, USA
| | - Matthew Trn
- Department of Cell Biology, Duke University School of Medicine, Durham, NC, USA
| | - Jieqing Zhao
- Department of Biology, Duke University, Durham, NC, USA
| | - Erik J Soderblom
- Department of Cell Biology, Duke University School of Medicine, Durham, NC, USA
- Proteomics and Metabolomics Shared Resource, Duke University School of Medicine, Durham, NC, USA
| | | | - Charles A Gersbach
- Department of Cell Biology, Duke University School of Medicine, Durham, NC, USA
- Department of Biomedical Engineering, Duke University, Durham, NC, USA
- Center for Advanced Genomic Technologies, Duke University, Durham, NC, USA
- Department of Surgery, Duke University Medical Center, Durham, NC, USA
| | - William C Wetsel
- Department of Cell Biology, Duke University School of Medicine, Durham, NC, USA
- Department of Psychiatry and Behavioral Sciences, Duke University School of Medicine, Durham, NC, USA
- Department of Neurobiology, Duke University School of Medicine, Durham, NC, USA
- Mouse Behavioral and Neuroendocrine Analysis Core Facility, Duke University School of Medicine, Durham, NC, USA
| | - Geraldine Dawson
- Department of Psychiatry and Behavioral Sciences, Duke University School of Medicine, Durham, NC, USA
| | - Dmitry Velmeshev
- Department of Neurobiology, Duke University School of Medicine, Durham, NC, USA
| | - Yong-Hui Jiang
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut, USA
- Department of Neuroscience, Yale University School of Medicine, New Haven, Connecticut, USA
- Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Laura G Sloofman
- Seaver Autism Center for Research and Treatment, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Joseph D Buxbaum
- Seaver Autism Center for Research and Treatment, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- The Mindich Child Health and Development Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Scott H Soderling
- Department of Cell Biology, Duke University School of Medicine, Durham, NC, USA.
- Department of Neurobiology, Duke University School of Medicine, Durham, NC, USA.
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Wang X, Wang Y, Cai Q, Zhang M. AIDA-1/ANKS1B Binds to the SynGAP Family RasGAPs with High Affinity and Specificity. J Mol Biol 2024; 436:168608. [PMID: 38759928 DOI: 10.1016/j.jmb.2024.168608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Revised: 05/04/2024] [Accepted: 05/08/2024] [Indexed: 05/19/2024]
Abstract
AIDA-1, encoded by ANKS1B, is an abundant postsynaptic scaffold protein essential for brain development. Mutations of ANKS1B are closely associated with various psychiatric disorders. However, very little is known regarding the molecular mechanisms underlying AIDA-1's involvements under physiological and pathophysiological conditions. Here, we discovered an interaction between AIDA-1 and the SynGAP family Ras-GTPase activating protein (GAP) via affinity purification using AIDA-1d as the bait. Biochemical studies showed that the PTB domain of AIDA-1 binds to an extended NPx[F/Y]-motif of the SynGAP family proteins with high affinities. The high-resolution crystal structure of AIDA-1 PTB domain in complex with the SynGAP NPxF-motif revealed the molecular mechanism governing the specific interaction between AIDA-1 and SynGAP. Our study not only explains why patients with ANKS1B or SYNGAP1 mutations share overlapping clinical phenotypes, but also allows identification of new AIDA-1 binding targets such as Ras and Rab interactors.
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Affiliation(s)
- Xueqian Wang
- Biomedical Research Institute, Shenzhen Peking University-The Hong Kong University of Science and Technology Medical Center, Shenzhen 518036, China.
| | - Yu Wang
- Division of Life Science, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China; School of Life Sciences, Southern University of Science and Technology, Shenzhen 518055, China
| | - Qixu Cai
- State Key Laboratory of Vaccines for Infectious Diseases, School of Public Health, Xiamen University, Xiamen, Fujian, China
| | - Mingjie Zhang
- Greater Bay Biomedical Innocenter, Shenzhen Bay Laboratory, Shenzhen 518036, China; School of Life Sciences, Southern University of Science and Technology, Shenzhen 518055, China.
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3
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Araki Y, Rajkovich KE, Gerber EE, Gamache TR, Johnson RC, Tran THN, Liu B, Zhu Q, Hong I, Kirkwood A, Huganir R. SynGAP regulates synaptic plasticity and cognition independently of its catalytic activity. Science 2024; 383:eadk1291. [PMID: 38422154 PMCID: PMC11188940 DOI: 10.1126/science.adk1291] [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: 08/04/2023] [Accepted: 12/28/2023] [Indexed: 03/02/2024]
Abstract
SynGAP is an abundant synaptic GTPase-activating protein (GAP) critical for synaptic plasticity, learning, memory, and cognition. Mutations in SYNGAP1 in humans result in intellectual disability, autistic-like behaviors, and epilepsy. Heterozygous Syngap1-knockout mice display deficits in synaptic plasticity, learning, and memory and exhibit seizures. It is unclear whether SynGAP imparts structural properties at synapses independently of its GAP activity. Here, we report that inactivating mutations within the GAP domain do not inhibit synaptic plasticity or cause behavioral deficits. Instead, SynGAP modulates synaptic strength by physically competing with the AMPA-receptor-TARP excitatory receptor complex in the formation of molecular condensates with synaptic scaffolding proteins. These results have major implications for developing therapeutic treatments for SYNGAP1-related neurodevelopmental disorders.
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Affiliation(s)
| | | | | | | | - Richard C. Johnson
- Department of Neuroscience, Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Thanh Hai N. Tran
- Department of Neuroscience, Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Bian Liu
- Department of Neuroscience, Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Qianwen Zhu
- Department of Neuroscience, Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Ingie Hong
- Department of Neuroscience, Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Alfredo Kirkwood
- Department of Neuroscience, Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Richard Huganir
- Department of Neuroscience, Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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4
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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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5
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Araki Y, Gerber EE, Rajkovich KE, Hong I, Johnson RC, Lee HK, Kirkwood A, Huganir RL. Mouse models of SYNGAP1-related intellectual disability. Proc Natl Acad Sci U S A 2023; 120:e2308891120. [PMID: 37669379 PMCID: PMC10500186 DOI: 10.1073/pnas.2308891120] [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: 05/27/2023] [Accepted: 07/28/2023] [Indexed: 09/07/2023] Open
Abstract
SYNGAP1 is a Ras-GTPase-activating protein highly enriched at excitatory synapses in the brain. De novo loss-of-function mutations in SYNGAP1 are a major cause of genetically defined neurodevelopmental disorders (NDDs). These mutations are highly penetrant and cause SYNGAP1-related intellectual disability (SRID), an NDD characterized by cognitive impairment, social deficits, early-onset seizures, and sleep disturbances. Studies in rodent neurons have shown that Syngap1 regulates developing excitatory synapse structure and function, and heterozygous Syngap1 knockout mice have deficits in synaptic plasticity, learning, and memory and have seizures. However, how specific SYNGAP1 mutations found in humans lead to disease has not been investigated in vivo. To explore this, we utilized the CRISPR-Cas9 system to generate knock-in mouse models with two distinct known causal variants of SRID: one with a frameshift mutation leading to a premature stop codon, SYNGAP1; L813RfsX22, and a second with a single-nucleotide mutation in an intron that creates a cryptic splice acceptor site leading to premature stop codon, SYNGAP1; c.3583-9G>A. While reduction in Syngap1 mRNA varies from 30 to 50% depending on the specific mutation, both models show ~50% reduction in Syngap1 protein, have deficits in synaptic plasticity, and recapitulate key features of SRID including hyperactivity and impaired working memory. These data suggest that half the amount of SYNGAP1 protein is key to the pathogenesis of SRID. These results provide a resource to study SRID and establish a framework for the development of therapeutic strategies for this disorder.
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Affiliation(s)
- Yoichi Araki
- Department of Neuroscience, Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine, Baltimore, MD21205
| | - Elizabeth E. Gerber
- Department of Neuroscience, Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine, Baltimore, MD21205
| | - Kacey E. Rajkovich
- Department of Neuroscience, Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine, Baltimore, MD21205
| | - Ingie Hong
- Department of Neuroscience, Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine, Baltimore, MD21205
| | - Richard C. Johnson
- Department of Neuroscience, Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine, Baltimore, MD21205
| | - Hey-Kyoung Lee
- Department of Neuroscience, Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine, Baltimore, MD21205
| | - Alfredo Kirkwood
- Department of Neuroscience, Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine, Baltimore, MD21205
| | - Richard L. Huganir
- Department of Neuroscience, Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine, Baltimore, MD21205
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6
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Araki Y, Gerber EE, Rajkovich KE, Hong I, Johnson RC, Lee HK, Kirkwood A, Huganir RL. Mouse models of SYNGAP1 -related intellectual disability. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.25.542312. [PMID: 37293116 PMCID: PMC10245951 DOI: 10.1101/2023.05.25.542312] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
SYNGAP1 is a Ras-GTPase activating protein highly enriched at excitatory synapses in the brain. De novo loss-of-function mutations in SYNGAP1 are a major cause of genetically defined neurodevelopmental disorders (NDD). These mutations are highly penetrant and cause SYNGAP1 -related intellectual disability (SRID), a NDD characterized by cognitive impairment, social deficits, early-onset seizures, and sleep disturbances (1-5). Studies in rodent neurons have shown that Syngap1 regulates developing excitatory synapse structure and function (6-11), and heterozygous Syngap1 knockout mice have deficits in synaptic plasticity, learning and memory, and have seizures (9, 12-14). However, how specific SYNGAP1 mutations found in humans lead to disease has not been investigated in vivo. To explore this, we utilized the CRISPR-Cas9 system to generate knock-in mouse models with two distinct known causal variants of SRID: one with a frameshift mutation leading to a premature stop codon, SYNGAP1; L813RfsX22, and a second with a single-nucleotide mutation in an intron that creates a cryptic splice acceptor site leading to premature stop codon, SYNGAP1; c.3583-9G>A . While reduction in Syngap1 mRNA varies from 30-50% depending on the specific mutation, both models show ∼50% reduction in Syngap1 protein, have deficits in synaptic plasticity, and recapitulate key features of SRID including hyperactivity and impaired working memory. These data suggest that half the amount of SYNGAP1 protein is key to the pathogenesis of SRID. These results provide a resource to study SRID and establish a framework for the development of therapeutic strategies for this disorder. Significance Statement SYNGAP1 is a protein enriched at excitatory synapses in the brain that is an important regulator of synapse structure and function. SYNGAP1 mutations cause SYNGAP1 -related intellectual disability (SRID), a neurodevelopmental disorder with cognitive impairment, social deficits, seizures, and sleep disturbances. To explore how SYNGAP1 mutations found in humans lead to disease, we generated the first knock-in mouse models with causal SRID variants: one with a frameshift mutation and a second with an intronic mutation that creates a cryptic splice acceptor site. Both models show decreased Syngap1 mRNA and Syngap1 protein and recapitulate key features of SRID including hyperactivity and impaired working memory. These results provide a resource to study SRID and establish a framework for the development of therapeutic strategies. Highlights Two mouse models with SYNGAP1 -related intellectual disability (SRID) mutations found in humans were generated: one with a frameshift mutation that results in a premature stop codon and the other with an intronic mutation resulting in a cryptic splice acceptor site and premature stop codon. Both SRID mouse models show 35∼50% reduction in mRNA and ∼50% reduction in Syngap1 protein.Both SRID mouse models display deficits in synaptic plasticity and behavioral phenotypes found in people. RNA-seq confirmed cryptic splice acceptor activity in one SRID mouse model and revealed broad transcriptional changes also identified in Syngap1 +/- mice. Novel SRID mouse models generated here provide a resource and establish a framework for development of future therapeutic intervention.
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Affiliation(s)
- Yoichi Araki
- Department of Neuroscience, Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine
| | - Elizabeth E Gerber
- Department of Neuroscience, Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine
| | - Kacey E Rajkovich
- Department of Neuroscience, Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine
| | - Ingie Hong
- Department of Neuroscience, Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine
| | - Richard C Johnson
- Department of Neuroscience, Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine
| | - Hey-Kyoung Lee
- Department of Neuroscience, Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine
| | - Alfredo Kirkwood
- Department of Neuroscience, Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine
| | - Richard L Huganir
- Department of Neuroscience, Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine
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7
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Zeng X, Chen Y, Yu X, Che Y, Chen H, Yi Z, Qin J, Zhong J. Novel variants of SYNGAP1 associated epileptic encephalopathy: two cases report and literature review. ACTA EPILEPTOLOGICA 2023. [DOI: 10.1186/s42494-022-00114-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2023] Open
Abstract
Abstract
Background
SYNGAP1 is a significant genetic risk factor for global developmental delay, autism spectrum disorder, and epileptic encephalopathy. De novo loss-of-function variants in this gene cause a neurodevelopmental disorder, for example, early-onset and drug-refractory seizures. We report two children with global developmental delay and epileptic encephalopathy, which are caused by SYNGAP1 gene novel mutations, and drug treatment is effective.
Case presentation
We report a boy and a girl presented with global developmental delay when they were young babies; as they grew up, cognitive impairment and social-communication disorder became more and more prominent; unfortunately, the patients developed into various seizure types, including eyelid myoclonia, myoclonic and absences when the boy was 1 year 8 mouths old and the girl was 3 years old. The two patients were found two previously unknown mutations by high throughput sequencing [c.3271_ c.3272insT; (p.L1091L fs*62), c.2515A > T (p.K839*)] in exon 15 of the SYNGAP in the proband. Sanger sequencing confirmed the heterozygous nature, and neither of their parents carried the same mutation. The girl treated with valproic acid and prednisone became seizure-free, and valproic acid and levetiracetam combined with clonazepam were influential in the other.
Conclusions
The global developmental delay and epileptic encephalopathy of the children were probably due to the pathogenic mutation of the SYNGAP1 gene, and prednisone and clonazepam may be effective in achieving seizure-free.
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8
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Petralia RS, Wang YX. Review of Post-embedding Immunogold Methods for the Study of Neuronal Structures. Front Neuroanat 2021; 15:763427. [PMID: 34720893 PMCID: PMC8551803 DOI: 10.3389/fnana.2021.763427] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Accepted: 09/28/2021] [Indexed: 01/03/2023] Open
Abstract
The post-embedding immunogold (PI) technique for immunolabeling of neuronal tissues utilizing standard thin-section transmission electron microscopy (TEM) continues to be a prime method for understanding the functional localization of key proteins in neuronal function. Its main advantages over other immunolabeling methods for thin-section TEM are (1) fairly accurate and quantifiable localization of proteins in cells; (2) double-labeling of sections using two gold particle sizes; and (3) the ability to perform multiple labeling for different proteins by using adjacent sections. Here we first review in detail a common method for PI of neuronal tissues. This method has two major parts. First, we describe the freeze-substitution embedding method: cryoprotected tissue is frozen in liquid propane via plunge-freezing, and is placed in a freeze-substitution instrument in which the tissue is embedded in Lowicryl at low temperatures. We highlight important aspects of freeze-substitution embedding. Then we outline how thin sections of embedded tissue on grids are labeled with a primary antibody and a secondary gold particle-conjugated antibody, and the particular problems encountered in TEM of PI-labeled sections. In the Discussion, we compare our method both to earlier PI methods and to more recent PI methods used by other laboratories. We also compare TEM immunolabeling using PI vs. various pre-embedding immunolabeling methods, especially relating to neuronal tissue.
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Affiliation(s)
- Ronald S. Petralia
- Advanced Imaging Core, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, United States
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9
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Tao-Cheng JH, Crocker V, Moreira SL, Azzam R. Optimization of protocols for pre-embedding immunogold electron microscopy of neurons in cell cultures and brains. Mol Brain 2021; 14:86. [PMID: 34082785 PMCID: PMC8173732 DOI: 10.1186/s13041-021-00799-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Accepted: 05/27/2021] [Indexed: 02/08/2023] Open
Abstract
Immunogold labeling allows localization of proteins at the electron microscopy (EM) level of resolution, and quantification of signals. The present paper summarizes methodological issues and experiences gained from studies on the distribution of synaptic and other neuron-specific proteins in cell cultures and brain tissues via a pre-embedding method. An optimal protocol includes careful determination of a fixation condition for any particular antibody, a well-planned tissue processing procedure, and a strict evaluation of the credibility of the labeling. Here, tips and caveats on different steps of the sample preparation protocol are illustrated with examples. A good starting condition for EM-compatible fixation and permeabilization is 4% paraformaldehyde in PBS for 30 min at room temperature, followed by 30 min incubation with 0.1% saponin. An optimal condition can then be readjusted for each particular antibody. Each lot of the secondary antibody (conjugated with a 1.4 nm small gold particle) needs to be evaluated against known standards for labeling efficiency. Silver enhancement is required to make the small gold visible, and quality of the silver-enhanced signals can be affected by subsequent steps of osmium tetroxide treatment, uranyl acetate en bloc staining, and by detergent or ethanol used to clean the diamond knife for cutting thin sections. Most importantly, verification of signals requires understanding of the protein of interest in order to validate for correct localization of antibodies at expected epitopes on particular organelles, and quantification of signals needs to take into consideration the penetration gradient of reagents and clumping of secondary antibodies.
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Affiliation(s)
- Jung-Hwa Tao-Cheng
- NINDS Electron Microscopy Facility, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, 20892, USA.
| | - Virginia Crocker
- NINDS Electron Microscopy Facility, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Sandra Lara Moreira
- NINDS Electron Microscopy Facility, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Rita Azzam
- NINDS Electron Microscopy Facility, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, 20892, USA
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10
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Multi-parametric analysis of 57 SYNGAP1 variants reveal impacts on GTPase signaling, localization, and protein stability. Am J Hum Genet 2021; 108:148-162. [PMID: 33308442 DOI: 10.1016/j.ajhg.2020.11.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 11/16/2020] [Indexed: 11/20/2022] Open
Abstract
SYNGAP1 is a neuronal Ras and Rap GTPase-activating protein with important roles in regulating excitatory synaptic plasticity. While many SYNGAP1 missense and nonsense mutations have been associated with intellectual disability, epilepsy, schizophrenia, and autism spectrum disorder (ASD), whether and how they contribute to individual disease phenotypes is often unknown. Here, we characterize 57 variants in seven assays that examine multiple aspects of SYNGAP1 function. Specifically, we used multiplex phospho-flow cytometry to measure variant impact on protein stability, pERK, pGSK3β, pp38, pCREB, and high-content imaging to examine subcellular localization. We find variants ranging from complete loss-of-function (LoF) to wild-type (WT)-like in their regulation of pERK and pGSK3β, while all variants retain at least partial ability to dephosphorylate pCREB. Interestingly, our assays reveal that a larger proportion of variants located within the disordered domain of unknown function (DUF) comprising the C-terminal half of SYNGAP1 exhibited higher LoF, compared to variants within the better studied catalytic domain. Moreover, we find protein instability to be a major contributor to dysfunction for only two missense variants, both located within the catalytic domain. Using high-content imaging, we find variants located within the C2 domain known to mediate membrane lipid interactions exhibit significantly larger cytoplasmic speckles than WT SYNGAP1. Moreover, this subcellular phenotype shows both correlation with altered catalytic activity and unique deviation from signaling assay results, highlighting multiple independent molecular mechanisms underlying variant dysfunction. Our multidimensional dataset allows clustering of variants based on functional phenotypes and provides high-confidence, multi-functional measures for making pathogenicity predictions.
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11
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Identification of an individual with a SYGNAP1 pathogenic mutation in India. Mol Biol Rep 2020; 47:9225-9234. [PMID: 33090308 DOI: 10.1007/s11033-020-05915-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Accepted: 10/10/2020] [Indexed: 10/23/2022]
Abstract
Exome sequencing is a prominent tool to identify novel and deleterious mutations which could be non-sense, frameshift, and canonical splice-site mutations in a specific gene. De novo mutations in SYNGAP1, which codes for synaptic RAS-GTPase activating the protein, causes Intellectual disability (ID) and Autism Spectrum Disorder (ASD). SYNGAP1 related ASD/ID is one of the rare diseases that are detrimental to the healthy neuronal developmental and disrupts the global development of a child. We report the first SYNGAP1 heterozygous patient from Indian cohort. We report a case of a child of 2-year old with global developmental delay, microcephaly subtle dysmorphism, absence seizures, disrupted sleep, delay in learning a language, and eating problems. Upon further validation, the child has a few traits of ASD. Here, based on focused exome sequencing, we report a de novo heterozygous mutation in SYNGAP1 exon 11 with c. 1861 C > T (p.arg621ter). Currently, the child is on Atorvastatin, a RAS inhibitor, already available in the market for the treatment of hypercholesterolemia and has shown considerable improvement in global behaviour and cognitive development. The long-term follow up of the child's development would contribute to the already existing knowledge of the developmental trajectory in individuals with SYNGAP1 heterozygous mutation. In this report, we discuss the finding of a novel mutation in one of the genes, SYNGAP1, implicated in ASD/ID. Besides, we discuss the current treatment prescribed to the patient and the progress of global developmental of the child.
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12
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Gou G, Roca-Fernandez A, Kilinc M, Serrano E, Reig-Viader R, Araki Y, Huganir RL, de Quintana-Schmidt C, Rumbaugh G, Bayés À. SynGAP splice variants display heterogeneous spatio-temporal expression and subcellular distribution in the developing mammalian brain. J Neurochem 2020; 154:618-634. [PMID: 32068252 PMCID: PMC7754318 DOI: 10.1111/jnc.14988] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 02/04/2020] [Accepted: 02/17/2020] [Indexed: 11/28/2022]
Abstract
The SynGAP protein is a major regulator of synapse biology and neural circuit function. Genetic variants linked to epilepsy and intellectual disability disrupt synaptic function and neural excitability. SynGAP has been involved in multiple signaling pathways and can regulate small GTPases with very different roles. Yet, the molecular bases behind this pleiotropy are poorly understood. We hypothesize that different SynGAP isoforms will mediate different sets of functions and that deciphering their spatio-temporal expression and subcellular localization will accelerate understanding their multiple functions. Using isoform-specific antibodies recognizing SynGAP in mouse and human samples we found distinctive developmental expression patterns for all SynGAP isoforms in five mouse brain areas. Particularly noticeable was the delayed expression of SynGAP-α1 isoforms, which directly bind to postsynaptic density-95, in cortex and hippocampus during the first 2 weeks of postnatal development. Suggesting that during this period other isoforms would have a more prominent role. Furthermore, we observed subcellular localization differences between isoforms, particularly throughout postnatal development. Consistent with previous reports, SynGAP was enriched in the postsynaptic density in the mature forebrain. However, SynGAP was predominantly found in non-synaptic locations in a period of early postnatal development highly sensitive to SynGAP levels. While, α1 isoforms were always found enriched in the postsynaptic density, α2 isoforms changed from a non-synaptic to a mostly postsynaptic density localization with age and β isoforms were always found enriched in non-synaptic locations. The differential expression and subcellular distribution of SynGAP isoforms may contribute to isoform-specific regulation of small GTPases, explaining SynGAP pleiotropy.
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Affiliation(s)
- Gemma Gou
- Molecular Physiology of the Synapse Laboratory, Biomedical Research Institute Sant Pau (IIB Sant Pau), Barcelona, Spain.,Universitat Autònoma de Barcelona, Bellaterra (Cerdanyola del Vallès), Spain
| | | | - Murat Kilinc
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL, USA
| | - Elena Serrano
- Biobank, Biomedical Research Institute Sant Pau (IIB Sant Pau), Barcelona, Spain
| | - Rita Reig-Viader
- Molecular Physiology of the Synapse Laboratory, Biomedical Research Institute Sant Pau (IIB Sant Pau), Barcelona, Spain.,Universitat Autònoma de Barcelona, Bellaterra (Cerdanyola del Vallès), Spain
| | - Yoichi Araki
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, USA.,Kavli Neuroscience Discovery Institute, Johns Hopkins University, Baltimore, MD, USA
| | - Richard L Huganir
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, USA.,Kavli Neuroscience Discovery Institute, Johns Hopkins University, Baltimore, MD, USA
| | | | - Gavin Rumbaugh
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL, USA
| | - Àlex Bayés
- Molecular Physiology of the Synapse Laboratory, Biomedical Research Institute Sant Pau (IIB Sant Pau), Barcelona, Spain.,Universitat Autònoma de Barcelona, Bellaterra (Cerdanyola del Vallès), Spain
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13
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Twenty Years of SynGAP Research: From Synapses to Cognition. J Neurosci 2020; 40:1596-1605. [PMID: 32075947 DOI: 10.1523/jneurosci.0420-19.2020] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 01/03/2020] [Accepted: 01/07/2020] [Indexed: 12/11/2022] Open
Abstract
SynGAP is a potent regulator of biochemical signaling in neurons and plays critical roles in neuronal function. It was first identified in 1998, and has since been extensively characterized as a mediator of synaptic plasticity. Because of its involvement in synaptic plasticity, SynGAP has emerged as a critical protein for normal cognitive function. In recent years, mutations in the SYNGAP1 gene have been shown to cause intellectual disability in humans and have been linked to other neurodevelopmental disorders, such as autism spectrum disorders and schizophrenia. While the structure and biochemical function of SynGAP have been well characterized, a unified understanding of the various roles of SynGAP at the synapse and its contributions to neuronal function remains to be achieved. In this review, we summarize and discuss the current understanding of the multifactorial role of SynGAP in regulating neuronal function gathered over the last two decades.
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14
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Araki Y, Hong I, Gamache TR, Ju S, Collado-Torres L, Shin JH, Huganir RL. SynGAP isoforms differentially regulate synaptic plasticity and dendritic development. eLife 2020; 9:56273. [PMID: 32579114 PMCID: PMC7314543 DOI: 10.7554/elife.56273] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2020] [Accepted: 06/07/2020] [Indexed: 11/14/2022] Open
Abstract
SynGAP is a synaptic Ras GTPase-activating protein (GAP) with four C-terminal splice variants: α1, α2, β, and γ. Although studies have implicated SYNGAP1 in several cognitive disorders, it is not clear which SynGAP isoforms contribute to disease. Here, we demonstrate that SynGAP isoforms exhibit unique spatiotemporal expression patterns and play distinct roles in neuronal and synaptic development in mouse neurons. SynGAP-α1, which undergoes liquid-liquid phase separation with PSD-95, is highly enriched in synapses and is required for LTP. In contrast, SynGAP-β, which does not bind PSD-95 PDZ domains, is less synaptically targeted and promotes dendritic arborization. A mutation in SynGAP-α1 that disrupts phase separation and synaptic targeting abolishes its ability to regulate plasticity and instead causes it to drive dendritic development like SynGAP-β. These results demonstrate that distinct intrinsic biochemical properties of SynGAP isoforms determine their function, and individual isoforms may differentially contribute to the pathogenesis of SYNGAP1-related cognitive disorders.
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Affiliation(s)
- Yoichi Araki
- Johns Hopkins University School of Medicine, Department of Neuroscience, Kavli Neuroscience Discovery Institute, Baltimore, United States
| | - Ingie Hong
- Johns Hopkins University School of Medicine, Department of Neuroscience, Kavli Neuroscience Discovery Institute, Baltimore, United States
| | - Timothy R Gamache
- Johns Hopkins University School of Medicine, Department of Neuroscience, Kavli Neuroscience Discovery Institute, Baltimore, United States
| | - Shaowen Ju
- Johns Hopkins University School of Medicine, Department of Neuroscience, Kavli Neuroscience Discovery Institute, Baltimore, United States
| | | | - Joo Heon Shin
- Lieber Institute for Brain Development, Baltimore, United States
| | - Richard L Huganir
- Johns Hopkins University School of Medicine, Department of Neuroscience, Kavli Neuroscience Discovery Institute, Baltimore, United States
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15
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Modified Glutamatergic Postsynapse in Neurodegenerative Disorders. Neuroscience 2019; 454:116-139. [PMID: 31887357 DOI: 10.1016/j.neuroscience.2019.12.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Revised: 10/02/2019] [Accepted: 12/02/2019] [Indexed: 01/27/2023]
Abstract
The postsynaptic density (PSD) is a complex subcellular domain important for postsynaptic signaling, function, and plasticity. The PSD is present at excitatory synapses and specialized to allow for precise neuron-to-neuron transmission of information. The PSD is localized immediately underneath the postsynaptic membrane forming a major protein network that regulates postsynaptic signaling and synaptic plasticity. Glutamatergic synaptic dysfunction affecting PSD morphology and signaling events have been described in many neurodegenerative disorders, either sporadic or familial forms. Thus, in this review we describe the main protein players forming the PSD and their activity, as well as relevant modifications in key components of the postsynaptic architecture occurring in Huntington's, Parkinson's and Alzheimer's diseases.
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16
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Tao-Cheng JH. Stimulation induces gradual increases in the thickness and curvature of postsynaptic density of hippocampal CA1 neurons in slice cultures. Mol Brain 2019; 12:44. [PMID: 31053145 PMCID: PMC6499976 DOI: 10.1186/s13041-019-0468-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Accepted: 04/25/2019] [Indexed: 11/10/2022] Open
Abstract
Activity can induce structural changes in glutamatergic excitatory synapses, including increase in thickness and curvature of the postsynaptic density (PSD); these structural changes can only be documented by electron microscopy. Here in organotypic hippocampal slice cultures where experimental conditions can be easily manipulated, increases in thickness and curvature of PSDs were noticeable within 30 s of stimulation and progressed with time up to 3 min. These structural changes were reversible upon returning the samples to control medium for 5-10 min. Thus, the postsynaptic density is a very dynamic structure that undergoes rapid reorganization of its components upon stimulation, and recovery upon cessation of stimulation. The gradual increase in thickness of PSD could result from a gradual translocation of some PSD proteins to the PSD, and the increase in curvature of the PSD is likely led by postsynaptic elements.
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Affiliation(s)
- Jung-Hwa Tao-Cheng
- NINDS Electron Microscopy Facility, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, 20892, USA.
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17
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Feng Z, Chen X, Zeng M, Zhang M. Phase separation as a mechanism for assembling dynamic postsynaptic density signalling complexes. Curr Opin Neurobiol 2018; 57:1-8. [PMID: 30599311 DOI: 10.1016/j.conb.2018.12.001] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Accepted: 12/04/2018] [Indexed: 10/27/2022]
Abstract
The postsynaptic density (PSD) is an electron dense, semi-membrane bound compartment that lies beneath postsynaptic membranes. This region is densely packed with thousands of proteins that are involved in extensive interactions. During synaptic plasticity, the PSD undergoes changes in size and composition along with changes in synaptic strength that lead to long term potentiation (LTP) or depression (LTD). It is therefore essential to understand the organization principles underlying PSD assembly and rearrangement. Here, we review exciting new findings from recent in vitro reconstitution studies and propose a hypothesis that liquid-liquid phase separation mediates PSD formation and regulation. We also discuss how the properties of PSD formed via phase separation might contribute to the biological functions observed from decades of researches. Finally, we highlight unanswered questions regarding PSD organization and how in vitro reconstitution systems may help to answer these questions in the coming years.
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Affiliation(s)
- Zhe Feng
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Xudong Chen
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Menglong Zeng
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Mingjie Zhang
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China; Center of Systems Biology and Human Health, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
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18
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Dosemeci A, Tao-Cheng JH, Loo H, Reese TS. Distribution of densin in neurons. PLoS One 2018; 13:e0205859. [PMID: 30325965 PMCID: PMC6191147 DOI: 10.1371/journal.pone.0205859] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Accepted: 10/02/2018] [Indexed: 11/18/2022] Open
Abstract
Densin is a scaffold protein known to associate with key elements of neuronal signaling. The present study examines the distribution of densin at the ultrastructural level in order to reveal potential sites that can support specific interactions of densin. Immunogold electron microscopy on hippocampal cultures shows intense labeling for densin at postsynaptic densities (PSDs), but also some labeling at extrasynaptic plasma membranes of soma and dendrites and endoplasmic reticulum. At the PSD, the median distance of label from the postsynaptic membrane was ~27 nm, with the majority of label (90%) confined within 40 nm from the postsynaptic membrane, indicating predominant localization of densin at the PSD core. Depolarization (90 mM K+ for 2 min) promoted a slight shift of densin label within the PSD complex resulting in 77% of label remaining within 40 nm from the postsynaptic membrane. Densin molecules firmly embedded within the PSD may target a minor pool of CaMKII to substrates at the PSD core.
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Affiliation(s)
- Ayse Dosemeci
- Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
| | - Jung-Hwa Tao-Cheng
- EM Facility, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Hannah Loo
- Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Thomas S. Reese
- Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
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19
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LTP requires postsynaptic PDZ-domain interactions with glutamate receptor/auxiliary protein complexes. Proc Natl Acad Sci U S A 2018; 115:3948-3953. [PMID: 29581259 DOI: 10.1073/pnas.1800719115] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Long-term potentiation (LTP) is a persistent strengthening of synaptic transmission in the brain and is arguably the most compelling cellular and molecular model for learning and memory. Previous work found that both AMPA receptors and exogenously expressed kainate receptors are equally capable of expressing LTP, despite their limited homology and their association with distinct auxiliary subunits, indicating that LTP is far more promiscuous than previously thought. What might these two subtypes of glutamate receptor have in common? Using a single-cell molecular replacement strategy, we demonstrate that the AMPA receptor auxiliary subunit TARP γ-8, via its PDZ-binding motif, is indispensable for both basal synaptic transmission and LTP. Remarkably, kainate receptors and their auxiliary subunits Neto proteins share the same requirement of PDZ-binding domains for synaptic trafficking and LTP. Together, these results suggest that a minimal postsynaptic requirement for LTP is the PDZ binding of glutamate receptors/auxiliary subunits to PSD scaffolding proteins.
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20
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Lisman J. Glutamatergic synapses are structurally and biochemically complex because of multiple plasticity processes: long-term potentiation, long-term depression, short-term potentiation and scaling. Philos Trans R Soc Lond B Biol Sci 2017; 372:rstb.2016.0260. [PMID: 28093558 DOI: 10.1098/rstb.2016.0260] [Citation(s) in RCA: 100] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/29/2016] [Indexed: 01/03/2023] Open
Abstract
Synapses are complex because they perform multiple functions, including at least six mechanistically different forms of plasticity. Here, I comment on recent developments regarding these processes. (i) Short-term potentiation (STP), a Hebbian process that requires small amounts of synaptic input, appears to make strong contributions to some forms of working memory. (ii) The rules for long-term potentiation (LTP) induction in CA3 have been clarified: induction does not depend obligatorily on backpropagating sodium spikes but, rather, on dendritic branch-specific N-methyl-d-aspartate (NMDA) spikes. (iii) Late LTP, a process that requires a dopamine signal (and is therefore neoHebbian), is mediated by trans-synaptic growth of the synapse, a growth that occurs about an hour after LTP induction. (iv) LTD processes are complex and include both homosynaptic and heterosynaptic forms. (v) Synaptic scaling produced by changes in activity levels are not primarily cell-autonomous, but rather depend on network activity. (vi) The evidence for distance-dependent scaling along the primary dendrite is firm, and a plausible structural-based mechanism is suggested.Ideas about the mechanisms of synaptic function need to take into consideration newly emerging data about synaptic structure. Recent super-resolution studies indicate that glutamatergic synapses are modular (module size 70-80 nm), as predicted by theoretical work. Modules are trans-synaptic structures and have high concentrations of postsynaptic density-95 (PSD-95) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor. These modules function as quasi-independent loci of AMPA-mediated transmission and may be independently modifiable, suggesting a new understanding of quantal transmission.This article is part of the themed issue 'Integrating Hebbian and homeostatic plasticity.'
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Affiliation(s)
- John Lisman
- Biology Department, Brandeis University, Waltham, MA, USA
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21
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Tau exacerbates excitotoxic brain damage in an animal model of stroke. Nat Commun 2017; 8:473. [PMID: 28883427 PMCID: PMC5589746 DOI: 10.1038/s41467-017-00618-0] [Citation(s) in RCA: 117] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Accepted: 07/13/2017] [Indexed: 02/07/2023] Open
Abstract
Neuronal excitotoxicity induced by aberrant excitation of glutamatergic receptors contributes to brain damage in stroke. Here we show that tau-deficient (tau−/−) mice are profoundly protected from excitotoxic brain damage and neurological deficits following experimental stroke, using a middle cerebral artery occlusion with reperfusion model. Mechanistically, we show that this protection is due to site-specific inhibition of glutamate-induced and Ras/ERK-mediated toxicity by accumulation of Ras-inhibiting SynGAP1, which resides in a post-synaptic complex with tau. Accordingly, reducing SynGAP1 levels in tau−/− mice abolished the protection from pharmacologically induced excitotoxicity and middle cerebral artery occlusion-induced brain damage. Conversely, over-expression of SynGAP1 prevented excitotoxic ERK activation in wild-type neurons. Our findings suggest that tau mediates excitotoxic Ras/ERK signaling by controlling post-synaptic compartmentalization of SynGAP1. Excitotoxicity contributes to neuronal injury following stroke. Here the authors show that tau promotes excitotoxicity by a post-synaptic mechanism, involving site-specific control of ERK activation, in a mouse model of stroke.
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22
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A novel synaptic junction preparation for the identification and characterization of cleft proteins. PLoS One 2017; 12:e0174895. [PMID: 28362857 PMCID: PMC5376301 DOI: 10.1371/journal.pone.0174895] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Accepted: 03/16/2017] [Indexed: 12/23/2022] Open
Abstract
Identification of synaptic cleft components has been hampered by the lack of a suitable preparation enriched in synaptic junctions devoid of adjoining peripheral membranes. Prior strategies for the isolation of synaptic junctions, relying on detergents for the removal of peripheral membranes, resulted in substantial loss of membranes lining the cleft. Here, a novel, detergent-free method is described for the preparation of a synaptic junction (SJ) fraction, using phospholipase A2. Limited digestion of synaptic plasma membrane (SPM) fraction with phospholipase A2 followed by centrifugation over a sucrose cushion results in selective removal of membranes peripheral to the cleft while junctional membranes remain relatively intact as observed by electron microscopy. Enrichment in synaptic junctional structures and loss of membranes peripheral to the junctional area are further verified by demonstrating enrichment in PSD-95 and loss in mGluR5, respectively. The SJ fraction is enriched in neuroligins and neurexins, in agreement with immuno-electron microscopy data showing their selective localization to the junctional area. Among additional cell adhesion molecules tested, N-cadherin and specific isoforms of the SynCAM and SALM families also show marked enrichment in the SJ fraction, suggesting preferential localization at the synaptic cleft while others show little enrichment or decrease, suggesting that they are not restricted to or concentrated at the synaptic cleft. Treatment of the SJ fraction with glycosidases results in electrophoretic mobility shifts of all cell adhesion molecules tested, indicating glycosylation at the synaptic cleft. Biochemical and ultrastructural data presented indicate that the novel synaptic junction preparation can be used as a predictive tool for the identification and characterization of the components of the synaptic cleft.
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23
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Dosemeci A, Toy D, Burch A, Bayer KU, Tao-Cheng JH. CaMKII-mediated displacement of AIDA-1 out of the postsynaptic density core. FEBS Lett 2016; 590:2934-9. [PMID: 27477489 DOI: 10.1002/1873-3468.12334] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Revised: 07/11/2016] [Accepted: 07/24/2016] [Indexed: 11/06/2022]
Abstract
Ankyrin repeat and sterile alpha motif domain-containing protein 1B (ANKS1B, also known as AIDA-1) is a major component of the postsynaptic density (PSD) in excitatory neurons where it concentrates at the electron-dense core under basal conditions and moves out during activity. This study investigates the molecular mechanism underlying activity-induced displacement of AIDA-1. Experiments with PSD fractions from brain indicate phosphorylation of AIDA-1 upon activation of endogenous CaMKII. Immuno-electron microscopy studies show that treatment of hippocampal neurons with NMDA results in an ~ 30 nm shift in the median distance of the AIDA-1 label from the postsynaptic membrane, an effect that is blocked by the CaMKII inhibitor tatCN21. CaMKII-mediated redistribution of AIDA-1 is similar to that observed for SynGAP. CaMKII-mediated removal of two abundant PSD-95-binding proteins from the PSD core during activity is expected to initiate a molecular reorganization at the PSD.
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Affiliation(s)
- Ayse Dosemeci
- Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Dana Toy
- Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Amelia Burch
- Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - K Ulrich Bayer
- Department of Pharmacology, School of Medicine, University of Colorado Denver, Aurora, CO, USA
| | - Jung-Hwa Tao-Cheng
- EM Facility, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
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24
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Dosemeci A, Weinberg RJ, Reese TS, Tao-Cheng JH. The Postsynaptic Density: There Is More than Meets the Eye. Front Synaptic Neurosci 2016; 8:23. [PMID: 27594834 PMCID: PMC4990544 DOI: 10.3389/fnsyn.2016.00023] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Accepted: 07/25/2016] [Indexed: 11/28/2022] Open
Abstract
The postsynaptic density (PSD), apparent in electron micrographs as a dense lamina just beneath the postsynaptic membrane, includes a deeper layer, the “pallium”, containing a scaffold of Shank and Homer proteins. Though poorly defined in traditionally prepared thin-section electron micrographs, the pallium becomes denser and more conspicuous during intense synaptic activity, due to the reversible addition of CaMKII and other proteins. In this Perspective article, we review the significance of CaMKII-mediated recruitment of proteins to the pallium with respect to both the trafficking of receptors and the remodeling of spine shape that follow synaptic stimulation. We suggest that the level and duration of CaMKII translocation and activation in the pallium will shape activity-induced changes in the spine.
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Affiliation(s)
- Ayse Dosemeci
- Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH) Bethesda, MD, USA
| | - Richard J Weinberg
- Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill Chapel Hill, NC, USA
| | - Thomas S Reese
- Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH) Bethesda, MD, USA
| | - Jung-Hwa Tao-Cheng
- Electron Microscopy Facility, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH) Bethesda, MD, USA
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25
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Depolarization of Hippocampal Neurons Induces Formation of Nonsynaptic NMDA Receptor Islands Resembling Nascent Postsynaptic Densities. eNeuro 2015; 2:eN-NWR-0066-15. [PMID: 26665164 PMCID: PMC4672205 DOI: 10.1523/eneuro.0066-15.2015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Revised: 10/15/2015] [Accepted: 11/03/2015] [Indexed: 01/11/2023] Open
Abstract
Depolarization of neurons in 3-week-old rat hippocampal cultures promotes a rapid increase in the density of surface NMDA receptors (NRs), accompanied by transient formation of nonsynaptic NMDA receptor clusters or NR islands. Islands exhibit cytoplasmic dense material resembling that at postsynaptic densities (PSDs), and contain typical PSD components, including MAGUKS (membrane-associated guanylate kinases), GKAP, Shank, Homer, and CaMKII detected by pre-embedding immunogold electron microscopy. In contrast to mature PSDs, islands contain more NMDA than AMPA receptors, and more SAP102 than PSD-95, features that are shared with nascent PSDs in developing synapses. Islands do not appear to be exocytosed or endocytosed directly as preformed packages because neurons lacked intracellular vacuoles containing island-like structures. Islands form and disassemble upon depolarization of neurons on a time scale of 2-3 min, perhaps representing an initial stage in synaptogenesis.
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26
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Dosemeci A, Toy D, Reese TS, Tao-Cheng JH. AIDA-1 Moves out of the Postsynaptic Density Core under Excitatory Conditions. PLoS One 2015; 10:e0137216. [PMID: 26356309 PMCID: PMC4565644 DOI: 10.1371/journal.pone.0137216] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Accepted: 08/13/2015] [Indexed: 11/18/2022] Open
Abstract
AIDA-1 is highly enriched in postsynaptic density (PSD) fractions and is considered a major component of the PSD complex. In the present study, immunogold electron microscopy was applied to determine localization as well as the activity-induced redistribution of AIDA-1 at the PSD using two antibodies that recognize two different epitopes. In cultured rat hippocampal neurons under basal conditions, immunogold label for AIDA-1 is mostly located within the dense core of the PSD, with a median distance of ~30 nm from the postsynaptic membrane. Under excitatory conditions, such as depolarization with high K+ (90 mM, 2 min) or application of NMDA (50 μM, 2 min), AIDA-1 label density at the PSD core is reduced to 40% of controls and the median distance of label from the postsynaptic membrane increases to ~55 nm. The effect of excitatory conditions on the postsynaptic distribution of AIDA-1 is reversed within 30 minutes after returning to control conditions. The reversible removal of AIDA-1 from the PSD core under excitatory conditions is similar to the redistribution of another abundant PSD protein, SynGAP. Both SynGAP-alpha1 and AIDA-1 are known to bind PSD-95. Activity-induced transient translocation of these abundant proteins from the PSD core could promote structural flexibility, vacate sites on PSD-95 for the insertion of other components and thus may create a window for synaptic modification.
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Affiliation(s)
- Ayse Dosemeci
- Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
| | - Dana Toy
- Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Thomas S. Reese
- Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Jung-Hwa Tao-Cheng
- EM Facility, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
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27
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Electron tomographic structure and protein composition of isolated rat cerebellar, hippocampal and cortical postsynaptic densities. Neuroscience 2015. [PMID: 26215919 DOI: 10.1016/j.neuroscience.2015.07.062] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Electron tomography and immunogold labeling were used to analyze similarities and differences in the morphology and protein composition of postsynaptic densities (PSDs) isolated from adult rat cerebella, hippocampi, and cortices. There were similarities in physical dimensions and gross morphology between cortical, hippocampal and most cerebellar PSDs, although the morphology among cerebellar PSDs could be categorized into three distinct groups. The majority of cerebellar PSDs were composed of dense regions of protein, similar to cortical and hippocampal PSDs, while others were either composed of granular or lattice-like protein regions. Significant differences were found in protein composition and organization across PSDs from the different brain regions. The signaling protein, βCaMKII, was found to be a major component of each PSD type and was more abundant than αCaMKII in both hippocampal and cerebellar PSDs. The scaffold molecule PSD-95, a major component of cortical PSDs, was found absent in a fraction of cerebellar PSDs and when present was clustered in its distribution. In contrast, immunogold labeling for the proteasome was significantly more abundant in cerebellar and hippocampal PSDs than cortical PSDs. Together, these results indicate that PSDs exhibit remarkable diversity in their composition and morphology, presumably as a reflection of the unique functional demands placed on different synapses.
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Araki Y, Zeng M, Zhang M, Huganir RL. Rapid dispersion of SynGAP from synaptic spines triggers AMPA receptor insertion and spine enlargement during LTP. Neuron 2015; 85:173-189. [PMID: 25569349 DOI: 10.1016/j.neuron.2014.12.023] [Citation(s) in RCA: 187] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/08/2014] [Indexed: 10/24/2022]
Abstract
SynGAP is a Ras-GTPase activating protein highly enriched at excitatory synapses in the brain. Previous studies have shown that CaMKII and the RAS-ERK pathway are critical for several forms of synaptic plasticity including LTP. NMDA receptor-dependent calcium influx has been shown to regulate the RAS-ERK pathway and downstream events that result in AMPA receptor synaptic accumulation, spine enlargement, and synaptic strengthening during LTP. However, the cellular mechanisms whereby calcium influx and CaMKII control Ras activity remain elusive. Using live-imaging techniques, we have found that SynGAP is rapidly dispersed from spines upon LTP induction in hippocampal neurons, and this dispersion depends on phosphorylation of SynGAP by CaMKII. Moreover, the degree of acute dispersion predicts the maintenance of spine enlargement. Thus, the synaptic dispersion of SynGAP by CaMKII phosphorylation during LTP represents a key signaling component that transduces CaMKII activity to small G protein-mediated spine enlargement, AMPA receptor synaptic incorporation, and synaptic potentiation.
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Affiliation(s)
- Yoichi Araki
- Department of Neuroscience and Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Menglong Zeng
- Division of Life Science, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
| | - Mingjie Zhang
- Division of Life Science, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
| | - Richard L Huganir
- Department of Neuroscience and Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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NMDA-induced accumulation of Shank at the postsynaptic density is mediated by CaMKII. Biochem Biophys Res Commun 2014; 450:808-11. [PMID: 24952157 DOI: 10.1016/j.bbrc.2014.06.049] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Accepted: 06/12/2014] [Indexed: 11/24/2022]
Abstract
Shank is a specialized scaffold protein present in high abundance at the postsynaptic density (PSD). Using pre-embedding immunogold electron microscopy on cultured hippocampal neurons, we had previously demonstrated further accumulation of Shank at the PSD under excitatory conditions. Here, using the same experimental protocol, we demonstrate that a cell permeable CaMKII inhibitor, tatCN21, blocks NMDA-induced accumulation of Shank at the PSD. Furthermore we show that NMDA application changes the distribution pattern of Shank at the PSD, promoting a 7-10 nm shift in the median distance of Shank labels away from the postsynaptic membrane. Inhibition of CaMKII with tatCN21 also blocks this shift in the distribution of Shank. Altogether these results imply that upon activation of NMDA receptors, CaMKII mediates accumulation of Shank, preferentially at the distal regions of the PSD complex extending toward the cytoplasm.
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Thein S, Tao-Cheng JH, Li Y, Bayer KU, Reese TS, Dosemeci A. CaMKII mediates recruitment and activation of the deubiquitinase CYLD at the postsynaptic density. PLoS One 2014; 9:e91312. [PMID: 24614225 PMCID: PMC3948843 DOI: 10.1371/journal.pone.0091312] [Citation(s) in RCA: 20] [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: 11/08/2013] [Accepted: 02/10/2014] [Indexed: 11/18/2022] Open
Abstract
NMDA treatment of cultured hippocampal neurons causes recruitment of CYLD, as well as CaMKII, to the postsynaptic density (PSD), as shown by immunoelectron microscopy. Recruitment of CYLD, a deubiquitinase specific for K63-linked polyubiquitins, is blocked by pre-treatment with tatCN21, a CaMKII inhibitor, at a concentration that inhibits the translocation of CaMKII to the PSD. Furthermore, CaMKII co-immunoprecipitates with CYLD from solubilized PSD fractions, indicating an association between the proteins. Purified CaMKII phosphorylates CYLD on at least three residues (S-362, S-418, and S-772 on the human CYLD protein Q9NQC7-1) and promotes its deubiquitinase activity. Activation of CaMKII in isolated PSDs promotes phosphorylation of CYLD on the same residues and also enhances endogenous deubiquitinase activity specific for K63-linked polyubiquitins. Since K63-linked polyubiquitin conjugation to proteins inhibits their interaction with proteasomes, CaMKII-mediated recruitment and upregulation of CYLD is expected to remove K63-linked polyubiquitins and facilitate proteasomal degradation at the PSD.
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Affiliation(s)
- Soe Thein
- Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail: (ST); (AD)
| | - Jung-Hwa Tao-Cheng
- EM Facility, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Yan Li
- Protein/Peptide Sequencing Facility, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
| | - K. Ulrich Bayer
- Department of Pharmacology, University of Colorado Denver School of Medicine, Aurora, Colorado, United States of America
| | - Thomas S. Reese
- Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Ayse Dosemeci
- Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail: (ST); (AD)
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Tao-Cheng JH, Thein S, Yang Y, Reese TS, Gallant PE. Homer is concentrated at the postsynaptic density and does not redistribute after acute synaptic stimulation. Neuroscience 2014; 266:80-90. [PMID: 24530450 DOI: 10.1016/j.neuroscience.2014.01.066] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Revised: 01/30/2014] [Accepted: 01/31/2014] [Indexed: 10/25/2022]
Abstract
Homer is a postsynaptic density (PSD) scaffold protein that is involved in synaptic plasticity, calcium signaling and neurological disorders. Here, we use pre-embedding immunogold electron microscopy to illustrate the differential localization of three Homer gene products (Homer 1, 2, and 3) in different regions of the mouse brain. In cross-sectioned PSDs, Homer occupies a layer ∼30-100nm from the postsynaptic membrane lying just beyond the dense material that defines the PSD core (∼30-nm-thick). Homer is evenly distributed within the PSD area along the lateral axis, but not at the peri-PSD locations within 60nm from the edge of the PSD, where type I-metabotropic glutamate receptors (mGluR1 and 5) are concentrated. This distribution of Homer matches that of Shank, another major PSD scaffold protein, but differs from those of other two major binding partners of Homer, type I mGluR and IP3 receptors. Many PSD proteins rapidly redistribute upon acute (2min) stimulation. To determine whether Homer distribution is affected by acute stimulation, we examined its distribution in dissociated hippocampal cultures under different conditions. Both the pattern and density of label for Homer 1, the isoform that is ubiquitous in hippocampus, remained unchanged under high K(+) depolarization (90mM for 2-5min), N-methyl-d-asparic acid (NMDA) treatment (50μM for 2min), and calcium-free conditions (EGTA at 1mM for 2min). In contrast, Shank and calcium/calmodulin-dependent kinase II (CaMKII) accumulate at the PSD upon NMDA treatment, and CaMKII is excluded from the PSD complex under low calcium conditions.
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Affiliation(s)
- J-H Tao-Cheng
- EM Facility, NINDS, NIH, Bethesda, MD, United States.
| | - S Thein
- Laboratory of Neurobiology, NINDS, NIH, Bethesda, MD, United States
| | - Y Yang
- Laboratory of Neurobiology, NINDS, NIH, Bethesda, MD, United States
| | - T S Reese
- Laboratory of Neurobiology, NINDS, NIH, Bethesda, MD, United States
| | - P E Gallant
- Laboratory of Neurobiology, NINDS, NIH, Bethesda, MD, United States
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Wang CC, Held RG, Hall BJ. SynGAP regulates protein synthesis and homeostatic synaptic plasticity in developing cortical networks. PLoS One 2013; 8:e83941. [PMID: 24391850 PMCID: PMC3877118 DOI: 10.1371/journal.pone.0083941] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2013] [Accepted: 11/19/2013] [Indexed: 12/23/2022] Open
Abstract
Disrupting the balance between excitatory and inhibitory neurotransmission in the developing brain has been causally linked with intellectual disability (ID) and autism spectrum disorders (ASD). Excitatory synapse strength is regulated in the central nervous system by controlling the number of postsynaptic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs). De novo genetic mutations of the synaptic GTPase-activating protein (SynGAP) are associated with ID and ASD. SynGAP is enriched at excitatory synapses and genetic suppression of SynGAP increases excitatory synaptic strength. However, exactly how SynGAP acts to maintain synaptic AMPAR content is unclear. We show here that SynGAP limits excitatory synaptic strength, in part, by suppressing protein synthesis in cortical neurons. The data presented here from in vitro, rat and mouse cortical networks, demonstrate that regulation of translation by SynGAP involves ERK, mTOR, and the small GTP-binding protein Rheb. Furthermore, these data show that GluN2B-containing NMDARs and the cognitive kinase CaMKII act upstream of SynGAP and that this signaling cascade is required for proper translation-dependent homeostatic synaptic plasticity of excitatory synapses in developing cortical networks.
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Affiliation(s)
- Chih-Chieh Wang
- Neuroscience Program, School of Science and Engineering, Tulane University, New Orleans, Louisiana, United States of America
| | - Richard G. Held
- Department of Cell and Molecular Biology, School of Science and Engineering, Tulane University, New Orleans, Louisiana, United States of America
| | - Benjamin J. Hall
- Neuroscience Program, School of Science and Engineering, Tulane University, New Orleans, Louisiana, United States of America
- Department of Cell and Molecular Biology, School of Science and Engineering, Tulane University, New Orleans, Louisiana, United States of America
- * E-mail:
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33
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Yang Y, Tao-Cheng JH, Bayer KU, Reese TS, Dosemeci A. Camkii-mediated phosphorylation regulates distributions of Syngap-α1 and -α2 at the postsynaptic density. PLoS One 2013; 8:e71795. [PMID: 23967245 PMCID: PMC3742523 DOI: 10.1371/journal.pone.0071795] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Accepted: 07/02/2013] [Indexed: 01/27/2023] Open
Abstract
SynGAP, a protein abundant at the postsynaptic density (PSD) of glutamatergic neurons, is known to modulate synaptic strength by regulating the incorporation of AMPA receptors at the synapse. Two isoforms of SynGAP, α1 and α2, which differ in their C-termini, have opposing effects on synaptic strength. In the present study, antibodies specific for SynGAP-α1 and SynGAP-α2 are used to compare the distribution patterns of the two isoforms at the postsynaptic density (PSD) under basal and excitatory conditions. Western immunoblotting shows enrichment of both isoforms in PSD fractions isolated from adult rat brain. Immunogold electron microscopy of rat hippocampal neuronal cultures shows similar distribution of both isoforms at the PSD, with a high density of immunolabel within the PSD core under basal conditions. Application of NMDA promotes movement of SynGAP-α1 as well as SynGAP-α2 out of the PSD core. In isolated PSDs both isoforms of SynGAP can be phosphorylated upon activation of the endogenous CaMKII. Application of tatCN21, a cell-penetrating inhibitor of CaMKII, to hippocampal neuronal cultures blocks NMDA-induced redistribution of SynGAP-α1 and SynGAP-α2. Thus CaMKII activation promotes the removal of two distinct C-terminal SynGAP variants from the PSD.
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Affiliation(s)
- Yijung Yang
- Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Jung-Hwa Tao-Cheng
- EM Facility, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
| | - K. Ulrich Bayer
- Department of Pharmacology, University of Colorado Denver School of Medicine, Aurora, Colorado, United States of America
| | - Thomas S. Reese
- Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Ayse Dosemeci
- Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
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34
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Fera A, Dosemeci A, Sousa AA, Yang C, Leapman RD, Reese TS. Direct visualization of CaMKII at postsynaptic densities by electron microscopy tomography. J Comp Neurol 2013; 520:4218-25. [PMID: 22627922 DOI: 10.1002/cne.23151] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Ca(2+) /calmodulin-dependent protein kinase II (CaMKII) is a major component of postsynaptic densities (PSDs) involved in synaptic regulation. It has been previously shown that upon activity CaMKII from the spine reversibly aggregates at the cytoplasmic surfaces of PSDs, where it encounters various targets for phosphorylation. Targets for CaMKII are also present within the PSD, but there has been no reliable method to pinpoint whether, or where, CaMKII is located inside the PSD. Here we show that CaMKII can be mapped molecule-by-molecule within isolated PSDs using negative stain electron microscopy tomography. CaMKII molecules found in the core of the PSD may represent a pool distinct from the CaMKII residing at the cytoplasmic surface.
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Affiliation(s)
- Andrea Fera
- Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA.
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35
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Dosemeci A, Thein S, Yang Y, Reese TS, Tao-Cheng JH. CYLD, a deubiquitinase specific for lysine63-linked polyubiquitins, accumulates at the postsynaptic density in an activity-dependent manner. Biochem Biophys Res Commun 2012; 430:245-9. [PMID: 23146630 DOI: 10.1016/j.bbrc.2012.10.131] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2012] [Accepted: 10/30/2012] [Indexed: 11/16/2022]
Abstract
Polyubiquitin chains on proteins flag them for distinct fates depending on the type of polyubiquitin linkage. While lysine48-linked polyubiquitination directs proteins to proteasomal degradation, lysine63-linked polyubiquitination promotes different protein trafficking and is involved in autophagy. Here we show that postsynaptic density (PSD) fractions from adult rat brain contain deubiquitinase activity that targets both lysine48 and lysine63-linked polyubiquitins. Comparison of PSD fractions with parent subcellular fractions by Western immunoblotting reveals that CYLD, a deubiquitinase specific for lysine63-linked polyubiquitins, is highly enriched in the PSD fraction. Electron microscopic examination of hippocampal neurons in culture under basal conditions shows immunogold label for CYLD at the PSD complex in approximately one in four synapses. Following depolarization by exposure to high K+, the proportion of CYLD-labeled PSDs as well as the labeling intensity of CYLD at the PSD increased by more than eighty percent, indicating that neuronal activity promotes accumulation of CYLD at the PSD. An increase in postsynaptic CYLD following activity would promote removal of lysine63-polyubiquitins from PSD proteins and thus could regulate their trafficking and prevent their autophagic degradation.
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Affiliation(s)
- Ayse Dosemeci
- Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.
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36
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Gold MG. A frontier in the understanding of synaptic plasticity: solving the structure of the postsynaptic density. Bioessays 2012; 34:599-608. [PMID: 22528972 PMCID: PMC3492911 DOI: 10.1002/bies.201200009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The postsynaptic density (PSD) is a massive multi-protein complex whose functions include positioning signalling molecules for induction of long-term potentiation (LTP) and depression (LTD) of synaptic strength. These processes are thought to underlie memory formation. To understand how the PSD coordinates bidirectional synaptic plasticity with different synaptic activation patterns, it is necessary to determine its three-dimensional structure. A structural model of the PSD is emerging from investigation of its molecular composition and connectivity, in addition to structural studies at different levels of resolution. Technical innovations including mass spectrometry of cross-linked proteins and super-resolution light microscopy can drive progress. Integrating different information relating to PSD structure is challenging since the structure is so large and complex. The reconstruction of a PSD subcomplex anchored by AKAP79 exemplifies on a small scale how integration can be achieved. With its entire molecular structure coming into focus, this is a unique opportunity to study the PSD.
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Affiliation(s)
- Matthew G Gold
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK.
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