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Eltokhi A, Bertocchi I, Rozov A, Jensen V, Borchardt T, Taylor A, Proenca CC, Rawlins JNP, Bannerman DM, Sprengel R. Distinct effects of AMPAR subunit depletion on spatial memory. iScience 2023; 26:108116. [PMID: 37876813 PMCID: PMC10590979 DOI: 10.1016/j.isci.2023.108116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 07/01/2023] [Accepted: 09/29/2023] [Indexed: 10/26/2023] Open
Abstract
Pharmacological studies established a role for AMPARs in the mammalian forebrain in spatial memory performance. Here we generated global GluA1/3 double knockout mice (Gria1/3-/-) and conditional knockouts lacking GluA1 and GluA3 AMPAR subunits specifically from principal cells across the forebrain (Gria1/3ΔFb). In both models, loss of GluA1 and GluA3 resulted in reduced hippocampal GluA2 and increased levels of the NMDAR subunit GluN2A. Electrically-evoked AMPAR-mediated EPSPs were greatly diminished, and there was an absence of tetanus-induced LTP. Gria1/3-/- mice showed premature mortality. Gria1/3ΔFb mice were viable, and their memory performance could be analyzed. In the Morris water maze (MWM), Gria1/3ΔFb mice showed profound long-term memory deficits, in marked contrast to the normal MWM learning previously seen in single Gria1-/- and Gria3-/- knockout mice. Our results suggest a redundancy of function within the pool of available ionotropic glutamate receptors for long-term spatial memory performance.
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Affiliation(s)
- Ahmed Eltokhi
- Departments of Molecular Neurobiology and Physiology, Max Planck Institute for Medical Research, Heidelberg, Germany
- Department of Pharmacolog, University of Washington, Seattle, WA, USA
| | - Ilaria Bertocchi
- Departments of Molecular Neurobiology and Physiology, Max Planck Institute for Medical Research, Heidelberg, Germany
- Department of Neuroscience Rita Levi Montalcini, University of Turin, 10126 Turin, Italy
- Neuroscience Institute - Cavalieri-Ottolenghi Foundation (NICO), Laboratory of Neuropsychopharmacology, Regione Gonzole 10, Orbassano, 10043 Torino, Italy
| | - Andrei Rozov
- Departments of Molecular Neurobiology and Physiology, Max Planck Institute for Medical Research, Heidelberg, Germany
- Institute of Neuroscience, Lobachevsky State University of Nizhniy, 603022 Novgorod, Russia
- Federal Center of Brain Research and Neurotechnology, 117997 Moscow, Russia
| | - Vidar Jensen
- Department of Molecular Medicine, Division of Physiology, Institute of Basic Medical Sciences, University of Oslo, 0372 Oslo, Norway
| | - Thilo Borchardt
- Departments of Molecular Neurobiology and Physiology, Max Planck Institute for Medical Research, Heidelberg, Germany
| | - Amy Taylor
- Department of Experimental Psychology, University of Oxford, Oxford, UK
| | - Catia C. Proenca
- Departments of Molecular Neurobiology and Physiology, Max Planck Institute for Medical Research, Heidelberg, Germany
| | | | | | - Rolf Sprengel
- Departments of Molecular Neurobiology and Physiology, Max Planck Institute for Medical Research, Heidelberg, Germany
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Zhang B, Wang ML, Huang SM, Cui Y, Li Y. Kaixin-San improves Aβ-induced synaptic plasticity inhibition by affecting the expression of regulation proteins associated with postsynaptic AMPAR expression. Front Pharmacol 2023; 14:1079400. [PMID: 36865910 PMCID: PMC9970989 DOI: 10.3389/fphar.2023.1079400] [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: 11/18/2022] [Accepted: 01/26/2023] [Indexed: 02/16/2023] Open
Abstract
Objective: To explore the mechanism underlying Kaixin-San (KXS) regulation of postsynaptic AMPA receptor (AMPAR) expression to mitigate toxic effects of the amyloid-β protein (Aβ). Methods: An animal model was established via intracerebroventricular injection of Aβ1-42. The Morris water maze test was conducted to evaluate learning and memory, while electrophysiological recording was conducted to assess the hippocampal long-term potentiation (LTP). Western blotting was used to detect expression levels of the hippocampal postsynaptic AMPAR and its accessory proteins. Results: The time spent to find the platform was significantly prolonged, the number of mice crossing the target site was significantly reduced, and the maintenance of LTP was inhibited in the Aβ group than in the control group. In the Aβ/KXS group, the time taken to find the platform was significantly shortened and the number of mice crossing the target site was significantly increased than in the Aβ group; furthermore, the inhibition of LTP induced by Aβ was reversed. The expression of GluR1, GluR2, ABP, GRIP1, NSF, and pGluR1-Ser845 was upregulated, while that of pGluR2-Ser880 and PKC δ was downregulated in the Aβ/KXS group. Conclusion: The increased expression of ABP, GRIP1, NSF, and pGluR1-Ser845 and the decreased expression of pGluR2-Ser880 and PKC δ under the influence of KXS, followed by the upregulation of postsynaptic GluR1 and GluR2, alleviated the inhibition of LTP induced by Aβ. Ultimately, the memory function of model animals was improved by KXS. Our study provides novel insights into the mechanism underlying KXS mitigation of Aβ-induced synaptic plasticity inhibition and memory impairment by altering the levels of accessory proteins associated with AMPAR expression.
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Affiliation(s)
- Bo Zhang
- Institute of Chinese Medicine, Heilongjiang University of Chinese Medicine, Harbin, China
| | - Meng-Lu Wang
- Institute of Chinese Medicine, Heilongjiang University of Chinese Medicine, Harbin, China
| | - Shu-Ming Huang
- Institute of Chinese Medicine, Heilongjiang University of Chinese Medicine, Harbin, China
| | - Yu Cui
- Department of Veterinary Medicine, Institute of tropical agriculture and forestry, Hainan University, Haikou, China,*Correspondence: Yu Cui, ; Yan Li,
| | - Yan Li
- Jiangsu Key Laboratory of Integrated Traditional Chinese and Western Medicine for Prevention and Treatment of Senile Diseases, Medical College of Yangzhou University, Yangzhou, China,*Correspondence: Yu Cui, ; Yan Li,
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van der Spek SJF, Pandya NJ, Koopmans F, Paliukhovich I, van der Schors RC, Otten M, Smit AB, Li KW. Expression and Interaction Proteomics of GluA1- and GluA3-Subunit-Containing AMPARs Reveal Distinct Protein Composition. Cells 2022; 11:cells11223648. [PMID: 36429079 PMCID: PMC9688267 DOI: 10.3390/cells11223648] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2022] [Revised: 10/27/2022] [Accepted: 11/14/2022] [Indexed: 11/19/2022] Open
Abstract
The AMPA glutamate receptor (AMPAR) is the major type of synaptic excitatory ionotropic receptor in the brain. AMPARs have four different subunits, GluA1-4 (each encoded by different genes, Gria1, Gria2, Gria3 and Gria4), that can form distinct tetrameric assemblies. The most abundant AMPAR subtypes in the hippocampus are GluA1/2 and GluA2/3 heterotetramers. Each subtype contributes differentially to mechanisms of synaptic plasticity, which may be in part caused by how these receptors are regulated by specific associated proteins. A broad range of AMPAR interacting proteins have been identified, including the well-studied transmembrane AMPA receptor regulatory proteins TARP-γ2 (also known as Stargazin) and TARP-γ8, Cornichon homolog 2 (CNIH-2) and many others. Several interactors were shown to affect biogenesis, AMPAR trafficking, and channel properties, alone or in distinct assemblies, and several revealed preferred binding to specific AMPAR subunits. To date, a systematic specific interactome analysis of the major GluA1/2 and GluA2/3 AMPAR subtypes separately is lacking. To reveal interactors belonging to specific AMPAR subcomplexes, we performed both expression and interaction proteomics on hippocampi of wildtype and Gria1- or Gria3 knock-out mice. Whereas GluA1/2 receptors co-purified TARP-γ8, synapse differentiation-induced protein 4 (SynDIG4, also known as Prrt1) and CNIH-2 with highest abundances, GluA2/3 receptors revealed strongest co-purification of CNIH-2, TARP-γ2, and Noelin1 (or Olfactomedin-1). Further analysis revealed that TARP-γ8-SynDIG4 interact directly and co-assemble into an AMPAR subcomplex especially at synaptic sites. Together, these data provide a framework for further functional analysis into AMPAR subtype specific pathways in health and disease.
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Wu MY, Zou WJ, Yu P, Yang Y, Li SJ, Liu Q, Xie J, Chen SQ, Lin WJ, Tang Y. Cranial irradiation impairs intrinsic excitability and synaptic plasticity of hippocampal CA1 pyramidal neurons with implications for cognitive function. Neural Regen Res 2022; 17:2253-2259. [PMID: 35259846 PMCID: PMC9083168 DOI: 10.4103/1673-5374.336875] [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] [Indexed: 11/04/2022] Open
Abstract
Radiation therapy is a standard treatment for head and neck tumors. However, patients often exhibit cognitive impairments following radiation therapy. Previous studies have revealed that hippocampal dysfunction, specifically abnormal hippocampal neurogenesis or neuroinflammation, plays a key role in radiation-induced cognitive impairment. However, the long-term effects of radiation with respect to the electrophysiological adaptation of hippocampal neurons remain poorly characterized. We found that mice exhibited cognitive impairment 3 months after undergoing 10 minutes of cranial irradiation at a dose rate of 3 Gy/min. Furthermore, we observed a remarkable reduction in spike firing and excitatory synaptic input, as well as greatly enhanced inhibitory inputs, in hippocampal CA1 pyramidal neurons. Corresponding to the electrophysiological adaptation, we found reduced expression of synaptic plasticity marker VGLUT1 and increased expression of VGAT. Furthermore, in irradiated mice, long-term potentiation in the hippocampus was weakened and GluR1 expression was inhibited. These findings suggest that radiation can impair intrinsic excitability and synaptic plasticity in hippocampal CA1 pyramidal neurons.
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Affiliation(s)
- Min-Yi Wu
- Department of Neurology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, Guangdong Province, China
| | - Wen-Jun Zou
- State Key Laboratory of Organ Failure Research, Key Laboratory of Mental Health of the Ministry of Education, Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Key Laboratory of Psychiatric Disorders of Guangdong Province, Collaborative Innovation Center for Brain Science, Department of Neurobiology, Southern Medical University, Guangzhou, Guangdong Province, China
| | - Pei Yu
- Department of Neurology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, Guangdong Province, China
| | - Yuhua Yang
- Department of Neurology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, Guangdong Province, China
| | - Shao-Jian Li
- Department of Neurology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, Guangdong Province, China
| | - Qiang Liu
- Department of Neurology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, Guangdong Province, China
| | - Jiatian Xie
- Department of Neurology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, Guangdong Province, China
| | - Si-Qi Chen
- Department of Anesthesiology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, Guangdong Province, China
| | - Wei-Jye Lin
- Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Guangdong-Hong Kong Joint Laboratory for RNA Medicine; Medical Research Center, Sun Yat-sen Memorial Hospital; Guangdong Province Key Laboratory of Brain Function and Disease, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong Province, China
| | - Yamei Tang
- Department of Neurology, Sun Yat-sen Memorial Hospital; Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Guangdong-Hong Kong Joint Laboratory for RNA Medicine, Sun Yat-sen Memorial Hospital; Guangdong Province Key Laboratory of Brain Function and Disease, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong Province, China
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Guerreiro I, Gu Z, Yakel JL, Gutkin BS. Recurring Cholinergic Inputs Induce Local Hippocampal Plasticity through Feedforward Disinhibition. eNeuro 2022; 9:ENEURO.0389-21.2022. [PMID: 36028329 PMCID: PMC9463983 DOI: 10.1523/eneuro.0389-21.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Revised: 04/22/2022] [Accepted: 05/15/2022] [Indexed: 11/30/2022] Open
Abstract
The CA1 pyramidal neurons are embedded in an intricate local circuitry that contains a variety of interneurons. The roles these interneurons play in the regulation of the excitatory synaptic plasticity remains largely understudied. Recent experiments showed that recurring cholinergic activation of α7 nACh receptors expressed in oriens-lacunosum-moleculare (OLMα2) interneurons can directly induce LTP in Schaffer collateral (SC)-CA1 synapses. Here, we pair in vitro studies with biophysically based modeling to uncover the underlying mechanisms. According to our model, α7 nAChR activation increases OLM GABAergic activity. This results in the inhibition of the fast-spiking interneurons that provide feedforward inhibition onto CA1 pyramidal neurons. This disinhibition, paired with tightly timed SC stimulation, can induce potentiation at the excitatory synapses of CA1 pyramidal neurons. Our work details the role of cholinergic modulation in disinhibition-induced hippocampal plasticity. It relates the timing of cholinergic pairing found experimentally in previous studies with the timing between disinhibition and hippocampal stimulation necessary to induce potentiation and suggests the dynamics of the involved interneurons play a crucial role in determining this timing.Significance StatementWe use a combination of experiments and mechanistic modeling to uncover the key role for cholinergic neuromodulation of feedforward disinhibitory circuits in regulating hippocampal plasticity. We found that cholinergic activation of α7 nAChR on α7 nACh receptors expressed in oriens-lacunosum-moleculare interneurons, when tightly paired with stimulation of the Schaffer collaterals, can cancel feedforward inhibition onto CA1 pyramidal cells, enabling the potentiation of the SC-CA1 synapse. Our work details how cholinergic action on GABAergic interneurons can tightly regulate the excitability and plasticity of the hippocampal network, unraveling the intricate interplay of the hierarchal inhibitory circuitry and cholinergic neuromodulation as a mechanism for hippocampal plasticity.
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Affiliation(s)
- Inês Guerreiro
- Group for Neural Theory, LNC2 INSERM U960, Département d'études cognitives, Ecole Normale Superieure, PSL Université Paris, 75005 Paris, France
| | - Zhenglin Gu
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC 27709, USA
| | - Jerrel L Yakel
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC 27709, USA
| | - Boris S Gutkin
- Group for Neural Theory, LNC2 INSERM U960, Département d'études cognitives, Ecole Normale Superieure, PSL Université Paris, 75005 Paris, France
- Center for Cognition and Decision Making, Institute for Cognitive Neuroscience, National Research University Higher School of Economics, Moscow 101000, Russia
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6
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Choquet D, Opazo P. The role of AMPAR lateral diffusion in memory. Semin Cell Dev Biol 2022; 125:76-83. [PMID: 35123863 DOI: 10.1016/j.semcdb.2022.01.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 01/26/2022] [Accepted: 01/27/2022] [Indexed: 12/17/2022]
Abstract
The accumulation of AMPARs to synapses is a fundamental step in Long-term potentiation (LTP) of synaptic transmission, a well-established cellular correlate of learning and memory. The discovery of a sizeable and highly mobile population of extrasynaptic AMPARs - randomly scanning the synaptic surface under basal conditions - provided a conceptual framework for a simplified model: LTP can be induced by the capture, and hence accumulation, of laterally diffusing extrasynaptic AMPARs. Here, we review the evidence supporting a rate-limiting role of AMPAR lateral diffusion in LTP and as consequence, in learning and memory. We propose that there are "multiple solutions" for achieving the diffusional trapping of AMPAR during LTP, mainly mediated by the interaction between interchangeable AMPAR auxiliary subunits and cell-adhesion molecules containing PDZ-binding domains and synaptic scaffolds containing PDZ-domains. We believe that this molecular degeneracy in the diffusional trapping of AMPAR during LTP serve to ensure the robustness of this crucial step in the making of memories. All in all, the role of AMPAR lateral diffusion in LTP is not only a conceptual leap in our understanding of memory, but it might also hold the keys for the development of therapeutics against disorders associated with memory deficits such as Alzheimer's disease.
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Affiliation(s)
- Daniel Choquet
- Interdisciplinary Institute for Neuroscience, CNRS, Univ. Bordeaux, IINS, UMR 5297, Bordeaux, France; Univ. Bordeaux, CNRS, INSERM, Bordeaux Imaging Center, BIC, UMS 3420, Bordeaux, France.
| | - Patricio Opazo
- UK Dementia Research Institute, Centre for Discovery Brain Sciences, University of Edinburgh, Chancellor's Building, Edinburgh Medical School, Edinburgh EH16 4SB, UK; Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia.
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7
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Ang G, Brown LA, Tam SKE, Davies KE, Foster RG, Harrison PJ, Sprengel R, Vyazovskiy VV, Oliver PL, Bannerman DM, Peirson SN. Deletion of AMPA receptor GluA1 subunit gene (Gria1) causes circadian rhythm disruption and aberrant responses to environmental cues. Transl Psychiatry 2021; 11:588. [PMID: 34782594 PMCID: PMC8593011 DOI: 10.1038/s41398-021-01690-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 10/19/2021] [Accepted: 10/21/2021] [Indexed: 12/19/2022] Open
Abstract
Dysfunction of the glutamate α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor GluA1 subunit and deficits in synaptic plasticity are implicated in schizophrenia and sleep and circadian rhythm disruption. To investigate the role of GluA1 in circadian and sleep behaviour, we used wheel-running, passive-infrared, and video-based home-cage activity monitoring to assess daily rest-activity profiles of GluA1-knockout mice (Gria1-/-). We showed that these mice displayed various circadian abnormalities, including misaligned, fragmented, and more variable rest-activity patterns. In addition, they showed heightened, but transient, behavioural arousal to light→dark and dark→light transitions, as well as attenuated nocturnal-light-induced activity suppression (negative masking). In the hypothalamic suprachiasmatic nuclei (SCN), nocturnal-light-induced cFos signals (a molecular marker of neuronal activity in the preceding ~1-2 h) were attenuated, indicating reduced light sensitivity in the SCN. However, there was no change in the neuroanatomical distribution of expression levels of two neuropeptides-vasoactive intestinal peptide (VIP) and arginine vasopressin (AVP)-differentially expressed in the core (ventromedial) vs. shell (dorsolateral) SCN subregions and both are known to be important for neuronal synchronisation within the SCN and circadian rhythmicity. In the motor cortex (area M1/M2), there was increased inter-individual variability in cFos levels during the evening period, mirroring the increased inter-individual variability in locomotor activity under nocturnal light. Finally, in the spontaneous odour recognition task GluA1 knockouts' short-term memory was impaired due to enhanced attention to the recently encountered familiar odour. These abnormalities due to altered AMPA-receptor-mediated signalling resemble and may contribute to sleep and circadian rhythm disruption and attentional deficits in different modalities in schizophrenia.
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Affiliation(s)
- Gauri Ang
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
- Department of Experimental Psychology, University of Oxford, Oxford, UK
- Sleep and Circadian Neuroscience Institute (SCNi), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Laurence A Brown
- Sleep and Circadian Neuroscience Institute (SCNi), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
- IT Services, University of Oxford, Oxford, UK
| | - Shu K E Tam
- Sleep and Circadian Neuroscience Institute (SCNi), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Kay E Davies
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - Russell G Foster
- Sleep and Circadian Neuroscience Institute (SCNi), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Paul J Harrison
- Department of Psychiatry, University of Oxford, Warneford Hospital, Oxford, UK
| | - Rolf Sprengel
- Research Group of the Max Planck Institute for Medical Research at the Institute for Anatomy and Cell Biology, Heidelberg University, Heidelberg, Germany
| | - Vladyslav V Vyazovskiy
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
- Sleep and Circadian Neuroscience Institute (SCNi), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Peter L Oliver
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK.
- Mammalian Genetics Unit, MRC Harwell Institute, Harwell, UK.
| | - David M Bannerman
- Department of Experimental Psychology, University of Oxford, Oxford, UK.
| | - Stuart N Peirson
- Sleep and Circadian Neuroscience Institute (SCNi), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK.
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Gugustea R, Jia Z. Genetic manipulations of AMPA glutamate receptors in hippocampal synaptic plasticity. Neuropharmacology 2021; 194:108630. [PMID: 34089730 DOI: 10.1016/j.neuropharm.2021.108630] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Revised: 05/06/2021] [Accepted: 05/18/2021] [Indexed: 01/17/2023]
Abstract
Alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) are the principal mediators of fast excitatory synaptic transmission and they are required for various forms of synaptic plasticity, including long-term potentiation (LTP) and depression (LTD), which are key mechanisms of learning and memory. AMPARs are tetrameric complexes assembled from four subunits (GluA1-4), however, the lack of subunit-specific pharmacological tools has made the assessment of individual subunits difficult. The application of genetic techniques, particularly gene targeting, allows for precise manipulation and dissection of each subunit in the regulation of neuronal function and behaviour. In this review, we summarize studies using various mouse models with genetically altered AMPARs and focus on their roles in basal synaptic transmission, LTP, and LTD at the hippocampal CA1 synapse. These studies provide strong evidence that there are multiple forms of LTP and LTD at this synapse which can be induced by various induction protocols, and they are differentially regulated by different AMPAR subunits and domains. We conclude that it is necessary to delineate the mechanism of each of these forms of plasticity and their contribution to memory and brain disorders.
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Affiliation(s)
- Radu Gugustea
- The Hospital for Sick Children, Neurosciences and Mental Health Program, Peter Gilgan Centre for Research and Learning, Toronto, ON, Canada; Department of Physiology, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Zhengping Jia
- The Hospital for Sick Children, Neurosciences and Mental Health Program, Peter Gilgan Centre for Research and Learning, Toronto, ON, Canada; Department of Physiology, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, Canada.
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9
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Tomko M, Benuskova L, Jedlicka P. A new reduced-morphology model for CA1 pyramidal cells and its validation and comparison with other models using HippoUnit. Sci Rep 2021; 11:7615. [PMID: 33828151 PMCID: PMC8027802 DOI: 10.1038/s41598-021-87002-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 02/19/2021] [Indexed: 01/13/2023] Open
Abstract
Modeling long-term neuronal dynamics may require running long-lasting simulations. Such simulations are computationally expensive, and therefore it is advantageous to use simplified models that sufficiently reproduce the real neuronal properties. Reducing the complexity of the neuronal dendritic tree is one option. Therefore, we have developed a new reduced-morphology model of the rat CA1 pyramidal cell which retains major dendritic branch classes. To validate our model with experimental data, we used HippoUnit, a recently established standardized test suite for CA1 pyramidal cell models. The HippoUnit allowed us to systematically evaluate the somatic and dendritic properties of the model and compare them to models publicly available in the ModelDB database. Our model reproduced (1) somatic spiking properties, (2) somatic depolarization block, (3) EPSP attenuation, (4) action potential backpropagation, and (5) synaptic integration at oblique dendrites of CA1 neurons. The overall performance of the model in these tests achieved higher biological accuracy compared to other tested models. We conclude that, due to its realistic biophysics and low morphological complexity, our model captures key physiological features of CA1 pyramidal neurons and shortens computational time, respectively. Thus, the validated reduced-morphology model can be used for computationally demanding simulations as a substitute for more complex models.
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Affiliation(s)
- Matus Tomko
- Centre for Cognitive Science, Department of Applied Informatics, Faculty of Mathematics, Physics and Informatics, Comenius University in Bratislava, 842 48, Bratislava, Slovakia.
| | - Lubica Benuskova
- Centre for Cognitive Science, Department of Applied Informatics, Faculty of Mathematics, Physics and Informatics, Comenius University in Bratislava, 842 48, Bratislava, Slovakia
| | - Peter Jedlicka
- ICAR3R-Interdisciplinary Centre for 3Rs in Animal Research, Faculty of Medicine, Justus-Liebig-University, Rudolf-Buchheim-Str. 6, 35392, Giessen, Germany. .,Institute of Clinical Neuroanatomy, NeuroScience Center, Goethe-University Frankfurt, Frankfurt am Main, Germany.
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10
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Liu A, Ji H, Ren Q, Meng Y, Zhang H, Collingride G, Xie W, Jia Z. The Requirement of the C-Terminal Domain of GluA1 in Different Forms of Long-Term Potentiation in the Hippocampus Is Age-Dependent. Front Synaptic Neurosci 2020; 12:588785. [PMID: 33192442 PMCID: PMC7661473 DOI: 10.3389/fnsyn.2020.588785] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Accepted: 09/25/2020] [Indexed: 11/13/2022] Open
Abstract
Long-term potentiation (LTP) at glutamatergic synapses is an extensively studied form of long-lasting synaptic plasticity widely regarded as the cellular basis for learning and memory. At the CA1 synapse, there are multiple forms of LTP with distinct properties. Although AMPA glutamate receptors (AMPARs) are a key target of LTP expression, whether they are required in all forms of LTP remains unclear. To address this question, we have used our recently developed mouse line, GluA1C2KI, where the c-terminal domain (CTD) of the endogenous GluA1 is replaced by that of GluA2. Unlike traditional GluA1 global or conditional KO mice, GluA1C2KI mice have no changes in basal AMPAR properties or synaptic transmission allowing a better assessment of GluA1 in synaptic plasticity. We previously showed that these mice are impaired in LTP induced by high-frequency stimulation (HFS-LTP), but whether other forms of LTP are also affected in these mice is unknown. In this study, we compared various forms of LTP at CA1 synapses between GluA1C2KI and wild-type littermates by using several induction protocols. We show that HFS-LTP is impaired in both juvenile and adult GluA1C2KI mice. The LTP induced by theta-burst stimulation (TBS-LTP) is also abolished in juvenile GluA1C2KI mice. Interestingly, TBS-LTP can still be induced in adult GluA1C2KI mice, but its mechanisms are altered becoming more sensitive to protein synthesis and the extracellular signal-regulated kinase (ERK) inhibitors compared to wild type (WT) control. The GluA1C2KI mice are also differentially altered in several forms of LTP induced under whole-cell recording paradigms. These results indicate that the CTD of GluA1 is differentially involved in different forms of LTP at CA1 synapse highlighting the complexity and adaptative potential of LTP expression mechanisms in the hippocampus.
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Affiliation(s)
- An Liu
- The Key Laboratory of Developmental Genes and Human Disease, Ministry of Education, School of Life Science and Technology, Jiangsu Co-Innovation Center of Neuroregeneration, Southeast University, Nanjing, China
| | - Hong Ji
- The Key Laboratory of Developmental Genes and Human Disease, Ministry of Education, School of Life Science and Technology, Jiangsu Co-Innovation Center of Neuroregeneration, Southeast University, Nanjing, China
| | - Qiaoyun Ren
- The Key Laboratory of Developmental Genes and Human Disease, Ministry of Education, School of Life Science and Technology, Jiangsu Co-Innovation Center of Neuroregeneration, Southeast University, Nanjing, China
| | - Yanghong Meng
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Haiwang Zhang
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada.,Neurosciences and Mental Health, The Hospital for Sick Children, Toronto, ON, Canada
| | - Graham Collingride
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Wei Xie
- The Key Laboratory of Developmental Genes and Human Disease, Ministry of Education, School of Life Science and Technology, Jiangsu Co-Innovation Center of Neuroregeneration, Southeast University, Nanjing, China
| | - Zhengping Jia
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada.,Neurosciences and Mental Health, The Hospital for Sick Children, Toronto, ON, Canada
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11
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Linking Nanoscale Dynamics of AMPA Receptor Organization to Plasticity of Excitatory Synapses and Learning. J Neurosci 2019; 38:9318-9329. [PMID: 30381423 DOI: 10.1523/jneurosci.2119-18.2018] [Citation(s) in RCA: 79] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Revised: 09/21/2018] [Accepted: 09/21/2018] [Indexed: 11/21/2022] Open
Abstract
The spatiotemporal organization of neurotransmitter receptors in the postsynaptic membrane is a fundamental determinant of synaptic transmission and thus of information processing by the brain. The ionotropic AMPA subtype of glutamate receptors (AMPARs) mediate fast excitatory synaptic transmission in the CNS. The number of AMPARs located en face presynaptic glutamate release sites sets the efficacy of synaptic transmission. Understanding how this number is set and regulated has been the topic of intense research in the last two decades. We showed that AMPARs are not stable in the synapse as initially thought. They continuously enter and exit the postsynaptic density by lateral diffusion, and they exchange between the neuronal surface and intracellular compartments by endocytosis and exocytosis at extrasynaptic sites. Regulation of these various trafficking pathways has emerged as a key mechanism for activity-dependent plasticity of synaptic transmission, a process important for learning and memory. I here present my view of these findings. In particular, the advent of super-resolution microscopy and single-molecule tracking has helped to uncover the intricacy of AMPARs' dynamic organization at the nanoscale. In addition, AMPAR surface diffusion is highly regulated by a variety of factors, including neuronal activity, stress hormones, and neurodegeneration, suggesting that AMPAR diffusion-trapping may play a central role in synapse function. Using innovative tools to understand further the link between receptor dynamics and synapse plasticity is now unveiling new molecular mechanisms of learning. Modifying AMPAR dynamics may emerge as a new target to correct synapse dysfunction in the diseased brain.
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12
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Pham TH, Gardier AM. Fast-acting antidepressant activity of ketamine: highlights on brain serotonin, glutamate, and GABA neurotransmission in preclinical studies. Pharmacol Ther 2019; 199:58-90. [DOI: 10.1016/j.pharmthera.2019.02.017] [Citation(s) in RCA: 73] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 02/25/2019] [Indexed: 12/13/2022]
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13
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Guo R, Li H, Li X, Xue Z, Sun Y, Ma D, Guan Y, Li J, Tian M, Wang Y. Downregulation of neuroligin1 ameliorates postoperative pain through inhibiting neuroligin1/postsynaptic density 95-mediated synaptic targeting of α-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptor GluA1 subunits in rat dorsal horns. Mol Pain 2018; 14:1744806918766745. [PMID: 29592780 PMCID: PMC5881971 DOI: 10.1177/1744806918766745] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Neuroligin1 is an important synaptic cell adhesion molecule that modulates the function of synapses through protein-protein interactions. Yet, it remains unclear whether the regulation of synaptic transmission in the spinal cord by neruoligin1 contributes to the development of postoperative pain. In a rat model of postoperative pain induced by plantar incision, we conducted Western blot study to examine changes in the expression of postsynaptic membrane of neuroligin1, postsynaptic density 95 (PSD-95), and α-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptor GluA1 and GluA2 subunits in the spinal cord dorsal horn after injury. The interaction between neuroligin1 and PSD-95 was further determined by using coimmunoprecipitation. Protein levels of neuroligin1 and GluA1, but not GluA2 and PSD-95, were significantly increased in the postsynaptic membrane of the ipsilateral dorsal horn at 3 h and 1 day after incision, as compared to that in control group (naïve). A greater amount of PSD-95 was coimmunoprecipitated with neuroligin1 at 3 h after incision than that in the control group. Intrathecal administration of small interfering RNAs (siRNAs) targeting neuroligin1 suppressed the expression of neuroligin1 in the spinal cord. Importantly, pretreatment with intrathecal neuroligin1 siRNA2497, but not scrambled siRNA or vehicle, prevented the upregulation of GluA1 expression at 3 h after incision, inhibited the enhanced neuroligin1/PSD-95 interaction, and attenuated postoperative pain. Together, current findings suggest that downregulation of spinal neuroligin1 expression may ameliorate postoperative pain through inhibiting neuroligin1/PSD-95 interaction and synaptic targeting of GluA1 subunit. Accordingly, spinal neuroligin1 may be a potential new target for postoperative pain treatment.
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Affiliation(s)
- Ruijuan Guo
- 1 Department of Anesthesiology, Beijing Friendship Hospital, Capital Medical University, Beijing, China
| | - Huili Li
- 2 Department of Anesthesiology, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China
| | - Xueyang Li
- 2 Department of Anesthesiology, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China
| | - Zhaojing Xue
- 1 Department of Anesthesiology, Beijing Friendship Hospital, Capital Medical University, Beijing, China
| | - Yuqing Sun
- 2 Department of Anesthesiology, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China
| | - Danxu Ma
- 2 Department of Anesthesiology, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China
| | - Yun Guan
- 3 Department of Anesthesiology and Critical Care Medicine, The 1466 Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Junfa Li
- 4 Department of Neurobiology, Capital Medical University, Beijing, China
| | - Ming Tian
- 1 Department of Anesthesiology, Beijing Friendship Hospital, Capital Medical University, Beijing, China
| | - Yun Wang
- 2 Department of Anesthesiology, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China
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14
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Haselmann H, Mannara F, Werner C, Planagumà J, Miguez-Cabello F, Schmidl L, Grünewald B, Petit-Pedrol M, Kirmse K, Classen J, Demir F, Klöcker N, Soto D, Doose S, Dalmau J, Hallermann S, Geis C. Human Autoantibodies against the AMPA Receptor Subunit GluA2 Induce Receptor Reorganization and Memory Dysfunction. Neuron 2018; 100:91-105.e9. [PMID: 30146304 DOI: 10.1016/j.neuron.2018.07.048] [Citation(s) in RCA: 67] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 03/14/2018] [Accepted: 07/27/2018] [Indexed: 11/29/2022]
Abstract
AMPA receptors are essential for fast excitatory transmission in the CNS. Autoantibodies to AMPA receptors have been identified in humans with autoimmune encephalitis and severe defects of hippocampal function. Here, combining electrophysiology and high-resolution imaging with neuronal culture preparations and passive-transfer models in wild-type and GluA1-knockout mice, we analyze how specific human autoantibodies against the AMPA receptor subunit GluA2 affect receptor function and composition, synaptic transmission, and plasticity. Anti-GluA2 antibodies induce receptor internalization and a reduction of synaptic GluA2-containing AMPARs followed by compensatory ryanodine receptor-dependent incorporation of synaptic non-GluA2 AMPARs. Furthermore, application of human pathogenic anti-GluA2 antibodies to mice impairs long-term synaptic plasticity in vitro and affects learning and memory in vivo. Our results identify a specific immune-neuronal rearrangement of AMPA receptor subunits, providing a framework to explain disease symptoms.
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Affiliation(s)
- Holger Haselmann
- Hans-Berger Department of Neurology, Jena University Hospital, Am Klinikum 1, 07747 Jena, Germany; Center for Sepsis Control and Care (CSCC), Jena University Hospital, Am Klinikum 1, 07747 Jena, Germany
| | - Francesco Mannara
- Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Hospital Clínic, Universitat de Barcelona, 08036 Barcelona, Spain
| | - Christian Werner
- Hans-Berger Department of Neurology, Jena University Hospital, Am Klinikum 1, 07747 Jena, Germany; Department of Biotechnology and Biophysics, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Jesús Planagumà
- Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Hospital Clínic, Universitat de Barcelona, 08036 Barcelona, Spain
| | - Federico Miguez-Cabello
- Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Hospital Clínic, Universitat de Barcelona, 08036 Barcelona, Spain; Laboratori de Neurofisiologia, Departament de Biomedicina, Facultat de Medicina i Ciències de la Salut, Institut de Neurociències, Universitat de Barcelona, 08036 Barcelona, Spain
| | - Lars Schmidl
- Hans-Berger Department of Neurology, Jena University Hospital, Am Klinikum 1, 07747 Jena, Germany
| | - Benedikt Grünewald
- Hans-Berger Department of Neurology, Jena University Hospital, Am Klinikum 1, 07747 Jena, Germany; Center for Sepsis Control and Care (CSCC), Jena University Hospital, Am Klinikum 1, 07747 Jena, Germany
| | - Mar Petit-Pedrol
- Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Hospital Clínic, Universitat de Barcelona, 08036 Barcelona, Spain
| | - Knut Kirmse
- Hans-Berger Department of Neurology, Jena University Hospital, Am Klinikum 1, 07747 Jena, Germany
| | - Joseph Classen
- Department of Neurology, University of Leipzig, Liebigstrasse 20, 04103 Leipzig, Germany
| | - Fatih Demir
- Institute of Neural and Sensory Physiology, Medical Faculty, University of Düsseldorf, Düsseldorf, Germany; Forschungszentrum Jülich, Central Institute for Engineering, Electronics and Analytics (ZEA-3), Wilhelm-Johnen-Strasse, 52425 Jülich, Germany
| | - Nikolaj Klöcker
- Institute of Neural and Sensory Physiology, Medical Faculty, University of Düsseldorf, Düsseldorf, Germany
| | - David Soto
- Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Hospital Clínic, Universitat de Barcelona, 08036 Barcelona, Spain; Laboratori de Neurofisiologia, Departament de Biomedicina, Facultat de Medicina i Ciències de la Salut, Institut de Neurociències, Universitat de Barcelona, 08036 Barcelona, Spain
| | - Sören Doose
- Department of Biotechnology and Biophysics, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Josep Dalmau
- Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Hospital Clínic, Universitat de Barcelona, 08036 Barcelona, Spain; Department of Neurology, University of Pennsylvania, Philadelphia, PA 19104, USA; Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig de Lluís Companys, 23, 08010 Barcelona, Spain; Centro de Investigación Biomédica en Red Enfermedades Raras (CIBERER), (Instituto Carlos III, Madrid), Av. Monforte de Lemos, 3-5 Pabellón 11, 28029 Madrid, Spain
| | - Stefan Hallermann
- Carl-Ludwig-Institute for Physiology, Medical Faculty, University of Leipzig, Liebigstrasse 27, 04103 Leipzig, Germany
| | - Christian Geis
- Hans-Berger Department of Neurology, Jena University Hospital, Am Klinikum 1, 07747 Jena, Germany; Center for Sepsis Control and Care (CSCC), Jena University Hospital, Am Klinikum 1, 07747 Jena, Germany.
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15
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Bannerman DM, Borchardt T, Jensen V, Rozov A, Haj-Yasein NN, Burnashev N, Zamanillo D, Bus T, Grube I, Adelmann G, Rawlins JNP, Sprengel R. Somatic Accumulation of GluA1-AMPA Receptors Leads to Selective Cognitive Impairments in Mice. Front Mol Neurosci 2018; 11:199. [PMID: 29988555 PMCID: PMC6026654 DOI: 10.3389/fnmol.2018.00199] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Accepted: 05/18/2018] [Indexed: 11/13/2022] Open
Abstract
The GluA1 subunit of the L-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) plays a crucial, but highly selective, role in cognitive function. Here we analyzed AMPAR expression, AMPAR distribution and spatial learning in mice (Gria1R/R ), expressing the "trafficking compromised" GluA1(Q600R) point mutation. Our analysis revealed somatic accumulation and reduction of GluA1(Q600R) and GluA2, but only slightly reduced CA1 synaptic localization in hippocampi of adult Gria1R/R mice. These immunohistological changes were accompanied by a strong reduction of somatic AMPAR currents in CA1, and a reduction of plasticity (short-term and long-term potentiation, STP and LTP, respectively) in the CA1 subfield following tetanic and theta-burst stimulation. Nevertheless, spatial reference memory acquisition in the Morris water-maze and on an appetitive Y-maze task was unaffected in Gria1R/R mice. In contrast, spatial working/short-term memory during both spontaneous and rewarded alternation tasks was dramatically impaired. These findings identify the GluA1(Q600R) mutation as a loss of function mutation that provides independent evidence for the selective role of GluA1 in the expression of short-term memory.
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Affiliation(s)
- David M Bannerman
- Department of Experimental Psychology, University of Oxford, Oxford, United Kingdom
| | - Thilo Borchardt
- Departments of Molecular Neurobiology and Cell Physiology, Max Planck Institute for Medical Research, Heidelberg, Germany.,EW-Nutrition GmbH, Visbek, Germany
| | - Vidar Jensen
- Department of Physiology, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Andrey Rozov
- Departments of Molecular Neurobiology and Cell Physiology, Max Planck Institute for Medical Research, Heidelberg, Germany.,Department of Physiology and Pathophysiology, Heidelberg University, Heidelberg, Germany.,OpenLab of Neurobiology, Kazan Federal University, Kazan, Russia
| | - Nadia N Haj-Yasein
- Department of Physiology, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Nail Burnashev
- Departments of Molecular Neurobiology and Cell Physiology, Max Planck Institute for Medical Research, Heidelberg, Germany.,INSERM UMR 1249 Mediterranean Institute of Neurobiology (INMED), Aix-Marseille University Parc Scientifique de Luminy, Marseille, France
| | - Daniel Zamanillo
- Departments of Molecular Neurobiology and Cell Physiology, Max Planck Institute for Medical Research, Heidelberg, Germany.,Esteve Pharmaceuticals, S.A., Barcelona, Spain
| | - Thorsten Bus
- Departments of Molecular Neurobiology and Cell Physiology, Max Planck Institute for Medical Research, Heidelberg, Germany
| | - Isabel Grube
- Institute of Anatomy and Cell Biology, University of Freiburg, Freiburg, Germany.,Department for Internal Medicine, Klinikum Landkreis Tuttlingen, Tuttlingen, Germany
| | - Giselind Adelmann
- Institute of Anatomy and Cell Biology, University of Freiburg, Freiburg, Germany
| | - J Nicholas P Rawlins
- Department of Experimental Psychology, University of Oxford, Oxford, United Kingdom
| | - Rolf Sprengel
- Departments of Molecular Neurobiology and Cell Physiology, Max Planck Institute for Medical Research, Heidelberg, Germany.,Institute for Anatomy and Cell Biology, Heidelberg University, Heidelberg, Germany
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16
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The C-terminal tails of endogenous GluA1 and GluA2 differentially contribute to hippocampal synaptic plasticity and learning. Nat Neurosci 2017; 21:50-62. [PMID: 29230056 DOI: 10.1038/s41593-017-0030-z] [Citation(s) in RCA: 93] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Accepted: 10/24/2017] [Indexed: 11/09/2022]
Abstract
Long-term potentiation (LTP) and depression (LTD) at glutamatergic synapses are intensively investigated processes for understanding the synaptic basis for learning and memory, but the underlying molecular mechanisms remain poorly understood. We have made three mouse lines where the C-terminal domains (CTDs) of endogenous AMPA receptors (AMPARs), the principal mediators of fast excitatory synaptic transmission, are specifically exchanged. These mice display profound deficits in synaptic plasticity without any effects on basal synaptic transmission. Our study reveals that the CTDs of GluA1 and GluA2, the key subunits of AMPARs, are necessary and sufficient to drive NMDA receptor-dependent LTP and LTD, respectively. In addition, these domains exert differential effects on spatial and contextual learning and memory. These results establish dominant roles of AMPARs in governing bidirectional synaptic and behavioral plasticity in the CNS.
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17
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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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18
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The AMPA Receptor Subunit GluA1 is Required for CA1 Hippocampal Long-Term Potentiation but is not Essential for Synaptic Transmission. Neurochem Res 2017; 44:549-561. [PMID: 29098531 DOI: 10.1007/s11064-017-2425-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Revised: 09/13/2017] [Accepted: 10/21/2017] [Indexed: 10/18/2022]
Abstract
AMPA receptors mediate the majority of excitatory glutamatergic transmission in the mammalian brain and are heterotetramers composed of GluA1-4 subunits. Despite genetic studies, the roles of the subunits in synaptic transmission and plasticity remain controversial. To address this issue, we investigated the effects of cell-specific removal of GluA1 in hippocampal CA1 pyramidal neurons using virally-expressed GluA1 shRNA in organotypic slice culture. We show that this shRNA approach produces a rapid, efficient and selective loss of GluA1, and removed > 80% of surface GluA1 from synapses. This loss of GluA1 caused a modest reduction (up to 57%) in synaptic transmission and when applied in neurons from GluA3 knock-out mice, a similar small reduction in transmission occurred. Further, we found that loss of GluA1 caused a redistribution of GluA2 to synapses that may compensate functionally for the absence of GluA1. We found that LTP was absent in neurons lacking GluA1, induced either by pairing or by a theta-burst pairing protocol previously shown to induce LTP in GluA1 knock-out mice. Our findings demonstrate a critical role of GluA1 in CA1 LTP, but no absolute requirement for GluA1 in maintaining synaptic transmission. Further, our results indicate that GluA2 homomers can mediate synaptic transmission and can compensate for loss of GluA1.
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19
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Renner MC, Albers EH, Gutierrez-Castellanos N, Reinders NR, van Huijstee AN, Xiong H, Lodder TR, Kessels HW. Synaptic plasticity through activation of GluA3-containing AMPA-receptors. eLife 2017; 6:25462. [PMID: 28762944 PMCID: PMC5578739 DOI: 10.7554/elife.25462] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Accepted: 07/31/2017] [Indexed: 11/13/2022] Open
Abstract
Excitatory synaptic transmission is mediated by AMPA-type glutamate receptors (AMPARs). In CA1 pyramidal neurons of the hippocampus two types of AMPARs predominate: those that contain subunits GluA1 and GluA2 (GluA1/2), and those that contain GluA2 and GluA3 (GluA2/3). Whereas subunits GluA1 and GluA2 have been extensively studied, the contribution of GluA3 to synapse physiology has remained unclear. Here we show in mice that GluA2/3s are in a low-conductance state under basal conditions, and although present at synapses they contribute little to synaptic currents. When intracellular cyclic AMP (cAMP) levels rise, GluA2/3 channels shift to a high-conductance state, leading to synaptic potentiation. This cAMP-driven synaptic potentiation requires the activation of both protein kinase A (PKA) and the GTPase Ras, and is induced upon the activation of β-adrenergic receptors. Together, these experiments reveal a novel type of plasticity at CA1 hippocampal synapses that is expressed by the activation of GluA3-containing AMPARs.
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Affiliation(s)
- Maria C Renner
- Synaptic Plasticity and Behavior Group, The Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands
| | - Eva Hh Albers
- Synaptic Plasticity and Behavior Group, The Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands
| | - Nicolas Gutierrez-Castellanos
- Synaptic Plasticity and Behavior Group, The Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands
| | - Niels R Reinders
- Synaptic Plasticity and Behavior Group, The Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands
| | - Aile N van Huijstee
- Synaptic Plasticity and Behavior Group, The Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands
| | - Hui Xiong
- Synaptic Plasticity and Behavior Group, The Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands
| | - Tessa R Lodder
- Synaptic Plasticity and Behavior Group, The Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands
| | - Helmut W Kessels
- Synaptic Plasticity and Behavior Group, The Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands
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20
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Geisheker MR, Heymann G, Wang T, Coe BP, Turner TN, Stessman HA, Hoekzema K, Kvarnung M, Shaw M, Friend K, Liebelt J, Barnett C, Thompson EM, Haan E, Guo H, Anderlid BM, Nordgren A, Lindstrand A, Vandeweyer G, Alberti A, Avola E, Vinci M, Giusto S, Pramparo T, Pierce K, Nalabolu S, Michaelson JJ, Sedlacek Z, Santen GW, Peeters H, Hakonarson H, Courchesne E, Romano C, Kooy RF, Bernier RA, Nordenskjöld M, Gecz J, Xia K, Zweifel LS, Eichler EE. Hotspots of missense mutation identify neurodevelopmental disorder genes and functional domains. Nat Neurosci 2017; 20:1043-1051. [PMID: 28628100 PMCID: PMC5539915 DOI: 10.1038/nn.4589] [Citation(s) in RCA: 124] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Accepted: 05/19/2017] [Indexed: 12/17/2022]
Abstract
Although de novo missense mutations have been predicted to account for more cases of autism than gene-truncating mutations, most research has focused on the latter. We identified the properties of de novo missense mutations in patients with neurodevelopmental disorders (NDDs) and highlight 35 genes with excess missense mutations. Additionally, 40 amino acid sites were recurrently mutated in 36 genes, and targeted sequencing of 20 sites in 17,688 patients with NDD identified 21 new patients with identical missense mutations. One recurrent site substitution (p.A636T) occurs in a glutamate receptor subunit, GRIA1. This same amino acid substitution in the homologous but distinct mouse glutamate receptor subunit Grid2 is associated with Lurcher ataxia. Phenotypic follow-up in five individuals with GRIA1 mutations shows evidence of specific learning disabilities and autism. Overall, we find significant clustering of de novo mutations in 200 genes, highlighting specific functional domains and synaptic candidate genes important in NDD pathology.
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Affiliation(s)
| | - Gabriel Heymann
- Department of Pharmacology, University of Washington, Seattle, Washington, USA
- Department of Psychiatry and Behavioral Sciences, University of Washington, Seattle, Washington, USA
| | - Tianyun Wang
- The State Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Bradley P. Coe
- Department of Genome Sciences, University of Washington, Seattle, Washington, USA
| | - Tychele N. Turner
- Department of Genome Sciences, University of Washington, Seattle, Washington, USA
| | - Holly A.F. Stessman
- Department of Genome Sciences, University of Washington, Seattle, Washington, USA
| | - Kendra Hoekzema
- Department of Genome Sciences, University of Washington, Seattle, Washington, USA
| | - Malin Kvarnung
- Department of Molecular Medicine and Surgery, Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden
- Department of Clinical Genetics, Karolinska University Hospital, Stockholm, Sweden
| | - Marie Shaw
- Robinson Research Institute and the University of Adelaide at the Women’s and Children’s Hospital, North Adelaide, South Australia, Australia
| | - Kathryn Friend
- Robinson Research Institute and the University of Adelaide at the Women’s and Children’s Hospital, North Adelaide, South Australia, Australia
- SA Pathology, Adelaide, South Australia, Australia
| | - Jan Liebelt
- South Australian Clinical Genetics Service, SA Pathology (at Women’s and Children’s Hospital), Adelaide, South Australia, Australia
| | - Christopher Barnett
- South Australian Clinical Genetics Service, SA Pathology (at Women’s and Children’s Hospital), Adelaide, South Australia, Australia
- School of Paediatrics and Reproductive Health, University of Adelaide, Adelaide, South Australia, Australia
| | - Elizabeth M. Thompson
- South Australian Clinical Genetics Service, SA Pathology (at Women’s and Children’s Hospital), Adelaide, South Australia, Australia
- School of Medicine, University of Adelaide, Adelaide, South Australia, Australia
| | - Eric Haan
- South Australian Clinical Genetics Service, SA Pathology (at Women’s and Children’s Hospital), Adelaide, South Australia, Australia
- School of Medicine, University of Adelaide, Adelaide, South Australia, Australia
| | - Hui Guo
- The State Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Britt-Marie Anderlid
- Department of Molecular Medicine and Surgery, Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden
- Department of Clinical Genetics, Karolinska University Hospital, Stockholm, Sweden
| | - Ann Nordgren
- Department of Molecular Medicine and Surgery, Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden
- Department of Clinical Genetics, Karolinska University Hospital, Stockholm, Sweden
| | - Anna Lindstrand
- Department of Molecular Medicine and Surgery, Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden
- Department of Clinical Genetics, Karolinska University Hospital, Stockholm, Sweden
| | - Geert Vandeweyer
- Department of Medical Genetics, University of Antwerp, Antwerp, Belgium
| | - Antonino Alberti
- Unit of Pediatrics & Medical Genetics, IRCCS Associazione Oasi Maria Santissima, Troina, Italy
| | - Emanuela Avola
- Unit of Pediatrics & Medical Genetics, IRCCS Associazione Oasi Maria Santissima, Troina, Italy
| | - Mirella Vinci
- Laboratory of Medical Genetics, IRCCS Associazione Oasi Maria Santissima, Troina, Italy
| | - Stefania Giusto
- Unit of Neurology, IRCCS Associazione Oasi Maria Santissima, Troina, Italy
| | - Tiziano Pramparo
- University of California, San Diego, Autism Center of Excellence, La Jolla, California, USA
| | - Karen Pierce
- University of California, San Diego, Autism Center of Excellence, La Jolla, California, USA
| | - Srinivasa Nalabolu
- University of California, San Diego, Autism Center of Excellence, La Jolla, California, USA
| | | | - Zdenek Sedlacek
- Department of Biology and Medical Genetics, Charles University 2nd Faculty of Medicine and University Hospital Motol, Prague, Czech Republic
| | - Gijs W.E. Santen
- Department of Clinical Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Hilde Peeters
- Centre for Human Genetics, KU Leuven and Leuven Autism Research, Leuven, Belgium
| | - Hakon Hakonarson
- Center for Applied Genomics, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
- Division of Genetics, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
- Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Eric Courchesne
- University of California, San Diego, Autism Center of Excellence, La Jolla, California, USA
| | - Corrado Romano
- Unit of Pediatrics & Medical Genetics, IRCCS Associazione Oasi Maria Santissima, Troina, Italy
| | - R. Frank Kooy
- Department of Medical Genetics, University of Antwerp, Antwerp, Belgium
| | - Raphael A. Bernier
- Department of Psychiatry and Behavioral Sciences, University of Washington, Seattle, Washington, USA
| | - Magnus Nordenskjöld
- Department of Molecular Medicine and Surgery, Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden
- Department of Clinical Genetics, Karolinska University Hospital, Stockholm, Sweden
| | - Jozef Gecz
- Robinson Research Institute and the University of Adelaide at the Women’s and Children’s Hospital, North Adelaide, South Australia, Australia
- South Australian Health and Medical Research Institute, Adelaide, South Australia, Australia
| | - Kun Xia
- The State Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Larry S. Zweifel
- Department of Pharmacology, University of Washington, Seattle, Washington, USA
- Department of Psychiatry and Behavioral Sciences, University of Washington, Seattle, Washington, USA
| | - Evan E. Eichler
- Department of Genome Sciences, University of Washington, Seattle, Washington, USA
- Howard Hughes Medical Institute, Seattle, Washington, USA
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21
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Lykens NM, Coughlin DJ, Reddi JM, Lutz GJ, Tallent MK. AMPA GluA1-flip targeted oligonucleotide therapy reduces neonatal seizures and hyperexcitability. PLoS One 2017; 12:e0171538. [PMID: 28178321 PMCID: PMC5298276 DOI: 10.1371/journal.pone.0171538] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Accepted: 01/23/2017] [Indexed: 12/24/2022] Open
Abstract
Glutamate-activated α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPA-Rs) mediate the majority of excitatory neurotransmission in brain and thus are major drug targets for diseases associated with hyperexcitability or neurotoxicity. Due to the critical nature of AMPA-Rs in normal brain function, typical AMPA-R antagonists have deleterious effects on cognition and motor function, highlighting the need for more precise modulators. A dramatic increase in the flip isoform of alternatively spliced AMPA-R GluA1 subunits occurs post-seizure in humans and animal models. GluA1-flip produces higher gain AMPA channels than GluA1-flop, increasing network excitability and seizure susceptibility. Splice modulating oligonucleotides (SMOs) bind to pre-mRNA to influence alternative splicing, a strategy that can be exploited to develop more selective drugs across therapeutic areas. We developed a novel SMO, GR1, which potently and specifically decreased GluA1-flip expression throughout the brain of neonatal mice lasting at least 60 days after single intracerebroventricular injection. GR1 treatment reduced AMPA-R mediated excitatory postsynaptic currents at hippocampal CA1 synapses, without affecting long-term potentiation or long-term depression, cellular models of memory, or impairing GluA1-dependent cognition or motor function in mice. Importantly, GR1 demonstrated anti-seizure properties and reduced post-seizure hyperexcitability in neonatal mice, highlighting its drug candidate potential for treating epilepsies and other neurological diseases involving network hyperexcitability.
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Affiliation(s)
- Nicole M. Lykens
- Graduate Program in Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America
- LifeSplice Pharma, Malvern, Pennsylvania, United States of America
| | - David J. Coughlin
- Department of Biology, Widener University, Chester, Pennsylvania, United States of America
| | - Jyoti M. Reddi
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Gordon J. Lutz
- LifeSplice Pharma, Malvern, Pennsylvania, United States of America
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Melanie K. Tallent
- LifeSplice Pharma, Malvern, Pennsylvania, United States of America
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America
- * E-mail:
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22
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Britten RA, Jewell JS, Davis LK, Miller VD, Hadley MM, Semmes OJ, Lonart G, Dutta SM. Changes in the Hippocampal Proteome Associated with Spatial Memory Impairment after Exposure to Low (20 cGy) Doses of 1 GeV/n 56Fe Radiation. Radiat Res 2017; 187:287-297. [PMID: 28156212 DOI: 10.1667/rr14067.1] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Exposure to low (∼20 cGy) doses of high-energy charged (HZE) particles, such as 1 GeV/n 56Fe, results in impaired hippocampal-dependent learning and memory (e.g., novel object recognition and spatial memory) in rodents. While these findings raise the possibility that astronauts on deep-space missions may develop cognitive deficits, not all rats develop HZE-induced cognitive impairments, even after exposure to high (200 cGy) HZE doses. The reasons for this differential sensitivity in some animals that develop HZE-induced cognitive failure remain speculative. We employed a robust quantitative mass spectrometry-based workflow, which links early-stage discovery to next-stage quantitative verification, to identify differentially active proteins/pathways in rats that developed spatial memory impairment at three months after exposure to 20 cGy of 1 GeV/n 56Fe (20/impaired), and in those rats that managed to maintain normal cognitive performance (20/functional). Quantitative data were obtained on 665-828 hippocampal proteins in the various cohorts of rats studied, of which 580 were expressed in all groups. A total of 107 proteins were upregulated in the irradiated rats irrespective of their spatial memory performance status, which included proteins involved in oxidative damage response, calcium transport and signaling. Thirty percent (37/107) of these "radiation biomarkers" formed a functional interactome of the proteasome and the COP9 signalosome. These data suggest that there is persistent oxidative stress, ongoing autophagy and altered synaptic plasticity in the irradiated hippocampus, irrespective of the spatial memory performance status, suggesting that the ultimate phenotype may be determined by how well the hippocampal neurons compensate to the ongoing oxidative stress and associated side effects. There were 67 proteins with expression that correlated with impaired spatial memory performance. Several of the "impaired biomarkers" have been implicated in poor spatial memory performance, neurodegeneration, neuronal loss or neuronal susceptibility to apoptosis, or neuronal synaptic or structural plasticity. Therefore, in addition to the baseline oxidative stress and altered adenosine metabolism observed in all irradiated rats, the 20/impaired rats expressed proteins that led to poor spatial memory performance, enhanced neuronal loss and apoptosis, changes in synaptic plasticity and dendritic remodeling. A total of 46 proteins, which were differentially upregulated in the sham-irradiated and 20/functional rat cohorts, can thus be considered as markers of good spatial memory, while another 95 proteins are associated with the maintenance of good spatial memory in the 20/functional rats. The loss or downregulation of these "good spatial memory" proteins would most likely exacerbate the situation in the 20/impaired rats, having a major impact on their neurocognitive status, given that many of those proteins play an important role in neuronal homeostasis and function. Our large-scale comprehensive proteomic analysis has provided some insight into the processes that are altered after exposure, and the collective data suggests that there are multiple problems with the functionality of the neurons and astrocytes in the irradiated hippocampi, which appear to be further exacerbated in the rats that have impaired spatial memory performance or partially compensated for in the rats with good spatial memory.
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Affiliation(s)
- Richard A Britten
- Department of a Radiation Oncology, Eastern Virginia Medical School, Norfolk, Virginia 23507.,b Department of Microbiology and Molecular Cell Biology, Eastern Virginia Medical School, Norfolk, Virginia 23507.,c Leroy T. Canoles Jr. Cancer Research Center, Eastern Virginia Medical School, Norfolk, Virginia 23507
| | - Jessica S Jewell
- Department of a Radiation Oncology, Eastern Virginia Medical School, Norfolk, Virginia 23507
| | - Leslie K Davis
- Department of a Radiation Oncology, Eastern Virginia Medical School, Norfolk, Virginia 23507
| | - Vania D Miller
- Department of a Radiation Oncology, Eastern Virginia Medical School, Norfolk, Virginia 23507
| | - Melissa M Hadley
- Department of a Radiation Oncology, Eastern Virginia Medical School, Norfolk, Virginia 23507
| | - O John Semmes
- b Department of Microbiology and Molecular Cell Biology, Eastern Virginia Medical School, Norfolk, Virginia 23507.,c Leroy T. Canoles Jr. Cancer Research Center, Eastern Virginia Medical School, Norfolk, Virginia 23507.,d Department of Pathology and Anatomy, Eastern Virginia Medical School, Norfolk, Virginia 23507
| | - György Lonart
- d Department of Pathology and Anatomy, Eastern Virginia Medical School, Norfolk, Virginia 23507
| | - Sucharita M Dutta
- c Leroy T. Canoles Jr. Cancer Research Center, Eastern Virginia Medical School, Norfolk, Virginia 23507
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23
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Changes in hippocampal AMPA receptors and cognitive impairments in chronic ketamine addiction models: another understanding of ketamine CNS toxicity. Sci Rep 2016; 6:38771. [PMID: 27934938 PMCID: PMC5146946 DOI: 10.1038/srep38771] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 11/10/2016] [Indexed: 01/20/2023] Open
Abstract
Ketamine has been reported to impair human cognitive function as a recreational drug of abuse. However, chronic effects of ketamine on central nervous system need to be further explored. We set out to establish chronic ketamine addiction models by giving mice a three or six month course of daily intraperitoneal injections of ketamine, then examined whether long-term ketamine administration induced cognition deficits and changed hippocampal post-synaptic protein expression in adult mice. Behavior tests results showed that mice exhibited dose- and time-dependent learning and memory deficits after long-term ketamine administration. Western blot results showed levels of GluA1, p-S845 and p-S831 proteins demonstrated significant decline with ketamine 60 mg/kg until six months administration paradigm. But levels of p-S845 and p-S831 proteins exhibited obvious increase with ketamine 60 mg/kg three months administration paradigm. NR1 protein levels significantly decrease with ketamine 60 mg/kg three and six months administration paradigm. Our results indicate that reduced expression levels and decreased phosphorylation levels of hippocampal post-synaptic membrane GluA1- containing AMPA receptors maybe involved in cognition impairment after long-term ketamine administration. These findings provide further evidence for the cognitive damage of chronic ketamine addiction as a recreational drug.
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Gu X, Mao X, Lussier MP, Hutchison MA, Zhou L, Hamra FK, Roche KW, Lu W. GSG1L suppresses AMPA receptor-mediated synaptic transmission and uniquely modulates AMPA receptor kinetics in hippocampal neurons. Nat Commun 2016; 7:10873. [PMID: 26932439 PMCID: PMC4778064 DOI: 10.1038/ncomms10873] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2015] [Accepted: 01/28/2016] [Indexed: 12/17/2022] Open
Abstract
Regulation of AMPA receptor (AMPAR)-mediated synaptic transmission is a key mechanism
for synaptic plasticity. In the brain, AMPARs assemble with a number of auxiliary
subunits, including TARPs, CNIHs and CKAMP44, which are important for AMPAR forward
trafficking to synapses. Here we report that the membrane protein GSG1L negatively
regulates AMPAR-mediated synaptic transmission. Overexpression of GSG1L strongly
suppresses, and GSG1L knockout (KO) enhances, AMPAR-mediated synaptic transmission.
GSG1L-dependent regulation of AMPAR synaptic transmission relies on the first
extracellular loop domain and its carboxyl-terminus. GSG1L also speeds up AMPAR
deactivation and desensitization in hippocampal CA1 neurons, in contrast to the
effects of TARPs and CNIHs. Furthermore, GSG1L association with AMPARs inhibits
CNIH2-induced slowing of the receptors in heterologous cells. Finally, GSG1L KO rats
have deficits in LTP and show behavioural abnormalities in object recognition tests.
These data demonstrate that GSG1L represents a new class of auxiliary subunit with
distinct functional properties for AMPARs. The molecular mechanism controlling the trafficking and function of
AMPARs at synapses are not fully understood. Here the authors show that GSG1L, a
membrane protein, negatively regulates AMPAR-mediated synaptic transmission and
represents a new class of AMPAR auxiliary subunit.
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Affiliation(s)
- Xinglong Gu
- Synapse and Neural Circuit Research Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 35 Convent Drive, 3C1000, Bethesda, Maryland 20892, USA
| | - Xia Mao
- Synapse and Neural Circuit Research Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 35 Convent Drive, 3C1000, Bethesda, Maryland 20892, USA
| | - Marc P Lussier
- Receptor Biology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 35 Convent Drive, 2C903, Bethesda, Maryland 20892, USA
| | - Mary Anne Hutchison
- Synapse and Neural Circuit Research Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 35 Convent Drive, 3C1000, Bethesda, Maryland 20892, USA
| | - Liang Zhou
- Synapse and Neural Circuit Research Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 35 Convent Drive, 3C1000, Bethesda, Maryland 20892, USA
| | - F Kent Hamra
- Department of Pharmacology, Cecil H. &Ida Green Center for Reproductive Biology Sciences, University of Texas Southwestern Medical Center in Dallas, Dallas, Texas 75390, USA
| | - Katherine W Roche
- Receptor Biology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 35 Convent Drive, 2C903, Bethesda, Maryland 20892, USA
| | - Wei Lu
- Synapse and Neural Circuit Research Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 35 Convent Drive, 3C1000, Bethesda, Maryland 20892, USA
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25
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Kirk LM, Ti SW, Bishop HI, Orozco-Llamas M, Pham M, Trimmer JS, Díaz E. Distribution of the SynDIG4/proline-rich transmembrane protein 1 in rat brain. J Comp Neurol 2015; 524:2266-80. [PMID: 26660156 DOI: 10.1002/cne.23945] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Revised: 11/17/2015] [Accepted: 12/01/2015] [Indexed: 12/22/2022]
Abstract
The modulation of AMPA receptor (AMPAR) content at synapses is thought to be an underlying molecular mechanism of memory and learning. AMPAR content at synapses is highly plastic and is regulated by numerous AMPAR accessory transmembrane proteins such as TARPs, cornichons, and CKAMPs. SynDIG (synapse differentiation-induced gene) defines a family of four genes (SynDIG1-4) expressed in distinct and overlapping patterns in the brain. SynDIG1 was previously identified as a novel transmembrane AMPAR-associated protein that regulates synaptic strength. The related protein SynDIG4 [also known as Prrt1 (proline-rich transmembrane protein 1)] has recently been identified as a component of AMPAR complexes. In this study, we show that SynDIG1 and SynDIG4 have distinct yet overlapping patterns of expression in the central nervous system, with SynDIG4 having especially prominent expression in the hippocampus and particularly within CA1. In contrast to SynDIG1 and other traditional AMPAR auxiliary subunits, SynDIG4 is de-enriched at the postsynaptic density and colocalizes with extrasynaptic GluA1 puncta in primary dissociated neuron culture. These results indicate that, although SynDIG4 shares sequence similarity with SynDIG1, it might act through a unique mechanism as an auxiliary factor for extrasynaptic GluA1-containing AMPARs. J. Comp. Neurol. 524:2266-2280, 2016. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- Lyndsey M Kirk
- Department of Pharmacology, University of California Davis School of Medicine, Davis, California, 95616
| | - Shu W Ti
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, California, 95616
| | - Hannah I Bishop
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, California, 95616
| | - Mayra Orozco-Llamas
- Department of Pharmacology, University of California Davis School of Medicine, Davis, California, 95616
| | - Michelle Pham
- Department of Pharmacology, University of California Davis School of Medicine, Davis, California, 95616
| | - James S Trimmer
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, California, 95616.,Department of Physiology and Membrane Biology, University of California Davis School of Medicine, Davis, California, 95616
| | - Elva Díaz
- Department of Pharmacology, University of California Davis School of Medicine, Davis, California, 95616
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26
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Mehta MR. From synaptic plasticity to spatial maps and sequence learning. Hippocampus 2015; 25:756-62. [DOI: 10.1002/hipo.22472] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/23/2015] [Indexed: 01/22/2023]
Affiliation(s)
- Mayank R. Mehta
- Department of Physics & Astronomy; UCLA; Keck Center for Neurophysics; UCLA
- Department of Neurology; UCLA
- Department of Neurobiology; UCLA, Integrative Center for Learning and Memory; UCLA
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27
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Freudenberg F, Celikel T, Reif A. The role of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors in depression: central mediators of pathophysiology and antidepressant activity? Neurosci Biobehav Rev 2015; 52:193-206. [PMID: 25783220 DOI: 10.1016/j.neubiorev.2015.03.005] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 02/23/2015] [Accepted: 03/06/2015] [Indexed: 12/27/2022]
Abstract
Depression is a major psychiatric disorder affecting more than 120 million people worldwide every year. Changes in monoaminergic transmitter release are suggested to take part in the pathophysiology of depression. However, more recent experimental evidence suggests that glutamatergic mechanisms might play a more central role in the development of this disorder. The importance of the glutamatergic system in depression was particularly highlighted by the discovery that N-methyl-D-aspartate (NMDA) receptor antagonists (particularly ketamine) exert relatively long-lasting antidepressant like effects with rapid onset. Importantly, the antidepressant-like effects of NMDA receptor antagonists, but also other antidepressants (both classical and novel), require activation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. Additionally, expression of AMPA receptors is altered in patients with depression. Moreover, preclinical evidence supports an important involvement of AMPA receptor-dependent signaling and plasticity in the pathophysiology and treatment of depression. Here we summarize work published on the involvement of AMPA receptors in depression and discuss a possible central role for AMPA receptors in the pathophysiology, course and treatment of depression.
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Affiliation(s)
- Florian Freudenberg
- Department of Psychiatry, Psychosomatics and Psychotherapy, University Hospital of Frankfurt, Heinrich-Hoffmann-Straße 10, 60528 Frankfurt am Main, Germany.
| | - Tansu Celikel
- Department of Neurophysiology, Donders Center for Neuroscience, Radboud University Nijmegen, 6500 AA Nijmegen, The Netherlands
| | - Andreas Reif
- Department of Psychiatry, Psychosomatics and Psychotherapy, University Hospital of Frankfurt, Heinrich-Hoffmann-Straße 10, 60528 Frankfurt am Main, Germany
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28
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Tian M, Zeng Y, Hu Y, Yuan X, Liu S, Li J, Lu P, Sun Y, Gao L, Fu D, Li Y, Wang S, McClintock SM. 7, 8-Dihydroxyflavone induces synapse expression of AMPA GluA1 and ameliorates cognitive and spine abnormalities in a mouse model of fragile X syndrome. Neuropharmacology 2015; 89:43-53. [DOI: 10.1016/j.neuropharm.2014.09.006] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2014] [Revised: 08/28/2014] [Accepted: 09/04/2014] [Indexed: 01/20/2023]
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29
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Barkus C, Sanderson DJ, Rawlins JNP, Walton ME, Harrison PJ, Bannerman DM. What causes aberrant salience in schizophrenia? A role for impaired short-term habituation and the GRIA1 (GluA1) AMPA receptor subunit. Mol Psychiatry 2014; 19:1060-70. [PMID: 25224260 PMCID: PMC4189912 DOI: 10.1038/mp.2014.91] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Revised: 06/19/2014] [Accepted: 06/25/2014] [Indexed: 01/13/2023]
Abstract
The GRIA1 locus, encoding the GluA1 (also known as GluRA or GluR1) AMPA glutamate receptor subunit, shows genome-wide association to schizophrenia. As well as extending the evidence that glutamatergic abnormalities have a key role in the disorder, this finding draws attention to the behavioural phenotype of Gria1 knockout mice. These mice show deficits in short-term habituation. Importantly, under some conditions the attention being paid to a recently presented neutral stimulus can actually increase rather than decrease (sensitization). We propose that this mouse phenotype represents a cause of aberrant salience and, in turn, that aberrant salience (and the resulting positive symptoms) in schizophrenia may arise, at least in part, from a glutamatergic genetic predisposition and a deficit in short-term habituation. This proposal links an established risk gene with a psychological process central to psychosis and is supported by findings of comparable deficits in short-term habituation in mice lacking the NMDAR receptor subunit Grin2a (which also shows association to schizophrenia). As aberrant salience is primarily a dopaminergic phenomenon, the model supports the view that the dopaminergic abnormalities can be downstream of a glutamatergic aetiology. Finally, we suggest that, as illustrated here, the real value of genetically modified mice is not as 'models of schizophrenia' but as experimental tools that can link genomic discoveries with psychological processes and help elucidate the underlying neural mechanisms.
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Affiliation(s)
- C Barkus
- Department of Psychiatry, University of Oxford, Warneford Hospital, Oxford, OX3 7JX, U.K
| | - DJ Sanderson
- Department of Psychology, Durham University, Durham, DH1 3LE, U.K
| | - JNP Rawlins
- Department of Experimental Psychology, University of Oxford, 9 South Parks Road, Oxford, OX1 3UD, U.K
| | - ME Walton
- Department of Experimental Psychology, University of Oxford, 9 South Parks Road, Oxford, OX1 3UD, U.K
| | - PJ Harrison
- Department of Psychiatry, University of Oxford, Warneford Hospital, Oxford, OX3 7JX, U.K
| | - DM Bannerman
- Department of Experimental Psychology, University of Oxford, 9 South Parks Road, Oxford, OX1 3UD, U.K
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30
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Abstract
Nitroaromatic photochemical protecting groups were developed for organic synthesis in 1966. Since the early 1990s, this type of chromophore has been used by neuroscientists to liberate a wide variety of amino acid neurotransmitters such as ACh, glutamate, GABA, and glycine, among others. Since 2001, several laboratories have used two-photon excitation of nitroaromatic cages for highly localized uncaging of glutamate in acute brain slices.
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31
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Han SM, Wan H, Kudo G, Foltz WD, Vines DC, Green DE, Zoerle T, Tariq A, Brathwaite S, D'Abbondanza J, Ai J, Macdonald RL. Molecular alterations in the hippocampus after experimental subarachnoid hemorrhage. J Cereb Blood Flow Metab 2014; 34:108-17. [PMID: 24064494 PMCID: PMC3887350 DOI: 10.1038/jcbfm.2013.170] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Revised: 08/06/2013] [Accepted: 08/27/2013] [Indexed: 11/09/2022]
Abstract
Patients with aneurysmal subarachnoid hemorrhage (SAH) frequently have deficits in learning and memory that may or may not be associated with detectable brain lesions. We examined mediators of long-term potentiation after SAH in rats to determine what processes might be involved. There was a reduction in synapses in the dendritic layer of the CA1 region on transmission electron microscopy as well as reduced colocalization of microtubule-associated protein 2 (MAP2) and synaptophysin. Immunohistochemistry showed reduced staining for GluR1 and calmodulin kinase 2 and increased staining for GluR2. Myelin basic protein staining was decreased as well. There was no detectable neuronal injury by Fluoro-Jade B, TUNEL, or activated caspase-3 staining. Vasospasm of the large arteries of the circle of Willis was mild to moderate in severity. Nitric oxide was increased and superoxide anion radical was decreased in hippocampal tissue. Cerebral blood flow, measured by magnetic resonance imaging, and cerebral glucose metabolism, measured by positron emission tomography, were no different in SAH compared with control groups. The results suggest that the etiology of loss of LTP after SAH is not cerebral ischemia but may be mediated by effects of subarachnoid blood such as oxidative stress and inflammation.
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Affiliation(s)
- Sang Myung Han
- Division of Neurosurgery, St Michael's Hospital, Labatt Family Centre of Excellence in Brain Injury and Trauma Research, Keenan Research Centre of the Li Ka Shing Knowledge Institute of St Michael's Hospital, Department of Surgery, University of Toronto, Toronto, Ontario, Canada
| | - Hoyee Wan
- Division of Neurosurgery, St Michael's Hospital, Labatt Family Centre of Excellence in Brain Injury and Trauma Research, Keenan Research Centre of the Li Ka Shing Knowledge Institute of St Michael's Hospital, Department of Surgery, University of Toronto, Toronto, Ontario, Canada
| | - Gen Kudo
- STTARR Innovation Centre, Department of Radiation Oncology, Princess Margaret Hospital, Toronto, Ontario, Canada
| | - Warren D Foltz
- 1] STTARR Innovation Centre, Department of Radiation Oncology, Princess Margaret Hospital, Toronto, Ontario, Canada [2] Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada
| | - Douglass C Vines
- 1] STTARR Innovation Centre, Department of Radiation Oncology, Princess Margaret Hospital, Toronto, Ontario, Canada [2] Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada
| | - David E Green
- STTARR Innovation Centre, Department of Radiation Oncology, Princess Margaret Hospital, Toronto, Ontario, Canada
| | - Tommaso Zoerle
- Division of Neurosurgery, St Michael's Hospital, Labatt Family Centre of Excellence in Brain Injury and Trauma Research, Keenan Research Centre of the Li Ka Shing Knowledge Institute of St Michael's Hospital, Department of Surgery, University of Toronto, Toronto, Ontario, Canada
| | - Asma Tariq
- Division of Neurosurgery, St Michael's Hospital, Labatt Family Centre of Excellence in Brain Injury and Trauma Research, Keenan Research Centre of the Li Ka Shing Knowledge Institute of St Michael's Hospital, Department of Surgery, University of Toronto, Toronto, Ontario, Canada
| | - Shakira Brathwaite
- Division of Neurosurgery, St Michael's Hospital, Labatt Family Centre of Excellence in Brain Injury and Trauma Research, Keenan Research Centre of the Li Ka Shing Knowledge Institute of St Michael's Hospital, Department of Surgery, University of Toronto, Toronto, Ontario, Canada
| | - Josephine D'Abbondanza
- Division of Neurosurgery, St Michael's Hospital, Labatt Family Centre of Excellence in Brain Injury and Trauma Research, Keenan Research Centre of the Li Ka Shing Knowledge Institute of St Michael's Hospital, Department of Surgery, University of Toronto, Toronto, Ontario, Canada
| | - Jinglu Ai
- Division of Neurosurgery, St Michael's Hospital, Labatt Family Centre of Excellence in Brain Injury and Trauma Research, Keenan Research Centre of the Li Ka Shing Knowledge Institute of St Michael's Hospital, Department of Surgery, University of Toronto, Toronto, Ontario, Canada
| | - R Loch Macdonald
- Division of Neurosurgery, St Michael's Hospital, Labatt Family Centre of Excellence in Brain Injury and Trauma Research, Keenan Research Centre of the Li Ka Shing Knowledge Institute of St Michael's Hospital, Department of Surgery, University of Toronto, Toronto, Ontario, Canada
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32
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Lohmann C, Kessels HW. The developmental stages of synaptic plasticity. J Physiol 2014; 592:13-31. [PMID: 24144877 PMCID: PMC3903349 DOI: 10.1113/jphysiol.2012.235119] [Citation(s) in RCA: 107] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Accepted: 10/16/2013] [Indexed: 01/17/2023] Open
Abstract
The brain is programmed to drive behaviour by precisely wiring the appropriate neuronal circuits. Wiring and rewiring of neuronal circuits largely depends on the orchestrated changes in the strengths of synaptic contacts. Here, we review how the rules of synaptic plasticity change during development of the brain, from birth to independence. We focus on the changes that occur at the postsynaptic side of excitatory glutamatergic synapses in the rodent hippocampus and neocortex. First we summarize the current data on the structure of synapses and the developmental expression patterns of the key molecular players of synaptic plasticity, N-methyl-d-aspartate (NMDA) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, as well as pivotal kinases (Ca(2+)/calmodulin-dependent protein kinase II, protein kinase A, protein kinase C) and phosphatases (PP1, PP2A, PP2B). In the second part we relate these findings to important characteristics of the emerging network. We argue that the concerted and gradual shifts in the usage of plasticity molecules comply with the changing need for (re)wiring neuronal circuits.
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Affiliation(s)
- Christian Lohmann
- C. Lohmann and H. W. Kessels: The Netherlands Institute for Neuroscience, the Royal Academy of Arts and Sciences, Meibergdreef 47, 1105 BA, Amsterdam, the Netherlands. Emails: ,
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Granger AJ, Nicoll RA. Expression mechanisms underlying long-term potentiation: a postsynaptic view, 10 years on. Philos Trans R Soc Lond B Biol Sci 2013; 369:20130136. [PMID: 24298139 DOI: 10.1098/rstb.2013.0136] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
This review focuses on the research that has occurred over the past decade which has solidified a postsynaptic expression mechanism for long-term potentiation (LTP). However, experiments that have suggested a presynaptic component are also summarized. It is argued that the pairing of glutamate uncaging onto single spines with postsynaptic depolarization provides the final and most elegant demonstration of a postsynaptic expression mechanism for NMDA receptor-dependent LTP. The fact that the magnitude of this LTP is similar to that evoked by pairing synaptic stimulation and depolarization leaves little room for a substantial presynaptic component. Finally, recent data also require a revision in our thinking about the way AMPA receptors (AMPARs) are recruited to the postsynaptic density during LTP. This recruitment is independent of subunit type, but does require an adequate reserve pool of extrasynaptic receptors.
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Affiliation(s)
- Adam J Granger
- Neuroscience Graduate Program, University of California San Francisco, , San Francisco, CA 94158, USA
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Abstract
The extensive dendritic arbor of a pyramidal cell introduces considerable complexity to the integration of synaptic potentials. Propagation of dendritic potentials is largely passive, in contrast to regenerative axonal potentials that are maintained by voltage-gated sodium channels, leading to a declination in amplitude as dendritic potentials travel toward the soma in a manner that disproportionally affects distal synaptic inputs. To counteract this amplitude filtering, Schaffer collateral synapses onto CA1 pyramidal cells contain a varying number of AMPA receptors (AMPARs) per synapse that increases with distance from the soma, a phenomenon known as distance-dependent scaling. Here, we undertake an investigation into the molecular mechanisms of distance-dependent scaling. Using dendritic recordings from rat pyramidal neurons, we confirm the basic scaling phenomenon and find that it is expressed and can be manipulated cell autonomously. Finally, we show that it depends on the presence of both a reserve pool of AMPARs and the AMPAR subunit GluA2.
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Simon CM, Hepburn I, Chen W, De Schutter E. The role of dendritic spine morphology in the compartmentalization and delivery of surface receptors. J Comput Neurosci 2013; 36:483-97. [PMID: 24113809 DOI: 10.1007/s10827-013-0482-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Revised: 09/10/2013] [Accepted: 09/24/2013] [Indexed: 11/24/2022]
Abstract
Since AMPA receptors are major molecular players in both short- and long-term plasticity, it is important to identify the time-scales of and factors affecting the lateral diffusion of AMPARs on the dendrite surface. Using a mathematical model, we study how the dendritic spine morphology affects two processes: (1) compartmentalization of the surface receptors in a single spine to retain local chemistry and (2) the delivery of receptors to the post-synaptic density (PSD) of spines via lateral diffusion following insertion onto the dendrite shaft. Computing the mean first passage time (MFPT) of surface receptors on a sample of real spine morphologies revealed that a constricted neck and bulbous head serve to compartmentalize receptors, consistent with previous works. The residence time of a Brownian diffusing receptor on the membrane of a single spine was computed to be ∼ 5 s. We found that the location of the PSD corresponds to the location at which the maximum MFPT occurs, the position that maximizes the residence time of a diffusing receptor. Meanwhile, the same geometric features of the spine that compartmentalize receptors inhibit the recruitment of AMPARs via lateral diffusion from dendrite insertion sites. Spines with narrow necks will trap a smaller fraction of diffusing receptors in the their PSD when considering competition for receptors between the spines, suggesting that ideal geometrical features involve a tradeoff depending on the intent of compartmentalizing the current receptor pool or recruiting new AMPARs in the PSD. The ultimate distribution of receptors among the spine PSDs by lateral diffusion from the dendrite shaft is an interplay between the insertion location and the shape and locations of both the spines and their PSDs. The time-scale for delivery of receptors to the PSD of spines via lateral diffusion was computed to be ∼ 60 s.
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Affiliation(s)
- Cory M Simon
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA, USA,
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Procaccini C, Maksimovic M, Aitta-Aho T, Korpi ER, Linden AM. Reversal of novelty-induced hyperlocomotion and hippocampal c-Fos expression in GluA1 knockout male mice by the mGluR2/3 agonist LY354740. Neuroscience 2013; 250:189-200. [PMID: 23867766 DOI: 10.1016/j.neuroscience.2013.07.010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Revised: 06/07/2013] [Accepted: 07/03/2013] [Indexed: 01/16/2023]
Abstract
Dysfunctional glutamatergic neurotransmission has been implicated in schizophrenia and mood disorders. As a putative model for these disorders, a mouse line lacking the GluA1 subunit (GluA1-KO) of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) glutamate receptor displays a robust novelty-induced hyperlocomotion associated with excessive neuronal activation in the hippocampus. Agonists of metabotropic glutamate 2/3 receptors (mGluR2/3) inhibit glutamate release in various brain regions and they have been shown to inhibit neuronal activation in the hippocampus. Here, we tested a hypothesis that novelty-induced hyperlocomotion in the GluA1-KO mice is mediated via excessive hippocampal neuronal activation by analyzing whether an mGluR2/3 agonist inhibits this phenotypic feature. GluA1-KO mice and littermate wildtype (WT) controls were administered with (1S,2S,5R,6S)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid (LY354740) (15 mg/kg, i.p.) 30 min before a 2-h exposure to novel arenas after which c-Fos immunopositive cells were analyzed in the hippocampus. LY354740 (15 mg/kg) decreased hyperactivity in male GluA1-KO mice, with only a minimal effect in WT controls. This was observed in two cohorts of animals, one naïve to handling and injections, another pre-handled and accustomed to injections. LY354740 (15 mg/kg) also reduced the excessive c-Fos expression in the dorsal hippocampal CA1 pyramidal cell layer in maleGluA1-KO mice, while not affecting c-Fos levels in WT mice. In female mice, no significant effect for LY354740 (15 mg/kg) on hyperactive behavior or hippocampal c-Fos was observed in either genotype or treatment cohort. A higher dose of LY354740 (30 mg/kg) alleviated hyperlocomotion of GluA1-KO males, but not that of GluA1-KO females. In conclusion, the excessive behavioral hyperactivity of GluA1-KO mice can be partly prevented by reducing neuronal excitability in the hippocampus with the mGluR2/3 agonist suggesting that the hippocampal reactivity is strongly involved in the behavioral phenotype of GluA1-KO mice.
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Affiliation(s)
- C Procaccini
- Institute of Biomedicine/Pharmacology, Biomedicum Helsinki, P.O.B. 63, FIN-00014 University of Helsinki, Finland
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Herring BE, Shi Y, Suh YH, Zheng CY, Blankenship SM, Roche KW, Nicoll RA. Cornichon proteins determine the subunit composition of synaptic AMPA receptors. Neuron 2013; 77:1083-96. [PMID: 23522044 DOI: 10.1016/j.neuron.2013.01.017] [Citation(s) in RCA: 110] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/15/2013] [Indexed: 10/27/2022]
Abstract
Cornichon-2 and cornichon-3 (CNIH-2/-3) are AMPA receptor (AMPAR) binding proteins that promote receptor trafficking and markedly slow AMPAR deactivation in heterologous cells, but their role in neurons is unclear. Using CNIH-2 and CNIH-3 conditional knockout mice, we find a profound reduction of AMPAR synaptic transmission in the hippocampus. This deficit is due to the selective loss of surface GluA1-containing AMPARs (GluA1A2 heteromers), leaving a small residual pool of synaptic GluA2A3 heteromers. The kinetics of AMPARs in neurons lacking CNIH-2/-3 are faster than those in WT neurons due to the fast kinetics of GluA2A3 heteromers. The remarkably selective effect of CNIHs on the GluA1 subunit is probably mediated by TARP γ-8, which prevents a functional association of CNIHs with non-GluA1 subunits. These results point to a sophisticated interplay between CNIHs and γ-8 that dictates subunit-specific AMPAR trafficking and the strength and kinetics of synaptic AMPAR-mediated transmission.
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Affiliation(s)
- Bruce E Herring
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94143, USA
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Kopach O, Voitenko N. Extrasynaptic AMPA receptors in the dorsal horn: Evidence and functional significance. Brain Res Bull 2013. [DOI: 10.1016/j.brainresbull.2012.11.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Adenosine A(2A) receptor blockade reverts hippocampal stress-induced deficits and restores corticosterone circadian oscillation. Mol Psychiatry 2013; 18:320-31. [PMID: 22371048 DOI: 10.1038/mp.2012.8] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Maternal separation (MS) is an early life stress model that induces permanent changes in the central nervous system, impairing hippocampal long-term potentiation (LTP) and spatial working memory. There are compelling evidences for a role of hippocampal adenosine A(2A) receptors in stress-induced modifications related to cognition, thus opening a potential window for therapeutic intervention. Here, we submitted rats to MS and evaluated the long-lasting molecular, electrophysiological and behavioral impairments in adulthood. We then assessed the therapeutic potential of KW6002, a blocker of A(2A) receptors, in stress-impaired animals. We report that the blockade of A(2A) receptors was efficient in reverting the behavior, electrophysiological and morphological impairments induced by MS. In addition, this effect is associated with restoration of the hypothalamic-pituitary-adrenal axis (HPA-axis) activity, as both the plasma corticosterone levels and hippocampal glucocorticoid receptor expression pattern returned to physiological-like status after the treatment. These results reveal the involvement of A(2A) receptors in the stress-associated impairments and directly in the stress response system by showing that the dysfunction of the HPA-axis as well as the long-lasting synaptic and behavioral effects of MS can be reverted by targeting adenosine A(2A) receptors. These findings provide a novel evidence for the use of adenosine A(2A) receptor antagonists as potential therapy against psychopathologies.
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TNiK is required for postsynaptic and nuclear signaling pathways and cognitive function. J Neurosci 2013; 32:13987-99. [PMID: 23035106 DOI: 10.1523/jneurosci.2433-12.2012] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Traf2 and NcK interacting kinase (TNiK) contains serine-threonine kinase and scaffold domains and has been implicated in cell proliferation and glutamate receptor regulation in vitro. Here we report its role in vivo using mice carrying a knock-out mutation. TNiK binds protein complexes in the synapse linking it to the NMDA receptor (NMDAR) via AKAP9. NMDAR and metabotropic receptors bidirectionally regulate TNiK phosphorylation and TNiK is required for AMPA expression and synaptic function. TNiK also organizes nuclear complexes and in the absence of TNiK, there was a marked elevation in GSK3β and phosphorylation levels of its cognate phosphorylation sites on NeuroD1 with alterations in Wnt pathway signaling. We observed impairments in dentate gyrus neurogenesis in TNiK knock-out mice and cognitive testing using the touchscreen apparatus revealed impairments in pattern separation on a test of spatial discrimination. Object-location paired associate learning, which is dependent on glutamatergic signaling, was also impaired. Additionally, TNiK knock-out mice displayed hyperlocomotor behavior that could be rapidly reversed by GSK3β inhibitors, indicating the potential for pharmacological rescue of a behavioral phenotype. These data establish TNiK as a critical regulator of cognitive functions and suggest it may play a regulatory role in diseases impacting on its interacting proteins and complexes.
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GluA1 and its PDZ-interaction: a role in experience-dependent behavioral plasticity in the forced swim test. Neurobiol Dis 2012; 52:160-7. [PMID: 23262314 DOI: 10.1016/j.nbd.2012.12.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2012] [Revised: 12/05/2012] [Accepted: 12/08/2012] [Indexed: 01/10/2023] Open
Abstract
Glutamate receptor dependent synaptic plasticity plays an important role in the pathophysiology of depression. Hippocampal samples from clinically depressed patients display reduced mRNA levels for GluA1, a major subunit of AMPA receptors. Moreover, activation and synaptic incorporation of GluA1-containing AMPA receptors are required for the antidepressant-like effects of NMDA receptor antagonists. These findings argue that GluA1-dependent synaptic plasticity might be critically involved in the expression of depression. Using an animal model of depression, we demonstrate that global or hippocampus-selective deletion of GluA1 impairs expression of experience-dependent behavioral despair. This impairment is mediated by the interaction of GluA1 with PDZ-binding domain proteins, as deletion of the C-terminal leucine alone is sufficient to replicate the behavioral phenotype. Our results provide evidence for a significant role of hippocampal GluA1-containing AMPA receptors and their PDZ-interaction in experience-dependent expression of behavioral despair and link mechanisms of hippocampal synaptic plasticity with behavioral expression of depression.
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LTP requires a reserve pool of glutamate receptors independent of subunit type. Nature 2012; 493:495-500. [PMID: 23235828 PMCID: PMC3998843 DOI: 10.1038/nature11775] [Citation(s) in RCA: 233] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Accepted: 11/09/2012] [Indexed: 11/27/2022]
Abstract
Long-term potentiation (LTP) of synaptic transmission is thought to be a key cellular mechanism underlying memory formation. A widely accepted model posits that LTP requires the cytoplasmic tail of the AMPA receptor subunit GluA1. To find the minimum necessary requirement of the GluA1 C-tail for LTP in CA1 hippocampal pyramidal neurons, we used a single-cell molecular replacement strategy to replace all endogenous AMPA receptors with transfected subunits. In striking contrast to the prevailing model, we found no requirement of the GluA1 C-tail for LTP. In fact, replacement with the GluA2 subunit showed normal LTP, as did an artificially expressed kainate receptor not normally found at these synapses. The only conditions under which LTP was impaired were those with dramatically decreased AMPA receptor surface expression, indicating a requirement for a reserve pool of receptors. These results demonstrate the synapse’s remarkable flexibility to potentiate with a variety of glutamate receptor subtypes, requiring a fundamental change in our thinking with regard to the core molecular events underlying synaptic plasticity.
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Abstract
The GluA1 subunit of AMPA receptors (AMPARs) is critical for hippocampal synaptic transmission and plasticity. Here, we measured the activity of single units from the CA1 region of the hippocampus while GluA1 knock-out (GluA1⁻/⁻) and wild-type (WT) mice traversed a linear track. Although overall firing rates were similar, GluA1⁻/⁻ neurons were more likely to spike in bursts, but at lower burst frequencies, compared with WT neurons. GluA1⁻/⁻ neurons showed large reductions in all measures of spatial and directional selectivity compared with WT neurons. Consistent with these alterations of single-neuron properties, the accuracy of the population code for position was substantially reduced in GluA1⁻/⁻, yet it is predicted to approach the accuracy of WT with increasing population size. The absolute representation of space, independent of movement direction, was greatly diminished in GluA1⁻/⁻ mice and is predicted to remain reduced even for larger populations. Finally, we found that the rate maps of GluA1⁻/⁻ neurons showed increased trial-by-trial variability but reduced experiential plasticity compared with the WT. These results reveal the critical contribution of GluA1-containing AMPARs to individual place cells and the hippocampal population code for space, which could explain the selective behavioral impairments observed in these mice.
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Allen NJ, Bennett ML, Foo LC, Wang GX, Chakraborty C, Smith SJ, Barres BA. Astrocyte glypicans 4 and 6 promote formation of excitatory synapses via GluA1 AMPA receptors. Nature 2012; 486:410-4. [PMID: 22722203 PMCID: PMC3383085 DOI: 10.1038/nature11059] [Citation(s) in RCA: 505] [Impact Index Per Article: 42.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2010] [Accepted: 03/16/2012] [Indexed: 12/02/2022]
Abstract
In the developing central nervous system (CNS), the control of synapse number and function is critical to the formation of neural circuits. We previously demonstrated that astrocyte-secreted factors powerfully induce the formation of functional excitatory synapses between CNS neurons1. Astrocyte-secreted thrombospondins induce structural synapses, however these synapses are post-synaptically silent2. Here we use biochemical fractionation of astrocyte conditioned media (ACM) to identify glypican 4 (Gpc4) and 6 (Gpc6) as astrocyte-secreted signals sufficient to induce functional synapses between purified retinal ganglion cell (RGC) neurons, and show that depletion of these molecules from ACM significantly reduces its ability to induce postsynaptic activity. Application of Gpc4 to purified neurons is sufficient to increase the frequency and amplitude of glutamatergic synaptic events. This is achieved by increasing the surface level and clustering, but not overall cellular protein level, of the GluA1 subunit of the AMPA glutamate receptor (AMPAR). Gpc4&6 are expressed by astrocytes in vivo in the developing CNS, with Gpc4 expression enriched in the hippocampus and Gpc6 in the cerebellum. Finally, we demonstrate that Gpc4-deficient mice have defective synapse formation, with decreased amplitude of excitatory synaptic currents in the developing hippocampus and reduced recruitment of AMPARs to synapses. These data identify glypicans as a family of novel astrocyte-derived molecules that are necessary and sufficient to promote glutamate receptor clustering and receptivity and induce the formation of post-synaptically functioning CNS synapses.
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Affiliation(s)
- Nicola J Allen
- Stanford University School of Medicine, Department of Neurobiology, 299 Campus Drive, Fairchild Science Building D231, Stanford, California 94305-5125, USA.
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Selcher JC, Xu W, Hanson JE, Malenka RC, Madison DV. Glutamate receptor subunit GluA1 is necessary for long-term potentiation and synapse unsilencing, but not long-term depression in mouse hippocampus. Brain Res 2011; 1435:8-14. [PMID: 22197030 DOI: 10.1016/j.brainres.2011.11.029] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Revised: 11/10/2011] [Accepted: 11/11/2011] [Indexed: 12/01/2022]
Abstract
Receptor subunit composition is believed to play a major role in the synaptic trafficking of AMPA receptors (AMPARs), and thus in activity-dependent synaptic plasticity. To isolate a physiological role of GluA1-containing AMPARs in area CA3 of the hippocampus, pair recordings were performed in organotypic hippocampal slices taken from genetically modified mice lacking the GluA1 subunit. We report here that long-term potentiation (LTP) is impaired not only at active but also at silent synapses when the GluA1 subunit is absent. The GluA1 knockout mice also exhibited reduced AMPAR-mediated evoked currents between pairs of CA3 pyramidal neurons under baseline conditions suggesting a significant role for GluA1-containing AMPARs in regulating basal synaptic transmission. In two independent measures, however, long-term depression (LTD) was unaffected in tissue from these mice. These data provide a further demonstration of the fundamental role that GluA1-containing AMPARs play in activity-dependent increases in synaptic strength but do not support a GluA1-dependent mechanism for reductions in synaptic strength.
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Affiliation(s)
- Joel C Selcher
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA
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Granger AJ, Gray JA, Lu W, Nicoll RA. Genetic analysis of neuronal ionotropic glutamate receptor subunits. J Physiol 2011; 589:4095-101. [PMID: 21768264 DOI: 10.1113/jphysiol.2011.213033] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
In the brain, fast, excitatory synaptic transmission occurs primarily through AMPA- and NMDA-type ionotropic glutamate receptors. These receptors are composed of subunit proteins that determine their biophysical properties and trafficking behaviour. Therefore, determining the function of these subunits and receptor subunit composition is essential for understanding the physiological properties of synaptic transmission. Here, we discuss and evaluate various genetic approaches that have been used to study AMPA and NMDA receptor subunits. These approaches have demonstrated that the GluA1 AMPA receptor subunit is required for activity-dependent trafficking and contributes to basal synaptic transmission, while the GluA2 subunit regulates Ca(2+) permeability, homeostasis and trafficking to the synapse under basal conditions. In contrast, the GluN2A and GluN2B NMDA receptor subunits regulate synaptic AMPA receptor content, both during synaptic development and plasticity. Ongoing research in this field is focusing on the molecular interactions and mechanisms that control these functions. To accomplish this, molecular replacement techniques are being used, where native subunits are replaced with receptors containing targeted mutations. In this review, we discuss a single-cell molecular replacement approach which should arguably advance our physiological understanding of ionotropic glutamate receptor subunits, but is generally applicable to study of any neuronal protein.
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Affiliation(s)
- Adam J Granger
- Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, CA 94143, USA.
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Ghafari M, Falsafi SK, Hoeger H, Lubec G. Hippocampal levels of GluR1 and GluR2 complexes are modulated by training in the Multiple T-maze in C57BL/6J mice. Brain Struct Funct 2011; 217:353-62. [PMID: 21695503 DOI: 10.1007/s00429-011-0335-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Accepted: 06/01/2011] [Indexed: 11/25/2022]
Abstract
A series of studies has shown the importance of AMPA-type glutamate receptors (AMPARs) for memory formation. The aim of the current study was to show whether GluR1 and GluR2 complexes rather than subunits in mouse hippocampus were involved in training in the multiple T-Maze (MTM). C57BL/6J mice were trained in the MTM and compared to yoked controls. 6 h following the completion of the fourth day training, mice were euthanized, hippocampi were taken and proteins extracted, run on blue native gels with subsequent immunoblotting with antibodies against mouse GluR1 and GluR2. On blue-native western blotting, GluR1 protein was represented by a single band at the apparent molecular weight of about 480 kDa probably indicating a tetrameric assembly. GluR2 protein was represented by a single band between apparent molecular weights of 480 and 720 kDa indicating a homo- or heteropolymer probably with other AMPAR or regulatory subunits. In mice trained in the MTM, protein levels for GluR1 were significantly increased while GluR2 levels were significantly decreased. On two-dimensional (2D) gel electrophoresis, the presence of GluR1 and GluR2 were identified by mass spectrometry, and 2D immunoblotting revealed several expression forms of these receptor subunits. Findings unequivocally show that GluR1 and GluR2 complexes are linked to training in the MTM in C57BL/6J mice. These results may not only form the basis for studying receptor complexes rather than receptor subunits in memory formation or mechanisms of potential cognitive enhancers but represent a tool for investigations into pharmacological studies including the use of glutamate receptor agonists and antagonists.
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Affiliation(s)
- Maryam Ghafari
- Department of Pediatrics, Medical University of Vienna, Währinger Gürtel 18, 1090, Vienna, Austria
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Do GluA1 knockout mice exhibit behavioral abnormalities relevant to the negative or cognitive symptoms of schizophrenia and schizoaffective disorder? Neuropharmacology 2011; 62:1263-72. [PMID: 21693126 DOI: 10.1016/j.neuropharm.2011.06.005] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2010] [Revised: 03/28/2011] [Accepted: 06/07/2011] [Indexed: 12/27/2022]
Abstract
The glutamate system has been strongly implicated in the pathophysiology of psychotic illnesses, including schizophrenia and schizoaffective disorder. We recently found that knockout (KO) mice lacking the AMPA GluA1 subunit displayed behavioral abnormalities relevant to some of the positive symptoms of these disorders. Here we phenotyped GluA1 KO mice for behavioral phenotypes pertinent to negative and cognitive/executive symptoms. GluA1 KO mice were tested for conspecific social interactions, the acquisition and extinction of an operant response for food-reward, operant-based pairwise visual discrimination and reversal learning, and impulsive choice in a delay-based cost/benefit decision-making T-maze task. Results showed that GluA1 KO mice engaged in less social interaction than wildtype (WT) controls when tested in a non-habituated, novel environment, but, conversely, displayed more social interaction in a well habituated, familiar environment. GluA1 KO mice were faster to acquire an operant stimulus-response for food reward than WT and were subsequently slower to extinguish the response. Genotypes showed similar pairwise discrimination learning and reversal, although GluA1 KO mice made fewer errors during early reversal. GluA1 KO mice also displayed increased impulsive choice, being less inclined to choose a delayed, larger reward when given a choice between this and a smaller, immediate reward, compared to WT mice. Finally, sucrose preference did not differ between genotypes. Collectively, these data add to the growing evidence that GluA1 KO mice display at least some phenotypic abnormalities mimicking those found in schizophrenia/schizoaffective disorder. Although these mice, like any other single mutant line, are unlikely to model the entire disease, they may nevertheless provide a useful tool for studying the role of GluA1 in certain aspects of the pathophysiology of major psychotic illness.
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Abstract
The Ras family GTPases (Ras, Rap1, and Rap2) and their downstream mitogen-activated protein kinases (ERK, JNK, and p38MAPK) and PI3K signaling cascades control various physiological processes. In neuronal cells, recent studies have shown that these parallel cascades signal distinct forms of AMPA-sensitive glutamate receptor trafficking during experience-dependent synaptic plasticity and adaptive behavior. Interestingly, both hypo- and hyperactivation of Ras/ Rap signaling impair the capacity of synaptic plasticity, underscoring the importance of a "happy-medium" dynamic regulation of the signaling. Moreover, accumulating reports have linked various genetic defects that either up- or down-regulate Ras/Rap signaling with several mental disorders associated with learning disability (e.g., Alzheimer's disease, Angelman syndrome, autism, cardio-facio-cutaneous syndrome, Coffin-Lowry syndrome, Costello syndrome, Cowden and Bannayan-Riley-Ruvalcaba syndromes, fragile X syndrome, neurofibromatosis type 1, Noonan syndrome, schizophrenia, tuberous sclerosis, and X-linked mental retardation), highlighting the necessity of happy-medium dynamic regulation of Ras/Rap signaling in learning behavior. Thus, the recent advances in understanding of neuronal Ras/Rap signaling provide a useful guide for developing novel treatments for mental diseases.
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Affiliation(s)
- Ruth L Stornetta
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, Virginia, USA
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Abstract
Both theoretical and experimental research has indicated that the synaptic strength between neurons in a network needs to be properly fine-tuned and controlled by homeostatic mechanisms to ensure proper network function. One such mechanism that has been extensively characterized is synaptic homeostatic plasticity or global synaptic scaling. This mechanism refers to the bidirectional ability of all synapses impinging on a neuron to actively compensate for changes in the neuron's overall excitability. Here, using a combination of electrophysiological, two-photon glutamate uncaging and imaging methods, we show that mature individual synapses, independent of neighboring synapses, have the ability to autonomously sense their level of activity and actively compensate for it in a homeostatic-like fashion. This synapse-specific homeostatic plasticity, similar to global synaptic plasticity, requires the immediate early gene Arc. Together, our results document an extra level of regulation of synaptic function that bears important computational consequences on information storage in the brain.
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