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Rinaldi B, Bayat A, Zachariassen LG, Sun JH, Ge YH, Zhao D, Bonde K, Madsen LH, Awad IAA, Bagiran D, Sbeih A, Shah SM, El-Sayed S, Lyngby SM, Pedersen MG, Stenum-Berg C, Walker LC, Krey I, Delahaye-Duriez A, Emrick LT, Sully K, Murali CN, Burrage LC, Plaud Gonzalez JA, Parnes M, Friedman J, Isidor B, Lefranc J, Redon S, Heron D, Mignot C, Keren B, Fradin M, Dubourg C, Mercier S, Besnard T, Cogne B, Deb W, Rivier C, Milani D, Bedeschi MF, Di Napoli C, Grilli F, Marchisio P, Koudijs S, Veenma D, Argilli E, Lynch SA, Au PYB, Ayala Valenzuela FE, Brown C, Masser-Frye D, Jones M, Patron Romero L, Li WL, Thorpe E, Hecher L, Johannsen J, Denecke J, McNiven V, Szuto A, Wakeling E, Cruz V, Sency V, Wang H, Piard J, Kortüm F, Herget T, Bierhals T, Condell A, Ben-Zeev B, Kaur S, Christodoulou J, Piton A, Zweier C, Kraus C, Micalizzi A, Trivisano M, Specchio N, Lesca G, Møller RS, Tümer Z, Musgaard M, Gerard B, Lemke JR, Shi YS, Kristensen AS. Gain-of-function and loss-of-function variants in GRIA3 lead to distinct neurodevelopmental phenotypes. Brain 2024; 147:1837-1855. [PMID: 38038360 PMCID: PMC11068105 DOI: 10.1093/brain/awad403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Revised: 10/17/2023] [Accepted: 11/09/2023] [Indexed: 12/02/2023] Open
Abstract
AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptors (AMPARs) mediate fast excitatory neurotransmission in the brain. AMPARs form by homo- or heteromeric assembly of subunits encoded by the GRIA1-GRIA4 genes, of which only GRIA3 is X-chromosomal. Increasing numbers of GRIA3 missense variants are reported in patients with neurodevelopmental disorders (NDD), but only a few have been examined functionally. Here, we evaluated the impact on AMPAR function of one frameshift and 43 rare missense GRIA3 variants identified in patients with NDD by electrophysiological assays. Thirty-one variants alter receptor function and show loss-of-function or gain-of-function properties, whereas 13 appeared neutral. We collected detailed clinical data from 25 patients (from 23 families) harbouring 17 of these variants. All patients had global developmental impairment, mostly moderate (9/25) or severe (12/25). Twelve patients had seizures, including focal motor (6/12), unknown onset motor (4/12), focal impaired awareness (1/12), (atypical) absence (2/12), myoclonic (5/12) and generalized tonic-clonic (1/12) or atonic (1/12) seizures. The epilepsy syndrome was classified as developmental and epileptic encephalopathy in eight patients, developmental encephalopathy without seizures in 13 patients, and intellectual disability with epilepsy in four patients. Limb muscular hypotonia was reported in 13/25, and hypertonia in 10/25. Movement disorders were reported in 14/25, with hyperekplexia or non-epileptic erratic myoclonus being the most prevalent feature (8/25). Correlating receptor functional phenotype with clinical features revealed clinical features for GRIA3-associated NDDs and distinct NDD phenotypes for loss-of-function and gain-of-function variants. Gain-of-function variants were associated with more severe outcomes: patients were younger at the time of seizure onset (median age: 1 month), hypertonic and more often had movement disorders, including hyperekplexia. Patients with loss-of-function variants were older at the time of seizure onset (median age: 16 months), hypotonic and had sleeping disturbances. Loss-of-function and gain-of-function variants were disease-causing in both sexes but affected males often carried de novo or hemizygous loss-of-function variants inherited from healthy mothers, whereas affected females had mostly de novo heterozygous gain-of-function variants.
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Affiliation(s)
- Berardo Rinaldi
- Medical Genetics Unit, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milan 20122, Italy
| | - Allan Bayat
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen 2100, Denmark
- Department of Epilepsy Genetics and Personalized Medicine, Danish Epilepsy Centre, Dianalund 4293, Denmark
- Department of Regional Health Research, University of Southern Denmark, Odense 5230Denmark
| | - Linda G Zachariassen
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen 2100, Denmark
| | - Jia-Hui Sun
- State Key Laboratory of Pharmaceutical Biotechnology, Model Animal Research Center, Department of Neurology, Nanjing Drum Tower Hospital, Medical School, Nanjing University, Nanjing 210032, China
- Zhejiang Key Laboratory of Organ Development and Regeneration, College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou 310030, China
| | - Yu-Han Ge
- State Key Laboratory of Pharmaceutical Biotechnology, Model Animal Research Center, Department of Neurology, Nanjing Drum Tower Hospital, Medical School, Nanjing University, Nanjing 210032, China
- Ministry of Education Key Laboratory of Model Animal for Disease Study, National Resource Center for Mutant Mice, Jiangsu Key Laboratory of Molecular Medicine, Medical School, Nanjing University, Nanjing 210032, China
| | - Dan Zhao
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen 2100, Denmark
| | - Kristine Bonde
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen 2100, Denmark
| | - Laura H Madsen
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen 2100, Denmark
| | | | - Duygu Bagiran
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen 2100, Denmark
| | - Amal Sbeih
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen 2100, Denmark
| | - Syeda Maidah Shah
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen 2100, Denmark
| | - Shaymaa El-Sayed
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen 2100, Denmark
| | - Signe M Lyngby
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen 2100, Denmark
| | - Miriam G Pedersen
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen 2100, Denmark
| | - Charlotte Stenum-Berg
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen 2100, Denmark
| | - Louise Claudia Walker
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa K1H 8M5, Canada
| | - Ilona Krey
- Institute of Human Genetics, University of Leipzig Medical Center, Leipzig 04103, Germany
| | - Andrée Delahaye-Duriez
- Unité fonctionnelle de médecine génomique et génétique clinique, Hôpital Jean Verdier, Assistance Publique des Hôpitaux de Paris, Bondy 93140, France
- NeuroDiderot, UMR 1141, Inserm, Université Paris Cité, Paris 75019, France
- UFR SMBH, Université Sorbonne Paris Nord, Bobigny 93000, France
| | - Lisa T Emrick
- Division of Neurology and Developmental Neurosciences, Department of Pediatrics, Baylor College of Medicine, Texas Children’s Hospital, Houston, TX 77030, USA
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Krystal Sully
- Division of Neurology and Developmental Neurosciences, Department of Pediatrics, Baylor College of Medicine, Texas Children’s Hospital, Houston, TX 77030, USA
| | - Chaya N Murali
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Lindsay C Burrage
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Julie Ana Plaud Gonzalez
- Division of Neurology and Developmental Neurosciences, Department of Pediatrics, Baylor College of Medicine, Texas Children’s Hospital, Houston, TX 77030, USA
| | - Mered Parnes
- Division of Neurology and Developmental Neurosciences, Department of Pediatrics, Baylor College of Medicine, Texas Children’s Hospital, Houston, TX 77030, USA
- Pediatric Movement Disorders Clinic, Texas Children’s Hospital and Baylor College of Medicine, Houston, TX 77030, USA
| | - Jennifer Friedman
- Rady Children’s Institute for Genomic Medicine, San Diego, CA 92123, USA
- Department of Neurosciences, University of California San Diego, San Diego, CA 92123, USA
- Department of Pediatrics, University of California San Diego, San Diego, CA 92123, USA
| | - Bertrand Isidor
- Nantes Université, CHU Nantes, Service de Génétique Médicale, Nantes 44000, France
| | - Jérémie Lefranc
- Pediatric Neurophysiology Department, CHU de Brest, Brest 29200, France
| | - Sylvia Redon
- Service de Génétique Médicale, CHU de Brest, Brest 29200, France
- Université de Brest, CHU de Brest, UMR 1078, Brest F29200, France
| | - Delphine Heron
- APHP Sorbonne Université, Département de Génétique, Hôpital Armand Trousseau and Groupe Hospitalier Pitié-Salpêtrière, Paris 75013, France
- Centre de Référence Déficiences Intellectuelles de Causes Rares, Paris 75013, France
| | - Cyril Mignot
- APHP Sorbonne Université, Département de Génétique, Hôpital Armand Trousseau and Groupe Hospitalier Pitié-Salpêtrière, Paris 75013, France
- Centre de Référence Déficiences Intellectuelles de Causes Rares, Paris 75013, France
| | - Boris Keren
- Genetic Department, APHP, Sorbonne Université, Pitié-Salpêtrière Hospital, Paris 75013, France
| | - Mélanie Fradin
- Service de Génétique Médicale, Hôpital Sud, CHU de Rennes, Rennes 35200, France
| | - Christele Dubourg
- Service de Génétique Moléculaire et Génomique, CHU de Rennes, Rennes 35200, France
- Université de Rennes, CNRS, Institut de Genetique et Developpement de Rennes, UMR 6290, Rennes 35200, France
| | - Sandra Mercier
- Nantes Université, CHU Nantes, Service de Génétique Médicale, Nantes 44000, France
- Nantes Université, CHU Nantes, CNRS, INSERM, l’institut du thorax, Nantes 44000, France
| | - Thomas Besnard
- Nantes Université, CHU Nantes, Service de Génétique Médicale, Nantes 44000, France
- Nantes Université, CHU Nantes, CNRS, INSERM, l’institut du thorax, Nantes 44000, France
| | - Benjamin Cogne
- Nantes Université, CHU Nantes, Service de Génétique Médicale, Nantes 44000, France
- Nantes Université, CHU Nantes, CNRS, INSERM, l’institut du thorax, Nantes 44000, France
| | - Wallid Deb
- Nantes Université, CHU Nantes, Service de Génétique Médicale, Nantes 44000, France
- Nantes Université, CHU Nantes, CNRS, INSERM, l’institut du thorax, Nantes 44000, France
| | - Clotilde Rivier
- Department of Paediatrics, Villefranche-sur-Saône Hospital, Villefranche-sur-Saône 69655, France
| | - Donatella Milani
- Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milan 20122, Italy
| | - Maria Francesca Bedeschi
- Medical Genetics Unit, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milan 20122, Italy
| | - Claudia Di Napoli
- Medical Genetics Unit, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milan 20122, Italy
| | - Federico Grilli
- Medical Genetics Unit, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milan 20122, Italy
| | - Paola Marchisio
- Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Pediatria Pneumoinfettivologia, Milan 20122, Italy
- University of Milan, Milan 20122, Italy
| | - Suzanna Koudijs
- Department of Neurology, ENCORE, Erasmus Medical Center-Sophia Children’s Hospital, Rotterdam 3015, The Netherlands
| | - Danielle Veenma
- Department of Pediatrics, ENCORE, Erasmus Medical Center-Sophia Children’s Hospital, Rotterdam 3015, The Netherlands
| | - Emanuela Argilli
- Institute of Human Genetics, University of California, San Francisco, CA 94143, USA
- Department of Neurology, Weill Institute for Neurosciences, University of California, San Francisco, CA 94143, USA
| | - Sally Ann Lynch
- Department of Clinical Genetics, Children’s Health Ireland Crumlin, Dublin D12 N512, Ireland
| | - Ping Yee Billie Au
- Department of Medical Genetics, Alberta Children’s Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada
| | | | | | - Diane Masser-Frye
- Division of Genetics, Department of Pediatrics, UC San Diego School of Medicine, Rady Children’s Hospital, San Diego, CA 92123, USA
| | - Marilyn Jones
- Division of Genetics, Department of Pediatrics, UC San Diego School of Medicine, Rady Children’s Hospital, San Diego, CA 92123, USA
| | - Leslie Patron Romero
- Facultad de Medicina y Psicología, Universidad Autónoma de Baja California, Tijuana 22010, Mexico
| | | | | | - Laura Hecher
- Department of Pediatrics, University Medical Center Hamburg-Eppendorf, Hamburg 20215, Germany
| | - Jessika Johannsen
- Department of Pediatrics, University Medical Center Hamburg-Eppendorf, Hamburg 20215, Germany
| | - Jonas Denecke
- Department of Pediatrics, University Medical Center Hamburg-Eppendorf, Hamburg 20215, Germany
| | - Vanda McNiven
- Division of Clinical and Metabolic Genetics, The Hospital for Sick Children, University of Toronto, Toronto, ON M5G 1E8, Canada
- Fred A Litwin Family Centre in Genetic Medicine, University Health Network and Mount Sinai Hospital, Toronto, ON M5G 2C4, Canada
| | - Anna Szuto
- Division of Clinical and Metabolic Genetics, The Hospital for Sick Children, University of Toronto, Toronto, ON M5G 1E8, Canada
- Department of Paediatrics, Hospital for Sick Children and University of Toronto, Toronto, ON M5G 1E8, Canada
| | - Emma Wakeling
- North East Thames Regional Genetics Service, Great Ormond Street Hospital for Children NHS Foundation Trust, London WC1N 3JH, UK
| | - Vincent Cruz
- DDC Clinic Center for Special Needs Children, Middlefield, OH 44062, USA
| | - Valerie Sency
- DDC Clinic Center for Special Needs Children, Middlefield, OH 44062, USA
| | - Heng Wang
- DDC Clinic Center for Special Needs Children, Middlefield, OH 44062, USA
| | - Juliette Piard
- Centre de Génétique Humaine, Centre Hospitalier Universitaire, Université de Franche-Comté, Besançon 25000, France
- UMR 1231 GAD, Inserm, Université de Bourgogne Franche-Comté, Dijon 21000, France
| | - Fanny Kortüm
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg 20246, Germany
| | - Theresia Herget
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg 20246, Germany
| | - Tatjana Bierhals
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg 20246, Germany
| | - Angelo Condell
- Brain and Mitochondrial Research Group, Murdoch Children’s Research Institute, Melbourne, Victoria 3052, Australia
| | - Bruria Ben-Zeev
- Pediatric Neurology Unit, Edmond and Lily Safra Children's Hospital, Sheba Medical Center, Ramat Gan 52621, Israel
- Faculty of Medicine, Tel Aviv University, Tel Aviv 4R73+8Q, Israel
| | - Simranpreet Kaur
- Brain and Mitochondrial Research Group, Murdoch Children’s Research Institute, Melbourne, Victoria 3052, Australia
- Department of Paediatrics, Melbourne Medical School, University of Melbourne, Melbourne, Victoria 3052, Australia
| | - John Christodoulou
- Brain and Mitochondrial Research Group, Murdoch Children’s Research Institute, Melbourne, Victoria 3052, Australia
- Department of Paediatrics, Melbourne Medical School, University of Melbourne, Melbourne, Victoria 3052, Australia
- Discipline of Genetic Medicine, Sydney Medical School, University of Sydney, Sydney, New South Wales 2050, Australia
- Discipline of Child and Adolescent Health, Sydney Medical School, University of Sydney, Sydney, NewSouth Wales 2050, Australia
| | - Amelie Piton
- Hôpitaux Universitaires de Strasbourg, Laboratoire de Diagnostic Génétique, Strasbourg 67000, France
| | - Christiane Zweier
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen 91054, Germany
- Department of Human Genetics, Inselspital Bern, University of Bern, Bern 3010, Switzerland
| | - Cornelia Kraus
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen 91054, Germany
| | - Alessia Micalizzi
- Translational Cytogenomics Research Unit, Bambino Gesù Children's Hospital, IRCCS, Rome 00165, Italy
| | - Marina Trivisano
- Neurology, Epilepsy and Movement Disorders, Bambino Gesù Children's Hospital, IRCCS, Full Member of European Reference Network EpiCARE, Rome 00165, Italy
| | - Nicola Specchio
- Neurology, Epilepsy and Movement Disorders, Bambino Gesù Children's Hospital, IRCCS, Full Member of European Reference Network EpiCARE, Rome 00165, Italy
| | - Gaetan Lesca
- Department of Medical Genetics, University Hospital of Lyon and Claude Bernard Lyon I University, Lyon 69100, France
- Pathophysiology and Genetics of Neuron and Muscle (PNMG), UCBL, CNRS UMR5261 - INSERM U1315, Lyon 69100, France
| | - Rikke S Møller
- Department of Epilepsy Genetics and Personalized Medicine, Danish Epilepsy Centre, Dianalund 4293, Denmark
- Department of Regional Health Research, University of Southern Denmark, Odense 5230Denmark
| | - Zeynep Tümer
- Kennedy Center, Department of Clinical Genetics, Copenhagen University Hospital, Rigshospitalet, Copenhagen 2100, Denmark
- Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen 2100, Denmark
| | - Maria Musgaard
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa K1H 8M5, Canada
| | - Benedicte Gerard
- Laboratoires de diagnostic genetique, Institut de genetique Medicale d'Alsace, Hopitaux Universitaires de Strasbourg, Strasbourg 67000, France
| | - Johannes R Lemke
- Center for Rare Diseases, University of Leipzig Medical Center, Leipzig 04103, Germany
| | - Yun Stone Shi
- State Key Laboratory of Pharmaceutical Biotechnology, Model Animal Research Center, Department of Neurology, Nanjing Drum Tower Hospital, Medical School, Nanjing University, Nanjing 210032, China
- Ministry of Education Key Laboratory of Model Animal for Disease Study, National Resource Center for Mutant Mice, Jiangsu Key Laboratory of Molecular Medicine, Medical School, Nanjing University, Nanjing 210032, China
- Guangdong Institute of Intelligence Science and Technology, Zhuhai 519031, China
| | - Anders S Kristensen
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen 2100, Denmark
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Spirou GA, Kersting M, Carr S, Razzaq B, Yamamoto Alves Pinto C, Dawson M, Ellisman MH, Manis PB. High-resolution volumetric imaging constrains compartmental models to explore synaptic integration and temporal processing by cochlear nucleus globular bushy cells. eLife 2023; 12:e83393. [PMID: 37288824 PMCID: PMC10435236 DOI: 10.7554/elife.83393] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Accepted: 06/07/2023] [Indexed: 06/09/2023] Open
Abstract
Globular bushy cells (GBCs) of the cochlear nucleus play central roles in the temporal processing of sound. Despite investigation over many decades, fundamental questions remain about their dendrite structure, afferent innervation, and integration of synaptic inputs. Here, we use volume electron microscopy (EM) of the mouse cochlear nucleus to construct synaptic maps that precisely specify convergence ratios and synaptic weights for auditory nerve innervation and accurate surface areas of all postsynaptic compartments. Detailed biophysically based compartmental models can help develop hypotheses regarding how GBCs integrate inputs to yield their recorded responses to sound. We established a pipeline to export a precise reconstruction of auditory nerve axons and their endbulb terminals together with high-resolution dendrite, soma, and axon reconstructions into biophysically detailed compartmental models that could be activated by a standard cochlear transduction model. With these constraints, the models predict auditory nerve input profiles whereby all endbulbs onto a GBC are subthreshold (coincidence detection mode), or one or two inputs are suprathreshold (mixed mode). The models also predict the relative importance of dendrite geometry, soma size, and axon initial segment length in setting action potential threshold and generating heterogeneity in sound-evoked responses, and thereby propose mechanisms by which GBCs may homeostatically adjust their excitability. Volume EM also reveals new dendritic structures and dendrites that lack innervation. This framework defines a pathway from subcellular morphology to synaptic connectivity, and facilitates investigation into the roles of specific cellular features in sound encoding. We also clarify the need for new experimental measurements to provide missing cellular parameters, and predict responses to sound for further in vivo studies, thereby serving as a template for investigation of other neuron classes.
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Affiliation(s)
- George A Spirou
- Department of Medical Engineering, University of South FloridaTampaUnited States
| | - Matthew Kersting
- Department of Medical Engineering, University of South FloridaTampaUnited States
| | - Sean Carr
- Department of Medical Engineering, University of South FloridaTampaUnited States
| | - Bayan Razzaq
- Department of Otolaryngology, Head and Neck Surgery, West Virginia UniversityMorgantownUnited States
| | | | - Mariah Dawson
- Department of Otolaryngology, Head and Neck Surgery, West Virginia UniversityMorgantownUnited States
| | - Mark H Ellisman
- Department of Neurosciences, University of California, San DiegoSan DiegoUnited States
- National Center for Microscopy and Imaging Research,University of California, San DiegoSan DiegoUnited States
| | - Paul B Manis
- Department of Otolaryngology/Head and Neck Surgery, University of North Carolina at Chapel HillChapel HillUnited States
- Department of Cell Biology and Physiology, University of North CarolinaChapel HillUnited States
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Saleh AJ, Ahmed Y, Peters LO, Nothwang HG. Comparative expression analysis of the Atoh7 gene regulatory network in the mouse and chicken auditory hindbrain. Cell Tissue Res 2023:10.1007/s00441-023-03763-9. [PMID: 36961563 DOI: 10.1007/s00441-023-03763-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Accepted: 03/09/2023] [Indexed: 03/25/2023]
Abstract
The mammalian and avian auditory brainstem likely arose by independent evolution. To compare the underlying molecular mechanisms, we focused on Atoh7, as its expression pattern in the mammalian hindbrain is restricted to bushy cells in the ventral cochlear nucleus. We thereby took advantage of an Atoh7 centered gene regulatory network (GRN) in the retina including upstream regulators, Hes1 and Pax6, and downstream targets, Ebf3 and Eya2. In situ hybridization demonstrated for the latter four genes broad expression in all three murine cochlear nuclei at postnatal days (P) 4 and P30, contrasting the restricted expression of Atoh7. In chicken, all five transcription factors were expressed in all auditory hindbrain nuclei at embryonic day (E) 13 and P14. Notably, all five genes showed graded expression in the embryonic nucleus magnocellularis (NM). Atoh7 was highly expressed in caudally located neurons, whereas the other four transcription factors were highly expressed in rostrally located neurons. Thus, Atoh7 shows a strikingly different expression between the mammalian and avian auditory hindbrain. This together with the consistent absence of graded expression of GRN components in developing mammalian nuclei provide the first molecular support to the current view of convergent evolution as a major mechanism in the amniote auditory hindbrain. The graded expression of five transcription factors specifically in the developing NM confirms this nucleus as a central organizer of tonotopic features in birds. Finally, the expression of all five retinal GRN components in the auditory system suggests co-options of genes for development of sensory systems of distinct modalities.
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Affiliation(s)
- Ali Jason Saleh
- Division of Neurogenetics and Cluster of Excellence "Hearing4all", School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26111, Oldenburg, Germany
| | - Yannis Ahmed
- Institute of Neurophysiopathology (INP), Aix-Marseille University, CNRS, Marseille, France
| | - Lars-Oliver Peters
- Division of Neurogenetics and Cluster of Excellence "Hearing4all", School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26111, Oldenburg, Germany
| | - Hans Gerd Nothwang
- Division of Neurogenetics and Cluster of Excellence "Hearing4all", School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26111, Oldenburg, Germany.
- Research Center for Neurosensory Science, Carl von Ossietzky University Oldenburg, 26111, Oldenburg, Germany.
- Department of Neuroscience, Cluster of Excellence "Hearing4all", Carl von Ossietzky University Oldenburg, 26111, Oldenburg, Germany.
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Baldassano JF, MacLeod KM. Kv1 channels regulate variations in spike patterning and temporal reliability in the avian cochlear nucleus angularis. J Neurophysiol 2022; 127:116-129. [PMID: 34817286 PMCID: PMC8742726 DOI: 10.1152/jn.00460.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Diverse physiological phenotypes in a neuronal population can broaden the range of computational capabilities within a brain region. The avian cochlear nucleus angularis (NA) contains a heterogeneous population of neurons whose variation in intrinsic properties results in electrophysiological phenotypes with a range of sensitivities to temporally modulated input. The low-threshold potassium conductance (GKLT) is a key feature of neurons involved in fine temporal structure coding for sound localization, but a role for these channels in intensity or spectrotemporal coding has not been established. To determine whether GKLT affects the phenotypical variation and temporal properties of NA neurons, we applied dendrotoxin-I (DTX), a potent antagonist of Kv1-type potassium channels, to chick brain stem slices in vitro during whole cell patch-clamp recordings. We found a cell-type specific subset of NA neurons that was sensitive to DTX: single-spiking NA neurons were most profoundly affected, as well as a subset of tonic-firing neurons. Both tonic I (phasic onset bursting) and tonic II (delayed firing) neurons showed DTX sensitivity in their firing rate and phenotypical firing pattern. Tonic III neurons were unaffected. Spike time reliability and fluctuation sensitivity measured in DTX-sensitive NA neurons was also reduced with DTX. Finally, DTX reduced spike threshold adaptation in these neurons, suggesting that GKLT contributes to the temporal properties that allow coding of rapid changes in the inputs to NA neurons. These results suggest that variation in Kv1 channel expression may be a key factor in functional diversity in the avian cochlear nucleus.NEW & NOTEWORTHY The dendrotoxin-sensitive voltage-gated potassium conductance typically associated with neuronal coincidence detection in the timing pathway for sound localization is demonstrated to affect spiking patterns and temporal input sensitivity in the intensity pathway in the avian auditory brain stem. The Kv1-family channels appear to be present in a subset of cochlear nucleus angularis neurons, regulate spike threshold dynamics underlying high-pass membrane filtering, and contribute to intrinsic firing diversity.
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Rapid Regulation of Glutamate Transport: Where Do We Go from Here? Neurochem Res 2022; 47:61-84. [PMID: 33893911 PMCID: PMC8542062 DOI: 10.1007/s11064-021-03329-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 04/08/2021] [Accepted: 04/13/2021] [Indexed: 01/03/2023]
Abstract
Glutamate is the predominant excitatory neurotransmitter in the mammalian central nervous system (CNS). A family of five Na+-dependent transporters maintain low levels of extracellular glutamate and shape excitatory signaling. Shortly after the research group of the person being honored in this special issue (Dr. Baruch Kanner) cloned one of these transporters, his group and several others showed that their activity can be acutely (within minutes to hours) regulated. Since this time, several different signals and post-translational modifications have been implicated in the regulation of these transporters. In this review, we will provide a brief introduction to the distribution and function of this family of glutamate transporters. This will be followed by a discussion of the signals that rapidly control the activity and/or localization of these transporters, including protein kinase C, ubiquitination, glutamate transporter substrates, nitrosylation, and palmitoylation. We also include the results of our attempts to define the role of palmitoylation in the regulation of GLT-1 in crude synaptosomes. In some cases, the mechanisms have been fairly well-defined, but in others, the mechanisms are not understood. In several cases, contradictory phenomena have been observed by more than one group; we describe these studies with the goal of identifying the opportunities for advancing the field. Abnormal glutamatergic signaling has been implicated in a wide variety of psychiatric and neurologic disorders. Although recent studies have begun to link regulation of glutamate transporters to the pathogenesis of these disorders, it will be difficult to determine how regulation influences signaling or pathophysiology of glutamate without a better understanding of the mechanisms involved.
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Karadas M, Olsson C, Winther Hansen N, Perrier JF, Webb JL, Huck A, Andersen UL, Thielscher A. In-vitro Recordings of Neural Magnetic Activity From the Auditory Brainstem Using Color Centers in Diamond: A Simulation Study. Front Neurosci 2021; 15:643614. [PMID: 34054404 PMCID: PMC8155532 DOI: 10.3389/fnins.2021.643614] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Accepted: 04/12/2021] [Indexed: 11/13/2022] Open
Abstract
Magnetometry based on nitrogen-vacancy (NV) centers in diamond is a novel technique capable of measuring magnetic fields with high sensitivity and high spatial resolution. With the further advancements of these sensors, they may open up novel approaches for the 2D imaging of neural signals in vitro. In the present study, we investigate the feasibility of NV-based imaging by numerically simulating the magnetic signal from the auditory pathway of a rodent brainstem slice (ventral cochlear nucleus, VCN, to the medial trapezoid body, MNTB) as stimulated by both electric and optic stimulation. The resulting signal from these two stimulation methods are evaluated and compared. A realistic pathway model was created based on published data of the neural morphologies and channel dynamics of the globular bushy cells in the VCN and their axonal projections to the principal cells in the MNTB. The pathway dynamics in response to optic and electric stimulation and the emitted magnetic fields were estimated using the cable equation. For simulating the optic stimulation, the light distribution in brain tissue was numerically estimated and used to model the optogenetic neural excitation based on a four state channelrhodopsin-2 (ChR2) model. The corresponding heating was also estimated, using the bio-heat equation and was found to be low (<2°C) even at excessively strong optic signals. A peak magnetic field strength of ∼0.5 and ∼0.1 nT was calculated from the auditory brainstem pathway after electrical and optical stimulation, respectively. By increasing the stimulating light intensity four-fold (far exceeding commonly used intensities) the peak magnetic signal strength only increased to 0.2 nT. Thus, while optogenetic stimulation would be favorable to avoid artefacts in the recordings, electric stimulation achieves higher peak fields. The present simulation study predicts that high-resolution magnetic imaging of the action potentials traveling along the auditory brainstem pathway will only be possible for next generation NV sensors. However, the existing sensors already have sufficient sensitivity to support the magnetic sensing of cumulated neural signals sampled from larger parts of the pathway, which might be a promising intermediate step toward further maturing this novel technology.
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Affiliation(s)
- Mürsel Karadas
- Department of Health Technology, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Christoffer Olsson
- Department of Health Technology, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Nikolaj Winther Hansen
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jean-François Perrier
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - James Luke Webb
- Department of Physics, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Alexander Huck
- Department of Physics, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Ulrik Lund Andersen
- Department of Physics, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Axel Thielscher
- Department of Health Technology, Technical University of Denmark, Kongens Lyngby, Denmark
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark
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7
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Balmer TS, Borges-Merjane C, Trussell LO. Incomplete removal of extracellular glutamate controls synaptic transmission and integration at a cerebellar synapse. eLife 2021; 10:e63819. [PMID: 33616036 PMCID: PMC7935485 DOI: 10.7554/elife.63819] [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] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Accepted: 02/19/2021] [Indexed: 11/27/2022] Open
Abstract
Synapses of glutamatergic mossy fibers (MFs) onto cerebellar unipolar brush cells (UBCs) generate slow excitatory (ON) or inhibitory (OFF) postsynaptic responses dependent on the complement of glutamate receptors expressed on the UBC's large dendritic brush. Using mouse brain slice recording and computational modeling of synaptic transmission, we found that substantial glutamate is maintained in the UBC synaptic cleft, sufficient to modify spontaneous firing in OFF UBCs and tonically desensitize AMPARs of ON UBCs. The source of this ambient glutamate was spontaneous, spike-independent exocytosis from the MF terminal, and its level was dependent on activity of glutamate transporters EAAT1-2. Increasing levels of ambient glutamate shifted the polarity of evoked synaptic responses in ON UBCs and altered the phase of responses to in vivo-like synaptic activity. Unlike classical fast synapses, receptors at the UBC synapse are virtually always exposed to a significant level of glutamate, which varies in a graded manner during transmission.
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Affiliation(s)
- Timothy S Balmer
- Vollum Institute and Oregon Hearing Research Center, Oregon Health & Science UniversityPortlandUnited States
| | - Carolina Borges-Merjane
- Vollum Institute and Oregon Hearing Research Center, Oregon Health & Science UniversityPortlandUnited States
- Neuroscience Graduate Program, Vollum Institute, Oregon Health & Science UniversityPortlandUnited States
| | - Laurence O Trussell
- Vollum Institute and Oregon Hearing Research Center, Oregon Health & Science UniversityPortlandUnited States
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8
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Devi SPS, Cheng Y, Tomita S, Howe JR, Zhang W. TARPs Modulate Receptor-Mediated Paired-Pulse Depression and Recovery from Desensitization. J Neurosci 2020; 40:8233-8247. [PMID: 32994336 PMCID: PMC7577600 DOI: 10.1523/jneurosci.3026-19.2020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2019] [Revised: 08/07/2020] [Accepted: 09/14/2020] [Indexed: 11/21/2022] Open
Abstract
Transmembrane AMPA receptor regulatory proteins (TARPs) are auxiliary AMPA receptor subunits that play a key role in receptor trafficking and in modulating receptor gating. The ability of TARPs to slow both deactivation and desensitization is isoform specific. However, TARP isoform-specific modulation of receptor properties remains uncharacterized. Here, we compare the isoform-specific effects of γ-2, γ-3, γ-4, and γ-8 TARPs on recovery from desensitization and responses to pairs of brief applications of glutamate. All four isoforms were able to reduce receptor-mediated paired-pulse depression and significantly speed recovery from desensitization in an isoform-specific manner. In the presence of TARPs, recovery time courses were observed to contain two components, fast and slow. The proportion of fast and slow components was determined by the TARP isoform. The time constant of recovery was also altered by the duration of glutamate application. When studies with TARP chimeras were performed, TARP extracellular loops were found to play a vital role in TARP modulation of recovery. Thus, isoform-specific differences in TARP modulation of recovery from desensitization influence receptor responses to repeated brief applications of glutamate, and these differences may impact frequency-dependent synaptic signaling in the mammalian central nervous system.SIGNIFICANCE STATEMENT AMPA receptors are major determinants of excitatory synaptic strength. The channel kinetics of AMPA receptors contribute to the kinetics of synaptic transmission. Transmembrane AMPA receptor regulatory proteins (TARPs) auxiliary subunits can modulate the decay kinetics of AMPA receptors. However, whether TARP isoforms specifically modulate receptor recovery is unclear. Here, we investigated the recovery kinetics of AMPA receptors by expressing various TARP isoforms and chimeras. We observed that the TARP isoforms and duration of glutamate application uniquely modulate time constants and the proportion of fast and slow components through a previously unidentified TARP domain. Given the impact of recovery kinetics on receptor responses to repetitive stimulation such as synaptic transmission, this work will be of great interest in the field of excitatory synaptic transmission research.
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Affiliation(s)
- Suma Priya Sudarsana Devi
- Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520
- Department of Surgery, University of Alabama at Birmingham, Birmingham, Alabama 35233
| | - Yiru Cheng
- Department of Pharmacology of Chinese Materia Medica, Institution of Chinese Integrative Medicine, Hebei Medical University, Shijiazhuang, Hebei Province 050017, China
| | - Susumu Tomita
- Department of Cellular and Molecular Physiology, Department of Neuroscience, and Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, Connecticut 06520
| | - James R Howe
- Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520
| | - Wei Zhang
- Department of Pharmacology of Chinese Materia Medica, Institution of Chinese Integrative Medicine, Hebei Medical University, Shijiazhuang, Hebei Province 050017, China
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9
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Role of GluA3 AMPA Receptor Subunits in the Presynaptic and Postsynaptic Maturation of Synaptic Transmission and Plasticity of Endbulb-Bushy Cell Synapses in the Cochlear Nucleus. J Neurosci 2020; 40:2471-2484. [PMID: 32051325 DOI: 10.1523/jneurosci.2573-19.2020] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 01/22/2020] [Accepted: 02/02/2020] [Indexed: 11/21/2022] Open
Abstract
The AMPA receptor (AMPAR) subunit GluA3 has been suggested to shape synaptic transmission and activity-dependent plasticity in endbulb-bushy cell synapses (endbulb synapses) in the anteroventral cochlear nucleus, yet the specific roles of GluA3 in the synaptic transmission at endbulb synapses remains unexplored. Here, we compared WT and GluA3 KO mice of both sexes and identified several important roles of GluA3 in the maturation of synaptic transmission and short-term plasticity in endbulb synapses. We show that GluA3 largely determines the ultrafast kinetics of endbulb synapses glutamatergic currents by promoting the insertion of postsynaptic AMPARs that contain fast desensitizing flop subunits. In addition, GluA3 is also required for the normal function, structure, and development of the presynaptic terminal which leads to altered short term-depression in GluA3 KO mice. The presence of GluA3 reduces and slows synaptic depression, which is achieved by lowering the probability of vesicle release, promoting efficient vesicle replenishment, and increasing the readily releasable pool of synaptic vesicles. Surprisingly, GluA3 also makes the speed of synaptic depression rate-invariant. We propose that the slower and rate-invariant speed of depression allows an initial response window that still contains presynaptic firing rate information before the synapse is depressed. Because this response window is rate-invariant, GluA3 extends the range of presynaptic firing rates over which rate information in bushy cells can be preserved. This novel role of GluA3 may be important to allowing the postsynaptic targets of spherical bushy cells in mice use rate information for encoding sound intensity and sound localization.SIGNIFICANCE STATEMENT We report novel roles of the glutamate receptor subunit GluA3 in synaptic transmission in synapses between auditory nerve fibers and spherical bushy cells (BCs) in the cochlear nucleus. We show that GluA3 contributes to the generation of ultrafast glutamatergic currents at these synapses, which is important to preserve temporal information about the sound. Furthermore, we demonstrate that GluA3 contributes to the normal function and development of the presynaptic terminal, whose properties shape short-term plasticity. GluA3 slows and attenuates synaptic depression, and makes it less dependent on the presynaptic firing rates. This may help BCs to transfer information about the high rates of activity that occur at the synapse in vivo to postsynaptic targets that use rate information for sound localization.
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10
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Zhou M, Yuan J, Yan Z, Dai J, Wang X, Xu T, Xu Z, Wang N, Liu J. Intrinsic and Miniature Postsynaptic Current Changes in Rat Principal Neurons of the Lateral Superior Olive after Unilateral Auditory Deprivation at an Early Age. Neuroscience 2019; 428:2-12. [PMID: 31866557 DOI: 10.1016/j.neuroscience.2019.12.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2019] [Revised: 11/30/2019] [Accepted: 12/02/2019] [Indexed: 01/13/2023]
Abstract
Unilateral auditory deprivation results in lateralization changes in the central auditory system, interfering with the integration of binaural information and thereby leading to a decrease in binaural auditory functions such as sound localization. Principal neurons of the lateral superior olive (LSO) are responsible for computing the interaural intensity differences that are critical for sound localization in the horizontal plane. To investigate changes caused by unilateral auditory deprivation, electrophysiological activity was recorded from LSO principal neurons in control rats and rats with unilateral cochlear ablation. At one week after unilateral cochlear ablation, the excitability of LSO principal neurons on the side ipsilateral to the ablation (the ablated side) was greater than that on the side contralateral to the ablation (the intact side); however, the input resistance increased on both sides. Furthermore, by analysing the miniature inhibitory postsynaptic currents and miniature excitatory postsynaptic currents, we found that unilateral auditory deprivation weakened the inhibitory driving force on the intact side, whereas it strengthened the excitatory driving force on the ablated side. In summary, asymmetric changes in the electrophysiological activity of LSO principal neurons were found on both sides at postnatal day 19, one week after unilateral cochlear ablation.
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Affiliation(s)
- Mo Zhou
- Department of Otorhinolaryngology Head and Neck Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China
| | - Jingjing Yuan
- Department of Otorhinolaryngology Head and Neck Surgery, Beijing Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China
| | - Zhanfeng Yan
- Department of Otorhinolaryngology Head and Neck Surgery, Beijing Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China
| | - Jinsheng Dai
- Department of Otorhinolaryngology Head and Neck Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China
| | - Xing Wang
- Department of Otorhinolaryngology Head and Neck Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China
| | - Tao Xu
- Department of Neurobiology, Beijing Key Laboratory of Neural Regeneration and Repair, Beijing Laboratory of Brain Disorders (Ministry of Science and Technology), Beijing Institute of Brain Disorders, Capital Medical University, Beijing, China
| | - Zhiqing Xu
- Department of Neurobiology, Beijing Key Laboratory of Neural Regeneration and Repair, Beijing Laboratory of Brain Disorders (Ministry of Science and Technology), Beijing Institute of Brain Disorders, Capital Medical University, Beijing, China
| | - Ningyu Wang
- Department of Otorhinolaryngology Head and Neck Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China.
| | - Jinfeng Liu
- Department of Otorhinolaryngology Head and Neck Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China.
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11
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Kuenzel T. Modulatory influences on time-coding neurons in the ventral cochlear nucleus. Hear Res 2019; 384:107824. [DOI: 10.1016/j.heares.2019.107824] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Revised: 09/10/2019] [Accepted: 10/14/2019] [Indexed: 02/07/2023]
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12
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Nazarova AA, Sedenkova KN, Karlov DS, Lavrov MI, Grishin YK, Kuznetsova TS, Zamoyski VL, Grigoriev VV, Averina EB, Palyulin VA. Bivalent AMPA receptor positive allosteric modulators of the bis(pyrimidine) series. MEDCHEMCOMM 2019; 10:1615-1619. [PMID: 31803402 PMCID: PMC6837176 DOI: 10.1039/c9md00262f] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Accepted: 07/10/2019] [Indexed: 12/17/2022]
Abstract
The first example of a novel class of AMPA receptor positive allosteric modulators of the bis(pyrimidine) series having a hydroquinone linker has been obtained and showed a potency to increase kainate-induced currents at subnanomolar concentrations.
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Affiliation(s)
- Anna A Nazarova
- Department of Chemistry , Lomonosov Moscow State University , 119991 Moscow , Russian Federation . ;
| | - Kseniya N Sedenkova
- Department of Chemistry , Lomonosov Moscow State University , 119991 Moscow , Russian Federation . ;
- Institute of Physiologically Active Compounds , Russian Academy of Sciences , 142432 Chernogolovka , Moscow Region , Russian Federation
| | - Dmitry S Karlov
- Department of Chemistry , Lomonosov Moscow State University , 119991 Moscow , Russian Federation . ;
- Center for Computational and Data-intensive Science and Engineering , Skolkovo Institute of Science and Technology , 121205 Moscow , Russian Federation
| | - Mstislav I Lavrov
- Department of Chemistry , Lomonosov Moscow State University , 119991 Moscow , Russian Federation . ;
- Institute of Physiologically Active Compounds , Russian Academy of Sciences , 142432 Chernogolovka , Moscow Region , Russian Federation
| | - Yuri K Grishin
- Department of Chemistry , Lomonosov Moscow State University , 119991 Moscow , Russian Federation . ;
| | - Tamara S Kuznetsova
- Department of Chemistry , Lomonosov Moscow State University , 119991 Moscow , Russian Federation . ;
| | - Vladimir L Zamoyski
- Institute of Physiologically Active Compounds , Russian Academy of Sciences , 142432 Chernogolovka , Moscow Region , Russian Federation
| | - Vladimir V Grigoriev
- Department of Chemistry , Lomonosov Moscow State University , 119991 Moscow , Russian Federation . ;
- Institute of Physiologically Active Compounds , Russian Academy of Sciences , 142432 Chernogolovka , Moscow Region , Russian Federation
| | - Elena B Averina
- Department of Chemistry , Lomonosov Moscow State University , 119991 Moscow , Russian Federation . ;
- Institute of Physiologically Active Compounds , Russian Academy of Sciences , 142432 Chernogolovka , Moscow Region , Russian Federation
| | - Vladimir A Palyulin
- Department of Chemistry , Lomonosov Moscow State University , 119991 Moscow , Russian Federation . ;
- Institute of Physiologically Active Compounds , Russian Academy of Sciences , 142432 Chernogolovka , Moscow Region , Russian Federation
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13
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Mechanisms of zinc modulation of olfactory bulb AMPA receptors. Neuroscience 2019; 410:160-175. [PMID: 31082537 DOI: 10.1016/j.neuroscience.2019.05.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 05/01/2019] [Accepted: 05/03/2019] [Indexed: 12/31/2022]
Abstract
The alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) subtype of ionotropic glutamate receptors mediates most fast excitatory transmission. Glutamate binding to AMPA receptors (AMPARs) causes most AMPARs to rapidly and completely desensitize, and their desensitization kinetics influence synaptic timing. Thus, factors that alter AMPAR desensitization influence synaptic transmission. Synaptically released zinc is such a factor. Zinc is a neuromodulator with effects on amino acid receptors and synaptic transmission in many brain regions, including the olfactory bulb (OB). We have previously shown in the OB that zinc potentiates AMPAR-mediated currents at low concentrations (30 μM, 100 μM) and inhibits them at a higher concentration (1 mM). It has been hypothesized that zinc potentiates AMPARs by decreasing receptor desensitization. Here, we used cyclothiazide (CTZ), a drug that blocks AMPAR desensitization, to determine whether zinc-mediated potentiation and/or inhibition of AMPA-evoked currents reflect(s) changes in AMPAR desensitization. Zinc largely had biphasic concentration-dependent effects at OB AMPARs. CTZ completely blocked potentiation by zinc but had no significant effect on inhibition. There was a significant negative correlation between the degree of potentiation of AMPAR-mediated currents by 100 μM zinc and a quantitative measure of the degree of AMPAR desensitization (the steady-state to peak [S:P] ratio of AMPA-evoked currents), but no correlation between the degree of current inhibition by 1 mM zinc and the S:P ratio. Together, these findings suggest that low zinc concentrations potentiate rat OB AMPARs by decreasing receptor desensitization, but that the inhibitory effects of higher zinc concentrations are mediated by a separate mechanism.
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14
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Dual Effects of TARP γ-2 on Glutamate Efficacy Can Account for AMPA Receptor Autoinactivation. Cell Rep 2018; 20:1123-1135. [PMID: 28768197 PMCID: PMC5554777 DOI: 10.1016/j.celrep.2017.07.014] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Revised: 06/12/2017] [Accepted: 07/09/2017] [Indexed: 11/10/2022] Open
Abstract
Fast excitatory transmission in the CNS is mediated mainly by AMPA-type glutamate receptors (AMPARs) associated with transmembrane AMPAR regulatory proteins (TARPs). At the high glutamate concentrations typically seen during synaptic transmission, TARPs slow receptor desensitization and enhance mean channel conductance. However, their influence on channels gated by low glutamate concentrations, as encountered during delayed transmitter clearance or synaptic spillover, is poorly understood. We report here that TARP γ-2 reduces the ability of low glutamate concentrations to cause AMPAR desensitization and enhances channel gating at low glutamate occupancy. Simulations show that, by shifting the balance between AMPAR activation and desensitization, TARPs can markedly facilitate the transduction of spillover-mediated synaptic signaling. Furthermore, the dual effects of TARPs can account for biphasic steady-state glutamate concentration-response curves—a phenomenon termed “autoinactivation,” previously thought to reflect desensitization-mediated AMPAR/TARP dissociation. TARP γ-2 reduces desensitization and enhances the gating of singly liganded AMPARs This accounts for biphasic steady-state dose-response curves (autoinactivation) The effects of γ-2 are predicted to enhance synaptic spillover currents Desensitization does not lead to functional dissociation of the AMPAR/TARP complex
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15
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Manis PB, Campagnola L. A biophysical modelling platform of the cochlear nucleus and other auditory circuits: From channels to networks. Hear Res 2017; 360:76-91. [PMID: 29331233 DOI: 10.1016/j.heares.2017.12.017] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 11/27/2017] [Accepted: 12/23/2017] [Indexed: 12/12/2022]
Abstract
Models of the auditory brainstem have been an invaluable tool for testing hypotheses about auditory information processing and for highlighting the most important gaps in the experimental literature. Due to the complexity of the auditory brainstem, and indeed most brain circuits, the dynamic behavior of the system may be difficult to predict without a detailed, biologically realistic computational model. Despite the sensitivity of models to their exact construction and parameters, most prior models of the cochlear nucleus have incorporated only a small subset of the known biological properties. This confounds the interpretation of modelling results and also limits the potential future uses of these models, which require a large effort to develop. To address these issues, we have developed a general purpose, biophysically detailed model of the cochlear nucleus for use both in testing hypotheses about cochlear nucleus function and also as an input to models of downstream auditory nuclei. The model implements conductance-based Hodgkin-Huxley representations of cells using a Python-based interface to the NEURON simulator. Our model incorporates most of the quantitatively characterized intrinsic cell properties, synaptic properties, and connectivity available in the literature, and also aims to reproduce the known response properties of the canonical cochlear nucleus cell types. Although we currently lack the empirical data to completely constrain this model, our intent is for the model to continue to incorporate new experimental results as they become available.
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Affiliation(s)
- Paul B Manis
- Dept. of Otolaryngology/Head and Neck Surgery, B027 Marsico Hall, 125 Mason Farm Road, UNC Chapel Hill, Chapel Hill, NC 27599-7070, USA.
| | - Luke Campagnola
- Dept. of Otolaryngology/Head and Neck Surgery, B027 Marsico Hall, 125 Mason Farm Road, UNC Chapel Hill, Chapel Hill, NC 27599-7070, USA
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16
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Lu HW, Balmer TS, Romero GE, Trussell LO. Slow AMPAR Synaptic Transmission Is Determined by Stargazin and Glutamate Transporters. Neuron 2017; 96:73-80.e4. [PMID: 28919175 DOI: 10.1016/j.neuron.2017.08.043] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Revised: 07/25/2017] [Accepted: 08/28/2017] [Indexed: 01/23/2023]
Abstract
AMPARs mediate the briefest synaptic currents in the brain by virtue of their rapid gating kinetics. However, at the mossy fiber-to-unipolar brush cell synapse in the cerebellum, AMPAR-mediated EPSCs last for hundreds of milliseconds, and it has been proposed that this time course reflects slow diffusion from a complex synaptic space. We show that upon release of glutamate, synaptic AMPARs were desensitized by transmitter by >90%. As glutamate levels subsequently fell, recovery of transmission occurred due to the presence of the AMPAR accessory protein stargazin that enhances the AMPAR response to low levels of transmitter. This gradual increase in receptor activity following desensitization accounted for the majority of synaptic transmission at this synapse. Moreover, the amplitude, duration, and shape of the synaptic response was tightly controlled by plasma membrane glutamate transporters, indicating that clearance of synaptic glutamate during the slow EPSC is dictated by an uptake process.
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Affiliation(s)
- Hsin-Wei Lu
- Neuroscience Graduate Program, Oregon Health and Science University, Portland, OR, USA
| | - Timothy S Balmer
- Oregon Hearing Research Center and Vollum Institute, Oregon Health and Science University, Portland, OR, USA
| | - Gabriel E Romero
- Department of Physiology and Pharmacology, Oregon Health and Science University, Portland, OR, USA
| | - Laurence O Trussell
- Oregon Hearing Research Center and Vollum Institute, Oregon Health and Science University, Portland, OR, USA.
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17
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Tonotopic Optimization for Temporal Processing in the Cochlear Nucleus. J Neurosci 2017; 36:8500-15. [PMID: 27511020 DOI: 10.1523/jneurosci.4449-15.2016] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2015] [Accepted: 06/27/2016] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED In the auditory system, sounds are processed in parallel frequency-tuned circuits, beginning in the cochlea. Auditory nerve fibers reflect this tonotopy and encode temporal properties of acoustic stimuli by "locking" discharges to a particular stimulus phase. However, physiological constraints on phase-locking depend on stimulus frequency. Interestingly, low characteristic frequency (LCF) neurons in the cochlear nucleus improve phase-locking precision relative to their auditory nerve inputs. This is proposed to arise through synaptic integration, but the postsynaptic membrane's selectivity for varying levels of synaptic convergence is poorly understood. The chick cochlear nucleus, nucleus magnocellularis (NM), exhibits tonotopic distribution of both input and membrane properties. LCF neurons receive many small inputs and have low input thresholds, whereas high characteristic frequency (HCF) neurons receive few, large synapses and require larger currents to spike. NM therefore presents an opportunity to study how small membrane variations interact with a systematic topographic gradient of synaptic inputs. We investigated membrane input selectivity and observed that HCF neurons preferentially select faster input than their LCF counterparts, and that this preference is tolerant of changes to membrane voltage. We then used computational models to probe which properties are crucial to phase-locking. The model predicted that the optimal arrangement of synaptic and membrane properties for phase-locking is specific to stimulus frequency and that the tonotopic distribution of input number and membrane excitability in NM closely tracks a stimulus-defined optimum. These findings were then confirmed physiologically with dynamic-clamp simulations of inputs to NM neurons. SIGNIFICANCE STATEMENT One way that neurons represent temporal information is by phase-locking, which is discharging in response to a particular phase of the stimulus waveform. In the auditory system, central neurons are optimized to retain or improve phase-locking precision compared with input from the auditory nerve. However, the difficulty of this computation varies systematically with stimulus frequency. We examined properties that contribute to temporal processing both physiologically and in a computational model. Neurons processing low-frequency input benefit from integration of many weak inputs, whereas those processing higher frequencies progressively lose precision by integration of multiple inputs. Here, we reveal general features of input-output optimization that apply to all neurons that process time varying input.
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18
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Brechet A, Buchert R, Schwenk J, Boudkkazi S, Zolles G, Siquier-Pernet K, Schaber I, Bildl W, Saadi A, Bole-Feysot C, Nitschke P, Reis A, Sticht H, Al-Sanna'a N, Rolfs A, Kulik A, Schulte U, Colleaux L, Abou Jamra R, Fakler B. AMPA-receptor specific biogenesis complexes control synaptic transmission and intellectual ability. Nat Commun 2017; 8:15910. [PMID: 28675162 PMCID: PMC5500892 DOI: 10.1038/ncomms15910] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Accepted: 05/11/2017] [Indexed: 11/25/2022] Open
Abstract
AMPA-type glutamate receptors (AMPARs), key elements in excitatory neurotransmission in the brain, are macromolecular complexes whose properties and cellular functions are determined by the co-assembled constituents of their proteome. Here we identify AMPAR complexes that transiently form in the endoplasmic reticulum (ER) and lack the core-subunits typical for AMPARs in the plasma membrane. Central components of these ER AMPARs are the proteome constituents FRRS1l (C9orf4) and CPT1c that specifically and cooperatively bind to the pore-forming GluA1-4 proteins of AMPARs. Bi-allelic mutations in the human FRRS1L gene are shown to cause severe intellectual disability with cognitive impairment, speech delay and epileptic activity. Virus-directed deletion or overexpression of FRRS1l strongly impact synaptic transmission in adult rat brain by decreasing or increasing the number of AMPARs in synapses and extra-synaptic sites. Our results provide insight into the early biogenesis of AMPARs and demonstrate its pronounced impact on synaptic transmission and brain function. The biogenesis of AMPA-type glutamate receptor (AMPAR) complexes is only partially understood. Here the authors identify transient assemblies of GluA1-4 proteins and proteins FRRS1l/CPT1c that drive formation of mature AMPAR complexes in the ER. Mutations in FRRS1l are associated with intellectual disability and epilepsy in three families.
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Affiliation(s)
- Aline Brechet
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, Freiburg 79104, Germany
| | - Rebecca Buchert
- Institute of Human Genetics, University of Erlangen, Schwabachanlage 10, Erlangen 91054, Germany
| | - Jochen Schwenk
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, Freiburg 79104, Germany.,Center for Biological Signaling Studies (BIOSS), Schänzlestr. 18, Freiburg 79104, Germany
| | - Sami Boudkkazi
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, Freiburg 79104, Germany
| | - Gerd Zolles
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, Freiburg 79104, Germany
| | - Karine Siquier-Pernet
- INSERM UMR 1163, Paris-Descartes-Sorbonne Paris Cité University, Institut IMAGINE, Necker-Enfants Malades Hospital, Paris 75015, France
| | - Irene Schaber
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, Freiburg 79104, Germany
| | - Wolfgang Bildl
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, Freiburg 79104, Germany
| | - Abdelkrim Saadi
- Department de Neurologie, Etablissement Hospitalier Specialisé de Benaknoun, Algers, Algeria
| | - Christine Bole-Feysot
- INSERM UMR 1163, Paris-Descartes-Sorbonne Paris Cité University, Institut IMAGINE, Necker-Enfants Malades Hospital, Paris 75015, France
| | - Patrick Nitschke
- INSERM UMR 1163, Paris-Descartes-Sorbonne Paris Cité University, Institut IMAGINE, Necker-Enfants Malades Hospital, Paris 75015, France
| | - Andre Reis
- Institute of Human Genetics, University of Erlangen, Schwabachanlage 10, Erlangen 91054, Germany
| | - Heinrich Sticht
- Institute of Biochemistry, Emil-Fischer Center, Fahrstraße 17, Erlangen 91054, Germany
| | - Nouriya Al-Sanna'a
- Dharan Health Center, 8131 Medical Access Rd 1, Gharb al Dharan, Dharan 34465, Saudi Arabia
| | - Arndt Rolfs
- Center for Biological Signaling Studies (BIOSS), Schänzlestr. 18, Freiburg 79104, Germany.,Albrecht-Kossel-Institute for Neuroregeneration, Medical University Rostock, Gehlsheimerstr. 20, Rostock 18147, Germany
| | - Akos Kulik
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, Freiburg 79104, Germany.,Center for Biological Signaling Studies (BIOSS), Schänzlestr. 18, Freiburg 79104, Germany
| | - Uwe Schulte
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, Freiburg 79104, Germany.,Center for Biological Signaling Studies (BIOSS), Schänzlestr. 18, Freiburg 79104, Germany.,Logopharm GmbH, Schlossstr. 14, March-Buchheim 79232, Germany
| | - Laurence Colleaux
- INSERM UMR 1163, Paris-Descartes-Sorbonne Paris Cité University, Institut IMAGINE, Necker-Enfants Malades Hospital, Paris 75015, France
| | - Rami Abou Jamra
- Institute of Human Genetics, University of Erlangen, Schwabachanlage 10, Erlangen 91054, Germany.,Institute of Human Genetics, University of Leipzig Hospitals and Clinics, Philipp-Rosenthal-Str. 55, 04103 Leipzig, Germany
| | - Bernd Fakler
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, Freiburg 79104, Germany.,Center for Biological Signaling Studies (BIOSS), Schänzlestr. 18, Freiburg 79104, Germany
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19
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Kaeser PS, Regehr WG. The readily releasable pool of synaptic vesicles. Curr Opin Neurobiol 2017; 43:63-70. [PMID: 28103533 DOI: 10.1016/j.conb.2016.12.012] [Citation(s) in RCA: 143] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Revised: 11/26/2016] [Accepted: 12/31/2016] [Indexed: 10/20/2022]
Abstract
Each presynaptic bouton is densely packed with many vesicles, only a small fraction of which are available for immediate release. These vesicles constitute the readily releasable pool (RRP). The RRP size, and the probability of release of each vesicle within the RRP, together determine synaptic strength. Here, we discuss complications and recent advances in determining the size of the physiologically relevant RRP. We consider molecular mechanisms to generate and regulate the RRP, and discuss the relationship between vesicle docking and the RRP. We conclude that many RRP vesicles are docked, that some docked vesicles may not be part of the RRP, and that undocked vesicles can contribute to the RRP by rapid recruitment to unoccupied, molecularly activated ready-to-release sites.
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Affiliation(s)
- Pascal S Kaeser
- Department of Neurobiology, Harvard Medical School, United States.
| | - Wade G Regehr
- Department of Neurobiology, Harvard Medical School, United States.
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20
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Han R, Wang J, Miao R, Deng B, Qin Y, Yu H, Wei X. Propagation of Collective Temporal Regularity in Noisy Hierarchical Networks. IEEE TRANSACTIONS ON NEURAL NETWORKS AND LEARNING SYSTEMS 2017; 28:191-205. [PMID: 28055909 DOI: 10.1109/tnnls.2015.2502993] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Neuronal communication between different brain areas is achieved in terms of spikes. Consequently, spike-time regularity is closely related to many cognitive tasks and timing precision of neural information processing. A recent experiment on primate parietal cortex reports that spike-time regularity increases consistently from primary sensory to higher cortical regions. This observation conflicts with the influential view that spikes in the neocortex are fundamentally irregular. To uncover the underlying network mechanism, we construct a multilayered feedforward neural information transmission pathway and investigate how spike-time regularity evolves across subsequent layers. Numerical results reveal that despite the obviously irregular spiking patterns in previous several layers, neurons in downstream layers can generate rather regular spikes, which depends on the network topology. In particular, we find that collective temporal regularity in deeper layers exhibits resonance-like behavior with respect to both synaptic connection probability and synaptic weight, i.e., the optimal topology parameter maximizes the spike-timing regularity. Furthermore, it is demonstrated that synaptic properties, including inhibition, synaptic transient dynamics, and plasticity, have significant impacts on spike-timing regularity propagation. The emergence of the increasingly regular spiking (RS) patterns in higher parietal regions can, thus, be viewed as a natural consequence of spiking activity propagation between different brain areas. Finally, we validate an important function served by increased RS: promoting reliable propagation of spike-rate signals across downstream layers.
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21
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Felix RA, Magnusson AK. Development of excitatory synaptic transmission to the superior paraolivary and lateral superior olivary nuclei optimizes differential decoding strategies. Neuroscience 2016; 334:1-12. [PMID: 27476438 DOI: 10.1016/j.neuroscience.2016.07.039] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2016] [Revised: 07/08/2016] [Accepted: 07/23/2016] [Indexed: 11/17/2022]
Abstract
The superior paraolivary nucleus (SPON) is a prominent structure in the mammalian auditory brainstem with a proposed role in encoding transient broadband sounds such as vocalized utterances. Currently, the source of excitatory pathways that project to the SPON and how these inputs contribute to SPON function are poorly understood. To shed light on the nature of these inputs, we measured evoked excitatory postsynaptic currents (EPSCs) in the SPON originating from the intermediate acoustic stria and compared them with the properties of EPSCs in the lateral superior olive (LSO) originating from the ventral acoustic stria during auditory development from postnatal day 5 to 22 in mice. Before hearing onset, EPSCs in the SPON and LSO are very similar in size and kinetics. After the onset of hearing, SPON excitation is refined to extremely few (2:1) fibers, with each strengthened by an increase in release probability, yielding fast and strong EPSCs. LSO excitation is recruited from more fibers (5:1), resulting in strong EPSCs with a comparatively broader stimulus-response range after hearing onset. Evoked SPON excitation is comparatively weaker than evoked LSO excitation, likely due to a larger fraction of postsynaptic GluR2-containing Ca2+-impermeable AMPA receptors after hearing onset. Taken together, SPON excitation develops synaptic properties that are suited for transmitting single events with high temporal reliability and the strong, dynamic LSO excitation is compatible with high rate-level sensitivity. Thus, the excitatory input pathways to the SPON and LSO mature to support different decoding strategies of respective coarse temporal and sound intensity information at the brainstem level.
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Affiliation(s)
- Richard A Felix
- Unit of Audiology, Department of Clinical Science Intervention and Technology, Karolinska Institutet, Stockholm, Sweden
| | - Anna K Magnusson
- Unit of Audiology, Department of Clinical Science Intervention and Technology, Karolinska Institutet, Stockholm, Sweden.
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22
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Pilati N, Linley DM, Selvaskandan H, Uchitel O, Hennig MH, Kopp-Scheinpflug C, Forsythe ID. Acoustic trauma slows AMPA receptor-mediated EPSCs in the auditory brainstem, reducing GluA4 subunit expression as a mechanism to rescue binaural function. J Physiol 2016; 594:3683-703. [PMID: 27104476 PMCID: PMC4929335 DOI: 10.1113/jp271929] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Accepted: 04/13/2016] [Indexed: 12/19/2022] Open
Abstract
KEY POINTS Lateral superior olive (LSO) principal neurons receive AMPA receptor (AMPAR) - and NMDA receptor (NMDAR)-mediated EPSCs and glycinergic IPSCs. Both EPSCs and IPSCs have slow kinetics in prehearing animals, which during developmental maturation accelerate to sub-millisecond decay time-constants. This correlates with a change in glutamate and glycine receptor subunit composition quantified via mRNA levels. The NMDAR-EPSCs accelerate over development to achieve decay time-constants of 2.5 ms. This is the fastest NMDAR-mediated EPSC reported. Acoustic trauma (AT, loud sounds) slow AMPAR-EPSC decay times, increasing GluA1 and decreasing GluA4 mRNA. Modelling of interaural intensity difference suggests that the increased EPSC duration after AT shifts interaural level difference to the right and compensates for hearing loss. Two months after AT the EPSC decay times recovered to control values. Synaptic transmission in the LSO matures by postnatal day 20, with EPSCs and IPSCs having fast kinetics. AT changes the AMPAR subunits expressed and slows the EPSC time-course at synapses in the central auditory system. ABSTRACT Damaging levels of sound (acoustic trauma, AT) diminish peripheral synapses, but what is the impact on the central auditory pathway? Developmental maturation of synaptic function and hearing were characterized in the mouse lateral superior olive (LSO) from postnatal day 7 (P7) to P96 using voltage-clamp and auditory brainstem responses. IPSCs and EPSCs show rapid acceleration during development, so that decay kinetics converge to similar sub-millisecond time-constants (τ, 0.87 ± 0.11 and 0.77 ± 0.08 ms, respectively) in adult mice. This correlated with LSO mRNA levels for glycinergic and glutamatergic ionotropic receptor subunits, confirming a switch from Glyα2 to Glyα1 for IPSCs and increased expression of GluA3 and GluA4 subunits for EPSCs. The NMDA receptor (NMDAR)-EPSC decay τ accelerated from >40 ms in prehearing animals to 2.6 ± 0.4 ms in adults, as GluN2C expression increased. In vivo induction of AT at around P20 disrupted IPSC and EPSC integration in the LSO, so that 1 week later the AMPA receptor (AMPAR)-EPSC decay was slowed and mRNA for GluA1 increased while GluA4 decreased. In contrast, GlyR IPSC and NMDAR-EPSC decay times were unchanged. Computational modelling confirmed that matched IPSC and EPSC kinetics are required to generate mature interaural level difference functions, and that longer-lasting EPSCs compensate to maintain binaural function with raised auditory thresholds after AT. We conclude that LSO excitatory and inhibitory synaptic drive matures to identical time-courses, that AT changes synaptic AMPARs by expression of subunits with slow kinetics (which recover over 2 months) and that loud sounds reversibly modify excitatory synapses in the brain, changing synaptic function for several weeks after exposure.
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Affiliation(s)
- Nadia Pilati
- Autifony Srl Laboratories, Medicines Research Centre, 37135, Verona, Italy.,MRC Toxicology Unit, Hodgkin Bldg, University of Leicester, Leicester, LE1 9HN, UK
| | - Deborah M Linley
- Department of Neuroscience, Psychology & Behaviour, University of Leicester, Leicester, LE1 9HN, UK
| | - Haresh Selvaskandan
- Department of Neuroscience, Psychology & Behaviour, University of Leicester, Leicester, LE1 9HN, UK
| | - Osvaldo Uchitel
- Instituto de Fisiología y Biología Molecular y Neurociencias, Universidad de Buenos Aires-CONICET, Facultad de Ciencias Exactas y Naturales, Ciudad Universitaria, C1428-Buenos Aires, Argentina
| | - Matthias H Hennig
- Institute for Adaptive and Neural Computation, School of Informatics, University of Edinburgh, Edinburgh, EH8 9AB, UK.,SynthSys, C. H. Waddington Building, The Kings Buildings Campus, Edinburgh, UK
| | - Cornelia Kopp-Scheinpflug
- MRC Toxicology Unit, Hodgkin Bldg, University of Leicester, Leicester, LE1 9HN, UK.,Department of Biology II, Ludwig-Maximilians-Universität München, Planegg-Martinsried, D-82152, Munich, Germany
| | - Ian D Forsythe
- MRC Toxicology Unit, Hodgkin Bldg, University of Leicester, Leicester, LE1 9HN, UK.,Department of Neuroscience, Psychology & Behaviour, University of Leicester, Leicester, LE1 9HN, UK
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23
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Yang Y, Xu-Friedman MA. Different pools of glutamate receptors mediate sensitivity to ambient glutamate in the cochlear nucleus. J Neurophysiol 2015; 113:3634-45. [PMID: 25855696 DOI: 10.1152/jn.00693.2014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Accepted: 04/08/2015] [Indexed: 01/14/2023] Open
Abstract
Ambient glutamate plays an important role in pathological conditions, such as stroke, but its role during normal activity is not clear. In addition, it is not clear how ambient glutamate acts on glutamate receptors with varying affinities or subcellular localizations. To address this, we studied "endbulb of Held" synapses, which are formed by auditory nerve fibers onto bushy cells (BCs) in the anteroventral cochlear nucleus. When ambient glutamate was increased by applying the glutamate reuptake inhibitor TFB-TBOA, BCs depolarized as a result of activation of N-methyl-D-aspartate receptors (NMDARs) and group I metabotropic glutamate receptors (mGluRs). Application of antagonists against NMDARs (in 0 Mg(2+)) or mGluRs caused hyperpolarization, indicating that these receptors were bound by a tonic source of glutamate. AMPA receptors did not show these effects, consistent with their lower glutamate affinity. We also evaluated the subcellular localization of the receptors activated by ambient glutamate. The mGluRs were not activated by synaptic stimulation and thus appear to be exclusively extrasynaptic. By contrast, NMDARs in both synaptic and extrasynaptic compartments were activated by ambient glutamate, as shown using the use-dependent antagonist MK-801. Levels of ambient glutamate appeared to be regulated in a spike-independent manner, and glia likely play a major role. These low levels of ambient glutamate likely have functional consequences, as even low concentrations of TBOA caused significant increases in BC spiking following synaptic stimulation. These results indicate that normal resting potential appears to be poised in the region of maximal sensitivity to small changes in ambient glutamate.
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Affiliation(s)
- Yang Yang
- Department of Biological Sciences, University at Buffalo, State University of New York, Buffalo, New York
| | - Matthew A Xu-Friedman
- Department of Biological Sciences, University at Buffalo, State University of New York, Buffalo, New York
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24
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Karim MR, Atoji Y. Distribution of Vesicular Glutamate Transporter 2 and Ionotropic Glutamate Receptors in the Auditory Ganglion and Cochlear Nuclei of Pigeons (Columba livia). Anat Histol Embryol 2015; 45:73-80. [PMID: 25639143 DOI: 10.1111/ahe.12173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Accepted: 01/11/2015] [Indexed: 10/24/2022]
Abstract
Glutamate is a principal excitatory neurotransmitter in the auditory system. Our previous studies revealed localization of glutamate receptor mRNAs in the pigeon cochlear nuclei, suggesting the existence of glutamatergic input from the auditory nerve to the brainstem. This study demonstrated localization of mRNAs for vesicular glutamate transporter 2 (vGluT2) and ionotropic glutamate receptors (AMPA, kainate and NMDA) in the auditory ganglion (AG) and cochlear nuclei (magnocellular, angular and laminar nuclei). VGluT2 mRNA was intensely expressed in AG and intensely or moderately in the cochlear nuclei. The AG and cochlear nuclei showed intense-to-moderate mRNA signals for GluA2, GluA3, GluA4, GluK4 and GluN1. These results suggest that the pigeon AG neurons receives glutamatergic input from hair cells and in turn projects to the magnocellular and angular nuclei. Glutamate may play a pivotal role in the excitatory synapse transmission in the peripheral auditory pathway of birds.
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Affiliation(s)
- M R Karim
- Department of Anatomy and Histology, Bangladesh Agricultural University, Mymensingh, 2202, Bangladesh.,Laboratory of Veterinary Anatomy, Faculty of Applied Biological Sciences, Gifu University, Gifu, 501-1193, Japan
| | - Y Atoji
- Laboratory of Veterinary Anatomy, Faculty of Applied Biological Sciences, Gifu University, Gifu, 501-1193, Japan
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25
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Regional Diversity and Developmental Dynamics of the AMPA-Receptor Proteome in the Mammalian Brain. Neuron 2014; 84:41-54. [DOI: 10.1016/j.neuron.2014.08.044] [Citation(s) in RCA: 175] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/19/2014] [Indexed: 12/20/2022]
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26
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Chen L, Dürr KL, Gouaux E. X-ray structures of AMPA receptor-cone snail toxin complexes illuminate activation mechanism. Science 2014; 345:1021-6. [PMID: 25103405 DOI: 10.1126/science.1258409] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
AMPA-sensitive glutamate receptors are crucial to the structural and dynamic properties of the brain, to the development and function of the central nervous system, and to the treatment of neurological conditions from depression to cognitive impairment. However, the molecular principles underlying AMPA receptor activation have remained elusive. We determined multiple x-ray crystal structures of the GluA2 AMPA receptor in complex with a Conus striatus cone snail toxin, a positive allosteric modulator, and orthosteric agonists, at 3.8 to 4.1 angstrom resolution. We show how the toxin acts like a straightjacket on the ligand-binding domain (LBD) "gating ring," restraining the domains via both intra- and interdimer cross-links such that agonist-induced closure of the LBD "clamshells" is transduced into an irislike expansion of the gating ring. By structural analysis of activation-enhancing mutants, we show how the expansion of the LBD gating ring results in pulling forces on the M3 helices that, in turn, are coupled to ion channel gating.
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Affiliation(s)
- Lei Chen
- Vollum Institute, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
| | - Katharina L Dürr
- Vollum Institute, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
| | - Eric Gouaux
- Vollum Institute, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA. Howard Hughes Medical Institute, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA.
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27
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Boudkkazi S, Brechet A, Schwenk J, Fakler B. Cornichon2 Dictates the Time Course of Excitatory Transmission at Individual Hippocampal Synapses. Neuron 2014; 82:848-58. [DOI: 10.1016/j.neuron.2014.03.031] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/21/2014] [Indexed: 11/16/2022]
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28
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Abstract
The cochlear nuclei are the first central processors of auditory information and provide inputs to all the major brainstem and midbrain auditory nuclei. Although the local circuits within the cochlear nuclei are understood at a cellular level, the spatial patterns of connectivity and the connection strengths in these circuits have been less well characterized. We have applied a novel, quantitative approach to mapping local circuits projecting to cells in the mouse anteroventral cochlear nucleus (AVCN) using laser-scanning photostimulation and glutamate uncaging. The amplitude and kinetics of individual evoked synaptic events were measured to reveal the patterns and strengths of synaptic connections. We found that the two major excitatory projection cell classes, the bushy and T-stellate cells, receive a spatially broad inhibition from D-stellate cells in the AVCN, and a spatially confined inhibition from the tuberculoventral cells of the dorsal cochlear nucleus. Furthermore, T-stellate cells integrate D-stellate inhibition from an area that spans twice the frequency range of that integrated by bushy cells. A subset of both bushy and T-stellate cells receives inhibition from an unidentified cell population at the dorsal-medial boundary of the AVCN. A smaller subset of cells receives local excitation from within the AVCN. Our results show that inhibitory circuits can have target-specific patterns of spatial convergence, synaptic strength, and receptor kinetics, resulting in different spectral and temporal processing capabilities.
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29
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Oline SN, Burger RM. Short-term synaptic depression is topographically distributed in the cochlear nucleus of the chicken. J Neurosci 2014; 34:1314-24. [PMID: 24453322 PMCID: PMC3898291 DOI: 10.1523/jneurosci.3073-13.2014] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2013] [Revised: 12/11/2013] [Accepted: 12/13/2013] [Indexed: 11/21/2022] Open
Abstract
In the auditory system, sounds are processed in parallel frequency-tuned circuits, beginning in the cochlea. Activity of auditory nerve fibers reflects this frequency-specific topographic pattern, known as tonotopy, and imparts frequency tuning onto their postsynaptic target neurons in the cochlear nucleus. In birds, cochlear nucleus magnocellularis (NM) neurons encode the temporal properties of acoustic stimuli by "locking" discharges to a particular phase of the input signal. Physiological specializations exist in gradients corresponding to the tonotopic axis in NM that reflect the characteristic frequency (CF) of their auditory nerve fiber inputs. One feature of NM neurons that has not been investigated across the tonotopic axis is short-term synaptic plasticity. NM offers a rather homogeneous population of neurons with a distinct topographical distribution of synaptic properties that is ideal for the investigation of specialized synaptic plasticity. Here we demonstrate for the first time that short-term synaptic depression (STD) is expressed topographically, where unitary high CF synapses are more robust with repeated stimulation. Correspondingly, high CF synapses drive spiking more reliably than their low CF counterparts. We show that postsynaptic AMPA receptor desensitization does not contribute to the observed difference in STD. Further, rate of recovery from depression, a presynaptic property, does not differ tonotopically. Rather, we show that another presynaptic feature, readily releasable pool (RRP) size, is tonotopically distributed and inversely correlated with vesicle release probability. Mathematical model results demonstrate that these properties of vesicle dynamics are sufficient to explain the observed tonotopic distribution of STD.
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Affiliation(s)
- Stefan N. Oline
- Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania 18015
| | - R. Michael Burger
- Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania 18015
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30
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Sylantyev S, Rusakov DA. Sub-millisecond ligand probing of cell receptors with multiple solution exchange. Nat Protoc 2013; 8:1299-306. [PMID: 23744290 PMCID: PMC3743020 DOI: 10.1038/nprot.2013.075] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The accurate knowledge of receptor kinetics is crucial to our understanding of cell signal transduction in general and neural function in particular. The classical technique of probing membrane receptors on a millisecond scale involves placing a recording micropipette with a membrane patch in front of a double-barrel (θ-glass) application pipette mounted on a piezo actuator. Driven by electric pulses, the actuator can rapidly shift the θ-glass pipette tip, thus exposing the target receptors to alternating ligand solutions. However, membrane patches survive for only a few minutes, thus normally restricting such experiments to a single-application protocol. In order to overcome this deficiency, we have introduced pressurized supply microcircuits in the θ-glass channels, thus enabling repeated replacement of application solutions within 10-15 s. This protocol, which has been validated in our recent studies and takes 20-60 min to implement, allows the characterization of ligand-receptor interactions with high sensitivity, thereby also enabling a powerful paired-sample statistical design.
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Affiliation(s)
- Sergiy Sylantyev
- UCL Institute of Neurology, University College London, London, UK.
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31
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Target-specific IPSC kinetics promote temporal processing in auditory parallel pathways. J Neurosci 2013; 33:1598-614. [PMID: 23345233 DOI: 10.1523/jneurosci.2541-12.2013] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The acoustic environment contains biologically relevant information on timescales from microseconds to tens of seconds. The auditory brainstem nuclei process this temporal information through parallel pathways that originate in the cochlear nucleus from different classes of cells. Although the roles of ion channels and excitatory synapses in temporal processing have been well studied, the contribution of inhibition is less well understood. Here, we show in CBA/CaJ mice that the two major projection neurons of the ventral cochlear nucleus, the bushy and T-stellate cells, receive glycinergic inhibition with different synaptic conductance time courses. Bushy cells, which provide precisely timed spike trains used in sound localization and pitch identification, receive slow inhibitory inputs. In contrast, T-stellate cells, which encode slower envelope information, receive inhibition that is eightfold faster. Both types of inhibition improved the precision of spike timing but engage different cellular mechanisms and operate on different timescales. Computer models reveal that slow IPSCs in bushy cells can improve spike timing on the scale of tens of microseconds. Although fast and slow IPSCs in T-stellate cells improve spike timing on the scale of milliseconds, only fast IPSCs can enhance the detection of narrowband acoustic signals in a complex background. Our results suggest that target-specific IPSC kinetics are critical for the segregated parallel processing of temporal information from the sensory environment.
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32
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Babiec WE, Faull KF, Feldman JL. Cyclothiazide-induced persistent increase in respiratory-related activity in vitro. J Physiol 2012; 590:4897-915. [PMID: 22753547 DOI: 10.1113/jphysiol.2012.232421] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Hypoglossal (XII) motoneurons (MNs) innervate the genioglossus muscle of the tongue, which plays an important role in maintaining upper airway patency, particularly during sleep, and modulating upper airway resistance. Discovering methods for inducing long-term increases in genioglossal motoneuronal excitability to AMPA-mediated drive may help in the development of therapeutics for upper airway motor disorders such as obstructive sleep apnoea. We show that the diuretic, anti-hypertensive, AMPA receptor modulator cyclothiazide (CTZ) induces a profound and long-lasting increase in the amplitude of respiratory-related XII nerve activity in rhythmically active neonatal rat medullary slices. Treatment of the slice with CTZ (90 μM) for 1 h increased the integrated XII ( XII) nerve burst amplitude to 262 ± 23% of pre-treatment control at 1 h post-treatment;much of this increase lasted at least 12 h. The amount of CTZ-induced facilitation (CIF) was dependent upon both CTZ dose and exposure time and was accompanied by a long-lasting increase in endogenous AMPA-mediated drive currents to XII MNs. CIF, however, is not a form of plasticity and does not depend on AMPA or NMDA receptor activation for its induction. Nor does it depend on coincident protein kinase A or C activity. Rather, measurement of mEPSCs along with mass spectrometric analysis of CTZ-treated slices indicates that the cause is prolonged bioavailability of CTZ. These results illustrate a latent residual capacity for potentiating AMPA-mediated inspiratory drive to XII MNs that might be applied to the treatment of upper airway motor deficits.
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Affiliation(s)
- Walter E Babiec
- Department of Physiology, David Geffen School of Medicine, UCLA, Box 951751, C8-161 NPI, Los Angeles,CA 90095-1751, USA.
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Schwenk J, Harmel N, Brechet A, Zolles G, Berkefeld H, Müller C, Bildl W, Baehrens D, Hüber B, Kulik A, Klöcker N, Schulte U, Fakler B. High-Resolution Proteomics Unravel Architecture and Molecular Diversity of Native AMPA Receptor Complexes. Neuron 2012; 74:621-33. [DOI: 10.1016/j.neuron.2012.03.034] [Citation(s) in RCA: 269] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/13/2012] [Indexed: 10/28/2022]
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Diamond JS. Calcium-permeable AMPA receptors in the retina. Front Mol Neurosci 2011; 4:27. [PMID: 21991245 PMCID: PMC3181435 DOI: 10.3389/fnmol.2011.00027] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Accepted: 09/07/2011] [Indexed: 01/11/2023] Open
Abstract
The retina transforms light entering the eye into a sophisticated neural representation of our visual world. Specialized synapses, cells, and circuits in the retina have evolved to encode luminance, contrast, motion, and other complex visual features. Although a great deal has been learned about the cellular morphology and circuitry that underlies this image processing, many of the synapses in the retina remain incompletely understood. For example, excitatory synapses in the retina feature the full panoply of glutamate receptors, but in most cases specific roles for different receptor subtypes are unclear. In this brief review, I will discuss recent progress toward understanding how Ca2+-permeable AMPA receptors (CP-GluARs) contribute to synaptic transmission and newly discovered forms of synaptic plasticity in the retina.
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Affiliation(s)
- Jeffrey S Diamond
- Synaptic Physiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health Bethesda, MD, USA
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Not all desensitizations are created equal: physiological evidence that AMPA receptor desensitization differs for kainate and glutamate. J Neurosci 2011; 31:9359-67. [PMID: 21697386 DOI: 10.1523/jneurosci.6761-10.2011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
AMPA receptor-mediated responses to the agonist kainate differ from those of glutamate in two important respects. Glutamate is a full agonist that elicits strongly desensitizing responses, whereas kainate is a partial agonist with responses that are often described as weakly desensitizing or non-desensitizing. The efficacy of kainate relative to glutamate has previously been shown to be increased by mutations in the AMPA receptor ligand-binding cleft (Mano et al., 1996) and by coexpression with the auxiliary subunit stargazin (Tomita et al., 2005; Turetsky et al., 2005), but much less is known about factors that affect kainate desensitization. We therefore designed experiments to compare kainate and glutamate desensitization and efficacy in wild-type and mutant AMPA receptors expressed with and without stargazin in HEK293 cells. Desensitization to the two agonists was differentially affected by mutations in the helices participating in bonds between two subunits in the active state of the receptor (Sun et al., 2002), indicating that the protein interactions maintaining the stability of the dimer interface differ depending on which agonist is bound. Kainate efficacy was affected by factors distinct from ligand-binding cleft closure, including mutations in the dimer interface and channel vestibule as well as receptor composition. The increase in kainate responses for AMPA receptors coexpressed with stargazin was the result of both reduced kainate desensitization and increased kainate efficacy. These results provide critical new insights into the agonist dependence of both AMPA receptor activation and desensitization and the mechanism of the effects of stargazin on responses of partial agonists.
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Yang YM, Aitoubah J, Lauer AM, Nuriya M, Takamiya K, Jia Z, May BJ, Huganir RL, Wang LY. GluA4 is indispensable for driving fast neurotransmission across a high-fidelity central synapse. J Physiol 2011; 589:4209-27. [PMID: 21690196 PMCID: PMC3180579 DOI: 10.1113/jphysiol.2011.208066] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2011] [Accepted: 06/14/2011] [Indexed: 01/01/2023] Open
Abstract
Fast excitatory synaptic transmission in central synapses is mediated primarily by AMPA receptors (AMPARs), which are heteromeric assemblies of four subunits, GluA1-4. Among these subunits, rapidly gating GluA3/4 appears to be the most abundantly expressed to enable neurotransmission with submillisecond precision at fast rates in subsets of central synapses. However, neither definitive identification of the molecular substrate for native AMPARs in these neurons, nor their hypothesized functional roles in vivo has been unequivocally demonstrated, largely due to lack of specific antagonists. Using GluA3 or GluA4 knockout (KO) mice, we investigated these issues at the calyx of Held synapse, which is known as a high-fidelity synapse involved in sound localization. Patch-clamp recordings from postsynaptic neurons showed that deletion of GluA4 significantly slowed the time course of both evoked and miniature AMPAR-mediated excitatory postsynaptic currents (AMPAR-EPSCs), reduced their amplitude, and exacerbated AMPAR desensitization and short-term depression (STD). Surprisingly, presynaptic release probability was also elevated, contributing to severe STD at GluA4-KO synapses. In contrast, only marginal changes in AMPAR-EPSCs were found in GluA3-KO mice. Furthermore, independent of changes in intrinsic excitability of postsynaptic neurons, deletion of GluA4 markedly reduced synaptic drive and increased action potential failures during high-frequency activity, leading to profound deficits in specific components of the auditory brainstem responses associated with synchronized spiking in the calyx of Held synapse and other related neurons in vivo. These observations identify GluA4 as the main determinant for fast synaptic response, indispensable for driving high-fidelity neurotransmission and conveying precise temporal information.
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Affiliation(s)
- Yi-Mei Yang
- Program in Neurosciences & Mental Health, The Hospital For Sick Children and Department of Physiology, University of Toronto, 555 University Avenue, Toronto, Ontario, Canada
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38
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Zaitsev AV, Kim KK, Fedorova IM, Dorofeeva NA, Magazanik LG, Tikhonov DB. Specific mechanism of use-dependent channel block of calcium-permeable AMPA receptors provides activity-dependent inhibition of glutamatergic neurotransmission. J Physiol 2011; 589:1587-601. [PMID: 21486838 DOI: 10.1113/jphysiol.2011.204362] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
This study examined the blocking action of the selective channel blocker of calcium-permeable (CP) AMPA receptors, N1-(1-phenylcyclohexyl)pentane-1,5-diaminium bromide (IEM-1925), on excitatory postsynaptic currents in rat neostriatal and cortical neurons and in fly neuromuscular junctions. In both preparations, the blocking of CP-AMPA receptor currents increased along with the stimulation frequency. The continuous presence of kainate, which activates AMPA receptors, in the external solution also caused an enhanced blocking effect. Likewise, decrease of the synaptic release by lowering calcium concentration resulted in significant reduction of the blocking action. The activity dependence of the block is explained using the guarded receptor model. The drug molecule can only bind if the channel is open. After the channel has closed, the drug molecule remains trapped inside. However, the trapped molecule slowly egresses from closed channels to the cytoplasm. The total block effect is determined by the equilibrium between accumulation of the drug in the open channels and relief from the closed channels. Therefore, the conditions that favour the open state result in enhanced inhibition. This significant finding reveals a new way to modulate CP-AMPAR-mediated transmission using a physiologically relevant approach. Moreover, it allows the involvement of CP-AMPARs in the physiological and pathological processes – such as high-frequency synaptic activity or increase of the steady-state glutamate concentration – to be examined.
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Affiliation(s)
- A V Zaitsev
- I.M. Sechenov Institute of Evolutionary Physiology and Biochemistry RAS, 44, Toreza Prospect, Saint-Petersburg, 194223 Russia.
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Jackson AC, Nicoll RA. The expanding social network of ionotropic glutamate receptors: TARPs and other transmembrane auxiliary subunits. Neuron 2011; 70:178-99. [PMID: 21521608 DOI: 10.1016/j.neuron.2011.04.007] [Citation(s) in RCA: 288] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/13/2011] [Indexed: 12/25/2022]
Abstract
Ionotropic glutamate receptors (iGluRs) underlie rapid, excitatory synaptic signaling throughout the CNS. After years of intense research, our picture of iGluRs has evolved from them being companionless in the postsynaptic membrane to them being the hub of dynamic supramolecular signaling complexes, interacting with an ever-expanding litany of other proteins that regulate their trafficking, scaffolding, stability, signaling, and turnover. In particular, the discovery that transmembrane AMPA receptor regulatory proteins (TARPs) are AMPA receptor auxiliary subunits that are critical determinants of their trafficking, gating, and pharmacology has changed the way we think about iGluR function. Recently, a number of novel transmembrane proteins have been uncovered that may also serve as iGluR auxiliary proteins. Here we review pivotal developments in our understanding of the role of TARPs in AMPA receptor trafficking and gating, and provide an overview of how newly discovered transmembrane proteins expand our view of iGluR function in the CNS.
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Affiliation(s)
- Alexander C Jackson
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94143, USA.
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40
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Timm DE, Benveniste M, Weeks AM, Nisenbaum ES, Partin KM. Structural and functional analysis of two new positive allosteric modulators of GluA2 desensitization and deactivation. Mol Pharmacol 2011; 80:267-80. [PMID: 21543522 DOI: 10.1124/mol.110.070243] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
At the dimer interface of the extracellular ligand-binding domain of α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors a hydrophilic pocket is formed that is known to interact with two classes of positive allosteric modulators, represented by cyclothiazide and the ampakine 2H,3H,6aH-pyrrolidino(2,1-3',2')1,3-oxazino(6',5'-5,4)benzo(e)1,4-dioxan-10-one (CX614). Here, we present structural and functional data on two new positive allosteric modulators of AMPA receptors, phenyl-1,4-bis-alkylsulfonamide (CMPDA) and phenyl-1,4-bis-carboxythiophene (CMPDB). Crystallographic data show that these compounds bind within the modulator-binding pocket and that substituents of each compound overlap with distinct moieties of cyclothiazide and CX614. The goals of the present study were to determine 1) the degree of modulation by CMPDA and CMPDB of AMPA receptor deactivation and desensitization; 2) whether these compounds are splice isoform-selective; and 3) whether predictions of mechanism of action could be inferred by comparing molecular interactions between the ligand-binding domain and each compound with those of cyclothiazide and CX614. CMPDB was found to be more isoform-selective than would be predicted from initial binding assays. It is noteworthy that these new compounds are both more potent and more effective and may be more clinically relevant than the AMPA receptor modulators described previously.
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Affiliation(s)
- David E Timm
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523-1617, USA
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41
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Mugnaini E, Sekerková G, Martina M. The unipolar brush cell: a remarkable neuron finally receiving deserved attention. BRAIN RESEARCH REVIEWS 2011; 66:220-45. [PMID: 20937306 PMCID: PMC3030675 DOI: 10.1016/j.brainresrev.2010.10.001] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2010] [Revised: 10/05/2010] [Accepted: 10/05/2010] [Indexed: 12/17/2022]
Abstract
Unipolar brush cells (UBC) are small, glutamatergic neurons residing in the granular layer of the cerebellar cortex and the granule cell domain of the cochlear nuclear complex. Recent studies indicate that this neuronal class consists of three or more subsets characterized by distinct chemical phenotypes, as well as by intrinsic properties that may shape their synaptic responses and firing patterns. Yet, all UBCs have a unique morphology, as both the dendritic brush and the large endings of the axonal branches participate in the formation of glomeruli. Although UBCs and granule cells may share the same excitatory and inhibitory inputs, the two cell types are distinctively differentiated. Typically, whereas the granule cell has 4-5 dendrites that are innervated by different mossy fibers, and an axon that divides only once to form parallel fibers after ascending to the molecular layer, the UBC has but one short dendrite whose brush engages in synaptic contact with a single mossy fiber terminal, and an axon that branches locally in the granular layer; branches of UBC axons form a non-canonical, cortex-intrinsic category of mossy fibers synapsing with granule cells and other UBCs. This is thought to generate a feed-forward amplification of single mossy fiber afferent signals that would reach the overlying Purkinje cells via ascending granule cell axons and their parallel fibers. In sharp contrast to other classes of cerebellar neurons, UBCs are not distributed homogeneously across cerebellar lobules, and subsets of UBCs also show different, albeit overlapping, distributions. UBCs are conspicuously rare in the expansive lateral cerebellar areas targeted by the cortico-ponto-cerebellar pathway, while they are a constant component of the vermis and the flocculonodular lobe. The presence of UBCs in cerebellar regions involved in the sensorimotor processes that regulate body, head and eye position, as well as in regions of the cochlear nucleus that process sensorimotor information suggests a key role in these critical functions; it also invites further efforts to clarify the cellular biology of the UBCs and their specific functions in the neuronal microcircuits in which they are embedded. High density of UBCs in specific regions of the cerebellar cortex is a feature largely conserved across mammals and suggests an involvement of these neurons in fundamental aspects of the input/output organization as well as in clinical manifestation of focal cerebellar disease.
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Affiliation(s)
- Enrico Mugnaini
- Department of Cellular and Molecular Biology, The Feinberg School of Medicine of Northwestern University, Chicago, IL, USA.
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42
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Wang Y, Ren C, Manis PB. Endbulb synaptic depression within the range of presynaptic spontaneous firing and its impact on the firing reliability of cochlear nucleus bushy neurons. Hear Res 2010; 270:101-9. [PMID: 20850512 DOI: 10.1016/j.heares.2010.09.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2009] [Revised: 09/03/2010] [Accepted: 09/05/2010] [Indexed: 10/19/2022]
Abstract
The majority of auditory nerve fibers exhibit prominent spontaneous activity in the absence of sound. More than half of all auditory nerve fibers in CBA mice have spontaneous firing rates higher than 20 spikes/s, with some fibers exceeding 100 spikes/s. We tested whether and to what extent endbulb synapses are depressed by activity between 10 and 100 Hz, within the spontaneous firing rates of auditory nerve fibers. In contrast to rate-dependent depression seen at rates >100 Hz, we found that the extent of depression was essentially rate-independent (∼35%) between 10 and 100 Hz. Neither cyclothiazide nor γ-d-glutamylglycine altered the rate-independent depression, arguing against receptor desensitization and/or vesicle depletion as major contributors for the depression. When endbulb synaptic transmission was more than half-blocked with the P/Q Ca(2+) channel blocker ω-agatoxin IVA, depression during 25 and 100 Hz trains was significantly attenuated, indicating P/Q Ca(2+) channel inactivation may contribute to low frequency synaptic depression. Following conditioning with a 100 Hz Poisson train, the EPSC paired-pulse ratio was increased, suggesting a reduced release probability. This in turn should reduce subsequent depletion-based synaptic depression at higher activation rates. To probe whether this conditioning of the synapse improves the reliability of postsynaptic responses, we tested the firing reliability of bushy neurons to 200 Hz stimulation after conditioning the endbulb with a 25 Hz or 100 Hz stimulus train. Although immediately following the conditioning train, bushy cells responded to minimal suprathreshold stimulation less reliably, the firing reliability eventually settled to the same level (<50%) regardless of the presence or absence of the preconditioning. However, when multiple presynaptic fibers were activated simultaneously, the postsynaptic response reliability did not drop significantly below 90%. These results suggest that single endbulb terminals do not reliably trigger action potentials in bushy cells under "normal" operating conditions. We conclude that the endbulb synapses are chronically depressed even by low rates of spontaneous activity, and are more resistant to further depression when challenged with a higher rate of activity. However, there seems to be no beneficial effect as assessed by the firing reliability of postsynaptic neurons for transmitting information about higher rates of activity.
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Affiliation(s)
- Yong Wang
- Division of Otolaryngology and the Program in Neuroscience, School of Medicine, Salt Lake City, University of Utah, UT 84132, USA.
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43
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Sanchez JT, Wang Y, Rubel EW, Barria A. Development of glutamatergic synaptic transmission in binaural auditory neurons. J Neurophysiol 2010; 104:1774-89. [PMID: 20668278 DOI: 10.1152/jn.00468.2010] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/06/2022] Open
Abstract
Glutamatergic synaptic transmission is essential for binaural auditory processing in birds and mammals. Using whole cell voltage clamp recordings, we characterized the development of synaptic ionotropic glutamate receptor (iGluR) function from auditory neurons in the chick nucleus laminaris (NL), the first nucleus responsible for binaural processing. We show that synaptic transmission is mediated by AMPA- and N-methyl-d-aspartate (NMDA)-type glutamate receptors (AMPA-R and NMDA-R, respectively) when hearing is first emerging and dendritic morphology is being established across different sound frequency regions. Puff application of glutamate agonists at embryonic day 9 (E9) revealed that both iGluRs are functionally present prior to synapse formation (E10). Between E11 and E19, the amplitude of isolated AMPA-R currents from high-frequency (HF) neurons increased 14-fold. A significant increase in the frequency of spontaneous events is also observed. Additionally, AMPA-R currents become faster and more rectifying, suggesting developmental changes in subunit composition. These developmental changes were similar in all tonotopic regions examined. However, mid- and low-frequency neurons exhibit fewer spontaneous events and evoked AMPA-R currents are smaller, slower, and less rectifying than currents from age-matched HF neurons. The amplitude of isolated NMDA-R currents from HF neurons also increased, reaching a peak at E17 and declining sharply by E19, a trend consistent across tonotopic regions. With age, NMDA-R kinetics become significantly faster, indicating a developmental switch in receptor subunit composition. Dramatic increases in the amplitude and speed of glutamatergic synaptic transmission occurs in NL during embryonic development. These changes are first seen in HF neurons suggesting regulation by peripheral inputs and may be necessary to enhance coincidence detection of binaural auditory information.
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Affiliation(s)
- Jason Tait Sanchez
- Virginia Merrill Bloedel Hearing Research Center, University of Washington, Box 357290, Seattle, WA 98195, USA
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44
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Tomita S. Regulation of ionotropic glutamate receptors by their auxiliary subunits. Physiology (Bethesda) 2010; 25:41-9. [PMID: 20134027 DOI: 10.1152/physiol.00033.2009] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Glutamate receptors are major excitatory receptors in the brain. Recent findings have established auxiliary subunits of glutamate receptors as critical modulators of synaptic transmission, synaptic plasticity, and neurological disorder. The elucidation of the molecular rules governing glutamate receptors and subunits will improve our understanding of synapses and of neural-circuit regulation in the brain.
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Affiliation(s)
- Susumu Tomita
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut, USA.
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45
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Abstract
Ligand-gated ion channels are an important class of signalling protein that depend on small chemical neurotransmitters such as acetylcholine, l-glutamate, glycine and gamma-aminobutyrate for activation. Although numerous in number, neurotransmitter substances have always been thought to drive the receptor complex into the open state in much the same way and not rely substantially on other factors. However, recent work on kainate-type (KAR) ionotropic glutamate receptors (iGluRs) has identified an exception to this rule. Here, the activation process fails to occur unless external monovalent anions and cations are present. This absolute requirement of ions singles out KARs from all other ligand-gated ion channels, including closely related AMPA- and NMDA-type iGluR family members. The uniqueness of ion-dependent gating has earmarked this feature of KARs as a putative target for the development of selective ligands; a prospect all the more compelling with the recent elucidation of distinct anion and cation binding pockets. Despite these advances, much remains to be resolved. For example, it is still not clear how ion effects on KARs impacts glutamatergic transmission. I conclude by speculating that further analysis of ion-dependent gating may provide clues into how functionally diverse iGluRs families emerged by evolution. Consequently, ion-dependent gating of KARs looks set to continue to be a subject of topical inquiry well into the future.
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Affiliation(s)
- Derek Bowie
- Department of Pharmacology & Therapeutics, McIntyre Medical Sciences Building, McGill University, Montreal, Québec, Canada H3A 1Y6.
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Yamashita T, Kanda T, Eguchi K, Takahashi T. Vesicular glutamate filling and AMPA receptor occupancy at the calyx of Held synapse of immature rats. J Physiol 2009; 587:2327-39. [PMID: 19332485 DOI: 10.1113/jphysiol.2008.167759] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
At central glutamatergic synapses, neurotransmitter often saturates postsynaptic AMPA receptors (AMPARs), thereby restricting the dynamic range of synaptic efficacy. Here, using simultaneous pre- and postsynaptic whole-cell recordings, at the calyx of Held synapse of immature rats, we have investigated the mechanism by which transmitter glutamate saturates postsynaptic AMPARs. When we loaded L-glutamate (1-100 mM) into presynaptic terminals, the quantal EPSC (qEPSC) amplitude changed in a concentration-dependent manner. At physiological temperature (36-37 degrees C), the qEPSC amplitude increased when intraterminal L-glutamate concentration was elevated from 1 mM to 10 mM, but it reached a plateau at 10 mM. This plateau persisted after bath-application of the low affinity AMPAR antagonist kynurenate, suggesting that it was caused by saturation of vesicular filling with glutamate rather than by saturation of postsynaptic AMPARs. In contrast to qEPSCs, action potential-evoked EPSCs remained unchanged by increasing intraterminal L-glutamate from 1 mM to 100 mM , even at room temperature, indicating that multi-quantal glutamate saturated postsynaptic AMPARs. This saturation could be relieved by blocking AMPAR desensitization using cyclothiazide (100 microM). The concentration of ambient glutamate in the slice, estimated from NMDA receptor current fluctuations, was 55 nM; this was far below the concentration required for AMPAR desensitization. We conclude that rapid AMPAR desensitization, caused by glutamate released from multiple vesicles during synaptic transmission, underlies postsynaptic AMPAR saturation at this immature calyceal synapse before the onset of hearing.
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Affiliation(s)
- Takayuki Yamashita
- Okinawa Institute of Science and Technology Promotion Corporation, Okinawa 904-2234, Japan.
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48
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Schwenk J, Harmel N, Zolles G, Bildl W, Kulik A, Heimrich B, Chisaka O, Jonas P, Schulte U, Fakler B, Klocker N. Functional Proteomics Identify Cornichon Proteins as Auxiliary Subunits of AMPA Receptors. Science 2009; 323:1313-9. [DOI: 10.1126/science.1167852] [Citation(s) in RCA: 304] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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Morimoto-Tomita M, Zhang W, Straub C, Cho CH, Kim KS, Howe JR, Tomita S. Autoinactivation of neuronal AMPA receptors via glutamate-regulated TARP interaction. Neuron 2009; 61:101-12. [PMID: 19146816 DOI: 10.1016/j.neuron.2008.11.009] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2008] [Revised: 11/10/2008] [Accepted: 11/12/2008] [Indexed: 10/21/2022]
Abstract
Neuronal AMPA receptors autoinactivate at high concentrations of glutamate, i.e., the current declines at glutamate concentrations above 10-100 microM. The mechanisms underlying this phenomenon are unclear. Stargazin-like TARPs are AMPA receptor auxiliary subunits that modulate receptor trafficking and channel properties. Here, we found that neuronal AMPA receptors and recombinant AMPA receptors coexpressed with stargazin autoinactivate at high concentrations of glutamate, whereas recombinant AMPA receptors expressed alone do not. The reduction of currents at high glutamate concentrations is not associated with a reduction of AMPA receptor number, but rather with the loss of stargazin-associated allosteric modulation of channel gating. We show that receptor desensitization promotes the dissociation of TARP-AMPA receptor complexes in a few milliseconds. This dissociation mechanism contributes to synaptic short-term modulation. The results demonstrate a mechanism for dynamic regulation of AMPA receptor activity to tune synaptic strength.
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Affiliation(s)
- Megumi Morimoto-Tomita
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06520, USA
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50
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Kuznetsova MS, Higgs MH, Spain WJ. Adaptation of firing rate and spike-timing precision in the avian cochlear nucleus. J Neurosci 2008; 28:11906-15. [PMID: 19005056 PMCID: PMC2693385 DOI: 10.1523/jneurosci.3827-08.2008] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2008] [Accepted: 10/01/2008] [Indexed: 11/21/2022] Open
Abstract
Adaptation is commonly defined as a decrease in response to a constant stimulus. In the auditory system such adaptation is seen at multiple levels. However, the first-order central neurons of the interaural time difference detection circuit encode information in the timing of spikes rather than the overall firing rate. We investigated adaptation during in vitro whole-cell recordings from chick nucleus magnocellularis neurons. Injection of noisy, depolarizing current caused an increase in firing rate and a decrease in spike time precision that developed over approximately 20 s. This adaptation depends on sustained depolarization, is independent of firing, and is eliminated by alpha-dendrotoxin (0.1 microM), implicating slow inactivation of low-threshold voltage-activated K+ channels as its mechanism. This process may alter both firing rate and spike-timing precision of phase-locked inputs to coincidence detector neurons in nucleus laminaris and thereby adjust the precision of sound localization.
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Affiliation(s)
- Marina S. Kuznetsova
- Department of Physiology and Biophysics
- Interdisciplinary Graduate Program in Neurobiology and Behavior, and
| | | | - William J. Spain
- Department of Physiology and Biophysics
- Department of Neurology, University of Washington, Seattle, Washington 98105, and
- Neurology Section, Veterans Affairs Puget Sound Health Care System, Seattle, Washington 98108
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