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Regulation of GABAergic synapse formation and plasticity by posttranslational control of gephyrin

English title Regulation of GABAergic synapse formation and plasticity by posttranslational control of gephyrin
Applicant Fritschy Jean-Marc
Number 130495
Funding scheme Project funding
Research institution Institut für Pharmakologie und Toxikologie Universität Zürich
Institution of higher education University of Zurich - ZH
Main discipline Neurophysiology and Brain Research
Start/End 01.04.2010 - 31.05.2013
Approved amount 600'000.00
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All Disciplines (4)

Discipline
Neurophysiology and Brain Research
Pharmacology, Pharmacy
Cellular Biology, Cytology
Molecular Biology

Keywords (8)

GABAA receptor; phosphorylation; SUMOylation; inhibitory neurotransmission; synaptic plasticity; Lithium; bipolar disorder; adult neurogenesis

Lay Summary (English)

Lead
Lay summary
Main applicant: Prof. Jean-Marc Fritschy, Institute of Pharmacology and Toxicology, University of ZurichOne sentence summary: This project aims to elucidate the mechanisms governing the formation and plasticity of GABAergic synapses, thereby providing a better understanding of the pathophysiology of CNS diseases and opening novel avenues for therapeutic intervention.Background: Inhibitory neurotransmission in the CNS plays a crucial role in the control of neuronal excitability and contributes to higher brain functions. The neurotransmittter GABA mainly acts on GABAA receptors, which are a major target for drugs used in the clinical management of anxiety, sleep disorders, muscle spasms, and epilepsy. In addition, dysfunctions of the GABAergic system likely contribute to the pathophysiology of prevalent psychiatric diseases, including autism and schizophrenia. The aim of this research project is to understand how synaptic transmission is regulated by altering the number and function of receptors present at GABAergic synapses. We will focus on gephyrin, a protein that anchors the receptors to the cell membrane. Our preliminary results show that by regulating gephyrin function, several proteins kinases modulate GABAergic synaptic transmission. In particular, lithium chloride, a drug used for the treatment of bipolar disorders and severe depression, increases GABAergic transmission by blocking a protein kinase, GSK-beta3, that phosphorylates gephyrin.SUMOylation is a second posttranslational mechanism contributing to the regulation of gephyrin. SUMOylation plays a key role in protein trafficking, stability, and protein-protein interactions. Therefore, it represents a novel mechanism regulating function of synaptic proteins.Experimental approach: We will use molecular and cell biological tools to study the regulation of gephyrin. In particular, neurons in culture expressing fluorescently-tagged, mutated gephyrin construct that cannot be modified by phosphorylation or SUMOylation , we will determine the impact of these processes on the formation of GABAergic synapses. The in vivo significance of these mutations will be tested by analyzing the development of newborn neurons transfected with lentiviruses expressing mutated gephyrin constructs. Significance: By using a multidisciplinary approach in vitro and in vivo, we expect to uncover novel molecular mechanisms underlying the regulation of GABAergic synapses by intracellular signaling cascades. Furthermore, by elucidating how the GABAergic system participates to the pharmacological action of lithium, our project will contribute to design improved treatment strategies of major brain disorders.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Extracellular signal-regulated kinase and glycogen synthase kinase 3β regulate gephyrin postsynaptic aggregation and GABAergic synaptic function in a calpain-dependent mechanism.
Tyagarajan Shiva K, Ghosh Himanish, Yévenes Gonzalo E, Imanishi Susumu Y, Zeilhofer Hanns Ulrich, Gerrits Bertran, Fritschy Jean-Marc (2013), Extracellular signal-regulated kinase and glycogen synthase kinase 3β regulate gephyrin postsynaptic aggregation and GABAergic synaptic function in a calpain-dependent mechanism., in The Journal of biological chemistry, 288(14), 9634-47.
Early formation of GABAergic synapses governs the development of adult-born neurons in the olfactory bulb.
Pallotto Marta, Nissant Antoine, Fritschy Jean-Marc, Rudolph Uwe, Sassoè-Pognetto Marco, Panzanelli Patrizia, Lledo Pierre-Marie (2012), Early formation of GABAergic synapses governs the development of adult-born neurons in the olfactory bulb., in The Journal of neuroscience : the official journal of the Society for Neuroscience, 32(26), 9103-15.
Adoptive transfer of T lymphocytes in immunodeficient mice influences epileptogenesis and neurodegeneration in a model of temporal lobe epilepsy.
Deprez Francine, Zattoni Michela, Mura Maria Luisa, Frei Karl, Fritschy Jean-Marc (2011), Adoptive transfer of T lymphocytes in immunodeficient mice influences epileptogenesis and neurodegeneration in a model of temporal lobe epilepsy., in Neurobiology of disease, 44(2), 174-84.
Distinct mechanisms regulate GABAA receptor and gephyrin clustering at perisomatic and axo-axonic synapses on CA1 pyramidal cells.
Panzanelli Patrizia, Gunn Benjamin G, Schlatter Monika C, Benke Dietmar, Tyagarajan Shiva K, Scheiffele Peter, Belelli Delia, Lambert Jeremy J, Rudolph Uwe, Fritschy Jean-Marc (2011), Distinct mechanisms regulate GABAA receptor and gephyrin clustering at perisomatic and axo-axonic synapses on CA1 pyramidal cells., in The Journal of physiology, 589(Pt 20), 4959-80.
Impaired reelin processing and secretion by Cajal-Retzius cells contributes to granule cell dispersion in a mouse model of temporal lobe epilepsy.
Duveau Venceslas, Madhusudan Amrita, Caleo Matteo, Knuesel Irene, Fritschy Jean-Marc (2011), Impaired reelin processing and secretion by Cajal-Retzius cells contributes to granule cell dispersion in a mouse model of temporal lobe epilepsy., in Hippocampus, 21(9), 935-44.
Spatiotemporal specificity of GABAA receptor-mediated regulation of adult hippocampal neurogenesis.
Duveau Venceslas, Laustela Simon, Barth Lydia, Gianolini Francesca, Vogt Kaspar E, Keist Ruth, Chandra Dev, Homanics Gregg E, Rudolph Uwe, Fritschy Jean-Marc (2011), Spatiotemporal specificity of GABAA receptor-mediated regulation of adult hippocampal neurogenesis., in The European journal of neuroscience, 34(3), 362-73.
Collybistin splice variants differentially interact with gephyrin and Cdc42 to regulate gephyrin clustering at GABAergic synapses.
Tyagarajan Shiva K, Ghosh Himanish, Harvey Kirsten, Fritschy Jean-Marc (2011), Collybistin splice variants differentially interact with gephyrin and Cdc42 to regulate gephyrin clustering at GABAergic synapses., in Journal of cell science, 124(Pt 16), 2786-96.
Presynaptic alpha 2-GABA(A) Receptors in Primary Afferent Depolarization and Spinal Pain Control
Witschi R, Punnakkal P, Paul J, Walczak JS, Cervero F, Fritschy JM, Kuner R, Keist R, Rudolph U, Zeilhofer HU (2011), Presynaptic alpha 2-GABA(A) Receptors in Primary Afferent Depolarization and Spinal Pain Control, in JOURNAL OF NEUROSCIENCE, 31(22), 8134-8142.
Early formation of GABAergic synapses governs the development of adult-born neurons in the olfactory bulb.
Pallotto M., Nissant A., Fritschy J.-M., Rudolph U., Sassoè-Pognetto M., Panzanelli P., Lledo P.M., Early formation of GABAergic synapses governs the development of adult-born neurons in the olfactory bulb., in Journal of Neuroscience.
Molecular and functional heterogeneity of GABAergic synapses.
Fritschy Jean-Marc, Panzanelli Patrizia, Tyagarajan Shiva K, Molecular and functional heterogeneity of GABAergic synapses., in Cellular and molecular life sciences : CMLS.
Selective distribution of GABAA receptor subtypes in mouse spinal dorsal horn neurons and primary afferents.
Paul J., Zeilhofer H.U., Fritschy J.-M., Selective distribution of GABAA receptor subtypes in mouse spinal dorsal horn neurons and primary afferents., in Journal of Comparative Neurology.
Tonic inhibition in the basolateral amygdala is mediated by 3 subunit-containing GABAA receptors.
Marowsky A., Rudolph U., Fritschy J.-M., Arand M., Tonic inhibition in the basolateral amygdala is mediated by 3 subunit-containing GABAA receptors., in Journal of Neuroscience.

Collaboration

Group / person Country
Types of collaboration
McGill University Canada (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Exchange of personnel
Institut Pasteur France (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Exchange of personnel
McLean Hospital United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
University of Torino Italy (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
- Exchange of personnel

Communication with the public

Communication Title Media Place Year
Talks/events/exhibitions Entdeckungen unter der Schädeldecke German-speaking Switzerland 23.10.2011

Associated projects

Number Title Start Funding scheme
146120 Signaling complexes associated with GABAergic synapses and their relevance for the regulation of adult neurogenesis 01.06.2013 Project funding
144199 Do limbic seizures contribute to Alzheimer's disease-like pathology? Relevance of immune-mediated mechanisms 01.10.2012 Project funding
132665 Molecular mechanisms of GABAergic synapse plasticity 01.11.2010 Sinergia

Abstract

1. SummaryInhibitory neurotransmission in the CNS plays a crucial role in the control of neuronal excitability and network synchronization, thereby contributing to the emergence of higher brain functions. It is mediated mainly by GABAAR, which belong to the family of ligand-gated ion channels and are assembled from a large family of subunits. GABAAR are a major target for drugs used in the clinical management of anxiety, sleep disorders, muscle spasms, and epilepsy. In addition, dysfunctions of the GABAergic system likely contribute to the pathophysiology of prevalent psychiatric diseases, including autism and schizophrenia. It is the long-term goal of my laboratory to elucidate the mechanisms governing the formation and plasticity of GABAergic local circuits in order to provide a better understanding of the pathophysiology of CNS diseases and design novel avenues for therapeutic intervention.Proper function of synapses depends on the appropriate targeting and localization of effector proteins in presynaptic terminals and at postsynaptic sites. This is ensured by scaffolding proteins, which built complexes of functionally related proteins and anchor them at the presynaptic active zone and at the postsynaptic density. In GABAergic synapses, the main scaffolding protein is gephyrin, a cytoskeletal protein forming aggregates responsible for anchoring of GABAAR (and glycine receptors) at postsynaptic sites. Our past work has shown that the synaptic localization of gephyrin is dependent on the presence of GABAAR, suggesting regulation by signaling mechanisms. Recently (see Own Contributions), we have identified two phosphorylation sites on gephyrin that regulate the formation and the size of postsynaptic clusters, and thereby the strength of GABAergic transmission. Furthermore, we have shown that LiCl, a drug used for the treatment of bipolar disorders, strongly influences gephyrin clustering by blocking its phosphorylation. Finally, we also have preliminary evidence for bidirectional regulation of gephyrin clustering by SUMOylation. Collectively, these findings suggest that intracellular signaling cascades (e.g., protein kinases and phosphatases activated by second messengers) regulate GABAergic transmission by acting on the gephyrin scaffold. The general aim of this research proposal is to explore the molecular mechanisms underlying gephyrin regulation and to determine how this regulation impacts the formation and plasticity of GABAergic synapses. To this end, we will pursue three major lines of research: First, we will further characterize gephyrin phosphorylation and its role for the control of clustering at postsynaptic sites. We will also analyze how gephyrin phosphorylation influences its interactions with GABAAR and their cell-surface dynamics. Second, we will investigate the effects of gephyrin SUMOylation on its aggregation, trafficking, and postsynaptic clustering, and explore whether SUMOylation and phosphorylation of gephyrin are functionally inter-related. Third, using in vivo transfection of newborn neurons with lentiviral vectors, we will determine the functional consequences of chronic perturbations of gephyrin phosphorylation and SUMOylation on GABAergic synapse formation and plasticity in adult CNS. This in vivo part will be complemented by experiments aiming at identifying novel therapeutic approaches for the treatment of mood-disorders, based on the effect of LiCl on gephyrin clustering.This project relies on our long-standing expertise on the functional organization of GABAergic neurotransmission. It is conceptually highly innovative and challenges traditional views about the role of gephyrin postsynaptic scaffolds for regulating plasticity and formation of GABAergic synapses. By using a multidisciplinary approach combining molecular biology, biochemistry, cell biology, and in vivo experiments, we expect to uncover novel molecular mechanisms underlying activity-dependent regulation of GABAergic synapses by intracellular signaling cascades. Furthermore, by elucidating how the regulation of gephyrin clustering leads to structural and functional adaptations of the GABAergic system and participates to the pharmacological action of LiCl, our project opens new avenues for therapeutic interventions, based on the modulation of signaling cascades regulating GABAergic transmission.
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