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Post-transcriptional and post-translational cellular signals organize gephyrin scaffolds to facilitate GABAergic synapse plasticity.

Applicant Tyagarajan Shiva
Number 159867
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 01.04.2015 - 30.09.2018
Approved amount 452'876.00
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All Disciplines (2)

Discipline
Neurophysiology and Brain Research
Molecular Biology

Keywords (4)

SUMOylation ; dendritic protein translation; post-translational modifications; Postsynaptic density proteins

Lay Summary (German)

Lead
Identifying new cellular mechanism(s) that facilitate inhibitory neurotransmission in the brain.
Lay summary

 Nervenzellen haben einzigartige morphologische und funktionnelle Eigenschaften im Vergleich zu anderen Zelltypen in der Haut, oder Leber, zum Beispiel. Sie besitzen Axone und Dendriten, die aus dem Zellkörper stammen, mehrere Mikrometer lang sind und spezialisierte Kontakte, sog. Synapsen, mit benachbarten Nervenzellen oder Zellen aus einer anderen Region des Zentralnervensystems etablieren, und damit neuronale Netzwerke bilden. Um diese Fernkommunikation aufrechtzu erhalten und gleichzeitig die metabolischen Bedürfnisse der Nervenzellen abzudecken, hat die Evolution neue Mechanismen etabliert, welche eine lokalte Regulation der Struktur und Funktion ermöglichen. Zum Beispiel, anstatt die Machinerie der Proteinsynthese im Zellkörper zu vergrössern, sind Nervenzellen in der Lage, mRNA-Transport und Proteinsynthese in verschiedenen Kompartmenten der Zelle durchzuführen, und damit die Bedürfnisse der Zelle und die Funktion von Synapsen an lokalen Veränderungen der Aktivität von Netzwerken anzupassen.Dieses Projekt hat für Ziel, die Signalkaskaden, welche die Regulation der Zellfunktion um GABAergen Synapsen steuern, zu untersuchen. Die GABAerge Transmission ist zuständig für die Hemmung der neuronalen Aktivität und die Synchronisation von neuronalen Netzwerken. Sie spielt eine zentrale Rolle in die Physiologie und Funktion des Gehirns. Zahlreiche Neuroentwicklungs- und psychiatrischen Kranheiten entstehen durch Störungen der Bildung und Regulation von GABAergen Synapsen. Es ist deshalb von grosser Bedeutung die molekularen Ursachen dieser Störungen zu identifizieren und besser zu verstehen.

 

Direct link to Lay Summary Last update: 20.04.2015

Responsible applicant and co-applicants

Employees

Publications

Publication
Activity-dependent inhibitory synapse scaling is determined by gephyrin phosphorylation and subsequent regulation of GABAA receptor diffusion
Battaglia S, Renner M, Russeau M, Etienne Côme, Tyagarajan SK, Lévi S (2018), Activity-dependent inhibitory synapse scaling is determined by gephyrin phosphorylation and subsequent regulation of GABAA receptor diffusion, in eNeuro, 5(1), 0203.
Emerging mechanisms underlying dynamics of GABAergic synapses
Maffei A, Charrier C, Caiati M, Barberis A, Mahadevan V, Woodin MA, Tyagarajan SK (2017), Emerging mechanisms underlying dynamics of GABAergic synapses, in Journal of Neuroscience, 37(45), 10792-10799.
RhoGEF9 splice isoforms influence neuronal maturation and synapse formation downstream of a2 GABAA receptors
DeGroot C, Floriou-Servou A, Tsai YC, Frueh S, Kohler M, Parkin G, Schwerdel C, Bosshard G, Kaila K, Fritschy JM, Tyagarajan SK (2017), RhoGEF9 splice isoforms influence neuronal maturation and synapse formation downstream of a2 GABAA receptors, in PLOS Genetics, 10(13), 1007073.
Several posttranslational modifications act in concert to regulate gephyrin scaffolding and GABAergic transmission.
Ghosh H, Auguadri L, Thirouin Z, Messner S, Acuna M, Wildner H, Yevenes G.E, Battaglia S, Dieter A, Kawasaki K, Hottiger M, Zeilhofer H.U, Fritschy J-M, Tyagarajan S.K (2016), Several posttranslational modifications act in concert to regulate gephyrin scaffolding and GABAergic transmission., in Nature Communication, 7(Nov 7), 13365.
The catalytic function of the gephyrin-binding protein IQSEC3 regulates neurotransmitter-specific matching of pre- and post-synaptic structures in primary hippocampal cultures
Früh S, Tyagarajan S, Campbell B, Bosshard G, Fritschy JM, The catalytic function of the gephyrin-binding protein IQSEC3 regulates neurotransmitter-specific matching of pre- and post-synaptic structures in primary hippocampal cultures, in J Neurochem.

Collaboration

Group / person Country
Types of collaboration
Prof. Steven Brown/ University of Zurich Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Exchange of personnel
Prof. Dominique Muller/ University of Geneva Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Gordon Research Conference Poster Dynamic gephyrin phosphorylation regulates barrel cortex plasticity 25.06.2017 les diablerets, Switzerland Tsai Yuan-Chen; Tyagarajan Shiva;
EpiGeneSwss Talk given at a conference A novel class of nuclear speckles that dynamically reorganize in response to synaptic activity 29.05.2017 Lucerne, Switzerland Tyagarajan Shiva;
Zurich Neuroscience Symposium Talk given at a conference Functional separation of RhoGEF9 isoforms during adult neurogenesis for Cdc42 regulation. 15.09.2016 Zurich, Switzerland Tyagarajan Shiva;
Gordon Research Conference Talk given at a conference The 'Histone code' of gephyrin cluster regulation 16.08.2015 Maine, United States of America Tyagarajan Shiva;


Self-organised

Title Date Place
2018 Meeting in Emerging mechanisms for GABAergic synapse plasticity 06.06.2018 Schaffhausen , Switzerland
Society for Neuroscience; mini Symposium 11.11.2017 Washington DC , United States of America

Communication with the public

Communication Title Media Place Year
Talks/events/exhibitions ART LAB International 2015
Talks/events/exhibitions ART LAB- Water of Life International 2015

Awards

Title Year
UZH Forschungskredit Grant 2016
Center for Neuroscience Grant 2015

Associated projects

Number Title Start Funding scheme
192522 A role for gephyrin phosphorylation in sexual dimorphism in the brain 01.06.2020 Project funding
170804 The airy scan detector for improved sensitivity and resolution analysis of functional neuroanatomy, neuronal regulation, and pericyte biology 01.04.2017 R'EQUIP

Abstract

The focus of my work is on gephyrin, a 83kDa scaffolding protein known to be the main “organizer” inhibitory synapses in the CNS, but whose functions and regulation are still unclear. My team has identified and characterized novel post-translational modifications on gephyrin demonstrating a complex cross talk between phosphorylation, acetylation and SUMOylation pathways to regulate gephyrin scaffold formation and activity-dependent dynamics, in turn modulating GABAergic mIPSC amplitude and frequency. The availability of specific gephyrin mutants that can rescue clustering in GABAAR deficient mouse, or disrupt scaffolding in WT mouse, offer a molecular tool to regulate downstream effects of GABAergic synapse function. Focusing on gephyrin interaction partners; specifically, collybistin (CB), whose function in neurons is essential for GABAergic synapse maintenance and function has offered insights into CB facilitated gephyrin scaffolding. Identification of multiple CB splice isoforms in the CNS has opened fresh speculations about their functional significance. Our data shows that CB isoforms have short protein half-life and the mRNA isoforms are dendritically transported for local protein synthesis. Taking full advantage of our knowledge including available tools and reagents this proposal aims to demonstrate the proof of concept that intracellular signaling downstream of GABAARs play an important role in hetero-synaptic cross talk and neuronal adaptations. This knowledge would be an invaluable asset to the neuroscience community to study and characterize the role of GABAergic synapse plasticity in diverse neuropsychiatric disorders. We hypothesize that we can modulate intracellular signaling downstream of GABAARs via transgenic expression of specific mutant gephyrin in vivo to alter function at both cellular and network level. Furthermore, with a focus on post-transcriptional regulation we hope to understand molecular basis for CB mRNA dendritic transport and local protein synthesis. Our interest in these studies is based on the hypothesis that local protein synthesis is an important and novel component of activity dependent gephyrin clustering dynamics for GABAergic synaptic plasticity. In order to test our first hypothesis we will investigate the consequences of gephyrin scaffold stabilization and/or destabilization using specific mutant gephyrin in vivo using recombinant AAV expression system. By expressing specific mCherry-gephyrin mutant constructs we plan to first rescue gephyrin scaffolding in the hippocampus of a2 GABAAR KO mice, a well-established model for anxiety and mood disorders to study the behavioral rescue using specific tests for anxiety; second, we also plan to disrupt gephyrin scaffolding in WT neurons by transgenic expression of dominant negative gephyrin mutant using AAV and examine the consequences on the hippocampal circuit function by conducting behavior analysis for anxiety. In order to understand the consequences of CB post-transcriptional regulation for gephyrin clustering we plan to delineate the molecular basis for CB mRNA recruitment into RNA transport granules for dendritic transport and local protein synthesis. Furthermore, using a combination of molecular biology, morphology and electrophysiology from Stau-1 and raptor KO mouse we aim to study the consequences of dendritic CB protein translation for gephyrin clustering and activity-dependent GABAergic plasticity.
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