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Regulation of cell surface GABA(B) receptors in cerebral ischemia: contribution to neuronal death and potential implications for novel therapeutic strategies

English title Regulation of cell surface GABA(B) receptors in cerebral ischemia: contribution to neuronal death and potential implications for novel therapeutic strategies
Applicant Benke Dietmar
Number 156648
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 01.11.2014 - 31.03.2018
Approved amount 454'000.00
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All Disciplines (2)

Discipline
Neurophysiology and Brain Research
Pharmacology, Pharmacy

Keywords (10)

GABA(B) receptor; Degradation; Receptor associated proteins; CHOP; ERAD; Cerebral ischemia; Interfering peptide; Proteasome; Neuronal death; Inhibitory neurotransmission

Lay Summary (German)

Lead
Der Schlaganfall ist die dritthäufigste Todesursache in den industrialisierten Ländern und die häufigste Ursache einer schweren Behinderung bei Erwachsenen. In der Schweiz erleiden jährlich etwa 16‘000 Menschen einen Schlaganfall. Der Schlaganfall entsteht in der Regel durch eine Durchblutungsstörung im Gehirn (zerebrale Ischämie), die nach einiger Zeit zum Absterben von Nervenzellen führt. Bis heute existiert keine pharmakologische Therapie, die das Absterben von Hirngewebe bei Hirnschlag-Patienten wirksam bekämpft. In diesem Forschungsprojekt werden Veränderungen der Regulationsmechanismen eines Rezeptors für den inhibitorischen Neurotransmitter GABA (GABA(B)-Rezeptor) unter ischämischen Bedingungen untersucht, mit dem Ziel neue therapeutische Ansätze zur Verhinderung des Absterbens von Nervenzellen zu entwickeln.
Lay summary

Inhalt und Ziele des Forschungsprojekts

Als eine der Hauptursachen für das Absterben von Nervenzellen infolge eines Schlaganfalls wird deren Übererregung durch die massive Freisetzung des Neurotransmitters Glutamat angesehen und die damit verbundene Überaktivierung der Glutamat-Rezeptoren. Unter normalen Bedingungen wird die Aktivität der Glutamat-Rezeptoren durch GABA(B)-Rezeptoren kontrolliert um eine Übererregung zu verhindern. Es gibt Hinweise darauf, dass die GABA(B)-Rezeptoren unter ischämischen Bedingungen von ihrem Wirkort, der Zelloberfläche, entfernt werden und somit die Glutamat-Rezeptoren nicht mehr ausreichend kontrollieren können. Wir haben bislang drei Mechanismen identifiziert, die mutmasslich an der Herunterregulierung der GABA(B)-Rezeptoren beteiligt sind. Ziel dieses Forschungsprojekts ist:

1.  Die eingehende Analyse der Faktoren, welche für die Herunterregulierung der GABA(B)-Rezeptoren unter ischämischen Bedingungen verantwortlich sind.

2.  Die Herunterregulierung der GABA(B)-Rezeptoren durch Unterbindung von relevanten Protein-Protein-Interaktion mittels spezifischer Peptide zu verhindern und so möglicherweise das Absterben von Nervenzellen zu verhindern.

Wissenschaftlicher und gesellschaftlicher Kontext des Forschungsprojekts

Wir erwarten, dass die Ergebnisse dieses Forschungsprojekts unser Wissen und Verständnis über die Regulation von Neurotransmitter-Rezeptoren sowohl unter physiologischen als auch unter pathologischen Bedingungen beträchtlich erweitert. Wenn sich unsere Hypothesen bestätigen, bilden die Ergebnisse dieses Projekts die Grundlage für die Entwicklung hochspezifischer therapeutischer Ansätze zur Bekämpfung des Absterbens von Nervenzellen nach einem Hirnschlag.

Direct link to Lay Summary Last update: 29.09.2014

Responsible applicant and co-applicants

Employees

Publications

Publication
Lys-63-linked Ubiquitination of γ-Aminobutyric Acid (GABA), Type B1, at Multiple Sites by the E3 Ligase Mind Bomb-2 Targets GABAB Receptors to Lysosomal Degradation
Zemoura Khaled, Trümpler Claudia, Benke Dietmar, Lys-63-linked Ubiquitination of γ-Aminobutyric Acid (GABA), Type B1, at Multiple Sites by the E3 Ligase Mind Bomb-2 Targets GABAB Receptors to Lysosomal Degradation, in Journal of Biological Chemistry, 291(41), 21682-21693.
Molecular organization, trafficking, and degradation of the GABA(B) receptor
Benke Dietmar, Balakrishnan Karthik, Zemoura Khaled, Molecular organization, trafficking, and degradation of the GABA(B) receptor, in Colombo Giancarlo (ed.), Humana Press (Springer International Publishing), Cham, Switzerland, 55-74.
Regulation of cell surface GABA receptors: Contribution to synaptic plasticity in neurological diseases
, Regulation of cell surface GABA receptors: Contribution to synaptic plasticity in neurological diseases, in Adv. Pharmacol., 73, 41-70.
The positive allosteric GABA(B) receptor modulator rac-BHFF enhances baclofen-mediated analgesia in neuropathic mice
Zemoura Khaled, Ralvenius William T., Malherbe Pari, Benke Dietmar, The positive allosteric GABA(B) receptor modulator rac-BHFF enhances baclofen-mediated analgesia in neuropathic mice, in Neuropharmacology, 108, 172-178.

Collaboration

Group / person Country
Types of collaboration
Prof. H. U. Zeilhofer, Institute of Pharmacology and Toxicology, University of Zurich Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
Prof. Jan Klohs Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
20th Swiss Society for Neuroscience Meeting Poster Phosphorylation of GABA(B1) by CaMKIIbeta triggers lysosomal degradation of GABA(B) receptors by regulating MIB2-mediated Lys63-linked ubiquitination 09.02.2018 Zürich, Switzerland Benke Dietmar; Balakrishnan Karthik;
Society for Neuroscience (SFN) - Annual Meeting 2017 Poster Phosphorylation of GABA(B1) by CaMKIIbeta triggers lysosomal degradation of GABA(B) receptors by regulating MIB2-mediated Lys63-linked ubiquitination 11.11.2017 Washington DC, United States of America Balakrishnan Karthik;
DDNZ Symposium: Drug Re-purposing in an Academic Environment Poster Restoring cell surface expression of GABA(B) receptors: A potential strategy to limit neuronal death in cerebral ischemia 10.02.2017 ZTurich, Switzerland Benke Dietmar; Balakrishnan Karthik;
LS2 Annual Meeting 2017 Talk given at a conference Restoring cell surface expression of GABA(B) receptors: A potential strategy to limit neuronal death in cerebral ischemia 02.02.2017 Zurich, Switzerland Balakrishnan Karthik; Benke Dietmar;
19th Annual Meeting of the Swiss Society for Neuroscience Poster Restoring cell surface expression of GABA(B) receptors: A potential strategy to limit neuronal death in cerebral ischemia 27.01.2017 Basel, Switzerland Benke Dietmar; Balakrishnan Karthik;
Society for Neuroscience (SFN) - Annual Meeting 2016 Poster The positive allosteric GABA(B) receptor modulator rac-BHFF enhances baclofen-mediated analgesia in neuropathic mice. 12.11.2016 San Diego, United States of America Zemoura Khaled;
Society for Neuroscience (SFN) - Annual Meeting 2016 Poster Restoring cell surface expression of GABA(B) receptors: a potential strategy to limit neuronal death in cerebral ischemia 12.11.2016 San Diego, United States of America Balakrishnan Karthik;
ZNZ Symposium Poster Restoring cell surface expression of GABA(B) receptors: a potential strategy to limit neuronal death in cerebral ischemia 14.09.2016 Zürich, Switzerland Benke Dietmar; Balakrishnan Karthik;
Society for Neuroscience (SFN) - Annual Meeting 2015 Poster CaMKII-dependent K63-linked ubiquitination of GABA(B1) drives lysosomal degradation of GABA(B) receptors 17.10.2015 Chicago, United States of America Zemoura Khaled;
ZNZ Symposium Poster Identification of a small interfering peptide preventing glutamate-induced downregulation of GABA(B) receptors: a potential strategy to limit neuronal death in cerebral ischemia 11.09.2015 Zürich, Switzerland Benke Dietmar; Balakrishnan Karthik;
ZNZ Symposium Poster CaMKII-dependent K63-linked ubiquitination of GABA(B1) drives lysosomal degradation of GABA(B) receptors 11.09.2015 Zürich, Switzerland Zemoura Khaled; Benke Dietmar;
DDNZ Symposium Talk given at a conference Interfering with GABA(B) receptor dynamics: target for the development of highly specific strategies to limit neuronal death in cerebral ischemia? 26.02.2015 Zürich, Switzerland Benke Dietmar;
Society for Neuroscience (SFN) - Annual Meeting 2014 Poster K63-linked ubiquitination of GABA(B1) sorts GABA(B) receptors to lysosomal degradation 15.11.2014 Washington, United States of America Zemoura Khaled;


Associated projects

Number Title Start Funding scheme
182325 Targeting GABA(B) receptor protein-protein interactions to correct compromised receptor expression in neurological diseases: potential for the development of highly selective therapeutic interventions 01.04.2019 Project funding
138382 Regulation of cell surface GABA(B) receptors by trafficking mechanisms: contribution to synaptic plasticity and disease states 01.11.2011 Project funding

Abstract

Cerebral ischemia often leads to death or long-term disability due to severe neuronal death. Cerebral ischemia is caused by perturbed blood supply to or within the brain, which deprives neurons from oxygen and energy. A main cause for delayed neuronal death associated with cerebral ischemia is the massive release of glutamate overstimulating glutamate receptors and triggering apoptosis. Currently, there is no treatment to protect neurons from dying after the infarct. More than 1000 potential neuroprotective treatments tested so far failed in clinical trials. Thus, there is an urgent need for new strategies that may lead to the development of safe and effective interventions limiting neuronal death associated with cerebral ischemia.Under normal conditions the activity of glutamate receptors is controlled by the G protein-coupled GABA(B) receptors. There is evidence that GABA(B) receptors are downregulated under ischemic conditions, which is expected to promote neuronal death due to a loss of GABA(B) receptor-mediated inhibition. We recently discovered three distinct mechanisms downregulating cell surface GABA(B) receptors most likely under ischemic conditions:1. Glutamate receptor-mediated downregulation of GABA(B) receptors2. ERAD-mediated downregulation of GABA(B) receptors3. CHOP-induced downregulation of GABA(B) receptorsAll these mechanisms affect trafficking events of GABA(B) receptors and are controlled by interactions of specific proteins with the receptors. In this proposal we aim at clarifying whether these mechanisms contribute to excitotoxicity in cerebral ischemia. We will explore whether interfering with these mechanisms restores normal GABA(B) receptor levels and limit ischemic neuronal death. We intend to study the involvement of GABA(B) receptor downregulation under ischemic conditions on three levels using models for cerebral ischemia: the in vitro model of oxygen and glucose deprivation using cultured cortical neurons as well as cortex slices and the in vivo mouse model of photothrombotic ischemia. We will use state of the art biochemical (e. g. in situ proximity ligation assay) and imaging techniques (e. g. live cell imaging confocal laser scanning, super resolution [STED] and two-photon microscopy) to monitor protein-protein interactions and GABA(B) receptor dynamics under ischemic conditions. We plan to screen for small synthetic peptides interfering with protein-protein interactions triggering the downregulation of GABA(B) receptors to preserve or restore normal levels of cell surface GABA(B) receptors. The potential neuroprotective effect of the interfering peptides will be analyzed in all three models of cerebral ischemia.We expect that the proposed work will greatly enhance our knowledge on the regulation of GABA(B) receptors under normal and pathological conditions. If preserving/restoring normal GABA(B) receptor expression levels under ischemic conditions indeed limit neuronal death our work will provide the basis for the development of highly specific novel therapeutic interventions to combat neuronal cell death.
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