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GABA-A receptors: Molecular analysis, function in liver and direct connection to the cannabinoid signaling system

English title GABA-A receptors: Molecular analysis, function in liver and direct connection to the cannabinoid signaling
Applicant Sigel Erwin
Number 132806
Funding scheme Project funding (Div. I-III)
Research institution Institut für Biochemie und Molekulare Medizin Universität Bern
Institution of higher education University of Berne - BE
Main discipline Neurophysiology and Brain Research
Start/End 01.10.2010 - 30.09.2014
Approved amount 415'000.00
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All Disciplines (2)

Discipline
Neurophysiology and Brain Research
Pharmacology, Pharmacy

Keywords (11)

GABA; GABA-A Receptor; Benzodiazepine; Xenopus oocyte; transfection; protein expression; ion channel; concatemer; liver; endocannabinoid; protein structure

Lay Summary (German)

Lead
Lay summary
Das einwandfreie Funktionieren unserer Hirnaktivität basiert auf einem subtilen Gleichgewicht von aktivierenden und inhibierenden Systemen. Unser Interesse gilt dem wichtigsten inhibitorischen System, dem GABA-A Rezeptor. Dieser Rezeptor ist auch der Angriffspunkt der viel verwendeten Medikamente der Gruppe der Benzodiazepine, von denen Valium der bekannteste Vertreter ist.Ein Teilprojekt befasst sich mit der Struktur der GABA-A Rezeptoren. Kenntnis der 3-D Struktur wird die gezielte Medikamentenentwicklung ermöglichen. Ein anderes charakterisiert die Rolle der kürzlich entdeckten GABA-A Rezeptoren in der Leber die vermutlich etwas mit der Leberkrebserkrankung zu tun haben. Ein drittes Teilprojekt befasst sich mit der kürzlich von uns entdeckten direkten Interaktion von Endocannabinoiden mit bestimmten Isoformen des GABA-A Rezeptors. Die Bindungsstelle für diese Substanzen soll charakterisiert werden und die Suche nach Kandidaten für die Medikamententwicklung beginnen.Eine wichtige Methode ist die "Transplantation" von GABA-A Rezeptoren und anderen Hirnproteinen in unreifen Froscheier. Genetische Information wird in die Eier mikroinjiziert und in der Folge nimmt die Oberfläche der Froscheier Hirneigenschaften an. So können die Eigenschaften von menschlichen GABA-A Rezeptoren bestimmt werden.Das Projekt wird zu einem besseren Verständnis des wichtigsten inhibitorischen Systems in unserem Hirn führen und die Entwicklung von neuen Medikamenten erleichtern.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
A pentasymmetric open channel blocker for Cys-loop receptor channels.
Carta Valentina, Pangerl Michael, Baur Roland, Puthenkalam Roshan, Ernst Margot, Trauner Dirk, Sigel Erwin (2014), A pentasymmetric open channel blocker for Cys-loop receptor channels., in PloS one, 9(9), 106688-106688.
Accelerated discovery of novel benzodiazepine ligands by experiment-guided virtual screening.
Middendorp Simon J, Puthenkalam Roshan, Baur Roland, Ernst Margot, Sigel Erwin (2014), Accelerated discovery of novel benzodiazepine ligands by experiment-guided virtual screening., in ACS chemical biology, 9(8), 1854-9.
Moderate concentrations of 4-O-methylhonokiol potentiate GABAA receptor currents stronger than honokiol.
Baur Roland, Schuehly Wolfgang, Sigel Erwin (2014), Moderate concentrations of 4-O-methylhonokiol potentiate GABAA receptor currents stronger than honokiol., in Biochimica et biophysica acta, 1840(10), 3017-21.
Relative positioning of classical benzodiazepines to the γ2-subunit of GABAA receptors.
Middendorp Simon J, Hurni Evelyn, Schönberger Matthias, Stein Marco, Pangerl Michael, Trauner Dirk, Sigel Erwin (2014), Relative positioning of classical benzodiazepines to the γ2-subunit of GABAA receptors., in ACS chemical biology, 9(8), 1846-53.
Trypanosoma brucei eflornithine transporter AAT6 is a low-affinity low-selective transporter for neutral amino acids.
Mathieu Christoph, González Salgado Amaia, Wirdnam Corina, Meier Stefan, Grotemeyer Marianne Suter, Inbar Ehud, Mäser Pascal, Zilberstein Dan, Sigel Erwin, Bütikofer Peter, Rentsch Doris (2014), Trypanosoma brucei eflornithine transporter AAT6 is a low-affinity low-selective transporter for neutral amino acids., in The Biochemical journal, 463(1), 9-18.
acr-23 Encodes a monepantel-sensitive channel in Caenorhabditis elegans.
Rufener Lucien, Bedoni Nicola, Baur Roland, Rey Samantha, Glauser Dominique A, Bouvier Jacques, Beech Robin, Sigel Erwin, Puoti Alessandro (2013), acr-23 Encodes a monepantel-sensitive channel in Caenorhabditis elegans., in PLoS pathogens, 9(8), 1003524-1003524.
Characterization of choline uptake in Trypanosoma brucei procyclic and bloodstream forms.
Macêdo Juan P, Schmidt Remo S, Mäser Pascal, Rentsch Doris, Vial Henri J, Sigel Erwin, Bütikofer Peter (2013), Characterization of choline uptake in Trypanosoma brucei procyclic and bloodstream forms., in Molecular and biochemical parasitology, 190(1), 16-22.
Do N-arachidonyl-glycine (NA-glycine) and 2-arachidonoyl glycerol (2-AG) share mode of action and the binding site on the β2 subunit of GABAA receptors?
Baur Roland, Gertsch Jürg, Sigel Erwin (2013), Do N-arachidonyl-glycine (NA-glycine) and 2-arachidonoyl glycerol (2-AG) share mode of action and the binding site on the β2 subunit of GABAA receptors?, in PeerJ, 1, 149-149.
Molecular analysis of the site for 2-arachidonylglycerol (2-AG) on the β₂ subunit of GABA(A) receptors.
Baur Roland, Kielar Marie, Richter Lars, Ernst Margot, Ecker Gerhard F, Sigel Erwin (2013), Molecular analysis of the site for 2-arachidonylglycerol (2-AG) on the β₂ subunit of GABA(A) receptors., in Journal of neurochemistry, 126(1), 29-36.
A Venom-derived Neurotoxin, CsTx-1, from the Spider Cupiennius salei Exhibits Cytolytic Activities
Kuhn-Nentwig Lucia, Fedorova Irina M., Luescher Benjamin P., Kopp Lukas S., Trachsel Christian, Schaller Johann, Vu Xuan Lan, Seebeck Thomas, Streitberger Kathrin, Nentwig Wolfgang, Sigel Erwin, Magazanik Lev G. (2012), A Venom-derived Neurotoxin, CsTx-1, from the Spider Cupiennius salei Exhibits Cytolytic Activities, in JOURNAL OF BIOLOGICAL CHEMISTRY, 287(30), 25640-25649.
Azo-Propofols: Photochromic Potentiators of GABA(A) Receptors.
Stein Marco, Middendorp Simon J, Carta Valentina, Pejo Ervin, Raines Douglas E, Forman Stuart A, Sigel Erwin, Trauner Dirk (2012), Azo-Propofols: Photochromic Potentiators of GABA(A) Receptors., in Angewandte Chemie (International ed. in English), 51(42), 10500-4.
Influence of GABA(A) receptor α subunit isoforms on the benzodiazepine binding site.
Lüscher Benjamin P, Baur Roland, Goeldner Maurice, Sigel Erwin (2012), Influence of GABA(A) receptor α subunit isoforms on the benzodiazepine binding site., in PloS one, 7(7), 42101-42101.
myo-Inositol uptake is essential for bulk inositol phospholipid but not glycosylphosphatidylinositol synthesis in Trypanosoma brucei.
Gonzalez-Salgado Amaia, Steinmann Michael E, Greganova Eva, Rauch Monika, Mäser Pascal, Sigel Erwin, Bütikofer Peter (2012), myo-Inositol uptake is essential for bulk inositol phospholipid but not glycosylphosphatidylinositol synthesis in Trypanosoma brucei., in The Journal of biological chemistry, 287(16), 13313-23.
The cannabinoid CB1 receptor antagonists rimonabant (SR141716) and AM251 directly potentiate GABA(A) receptors
Baur R, Gertsch J, Sigel E (2012), The cannabinoid CB1 receptor antagonists rimonabant (SR141716) and AM251 directly potentiate GABA(A) receptors, in BRITISH JOURNAL OF PHARMACOLOGY, 165(8), 2479-2484.
A Closer Look at the High Affinity Benzodiazepine Binding Site on GABA(A) Receptors
Sigel E, Luscher BP (2011), A Closer Look at the High Affinity Benzodiazepine Binding Site on GABA(A) Receptors, in CURRENT TOPICS IN MEDICINAL CHEMISTRY, 11(2), 241-246.
The major central endocannabinoid directly acts at GABA(A) receptors
Sigel E, Baur R, Racz I, Marazzi J, Smart TG, Zimmer A, Gertsch J (2011), The major central endocannabinoid directly acts at GABA(A) receptors, in PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 108(44), 18150-18155.
A residue close to alpha(1) loop F disrupts modulation of GABA(A) receptors by benzodiazepines while their binding is maintained
Baur R, Luscher BP, Richter L, Sigel E (2010), A residue close to alpha(1) loop F disrupts modulation of GABA(A) receptors by benzodiazepines while their binding is maintained, in JOURNAL OF NEUROCHEMISTRY, 115(6), 1478-1485.
Structure, Function and Modulation of GABAA receptors.
Sigel Erwin, Steinmann Michael E, Structure, Function and Modulation of GABAA receptors., in The Journal of biological chemistry.

Collaboration

Group / person Country
Types of collaboration
University of Bonn, Dr. C. Müller Germany (Europe)
- Publication
Novartis Animal Health Switzerland (Europe)
- Industry/business/other use-inspired collaboration
University of Bern, Prof. L. Kuhn-Nentwig Switzerland (Europe)
- Publication
University of Vienna, Dr. M. Ernst Austria (Europe)
- Publication
MIT, Prof. S.A. Forman United States of America (North America)
- Publication
University of Bern, Prof. J.-L. Reymond Switzerland (Europe)
- Publication
University of Bern, Prof. M. Lochner Switzerland (Europe)
- Publication
St. Aubin, Novartis, Dr. L. Rufener Switzerland (Europe)
- Publication
BASF Germany (Europe)
- Industry/business/other use-inspired collaboration
University of Munich, Prof. D. Trauner Germany (Europe)
- Publication

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Medicinal Chemistry Talk given at a conference Discovery and molecular description of the site of action of a novel endogenous ligand of GABAA receptors 17.03.2013 Munich, Germany Sigel Erwin;
Science Day of the Graduate School MolTag Talk given at a conference Keynote lecture 22.02.2013 Wien, Austria Sigel Erwin;
Scandinavian Physiological Society Talk given at a conference The modulatory site for the endocannabinoid 2-arachidonoyl glycerol (2-AG) on the 2 subunit of GABAA receptors 24.08.2012 Helsinki, Finland Sigel Erwin;
Birthday symposium Prof. W. Sieghart Talk given at a conference Modulation of GABA-A/benzodiazepine receptors 25.11.2011 Wien, Austria Sigel Erwin;


Communication with the public

Communication Title Media Place Year
Media relations: print media, online media Wie Cannabinoide und Valium im Gehirn zusammenspielen German-speaking Switzerland 2011

Associated projects

Number Title Start Funding scheme
156929 Towards an understanding of allosteric modulation of GABA-A receptor isoforms 01.10.2014 Project funding (Div. I-III)
105272 The GABA-A receptors: Application of subunit concatenation and benzodiazepine binding site 01.10.2004 Project funding (Div. I-III)

Abstract

SUMMARY Background: GABAA receptors are the most important mediators of neuronal inhibition. The first part of this proposal is devoted to applications of subunit concatenation of the GABAA receptor, among them over-expression and crystallization. The second part investigates the role of GABAA receptor subunits in the liver. The third part characterizes the influence of endocannabinoids on GABAA receptors. Specific Aims:Applications of GABAA receptor subunit concatenation: 1) We will characterize a novel site of action of benzodiazepines; 2) We will study a putative contribution of the d subunit to an agonist site; 3) We will try to identify protein sequences providing targeting information to different domains in a neuron and investigate whether there is a positional effect of the subunits within the receptor. 4) Different concatenated receptors among them the major adult isoform a1-ß2-a1-ß2-?2 will be over-expressed and purified. The availability of large amounts of pure protein would allow many different investigations. B. Role of the GABAA receptor in liver cancer. The localization and functional role of the recently described ß3 and e subunits in hepatocytes will be characterized. C. Crosstalk between GABAA receptors and cannabinoid receptor system. The modulation of GABAA receptor subtypes by endocannabinoids will be studied, as well as the consequences of this interaction. Experimental Design:For project A, a number of concatenated subunits are available. Methods that will be used include expression in Xenpopus oocytes combined with electrophysiological analysis, point mutations, transfection into cultured neurons, localization of subunits by immunofluorescence and formation of subunit chimera. Different concatenated receptors will be expressed in insect SF-9 cells. For project B, we plan to characterize the functional properties of GABAA receptor subunits in hepatocytes using the patch-clamp technique. The expressed subunits will be localized in the cell membrane using immunofluorescence. The effects of down-regulation with siRNA of GABAA receptor subunits on ion current, and several additional parameters will be studied. For project C, GABAA receptors of different subunit composition, some of them enginerered, will be expressed in Xenopus oocytes and the modulation of the resulting currents by endocannabinoids and neurosteroids characterized by electrophysiological means. Behavioral studies will be carried out in collaborations. Expected Value of the Proposed Project: Project A will provide data on the molecular properties of GABAA receptors and their modulation by benzodiazepines. Project B: We expect to obtain information on the type of conductivity that GABAA receptor subunits provide to hepatocytes and how it may be modulated in order to counteract cancer development. Project C: This is an investigation of a novel cross-talk between GABAA receptors and cannabinoid signalling. Keywords: GABAA receptor, GABA, benzodiazepine, Xenopus oocyte, transfection, protein expression, ion channel, concatemer, liver, endocannabinoids, protein structure.
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