title: A pentasymmetric open channel blocker for Cys-loop receptor channels.
abstract: γ-Aminobutyric acid type A receptors (GABAA receptors) are chloride ion channels composed of five subunits, mediating fast synaptic and tonic inhibition in the mammalian brain. These receptors show near five-fold symmetry that is most pronounced in the second trans-membrane domain M2 lining the Cl- ion channel. To take advantage of this inherent symmetry, we screened a variety of aromatic anions with matched symmetry and found an inhibitor, pentacyanocyclopentdienyl anion (PCCP-) that exhibited all characteristics of an open channel blocker. Inhibition was strongly dependent on the membrane potential. Through mutagenesis and covalent modification, we identified the region α1V256-α1T261 in the rat recombinant GABAA receptor to be important for PCCP- action. Introduction of positive charges into M2 increased the affinity for PCCP- while PCCP- prevented the access of a positively charged molecule into M2. Interestingly, other anion selective cys-loop receptors were also inhibited by PCCP-, among them the Drosophila RDL GABAA receptor carrying an insecticide resistance mutation, suggesting that PCCP- could serve as an insecticide.
authors.affiliation: Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland.
authors.forename: Valentina
authors.initials: V
authors.lastname: Carta
authors.affiliation: Department of Chemistry, Ludwig-Maximilians-Universität München and Center of Integrated Protein Science, Munich, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Pangerl
authors.affiliation: Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland.
authors.forename: Roland
authors.initials: R
authors.lastname: Baur
authors.affiliation: Department of Biochemistry and Molecular Biology, Center for Brain Research, Medical University of Vienna, Vienna, Austria.
authors.forename: Roshan
authors.initials: R
authors.lastname: Puthenkalam
authors.affiliation: Department of Biochemistry and Molecular Biology, Center for Brain Research, Medical University of Vienna, Vienna, Austria.
authors.forename: Margot
authors.initials: M
authors.lastname: Ernst
authors.affiliation: Department of Chemistry, Ludwig-Maximilians-Universität München and Center of Integrated Protein Science, Munich, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Trauner
authors.affiliation: Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland.
authors.forename: Erwin
authors.initials: E
authors.lastname: Sigel
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D029721:Drosophila Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000378:metabolism; D004331:Drosophila melanogaster; D058787:GABA-A Receptor Antagonists / Q000737:chemistry*; D020125:Mutation, Missense; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D051381:Rats; D011963:Receptors, GABA-A / Q000737:chemistry* / Q000235:genetics
chemical_list: D029721:Drosophila Proteins; D058787:GABA-A Receptor Antagonists; D011963:Receptors, GABA-A