title: Probing the pharmacological properties of distinct subunit interfaces within heteromeric glycine receptors reveals a functional ββ agonist-binding site.
abstract: Synaptic glycine receptors (GlyRs) are hetero-pentameric chloride channels composed of α and β subunits, which are activated by agonist binding at subunit interfaces. To examine the pharmacological properties of each potential agonist-binding site, we substituted residues of the GlyR α(1) subunit by the corresponding residues of the β subunit, as deduced from sequence alignment and homology modeling based on the recently published crystal structure of the glutamate-gated chloride channel GluCl. These exchange substitutions allowed us to reproduce the βα, αβ and ββ subunit interfaces present in synaptic heteromeric GlyRs by generating recombinant homomeric receptors. When the engineered α(1) GlyR mutants were expressed in Xenopus oocytes, all subunit interface combinations were found to form functional agonist-binding sites as revealed by voltage clamp recording. The ββ-binding site displayed the most distinct pharmacological profile towards a range of agonists and modulators tested, indicating that it might be selectively targeted to modulate the activity of synaptic GlyRs. The mutational approach described here should be generally applicable to heteromeric ligand-gated ion channels composed of homologous subunits and facilitate screening efforts aimed at targeting inter-subunit specific binding sites.
authors.affiliation: Department of Neurochemistry, Max-Planck-Institute for Brain Research, Frankfurt am Main, Germany.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Dutertre
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Drwal
authors.forename: Bodo
authors.initials: B
authors.lastname: Laube
authors.forename: Heinrich
authors.initials: H
authors.lastname: Betz
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000187:drug effects; D003198:Computer Simulation; D003300:Copper; D000431:Ethanol / Q000494:pharmacology; D018684:Glycine Agents / Q000494:pharmacology; D020128:Inhibitory Concentration 50; D007559:Ivermectin / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000235:genetics; D008845:Microinjections; D008958:Models, Molecular; D016296:Mutagenesis; D009154:Mutation / Q000235:genetics; D009662:Nortropanes / Q000494:pharmacology; D009865:Oocytes; D018408:Patch-Clamp Techniques; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018009:Receptors, Glycine / Q000819:agonists* / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D014982:Xenopus laevis; D015032:Zinc / Q000494:pharmacology
chemical_list: D018684:Glycine Agents; D009662:Nortropanes; D021122:Protein Subunits; D018009:Receptors, Glycine; D000431:Ethanol; D007559:Ivermectin; D003300:Copper; D015032:Zinc