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Ethanol Modulation is Quantitatively Determined by the Transmembrane Domain of Human α 1 Glycine Receptors
Author(s) -
Horani Suzzane,
Stater Evan P.,
Corringer PierreJean,
Trudell James R.,
Harris R. Adron,
Howard Rebecca J.
Publication year - 2015
Publication title -
alcoholism: clinical and experimental research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.267
H-Index - 153
eISSN - 1530-0277
pISSN - 0145-6008
DOI - 10.1111/acer.12735
Subject(s) - glycine receptor , ligand gated ion channel , ion channel , chemistry , transmembrane domain , biophysics , voltage clamp , receptor , allosteric regulation , homomeric , amino acid , biochemistry , xenopus , concatemer , glycine , biology , membrane potential , protein subunit , gene , genome
Background Mutagenesis and labeling studies have identified amino acids from the human α 1 glycine receptor (GlyR) extracellular, transmembrane ( TM ), and intracellular domains in mediating ethanol (EtOH) potentiation. However, limited high‐resolution structural data for physiologically relevant receptors in this Cys‐loop receptor superfamily have made pinpointing the critical amino acids difficult. Homologous ion channels from lower organisms provide conserved models for structural and functional properties of Cys‐loop receptors. We previously demonstrated that a single amino acid variant of the Gloeobacter violaceus ligand‐gated ion channel ( GLIC ) produced EtOH and anesthetic sensitivity similar to that of GlyRs and provided crystallographic evidence for EtOH binding to GLIC . Methods We directly compared EtOH modulation of the α 1 GlyR and GLIC to a chimera containing the TM domain from human α 1 GlyRs and the ligand‐binding domain of GLIC using 2‐electrode voltage‐clamp electrophysiology of receptors expressed in Xenopus laevis oocytes. Results EtOH potentiated α 1 GlyRs in a concentration‐dependent manner in the presence of zinc‐chelating agents, but did not potentiate GLIC at pharmacologically relevant concentrations. The GLIC /GlyR chimera recapitulated the EtOH potentiation of GlyRs, without apparent sensitivity to zinc chelation. For chimera expression in oocytes, it was essential to suppress leakage current by adding 50 μ M picrotoxin to the media, a technique that may have applications in expression of other ion channels. Conclusions Our results are consistent with a TM mechanism of EtOH modulation in Cys‐loop receptors. This work highlights the relevance of bacterial homologs as valuable model systems for studying ion channel function of human receptors and demonstrates the modularity of these channels across species.