Molecular mechanism for the dual alcohol modulation of Cys-loop receptors.
Cys-loop receptors constitute a superfamily of pentameric ligand-gated ion channels (pLGICs), including receptors for acetylcholine, serotonin, glycine and γ-aminobutyric acid. Several bacterial homologues have been identified that are excellent models for understanding allosteric binding of alcohols and anesthetics in human Cys-loop receptors. Recently, we showed that a single point mutation on a prokaryotic homologue (GLIC) could transform it from a channel weakly potentiated by ethanol into a highly ethanol-sensitive channel. Here, we have employed molecular simulations to study ethanol binding to GLIC, and to elucidate the role of the ethanol-enhancing mutation in GLIC modulation. By performing 1-µs simulations with and without ethanol on wild-type and mutated GLIC, we observed spontaneous binding in both intra-subunit and inter-subunit transmembrane cavities. In contrast to the glycine receptor GlyR, in which we previously observed ethanol binding primarily in an inter-subunit cavity, ethanol primarily occupied an intra-subunit cavity in wild-type GLIC. However, the highly ethanol-sensitive GLIC mutation significantly enhanced ethanol binding in the inter-subunit cavity. These results demonstrate dramatic effects of the F(14')A mutation on the distribution of ligands, and are consistent with a two-site model of pLGIC inhibition and potentiation.
Science for Life Laboratory, KTH Royal Institute of Technology & Stockholm University, Stockholm, Sweden.
Samuel
S
Murail
Rebecca J
RJ
Howard
Torben
T
Broemstrup
Edward J
EJ
Bertaccini
R Adron
RA
Harris
James R
JR
Trudell
Erik
E
Lindahl
D029742:Caenorhabditis elegans Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018118:Chloride Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D058466:Cysteine Loop Ligand-Gated Ion Channel Receptors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000431:Ethanol / Q000737:chemistry* / Q000378:metabolism; D008051:Lipid Bilayers / Q000737:chemistry; D008954:Models, Biological; D056004:Molecular Dynamics Simulation; D009154:Mutation; D010713:Phosphatidylcholines / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D015203:Reproducibility of Results; D014867:Water / Q000737:chemistry
D029742:Caenorhabditis elegans Proteins; D018118:Chloride Channels; D058466:Cysteine Loop Ligand-Gated Ion Channel Receptors; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; C109777:glutamate-gated chloride channels; D014867:Water; D000431:Ethanol; C017251:1,2-oleoylphosphatidylcholine