Structural basis for alcohol modulation of a pentameric ligand-gated ion channel
2011 (English)In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 108, no 29, 12149-54 p.Article in journal (Refereed) Published
Despite its long history of use and abuse in human culture, the molecular basis for alcohol action in the brain is poorly understood. The recent determination of the atomic-scale structure of GLIC, a prokaryotic member of the pentameric ligand-gated ion channel (pLGIC) family, provides a unique opportunity to characterize the structural basis for modulation of these channels, many of which are alcohol targets in brain. We observed that GLIC recapitulates bimodal modulation by n-alcohols, similar to some eukaryotic pLGICs: methanol and ethanol weakly potentiated proton-activated currents in GLIC, whereas n-alcohols larger than ethanol inhibited them. Mapping of residues important to alcohol modulation of ionotropic receptors for glycine, γ-aminobutyric acid, and acetylcholine onto GLIC revealed their proximity to transmembrane cavities that may accommodate one or more alcohol molecules. Site-directed mutations in the pore-lining M2 helix allowed the identification of four residues that influence alcohol potentiation, with the direction of their effects reflecting α-helical structure. At one of the potentiation-enhancing residues, decreased side chain volume converted GLIC into a highly ethanol-sensitive channel, comparable to its eukaryotic relatives. Covalent labeling of M2 positions with an alcohol analog, a methanethiosulfonate reagent, further implicated residues at the extracellular end of the helix in alcohol binding. Molecular dynamics simulations elucidated the structural consequences of a potentiation-enhancing mutation and suggested a structural mechanism for alcohol potentiation via interaction with a transmembrane cavity previously termed the "linking tunnel." These results provide a unique structural model for independent potentiating and inhibitory interactions of n-alcohols with a pLGIC family member.
Place, publisher, year, edition, pages
2011. Vol. 108, no 29, 12149-54 p.
Biophysics Bioinformatics and Systems Biology Theoretical Chemistry
Research subject SRA - E-Science (SeRC)
IdentifiersURN: urn:nbn:se:kth:diva-82584DOI: 10.1073/pnas.1104480108ISI: 000292876900084PubMedID: 21730162ScopusID: 2-s2.0-79961074761OAI: oai:DiVA.org:kth-82584DiVA: diva2:498397
FunderSwedish Research CouncilSwedish e‐Science Research Center
Conference Neuroscience 2011. QC 201202172012-02-122012-02-122012-05-23Bibliographically approved