Structural Basis of Alcohol Inhibition of the Pentameric Ligand-Gated Ion Channel ELIC

Abstract

SUMMARYThe structural basis for alcohol modulation of neuronal pentameric ligand-gated ion channels (pLGICs) remains elusive. We determined an inhibitory mechanism of alcohol on the pLGIC Erwinia chrysanthemi (ELIC) through direct binding to the pore. X-ray structures of ELIC cocrystallized with 2-bromoethanol, in both the absence and presence of agonist, reveal 2-bromoethanol binding in the pore near T237(6′) and the extracellular domain (ECD) of each subunit at three different locations. Binding to the ECD does not appear to contribute to the inhibitory action of 2-bromoethanol and ethanol as indicated by the same functional responses of wild-type ELIC and mutants. In contrast, the ELIC-α1β3GABA A R chimera, replacing the ELIC transmembrane domain (TMD) with the TMD of α1β3GABA A R, is potentiated by 2-bromoethanol and ethanol. The results suggest a dominant role of the TMD in modulating alcohol effects. The X-ray structures and functional measurements support a pore-blocking mechanism for inhibitory action of short chain alcohols. *Correspondence and lead contact: Pei Tang: ptang@pitt.edu. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. ACCESSION NUMBERSCrystal structures of BrEtOH-bound ELIC with (5SXU) and without (5SXV) PPA are deposited in the PDB. SUPPLEMENTAL INFORMATIONFigs. S1-3, Table S1, and experimental details. AUTHOR CONTRIBUTIONSQC conducted most of the experiments and analyzed the results. TST and MMW performed TEVC measurements and participated in manuscript preparation. MNK expressed and prepared ELIC mutants for functional studies. AC along with QC contributed to X-ray data collection. YX and PT designed the project. PT and QC wrote the manuscript. All authors reviewed the results and approved the final version of the manuscript.The authors declare no conflicts of interest with the contents of this article. HHS Public Access