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

The 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 co-crystallized 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-α1β3GABAAR chimera, replacing the ELIC transmembrane domain (TMD) with the TMD of α1β3GABAAR, 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. [Display omitted] •n-Alcohols, including 2-bromoethanol (BrEtOH), inhibit the function of ELIC•Crystal structures show BrEtOH-binding sites in the pore and the ECD of ELIC•BrEtOH binding to the pore at the 6′ position dominates its inhibitory action Using X-ray crystallography and functional measurements, Chen et al. provide a structural basis for the pore-blocking mechanism for alcohol inhibition of ELIC, a pentameric ligand-gated ion channel.