Based on our mutagenesis data and structural analyses, we propose a tenable model for alcohol activation of GIRK channels. At rest, GIRK2 channels undergo infrequent structural rearrangements in the pocket that correlate with the open and closed positions of the channel's cytoplasmic gates, the G loops24,39 and M2 transmembrane domains40-42 (Fig. 8c). Alcohol entering the pocket could then stabilize the open conformation, leading to alcohol-activated currents. Bulky substitutions at L257/L252 of GIRK channels, located at the base of the alcohol pocket, would hinder alcohols from filling the pocket. Alcohols might also displace other amino acids that fill the hydrophobic pocket in the closed state (Fig. 8c), promoting the open state. Previous studies have suggested that Gβγ-dependent activation of GIRK channels involves increases in PIP2 affinity28,31. Similarly, changes in PIP2 binding may also be involved in alcohol-dependent activation of GIRK channels. Studies in the future will need to investigate the molecular relationships between movement of the N-terminal domain, βD-βE and βL-βM ribbons within the hydrophobic pocket, PIP2 interactions, and the channel gates.
