Pertussis toxin treatment does not prevent EtOH activation of GIRK channels, indicating that GPCR coupling to G proteins is not involved8. To rule out the possibility that alcohols activate GIRK channels by directly stimulating G protein heterotrimers and liberating Gβγ subunits, we measured the alcohol response of GIRK2 channels in cells co-expressing a myristoylated form of phosducin (m-Phos) that chelates Gβγ following stimulation of GPCRs26. Compared to controls, carbachol application led to smaller and rapidly desensitizing m2R evoked GIRK2 currents in cells coexpressing m-Phos (Fig. 2c–e). All three alcohols, on the other hand, activated GIRK2 channels to the same extent in the presence of m-Phos (Fig. 2d,e). Thus, alcohol-dependent activation of GIRK2 channels does not appear to require free Gβγ subunits. Together, these results support the interpretation that alcohols directly activate GIRK channels through a physical alcohol-bound pocket.
