Previous studies suggested that alcohol activation occurs independently from receptor-dependent activation (Kobayashi et al., 1999; Lewohl et al., 1999). Using an alcohol tagging strategy with GIRK2, Bodhinathan and Slesinger (2013) found that MTS-HE modification of the Gβγ L344 site reduced basal GIRK2 current, while modification of L257 increased the basal GIRK2 current. Furthermore, varying the levels of Gβγ subunits consistently altered the rate of MTS-HE-dependent inhibition of L344C but had little effect on modification of L257C. Thus, in spite of the considerable overlap in the alcohol and Gβγ binding sites, activation by MTS-HE does not seem to be influenced by alterations in the Gβγ levels. Taken together, these results support a model where association between Gβγ and GIRK2 L344 in the βL-βM loop, similar to L333 in GIRK1 (Mahajan et al., 2013), precedes alcohol-mediated activation in the pocket.
