Prior work on GIRK channels has focused on delineating the G protein-dependent pathway for activation of GIRK channels. Following stimulation of GPCRs that couple to pertussis toxin-sensitive Gi/o G proteins, the G protein Gβγ subunits bind directly to the channel, and induce a conformational change that opens the channel in a manner that depends on the membrane phospholipid PI(4,5)P2 (referred to as PIP2)10–14. Recently, this interaction was confirmed in an atomic resolution structure based on x-ray crystallography of GIRK2 in complex with Gβγ15. Activation of GIRK channels through so-called ‘G protein-independent’ pathways, however, are poorly understood. For example, GIRK channels are activated by alcohol16–18 and, similar to Gβγ activation, requires PIP2 19. However, while previous studies with heterologous expression systems and neurons suggested that alcohol directly activates GIRK channels16–19, the role of endogenous Gβγ subunits could not be unequivocally dismissed. Furthermore, alternative mechanisms through which alcohol could exert its effects were possible, such as increasing the fluidity of the plasma membrane20, 21. Another example of a putative G protein-independent modulator is cholesterol. Cholesterol, which accounts for up to 50% of
