We next examined whether GIRK2 channels could be directly activated by PIP2 applied in real-time. Previous studies demonstrated that analogs of PIP2 with shorter tails, e.g., diC8-PIP2, can also activate GIRK channels38. With GIRK2-containing liposomes, the acute addition of diC8-PIP2 (30 μM) revealed potent activation, i.e., increase in the rate of quenching (Fig. 1c). To quantify the change in K+ flux, we measured both the steady state fluorescence at the end of 15 minutes and the rate of quenching following the addition of diC8-PIP2 (see methods for details). Using both analyses, diC8-PIP2 clearly activates GIRK2 channels (Figs 1d and 2a,b).
