To confirm that GIRK2 expression contributes to potassium channel function, we treated iN cultures with ML297, a selective activator of the GIRK1/GIRK2 heterotetramer complex [43, 44]. Results show that the magnitude and frequency of native (basal) currents observed in human iN were relatively small (Fig. 2D.b), with only 6.8% of the neurons responding to a shift in membrane potential holding current (~10 pA). However, cells overexpressing GIRK2 (identified by mCherry co-expression; Fig. 2D.c), exhibited an increased frequency of response (GIRK currents) to 30% of the cells after ML297 addition (Fig. 2D.b) without a change in magnitude (Fig. 2D.e). Importantly, GIRK activation affected excitability of the neurons by shifting resting membrane potential to more negative values (Fig. 2D.d), affecting the ability of neurons to fire APs when induced (Fig. 2D.f). We conclude that increased KCNJ6 expression affects neuronal excitability by altering GIRK channel activity.
