Figure 5.
Activation of immobile GIRK channels by immobile GPCRs and G-protein heterotrimers. A, Normalized current traces recorded from HEK 293 cells expressing pH-A1R, ECFP-TM-Gαi1, Gβ1, Gγ2, and pH-GIRK4*; cells were treated overnight with PTX (500 ng/dish) to inactivate native G-proteins. Application of adenosine (50 μm; horizontal bar) reversibly activated pH-GIRK4* in both control and avidin-cross-linked cells. Application of barium (Ba2+; 200 μm) blocked basal current pH-GIRK4*, and currents are normalized as fold-activation over basal. B, Summary data from experiments identical with that shown in A. Activation half-time (T1/2) and fold activation over basal were not significantly different in control (n = 9) and avidin-cross-linked (n = 9) cells (p = 0.68 and 0.74). The time to half current recovery after agonist washout was also not significantly different between the two groups (biotin, 36 ± 5 s, vs avidin, 27 ± 7 s; p = 0.26). Error bars indicate SEM.