(A) The ionic current through KCNQ2/3 was not decreased after depolarization when coexpressed with the mutant R253K-R254K. (B) Ci-VSP is shown to be expressed because its sensing currents can be observed immediately after depolarization. (C) The phosphatase-inactivated mutant R253K-R254K-C363S was expressed alone to study sensing currents. The R253K-R254K-C363S mutant exhibits ON sensing currents that look very similar to those observed from the C363S mutant, although the OFF currents did not display the typical change in mode, observed with the C363S mutant (see Fig. 3). Pulses range from −100 to +100 mV. HP = −90 mV for ionic currents and −60 mV for sensing currents.