CLH-3b is inhibited by GCK-3. (A) Examples of whole cell currents in HEK293 cells coexpressing CLH-3b and functional or KD GCK-3. Currents were evoked by stepping membrane voltage for 1 s between −140 and +60 mV in 20-mV increments from a holding potential of 0 mV. Test pulses were followed by a 1-s interval at 0 mV. (B) Current-to-voltage relationships of CLH-3b coexpressed with functional or KD GCK-3. Coexpression of CLH-3b and GCK-3 significantly (P < 0.001) reduced current density over the entire range of potentials where the channels were active. Values are means ± SE (n = 8–12). (C) Activation voltages and 50% rise times of whole cell currents in cells coexpressing CLH-3b and KD GCK-3 or GCK-3. Values were recorded before and 1 min after exposure to a hypotonic bath. Rise times were measured after current activation at −100 mV. (D) Effect of cell swelling on current amplitude in cells coexpressing CLH-3b and KD GCK-3 or GCK-3. Currents were recorded at −100 mV before and 1 min after exposure to a hypotonic bath. Values are means ± SE (n = 8–12). *, P < 0.0001 compared with non-swollen (i.e., isotonic) cells expressing CLH-3b and KD GCK-3. †, P < 0.005 compared with non-swollen cells expressing CLH-3b and GCK-3.