Cysteine-modifying reagents alter the gating of the rat cloned potassium channel Kv1.4

The effects of cysteine-modifying reagents on the gating of rat cloned Kv1.4 channels expressed in HEK-293 cells were examined using the whole-cell patch-clamp technique, Cells transfected with Kv1.4 expressed a rapidly inactivating K+ current with a midpoint of activation of -31 mV and a slope factor of 5 mV measured with tail current protocols in 35 mM Rb+ external solutions. The cysteine-specific oxidizing agents 2,2'-dithiobis-5-nitropyridine (DTBNP, 50 mu M) and chloramine-T (CL-T, 500 mu M) removed inactivation of Kv1.4. These effects were reversed by the reducing agent dithiothreitol (DTT, 10 mM). III addition, DTBNP and CL-T also slowed Kv1.4 deactivation and increased the voltage sensitivity of deactivation. The action of cysteine-modifying reagents on Kv1.4 suggests that redox state affects channel gating, with oxidation tending to stabilize the open state of the channel, both by removing inactivation and slowing deactivation.