Time- and voltage-dependent modulation of a Kv1.4 channel by a β-subunit (Kvβ3) cloned from ferret ventricle

In mammals, voltage-gated K⁺ channels can be made of complexes containing α-subunits similar to the Shaker K⁺ channel and smaller cytoplasmic β- subunits. Recent studies have suggested that these ancillary β-subunits can modulate K⁺ channel gating properties. We studied the effects of a K⁺ channel β-subunit, Kvβ3, coexpressed with a Kv1.4 α-subunit, FK1, on the time and voltage dependence of channel activation, inactivation, recovery from inactivation, and deactivation, using an oocyte expression system. Kvβ3 was found to accelerate both the fast and the slow component of Kv1.4 inactivation. Kvβ3 also altered the relative contributions of the two components of inactivation by increasing the contribution of the slow component to the inactivation process. Kvβ3 slowed recovery from inactivation for Kv1.4, but not for a Kv1.4 deletion mutant lacking N-type inactivation. Finally, steady-state activation and the time course of Kv1.4 current activation were not strongly influenced by Kvβ3; however, deactivation was slowed in the presence of Kvβ3. This study suggests that Kvβ3 alters channel states which follow activation.