In vivo analysis of Kvβ2 function in Xenopus embryonic myocytes

Kv1 potassium channels consist of pore‐forming α subunits as well as auxiliary β subunits. In heterologous systems, Kv1α subunits suffice for induction of voltage‐dependent potassium current ( I Kv ). Although Kv1 channels can be expressed without auxiliary subunits in heterologous systems, coexpression with Kvβ subunits has dramatic effects on surface expression and kinetic properties. Much less is known about the functional roles of Kvβ subunits in vivo , despite their presence in the majority of native Kv1 channel complexes. We used an antisense approach to probe the contribution of Kvβ2 subunits to native Kv1 channel function in embryonic myocytes. We compared the effects of antisense Kvβ2 treatment on the whole cell I Kv to those produced by overexpression of a dominant‐negative Kv1α subunit. The reductions in the maximal potassium conductance produced by antisense Kvβ2 treatment and elimination of Kv1α subunit function were not significantly different from each other. In addition, simultaneous elimination of Kv1α and Kvβ2 subunit function resulted in no further reduction of the maximal conductance. The Kv channel complexes targeted by Kvβ2 and/or Kv1α subunit elimination contributed to action potential repolarization because elimination of either or both subunits led to increases in the duration of the action potential. As for potassium conductance, the effects of elimination of both α and β subunits on the duration of the action potential were not additive. Taken together, the results suggest that Kv1 potassium channel complexes in vivo have a strong requirement for both α and β subunits.