Up-Regulation of Voltage Gated K+ Channels Kv1.3 and Kv1.5 by Protein Kinase PKB/Akt

Abstract

Background: The voltage gated K+ channels Kv1.3 and Kv1.5 contribute to the orchestration of cell proliferation. Kinases participating in the regulation of cell proliferation include protein kinase B (PKB/Akt). The present study thus explored whether PKB/Akt modifies the abundance and function of Kv1.3 and Kv1.5.

Methods: Kv1.3 or Kv1.5 was expressed in Xenopus laevis oocytes with or without wild-type PKB/Akt, constitutively active T308D/S473DPKB/Akt or inactive T308A/S473APKB/Akt. The channel activity was quantified utilizing dual electrode voltage clamp. Moreover, HA-tagged Kv1.5 protein was determined utilizing chemiluminescence.

Results: Voltage gated K+ currents were observed in Kv1.3 or Kv1.5 expressing oocytes but not in water-injected oocytes or in oocytes expressing PKB/Akt alone. Co-expression of PKB/Akt or T308D/S473DPKB/Akt, but not co-expression of T308A/S473APKB/Akt significantly increased the voltage gated current in both Kv1.3 and Kv1.5 expressing oocytes. As shown for Kv1.5, co-expression of PKB/Akt enhanced the channel protein abundance in the cell membrane. In Kv1.5 expressing oocytes voltage gated current decreased following inhibition of carrier insertion by brefeldin A (5 µM) to similarly low values in the absence and presence of PKB/Akt, suggesting that PKB/Akt stimulated carrier insertion into rather than inhibiting carrier retrieval from the cell membrane.

Conclusion: PKB/Akt up-regulates both, Kv1.3 and Kv1.5 K+ channels.