KChAP/Kv beta 1.2 interactions and their effects on cardiac Kv channel expression

KChAP and voltage-dependent K+ (Kv) beta -subunits are two different types of cytoplasmic proteins that interact with Kv channels. KChAP acts as a cha perone for Kv2.1 and Kv4.3 channels. It also binds to Kv1.x channels but, w ith the exception of Kv1.3, does not increase Kv1.x currents. Kv beta -subu nits are assembled with Kv1.x channels; they exhibit "chaperone-like" behav ior and change gating properties. In addition, KChAP and Kv beta -subunits interact with each other. Here we examine the consequences of this interact ion on Kv currents in Xenopus oocytes injected with different combinations of cRNAs, including Kv beta1.2, KChAP, and either Kv1.4, Kv1.5, Kv2.1, or K v4.3. We found that KChAP attenuated the depression of Kv1.5 currents produ ced by Kvb1.2, and Kvb1.2 eliminated the increase of Kv2.1 and Kv4.3 curren ts produced by KChAP. Both KChAP and Kvb1.2 are expressed in cardiomyocytes , where Kv1.5 and Kv2.1 produce sustained outward currents and Kv4.3 and Kv 1.4 generate transient outward currents. Because they interact, either KChA P or Kvb1.2 may alter both sustained and transient cardiac Kv currents. The interaction of these two different classes of modulatory proteins may cons titute a novel mechanism for regulating cardiac K+ currents.