Effect of the I_to activator NS5806 on cloned K_v4 channels depends on the accessory protein KChIP2

Abstract

BACKGROUND AND PURPOSE The compound NS5806 increases the transient outward current (Ito) in canine ventricular cardiomyocytes and slows current decay. In human and canine ventricle, Ito is thought to be mediated by KV4.3 and various ancillary proteins, yet, the exact subunit composition of Ito channels is still debated. Here we characterize the effect of NS5806 on heterologously expressed putative Ito channel subunits and other potassium channels. EXPERIMENTAL APPROACH Cloned KV4 channels were co‐expressed with KChIP2, DPP6, DPP10, KCNE2, KCNE3 and KV1.4 in Xenopus laevis oocytes or CHO‐K1 cells. KEY RESULTS NS5806 increased KV4.3/KChIP2 peak current amplitudes with an EC50 of 5.3 ± 1.5µM and significantly slowed current decay. KCNE2, KCNE3, DPP6 and DPP10 modulated KV4.3 currents and the response to NS5806, but current decay was slowed only in complexes containing KChIP2. The effect of NS5806 on KV4.2 was similar to that on KV4.3, and current decay was only slowed in presence of KChIP2. However, for KV4.1, the slowing of current decay by NS5806 was independent of KChIP2. KV1.4 was strongly inhibited by 10 µM NS5806 and KV1.5 was inhibited to a smaller extent. Effects of NS5806 on kinetics of currents generated by KV4.3/KChIP2/DPP6 with KV1.4 in oocytes could reproduce those on cardiac Ito in canine ventricular myocytes. KV7.1, KV11.1 and Kir2 currents were unaffected by NS5806. CONCLUSION AND IMPLICATIONS NS5806 modulated KV4 channel gating depending on the presence of KChIP2, suggesting that NS5806 can potentially be used to address the molecular composition as well as the physiological role of cardiac Ito.

Identification and characterization of a transient outward K+ current in human induced pluripotent stem cell-derived cardiomyocytes

“…We have previously shown that the I to agonist NS5806 works through KChIP2 to produce a pharmacological enhancement of I to carried through K v 4.3 channels [28,36], although application of the agonist to K v 1.4 channels resulted in blockade of the current. In the next series of experiments, we attempted to enhance I to in hiPSC-CM by application of 10 µM NS5806 (Fig.…”

Cardiac Potassium Channel Subtypes: New Roles in Repolarization and Arrhythmia

“…Furthermore, in coronary-perfused wedge preparations, NS5806 recapitulated the features of Brugada Syndrome phenotype visible as increase in phase 1 and notch amplitudes (62). The effect was later shown to be dependent on the presence of the I to subunit K channel interacting protein (KChIP) 2 (65,263). Accordingly, the transmural KChIP2 gradient across the ventricular wall led to differential effects of NS5806 in epi-, mid-, and endocardial cells (65).…”

Type 2 diabetes induces subendocardium-predominant reduction in transient outward K+ current with downregulation of Kv4.2 and KChIP2

“…8). KChIP2 modulates the function of Kv channels by modifying trafficking of Kv channel proteins and the kinetics of inactivation and also by acceleration of the kinetics from recovery from inactivation (1,12,15,23). Although specific effects of KChIP2 deletion on the fast and slow components of I to recovery have not been systematically examined, a previous study (12) showed that the effect of a lack of KChIP2 on the fast component of recovery of I to was more predominant than that on the slow component.…”