Abstract 19826: Cardiac Potassium Channel IKs Regulation by Isoform Specific PKC: Implications for Long QT Syndrome
Background: The cardiac voltage-gated potassium channel (IKs) is composed of KCNQ1 and KCNE1 subunits. Mutations in the KCNQ1 gene lead to the most common form of inherited cardiac arrhythmia, Long QT type 1 (LQT1). Protein kinase C (PKC) is activated in response to stress stimulus and is chronically activated in heart disease, but little is known about IKs regulation by prolonged PKC activation.
Methods: GFP-KCNQ1 and KCNE1 subunits were co-transfected with alpha1 adrenergic receptor (α1-AR) in HEK293T cells. Channel localization was measured using confocal microscopy and biotinylation technique.
Results: To determine IKs membrane expression regulation by sustained PKC stimulation (hours) we both stimulated α1-AR and directly stimulated calcium dependent (cPKC) and calcium independent PKC isoforms. Our results show that: 1) prolonged receptor stimulation strongly decreased IKs membrane expression. 2) Prolonged stimulation of cPKC but not the calcium independent isoform PKCε mimicked the effect of receptor stimulation. 3) General PKCβ and PKCβII inhibitors, but not PKCα or PKCβI inhibitors blocked the effect of cPKC. Many LQT1 mutations have decreased membrane expression. In order to investigate the implication of PKCβII regulation of IKs membrane expression to LQT1 syndrome we studied 8 LQT1 associated mutations. For two LQT1 mutants, PKCβ inhibition restored membrane expression, both in the presence and absence of the WT subunit, suggesting an increased sensitivity to basal PKCβ activity. Surprisingly, for one mutant membrane expression was decreased by PKCβ inhibition.
Conclusions: Our results indicate that membrane expression of IKs is decreased in response to PKCβII isoform stimulation. This is particularly important because PKCβ expression and activation are strongly increased in heart disease. Specific inhibition of PKCβ restored IKs channel localization for two out of eight LQT1 mutant channels tested. Thus, our results suggest that PKCβII inhibition may protect against QT prolongation and may serve as a novel mutation-specific target for treatment of LQT1 patients.
Author Disclosures: C. Kaplan: None. C.M. Lopes: None.
- © 2016 by American Heart Association, Inc.