Abstract 16072: Calcium-Dependent PKC Activation Inhibits Slow Repolarizing Cardiac Current by Decreasing Ion Channel Membrane Expression
Background: Sudden cardiac death due to fatal arrhythmias is a major cause of mortality in patients with congestive heart failure. Decrease in the slow delayed rectifier K+ current (IKs) is linked to increased propensity to ventricular arrhythmias observed in human failing hearts and animal models of heart failure, but the mechanisms are largely unknown. Ca2+-dependent PKC isoforms (cPKC) are strongly activated in human heart failure.
Methods: Human IKs channels were expressed in HEK293T cells and infected into isolated adult rat ventricular myocytes. IKs current was measured by patch clamp. Subcellular localization of GFP-tagged KCNQ1 subunits was observed by confocal microscopy.
Results: IKs currents were inhibited by α1-adrenergic receptor stimulation (α1-AR), application of a cPKC activator peptide, or overexpression of PKCα catalytic subunit, due to a dramatic decrease in plasma membrane localization (Figure A&B). Internalization was abolished by expression of dominant-negative dynamin. Application of a non-isoform-specific PKC inhibitors or cPKC inhibitory peptide abolished channel internalization (Figure B). Expression of the auxiliary KCNE1 subunit was necessary for the effect and mutation of a putative cPKC phosphorylation site in KCNE1 abolished inhibition. In adult ventricular myocytes, 2-hr α1-AR-cPKC stimulation strongly decreased IKs membrane expression at transverse tubule.
Conclusion: Persistent cPKC activation strongly inhibits IKs currents by decreasing channel plasma membrane expression via direct phosphorylation of the KCNE1 auxiliary subunit. Our results suggest that PKCα-dependent phosphorylation of the IKs channel contributes to QT prolongation and arrhythmogenesis in heart failure and implicate cPKC inhibitors as potential novel antiarrhythmic drugs.
- Protein kinase C
- Arrhythmias, treatment of
- Heart failure
- Alpha-adrenergic receptor blockers
- © 2011 by American Heart Association, Inc.