PKC beta II specifically regulates KCNQ1/KCNE1 channel membrane localization

摘要

The slow voltage-gated potassium channel (IKs) is composed of the KCNQ1 and KCNE1 subunits and is one of the major repolarizing currents in the heart. Activation of protein kinase C (PKC) has been linked to cardiac arrhythmias. Although PKC has been shown to be a regulator of a number of cardiac channels, including IKs, little is known about regulation of the channel by specific isoforms of PKC. Here we studied the role of different PKC isoforms on IKs channel membrane localization and function. Our studies focused on PKC isoforms that translocate to the plasma membrane in response to Gq-coupled receptor (GqPCR) stimulation: PKC alpha, PKC beta I, PKC beta II and PKC epsilon. Prolonged stimulation of GqPCRs has been shown to decrease IKs membrane expression, but the specific role of each PKC isoform is unclear. Here we show that stimulation of calcium-dependent isoforms of PKC (cPKC) but not PKC epsilon mimic receptor activation. In addition, we show that general PKC beta (LY-333531) and PKC beta II inhibitors but not PKC alpha or PKC beta I inhibitors blocked the effect of cPKC on the KCNQ1/KCNE1 channel. PKC beta inhibitors also blocked GqPCR-mediated decrease in channel membrane expression in cardiomyocytes. Direct activation of PKC beta II using constitutively active PKC beta II construct mimicked agonist-induced decrease in membrane expression and channel function, while dominant negative PKC beta II showed no effect. This suggests that the KCNQ1/KCNE1 channel was not regulated by basal levels of PKC beta II activity. Our results indicate that PKC beta II is a specific regulator of IKs membrane localization. PKC beta II expression and activation are strongly increased in many disease states, including heart disease and diabetes. Thus, our results suggest that PKC beta II inhibition may protect against acquired QT prolongation associated with heart disease.