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: PKCα, PKCβI, PKCβII and PKCε. 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 PKCε mimic receptor activation. In addition, we show that general PKCβ (LY-333531) and PKCβII inhibitors but not PKCα or PKCβI inhibitors blocked the effect of cPKC on the KCNQ1/KCNE1 channel. PKCβ inhibitors also blocked GqPCR-mediated decrease in channel membrane expression in cardiomyocytes. Direct activation of PKCβII using constitutively active PKCβII construct mimicked agonist-induced decrease in membrane expression and channel function, while dominant negative PKCβII showed no effect. This suggests that the KCNQ1/KCNE1 channel was not regulated by basal levels of PKCβII activity. Our results indicate that PKCβII is a specific regulator of IKs membrane localization. PKCβII expression and activation are strongly increased in many disease states, including heart disease and diabetes. Thus, our results suggest that PKCβII inhibition may protect against acquired QT prolongation associated with heart disease.

中文翻译：

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PKCβII特异性调节KCNQ1 / KCNE1通道膜的定位。

慢速电压门控钾离子通道（IKs）由KCNQ1和KCNE1亚基组成，是心脏中的主要复极化电流之一。蛋白激酶C（PKC）的激活与心律不齐有关。尽管已证明PKC是包括IKs在内的许多心脏通道的调节剂，但关于通过PKC的特定同工型调节通道的了解甚少。在这里，我们研究了不同的PKC亚型对IKs通道膜定位和功能的作用。我们的研究集中在响应Gq偶联受体（GqPCR）刺激而移位到质膜的PKC亚型：PKCα，PKCβI，PKCβII和PKCε。长期刺激GqPCRs已显示可降低IKs膜表达，但每种PKC亚型的具体作用尚不清楚。在这里，我们显示了PKC（cPKC）的钙依赖性同工型的刺激，但不是PKCε模拟受体激活。此外，我们显示了一般的PKCβ（LY-333531）和PKCβII抑制剂，但没有PKCα或PKCβI抑制剂阻止了cPKC对KCNQ1 / KCNE1通道的作用。PKCβ抑制剂还阻断了心肌细胞中GqPCR介导的通道膜表达下降。使用组成型活性PKCβII构建体直接激活PKCβII可以模拟激动剂诱导的膜表达和通道功能下降，而显性负PKCβII则没有作用。这表明KCNQ1 / KCNE1通道不受PKCβII活性的基础水平调节。我们的结果表明PKCβII是IKs膜定位的特定调节剂。在许多疾病状态下，PKCβII的表达和激活都大大增加，包括心脏病和糖尿病。因此，我们的结果表明，PKCβII抑制作用可以预防与心脏病有关的后天QT延长。