Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester, 601 Elmwood Avenue, Rochester, NY 14642, United States of America.
Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester, 601 Elmwood Avenue, Rochester, NY 14642, United States of America.
J Mol Cell Cardiol. 2020 Jan;138:283-290. doi: 10.1016/j.yjmcc.2019.10.010. Epub 2019 Nov 27.
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.
缓慢电压门控钾通道（IKs）由 KCNQ1 和 KCNE1 亚基组成，是心脏复极化的主要电流之一。蛋白激酶 C（PKC）的激活与心脏心律失常有关。虽然已经证明 PKC 是许多心脏通道的调节剂，包括 IKs，但对于 PKC 的特定同工型对通道的调节知之甚少。在这里，我们研究了不同 PKC 同工型对 IKs 通道膜定位和功能的作用。我们的研究集中在那些响应 Gq 偶联受体（GqPCR）刺激而向质膜易位的 PKC 同工型上：PKCα、PKCβI、PKCβII 和 PKCε。已经证明，GqPCR 的长期刺激会降低 IKs 的膜表达，但每种 PKC 同工型的具体作用尚不清楚。在这里，我们表明钙依赖性 PKC（cPKC）的刺激而不是 PKCε模拟受体激活。此外，我们表明，一般的 PKCβ（LY-333531）和 PKCβII 抑制剂，但不是 PKCα 或 PKCβI 抑制剂，阻断了 cPKC 对 KCNQ1/KCNE1 通道的作用。PKCβ 抑制剂也阻断了 GqPCR 介导的心肌细胞中通道膜表达的减少。使用组成型激活的 PKCβII 构建体直接激活 PKCβII 模拟激动剂诱导的膜表达和通道功能下降，而显性负 PKCβII 则没有影响。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 膜定位的特异性调节剂。PKCβII 的表达和激活在许多疾病状态下（包括心脏病和糖尿病）显著增加。因此，我们的结果表明，PKCβII 抑制可能有助于预防与心脏病相关的获得性 QT 延长。
