Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada.
Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
Mol Pharmacol. 2019 Jul;96(1):1-12. doi: 10.1124/mol.118.115188. Epub 2019 Apr 23.
The () encodes the channel that conducts the rapidly activating delayed rectifier potassium current (I) in the heart. Reduction in I causes long QT syndrome, which can lead to fatal arrhythmias triggered by stress. One potential link between stress and hERG function is protein kinase C (PKC) activation; however, seemingly conflicting results regarding PKC regulation of hERG have been reported. We investigated the effects of PKC activation using phorbol 12-myristate 13-acetate (PMA) on hERG channels expressed in human embryonic kidney cell line 293 (HEK293) cells and I in isolated neonatal rat ventricular myocytes. Acute activation of PKC by PMA (30 nM, 30 minutes) reduced both hERG current (I) and I Chronic activation of PKC by PMA (30 nM, 16 hours) increased I in cardiomyocytes and the expression level of hERG proteins; however, chronic (30 nM, 16 hours) PMA treatment decreased I, which became larger than untreated control I after PMA removal for 4 hours. Deletion of amino acid residues 2-354 (Δ2-354 hERG) or 1-136 of the N terminus (ΔN 136 hERG) abolished acute PMA (30 nM, 30 minutes)-mediated I reduction. In contrast to wild-type hERG channels, chronic activation of PKC by PMA (30 nM, 16 hours) increased both Δ2-354 hERG and ΔN136 hERG expression levels and currents. The increase in hERG protein was associated with PKC-induced phosphorylation (inhibition) of Nedd4-2, an E3 ubiquitin ligase that mediates hERG degradation. We conclude that PKC regulates hERG in a balanced manner, increasing expression through inhibiting Nedd4-2 while decreasing current through targeting a site(s) within the N terminus.
该基因编码心脏中快速激活延迟整流钾电流（I）的通道。I 的减少会导致长 QT 综合征，从而导致应激引发的致命心律失常。应激和 hERG 功能之间的一个潜在联系是蛋白激酶 C（PKC）的激活；然而，关于 PKC 对 hERG 的调节，已经报道了看似相互矛盾的结果。我们使用佛波醇 12-肉豆蔻酸 13-乙酸酯（PMA）研究了 PKC 激活对在人胚肾细胞系 293（HEK293）细胞中表达的 hERG 通道和分离的新生大鼠心室肌细胞中的 I 的影响。PMA（30 nM，30 分钟）的 PKC 急性激活减少了 hERG 电流（I）和 I。PMA（30 nM，16 小时）的 PKC 慢性激活增加了心肌细胞中的 I 和 hERG 蛋白的表达水平；然而，慢性（30 nM，16 小时）PMA 处理减少了 I，在去除 PMA 4 小时后，I 变得比未处理的对照 I 更大。缺失氨基酸残基 2-354（Δ2-354 hERG）或 N 端的 1-136（ΔN 136 hERG）消除了急性 PMA（30 nM，30 分钟）介导的 I 减少。与野生型 hERG 通道相反，PMA（30 nM，16 小时）的 PKC 慢性激活增加了 Δ2-354 hERG 和 ΔN136 hERG 的表达水平和电流。hERG 蛋白的增加与 PKC 诱导的 Nedd4-2 磷酸化（抑制）有关，Nedd4-2 是一种介导 hERG 降解的 E3 泛素连接酶。我们的结论是，PKC 以一种平衡的方式调节 hERG，通过抑制 Nedd4-2 增加表达，同时通过靶向 N 端的一个（或多个）位点减少电流。
