Department of Physiology, Queen's University, 18 Stuart Street, Kingston, Ontario, Canada.
Circ Res. 2010 Apr 2;106(6):1072-82. doi: 10.1161/CIRCRESAHA.109.215970. Epub 2010 Feb 4.
The human ether-a-go-go-related gene (HERG) encodes the pore-forming subunits of the rapidly activating delayed rectifier potassium channel (I(Kr)) that is important for cardiac repolarization. Dysfunction of HERG causes long QT syndrome (LQTS) which can lead to sudden cardiac death. We previously showed that a reduction in extracellular K(+) concentration (K(+)) prolongs QT intervals in intact rabbits, and decreases the cell surface density of I(Kr) in rabbit ventricular myocytes and of the HERG channel expressed in human embryonic kidney (HEK) cells.
The goal of the present study was to gain insights into the mechanisms for low K(+) induced reduction in HERG expression levels.
Using patch clamp, Western blot and confocal imaging methods, we demonstrated that at low K(+), the HERG channel entered a novel nonconducting state. Furthermore, this novel functional state triggered rapid internalization and degradation of the cell surface HERG channels. Thus, our data demonstrated for the first time a direct link between a gating state and the plasma membrane stability of an ion channel, HERG. Using HERG-permeant cations and site-directed mutagenesis, we identified the sites in the channel which are involved in the K(+)(o) dependence of HERG channels.
Extracellular K(+) is a prerequisite for HERG function and membrane stability.
人类 ether-a-go-go 相关基因（HERG）编码快速激活延迟整流钾通道（I(Kr)）的孔形成亚基，该通道对于心脏复极化很重要。HERG 功能障碍会导致长 QT 综合征（LQTS），从而导致心脏性猝死。我们之前的研究表明，降低细胞外钾离子浓度(K(+))会延长完整兔子的 QT 间期，并降低兔心室肌细胞中 I(Kr)的细胞表面密度和人胚肾（HEK）细胞中 HERG 通道的表达。
本研究的目的是深入了解低 K(+) 诱导 HERG 表达水平降低的机制。
通过膜片钳、Western blot 和共聚焦成像方法，我们证明在低 K(+) 下，HERG 通道进入一种新的非传导状态。此外，这种新的功能状态触发了细胞表面 HERG 通道的快速内化和降解。因此，我们的数据首次证明了门控状态与离子通道 HERG 的质膜稳定性之间的直接联系。通过使用 HERG 通透阳离子和定点突变，我们确定了通道中参与 HERG 通道对 K(+)(o) 依赖性的位点。
细胞外钾离子是 HERG 功能和膜稳定性的前提。
