Downregulation of the HERG (KCNH2) K+ channel by ceramide:: evidence for ubiquitin-mediated lysosomal degradation
Downregulation of the HERG (KCNH2) K+ channel by ceramide:: evidence for ubiquitin-mediated lysosomal degradation
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DOI：
10.1242/jcs.02635
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发表时间：
2005-11-15
影响因子：
4
通讯作者：
Törnquist, K
中科院分区：
文献类型：
--
作者：
Chapman, H;Ramström, C;Törnquist, K
HERG（KCNH 2）钾通道是延迟整流电流（I-kr）快速成分的基础，该电流有助于心脏动作电位的复极化。HERG基因突变可导致遗传性短QT和长QT综合征，诱发室性心律失常和心源性猝死。HERG主要在心肌细胞的细胞膜中表达，但也在一系列其他细胞的细胞膜中被鉴定，包括平滑肌和神经元。然而，调节表面表达的机制尚未阐明。在这里，我们表明，使用稳定的HERG表达HEK 293细胞，神经酰胺引起HERG电流的时间依赖性降低，这不是由于通道的门控特性的变化。HERG通道蛋白的表面表达被神经酰胺降低，如表面蛋白的生物素化、蛋白质印迹和免疫细胞化学所示。神经酰胺刺激后HERG蛋白的快速下降是由于蛋白泛素化及其与溶酶体的结合。结果表明，HERG的表面表达受到严格调控，神经酰胺修饰HERG电流并靶向蛋白质进行溶酶体降解。
The HERG (KCNH2) potassium channel underlies the rapid component of the delayed rectifier current (I-kr), a current contributing to the repolarisation of the cardiac action potential. Mutations in HERG can cause the hereditary forms of the short-QT and long-QT syndromes, predisposing to ventricular arrhythmias and sudden cardiac death. HERG is expressed mainly in the cell membrane of cardiac myocytes, but has also been identified in cell membranes of a range of other cells, including smooth muscle and neurones. The mechanisms regulating the surface expression have however not yet been elucidated. Here we show, using stable HERG-expressing HEK 293 cells, that ceramide evokes a time-dependent decrease in HERG current which was not attributable to a change in gating properties of the channel. Surface expression of the HERG channel protein was reduced by ceramide as shown by biotinylation of surface proteins, western blotting and immunocytochemistry. The rapid decline in HERG protein after ceramide stimulation was due to protein ubiquitylation and its association with lysosomes. The results demonstrate that the surface expression of HERG is strictly regulated, and that ceramide modifies HERG currents and targets the protein for lysosomal degradation.