Naruse Keiji, Tang Qiong-Yao, Sokabe Masahiro
Department of Cardiovascular Physiology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan.
Biochem Biophys Res Commun. 2009 Aug 7;385(4):634-9. doi: 10.1016/j.bbrc.2009.05.105. Epub 2009 May 29.
We previously reported that SAK(CA), a stretch-activated, large-conductance, calcium- and voltage-activated potassium (BK(Ca)) channel is present in chick embryonic heart. Here, we cloned SAK(CA) and identified that Stress-Axis Regulated Exon (STREX) is responsible for the stretch sensitivity. Single patch-clamp recordings from CHO cells transfected with the cloned SAK(CA) showed stretch sensitivity, whereas deletion of the STREX insert diminished the stretch sensitivity of the channel. Sequence analysis revealed that the ERA (672-674) sequence of the STREX is indispensable for channel stretch sensitivity and single amino acid substitution from Ala674 to Thr674 completely eliminated the stretch sensitivity. Co-expression of chick STREX-EGFP and SAK(CA) in CHO cells, induced a strong GFP signal in the cell membrane and inhibited the stretch sensitivity significantly. These results suggest that SAK(CA) senses membrane tension through an interaction between STREX and submembranous components.
我们之前报道过，SAK(CA)，一种牵张激活、大电导、钙和电压激活的钾（BK(Ca)）通道存在于鸡胚心脏中。在此，我们克隆了SAK(CA)，并确定应激轴调节外显子（STREX）负责牵张敏感性。对转染了克隆的SAK(CA)的CHO细胞进行的单膜片钳记录显示出牵张敏感性，而缺失STREX插入片段则降低了通道的牵张敏感性。序列分析表明，STREX的ERA（672 - 674）序列对于通道牵张敏感性必不可少，并且从Ala674到Thr674的单个氨基酸替换完全消除了牵张敏感性。鸡STREX - EGFP与SAK(CA)在CHO细胞中共表达，在细胞膜中诱导出强烈的GFP信号，并显著抑制牵张敏感性。这些结果表明，SAK(CA)通过STREX与膜下成分之间的相互作用感知膜张力。
