Dyachenko Vitaly, Zuzarte Marylou, Putzke Caroline, Preisig-Müller Regina, Isenberg Gerrit, Daut Jürgen
Institut für Physiologie, Universität Marburg, Deutschhausstr. 2, 35037 Marburg, Germany.
Cardiovasc Res. 2006 Jan;69(1):86-97. doi: 10.1016/j.cardiores.2005.08.018. Epub 2005 Oct 24.
The biophysical properties and the regulation of the two-pore-domain potassium channel TREK-1 were studied in rat cardiomyocytes.
RT-PCR, immunohistochemistry and patch-clamp recording were performed in isolated rat ventricular cardiomyocytes. In some whole-cell-clamp experiments the myocytes were mechanically stretched using a glass stylus.
We found strong expression of a splice variant of TREK-1 in rat heart. Immunohistochemistry with antibodies against TREK-1 showed localization of the channel in longitudinal stripes at the external surface membrane of cardiomyocytes. When the cardiomyocytes were mechanically stretched, an outwardly rectifying K+ current component could be detected in whole-cell recordings. In single-channel recordings with symmetrical high K+ solution, two TREK-like channels with 'flickery-burst' kinetics were found: a 'large conductance' K+ channel (132+/-5 pS at positive potentials) and a novel 'low-conductance' channel (41+/-5 pS at positive potentials). The low-conductance channel could be activated by negative pressure in inside-out patches, positive pressure in outside-out patches, intracellular acidification and application of arachidonic acid. Its open probability was strongly increased by depolarization, due to decreased duration of gaps between bursts. The biophysical properties of the two cardiac TREK-like channels were similar to those of TREK-1 channels expressed in HEK293 cells, which both displayed low- and high-conductance modes.
Our results suggest that the two TREK-like channels found in rat cardiomyocytes may reflect two different operating modes of TREK-1. The novel low-conductance channels described here may represent the major operating mode of TREK-1. The current flowing through mechanogated TREK-1 channels may serve to counterbalance the inward current flowing through stretch-activated non-selective cation channels during the filling phase of the cardiac cycle and thus to prevent the occurrence of ventricular extrasystoles.
在大鼠心肌细胞中研究双孔结构域钾通道TREK - 1的生物物理特性及其调控机制。
对分离的大鼠心室肌细胞进行逆转录聚合酶链反应（RT-PCR）、免疫组织化学和膜片钳记录。在一些全细胞钳实验中，使用玻璃针机械拉伸心肌细胞。
我们发现TREK - 1的一种剪接变体在大鼠心脏中高表达。用抗TREK - 1抗体进行免疫组织化学显示该通道定位于心肌细胞外表面膜的纵向条纹处。当心肌细胞被机械拉伸时，在全细胞记录中可检测到外向整流性钾电流成分。在对称高钾溶液的单通道记录中，发现了两个具有“闪烁式爆发”动力学的TREK样通道：一个“大电导”钾通道（正向电位时为132±5 pS）和一个新的“低电导”通道（正向电位时为41±5 pS）。低电导通道可被内向外膜片的负压、外向内膜片的正压、细胞内酸化以及花生四烯酸的应用所激活。由于爆发之间间隙持续时间的缩短，其开放概率因去极化而显著增加。两种心脏TREK样通道的生物物理特性与在人胚肾293（HEK293）细胞中表达的TREK - 1通道相似，两者均表现出低电导和高电导模式。
我们的结果表明，在大鼠心肌细胞中发现的两种TREK样通道可能反映了TREK - 1的两种不同运作模式。这里描述的新的低电导通道可能代表了TREK - 1的主要运作模式。在心动周期的充盈期，流经机械门控TREK - 1通道的电流可能用于抵消流经牵张激活的非选择性阳离子通道的内向电流，从而防止室性期前收缩的发生。
