Siemen D, Loupatatzis C, Borecky J, Gulbins E, Lang F
Department of Physiology, Tuebingen, Gmelinstrasse 5, D-72076, Germany.
Biochem Biophys Res Commun. 1999 Apr 13;257(2):549-54. doi: 10.1006/bbrc.1999.0496.
A single channel current was recorded from mitoplasts (i.e., inner mitochondrial membrane) of the human glioma cell line LN229 using patch-clamp techniques in the mitoplast-attached mode. We frequently found a 295 +/- 18 pS channel that showed a straight i-E relation in the range +/-60 mV in 150 mM KCl solutions on either side of the mitoplast. If KCl in the bath was exchanged against NaCl, outward currents were undetectable, indicating potassium selectivity. Channel activity determined as open probability increased with increasing Ca2+ concentrations (EC50 = 0.9 microM at 60 mV). Open probability was voltage dependent. An e-fold increase of time spent in the open state was induced by a depolarization of 10.5 mV. Open probability was decreased by charybdotoxin concentration and voltage dependently (EC50 = 1.4 nM). In conclusion, we show for the first time that the inner mitochondrial membrane in human glioma cells contains a calcium-dependent K channel of the BK-type.
采用膜片钳技术的线粒体附着模式，从人胶质瘤细胞系LN229的线粒体（即线粒体内膜）记录单通道电流。我们经常发现一个295±18 pS的通道，在150 mM KCl溶液中，线粒体内外两侧±60 mV范围内呈现线性电流-电压关系。如果将浴槽中的KCl换成NaCl，则检测不到外向电流，表明该通道具有钾选择性。以开放概率确定的通道活性随Ca2+浓度增加而增加（60 mV时EC50 = 0.9 μM）。开放概率依赖于电压。10.5 mV的去极化可使通道开放时间增加一倍。开放概率受大电导钙激活钾通道阻断剂（charybdotoxin）浓度影响且依赖于电压（EC50 = 1.4 nM）。总之，我们首次表明人胶质瘤细胞的线粒体内膜含有BK型钙依赖性钾通道。
