Gnatenco Carmen, Han Jaehee, Snyder Ann K, Kim Donghee
Department of Physiology and Biophysics, Finch University of Health Sciences/The Chicago Medical School, 3333 Green Bay Road, North Chicago, IL 60064-3095, USA.
Brain Res. 2002 Mar 22;931(1):56-67. doi: 10.1016/s0006-8993(02)02261-8.
Background K+ channels whose subunit contains four transmembrane segments and two pore-forming domains (4TM/2P) have been cloned recently. We studied whether 4TM/2P K+ channels are functionally expressed in astrocytes that are known to have a large background (resting) K+ conductance and a large resting membrane potential. Reverse transcriptase-PCR analysis showed that, among five 4TM/2P K+ channels examined, TASK-1, TASK-3 and TREK-2 mRNAs were expressed in cultured astrocytes from rat cortex. In cell-attached patches, we mainly observed three K+ channels with single-channel conductances of 30, 117 and 176 pS (-40 mV) in symmetrical 140 mM KCl. The 30 pS channel was the inward rectifying K+ channel that has been previously described in astrocytes. The 117 pS K+ channel also showed inward rectification and was insensitive to 1 mM tetraethylammonium and 1 mM 4-aminopyridine. The 176 pS channel was the Ca2+-activated K+ channel. The 117 pS K+ channel was determined to be TREK-2, as judged by its electrophysiological properties and activation by membrane stretch, free fatty acids and intracellular acidosis. In approximately 50% of astrocytes in culture, whole-cell K+ current increased markedly following application of arachidonic acid. The number of TREK-2 channels in these cells was estimated to be approximately 500-1000/cell. Our results show that TREK-2 is functionally expressed in cortical astrocytes in culture, and suggest that TREK-2 may be involved in K+ homeostasis of astrocytes during pathological states.
背景 最近已克隆出其亚基包含四个跨膜片段和两个成孔结构域（4TM/2P）的钾离子通道。我们研究了4TM/2P钾离子通道是否在已知具有大背景（静息）钾离子电导和大静息膜电位的星形胶质细胞中功能性表达。逆转录聚合酶链反应分析表明，在所检测的五个4TM/2P钾离子通道中，TASK-1、TASK-3和TREK-2 mRNA在大鼠皮质培养的星形胶质细胞中表达。在细胞贴附式膜片钳中，我们主要观察到三个钾离子通道，在对称的140 mM KCl中，单通道电导分别为30、117和176 pS（-40 mV）。30 pS通道是先前在星形胶质细胞中描述过的内向整流钾离子通道。117 pS钾离子通道也表现出内向整流，并且对1 mM四乙铵和1 mM 4-氨基吡啶不敏感。176 pS通道是钙激活钾离子通道。根据其电生理特性以及膜拉伸、游离脂肪酸和细胞内酸中毒对其的激活作用判断，117 pS钾离子通道为TREK-2。在培养的星形胶质细胞中，约50%的细胞在应用花生四烯酸后全细胞钾离子电流显著增加。这些细胞中TREK-2通道的数量估计约为500 - 1000个/细胞。我们的结果表明，TREK-2在培养的皮质星形胶质细胞中功能性表达，并提示TREK-2可能在病理状态下参与星形胶质细胞的钾离子稳态。
