Kang Dawon, Kim Donghee
Department of Physiology and Biophysics, Rosalind Franklin University of Medicine and Science, Chicago Medical School, 3333 Green Bay Road, North Chicago, IL 60064, USA.
Am J Physiol Cell Physiol. 2006 Jul;291(1):C138-46. doi: 10.1152/ajpcell.00629.2005. Epub 2006 Feb 22.
Dorsal root ganglion (DRG) neurons express mRNAs for many two-pore domain K(+) (K(2P)) channels that behave as background K(+) channels. To identify functional background K(+) channels in DRG neurons, we examined the properties of single-channel openings from cell-attached and inside-out patches from the cell bodies of DRG neurons. We found seven types of K(+) channels, with single-channel conductance ranging from 14 to 120 pS in 150 mM KCl bath solution. Four of these K(+) channels showed biophysical and pharmacological properties similar to TRESK (14 pS), TREK-1 (112 pS), TREK-2 (50 pS), and TRAAK (73 pS), which are members of the K(2P) channel family. The molecular identity of the three other K(+) channels could not be determined, as they showed low channel activity and were observed infrequently. Of the four K(2P) channels, the TRESK-like (14 pS) K(+) channel was most active at 24 degrees C. At 37 degrees C, the 50-pS (TREK-2 like) channel was the most active and contributed the most (69%) to the resting K(+) current, followed by the TRESK-like 14-pS (16%), TREK-1-like 112-pS (12%), and TRAAK-like 73-pS (3%) channels. In DRG neurons, mRNAs of all four K(2P) channels, as well as those of TASK-1 and TASK-3, were expressed, as judged by RT-PCR analysis. Our results show that TREKs and TRESK together contribute >95% of the background K(+) conductance of DRG neurons at 37 degrees C. As TREKs and TRESK are targets of modulation by receptor agonists, they are likely to play an active role in the regulation of excitability in DRG neurons.
背根神经节（DRG）神经元表达许多双孔结构域钾离子（K(2P)）通道的信使核糖核酸（mRNAs），这些通道表现为背景钾离子通道。为了鉴定DRG神经元中的功能性背景钾离子通道，我们研究了DRG神经元细胞体的细胞贴附式和内面向外式膜片上单通道开放的特性。我们发现了七种类型的钾离子通道，在150 mM氯化钾浴液中，其单通道电导范围为14至120皮西门子（pS）。其中四种钾离子通道表现出与TRESK（14 pS）、TREK-1（112 pS）、TREK-2（50 pS）和TRAAK（73 pS）相似的生物物理和药理学特性，它们是K(2P)通道家族的成员。另外三种钾离子通道的分子身份无法确定，因为它们表现出低通道活性且很少被观察到。在这四种K(2P)通道中，类似TRESK（14 pS）的钾离子通道在24摄氏度时活性最高。在37摄氏度时，50 pS（类似TREK-2）的通道活性最高，对静息钾离子电流的贡献最大（69%），其次是类似TRESK的14 pS通道（16%）、类似TREK-1的112 pS通道（12%）和类似TRAAK的73 pS通道（3%）。通过逆转录聚合酶链反应（RT-PCR）分析判断，在DRG神经元中，所有四种K(2P)通道以及TASK-1和TASK-3的信使核糖核酸均有表达。我们的结果表明，在37摄氏度时，TREKs和TRESK共同贡献了DRG神经元背景钾离子电导的95%以上。由于TREKs和TRESK是受体激动剂调节的靶点，它们可能在DRG神经元兴奋性调节中发挥积极作用。
