Kurachi Y, Takahashi N
Second Department of Pharmacology, Faculty of Medicine, Osaka University, Japan.
J Card Fail. 1996 Dec;2(4 Suppl):S59-62. doi: 10.1007/978-4-431-65952-5_6.
We have cloned cDNAs encoding three background inward rectifier potassium channels from a mouse brain cDNA library. We designated them mouse brain (MB)- IRK1, MB-IRK2, and MB-IRK3, based on their amino acid sequences and the electrophysiological properties of currents expressed in Xenopus oocytes. Xenopus oocytes injected with cRNAs derived from these clones expressed K+ currents that showed classical inward rectifier potassium channel characteristics at whole cell current level and that were blocked by Ba2+ and Ca+ in a concentration- and voltage- dependent manner. The single channel recordings revealed, however, that the unitary conductance of MB-IRKI was approximately 22pS; MB-IRK2, approximately 34pS; and MB-IRK3, approximately 12pS. By Northern blot analysis, MB-IRKI was more predominantly expressed in forebrain than in cerebellum, and vice versa in the case MB-IRK2. MB-IRK3 was expressed specifically in forebrain. On the other hand, MB-IRK1 and MB-IRK2, but not MB-IRK3, were expressed in heart. These results indicate the heterogeneity of the molecular structure and functional role of the two transmembrane region type of background inward rectifier potassium channels in brain and heart.
我们从一个小鼠脑cDNA文库中克隆了编码三种背景内向整流钾通道的cDNA。根据它们的氨基酸序列以及在非洲爪蟾卵母细胞中表达的电流的电生理特性，我们将它们命名为小鼠脑（MB）-IRK1、MB-IRK2和MB-IRK3。注射了源自这些克隆的cRNA的非洲爪蟾卵母细胞表达出K+电流，在全细胞电流水平上显示出典型的内向整流钾通道特征，并且被Ba2+和Ca+以浓度和电压依赖性方式阻断。然而，单通道记录显示，MB-IRK1的单位电导约为22pS；MB-IRK2约为34pS；MB-IRK3约为12pS。通过Northern印迹分析，MB-IRK1在前脑中的表达比在小脑中更为主，反之，MB-IRK2则在小脑中表达为主。MB-IRK3在前脑中特异性表达。另一方面，MB-IRK1和MB-IRK2，但不是MB-IRK3，在心脏中表达。这些结果表明了在脑和心脏中两种跨膜区域类型的背景内向整流钾通道的分子结构和功能作用的异质性。
