Meves H, Schwarz J R, Wulfsen I
Physiologisches Institut, Universität des Saarlandes, Homburg-Saar, Germany.
Br J Pharmacol. 1999 Jul;127(5):1213-23. doi: 10.1038/sj.bjp.0702642.
Differentiated NG108-15 neuroblastoma x glioma hybrid cells were whole-cell voltage-clamped. Hyperpolarizing pulses, superimposed on a depolarized holding potential (-30 or -20 mV), elicited deactivation currents which consisted of two components, distinguishable by fitting with two exponential functions. Linopirdine [DuP 996, 3,3-bis(4-pyridinylmethyl)-1-phenylindolin-2-one), a neurotransmitter-release enhancer known as potent and selective blocker of the M-current of rat sympathetic neurons, in concentrations of 5 or 10 microM selectively inhibited the fast component (IC50 = 14.7 microM). The slow component was less sensitive to linopirdine (IC50>20 microM). The class III antiarrhythmics [(4-methylsulphonyl)amido]benzenesulphonamide (WAY-123.398) and 1-[2-(6-methyl-2-pyrydinil)ethyl]-4-(4-methylsulphonylaminobenz oyl) piperidine (E-4031), selective inhibitors of the inwardly rectifying ERG (ether-à-go-go-related gene) potassium channel, inhibited predominantly the slow component (IC50 = 38 nM for E-4031). The time constant of the WAY-123.398-sensitive current resembled the time constant of the slow component in size and voltage dependence. Inwardly rectifying ERG currents, recorded in K+ -rich bath at strongly negative pulse potentials, resembled the slow component of the deactivation current in their low sensitivity to linopirdine (28% inhibition at 50 microM). The size of the slow component varied greatly between cells. Accordingly, varied the effect of WAY-123.398 on deactivation current and holding current. RNA transcripts for the following members of the ether-à-go-go gene (EAG) K+ channel family were found in differentiated NG108-15 cells: ERG1, ERG2, EAGI, EAG-like (ELK)1, ELK2; ERG3 was only present in non-differentiated cells. In addition, RNA transcripts for KCNQ2 and KCNQ3 were found in differentiated and non-differentiated cells. We conclude that the fast component of the deactivation current is M-like current and the slow component is deactivating ERG current. The molecular correlates are probably KCNQ2/KCNQ3 and ERG1/ERG2, respectively.
对分化型NG108 - 15神经母细胞瘤x胶质瘤杂交细胞进行全细胞膜片钳记录。在去极化的钳制电位（-30或-20 mV）上叠加超极化脉冲，可诱发失活电流，该电流由两个成分组成，通过拟合两个指数函数可区分。利诺吡啶[DuP 996，3,3 - 双（4 - 吡啶基甲基）- 1 - 苯基吲哚 - 2 - 酮]，一种已知为大鼠交感神经元M电流的强效和选择性阻滞剂的神经递质释放增强剂，浓度为5或10 μM时选择性抑制快速成分（IC50 = 14.7 μM）。慢成分对利诺吡啶的敏感性较低（IC50>20 μM）。Ⅲ类抗心律失常药[（4 - 甲基磺酰基）氨基]苯磺酰胺（WAY - 123.398）和1 - [2 - （6 - 甲基 - 2 - 吡啶基）乙基] - 4 - （4 - 甲基磺酰基氨基苯甲酰基）哌啶（E - 4031），内向整流ERG（去极化相关基因）钾通道的选择性抑制剂，主要抑制慢成分（E - 4031的IC50 = 38 nM）。WAY - 123.398敏感电流的时间常数在大小和电压依赖性方面与慢成分的时间常数相似。在强负脉冲电位下于富含K + 的浴中记录的内向整流ERG电流，在对利诺吡啶的低敏感性方面（50 μM时抑制28%）与失活电流的慢成分相似。慢成分的大小在不同细胞间差异很大。因此，WAY - 123.398对失活电流和钳制电流的影响也有所不同。在分化的NG108 - 15细胞中发现了以下去极化基因（EAG）钾通道家族成员的RNA转录本：ERG1、ERG2、EAGI、EAG样（ELK）1、ELK2；ERG3仅存在于未分化细胞中。此外，在分化和未分化细胞中均发现了KCNQ2和KCNQ3的RNA转录本。我们得出结论，失活电流的快速成分是M样电流，慢成分是失活的ERG电流。其分子相关性可能分别为KCNQ2/KCNQ3和ERG1/ERG2。
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