Song Ming-Ke, Liu Hong, Jiang Hua-Liang, Yue Jian-Min, Hu Guo-Yuan
State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 555 Zu-Chong-Zhi Road, Shanghai 201203, PR China.
Eur J Pharmacol. 2006 Feb 15;531(1-3):47-53. doi: 10.1016/j.ejphar.2005.12.029. Epub 2006 Jan 25.
14-Benzoyltalatisamine is a potent and selective blocker of the delayed rectifier K+ channel found in a computational virtual screening study. The compound was found to block the K+ channel from the extracellular side. However, it is unclear whether 14-benzoyltalatisamine shares the same block mechanism with tetraethylammonium (TEA). In order to elucidate how the hit compound found by the virtual screening interacts with the outer vestibule of the K+ channel, the effects of 14-benzoyltalatisamine and TEA on the delayed rectifier K+ current of rat dissociated hippocampal neurons were compared using whole-cell voltage-clamp recording. External application of 14-benzoyltalatisamine and TEA reversibly inhibited the current with IC50 values of 10.1+/-2.2 microM and 1.05+/-0.21 mM, respectively. 14-Benzoyltalatisamine exerted voltage-dependent inhibition, markedly accelerated the decay of the current, and caused a significant hyperpolarizing shift of the steady-state activation curve, whereas TEA caused voltage-independent inhibition, without affecting the kinetic parameters of the current. The blockade by 14-benzoyltalatisamine, but not by TEA, was significantly diminished in a high K+ (60 mM) external solution. The potency of 14-benzoyltalatisamine was markedly reduced in the presence of 15 mM TEA. The results suggest that 14-benzoyltalatisamine bind to the external pore entry of the delayed rectifier K+ channel with partial insertion into the selectivity filter, which is in conformity with that predicted by the molecular docking model in the virtual screening.
14-苯甲酰拉替胺是在一项计算虚拟筛选研究中发现的一种强效且选择性的延迟整流钾通道阻滞剂。该化合物被发现可从细胞外侧阻断钾通道。然而，尚不清楚14-苯甲酰拉替胺与四乙铵（TEA）是否具有相同的阻断机制。为了阐明虚拟筛选中发现的命中化合物如何与钾通道的外前庭相互作用，使用全细胞电压钳记录比较了14-苯甲酰拉替胺和TEA对大鼠离体海马神经元延迟整流钾电流的影响。外部施加14-苯甲酰拉替胺和TEA可分别以10.1±2.2 microM和1.05±0.21 mM的IC50值可逆地抑制电流。14-苯甲酰拉替胺产生电压依赖性抑制，显著加速电流衰减，并导致稳态激活曲线发生明显的超极化偏移，而TEA则产生电压非依赖性抑制，不影响电流的动力学参数。在高钾（60 mM）外部溶液中，14-苯甲酰拉替胺的阻断作用显著减弱，而TEA则不然。在15 mM TEA存在的情况下，14-苯甲酰拉替胺的效力显著降低。结果表明，14-苯甲酰拉替胺与延迟整流钾通道的外部孔入口结合，并部分插入选择性过滤器，这与虚拟筛选中的分子对接模型预测一致。
