Mechanism of hERG Channel Block by the Psychoactive Indole Alkaloid Ibogaine
Mechanism of hERG Channel Block by the Psychoactive Indole Alkaloid Ibogaine
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DOI：
10.1124/jpet.113.209643
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发表时间：
2014-02
期刊：
影响因子：
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通讯作者：
P. Thurner;A. Stary-Weinzinger;Hend Gafar;V. Gawali;O. Kudlacek;Juergen Zezula;K. Hilber;S. Boehm;W. Sandtner;Xaver Koenig
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文献类型：
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作者：
P. Thurner;A. Stary-Weinzinger;Hend Gafar;V. Gawali;O. Kudlacek;Juergen Zezula;K. Hilber;S. Boehm;W. Sandtner;Xaver Koenig
伊博格碱是一种具有精神活性的吲哚类生物碱。它作为一种抗成瘾性药物的使用伴随着QT间期延长和心律失常，这很可能是由人类乙醚-go -go相关基因（hERG）钾通道抑制引起的。因此，我们详细研究了伊博格碱与哺乳动物肾tsA-201细胞中异源表达的hERG通道的相互作用。无论伊博加因是通过细胞外溶液还是细胞内溶液施用，通过hERG通道的电流都被阻断。抑制程度由相对pH值决定。阻滞发生在通道激活期间，而在静息通道中未观察到。随着去极化的增加，伊博加因阻滞的增长和发展更快。稳态激活和失活的通道转移到更多的负电位。失活速度减慢，而失活速度加快。其他hERG通道阻滞剂（Y652A和F656A）结合位点的突变降低了伊博格碱的效力，而失活缺陷双突变体（G628C/S631C）与野生型通道一样敏感。分子药物对接表明，在独立于伊博格碱质子化的通道内腔内结合。实验电流轨迹符合hERG通道门控的动力学模型，揭示了伊博格碱对打开和失活状态的优先结合。综上所述，这些发现表明，伊博格碱无论是单独以带电形式还是以不带电形式从细胞质侧阻断hERG通道，并通过改变通道状态随时间的相对贡献来改变电流。
Ibogaine is a psychoactive indole alkaloid. Its use as an antiaddictive agent has been accompanied by QT prolongation and cardiac arrhythmias, which are most likely caused by human ether a go-go–related gene (hERG) potassium channel inhibition. Therefore, we studied in detail the interaction of ibogaine with hERG channels heterologously expressed in mammalian kidney tsA-201 cells. Currents through hERG channels were blocked regardless of whether ibogaine was applied via the extracellular or intracellular solution. The extent of inhibition was determined by the relative pH values. Block occurred during activation of the channels and was not observed for resting channels. With increasing depolarizations, ibogaine block grew and developed faster. Steady-state activation and inactivation of the channel were shifted to more negative potentials. Deactivation was slowed, whereas inactivation was accelerated. Mutations in the binding site reported for other hERG channel blockers (Y652A and F656A) reduced the potency of ibogaine, whereas an inactivation-deficient double mutant (G628C/S631C) was as sensitive as wild-type channels. Molecular drug docking indicated binding within the inner cavity of the channel independently of the protonation of ibogaine. Experimental current traces were fit to a kinetic model of hERG channel gating, revealing preferential binding of ibogaine to the open and inactivated state. Taken together, these findings show that ibogaine blocks hERG channels from the cytosolic side either in its charged form alone or in company with its uncharged form and alters the currents by changing the relative contribution of channel states over time.