The mechanistic basis for noncompetitive ibogaine inhibition of serotonin and dopamine transporters.
The mechanistic basis for noncompetitive ibogaine inhibition of serotonin and dopamine transporters.
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非竞争性ibogaine抑制5-羟色胺和多巴胺转运蛋白的机械基础。
DOI：
10.1074/jbc.m112.343681
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发表时间：
2012-05-25
期刊：
影响因子：
--
通讯作者：
Sandtner W
中科院分区：
文献类型：
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作者：
Bulling S;Schicker K;Zhang YW;Steinkellner T;Stockner T;Gruber CW;Boehm S;Freissmuth M;Rudnick G;Sitte HH;Sandtner W
背景：伊波甘是一种SERT的非竞争性抑制物，可以将转运蛋白稳定在内向开放的构象中。结果：伊博甘结合到一个可从细胞外部到达的部位，该部位不与底物结合部位重叠。结论：伊波甘与SERT和DAT上一个新的结合位点结合。意义：这项研究提供了一种独特的SERT和DAT抑制剂的机制理解。伊博甘是一种用于治疗阿片类药物戒断的致幻生物碱，已被证明对5-羟色胺转运体(SERT)具有非竞争性抑制作用，而所有其他已知的抑制剂都与底物竞争。Ibogaine与SERT的结合增加了连接底物结合部位和细胞质的渗透途径的可及性。由于伊波甘与5-羟色胺在结构上的相似性，人们认为伊波甘与SERT的底物结合。实验结果表明，伊博甘与细胞外部的不同部位结合，抑制5-羟色胺的转运和5-羟色胺诱导的离子电流。Ibogaine非竞争性抑制SERT和同源多巴胺转运体(DAT)的转运。伊波甘也阻断了DAT中底物诱导的电流，并增加了DAT细胞质渗透途径的可达性。当伊波甘存在于细胞表面时，抑制SERT底物诱导的电流，但当它通过贴片电极进入细胞质时则不抑制。与非竞争性转运抑制类似，增加底物浓度不能逆转电流阻断。根据其对SERT电流的影响，抑制物结合和解离的动力学表明，伊波甘不是通过与SERT形成一个长寿命的复合体来抑制的，而是以一种向内开放的构象直接与转运体结合。描述伊波甘的非竞争性作用和可卡因的竞争性作用的转运动力学模型很好地解释了本研究的结果。
Background: Ibogaine is a noncompetitive inhibitor of SERT that stabilizes the transporter in an inward-open conformation. Results: Ibogaine binds to a site accessible from the cell exterior that does not overlap with the substrate-binding site. Conclusion: Ibogaine binds to a novel binding site on SERT and DAT. Significance: This study provides a mechanistic understanding of an unique inhibitor of SERT and DAT. Ibogaine, a hallucinogenic alkaloid proposed as a treatment for opiate withdrawal, has been shown to inhibit serotonin transporter (SERT) noncompetitively, in contrast to all other known inhibitors, which are competitive with substrate. Ibogaine binding to SERT increases accessibility in the permeation pathway connecting the substrate-binding site with the cytoplasm. Because of the structural similarity between ibogaine and serotonin, it had been suggested that ibogaine binds to the substrate site of SERT. The results presented here show that ibogaine binds to a distinct site, accessible from the cell exterior, to inhibit both serotonin transport and serotonin-induced ionic currents. Ibogaine noncompetitively inhibited transport by both SERT and the homologous dopamine transporter (DAT). Ibogaine blocked substrate-induced currents also in DAT and increased accessibility of the DAT cytoplasmic permeation pathway. When present on the cell exterior, ibogaine inhibited SERT substrate-induced currents, but not when it was introduced into the cytoplasm through the patch electrode. Similar to noncompetitive transport inhibition, the current block was not reversed by increasing substrate concentration. The kinetics of inhibitor binding and dissociation, as determined by their effect on SERT currents, indicated that ibogaine does not inhibit by forming a long-lived complex with SERT, but rather binds directly to the transporter in an inward-open conformation. A kinetic model for transport describing the noncompetitive action of ibogaine and the competitive action of cocaine accounts well for the results of the present study.