Location of the Antidepressant Binding Site in the Serotonin Transporter IMPORTANCE OF SER-438 IN RECOGNITION OF CITALOPRAM AND TRICYCLIC ANTIDEPRESSANTS
Location of the Antidepressant Binding Site in the Serotonin Transporter IMPORTANCE OF SER-438 IN RECOGNITION OF CITALOPRAM AND TRICYCLIC ANTIDEPRESSANTS
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DOI：
10.1074/jbc.m806907200
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发表时间：
2009-04-10
影响因子：
4.8
通讯作者：
Kristensen, Anders S.
中科院分区：
文献类型：
--
作者：
Andersen, Jacob;Taboureau, Olivier;Kristensen, Anders S.
血清素转运蛋白 (SERT) 通过将 5HT 转运到神经元和神经胶质细胞中来调节大脑中血清素（5-羟色胺，5HT）的细胞外水平。人类 SERT (hSERT) 是用于治疗情绪障碍（包括抑郁症）的药物的主要靶点。 hSERT 属于溶质载体 6 家族，其中包括细菌亮氨酸转运蛋白 (LeuT)，其高分辨率晶体结构已可用。 LeuT 已被证明是人类转运蛋白的优秀模型，并促进了对溶质载体 6 转运蛋白结构与功能关系的理解。然而，抗抑郁药抑制 hSERT 的精确结构机制及其结合口袋的位置仍然难以捉摸。我们已经鉴定出位于 hSERT 中 5HT 结合袋内的残基 (Ser-438) 是几种抗抑郁药效力的关键决定因素，包括选择性血清素再摄取抑制剂西酞普兰和三环类抗抑郁药丙咪嗪、氯米帕明和阿米替林。 Ser-438 保守突变为苏氨酸 (S438T)，选择性地将这些抗抑郁药的 K-i 值提高至 175 倍。对于这些缺乏单个甲基的抗抑郁药类似物来说，通过 S438T 将蛋白质甲基引入 5HT 结合口袋的作用不存在或减弱。这表明这些抗抑郁药在与 hSERT 结合期间直接与 Ser-438 相互作用，这意味着 hSERT 中底物和抑制剂结合位点的重叠定位，表明抗抑郁药通过涉及直接封闭 5HT 结合位点的机制发挥作用。
The serotonin transporter (SERT) regulates extracellular levels of serotonin (5-hydroxytryptamine, 5HT) in the brain by transporting 5HT into neurons and glial cells. The human SERT (hSERT) is the primary target for drugs used in the treatment of emotional disorders, including depression. hSERT belongs to the solute carrier 6 family that includes a bacterial leucine transporter (LeuT), for which a high resolution crystal structure has become available. LeuT has proved to be an excellent model for human transporters and has advanced the understanding of solute carrier 6 transporter structure-function relationships. However, the precise structural mechanism by which antidepressants inhibit hSERT and the location of their binding pockets are still elusive. We have identified a residue (Ser-438) located within the 5HT-binding pocket in hSERT to be a critical determinant for the potency of several antidepressants, including the selective serotonin reuptake inhibitor citalopram and the tricyclic antidepressants imipramine, clomipramine, and amitriptyline. A conservative mutation of Ser-438 to threonine (S438T) selectively increased the K-i values for these antidepressants up to 175-fold. The effects of introducing a protein methyl group into the 5HT-binding pocket by S438T were absent or reduced for analogs of these antidepressants lacking a single methyl group. This suggests that these antidepressants interact directly with Ser-438 during binding to hSERT, implying an overlapping localization of substrate- and inhibitor-binding sites in hSERT suggesting that antidepressants function by a mechanism that involves direct occlusion of the 5HT-binding site.