Laboratory for Membrane Protein Dynamics. Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
Computational Chemistry and Molecular Biophysics Unit, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse-Intramural Research Program, National Institutes of Health, Baltimore, MD, USA.
Nat Commun. 2020 Mar 20;11(1):1491. doi: 10.1038/s41467-020-15292-y.
The serotonin transporter (SERT) terminates serotonin signaling by rapid presynaptic reuptake. SERT activity is modulated by antidepressants, e.g., S-citalopram and imipramine, to alleviate symptoms of depression and anxiety. SERT crystal structures reveal two S-citalopram binding pockets in the central binding (S1) site and the extracellular vestibule (S2 site). In this study, our combined in vitro and in silico analysis indicates that the bound S-citalopram or imipramine in S1 is allosterically coupled to the ligand binding to S2 through altering protein conformations. Remarkably, SERT inhibitor Lu AF60097, the first high-affinity S2-ligand reported and characterized here, allosterically couples the ligand binding to S1 through a similar mechanism. The SERT inhibition by Lu AF60097 is demonstrated by the potentiated imipramine binding and increased hippocampal serotonin level in rats. Together, we reveal a S1-S2 coupling mechanism that will facilitate rational design of high-affinity SERT allosteric inhibitors.
血清素转运体（SERT）通过快速突触前再摄取终止血清素信号。SERT 的活性受抗抑郁药（如 S-西酞普兰和丙咪嗪）的调节，以减轻抑郁和焦虑的症状。SERT 的晶体结构揭示了中央结合（S1）位点和细胞外前庭（S2）位点中的两个 S-西酞普兰结合口袋。在这项研究中，我们的体外和计算分析表明，结合在 S1 中的 S-西酞普兰或丙咪嗪通过改变蛋白质构象与结合在 S2 的配体进行变构偶联。值得注意的是，SERT 抑制剂 Lu AF60097 是第一个被报道和表征的高亲和力 S2-配体，通过类似的机制变构偶联配体与 S1 的结合。Lu AF60097 通过增强丙咪嗪的结合和增加大鼠海马中的血清素水平来抑制 SERT。总之，我们揭示了 S1-S2 偶联机制，这将有助于合理设计高亲和力 SERT 变构抑制剂。
