Molecular Basis for Selective Serotonin Reuptake Inhibition by the Antidepressant Agent Fluoxetine (Prozac)
作者:Jacob Andersen、Nicolai Stuhr-Hansen、Linda Grønborg Zachariassen、Heidi Koldsø、Birgit Schiøtt、Kristian Strømgaard、Anders S. Kristensen
DOI:10.1124/mol.113.091249
日期:2014.5
Inhibitors of the serotonin transporter (SERT) are widely used antidepressant agents, but the structural mechanism for inhibitory activity and selectivity over the closely related norepinephrine transporter (NET) is not well understood. Here we use a combination of chemical, biological, and computational methods to decipher the molecular basis for high-affinity recognition in SERT and selectivity over NET for the prototypical antidepressant drug fluoxetine (Prozac; Eli Lilly, Indianapolis, IN). We show that fluoxetine binds within the central substrate site of human SERT, in agreement with recent X-ray crystal structures of LeuBAT, an engineered monoamine-like version of the bacterial amino acid transporter LeuT. However, the binding orientation of fluoxetine is reversed in our experimentally supported model compared with the LeuBAT structures, emphasizing the need for careful experimental verification when extrapolating findings from crystal structures of bacterial transporters to human relatives. We find that the selectivity of fluoxetine and nisoxetine, a NET selective structural congener of fluoxetine, is controlled by residues in different regions of the transporters, indicating a complex mechanism for selective recognition of structurally similar compounds in SERT and NET. Our findings add important new information on the molecular basis for SERT/NET selectivity of antidepressants, and provide the first assessment of the potential of LeuBAT as a model system for antidepressant binding in human transporters, which is essential for future structure-based drug development of antidepressant drugs with fine-tuned transporter selectivity.
血清素转运体(SERT)的抑制剂被广泛用作抗抑郁剂,但其抑制活性和对密切相关的去甲肾上腺素转运体(NET)的选择性背后的结构机制尚不清楚。在这里,我们结合化学、生物学和计算方法,解析了典型抗抑郁药物氟西汀(Prozac;礼来制药,印第安纳波利斯)在SERT中的高亲和力识别以及对NET的选择性的分子基础。我们发现氟西汀结合在人体SERT的中心底物位点,这与最近的LeuBAT X射线晶体结构保持一致,LeuBAT是细菌氨基酸转运蛋白LeuT的工程化单胺样版本。然而,在我们支持的实验模型中,氟西汀的结合方向与LeuBAT结构相比是反向的,这强调了在将细菌转运体的晶体结构发现推及到与人类相关的转运体时需要进行谨慎的实验验证。我们发现氟西汀和其NET选择性结构同源物nisoxetine的选择性由转运体不同区域的氨基酸残基控制,这表明在SERT和NET中对结构相似化合物具有复杂的选择性识别机制。我们的发现为抗抑郁剂的SERT/NET选择性的分子基础提供了重要的新信息,并首次评估了LeuBAT作为人类转运体中抗抑郁药结合模型系统的潜力,这对于未来基于结构的抗抑郁药物开发具有重要意义,特别是对转运体选择性的细致调控。