X-ray structure of dopamine transporter elucidates antidepressant mechanism

摘要

Antidepressants targeting Na~+/Cl~- -coupled neurotransmitter uptake define a key therapeutic strategy to treat clinical depression and neuropathic pain. However, identifying the molecular interactions that underlie the pharmacological activity of these transport inhibitors, and thus the mechanism by which the inhibitors lead to increased synaptic neurotransmitter levels, has proven elusive. Here we present the crystal structure of the Drosophila melanogaster dopamine transporter at 3.0 A resolution bound to the tricyclic antidepressant nortriptyline. The transporter is locked in an outward-open conformation with nortriptyline wedged between transmembrane helices 1,3,6 and 8, blocking the transporter from binding substrate and from isomerizing to an inward-facing conformation. Although the overall structure of the dopamine transporter is similar to that of its prokaryotic relative LeuT, there are multiple distinctions, including a kink in transmembrane helix 12 halfway across the membrane bilayer, a latch-like carboxy-terminal helix that caps the cytoplasmic gate, and a cholesterol molecule wedged within a groove formed by transmembrane helices la, 5 and 7. Taken together, the dopamine transporter structure reveals the molecular basis for antidepressant action on sodium-coupled neurotransmitter symporters and elucidates critical elements of eukaryotic transporter structure and modulation by lipids, thus expanding our understanding of the mechanism and regulation of neurotransmitter uptake at chemical synapses.%多巴胺运输蛋白（DAT)是一种膜蛋白，将神经传输物质多巴胺从突触间隙中清除，将其输入到周围细胞的细胞溶质内，从而终止神经传输物质的信号。Eic Gouaux及同事报告了与三环抗抑郁药物"去甲替林"结合在一起的果蝇DAT的X-射线结构。这是迄今确定的一种真核生物神经传输物质钠"共输送体"的第一个晶体结构。果蝇DAT的整体结构与LeuT的结构相似，但作者也发现了几个差别，这些差别在真核蛋白的运输机制及其被磷酸化的调控中可能起重要作用。