Zhou Zheng, Zhen Juan, Karpowich Nathan K, Goetz Regina M, Law Christopher J, Reith Maarten E A, Wang Da-Neng
Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine and Department of Cell Biology, New York University School of Medicine, 540 First Avenue, New York, NY 10016, USA.
Science. 2007 Sep 7;317(5843):1390-3. doi: 10.1126/science.1147614. Epub 2007 Aug 9.
Tricyclic antidepressants exert their pharmacological effect-inhibiting the reuptake of serotonin, norepinephrine, and dopamine-by directly blocking neurotransmitter transporters (SERT, NET, and DAT, respectively) in the presynaptic membrane. The drug-binding site and the mechanism of this inhibition are poorly understood. We determined the crystal structure at 2.9 angstroms of the bacterial leucine transporter (LeuT), a homolog of SERT, NET, and DAT, in complex with leucine and the antidepressant desipramine. Desipramine binds at the inner end of the extracellular cavity of the transporter and is held in place by a hairpin loop and by a salt bridge. This binding site is separated from the leucine-binding site by the extracellular gate of the transporter. By directly locking the gate, desipramine prevents conformational changes and blocks substrate transport. Mutagenesis experiments on human SERT and DAT indicate that both the desipramine-binding site and its inhibition mechanism are probably conserved in the human neurotransmitter transporters.
三环类抗抑郁药通过直接阻断突触前膜中的神经递质转运体（分别为5-羟色胺转运体、去甲肾上腺素转运体和多巴胺转运体）来发挥其药理作用——抑制5-羟色胺、去甲肾上腺素和多巴胺的再摄取。药物结合位点及其抑制机制目前仍知之甚少。我们确定了细菌亮氨酸转运体（LeuT）（5-羟色胺转运体、去甲肾上腺素转运体和多巴胺转运体的同源物）与亮氨酸和抗抑郁药地昔帕明复合物的2.9埃晶体结构。地昔帕明结合在转运体细胞外腔的内端，并通过一个发夹环和一个盐桥固定在位。该结合位点通过转运体的细胞外门与亮氨酸结合位点分开。通过直接锁定门，地昔帕明可防止构象变化并阻断底物转运。对人类5-羟色胺转运体和多巴胺转运体进行的诱变实验表明，地昔帕明结合位点及其抑制机制在人类神经递质转运体中可能是保守的。
