Dopamine transport by the serotonin transporter: a mechanistically distinct mode of substrate translocation.
Dopamine transport by the serotonin transporter: a mechanistically distinct mode of substrate translocation.
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DOI：
10.1523/jneurosci.0576-11.2011
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发表时间：
2011-04-27
期刊：
影响因子：
--
通讯作者：
Amara SG
中科院分区：
文献类型：
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作者：
Larsen MB;Sonders MS;Mortensen OV;Larson GA;Zahniser NR;Amara SG
5-羟色胺转运体（SERT）是神经系统中终止5-羟色胺（5-HT）信号的主要机制，也是多种精神活性药物（包括抗抑郁药、安非他明和可卡因）的作用部位。在这里，我们表明，人类SERT（hSERT）和大鼠SERT能够强大的多巴胺（DA）的摄取通过一个过程，不同的机制从5 HT运输在几个意想不到的方式。通过hSERT的DA转运具有比5 HT转运更高的最大速度，需要显著更高的Na+和Cl−浓度来维持转运，被5 HT非竞争性抑制，并且对SERT抑制剂（包括选择性5-羟色胺再摄取抑制剂（SSRI））更敏感。我们使用硫醇反应性甲烷硫代磺酸盐（MTS）试剂来修饰构象敏感的半胱氨酸残基，以证明hSERT在转运DA时比转运5 HT时花费更多的时间处于外向构象。无活性或MTS敏感的SERT与野生型SERT亚基的共转染揭示了在DA转运过程中亚基之间不存在合作相互作用，但不存在5 HT转运。为了建立DA清除机制的生理相关性，我们使用体内高速计时电流法表明，SERT具有清除麻醉大鼠海马CA 3区细胞外应用DA的能力。总之，这些观察结果表明，SERT作为一种DA转运蛋白在体内的可能性，并强调了这样一种想法，即可以有不同的模式运输替代生理底物的SERT。
The serotonin transporter (SERT) is the principal mechanism for terminating serotonin (5HT) signals in the nervous system and is a site of action for a variety of psychoactive drugs including antidepressants, amphetamines, and cocaine. Here we show that human SERTs (hSERTs) and rat SERTs are capable of robust dopamine (DA) uptake through a process that differs mechanistically from 5HT transport in several unanticipated ways. DA transport by hSERT has a higher maximum velocity than 5HT transport, requires significantly higher Na+ and Cl− concentrations to sustain transport, is inhibited non-competitively by 5HT and is more sensitive to SERT inhibitors, including selective serotonin reuptake inhibitors (SSRIs). We use a thiol reactive methane thiosulfonate (MTS) reagent to modify a conformationally-sensitive cysteine residue to demonstrate that hSERT spends more time in an outward facing conformation when transporting DA than when transporting 5HT. Co-transfection of an inactive or an MTS-sensitive SERT with wild type SERT subunits reveals an absence of cooperative interactions between subunits during DA, but not 5HT transport. To establish the physiological relevance of this mechanism for DA clearance, we show using in vivo high-speed chronoamperometry that SERT has the capacity to clear extracellularly applied DA in the hippocampal CA3 region of anesthetized rats. Together, these observations suggest the possibility that SERT serves as a DA transporter in vivo and highlight the idea that there can be distinct modes of transport of alternative physiological substrates by SERT.