Structural characterization of a human neurotransmitter transporter

描述（由申请人提供）：神经元之间信号传导的调节取决于神经递质释放的频率和突触中存在的神经递质的量。信号传导的有效终止是为了重置突触的状态以用于随后的神经递质释放事件。突触前神经元和神经胶质细胞对神经递质分子的重摄取依赖于膜包埋转运蛋白。这些酶将神经递质从细胞外空间运输到细胞内，因此沿着浓度梯度向上。为了给这一能量上不利的过程提供动力，这些转运蛋白还将钠离子沿其浓度梯度移动并进入细胞。虽然在人类中已经确立神经递质转运蛋白直接调节焦虑和寻求奖励等心理状态，但对临床相关拮抗剂的底物识别和抑制机制知之甚少。这些努力受到了阻碍，缺乏原子分辨率的结构信息的任何真核神经递质转运。本申请详述了表达和纯化人神经递质转运蛋白用于结晶和通过X射线衍射进行结构测定的策略。本申请的主要目标是揭示与神经递质和拮抗剂复合的神经递质转运蛋白的三维结构。这一进展将提供结合位点的位置，并产生可检验的假设，以探测转运蛋白如何特异性地识别其底物并被拮抗剂抑制。 公共卫生相关性：精神活性药物和抗抑郁药被认为作用于位于大脑神经元细胞中的神经递质转运蛋白。这些转运蛋白通常将神经递质吸收回神经元细胞，这种活动的失调可能导致药物成瘾和心理障碍。该应用旨在更好地了解药物如何通过滥用和治疗药物影响神经递质转运蛋白，希望能够开发出更有效的化合物。

DESCRIPTION (provided by applicant): The regulation of signaling between neurons depends on the frequency of neurotransmitter release and quantity of neurotransmitter present in the synapse. Efficient termination of signaling is required for resetting the state of the synapse for a subsequent event of neurotransmitter release. The reuptake of neurotransmitter molecules by presynaptic neurons and glial cells depends on membrane-embedded transporter proteins. These enzymes transport neurotransmitters from the extracellular space into the cell and therefore up a concentration gradient. To power this energetically unfavorable process, these transporters also move sodium ions down their concentration gradient and into the cell. Although it is well-established in humans that neurotransmitter transporters directly regulate psychological states such as anxiety and reward-seeking, much less is known about the mechanisms of substrate recognition and inhibition by clinically relevant antagonists. These efforts have been hampered by the absence of atomic-resolution structural information for any eukaryotic neurotransmitter transporters. This application details strategies to express and purify a human neurotransmitter transporter for crystallization and structural determination via x- ray diffraction. The primary goal of this application is to uncover the three-dimensional structure of a neurotransmitter transporter in complex with neurotransmitter and antagonists. This advance will provide the locations of binding sites and generate testable hypotheses to probe how transporters specifically recognize their substrates and are inhibited by antagonists. PUBLIC HEALTH RELEVANCE: Psychoactive drugs and antidepressants are thought to act on neurotransmitter transporters located in neuronal cells in the brain. These transporters normally absorb neurotransmitters back into neuronal cells, and misregulation of this activity can lead to drug addiction and psychological disorders. This application seeks to better understand how drugs affect neurotransmitter transporters by both abused and therapeutic drugs in the hope that more effective compounds can be developed.