Structure and Function of Neurotransmitter Transporters

描述(申请人提供)：人类神经系统的功能依赖于数十亿个神经细胞。这些大量细胞交流的一个主要机制涉及化学突触--一个细胞释放的小分子神经递质与相邻细胞上的受体结合并激活的专门连接。为了让这一神经传递循环迅速而忠实地重复，神经递质必须被清除或从突触中移除。有大量的治疗药物和各种各样的非法化合物来调节转运蛋白的功能，包括抗抑郁剂、可卡因和苯丙胺。在大多数化学突触中，递质的移除是由称为转运蛋白的完整膜蛋白完成的。在许多情况下，例如谷氨酸、GABA、甘氨酸和生物胺转运体，转运蛋白利用依赖于ATP的泵建立的离子梯度来热力学地驱动或泵送递质到相邻细胞；这些蛋白质通常被称为离子偶联转运体。在其他情况下，如谷氨酸/半胱氨酸交换器，转运蛋白必须将一种底物(谷氨酸)交换为另一种底物(胱氨酸)；这些转运蛋白通常被称为逆向转运蛋白。由于共转运蛋白和反向转运蛋白都是高度疏水的整膜蛋白，用X射线衍射法研究它们的原子结构已被证明是困难的。我建议对神经递质转运蛋白和反向转运蛋白的细菌同源蛋白进行高分辨率的结晶学研究，并结合补充的功能研究，开发这些关键转运蛋白功能的分子机制。此外，我建议在我的实验室开发的新技术的帮助下，开始真核神经递质转运体的结构研究。通过完成拟议的研究，我们不仅将了解这些蛋白质的功能，而且我们还将获得开发新化合物以治疗广泛的神经疾病和障碍的基本信息。公共卫生相关性：完整的膜运输蛋白从神经细胞之间称为突触的特殊连接中移除化学信使或神经递质，它们的功能障碍与许多神经疾病和障碍有关。转运蛋白既是抗抑郁剂等治疗剂的靶标，也是可卡因等非法物质的靶标。本申请中提出的工作的目的是确定这些重要转运蛋白的分子结构和功能。

DESCRIPTION (provided by applicant): The function of the human nervous system is dependent upon billions of nerve cells. A primary mechanism by which this vast number of cells communicates involves chemical synapses - specialized junctions where a small molecule neurotransmitter released by one cell binds to and activates receptors on an adjacent cell. In order for this cycle of neurotransmission to rapidly and faithfully repeat, the neurotransmitter must be cleared or removed from synapses. There are a large number of therapeutic drugs and a wide array of illicit compounds that modulate transporter function, including antidepressants, cocaine and amphetamines. At most chemical synapses, the removal of transmitter is accomplished by integral membrane proteins called transporters. In many cases, such as with glutamate, GABA, glycine and the biogenic amine transporters, the transporter proteins harness ion gradients established by ATP-dependent pumps to thermodynamically drive or pump transmitter into adjacent cells; these proteins are commonly referred to as ion-coupled symporters. In other cases, such as with the glutamate/cystine exchanger, the transporter protein obligatorily exchanges one substrate (glutamate) for another (cystine); these transporters are generally referred to as antiporters. Because both symporters and antiporters are highly hydrophobic integral membrane proteins, studies of their atomic structures by x-ray diffraction methods have proven difficult. I propose to carry out high resolution crystallographic studies of bacterial orthologs of neurotransmitter symporters and antiporters and, in combination with complimentary functional studies, develop molecular mechanisms for the function of these crucial transporter proteins. In addition, I propose to commence structural studies of eukaryotic neurotransmitter transporters facilitated by new technology developed in my laboratory. By accomplishing the proposed studies, we will not only learn how these proteins function, but we will also have the fundamental information for the development of new compounds to treat a wide range of neurological diseases and disorders. PUBLIC HEALTH RELEVANCE: Integral membrane transport proteins remove chemical messengers or neurotransmitters from special junctions between nerve cells called synapses and their dysfunction is associated with numerous neurological diseases and disorders. The transport proteins are the targets of both therapeutic agents, such as antidepressants, and illicit substances, such as cocaine. The aims of the work proposed in this application are to determine the molecular structure and function of these important transporter proteins.