Structure and Function of Neurotransmitter Transporters

描述（由申请人提供）：中性和阴离子氨基酸转运蛋白在人体生理学中起关键作用，在肾脏和大脑等多种器官中具有活性。在中枢神经系统中，谷氨酸介导大部分快速兴奋性信号传导，这是神经元-神经元通信的一种形式，对神经系统的发育和维持至关重要。谷氨酸介导的信号传导的一个基本组成部分是在兴奋性刺激后，神经元和其他细胞（例如神经胶质细胞）中的钠依赖性、高亲和力谷氨酸转运蛋白从突触间隙中去除谷氨酸。目前，还没有谷氨酸转运蛋白的原子分辨率结构信息，这极大地阻碍了我们对其结构和作用机制的理解。在这个应用程序中，我建议确定的细菌蛋白质，具有显着的序列同一性的真核谷氨酸转运蛋白的结构，使用X-射线晶体学。此外，我计划确定细菌同系物的功能行为，并测试基于结构的转运功能机制。此外，通过使用细菌蛋白的晶体结构作为指导，我将创建选定的真核转运蛋白的同源性模型，并与先前确定的结构和功能信息一起，这将把真核转运蛋白的结构和功能关系置于原子分辨率的三维环境中。两者合计，拟议的研究将大大提高我们对真核生物和原核生物谷氨酸转运蛋白的理解，而且，因为它们与二羧酸和中性氨基酸的转运蛋白有关，我们对这些二级转运蛋白的了解也将增加。最后，由于神经元能信号在人类神经系统中是普遍存在的，细菌转运蛋白的结构，沿着真核转运蛋白的同源模型，应该有助于设计可能具有治疗潜力的新分子。

DESCRIPTION (provided by applicant): Transporters for neutral and anionic amino acids play keys roles in human physiology and are active in organs as diverse as the kidney and brain. In the central nervous system, glutamate mediates the majority of fast excitatory signaling, a form of neuron-neuron communication that is essential to the development and maintenance of the nervous system. A fundamental component of glutamate-mediated signaling is the removal of glutamate from the synaptic cleft, following an excitatory stimulus, by sodium-dependent, high affinity glutamate transporters in neurons and other cells, such as glial cells. At the present time, there is no atomic resolution structural information on a glutamate transporter, which greatly hampers our understanding of their architecture and mechanism of action. In this application I propose to determine the structure of a bacterial protein that has significant sequence identity to the eukaryotic glutamate transporters, using x-ray crystallography. Furthermore, I plan to determine the functional behavior of the bacterial homolog, and to test structure-based mechanisms of transporter function. In addition, by using the crystal structure(s) of the bacterial protein as a guide, I will create a homology model of selected eukaryotic transporters and, together with previously determined structure and function information, this will place structure and function relationships of the eukaryotic transporters in an atomic-resolution, three-dimensional context. Taken together, the proposed research will substantially further our understanding of both eukaryotic and prokaryotic glutamate transporters, and, because they are related to transporters of dicarboxylic acids and of neutral amino acids, our knowledge of these secondary transporters will be increased as well. Lastly, because glutamatergic signaling is pervasive in the human nervous system, the structure of the bacterial transporter, along with the homology models of the eukaryotic transporters, should facilitate the design of new molecules that may have therapeutic potential.