Structural Study of Semaphorins, Neuropilins and Plexins

描述(申请人提供)：信号素是一大组细胞外蛋白质，参与发育过程中的各种过程，包括神经元迁移和轴突引导。它们的作用是作为化学排斥剂，引导轴突远离其表达标记的组织，但在某些情况下，它们也可以作为化学诱导剂。信号素受体是多蛋白复合体，其中包括作为信号转导亚单位的丛状分子。此外，一些信号素受体包括一个神经毛细蛋白配体结合亚单位。这项建议的研究集中在信号素、神经粘连蛋白、丛状蛋白及其相互作用的详细结构特征上。对信号素和神经毛膜蛋白的初步研究已经确定了它们的相互作用区域。在2.8A分辨率下测定了Semaphorin-3A受体结合模块的晶体结构，揭示了意想不到的β螺旋桨分子结构。接下来将使用X射线结晶学来确定全长Semaphorin-3A的结构以及从其他类别中选择的信号素的结构。对这些结构的分析将集中于识别对确定信号素的受体和辅助受体的特异性至关重要的结构元素。神经粘连蛋白和神经丛蛋白相互作用区域的晶体结构也将被确定。最后，将确定一系列信号素/神经粘连蛋白、神经粘连蛋白/丛状蛋白、信号素/丛状蛋白以及信号素/神经粘连蛋白/丛状蛋白复合体的结构，阐明导致信号素信号起始的分子事件。这些结构数据将得到基于生物物理、生化和荧光/FRET的信号素/神经粘连蛋白/丛状蛋白相互作用研究的补充。结合的结构和生物物理信息将提供对信号素、神经粘连蛋白和神经丛蛋白生物学功能的分子机制的基本见解，并可能在开发治疗脑和脊髓损伤的治疗剂方面具有重要应用。

DESCRIPTION (provided by applicant): The semaphorins are a large group of extracellular proteins involved in a variety of processes during development, including neuronal migration and axon guidance. They function as chemorepellents that direct axons away from tissues marked by their expression, but in some cases can also act as chemoattractants. The semaphorin receptors are multiprotein complexes, which include a plexin molecule serving as the signal-transducing subunit. In addition, some semaphorin receptors include a neuropilin ligand-binding subunit. Research in this proposal focuses on detailed structural characterization of the semaphorins, neuropilins, plexins, and their interactions. Preliminary studies of semaphorins and neuropilins have identified their interacting domains. The crystal structure of the receptor-binding module of Semaphorin-3A was determined at 2.8 A resolution, revealing an unexpected beta propeller molecular architecture. X-ray crystallography will be used next to determine the structure of full-length Semaphorin-3A and structures of selected semaphorins from other classes. The analysis of these structures will focus on identifying structural elements important for defining the receptor and co-receptor specificities of semaphorins. The crystal structures of the interacting domains of neuropilins and plexins will also be determined. Finally, the structures of a series of semaphorin/neuropilin, neuropilin/plexin, semaphorin/plexin, and semaphorin/neuropilin/plexin complexes will be determined, illuminating the molecular events leading to the initiation of semaphorin signaling. The structural data will be complemented by biophysical, biochemical and fluorescence/FRET-based studies of the semaphorin/neuropilin/plexin interactions. The combined structural and biophysical information will provide fundamental insights into the molecular mechanisms underlying the biological functions of semaphorins, neuropilins, and plexin, and could have significant applications in development of therapeutic agents for treatment of brain and spinal cord injuries.