Structural Study of Semaphorins, Neuropilins and Plexins

描述（由申请人提供）：信号蛋白是一大类细胞外蛋白，参与发育过程中的各种过程，包括神经元迁移和轴突引导。它们的作用是将轴突从其表达的组织中引导出来，但在某些情况下也可以作为趋化剂。信号蛋白受体是多蛋白复合物，其中包括一个作为信号转导亚基的丛蛋白分子。此外，一些信号素受体包括神经匹林配体结合亚基。本提案的研究重点是信号蛋白、神经蛋白、丛蛋白及其相互作用的详细结构表征。信号素和神经匹林的初步研究已经确定了它们的相互作用域。Semaphorin-3A受体结合模块的晶体结构在2.8 A分辨率下被确定，揭示了一个意想不到的β螺旋桨分子结构。接下来将使用x射线晶体学来确定全长Semaphorin-3A的结构以及从其他类别中选择的semaphorin的结构。对这些结构的分析将集中在识别对定义信号蛋白的受体和共受体特异性重要的结构元素上。神经蛋白和丛蛋白相互作用域的晶体结构也将被确定。最后，我们将确定一系列信号素/神经匹林、神经匹林/丛蛋白、信号素/丛蛋白和信号素/神经匹林/丛蛋白复合物的结构，阐明导致信号素信号启动的分子事件。结构数据将由信号素/神经磷脂/丛蛋白相互作用的生物物理、生化和荧光/ fret研究补充。结合结构和生物物理信息，将为信号蛋白、神经肽和神经丛蛋白生物学功能的分子机制提供基本见解，并可能在开发治疗脑和脊髓损伤的治疗药物方面具有重要应用。

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.