ANALYSIS OF AXON FASCICLE SPECIFIC PROTEINS

描述（来自申请人的摘要）：本研究的长期目标 该项目旨在阐明神经分子在神经系统中的功能作用。 共同神经通路和选择性轴突成束的发展。朝向 通过用mAb Lan 3 -2进行免疫亲和纯化， 和同事已经确定了一个新的成员的L1家族的CAM， Tractin是一种多结构域切割蛋白，具有几个独特的结构域， 功能.它含有6个Ig结构域，4个FNIII样结构域，一个酸性结构域，12个 一种新的胶原蛋白样富含脯氨酸和甘氨酸的序列基序的重复， 跨膜结构域，以及具有锚蛋白和跨膜结构域的细胞内尾区。 PDZ结构域结合基序。牵引蛋白由所有神经元表达， 与Lan 3 -2和Laz 2 -369糖表位的差异糖基化仅在 外周感觉神经元的集合和子集，形成特定的神经束， CNS。这些糖表位的体内和体外抗体扰动具有 表明它们可以选择性地调节轴突生长和突触 阵此外，至少三种其他mAb（Lan 2 -3. Laz 6 -212，以及 Laz 7 -79），其识别对不同子集特异性的不同糖表位 这些神经元中的一部分已经被识别出来。我们将测试这些假设， 糖表位代表对牵引蛋白的额外翻译后修饰 并且这种广泛表达的神经CAM的差异糖基化可以 在功能上辅助调节神经元生长和突触形成 不同的神经元亚群。由于牵引蛋白也由所有中央 这些发现表明，牵引蛋白可能作为一个主要的调节器， 轴突成束、轴突延伸和轴突引导在早期 神经系统发育拟议中的实验将检验这一假设 并确定牵引蛋白不同结构域的相对贡献， 这些过程在体内，并将确定其他蛋白质与牵引蛋白 相互作用来调节这些功能。此外，S2中的表达研究 细胞系将提供有关生物合成和机制的新信息 L1家族CAM的翻译后加工。人类和 小鼠L1导致严重的大脑异常;然而， 这些大脑缺陷的发育机制还没有得到很好的理解， 可能涉及L1与细胞外配体以及与 与细胞骨架元件相连的细胞内信号通路。是 因此，重要的是探索这种相互作用的分子基础， 各种模型系统，其中这种相互作用是易于处理的，以便定义 L1的结构多样性、功能和信号能力的范围 家庭摄像机因此，这些研究将提供有价值的新见解， 神经连接异常和大脑异常的根本原因 发展

DESCRIPTION (From applicant's abstract): The long range objective of this project is to elucidate the functional role of neural molecules in the development of common nerve pathways and selective axon fasciculation. Towards this end by immunoaffinity purification with the mAb Lan3-2, the investigator and associates have identified a novel member of the L1 family of CAMs, Tractin, which is a multiple domain cleaved protein with several unique features. It contains 6 Ig-domains, 4 FNIII-like domains, an acidic domain, 12 repeats of a novel collagen-like proline- and glycine-rich sequence motif, a transmembrane domain, and an intracellular tail with an ankyrin and a PDZ-domain binding motif. Tractin is expressed by all neurons but is differentially glycosylated with the Lan3-2 and Laz2-369 glycoepitopes only in sets and subsets of peripheral sensory neurons that form specific fascicles in the CNS. In vivo and in vitro antibody perturbation of these glycoepitopes have demonstrated that they can selectively regulate axonal outgrowth and synapse formation. In addition, at least three other mAbs (Lan2-3. Laz6-212, and Laz7-79) which recognize different glycoepitopes specific to distinct subsets of these neurons have been identified. We will test the hypothesis that these glycoepitopes represent additional posttranslational modifications to Tractin and that such differential glycosylation of a widely expressed neural CAM can functionally assist in regulation neuronal outgrowth and synapse formation of distinct neuronal subpopulations. As Tractin is also expressed by all central neurons these findings suggest that Tractin may function as a major regulator of axon fasciculation, neurite extension, and axonal guidance during early nervous system development. The proposed experiments will test this hypothesis and determine the relative contributions of the different domains of Tractin to these processes in vivo and will identify other proteins with which Tractin interacts to mediate these functions. In addition, expression studies in the S2 cell line will provide novel information about the biosynthesis and mechanisms of posttranslational processing of the L1 family CAMs. Mutations in human and murine L1 lead to severe brain abnormalities; however, the causative developmental mechanisms of these brain defects are not well understood and are likely to involve interaction of L1 with extracellular ligands as well as with intracellular signaling pathways linked to cytoskeletal elements. It is therefore of importance to explore the molecular basis for such interactions in various model systems where such interactions are tractable in order to define the range of structural diversity, functions, and signaling capabilities of L1 family CAMs. Thus, these studies will provide valuable new insights into the underlying causes of aberrant neural connections and abnormal brain development.