ANALYSIS OF AXON FASCICLE SPECIFIC PROTEINS

描述(摘自申请者的摘要)：这项工作的长期目标 该项目旨在阐明神经分子在神经细胞中的功能作用。 共同神经通路的发展和选择性轴突丛生。朝向 为此，用单抗LAN3-2进行免疫亲和纯化 和同事们已经确定了L1凸轮家族的一个新成员， Tractin是一种多结构域切割的蛋白质，具有几个独特的 功能。它含有6个Ig结构域，4个FNIII样结构域，1个酸性结构域，12 一个新的类胶原蛋白的富含脯氨酸和甘氨酸的序列基序a的重复序列 跨膜结构域，以及带有锚蛋白和 PDZ结构域结合基序。Tractin在所有神经元中都有表达，但 仅用Laz3-2和Laz2-369糖表位进行差异糖基化 形成特定神经束的外周感觉神经元的集合和亚群 中枢神经系统。这些糖表位的体内和体外抗体扰动有 证明它们可以选择性地调节轴突生长和突触 队形。此外，至少还有另外三株单抗(Lan2-3.Laz6-212，以及 Laz7-79)识别不同亚群所特有的不同糖表位 其中的神经元已经被识别出来。我们将检验这样的假设：这些 糖表位代表Tractin的额外翻译后修饰 而广泛表达的神经CAM的这种差异糖基化可以 功能辅助调节神经元突触生长和突触形成 不同的神经元亚群。因为Tractin也是由所有中枢 神经元这些发现表明Tractin可能是一种主要的调节因子 早期轴突丛生、轴突延伸和轴突引导的研究 神经系统发育。拟议中的实验将验证这一假设。 并确定Tractin的不同结构域对 这些过程在体内并将识别Tractin与其他蛋白质 通过相互作用来协调这些功能。此外，在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系列凸轮的翻译后处理。人类和人类的突变 小鼠L1导致严重的大脑异常；然而，导致 这些大脑缺陷的发育机制还没有被很好地理解 可能涉及L1与细胞外配体以及与L1的相互作用 与细胞骨架元素相关的细胞内信号通路。它是 因此，探索这种相互作用的分子基础具有重要意义。 各种模型系统，其中这种交互是容易处理的，以便定义 L1的结构多样性、功能和信令能力的范围 家庭摄像头。因此，这些研究将为我们提供对 神经连接异常和脑异常的根本原因 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.