Cytoskeleton Coordination in Neuronal Morphogenesis

描述（由申请人提供）：神经元的特征性特征 形态发生是长的、分支的膜延伸的形成，称为 神经突，寻找并形成神经元之间的高度选择性连接。 我们的长期目标是了解细胞骨架网络是如何指定 神经突延伸所需的膜动力学的复杂变化，以及如何 信号通路调节这种行为。肌动蛋白和微管的变化 细胞骨架组装和组织在神经突生长中是重要的， 钙粘蛋白和蛋白质腺瘤性结肠息肉病（APC）是很好的位置， 在协调这些变化中发挥关键作用。钙粘蛋白细胞间粘附 蛋白质参与轴突路径的寻找， 神经突延伸和突触功能之间的联系钙粘蛋白与 肌动蛋白细胞骨架的β-和α-连环蛋白，这种复合物是必不可少的 对于钙粘蛋白在粘附中的功能。APC还结合细胞质β-连环蛋白， 靶向β-连环蛋白进行降解，从而调节 β-连环蛋白在响应Wnt信号传导中控制基因表达。APC 蛋白质与微管结合，刺激微管组装和捆绑， 在体外，在微管的正端积累在蛋白质簇中， 上皮和神经元膜延伸的尖端，并在轴突中富集 生长锥和突触。β-连环蛋白与APC的结合 细胞膜上的微管相关簇减少了细胞膜 结果表明β-连环蛋白在调节细胞增殖中的另一种功能， 通过APC进行形态发生。我们的假设是 皮层微管相关APC簇局部调节细胞骨架 在神经突生长和接触形成过程中重新组织，APC 簇依次受Wnt信号和来自钙粘蛋白的信号调节 在细胞表面形成复合物。这个假设将被检验：1）。识别和 表征皮质APC簇中的蛋白质，并确定它们在APC中的作用 团簇形成; 2）.表征膜附着APC的功能 微管组装中的簇和神经突延伸的形成;和3）。 识别和表征来自Wnt和钙粘蛋白的信号通路， 调节APC簇功能。这些拟议研究的意义在于 他们将提供新的理解细胞骨架重组是如何 控制在局部定义的亚细胞区域，以指定神经突 生长和细胞-细胞接触响应细胞外信号。

DESCRIPTION (provided by applicant): A characteristic feature of neuronal morphogenesis is the formation of long, branched membrane extensions, termed neurites, which seek out and form highly selective connections between neurons. Our long-term objective is to understand how cytoskeletal networks specify complex changes in membrane dynamics required for neurite extension, and how signaling pathways regulate this behavior. Changes in actin and microtubule cytoskeleton assembly and organization are important in neurite outgrowth, and cadherins and the protein adenomatous polyposis coli (APC) are well placed to play key roles in coordinating these changes. Cadherin cell-cell adhesion proteins are involved in axonal path finding, the initiation of contacts between neurite extensions, and synapse function. Cadherins are linked to the actin cytoskeleton by beta- and alpha-catenin, and this complex is essential for cadherin function in adhesion. APC also binds cytoplasmic beta-catenin and targets beta-catenin for degradation thereby regulating another function of beta-catenin in controlling gene expression in response to Wnt signaling. APC protein binds to microtubules, stimulates microtubule assembly and bundling in vitro, accumulates in protein clusters at the plus-end of microtubules at the tips of epithelial and neuronal membrane extensions, and is enriched in axonal growth cones and at synapses. Binding of beta-catenin to APC in microtubule-associated clusters at the plasma membrane decreases membrane outgrowth indicating another function for beta-catenin in regulating cellular morphogenesis through APC. Our working hypothesis is that microtubule-associated APC clusters at the cortex locally regulate cytoskeletal re-organization during neurite outgrowth and contact formation, and that APC clusters are in turn regulated by Wnt signaling and signals from the cadherin complex at the cell surface. This hypothesis will be tested: 1). Identify and characterize proteins in cortical APC clusters, and determine their role in APC cluster formation; 2). Characterize the function of membrane-attached APC clusters in microtubule assembly and formation of neurite extensions; and 3). Identify and characterize signaling pathways from Wnt and cadherins that regulate APC cluster function. The significance of these proposed studies is they will provide novel understanding of how cytoskeletal restructuring is controlled in locally defined, subcellular domains in order to specify neurite outgrowth and cell-cell contacts in response to extracellular signals.