Cytoskeleton Coordination in Neuronal Morphogenesis

描述(申请人提供)：神经元性特征 形态发生是形成长的、分枝的膜延伸，称为 神经突起，寻找并在神经元之间形成高度选择性的连接。 我们的长期目标是了解细胞骨架网络如何指定 神经突起延伸所需的膜动力学的复杂变化，以及如何 信号通路调节这一行为。肌动蛋白和微管的变化 细胞骨架的组装和组织在轴突生长中很重要，并且 钙粘附素和蛋白质腺瘤性息肉病(APC)很好地定位于 在协调这些变化方面发挥关键作用。钙粘附素细胞-细胞黏附 蛋白质参与轴突路径的寻找，即接触的启动 神经突起延伸和突触功能之间的关系。钙粘附素与 肌动蛋白的细胞骨架由β-和α-连环蛋白组成，而这种复合体是必不可少的 钙粘附素在粘连中的作用。APC还结合细胞质中的β-连环蛋白和 靶向β-连环蛋白的降解，从而调节 β-连环蛋白在调控Wnt信号反应中的基因表达。装甲运兵车 蛋白质与微管结合，刺激微管组装和捆绑在 在体外，聚集在微管正端的蛋白质簇中 上皮和神经元膜延伸的尖端，并富含轴突 生长锥体和突触。β-连环蛋白与APC的结合 质膜上的微管相关簇减少了细胞膜 生长表明β-连环蛋白在调节细胞中的另一种功能 通过APC的形态发生。我们的工作假设是 大脑皮层微管相关的APC簇局部调节细胞骨架 轴突生长和接触形成过程中的重新组织，以及APC 簇又受Wnt信号和钙粘附素信号的调节 细胞表面的复合体。这一假设将得到检验：1)。确定和 鉴定皮质APC簇中的蛋白质，并确定它们在APC中的作用 集群形成；2)。表征膜附着型APC的功能 微管中的簇团组装和形成突起；3)。 识别和表征Wnt和钙粘附素的信号通路 调整APC集群功能。这些拟议研究的意义在于 他们将提供细胞骨架重组是如何进行的新的理解 控制在局部定义的亚细胞域中，以便指定轴突 细胞外信号对细胞生长和细胞间接触的响应。

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.