Molecular Mechanisms of Neuronal Differentiation

描述（由申请人提供）：神经营养因子介导的细胞存活和神经元表型控制需要从神经末梢到索马的长距离逆行信号传导。尽管其非常重要，但有关这个信号传导过程（涉及信号内体的形成和运输）的基本问题仍然没有得到解决。一些问题存在很大争议，例如基于内体的系统如何实现持久的长距离信号传递。我们的实验室最近提供了一个潜在的解决方案，指出了神经营养因子及其Trk受体的一种新的、专门的内吞途径的参与。解剖这个新发现的神经营养因子/Trk信号通路及其在逆行轴突信号传导中的作用是这项资助的主要重点。该信号通路的核心是我们实验室鉴定的新型蛋白质Pincher（Pinocytic Chaperone）。Pincher介导NGF和其他神经营养因子Trk受体的主要逆行信号传导途径，但不介导其他受体酪氨酸激酶。例如，与NGF不同，EGF不介导长距离神经元存活，其利用经典的短寿命的、不依赖于Pincher的网格蛋白介导的内体途径。我们计划明确表明EGF和NGF信号通路在内体水平上是不同的，并进一步确定导致这些差异的Pincher相关蛋白。为了实现这一目标，我们提出了三个具体的目标：（1）确定的分子组成部分，和他们的功能作用，在Pincher/TrkA内体的细胞索马（2）确定的分子蓝图Pincher/Trk内体在不同阶段的逆行转运途径（3）确定网格蛋白和Pincher相关蛋白的相对贡献神经元的生存。我们的研究与唐氏综合征和阿尔茨海默病直接相关，其中逆行营养支持是有缺陷的和/或这种支持的恢复可以在预防神经元损失和功能障碍方面具有治疗性。理解所提出的营养因子信号传导和递送的机制对于合理设计用于对抗这些和其他相关疾病的治疗剂是至关重要的。

DESCRIPTION (provided by applicant): Long distance retrograde signaling from nerve endings to the soma is required for Neurotrophin-mediated cell survival and the control of neuronal phenotype. Despite its great importance, fundamental questions about this signaling process, which involves formation and transport of signaling endosomes, remain unresolved. Some issues are highly contested, such as how persistent, long-distance signaling can be achieved by an endosome-based system. A potential resolution was provided recently by our lab that pointed to involvement of a novel, specialized endocytotic pathway for neurotrophins and their Trk receptors. Dissecting this newly identified Neurotrophin/Trk signaling pathway and its role in retrograde axonal signaling is the primary focus of this grant. At the heart of this signaling pathway is the novel protein Pincher (Pinocytic Chaperone) identified in our lab. Pincher mediates the primary retrograde signaling pathway for NGF and the other neurotrophin Trk receptors, but not other receptor tyrosine kinases. EGF for example, which unlike NGF does not mediate long-distance neuronal survival, utilizes the classic short-lived, clathrin-mediated endosomal pathway that is Pincher-independent. We plan to definitively show that the EGF and NGF signaling pathways are distinct at the level of endosomes and, further, to identify the Pincher-associated proteins that account for these differences. To achieve this goal we propose three specific aims: (1) Identify the molecular components, and their functional roles, in Pincher/TrkA endosomes in the cell soma (2) Identify the molecular blueprint of Pincher/Trk endosomes at distinct stages in the retrograde transport pathway (3) Determine the relative contributions of clathrin and Pincher associated proteins to neuronal survival. Our studies are directly relevant to both Down's syndrome and Alzheimer's disease, wherein retrograde trophic support is defective and/or restoration of such support can be therapeutic in preventing neuronal loss and dysfunction. An understanding of the mechanisms for trophic factor signaling and delivery as proposed is essential to the rational design of therapeutics for combating these and other related diseases.