Molecular Mechanisms of Neuronal Differentiation

描述(由申请人提供)：从神经末梢到胞体的长距离逆行信号是神经营养素介导的细胞生存和控制神经元表型所必需的。尽管它非常重要，但关于这个涉及信号内体形成和运输的信号过程的基本问题仍然没有解决。有些问题争论不休，例如基于内体的系统如何实现持久的长距离信号。我们的实验室最近提供了一个潜在的解决方案，指出神经营养因子及其Trk受体参与了一种新的、专门的内吞途径。剖析这一新发现的神经营养因子/Trk信号通路及其在逆行轴突信号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发现的一种新的蛋白质Pincher(Pincytic Chaperone)。Pincher介导了NGF和其他神经营养因子Trk受体的主要逆行信号通路，而不是其他受体酪氨酸激酶。例如，EGF与NGF不同，它不参与远距离神经元的存活，它利用经典的短暂的、网状蛋白介导的非Pincher依赖的内体途径。我们计划明确地表明EGF和NGF信号通路在内体水平上是不同的，并进一步确定解释这些差异的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)确定细胞胞体中Pincher/TrkA内涵体的分子组成及其功能作用(2)确定Pincher/Trk内涵体在逆行运输途径不同阶段的分子蓝图(3)确定网状蛋白和Pincher相关蛋白对神经元存活的相对贡献。我们的研究与唐氏综合症和阿尔茨海默病直接相关，在这些疾病中，逆行营养支持是有缺陷的和/或恢复这种支持可以在预防神经元丢失和功能障碍方面具有治疗作用。了解所建议的营养因子信号和传递机制，对于合理设计治疗这些疾病和其他相关疾病的疗法至关重要。

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.