Signal transduction in axon guidance

描述(申请人提供)：大脑的功能依赖于最初在发育过程中建立的复杂的轴突连接模式。该项目广泛的长期目标是了解分子信号机制，这些机制是轴突向正确目标生长所需的寻路过程的基础。目前的建议特别关注基于RNA的机制，这些机制在轴突中还没有得到广泛的表征。目的1建立在我们最近工作的基础上，表明跨膜轴突引导受体DCC在物理上与翻译起始机制有关，包括EIF和核糖体亚基。细胞表面受体与翻译机制的功能和物理联系的这一发现，导致了一个基于跨膜翻译调控复合体的细胞外调控和翻译定位的通用模型。在这里，我们建议进行进一步的研究，以调查这种现象对于不同类别的受体可能有多普遍，重点是参与神经发育的受体。对这种新的调控机制的识别也提出了我们将解决的关于复合体中涉及的分子组成和相互作用的有趣问题。Aim 2扩展了我们之前发现的基于RNA的机制，当脊髓连合轴突通过其特征良好的中间引导靶点-脊髓底板时，可以调节这些轴突内的蛋白质表达。我们已经确定了CPEB家族中的RNA结合蛋白，它们与脊髓连合神经元的发现有关。我们建议使用体外和体内功能系统进一步研究这些RNA结合蛋白在轴突引导中的功能。我们还建议对这些蛋白质结合的下游靶mRNAs进行研究，这将有助于深入了解它们的调控相互作用网络。虽然我们的工作主要集中在神经元发育的基础生物学上，但它对健康研究具有广泛的影响。正确的轴突寻路是正常神经发育所必需的，而基于RNA的机制已知会导致智力低下等疾病。此外，成年神经元无法再生是一个主要的健康问题，最终对发育路径的研究可能有助于轴突再生的策略。更广泛地说，我们在神经元上的工作提供了一个模型，以揭示对生物医学研究具有非常普遍意义的基本原理。

DESCRIPTION (provided by applicant): The brain relies for its function on a complex pattern of axonal connections that are initially set up during development. The broad long-term goal of the project is to understand molecular signaling mechanisms that underly the process of pathfinding required for axons to grow toward their correct targets. The current proposal focuses particularly on RNA-based mechanisms, which have not been characterized extensively in the axon. Aim 1 builds on our recent work showing that the transmembrane axon guidance receptor DCC physically associates with translation initiation machinery, including eIFs and ribosomal subunits. This finding of functional and physical association of a cell surface receptor with the translation machinery leads to a generalizable model for extracellular regulation and localization of translation, based on a transmembrane translation regulation complex. Here we propose further studies to survey how general this phenomenon may be for different classes of receptor, focusing on receptors involved in neural development. Identification of this novel regulatory mechanism also raises interesting questions we will address regarding molecular components and interactions involved in the complex. Aim 2 extends our work which previously identified RNA-based mechanisms that can regulate protein expression within spinal commissural axons as they navigate past their well characterized intermediate guidance target, the floor plate of the spinal cord. We have identified RNA-binding proteins in the CPEB family that are involved in spinal commissural neuron pathfinding. We propose further studies of the functions of these RNA-binding proteins in axon guidance, using both in vitro and in vivo functional systems. We also propose studies of the downstream target mRNAs bound by these proteins, which will yield insight into their network of regulatory interactions. While our work focuses primarily on the basic biology of neuron development, it has broad implications for health research. Correct axon pathfinding is required for normal neural development, and RNA-based mechanisms are known to contribute to diseases such as mental retardation. Also, a major health problem is created by inability of adult neurons to regenerate, and ultimately the study of developmental pathfinding is likely to contribute to strategies for axon regeneration. More broadly, our work on the neuron provides a model to uncover fundamental principles with very general implications for biomedical research.