Signal transduction in axon guidance

描述（由申请人提供）：大脑的功能依赖于一种复杂的轴突连接模式，这种模式最初是在发育过程中建立的。该项目的长期目标是了解轴突向正确目标生长所需的寻路过程的分子信号机制。目前的建议特别侧重于基于rna的机制，这在轴突中尚未广泛表征。Aim 1建立在我们最近的工作基础上，表明跨膜轴突引导受体DCC与翻译起始机制（包括eif和核糖体亚基）有物理关联。细胞表面受体与翻译机制的功能和物理关联的这一发现导致了基于跨膜翻译调节复合物的细胞外调节和翻译定位的可推广模型。在这里，我们提出进一步的研究，以调查这种现象在不同类别的受体中可能有多普遍，重点是参与神经发育的受体。这种新的调节机制的识别也提出了有趣的问题，我们将解决有关分子成分和参与复合物的相互作用。Aim 2扩展了我们之前发现的基于rna的机制，该机制可以调节脊髓联合轴突内的蛋白质表达，因为它们经过了其特征明确的中间引导靶点，即脊髓底板。我们已经确定了CPEB家族中参与脊髓联合神经元寻路的rna结合蛋白。我们建议进一步研究这些rna结合蛋白在轴突引导中的功能，使用体外和体内功能系统。我们还建议对这些蛋白结合的下游靶mrna进行研究，这将深入了解它们的调节相互作用网络。虽然我们的工作主要集中在神经元发育的基本生物学上，但它对健康研究具有广泛的意义。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迟钝等疾病。此外，一个主要的健康问题是由成年神经元无法再生造成的，最终，对发育寻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为揭示对生物医学研究具有非常普遍意义的基本原理提供了一个模型。

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.