mRNA transport and local translation after axotomy

描述(申请人提供)：神经元可以通过靶向亚细胞区域的mRNAs来局部产生新的蛋白质，从而在空间上调节基因表达。虽然最好的特征是树突间，但最近的研究证明轴突间也有局部蛋白质合成的能力。这种局部的轴突蛋白质合成受改变轴突生长的细胞外刺激的调节。从基于蛋白质组学的研究中，我们已经确定了大量在培养的DRG神经元的再生轴突中合成的蛋白质。这种在轴突中局部合成的蛋白质的新知识使我们能够问：mRNAs的运输和特定mRNAs的翻译在轴突中是如何调节的。这一提议的中心假设是，神经元通过专门改变mRNAs的运输和直接在生长的轴突中合成新的蛋白质，来调节轴突亚域的蛋白质组成，以响应环境提示。我将用两个具体目标来检验这一假设。首先，我将讨论细胞外刺激对轴突mRNA运输的调节，并检验mRNAs进入再生轴突的运输是由受体介导的信号转导途径调节的细胞外信号的假说。其次，我将检验轴突内蛋白质合成的特异性，以及轴突蛋白质合成受环境刺激的不同调节的假设。我将把这些分析集中在编码结构蛋白(β-肌动蛋白、外周蛋白和波形蛋白)和损伤反应蛋白(HSP70、GRP78/Bip和Importin beta1)的轴突mRNAs上，它们在轴突生长中发挥核心作用。

DESCRIPTION (provided by applicant): Neurons can spatially regulate gene expression by targeting mRNAs to subcellular domains to locally generate new proteins. Although best characterized in the dendritic compartment, recent studies have proven that the axonal compartment is also capable of local protein synthesis. This localized axonal protein synthesis is regulated by extracellular stimuli that alter axonal growth. From proteomics-based studies, we have identified a substantial number of proteins that are synthesized in the regenerating axons of cultured DRG neurons. This new knowledge of the proteins that are locally synthesized in axons allows us to ask how transport of mRNAs and translation of specific mRNAs is regulated in the axons. The central hypothesis of this proposal is that neurons modulate the protein makeup of axonal subdomains in response to environmental cues by specifically altering transport of mRNAs into, and synthesis of new proteins directly in, growing axons. I will test this hypothesis with two specific aims. First, I will address the regulation of axonal mRNA trafficking by extracellular stimuli and test the hypothesis that transport of mRNAs into the regenerating axon is modulated by extracellular signals acting through receptor-mediated signal transduction pathways. Second, I will test the specificity of intra-axonal protein synthesis and the hypothesis that axonal protein synthesis is differentially regulated by environmental stimuli. I will focus these analyses on axonal mRNAs encoding structural proteins (Beta-actin, peripherin and vimentin) and injury-response proteins (HSP70, grp78/BiP and Importin Beta1) that play central roles in axonal growth.