Drug abuse signaling pathways that regulate CREB mRNA translation in dendrites

描述(申请人提供)：拟议研究的目标是了解滥用药物刺激突触如何导致核内转录效应。所有滥用药物都被证明会刺激基因表达的变化。这些变化被认为是反复接触毒品后出现的许多长期变化的基础，这些变化是成瘾的特征。然而，目前尚不清楚突触上的信号如何影响核内的基因转录，核内的基因转录可能相隔数百微米。我们最近发现，编码转录因子CREB的mRNA存在于发育中的神经元的轴突和生长锥中，当暴露于NGF时，该mRNA被“局部”翻译，导致CREB在生长锥中积累，然后被磷酸化并逆行运输到细胞核。这种轴突来源的CREB与启动子序列结合，刺激神经元生存所需的基因转录。因此，生长锥体到细胞核的信号转导需要局部翻译和逆行运输。除了在神经元存活中的作用外，CREB还在调节与滥用药物相关的长期变化方面发挥关键作用。我们的初步数据表明，CREB在树突内翻译。在这一应用中，我们建议通过实验来识别与药物滥用相关的突触信号通路，这些信号通路调节树突状CREB的翻译、磷酸化和核转位。此外，利用树突状CREB mRNA选择性缺失的神经元，我们将确定树突状CREB mRNA在核基因转录中的作用。总之，CEBRA应用中的实验将探索这种意想不到的信号模式的作用，它将显著影响我们目前对滥用药物所使用的分子机制的思考。

DESCRIPTION (provided by applicant): The objective of the proposed research is to understand how synaptic stimulation by drugs of abuse leads to transcriptional effects in the nucleus. All drugs of abuse have been shown to stimulate changes in gene expression. These changes are thought to underlie many of the long-term changes seen following repeated drug exposure that characterize addiction. However, it is unclear how signaling at a synapse could affect gene transcription in the nucleus, which can be separated by a distance of several hundred micrometers. We have recently discovered that the mRNA encoding CREB, a transcription factor, is present in the axons and growth cones of developing neurons, and this mRNA is translated 'locally' upon exposure to NGF, resulting in the accumulation of CREB in growth cones, which is then phosphorylated and retrogradely trafficked to the nucleus. This axonally-derived CREB binds to promoter sequences and stimulates the gene transcription necessary for neuronal survival. Thus, local translation and retrograde trafficking is required for growth cone- to-nucleus signaling. In addition to its role in neuronal survival, CREB has critical roles in mediating the long- term changes associated with drugs of abuse. Our preliminary data show that CREB is translated within dendrites. In this application, we propose experiments to identify drug abuse-related synaptic signaling pathways that regulate dendritic CREB translation, phosphorylation, and nuclear translocation. Furthermore, using neurons selectively-deficient in dendritic CREB mRNA, we will determine the role of dendritic CREB mRNA in nuclear gene transcription. Together, the experiments in this CEBRA application will explore the role of this unanticipated mode of signaling which would significantly impact our current thinking about the molecular mechanisms employed by drugs of abuse.