Regulation of c-fos By Nerve Growth Factor

描述（由申请人提供）：尽管最初认为细胞外信号调节激酶（ERK）激活作为控制增殖的简单ON-OFF开关起作用，但现在清楚的是，激酶激活的持续时间可以编码特定的细胞应答。使用大鼠嗜铬细胞瘤细胞系PC 12细胞最佳地显示了这种现象。在该模型中，神经生长因子（NGF）产生持续的ERK激活，导致分化。神经生长因子的作用机制之一是调节核效应子，如c-fos。然而，c-fos作为NGF的持续ERK激活的功能效应器的作用尚未确定。本提案将研究在NGF介导的c-fos调节中持续激活ERK级联的需要（目标#1）。此外，还将研究小G蛋白Rap 1在NGF作用中的作用（目标#2）。我们将测量激活蛋白-1依赖的基因表达和神经生长因子介导的c-fos蛋白稳定性作为c-fos功能的读数。此外，我们将测试在PC 12细胞中的神经生长因子依赖的稳定和转录激活的c-fos中的特定ERK磷酸化位点的要求。这一工作将有助于我们进一步了解神经元分化的调控。

DESCRIPTION (provided by applicant): Although extracellular signal-regulated kinase (ERK) activation was originally thought to operate as a simple ON-OFF switch governing proliferation, it is now clear that duration of kinase activation can encode specific cellular responses. This phenomonon is best shown using the rat pheochromocytoma cell line, PC12 cells. In this model, nerve growth factor (NGF) produces sustained ERK activation resulting in differentiation. One mechanism underlying NGF's action is regulation of nuclear effectors, such as c-fos. However, a role for c-fos as a functional effector of NGF's sustained ERK activation has not been established. This proposal will examine the requirement for sustained activation of the ERK cascade in NGF-mediated c-fos regulation (Aim #1). In addition, the role of the small G protein Rap1 in NGF's actions will be investigated (Aim #2). We will be measuring activator protein-1-dependent gene expression and NGF-mediated c-fos protein stabilization as a readout of c-fos function. In addition, we will test the requirement of specific ERK phosphorylation sites in c-fos for NGF-dependent stabilization and transactivation in PC12 cells. This work will help us to further understand the regulation of neuronal differentiation.