Regulation of c-fos By Nerve Growth Factor

描述（由申请人提供）：虽然细胞外信号调节激酶（ERK）激活最初被认为是一个简单的控制增殖的开关，但现在很清楚，激酶激活的持续时间可以编码特定的细胞反应。这种现象在大鼠嗜铬细胞瘤细胞系PC12细胞中表现得最好。在该模型中，神经生长因子（NGF）产生持续的ERK激活，导致分化。NGF的作用机制之一是对核效应物（如c-fos）的调节。然而，c-fos作为NGF持续ERK激活的功能性效应者的作用尚未确定。本提案将研究在ngf介导的c-fos调节中ERK级联持续激活的要求（目的1）。此外，还将研究小G蛋白Rap1在NGF作用中的作用（Aim #2）。我们将测量激活蛋白1依赖性基因表达和ngf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c-fos中特定ERK磷酸化位点对PC12细胞中ngf依赖性稳定和转激活的要求。这项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.