Cellular Responses to Stress

描述（由申请人提供）：细胞已经进化出多种策略来应对生存的各种和不可避免的压力。应激反应的扰动是许多疾病的基础。最近发现的一种策略涉及形成应力颗粒。我们发现了应激颗粒与丝氨酸/苏氨酸激酶RSK2之间的一种新的、意想不到的联系。我们发现，在氧化应激或血清饥饿的乳腺癌细胞系中，内源性RSK2与促凋亡蛋白TIA-1结合并共定位，TIA-1是应激颗粒的重要成分。出乎意料的是，RSK2通过涉及eIF21的途径调节应激颗粒的形成。有丝分裂原的加入触发应激颗粒的溶解，释放的RSK2在细胞核中积累，诱导细胞周期蛋白D1的表达，驱动进入细胞周期。我们提出了一种双向调控机制，其中应力颗粒隔离RSK2以防止不适当的细胞周期进入，而RSK2促进应力颗粒组装以抑制翻译。因此，RSK2可能是连接应激反应与生存和增殖的关键因素。一个重要的目标是阐明，在分子水平上，这种联系的机制。具体目的是：(1)验证RSK2通过调控应力颗粒组装来控制应激反应的假设。RSK2在启动和维持应激颗粒中的功能将通过体外结合研究、基因沉默、免疫荧光和活细胞成像来研究。(2)验证应激后恢复依赖于RSK2核易位的假设。RSK2核输入的机制和RSK2在生存中的功能将使用与Aim 1中使用的方法相似的方法进行研究。

DESCRIPTION (provided by applicant): Cells have evolved multiple strategies to cope with the varied and inevitable stresses of existence. Perturbation of stress responses underlies numerous diseases. One recently discovered strategy involves the formation of stress granules. We have discovered a novel, unanticipated link between stress granules and the Ser/Thr kinase, RSK2. We found that in breast cancer lines subjected to oxidative stress or serum starvation, endogenous RSK2 associates with and co-localizes with the pro-apoptotic protein, TIA-1, an essential component of stress granules. Unexpectedly, RSK2 regulates stress granule formation through a pathway involving eIF21. Addition of mitogens triggers the dissolution of stress granules, and the released RSK2 accumulates in the nucleus where it induces cyclin D1 expression, driving entry into the cell cycle. We propose a bidirectional regulatory mechanism in which stress granules sequester RSK2 to prevent inappropriate cell cycle entry, and RSK2 facilitates stress granule assembly to repress translation. Thus, RSK2 may be a pivotal factor linking the stress response to survival and proliferation. An essential goal is to elucidate, at a molecular level, the mechanism of this linkage. The specific aims are: (1) Test the hypothesis that RSK2 controls the stress response through regulation of stress granule assembly. The function of RSK2 in initiation and maintenance of stress granules will be investigated using in vitro binding studies, gene silencing, immunofluorescence and live cell imaging. (2) Test the hypothesis that post-stress recovery depends on RSK2 nuclear translocation. The mechanism of RSK2 nuclear import and the function of RSK2 in survival will be investigated using similar approaches to those used in Aim 1. These studies will increase our mechanistic understanding of the function of RSK2 in promoting disease, in particular cancer, and may identify new targets for therapeutic intervention. PUBLIC HEALTH RELEVANCE: We have discovered a novel mechanism that links the protein kinase RSK2 with survival in response to stress. Perturbation of stress responses underlies numerous diseases. Our studies may identify new targets for therapeutic intervention in cancer and inflammatory diseases.