The Role and Biology of Fra-1 in Lung Injury and Repair

描述（由申请人提供）：转录“激活子”和“阻遏子”之间的平衡作用似乎在维持组织稳态中起关键作用。然而，将平衡转移到激活子或阻遏子的功能上会使转录（基因表达的初始步骤）失调，最终导致病理状态。事实上，新出现的数据已经将参与损伤和修复的基因的异常表达与各种环境损伤因果联系起来，这些环境损伤导致或增强了对各种病理状态的易感性，包括急性和慢性肺部疾病。这项竞争性的更新申请专注于扩大我们正在进行的Fra 1转录在肺损伤和修复中的新作用的研究。Fra 1是AP 1（Jun/Fos）的二聚体伴侣，其被环境损伤激活并调节参与正常和病理过程的基因表达。在上一个资助期间，我们已经表明，上游启动子元件和血清反应元件之间的相互作用驱动Fra 1诱导。我们已经证明，异位Fra 1促进肺细胞的运动和入侵在体外，但它需要其他激活的原癌基因（S）赋予其致癌潜力在体内。虽然新出现的数据已经明确证明了Fra 1在癌细胞进展和侵袭中的致病作用，但Fra 1在非恶性肺部疾病中的确切作用仍不清楚。有趣的是，我们发现，与对照小鼠相比，Fra 1的缺失增强了对促氧化剂诱导的肺损伤的保护作用。我们还发现，Fra 1缺陷的细胞比Fra 1充足的细胞对促氧化剂诱导的细胞死亡具有更强的抵抗力。在报告基因检测中，异位Fra 1表达降低了肺上皮细胞中AP 1依赖性和非依赖性转录反应。基于这些新的初步观察，我们假设Fra 1作为一种“转录抑制因子”发挥作用，从而在促进细胞损伤和肺发病机制中发挥关键作用。为了验证我们的假设，并进一步剖析Fra 1启动子调控，我们提出了以下具体目标：1）使用基因靶向小鼠和急性肺损伤实验模型，确定Fra 1缺陷对促氧化剂暴露的保护机制; 2）剖析体外调节基础水平和诱导型Fra 1表达的关键因素;以及3）通过使用基于tdTomato的体内和离体非侵入性光学成像来检查肺疾病中以及损伤和修复期间Fra 1诱导的模式。拟议的研究不仅在阐明Fra 1的生物学和功能方面是新颖的，而且还将为促氧化剂诱导的细胞应激和非恶性肺发病机制的机制基础提供重要的见解。由于细胞应激是许多肺部疾病和恶性肿瘤的一个组成部分，这些结果可以使我们能够靶向Fra 1，或特异性调节Fra 1的步骤，作为新的治疗药物。公共卫生相关性：了解Fra 1在急性肺损伤中的作用，并阐明Fra 1诱导的机制以及体内人Fra 1启动子激活的非侵入性基于红色荧光的光学成像的发展将有助于我们监测和跟踪宿主对正在经历损伤和修复或与病理/疾病状态相关的细胞中的促凝剂和毒物的转录反应。本研究的结果对于我们理解MAP激酶/AP 1-Fra 1信号在应激刺激下调控的氧化应激、DNA损伤和炎症等疾病机制具有重要意义。

DESCRIPTION (provided by applicant): A balancing act between transcriptional "activators" and "repressors" appears to play a key role in maintaining tissue homeostasis. However, shifting the balance in favor of activator or repressor functions can deregulate transcription (the initial step in gene expression), ultimately leading to a pathologic state. Indeed, emerging data have causally linked abnormal expression of genes involved in injury and repair to a wide variety of environmental insults, which either cause or enhance susceptibility to a variety of pathologic states, including acute and chronic lung diseases. This competing renewal application is focused on expanding our ongoing studies of the novel roles of Fra1 transcription in lung injury and repair. Fra1 is a dimeric partner of AP1 (Jun/Fos), which is activated by environmental insults and regulates gene expression that is involved in both normal and pathologic processes. During the last funding period, we have shown that interplay between the upstream promoter elements and the serum response element drives the Fra1 induction. We have shown that ectopic Fra1 promotes lung cell motility and invasion in vitro, but it requires other activated protooncogene(s) to impart its oncogenic potential in vivo. Although emerging data have unequivocally demonstrated a causative role for Fra1 in cancer cell progression and invasion, the exact role of Fra1 in non-malignant lung diseases remains unclear. Intriguingly, we have found that deletion of Fra1 confers increased protection against prooxidant-induced lung injury, when compared to results in control mice. We have also found that Fra1-deficient cells are remarkably more resistant than Fra1-sufficient cells to prooxidant-induced cell death. In reporter assays, ectopic Fra1 expression decreased both AP1-dependent and -independent transcriptional responses in lung epithelial cells. Based on these novel preliminary observations, we hypothesize that Fra1 functions as a "transcriptional repressor," thereby playing a key role in promoting cellular injury and lung pathogenesis. To test our hypothesis and to further to dissect Fra1 promoter regulation, we propose the following specific aims: 1) To determine the mechanisms involved in protection against prooxidant exposure by Fra1 deficiency using gene-targeted mice and experimental models of acute lung injury, 2) to dissect the critical factors that regulate basal-level and inducible Fra1 expression in vitro; and 3) to examine the patterns of Fra1 induction in lung disease and during injury and repair by using tdTomato-based noninvasive optical imaging in vivo and ex vivo. The proposed studies are not only novel in terms of elucidating the biology and functions of Fra1 but will also provide critical insights into the mechanistic basis underlying prooxidant-induced cellular stress and non-malignant lung pathogenesis. Because cellular stress is an integral part of many lung diseases and malignancy, these results could enable us to target Fra1, or steps that specifically regulate Fra1, as novel therapeutic agent(s). PUBLIC HEALTH RELEVANCE: Understanding the role of Fra1 in acute lung injury and delineating the mechanisms underlying FRA1 induction and the development of noninvasive red florescence-based optical imaging of human FRA1 promoter activation in vivo will be helpful in allowing us to monitor and track the host transcriptional response to proxidants and toxicants over time in cells that are undergoing injury and repair or are associated with a pathological/disease state. The results obtained from this study will be of great significance for our understanding of disease mechanisms such as oxidative stress, DNA damage, and inflammation regulated by MAP kinase/AP1-Fra1 signaling in response to stressful stimuli.