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

描述（由申请人提供）：转录“激活因子”和“抑制因子”之间的平衡似乎在维持组织稳态中起关键作用。然而，将平衡转向激活因子或抑制因子功能会导致转录失调（基因表达的初始步骤），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异常表达与各种环境损害联系起来，这些损害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。这一竞争性更新应用的重点是扩展我们正在进行的关于Fra1转录在肺损伤和修复中的新作用的研究。Fra1是AP1 （Jun/Fos）的二聚体伙伴，它在环境损伤下被激活，并调节参与正常和病理过程的基因表达。在上一个资助期内，我们已经证明上游启动子元件和血清应答元件之间的相互作用驱动Fra1诱导。我们已经证明异位Fra1在体外促进肺细胞的运动和侵袭，但它需要其他激活的原癌基因来传递其体内的致癌潜力。尽管新出现的数据明确表明Fra1在癌细胞进展和侵袭中的致病作用，但Fra1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，Fra1的缺失可以增强对促氧化剂诱导的肺损伤的保护。我们还发现，缺乏fra1的细胞比fra1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。在报告细胞实验中，异位Fra1的表达降低了肺上皮细胞中ap1依赖性和非依赖性的转录反应。基于这些新颖的初步观察，我们假设Fra1作为一种“转录抑制因子”，因此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分析Fra1启动子的调控，我们提出了以下具体目标：1)利用基因靶向小鼠和急性肺损伤实验模型确定Fra1缺乏对促氧化暴露的保护机制；2)在体外分析调节基础水平和诱导水平Fra1表达的关键因素；3)利用基于tdtomato的体内和体外无创光学成像技术，研究Fra1在肺部疾病以及损伤和修复过程中的诱导模式。提出的研究不仅在阐明Fra1的生物学和功能方面是新颖的，而且还将为促进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见解。由于细胞应激是许多肺部疾病和恶性肿瘤的组成部分，这些结果使我们能够靶向Fra1，或特异性调节Fra1的步骤，作为新的治疗剂。公共卫生相关性：了解Fra1在急性肺损伤中的作用，描述Fra1诱导的潜在机制，以及在体内发展基于红色荧光的人类Fra1启动子激活的非侵入性光学成像，将有助于我们监测和跟踪宿主对氧化剂和毒物的转录反应，这些细胞正在经历损伤和修复或与病理/疾病状态相关。本研究结果将对我们了解应激刺激下MAP激酶/AP1-Fra1信号调控的氧化应激、DNA损伤、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.