Role of TACC2 in smoking-induced COPD

项目摘要 慢性阻塞性肺疾病(COPD)是美国第三大死亡原因， 以对有害刺激(如香烟烟雾)做出不可逆的呼气气流限制为特征的。 肺气肿是慢性阻塞性肺疾病的一种重要表现型，伴有破坏性的空隙扩大。 因为高死亡率。越来越多的证据表明DNA损伤和肺上皮细胞的致病作用 肺气肿发病机制中的细胞凋亡。然而，香烟烟雾引起DNA损伤的分子基础 而细胞凋亡仍有待阐明。我们的基因组和功能研究发现TACC2编码一种 中心体相互作用蛋白作为COPD候选基因。我们新的初步数据表明 与没有COPD的吸烟者相比，患有COPD的吸烟者的TACC2显著降低。我们还观察到 Tacc2-/-与暴露在香烟烟雾中的Tacc2/小鼠相比显示出肺气肿的变化 伴随着DNA损伤。TACC2基因敲除削弱同源重组，并增加香烟 吸烟对永生化人支气管上皮细胞的DNA损伤和细胞毒作用。香烟 烟雾通过泛素-蛋白酶体途径显著降低TACC2蛋白。事实上，一个促凋亡者， 泛素E3连接酶亚基，称为F盒L7(FBXL7)，靶向TACC2在细胞内的降解。此外， TACC2被发现与共济失调毛细血管扩张突变(ATM)有关，ATM是一种关键的DNA损伤感知激酶，以及 这种联系是由香烟烟雾刺激的。这些初步数据使我们得出了一个重要的假设 香烟烟雾通过依赖TACC2诱导ATM介导的DNA损伤反应 COPD受损，导致肺上皮细胞凋亡和肺气肿形成的机制。 在目标1中，我们将确定TACC2是否通过ATM作用于控制吸烟引起的DNA损伤 肺上皮细胞的反应和细胞毒性。在目标2中，我们将确定自动柜员机依赖 TACC2磷酸化促进其FBXL7介导的香烟烟雾暴露肺上皮细胞降解 细胞。在目标3中，我们将确定增加的TACC2稳定性是否可以防止香烟烟雾 DNA损伤反应、肺上皮细胞凋亡和肺气肿。建议的研究完成后， 阐明吸烟导致COPD肺组织DNA损伤蓄积的机制，并可能 从而开发出一种治疗这种衰弱疾病的新方法。

Project Summary Chronic obstructive pulmonary disease (COPD) is the third leading cause of death in the United States and is characterized by irreversible expiratory airflow limitation in response to noxious stimuli (e.g., cigarette smoke). Emphysema, with destructive enlargement of the airspaces, is an important phenotype of COPD that accounts for high mortality rates. Accumulating evidence suggest a causative role of DNA damage and lung epithelial cell apoptosis in emphysema pathogenesis. However, the molecular basis for cigarette smoke-induced DNA damage and apoptosis remains to be elucidated. Our genomic and functional studies identified TACC2 that encodes a centrosome-interacting protein as a COPD candidate gene. Our novel preliminary data demonstrate that smokers with COPD exhibit a marked decrease in TACC2 relative to smokers without COPD. We also observed that Tacc2-/- compared to Tacc2+/+ mice when exposed to cigarette smoke exhibit emphysematous changes accompanied by DNA damage. TACC2 knockdown impairs homologous recombination, and augments cigarette smoke-induced DNA damage and cytotoxicity in immortalized human bronchial epithelial cells (HBEC). Cigarette smoke significantly reduces TACC2 protein via the ubiquitin-proteasome pathway. Indeed, a proapoptotic, ubiquitin E3 ligase subunit, termed F box L7 (FBXL7), targets TACC2 for its degradation in cells. Furthermore, TACC2 is found to associate with ataxia telangiectasia mutated (ATM), a key DNA damage-sensing kinase, and the association is stimulated by cigarette smoke. These preliminary data led us to an overarching hypothesis that cigarette smoke induces the ATM-mediated DNA damage response through a TACC2-dependent mechanism that is impaired in COPD, leading to lung epithelial cell apoptosis and the formation of emphysema. In Aim 1, we will determine whether TACC2 acts through ATM to control cigarette smoke-induced DNA damage response and cytotoxicity in lung epithelial cells. In Aim 2, we will determine whether ATM-dependent phosphorylation of TACC2 promotes its FBXL7-mediated degradation in cigarette smoke-exposed lung epithelial cells. In Aim 3, we will determine whether increased TACC2 stability protects against cigarette smoke-induced DNA damage response, lung epithelial cell apoptosis, and emphysema. Completion of the proposed studies will elucidate the mechanisms of smoking-induced DNA damage accumulation in COPD lungs and will potentially lead to development of a novel therapeutic approach for this debilitating disease.