Role of TACC2 in smoking-induced COPD

项目摘要 慢性阻塞性肺病（COPD）是美国第三大死亡原因， 其特征在于响应于有害刺激的不可逆呼气气流限制（例如，香烟烟雾）。 肺气肿是COPD的一种重要表型，伴有破坏性的气道扩大， 高死亡率。越来越多的证据表明，DNA损伤和肺上皮细胞 凋亡在肺气肿发病机制中的作用。然而，香烟烟雾诱导的DNA损伤的分子基础 细胞凋亡仍有待阐明。我们的基因组和功能研究鉴定了TACC 2，它编码一种 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， 患有COPD的吸烟者相对于没有COPD的吸烟者表现出TACC 2的显著降低。我们还观察到 与Tacc 2 +/+小鼠相比，Tacc 2-/-小鼠在暴露于香烟烟雾时表现出肺气肿变化 伴随着DNA损伤。TACC 2敲低损害同源重组，并增加香烟 烟雾诱导永生化人支气管上皮细胞（HBEC）DNA损伤和细胞毒性。香烟 吸烟通过泛素-蛋白酶体途径显著降低TACC 2蛋白。事实上，一个促凋亡的， 泛素E3连接酶亚基，称为F盒L7（FBXL 7），靶向TACC 2在细胞中降解。此外，委员会认为， 发现TACC 2与共济失调毛细血管扩张突变（ATM）相关，ATM是一种关键的DNA损伤敏感激酶， 这种联系是由香烟烟雾刺激的。这些初步数据使我们得出一个总体假设 香烟烟雾诱导ATM介导的DNA损伤反应，通过TACC 2依赖的 在COPD中受损，导致肺上皮细胞凋亡和肺气肿的形成。 在目标1中，我们将确定TACC 2是否通过ATM来控制香烟烟雾诱导的DNA损伤 反应和细胞毒性。在目标2中，我们将确定是否依赖ATM TACC 2的磷酸化促进香烟烟雾暴露的肺上皮细胞中其FBXL 7介导的降解 细胞在目标3中，我们将确定增加的TACC 2稳定性是否能防止香烟烟雾诱导的TACC 2表达。 DNA损伤反应、肺上皮细胞凋亡与肺气肿。完成拟议的研究将 阐明吸烟诱导的COPD肺DNA损伤累积的机制， 从而导致开发了用于这种使人衰弱疾病的新的治疗方法。

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.