FTO泛素化介导MFG-E8m6A甲基化动态修饰调控COPD肺泡上皮细胞凋亡的机制研究

吸烟所致肺泡上皮细胞凋亡是COPD的重要发病机制。N6-甲基腺嘌呤（m6A）是mRNA最常见的表观遗传修饰方式，去甲基化酶FTO可通过调控m6A修饰参与细胞凋亡。前期研究发现香烟烟雾通过抑制去泛素化酶OTUD4的表达促进FTO经泛素/蛋白酶体途径降解，而FTO表达降低诱导乳脂球表皮生长因子8（MFG-E8）mRNA的m6A修饰水平升高引起MFG-E8表达下降。此外，COPD肺组织中MFG-E8表达减少并可通过抑制抗凋亡因子BCL2的表达促进肺泡上皮细胞凋亡。由此申请人推测香烟烟雾诱导FTO经泛素/蛋白酶体途径降解引起MFG-E8m6A水平升高，导致MFG-E8表达下调，促使肺泡上皮细胞凋亡参与COPD形成。本项目将通过构建FTO条件性敲除鼠和定向诱变m6A修饰位点阐明FTO泛素化调控MFG-E8m6A修饰在COPD肺泡上皮细胞凋亡中的作用，为COPD的防治提供全新的干预途径及理论依据。

COPD is a major cause of chronic morbidity and mortality throughout the world. Apoptosis of alveolar epithelial cells induced by cigarette smoke plays the pivotal role in pathogenesis of COPD. Recent studies have reported that N6-methyladenosine (m6A) is the most abundant epigenetic modification of mRNA and the demethylase FTO conducts dynamic regulation of m6A status, which is involved in apoptosis. Albeit, the regulation of m6A in COPD is largely unknown. Our preliminary study observed that cigarette smoke promoted the ubiquitin/proteasome degradation of FTO by inhibiting the deubiquitinase OTUD4. Besides, FTO reduction increased the m6A methylation of MFG-E8 mRNA and further decreased the MFG-E8 expression. Moreover, the decreased MFG-E8 in COPD patient lung tissues promoted the apoptosis of alveolar epithelial cells via inhibiting the release of anti-apoptotic factor BCL2. Therefore, we hypothesized that smoking-induced ubiquitin/proteasome degradation of FTO increased MFG-E8 m6A methylation level and decreased the expression of MFG-E8, initiating the apoptosis of alveolar epithelial cells in COPD. Our program will elucidate the role of m6A modification of MFG-E8 mRNA regulated by FTO ubiquitination in alveolar epithelial cell apoptosis of COPD through constructing FTO conditional knockout mice and m6A sites targeted mutation. This project will provide a new insight for the prevention and treatment of COPD.