SIRT1蛋白O-GlcNAc糖基化修饰在非小细胞肺癌生长和侵袭过程中的功能和机制研究

SIRT1 is a NAD+-dependent deacetylase, and O-linked N-acetyl-β-D-glucosamine (O-GlcNAc) is a ubiquitous, dynamic and reversible post-translational modification on hydroxyl groups of serine and/or threonine residues of nuclear and cytoplasmic proteins, the aberrance of both SIRT1 and O-GlcNAc is involved in the formation and progression of lung cancer. In the previous study, we have found that SIRT1 is dynamically modified by O-GlcNAc at Ser 549, which directly increases its deacetylase activity both in vitro and in vivo. The O-GlcNAcylation of SIRT1 is elevated during genotoxic, oxidative and metabolic stress stimuli in both cellular and mouse models, thereby activating SIRT1 and protecting cells from stress-induced apoptosis by deacetylating p53 and FOXO3. Therefore, we proposed that O-GlcNAcylation of SIRT1 might promote the formation and progression of lung cancer. In line with our hypothesis, we found that the O-GlcNAcylation levels of SIRT1 are elevated in non-small cell lung cancer (NSCLC) cells and tissues compared with normal cells and the corresponding adjacent tissues respectively. Additionally, we also found that the O-GlcNAcylation of SIRT1 promotes the proliferation, colony formation and invasion of NSCLC cells. Excitingly, we found that there are mutations of Ser→Cys and Ser→Phe at Ser 549 (S549) of SIRT1 in NSCLC tumor samples. In this research project, we will carry out the following research. Firstly, we will reveal the molecular mechanism underlying the increase of O-GlcNAcylation of SIRT1 in NSCLC cells. Secondly, we will elucidate the role and mechanism of SIRT1 O-GlcNAcylation in the formation and progression of NSCLC. Lastly, we will investigate the effect of SIRT1 mutations (Ser→Cys and Ser→Phe at Ser 549) on the development of NSCLC. This study will be of great theoretical significance for elucidating the regulatory mechanism of SIRT1 in NSCLC and understanding the roles and mechanisms of SIRT1 and O-GlcNAcylation in the formation and progression of NSCLC, which will also provide a new theoretical basis for the treatment of NSCLC.

SIRT1是一个NAD+依赖的蛋白质脱乙酰化酶而O-GlcNAc是一种真核生物普遍存在的蛋白质翻译后修饰，它们均参与驱动肺癌的发生发展；申请人最近发现O-GlcNAc修饰SIRT1蛋白549位丝氨酸并激活SIRT1。因此，申请人提出“SIRT1蛋白的O-GlcNAc修饰促进肺癌发生发展”的科学假设。预实验表明非小细胞肺癌（NSCLC）中SIRT1的O-GlcNAc修饰增加并促进其恶性转化，另外也发现SIRT1的549位点在NSCLC组织中存在突变。上述结果表明该科学假设是合理可行的，本项目将深入开展如下工作：揭示NSCLC中SIRT1蛋白O-GlcNAc修饰增加的机制；阐明SIRT1蛋白的O-GlcNAc修饰和549位点突变在NSCLC发生发展中的作用和机制。本项目对于阐明SIRT1和O-GlcNAc修饰在NSCLC中的作用及机制具有重要的理论意义，将为肺癌的预防和治疗提供新的理论依据。

SIRT1是一个NAD+依赖的蛋白质脱乙酰化酶而O-GlcNAc是一种真核生物普遍存在的蛋白质翻译后修饰，它们均参与驱动肺癌的发生发展；申请人前期研究发现O-GlcNAc修饰SIRT1蛋白549位丝氨酸残基并激活SIRT1。因此，申请人提出“SIRT1蛋白的O-GlcNAc修饰促进肺癌发生发展”的科学假设。本项目研究了SIRT1蛋白O-GlcNAc修饰在NSCLC细胞增殖和侵袭过程中的作用，结果表明SIRT1 蛋白O-GlcNAc修饰促进肿瘤细胞增殖、克隆形成和迁移能力；研究了NSCLC细胞中SIRT1蛋白O-GlcNAc修饰增加的分子机制，阐明了细胞应激时SIRT1蛋白O-GlcNAc修饰增加依赖于AMPK的激活及其介导的OGT磷酸化修饰；发现SIRT1的549丝氨酸位点也是一个磷酸化修饰位点，并揭示了SIRT1的549位点磷酸化修饰受AMPK信号通路负调控、受mTOR/S6K正调控；研究了SIRT1蛋白549位点磷酸化在NSCLC发生和发展过程中的作用，结果表明SIRT1蛋白549位点磷酸化在肺癌组织中下调，并且揭示其抑制肿瘤细胞增殖、克隆形成、迁移能力和体内成瘤的能力。本项目研究成果将为肺癌的治疗提供新的理论依据。