Sirtuin及其激活剂抑制AIF介导的程序性细胞死亡和组织损伤的机制及效应研究

AIF is a mitochondrial protein. Under stress conditions, AIF releases from mitochondria to the cytosol and to the nucleus where it induces parthanatos programmed cell death, which finally lead to brain injury. However, the mechanism and the regulation of AIF-induced cell death is still largely unknown. Early study suggested that parthanatos cannot be prevented once AIF translocated to the nucleus. Our primary studies identified that AIF can be modified by acetylation, and its acetylation levels are markedly upregulated under stress conditions including alkylating agents, hypoxia or excitative amino acid treatments. Moreover, SirT1 deacetylates AIF and inhibits cell death under stress conditions including alkylating agents, hypoxia and excitatory amino acids in an AIF-dependent manner. Furthermore, SirT1 activator SIR1720 pretreatment markedly attenuates hypoxic-ischemic brain injury in mice. We also observed that other SirT1 homeloges also interact with AIF in cells. In addition, the SirT1 knockdout mice showed retinopathy associated with abnormal AIF acetylation in the ganglion cell layer. In this proposal, we plan to study the regulatory mechanisms and functions of AIF acetylation, reveal how SirT proteins negatively regulates AIF-induced cell death and tissue damage, with aims to provide clues to new ways for using SirT1 activators to prevent parthanatos, downregulate hypoxic-ischemic tissue injury, or attenuate retinopathy.

AIF是线粒体定位蛋白，胁迫条件下可离开线粒体经胞浆入核诱发一类被称为parthanatos的程序性细胞死亡，导致脑损伤。目前该类细胞死亡的发生及调控研究匮乏。以往认为AIF一旦入核，细胞就难逃死亡。我们发现：缺氧或烷化剂都显著诱导AIF乙酰化；去乙酰化酶SirT1可负调控AIF并抑制缺氧、烷化剂及兴奋性氨基酸诱发的AIF依赖的细胞死亡，SirT1激活剂SIR1720可显著降低脑缺血缺氧损伤；AIF也与其它SirT1同源家族蛋白结合；SirT1敲除小鼠有视网膜病变发生，并伴随神经节细胞层AIF高度乙酰化。本课题拟研究AIF乙酰化修饰的发生及功能调控机制，解析SirT蛋白如何负调控AIF介导的细胞死亡及组织损伤，探讨SirT1激活剂用于阻断parthanatos、抵抗组织缺血缺氧损伤、或减缓视网膜病变的可行性。

Sirtuins（SirT1至SirT7）是一类与衰老、癌症和代谢紊乱疾病相关的去乙酰化酶。申请人前期报道了SirT1与蛋白酶体激活因子REGγ形成复合体，该复合体的动态变化可通过调控自噬进而干预肝脏脂肪代谢的研究论文（Cell Metabolism. 2013)。本课题的主要目标是研究SIRTUIN及其相关因子在细胞能量代谢、肿瘤细胞应激与细胞/组织死亡或死亡逃逸中的作用。课题执行期间，已发表标准本课题资助的研究SCI论文3篇，其中课题主持人作为通讯作者，在Current Biology（2017）和Nature Communications (2021) 发表了细胞能量及药物压力应激相关研究论文，并提交了2项课题研究计划相关的国家发明专利（注册号：202011278356.3和202011110775.6），另外以合作形式发表在（EMBO J. 2020；Science Adances 2020 in press；Clin Cancer Res. 2019）发表研究论文。目前SIRT1通过去乙酰化AIF调控细胞坏死的研究论文也在投稿阶段。以下内容为申请人围绕课题计划发表的代表性研究论文：(1) 报道SIRT1磷酸化修饰通过去乙酰化修饰poly(A)-mRNA结合蛋白PABP1，参与能量限制情况下的保持细胞能量稳态以实现细胞存活（Current Biology. 2017; 27(15):2271-2284）。该论文被Nature Reviews Molecular Cell Biology杂志发表论文专评 (Stress responses: SIRT1 puts an embargo on mRNA export) 。该论文内容符合本课题的SIRT1参与压力应激和细胞死亡逃逸调控的研究计划。(2)报道DNA损伤化疗药物如何激活中心体凝聚、诱发基因组不稳定进而产生肿瘤耐药和复发（Nature Communications. 2021 Jan, 10.1038/s41467-020-20208-x）。该论文内容符合本课题的肿瘤细胞应激与细胞死亡或逃逸的研究内容。