自吞噬是真核细胞在营养缺失等压力条件下发生的一种保护性反应，近年研究证实，电离辐射损伤可诱发细胞自吞噬，但其作用机制及对细胞命运的影响还需要更深入研究阐明。我们前期研究发现，DNA损伤信号响应的重要调节分子DNA-PKcs与盐诱导激酶SIK2相互作用，前者早被发现参与放射损伤细胞的自噬调节，后者被最新发现是细胞自吞噬体成熟过程的重要调节物，只是各自机制不清。本项目将以DNA-PKcs与SIK2相互作为切入点，在验证SIK2在电离辐射诱发细胞自吞噬中的作用的基础上，建立和利用SIK2基因敲除细胞、SIK2的磷酸化和乙酰化位点的系列突变体，探讨电离辐射DNA损伤信号是如何由DNA-PKcs或其他激酶并通过SIK2传递到细胞自吞噬途径中，然后再详细阐明SIK2的激活和定位到自吞噬体及参与自吞噬过程的机制。本研究不仅对放射损伤细胞自噬机制有新阐述，还将为针对自吞噬研发辐射增敏或防护剂提供重要信息。

Autophagy is a ubiquitous highly conserved pathway in eukaryotic cells that takes place as a response to a variety of conditions, such as nutrient deprivation.It has already been shown that autophagy is one of the cellular responses to ionizing radiation (IR) injury. However, it is still unclear the mechanism of IR-induced autophagy and that how it determines the cell fate. Our recent study have uncovered the interaction of DNA-PKcs, a critical molecule in DNA damage early signaling event, and the salt-inducible kinase 2(SIK2). DNA-PKcs has already well demonstrated to involve in the IR-induced autophagy, while SIK2 was newly shown to plays an important role in the autophagosome maturation processing. What their acting mechanisms are still unknown.In this project, we will start from the interaction of DNA-PKcs and SIK2. Firstly, the role will verified for SIK2 to play on the IR-induced autophagy, and to clear what is the major consequence of SIK2-associated autophagy on cellular radiosensitivity. The SIK2 gene knock-out cells will be constructed by using the TALEN technology. A series of mutants of SIK2 phosphorylation sites and K53 acetalytion site will also been constrcuted and used in this project, to investigate how the IR-induced DNA damage signaling is transduced into the autophagy processing through the DNA-PKcs and SIK2 signal pathway. The regulation mechanism of the translocation and sequestered of SIK2 from whole cytoplasm into the autophagosome, and its effction on autophagy maturation.The results and outcome information from this project will be necessary for the mechanisitc elucidation of IR-induced autophagy. The knowledge from this study will be also useful for the study and development of new radioprotection agents or radiosensitizers targating the autophagy pathway.