自噬与肿瘤发生发展密切相关，ULK1是自噬途径的核心蛋白，对其调控机制的研究是关注的焦点。我们研究发现ULK1结构域上具有GSK-3β磷酸化底物的共同保守序列；GSK-3β能与ULK1结合，负性调控ULK1蛋白的表达,并在体内外均能磷酸化ULK1的S409位点；细胞内激活的AKT可以通过磷酸化并灭活GSK-3β上调ULK1的表达；食管癌组织中ULK1高表达与预后负相关。本课题拟深入研究GSK-3β通过磷酸化ULK1(S409)致其泛素化降解，进而调控自噬的分子机制；研究激活的AKT通过上调ULK1来维持肿瘤细胞线粒体稳定的机制，探讨体内外靶向ULK1能否增强AKT高表达的肿瘤细胞对化疗的敏感性；并在多种肿瘤组织芯片标本中研究p-AKT, p-GSK-3β及ULK1表达的相关性及其对肿瘤发展进程及预后的影响。为深入理解自噬在肿瘤中的作用、靶向ULK1药物研究及其在肿瘤防治中的应用提供指导。

Increasing evidence indicates the importance of autophagy in human cancers. ULK1 is the furthest upstream kinase involved in autophagosome formation. The identification of intimate regulatory pathways and their functions in cancer may prove useful for cancer treatment. In our prelimilary study, we identified that ULK1 shared a structurally conserved domain with the phosphorylation substrate of GSK-3β. GSK-3β could interact with ULK1 and phosphorylate ULK1 on Ser409， and the expression level of ULK1 was negatively regulated by GSK-3β. Additionally, constitutively activated AKT transfection could up-regulate ULK1 expression through phosphorylating GSK-3β and inhibiting its activity. In esophagus squamous cell carcinoma, intensive ULK1 expression was correlated with poor prognosis. In this proposal, we will further extend our study to demonstrate the molecular mechanism that GSK-3β can phosphorylate Ser409 of ULK1 and subsequently regulate autophagy through promoting ubiquitin-mediated ULK1 proteolysis. Moreover, we will explore whether ULK1 knockdown can promote abnormal mitochondria potential and sensitize cancer cells to apoptotic inducers particularly during GSK-3β inactivation by hyperactivated AKT. The correlation of p-AKT, p-GSK-3β and ULK1 expression and their clinical significance in human tumor tissue will be investigated. The study will provide a comprehensive understanding of relationship between autophagy and cancer, and identify a previously unrecognized cancer cell vulnerability, which may provide a new therapeutic target in malignancies with dysregulated ULK1.