Downregulation of G2/mitotic-specific cyclinB1 triggers autophagy via AMPK-ULK1-dependent signal pathway in nasopharyngeal carcinoma cells.

CyclinB1 is a regulatory protein involved in mitosis. Multiple lines of evidence indicate that cyclinB1 depletion constrains proliferation and induces apoptosis in human tumor cells. The cells become susceptible to suffer a critical situation when cyclinB1 is downregulated. Autophagy is a major intracellular degradation system that recycles nutrients, removes damaged organelles, and promotes cell survival under stressful conditions, whereas the role of autophagy in cyclinB1-deprived neoplastic cell as well as the underlying molecular mechanism remains obscure. Here we pioneeringly elaborated that specific knockdown of cyclinB1 triggered autophagy via AMPK-ULK1-dependent signal pathway through the elevation of ROS, rather than ATP in the cell lines of CNE-1 and CNE-2. Moreover, ROS scavengers demonstrated that the observed effect of cyclinB1 silencing on AMPK phosphorylation was ROS dependent. Additionally, double knockdown of AMPK and cyclinB1 evidently abrogated cyclinB1 silencing-induced autophagy. Summarily, this study first revealed that downregulation of cyclinB1 induced autophagy via AMPK-ULK1-dependent signal pathway, which represents a key step toward unveiling the mechanism how cell cycle checkpoint proteins regulate autophagy.