Ubiquitylation of cyclin C by HACE1 regulates cisplatin‐associated sensitivity in gastric cancer

BACKGROUND: Cyclin C (CCNC) was reported to take part in regulating mitochondria‐derived oxidative stress under cisplatin stimulation. However, its effect in gastric cancer is unknown. This study aimed to investigate the role of cyclin C and its ubiquitylation in regulating cisplatin resistance in gastric cancer. METHODS: The interaction between HECT domain and ankyrin repeat‐containing E3 ubiquitin‐protein ligase 1 (HACE1) and cyclin C was investigated by GST pull‐down assay, co‐immunoprecipitation and ubiquitylation assay. Mitochondria‐derived oxidative stress was studied by MitoSOX Red assay, seahorse assay and mitochondrial membrane potential measurement. Cyclin C‐associated cisplatin resistance was studied in vivo via xenograft. RESULTS: HACE1 catalysed the ubiquitylation of cyclin C by adding Lys11‐linked ubiquitin chains when cyclin C translocates to cytoplasm induced by cisplatin treatment. The ubiquitin‐modified cyclin C then anchor at mitochondira, which induced mitochondrial fission and ROS synthesis. Depleting CCNC or mutation on the ubiquitylation sites decreased mitochondrial ROS production and reduced cell apoptosis under cisplatin treatment. Xenograft study showed that disrupting cyclin C ubiquitylation by HACE1 conferred impairing cell apoptosis response upon cisplatin administration. CONCLUSIONS: Cyclin C is a newly identified substrate of HACE1 E3 ligase. HACE1‐mediated ubiquitylation of cyclin C sheds light on a better understanding of cisplatin‐associated resistance in gastric cancer patients. Ubiquitylation of cyclin C by HACE1 regulates cisplatin‐associated sensitivity in gastric cancer. With cisplatin‐induced nuclear–mitochondrial translocation of cyclin C, its ubiquitylation by HACE1 increased mitochondrial fission and mitochondrial‐derived oxidative stress, leading to cell apoptosis.