IDDF2018-ABS-0039 O-glcnacylation on RAB3A attenuates its effects on mitochondrial oxidative phosphorylation and metastasis in hepatocellular carcinoma

Background Metabolic reprogramming is widely observed in different cancers including Hepatocellular carcinoma (HCC). Reprogrammed metabolism results in hyper-O-GlcNAcylation in tumour cells, which can regulate transcription factors or tumour suppressors to modulate cancer metabolic reprogramming. Rab3A has been reported as an oncogenic factor in some cancers. However, the functions of Rab3A in HCC are never determined. Here we investigated the potential roles of Rab3A in HCC progression and determined how hyper-O-GlcNAcylation regulates the functions of Rab3A. Methods Western blot, qPCR, and immunohistochemistry assays were performed to quantify the relative expression of Rab3A in HCC. The functions of Rab3A in tumour progression were evaluated in HCC cell lines and nude mice. The interaction between Rab3A and OGT was determined by IP and GST pull-down. The GTP-binding affinity was observed in GTP-binding assays. The mitochondrial respiratory capacity was determined by XF cell Mito stress analysis, lactate assays, ROS-Glo H2O2 assays, and MitoSOX assays. Results Both the mRNA and protein levels of Rab3A were elevated in HCC. However, decreasing Rab3A in HCC cells had no significant effects on tumour progression, and the upregulation of Rab3A in HCC patients conferred no correlations with metastasis or overall survival. We determined that Rab3A is modified with O-GlcNAcylation in HCC, which attenuated the Rab3A-mediated inhibition on HCC metastasis. Further analysis proved that Rab3A and its O-GlcNAcylation also played opposite roles in mitochondria oxidative phosphorylation (mtOXPHOS), and their functions on HCC metastasis partially depended on their effects on metabolic reprogramming. Conclusions This study evaluated Rab3A as a tumour suppressor in HCC and revealed that the functions of Rab3A in both metastasis and metabolic reprogramming were attenuated by its modification of O-GlcNAcylation in HCC. Mechanistically, Rab3A elevated the expression of some mtOXPHOS-related genes, and O-GlcNAcylation decreased the GTP-binding affinity of Rab3A.