O -GlcNAcylation on Rab3A attenuates its effects on mitochondrial oxidative phosphorylation and metastasis in hepatocellular carcinoma

Rab3A is a small Ras-like GTPase critical for membrane traffic. Although the functions of Rab3A have been reported in several cancers, the roles of Rab3A in hepatocellular carcinoma ( HCC) have never been determined. To investigate the potential roles of Rab3A in HCCprogression, we first determined Rab3A levels in HCCtissues and observed upregulated mRNA and protein levels of Rab3A in most tumor tissues. However, in vitro data showed that decreasing Rab3A in most HCCcell lines conferred no significant effects and overexpressing Rab3A in PLC/PRF/ 5 cellseven inhibited migration and invasion. Meanwhile, the upregulation of Rab3A in HCCpatients did not correlate with metastasis or overall survival of HCCpatients. These contradict data suggested that Rab3A might act as metastatic suppressor and its effects might be attenuated in most HCCcells. Further experiments revealed that O-GlcNAcylation on Rab3A was key for attenuating Rab3A-mediated effects by regulating its GTP-binding activity, and verified the effects of Rab3A and its aberrant O-GlcNAcylation on HCCmetastasis in vitro and in vivo. We also found that Rab3A and its O-GlcNAcylation had opposite roles in mitochondria oxidative phosphorylation(mtOXPHOS), and their functions on HCCmetastasis were partially depended on their effects on metabolic reprogramming.