O-GlcNAcylation of FBP1 promotes pancreatic cancer progression by facilitating its Lys48-linked polyubiquitination in hypoxic environments

Fructose-1,6-bisphosphatase 1 (FBP1), a rate-limiting enzyme in gluconeogenesis, is important for cancer progression. The post-translational regulation of FBP1 in hypoxic environments is still unclear. Here, we report that FBP1 is down-regulated, and a low expression level of FBP1 predicts a poor prognosis in pancreatic cancer. A hypoxic environment makes FBP1 more prone to degradation, and this effect can be reversed by inhibiting global O-GlcNAcylation signalling. O-linked N-acetylglucosamine transferase (OGT) interacts with FBP1 and induces its O-GlcNAcylation at serine 47 residue (FBP1-S47) to modulate its protein function in pancreatic cancer cells. O-GlcNAcylation of FBP1-S47 promotes FBP1 degradation and also influences the expression of canonical HIF-1α target genes involved in glucose metabolism, resulting in an increase in glucose uptake and lactate secretion in pancreatic cancer cells. In addition, O-GlcNAcylation of FBP1-S47 facilitates FBP1 K48-linked polyubiquitination at lysine 51 residue (FBP1-K51), in which GlcNAc moiety can serve as a prerequisite for an FBP1 ubiquitin ligase. FBP1 (K51) K48-linked polyubiquitination mediated protein degradation can also promote cancer progression, similarly to the O-GlcNAcylation of FBP1-S47. Our data uncover a mechanism whereby FBP1 can be regulated by a protein O-GlcNAcylation-polyubiquitination axis, paving the way to cancer cell metabolic reprogramming.