Phosphorylation of UDP-glucose dehydrogenase increases glycosaminoglycan biosynthesis and promotes tumor cell motility, spheroid growth, and therapeutic resistance

UDP-glucose 6-dehydrogenase (UGDH) is an essential enzyme that catalyzes the oxidation of UDP-glucose to UDP-glucuronate. UGDH is elevated in multiple cancers, including prostate cancer, and is functionally implicated in castration resistant recurrence. UGDH is composed of three dimeric units that associate stably as a hexamer in cellular conditions. The dynamic reorganization of noncovalent interactions at the dimer contact interfaces is essential for UGDH activity. In this study, we examined the functional relevance of a putative AGC kinase motif located at the dimer-dimer interface. We demonstrated that UGDH is phosphorylated in LNCaP cells, specifically at serine 316, by RSK2, p70S6K, and SGK1. To determine the functional implications of UGDH S316 phosphorylation, we generated and characterized phosphomimetic (S316D) and phosphodeficient (S316A) point mutations. Intrinsic properties of the purified recombinant proteins were only modestly affected by the substitutions. The stable overexpression of UGDH S316D in LNCaP cells significantly increased the rate of N- and O-glycan synthesis, as well as the production of hyaluronan and sulfated glycosaminoglycans, while reducing DHT glucuronidation, resulting in significant increases in growth of tumor spheroids, cell proliferation and motility, and resistance to enzalutamide. In contrast, UGDH S316A expression reduced the production of glycans and glycosaminoglycans, restored DHT glucuronidation, and impaired growth and motility. Overall, our results support UGDH phosphorylation as a point of control for intracellular and cell surface glycan production, thereby regulating cell proliferation, anchorage dependence, motility, and tumor cell therapeutic resistance.