Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a key enzyme involved in energy metabolism. Recently, GAPDH has been suggested to have extraglycolytic functions in DNA repair, but the underlying mechanism for the GAPDH response to DNA damage remains unclear. Here, we demonstrate that the tyrosine kinase Src is activated under DNA damage stress and phosphorylates GAPDH at Tyr41. This phosphorylation of GAPDH is essential for its nuclear translocation and DNA repair function. Blocking the nuclear import of GAPDH by suppressing Src signaling or through a GAPDH Tyr41 mutation impairs its response to DNA damage. Nuclear GAPDH is recruited to DNA lesions and associates with DNA polymerase β (Pol β) to function in DNA repair. Nuclear GAPDH promotes Pol β polymerase activity and increases base excision repair (BER) efficiency. Furthermore, GAPDH knockdown dramatically decreases BER efficiency and sensitizes cells to DNA damaging agents. Importantly, the knockdown of GAPDH in colon cancer SW480 cells and xenograft models effectively enhances their sensitivity to the chemotherapeutic drug 5-FU. In summary, our findings provide mechanistic insight into the new function of GAPDH in DNA repair and suggest a potential therapeutic target in chemotherapy.

No abstract

Short-term starvation (STS) during chemotherapy can block the nutrient supply to tumors and make tumor cells much more sensitive to chemotherapeutic drugs than normal cells. However, because of the diversity of starvation methods and the heterogeneity of tumors, this method’s specific effects and mechanisms for chemotherapy are still poorly understood. In this study, we used HeLa cells as a model for short-term starvation and etoposide (ETO) combined treatment, and we also mimicked the short-term starvation effect by knocking down the glycolytic enzyme GAPDH to explore the exact molecular mechanism. In addition, our study demonstrated that short-term starvation protects cancer cells against the chemotherapeutic agent ETO by reducing DNA damage and apoptosis due to the STS-induced cell cycle G1 phase block and S phase reduction, thereby diminishing the effect of ETO. Furthermore, these results suggest that starvation therapy in combination with cell cycle-specific chemotherapeutic agents must be carefully considered.