Hexokinase II promotes the Warburg effect by phosphorylating alpha subunit of pyruvate dehydrogenase

Abstract

Objective Tumor cells rely heavily on glycolysis regardless of oxygen tension, a phenomenon called the Warburg effect. Hexokinase II (HKII) catalyzes the first irreversible step of glycolysis and is often overexpressed in tumor cells. Mitochondrial HKII couples glycolysis and oxidative phosphorylation while maintaining mitochondrial membrane integrity. In this study, we investigated the role of HKII in promoting the Warburg effect in cancer cells. Methods HKII-mediated phosphorylation of the alpha subunit of pyruvate dehydrogenase (PDHA1) was tested in HEK293T cells and clear cell renal cell carcinoma (ccRCC) specimens using gene knockdown, western blotting, immunohistochemistry, and immunofluorescence. Results It was determined that HKII could not only transform glucose into glucose-6-phosphate, but also transfer the phosphate group of ATP onto PDHA1. In addition, it was found that HKII increased the phosphorylation of Ser293 on PDHA1, decreasing pyruvate dehydrogenase (PDH) complex activity and thus rerouting the metabolic pathway and promoting the Warburg effect. The overexpression of HKII correlated with the phosphorylation of PDHA1 and disease progression in ccRCC. Conclusions The data presented here suggest that HKII is an important biomarker in the evaluation and treatment of cancer.