Abstract
Pyruvate kinase (PK) catalyzes the conversion of phosphoenolpyruvate and ADP to pyruvate and ATP, a rate-limiting reaction in glycolysis. M2 isoform of PK (PKM2) is the predominant form of PK expressed in tumors. In addition to its well established cytosolic functions as a glycolytic enzyme, PKM2 displays nuclear localization and important nonmetabolic functions in tumorigenesis. Herein, we report that nuclear PKM2 interacts with histone H2AX under DNA damage conditions. Depletion of PKM2 decreased the level of serine 139-phosphorylated H2AX (γ-H2AX) in response to DNA damage. The in vitro kinase assay reveals that PKM2 directly phosphorylates H2AX at serine 139, which is abolished by the deletion of FBP-binding pocket of PKM2 (PKM2-Del515-520). Replacement of wild type PKM2 with the kinase dead mutant PKM2-Del515-520 leads to decreased cell proliferation and chromosomal aberrations under DNA damage conditions. Together, we propose that PKM2 promotes genomic instability in tumor cells which involves direct phosphorylation of H2AX. These findings reveal PKM2 as a novel modulator for genomic instability in tumor cells.
Highlights
Cancer cells have increased glucose uptake and lactate production with concomitant decreased oxygen consumption, a phenomenon known as aerobic glycolysis or the Warburg effect
To explore the potential functions of nuclear pyruvate kinase M2 (PKM2) during DNA damage response (DDR), we previously performed immunoprecipitation-coupled liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) using anti-PKM2 antibody in human breast cancer cell line MCF7 and identified a number of nuclear proteins in DNA damage signaling as PKM2 binding partners, among which histone H2AX appeared (Figure 1A and 1B) [27]
The results showed that anti-PKM2 antibody could pull down H2AX in MCF7 cells treated with etoposide but not untreated MCF7 cells (Figure 1B and 1C)
Summary
Cancer cells have increased glucose uptake and lactate production with concomitant decreased oxygen consumption, a phenomenon known as aerobic glycolysis or the Warburg effect. It was shown that tumor cells develop multiple post-translational strategies to decrease enzymatic activity of PKM2 including phosphotyrosine-binding, phosphorylation, acetylation and oxidation, leading to the accumulation of glycolytic intermediates for biosynthetic reactions to support proliferation [15,16,17,18]. These inhibitory effects on PKM2 activity occur in response to various stimuli that tumor cells may encounter during tumor initiation or maintenance, such as excessive growth factors, high glucose or high reactive oxygen species concentrations [15,16,17,18]
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