Regulation of mitochondrial respiration by LDHB suppression in hepatoma cell
Park, Imkyong; Lee, Young-Kyoung; Kim, Gyeong-Hyeon; Yoon, Gyesoon
Department of Biochemistry & Molecular Biology, Ajou University School of Medicine; Department of Biomedical Sciences, Graduate School of Ajou University
Aerobic glycolysis and mitochondrial dysfunction are distinctive metabolic hallmarks of solid tumor. However, it is unclear how these phenomena are developed during tumorigenesis. To maintain aerobic glycolysis, continuous generation of NAD+ by lactate dehydrogenase (LDH) is essential. Recently, we reported that LDH5 isoenzyme formed by LDHB suppression is involved in increased glycolytic lactate production and mitochondrial respiratory defects in hepatoma cells. In this study, we aimed to investigate how LDHB suppression is linked with mitochondrial respiratory dysfunction. We have suggested that LDHB suppression might control mitochondrial respiration through posttranslational modification of respiratory related protein, thus, we have attempted to focus on pyruvate dehydrogenase (PDH) which is regulated by phosphorylation. Interestingly, LDHB knockdown effectively increased phosphorylation of PDH, indicating its inactivation. Treatment of lactate was increased PDH phosphorylation with lowering pH. This result implies that PDH phosphorylation is correlated with acidification, but is not lactate-specific event. Collectively, our results suggest that lactate-mediated PDH inactivation is the key mechanism to induce mitochondrial dysfunction in LDHB-suppressed hepatoma cell.
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