An Artificial Reaction Promoter Modulates Mitochondrial Functions via Chemically Promoting Protein Acetylation

Acetylation, which modulates protein function, is an important process in intracellular signalling. In mitochondria, protein acetylation regulates a number of enzymatic activities and, therefore, modulates mitochondrial functions. Our previous report showed that tributylphosphine (PBu(3)), an artificial reaction promoter that promotes acetylransfer reactions in vitro, also promotes the reaction between acetyl-CoA and an exogenously introduced fluorescent probe in mitochondria. In this study, we demonstrate that PBu(3) induces the acetylation of mitochondrial proteins and a decrease in acetyl-CoA concentration in PBu(3)-treated HeLa cells. This indicates that PBu(3) can promote the acetyltransfer reaction between acetyl-CoA and mitochondrial proteins in living cells. PBu(3)-induced acetylation gradually reduced mitochondrial ATP concentrations in HeLa cells without changing the cytoplasmic ATP concentration, suggesting that PBu(3) mainly affects mitochondrial functions. In addition, pyruvate, which is converted into acetyl-CoA in mitochondria and transiently increases ATP concentrations in the absence of PBu(3), elicited a further decrease in mitochondrial ATP concentrations in the presence of PBu(3). Moreover, the application and removal of PBu(3) reversibly alternated mitochondrial fragmentation and elongation. These results indicate that PBu(3) enhances acetyltransfer reactions in mitochondria and modulates mitochondrial functions in living cells.