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 (PBu₃), 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 PBu₃ induces the acetylation of mitochondrial proteins and a decrease in acetyl-CoA concentration in PBu₃-treated HeLa cells. This indicates that PBu₃ can promote the acetyltransfer reaction between acetyl-CoA and mitochondrial proteins in living cells. PBu₃-induced acetylation gradually reduced mitochondrial ATP concentrations in HeLa cells without changing the cytoplasmic ATP concentration, suggesting that PBu₃ mainly affects mitochondrial functions. In addition, pyruvate, which is converted into acetyl-CoA in mitochondria and transiently increases ATP concentrations in the absence of PBu₃, elicited a further decrease in mitochondrial ATP concentrations in the presence of PBu₃. Moreover, the application and removal of PBu₃ reversibly alternated mitochondrial fragmentation and elongation. These results indicate that PBu₃ enhances acetyltransfer reactions in mitochondria and modulates mitochondrial functions in living cells.