Acetylation Promotes Pyruvate Kinase M2 By The Accumulation Of Autophagic Degradation Of Metabolic Intermediates

As a key posttranslational modification, protein acetylation was studied comprehensively, but the majority of acetylation studies have been focused on histones and nuclear transcription regulators. We use tandem liquid chromatography-tandem mass spectrometry (LC/LC-MS/MS) to analyse the affinity-purified acetylated peptides from cytoplasmic fraction of human prostate tissues and found that many acetylated proteins including metabolism enzymes in glycolysis, gluconeogenesis, tricarboxylic acid (TCA) cycle and fatty acid metabolism.We selected Pyruvate kinase M2 (PKM2) which is important for tumor cell growth to elucidate the acetylation how to regulate metabolic enzymes'function. Pyruvate kinase is one of the three key regulators of glycolysis pathway, catalyzes the last step, changing phosphoenolpyruvate and ADP to pyruvate and ATP. Pyruvate kinase has four isoforms:PKL, PKR, PKM1 and PKM2 which are expressed in a tissue-specific manner. L-type is mostly present in liver; R-type is found exclusively in erythrocytes; Ml-type is mostly in normal adult tissue while M2-type is found in embryo and tumor tissue.We identified that PKM2 is acetylated on lysine residues, including K305 and K433 (which is undering characterization). We have demonstrated acetylation at K305 promotes PKM2 degradation through chaperone mediated autophagy (CMA). We also defined the acetyltransferase (pCAF) and deacetylase (Sirtl) are responsible for K305 acetylation and deactylation respectively. Further more, we found that K305 acetylation is upregulated by high concentration of glucose in cells, resulting in accumulation of the intermediate metabolites as well as NADPH, which are essential material for growing tumor cells to build up tumor mass.In the thesis, we have demonstrated that PKM2 acetylation promotes CMA for the first time, leads to accumulation of the intermediate metabolites as well as NADPH which may consequently promotes cancer development. This work has not only shed light on the molecular mechanism underlying Warburg effects but also is meaningful for the potential tumor therapy.