Characterization of posttranslational modification in metabolic dysfunction-associated steatohepatitis: acetylation, lactylation, and phosphorylation.

In metabolic dysfunction-associated steatohepatitis (MASH), abnormalities in posttranslational modification (PTM) are both a consequence of the pathological process and a driving force for disease progression. Therefore, this study intends to characterize the PTM features (acetylation, lactylation, and phosphorylation) of MASH, which will provide a crucial theoretical basis for the diagnosis and development of new targets for MASH. In this study, protein/modification profiles of clinical liver tissues from Normal and MASH were analyzed by LC-MS to identify differentially expressed proteins (DEPs) and differentially modified proteins with acetylation, lactylation, and phosphorylation. This study found that acetylation and lactylation occurred mainly in K, whose upstream and downstream amino acids consisted of A, G, K, R, and V. Phosphorylation occurred mainly in S and T, whose upstream and downstream ones consisted of D, E, P, R, and S. Proteomics with ordinary, acetylation, lactylation, and phosphorylation identified 468, 433, 434, and 1,471 DEPs/differentially modified proteins, respectively, which mainly regulate cytoskeleton, immunity, proliferation, oxidative stress, inflammatory cascades, and various metabolisms (sugars, amino acids, lipids, and carbon). CMKLR1, CYP2E1, GLRX, and XRCC1 were identified as key regulators in the shared DEPs of ordinary proteomics and modification proteomics. Notably, the differences in expression of the four proteins in clinical liver tissues from Normal and MASH were consistent with the proteomics results. In conclusion, this study systematically revealed the protein expression profiles associated with acetylation, lactylation, and phosphorylation in MASH, and highlighted that modifications of CMKLR1, CYP2E1, GLRX, and XRCC1 represent potential therapeutic targets for MASH.