Characterization of RAS/RAF/ERK signal cascade as a novel regulating factor in alpha-amanitin-induced liver injury

The well-known hepatotoxicity mechanism resulting from alpha-amanitin (-AMA) exposure arises from RNA polymerase II (RNAP II) inhibition. RNAP Ⅱ inhibition occurs through the dysregulation of mRNA synthesis. However, the signaling pathways in hepatocytes that arise from -AMA have not yet been fully elucidated. Here, we identified that the RAS/RAF/ERK signaling pathway was activated through quantitative phosphoproteomic and molecular biological analyses. Bioinformatics analysis showed that AMA exposure increased protein phosphorylation in a time-dependent AMA AMA exposure. In addition, phosphorylation increased not only the components of the ERK signaling pathway but also U2AF65 and SPF45, known splicing factors. Therefore, we propose a novel mechanism of -AMA as follows. The RAS/RAF/ERK signaling pathway involved in aberrant splicing events is activated by -AMA exposure followed by aberrant splicing events leading to cell death.