SUMOylation regulates cytochrome P450 2E1 expression and activity in alcoholic liver disease

Abstract

Alcohol acts through numerous pathways leading to alcoholic liver disease (ALD). Cytochrome P450 (CYP2E1), an ethanol-inducible enzyme,metabolizes ethanol-producing toxic reactive oxygen species (ROS) and is regulated at the posttranslational level. Small ubiquitin-like modifier (SUMO)ylation is a posttranslational modification that involves the addition of SUMOs, which modulate protein stability, activity, and localization. We demonstrated that ubiquitin-conjugation enzyme 9, the SUMO-conjugating enzyme, is induced in the livers of an intragastric ethanol mouse model. Our aim is to examine whether SUMOylation could regulate ethanol-induced CYP2E1 expression inALDand to elucidate the molecularmechanism(s).CYP2E1 andUBC9 expression in vitro and in vivo was detected by real-time PCR and immunoblotting/immunostaining. SUMOylation was assayed by mass spectrometry and coimmunoprecipitation.Ubc9 expressionwas induced in ethanol-fed mouse livers, and silencing inhibited ethanol-mediated CYP2E1 microsomal retention and enzymatic activity. CYP2E1 SUMOylation was foundto be inducedby ethanol in vitroandin vivo.Ubc9silencingprevents ethanol-induced lipidaccumulation and ROS production. UBC9 was highly expressed in human ALD livers. Finally, we found that lysine 410 is a key SUMOylated residue contributing to CYP2E1 protein stability and activity preventing CYP2E1 SUMOylation. Ethanol-mediated up-regulation of CYP2E1 via SUMOylation enhancing its protein stability and activity and may have important implications in ALD.