Ethanol induces CYP2E1 by protein stabilization. Role of ubiquitin conjugation in the rapid degradation of CYP2E1.

In the present study, we demonstrate that ethanol induces CYP2E1 by protein stabilization in vivo. The control half-life of CYP2E1 was determined to be 6-7 h followed by a slower secondary phase. The half-life of ethanol-stabilized CYP2E1 was calculated to be 38 h. The mechanism underlying the rapid degradation of CYP2E1 was also investigated and appears to involve the ubiquitin-proteasome proteolytic pathway. An in vitro assay using the cytosolic fraction was developed to further characterize CYP2E1 degradation. Using this assay, 40-50% loss of CYP2E1 was observed in 1 h, coincident with the formation of high M(r) ubiquitin-CYP2E1 conjugates. At concentrations approximating those found in vivo, ethanol protects CYP2E1 from cytosolic degradation. No loss of CYP2B1/2 was observed under identical conditions, suggesting that this reaction is specific for certain P-450s which are rapidly turned over.