Bax inhibitor-1 regulates the expression of P450 2E1 through enhanced lysosome activity.
In this study, we explored the role of Bax inhibitor-1 (BI-1) on the expression of P450 2E1 and related ROS production. P450 2E1 protein, not mRNA, was expressed at relatively low levels in BI-1 plasmid-transfected cells (BI-1 cells) compared with neomycin-resistant vector-transfected cells (Neo cells). When exposed to ER stress, P450 2E1 expression and activity and ER membrane lipid peroxidation increased in both Neo cells and BI-1 cells, but to a lesser degree in BI-1 cells. This observation correlated with the lower level of ER stress in BI-1 cells than Neo cells. To examine the BI-1-associated P450 2E1 degradation mechanism, cells were treated with the lysosome inhibitor, bafilomycin and the proteasome inhibitor, MG132. Bafilomycin recovered the reduced P450 2E1 expression in BI-1 cells, but did not affect P450 2E1 expression in Neo cells. Next, proteosomal and lysosomal activities in Neo cells were compared to those in BI-1 cells. Although proteosomal activity was similar between Neo and BI-1 cells, LysoTracker and acridine orange labeling, lysosomal V-ATPase activity, and lysosomal cathepsin B expression were higher in BI-1 cells than in Neo cells. In the presence of ER stress, lysosomal activities decreased in Neo cells but did not change in BI-1 cells. P450 2E1 expression and ER membrane lipid peroxidation were greater in the hepatocytes and livers of BI-1 knock-out mice than in BI-1 wild-type cells and mice. Our results suggest that the BI-1-mediated enhancement of lysosomal activity regulates P450 2E1 expression and resultant ROS accumulation.
Department of Dental Pharmacology, School of Dentistry, Wonkwang University, Iksan, Chonbuk 570-749, Republic of Korea.
Geum-Hwa
GH
Lee
Hyung-Ryong
HR
Kim
Han-Jung
HJ
Chae
D000818:Animals; D019392:Cytochrome P-450 CYP2E1 / Q000235:genetics*; D004351:Drug Resistance / Q000187:drug effects; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D055786:Gene Knockout Techniques; D056945:Hep G2 Cells; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D006801:Humans; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism; D015227:Lipid Peroxidation / Q000187:drug effects; D008247:Lysosomes / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D008565:Membrane Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009355:Neomycin / Q000494:pharmacology; D059748:Proteolysis / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism; D025262:Vacuolar Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism
D004791:Enzyme Inhibitors; D008565:Membrane Proteins; D017382:Reactive Oxygen Species; C490015:Tmbim6 protein, mouse; D019392:Cytochrome P-450 CYP2E1; D025262:Vacuolar Proton-Translocating ATPases; D009355:Neomycin