title: Role of CYP2E1 activity in endoplasmic reticulum ubiquitination, proteasome association, and the unfolded protein response.
abstract: In an experimental model of liver cirrhosis, marked increases in ER proteasome content in rat livers were observed 5 h after acute i.p. injection of the hepatotoxicant CCl4. To confirm the role of CYP2E1 in mediating protein misfolding/damage in the ER via its metabolism of CCl4, 293T cells stably transfected with human CYP2E1 were exposed to CCl4 and cell ER fractions assessed for ubiquitination. Increases in ER ubiquitin conjugates were noted in CYP2E1/293T cells treated with CCl4 and not in controls, suggesting these effects are CYP2E1 specific. Finally, the role of CYP2E1 in ER homeostasis was investigated by examining the unfolded protein response (UPR). When exposed to CCl4, CYP2E1/293T cells but not 293T or CYP1A2/293T cells showed rapid induction of the UPR-inducible ER chaperone BiP. Collectively, the data presented suggest that CYP2E1 is capable of inducing significant ER protein damage and stress via its catalytic activation of pro-oxidants.
authors.affiliation: School of Pharmaceutical, Molecular and Biomedical Sciences, Reid Building, Frome Road University of South Australia, Adelaide 5000, Australia.
authors.forename: Martin D
authors.initials: MD
authors.lastname: Lewis
authors.forename: Ben J
authors.initials: BJ
authors.lastname: Roberts
mesh_terms: D000818:Animals; D015152:Blotting, Northern; D002251:Carbon Tetrachloride / Q000494:pharmacology; D002460:Cell Line; D019392:Cytochrome P-450 CYP2E1 / Q000737:chemistry / Q000502:physiology*; D003600:Cytosol / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins / Q000494:pharmacology; D006801:Humans; D015151:Immunoblotting; D008099:Liver / Q000378:metabolism; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism; D018832:Molecular Chaperones / Q000494:pharmacology; D016877:Oxidants / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D017510:Protein Folding; D012313:RNA / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013347:Subcellular Fractions; D013997:Time Factors; D014162:Transfection; D025801:Ubiquitin / Q000737:chemistry / Q000378:metabolism*
chemical_list: D018076:DNA, Complementary; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D016877:Oxidants; D025801:Ubiquitin; D012313:RNA; D002251:Carbon Tetrachloride; D019392:Cytochrome P-450 CYP2E1; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease