Nitric oxide-dependent proteasomal degradation of cytochrome P450 2B proteins

• Type of Material: Article
• Authors: Choon-Myung Lee, Emory University; Bong-Yoon Kim, Emory University; Lian Li, Emory University; Edward T Morgan, Emory University
• Language: English
• Date: 2008-01-11
• Publisher: American Society for Biochemistry and Molecular Biology
• Publication Version: Final Published Version
• Copyright Statement: © 2008 by The American Society for Biochemistry and Molecular Biology, Inc.
• Final Published Version (URL): http://www.jbc.org/content/283/2/889.long
• Title of Journal or Parent Work: Journal of Biological Chemistry
• ISSN: 0021-9258
• Volume: 283
• Issue: 2
• Start Page: 889
• End Page: 898
• Grant/Funding Information: This work was supported by a grant from the National Institutes of Health (GM066971, E.T.M).; C.-M.L was supported by a Training Grant from the National Institutes of Health (T32ES01287).
• Research Categories: Health Sciences, Pharmacology; Chemistry, Biochemistry

Abstract

Exposure to inflammatory agents or cytokines causes the suppression of cytochrome P450 (CYP) enzyme activities and expression in liver and primary hepatocyte cultures. We showed previously that phenobarbital-induced CYP2B protein is down-regulated in primary cultures of rat hepatocytes following exposure to bacterial endotoxin (LPS) in a nitric oxide (NO)-dependent manner. In the present study, we found that CYP2B proteins in primary rat hepatocyte cultures were suppressed more than 60% after 6h treatment with interleukin-1β (IL-1). This effect was NO-dependent, and treatment of cells with the NO-donors (Z)-1-[2-(2-aminoethyl)-N-(2-ammonioethyl)amino] diazen-1-ium-1,2-diolate (NOC-18), S-nitrosoglutathione (GSNO), and S-nitroso, N-acetylpenicillamine (SNAP) also suppressed CYP2B proteins. However, the down-regulation by IL-1 was insensitive to inhibition of cGMP-dependent protein kinases. The down-regulation by IL-1 or NO donors was abolished by treatments with the proteasome inhibitors MG132 and lactacystin that did not affect NO production. The calpain inhibitor E64-d or the lysosomal protease inhibitors NH4Cl and chloroquine did not attenuate the down-regulation of CYP2B by IL-1. Treatment of HeLa cells expressing c-myc-tagged CYP2B1 with NOC-18 down-regulated its expression and enhanced its ubiquitination. Treatment of rat liver microsomes with GSNO caused S-nitrosylation of CYP2B protein, and enhanced the ubiquitination pattern of CYP2B compared to unmodified CYP2B in an in vitro ubiquitination assay. These data are consistent with the hypothesis that NO-dependent CYP2B ubiquitination and proteasomal degradation are dependent on protein modification by reactive nitrogen species.