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Author Notes:

Address Correspondence to: Edward T. Morgan, Department of Pharmacology, Emory University, Atlanta GA 30322. Tel. 404 727-5986; Fax. 404 727-0365; E-mail: edward.morgan@emory.edu

Current address is School of Biological Sciences, Seoul National University, Seoul 151-742, Korea. Tel +82-2-888-1503.

We thank Kimberly Pierce, Malik Raynor, and Dr. Alison Aitken for expert technical assistance; Dr. T.J. Murphy for the KXUa1-eGFP vector, Dr. James Halpert for antibodies to CYP2B1, Dr. Bettie Sue Masters for antibodies to CPR, and Drs. Keith Wilkinson, Emory University and Dennis Koop, Oregon Health and Science University, for helpful consultations.


Research Funding:

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).

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


Journal Title:

Journal of Biological Chemistry


Volume 283, Number 2


, Pages 889-898

Type of Work:

Article | Final Publisher PDF


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.

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© 2008 by The American Society for Biochemistry and Molecular Biology, Inc.

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