ALCOHOL TOXICITY: ROLE OF ETHANOL-INDUCIBLE P-450

Project: Research project

Description

Alcohol potentiate xenobiotic toxicity is mediated in part by the induction
of a unique isozyme of cytochrome P450, referred to as P450IIE1. This
isozyme of P450 catalyzes the metabolic activation of compounds such as
acetaminophen, CCI 4, phenol, benzene, and N-nitrosopyrrolidine. Thus, the
concentration of reactive metabolites generated from these xenobiotics is
dictated, in part, by the concentration of P450IIE1. Since the steady state
concentration of an enzyme is a function of both the rate of synthesis and
the rate of degradation, it is important to understand the regulation of
both processes. Control of hepatic P450IIE1 is complex and is regulated at
the level of transcription, mRNA stabilization, and protein stabilization
depending on the metabolic state and age of the animal under investigation.
Little is known about the mechanism of P450 degradation despite the
important role degradation has in the regulation of enzyme concentration.
The long range goal of our proposal is to determine the factors which
target P450IIE1 for degradation and subsequently determine the proteolytic
path of degradation. Ethanol could have an effect on both the targeting and
the degradative path. This goal will be accomplished by the following
specific aims: 1.Characterize stabilizers and labilizers for P450IIE1. Compounds
interacting with P450IIE1 may act as either stabilizers, preventing
degradation of the enzyme, or may act as labilizers, targeting the enzyme
for degradation. Potential substrates and ligands for P450IIE1 will be
screened labilizers and stabilizers by examining what effect they have on
electron flux, oxygen activation and enzyme modification. 2.Characterize the time course of induction and degradation of P450IIE1 in
mice. We have found that a single oral dose of ethanol or acetone leads to
a rapid and significant increase in the concentration of P450IIE1 in CF-I
mice. We will further characterize the induction time course by monitoring
holoenzyme, apoprotein, heme, mRNA and cytosolic protein during the
induction and degradation time course. Strain differences were observed
which suggests a genetic difference in P450IIE1 regulation. We will examine
various strains in more detail to determine whether the difference is at
the level of synthesis or degradation. 3.Characterize the signal(s) which target P450IIE1 for degradation. There
are a number of potential signals for the degradation of P450IIE1. These
include, among others, phosphorylation ubiquitination, oxygen
radical-dependent oxidation of critical amino acid residues, or other
modification of the protein. Each of these events may be coupled with heme
loss. Both whole animal and tissue culture models will be used to determine
which signals may be involved in P450IIE1 degradation.
StatusFinished
Effective start/end date6/1/902/28/09

Funding

  • National Institutes of Health
  • National Institutes of Health: $229,594.00
  • National Institutes of Health: $10,011.00
  • National Institutes of Health: $245,851.00
  • National Institutes of Health: $253,227.00
  • National Institutes of Health: $6,840.00
  • National Institutes of Health: $362,210.00
  • National Institutes of Health: $166,531.00
  • National Institutes of Health
  • National Institutes of Health: $373,077.00
  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health: $384,268.00
  • National Institutes of Health
  • National Institutes of Health: $248,610.00
  • National Institutes of Health: $386,492.00
  • National Institutes of Health: $146,942.00
  • National Institutes of Health
  • National Institutes of Health: $260,825.00

Fingerprint

Ethanol
Proteasome Endopeptidase Complex
Alcohols
Enzymes
Proteins
Xenobiotics
Cytochrome P-450 CYP2E1
N-Nitrosopyrrolidine
Ubiquitin
Acetone
Proteolysis
Heme
Messenger RNA
Apoproteins
Enzyme Activation
Ubiquitination
Cytochrome P-450 Enzyme System
Liver
Phenol
Benzene

ASJC

  • Medicine(all)