Project: Research project

Project Details


The Ah receptor plays a central role in the biological response to
halogenated polycyclic aromatic hydrocarbons (HPAH), a major class
of environmental contaminants, many of these components are known
to be carcinogenic (e.g. dioxins). This receptor, upon binding a
HPAH, is thought to translocate into the nucleus and induce the
synthesis of enzymes involved in the metabolism of xenobiotics.
The non-ligand binding protein composition of the Ah receptor
complex has no been determined. Using 2-azido-3-(125I)7,8-
dibromodibenzo-p-dioxin (a photoaffinity ligand), a monoclonal
antibody to an Ah receptor, and cross-linking reagents, a series
of experiments will be performed to determine the protein
composition of the Ah receptor in the Hepa lcl cell line. Since
phosphorylation is an important post-transnational modification
involved in the regulation of receptor systems, and indirect
evidence has suggested that the Ah receptor is phosphorylated, the
studies outlined here will directly examine this possibility. Hepa
1 cells will be incubated in the presence of (32P) orthophosphate
followed by the isolation of a cytosolic fraction. This
preparation will be immunoprecipitated, subjected to two-
dimensional gel electrophoresis, and the (32P)-labeled polypeptide
pattern will be compared to photoaffinity-labeled control samples.
In addition, studies will be performed to determine whether
phosphorylation is required for Ah receptor ligand binding
activity. The rate of Ah receptor turnover in Hepa 1 cells will
be determined using a dense amino acid labeling method. The
influence of ligand occupation on the rate of receptor turnover
will also be determined. A number of compounds have been found to
alter in vivo Ah receptor activity levels, studies will be
performed to examine the ability of certain exogenous compounds to
influence receptor levels in cell culture. Any differences seen
can then be further examined by turnover experiments to determine
if the rate of receptor synthesis has changed. The experiments
proposed here will enable a better understanding of possible
mechanisms of Ah receptor regulation.
Effective start/end date1/1/9012/31/93


  • National Institute of Environmental Health Sciences
  • National Institute of Environmental Health Sciences
  • National Institute of Environmental Health Sciences


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