Project: Research project

Project Details


Compounds which result in the proliferation of peroxisomes represent a
diverse group of chemicals which have important biological and
toxicological effects in mammalian cells. Peroxisome proliferators include
certain hypolipidemic drugs, phthalate ester plasticizers and various
herbicides and pesticides. Recent studies have shown that many genes
affected by peroxisome proliferators are regulated by a novel member of
the steroid hormone receptor superfamily, the peroxisome proliferator-
activated receptor (PPAR). The role of this protein in maintaining normal
cellular physiology is not known, although many lines of evidence suggest
that it is involved in lipid metabolism and possibly growth regulation.
The present grant proposal will explore how the function of this
potentially important steroid hormone receptor is regulated. First, the
overall response of cells to peroxisome proliferators may be regulated by
the concentration of their cognate receptor. The mechanism for control of
PPAR expression has not been thoroughly examined, although studies in our
laboratory have shown that peroxisome proliferators as well as factors
affected by nutritional status regulate the accumulation of the messenger
RNA for the predominant form of PPAR found in rodent liver (PPARalpha).
The factors that effect PPARalpha expression will be examined in rat
hepatoma cells to determine possible endogenous and exogenous modes of
regulation. Based on preliminary studies, the induction of PPARalpha mRNA
by peroxisome proliferators is predominantly a post-transcriptional event.
The effect of peroxisome proliferators on PPARalpha mRNA stability will be
examined and possible mechanisms explored. Second, based on studies with
closely related steroid hormone receptors, numerous protein-protein
interactions may affect the process of PPAR-mediated gene regulation.
Novel proteins which interact with PPARalpha will be examined using
interaction cloning, a technique which examines the binding of a
bacterial-expressed PPARalpha to a rat hepatoma cDNA expression library.
The binding of PPARalpha to these novel proteins will be characterized to
determine the strength of binding and the domain of PPARalpha involved.
Finally, studies will be implemented to determine the result of the
protein-protein interactions on peroxisome proliferator-dependent gene
regulation to determine if PPARalpha heterodimers are involved in DNA
binding, receptor phosphorylation or cell growth. Taken together these
studies enhance our knowledge of the molecular mechanisms of peroxisome
proliferator-dependent gene regulation and will greatly enhance our
understanding of the role played by PPAR in mediating cellular responses
to this important group of rodent carcinogens.
Effective start/end date8/10/953/31/05