Abstract
Angiopoietin-like protein 3 (angptl3), a member of the vascular endothelial growth factor family, was shown to play an important role in regulating lipid metabolism. To elucidate the mechanism by which PPARbeta represses angptl3 promoter activity, reporter constructs were prepared and transfection analysis carried out. PPARbeta repressed angptl3-Luc promoter activity and activation of PPARbeta by L-165041, a PPARbeta-specific ligand, increased the extent of repression. The repression by L-165041 was lost in angptl3-Luc plasmids having a deleted or mutated LXRalpha binding site (DR4). PPARbetaL405R, deficient in RXRalpha binding, had no effect on angptl3-Luc promoter activity. PPARbeta did not repress the activity of GAL4-LXRalpha which activates of GAL4DBD TK-Luc independent of RXR. Addition of RXRalpha completely abolished the repression of angptl3-Luc activity by PPARbeta. Mammalian two-hybrid analysis revealed that PPARbeta ligand binding enhanced the dissociation of the LXRalpha-RXRalpha heterodimer. Gel shift assays also indicated that PPARbeta ligand binding increased dissociation of LXRalpha/RXRalpha binding to a DR4 oligonucleotide probe; addition of RXRalpha restored the binding lost by addition of PPARbeta. Collectively, these results suggest that the binding of PPARbeta-specific ligand enhances the affinity between RXRalpha and activated PPARbeta and thus may regulate angptl3 gene expression through a DR4 element by competing with LXRalpha for RXRalpha.
Publication types
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Research Support, N.I.H., Intramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Acetates / metabolism
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Amino Acid Sequence
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Angiopoietin-Like Protein 3
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Angiopoietin-like Proteins
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Angiopoietins
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Animals
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Binding Sites
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Cell Line
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism*
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Gene Expression Regulation*
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Genes, Reporter
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Humans
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Intercellular Signaling Peptides and Proteins / genetics
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Intercellular Signaling Peptides and Proteins / metabolism*
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Ligands
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Liver X Receptors
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Mice
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Molecular Sequence Data
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Orphan Nuclear Receptors
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PPAR-beta / genetics
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PPAR-beta / metabolism*
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Phenols / metabolism
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Phenoxyacetates
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Promoter Regions, Genetic*
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Receptors, Cytoplasmic and Nuclear / genetics
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Receptors, Cytoplasmic and Nuclear / metabolism*
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Receptors, TNF-Related Apoptosis-Inducing Ligand / metabolism
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Retinoid X Receptor alpha / genetics
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Retinoid X Receptor alpha / metabolism*
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Transcription Factors / genetics
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Transcription Factors / metabolism
Substances
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4-(3-(2-propyl-3-hydroxy-4-acetyl)phenoxy)propyloxyphenoxy acetic acid
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Acetates
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Angiopoietin-Like Protein 3
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Angiopoietin-like Proteins
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Angiopoietins
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Angptl3 protein, mouse
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DNA-Binding Proteins
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Intercellular Signaling Peptides and Proteins
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Ligands
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Liver X Receptors
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NR1H3 protein, human
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Nr1h3 protein, mouse
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Orphan Nuclear Receptors
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PPAR-beta
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Phenols
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Phenoxyacetates
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Receptors, Cytoplasmic and Nuclear
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Receptors, TNF-Related Apoptosis-Inducing Ligand
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Retinoid X Receptor alpha
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Transcription Factors
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farnesoid X-activated receptor