title: Use of [125I]4'-iodoflavone as a tool to characterize ligand-dependent differences in Ah receptor behavior.
abstract: We have synthesized [(125)I]4'-iodoflavone to study Ah receptor (AhR)-ligand interactions by a class of AhR ligands distinct from the prototypic ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). This radioligand allows the comparison of AhR-ligand interactions using a ligand that differs in AhR affinity, and yet has the same radiospecific activity as [(125)I]2-iodo-7,8-dibromodibenzo-p-dioxin. Specific binding of [(125)I]4'-iodoflavone with the AhR was detected as a single radioactive peak ( approximately 9.7 S) following density sucrose gradient analysis. Cytosolic extracts from both Hepa 1 and HeLa cells were used as the source of mouse and human AhR, respectively. A approximately 6.7 S form of radioligand-bound Ah receptor was detected in the high salt nuclear extracts of both cell lines. In HeLa cells approximately twofold more [(125)I]4'-iodoflavone-AhR 6 S complex, compared with [(125)I]2-iodo-7,8-dibromodibenzo-p-dioxin, was recovered in nuclear extracts. A comparison of the ability of 4'-iodoflavone and TCDD to cause time-dependent translocation of AhR-yellow fluorescent protein revealed that 4'-iodoflavone was more efficient at enhancing nuclear accumulation of the receptor. These results suggest that [(125)I]4'-iodoflavone is a particularly useful and easily synthesized ligand for studying the AhR.
authors.affiliation: Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary Science, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Hollie I
authors.initials: HI
authors.lastname: Swanson
authors.forename: Murray L
authors.initials: ML
authors.lastname: Whitelaw
authors.forename: John R
authors.initials: JR
authors.lastname: Petrulis
authors.forename: Gary H
authors.initials: GH
authors.lastname: Perdew
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001667:Binding, Competitive; D003600:Cytosol / Q000378:metabolism; D005419:Flavonoids / Q000737:chemistry / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D007457:Iodine Radioisotopes; D008024:Ligands; D008164:Luminescent Proteins / Q000737:chemistry / Q000378:metabolism; D051379:Mice; D009687:Nuclear Proteins / Q000378:metabolism; D000072317:Polychlorinated Dibenzodioxins / Q000737:chemistry / Q000378:metabolism; D021381:Protein Transport; D018336:Receptors, Aryl Hydrocarbon / Q000819:agonists / Q000737:chemistry / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D014407:Tumor Cells, Cultured
chemical_list: C099018:4'-iodoflavone; D001426:Bacterial Proteins; D005419:Flavonoids; D007457:Iodine Radioisotopes; D008024:Ligands; D008164:Luminescent Proteins; D009687:Nuclear Proteins; D000072317:Polychlorinated Dibenzodioxins; D018336:Receptors, Aryl Hydrocarbon; C054562:yellow fluorescent protein, Bacteria