title: An estrogen receptor chimera senses ligands by nuclear translocation.
abstract: We have developed a new mammalian cell-based assay to screen for ligands of the estrogen receptor. A fluorescently tagged chimera between the glucocorticoid and the estrogen receptors, unlike the constitutively nuclear estrogen receptor, is cytoplasmic in the absence of hormone and translocates to the nucleus in response to estradiol. The chimera maintains specificity for estrogen receptor alpha ligands and does not show cross-reactivity with other steroids, providing a clean system for drug discovery. Natural and synthetic estrogen receptor alpha agonists as well as phytoestrogens effectively translocate the receptor to the nucleus in a dose-dependent manner. Antagonists of the estrogen receptor can also transmit the structural signals that result in receptor nuclear translocation. The potency and efficacy of high-affinity ligands can be evaluated in our system by measuring the nuclear translocation of the fluorescently labeled receptor in response to increasing ligand concentrations. The chimera is transcriptionally competent on transient and replicating templates, and is inhibited by estrogen receptor antagonists. Interestingly, the nucleoplasmic mobility of the chimera, determined by FRAP analysis, is faster than that of the wild type estrogen receptor, and the chimera is resistant to ICI immobilization. The translocation properties of this chimera can be utilized in high content screens for novel estrogen receptor modulators.
authors.affiliation: Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health (NIH), Bethesda, MD 20892-5055, USA.
authors.forename: Elisabeth D
authors.initials: ED
authors.lastname: Martinez
authors.forename: Geetha V
authors.initials: GV
authors.lastname: Rayasam
authors.forename: Angie B
authors.initials: AB
authors.lastname: Dull
authors.forename: Dawn A
authors.initials: DA
authors.lastname: Walker
authors.forename: Gordon L
authors.initials: GL
authors.lastname: Hager
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D001671:Biochemistry / Q000379:methods*; D019556:COS Cells; D002460:Cell Line; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D003593:Cytoplasm / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology; D004958:Estradiol / Q000378:metabolism; D005456:Fluorescent Dyes / Q000494:pharmacology; D049452:Green Fluorescent Proteins / Q000737:chemistry; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D008024:Ligands; D051379:Mice; D008856:Microscopy, Fluorescence; D041681:NIH 3T3 Cells; D011485:Protein Binding; D021381:Protein Transport; D011960:Receptors, Estrogen / Q000737:chemistry*; D011965:Receptors, Glucocorticoid / Q000737:chemistry; D011993:Recombinant Fusion Proteins / Q000737:chemistry*; D013256:Steroids / Q000737:chemistry; D013629:Tamoxifen / Q000494:pharmacology; D013997:Time Factors; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection
chemical_list: D005456:Fluorescent Dyes; D018841:HSP90 Heat-Shock Proteins; D008024:Ligands; D011960:Receptors, Estrogen; D011965:Receptors, Glucocorticoid; D011993:Recombinant Fusion Proteins; D013256:Steroids; D013629:Tamoxifen; D049452:Green Fluorescent Proteins; D004958:Estradiol; D003907:Dexamethasone