title: Homology-modeled ligand-binding domains of zebrafish estrogen receptors alpha, beta1, and beta2: from in silico to in vivo studies of estrogen interactions in Danio rerio as a model system.
abstract: Homology models were constructed for the ligand-binding domains of zebrafish estrogen receptors (zfERs) alpha, beta(1), and beta(2). Estradiol-binding sites are nearly identical in zfERs and their human homologs, suggesting that zebrafish will serve as a good model system for studying human ER-binding drugs. Conversely, studies of endocrine disruptor effects on zebrafish will benefit from the wealth of data available on xenoestrogen interactions with human ERs. Compounds flagged by the Interagency Coordinating Committee on the Validation of Alternative Methods for endocrine disruptor screening were docked into our zfER homology models. Ideally, these in silico docking studies would be complemented with in vivo binding studies. To this end, fluorescently tagged estradiol was docked into zfERalpha and found to bind in the same manner as in human ERalpha, with fluorescein preferentially occupying a region between helices 11 and 12. Fluorescently tagged estradiol was synthesized and was found to localize along the path of primordial germ cell migration in the developing zebrafish embryo 3 d after fertilization, consistent with previous reports of 1) a role for estradiol in sex determination, and 2) the first appearance of ERs 2 d after fertilization. These data provide a foundation for future in silico and in vivo binding studies of estrogen agonists and antagonists with zebrafish ERs.
authors.affiliation: Chemical Proteomics Facility at Marquette, Department of Chemistry, Marquette University, P.O. Box 1881, Milwaukee, WI 53201, USA.
authors.forename: Aurora D
authors.initials: AD
authors.lastname: Costache
authors.forename: Phani Kumar
authors.initials: PK
authors.lastname: Pullela
authors.forename: Purnachandar
authors.initials: P
authors.lastname: Kasha
authors.forename: Henry
authors.initials: H
authors.lastname: Tomasiewicz
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Sem
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003198:Computer Simulation; D004958:Estradiol / Q000032:analysis; D047628:Estrogen Receptor alpha / Q000737:chemistry* / Q000378:metabolism; D047629:Estrogen Receptor beta / Q000737:chemistry / Q000378:metabolism; D004967:Estrogens / Q000378:metabolism*; D005453:Fluorescence; D005854:Germ Cells / Q000737:chemistry; D008024:Ligands; D008954:Models, Biological; D008969:Molecular Sequence Data; D011487:Protein Conformation; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015027:Zebrafish / Q000254:growth & development / Q000378:metabolism*; D029961:Zebrafish Proteins / Q000737:chemistry* / Q000378:metabolism
chemical_list: D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D004967:Estrogens; D008024:Ligands; D029961:Zebrafish Proteins; D004958:Estradiol