title: Molecular cloning and characterization of the corticoid receptors from the American alligator.
abstract: Steroid hormones are essential for health in vertebrates. Corticosteroids, for example, have a regulatory role in many physiological functions, such as osmoregulation, respiration, immune responses, stress responses, reproduction, growth, and metabolism. Although extensively studied in mammals and some non-mammalian species, the molecular mechanisms of corticosteroid hormone (glucocorticoids and mineralocorticoids) action are poorly understood in reptiles. Here, we have evaluated hormone receptor-ligand interactions in the American alligator (Alligator mississippiensis), following the isolation of cDNAs encoding a glucocorticoid receptor (GR) and a mineralocorticoid receptor (MR). The full-length alligator GR (aGR) and aMR cDNAs were obtained using 5' and 3' rapid amplification cDNA ends (RACE). The deduced amino acid sequences exhibited high identity to the chicken orthologs (aGR: 83%; aMR: 90%). Using transient transfection assays of mammalian cells, both aGR and aMR proteins displayed corticosteroid-dependent activation of transcription from keto-steroid hormone responsive, murine mammary tumor virus promoters. We further compared the ligand-specifity of human, chicken, Xenopus, and zebrafish GR and MR. We found that the alligator and chicken GR/MR have very similar amino acid sequences, and this translates to very similar ligand specificity. This is the first report of the full-coding regions of a reptilian GR and MR, and the examination of their transactivation by steroid hormones.
authors.affiliation: Graduate School of Life Science, Hokkaido University, Sapporo 060-0810, Japan.
authors.forename: Kaori
authors.initials: K
authors.lastname: Oka
authors.forename: Satomi
authors.initials: S
authors.lastname: Kohno
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Urushitani
authors.forename: Louis J
authors.initials: LJ
authors.lastname: Guillette
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Ohta
authors.forename: Taisen
authors.initials: T
authors.lastname: Iguchi
authors.forename: Yoshinao
authors.initials: Y
authors.lastname: Katsu
mesh_terms: D000450:Aldosterone / Q000502:physiology; D000489:Alligators and Crocodiles / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D003001:Cloning, Molecular; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D006854:Hydrocortisone / Q000502:physiology; D008024:Ligands; D008297:Male; D008969:Molecular Sequence Data; D009928:Organ Specificity; D010802:Phylogeny; D011485:Protein Binding; D011965:Receptors, Glucocorticoid / Q000235:genetics* / Q000378:metabolism; D018161:Receptors, Mineralocorticoid / Q000235:genetics* / Q000378:metabolism; D030162:Reptilian Proteins / Q000235:genetics* / Q000378:metabolism; D020218:Response Elements; D015533:Transcriptional Activation; D014982:Xenopus laevis; D015027:Zebrafish
chemical_list: D008024:Ligands; D011965:Receptors, Glucocorticoid; D018161:Receptors, Mineralocorticoid; D030162:Reptilian Proteins; D000450:Aldosterone; D006854:Hydrocortisone