title: Dissecting physiological roles of estrogen receptor alpha and beta with potent selective ligands from structure-based design.
abstract: The distinct roles of the two estrogen receptor (ER) isotypes, ERalpha and ERbeta, in mediating the physiological responses to estrogens are not completely understood. Although knockout animal experiments have been aiding to gain insight into estrogen signaling, additional information on the function of ERalpha and ERbeta will be provided by the application of isotype-selective ER agonists. Based on the crystal structure of the ERalpha ligand binding domain and a homology model of the ERbeta-ligand binding domain, we have designed steroidal ligands that exploit the differences in size and flexibility of the two ligand binding cavities. Compounds predicted to bind preferentially to either ERalpha or ERbeta were synthesized and tested in vitro using radio-ligand competition and transactivation assays. This approach directly led to highly ER isotype-selective (approximately 200-fold) and potent ligands. To unravel physiological roles of the two receptors, in vivo experiments with rats were conducted using the ERalpha- and ERbeta-selective agonists in comparison to 17beta-estradiol. The ERalpha agonist induced uterine growth, caused bone-protective effects, reduced LH and FSH plasma levels, and increased angiotensin I, whereas the ERbeta agonist did not at all or only at high doses lead to such effects, despite high plasma levels. It can thus be concluded that estrogen effects on the uterus, pituitary, bone, and liver are primarily mediated via ERalpha. Simultaneous administration of the ERalpha and ERbeta ligand did not lead to an attenuation of ERalpha-mediated effects on the uterus, pituitary, and liver parameters.
authors.affiliation: EnTec Gesellschaft für Endokrinologische Technologie GmbH, D-13342 Berlin, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Hillisch
authors.forename: Olaf
authors.initials: O
authors.lastname: Peters
authors.forename: Dirk
authors.initials: D
authors.lastname: Kosemund
authors.forename: Gerd
authors.initials: G
authors.lastname: Müller
authors.forename: Alexander
authors.initials: A
authors.lastname: Walter
authors.forename: Birgitt
authors.initials: B
authors.lastname: Schneider
authors.forename: Gudrun
authors.initials: G
authors.lastname: Reddersen
authors.forename: Walter
authors.initials: W
authors.lastname: Elger
authors.forename: Karl-Heinrich
authors.initials: KH
authors.lastname: Fritzemeier
mesh_terms: D000595:Amino Acid Sequence; D000803:Angiotensin I / Q000097:blood / Q000187:drug effects; D000818:Animals; D001665:Binding Sites; D001671:Biochemistry / Q000379:methods; D001842:Bone and Bones / Q000187:drug effects / Q000378:metabolism; D004958:Estradiol / Q000494:pharmacology; D047628:Estrogen Receptor alpha / Q000819:agonists / Q000737:chemistry / Q000502:physiology*; D047629:Estrogen Receptor beta / Q000819:agonists / Q000737:chemistry / Q000502:physiology*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D008024:Ligands; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D008969:Molecular Sequence Data; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013329:Structure-Activity Relationship; D014599:Uterus / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism
chemical_list: D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D008024:Ligands; D004958:Estradiol; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D000803:Angiotensin I