Distinct effects on the conformation of estrogen receptor alpha and beta by both the antiestrogens ICI 164,384 and ICI 182,780 leading to opposite effects on receptor stability.
Tissue-specific effects of 17beta-estradiol (E(2)) and synthetic estrogen receptor (ER) ligands on target gene regulation might, at least partly, be explained by a selective ligand-induced conformational change of their receptors (ERalpha and ERbeta). In this study, the effects of E(2) and the synthetic ER ligands tamoxifen (TAM), ICI 164,384, and ICI 182,780 on the conformation of ERalpha and ERbeta were examined using limited proteolytic digestion analysis. We found that E(2) induced a conformational change of ERalpha resulting in the protection of a 30-kDa product, whereas TAM protected a 28-kDa fragment. Strikingly, the ERalpha conformational change induced by both ICI 164,384 and ICI 182,780 did not result in protection but rather seems to induce a ligand concentration-dependent increase in proteolytic degradation of the 30- and 28-kDa products. Incubation of ERbeta with E(2) resulted in an increased protection of a 30-kDa fragment, whereas with TAM protection of a 29-kDa fragment was observed. In contrast to the situation with ERalpha, ICI 164,384 and ICI 182,780 incubation induced the protection in a manner similar to 30-kDa fragment E(2). In addition, the ICI compounds also induced in a dose-dependent manner the preservation of a 32-kDa fragment. Our observations demonstrate that ICI 164,384 and ICI 182,780 have distinct effects on the conformation of ERalpha and ERbeta, resulting in receptor subtype-selective opposite effects on receptor stability in vitro.
Department of Internal Medicine III, Erasmus Medical Center Rotterdam, The Netherlands.
G J
GJ
Van Den Bemd
G G
GG
Kuiper
H A
HA
Pols
J P
JP
Van Leeuwen
D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000031:analogs & derivatives* / Q000494:pharmacology; D004965:Estrogen Antagonists / Q000494:pharmacology*; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D000077267:Fulvestrant; D006801:Humans; D008024:Ligands; D008970:Molecular Weight; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D053284:Polyunsaturated Alkamides; D011487:Protein Conformation / Q000187:drug effects; D011960:Receptors, Estrogen / Q000819:agonists / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D013629:Tamoxifen / Q000494:pharmacology; D014357:Trypsin / Q000378:metabolism
D004965:Estrogen Antagonists; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D008024:Ligands; D010446:Peptide Fragments; D053284:Polyunsaturated Alkamides; D011960:Receptors, Estrogen; D013629:Tamoxifen; D000077267:Fulvestrant; D004958:Estradiol; C051781:ICI 164384; D014357:Trypsin