The antiprogesterone RU486 stabilizes the heterooligomeric, non-DNA-binding, 8S-form of the rabbit uterus cytosol progesterone receptor.
The salt-induced (0.3 M KCl) transformation of the non-transformed, heterooligomeric 8S-form of the rabbit uterus cytosol progesterone receptor (PR) was analyzed by density gradient ultracentrifugation (8S----4S conversion) and DNA-cellulose chromatography (non-binding----binding forms). After 1 h treatment at 2 C, greater than 90% of agonist (R5020 or Org2058)-PR complexes were transformed, contrary to antagonist (RU486)-PR complexes, which did not undergo any transformation. Thus, there is stabilization of the non-transformed receptor form by RU486 as compared to the effect of agonist binding. The hydrodynamic parameters of both agonist- and antagonist-bound non-transformed receptors were similar and the calculated Mr were approximately 283,000 and approximately 293,000, respectively. In both cases, purification indicated the presence of a 90-kD non-hormone-binding protein associated with the hormone binding unit(s). Transformation of RU486-PR complexes occurred after exposure to high salt at increased temperature and was correlated to the dissociation of the 90-kD protein from the receptor. Both agonist- and antagonist-bound transformed forms of PR had apparent similar affinities for DNA-cellulose. Molybdate-stabilized and KCl-treated RU486-PR complexes were more stable, as assessed by steroid binding, than the corresponding R5020-PR complexes, arguing in favor of a stabilizing effect of both the 90-kD protein and RU486 against inactivation. These cell-free experiments support the concept that RU486 in the rabbit uterus system stabilizes the 8S non-DNA binding, non-transformed form of the receptor at low temperature. The possibility that impaired dissociation of the heterooligomeric receptor form is involved in the antiprogesterone activity of RU486 is discussed.
INSERM U 33, Lab. Hormones, Le Kremlin-Bicêtre, France.
J M
JM
Renoir
C
C
Radanyi
E E
EE
Baulieu
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003600:Cytosol / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004963:Estrenes / Q000494:pharmacology*; D005260:Female; D015735:Mifepristone; D011372:Progestins / Q000037:antagonists & inhibitors*; D011817:Rabbits; D011980:Receptors, Progesterone / Q000187:drug effects* / Q000378:metabolism; D012588:Scintillation Counting; D013696:Temperature; D014599:Uterus / Q000378:metabolism*
D004963:Estrenes; D011372:Progestins; D011980:Receptors, Progesterone; D015735:Mifepristone; D004247:DNA