Renoir JM, Radanyi C, Baulieu EE. The antiprogesterone RU486 stabilizes the heterooligomeric, non-DNA-binding, 8S-form of the rabbit uterus cytosol progesterone receptor.
Steroids 1989;
53:1-20. [PMID:
2772964 DOI:
10.1016/0039-128x(89)90142-6]
[Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
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.
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