Binding of steroids to progesterone receptor proteins in chick oviduct and human uterus (original) (raw)
Related papers
Bioorganic & Medicinal Chemistry, 2011
The biological activity of two seven-membered A-ring (A-homo) analogues of progesterone was evaluated by transactivation assays in Cos-1 cells and by determination of Bcl-x L expression levels in T47D cells. The results show that both compounds act as selective progesterone receptor (PR) agonists but lack mineralocorticoid receptor (MR) activity. Molecular modelling using semiempirical AM1 and ab initio HF/ 6-31G ⁄⁄ calculations, showed that the A-ring of the A-homo steroids may adopt five different conformations, although only three correspond to low energy conformers. The low energy conformers of each analogue were introduced into the ligand binding pocket of the PR ligand binding domain (LBD) obtained from the PR LBD-progesterone crystal structure. The steroid binding mode was then analyzed using 10 ns of molecular dynamics (MD) simulation. The PR LBD-progesterone complex was also simulated as a control system. The MD results showed that both A-homo steroids have one conformer that may be properly recognized by the PR, in agreement with the observed progestagen activity. Moreover, the simulation revealed the importance of a water molecule in the formation of a hydrogen bonding network among specific receptor residues and the steroid A-ring carbonyl.
Steroids, 2010
Recent results showing that the binding characteristics of 33 steroids for human membrane progesterone receptor alpha (hu-mPRα) differ from those for the nuclear progesterone receptor (nPR) suggest that hu-mPRα-specific agonists can be identified for investigating its physiological functions. The binding affinities of an additional 21 steroids for hu-mPRα were determined to explore the structure-activity relationships in more detail and to identify potent, specific mPRα agonists. Four synthetic progesterone derivatives with methyl or methylene groups on positions 18 or 19, 18a-methylprogesterone (18-CH 3 P4, Org OE 64-0), 13-ethenyl-18-norprogesterone (18-CH 2 P4, Org 33663-0), 19a-methylprogesterone (19-CH 3 P4, Org OD 13-0) and 10-ethenyl-19norprogesterone (19-CH 2 P4, Org OD 02-0), showed similar or higher affinities than progesterone for hu-mPRα and displayed mPRα agonist activities in G-protein and MAP kinase activation assays. All four steroids also bound to the nPR in cytosolic fractions of MCF-7 cells. However, two compounds, 19-CH 2 P4 and 19-CH 3 P4, showed no nPR agonist activity in a nPR reporter assay and therefore are selective mPRα agonists suitable for physiological investigations. The structure-binding relationships of the combined series of 54 steroids for hu-mPRα deviated strikingly from those of a published set of 60 3-keto or 3-desoxy steroids for nPR. Close correlations were observed between the receptor binding affinities of the steroids and their physicochemical properties calculated by comparative molecular field analysis (CoMFA) for both hu-mPRα and nPR. A comparison of the CoMFA field graphs for the two receptors revealed several differences in the structural features required for binding to hu-mPRα and nPR which could be exploited to develop additional mPR-specific ligands.
Steroids, 1987
A number of progesterone derivatives, having a 17a-acetoxy group and various functions at c-3 ti C-6, interact at the cardiac glycoside (a;) binding site, using P~loualxin in a radioligtiE;ing assay (RBA) withmembranes from dog myocardium. We now on results of structure-activity studies concerned with modification of the A and B rings as they influence potency in the RBA. Some progesterone derivatives with !%I-or 5p-stereochemistry show weak receptor competing activity. Among thecongenershighestpotency is associated with the presence of C-4 or C-4,6 unsaturation and a C-6 substitutent (CH3, Cl, Br) whose importance appears to reside in its steric rather thanelectronic character. The C-3 function may be carbonyl, 3/3-hydroq or 3p-acetoxy when associated with C-4 or C-4,6 unsaturation. In compounds with other substituents that promote activity, C-6u substitution with -CH3, -Cl, or -Br strongly enhances activity; -F,-OCH carbonyl, or the unsubstitxted cog promotes weak binding; an d?-CC2HS, -OAc, -OCOOCH3,0r -OH eliminates binding activity. Receptor interaction with the double bond. at C-4, but not C-5, appears to be particularly impxtant for binding. The most potent analog identified thus far is chlormadinone acetate (17@-a&zoxy-+chforopregna-4,6-diene-3,20_dione), which has l/20 the potency of ouabain in the RBA.
Comparative binding affinity of estrogens and its relation to estrogenic potency
Steroids, 1969
The comparative affinity of steroidal and non-steroidal estrogens for binding sites in rabbit uterine cytosol was determined quantitatively using an in vitro assay system. It was found that with few exceptionsrelative binding affinity paralleled uterotropic activity. Binding affinity of steroids depended strongly on the phenolic hydroxyl and on substitutions in ring D. Additional substitutions of oxygen functions or unsaturation of the estra-triene nucleus were inhibitory.
The Journal of Steroid Biochemistry and Molecular Biology, 1992
We have examined steroid binding parameters and transformation of calf uterine progesterone receptor (PR) liganded with progestins (progesterone and R5020) and the newly synthesized antiprogestins (Org 31806 and 31710). Species specificity analysis indicated that [3H]R5020 binding in the chicken oviduct cytosol could be eliminated in the presence of 100-fold excess radioinert progesterone and R5020 but not Org 31806 and 31710. In the calf uterine cytosol, the progestins and the antiprogestins appeared to interact with the same PR as revealed by the displacement of [3 H]RS020 by all of the above steroids. When the extent of [3H]RS020 binding was examined in the presence of different concentrations of radioinert steroids, the relative affinity with which these compounds interacted with the uterine PR was found to be comparable. A 23°C incubation of cytosol transformed the progestin-bound PR complexes increasing their binding to DNA-ceilulose from 5 (0°C, nontransformed) to 35%. Under these conditions, 20% Org 31710-and RU486-occupied PR complexes bound to DNA-cellulose whereas only 10% Org 31806-receptor complexes were retained by the resin. Transformation (23°C) of cytosol receptor caused a loss of the larger 8 S form and an increase in the smaller 4 S form. In its unliganded state or when it was complexed with R5020 or the antiprogestins, incubation of PR at 23°C led to dissociation of the receptor-associated 90 kDa heat-shock protein (hsp90). The PR-hsp90 association was stabilized in the presence of l0 mM iodoacetamide when the ligand binding site was occupied by Org 31806 and 31710. The RS020-receptor complexes, however, allowed release of hsp90 under the above transforming conditions. Our results indicate that although Org 31806 and 31710 show no affinity for the avian PR, these steroids interact with the mammalian PR. We propose that the reported antiprogestational effects of Org 31806 and 31710 are mediated via their interaction with PR which appears similar to one that exists between PR and RU486.
Journal of steroid biochemistry, 1983
Uteroglobin binds progesterone with high affinity. A few substituted diphenyl ketones were observed to inhibit uteroglobin-progesterone binding in a dose-dependent manner. 4,4'-Dimethoxy-2-hydroxy benzophenone had relatively higher affinity for uteroglobin. The structure-activity relationship amongst the substituted diphenyl ketones indicated considerable sensitivity towards minor structural modifications. These observations offer a tool to investigate nonsteroidal compounds in relation to progesterone related functions of uteroglobin in pregnancy.
Purification and Properties of Progesterone Receptors from Chick Oviduct
Annals of the New York Academy of Sciences, 1977
Steroid hormone receptor proteins have been the subject of intensive study for more than 10 years. This research has clearly implicated these molecules in the process of steroid hormone-induced cell development and differentiation. These studies have also shown that receptor proteins are structurally complex, undergoing changes in aggregation, conformation, and binding activities before and during their interaction with nuclear acceptor sites.lB2 The importance of these properties is apparent from the extensive similarities among all steroid receptor proteins studied, regardless of source or steroid-binding specificity. Work in this laboratory has centered on the purification and characterization of progesterone receptors in chick oviduct. This research has been performed with two goals in mind. First, we have studied these proteins to gain information on the relationship between their structure and in vivo mechanism of action. Second, we have sought to purify these proteins to investigate their effect on gene expression in vitro. Chick oviduct progesterone receptor contains two 4s components, designated A and B, which can be resolved by chromatography on a variety of ion-exchange These two components, which are present in approximately equal amounts in crude oviduct cytoplasmic extracts,s are not interconvertable. They have similar hormone-binding sites with respect to equilibrium and kinetic binding constants and hormonal stereospecificity.3 Although both receptor forms are taken up by oviduct nuclei in v i t r~,~'~ they have distinct specificities for binding to nuclear components. The receptor A component binds only to DNA, whereas the B component binds only to chro-Furthermore, B-component binding to chromatin is target tissue ~p e c i f i c .~J~ These properties of the progesterone receptor led us to p r o p o~e~~'~~~~ that both chromatin-and DNA-binding forms might be necessary for receptor function in vivo. We have recently shown in an in vitro system that steroid hormones regulate gene expression in the chick oviduct at the level of messenger RNA transcription.I3 In our hypothetical model, the chromatin-binding B protein would function to specify regions in the chromatin adjacent to hormonally regulated genes. This specifier activity would then direct the A protein to its site of action, where it would bind to the DNA and thus modify transcription by RNA polymerases. This model would suggest that aggregated forms of the receptor that contain