Carrier protein effects on DNA-cellulose chromatography of putative steroid receptors

Estrogen receptors in the wobbler mouse

Recent research has raised the interesting possibility that the neurological mutant mouse, wobbler (wr/wr), possesses an estrogen receptor deficit analogous to the androgen receptor deficiency found in androgen-resistant mice with testicular feminization. In the present report we examined estrogen-binding activity in cytosolic extracts of kidney, liver, and brain from wobbler mice, littermate control animals, and C57BL/6J mice, using DNA-cellulose chromatography. Estrogen binding components exhibiting properties of estrogen receptors were present in all tissues examined. Estrogen receptors adhered to DNA, displayed characteristic elution profiles from DNA-cellulose, and showed high affinity and limited capacity for estradiol, in contrast to non-receptor entities which bind estradiol. The qualitative elution patterns for estrogen receptors did not differ among groups within each tissue studied, and were similar to those reported previously in mouse kidney and brain. While estrogen receptors have been shown in mouse liver by other techniques, this is the first demonstration of putative estrogen receptors in mouse liver by DNA-cellulose chromatography. No consistent deficits in estrogen receptor concentration were found in wobblers compared to littermates. Thus, the data do not support the hypothesis that the wobbler mouse is an estrogen receptor-deficient mutant.

Characterization of 7-8S progestin binding protein in human prostate using vertical tube rotor

The specific binding of the synthetic progestin, 17 alpha-methyl[3H]promegestone (R5020), to the cytosol of human benign hyperplastic prostate has been studied in sucrose density gradients using a vertical tube rotor. The cytosol of human prostate was shown to contain substantial amounts of a 7-8S macromolecule with a high affinity (Kd = 0.5-1 nM) for R5020 which is saturated at low concentrations (10 nM). The conventional technique of sucrose density gradient analysis in a swinging bucket rotor was not suitable for reproducible optimal analysis of a 7-8S high affinity complex. The use of the salt, Na2MoO4, had a stabilizing effect on the complex. Comparison of saturation analysis assays using dextran charcoal assay and vertical tube rotor assay showed that the charcoal assay can give an over-estimation of the 7-8S saturable binding. Progestational steroids competed with R5020 for binding to 7-8S, whereas androgenic steroids, with the exception of 19-nor-testosterone, did not compete. Incubation of cytosol at elevated temperatures in the presence of DNA-cellulose resulted in the binding of the hormone-protein complex to DNA-cellulose. High ionic strength buffer was required to extract the complex which sedimented at 4.5S in sucrose gradients prepared in 0.4 M KCl. Based on the data presented, progestin binding in human prostate is clearly similar in physical chemical properties to progesterone receptors in "classical" target tissues. However, rapid sucrose gradient analysis with a vertical tube rotor is preferred over conventional techniques to evaluate progestin receptor binding in human prostate.

Differential release of estradiol from immobilized estrogen receptors by p-sec-amylphenol: evidence for a functional microheterogeneity of estrogen receptors

3H-Estradiol-estrogen receptor complexes were adsorbed on a column of heparin-agarose and subjected to a gradient of increasing concentrations of p-sec-amylphenol. At least five peaks of released 3H-estradiol were observed--demonstrating the existence of subsets of heparin-immobilized receptors with different affinities for estradiol. This finding is presented as further evidence for a functional micro-heterogeneity among estrogen receptors. The origin of the observed differences in estrogen receptors and possible relevance of the findings to receptor-mediated responses are discussed.

Release of receptor-bound estradiol by heparin or dextran sulfate in combination with tetracaine

The rapid release of 3H-estradiol from estrogen-receptor complexes at 0 degrees C is implemented by combinations of the local anesthetic tetracaine and certain sulfated polysaccharides. The simultaneous presence of both classes of compounds was found necessary for the displacement of 3H-estradiol to occur. A limited survey of some sulfated polysaccharides and other anionic compounds for their ability to synergize with tetracaine revealed a specificity for the charge-carrying polysaccharide. The present data support the view that the cooperative interaction of sulfated polysaccharides and certain charged hydrophobic compounds with estrogen receptors determines the ability of the receptors to bind estradiol.

Resolution of two fractions of androgen receptor from mouse kidney

Putative androgen receptors from mouse kidney were separated and re-chromatographed on DNA-cellulose columns. With either [3H]-dihydrotestosterone or [3H]-testosterone as ligands, two major fractions of androgen receptors were obtained in both elutions from DNA-cellulose columns; these eluted, respectively, at 140-150 mM NaCl (lower-salt) and 180-190 mM NaCl (higher-salt). Therefore, the two major peaks detectable with extracts of mouse kidney result from differences that are intrinsic to the receptor complexes rather than heterogeneity of the DNA-cellulose matrix. These findings are discussed in relation to two forms of androgen receptors that exist in a different proportion in extracts of brain and in relation to other steroid receptors.

A DNA-binding fraction of mouse kidney 3-ketosteroid reductase: comparison with androgen receptors

Since approximately 1% of 3-ketosteroid reductase (which metabolizes dihydrotestosterone (17 beta-hydroxyl-5 alpha-androstan-3-one] to 5 alpha-androstane-3 alpha, 17 beta-diol or 5 alpha-androstane-3 beta, 17 beta-diol) from mouse kidney cytosol adheres to DNA under conditions that allow virtually complete androgen receptor binding, these two DNA-binding activities were compared in cytosol extracts of mouse kidney and hypothalamus-preoptic area. This DNA-binding fractions of 3-ketosteroid reductase was distinguished from androgen receptor in several ways: (1) its pattern of elution from DNA-cellulose with steps of increasing NaCl concentration differed from that for receptors from wild-type kidney; (2) it was influenced differently by the mutation Tfm, both in level and in DNA-cellulose elution pattern; (3) in mouse kidney cytosol it was relatively stable at moderate (25 degrees C) temperatures which rapidly inactivated ligand-free androgen receptors in the same cytosols; (4) the DNA-binding was not proportional to androgen receptor levels between two wild-type tissues, the hypothalamus-preoptic area and kidney. By these criteria, a simple relationship of androgen receptors and a DNA-binding fraction of 3-ketosteroid reductase activity is unlikely.

Transformation of the estrogen-receptor complex from chick oviduct in 2 steps

Salt treatment of the cytoplasmic estradiol-receptor complex from chick oviduct induces a strong affinity of the complex for DNA-cellulose and phenyl-sepharose. This process is called activation. Binding to heparin- and lysozyme-sepharose is also observed with the untreated complex. But, the salt treatment, additional binding of the complex to these adsorbents is seen. The increased ability of the complex to bind to polyanions and polycations is destroyed by mild trypsination. The binding to the hydrophobic adsorbent is not affected by this treatment. Neither a change of the sedimentation constant nor of the size of the receptor protein is observed after salt treatment in the cold. After binding of the salt-activated estradiol-receptor complex to DNA-cellulose in the cold, an increase of its sedimentation constant and its size, as measured by density-gradient centrifugation and agarose gel chromatography, resp., becomes apparent. A similar phenomenon is observed after binding to DEAE-cellulose and to some extent after binding to heparin-sepharose. The nuclear complex seems to have the same sedimentation constant as the cytoplasmic complex eluted from DNA-cellulose. The sedimentation constant of the nuclear complex is not changed after DNA-cellulose chromatography. The cytoplasmic progesterone-receptor complex from the same tissue, i.e. the oviduct, does not show any change of size. Thus the well-known process of transformation can now be separated into 2 steps. (1) Activation of the estradiol-receptor complex for its binding to various adsorbents in vitro and probably to its acceptor site(s) in vivo. (2) Increase of receptor size. This second step seems to be a special property of the estradiol-receptor complex. Its physiological significance is unclear.

Characterization and quantification of the androgen and glucocorticoid receptors in cytosol from rat skeletal muscle

The binding of the radioactive synthetic hormonal steroids [3H]dexamethasone (9 alpha-fluoro-11 beta, 17 alpha, 21-trihydroxy-16 alpha-methyl-1,4-pregnadiene-3,20-dione) and [3H]methyltrienolone (17 beta-hydroxy-17 alpha-methyl-4,9,11-estratien-3-one) to cytosol from rat skeletal muscle was studied using dextran-coated charcoal to separate unbound and receptor-bound steroid. The rates of association, dissociation, and degradation of the complexes of dexamethasone and methyltrienolone with receptor were highly dependent on temperature. The temperature dependence of association was greater for dexamethasone, and that of degradation was greater for methyltrienolone. Dissociation rates were insignificant for both steroid-receptor complexes compared to association and degradation rates. The apparent equilibrium dissociation constants for the binding of dexamethasone and methyltrienolone to their receptor binding sites were about 7 and 0.3 nM, respectively, regardless of temperature (0. 15 or 23 degrees C). The lack of influence of temperature on the equilibrium constants indicate that the binding was of hydrophobic character, and the corresponding free energy changes upon binding of dexamethasone and methyltrienolone to their respective binding sites were -41 and -49 kJ mol-1 under equilibrium conditions at 0 degrees C. The apparent maximum number of binding sites determined from Scatchard plots under these conditions was about 1900 fmol/g of tissue, 3500 fmol/mg of DNA or 30 fmol/mg of protein in the case of the dexamethasone receptor, and the corresponding figures for the methyltrienolone were about 100 fmol/g of tissue, 200 fmol/mg of DNA or 2 fmol/mg of protein. The ligand specificities of the binding sites for dexamethasone and methyltrienolone were typical of a glucocorticoid and an androgen receptor, respectively. Both steroid-receptor complexes were retained on DNA-cellulose columns, and were eluted by NaCl at an ionic strength of 0.1. The DNA-cellulose step purified about 20 times, and was used to allow gel exclusion chromatography and electrofocusing. Both steroid-receptor complexes were excluded from a column of Sephadex G-150. Electrofocusing in preparative columns gave reproducible patterns consisting of three peaks for each receptor. The apparent isoelectric points were 5.4, 5.6 and 6.2 for the glucocorticoid receptor, and 5.9, 6.2 and 8.5 for the androgen receptor.