Binding Of Hormone-receptor Complex Research Articles

Differential regulation of cyclic AMP synthesis by estrogen in MCF7 cells

The classical view of the molecular actions of estrogen is described by its interaction with the intracellular estrogen receptor (ER), the binding of hormone receptor complex to the estrogen response element (ERE) on the DNA and followed by the alterations of gene expressions. Recently it has been reported that membrane estrogen receptor (mER) exist and it is suggested to be G protein linked receptor. In this report we show that under steroid-free culture conditions supplemented with low percentage of charcoal-stripped serum, differential estrogen treatments of human breast cancer MCF7 cells induce different responses of cyclic AMP (cAMP) productions. Treating [2- 3H]adenine-labeled MCF7 cells with 1 nM estrogen for 30 min stimulates cAMP production by measuring the ratio of [ 3H]cAMP:Total [ 3H]adenine nucleotides (ATP + ADP + cAMP), as determined by column chromatography, when compared with the control. This short-term estrogen treatment also significantly enhanced forskolin stimulated cAMP production when compared with the ratio of cAMP/Total measured in cells stimulated with forskolin alone. Pre-treating MCF7 cells with the same concentration of estrogen for 24 h before the assay, on the contrary, significantly decreased the basal cAMP level and it also suppressed cAMP production stimulated with forskolin when compared with its respective value under short-term estrogen treatment. Estrogen receptor antagonist ICI 182780 abolished both the stimulatory and suppressive effect of estrogen on cAMP synthesis indicating both effects were mediated through ER. Pre-treating cells with pertussis toxin relieved the suppression of cAMP synthesis by chronic estrogen treatment. Our data suggest that estrogen exerts differential effects on the cAMP production in MCF7 cells, involving the activations Gα i and Gα s family of G proteins, depending on the length of time of hormone treatment.

Effects of steroid hormones and steroid-free fetal calf serum on muc 1 gene expression in the breast carcinoma cell line mcf7.

The classical view of the molecular actions of estrogen is described by its interaction with the intracellular estrogen receptor (ER), the binding of hormone receptor complex to the estrogen response element (ERE) on the DNA and followed by the alterations of gene expressions. Recently it has been reported that membrane estrogen receptor (mER) exist and it is suggested to be G protein linked receptor. In this report we show that under steroid-free culture conditions supplemented with low percentage of charcoal-stripped serum, differential estrogen treatments of human breast cancer MCF7 cells induce different responses of cyclic AMP (cAMP) productions. Treating [2-3H]adenine-labeled MCF7 cells with 1 nM estrogen for 30 min stimulates cAMP production by measuring the ratio of [3H]cAMP:Total [3H]adenine nucleotides (ATP + ADP + cAMP), as determined by column chromatography, when compared with the control. This short-term estrogen treatment also significantly enhanced forskolin stimulated cAMP production when compared with the ratio of cAMP/Total measured in cells stimulated with forskolin alone. Pre-treating MCF7 cells with the same concentration of estrogen for 24 h before the assay, on the contrary, significantly decreased the basal cAMP level and it also suppressed cAMP production stimulated with forskolin when compared with its respective value under short-term estrogen treatment. Estrogen receptor antagonist ICI 182780 abolished both the stimulatory and suppressive effect of estrogen on cAMP synthesis indicating both effects were mediated through ER. Pre-treating cells with pertussis toxin relieved the suppression of cAMP synthesis by chronic estrogen treatment. Our data suggest that estrogen exerts differential effects on the cAMP production in MCF7 cells, involving the activations Gαi and Gαs family of G proteins, depending on the length of time of hormone treatment.

Interaction between dexamethasone receptor complexes and isolated nuclei from zajdela hepatoma and rat liver cells

Temperature-activation of the hormone-receptor complex (HRC) was shown to be necessary to ensure its translocation from cytoplasm to nucleus both in the rat liver and hepatoma. Hepatoma nuclei bind 20 times less HRC derived from homologous hepatoma cytosol (0.15 pmol/mg DNA), but twice as much (5.6 pmol/mg DNA) of HRC from heterologous liver cytosol, as compared with the binding of HRC from normal liver cytosol by liver nuclei (3 pmol/mg DNA), Ka of HRC with the acceptor sites in hepatoma and liver nuclei were found to be practically of the same order of magnitude. The above findings suggest an inhibition of cytosol-nucleus translocation of HRC from the cytosol of hepatoma cells as a possible cause of the nonresponsiveness of the latter to the hormone.

Binding of cytoplasmic 5alpha-dihydrotestosterone-receptor complex by nuclei from the ventral prostate, liver, and spleen of rats.

Cytoplasmic 3H-5alpha-dihydrotestosterone-receptor complex of the rat ventral prostate was efficiently taken up by nuclei isolated from the liver, the ventral prostate and the spleen. The amount of the complex bound to liver nuclei was approximately 3 times that to prostate nuclei, and a relatively small amount of the complex was taken up by spleen nuclei under the incubation conditions: 0.16 nM complex (2.0 mg as protein) was used. Binding of the complex to liver nuclei was low-affinity and non-saturable, while in nuclei from the ventral prostate and the spleen, high-affinity and saturable binding was observed. Kd of nuclear binding in the latter two tissues was roughly of the order of 10(-10) M. Castration caused a reduction in the binding of the complex to prostate nuclei and replacement therapy with testosterone propionate completely blocked the effect of castration on the nuclear binding. The affinity of high-affinity binding was not changed significantly after castration. No significant effects of castration and testosterone treatment were observed in the binding of nuclei from the other two tissues examined. The physiological significance of the nuclear binding of hormone-receptor complexes in the action of steroid hormones is discussed.