Cyclic AMP-binding protein and estrogen receptor: antagonism during nuclear translocation in a hormone-dependent mammary tumor |
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Authors: | J S Bodwin P H Hirayama Y S Cho-Chung |
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Institution: | Laboratory of Pathophysiology National Cancer Institute National Institutes of Health Bethesda, Maryland 20205 USA |
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Abstract: | Incubation of nuclei from hormone-dependent rat mammary tumors with its cytosol activated with 5 nM 17β-estradiol resulted in a 4-fold increase of nuclear estrogen binding activity over the control nuclei. The presence of 100 nM cAMP in the activated cytosol inhibited this nuclear uptake of estrogen receptor by 50%. Conversely, incubation of the nuclei with cytosol activated with 100 nM cAMP increased nuclear cAMP binding and cAMP-dependent protein kinase activity 4-fold, while the presence of 5 nM 17β-estradiol in the activated cytosol inhibited the nuclear cAMP binding and the protein kinase activity by 50%. No competition was found between estrogen and cAMP for each other's cytoplasmic binding proteins or the nuclear acceptor sites. These data suggest that a mutual antagonism exists between the cAMP-binding protein and estrogen receptor during their nuclear translocation. |
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