Estradiol-stimulated proteolytic cleavage of the estrogen receptor in mouse uterus.
Increased proteolytic degradation of the estrogen receptor (ER) was detected in uterine cytosol of estradiol-treated ovariectomized mice compared to saline controls. Estradiol had no direct effect on the proteinase activity or susceptibility of the ER to the enzyme. The proteolytic activity gradually increased after a single injection of estradiol with early increases at 2 and 8 h followed by a progressive increase which reached a maximum at 36 h. The proteinase(s) activity resulted in cleavage of the native ER form of 65,000 (65 K ER) to a product of limited proteolysis having an apparent molecular weight of 54,000 (54 K ER). The pH optimum for this proteinase activity was 6.0. The proteinase was inhibited by 2.5 mM p-chloromercuribenzoic acid and 2.5 mM p-chloromercuriphenylsulfonate and partially inhibited by 2.5 mM iodoacetamide but not by 1 mg/ml leupeptin, 0.1 mg/ml antipain, 0.1 mg/ml chymostatin, 0.1 mg/ml pepstatin, 0.1 mg/ml E-64, 2.5 mg/ml soybean trypsin inhibitor, 2.5 mM phenylmethylsulfonylfluoride, 2.5 mM diisopropylfluorophosphate, and 10 mM EGTA. The results suggested that the proteinase(s) had a thiol group essential for its activity. Estrogen receptor in the mouse uterine cytosol fraction appears to be degraded sequentially in two steps in which 65 K ER is cleaved to a 54 K ER which upon longer incubation is further degraded to a 37 K form. The second step was inhibited by leupeptin, antipain, chymostatin, E-64, and p-chloromercuribenzoic acid. A possible function of the 54 K ER under physiological conditions is discussed since the 54 K ER was also found in nuclear samples. This form of the ER still retains the ability to bind estradiol and DNA.
Horigome
T
T
Receptor Biology Section, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709.
Ogata
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F
Golding
T S
TS
Korach
K S
KS
D002731:4-Chloromercuribenzenesulfonate / Q000494:pharmacology; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D002729:Chloromercuribenzoates / Q000494:pharmacology; D003600:Cytosol / Q000201:enzymology; D004247:DNA / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D007460:Iodoacetamide / Q000494:pharmacology; D007700:Kinetics; D051379:Mice; D008970:Molecular Weight; D010052:Ovariectomy; D010447:Peptide Hydrolases / Q000378:metabolism*; D011480:Protease Inhibitors / Q000494:pharmacology; D011960:Receptors, Estrogen / Q000378:metabolism*; D014599:Uterus / Q000187:drug effects / Q000201:enzymology*; D020245:p-Chloromercuribenzoic Acid
D002729:Chloromercuribenzoates; D011480:Protease Inhibitors; D011960:Receptors, Estrogen; D004958:Estradiol; D020245:p-Chloromercuribenzoic Acid; D002731:4-Chloromercuribenzenesulfonate; D004247:DNA; D010447:Peptide Hydrolases; D007460:Iodoacetamide