Differential regulation of proteasome-dependent estrogen receptor alpha and beta turnover in cultured human uterine artery endothelial cells.
Estrogen-induced loss of estrogen receptor (ER) alpha expression limits estrogen responsiveness in many target cells. However, whether such a mechanism contributes to changes in vascular endothelial ER alpha and/or ER beta levels is unclear. Using RT-PCR assays, we did not find any regulation of ER alpha or ER beta mRNA expression in human uterine artery endothelial cell (HUAEC) nuclear extracts on stimulation with 17 beta-estradiol for 1 or 2 h. By contrast, Western analysis on HUAEC extracts revealed that 17 beta-estradiol was capable of down-regulating both ER alpha and ER beta protein starting 1 h after treatment, an effect that can be blocked by pretreatment with tamoxifen as well as with the proteasome inhibitor lactacystin. The proteolysis inhibitors insulin, cycloheximide, and puromycin impede ER alpha, but not ER beta, turnover. Ubiquitin, but not its competitive inhibitor methyl-ubiquitin, induces rapid turnover of both ERs in a cell-free system of MCF-7 and HUAEC extracts. We, thus, propose the existence of estrogen-induced ER degradation that serves to control physiological responses in an estrogen target tissue, i.e. human vascular endothelium, by down- regulating ER alpha as well as ER beta through different proteasomal uptake mechanisms.
Tschugguel
Walter
W
Department of Obstetrics and Gynecology, Division of Gynecological Endocrinology and Reproductive Medicine, University of Vienna Medical School, General Hospital, A-1090 Vienna, Austria. walter.tschugguel@akh-wien.ac.at
Dietrich
Wolf
W
Zhegu
Zyhdi
Z
Stonek
Felix
F
Kolbus
Andrea
A
Huber
Johannes C
JC
D000111:Acetylcysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000918:Antibody Specificity; D001158:Arteries; D015153:Blotting, Western; D002467:Cell Nucleus / Q000378:metabolism; D002474:Cell-Free System; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D003546:Cysteine Endopeptidases / Q000494:pharmacology*; D004730:Endothelium, Vascular / Q000378:metabolism* / Q000648:ultrastructure; D004958:Estradiol / Q000494:pharmacology; D004965:Estrogen Antagonists / Q000494:pharmacology; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D007700:Kinetics; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D046988:Proteasome Endopeptidase Complex; D011691:Puromycin / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism*; D013629:Tamoxifen / Q000494:pharmacology; D014599:Uterus / Q000098:blood supply*
D004965:Estrogen Antagonists; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D007328:Insulin; D009097:Multienzyme Complexes; D012333:RNA, Messenger; D011960:Receptors, Estrogen; D013629:Tamoxifen; C067713:lactacystin; D011691:Puromycin; D004958:Estradiol; D000255:Adenosine Triphosphate; D003513:Cycloheximide; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D000111:Acetylcysteine