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Decrease of estrogen receptor expression and associated ERE-dependent transcription in MCF-7 breast cancer cells
Hye-Sook Seo1, Fabrice Journé, Denis Larsimont
1Laboratoire J.-C. Heuson de Cancérologie Mammaire, Service de Médecine Interne, Institut Jules Bordet, Université Libre de Bruxelles, Brussels, Belgium.
Steroids
|March 12, 2003
Summary
Oligomycin rapidly decreases estrogen receptor (ER) levels and function in MCF-7 cells by inhibiting ATP synthesis, impacting ER turnover and transcription. This suggests ER phosphorylation regulates its stability and response to ligands.
Area of Science:
- Cell Biology
- Molecular Endocrinology
- Biochemistry
Background:
- Estrogen receptor (ER) is crucial for regulating gene expression in hormone-responsive cells.
- ER activity is modulated by ligand binding, post-translational modifications like phosphorylation, and protein turnover.
- Understanding factors influencing ER stability and function is key to developing targeted therapies.
Purpose of the Study:
- To investigate the effect of oligomycin, an ATP synthesis inhibitor, on ER expression and function in MCF-7 cells.
- To explore the role of ER phosphorylation in oligomycin-induced changes and ligand interactions.
- To determine if oligomycin affects other nuclear receptors.
Main Methods:
- MCF-7 cells were treated with oligomycin in glucose- and serum-free medium.
- Estrogen receptor (ER) binding capacity was measured using [3H]estradiol.
- ER levels were assessed, along with ERE-luciferase reporter gene expression.
- Cell viability was evaluated using MTT assay.
- Progesterone receptor (PR) levels and phosphorylation status were analyzed.
Main Results:
- Oligomycin rapidly decreased ER binding capacity and levels, independent of major cell death.
- Basal ERE-luciferase activity was reduced, indicating impaired transcriptional function.
- Oligomycin down-regulated PR levels and interfered with E2-induced PR upregulation.
- ER phosphorylation was required for hormone binding, and oligomycin affected ER phosphorylation patterns.
- Ligand-specific effects on ER phosphorylation and turnover were observed, with partial rescue by E2 and partial anti-estrogens.
Conclusions:
- Oligomycin-induced ATP synthesis inhibition accelerates ER turnover, leading to rapid loss of receptor and function.
- ER phosphorylation plays a critical role in regulating ER stability and hormone binding.
- Oligomycin impacts multiple nuclear receptors, suggesting broader effects on endocrine signaling.
- These findings highlight the intricate regulation of ER by cellular energy status and post-translational modifications.