Related Experiment Videos
Antagonist-induced, activation function-2-independent estrogen receptor alpha phosphorylation
Lorraine Lipfert1, John E Fisher, Nan Wei
1Molecular Endocrinology and Bone Biology, Merck Research Laboratories, WP26A-1000, West Point, Pennsylvania 19486, USA.
Molecular Endocrinology (Baltimore, Md.)
|October 15, 2005
Summary
Estrogen receptor alpha (ERalpha) serine 118 phosphorylation can occur independently of the AF2 domain, suggesting a novel pathway. Ligand-induced redistribution of phosphorylated ERalpha out of the nucleus may precede receptor degradation.
Area of Science:
- Molecular Endocrinology
- Cell Biology
Background:
- Estrogen receptor alpha (ERalpha) serine 118 (Ser118) phosphorylation is critical for its function.
- This phosphorylation is typically mediated by cyclin-dependent kinase-7, requiring correct helix 12 positioning for agonist-dependent recruitment.
Purpose of the Study:
- To investigate cyclin-dependent kinase-7-independent, AF2 antagonist-induced Ser118 phosphorylation of ERalpha.
- To elucidate the cellular localization and fate of phosphorylated ERalpha in response to various ligands.
Main Methods:
- Utilized COS-1 and MCF-7 cell lines.
- Investigated ERalpha phosphorylation and cellular localization using estradiol (E2), ICI-182,780 (ICI-780), and selective ER modulators (SERMs).
- Assessed protein degradation using proteasome inhibitors and correlated cellular redistribution with in vivo uterotropism and in vitro transrepression.
Main Results:
- Demonstrated robust cyclin-dependent kinase-7-independent, AF2 antagonist-induced Ser118 phosphorylation of ERalpha.
- Observed ligand-induced redistribution of phosphorylated ERalpha from the nucleus to detergent-insoluble fractions (cytoplasm/cell debris), not degradation.
- Correlated redistribution magnitude with receptor degradation and inversely with uterotropism, directly with transrepression.
Conclusions:
- Ligand-induced Ser118 phosphorylation of ERalpha can be AF2-independent.
- Translocation of Ser118-phosphorylated ERalpha out of the nucleus and cytoplasmic aggregation represent an antagonist pathway preceding receptor degradation.