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Mouse estrogen receptor beta isoforms exhibit differences in ligand selectivity and coactivator recruitment
Chunyan Zhao1, Gudrun Toresson, Li Xu
1Department of Biosciences at Novum, Karolinska Institutet, SE-141 57 Huddinge, Sweden. chunyan.zhao@cnt.ki.se
Biochemistry
|June 1, 2005
Summary
This study reveals that estrogen receptor beta (ERbeta) isoforms, ERbeta1 and ERbeta2, exhibit distinct ligand selectivities and coactivator interactions. These differences in binding and transcriptional activity are crucial for understanding estrogen signaling specificity.
Area of Science:
- Molecular Endocrinology
- Receptor Biology
- Pharmacology
Background:
- Estrogen signaling is mediated by estrogen receptor (ER) subtypes, ERalpha and ERbeta.
- A mouse splice variant, mERbeta2, with an 18 amino acid insertion in the ligand-binding domain, adds complexity to ER signaling.
- Understanding ERbeta isoform-specific interactions is key to deciphering estrogenic effects.
Purpose of the Study:
- To investigate the differential binding affinities of ligands to mERbeta1 and mERbeta2.
- To analyze the impact of these isoforms on transactivation and coactivator recruitment.
- To elucidate the structural basis for ligand selectivity in ERbeta isoforms.
Main Methods:
- Ligand binding assays were performed using estradiol and raloxifene.
- Transactivation assays were used to measure gene expression changes.
- Pull-down assays and surface plasmon resonance analyzed coactivator interactions (TIF2, RAP250).
Main Results:
- Estradiol bound mERbeta1 with 14-fold higher affinity than mERbeta2.
- Raloxifene showed 8-fold selectivity for mERbeta2, dependent on its 3-aroyl side chain.
- mERbeta2 exhibited reduced estradiol-induced transcriptional activity and weaker interactions with coactivators TIF2 and RAP250.
Conclusions:
- Ligand selectivity and coactivator recruitment differ significantly between ERbeta isoforms.
- These isoform-specific interactions contribute to the fine-tuning of estrogen target cell responses.
- The findings highlight ERbeta isoforms as critical determinants of estrogen signaling specificity.