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Biochemical Reconstitution of Steroid Receptor•Hsp90 Protein Complexes and Reactivation of Ligand Binding
Published on: September 21, 2011
Steroid receptor coactivator-1 from brain physically interacts differentially with steroid receptor subtypes
Heather A Molenda-Figueira1, Suzanne D Murphy, Katherine L Shea
1Center for Neuroendocrine Studies, Neuroscience, and Behavior Program, University of Massachusetts, Amherst, MA 01003, USA.
Steroid receptor coactivator-1 (SRC-1) interacts with estrogen (ER) and progestin receptors (PR) in the brain. These interactions are ligand-dependent and vary by receptor subtype and brain region, impacting steroid-regulated behaviors.
Area of Science:
- Neuroendocrinology
- Molecular Endocrinology
- Cell Biology
Background:
- Nuclear receptor coactivators, like steroid receptor coactivator-1 (SRC-1), are crucial for enhancing transcriptional activity of steroid receptors.
- While SRC-1's role in estrogen receptor (ER) and progestin receptor (PR) action in the brain is established, its specific interactions with these receptors in brain tissue remain largely uncharacterized.
- Understanding these interactions is vital for elucidating the mechanisms of steroid hormone action in the central nervous system.
Purpose of the Study:
- To investigate the ligand-dependent physical association of SRC-1 with ER and PR in hypothalamic and hippocampal tissues.
- To determine if SRC-1 interacts differently with PR-A and PR-B isoforms, and with ERalpha and ERbeta subtypes.
- To explore potential regional differences in SRC-1 interactions with ER in the hypothalamus versus the hippocampus.
Main Methods:
- Pull-down assays were employed to assess the binding of SRC-1 from hypothalamic and hippocampal extracts to recombinant PR and ER.
- Ligand-dependent interactions were tested using agonists, unliganded receptors, and selective receptor modulators (RU486 for PR, tamoxifen for ER).
- Mass spectrometry was used to confirm the identity of SRC-1 in brain extracts.
Main Results:
- SRC-1 from both hypothalamus and hippocampus physically associated with PR-A and PR-B in the presence of an agonist, but not with unliganded receptors or in the presence of RU486.
- SRC-1 demonstrated a stronger interaction with the PR-B isoform compared to PR-A.
- SRC-1 interacted with both ERalpha and ERbeta in the presence of an agonist, but not when unliganded or with tamoxifen.
- Hypothalamic SRC-1 showed a greater interaction with ERalpha than ERbeta, unlike hippocampal SRC-1, suggesting regional differences in cofactor expression.
Conclusions:
- SRC-1 interactions with PR and ER in the brain are critically dependent on ligand binding, receptor subtype, and specific brain region.
- These findings highlight distinct contrasts with in vitro cell culture studies, emphasizing the importance of investigating receptor-coactivator dynamics within biologically relevant tissue contexts.
- The differential interactions observed suggest a complex regulatory network governing steroid-regulated behaviors in the brain.
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