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Glucocorticoid receptor phosphorylation in mouse L-cells.
E R Sanchez1, W Tienrungroj, F C Dalman
1Department of Pharmacology, University of Michigan Medical School, Ann Arbor 48109.
Journal of Steroid Biochemistry
|January 1, 1987
Summary
Phosphorylation patterns of glucocorticoid receptors were studied. The DNA-binding domain is phosphorylated, while the steroid-binding domain is not, offering insights into receptor function.
Area of Science:
- Molecular Biology
- Cell Signaling
- Biochemistry
Background:
- Glucocorticoid receptors (GRs) mediate cellular responses to glucocorticoids.
- The GR complex undergoes conformational changes upon activation, involving heat shock proteins (hsp90).
- Phosphorylation is a key post-translational modification regulating protein function.
Purpose of the Study:
- To investigate the phosphorylation status of untransformed and transformed glucocorticoid receptors.
- To determine which domains of the glucocorticoid receptor are phosphorylated.
- To understand the role of phosphorylation in glucocorticoid receptor transformation and DNA binding.
Main Methods:
- Utilized 32P-labeled L-cells to isolate and study glucocorticoid receptors.
- Employed limited proteolysis on 32P-labeled receptors to identify phosphorylated domains.
- Analyzed receptor complexes using size exclusion chromatography (9S vs. 4S states).
Main Results:
- The untransformed GR complex (9S) includes a 100-kDa steroid-binding phosphoprotein and hsp90.
- Transformation to the 4S DNA-binding state involves dissociation of hsp90 without significant changes in steroid-binding protein phosphorylation.
- Limited proteolysis indicated phosphorylation of the 16-kDa DNA-binding domain, but not the 28-kDa steroid-binding domain.
Conclusions:
- The DNA-binding domain of the glucocorticoid receptor is phosphorylated.
- The steroid-binding domain is not phosphorylated.
- Phosphorylation likely plays a role in regulating glucocorticoid receptor function and DNA interaction.