Hormone-dependent phosphorylation of the glucocorticoid receptor occurs mainly in the amino-terminal transactivation domain

• Published in: The Journal of biological chemistry Vol. 265; no. 10; pp. 5403 - 5408
• Main Authors: HOECK, W, GRONER, B
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Biochemistry and Molecular Biology 05.04.1990
• Subjects: Animals; Binding Sites; Biological and medical sciences; Cell receptors; Cell structures and functions; Chymotrypsin; Cyanogen Bromide; Fundamental and applied biological sciences. Psychology; Gene Expression; Glucocorticoids - pharmacology; Haplorhini; hepatoma; hormones; Hydroxylamine; Hydroxylamines; Immunosorbent Techniques; Liver Neoplasms, Experimental; Molecular and cellular biology; Mutation; Peptide Fragments - metabolism; Peptide Mapping; Phosphates - metabolism; Phosphorylation; Phosphoserine - metabolism; Rats; Receptors, Glucocorticoid - genetics; Receptors, Glucocorticoid - metabolism; Transcriptional Activation; Transfection; Trypsin; Tumor Cells, Cultured; Hormone; Phosphorylation; Rat; Steroid hormone; Rodentia; Glucocorticoid; Site of action; Vertebrata; Immunoprecipitation reaction; Mammalia; Cell line; Transfection; Liver cell carcinoma; Immunoblotting assay; Digestive diseases; Tumor; Mutation; Hormonal receptor
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(19)39373-1

Phosphorylation of glucocorticoid receptors is increased by hormone binding and has been implicated in transcriptional regulation. We performed a phosphoamino acid analysis and identified the phosphorylated regions of the glucocorticoid receptor with respect to its functional domains before and after hormone activation. Receptor was isolated by immunoprecipitation from [32P]orthophosphate-labeled FTO 2B rat hepatoma cells grown in the absence or presence of glucocorticoids. The receptor contained mainly phosphoserine, with little phosphothreonine and no phosphotyrosine. Partial proteolysis of receptor from hormone-treated or control cells revealed a similar phosphopeptide pattern. Chemical cleavage with hydroxylamine and cyanogen bromide or digestion with trypsin and chymotrypsin localized the majority of receptor phosphorylation sites to a transactivation domain amino-terminal of the DNA-binding domain. Phosphorylation of this region, termed tau 1/enh2, was increased 2-3-fold by hormone treatment. The DNA-binding domain itself is weakly phosphorylated; no phosphorylation was found in the hormone-binding domain. Phosphorylated regions were also identified in receptor deletion mutants stably transfected into CV-1 monkey kidney cells. Hormone-independent phosphorylation was observed with a strong constitutively active mutant lacking the hormone-binding domain. No phosphorylation was detected in a mutant lacking the amino-terminal region, which showed only weak, hormone-dependent activity. These results support the idea that phosphorylation is important for the strength of the glucocorticoid receptor as a transcriptional regulator.