Differential autoregulation of glucocorticoid receptor expression in human T- and B-cell lines.
Regulation of glucocorticoid receptor (GR) expression by its cognate ligand was examined in the glucocorticoid-sensitive human leukemic T-cell line 6TG1.1 and in the human B-cell line IM-9. In contrast to the decrease in GR mRNA seen in IM-9 cells after treatment with 1 microM dexamethasone for 16-18 h, treatment of 6TG1.1 cells resulted in an 8-fold increase in GR mRNA, as determined by Northern blot and RNase protection analysis, with a corresponding 3- to 4-fold increase in GR protein. Half-maximal induction of GR mRNA and protein in 6TG1.1 cells was observed between 10-100 nM dexamethasone, and inclusion of 1 microM RU 38486 completely blocked the effects of 100 nM dexamethasone, demonstrating that positive autoregulation of GR expression in 6TG1.1 cells is a receptor-mediated response. Positive autoregulation of GR expression was also observed in glucocorticoid-resistant CEM-C1 cells, which contain functional GR, but whose growth is unaffected by glucocorticoids. Thus, positive autoregulation is neither a consequence nor the sole cause of growth arrest. The degree of negative autoregulation in IM-9 cells and positive autoregulation in 6TG1.1 cells was unaffected by inhibition of protein synthesis with cycloheximide. Measurement of GR mRNA turnover in 6TG1.1 cells treated with actinomycin-D revealed a half-life of 2.5 h, which was unaffected by dexamethasone treatment. A similar half-life was determined in IM-9 cells and was also unaffected by steroid treatment. These results are consistent with the interpretation that glucocorticoid-mediated autoregulation of GR expression is a tissue-specific primary transcriptional response.
Denton
R R
RR
Department of Pharmacology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814-4799.
Eisen
L P
LP
Elsasser
M S
MS
Harmon
J M
JM
D001402:B-Lymphocytes / Q000378:metabolism*; D015152:Blotting, Northern; D003609:Dactinomycin / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D015347:RNA Probes; D012333:RNA, Messenger / Q000378:metabolism; D011965:Receptors, Glucocorticoid / Q000235:genetics*; D012260:Ribonucleases; D013601:T-Lymphocytes / Q000378:metabolism*
D015347:RNA Probes; D012333:RNA, Messenger; D011965:Receptors, Glucocorticoid; D003609:Dactinomycin; D003907:Dexamethasone; D012260:Ribonucleases