Glucocorticoids inhibit calcium-and calcineurin-dependent activation of the human IL-4 promoter

R Chen, TF Burke, JE Cumberland… - The Journal of …, 2000 - journals.aai.org
R Chen, TF Burke, JE Cumberland, M Brummet, LA Beck, V Casolaro, SN Georas
The Journal of Immunology, 2000journals.aai.org
The mechanism by which glucocorticoids (GC) inhibit IL-4 gene expression is currently
unknown. In T lymphocytes, IL-4 gene expression is regulated at the level of transcription by
increases in intracellular calcium concentration and by the calcium-activated phosphatase
calcineurin. In this paper we report that dexamethasone (Dex) inhibits calcium ionophore-
induced activation of the human IL-4 promoter in transiently transfected Jurkat T cells.
Inhibition of the promoter by Dex is dependent on expression of the GC receptor (GR) …
Abstract
The mechanism by which glucocorticoids (GC) inhibit IL-4 gene expression is currently unknown. In T lymphocytes, IL-4 gene expression is regulated at the level of transcription by increases in intracellular calcium concentration and by the calcium-activated phosphatase calcineurin. In this paper we report that dexamethasone (Dex) inhibits calcium ionophore-induced activation of the human IL-4 promoter in transiently transfected Jurkat T cells. Inhibition of the promoter by Dex is dependent on expression of the GC receptor (GR), because it does not occur in GR-deficient cells. Dex also represses activation of the promoter induced by cotransfecting cells with a constitutively active mutant of calcineurin. Using a series of deletion constructs, we show that the proximal 95 bp of the IL-4 promoter contain a Dex-sensitive regulatory element. This region contains the P1 sequence, a proximal binding site for NF-AT. A calcium-induced but Dex-inhibited nuclear complex containing NF-AT binds to the P1 element in EMSA. Using immunoprecipitation under nondenaturing conditions, we found that the GRα isoform coprecipitates with NF-ATc in nuclear extracts of calcium ionophore-and Dex-treated cells. Taken together, our results show that GC inhibit IL-4 gene expression by interfering with NF-AT-dependent transactivation of the proximal human IL-4 promoter.
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