Glucocorticoid receptor-mediated suppression of the interleukin 2 gene expression through impairment of the cooperativity between nuclear factor of activated T cells and AP-1 enhancer elements.

Abstract

SummaryThe immunosuppressant hormone dexamethasone (Dex) interferes with T cell-specific signals activating the enhancer sequences directing interleukin 2 (IL-2) transcription. We report that the Dex-dependent downregulation of 12-O-tetradecanoyl-phorbo1-13-acetate (TPA) and calcium ionophore-induced activity of the I1,2 enhancer are mediated by glucocorticoid receptor (GR) via a process that requires intact NH2-and COOH-terminal and DNA-binding domains. Functional analysis of chloramphenicol acetyltransferase (CAT) vectors containing internal ddetions of the -317 to + 47 bp I1,2 enhancer showed that the GR-responsive elements mapped to regions containing nuclear factor of activated T cells protein (NFAT) (-279 to -263 bp) and AP-1 (-160 to -150 bp) motifs. The AP-1 motif binds TPA and calcium ionophore-induced nuclear factor(s) containing los protein. TPA and calcium ionophore-induced transcriptional activation of homooligomers of the NFAT dement were not inhibited by Dex, while AP-1 motif concatemers were not stimulated by TPA and calcium ionophore. When combined, NFAT and AP-1 motifs significantly synergized in directing CAT transcription. Such a synergism was impaired by specific mutations affecting the tram-acting factor binding to either NFAT or AP-1 motifs. In spite of the lack of hormone regulation of isolated c/s dements, TPA/calcium ionophore-mediated activation of CAT vectors containing a combination of the NFAT and the AP-1 motifs became suppressible by Dex. Our results show that the IL-2-AP-1 motif confers GR sensitivity to a flanking region containing a NFAT dement and suggest that synergistic cooperativity between the NFAT and AP-1 sites allows GR to mediate the Dex inhibition of I1`2 gene transcription. Therefore, a Dex-modulated second level of II:2 enhancer regulation, based on a combinatorial modular interplay, appears to be present.

Glucocorticoid Receptor Down–Regulates C–Jun Amino Terminal Kinases Induced by Tumor Necrosis Factor α in Fetal Rat Hepatocyte Primary Cultures

“…40,42,43 Phosphorylated JUN as homodimer, or heterodimer with FOS, has potent AP-1 activity, regulating the expression of a number of genes, including c-jun itself 44 and cytokines. 45 We show here that incubation of the hepatocytes in the presence of both EGF and TNF-␣ clearly produced an activation of JNK, which was higher than that observed by each one of those factors acting independently (Fig. 3).…”

Suppression of Granulocyte-Macrophage Colony-Stimulating Factor Expression by Glucocorticoids Involves Inhibition of Enhancer Function by the Glucocorticoid Receptor Binding to Composite NF-AT/Activator Protein-1 Elements

“…Regulation of the IL-2 gene occurs through a cooperative mechanism involving NF-AT and AP-1 interaction at the promoter. Inhibition by glucocorticoids involves disruption of this cooperativity (69) through the GR binding to AP-1 that disrupts binding to NF-AT (70). NF-AT and AP-1 can bind to the CLE0 element in the GM-CSF promoter (15).…”

Characterization of type 1 and type 2 cytokine production profile in physiologic and pathologic human pregnancy

“…The role of steroid hormones in inducing secretion of different cytokines by Th lymphocytes is currently under examination. It has been reported that cortisol and pharmacological doses of glucocorticoids (GC) reduce the production of IL-1, which acts as a costimulator on T cell activation [34], and of the type 1 cytokines IL-2 and IFN- [35,36], impairing antigen-and mitogen-induced T lymphocyte proliferation [37]. Additionally, GC favour the production of type 2 cytokines by inhibiting the transcription of IL-2 and IFN-genes and by favouring the production of IL-4, thus stimulating Th2 cells, and suppressing Th1 cells [38,39].…”