Glucocorticoids inhibit calcium- and calcineurin-dependent activation of the human IL-4 promoter.
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 GRalpha 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.
Chen
R
R
Division of Pulmonary Medicine, Johns Hopkins Asthma and Allergy Center, Baltimore, MD 21224, USA.
Burke
T F
TF
Cumberland
J E
JE
Brummet
M
M
Beck
L A
LA
Casolaro
V
V
Georas
S N
SN
D001482:Base Composition; D019703:Calcineurin / Q000378:metabolism / Q000502:physiology*; D065095:Calcineurin Inhibitors; D002118:Calcium / Q000037:antagonists & inhibitors / Q000502:physiology*; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology*; D004789:Enzyme Activation / Q000235:genetics / Q000276:immunology; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D015847:Interleukin-4 / Q000235:genetics* / Q000378:metabolism; D019169:Jurkat Cells; D008213:Lymphocyte Activation / Q000187:drug effects*; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000276:immunology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology; D020218:Response Elements / Q000187:drug effects / Q000276:immunology; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D014162:Transfection
D065095:Calcineurin Inhibitors; D004268:DNA-Binding Proteins; D007166:Immunosuppressive Agents; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D014157:Transcription Factors; D015847:Interleukin-4; D003907:Dexamethasone; D011493:Protein Kinase C; D019703:Calcineurin; D002118:Calcium