Glucocorticoids antagonize AP-1 by inhibiting the Activation/phosphorylation of JNK without affecting its subcellular distribution.
The immunosuppressive and antiinflammatory actions of glucocorticoid hormones are mediated by their transrepression of activating protein-1 (AP-1) and nuclear factor-kappa B (NFkappaB) transcription factors. Inhibition of the c-Jun NH(2)-terminal kinase (JNK) signaling pathway, the main mediator of AP-1 activation, has been described in extracts of hormone-treated cells. Here, we show by confocal laser microscopy, enzymatic assays, and immunoblotting that the synthetic glucocorticoid dexamethasone inhibited tumor necrosis factor alpha (TNF-alpha)-induced phosphorylation and activation of JNK in the cytoplasm and nucleus of intact HeLa cells. As a result, c-Jun NH(2)-terminal domain phosphorylation and induction were impaired. Dexamethasone did not block the TNF-alpha-induced JNK nuclear translocation, but rather induced, per se, nuclear accumulation of the enzyme. Consistently with previous findings, a glucocorticoid receptor mutant (GRdim), which is deficient in dimerization, DNA binding, and transactivation, but retains AP-1 transrepressing activity, was as efficient as wild-type GR in mediating the same effects of dexamethasone on JNK in transfected Cos-7 cells. Our results show that glucocorticoids antagonize the TNF-alpha-induced activation of AP-1 by causing the accumulation of inactive JNK without affecting its subcellular distribution.
González
M V
MV
Instituto de Investigaciones Biomédicas Alberto Sols, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, E-28029 Madrid, Spain.
Jiménez
B
B
Berciano
M T
MT
González-Sancho
J M
JM
Caelles
C
C
Lafarga
M
M
Muñoz
A
A
D000818:Animals; D019556:COS Cells; D002458:Cell Fractionation; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism*; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology*; D004789:Enzyme Activation; D005938:Glucocorticoids / Q000494:pharmacology*; D006367:HeLa Cells; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D007700:Kinetics; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D018808:Transcription Factor AP-1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D005938:Glucocorticoids; D011994:Recombinant Proteins; D018808:Transcription Factor AP-1; D014409:Tumor Necrosis Factor-alpha; D003907:Dexamethasone; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases