Glucocorticoid receptor down-regulates c-Jun amino terminal kinases induced by tumor necrosis factor alpha in fetal rat hepatocyte primary cultures.
The effect of dexamethasone on Jun N-terminal kinase (JNK) activity was assayed by using fetal hepatocytes in primary culture. The addition of tumor necrosis factor alpha (TNF-alpha) caused an increase in JNK in a dose- and time-dependent manner. We show that activation of JNK by this extracellular signal is inhibited by dexamethasone in a dose-dependent fashion. This inhibitory effect was observed in cells treated for 10 minutes with dexamethasone in the presence of protein phosphatase inhibitors such as orthovanadate or okadaic acid, or in cells previously treated with actinomycin D. Glucocorticoid receptor (GR) can be precipitated with the fusion protein, GST-c-Jun (1-79), bound to agarose beads. However, the inhibitory effect of glucocorticoids on JNK activity was also observed using ATF-2 as substrate. In addition, dexamethasone inhibits JNK phosphorylation induced by TNF-alpha. Finally, we show that GR can also be phosphorylated in tyrosine residues in response to TNF-alpha and epidermal growth factor (EGF) upon ligand-binding. Our results suggest that the anti-inflammatory effect of glucocorticoids on the inflammatory pathways induced by TNF-alpha can be explained, at least in part, by modulating JNK activity through a direct protein-protein interaction; the JNK phosphorylation and tyrosine-phosphorylation state of GR may be regulatory steps also involved in that effect.
Departamento de Bioquímica y Biología Molecular, Centro Mixto C.S. I.C./U.C.M., Facultad de Farmacia, Universidad Complutense de Madrid, Madrid, Spain.
J J
JJ
Ventura
C
C
Roncero
I
I
Fabregat
M
M
Benito
D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology; D015536:Down-Regulation / Q000502:physiology; D004789:Enzyme Activation / Q000187:drug effects; D004790:Enzyme Induction / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005333:Fetus / Q000166:cytology / Q000378:metabolism*; D005938:Glucocorticoids / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases; D008099:Liver / Q000187:drug effects / Q000196:embryology*; D020928:Mitogen-Activated Protein Kinases; D019319:Okadaic Acid / Q000494:pharmacology; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats / Q000196:embryology; D017208:Rats, Wistar; D011965:Receptors, Glucocorticoid / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D004791:Enzyme Inhibitors; D005938:Glucocorticoids; D016755:Proto-Oncogene Proteins c-jun; D012333:RNA, Messenger; D011965:Receptors, Glucocorticoid; D014409:Tumor Necrosis Factor-alpha; D019319:Okadaic Acid; D003907:Dexamethasone; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D010744:Phosphoric Monoester Hydrolases