Inhibition of tumor necrosis factor-induced p42/p44 mitogen-activated protein kinase activation by sodium salicylate.
Tumor necrosis factor (TNF) activates both p42 and p44 mitogen-activated protein kinases (MAPK) in human FS-4 fibroblasts, cells for which TNF is mitogenic. We now show that TNF activates p42 MAPK in two cell lines whose growth is inhibited by TNF. A mutant TNF that binds only to the p55 TNF receptor (TNFR) produced a similar degree of activation as wild-type TNF in FS-4 fibroblasts, indicating that the p55 TNFR is sufficient to mediate p42/p44 MAPK activation. The upstream intracellular signals that couple the TNFR to MAPK activation are still poorly defined. We now show that neither phorbol ester-sensitive protein kinase C nor Gialpha link TNF to p42/p44 MAPK activation, because pretreatment of FS-4 cells with phorbol ester to down-regulate protein kinase C or pretreatment with pertussis toxin to block Gialpha does not inhibit p42/p44 MAPK activation by TNF. To further analyze MAPK activation in FS-4 cells, we compared p42/p44 MAPK activation by TNF and epidermal growth factor (EGF). While tyrosine phosphorylation of p42/p44 MAPK was detected almost immediately (30 s) after stimulating cells with EGF, TNF-induced tyrosine phosphorylation was detected only after a more prolonged time interval (initially detected at 5 min and peaking at 15-30 min). In addition, the anti-inflammatory drug sodium salicylate, previously demonstrated to inhibit NF- kappaB activation by TNF, blocked the activation of p42/p44 MAPK in response to TNF but not in response to EGF. These findings demonstrate that the TNF and EGF receptors utilize distinct signaling molecules to couple to MAPK activation. Elucidation of the mechanism whereby sodium salicylate blocks TNF-induced p42/p44 MAPK activation may help to clarify TNF-activated signaling pathways.
Schwenger
P
P
Department of Microbiology, Skirball Institute for Biomolecular Medicine, New York, New York 10016, USA.
Skolnik
E Y
EY
Vilcek
J
J
D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D004815:Epidermal Growth Factor / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D037342:Pertussis Toxin; D019000:Phosphotyrosine / Q000378:metabolism; D011493:Protein Kinase C / Q000502:physiology; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D018124:Receptors, Tumor Necrosis Factor / Q000502:physiology; D012980:Sodium Salicylate / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D018124:Receptors, Tumor Necrosis Factor; D014409:Tumor Necrosis Factor-alpha; D010566:Virulence Factors, Bordetella; D019000:Phosphotyrosine; D004815:Epidermal Growth Factor; D037342:Pertussis Toxin; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D012980:Sodium Salicylate