Tumor necrosis factor increases stability of interleukin-1 mRNA by activating protein kinase C.
The mRNAs coding for interleukin-1 alpha (IL-1 alpha) and IL-1 beta are constitutively transcribed but do not accumulate in human diploid fibroblasts and in fibrosarcoma cells. Treatment of these cells with tumor necrosis factor (TNF) induces accumulation of IL-1 mRNA by an unknown mechanism. This induction of IL-1 mRNA was investigated in HT-1080 cells. The induction was quite fast, with maximum levels of IL-1 alpha and beta mRNA reached 4 h after addition of TNF. Nuclear run-off experiment showed that TNF did not increase the rate of transcription of IL-1 mRNA. This mRNA was apparently unstable in untreated cells, but it accumulated in cycloheximide-treated cells. Phorbol esters induced IL-1 mRNA, suggesting that activation of protein kinase C was responsible for the accumulation of this mRNA. This hypothesis was confirmed by experiments with the PKC inhibitors staurosporine and calphostin C, which prevented the induction of IL-1 mRNA by TNF and accelerated the decay of this mRNA in cells pretreated with TNF. Both IL-1 alpha and IL-1 beta were detected in TNF-treated cells by Western blot analysis and enzyme-linked immunosorbent assay. These results indicate that the TNF-mediated induction of IL-1 can be entirely accounted for by stabilization of this mRNA.
Gorospe
M
M
Department of Biological Sciences, State University of New York, Albany 12222.
Kumar
S
S
Baglioni
C
C
D000470:Alkaloids / Q000494:pharmacology; D015153:Blotting, Western; D003513:Cycloheximide / Q000494:pharmacology; D004789:Enzyme Activation; D006801:Humans; D007375:Interleukin-1 / Q000235:genetics* / Q000378:metabolism; D007700:Kinetics; D009281:Naphthalenes; D011083:Polycyclic Compounds / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D000470:Alkaloids; D007375:Interleukin-1; D009281:Naphthalenes; D011083:Polycyclic Compounds; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D003513:Cycloheximide; D011493:Protein Kinase C; D019311:Staurosporine; C058819:calphostin C; D013755:Tetradecanoylphorbol Acetate