Tumor necrosis factor (TNF)-alpha activates c-raf-1 kinase via the p55 TNF receptor engaging neutral sphingomyelinase

EMBO J. 1995 Mar 15;14(6):1156-65.


TNF-alpha mediates proliferation, functional activation and apoptotic death of cells depending upon its concentration and target cell type. The signaling pathways used by TNF-alpha to mount these responses are, at present, not completely understood. We report here that TNF-alpha promotes dose- and time-dependent phosphorylation and activation of the c-raf-1 kinase engaging the type I p55 TNF receptor (TNF-R). c-raf-kinase activation was duplicated by an agonistic monoclonal antibody directed against the p55 TNF-R. Moreover, ectopic expression of the human p55 TNF-R in murine pre-B 70Z/3 cells was sufficient to confer c-raf-1-kinase activation by human TNF-alpha. By inhibiting intracellular activation of acidic sphingomyelinase (SMase) and by using deleted forms of the type I TNF-R it was shown that the neutral, but not the acidic SMase, participated in TNF-alpha-mediated phosphorylation and activation of the c-raf kinase. TNF-alpha-induced transcriptional activation of a heterologous promoter construct harboring the AP-1 binding site was also mediated by the type I p55 TNF-R. In this case the initiation of transcription required the same cytoplasmic domain as that responsible for activation of c-raf-1 kinase and was liberated in the presence of a dominant negative mutant of c-raf-1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Monoclonal
  • Antigens, CD*
  • Cells, Cultured
  • Enzyme Activation
  • Fibroblasts
  • Genes, Reporter
  • Humans
  • Hydrogen-Ion Concentration
  • Mice
  • Monocytes
  • Mutation / physiology
  • Phosphorylation
  • Promoter Regions, Genetic / genetics
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • Proto-Oncogene Proteins / genetics
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins c-raf
  • Receptors, Tumor Necrosis Factor / biosynthesis
  • Receptors, Tumor Necrosis Factor / immunology
  • Receptors, Tumor Necrosis Factor / physiology*
  • Receptors, Tumor Necrosis Factor, Type I
  • Signal Transduction / physiology*
  • Sphingomyelin Phosphodiesterase / metabolism*
  • Transcriptional Activation
  • Transfection
  • Tumor Necrosis Factor-alpha / pharmacology*


  • Antibodies, Monoclonal
  • Antigens, CD
  • Proto-Oncogene Proteins
  • Receptors, Tumor Necrosis Factor
  • Receptors, Tumor Necrosis Factor, Type I
  • Tumor Necrosis Factor-alpha
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-raf
  • Sphingomyelin Phosphodiesterase