Ceramide-induced cell death is independent of the Fas/Fas ligand pathway and is prevented by Nur77 overexpression in A20 B cells

Cell Death Differ. 2000 Mar;7(3):262-71. doi: 10.1038/sj.cdd.4400653.

Abstract

The role of ceramide in triggering apoptosis is still a matter of debate. While in some experimental systems, ceramide was shown to mediate Fas-induced cell death, in other instances it was claimed to induce the expression of Fas ligand (FasL), killing cells in a caspase-dependent fashion. We found that, in mature A20 B cells, ceramide-induced apoptosis is independent of the caspase pathway, since we observed no ICE-like, CPP32-like and Mch2 activities and no PARP proteolysis. Moreover, we were unable to protect these cells from ceramide-induced apoptosis using caspase inhibitors, while they blocked Fas-induced apoptosis and no FasL induction could be detected following ceramide treatment. These results suggest that ceramide does not induce apoptosis through the Fas/FasL pathway. We also found that overexpression of Nur77, a zinc-finger transcription factor described to upregulate FasL, antagonizes ceramide-induced apoptosis, but not Fas-induced apoptosis. This further supports the hypothesis that Fas and ceramide death pathways are independent in A20 cells. Ceramide-induced cell death was associated with increased c-myc, p53, Bax and p27kip1 levels; in contrast, cells transfected with Nur77 (A20Nur77), resistant to ceramide-induced apoptosis, showed a marked downregulation of p53 after ceramide treatment, with neither Bax nor p27kip1 induction. In conclusion, our results suggest that, in the A20 B cell line, Fas and ceramide trigger two distinct pathways and that Nur77 overexpression confers protection against ceramide-mediated apoptosis which correlates with inhibition of p53, Bax and p27kip1 induction.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / drug effects*
  • B-Lymphocytes / drug effects
  • B-Lymphocytes / metabolism
  • Caspase 1 / metabolism
  • Caspase 3
  • Caspases / metabolism
  • Cell Cycle Proteins*
  • Ceramides / pharmacology*
  • Cyclin A / metabolism
  • Cyclin E / metabolism
  • Cyclin-Dependent Kinase Inhibitor p27
  • Cysteine Endopeptidases / metabolism
  • DNA-Binding Proteins / biosynthesis
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / physiology*
  • Enzyme Activation
  • Fas Ligand Protein
  • Gene Expression
  • Membrane Glycoproteins / metabolism*
  • Mice
  • Microtubule-Associated Proteins / metabolism
  • Nuclear Receptor Subfamily 4, Group A, Member 1
  • Proto-Oncogene Proteins c-myc / metabolism
  • Receptors, Cytoplasmic and Nuclear
  • Receptors, Steroid
  • Retinoblastoma Protein / metabolism
  • Sphingosine / analogs & derivatives*
  • Sphingosine / antagonists & inhibitors
  • Sphingosine / pharmacology
  • Transcription Factors / biosynthesis
  • Transcription Factors / genetics
  • Transcription Factors / physiology*
  • Tumor Cells, Cultured
  • Tumor Suppressor Protein p53 / metabolism
  • Tumor Suppressor Proteins*
  • fas Receptor / metabolism*

Substances

  • Cdkn1b protein, mouse
  • Cell Cycle Proteins
  • Ceramides
  • Cyclin A
  • Cyclin E
  • DNA-Binding Proteins
  • Fas Ligand Protein
  • Fasl protein, mouse
  • Membrane Glycoproteins
  • Microtubule-Associated Proteins
  • N-acetylsphingosine
  • Nr4a1 protein, mouse
  • Nuclear Receptor Subfamily 4, Group A, Member 1
  • Proto-Oncogene Proteins c-myc
  • Receptors, Cytoplasmic and Nuclear
  • Receptors, Steroid
  • Retinoblastoma Protein
  • Transcription Factors
  • Tumor Suppressor Protein p53
  • Tumor Suppressor Proteins
  • dihydroceramide
  • fas Receptor
  • Cyclin-Dependent Kinase Inhibitor p27
  • Casp3 protein, mouse
  • Caspase 3
  • Caspases
  • Cysteine Endopeptidases
  • Caspase 1
  • Sphingosine