Lack of a role for Jun kinase and AP-1 in Fas-induced apoptosis.
Cross-linking of Fas (CD95) induces apoptosis, a response that has been reported to depend upon the Ras activation pathway. Since many examples of apoptosis have been reported to involve AP-1 and/or the AP-1-activation pathway. Since many examples of apoptosis have been reported to involve AP-1 and/or the AP-1-activating enzyme Jun kinase (JNK), downstream effectors of Ras or Ras-like small GTP-binding proteins, we evaluated the role of these molecules in Fas-mediated apoptosis. Although cross-linking of Fas on Jurkat T cells did result in JNK activation, increased activity was observed relatively late, being detectable only after 60 min of stimulation. Expression of a dominant negative form of SEK1 that blocked Fas-mediated induction of JNK activity had no effect on Fas-mediated apoptosis. Furthermore, maximally effective concentrations of anti-Fas did not cause JNK activation if apoptosis was blocked by a cysteine protease inhibitor, suggesting that under these conditions, activation of JNK may be secondary to the stress of apoptosis rather than a direct result of Fas engagement. Despite the activation of JNK, there was no induction of AP-1 activity as determined by gel shift assay or induction of an AP-1-responsive reporter. The lack of a requirement for AP-1 induction in Fas-mediated death was further substantiated with Jurkat cells that were stably transfected with a dominant negative cJun, TAM-67. While TAM-67 effectively prevented AP-1-dependent transcription of both the interleukin-2 and cJun genes, it had no effect on Fas-induced cell death, even at limiting levels of Fas signaling. Thus, induction of JNK activity in Jurkat cells by ligation of Fas at levels sufficient to cause cell death is likely a result, rather than a cause, of the apoptotic response, and AP-1 function is not required for Fas-induced apoptosis.
Lenczowski
J M
JM
Laboratory of Immune Cell Biology, National Institutes of Health, Bethesda, Maryland 20892-1152, USA.
Dominguez
L
L
Eder
A M
AM
King
L B
LB
Zacharchuk
C M
CM
Ashwell
J D
JD
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000502:physiology*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics; D004789:Enzyme Activation; D006801:Humans; D007376:Interleukin-2 / Q000096:biosynthesis; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases; D019169:Jurkat Cells / Q000166:cytology / Q000378:metabolism; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D011494:Protein Kinases / Q000502:physiology; D016755:Proto-Oncogene Proteins c-jun / Q000096:biosynthesis / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics; D019014:fas Receptor / Q000502:physiology*
D000590:Amino Acid Chloromethyl Ketones; D015853:Cysteine Proteinase Inhibitors; D004268:DNA-Binding Proteins; D007376:Interleukin-2; D007476:Ionophores; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D016755:Proto-Oncogene Proteins c-jun; D018808:Transcription Factor AP-1; D014157:Transcription Factors; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D019014:fas Receptor; D015759:Ionomycin; D004247:DNA; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; C482559:MAP2K4 protein, human; D020929:Mitogen-Activated Protein Kinase Kinases; D013755:Tetradecanoylphorbol Acetate