CD95-induced JNK activation signals are transmitted by the death-inducing signaling complex (DISC), but not by Daxx.
Here we investigated CD95-mediated JNK activation pathways and their physiological relevance by employing a variety of cell lines with deficiencies in individual signal transmitting proteins. JNK activation was completely dependent on the activation of caspases in type I and type II cells, as revealed by the inhibitory effects of the caspase inhibitors zVAD-fmk or the cowpoxvirus-encoded CrmA protein. Jurkat cells deficient in caspase-8 or expressing a dominant negative (DN) form of FADD were unable to induce JNK in response to CD95 ligation, indicating that these death-inducing signaling complex (DISC) proteins are required for signal transmission. Activation of caspases, JNK and apoptosis occurred with a markedly slower kinetics in cells expressing a DN version of ASK1, revealing an important contribution of ASK1 for these processes. A C-terminally truncated version of Daxx impaired CD95-mediated apoptosis without affecting the JNK signal. DN forms of FADD, MKK4 and MKK7 completely inhibited CD95-mediated JNK activation but remained without impact on cell killing, indicating that JNK activation is not required for the execution process of CD95-mediated cell killing.
Hofmann
T G
TG
Division of Immunohistochemistry, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg, Germany.
Möller
A
A
Hehner
S P
SP
Welsch
D
D
Dröge
W
W
Schmitz
M L
ML
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D017209:Apoptosis; D002352:Carrier Proteins / Q000378:metabolism*; D020169:Caspases / Q000378:metabolism; D056970:Co-Repressor Proteins; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D048031:JNK Mitogen-Activated Protein Kinases; D019169:Jurkat Cells; D048670:MAP Kinase Kinase 4; D048848:MAP Kinase Kinase Kinase 5; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000502:physiology; D018832:Molecular Chaperones; D009687:Nuclear Proteins; D015398:Signal Transduction / Q000502:physiology*; D014407:Tumor Cells, Cultured; D019014:fas Receptor / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D056970:Co-Repressor Proteins; C106985:DAXX protein, human; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D018832:Molecular Chaperones; D009687:Nuclear Proteins; D019014:fas Receptor; D048031:JNK Mitogen-Activated Protein Kinases; D048848:MAP Kinase Kinase Kinase 5; D020930:MAP Kinase Kinase Kinases; C482858:MAP3K5 protein, human; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; D020169:Caspases