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JNK/SAPK activity is not sufficient for anticancer therapy-induced apoptosis involving CD95-L, TRAIL and TNF-alpha
1Division of Molecular Oncology, Deutsches Krebsforschungszentrum, Heidelberg, Germany.
Abstract:
We report here that stress stimuli such as gamma-irradiation or the anticancer drug doxorubicin activate expression of the death-inducing ligands (DILs) CD95-L, TNF-alpha and TRAIL. Apoptosis induced by gamma-irradiation or doxorubicin engages a FADD- and caspase-dependent apoptosis pathway which is inhibited by dominant negative FADD or the caspase inhibitor zVAD. zVAD did not prevent activity of JNK/SAPKs in response to doxorubicin suggesting that JNK/SAPK activity is independent of death receptor triggering during cellular stress-induced apoptosis. In addition, JNK/SAPKs remained activated by doxorubicin in resistant cell lines in which cleavage of caspases and apoptosis was not observed. These data uncouple JNK/SAPK activation and apoptosis signaling and indicate that cellular stress-induced apoptosis involves signaling via DILs which is paralleled by activation of JNK/SAPKs. Activation of these kinases may contribute e.g., to the expression of molecules involved in apoptosis but is not sufficient for induction of the apoptosis program following cellular stress.
Insights
Cellular stress, like gamma-irradiation or doxorubicin, triggers apoptosis via death-inducing ligands (DILs) and caspase pathways. JNK/SAPK activation occurs independently and does not solely induce apoptosis.
Area of Science:
- Cellular stress response
- Apoptosis signaling pathways
- Molecular biology
Background:
- Cellular stress stimuli, including gamma-irradiation and doxorubicin, are known to induce cell death.
- The precise molecular mechanisms linking stress stimuli to apoptosis, particularly the roles of death-inducing ligands (DILs) and kinase signaling, require further elucidation.
Purpose of the Study:
- To investigate the activation of DILs (CD95-L, TNF-alpha, TRAIL) by cellular stress.
- To delineate the involvement of FADD- and caspase-dependent pathways in stress-induced apoptosis.
- To examine the relationship between JNK/SAPK activation and apoptosis signaling under cellular stress.
Main Methods:
- Treatment of cells with gamma-irradiation and doxorubicin.
- Analysis of death-inducing ligand expression.
- Assessment of apoptosis using FADD and caspase inhibitors (dominant negative FADD, zVAD).
- Monitoring of JNK/SAPK activity in response to doxorubicin.
Main Results:
- Gamma-irradiation and doxorubicin activate expression of CD95-L, TNF-alpha, and TRAIL.
- Stress-induced apoptosis is mediated by a FADD- and caspase-dependent pathway.
- JNK/SAPK activation by doxorubicin is independent of death receptor triggering and occurs even in resistant cell lines.
- JNK/SAPK activation is uncoupled from caspase activation and apoptosis induction.
Conclusions:
- Cellular stress-induced apoptosis involves signaling via DILs, paralleled by JNK/SAPK activation.
- JNK/SAPK activation may contribute to apoptosis-related gene expression but is insufficient for inducing the apoptosis program.
- Stress-induced apoptosis relies on a distinct FADD- and caspase-dependent pathway separate from JNK/SAPK activation.