Related Experiment Videos
The recruitment of Fas-associated death domain/caspase-8 in Ras-induced apoptosis
1Cancer Research Center, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts 02118, USA. yanyan@bu.edu
Abstract:
Oncogenic Ras induces cells to undergo apoptosis after inhibition of protein kinase C (PKC) activity. The integration of differential signaling pathways is required for full execution of apoptosis. In this study, we used Jurkat as well as Fas/FADD-defective cell lines expressing v-ras to determine the upstream elements required for activation of the caspase cascade in PKC/Ras-mediated apoptosis. During this Ras-induced apoptotic process, caspase-8 was activated, possibly through its binding to Fas-associated death domain (FADD), in Jurkat/ras and Jurkat/Fas(m)/ras cells but not in Jurkat/FADD(m)/ras cells. c-Jun NH(2)-terminal kinase (JNK) was activated in all three cell lines expressing ras in response to apoptotic stimulation. Suppression of JNK by dn-JNK1 blocked the interaction of FADD and caspase-8 and partially protected Jurkat/ras and Jurkat/Fas(m)/ras cells from apoptosis. However, dn-JNK1 had no effect on PKC/Ras-induced apoptosis in Jurkat/FADD(m)/ras cells. The results indicate that FADD/caspase-8 signaling is involved in PKC/Ras-mediated apoptosis, and JNK may be an upstream effector of caspase activation.
Insights
Oncogenic Ras triggers apoptosis by inhibiting protein kinase C (PKC). Fas-associated death domain (FADD) and caspase-8 are crucial for this process, with c-Jun NH2-terminal kinase (JNK) acting as an upstream effector.
Area of Science:
- Cellular biology
- Molecular oncology
- Signal transduction
Background:
- Oncogenic Ras signaling is implicated in cellular apoptosis.
- Protein Kinase C (PKC) activity inhibition is a trigger for Ras-induced apoptosis.
- Understanding the upstream signaling pathways is critical for elucidating apoptosis execution.
Purpose of the Study:
- To investigate the upstream elements responsible for caspase cascade activation in PKC/Ras-mediated apoptosis.
- To determine the roles of Fas-associated death domain (FADD) and c-Jun NH2-terminal kinase (JNK) in this apoptotic pathway.
Main Methods:
- Utilized Jurkat and Fas/FADD-defective cell lines engineered to express v-ras.
- Assessed caspase-8 activation through FADD binding in response to Ras expression.
- Investigated the effect of c-Jun NH2-terminal kinase (JNK) suppression using dn-JNK1 on apoptosis and FADD-caspase-8 interaction.
Main Results:
- Caspase-8 activation, potentially via FADD, was observed in Jurkat/ras and Jurkat/Fas(m)/ras cells, but not in Jurkat/FADD(m)/ras cells.
- JNK was activated in all ras-expressing cell lines.
- dn-JNK1 inhibited FADD-caspase-8 interaction and partially protected cells, but did not affect apoptosis in FADD-defective cells.
Conclusions:
- FADD/caspase-8 signaling pathway is integral to PKC/Ras-mediated apoptosis.
- JNK activation appears to be an upstream event that facilitates caspase activation in this context.
- These findings highlight JNK as a potential therapeutic target in Ras-driven cancers.