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Mitogen-activated protein kinase kinase antagonized fas-associated death domain protein-mediated apoptosis by induced
1Graduate Institute of Microbiology and Immunology, National Yang-Ming University, Taipei 11217, Taiwan.
Abstract:
Fas and Fas-associated death domain (FADD) play a critical role in the homeostasis of different cell types. The regulation of Fas and FADD-mediated cell death is pivotal to many physiological functions. The activation of T lymphocytes by concanavalin A (Con A) inhibited Fas-mediated cell death. We identified that among the several activation signals downstream of Con A stimulation, mitogen-activated protein (MAP) kinase kinase (MKK) was the major kinase pathway that antagonized Fas-triggered cell death. MKK1 suppressed FADD- but not caspase-3- induced apoptosis, indicating that antagonism occurred early along the Fas-initiated apoptotic cascade. We further demonstrated that activation of MKK1 led to expression of FLIP, a specific inhibitor of FADD. MKK1 inhibition of FADD-induced cell death was abrogated if induction of FLIP was prevented, indicating that FLIP mediates MKK1 suppression of FADD-mediated apoptosis. Our results illustrate a general mechanism by which activation of MAP kinase attenuates apoptotic signals initiated by death receptors in normal and transformed cells.
Insights
Mitogen-activated protein kinase kinase (MKK) activation inhibits Fas-mediated cell death by upregulating FLIP, a Fas-associated death domain (FADD) inhibitor. This pathway regulates apoptosis in various cell types.
Area of Science:
- Cellular Biology
- Immunology
- Molecular Biology
Background:
- Fas and FADD are crucial for cell homeostasis and regulating cell death.
- Fas-mediated apoptosis is vital for numerous physiological processes.
- T lymphocyte activation by Concanavalin A (Con A) suppresses Fas-mediated cell death.
Purpose of the Study:
- To elucidate the molecular mechanisms by which Con A activation inhibits Fas-mediated apoptosis.
- To identify the specific signaling pathways involved in antagonizing Fas-triggered cell death.
- To understand the role of mitogen-activated protein (MAP) kinase kinase (MKK) in this process.
Main Methods:
- T lymphocyte activation using Concanavalin A (Con A).
- Analysis of downstream signaling pathways, focusing on MAP kinase kinase (MKK).
- Investigation of apoptosis markers, including FADD and caspase-3, and the expression of FLIP.
Main Results:
- MKK activation was identified as the primary pathway antagonizing Fas-triggered cell death following Con A stimulation.
- MKK1 specifically suppressed FADD-induced apoptosis, indicating early antagonism in the apoptotic cascade.
- MKK1 activation led to increased expression of FLIP, a known inhibitor of FADD.
- Inhibition of FLIP induction abrogated MKK1's effect, confirming FLIP's role in mediating the suppression of FADD-induced cell death.
Conclusions:
- MAP kinase activation provides a general mechanism to attenuate death receptor-initiated apoptotic signals.
- FLIP acts as a key mediator through which MKK1 suppresses FADD-dependent apoptosis.
- This finding sheds light on the regulation of apoptosis in both normal and transformed cells.