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Intracellular mediators of programmed cell death initiated at the cell surface receptor Fas
1Department of Experimental Medicine and Biochemical Sciences, University of Rome Tor Vergata, Italy.
Abstract:
Apoptosis is a programmed cell death process, which plays a pivotal role in development, in tissue homeostasis and in several human diseases. Fas (CD95/Apo-1) is a member of the "death receptors" family, a group of cell surface proteins that trigger apoptosis upon binding with their natural ligands. In the immune system, intracellular signal transduction triggered from Fas splits into two different pathways. The proteolytic pathway is mediated by a family of cysteine proteases, the caspases, responsible for the morphological changes occurring in the apoptotic process. To complete this death program, another series of events, involving a lipid pathway, is necessary. Upon Fas stimulation, a sequential activation of specific enzymes results in the accumulation of ceramides and GD3 ganglioside. GD3 directly induces mitochondrial damage and triggers the release of apoptogenic factors, allowing efficient execution of Fas-mediated apoptosis.
Insights
Programmed cell death, or apoptosis, is crucial for development and health. Fas receptor signaling activates caspase and lipid pathways, involving ceramides and GD3, to effectively execute apoptosis.
Area of Science:
- Cell Biology
- Molecular Biology
- Immunology
Background:
- Apoptosis is a vital programmed cell death process in development, homeostasis, and disease.
- Fas (CD95/Apo-1) is a death receptor that initiates apoptosis upon ligand binding.
- Fas signaling in the immune system branches into distinct proteolytic and lipid pathways.
Purpose of the Study:
- To elucidate the molecular mechanisms underlying Fas-mediated apoptosis.
- To investigate the roles of caspases and lipid mediators in Fas signaling.
- To understand how GD3 ganglioside contributes to mitochondrial damage and apoptosis execution.
Main Methods:
- Analysis of intracellular signal transduction pathways triggered by Fas stimulation.
- Investigation of enzyme activation sequences leading to ceramide and GD3 accumulation.
- Assessment of GD3's role in mitochondrial dysfunction and apoptogenic factor release.
Main Results:
- Fas stimulation activates both caspase-dependent proteolytic and lipid-dependent pathways.
- Sequential enzyme activation leads to increased ceramide and GD3 levels.
- GD3 directly causes mitochondrial damage, releasing factors that promote apoptosis.
Conclusions:
- Fas-mediated apoptosis involves a coordinated interplay between proteolytic and lipid signaling pathways.
- Ceramide and GD3 accumulation are critical events in the execution phase of Fas-induced cell death.
- GD3's direct action on mitochondria is essential for efficient Fas-mediated apoptosis.