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Dominant cell death induction by extramitochondrially targeted apoptosis-inducing factor
M Loeffler1, E Daugas, S A Susin
1Centre National de la Recherche Scientifique, UMR1599, Institut Gustave Roussy, F-94805 Villejuif, France.
Summary
AIF (apoptosis-inducing factor) translocation from mitochondria induces cell death independently of caspase activity. Targeting AIF outside mitochondria triggers apoptosis, highlighting its role as a potent cell death inducer.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Apoptosis-inducing factor (AIF) is a key protein involved in programmed cell death.
- AIF's localization and function within mitochondria are crucial for its role in apoptosis.
- Understanding AIF's translocation mechanisms is vital for deciphering cell death pathways.
Purpose of the Study:
- To investigate the role of AIF in mitochondrial outer membrane permeabilization and apoptosis.
- To determine the caspase-independent mechanisms underlying AIF-mediated cell death.
- To explore the influence of AIF localization and function on apoptosis induction.
Main Methods:
- Engineering of an AIF-GFP fusion protein for mitochondrial targeting.
- Induction of apoptosis and monitoring of AIF-GFP translocation.
- Microinjection of recombinant AIF and analysis of its effects.
- Overexpression of wild-type and mutant AIF proteins.
- Inhibition of caspases using Z-VAD.fmk.
- Overexpression of Bcl-2 proteins targeted to different cellular compartments.
Main Results:
- AIF-GFP fusion protein correctly localized to the mitochondrial intermembrane space.
- AIF-GFP translocated to the extramitochondrial compartment during apoptosis, along with cytochrome c.
- Microinjection of AIF induced outer mitochondrial membrane permeabilization and release of AIF-GFP and cytochrome c.
- AIF-induced mitochondrial effects and cell death were caspase-independent.
- Overexpression of AIF led to spontaneous translocation, chromatin condensation, and cell death.
- Mitochondrial targeting of Bcl-2, but not ER targeting, inhibited AIF-induced apoptosis.
- Deletion of the mitochondrial localization sequence (MLS) resulted in cytosolic AIF accumulation and potent, Bcl-2- and caspase-independent cell death.
Conclusions:
- Extramitochondrial targeting of AIF is a dominant inducer of cell death.
- AIF-mediated apoptosis can occur independently of caspases and its oxidoreductase function.
- Mitochondrial integrity and localization play critical roles in regulating AIF's apoptotic activity.