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Molecular characterization of mitochondrial apoptosis-inducing factor
S A Susin1, H K Lorenzo, N Zamzami
1Centre National de la Recherche Scientifique, UPR 420, Villejuif, France.
Nature
|February 16, 1999
Summary
Mitochondria contain a novel apoptosis-inducing factor (AIF) that triggers cell death. This protein translocates to the nucleus, causing DNA fragmentation and chromatin condensation, independent of caspases.
Area of Science:
- Cell Biology
- Biochemistry
- Molecular Biology
Background:
- Mitochondria are central regulators of apoptosis.
- Key apoptosis-regulating proteins reside in the mitochondrial intermembrane space.
- These proteins are released to initiate the cell death cascade.
Purpose of the Study:
- To identify and characterize a novel apoptosis-inducing factor (AIF) from mitochondria.
- To elucidate the mechanism by which AIF induces apoptosis.
- To determine AIF's role as a mitochondrial effector in cell death.
Main Methods:
- Identification and cloning of the AIF gene.
- Expression of recombinant AIF.
- In vitro assays using isolated nuclei and mitochondria.
- Microinjection of AIF into intact cells.
- Assessment of caspase-dependent and independent pathways.
Main Results:
- AIF is a 57,000 MW flavoprotein, homologous to bacterial oxidoreductases.
- Recombinant AIF induces chromatin condensation and DNA fragmentation in isolated nuclei.
- AIF triggers the release of cytochrome c and caspase-9 from purified mitochondria.
- AIF induces apoptosis-like changes in intact cells, independent of caspase activity.
- Bcl-2 overexpression inhibits AIF release but not its apoptotic activity.
Conclusions:
- AIF is a novel mitochondrial protein that directly induces apoptosis.
- AIF acts as a mitochondrial effector, translocating to the nucleus to trigger cell death.
- AIF-mediated apoptosis is independent of the caspase pathway.