Molecular characterization of mitochondrial apoptosis-inducing factor

Abstract

Mitochondria play a key part in the regulation of apoptosis (cell death). Their intermembrane space contains several proteins that are liberated through the outer membrane in order to participate in the degradation phase of apoptosis. Here we report the identification and cloning of an apoptosis-inducing factor, AIF, which is sufficient to induce apoptosis of isolated nuclei. AIF is a flavoprotein of relative molecular mass 57,000 which shares homology with the bacterial oxidoreductases; it is normally confined to mitochondria but translocates to the nucleus when apoptosis is induced. Recombinant AIF causes chromatin condensation in isolated nuclei and large-scale fragmentation of DNA. It induces purified mitochondria to release the apoptogenic proteins cytochrome c and caspase-9. Microinjection of AIF into the cytoplasm of intact cells induces condensation of chromatin, dissipation of the mitochondrial transmembrane potential, and exposure of phosphatidylserine in the plasma membrane. None of these effects is prevented by the wide-ranging caspase inhibitor known as Z-VAD.fmk. Overexpression of Bcl-2, which controls the opening of mitochondrial permeability transition pores, prevents the release of AIF from the mitochondrion but does not affect its apoptogenic activity. These results indicate that AIF is a mitochondrial effector of apoptotic cell death.

Physical interaction of apoptosis-inducing factor with DNA and RNA

“…Moreover, AIF is imported into the nucleus by virtue of its nuclear localization sequences (Susin et al, 1999). So, it is not clear whether the interaction of AIF with RNA actually contributes to the apoptotic process (for instance by inhibiting translation) or whether this interaction rather retards the lethal interaction of AIF with DNA, for instance in cells that are particularly active in protein synthesis and hence abundant in RNA.…”

“…So, it is not clear whether the interaction of AIF with RNA actually contributes to the apoptotic process (for instance by inhibiting translation) or whether this interaction rather retards the lethal interaction of AIF with DNA, for instance in cells that are particularly active in protein synthesis and hence abundant in RNA. While the biological significance of the AIF-RNA interaction remains a conundrum, AIF binding to DNA has been amply documented in apoptotic cells (Susin et al, 1999Daugas et al, 2000;Cande et al, 2002Cande et al, , 2004aZhu et al, 2003), and it appears clear that AIF can mediate chromatin condensation. Thus, recombinant AIF induces marked pyknosis when added to isolated nuclei or when microinjected into intact cells Loeffler et al, 2001).…”

“…Apoptosis-inducing factor (AIF) was discovered as a mitochondrial protein endowed with the capacity of inducing chromatin condensation in isolated nuclei (Susin et al, 1999). It is now considered to be one of the principal caspase-independent death effectors Cande et al, 2002;Cregan et al, 2004;Cheung et al, 2005;Kroemer and Martin, 2005), although its biology is surprisingly complex.…”

Retinoid-related molecules require caspase 9 for the effective release of Smac and the rapid induction of apoptosis

“…3 Mitochondrial membrane potential is rapidly lost and there is a massive release of proapoptotic factors into the cytosol, including cytochrome c, apoptosis-inducing factor, second mitochondria-derived activator of caspase (Smac)/ Diablo, endonuclease G, and the serine protease Omi/HtrA. [4][5][6][7][8] Released cytochrome c, along with Apaf-1 and procaspase 9, forms the apoptosome, 9,10 causing the proteolytic autoactivation of caspase 9, which in turn cleaves and activates effector caspases 3 and 7. [11][12][13][14] Smac release is necessary for the effective activation of caspases through interactions with inhibitor of apoptosis proteins (IAPs).…”

Dissociation of DNA damage and mitochondrial injury caused by hydrogen peroxide in SV-40 transformed lung epithelial cells

“…In certain situations, death stimuli induce an increase in the permeability of the outer mitochondrial membrane that releases apoptosis inducers, such as cytochrome c [39] and apoptosis-inducing factor (AIF) [40]. In our study, the ΔΨm was quantified by the flow cytometric analysis of JC-1-stained cells.…”