title: Oxidative modification sensitizes mitochondrial apoptosis-inducing factor to calpain-mediated processing.
abstract: Although processing of mitochondrial apoptosis-inducing factor (AIF) is essential for its function during apoptosis in most cell types, the detailed mechanisms of AIF cleavage remain elusive. Recent findings indicate that the proteolytic process is Ca(2+)-dependent and that it is mediated by a calpain located in the mitochondrial intermembrane space. We can now report that, in addition to a sustained intracellular Ca(2+) elevation, enhanced formation of reactive oxygen species (ROS) is a prerequisite step for AIF to be cleaved and released from mitochondria in staurosporine-treated cells. These events occurred independent of the redox state of the mitochondria and were not influenced by binding of pyridine nucleotides to AIF. Chelation of cytosolic Ca(2+) by BAPTA/AM suppressed the elevation of both Ca(2+) and ROS, suggesting that the Ca(2+) rise was the most upstream signal required for AIF processing. We could further show that the stimulated ROS production leads to oxidative modification (carbonylation) of AIF, which markedly increases its rate of cleavage by calpain. Accordingly, pretreatment of the cells with antioxidants blocked AIF carbonylation, as well as its subsequent cleavage and release from the mitochondria. Combined, our data provide evidence that ROS-mediated, posttranslational modification of AIF is critical for its cleavage by calpain and thus for AIF-mediated cell death.
authors.affiliation: Institute of Environmental Medicine, Division of Toxicology, Karolinska Institutet, SE-171 77 Stockholm, Sweden.
authors.forename: Erik
authors.initials: E
authors.lastname: Norberg
authors.forename: Vladimir
authors.initials: V
authors.lastname: Gogvadze
authors.forename: Helin
authors.initials: H
authors.lastname: Vakifahmetoglu
authors.forename: Sten
authors.initials: S
authors.lastname: Orrenius
authors.forename: Boris
authors.initials: B
authors.lastname: Zhivotovsky
mesh_terms: D000818:Animals; D051033:Apoptosis Inducing Factor / Q000378:metabolism*; D002154:Calpain / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008930:Mitochondria, Liver / Q000378:metabolism; D010084:Oxidation-Reduction; D011725:Pyridines / Q000378:metabolism; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D012680:Sensitivity and Specificity; D013997:Time Factors; D014407:Tumor Cells, Cultured
chemical_list: D051033:Apoptosis Inducing Factor; D011725:Pyridines; D017382:Reactive Oxygen Species; D002154:Calpain