title: Nuclear localization of procaspase-9 and processing by a caspase-3-like activity in mammary epithelial cells.
abstract: Caspases are aspartate-specific proteases that are specifically activated by numerous death stimuli. Caspase activation is thought to play a major role for the execution of apoptosis. Inactive caspase-9 zymogen is known to be localized within the mitochondrial intermembrane space where it is involved in monitoring mitochondrial damage-associated cytochrome c release and subsequent activation of procaspase-3. Here we show that in mammary epithelial cell lines a significant fraction of caspase-9 proform is associated with discrete structures in the nucleus. Stimulation of cells with chemotherapeutic agents leads to the processing of nuclear procaspase-9 and to the accumulation of nuclear and cytoplasmic caspase activity. Using cell-free extracts from caspase-3-deficient MCF-7 cells we show that caspase-8-mediated processing of nuclear procaspase-9 requires caspase-3. In caspase-3-expressing breast cancer cells, cytochrome c-induced processing of nuclear procaspase-9 is blocked by the caspase inhibitors z-VAD and DEVD but not by YVAD. Purified active caspase-3 is sufficient to cleave nuclear caspase-9 zymogen. These results suggest that, in addition to the mitochondrial localization, caspase-9 proform is found within the nucleus and its processing can be regulated by caspase-3.
authors.affiliation: Department for Clinical Research, University of Bern, Switzerland.
authors.forename: P M
authors.initials: PM
authors.lastname: Ritter
authors.forename: A
authors.initials: A
authors.lastname: Marti
authors.forename: C
authors.initials: C
authors.lastname: Blanc
authors.forename: A
authors.initials: A
authors.lastname: Baltzer
authors.forename: S
authors.initials: S
authors.lastname: Krajewski
authors.forename: J C
authors.initials: JC
authors.lastname: Reed
authors.forename: R
authors.initials: R
authors.lastname: Jaggi
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D015153:Blotting, Western; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases / Q000276:immunology / Q000378:metabolism*; D002458:Cell Fractionation; D002460:Cell Line; D002467:Cell Nucleus / Q000201:enzymology / Q000378:metabolism; D002945:Cisplatin / Q000494:pharmacology; D003574:Cytochrome c Group / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004792:Enzyme Precursors / Q000276:immunology / Q000378:metabolism*; D004847:Epithelial Cells / Q000187:drug effects / Q000201:enzymology; D005260:Female; D007150:Immunohistochemistry; D007527:Isoenzymes; D008321:Mammary Glands, Animal / Q000166:cytology / Q000201:enzymology*; D051379:Mice; D018613:Microscopy, Confocal; D008928:Mitochondria / Q000201:enzymology; D011499:Protein Processing, Post-Translational / Q000187:drug effects
chemical_list: D003574:Cytochrome c Group; D004791:Enzyme Inhibitors; D004792:Enzyme Precursors; D007527:Isoenzymes; D004247:DNA; C505409:Casp3 protein, mouse; C506434:Casp9 protein, mouse; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases; D002945:Cisplatin