Nuclear localization of procaspase-9 and processing by a caspase-3-like activity in mammary epithelial cells

• Published in: European journal of cell biology 2000-05, Vol.79 (5), p.358-364
• Main Authors: Ritter, Philipp M., Marti, Andreas, Blanc, Céline, Baltzer, Anna, Krajewski, Stanislaw, Reed, John C., Jaggi, Rolf
• Format: Article
• Language: English
• Subjects: Animals; Apoptosis; Apoptosis - drug effects; Apoptosis - physiology; Blotting, Western; Caspase 3; Caspase 9; caspases; Caspases - immunology; Caspases - metabolism; Cell Fractionation; Cell Line; Cell Nucleus - enzymology; Cell Nucleus - metabolism; Cisplatin - pharmacology; Cytochrome c Group - metabolism; DNA - metabolism; Enzyme Activation; Enzyme Inhibitors - pharmacology; Enzyme Precursors - immunology; Enzyme Precursors - metabolism; Epithelial Cells - drug effects; Epithelial Cells - enzymology; Female; Immunohistochemistry; Isoenzymes; mammary epithelial cells; Mammary Glands, Animal - cytology; Mammary Glands, Animal - enzymology; Mice; Microscopy, Confocal; mitochondria; Mitochondria - enzymology; Protein Processing, Post-Translational - drug effects
• ISSN: 0171-9335; 1618-1298
• DOI: 10.1078/S0171-9335(04)70040-0

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.