Caspase-3 activation by lysosomal enzymes in cytochrome c-independent apoptosis in myelodysplastic syndrome-derived cell line P39

In most cases, apoptosis is considered to involve mitochondrial dysfunction with sequential release of cytochrome c from mitochondria, resulting in activation of caspase-3. However, we found that etoposide induced apoptosis in P39 cells, a myelodysplastic syndrome-derived cell line, without the rele...

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Published in:Cancer research (Chicago, Ill.) Ill.), 2001-04, Vol.61 (7), p.2878-2884
Main Authors: HISHITA, Terutoshi, TADA-OIKAWA, Saeko, TOHYAMA, Kaoru, MIURA, Yasuo, NISHIHARA, Toshio, TOHYAMA, Yumi, YOSHIDA, Yataro, UCHIYAMA, Takashi, KAWANISHI, Shosuke
Format: Article
Language:English
Subjects:
Anti-Bacterial Agents - pharmacology
Antineoplastic agents
Apoptosis - drug effects
Apoptosis - physiology
Biological and medical sciences
Caspase 3
Caspase Inhibitors
Caspases - metabolism
Cathepsin L
Cathepsins - biosynthesis
Cell Line
Chemotherapy
Cysteine Endopeptidases
Cysteine Proteinase Inhibitors - pharmacology
Cytochrome c Group - physiology
Endopeptidases
Enzyme Activation
Enzyme Inhibitors - pharmacology
Etoposide - pharmacology
Humans
Hydrogen-Ion Concentration
Intracellular Membranes - physiology
Leucine - analogs & derivatives
Leucine - pharmacology
Lysosomes - enzymology
Macrolides
Medical sciences
Membrane Potentials - physiology
Mitochondria - physiology
Myelodysplastic Syndromes - enzymology
Myelodysplastic Syndromes - pathology
Pharmacology. Drug treatments
Proton-Translocating ATPases - antagonists & inhibitors
Vacuolar Proton-Translocating ATPases
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Summary:In most cases, apoptosis is considered to involve mitochondrial dysfunction with sequential release of cytochrome c from mitochondria, resulting in activation of caspase-3. However, we found that etoposide induced apoptosis in P39 cells, a myelodysplastic syndrome-derived cell line, without the release of cytochrome c. Furthermore, in etoposide-treated P39 cells, no changes in mitochondrial membrane potential (delta psi m) were detected by flow cytometry. Flow cytometry using a pH-sensitive probe demonstrated that lysosomal pH increased during early apoptosis in P39 cells treated with etoposide. A reduction in the ATP level preceded the elevation of lysosomal pH. In addition, specific inhibitors of vacuolar H+-ATPase induced apoptosis in P39 cells but not in HL60 cells. Although etoposide-induced activation of caspase-3 was followed by DNA ladder formation in P39 cells, E-64d, an inhibitor of lysosomal thiol proteases, specifically suppressed etoposide-induced activation of caspase-3. Western blotting analysis provided direct evidence for the involvement of a lysosomal enzyme, cathepsin L. These findings indicate that lysosomal dysfunction induced by a reduction in ATP results in leakage of lysosomal enzymes into the cytosolic compartment and that lysosomal enzyme(s) may be involved in activation of caspase-3 during apoptosis in P39 cells treated with etoposide.
ISSN:0008-5472
1538-7445