Temporal relationship between cytochrome c release and mitochondrial swelling during UV-induced apoptosis in living HeLa cells.
During apoptosis, cytochrome c is released from mitochondria to the cytosol to activate a caspase cascade, which commits the cell to the death process. It has been proposed that the release of cytochrome c is caused by a swelling of the mitochondrial matrix triggered by the apoptotic stimuli. To test this theory, we measured directly the dynamic re-distribution of green fluorescence protein (GFP)-tagged cytochrome c and morphological change of mitochondria within living HeLa cells during u.v.-induced apoptosis. We observed that mitochondria did not swell when cytochrome c was released from mitochondria to cytosol during apoptosis. Instead, mitochondria swelled to spherical shapes within 10 minutes of cytochrome c release. This finding strongly suggests that cytochrome c release in apoptosis was not caused by mitochondrial swelling. This conclusion was further supported in two separated experiments using an immunostaining method and carbonyl cyanide m-chlorophenyl-hydrazone (CCCP) treatment. In addition, we found evidence that cytochrome c was also released before mitochondrial swelling in apoptosis induced by other cell death-inducing treatments, including tumor necrosis factor (TNF) and actinomycin D.
Gao
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Department of Biology, The Hong Kong University of Science and Technology, Clear Water Bay, China.
Pu
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Luo
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Chang
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D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000502:physiology* / Q000528:radiation effects; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003574:Cytochrome c Group / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D049452:Green Fluorescent Proteins; D006367:HeLa Cells; D006801:Humans; D007202:Indicators and Reagents / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics; D008856:Microscopy, Fluorescence / Q000379:methods; D008928:Mitochondria / Q000378:metabolism; D008933:Mitochondrial Swelling / Q000187:drug effects / Q000502:physiology*; D014466:Ultraviolet Rays; D014475:Uncoupling Agents / Q000494:pharmacology
D000590:Amino Acid Chloromethyl Ketones; D015853:Cysteine Proteinase Inhibitors; D003574:Cytochrome c Group; D007202:Indicators and Reagents; D008164:Luminescent Proteins; D014475:Uncoupling Agents; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D049452:Green Fluorescent Proteins; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone