c-Myc induces cytochrome c release in Rat1 fibroblasts by increasing outer mitochondrial membrane permeability in a Bid-dependent manner.
Ectopic expression of c-myc sensitises cells to a wide range of apoptotic stimuli by inducing the release of cytochrome c from the mitochondrial intermembrane space into the cytosol. To elucidate the molecular mechanisms of mitochondrial permeabilisation in response to c-Myc activation, we carried out a biochemical fractionation analysis of Rat1 fibroblasts expressing an inducible c-Myc protein. We find that cytoplasmic extracts from cells in which c-Myc has been activated contain a soluble factor capable of inducing cytochrome c release from isolated mouse liver mitochondria. This factor is present only under growth factor deprivation conditions and its activity is inhibited by addition of Bcl-X(L). The c-Myc-induced factor copurifies with full-length Bid, a "BH3-only" proapoptotic member of the Bcl-2 family, and antibodies raised against the BH3 domain of Bid inhibit c-Myc-induced cytochrome c releasing activity. These results are consistent with a model in which the activation of c-Myc regulates factors capable of enhancing the mitochondrial membrane destabilisation function of "BH3-only" proteins.
Cancer Research UK, London Research Institute, 44, Lincoln's Inn Fields, London WC 2A 3PX, UK.
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Iaccarino
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Hancock
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Evan
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Downward
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D017209:Apoptosis / Q000502:physiology; D051023:BH3 Interacting Domain Death Agonist Protein; D015153:Blotting, Western; D002352:Carrier Proteins / Q000276:immunology / Q000378:metabolism*; D002463:Cell Membrane Permeability / Q000502:physiology*; D045304:Cytochromes c / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007425:Intracellular Membranes / Q000502:physiology; D051379:Mice; D008930:Mitochondria, Liver / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000494:pharmacology; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D013629:Tamoxifen / Q000031:analogs & derivatives* / Q000494:pharmacology; D013997:Time Factors; D051020:bcl-X Protein
D000906:Antibodies; D051023:BH3 Interacting Domain Death Agonist Protein; C494812:Bcl2l1 protein, mouse; C494813:Bcl2l1 protein, rat; C494815:Bid protein, mouse; C494816:Bid protein, rat; D002352:Carrier Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D016271:Proto-Oncogene Proteins c-myc; D051020:bcl-X Protein; D013629:Tamoxifen; C016601:afimoxifene; D045304:Cytochromes c