p53 triggers apoptosis in oncogene-expressing fibroblasts by the induction of Noxa and mitochondrial Bax translocation.
The mechanism of p53-dependent apoptosis is still only partly defined. Using early-passage embryonic fibroblasts (MEF) from wild-type (wt), p53(-/-) and bax(-/-) mice, we observe a p53-dependent translocation of Bax to the mitochondria and a release of mitochondrial Cytochrome c during stress-induced apoptosis. These events proceed independent of zVAD-inhibitable caspase activation, are not prevented by dominant negative FADD (DN-FADD), but are negatively regulated by Mdm-2. Bcl-x(L) expression prevents the release of mitochondrial Cytochrome c and apoptosis, but not Bax translocation. At a single-cell level, enforced expression of p53 is sufficient to induce Bax translocation and Cytochrome c release. Real-time RT-PCR analysis reveals a significant induction of RNA expression of Noxa and Bax in p53(+/+), but not in p53(-/-) MEF. Noxa protein expression becomes detectable prior to Bax translocation, and downregulation of endogenous Noxa by RNA interference protects wt MEF against p53-dependent apoptosis. Hence, in oncogene-expressing MEF p53 induces apoptosis by BH3 protein-dependent caspase activation.
Division of Cellular Immunology, La Jolla Institute for Allergy, San Diego, CA, USA.
M
M
Schuler
U
U
Maurer
J C
JC
Goldstein
F
F
Breitenbücher
S
S
Hoffarth
N J
NJ
Waterhouse
D R
DR
Green
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D017209:Apoptosis / Q000235:genetics*; D002352:Carrier Proteins / Q000235:genetics; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D003574:Cytochrome c Group / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D053200:Fas-Associated Death Domain Protein; D005333:Fetus; D005347:Fibroblasts / Q000166:cytology / Q000201:enzymology*; D005786:Gene Expression Regulation / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D008928:Mitochondria / Q000201:enzymology* / Q000235:genetics; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000172:deficiency* / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis* / Q000235:genetics; D016159:Tumor Suppressor Protein p53 / Q000172:deficiency* / Q000235:genetics; D051028:bcl-2-Associated X Protein
D048868:Adaptor Proteins, Signal Transducing; C494827:Bax protein, mouse; D002352:Carrier Proteins; D003574:Cytochrome c Group; D004791:Enzyme Inhibitors; C505534:Fadd protein, mouse; D053200:Fas-Associated Death Domain Protein; C408009:Pmaip1 protein, mouse; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D020169:Caspases