Bax and Bak independently promote cytochrome C release from mitochondria.
Pro-apoptotic Bax and Bak have been implicated in the regulation of p53-dependent apoptosis. We assessed the ability of primary baby mouse kidney (BMK) epithelial cells from bax(-/-), bak(-/-), and bax(-/-) bak(-/-) mice to be transformed by E1A alone or in conjunction with dominant-negative p53 (p53DD). Although E1A alone transformed BMK cells from p53-deficient mice, E1A alone did not transform BMK cells from bax(-/-), bak(-/-), or bax(-/-) bak(-/-) mice. Thus, the loss of both Bax and Bak was not sufficient to relieve p53-dependent suppression of transformation in epithelial cells. To test the requirement for Bax and Bak in other death signaling pathways, stable E1A plus p53DD-transformed BMK cell lines were derived from the bax(-/-), bak(-/-), and bax(-/-) bak(-/-) mice and characterized for their response to tumor necrosis factor-alpha (TNF-alpha)-mediated apoptosis. The loss of both Bax and Bak severely impaired TNF-alpha-mediated apoptosis, but the presence of either Bax or Bak alone was sufficient for cell death. Cytochrome c was released from mitochondria, and caspase-9 was activated in Bax- or Bak-deficient cells in response to TNF-alpha but not in cells deficient in both. Thus, either Bax or Bak is required for death signaling through mitochondria in response to TNF-alpha, but both are dispensable for p53-dependent transformation inhibition.
Degenhardt
Kurt
K
Department of Molecular Biology, the Cancer Institute of New Jersey, Rutgers University, Piscataway, New Jersey 08854, USA.
Sundararajan
Ramya
R
Lindsten
Tullia
T
Thompson
Craig
C
White
Eileen
E
D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D016923:Cell Death; D002478:Cells, Cultured; D003574:Cytochrome c Group / Q000378:metabolism*; D019281:Dimerization; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D015151:Immunoblotting; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008858:Microscopy, Phase-Contrast; D008928:Mitochondria / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2; D015398:Signal Transduction; D013347:Subcellular Fractions; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein
C494773:Bak1 protein, mouse; C494827:Bax protein, mouse; D003574:Cytochrome c Group; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D014409:Tumor Necrosis Factor-alpha; D016159:Tumor Suppressor Protein p53; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; C506434:Casp9 protein, mouse; D053453:Caspase 9; D020169:Caspases