Tumor necrosis factor-alpha induces Bax-Bak interaction and apoptosis, which is inhibited by adenovirus E1B 19K.
Tumor necrosis factor (TNF)-alpha-mediated death signaling induces oligomerization of proapoptotic Bcl-2 family member Bax into a high molecular mass protein complex in mitochondrial membranes. Bax complex formation is associated with the release of cytochrome c, which propagates death signaling by acting as a cofactor for caspase-9 activation. The adenovirus Bcl-2 homologue E1B 19K blocks TNF-alpha-mediated apoptosis by preventing cytochrome c release, caspase-9 activation, and apoptosis of virus-infected cells. TNF-alpha induces E1B 19K-Bax interaction and inhibits Bax oligomerization. Oligomerized Bax may form a pore to release mitochondrial proteins, analogous to the homologous pore-forming domains of bacterial toxins. E1B 19K can also bind to proapoptotic Bak, but the functional significance is not known. TNF-alpha signaling induced Bak-Bax interaction and both Bak and Bax oligomerization. E1B 19K was constitutively in a complex with Bak, and blocked the Bak-Bax interaction and oligomerization of both. The TNF-alpha-mediated cytochrome c and Smac/DIABLO release from mitochondria was inhibited by E1B 19K expression in adenovirus-infected cells. Since either Bax or Bak is essential for death signaling by TNF-alpha, the interaction between E1B 19K and both Bak and Bax may be required to inhibit their cooperative or independent oligomerization to release proteins from mitochondria which promote caspase activation and cell death.
Sundararajan
R
R
Rutgers University, Piscataway, New Jersey 08854, USA.
Cuconati
A
A
Nelson
D
D
White
E
E
D000256:Adenoviridae / Q000235:genetics; D017501:Adenovirus E1B Proteins / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins / Q000378:metabolism; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D016923:Cell Death; D002850:Chromatography, Gel; D003432:Cross-Linking Reagents / Q000494:pharmacology; D003574:Cytochrome c Group / Q000378:metabolism; D004789:Enzyme Activation; D019084:Fluorescent Antibody Technique, Indirect; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000378:metabolism; D008970:Molecular Weight; D011233:Precipitin Tests; D011485:Protein Binding; D011487:Protein Conformation; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2; D015398:Signal Transduction; D013347:Subcellular Fractions / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein
D017501:Adenovirus E1B Proteins; D051017:Apoptosis Regulatory Proteins; C494772:BAK1 protein, human; C494826:BAX protein, human; D002352:Carrier Proteins; D003432:Cross-Linking Reagents; D003574:Cytochrome c Group; C412403:DIABLO protein, human; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D014409:Tumor Necrosis Factor-alpha; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; C506433:CASP9 protein, human; D053453:Caspase 9; D020169:Caspases