title: The molecular mechanism of Noxa-induced mitochondrial dysfunction in p53-mediated cell death.
abstract: Genotoxic stresses stabilize the p53 tumor suppressor protein which, in turn, transactivates target genes to cause apoptosis. Although Noxa, a "BH3-only" member of the Bcl-2 family, was shown to be a target of p53-mediated transactivation and to function as a mediator of p53-dependent apoptosis through mitochondrial dysfunction, the molecular mechanism by which Noxa causes mitochondrial dysfunction is largely unknown. Here we show that two domains (BH3 domain and mitochondrial targeting domain) in Noxa are essential for the release of cytochrome c from mitochondria. Noxa-induced cytochrome c release is inhibited by permeability transition pore inhibitors such as CsA or MgCl2, and Noxa induces an ultra-structural change of mitochondria yielding "swollen" mitochondria that are unlike changes induced by tBid. This indicates that Noxa may activate the permeability transition-related pore to release cytochrome c from mitochondria into cytosol. Moreover, Bak-oligomerization, which is an essential event for tBid-induced cytochrome c release in the extrinsic death signaling pathway, is not associated with Noxa-induced cytochrome c release. This finding suggests that the pathway of Noxa-induced mitochondrial dysfunction is distinct from the one of tBid-induced mitochondrial dysfunction. Thus, we propose that there are at least two different pathways of mitochondrial dysfunction; one mediated through Noxa in response to genotoxic stresses and the other through tBid in response to death ligands.
mesh_terms: D000595:Amino Acid Sequence; D017209:Apoptosis; D051023:BH3 Interacting Domain Death Agonist Protein; D015153:Blotting, Western; D002352:Carrier Proteins / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004706:Endodeoxyribonucleases / Q000378:metabolism; D049452:Green Fluorescent Proteins; D006367:HeLa Cells; D006801:Humans; D008024:Ligands; D008164:Luminescent Proteins / Q000378:metabolism; D015636:Magnesium Chloride / Q000737:chemistry; D008565:Membrane Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000378:metabolism* / Q000648:ultrastructure; D008969:Molecular Sequence Data; D010957:Plasmids / Q000378:metabolism; D017434:Protein Structure, Tertiary; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D015533:Transcriptional Activation; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D050998:bcl-2 Homologous Antagonist-Killer Protein
chemical_list: C494772:BAK1 protein, human; D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D002352:Carrier Proteins; D008024:Ligands; D008164:Luminescent Proteins; D008565:Membrane Proteins; C498702:PMAIP1 protein, human; D019253:Proto-Oncogene Proteins c-bcl-2; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D016159:Tumor Suppressor Protein p53; D050998:bcl-2 Homologous Antagonist-Killer Protein; D015636:Magnesium Chloride; D049452:Green Fluorescent Proteins; D045304:Cytochromes c; D004706:Endodeoxyribonucleases; C052391:endonuclease G