title: Endoplasmic reticulum stress-induced apoptosis: multiple pathways and activation of p53-up-regulated modulator of apoptosis (PUMA) and NOXA by p53.
abstract: Endoplasmic reticulum (ER) stress-induced apoptosis has been implicated in the development of multiple diseases. However, the in vivo signaling pathways are still not fully understood. In this report, through the use of genetically deficient mouse embryo fibroblasts (MEFs) and their matched wild-type controls, we have demonstrated that the mitochondrial apoptotic pathway mediated by Apaf-1 is an integral part of ER stress-induced apoptosis and that ER stress activates different caspases through Apaf-1-dependent and -independent mechanisms. In search of the molecular link between ER stress and the mitochondrial apoptotic pathway, we have discovered that in MEFs, ER stress selectively activates BH3-only proteins PUMA and NOXA at the transcript level through the tumor suppressor gene p53. In p53(-/-) MEFs, ER stress-induced apoptosis is partially suppressed. The p53-independent apoptotic pathway may be mediated by C/EBP homologous protein (CHOP) and caspase-12, as their activation is intact in p53(-/-) MEFs. In multiple MEF lines, p53 is primarily nuclear and its level is elevated upon ER stress. To establish the role of NOXA and PUMA in ER stress-induced apoptosis, we have shown that, in MEFs deficient in NOXA or PUMA, ER stress-induced apoptosis is reduced. Reversibly, overexpression of NOXA or PUMA induces apoptosis as evidenced by the activation of BAK and caspase-7. Our results provide new evidence that, in MEFs, in addition to PUMA, p53 and NOXA are novel components of the ER stress-induced apoptotic pathway, and both contribute to ER stress-induced apoptosis.
authors.affiliation: Department of Biochemistry and Molecular Biology, USC/Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, 1441 Eastlake Avenue, Los Angeles, CA 90089-9176, USA.
authors.forename: Jianze
authors.initials: J
authors.lastname: Li
authors.forename: Brenda
authors.initials: B
authors.lastname: Lee
authors.forename: Amy S
authors.initials: AS
authors.lastname: Lee
mesh_terms: D000818:Animals; D017304:Annexin A5 / Q000737:chemistry; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism / Q000502:physiology*; D053477:Apoptotic Protease-Activating Factor 1; D015152:Blotting, Northern; D015153:Blotting, Western; D022762:CCAAT-Enhancer-Binding Proteins / Q000378:metabolism; D053454:Caspase 12; D053179:Caspase 7; D020169:Caspases / Q000737:chemistry / Q000378:metabolism; D002460:Cell Line; D002478:Cells, Cultured; D045304:Cytochromes c / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D004789:Enzyme Activation; D005347:Fibroblasts / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000378:metabolism; D008954:Models, Biological; D010957:Plasmids / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism / Q000502:physiology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D013997:Time Factors; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D015854:Up-Regulation; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000378:metabolism
chemical_list: C506592:APAF1 protein, human; D017304:Annexin A5; C506593:Apaf1 protein, mouse; D051017:Apoptosis Regulatory Proteins; D053477:Apoptotic Protease-Activating Factor 1; C438378:BBC3 protein, human; D022762:CCAAT-Enhancer-Binding Proteins; D018076:DNA, Complementary; D047908:Intracellular Signaling Peptides and Proteins; C498702:PMAIP1 protein, human; D011506:Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D050998:bcl-2 Homologous Antagonist-Killer Protein; D049452:Green Fluorescent Proteins; D045304:Cytochromes c; C506444:CASP12 protein, human; C505520:CASP7 protein, human; C506440:Casp12 protein, mouse; C505524:Casp7 protein, mouse; D053454:Caspase 12; D053179:Caspase 7; D020169:Caspases