Autocrine tumor necrosis factor alpha links endoplasmic reticulum stress to the membrane death receptor pathway through IRE1alpha-mediated NF-kappaB activation and down-regulation of TRAF2 expression.
NF-kappaB is critical for determining cellular sensitivity to apoptotic stimuli by regulating both mitochondrial and death receptor apoptotic pathways. The endoplasmic reticulum (ER) emerges as a new apoptotic signaling initiator. However, the mechanism by which ER stress activates NF-kappaB and its role in regulation of ER stress-induced cell death are largely unclear. Here, we report that, in response to ER stress, IKK forms a complex with IRE1alpha through the adapter protein TRAF2. ER stress-induced NF-kappaB activation is impaired in IRE1alpha knockdown cells and IRE1alpha(-/-) MEFs. We found, however, that inhibiting NF-kappaB significantly decreased ER stress-induced cell death in a caspase-8-dependent manner. Gene expression analysis revealed that ER stress-induced expression of tumor necrosis factor alpha (TNF-alpha) was IRE1alpha and NF-kappaB dependent. Blocking TNF receptor 1 signaling significantly inhibited ER stress-induced cell death. Further studies suggest that ER stress induces down-regulation of TRAF2 expression, which impairs TNF-alpha-induced activation of NF-kappaB and c-Jun N-terminal kinase and turns TNF-alpha from a weak to a powerful apoptosis inducer. Thus, ER stress induces two signals, namely TNF-alpha induction and TRAF2 down-regulation. They work in concert to amplify ER-initiated apoptotic signaling through the membrane death receptor.
Hu
Ping
P
Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, 702 Light Hall, Nashville, TN 37232-0615, USA.
Han
Zhang
Z
Couvillon
Anthony D
AD
Kaufman
Randal J
RJ
Exton
John H
JH
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics*; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology; D053181:Caspase 8; D020169:Caspases / Q000032:analysis / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D015536:Down-Regulation; D024202:Electrophoretic Mobility Shift Assay; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D004722:Endoribonucleases; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006801:Humans; D020672:I-kappa B Proteins / Q000235:genetics / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D007700:Kinetics; D007739:L Cells; D008156:Luciferases / Q000378:metabolism; D008175:Lung Neoplasms / Q000378:metabolism / Q000473:pathology; D008297:Male; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D011233:Precipitin Tests; D011471:Prostatic Neoplasms / Q000378:metabolism / Q000473:pathology; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D047992:TNF Receptor-Associated Factor 2 / Q000235:genetics / Q000378:metabolism*; D019284:Thapsigargin / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D014415:Tunicamycin / Q000494:pharmacology
D020672:I-kappa B Proteins; D008565:Membrane Proteins; D016328:NF-kappa B; D034741:RNA, Small Interfering; D047992:TNF Receptor-Associated Factor 2; D014409:Tumor Necrosis Factor-alpha; D014415:Tunicamycin; D019284:Thapsigargin; D008156:Luciferases; C403982:ERN2 protein, human; C486556:Ern2 protein, mouse; D017346:Protein Serine-Threonine Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D004722:Endoribonucleases; C505530:CASP8 protein, human; C505526:Casp8 protein, mouse; D053181:Caspase 8; D020169:Caspases