TNF-alpha-induced mitochondrial alterations in human T cells requires FADD and caspase-8 activation but not RIP and caspase-3 activation.
Although much is known about how TNF-alpha induces apoptosis in the presence of inhibitors of protein synthesis, little is known about how it induces apoptosis without these inhibitors. In this report we investigated temporal sequence of events induced by TNF-alpha in the absence of protein synthesis. Regardless of whether we measured the effects by plasma membrane phosphotidylserine accumulation, by DNA strand breaks, or activation of caspases, significant changes were observed only between 12-24 h of TNF-alpha treatment. One of the earliest changes observed after TNF-alpha treatment was mitochondrial swelling at 10 min; followed by cytochrome c and Smac release at 10-30 min, and then heterochromatin clumping occurred at 60 min. While genetic deletion of receptor-interaction protein (RIP) had no effect on TNF-alpha-induced mitochondrial damage, deletion of Fas-associated death domain (FADD) abolished the TNF-induced mitochondrial swelling. Since pan-caspase inhibitor z-VAD-fmk abolished the TNF-alpha-induced mitochondrial changes, z-DEVD-fmk, an inhibitor of caspase-3 had no effect, suggesting that TNF-alpha-induced mitochondrial changes or cytochrome c and Smac release requires caspase-8 but not caspase-3 activation. Overall, our results indicated that mitochondrial changes are early events in TNF-alpha-induced apoptosis and that these mitochondrial changes require recruitment of FADD and caspase-8 activation, but not caspase-3 activation or RIP recruitment.
Musculoskeletal Research Group, Institute of Anatomy, Ludwig-Maximilian-University Munich, Munich, Germany.
Mehdi
M
Shakibaei
Bokyung
B
Sung
Gautam
G
Sethi
Bharat B
BB
Aggarwal
D051017:Apoptosis Regulatory Proteins; D053148:Caspase 3 / Q000378:metabolism*; D053181:Caspase 8 / Q000378:metabolism*; D045304:Cytochromes c / Q000378:metabolism; D053960:DNA Breaks; D004789:Enzyme Activation; D053200:Fas-Associated Death Domain Protein / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D019169:Jurkat Cells; D046529:Microscopy, Electron, Transmission; D008928:Mitochondria / Q000378:metabolism* / Q000648:ultrastructure; D024101:Mitochondrial Proteins / Q000378:metabolism; D008933:Mitochondrial Swelling; D053422:Receptor-Interacting Protein Serine-Threonine Kinases / Q000378:metabolism*; D013601:T-Lymphocytes / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
D051017:Apoptosis Regulatory Proteins; C412403:DIABLO protein, human; C505533:FADD protein, human; D053200:Fas-Associated Death Domain Protein; D047908:Intracellular Signaling Peptides and Proteins; D024101:Mitochondrial Proteins; D014409:Tumor Necrosis Factor-alpha; D045304:Cytochromes c; D053422:Receptor-Interacting Protein Serine-Threonine Kinases; C505407:CASP3 protein, human; C505530:CASP8 protein, human; D053148:Caspase 3; D053181:Caspase 8