Abstract
Cell death is achieved by two fundamentally different mechanisms: apoptosis and necrosis. Apoptosis is dependent on caspase activation, whereas the caspase-independent necrotic signaling pathway remains largely uncharacterized. We show here that Fas kills activated primary T cells efficiently in the absence of active caspases, which results in necrotic morphological changes and late mitochondrial damage but no cytochrome c release. This Fas ligand-induced caspase-independent death is absent in T cells that are deficient in either Fas-associated death domain (FADD) or receptor-interacting protein (RIP). RIP is also required for necrotic death induced by tumor necrosis factor (TNF) and TNF-related apoptosis-inducing ligand (TRAIL). In contrast to its role in nuclear factor kappa B activation, RIP requires its own kinase activity for death signaling. Thus, Fas, TRAIL and TNF receptors can initiate cell death by two alternative pathways, one relying on caspase-8 and the other dependent on the kinase RIP.
MeSH terms
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Adaptor Proteins, Signal Transducing*
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Animals
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Apoptosis / physiology
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Apoptosis Regulatory Proteins
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Carrier Proteins / metabolism
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Caspase 8
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Caspase 9
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Caspases / metabolism*
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Cell Death / physiology*
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Fas Ligand Protein
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Fas-Associated Death Domain Protein
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Humans
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In Vitro Techniques
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Jurkat Cells
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Membrane Glycoproteins / metabolism
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Mice
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Mice, Inbred BALB C
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Models, Biological
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Necrosis
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Proteins / metabolism*
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Receptor-Interacting Protein Serine-Threonine Kinases
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Signal Transduction
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T-Lymphocytes / cytology
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T-Lymphocytes / metabolism
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TNF-Related Apoptosis-Inducing Ligand
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Tumor Necrosis Factor-alpha / metabolism
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fas Receptor / metabolism*
Substances
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Adaptor Proteins, Signal Transducing
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Apoptosis Regulatory Proteins
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Carrier Proteins
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FADD protein, human
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FASLG protein, human
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Fadd protein, mouse
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Fas Ligand Protein
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Fas-Associated Death Domain Protein
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Fasl protein, mouse
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Membrane Glycoproteins
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Proteins
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TNF-Related Apoptosis-Inducing Ligand
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TNFSF10 protein, human
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Tnfsf10 protein, mouse
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Tumor Necrosis Factor-alpha
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fas Receptor
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RIPK1 protein, human
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Receptor-Interacting Protein Serine-Threonine Kinases
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Ripk1 protein, mouse
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CASP8 protein, human
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CASP9 protein, human
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Casp8 protein, mouse
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Casp9 protein, mouse
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Caspase 8
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Caspase 9
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Caspases