Abstract
Current models for Fas (CD95)-mediated apoptosis suggest that FLICE/caspase-8 is recruited and activated, which results in cell death. However, the role of additional molecules in Fas signaling and FLICE activation is not clear. A chimeric Fas/FLICE (F/F) receptor, containing the extracellular/transmembrane portion of Fas and the caspase region of FLICE, mediated anti-Fas apoptosis. FLICE protease subunits were generated from the F/F precursor. Killing induced by Fas, but not F/F, was blocked by a dominant negative FADD. Apoptosis triggered through Fas and F/F was inhibited by coexpression of CrmA and p35, but not Bcl-xL. F/F bypassed Fas resistance in COS-7 cells and blocking by the death effector domain (DED)-containing viral protein MC159. These results show that: 1) F/F induces cell death, indicating that FLICE activation is sufficient for apoptosis and does not require additional Fas- or FADD-binding proteins; and 2) F/F bypasses proximal defects in Fas signaling that prevent FLICE recruitment or activation.
MeSH terms
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Adaptor Proteins, Signal Transducing*
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Animals
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Apoptosis / genetics
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Apoptosis / immunology*
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COS Cells
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Carrier Proteins / genetics
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Carrier Proteins / metabolism*
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Carrier Proteins / physiology
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Caspase 8
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Caspase 9
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Caspases*
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Cell Line
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Cysteine Endopeptidases / genetics*
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Cysteine Endopeptidases / physiology
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Cytotoxicity, Immunologic
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Fas Ligand Protein
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Fas-Associated Death Domain Protein
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Genes, Dominant / immunology
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Hybridomas
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Inhibitor of Apoptosis Proteins
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Leukemia L1210
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Ligands
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Membrane Glycoproteins / genetics*
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Membrane Glycoproteins / physiology
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Mice
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Proto-Oncogene Proteins c-bcl-2 / physiology
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Recombinant Fusion Proteins / chemical synthesis
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Recombinant Fusion Proteins / immunology*
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Recombinant Fusion Proteins / physiology
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Serpins / physiology
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T-Lymphocytes
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Viral Proteins / physiology
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bcl-X Protein
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fas Receptor / genetics*
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fas Receptor / metabolism
Substances
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Adaptor Proteins, Signal Transducing
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Bcl2l1 protein, mouse
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Carrier Proteins
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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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Inhibitor of Apoptosis Proteins
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Ligands
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Membrane Glycoproteins
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Proto-Oncogene Proteins c-bcl-2
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Recombinant Fusion Proteins
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Serpins
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Viral Proteins
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bcl-X Protein
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fas Receptor
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inhibitor of apoptosis, Nucleopolyhedrovirus
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interleukin-1beta-converting enzyme inhibitor
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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
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Cysteine Endopeptidases