Abstract
The death receptor Fas transduces apoptotic death signaling mediated by caspases. In the present study, human hepatoma HepG2 cells showed the Fas-mediated apoptosis mediated by caspase, especially caspase 3, only in the presence of actinomycin D. Interestingly, cytosolic proteins extracted from intact HepG2 cells induced caspase 3 inactivation. Our results reveal that this inactivation was triggered by the direct inhibition of activated caspase 3 by IAP gene family ILP. In addition, a 53 kDa protein was co-immunoprecipitated with anti-human caspase 3 antibody from intact HepG2 cells. This protein was a complex-protein of procaspase 3 and the cell cycle regulator p21WAF1 (p21). P21 bound to only procaspase 3, but not to activated caspase 3. We also demonstrate that p21 protein-loaded HepG2 cells resist to Fas-mediated apoptosis even in the presence of actinomycin D. Here we report that caspase 3 inactivation for the resistance to Fas-mediated apoptosis is induced by a procaspase 3/p21 complex formation and direct inhibition of activated caspase 3 by ILP.
MeSH terms
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Antibodies, Monoclonal / physiology
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Apoptosis / immunology
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Apoptosis / physiology*
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Carcinoma, Hepatocellular / enzymology
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Carcinoma, Hepatocellular / pathology
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Caspase 3
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Caspases*
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Cyclin-Dependent Kinase Inhibitor p21
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Cyclins / immunology
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Cyclins / metabolism
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Cyclins / physiology*
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Cysteine Endopeptidases / immunology
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Cysteine Endopeptidases / metabolism*
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Cysteine Endopeptidases / physiology
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Cysteine Proteinase Inhibitors / physiology
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Enzyme Activation / drug effects
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Enzyme Precursors / immunology
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Enzyme Precursors / metabolism
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Enzyme Precursors / physiology
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Humans
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Inhibitor of Apoptosis Proteins
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Multigene Family
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Precipitin Tests
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Proteins / genetics
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Proteins / physiology*
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Tumor Cells, Cultured
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X-Linked Inhibitor of Apoptosis Protein
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fas Receptor / immunology
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fas Receptor / physiology*
Substances
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Antibodies, Monoclonal
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CDKN1A protein, human
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Cyclin-Dependent Kinase Inhibitor p21
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Cyclins
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Cysteine Proteinase Inhibitors
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Enzyme Precursors
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Inhibitor of Apoptosis Proteins
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Proteins
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X-Linked Inhibitor of Apoptosis Protein
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XIAP protein, human
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fas Receptor
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CASP3 protein, human
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Caspase 3
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Caspases
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Cysteine Endopeptidases