Abstract
Exposure to anti-Fas antibody in Jurkat cells (type II cells), which are characterized by a weak caspase-8 activation at the death-inducing signaling complex (DISC), induced a biphasic increase in ceramide levels. The early generation of ceramide preceded transient activation of acidic ceramidase and subsequent production of sphingosine, followed by cytochrome c release, activation of caspases-2, -3, -6, -7, -8, and -9, Bid cleavage, and a later sustained ceramide accumulation. The caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone inhibited early increases of ceramide and sphingosine, whereas overexpression of Bcl-x(L) had no effect, and both prevented the later sustained ceramide accumulation. Exogenous sphingosine, as well as cell-permeable C(2)-ceramide, induced cytochrome c release from mitochondria in a caspase-independent fashion leading to activation of caspase-9 and executioner caspases and, surprisingly, activation of the initiator caspase-8 and processing of its substrate Bid. These effects were also completely abolished by Bcl-x(L) overexpression. Our results suggest that sphingosine might also be involved in the mitochondria-mediated pathway of Fas-induced cell death in type II cells.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Chloromethyl Ketones / pharmacology
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Antibodies, Monoclonal / pharmacology
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Apoptosis*
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BH3 Interacting Domain Death Agonist Protein
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Carboxylic Acids / pharmacology
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Carrier Proteins / metabolism
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Caspases / metabolism
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Ceramides / metabolism
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Cysteine Proteinase Inhibitors / pharmacology
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Cytochrome c Group / metabolism
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Enzyme Activation
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Fumonisins*
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Gene Expression Regulation
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Humans
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Jurkat Cells
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Mitochondria / metabolism*
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Oligopeptides / pharmacology
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Proto-Oncogene Proteins c-bcl-2 / metabolism
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Sphingosine / analogs & derivatives
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Sphingosine / metabolism*
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Sphingosine / pharmacology
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Transfection
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bcl-X Protein
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fas Receptor / immunology
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fas Receptor / metabolism*
Substances
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Amino Acid Chloromethyl Ketones
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Antibodies, Monoclonal
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BCL2L1 protein, human
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BH3 Interacting Domain Death Agonist Protein
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BID protein, human
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Carboxylic Acids
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Carrier Proteins
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Ceramides
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Cysteine Proteinase Inhibitors
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Cytochrome c Group
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Fumonisins
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Oligopeptides
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Proto-Oncogene Proteins c-bcl-2
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bcl-X Protein
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benzyloxycarbonyl-valyl-alanyl-aspartyl-fluoromethane
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benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone
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fas Receptor
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fumonisin B1
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Caspases
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N,N-dimethylsphingosine
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Sphingosine