Involvement of sphingosine in mitochondria-dependent Fas-induced apoptosis of type II Jurkat T cells.
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.
Cuvillier
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O
Department of Biochemistry and Molecular Biology, Georgetown University Medical Center, Washington, D. C. 20007, USA.
Edsall
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L
Spiegel
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D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D017209:Apoptosis; D051023:BH3 Interacting Domain Death Agonist Protein; D002264:Carboxylic Acids / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism; D020169:Caspases / Q000378:metabolism; D002518:Ceramides / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003574:Cytochrome c Group / Q000378:metabolism; D004789:Enzyme Activation; D037341:Fumonisins; D005786:Gene Expression Regulation; D006801:Humans; D019169:Jurkat Cells; D008928:Mitochondria / Q000378:metabolism*; D009842:Oligopeptides / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D013110:Sphingosine / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D014162:Transfection; D051020:bcl-X Protein; D019014:fas Receptor / Q000276:immunology / Q000378:metabolism*
D000590:Amino Acid Chloromethyl Ketones; D000911:Antibodies, Monoclonal; C494811:BCL2L1 protein, human; D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D002264:Carboxylic Acids; D002352:Carrier Proteins; D002518:Ceramides; D015853:Cysteine Proteinase Inhibitors; D003574:Cytochrome c Group; D037341:Fumonisins; D009842:Oligopeptides; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; C103712:benzyloxycarbonyl-valyl-alanyl-aspartyl-fluoromethane; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D019014:fas Receptor; C056933:fumonisin B1; D020169:Caspases; C061800:N,N-dimethylsphingosine; D013110:Sphingosine