Involvement of caspase-2 long isoform in Fas-mediated cell death of human leukemic cells.
Engagement of the plasma membrane receptor Fas can induce apoptosis of leukemic cells. Signaling through Fas requires the formation of a death-inducing signaling complex (DISC) that involves the cytoplasmic domain of Fas, the adaptor molecule FADD/MORT-1, and procaspase-8. The present study investigated whether another caspase, known as procaspase-2L, played a role in Fas-mediated cell death. A series of human leukemic variant cells was derived by stable transfection with a CASP2L antisense construct (CASP2L/AS). Specific down-regulation of procaspase-2L decreased the sensitivity of these cells to apoptosis induced by an agonistic anti-Fas antibody (Ab, clone CH11), as determined by studying DNA fragmentation, chromatin condensation, and externalization of phosphatidylserine on the plasma membrane. In leukemic cells transfected with an empty vector, anti-Fas Ab treatment activated caspase-8, decreased the expression of the BH3 domain-only protein Bid, triggered the release of cytochrome c from the mitochondria to the cytosol, and activated caspase-3. All these events could not be observed when CASP2L/AS cells were similarly treated with anti-Fas Abs. CASP2L/AS transfection did not inhibit the formation of the DISC and no direct interaction between procaspase-2L and either Fas or FADD or procaspase-8 was identified. Down-regulation of procaspase-2L inhibited anti-Fas Ab-mediated cleavage of c-FLIP (FLICE-inhibitory protein), a protein that interferes with the formation of a functional DISC. These results suggest that the long isoform of caspase-2 plays a role in the Fas-mediated pathway to cell death by contributing to caspase-8 activation at the DISC level.
INSERM U517, Faculties of Medicine and Pharmacy, Dijon, France.
N
N
Droin
F
F
Bichat
C
C
Rébé
A
A
Wotawa
O
O
Sordet
A
A
Hammann
R
R
Bertrand
E
E
Solary
D017209:Apoptosis / Q000187:drug effects*; D051023:BH3 Interacting Domain Death Agonist Protein; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins / Q000187:drug effects / Q000378:metabolism; D053143:Caspase 2; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D003574:Cytochrome c Group / Q000187:drug effects / Q000378:metabolism; D016373:DNA, Antisense / Q000494:pharmacology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D007938:Leukemia / Q000188:drug therapy* / Q000473:pathology; D020033:Protein Isoforms / Q000235:genetics / Q000494:pharmacology / Q000502:physiology; D014162:Transfection; D014407:Tumor Cells, Cultured; D019014:fas Receptor / Q000494:pharmacology*
D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D002352:Carrier Proteins; D003574:Cytochrome c Group; D016373:DNA, Antisense; D047908:Intracellular Signaling Peptides and Proteins; D020033:Protein Isoforms; D019014:fas Receptor; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053143:Caspase 2; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases