FLICE/caspase-8 activation triggers anoikis induced by beta1-integrin blockade in human keratinocytes.
Beta1-integrin protects keratinocyte stem cells (KSC) from cell-detachment apoptosis ('anoikis'). Here we show that caspase-8 active protein is detected in both young transit amplifying (TA) cells and TA cells, but not in KSC. On suspension, caspases are activated earlier in young TA than in KSC, whereas anti-beta1-integrin neutralizing antibody accelerates caspase activation in both KSC and young TA. Caspases 8 and 10 are the first caspases to be activated whereas caspase-8 inhibitor zIETD-fmk delays the activation of Bid, caspase-9 and caspase-3. However, the caspase-9 inhibitor zLEDH-fmk does not block the activation of caspase-8, Bid, caspase-10 and caspase-3. Moreover, caspase-8, but not caspase-9 inhibitor partially prevents keratinocyte anoikis. As FLIP inhibits caspase-8 processing, we retrovirally infected HaCaT keratinocytes with c-FLIP(L). Anti-beta1-integrin fails to activate caspase-8, Bid, caspase-9 and to induce the release of cytochrome c in c-FLIP(L) overexpressing keratinocytes. Finally, overexpression of c-FLIP(L) partially prevents anoikis in both suspended and anti-beta1 integrin-treated cells. Taken together, these results indicate that the extrinsic apoptotic pathway triggered by caspase-8 predominates in keratinocyte anoikis. However, the release of cytochrome c and the later activation of caspase-9 seem to suggest that the intrinsic mitochondrial pathway may intervene as a positive feedback loop of caspase activation.
Marconi
Alessandra
A
Institute of Dermatology, University of Modena and Reggio Emilia, Via del Pozzo 71, 41100 Modena, Italy.
Atzei
Paola
P
Panza
Cristina
C
Fila
Chiara
C
Tiberio
Rossana
R
Truzzi
Francesca
F
Wachter
Tina
T
Leverkus
Martin
M
Pincelli
Carlo
C
D023102:Anoikis; D051017:Apoptosis Regulatory Proteins; D051023:BH3 Interacting Domain Death Agonist Protein; D015153:Blotting, Western; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins / Q000378:metabolism; D053455:Caspase 10; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism*; D016923:Cell Death; D002460:Cell Line; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007150:Immunohistochemistry; D019012:Integrin beta1 / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D015603:Keratinocytes / Q000166:cytology* / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D012190:Retroviridae / Q000378:metabolism; D053221:TNF-Related Apoptosis-Inducing Ligand; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D051017:Apoptosis Regulatory Proteins; 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; D004791:Enzyme Inhibitors; D019012:Integrin beta1; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053455:Caspase 10; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; C506438:CASP10 protein, human