Involvement of caspase-dependent activation of cytosolic phospholipase A2 in tumor necrosis factor-induced apoptosis.
Tumor necrosis factor (TNF)-induced apoptosis is mediated by caspases, which are cysteine proteases related to interleukin 1beta-converting enzyme. We report here that TNF-induced activation of caspases results in the cleavage and activation of cytosolic phospholipase A2 (cPLA2) and that activated cPLA2 contributes to apoptosis. Inhibition of caspases by expression of a cowpox virus-derived inhibitor, CrmA, or by a specific tetrapeptide inhibitor of CPP32/caspase-3, acetyl-Asp-Glu-Val-Asp-aldehyde (Ac-DEVD-CHO), inhibited TNF-induced activation of cPLA2 and apoptosis. TNF-induced activation of cPLA2 was accompanied by a cleavage of the 100-kDa cPLA2 to a 70-kDa proteolytic fragment. This cleavage was inhibited by Ac-DEVD-CHO in a similar manner as that of poly(ADP)ribose polymerase, a known substrate of CPP32/caspase-3. Interestingly, specific inhibition of cPLA2 enzyme activity by arachidonyl trifluoromethylketone (AACOCF3) partially inhibited TNF-induced apoptosis without inhibition of caspase activity. Thus, our results suggest a novel caspase-dependent activation pathway for cPLA2 during apoptosis and identify cPLA2 as a mediator of TNF-induced cell death acting downstream of caspases.
Wissing
D
D
Apoptosis Laboratory, Division for Cancer Biology, Danish Cancer Society, Strandboulevarden 49, DK-2100 Copenhagen, Denmark.
Mouritzen
H
H
Egeblad
M
M
Poirier
G G
GG
Jäättelä
M
M
D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies; D001943:Breast Neoplasms; D020170:Caspase 1; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation; D005260:Female; D005354:Fibrosarcoma; D006801:Humans; D007700:Kinetics; D051379:Mice; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000276:immunology; D010741:Phospholipases A / Q000737:chemistry / Q000378:metabolism*; D054467:Phospholipases A2; D011994:Recombinant Proteins / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D000906:Antibodies; D010446:Peptide Fragments; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D010741:Phospholipases A; D054467:Phospholipases A2; D003546:Cysteine Endopeptidases; D020170:Caspase 1