title: Activation of CPP32-like proteases is not sufficient to trigger apoptosis: inhibition of apoptosis by agents that suppress activation of AP24, but not CPP32-like activity.
abstract: The 24-kD apoptotic protease (AP24) is a serine protease that is activated during apoptosis and has the capacity to activate internucleosomal DNA fragmentation in isolated nuclei. This study examined the following: (a) the functional relationship between AP24 and the CPP32-like proteases of the caspase family; and (b) whether activation of CPP32-like proteases is sufficient to commit irreversibly a cell to apoptotic death. In three different leukemia cell lines, we showed that agents that directly (carbobenzoxy-Ala-Ala-borophe (DK120) or indirectly inhibit activation of AP24 (protein kinase inhibitors, basic fibroblast growth factor, tosylphenylalaninechloromethylketone, and caspase inhibitors) protected cells from apoptosis induced by TNF or UV light. Only the caspase inhibitors, however, prevented activation of CPP32-like activity as revealed by cleavage of the synthetic substrate, DEVD-pNa, by cell cytosols, and also by in vivo cleavage of poly (ADP-ribosyl) polymerase, a known substrate of CPP32. Activation of DEVD-pNa cleaving activity without apoptosis was also demonstrated in two variants derived from the U937 monocytic leukemia in the absence of exogenous inhibitors. Cell-permeable peptide inhibitors selective for CPP32-like proteases suppressed AP24 activation and apoptotic death. These findings indicate that CPP32-like activity is one of several upstream signals required for AP24 activation. Furthermore, activation of CPP32-like proteases alone is not sufficient to commit irreversibly a cell to apoptotic death under conditions where activation of AP24 is inhibited.
authors.affiliation: Palo Alto Institute of Molecular Medicine, Mountain View, California 94043, USA.
authors.forename: S C
authors.initials: SC
authors.lastname: Wright
authors.forename: U
authors.initials: U
authors.lastname: Schellenberger
authors.forename: H
authors.initials: H
authors.lastname: Wang
authors.forename: D H
authors.initials: DH
authors.lastname: Kinder
authors.forename: J W
authors.initials: JW
authors.lastname: Talhouk
authors.forename: J W
authors.initials: JW
authors.lastname: Larrick
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D020170:Caspase 1; D053148:Caspase 3; D020169:Caspases; D002463:Cell Membrane Permeability; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D053938:DNA Fragmentation; D004789:Enzyme Activation; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D006801:Humans; D008223:Lymphoma; D009842:Oligopeptides / Q000494:pharmacology; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D047428:Protein Kinase Inhibitors; D012697:Serine Endopeptidases / Q000378:metabolism*; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology; D014108:Tosylphenylalanyl Chloromethyl Ketone / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D014466:Ultraviolet Rays
chemical_list: D015853:Cysteine Proteinase Inhibitors; D009842:Oligopeptides; D047428:Protein Kinase Inhibitors; D015842:Serine Proteinase Inhibitors; D014409:Tumor Necrosis Factor-alpha; D016222:Fibroblast Growth Factor 2; D014108:Tosylphenylalanyl Chloromethyl Ketone; D011065:Poly(ADP-ribose) Polymerases; C108734:AP24 apoptotic protease; D012697:Serine Endopeptidases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D003546:Cysteine Endopeptidases; D020170:Caspase 1