title: Activation of caspase-8 in 3-deazaadenosine-induced apoptosis of U-937 cells occurs downstream of caspase-3 and caspase-9 without Fas receptor-ligand interaction.
abstract: 3-Deazaadenosine (DZA), a cellular methylation blocker was reported to induce the caspase-3-like activities-dependent apoptosis in U-937 cells. In this study, we analyzed the activation pathway of the caspase cascade involved in the DZA-induced apoptosis using specific inhibitors of caspases. In the U-937 cells treated with DZA, cytochrome c release from mitochondria and subsequent activation of caspase-9, -8 and -3 were observed before the induction of apoptosis. zDEVD-Fmk, a specific inhibitor of caspase-3, and zLEHD-Fmk, a specific inhibitor of caspase-9, prevented the activation of caspase-8 but neither caspase-3 nor caspase-9, indicating that caspase-8 is downstream of both caspase-3 and caspase-9, which are activated by independent pathways. zVAD-Fmk, a universal inhibitor of caspases, kept the caspase-3 from being activated but not caspase-9. Moreover, ZB4, an antagonistic Fas-antibody, exerted no effect on the activation of caspase-8 and induction of apoptosis by DZA. In addition, zVAD-Fmk and mitochondrial permeability transition pore (MPTP) inhibitors such as cyclosporin A (CsA) and bongkrekic acid (BA) did not block the release of cytochrome c from mitochondria. Taken together, these results suggest that in the DZA-induced apoptosis, caspase-8 may serve as an executioner caspase and be activated downstream of both caspase-3 and caspase-9, independently of Fas receptor-ligand interaction. And caspase-3 seems to be activated by other caspses including IETDase-like enzyme and caspse-9 seems to be activated by cytochrome c released from mitochondria without the involvement of caspases and CsA- and BA- inhibitory MPTP.
authors.affiliation: Department of Biochemistry, College of Medicine, The Catholic University of Korea, Seoul.
authors.forename: Y J
authors.initials: YJ
authors.lastname: Cha
authors.forename: H S
authors.initials: HS
authors.lastname: Kim
authors.forename: H
authors.initials: H
authors.lastname: Rhim
authors.forename: B E
authors.initials: BE
authors.lastname: Kim
authors.forename: S W
authors.initials: SW
authors.lastname: Jeong
authors.forename: I K
authors.initials: IK
authors.lastname: Kim
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D001865:Bongkrekic Acid / Q000494:pharmacology; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism*; D002460:Cell Line; D016572:Cyclosporine / Q000494:pharmacology; D003574:Cytochrome c Group / Q000187:drug effects / Q000378:metabolism; D004789:Enzyme Activation; D053222:Fas Ligand Protein; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000166:cytology; D008024:Ligands; D008562:Membrane Glycoproteins / Q000378:metabolism; D014372:Tubercidin / Q000494:pharmacology*; D020298:U937 Cells
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D003574:Cytochrome c Group; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D008024:Ligands; D008562:Membrane Glycoproteins; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; C018258:3-deazaadenosine; D001865:Bongkrekic Acid; D016572:Cyclosporine; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D014372:Tubercidin