title: Caspase-3 is a component of Fas death-inducing signaling complex in lipid rafts and its activity is required for complete caspase-8 activation during Fas-mediated cell death.
abstract: Since its discovery, caspase-8 has been placed at the apex of the proteolytic cascade triggered by death receptor (DR) cross-linking. Because of its capacity to interact with the cytoplasmic portion of DR, it has been suggested that caspase-8 acts independently of other caspases in the initiation of Fas and other DR signaling. In this study, we demonstrate that in Jurkat cells, caspase-3 cleavage is an early step during Fas-induced apoptosis. We show that caspase-3 processing into its p20 occurs rapidly after Fas cross-linking, in the absence of mitochondrial depolarization and caspase-9 activation. Moreover, caspase-3 is present in lipid rafts of untreated Jurkat cells and peripheral T lymphocytes. Caspase-3, caspase-8, and Fas-associated death domain are further recruited to lipid rafts of Jurkat cells following anti-Fas treatment. Fas immunoprecipitation reveals that caspase-3 is a component of the death-inducing signaling complex, suggesting that this cysteine protease is in close proximity to caspase-8. Furthermore, transduction of Jurkat cells with a caspase-3 dominant-negative form inhibits caspase-8 processing and results in inhibition of apoptosis, suggesting that caspase-3 activity is required for caspase-8 activation. Overall, these findings support a model whereby caspase-3 is a component of the death-inducing signaling complex located in lipid rafts, and as such, is involved in the amplification of caspase-8 activity by the mitochondrion.
authors.affiliation: Département de Microbiologie et Immunologie, Université de Montréal, Montreal, Quebec, Canada.
authors.forename: Salah M
authors.initials: SM
authors.lastname: Aouad
authors.forename: Luchino Y
authors.initials: LY
authors.lastname: Cohen
authors.forename: Ehsan
authors.initials: E
authors.lastname: Sharif-Askari
authors.forename: Elias K
authors.initials: EK
authors.lastname: Haddad
authors.forename: Antoine
authors.initials: A
authors.lastname: Alam
authors.forename: Rafick-Pierre
authors.initials: RP
authors.lastname: Sekaly
mesh_terms: D017209:Apoptosis / Q000276:immunology*; D053148:Caspase 3; D053181:Caspase 8; D020169:Caspases / Q000096:biosynthesis / Q000378:metabolism* / Q000502:physiology; D053418:Death Domain Receptor Signaling Adaptor Proteins; D004789:Enzyme Activation / Q000276:immunology; D053222:Fas Ligand Protein; D006801:Humans; D006868:Hydrolysis; D007425:Intracellular Membranes / Q000201:enzymology / Q000276:immunology; D019169:Jurkat Cells; D008024:Ligands; D008562:Membrane Glycoproteins / Q000378:metabolism / Q000502:physiology; D021962:Membrane Microdomains / Q000201:enzymology / Q000502:physiology*; D008564:Membrane Potentials / Q000276:immunology; D008928:Mitochondria / Q000201:enzymology / Q000276:immunology; D011499:Protein Processing, Post-Translational / Q000276:immunology; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction / Q000276:immunology*; D013601:T-Lymphocytes / Q000166:cytology / Q000201:enzymology / Q000276:immunology; D019014:fas Receptor / Q000276:immunology / Q000378:metabolism / Q000502:physiology*
chemical_list: D053418:Death Domain Receptor Signaling Adaptor Proteins; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D008024:Ligands; D008562:Membrane Glycoproteins; D018124:Receptors, Tumor Necrosis Factor; D019014:fas Receptor; C505407:CASP3 protein, human; C505530:CASP8 protein, human; D053148:Caspase 3; D053181:Caspase 8; D020169:Caspases