title: Caspase-dependent generation of reactive oxygen species in human astrocytoma cells contributes to resistance to TRAIL-mediated apoptosis.
abstract: Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), a member of the TNF family of cytokines, causes apoptosis by caspase activation in various cell types, particularly in transformed cells. Numerous types of tumors are relatively resistant to TRAIL-induced cytotoxicity; however, the reasons for this are not yet fully understood. We report here a new signal transduction pathway involving protein kinase Cdelta (PKCdelta), NADPH oxidase 4 (NOX4) and reactive oxygen species (ROS), that inhibits caspase-dependent cell death induced by TRAIL ligation in human malignant astrocytoma cells. In our experiments, TRAIL ligation-induced generation of intracellular ROS through caspase-dependent proteolytic activation of PKCdelta and subsequent activation of the NOX4 complex. Suppression of intracellular ROS induction using various pharmacological inhibitors or PKCdelta- or NOX4-specific RNA interference enhanced the enzymatic activity of caspase-3 by blocking the oxidative modification of its catalytic cysteine residue, resulting in marked augmentation of TRAIL-mediated cell death. These results collectively indicate that TRAIL-induced activation of PKCdelta and NOX4 can modulate TRAIL-mediated apoptosis by promoting oxidative modification of active caspase-3 in a negative-feedback manner.
authors.affiliation: Department of Bio and Brain Engineering, KAIST, Daejeon, Korea.
authors.forename: K
authors.initials: K
authors.lastname: Choi
authors.forename: S-W
authors.initials: SW
authors.lastname: Ryu
authors.forename: S
authors.initials: S
authors.lastname: Song
authors.forename: H
authors.initials: H
authors.lastname: Choi
authors.forename: S W
authors.initials: SW
authors.lastname: Kang
authors.forename: C
authors.initials: C
authors.lastname: Choi
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D001254:Astrocytoma / Q000378:metabolism*; D053148:Caspase 3 / Q000378:metabolism*; D045744:Cell Line, Tumor; D015180:Electrophoresis, Gel, Two-Dimensional; D006801:Humans; D015151:Immunoblotting; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism*
chemical_list: D017382:Reactive Oxygen Species; D053221:TNF-Related Apoptosis-Inducing Ligand; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C498910:NOX4 protein, human; D053148:Caspase 3