Glutathione Dependence of Caspase-8 Activation at the Death-inducing Signaling Complex

Abstract

Apoptosis triggered by the death receptor CD95 (APO-1 or Fas) is pivotal for the homeostasis of the immune system. We investigated differential effects of glutathione depletion on CD95-triggered apoptosis in T and B cell lines as well as the glutathione dependence of caspase-8 activation. In B lymphoblastoid SKW6.4 cells, CD95-mediated apoptosis was prevented upstream of caspase-8 activation and caspase-3-like activity after acute glutathione depletion by diethyl maleate or cischloro-dinitrobenzene. Immunoprecipitation of the death-inducing signaling complex (DISC) revealed that the DISC was still formed in the glutathione-depleted state. The first cleavage step of procaspase-8 activation at the DISC, however, was inhibited. Accordingly, under cell-free conditions, radiolabeled procaspase-8 was processed at the immunoprecipitated DISC only after the addition of exogenous dithiothreitol or reduced glutathione. We also observed suppression of CD95-mediated apoptosis in glutathione-depleted CEM and H9 cells. Notably, Jurkat cells still died upon CD95 engagement under this condition, displaying incomplete nuclear fragmentation and a partial switch to necrosis; this may be explained by reduced cytochrome c/dATP-mediated caspase activation observed in cytosol from glutathionedepleted Jurkat cytosol. Our data indicate that the activation of caspase-8 at the DISC and hence CD95-mediated apoptosis induction shows a cell-specific requirement for intracellular glutathione.Elimination of functionally impaired or potentially dangerous cells by apoptosis is of paramount importance for the organism. Apoptosis mediated by the death receptor CD95 (also called APO-1 and Fas) has previously been investigated intensively, especially in the immune system and the liver. Triggering of CD95 by agonistic antibodies (␣CD95) or the naturally occurring CD95 ligand (CD95L) initiates trimerization of CD95

Bistability Analyses of a Caspase Activation Model for Receptor-induced Apoptosis

“…In experimental studies the activation of effector caspases both in type I as well as type II cell populations occurs gradually within a few hours (13,39,40), as schematically depicted in Fig. 5A.…”

“…However, most experimental studies have been performed using cell populations where effector-caspase activation is typically observed within a range of a few hours (13,39,40). Fig.…”

Glutathione S-Transferase Omega 1-1 Is a Target of Cytokine Release Inhibitory Drugs and May Be Responsible for Their Effect on Interleukin-1औ Posttranslational Processing

“…Indeed, purified caspase-3 forms a mixed disulfide and is inactivated following treatment with oxidized glutathione (87). Interestingly, activation of caspase-8 via the death-inducing signaling complex in FAS-induced lymphocytes is dependent on the presence of glutathione (88). The glutathione-dependent step has not been determined, but appears to occur after assembly of the protein complex (88).…”

“…Interestingly, activation of caspase-8 via the death-inducing signaling complex in FAS-induced lymphocytes is dependent on the presence of glutathione (88). The glutathione-dependent step has not been determined, but appears to occur after assembly of the protein complex (88). The mechanism of procaspase-1 activation is not well understood, but like caspase-8, appears to involve a large protein assembly termed the inflammasome (89).…”

Caspase-dependent generation of reactive oxygen species in human astrocytoma cells contributes to resistance to TRAIL-mediated apoptosis

“…10,11 On the other hand, H 2 O 2 attenuates Fasmediated apoptosis by inhibiting caspase-3 activity 12,13 Glutathione depletion suppresses Fas-mediated caspase-8 activation and apoptosis induction, thereby suggesting that pro-oxidative conditions are cytoprotective under certain circumstances. 14 TRAIL has been reported to induce ROS potentiation of receptor-mediated activation of caspases and apoptotic cell death in HeLa human adenocarcinoma cells. 15 As ROS have been postulated to act as second messengers in signaling through various receptors, we investigated whether intracellular ROS also have roles in TRAIL-mediated signaling as molecular modifiers.…”