TRAIL/Apo2L Activates c-Jun NH2-terminal Kinase (JNK) via Caspase-dependent and Caspase-independent Pathways

Abstract

In this study we show that TRAIL (tumor necrosis factor-related apoptosis-inducing ligand), also called Apo2L, activates the c-Jun N-terminal kinase (JNK). Interestingly, TRAIL-induced JNK activation occurs in a cell type-specific manner. In HeLa cells, TRAIL-induced JNK activation can be completely blocked with the cysteine protease inhibitor zVAD-fmk, whereas the same inhibitor has no, or even a stimulatory, effect on JNK activation in Kym-1 cells. Hence, TRAIL can engage at least two independent pathways leading to JNK activation, one that is cysteine protease-dependent and one that is cysteine protease-independent. To investigate whether the cysteine protease-dependent signaling of TRAIL leading to JNK activation is related to the apoptotic pathway engaged by this ligand, we investigated HeLa cells stably overexpressing a dominant negative mutant of FADD (Fas-associating protein with death domain) (GFP(green fluorescent protein)⌬FADD). In these cells, TRAIL-induced cell death and activation of the apoptosis executioner caspase-8 (FLICE/MACH) and caspase-3 (YAMA, CPP-32, Apopain), that belong to caspase subfamily of cysteine proteases, were abrogated, whereas JNK activation remained unaffected and was still sensitive toward z-VAD-fmk. Similar data were found in HeLa cells overexpressing Apo1/Fas and GFP⌬FADD upon stimulation with agonistic antibodies. These data suggest that cross-linking of the TRAIL receptors and Apo1/Fas, respectively, engages a FADD-dependent pathway leading to the activation of apoptotic caspases and, in parallel, a FADD-independent pathway leading to the stimulation of one or more cysteine proteases capable to activate JNK but not sufficient for the induction of cell death.

Tumor necrosis factor signaling

“…Indeed, especially under apoptotic conditions, TNF activates JNK, but also p38, with biphasic kinetics. 264 The first transient phase of JNK activation is caspase-independent 269,270 and almost completely inhibited in MKK7-deficient mouse embryonic fibroblasts. 139 In contrast, the second phase of TNF-induced JNK activation correlates with apoptosis-induction and is blocked by caspase inhibitors.…”

Caspase 8-dependent sensitization of cancer cells to TRAIL-induced apoptosis following reovirus-infection

“…Since both TRAIL (Muhlenbeck et al, 1998) and reovirus-induced (Kominsky et al, submitted) apoptosis are associated with the activation of caspase 8 we wished to determine whether caspase 8 was involved in reovirusinduced sensitization of cells to TRAIL. As expected high doses of TRAIL alone (200 ng/ml) and of reovirus alone (MOI 100) activated caspase 8 in H157 cells, as determined by the cleavage of pro-caspase 8 ( Figure 6A).…”

Increased sensitivity to TRAIL-induced apoptosis occurs during the adenoma to carcinoma transition of colorectal carcinogenesis

“…The activation of the caspase cascade leads, in turn, to cleavage of intracellular substrates such as poly-(ADP-ribose) polymerase (PARP) (Lazebnik et al, 1994). However, the death receptors can also transmit signals for cell survival through NF-kB, and via caspase-8 can activate JNK and p38 MAP kinase pathways (Chaudhary et al, 1997;Schneider et al, 1997;Mühlenbeck et al, 1998;MacFarlane et al, 2000b). TRAIL-R3 and TRAIL-R4 are unable to transmit the death signal, since TRAIL-R3 does not have a death domain and TRAIL-R4 has a death domain that is substantially deleted (French and Tschopp, 1999).…”