Inhibition of the NF-κB survival pathway via caspase-dependent cleavage of the IKK complex scaffold protein and NF-κB essential modulator NEMO

Abstract

Apoptosis is mediated by cysteine-dependent, aspartate-directed proteases of the caspase family that proteolyse strategic intracellular substrates to induce cell suicide. We describe here that engagement of apoptotic processes by Fas triggering or by staurosporine stimulation leads to the caspase-dependent inactivation of the nuclear factor kappa B (NF-jB) pathway after cleavage of IKK1 (IjB kinase 1) and NEMO (NF-jB essential modulator), which are needed to transduce NF-jB activation signals. In this study, we have analyzed in more detail, the role of NEMO cleavage, as NEMO, but not IKK1, is important for the prosurvival actions of NF-jB. We demonstrate that NEMO is cleaved after Asp355 to remove the last 64 C-terminal amino acids. This short form was unable to rescue NF-jB activation by tumor necrosis factor-a (TNF-a) when transfected in NEMO-deficient cells. Consequently, inactivation of NEMO resulted in an inhibition of the expression of antiapoptotic NF-jB-target genes coding for caspase inhibitors (cIAP-1, cIAP-2) or adaptors of the TNF receptor family. NEMO-deficient Jurkat cells transiently expressing a non-cleavable mutant of NEMO were less sensitive to TNF-a-induced apoptosis. Therefore, downmodulation of NF-jB activation via the proteolytic cleavage of NEMO could represent an amplification loop for apoptosis.

Cell Death Triggered by Yersinia enterocolitica Identifies Processing of the Proinflammatory Signal Adapter MyD88 as a General Event in the Execution of Apoptosis

“…The concerted actions of both MyD88 fragments may fine-tune the apoptotic process, which could govern specific cell death-related events in a temporary or spatial manner. Similar features have been reported for other signal transmitters of the NF-kB pathway that are cleaved by caspases, including TRAF1, receptor-interacting protein 1, IKKb, IKKg/NEMO, and NF-kB p65 (19,20,22). The processing of these molecules hampers their prosurvival functions and accelerates apoptosis.…”

“…The cleavage of MyD88 therefore may help to uncouple the engagement of these transmembrane receptors from the initiation of proinflammatory signaling in apoptotic cells. Several proinflammatory signal transmitters have been reported to be cleaved during apoptosis, such as NFkB p65, components of the IKK complex, receptor-interacting protein kinases, and TRIF itself (19)(20)(21)(22). The degradation and processing of MyD88 could complementarily reduce the sensitivity of apoptotic cells to proinflammatory stimuli and thereby counteract inflammation triggered by the TLR and IL-1R family.…”

Uncovering operational interactions in genetic networks using asynchronous Boolean dynamics

“…The anti-apoptotic pathway is based on the pioneering work of [17] and on the models developed in [17,22], and represents the Nuclear Factor κB (NFκB) signalling pathway. It is well known that the NFκB signalling pathway is responsible for activating transcription of both pro-and anti-apoptotic genes [13,23], and thus plays an important role in regulating apoptosis. The components of the NFκB pathway are as follows (in biological terminology): Nuclear Factor κB in the cytoplasm (NFκB) and in the nucleus (NFκBnuc); inhibitor of NFκB (IκB); inhibitor of IκB kinases (IKKa); inhibitor of apoptosis proteins (IAP); caspase-8 and -10-associated RING proteins (CARP); a protein associated with inhibition of complex T2 (FLIP); and a protein regulating IKK activity (A20a).…”

“…→ mark node v i as treated 10: end if 11: end for 12: end for 13: end for of (ordered) k-tuples (i 1 , . .…”

Heat stress triggers apoptosis by impairing NF-κB survival signaling in malignant B cells

“…Rapid caspase activation may be in part responsible for prolonged NF-kB inhibition, as the regulatory subunit of IKK (IKKg or NEMO) has been shown to be proteolysed by cellular caspases, leading to NF-kB inactivation. 36 We then evaluated the effect of heat shock on the level of cIAP-2 and XIAP anti-apoptotic proteins, which are direct inhibitors of caspase-3 activity and whose expression is transcriptionally regulated by NF-kB, 37 in the same samples. As shown in Figures 4a and c, cIAP-2 levels were rapidly reduced in HS-Sultan cells with kinetics similar to caspase-3 activation and PARP cleavage.…”