Geserick P, Hupe M, Moulin M et al.Cellular IAPs inhibit a cryptic CD95-induced cell death by limiting RIP1 kinase recruitment. J Cell Biol 187:1037-1054

Department of Dermatology and Venereology, Otto-von-Guericke University Magdeburg, Germany.
The Journal of Cell Biology (Impact Factor: 9.83). 12/2009; 187(7):1037-54. DOI: 10.1083/jcb.200904158
Source: PubMed


A role for cellular inhibitors of apoptosis (IAPs [cIAPs]) in preventing CD95 death has been suspected but not previously explained mechanistically. In this study, we find that the loss of cIAPs leads to a dramatic sensitization to CD95 ligand (CD95L) killing. Surprisingly, this form of cell death can only be blocked by a combination of RIP1 (receptor-interacting protein 1) kinase and caspase inhibitors. Consistently, we detect a large increase in RIP1 levels in the CD95 death-inducing signaling complex (DISC) and in a secondary cytoplasmic complex (complex II) in the presence of IAP antagonists and loss of RIP1-protected cells from CD95L/IAP antagonist-induced death. Cells resistant to CD95L/IAP antagonist treatment could be sensitized by short hairpin RNA-mediated knockdown of cellular FLICE-inhibitory protein (cFLIP). However, only cFLIP(L) and not cFLIP(S) interfered with RIP1 recruitment to the DISC and complex II and protected cells from death. These results demonstrate a fundamental role for RIP1 in CD95 signaling and provide support for a physiological role of caspase-independent death receptor-mediated cell death.

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    • "Only prior addition of pan-caspase inhibitor Z-VAD-FMK and caspase-8 inhibitor Z-IETD-FMK reduced TRAIL-dependent cIAP1 degradation but not treatment with the lysosomal inhibitor bafilomycin A1 or the proteasomal inhibitor MG132 (Supplementary Fig S2D). Accordingly, depleting cIAP1 by siRNA treatment increased caspase activity after TRAIL stimulation (Fig 2E), presumably due to the formation of the previously described ‘ripoptosome’ complex (Geserick et al, 2009; Tenev et al, 2011). To test the involvement of cIAP1 in our sensitivity phenotype, we induced overexpression of cIAP1 after FAT1 depletion and TRAIL stimulation. "
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    ABSTRACT: The extrinsic apoptosis pathway is initiated by binding of death ligands to death receptors resulting in the formation of the death-inducing signaling complex (DISC). Activation of procaspase-8 within the DISC and its release from the signaling complex is required for processing executor caspases and commiting cell death. Here, we report that the atypical cadherin FAT1 interacts with caspase-8 preventing the association of caspase-8 with the DISC. We identified FAT1 in a genome-wide siRNA screen for synthetic lethal interactions with death receptor-mediated apoptosis. Knockdown of FAT1 sensitized established and patient-derived glioblastoma cell lines for apoptosis transduced by cell death ligands. Depletion of FAT1 resulted in enhanced procaspase-8 recruitment to the DISC and increased formation of caspase-8 containing secondary signaling complexes. In addition, FAT1 knockout cell lines generated by CRISPR/Cas9-mediated genome engineering were more susceptible for death receptor-mediated apoptosis. Our findings provide evidence for a mechanism to control caspase-8-dependent cell death by the atypical cadherin FAT1. These results contribute towards the understanding of effector caspase regulation in physiological conditions.
    The EMBO Journal 02/2014; 33(3). DOI:10.1002/embj.201385686 · 10.43 Impact Factor
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    • "cFLIP inhibits active caspase-8 release from the DISC, thereby suppressing TRAIL-or CD95L- induced apoptosis in melanoma (Geserick et al., 2008). In addition, suppression of the caspase-3/caspase-9 inhibitor XIAP by mitochondrial smac or small-molecule smac mimetics (IAP antagonists) also promotes DRmediated cell death (Geserick et al., 2009). "
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    ABSTRACT: BRAF inhibition has been an instant, although short-lasting, success in BRAF-mutated melanoma treatment. Novel data by Berger et al. now suggest that BRAF-inhibitor-mediated "priming to death" facilitates tumor necrosis factor-related apoptosis-inducing ligand-mediated apoptosis. We give an overview about the importance of the crosstalk of extrinsic and mitochondrial apoptotic signaling and propose other combination therapies that may prevent or overcome secondary resistance in melanoma.
    Journal of Investigative Dermatology 02/2014; 134(2):315-8. DOI:10.1038/jid.2013.348 · 7.22 Impact Factor
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    • "Furthermore, intracellular localization of caspase- 8's activity within or outside of the signaling platforms, as well as its proteasomal degradation-dependent half-life in the cytoplasm (Gonzalvez et al., 2012), is of major importance for the differential regulation of apoptosis versus necroptosis. These aspects of caspase-8 activity are critically regulated by cFLIP and its different isoforms (Feoktistova et al., 2011; Geserick et al., 2009). Thus, both apoptosis and necroptosis signaling pathways are closely intertwined in a number of caspase-8 and cFLIP isoform-containing intracellular death platforms that are involved in the outcome of cellular stress signaling in a number of organs, including the skin. "
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    ABSTRACT: FADD, caspase-8, and cFLIP regulate the outcome of cell death signaling. Mice that constitutively lack these molecules die at an early embryonic age, whereas tissue-specific constitutive deletion of FADD or caspase-8 results in inflammatory skin disease caused by increased necroptosis. The function of cFLIP in the skin in vivo is unknown. In contrast to tissue-specific caspase-8 knockout, we show that mice constitutively lacking cFLIP in the epidermis die around embryonic days 10 and 11. When cFLIP expression was abrogated in adult skin of cFLIP(fl/fl)-K14CreER(tam) mice, severe inflammation of the skin with concomitant caspase activation and apoptotic, but not necroptotic, cell death developed. Apoptosis was dependent of autocrine tumor necrosis factor production triggered by loss of cFLIP. In addition, epidermal cFLIP protein was lost in patients with severe drug reactions associated with epidermal apoptosis. Our data demonstrate the importance of cFLIP for the integrity of the epidermis and for silencing of spontaneous skin inflammation. VIDEO ABSTRACT:
    Cell Reports 10/2013; 5(2). DOI:10.1016/j.celrep.2013.09.035 · 8.36 Impact Factor
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