Search results for CASP8

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Pathway (3 results from a total of 3)

Identifier: R-HSA-5218900
Species: Homo sapiens
Cell death triggered by extrinsic stimuli via death receptors or toll-like receptors (e.g., TLR3, TLR4) may result in either apoptosis or regulated necrosis (necroptosis) (Holler N et al. 2000; Kalai M et al. 2002; Kaiser WJ and Offermann MK 2005; Yang P et al. 2007). Caspase-8 (CASP8) is a cysteine protease, which functions as a key mediator for determining which form of cell death will occur (Kalai M et al. 2002). The proteolytic activity of a fully processed, heterotetrameric form of CASP8 in human and rodent cells is required for proapoptotic signaling and also for a cleavage of kinases RIPK1 and RIPK3, while at the same time preventing RIPK1/RIPK3-dependent regulated necrosis (Juo P et al. 1998; Lin Y et al. 1999; Holler N et al. 2000; Hopkins-Donaldson S et al. 2000). A blockage of CASP8 activity in the presence of caspase inhibitors such as Z-VAD-FMK (pan-caspase inhibitor), endogenous FLIP(S) or viral FLIP-like protein was found to switch signaling to necrotic cell death (Thome M et al. 1997; Kalai M et al. 2002; Feoktistova M et al. 2011; Sawai H 2013).
Identifier: R-HSA-3371378
Species: Homo sapiens
c-FLIP proteins (CASP8 and FADD-like apoptosis regulators or c-FLICE inhibitory proteins) are death effector domain (DED)-containing proteins that are recruited to the death-inducing signaling complex (DISC) to regulate activation of caspases-8. Three out of 13 distinct spliced variants of c-FLIP had been found to be expressed at the protein level, the 26 kDa short form FLIP(S), the 24 kDa form FLIP(R), and the 55 kDa long form FLIP(L) (Irmler M et al. 1997; Shu HB et al. 1997; Srinivasula SM et al. 1997; Scaffidi C et al. 1999; Golks A et al. 2005; Haag C et al. 2011)

All c-FLIP proteins carry two DEDs at their N termini, which can bind FADD and procaspase-8. In addition to two DEDs, FLIP(L) contains a large (p20) and a small (p12) caspase-like domain without catalytic activity. FLIP(S) and FLIP(R) consist of two DEDs and a small C terminus. Depending on its level of expression FLIP(L) may function as an anti-apoptotic or pro-apoptotic factor, while FLIP(S) and FLIP(R) protect cells from apoptosis by blocking the processing of caspase-8 at the receptor level (Scaffidi C et al. 1999; Golks A et al. 2005; Toivonen HT et al. 2011; Fricker N et al. 2010).

Identifier: R-HSA-5620971
Species: Homo sapiens
Pyroptosis is a form of lytic inflammatory programmed cell death that is triggered by microbial infection or pathological stimuli, such as stroke or cancer (reviewed in Shi J et al. 2017; Man SM et al. 2017; Tang D et al. 2019; Zheng Z & Li G 2020). The process of pyroptosis protects the host from microbial infection but can also lead to pathological inflammation if overactivated. The morphologic characteristics of pyroptosis include cell swelling, rupture of the cell membrane and release of intracellular contents into the extracellular environment. Pyroptosis is also characterized by chromatin condensation, however this is not the key or universal feature of pyroptosis (reviewed in Man SM et al. 2017; Tang D et al. 2019). Pyroptosis is executed by proteins of the gasdermin family, which mediate formation of membrane pores (Liu X et al. 2016; Ding J et al. 2016; Mulvihill E et al. 2018; Broz P et al. 2020). Pyroptosis can be defined as gasdermin-mediated programmed necrotic cell death (Shi J et al. 2017; Galluzzi L et al. 2018). The gasdermin (GSDM) superfamily includes GSDMA, GSDMB, GSDMC, GSDMD, GSDME (or DFNA5) and PJVK (DFNB59) (Kovacs SB & Miao EA 2018). Each protein contains an N-terminal domain with intrinsic necrotic pore-forming activity and a C‑terminal domain reported to inhibit cell death through intramolecular domain association (Liu X et al. 2016; Ding J et al. 2016; Liu Z et al. 2018, 2019; Kuang S et al. 2017). Proteolytic cleavage in the linker connecting the N‑ and C‑terminal domains of gasdermins releases the C‑terminus, allowing the gasdermin N‑terminus to translocate to the cell membrane and oligomerize to form pores (Shi J et al. 2015; Ding J et al. 2016; Sborgi L et al. 2016; Feng S et al. 2018; Yang J et al. 2018; Mulvihill E et al. 2018). Although PJVK (DFNB59) is included to the gasdermin family, it is not known whether PJVK is cleaved and whether the full length or the N-terminal portion of PJVK is responsible for forming membrane pores. The N‑terminal fragments of GSDMs strongly bind to phosphatidylinositol phosphates and weakly to phosphatidylserine, found on the inner leaflet of the plasma membrane (Liu X et al. 2016; Ding J et al. 2016; Mulvihill E et al. 2018). Gasdermins are also able to target cardiolipin, which is often found in mitochondrial membranes and membranes of bacteria (Liu X et al. 2016; Rogers C et al. 2019). The size of the GSDMD pore is estimated to be 10–20 nm (Ding J et al. 2016; Sborgi L et al. 2016). The pore‑forming activity of GSDMs in the cell membrane facilitates the release of inflammatory molecules such as interleukin (IL)‑1β and IL‑18 (mainly in GSDMD-mediated pyroptosis), and eventually leads to cytolysis in mammalian cells, releasing additional proinflammatory cellular contents including danger signals such as high mobility group box‑1 (HMGB1) (Shi J et al. 2015; He W et al. 2015; Evavold CL et al. 2017; Semino C et al. 2018; Volchuk A et al. 2020). Pyroptosis can occur in immune cells such as macrophages, monocytes and dendritic cells and non‑immune cell types such as intestinal epithelial cells, trophoblasts and hepatocytes (Taabazuing CY et al. 2017; Li H et al. 2019; Jia C et al. 2019). GSDME can be cleaved by caspase‑3 (CASP3) to induce pyroptosis downstream of the “apoptotic” machinery (Wang Y et al. 2017; Rogers C et al. 2017), whereas GSDMD is cleaved by inflammatory CASP1, CASP4 and CASP5 in humans, and CASP1, CASP11 in mice to induce pyroptosis associated with inflammasome activation (Shi J et al. 2015; Kayagaki N et al. 2015). CASP3 cleavage of GSDMD results in its inactivation (Taabazuing et al. 2017). In mouse macrophages, CASP8 can also cleave GSDMD and cause pyroptosis when TAK1 is inhibited (Malireddi R et al. 2018; Orning P et al. 2018; Sarhan J et al. 2018), and TAK1 inhibition also leads to GSDME cleavage (Sarhan J et al. 2018). Furthermore, activated CASP8 can drive inflammasome-independent cleavage of both pro-IL-1β and GSDMD downstream of the extrinsic cell death receptor signaling pathway switching apoptotic signaling to GSDMD-dependent pyroptotic-like cell death (Donado CA et al. 2020). The cleavage and activation of GSDMD in neutrophils is mediated by neutrophil elastase (NE or ELANE), which is released from azurophil granules into the cytosol during neutrophil extracellular trap (NET) formation (Kambara H et al. 2018). Further, granzyme A (GZMA) released from cytotoxic T lymphocytes and natural killer (NK) cells specifically target GSDMB for interdomain cleavage to activate GSDMB-dependent pyroptosis in target tumor cells (Zhou Z et al. 2020). Similarly, granzyme B (GZMB) released from cytotoxic T lymphocytes and natural killer (NK) cells, can induce GSDME‑dependent lytic cell death in tumor targets via the CASP3‑mediated cleavage of GSDME (Zhang Z et al. 2020).

This Reactome module describes pyroptotic activities of GSDMD and GSDME. While the N‑terminal domains of mammalian GSDMA, GSDMB, and GSDMC also have the ability to form pores (Feng S et al. 2018; Ruan J et al. 2018), their functions in the induction of pyroptosis, secretion of proinflammatory cytokines or in bactericidal activity in host remain to be studied and are not covered by this Reactome module.

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