Activity of caspase-8 determines plasticity between cell death pathways

The receptor-interacting protein kinase 1 (RIPK1) is recognized as a master upstream regulator that controls cell survival and inflammatory signaling as well as multiple cell death pathways, including apoptosis and necroptosis. The activation of RIPK1 kinase is extensively modulated by ubiquitination and phosphorylation, which are mediated by multiple factors that also control the activation of the NF-κB pathway. We discuss current findings regarding the genetic modulation of RIPK1 that controls its activation and interaction with downstream mediators, such as caspase-8 and RIPK3, to promote apoptosis and necroptosis. We also address genetic autoinflammatory human conditions that involve abnormal activation of RIPK1. Leveraging these new genetic and mechanistic insights, we postulate how an improved understanding of RIPK1 biology may support the development of therapeutics that target RIPK1 for the treatment of human inflammatory and neurodegenerative diseases.

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Mouse cytomegalovirus M36 and M45 death suppressors cooperate to prevent inflammation resulting from antiviral programmed cell death pathways

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1616829114 ◽

2017 ◽

Vol 114 (13) ◽

pp. E2786-E2795 ◽

Cited By ~ 22

Author(s):

Lisa P. Daley-Bauer ◽

Linda Roback ◽

Lynsey N. Crosby ◽

A. Louise McCormick ◽

Yanjun Feng ◽

...

Keyword(s):

Cell Death ◽

Programmed Cell Death ◽

Double Mutant ◽

Kinase Domain ◽

Murine Cytomegalovirus ◽

Caspase 8 ◽

Interacting Protein ◽

Antiviral Responses ◽

Cell Death Pathways ◽

Infected Cells

The complex interplay between caspase-8 and receptor-interacting protein (RIP) kinase RIP 3 (RIPK3) driving extrinsic apoptosis and necroptosis is not fully understood. Murine cytomegalovirus triggers both apoptosis and necroptosis in infected cells; however, encoded inhibitors of caspase-8 activity (M36) and RIP3 signaling (M45) suppress these antiviral responses. Here, we report that this virus activates caspase-8 in macrophages to trigger apoptosis that gives rise to secondary necroptosis. Infection with double-mutant ΔM36/M45mutRHIM virus reveals a signaling pattern in which caspase-8 activates caspase-3 to drive apoptosis with subsequent RIP3-dependent activation of mixed lineage kinase domain-like (MLKL) leading to necroptosis. This combined cell death signaling is highly inflammatory, greater than either apoptosis induced by ΔM36 or necroptosis induced by M45mutRHIM virus. IL-6 production by macrophages is dramatically increased during double-mutant virus infection and correlates with faster antiviral responses in the host. Collaboratively, M36 and M45 target caspase-8 and RIP3 pathways together to suppress this proinflammatory cell death. This study reveals the effect of antiviral programmed cell death pathways on inflammation, shows that caspase-8 activation may go hand-in-hand with necroptosis in macrophages, and revises current understanding of independent and collaborative functions of M36 and M45 in blocking apoptotic and necroptotic cell death responses.

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Multiple Autonomous Cell Death Suppression Strategies Ensure Cytomegalovirus Fitness

Viruses ◽

10.3390/v13091707 ◽

2021 ◽

Vol 13 (9) ◽

pp. 1707

Author(s):

Pratyusha Mandal ◽

Lynsey N. Nagrani ◽

Liliana Hernandez ◽

Anita Louise McCormick ◽

Christopher P. Dillon ◽

...

Keyword(s):

Cell Death ◽

Murine Cytomegalovirus ◽

Mammalian Host ◽

Caspase 8 ◽

Intrinsic Apoptosis ◽

Pathogen Invasion ◽

Cell Death Pathways ◽

Viral Inhibitor ◽

Extrinsic Apoptosis ◽

Infected Cells

Programmed cell death pathways eliminate infected cells and regulate infection-associated inflammation during pathogen invasion. Cytomegaloviruses encode several distinct suppressors that block intrinsic apoptosis, extrinsic apoptosis, and necroptosis, pathways that impact pathogenesis of this ubiquitous herpesvirus. Here, we expanded the understanding of three cell autonomous suppression mechanisms on which murine cytomegalovirus relies: (i) M38.5-encoded viral mitochondrial inhibitor of apoptosis (vMIA), a BAX suppressor that functions in concert with M41.1-encoded viral inhibitor of BAK oligomerization (vIBO), (ii) M36-encoded viral inhibitor of caspase-8 activation (vICA), and (iii) M45-encoded viral inhibitor of RIP/RHIM activation (vIRA). Following infection of bone marrow-derived macrophages, the virus initially deflected receptor-interacting protein kinase (RIPK)3-dependent necroptosis, the most potent of the three cell death pathways. This process remained independent of caspase-8, although suppression of this apoptotic protease enhances necroptosis in most cell types. Second, the virus deflected TNF-mediated extrinsic apoptosis, a pathway dependent on autocrine TNF production by macrophages that proceeds independently of mitochondrial death machinery or RIPK3. Third, cytomegalovirus deflected BCL-2 family protein-dependent mitochondrial cell death through combined TNF-dependent and -independent signaling even in the absence of RIPK1, RIPK3, and caspase-8. Furthermore, each of these cell death pathways dictated a distinct pattern of cytokine and chemokine activation. Therefore, cytomegalovirus employs sequential, non-redundant suppression strategies to specifically modulate the timing and execution of necroptosis, extrinsic apoptosis, and intrinsic apoptosis within infected cells to orchestrate virus control and infection-dependent inflammation. Virus-encoded death suppressors together hold control over an intricate network that upends host defense and supports pathogenesis in the intact mammalian host.

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DOP86 An IFN-STAT1-MLKL axis drives programmed necrosis of Paneth cells in Crohn’s ileitis

Journal of Crohn s and Colitis ◽

10.1093/ecco-jcc/jjz203.125 ◽

2020 ◽

Vol 14 (Supplement_1) ◽

pp. S125-S126

Author(s):

L HARTMANN ◽

B Siegmund ◽

C Weidinger ◽

C Becker ◽

M F Neurath ◽

...

Keyword(s):

Cell Death ◽

Intestinal Inflammation ◽

Paneth Cell ◽

Signalling Pathways ◽

Caspase 8 ◽

Programmed Necrosis ◽

Cell Death Pathways ◽

Small Intestinal

Abstract Background Interferons (IFNs) are immune-modulatory cytokines expressed by epithelial and mucosal cells in response to viral and bacterial infection. Just recently, we discovered a correlation between IFN-λ expression and disease activity, including small intestinal inflammation and Paneth cell dysfunction, in human Crohn’s disease patients. On a molecular level, we uncovered that IFN-λ mediates epithelial cell death, in particular, Paneth cell death by a programmed necrosis, dependent on STAT1 activation and controlled by caspase-8. These results suggested that IFN-λ can be considered as a pathogenic cytokine in Crohn′s ileitis and should be considered as a new and promising target for future therapeutic intervention for this particular subtype of IBD. Our central question is now by which pathways interferon-regulated programmed necrosis of epithelial cells contributes to intestinal inflammation and how these mechanisms could be targeted for future therapeutic intervention. Methods We use a mouse model for Crohn’s Disease like inflammation and Paneth cell death that has a specific deletion of Caspase-8 in intestinal epithelial cells (Casp8∆IEC). We stimulate small intestinal organoids derived from Casp8∆IEC mice with IFNs in vitro and we overexpress IFN-λ in these mice in vivo by hydrodynamic tail vein injection of an IFN-λ expression vector. Furthermore, we use JAK-inhibitors to impede pharmacologically cell death pathways in the pathogenesis of intestinal inflammation in vitro and in vivo. Results We uncovered that gene expression of the cell death mediators Mlkl and Caspase-8 is dependent on IFN-λ-mediated JAK-STAT1 signalling. The non-specific pan JAK-inhibitor Tofacitinib is able to attenuate gene expression of Mlkl and Caspase-8 in vitro as well as in vivo. It prevents non-apoptotic as well as apoptotic cell death of small intestinal organoids stimulated with IFN-λ and is sufficient to prevent small intestinal tissue destruction in Casp8∆IEC mice challenged with IFN-λ. Additionally, we use the selective JAK1-inhibitor Filgotinib to limit the targeted JAK-STAT signalling pathways to only JAK1-STAT1 signalling and thus reduce side effects of the inhibitor on other signalling pathways. This had a similar effect as Tofacitinib suggesting that IFN controls MLKL-mediated cell death via JAK1. Conclusion In summary, our results indicate that targeting IFN-λ-mediated JAK-STAT1 signalling by the small-molecules Tofacitinib and Filgotinib impedes induction of Mlkl and Caspase-8-mediated cell death pathways. Therefore, JAK1 inhibitors such as Filgotinib might represent a promising novel therapy that may be sufficient to achieve efficacy particularly in Crohn′s ileitis patients who display elevated IFN-l serum levels.

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Targeting Caspase 8: Using Structural and Ligand-Based Approaches to Identify Potential Leads for the Treatment of Multi-Neurodegenerative Diseases

Molecules ◽

10.3390/molecules24091827 ◽

2019 ◽

Vol 24 (9) ◽

pp. 1827 ◽

Cited By ~ 1

Author(s):

Khurshid Ahmad ◽

Vishal M. Balaramnavar ◽

Navaneet Chaturvedi ◽

Saif Khan ◽

Shafiul Haque ◽

...

Keyword(s):

Cell Death ◽

Neurodegenerative Diseases ◽

Structural Information ◽

Apoptotic Cell ◽

Critical Role ◽

Caspase 8 ◽

Cell Death Pathways ◽

Cell Death Pathway ◽

Zinc Database ◽

Dynamics Simulations

Caspase 8 is a central player in the apoptotic cell death pathway and is also essential for cytokine processing. The critical role of this protease in cell death pathways has generated research interest because its activation has also been linked with neural cell death. Thus, blocking the activity of caspase 8 is considered a potential therapy for neurodegenerative diseases. To extend the repertoire of caspase 8 inhibitors, we employed several computational approaches to identify potential caspase 8 inhibitors. Based on the structural information of reported inhibitors, we designed several individual and consensus pharmacophore models and then screened the ZINC database, which contains 105,480 compounds. Screening generated 5332 candidates, but after applying stringent criteria only two candidate compounds, ZINC19370490 and ZINC04534268, were evaluated by molecular dynamics simulations and subjected to Molecular Mechanics/Poisson Boltzmann Surface Area (MM-PBSA) analysis. These compounds were stable throughout simulations and interacted with targeted protein by forming hydrogen and van der Waal bonds. MM-PBSA analysis showed that these compounds were comparable or better than reported caspase 8 inhibitors. Furthermore, their physical properties were found to be acceptable, and they are non-toxic according to the ADMET online server. We suggest that the inhibitory efficacies of ZINC19370490 and ZINC04534268 be subjected to experimental validation.

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A20 protects endothelial cells from TNF-, Fas-, and NK-mediated cell death by inhibiting caspase 8 activation

Blood ◽

10.1182/blood-2003-02-0635 ◽

2004 ◽

Vol 104 (8) ◽

pp. 2376-2384 ◽

Cited By ~ 98

Author(s):

Soizic Daniel ◽

Maria B. Arvelo ◽

Virendra I. Patel ◽

Christopher R. Longo ◽

Gautam Shrikhande ◽

...

Keyword(s):

Endothelial Cells ◽

Cell Death ◽

Killer Cell ◽

Nuclear Factor Κb ◽

Caspase 8 ◽

Apoptotic Pathway ◽

Cell Death Pathways ◽

Executioner Caspases ◽

First Time ◽

Necrosis Factor

Abstract A20 is a stress response gene in endothelial cells (ECs). A20 serves a dual cytoprotective function, protecting from tumor necrosis factor (TNF)–mediated apoptosis and inhibiting inflammation via blockade of the transcription factor nuclear factor–κB (NF-κB). In this study, we evaluated the molecular basis of the cytoprotective function of A20 in EC cultures and questioned whether its protective effect extends beyond TNF to other apoptotic and necrotic stimuli. Our data demonstrate that A20 targets the TNF apoptotic pathway by inhibiting proteolytic cleavage of apical caspases 8 and 2, executioner caspases 3 and 6, Bid cleavage, and release of cytochrome c, thus preserving mitochondrion integrity. A20 also protects from Fas/CD95 and significantly blunts natural killer cell–mediated EC apoptosis by inhibiting caspase 8 activation. In addition to protecting ECs from apoptotic stimuli, A20 safeguards ECs from complement-mediated necrosis. These data demonstrate, for the first time, that the cytoprotective effect of A20 in ECs is not limited to TNF-triggered apoptosis. Rather, A20 affords broad EC protective functions by effectively shutting down cell death pathways initiated by inflammatory and immune offenders.

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The Human Cytomegalovirus UL36 Gene Controls Caspase-Dependent and -Independent Cell Death Programs Activated by Infection of Monocytes Differentiating to Macrophages

Journal of Virology ◽

10.1128/jvi.01345-09 ◽

2010 ◽

Vol 84 (10) ◽

pp. 5108-5123 ◽

Cited By ~ 44

Author(s):

A. Louise McCormick ◽

Linda Roback ◽

Devon Livingston-Rosanoff ◽

Courtney St. Clair

Keyword(s):

Cell Death ◽

Human Cytomegalovirus ◽

Caspase 8 ◽

Specific Cell ◽

Macrophage Differentiation ◽

Antiviral Responses ◽

Cell Death Pathways ◽

Cell Death Pathway ◽

The Impact ◽

Late Stages

ABSTRACT The cellular protease caspase-8 activates extrinsic apoptosis and also functions to promote monocyte-to-macrophage differentiation. Differentiation-induced alterations to antiviral caspase-8-dependent cell death pathways are unclear. Here, we show THP-1 monocyte-to-macrophage differentiation alters the specific cell death pathways activated in response to human cytomegalovirus (HCMV) infection. Employing viruses with mutations in UL36, the gene that encodes the viral inhibitor of caspase-8 activation (vICA), our data indicate that both caspase-dependent and -independent death pathways are activated in response to infection. Activation of caspase-dependent and -independent cell death responses restricted growth of vICA-deficient viruses, and vICA/pUL36 inhibited either response. Thus, these studies also reveal that the UL36 gene controls a caspase-independent cell death pathway. The impact of caspases on control of antiviral responses differed at early and late stages of macrophage differentiation. Early in differentiation, vICA-deficient virus-induced cell death was dependent on caspases and inhibited by the pan-caspase inhibitor z-VAD(OMe)-fluoromethyl ketone. In contrast, virus-induced death at late times of differentiation was caspase independent. Additional unlabeled and fluorescent inhibitors indicated that caspase-8 promoted death from within infected cells at early but not late stages of differentiation. These data highlight the multifunctional role of vICA/pUL36 as HCMV encounters various antiviral responses during macrophage differentiation.

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Sulforaphane reduction of testicular apoptotic cell death in diabetic mice is associated with the upregulation of Nrf2 expression and function

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00702.2013 ◽

2014 ◽

Vol 307 (1) ◽

pp. E14-E23 ◽

Cited By ~ 51

Author(s):

Yonggang Wang ◽

Zhiguo Zhang ◽

Weiying Guo ◽

Weixia Sun ◽

Xiao Miao ◽

...

Keyword(s):

Cell Death ◽

Apoptotic Cell ◽

Normal Diet ◽

Caspase 8 ◽

Testicular Cell ◽

Cell Death Pathways ◽

Induce Insulin Resistance ◽

And Function ◽

Nrf2 Expression

Diabetes-induced testicular cell death is due predominantly to oxidative stress. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is an important transcription factor in controlling the antioxidative system and is inducible by sulforaphane (SFN). To test whether SFN prevents diabetes-induced testicular cell death, an insulin-defective stage of type 2 diabetes (IDS-T2DM) was induced in mice. This was accomplished by feeding them a high-fat diet (HFD) for 3 mo to induce insulin resistance and then giving one intraperitoneal injection of streptozotocin to induce hyperglycemia while age-matched control mice were fed a normal diet (ND). IDS-T2DM and ND-fed control mice were then further subdivided into those with or without 4-mo SFN treatment. IDS-T2DM induced significant increases in testicular cell death presumably through receptor and mitochondrial pathways, shown by increased ratio of Bax/Bcl2 expression and cleavage of caspase-3 and caspase-8 without significant change of endoplasmic reticulum stress. Diabetes also significantly increased testicular oxidative damage and inflammation. All of these diabetic effects were significantly prevented by SFN treatment with upregulated Nrf2 expression. These results suggest that IDS-T2DM induces testicular cell death presumably through caspase-8 activation and mitochondria-mediated cell death pathways and also by significantly downregulating testicular Nrf2 expression and function. SFN upregulates testicular Nrf2 expression and its target antioxidant expression, which was associated with significant protection of the testis from IDS-T2DM-induced germ cell death.

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