scholarly journals Activation of caspases-8 and -10 by FLIPL

2004 ◽  
Vol 382 (2) ◽  
pp. 651-657 ◽  
Author(s):  
Kelly M. BOATRIGHT ◽  
Cristina DEIS ◽  
Jean-Bernard DENAULT ◽  
Daniel P. SUTHERLIN ◽  
Guy S. SALVESEN
Keyword(s):  
Active Form ◽  
Caspase 8 ◽  
Death Domain ◽  
Caspase Activation ◽  
Inhibitory Protein ◽  
Long Form ◽  
Initiator Caspases ◽  
Domain Protein ◽  
Enzyme Molecules

The first step in caspase activation is transition of the latent zymogen to an active form. For the initiator caspases, this occurs through dimerization of monomeric zymogens at an activating complex. Recent studies have suggested that FLIPL [FLICE-like inhibitory protein, long form; FLICE is FADD (Fas-associated death domain protein)-like interleukin-1β-converting enzyme], previously thought to act solely as an inhibitor of caspase-8 activation, can under certain circumstances function to enhance caspase activation. Using an in vitro induced-proximity assay, we demonstrate that activation of caspases-8 and -10 occurs independently of cleavage of either the caspase or FLIPL. FLIPL activates caspase-8 by forming heterodimeric enzyme molecules with substrate specificity and catalytic activity indistinguishable from those of caspase-8 homodimers. Significantly, the barrier for heterodimer formation is lower than that for homodimer formation, suggesting that FLIPL is a more potent activator of caspase-8 than is caspase-8 itself.

scholarly journals The flip side of FLIP

2004 ◽  
Vol 382 (2) ◽  
Author(s):  
Marcus E. PETER
Keyword(s):  
Mammalian Cells ◽  
Caspase 8 ◽  
Death Domain ◽  
Extrinsic Pathway ◽  
Inhibitory Protein ◽  
Apoptosis Pathway ◽  
Surface Receptors ◽  
Biochemical Journal ◽  
Initiator Caspases ◽  
Extrinsic Apoptosis

Two major pathways regulate apoptosis induction in mammalian cells. In the extrinsic pathway, apoptosis is induced through specialized surface receptors, whereas in the intrinsic pathway, apoptosis is induced from within the cell, mainly through activation of mitochondria. Shortly after the major mediators of the extrinsic apoptosis pathway, the initiator caspases-8 and -10, were identified, c-FLIP [FLICE-like inhibitory protein; FLICE is FADD (Fas-associated death domain protein)-like interleukin-1β-converting enzyme], a catalytically inactive caspase-8/-10 homologue, was reported. Whether this structure acts as an inhibitor or promoter of the extrinsic apoptosis pathway has been the subject of much debate. In this issue of the Biochemical Journal, Boatright et al. provide further evidence for the long splice form of c-FLIP (c-FLIPL) being an activator of caspase-8/-10, and demonstrate that the resulting heterodimer is enzymically active with a substrate specificity identical with that of the caspase-8 homodimer. Our understanding of the regulators of the extrinsic apoptosis signalling pathway biochemically may provide the means to design drugs to correct the imbalance between apoptosis and proliferation, as found in many diseases.

scholarly journals Hepatitis C Virus Core Protein Inhibits Tumor Necrosis Factor Alpha-Mediated Apoptosis by a Protective Effect Involving Cellular FLICE Inhibitory Protein

2006 ◽  
Vol 80 (9) ◽  
pp. 4372-4379 ◽  
Author(s):  
Kousuke Saito ◽  
Keith Meyer ◽  
Rebecca Warner ◽  
Arnab Basu ◽  
Ratna B. Ray ◽  
...  
Keyword(s):  
Tumor Necrosis ◽  
Core Protein ◽  
Death Domain ◽  
Inhibitory Protein ◽  
Necrosis Factor Alpha ◽  
Hcv Core Protein ◽  
Tnf Α ◽  
Factor Alpha ◽  
Domain Protein ◽  
Necrosis Factor

ABSTRACT We have previously shown that hepatitis C virus (HCV) core protein modulates multiple cellular processes, including those that inhibit tumor necrosis factor alpha (TNF-α)-mediated apoptosis. In this study, we have investigated the signaling mechanism for inhibition of TNF-α-mediated apoptosis in human hepatoma (HepG2) cells expressing core protein alone or in context with other HCV proteins. Activation of caspase-3 and the cleavage of DNA repair enzyme poly(ADP-ribose) polymerase were inhibited upon TNF-α exposure in HCV core protein-expressing HepG2 cells. In vivo protein-protein interaction studies displayed an association between TNF receptor 1 (TNFR1) and TNFR1-associated death domain protein (TRADD), suggesting that the core protein does not perturb this interaction. A coimmunoprecipitation assay also suggested that HCV core protein does not interfere with the TRADD-Fas-associated death domain protein (FADD)-procaspase-8 interaction. Further studies indicated that HCV core protein expression inhibits caspase-8 activation by sustaining the expression of cellular FLICE (FADD-like interleukin-1β-converting enzyme)-like inhibitory protein (c-FLIP). Similar observations were also noted upon expression of core protein in context to other HCV proteins expressed from HCV full-length plasmid DNA or a replicon. A decrease in endogenous c-FLIP by specific small interfering RNA induced TNF-α-mediated apoptotic cell death and caspase-8 activation. Taken together, our results suggested that the TNF-α-induced apoptotic pathway is inhibited by a sustained c-FLIP expression associated with the expression of HCV core protein, which may play a role in HCV-mediated pathogenesis.

scholarly journals p38-mediated Regulation of an Fas-associated Death Domain Protein-independent Pathway Leading to Caspase-8 Activation during TGFβ-induced Apoptosis in Human Burkitt Lymphoma B Cells BL41

2001 ◽  
Vol 12 (10) ◽  
pp. 3139-3151 ◽  
Author(s):  
Nicolas Schrantz ◽  
Marie-Françoise Bourgeade ◽  
Shahul Mouhamad ◽  
Gérald Leca ◽  
Surendra Sharma ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Mitochondrial Membrane Potential ◽  
Mitochondrial Membrane ◽  
Transforming Growth Factor ◽  
Dominant Negative ◽  
Dominant Negative Mutant ◽  
Caspase 8 ◽  
Death Domain ◽  
Apoptotic Pathway ◽  
Domain Protein

On binding to its receptor, transforming growth factor β (TGFβ) induces apoptosis in a variety of cells, including human B lymphocytes. We have previously reported that TGFβ-mediated apoptosis is caspase-dependent and associated with activation of caspase-3. We show here that caspase-8 inhibitors strongly decrease TGFβ-mediated apoptosis in BL41 Burkitt's lymphoma cells. These inhibitors act upstream of the mitochondria because they inhibited the loss of mitochondrial membrane potential observed in TGFβ-treated cells. TGFβ induced caspase-8 activation in these cells as shown by the cleavage of specific substrates, including Bid, and the appearance of cleaved fragments of caspase-8. Our data show that TGFβ induces an apoptotic pathway involving sequential caspase-8 activation, loss of mitochondrial membrane potential, and caspase-9 and -3 activation. Caspase-8 activation was Fas-associated death domain protein (FADD)-independent because cells expressing a dominant negative mutant of FADD were still sensitive to TGFβ-induced caspase-8 activation and apoptosis. This FADD-independent pathway of caspase-8 activation is regulated by p38. Indeed, TGFβ-induced activation of p38 and two different inhibitors specific for this mitogen-activated protein kinase pathway (SB203580 and PD169316) prevented TGFβ-mediated caspase-8 activation as well as the loss of mitochondrial membrane potential and apoptosis. Overall, our data show that p38 activation by TGFβ induced an apoptotic pathway via FADD-independent activation of caspase-8.

scholarly journals Stimulation of Toll-like receptor 3 and 4 induces interleukin-1β maturation by caspase-8

2008 ◽  
Vol 205 (9) ◽  
pp. 1967-1973 ◽  
Author(s):  
Jonathan Maelfait ◽  
Elisabeth Vercammen ◽  
Sophie Janssens ◽  
Peter Schotte ◽  
Mira Haegman ◽  
...  
Keyword(s):  
Active Form ◽  
Biologically Active ◽  
Poly I:C ◽  
Caspase 8 ◽  
Caspase 1 ◽  
Polyinosinic:Polycytidylic Acid ◽  
Membrane Bound ◽  
Acute And Chronic Inflammation ◽  
Stimulation Of

The cytokine interleukin (IL)-1β is a key mediator of the inflammatory response and has been implicated in the pathophysiology of acute and chronic inflammation. IL-1β is synthesized in response to many stimuli as an inactive pro–IL-1β precursor protein that is further processed by caspase-1 into mature IL-1β, which is the secreted biologically active form of the cytokine. Although stimulation of membrane-bound Toll-like receptors (TLRs) up-regulates pro–IL-1β expression, activation of caspase-1 is believed to be mainly initiated by cytosolic Nod-like receptors. In this study, we show that polyinosinic:polycytidylic acid (poly[I:C]) and lipopolysaccharide stimulation of macrophages induces pro–IL-1β processing via a Toll/IL-1R domain–containing adaptor-inducing interferon-β–dependent signaling pathway that is initiated by TLR3 and TLR4, respectively. Ribonucleic acid interference (RNAi)–mediated knockdown of the intracellular receptors NALP3 or MDA5 did not affect poly(I:C)-induced pro–IL-1β processing. Surprisingly, poly(I:C)- and LPS-induced pro–IL-1β processing still occurred in caspase-1–deficient cells. In contrast, pro–IL-1β processing was inhibited by caspase-8 peptide inhibitors, CrmA or vFLIP expression, and caspase-8 knockdown via RNAi, indicating an essential role for caspase-8. Moreover, recombinant caspase-8 was able to cleave pro–IL-1β in vitro at exactly the same site as caspase-1. These results implicate a novel role for caspase-8 in the production of biologically active IL-1β in response to TLR3 and TLR4 stimulation.

scholarly journals Distinct Roles of the Antiapoptotic Effectors NleB and NleF from Enteropathogenic Escherichia coli

2017 ◽  
Vol 85 (4) ◽  
Author(s):  
Georgina L. Pollock ◽  
Clare V. L. Oates ◽  
Cristina Giogha ◽  
Tania Wong Fok Lung ◽  
Sze Ying Ong ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Fas Ligand ◽  
Death Receptor ◽  
Effector Proteins ◽  
Host Cells ◽  
Caspase 8 ◽  
Death Domain ◽  
Content Type ◽  
Fas Signaling

ABSTRACT During infection, enteropathogenic Escherichia coli (EPEC) translocates effector proteins directly into the cytosol of infected enterocytes using a type III secretion system (T3SS). Once inside the host cell, these effector proteins subvert various immune signaling pathways, including death receptor-induced apoptosis. One such effector protein is the non-locus of enterocyte effacement (LEE)-encoded effector NleB1, which inhibits extrinsic apoptotic signaling via the FAS death receptor. NleB1 transfers a single N-acetylglucosamine (GlcNAc) residue to Arg117 in the death domain of Fas-associated protein with death domain (FADD) and inhibits FAS ligand (FasL)-stimulated caspase-8 cleavage. Another effector secreted by the T3SS is NleF. Previous studies have shown that NleF binds to and inhibits the activity of caspase-4, -8, and -9 in vitro. Here, we investigated a role for NleF in the inhibition of FAS signaling and apoptosis during EPEC infection. We show that NleF prevents the cleavage of caspase-8, caspase-3, and receptor-interacting serine/threonine protein kinase 1 (RIPK1) in response to FasL stimulation. When translocated into host cells by the T3SS or expressed ectopically, NleF also blocked FasL-induced cell death. Using the EPEC-like mouse pathogen Citrobacter rodentium, we found that NleB but not NleF contributed to colonization of mice in the intestine. Hence, despite their shared ability to block FasL/FAS signaling, NleB and NleF have distinct roles during infection.

scholarly journals Synergistic interactions between interferon-γ and TRAIL modulate c-FLIP in endothelial cells, mediating their lineage-specific sensitivity to thrombotic thrombocytopenic purpura plasma–associated apoptosis

Blood ◽  
2008 ◽  
Vol 112 (2) ◽  
pp. 340-349 ◽  
Author(s):  
Radu Stefanescu ◽  
Dustin Bassett ◽  
Rozbeh Modarresi ◽  
Francisco Santiago ◽  
Mohamad Fakruddin ◽  
...  
Keyword(s):  
Thrombotic Thrombocytopenic Purpura ◽  
Interferon Γ ◽  
Microvascular Endothelial Cell ◽  
Caspase 8 ◽  
Inhibitory Protein ◽  
Thrombocytopenic Purpura ◽  
Ifn Γ ◽  
Interfering Rna

Abstract Microvascular endothelial cell (MVEC) injury coupled to progression of platelet microthrombi facilitated by ADAMTS13 deficiency is characteristic of idiopathic and HIV-linked thrombotic thrombocytopenic purpura (TTP). Cytokines capable of inducing MVEC apoptosis in vitro are up-regulated in both TTP and HIV infection. However, the concentrations of these cytokines required to elicit EC apoptosis in vitro are 2- to 3-log–fold greater than present in patient plasmas. We report that clinically relevant levels of tumor necrosis factor–related apoptosis-inducing ligand (TRAIL) and interferon (IFN)–γ act in synergy to induce apoptosis in dermal MVECs, but have no effect on large-vessel ECs or pulmonary MVECs. This reflects the tissue distribution of TTP lesions in vivo. Sensitivity to TTP plasma or TRAIL plus IFN-γ is paralleled by enhanced ubiquitination of the caspase-8 regulator cellular FLICE-like inhibitory protein (c-FLIP), targeting it for proteasome degradation. c-FLIP silencing with anti-FLIP short interfering RNA (siRNA) in pulmonary MVECs rendered them susceptible to TTP plasma– and cytokine-mediated apoptosis, while up-regulation of c-FLIP by gene transfer partially protected dermal MVECs from such injury. TTP plasma–mediated apoptosis appears to involve cytokine-induced acceleration of c-FLIP degradation, sensitizing cells to TRAIL-mediated caspase-8 activation and cell death. Suppression of TRAIL or modulation of immunoproteasome activity may have therapeutic relevance in TTP.

scholarly journals FLIPL induces caspase 8 activity in the absence of interdomain caspase 8 cleavage and alters substrate specificity

2011 ◽  
Vol 433 (3) ◽  
pp. 447-457 ◽  
Author(s):  
Cristina Pop ◽  
Andrew Oberst ◽  
Marcin Drag ◽  
Bram J. Van Raam ◽  
Stefan J. Riedl ◽  
...  
Keyword(s):  
Catalytic Domain ◽  
Functional Divergence ◽  
Caspase 8 ◽  
Death Domain ◽  
Extrinsic Pathway ◽  
Inhibitory Protein ◽  
Developmental Abnormalities ◽  
Developmental Role ◽  
Apoptotic Pathways

Caspase 8 is an initiator caspase that is activated by death receptors to initiate the extrinsic pathway of apoptosis. Caspase 8 activation involves dimerization and subsequent interdomain autoprocessing of caspase 8 zymogens, and recently published work has established that elimination of the autoprocessing site of caspase 8 abrogates its pro-apoptotic function while leaving its proliferative function intact. The observation that the developmental abnormalities of caspase 8-deficient mice are shared by mice lacking the dimerization adapter FADD (Fas-associated death domain) or the caspase paralogue FLIPL [FLICE (FADD-like interleukin 1β-converting enzyme)-inhibitory protein, long form] has led to the hypothesis that FADD-dependent formation of heterodimers between caspase 8 and FLIPL could mediate the developmental role of caspase 8. In the present study, using an inducible dimerization system we demonstrate that cleavage of the catalytic domain of caspase 8 is crucial for its activity in the context of activation by homodimerization. However, we find that use of FLIPL as a partner for caspase 8 in dimerization-induced activation rescues the requirement for intersubunit linker proteolysis in both protomers. Moreover, before processing, caspase 8 in complex with FLIPL does not generate a fully active enzyme, but an attenuated species able to process only selected natural substrates. Based on these results we propose a mechanism of caspase 8 activation by dimerization in the presence of FLIPL, as well as a mechanism of caspase 8 functional divergence in apoptotic and non-apoptotic pathways.

Neuronal expression of Fas-associated death domain protein and caspase-8 in the perinidal parenchyma of cerebral arteriovenous malformations

2007 ◽  
Vol 106 (2) ◽  
pp. 275-282 ◽  
Author(s):  
Yasushi Takagi ◽  
Ken-Ichiro Kikuta ◽  
Kazuhiko Nozaki ◽  
Motoaki Fujimoto ◽  
Junya Hayashi ◽  
...  
Keyword(s):  
Image Analysis ◽  
Arteriovenous Malformations ◽  
Morphological Characteristics ◽  
Terminal Deoxynucleotidyl Transferase ◽  
Caspase 8 ◽  
Image Analysis System ◽  
Death Domain ◽  
Cerebral Arteriovenous Malformations ◽  
Domain Protein ◽  
Analysis System

Object The expression and localization of phosphorylated Fas-associated death domain protein (pFADD) and cleaved caspase-8 was examined in human cerebral arteriovenous malformations (AVMs). The authors focused on the perinidal parenchyma to clarify the effect of AVMs on perinidal brain tissue. Methods Seventeen cerebral AVMs were analyzed using immunohistochemical methods. Specimens were removed from patients during surgical procedures. The characteristics of the areas that stained positively for pFADD or cleaved caspase-8 were also assessed using an image analysis system. Eleven (65%) of the 17 lesions demonstrated anti-pFADD immunoreactivity and 12 (71%) showed anti–cleaved caspase-8 immunoreactivity. The immunoreactive cells in the perinidal parenchyma demonstrated obvious neuronal morphological characteristics. The characteristics of pFADD-positive and cleaved caspase-8–positive areas were assessed using the image analysis system. The mean distance from the nidus adjacent to either area was not affected by preoperative hemorrhage. The neuronal densities of pFADD-positive and cleaved caspase-8–positive areas were analyzed using the same system. The density of the control area (samples that were pFADD-negative and cleaved caspase-8 negative) was significantly higher when compared with that of pFADD-positive and cleaved caspase-8–positive areas (p < 0.05). The expressions of cleaved caspase-9, cleaved poly(adenosine diphosphate–ribose) polymerase, and apoptotic cells were analyzed using the terminal deoxynucleotidyl transferase–mediated deoxyuridine triphosphate nick-end labeling method. Conclusions Neuronal areas that stained positively for pFADD and cleaved caspase-8 existed around the nidus of AVMs. In these areas, the neuronal density was lower than that in the other parenchyma around the AVM. Neuronal loss around the nidus may be the origin of brain dysfunction around AVMs.

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