Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.22.61 (caspase-8)
 6,833 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Induction of apoptosis by the cell surface receptor CD95 (APO-1/Fas) has been shown to involve activation of a family of cysteine proteases (caspases). Recently, a new member of this family has been identified, designated FLICE (caspase-8/MACH/Mch5). FLICE is part of the CD95 death-inducing signaling complex and is therefore the most upstream caspase in the CD95 apoptotic pathway. A total of eight different isoforms of FLICE (caspase-8/a-h) have been described. To determine which isoforms are expressed in different cells we have generated a panel of monoclonal antibodies directed against all functional domains of FLICE. Using these antibodies we could show that only two of the FLICE isoforms (caspase-8/a and caspase-8/b) were predominantly expressed in cells of different origin. Both isoforms were recruited to the CD95 death-inducing signaling complex and were activated upon CD95 stimulation with similar kinetics. Taken together, only two of the eight published caspase-8 isoforms could be detected in significant amounts at the protein level.
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PMID:FLICE is predominantly expressed as two functionally active isoforms, caspase-8/a and caspase-8/b. 934 Nov 31

Fas- and tumor necrosis factor receptor 1 (TNFR1)-induced apoptosis is mediated by the interaction of FADD with caspase-8. Here, we report that the bovine herpesvirus 4 (BHV4) BORFE2 gene encodes a protein that inhibits Fas- and TNFR1-induced apoptosis and contains death effector domains (DEDs). Using the yeast two-hybrid system, we found that the BORFE2 protein interacts with the prodomain of caspase-8. Furthermore, we show that BHV4 BORFE2 is a member of a family of DED-containing proteins that includes other gamma-2 herpesviruses, such as Kaposi's sarcoma-associated herpesvirus and herpesvirus saimiri.
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PMID:Bovine herpesvirus 4 BORFE2 protein inhibits Fas- and tumor necrosis factor receptor 1-induced apoptosis and contains death effector domains shared with other gamma-2 herpesviruses. 934 61

Upon activation, cell surface death receptors, Fas/APO-1/CD95 and tumor necrosis factor receptor-1 (TNFR-1), are attached to cytosolic adaptor proteins, which in turn recruit caspase-8 (MACH/FLICE/Mch5) to activate the interleukin-1 beta-converting enzyme (ICE)/CED-3 family protease (caspase) cascade. However, it remains unknown whether these apoptotic proteases are generally involved in apoptosis triggered by other stimuli such as Myc and p53. In this study, we provide lines of evidence that a death protease cascade consisting of caspases and serine proteases plays an essential role in Myc-mediated apoptosis. When Rat-1 fibroblasts stably expressing either s-Myc or c-Myc were induced to undergo apoptosis by serum deprivation, a caspase-3 (CPP32)-like protease activity that cleaves a specific peptide substrate, Ac-DEVD-MCA, appeared in the cell lysates. Induction of s-Myc- and c-Myc-mediated apoptotic cell death was effectively prevented by caspase inhibitors such as Z-Asp-CH2-DCB and Ac-DEVD-CHO. Furthermore, exposing the cells to a serine protease inhibitor, 4-(2-aminoethyl)benzenesulfonyl fluoride (AEBSF), also significantly inhibited s-Myc- and c-Myc-mediated apoptosis and the appearance of the caspase-3-like protease activity in vivo. However, AEBSF did not directly inhibit caspase-3-like protease activity in the apoptotic cell lysates in vitro. Together, these results indicate that caspase-3-like proteases play a critical role in both s-Myc- and c-Myc-mediated apoptosis and that caspase-3-like proteases function downstream of the AEBSF-sensitive step in the signaling pathway of Myc-mediated apoptosis.
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PMID:A functional role for death proteases in s-Myc- and c-Myc-mediated apoptosis. 934 38

We have identified and characterized CLARP, a caspase-like apoptosis-regulatory protein. Sequence analysis revealed that human CLARP contains two amino-terminal death effector domains fused to a carboxyl-terminal caspase-like domain. The structure and amino acid sequence of CLARP resemble those of caspase-8, caspase-10, and DCP2, a Drosophila melanogaster protein identified in this study. Unlike caspase-8, caspase-10, and DCP2, however, two important residues predicted to be involved in catalysis were lost in the caspase-like domain of CLARP. Analysis with fluorogenic substrates for caspase activity confirmed that CLARP is catalytically inactive. CLARP was found to interact with caspase-8 but not with FADD/MORT-1, an upstream death effector domain-containing protein of the Fas and tumor necrosis factor receptor 1 signaling pathway. Expression of CLARP induced apoptosis, which was blocked by the viral caspase inhibitor p35, dominant negative mutant caspase-8, and the synthetic caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-(OMe)-fluoromethylketone (zVAD-fmk). Moreover, CLARP augmented the killing ability of caspase-8 and FADD/MORT-1 in mammalian cells. The human clarp gene maps to 2q33. Thus, CLARP represents a regulator of the upstream caspase-8, which may play a role in apoptosis during tissue development and homeostasis.
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PMID:CLARP, a death effector domain-containing protein interacts with caspase-8 and regulates apoptosis. 938 Jul 1

Fas/Apo1 and other cytotoxic receptors of the tumor necrosis factor receptor (TNFR) family contain a cytoplasmic death domain (DD) [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] that activates the apoptotic process by interacting with the DD-containing adaptor proteins TNFR-associated DD protein (TRADD) [12] [13] and Fas-associated DD protein (FADD/MORT1) [14] [15], leading to the activation of cysteine proteases of the caspase family [16]. Stimulation of Fas/Apo1 leads to the formation of a receptor-bound death-inducing signaling complex (DISC), consisting of FADD and two different forms of caspase-8 [17] [18] [19]. Transient expression of a dominant-negative mutant of FADD impairs TNFR60-mediated and Fas/Apo1-mediated apoptosis [13] [20], but has no effect on TNF-related apoptosis-inducing ligand (TRAIL/Apo2L)-induced cell death [7] [8] [9] [10] [21]. To study the function of FADD in DD-receptor signaling in more detail, we established HeLa cells that stably expressed a green fluorescent protein (GFP)-tagged dominant-negative mutant of FADD, GFP-DeltaFADD. Interestingly, expression of this mutant inhibited cell death induced by TNFR60, Fas/Apo1 and TRAIL-R/Apo2. In addition, GFP-DeltaFADD did not interfere with TNF-mediated gene induction or with activation of NF-kappaB or Jun N-terminal kinase (JNK), demonstrating that FADD is part of the TNFR60-initiated apoptotic pathway but does not play a role in TNFR60-mediated gene induction. Fas/Apo1-mediated activation of JNK was unaffected by the expression of GFP-DeltaFADD, suggesting that in Fas/Apo1 signaling the apoptotic pathway and the activation of JNK diverge at a level proximal to the receptor, upstream of or parallel to FADD.
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PMID:Dominant-negative FADD inhibits TNFR60-, Fas/Apo1- and TRAIL-R/Apo2-mediated cell death but not gene induction. 942 46

Ceramide, a sphingolipid generated by the hydrolysis of membrane-associated sphingomyelin, appears to play a role as a gauge of apoptosis. A further metabolite of ceramide, sphingosine 1-phosphate (SPP), prevents ceramide-mediated apoptosis, and it has been suggested that the balance between intracellular ceramide and SPP levels may determine the cell fate (Cuvillier, O., Pirianov, G, Kleuser, B., Vanek, P. G., Coso, O. A., Gutkind, J. S., and Spiegel, S. (1996) Nature 381, 800-803). Here, we investigated the role of SPP and the protein kinase C activator, phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA), in the caspase cascade leading to the proteolysis of poly(ADP-ribose) polymerase (PARP) and lamins. In Jurkat T cells, Fas ligation or addition of exogenous C2-ceramide induced activations of caspase-3/CPP32 and caspase-7/Mch3 followed by PARP cleavage, effects that can be blocked either by SPP or TPA. Furthermore, both SPP and TPA inhibit the activation of caspase-6/Mch2 and subsequent lamin B cleavage. Ceramide, in contrast to Fas ligation, did not induce activation of caspase-8/FLICE and neither SPP nor TPA were able to prevent this activation. Thus, SPP, likely generated via protein kinase C-mediated activation of sphingosine kinase, suppresses the apoptotic pathway downstream of FLICE but upstream of the executioner caspases, caspase-3, -6, and -7.
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PMID:Sphingosine 1-phosphate inhibits activation of caspases that cleave poly(ADP-ribose) polymerase and lamins during Fas- and ceramide-mediated apoptosis in Jurkat T lymphocytes. 944 2

The assembly of the CD-95 (Fas/Apo-1) receptor death-inducing signaling complex occurs in a hierarchical manner; the death domain of CD-95 binds to the corresponding domain in the adapter molecule Fas-associated death domain (FADD) Mort-1, which in turn recruits the zymogen form of the death protease caspase-8 (FLICE/Mach-1) by a homophilic interaction involving the death effector domains. Immediately after recruitment, the single polypeptide FLICE zymogen is proteolytically processed to the active dimeric species composed of large and small catalytic subunits. Since all caspases cleave their substrates after Asp residues and are themselves processed from the single-chain zymogen to the two-chain active enzyme by cleavage at internal Asp residues, it follows that an upstream caspase can process a downstream zymogen. However, since FLICE represents the most apical caspase in the Fas pathway, its mode of activation has been enigmatic. We hypothesized that the FLICE zymogen possesses intrinsic enzymatic activity such that when approximated, it autoprocesses to the active protease. Support for this was provided by (i) the synthesis of chimeric Fpk3FLICE molecules that can be oligomerized in vivo by the synthetic cell-permeable dimerizer FK1012H2. Cells transfected with Fpk3FLICE underwent apoptosis after exposure to FK1012H2; (ii) the creation of a nonprocessable zymogen form of FLICE that retained low but detectable protease activity.
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PMID:An induced proximity model for caspase-8 activation. 944 4

The Bcl-2 family member Bcl-xL has often been correlated with apoptosis resistance. We have shown recently that in peripheral human T cells resistance to CD95-mediated apoptosis is characterized by a lack of caspase-8 recruitment to the CD95 death-inducing signaling complex (DISC) and by increased expression of Bcl-xL (Peter, M. E., Kischkel, F. C., Scheuerpflug, C. G., Medema, J. P., Debatin, K.-M., and Krammer, P. H. (1997) Eur. J. Immunol. 27, 1207-1212). This raises the possibility that Bcl-xL directly prevents caspase-8 activation by the DISC. To test this hypothesis a cell line in which CD95 signaling was inhibited by overexpression of Bcl-xL was used. In these MCF7-Fas-bcl-xL cells Bcl-xL had no effect on the recruitment of caspase-8 to the DISC. It did not affect the activity of the DISC nor the generation of the caspase-8 active subunits p18 and p10. In contrast, cleavage of a typical substrate for caspase-3-like proteases, poly(ADP-ribose) polymerase, was inhibited in comparison with the control-transfected CD95-sensitive MCF7-Fas cells. To test whether Bcl-xL would inhibit active caspase-8 subunits in the cytoplasm, a number of immunoprecipitation experiments were performed. Using monoclonal antibodies directed against different domains of caspase-8, anti-Bcl-xL antibodies, or fusion proteins of glutathione S-transferase with different domains of caspase-8, no evidence for a direct or indirect physical interaction between caspase-8 and Bcl-xL was found. Moreover, overexpression of Bcl-xL did not inhibit the activity of the caspase-8 active subunits p18/p10. Therefore, in this cell line that has become resistant to CD95-induced apoptosis due to overexpression of Bcl-xL, Bcl-xL acts independently and downstream of caspase-8.
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PMID:Bcl-xL acts downstream of caspase-8 activation by the CD95 death-inducing signaling complex. 945 59

Two novel synthetic tetrapeptides, VEID-CHO and DMQD-CHO, could selectively inhibit caspase-6 and caspase-3, respectively. We used these inhibitors to dissect the pathway of caspase activation in Fas-stimulated Jurkat cells and identify the roles of each active caspase in apoptotic processes. Affinity labeling techniques revealed a branched protease cascade in which caspase-8 activates caspase-3 and -7, and caspase-3, in turn, activates caspase-6. Both caspase-6 and -3 have major roles in nuclear apoptosis. Caspase-6 cleaves nuclear mitotic apparatus protein (NuMA) and mediates the shrinkage and fragmentation of nuclei. Caspase-3 cleaves NuMA at sites distinct from caspase-6, and mediates DNA fragmentation and chromatin condensation. It is also involved in extranuclear apoptotic events: cleavage of PAK2, formation of apoptotic bodies, and exposure of phosphatidylserine on the cell surface. In contrast, a caspase(s) distinct from caspase-3 or -6 mediates the disruption of mitochondrial membrane potential (permeability transition) and the shrinkage of cytoplasm. These findings demonstrate that caspases are organized in a protease cascade, and that each activated caspase plays a distinct role(s) in the execution of Fas-induced cell death.
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PMID:Caspases are activated in a branched protease cascade and control distinct downstream processes in Fas-induced apoptosis. 946 9

Cytotoxic T lymphocytes induce apoptosis in target cells through the CD95(APO-1/Fas) and the perforin/granzyme B (GrB) pathway. The exact substrate of GrB in vivo is still unknown, but to induce apoptosis GrB requires the activity of caspases in target cells. We show here that in HeLa target cells induction of apoptosis through the perforin/GrB pathway resulted in minor direct cleavage of CPP32 (caspase-3) by GrB. Most caspase-3 cleavage resulted from activation of an upstream caspase. Moreover, target cells derived from caspase-3(-/-) mice displayed GrB-induced poly(ADP-ribose) polymerase (PARP) cleavage with only partially reduced efficiency compared to wild-type target cells. This indicates that other PARP-cleaving caspases can be activated during perforin/GrB-induced cell death. In contrast to caspase-3, FLICE (caspase-8) was directly cleaved by GrB in HeLa cells. We therefore conclude that FLICE not only plays a central role in CD95(APO-1/Fas)-induced apoptosis but can also be directly activated during perforin/GrB-induced apoptosis.
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PMID:Cleavage of FLICE (caspase-8) by granzyme B during cytotoxic T lymphocyte-induced apoptosis. 946 39


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