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

Interferon gamma (IFNgamma) induces apoptosis in purified human erythroid colony-forming cells (ECFC) and inhibits cell growth. Fas (APO-1; CD95) and Fas ligand (FasL) mediate apoptosis induced by IFNgamma, because Fas is significantly upregulated by IFNgamma, whereas Fas ligand is constitutively present in the ECFC and neutralization of FasL greatly reduces the apoptosis. Because conversion of caspases from their dormant proenzyme forms to active enzymes has a critical role in transducing a cascade leading to apoptosis, we performed further studies of the expression and activation of caspases in normal human and IFNgamma-treated day-6 ECFC to better understand the mechanism of IFNgamma action in producing this cell death. RNase protection assays showed that the caspase-1, -2, -6, -8, and -9 mRNAs were upregulated by IFNgamma, whereas the caspase-5 and -7 mRNAs were not increased. Western blots showed that FLICE/caspase-8 was upregulated and activated by 24 hours of incubation with IFNgamma. FADD was not similarly altered by incubation with IFNgamma. Western blots of ICE/caspase-1, which might be required for amplification of the initial FLICE activation signal, showed that pro-ICE expression significantly increased after treatment with IFNgamma for 24 hours and cleavage of pro-ICE also increased. CPP32/apopain/caspase-3, responsible for the proteolytic cleavage of poly (ADP) ribose polymerase (PARP), was also studied and treatment of ECFC with IFNgamma resulted in an increased concentration of caspase-3 by 24 hours and a clear induction of enzyme activation by 48 hours, which was identified by the appearance of its p17-kD peptide fragment. The cleavage of PARP was demonstrated by an obvious increase of the 89-kD PARP cleavage product, which was observed at almost the same time as caspase-3 activation in the IFNgamma-treated cells, whereas untreated ECFC showed little change. Peptide inhibitors of the caspase proteins, DEVD-fmk, DEVD-cho, YVAD-cho, and IETD-fmk, were incubated with the ECFC to obtain further evidence for the involvement of caspases in IFNgamma-induced apoptosis. The activation of FLICE/caspase-8 and CPP32/caspase-3 and cleavage of PARP clearly were inhibited, but the reduction of cell growth due to apoptosis, induced by IFNgamma, was only partially blocked by the presence of the inhibitors. These results indicate that IFNgamma acts on ECFC not only to upregulate Fas, but also to selectively upregulate caspases-1, -3, and -8, which are activated and produce apoptosis, whereas the concentrations of FasL and FADD are not demonstrably changed.
 ...
PMID:Interferon gamma induces upregulation and activation of caspases 1, 3, and 8 to produce apoptosis in human erythroid progenitor cells. 1023 83

Brief periods of in vitro hypoxia/ischemia induce apoptosis of cultured renal epithelial cells, but the underlying mechanisms remain unknown. We show that partial ATP depletion (approximately 10-65% of control) results in a duration-dependent induction of apoptosis in Madin-Darby canine kidney (MDCK) cells, as evidenced by internucleosomal DNA cleavage (DNA laddering and in situ nick end labeling), morphological changes (cell shrinkage), and plasma membrane alterations (externalization of phosphatidylserine). The ATP-depleted cells display a significant upregulation of Fas, Fas ligand, and the Fas-associating protein with death domain (FADD). Exogenous application of stimulatory Fas monoclonal antibodies also induces apoptosis in nonischemic MDCK cells, indicating that they retain Fas-dependent pathways of programmed cell death. Furthermore, cleavage of poly(ADP)ribose polymerase (PARP) is evident after ATP depletion, indicating activation of caspases. Indeed, the apoptotic cells display a significant increase in caspase-8 (FLICE) activity. Finally, apoptosis induced by ATP depletion is ameliorated by pretreatment with inhibitors of caspase-8 (IETD), caspase-1 (YVAD), or caspase-3 (DEVD) but is not affected by inhibitors of serine proteases (TPCK). Our results indicate that partial ATP depletion of MDCK cells results in apoptosis and that Fas- and caspase-mediated pathways may play a critical role.
 ...
PMID:Partial ATP depletion induces Fas- and caspase-mediated apoptosis in MDCK cells. 1036 72

The recruitment and cleavage of pro-caspase-8 to produce the active form of caspase-8 is a critical biochemical event in death receptor-mediated apoptosis. However, the source of pro-caspase-8 available for activation by apoptotic triggers is unknown. In human fibroblasts and mouse clonal striatal cells, confocal microscopy revealed that pro-caspase-8 immunofluorescence was colocalized with cytochrome c in mitochondria and was also distributed diffusely in some nuclei. Biochemical analysis of subcellular fractions indicated that pro-caspase-8 was enriched in mitochondria and in nuclei. Pro-caspase-8 was found in the intermembrane space, inner membrane, and matrix of mitochondria after limited digestion of mitochondrial fractions, and this distribution was confirmed by immunogold electron microscopy. Pro-caspase-8 and cytochrome c were released from isolated mitochondria that were treated with an inhibitor of the ADP/ATP carrier atractyloside, which opens the mitochondria permeability transition pore. Release was blocked by the mitochondria permeability transition pore inhibitor cyclosporin A (CsA). After clonal striatal cells were exposed for 6 h to an apoptotic inducer tumor necrosis factor-alpha (TNF-alpha), mitochondria immunoreactive for cytochrome c and pro-caspase-8 became clustered at perinuclear sites. Pro-caspase-8 and cytochrome c levels decreased in mitochondrial fractions and increased, along with pro-caspase-8 cleavage products, in the cytoplasm of the TNF-alpha-treated striatal cells. CsA blocked the TNF-alpha-induced release of pro-caspase 8 but not cytochrome c. Internucleosomal DNA fragmentation started at 6 h and peaked 12 h after TNF-alpha treatment. These results suggest that pro-caspase-8 is predominantly localized in mitochondria and is released upon apoptotic stimulation through a CsA-sensitive mechanism.
 ...
PMID:Pro-caspase-8 is predominantly localized in mitochondria and released into cytoplasm upon apoptotic stimulation. 1110 41

To clarify the chronology of events leading to anti-Fas-induced apoptosis, and the mechanisms of resistance to this death effector, we compared the response kinetics of three tumour cell lines that display varying sensitivity to anti-Fas (based on levels of apoptosis), in terms of ceramide release, mitochondrial function and the caspase-activation pathway. In the highly sensitive Jurkat cell line, early caspase-8 activation, observed from 2 h after treatment, was chronologically associated with an acute depletion of glutathione and the cleavage of caspase-3 and poly-ADP ribosyl polymerase (PARP), followed by a progressive fall in the mitochondrial transmembrane potential (Delta(psi)m), between 4 and 48 h after treatment. Ceramide levels began to increase 2 h after the addition of anti-Fas (with no increase during the first hour), and increased continuously to 640% of control cells at 48 h. In the moderately sensitive SCC61 adherent cells, comparable results were observed, though with lower levels of ceramide and a delay in the response kinetics, with apoptotic cells becoming flotant. Finally, despite early cleavage of caspase-8 at 2 h, and a sustained level of activation until 48 h, no apoptotic response was observed in anti-Fas-resistant SQ20B cells. This was confirmed by a lack of ceramide generation and mitochondrial changes, and by the absence of any detectable cleavage of caspase-3 or PARP. Inhibition of caspase processing, and amplification of endogenous ceramide signalling by pharmacological agents, allowed us to establish the order of cellular events, locating ceramide release after caspase-8 activation and before caspase-3 activation, and demonstrating a direct involvement for ceramide release in mitochondrial dysfunction. Furthermore, these experiments provide strong arguments for the role of endogenous ceramide as a key executor of apoptosis, rather than as a consequence of membrane alterations.
 ...
PMID:Temporal relationships between ceramide production, caspase activation and mitochondrial dysfunction in cell lines with varying sensitivity to anti-Fas-induced apoptosis. 1143 90

Caspase-8 is the prototypic initiator of the death domain receptor pathway of apoptosis. Here, we report that caspase-8 not only triggers and amplifies the apoptotic process at cytoplasmic sites but can also act as an executioner at nuclear levels. In a murine model of acute ischemia, caspase-8 is relocated into the nucleus of apoptotic neurons, where it cleaves PARP-2, a member of the poly(ADP-ribose) polymerase family involved in DNA repair. As indicated by site-directed mutagenesis, PARP-2 cleavage occurs preferentially at the LQMD sequence mapped between the DNA binding and the catalytic domains of the protein. This is close to the cleavage sequence found in Bid, the cytoplasmic target of caspase-8. Activity assays confirm that cleavage of PARP-2 results in inactivation of its poly(ADP-ribosylation) property, proportional to the efficiency of the cleavage. Our findings add to the complexity of proteolytic caspase networks by demonstrating that caspase-8 is in turn an initiator, amplifier, and effector caspase.
 ...
PMID:Active caspase-8 translocates into the nucleus of apoptotic cells to inactivate poly(ADP-ribose) polymerase-2. 1206 91

In vivo and in vitro studies have shown an increase in apoptosis in gastric epithelial cells in persons infected with Helicobacter pylori. H. pylori-induced activation of caspase-8 and -3 was evaluated using a human gastric adenocarcinoma cell line (AGS) and gastric tissue from humans and monkeys colonized with H. pylori. The enzymatic activity of caspase-8 was detected only in AGS cells exposed to H. pylori up to 24 h. The active form of caspase-8 was present by Western blot after exposure to H. pylori for 3 h and persisted through 24 h. Caspase-3 activity was present in AGS cells exposed to H. pylori for 3 h, reaching a maximum after 24 h (a sevenfold increase in activity). Caspase-8-mediated cleavage of procaspase-3 generated a 20-kDa band (indicative of the presence of active caspase-3) present only in AGS cells exposed to H. pylori. Active caspase-3 staining was markedly increased in gastric mucosa from infected persons and animals, compared to uninfected controls by immunohistochemistry. Stimulation of downstream events leading to apoptosis, such as the cleavage of PARP (poly adenosine-diphosphate-ribose polymerase) and DFF45 (DNA fragmentation factor 45) as a result of activation of caspase-3, was evaluated. PARP was cleaved, resulting in the presence of both an 89- and a 24-kDa band along with DFF45, resulting in the presence of 10- and 12-kDa bands only in gastric cells exposed to H. pylori. Our data show that H. pylori stimulates the activation of caspases and downstream mediators of caspase-induced apoptosis. This suggests that H. pylori-induced apoptosis is mediated through caspase pathways, which include the activation of caspase-8 and subsequent cleavage and activation of caspase-3. This is consistent with caspase-3 activation that was found in the gastric mucosa of humans and monkeys infected with H. pylori.
 ...
PMID:In vivo and in vitro activation of caspase-8 and -3 associated with Helicobacter pylori infection. 1206 31

Small GTP-binding Rho GTPases regulate important signaling pathways in endothelial cells, but little is known about their role in endothelial cell apoptosis. Clostridial cytotoxins specifically inactivate GTPases by glucosylation [Clostridium difficile toxin B-10463 (TcdB-10463), C. difficile toxin B-1470 (TcdB-1470)] or ADP ribosylation (C. botulinum C3 toxin). Exposure of human umbilical cord vein endothelial cells (HUVEC) to TcdB-10463, which inhibits RhoA/Rac1/Cdc42, or to C3 toxin, which inhibits RhoA, -B, -C, resulted in apoptosis, whereas inactivation of Rac1/Cdc42 with TcdB-1470 was without effect, suggesting that Rho inhibition was responsible for endothelial apoptosis. Disruption of endothelial microfilaments as well as inhibition of p160ROCK did not induce endothelial apoptosis. Exposure to TcdB-10463 resulted in activation of caspase-9 and -3 but not caspase-8 in HUVEC. Moreover, Rho inhibition reduced expression of antiapoptotic Bcl-2 and Mcl-1 and increased proapoptotic Bid but had no effect on Bax or FLIP protein levels. Caspase-3 activity and apoptosis induced by TcdB-10463 were abolished by cAMP elevation. In summary, inhibition of Rho in endothelial cells activates caspase-9- and -3-dependent apoptosis, which can be antagonized by cAMP elevation.
 ...
PMID:Rho protein inactivation induced apoptosis of cultured human endothelial cells. 1222 60

Chronic lymphocytic leukemia (CLL) cells, but not peripheral blood T cells, undergo apoptosis following treatment with inhibitors of type 4 cyclic nucleotide phosphodiesterase (PDE4), a process that correlates dose dependently with elevation of adenosine 3',5'-cyclic monophosphate (cAMP) in leukemic cells. We show that treatment of CLL cells with rolipram, a prototypic PDE4 inhibitor, and forskolin, an adenylate cyclase activator, induces mitochondrial depolarization, release of cytochrome c into the cytosol, caspase-9 and -3 activation, and cleavage of poly(adenosine diphosphate [ADP]-ribose)polymerase. Inhibitors of caspase-9, but not caspase-8, block rolipram/forskolin-induced CLL apoptosis. In a subset of CLL patients, B-cell lymphoma 2 (Bcl-2)-associated death promoter homolog (Bad), a proapoptotic Bcl-2 family member that when phosphorylated on specific serine residues is sequestered in the cytosol by 14-3-3, was dephosphorylated at Ser112 following rolipram/forskolin treatment of leukemic cells. Rolipram/forskolin treatment also induced Bad to accumulate in CLL heavy-membrane fractions, consistent with Bad translocation to mitochondria. To determine the mechanism for rolipram/forskolin-induced Bad dephosphorylation, we examined CLL phosphatase activity. Rolipram/forskolin treatment augmented protein phosphatase 2A (PP2A) activity, as well as levels of immunoreactive PP2A catalytic subunit. Treatment of CLL cells with a concentration of okadaic acid (5 nM) that selectively inhibits PP2A, reduced both rolipram/forskolin-induced mitochondrial cytochrome c release and mitochondrial depolarization. Okadaic acid restored Bad Ser112 phosphorylation and Bad association with 14-3-3 in rolipram/forskolin-treated CLL cells. These results suggest that PDE4 inhibitors may induce CLL apoptosis by activating PP2A-induced dephosphorylation of proapoptotic BH3-only Bcl-2 family members such as Bad.
 ...
PMID:PDE4 inhibitors activate a mitochondrial apoptotic pathway in chronic lymphocytic leukemia cells that is regulated by protein phosphatase 2A. 1253 92

Histone acetylation modulates gene expression, cellular differentiation, and survival and is regulated by the opposing activities of histone acetyltransferases (HATs) and histone deacetylases (HDACs). HDAC inhibition results in accumulation of acetylated nucleosomal histones and induces differentiation and/or apoptosis in transformed cells. In this study, we characterized the effect of suberoylanilide hydroxamic acid (SAHA), the prototype of a series of hydroxamic acid-based HDAC inhibitors, in cell lines and patient cells from B-cell malignancies, including multiple myeloma (MM) and related disorders. SAHA induced apoptosis in all tumor cells tested, with increased p21 and p53 protein levels and dephosphorylation of Rb. We also detected cleavage of Bid, suggesting a role for Bcl-2 family members in regulation of SAHA-induced cell death. Transfection of Bcl-2 cDNA into MM.1S cells completely abrogated SAHA-induced apoptosis, confirming its protective role. SAHA did not induce cleavage of caspase-8, -9, or -3 in MM.1S cells during the early phase of apoptosis, and the pan-caspase inhibitor ZVAD-FMK did not protect against SAHA. Conversely, poly(ADP)ribose polymerase (PARP) was cleaved in a pattern indicative of calpain activation, and the calpain inhibitor calpeptin abrogated SAHA-induced cell death. Importantly, SAHA sensitized MM.1S cells to death receptor-mediated apoptosis and inhibited the secretion of interleukin 6 (IL-6) induced in bone marrow stromal cells (BMSCs) by binding of MM cells, suggesting that it can overcome cell adhesion-mediated drug resistance. Our studies delineate the mechanisms whereby HDAC inhibitors mediate anti-MM activity and overcome drug resistance in the BM milieu and provide the framework for clinical evaluation of SAHA, which is bioavailable, well tolerated, and bioactive after oral administration, to improve patient outcome.
 ...
PMID:Molecular sequelae of histone deacetylase inhibition in human malignant B cells. 1253 99

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been shown to exert potent cytotoxic activity against many tumor cells but not normal cells. However, some tumor cells are resistant to TRAIL, and it has not been determined how this occurs. In the present study, we obtained three subgroups of Jurkat clones with TRAIL-sensitive, -partial resistant and -resistant phenotypes. We found that most TRAIL-resistant and -partial resistant clones expressed low levels of DR5, whereas most TRAIL-sensitive clones expressed high levels of Death Receptor (DR5). However, there were clones with a range of different TRAIL-sensitivities that had similar levels of DR5 expression. The expression levels of DR4 and the decoy receptors, DcR1 and DcR2, did not correlate with TRAIL sensitivities. We also compared the subgroups in terms of the expression of Fas-associated death domain protein (FADD), the levels of activation of Receptor Interacting Protein (RIP) and caspases, and cleavage of Poly (ADP-Ribose)Polymerase (PARP). Basal expression levels of FADD were not significantly different among the subgroups. After treatment with TRAIL, both TRAIL-sensitive and partial resistant clones showed high levels of activation of caspase-3, caspase-8, RIP and PARP. Relative basal level and induced level of Phosphoprotein over Expressed in Diabetes/Phosphoprotein Enriched in Astrocytes (PED/PEA-15) after TRAIL treatment were compared in the clones. Basal levels of PED/PEA-15 expression were similar among sensitive, partial resistant and resistant clones. TRAIL did not change the PED/PEA-15 level in the clones. In addition, transduction and expression of the dominant negative form of the I-kBalpha gene did not change TRAIL-sensitivities. Our results showed that the expression levels of DR5, the activation levels of caspase-8, -3 and RIP were critical factors in determining TRAIL-sensitivities in Jurkat cells. The results of our study also suggest that cells with different TRAIL-sensitivities arise through multiple mechanisms even within a single cell line.
 ...
PMID:Analysis of the phenotypes of Jurkat clones with different TRAIL-sensitivities. 1270 64


1 2 3 4 5 6 Next >>