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)

We have previously shown an increased susceptibility of T cell subsets to anti-Fas-induced apoptosis in human ageing [1]. In this study, we have examined the role of downstream mediators, including caspases, in Fas-mediated apoptosis in lymphocytes from ageing humans. The cleavage activity of caspase-8 and caspase-3 was compared between ageing and young subjects at different times following anti-Fas treatment, using colorimetric detection analysis. The expression of Fas-associated death domain (FADD), caspase-8, and caspase-3 in lymphocytes was compared at the protein level using Western blotting, and at the mRNA level by Northern blot analysis. In lymphocytes from ageing subjects, there was an early increase in the cleavage activity of caspase-8 and caspase-3 compared with young controls. Furthermore, increased protein expression of FADD, caspase-8 and caspase-3 at the basal level was observed in lymphocytes from ageing humans. Our results suggest that the altered expression and activity of molecules in the Fas/FasL signalling pathway may play a role in increased Fas-induced apoptosis and T cell deficiency in ageing humans.
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PMID:Increased activity of caspase 3 and caspase 8 in anti-Fas-induced apoptosis in lymphocytes from ageing humans. 1044 59

Previously we have reported that induction of apoptosis in Jurkat cells results in an inhibition of overall protein synthesis with the selective and rapid cleavage of eukaryotic initiation factor (eIF) 4GI. For the cleavage of eIF4GI, caspase-3 activity is both necessary and sufficient in vivo, in a process which does not require signaling through the p38 MAP kinase pathway. We now show that activation of the Fas/CD95 receptor promotes an early, transient increase in the level of eIF2alpha phosphorylation, which is temporally correlated with the onset of the inhibition of translation. This is associated with a modest increase in the autophosphorylation of the protein kinase activated by double-stranded RNA. Using a Jurkat cell line that is deficient in caspase-8 and resistant to anti-Fas-induced apoptosis, we show that whilst the cleavage of eIF4GI is caspase-8-dependent, the enhancement of eIF2alpha phosphorylation does not require caspase-8 activity and occurs prior to the cleavage of eIF4GI. In addition, activation of the Fas/CD95 receptor results in the caspase-8-dependent dephosphorylation and degradation of p70(S6K), the enhanced binding of 4E-BP1 to eIF4E, and, at later times, the cleavage of eIF2alpha. These data suggest that apoptosis impinges upon the activity of several polypeptides which are central to the regulation of protein synthesis and that multiple signaling pathways are involved in vivo.
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PMID:Differential requirements for caspase-8 activity in the mechanism of phosphorylation of eIF2alpha, cleavage of eIF4GI and signaling events associated with the inhibition of protein synthesis in apoptotic Jurkat T cells. 1090 26

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.
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PMID:Temporal relationships between ceramide production, caspase activation and mitochondrial dysfunction in cell lines with varying sensitivity to anti-Fas-induced apoptosis. 1143 90

UV radiation from the sun activates both the membrane death receptor and the intrinsic or mitochondrial apoptotic signaling pathways in epidermal keratinocytes, triggering apoptosis and affording protection against skin cancer formation. We have investigated the involvement of caspase-9 in the UV death effector pathway in human keratinocytes, since this is the initiating caspase in the mitochondrial pathway required for UV-induced apoptosis in some, but not all, cell types. UV radiation triggered activation of caspase-3, caspase-9, and caspase-8 with similar kinetics, although the rank order of activation was caspase-3 > caspase-9 > caspase-8. Inhibition of caspase-9 with either the peptide inhibitor benzyloxycarbonyl-Leu-Glu(OCH(3))-His-Asp(OCH(3))-fluoromethyl ketone, or expression of a catalytically inactive caspase-9 by retroviral transduction, protected normal keratinocytes from UV-induced apoptosis. HaCaT keratinocytes harboring mutant p53 alleles were also protected from UV-induced apoptosis by the dominant negative caspase-9. The dominant negative caspase-9 blocked UV-induced activation of caspase-3, caspase-9, and caspase-8, and also protected cells from the loss of mitochondrial membrane potential. In contrast, the dominant negative caspase-9 did not protect from anti-Fas-induced apoptosis or caspase activation. These results identify caspase-9 as the critical upstream caspase initiating apoptosis by UV radiation in human keratinocytes, the relevant cell type for this important environmental carcinogen.
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PMID:Activation of caspase-9 is required for UV-induced apoptosis of human keratinocytes. 1191 92

The Fas up-regulated in adult T-cell leukemia (ATL) cells is usually the wild-type protein and is usually functional, at least in vitro. However, primary ATL cells, in contrast to ATL cell lines, are not necessarily susceptible to anti-Fas-induced apoptosis. To clarify the mechanism tuning the apoptotic signal transduction initiated by the activation caspase-8 in ATL cells and ATL cell lines, we examined the expression profile of caspase-8, of which there are at least 8 isoforms at the messenger RNA (mRNA) level with the potential to finely tune the signal transduction. Reverse transcription polymerase chain reaction disclosed the 2 major mRNA bands of 815 bp (casp-8S) and 951 bp (casp-8L) with different expression profiles among normal CD4 T-cells, primary ATL cells, and ATL cell lines. Casp-8L was the predominant form in primary ATL cells, whereas casp-8S was predominant in ATL cell lines. Casp-8S was structurally intact as shown by nucleotide analysis, whereas casp-8L was shown to be generated by a 136-bp insertion between exons 8 and 9 and to carry a frame shift in the transcript, introducing a premature stop codon and probably resulting in a truncated protein of approximately 30 kd deduced for the casp-8L transcript. These results suggest that an imbalanced expression of casp-8 isoforms, especially the dominant casp-8L in primary ATL cells, is in part responsible for tumor pathology through the modulation of cell death via Fas-mediated signaling.
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PMID:Possible attenuation of fas-mediated signaling by dominant expression of caspase-8 aberrant isoform in adult T-cell leukemia cells. 1213 95

Mouse TOSO, the homologue of human TOSO gene, was cloned and characterized in the present study. Using immunofluorescence confocal microscopy we localized TOSO to the cytoplasmic membrane of expressing cells. Using stably transfected mouse TOSO (mTOSO)-expressing Jurkat cells, we show that TOSO protects cells from Fas/Fas ligand- and tumor necrosis factor-induced apoptosis but not from TNF-related apoptosis-inducing ligand-induced apoptosis. The Fas-induced activation of caspase-8 was significantly inhibited by the expression of mTOSO. Using deletion mutants and glutathione S-transferase pull-down approaches, we have shown that mTOSO regulates apoptosis by directly binding to Fas-associated death domain through its C-terminal domain, suggesting the disruption of death-inducing signaling complex formation as mechanism of action. Furthermore, we have expressed mTOSO in transgenic mice and show that mTOSO overexpressing primary T lymphocytes are resistant to Fas/Fas ligand-induced apoptosis.
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PMID:The mouse cell surface protein TOSO regulates Fas/Fas ligand-induced apoptosis through its binding to Fas-associated death domain. 1563 12

Conflicting reports exist on the effect of actin depolymerization in anti-Fas-induced apoptosis. Lysophosphatidic acid (LPA) has been found to inhibit apoptosis in variable cell types. In this study, we evaluated LPA's protective effects on anti-Fas-induced apoptosis enhanced by actin depolymerization and possible mechanisms in epithelial ovarian cancer. OVCAR3 cells were pretreated with vehicle or LPA, then treated with Cytochalasin D (Cyto D), followed with anti-Fas mAb to induce apoptosis. Cells were stained with apoptotic markers and analyzed by flow cytometry. We report that LPA inhibited anti-Fas-induced apoptosis enhanced by actin depolymerization. Immunoprecipition of Fas death-inducing signaling complex (DISC) and Western blot suggested that the actin depolymerization accelerated caspase-8 activation, while LPA inhibited the association and activation of caspase-8 at the DISC. LPA inhibited caspase-3 and 7 activation induced by anti-Fas and/or Cyto D in cytosols. Phosphorylation of ERK and Bad112 by LPA may play a role in preventing caspase-3 activation through mitochondrial pathway induced by Cyto D. Our investigation found that LPA inhibited anti-Fas-induced apoptosis enhanced by actin depolymerization, and LPA may protect epithelial ovarian cancer from immune cell attack and cytoskeleton disrupting reagents induced apoptosis through multiple pathways.
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PMID:Lysophosphatidic acid inhibits anti-Fas-mediated apoptosis enhanced by actin depolymerization in epithelial ovarian cancer. 1571 Apr 31