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)

Caspase-3 initiates apoptotic DNA fragmentation by proteolytically inactivating DFF45 (DNA fragmentation factor-45)/ICAD (inhibitor of caspase-activated DNase), which releases active DFF40/CAD (caspase-activated DNase), the inhibitor's associated endonuclease. Here, we examined whether other apoptotic proteinases initiated DNA fragmentation via DFF45/ICAD inactivation. In a cell-free assay, caspases-3, -6, -7, -8, and granzyme B initiated benzoyloxycarbonyl-Asp-Glu-Val-Asp (DEVD) cleaving caspase activity, DFF45/ICAD inactivation, and DNA fragmentation, but calpain and cathepsin D failed to initiate these events. Strikingly, only the DEVD cleaving caspases, caspase-3 and caspase-7, inactivated DFF45/ICAD and promoted DNA fragmentation in an in vitro DFF40/CAD assay, suggesting that granzyme B, caspase-6, and caspase-8 promote DFF45/ICAD inactivation and DNA fragmentation indirectly by activating caspase-3 and/or caspase-7. In vitro, however, caspase-3 inactivated DFF45/ICAD and promoted DNA fragmentation more effectively than caspase-7 and endogenous levels of caspase-7 failed to inactivate DFF45/ICAD in caspase-3 null MCF7 cells and extracts. Together, these data suggest that caspase-3 is the primary inactivator of DFF45/ICAD and therefore the primary activator of apoptotic DNA fragmentation.
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PMID:Caspase-3 is the primary activator of apoptotic DNA fragmentation via DNA fragmentation factor-45/inhibitor of caspase-activated DNase inactivation. 1052 51

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL, Apo2 ligand) effectively kills multiple myeloma (MM) cells in vitro irrespective of refractoriness to dexamethasone and chemotherapy. Because clinical trials with this anticancer agent are expected shortly, we investigated the signaling pathway of TRAIL-induced apoptosis in MM. We detected rapid cleavage of caspases-8, -9, -3, and -6, as well as the caspase substrates poly(ADP-ribose) polymerase (PARP) and DNA fragmentation factor-45 (DFF45), but not caspase-10, upon TRAIL treatment in sensitive MM cells, pointing to caspase-8 as the apical caspase of TRAIL signaling in MM cells. These phenomena were not observed or were significantly delayed in TRAIL-resistant MM cells, suggesting that resistance may arise from inhibition at the level of caspase-8 activation. Higher levels of expression for various apoptosis inhibitors, including FLICE-inhibitory protein (FLIP), and lower procaspase-8 levels were present in TRAIL-resistant cells and sensitivity was restored by the protein synthesis inhibitor cycloheximide (CHX) and the protein kinase C (PKC) inhibitor bisindolylmaleimide (BIM), which both lowered FLIP and cellular inhibitor of apoptosis protein-2 (cIAP-2) protein levels. Forced expression of procaspase-8 or FLIP antisense oligonucleotides also sensitized TRAIL-resistant cells to TRAIL. Moreover, the cell permeable nuclear factor (NF)-kappaB inhibitor SN50, which sensitizes TRAIL-resistant cells to TRAIL, also inhibited cIAP2 protein expression. Finally, CHX, BIM, and SN50 facilitated the cleavage and activation of procaspase-8 in TRAIL-resistant cells, confirming that inhibition of TRAIL-induced apoptosis occurs at this level and that these agents sensitize MM cells by relieving this block. Our data set a framework for the clinical use of approaches that sensitize MM cells to TRAIL by agents that inhibit FLIP and cIAP-2 expression or augment caspase-8 activity.
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PMID:Intracellular regulation of tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis in human multiple myeloma cells. 1238 43

Shikonin, isolated from the plant Lithospermum erythrorhizon Sieb. ET Zucc, inhibited tumor cell growth and induced cell death in various tumor cells, with 50% growth inhibition of human cervical cancer cells, HeLa, at 18.9 +/- 1.1 mumol L-1. Treated with 40 mumol L-1 shikonin, HeLa cells underwent marked apoptotic morphological changes such as a round shape, membrane blebbing and apoptotic bodies derived from the fragmented nuclei. Another hallmark of apoptosis, DNA fragmentation, was observed by gel electrophoresis. Shikonin (10 mumol L-1) significantly blocked the transition from G1 to S phase in the HeLa cell cycle. Pan-caspase inhibitor (Z-VAD-FMK), caspase-3 inhibitor (Z-DEVD-FMK) or caspase-8 inhibitor (Z-IETD-FMK) effectively inhibited shikonin-induced cell death, while caspase-1 inhibitor (Ac-YVAD-CMK) and caspase-9 inhibitor (Z-LEHD-FMK) failed to affect cell death. Caspase-3 activity significantly increased within 12 h after shikonin treatment. Reduced expression of inhibitor of caspase-activated deoxyribonuclease (ICAD) after exposure to shikonin for 12 h suggests the resultant activation of caspase-activated deoxyribonuclease (CAD), leading to apoptosis.
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PMID:Shikonin regulates HeLa cell death via caspase-3 activation and blockage of DNA synthesis. 1522 12

Tri-n-butyltin (TBT), a biocide, is known for its immunotoxicity and hepatotoxicity and is a well-characterised mitochondrial toxin. This report investigates the mechanisms involved in induction of apoptosis by TBT in primary cultures of rat hepatocytes. Release of cytochrome c from mitochondria into the cytosol was apparent after 15 min of exposure to 2.5 microM TBT. In addition, activity of initiator caspase-9 increased after 30 min, representing activation of the mitochondrial pathway in hepatocytes. The death receptor pathway was also activated by TBT, as indicated by recruitment of the adaptor protein FADD from the cytosol to the membrane as soon as 15 min after treatment. In addition, levels of the pro-apoptotic protein Bid decreased in the cytosol, while there was an increase in levels of the cleaved form tBid, in TBT-treated hepatocytes. Activity of initiator caspase-8 increased after 30 min. The principal effector caspase-3 was activated following 30 min of treatment with TBT. Activation was confirmed by immunodetection of a 17-kDa cleaved fragment. Apoptotic substrates such as Poly(ADP-ribose) polymerase and DNA fragmentation factor-45 are cleaved by caspase-3 to ensure the dismantlement of the cell. Cleavage of Poly(ADP-ribose) polymerase into a 85-kDa fragment appeared after 30 min of TBT treatment. DNA fragmentation factor-45 disappeared in TBT-exposed rat hepatocytes. This is the first detailed study reporting the involvement of initiator and effector caspases, cleavage of their intracellular substrates and activation of both death receptor and mitochondrial pathways in TBT-induced apoptosis in rat hepatocytes. The comprehension of molecular events of apoptosis is important for the evaluation of the risk to humans and animals.
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PMID:Involvement of mitochondrial and death receptor pathways in tributyltin-induced apoptosis in rat hepatocytes. 1527 21

Trichostatin A (TSA), originally developed as an antifungal agent, is one of potent histone deacetylase (HDAC) inhibitors, which are known to cause growth arrest and apoptosis induction of transformed cells, including urinary bladder, breast, prostate, ovary, and colon cancers. However, the effect of HDAC inhibitors on human non-small cell lung cancer cells is not clearly known yet. Herein, we demonstrated that treatment of TSA resulted in a significant decrease of the viability of H157 cells in a dose-dependent manner, which was revealed as apoptosis accompanying with nuclear fragmentation and an increase in sub-G0/G1 fraction. In addition, it induced the expression of Fas/FasL, which further triggered the activation of caspase-8. Catalytic activation of caspase-9 and decreased expression of anti-apoptotic Bcl-2 and Bcl-XL proteins were observed in TSA-treated cells. Catalytic activation of caspase-3 by TSA was further confirmed by cleavage of pro-caspase-3 and intracellular substrates, including poly (ADP-ribose) polymerase (PARP) and inhibitor of caspase-activated deoxyribonuclease (ICAD). In addition, a characteristic phenomenon of mitochondrial dysfunction, including mitochondrial membrane potential transition and release of mitochondrial cytochrome c into the cytosol was apparent in TSA-treated cells. Taken together, our data indicate that inhibition of HDAC by TSA induces the apoptosis of H157 cells through signaling cascade of Fas/FasL-mediated extrinsic and mitochondria-mediated intrinsic caspases pathway.
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PMID:Trichostatin A induces apoptosis in lung cancer cells via simultaneous activation of the death receptor-mediated and mitochondrial pathway? 1720 37

It has recently become apparent that the microenvironment made up of the extracellular matrix may affect cell signaling. In this study, we evaluated Fas-triggered apoptosis in T cells in contact with tumor cells, which resembles the cell-to-cell interactions found in tumor regions. Jurkat cells were less susceptible to the Fas-mediated apoptosis when cocultured with U118, HeLa, A549, and Huh-7 tumor cells. This was indicated by less plasma membrane alteration, an amelioration of the loss of mitochondria membrane potential, a decrease in caspase-8 and caspase-3 activation, a decrease in DNA fragmentation factor-45/35 cleavage, and a reduction in the breakage of DNA when compared with Jurkat cells cultured alone. In contrast, the tumor cell lines MCF-7 and HepG2 produced no such protective effect. This protective event was independent of the expression of Fas ligand on the tumor cells. Interrupting the beta integrins-matrix interaction diminished the coculture effect. In Jurkat cells, cell matrix contact reduced the assembly of the Fas death-inducing signaling complex and Bcl-x(L) cleavage, but enhanced the phosphorylation of ERK1/2, p38 MAPK, and Akt. Only PI3K inhibitor, but not kinase inhibitors for MEK, ERK1/2, p38 MAPK, JNK, protein kinase C, and protein kinase A, completely abolished this tumor cell contact-associated protection and in parallel restored Fas-induced Bcl-x(L) cleavage as well as decreasing the phosphorylation of Bad at serine 136. Together, our results indicate that stimulation of the beta integrin signal of T cells by contact with tumor cells may trigger a novel protective signaling through the PI3K/Akt pathway of T cells against Fas-mediated apoptosis.
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PMID:Phosphatidylinositol 3-kinase/Akt activation by integrin-tumor matrix interaction suppresses Fas-mediated apoptosis in T cells. 1787 56