EC:3.4.22.56 - FACTA Search

Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.22.56 (caspase-3)
35,750 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The familial Alzheimer's disease gene products, presenilin-1 and presenilin-2, have been reported to be functionally involved in amyloid precursor protein processing, notch receptor signaling, and programmed cell death or apoptosis. However, the molecular mechanisms by which presenilins regulate these processes remain unknown. With regard to the latter, we describe a molecular link between presenilins and the apoptotic pathway. Bcl-X(L), an anti-apoptotic member of the Bcl-2 family was shown to interact with the carboxyl-terminal fragments of PS1 and PS2 by the yeast two-hybrid system. In vivo interaction analysis revealed that both PS2 and its naturally occurring carboxyl-terminal products, PS2short and PS2Ccas, associated with Bcl-X(L), whereas the caspase-3-generated amino-terminal PS2Ncas fragment did not. This interaction was corroborated by demonstrating that Bcl-X(L) and PS2 partially co-localized to sites of the vesicular transport system. Functional analysis revealed that presenilins can influence mitochondrial-dependent apoptotic activities, such as cytochrome c release and Bax-mediated apoptosis. Together, these data support a possible role of the Alzheimer's presenilins in modulating the anti-apoptotic effects of Bcl-X(L).
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PMID:Interaction of Alzheimer's presenilin-1 and presenilin-2 with Bcl-X(L). A potential role in modulating the threshold of cell death. 1044 69

Mitochondria are sites of cellular energy production but may also influence life and death decisions by initiating or inhibiting cell death. Mitochondrial depolarization and the subsequent release of pro-apoptotic factors have been suggested to be required for the activation of a cell death program in some forms of neuronal apoptosis. We induced apoptosis in cultured rat hippocampal neurons by exposure to the protein kinase inhibitor staurosporine (STS) (300 nM). The time course of mitochondrial membrane potential (DeltaPsi(m)) during apoptosis was examined using the probe tetramethylrhodamine ethyl ester (TMRE). Cells exhibited no decrease in TMRE fluorescence, indicative of mitochondrial depolarization, up to 8 hr after STS exposure. Rather, baseline TMRE fluorescence remained unchanged up to 2 hr and thereafter actually increased significantly. Throughout this time period, the mitochondria could also be depolarized with the protonophore carbonyl cyanide p-trifluoromethoxy-phenylhydrazone (FCCP, 0.1 microM), exhibiting the same relative magnitude of fluorescence release (unquenching) as controls. Even after 16 hr of staurosporine treatment, neurons that showed signs of nuclear apoptosis maintained DeltaPsi(m) and could be depolarized with FCCP. In contrast, caspase-3-like activity had increased roughly sevenfold by 2 hr and >20-fold by 8 hr. Double-labeling of hippocampal neurons with the potential-sensitive probe Mitotracker Red Chloromethyl X-Rosamine and an antibody to cytochrome c demonstrated at the subcellular level that mitochondrial cytochrome c release also occurred in the absence of mitochondrial depolarization. These data suggest that mitochondrial depolarization is not a decisive event in neuronal apoptosis.
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PMID:Mitochondrial depolarization is not required for neuronal apoptosis. 1046 Feb 46

Mitochondria have recently been shown to serve a central role in programmed cell death. In addition, reactive oxygen species (ROS) have been implicated in cell death pathways upon treatment with a variety of agents; however, the specific cellular source of the ROS generation is unknown. We hypothesize that mitochondria-derived free radicals play a critical role in apoptotic cell death. To directly test this hypothesis, we treated murine fibrosarcoma cell lines, which expressed a range of mitochondrial manganese superoxide dismutase (MnSOD) activities, with respiratory chain inhibitors. Apoptosis was confirmed by DNA fragmentation analysis and electron microscopy. MnSOD overexpression specifically protected against cell death upon treatment with rotenone or antimycin. We examined bcl-x(L), p53 and poly(ADP-ribose) polymerase (PARP) to identify specific cellular pathways that might contribute to the mitochondrial-initiated ROS-mediated cell death. Cells overexpressing MnSOD contained less bcl-x(L) within the mitochondria compared to control (NEO) cells, therefore excluding the role of bcl-x(L). p53 was undetectable by Western analysis and examination of the proapoptotic protein bax, a p53 target gene, did not increase with treatment. Activation of caspase-3 (CPP-32) occurred in the NEO cells independent of cytochrome c release from the mitochondria. PARP, a target protein of CPP-32 activity, was cleaved to a 64 kDa fragment in the NEO cells prior to generation of nucleosomal fragments. Taken together, these findings suggest that mitochondrial-mediated ROS generation is a key event by which inhibition of respiration causes cell death, and identifies CPP-32 and the PARP-linked pathway as targets of mitochondrial-derived ROS-induced cell death.
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PMID:Overexpression of manganese superoxide dismutase protects against mitochondrial-initiated poly(ADP-ribose) polymerase-mediated cell death. 1046 52

Many cell types undergo apoptosis under conditions of ischemia. Little is known, however, about the molecular pathways that mediate this response. A cellular and biochemical approach to elucidate such signaling pathways was undertaken in primary cultures of cardiac myocytes, a cell type that is especially sensitive to ischemia-induced apoptosis. Deprivation of serum and glucose, components of ischemia in vivo, resulted in myocyte apoptosis, as determined by nuclear fragmentation, internucleosomal cleavage of DNA, and processing of caspase substrates. These manifestations of apoptosis were blocked by zVAD-fmk, a peptide caspase inhibitor, indicating that caspase activity is necessary for the progression of apoptosis in this model. In contrast to control cells, apoptotic myocytes exhibited cytoplasmic accumulation of cytochrome c, indicating release from the mitochondria. Furthermore, both caspase-9 and caspase-3 were processed to their active forms in serum-/glucose-deprived myocytes. Caspase processing, but not cytochrome c release, was inhibited by zVAD-fmk, placing the latter event upstream of caspase activation. This evidence demonstrates that components of ischemia activate the mitochondrial death pathway in cardiac myocytes.
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PMID:The mitochondrial apoptotic pathway is activated by serum and glucose deprivation in cardiac myocytes. 1047 70

Apoptosis and platelet activation share common morphological and biochemical features. Because caspases are essential mediators of apoptosis, we examined whether platelets contain these proteinases and use them during platelet activation. Human platelets contained caspase-9, caspase-3, and the caspase activators APAF-1 and cytochrome c as shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting. Upon treatment with cytochrome c and dATP, platelet cytoplasmic extracts recapitulated apoptotic events, including sequential activation of procaspase-9 and procaspase-3 and subsequent proteolysis of caspase substrates. Calcium ionophore-stimulated platelets also recapitulated apoptotic events, including cell shrinkage, plasma membrane microvesiculation, phosphatidyl serine externalization, and proteolysis of procaspase-9, procaspase-3, gelsolin, and protein kinase C-delta. Strikingly, however, these events occurred without caspase activation or release of mitochondrial cytochrome c, suggesting a role for a noncaspase proteinase. Supporting this, inhibition of the calcium-dependent proteinase, calpain, prevented caspase proteolysis, 'apoptotic' substrate cleavage, and platelet microvesiculation. In vitro, purified calpain cleaved recombinant procaspase-9 and procaspase-3 without activating either caspase, confirming the inhibitor studies. These data implicate calpain as a potential regulator of caspases and suggest that calpain, not caspases, promotes apoptosis-like events during platelet activation.
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PMID:Calpain functions in a caspase-independent manner to promote apoptosis-like events during platelet activation. 1047 93

Neuronal apoptotic execution uses a cytochrome c-dependent caspase activation mechanism that is conserved in other cell types. Phosphatidylinositol 3-kinase and its downstream effector, Akt/protein kinase B, appear to control this mechanism and govern the life/death decision. We have developed a cell-free system using cytosol from human neuroblastoma (SY5Y) cells that reconstitutes biochemical features of neuronal apoptosis. In the presence of cytochrome c and ATP, caspase-9 and -3 were activated, which initiated chromatin condensation and DNA cleavage in rat pheochromocytoma (PC12) nuclei. Akt was cleaved in reactions where caspase-3 was activated and its cleavage was prevented by the caspase inhibitor DEVD-aldehyde. The phosphatase inhibitors orthovanadate and okadaic acid prevented catalytic processing and activation of caspase-3 and digestion of Akt and partially inhibited cleavage of caspase-9. Caspase-dependent destruction of Akt irreversibly inactivates this key mediator of survival signaling, ensuring that the execution pathway will prevail.
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PMID:Phosphorylation-dependent Akt cleavage in neural cell in vitro reconstitution of apoptosis. 1050 Dec 28

Phospholipid hydroperoxide glutathione peroxidase (PHGPx) is a key enzyme in the protection of biomembranes exposed to oxidative stress. We investigated the role of mitochondrial PHGPx in apoptosis using RBL2H3 cells that overexpressed mitochondrial PHGPx (M15 cells), cells that overexpressed non-mitochondrial PHGPx (L9 cells), and control cells (S1 cells). The morphological changes and fragmentation of DNA associated with apoptosis occurred within 15 h in S1 and L9 cells upon exposure of cells to 2-deoxyglucose (2DG). The release of cytochrome c from mitochondria was observed in S1 cells after 4 h and was followed by the activation of caspase-3 within 6 h. Overexpression of mitochondrial PHGPx prevented the release of cytochrome c, the activation of caspase-3, and apoptosis, but non-mitochondrial PHGPx lacked the ability to prevent the induction of apoptosis by 2DG. An ability to protect cells from 2DG-induced apoptosis was abolished when the PHGPx activity of M15 cells was inhibited by diethylmalate, indicating that the resistance of M15 cells to apoptosis was indeed due to the overexpression of PHGPx in the mitochondria. The expression of members of the Bcl-2 family of proteins, such as Bcl-2, Bcl-xL, Bax, and Bad, was unchanged by the overexpression of PHGPx in cells. The levels of hydroperoxides, including hydrogen and lipid peroxide, in mitochondria isolated from S1 and L9 cells were significantly increased after the exposure to 2DG for 2 h, while the level of hydroperoxide in mitochondria isolated from M15 cells was lower than that in S1 and L9 cells. M15 cells were also resistant to apoptosis induced by etoposide, staurosporine, UV irradiation, cycloheximide, and actinomycin D, but not to apoptosis induced by Fas-specific antibodies, which induces apoptosis via a pathway distinct from the pathway initiated by 2DG. Our results suggest that hydroperoxide, produced in mitochondria, is a major factor in apoptosis and that mitochondrial PHGPx might play a critical role as an anti-apoptotic agent in mitochondrial death pathways.
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PMID:Mitochondrial phospholipid hydroperoxide glutathione peroxidase suppresses apoptosis mediated by a mitochondrial death pathway. 1050 88

The effects of the protein kinase C (PKC) activator and down-regulator bryostatin 1 were examined with respect to paclitaxel-induced apoptosis and antiproliferative activity in human myeloid leukemia cells (U937) displaying enforced expression of the anti-apoptotic protein Bcl-xL. Overexpression of Bcl-xL blocked various aspects of paclitaxel-mediated apoptosis, including caspase-3 activation, degradation of poly(ADP-ribose) polymerase (PARP), loss of mitochondrial membrane potential (Delta Psim), and release of cytochrome c. However, subsequent (but not prior) exposure of paclitaxel-treated U937/Bcl-xL cells (500 nM; 6 h) to bryostatin 1 (10 nM; 15 h) restored the extent of apoptosis, caspase activation, and mitochondrial damage to levels approximating those in paclitaxel-treated empty-vector control cells (U937/Neo). Potentiation of paclitaxel-induced apoptosis by bryostatin 1 in U937/Bcl-xL cells occurred primarily in the G2M cell population, and was associated with alterations in Bcl-xL gel mobility and a reduction in paclitaxel-mediated stimulation of CDK1 activity. Enhancement of paclitaxel-induced apoptosis by bryostatin 1 in Bcl-xL overexpressors was accompanied by a corresponding reduction in clonogenic potential. In contrast to its effects on apoptosis, bryostatin 1 failed to restore paclitaxel-mediated increases in free Bax levels in U937/Bcl-xL cells. Lastly, the actions of bryostatin 1 were mimicked by a pharmacologic inhibitor of the MEK1/MAP kinase pathway (PD98059), but not by SB203580, an inhibitor of p 38 MAP kinase. Moreover, sequential exposure of both U937/Neo or/Bcl-xL cells to paclitaxel followed by bryostatin 1 or PD98059 was associated with a net reduction in MAP kinase activity. Collectively, these findings indicate that protection against paclitaxel-mediated mitochondrial dysfunction and apoptosis in human U937 leukemia cells conferred by Bcl-xL overexpression can be substantially overcome by bryostatin 1 and possibly other agents that interrupt the MAP kinase signal transduction pathway.
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PMID:Bryostatin 1 enhances paclitaxel-induced mitochondrial dysfunction and apoptosis in human leukemia cells (U937) ectopically expressing Bcl-xL. 1051 58

CTLs kill targets by inducing them to die through apoptosis. A number of morphological and biochemical events are now recognized as characteristic features of the apoptotic program. Among these, the disruption of the inner mitochondrial transmembrane potential (Delta Psi m) and the release of cytochrome c into the cytoplasm appear to be early events in many systems, leading to the activation of caspase-3 and, subsequently, nuclear apoptosis. We show here that, in Jurkat targets treated in vitro with purified granzyme B and perforin or granzyme B and adenovirus, Delta Psi m collapse, reactive oxygen species production, and cytochrome c release from mitochondria were observed. Loss of Delta Psi m was also detected in an in vivo system where green fluorescent protein-expressing targets were attacked by a cytotoxic T cell line that kills predominantly through the granzyme pathway. DNA fragmentation, phosphatidylserine externalization, and reactive oxygen species production were inhibited in the presence of the caspase inhibitors benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (zVAD-fmk) and benzyloxycarbonyl-Asp-Glu-Val-Asp-fluoromethyl ketone (zDEVD-fmk) in our in vitro system. Importantly, in either the in vitro or in vivo systems, these inhibitors at concentrations up to 100 microM did not prevent Delta Psi m collapse. In addition, cytochrome c release was observed in the in vitro system in the absence or presence of zVAD-fmk. Thus the granzyme B-dependent killing pathway in Jurkat targets involves mitochondrial alterations that occur independently of caspases.
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PMID:Granzyme B-induced loss of mitochondrial inner membrane potential (Delta Psi m) and cytochrome c release are caspase independent. 1052 65

Caspase-3 is essential for Fas-mediated apoptosis in vitro. We investigated the role of caspase-3 in Fas-mediated cell death in vivo by injecting caspase-3-deficient mice with agonistic anti-Fas Ab. Wild-type controls died rapidly of fulminant hepatitis, whereas the survival of caspase-3-/- mice was increased due to a delay in hepatocyte cell death. Bcl-2 expression in the liver was dramatically decreased in wild-type mice following anti-Fas injection, but was unchanged in caspase-3-/- mice. Hepatocytes from anti-Fas-injected wild-type, but not caspase-3-/-, mice released cytochrome c into the cytoplasm. Western blotting confirmed the lack of caspase-3-mediated cleavage of Bcl-2. Presumably the presence of intact Bcl-2 in caspase-3-/- hepatocytes prevents the release of cytochrome c from the mitochondria, a required step for the mitochondrial death pathway. We also show by Western blot that Bcl-xL, caspase-9, caspase-8, and Bid are processed by caspase-3 in injected wild-type mice but that this processing does not occur in caspase-3-/- mice. This study thus provides novel in vivo evidence that caspase-3, conventionally known for its downstream effector function in apoptosis, also modifies Bcl-2 and other upstream proteins involved in the regulation of Fas-mediated apoptosis.
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PMID:In vivo evidence that caspase-3 is required for Fas-mediated apoptosis of hepatocytes. 1052 93

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