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)

Caspase-3 plays an important role in programmed cell death as an execution-phase caspase in degradation of many substrate proteins. We identified a naturally occurring short caspase-3 variant (caspase-3s) from a human carcinoma cell line that is resulted from alternative mRNA splicing. Analysis of nucleotide sequence reveals a deletion of the exon 6 in this variant that resulted in an altered reading frame in the C-terminus, leading to an altered amino acid sequence and a truncated protein. Caspase-3s shares the same amino acid sequence as caspase-3 in the N-terminus containing the prodomain and the majority of the large subunit. The variant is 95 amino acid residues shorter at the C-terminus and is missing the conserved QACRG sequence in the catalytic site. Caspase-3 and caspase-3s are coexpressed in all human tissues examined. Several cancer cell lines also show coexpression of caspase-3 and caspase-3s, both at the mRNA and protein levels. Overexpression of caspase-3s in 293 cells is more resistant to apoptosis induced by proteasome inhibition. Furthermore, we identified that proteasome inhibition stabilized the level of caspase-3s.
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PMID:Molecular cloning and characterization of a novel caspase-3 variant that attenuates apoptosis induced by proteasome inhibition. 1135 49

Exposure of human mammary carcinoma cell line MCF-7 to TNF-alpha leads to apoptotic cell death within 24 h. In search for apoptosis-preventing signals, we identified glucocorticoids as potent death-preventing compounds. Ten nM dexamethasone provided a significant protective effect whereas 100 nM dexamethasone roughly blocked 80 - 90% of TNF-alpha-induced apoptosis. Surprisingly, dexamethasone exerted a protective effect even when supplied several hours after TNF-alpha. This points to a powerful inhibition of even advanced apoptotic processes by dexamethasone. To further pinpoint the anti-apoptotic glucocorticoid action, we investigated the expression levels of several members of the inhibitors of apoptosis (IAPs) family of proteins in response to TNF-alpha and dexamethasone. IAP proteins directly block caspase protease activities including caspase-3, caspase-7, and caspase-9. Exposure of MCF-7 cells to TNF caused an extensive downregulation of cIAP1, cIAP2, and XIAP protein levels. The decline of the IAP protein levels temporally paralleled the appearance of apoptotic DNA fragments which started 12 - 14 h following TNF-alpha addition and maximal effects were seen within 24 h. Coincubation of cells with TNF-alpha and dexamethasone potently blocked cIAP1, cIAP2, and XIAP downregulation. TNF-alpha-mediated IAP protein downregulation was not affected by proteasome inhibitors like lactacystin, ALLN or ALLM, whereas it was blocked by the broad-spectrum caspase inhibitor Z-VAD-fmk which also prevented TNF-alpha-induced apoptotic cell death. These data suggest that inhibition of IAP downregulation mediated by a caspase proteolytic activity constitutes the anti-apoptotic action of glucocorticoids in MCF-7 carcinoma cells.
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PMID:Dexamethasone inhibits TNF-alpha-induced apoptosis and IAP protein downregulation in MCF-7 cells. 1139 63

The basic treatment of leishmaniasis consists in the administration of pentavalent antimonials. The mechanisms that contribute to pentavalent antimonial toxicity against the intracellular stage of the parasite (i.e., amastigote) are still unknown. In this study, the combined use of several techniques including DNA fragmentation assay and in situ and cytofluorometry terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling methods and YOPRO-1 staining allowed us to demonstrate that potassium antimonyl tartrate, an Sb(III)-containing drug, was able to induce cell death associated with DNA fragmentation in axenic amastigotes of Leishmania infantum at low concentrations (10 microg/ml). This observation was in close correlation with the toxicity of Sb(III) species against axenic amastigotes (50% inhibitory concentration of 4.75 microg/ml). Despite some similarities to apoptosis, nuclease activation was not a consequence of caspase-1, caspase-3, calpain, cysteine protease, or proteasome activation. Altogether, our results demonstrate that the antileishmanial toxicity of Sb(III) antimonials is associated with parasite oligonucleosomal DNA fragmentation, indicative of the occurrence of late events in the overall process of apoptosis. The elucidation of the biochemical pathways leading to cell death could allow the isolation of new therapeutic targets.
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PMID:Antimonial-mediated DNA fragmentation in Leishmania infantum amastigotes. 1140 24

The inhibitor of apoptosis (IAP) family of anti-apoptotic proteins regulate programmed cell death and/or apoptosis. One such protein, X-linked IAP (XIAP), inhibits the activity of the cell death proteases, caspase-3, -7, and -9. In this study, using constitutively active mutants of caspase-3, we found that XIAP promotes the degradation of active-form caspase-3, but not procaspase-3, in living cells. The XIAP mutants, which cannot interact with caspase-3, had little or no activity of promoting the degradation of caspase-3. RING finger mutants of XIAP also could not promote the degradation of caspase-3. A proteasome inhibitor suppressed the degradation of caspase-3 by XIAP, suggesting the involvement of a ubiquitin-proteasome pathway in the degradation. An in vitro ubiquitination assay revealed that XIAP acts as a ubiquitin-protein ligase for caspase-3. Caspase-3 was ubiquitinated in the presence of XIAP in living cells. Both the association of XIAP with caspase-3 and the RING finger domain of XIAP were essential for ubiquitination. Finally, the RING finger mutants of XIAP were less effective than wild-type XIAP at preventing apoptosis induced by overexpression of either active-form caspase-3 or Fas. These results demonstrate that the ubiquitin-protein ligase activity of XIAP promotes the degradation of caspase-3, which enhances its anti-apoptotic effect.
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PMID:Ubiquitin-protein ligase activity of X-linked inhibitor of apoptosis protein promotes proteasomal degradation of caspase-3 and enhances its anti-apoptotic effect in Fas-induced cell death. 1144 97

The ubiquitin-proteasome pathway plays a critical role in the degradation of cellular proteins and cell cycle control. Dysregulating the degradation of such proteins should have profound effects on tumor growth and causes cells to undergo apoptosis. The aims of this study are to evaluate the ubiquitin-proteasome pathway in gastric cancer and the potential role of pharmacological inhibition of proteasome on induction of apoptosis in gastric cancer cells. Gastric cancer cell lines AGS (p53 wild-type) and MKN-28 (p53 mutant) were treated with proteasome inhibitor MG132. The results showed that MG132 inhibited cell proliferation in AGS and MKN-28 cells in a time- and dose-dependent manner. The inhibition of cell proliferation was caused by apoptosis which was also time- and dose-dependent. AGS cells were more responsive to MG132 than MKN-28 cells. Induction of apoptosis was preceded by the activation of caspase-3, as measured by a colorimetric caspase-3 cellular activity and Western blotting of the cleavage of caspase-3 and its substrate PARP. Activation of caspase-7 was also exhibited. In addition, z-VAD-fmk, a broad spectrum caspase inhibitor, reversed apoptosis induced by MG132 in AGS and MKN28 cells. Although z-DEVD-fmk, a specific caspase-3 inhibitor, suppressed MG132-induced apoptosis in MKN28 cells, it only partially rescued the apoptotic effect in AGS cells. Caspase-3 activation was the result of release of cytochrome c from mitochondria into the cytosol, as a consequence of upregulation of bax. There were overexpressions of all the proteasome-related proteins p53, p21(waf1) and p27(kip1) at 4 hr after proteasome inhibition which was identified by the accumulation of ubiquitin-tagged proteins. This was accompanied by accumulation of cells at G(1) phase. Our present study suggests that inhibition of proteasome function in gastric cancer cells induces apoptosis and proteasomal inhibitors have potential use as novel anticancer drugs in gastric cancer.
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PMID:Inhibition of proteasome function induced apoptosis in gastric cancer. 1147 51

Early preneoplastic cells (sup+) exhibit increased susceptibility to apoptosis, which is lost in late stage preneoplastic cells (sup-). Sup+ cells, which undergo apoptosis when cultured in low serum, show little or no DNA binding activity to nuclear factor (NF)-kappa B either in 10% or 0.2% serum. In contrast sup- cells, which are resistant to apoptosis in low serum, show a sustained constitutive activation of NF-kappa B. The constitutive activation of NF-kappa B observed in sup- cells is not due to loss of I kappa B alpha. We considered that the activation of NF-kappa B in sup- cells might be secondary to an increase in cytosolic Ca(2+), since sup- cells have a cytosolic Ca(2+) level that is double that in sup+ cells. In support of a role for Ca(2+), lowering cytosolic Ca(2+) in sup- cells by addition of the cell-permeable Ca(2+) chelator 1,2 bis(O-aminophenoxy)ethane-N, N, N', N'-tetraacetic acid-acetoxymethyl ester (BAPTA-AM) reduced cytosolic Ca(2+) by approximately 31% relative to untreated sup- cells, concomitant with a 65% reduction in NF-kappa B DNA binding activity and a reduction in I kappa B kinase (IKK) activity. In sup- cells in low serum, addition of BAPTA-AM also resulted in a significant ( approximately 50%) increase in caspase-3 activity. Raising extracellular Ca(2+) in sup+ cells resulted in a slight activation of I kappa B kinase and in enhanced NF-kappa B DNA binding activity. Using proteasome and calpain inhibitors, we determined that the basal activity of NF-kappa B in sup- cells is largely proteasome-independent, but sensitive to calpain inhibitors. Taken together these data suggest that the elevated Ca(2+) in sup- cells causes a modest activation of IKK, which likely contributes to the enhanced basal activation of NF-kappa B in sup- cells; however, the predominant effect of Ca(2+) appears to be mediated by Ca(2+)-enhanced degradation by calpain.
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PMID:Elevated calcium in preneoplastic cells activates NF-kappa B and confers resistance to apoptosis. 1147 82

Previously, we have shown that translation eukaryotic initiation factor (eIF) 4GI is cleaved during anti-Fas-mediated apoptosis. Here, we have investigated the effects of the proteasome inhibitors, MG132 and lactacystin, and the immunosuppressants, 2-amino-2[2-(4-octylphenyl)ethyl]-1,3,propane diol (FTY720) and cyclosporin A, on the integrity of eIF4GI and eIF4GII in T cells. Using wild-type Jurkat T cells, we show that the proteasome inhibitors MG132 and lactacystin promote the cleavage of eIF4G, activate caspase-8 and caspase-3-like activities and decrease cell viability. Furthermore, MG132 also promotes the cleavage of eIF4G and the activation of caspase-3-like activity in a caspase-8-deficient Jurkat cell line which is resistant to anti-Fas-mediated apoptosis. Using specific anti-peptide antisera, we show that both eIF4GI and eIF4GII are cleaved in either cell line in response to MG132 and lactacystin. In response to such treatments, we demonstrate that the fragments of eIF4GI generated include those previously observed with anti-Fas antiserum together with a novel product which lacks the ability to interact with eIF4E. In contrast, cells treated with the immunosuppressants FTY720 and cyclosporin A appear to contain only the novel cleavage fragment of eIF4GI and to lack those characteristic of cells treated with anti-Fas antiserum. These data suggest that caspase-8 activation is not required for apoptosis and eIF4G cleavage mediated by proteasome inhibitors and immunosuppressants in human T cells.
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PMID:Proteasome inhibitors and immunosuppressive drugs promote the cleavage of eIF4GI and eIF4GII by caspase-8-independent mechanisms in Jurkat T cell lines. 1151 83

Proteasome inhibitors were shown previously to induce mitochondria-independent and caspase-3-dependent apoptosis in human glioma cell lines by unknown mechanisms. Here, we showed that treatment with proteasome inhibitors, lactacystin or acetyl-leucinyl-leucinyl-norleucinal, led to elevation of the steady-state c-Myc protein but not c-myc mRNA, suggesting the accumulation of c-Myc protein by proteasome inhibitors. In addition, the marked association of c-Myc protein with ubiquitin by treatment with proteasome inhibitors indicated the involvement of proteasome in c-Myc proteolysis and the stabilization of c-Myc protein by proteasome inhibitors in vivo. The expression of Fas (also termed CD95 or APO-1) mRNA, if analyzed by reverse transcriptase polymerase chain reaction assay, was found to occur constitutively, and increased slightly by the treatment with proteasome inhibitors. In contrast, the expression of Fas ligand (FasL) mRNA was markedly induced temporarily before the activation of caspase-3 by the treatment. Agonistic anti-Fas antibody (CH11) induced apoptotic cell death, suggesting the presence of a functional Fas receptor. In addition, proteasome inhibitor-induced apoptosis was prevented by the addition of antagonistic anti-FasL antibody (4A5) or z-IETD.fmk, a potent inhibitor of caspase-8, indicating the involvement of the Fas receptor-ligand apoptotic signaling system in proteasome inhibitor-mediated apoptosis. Thus, it is suggested that proteasome inhibitors cause the accumulation of c-Myc protein which induces transiently FasL message to stimulate the Fas receptor-ligand apoptotic signaling pathway.
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PMID:Proteasome inhibitors induce Fas-mediated apoptosis by c-Myc accumulation and subsequent induction of FasL message in human glioma cells. 1152 96

Spinocerebellar ataxia type 7 (SCA7) is an autosomal dominant polyglutamine disorder presenting with progressive cerebellar ataxia and blindness. The molecular mechanisms underlying the selective neuronal death typical of SCA7 are unknown. We have established SCA7 cell culture models in HEK293 and SH-SY5Y cells, in order to analyse the effects of overexpression of the mutant ataxin-7 protein. The cells readily formed anti-ataxin-7 positive, fibrillar inclusions and small, nuclear electron dense structures. We have compared the inclusions in cells expressing mutant ataxin-7 and in human SCA7 brain tissue. There were consistent signs of ongoing abnormal protein folding, including the recruitment of heat-shock proteins and proteasome subunits. Occasionally, sequestered transcription factors were found. Activated caspase-3 was recruited into the inclusions in both the cell models and human SCA7 brain and its expression was upregulated in cortical neurones, suggesting that it may play a role in the disease process. Finally, on the ultrastructural level, there were signs of autophagy and nuclear indentations, indicative of a major stress response in cells expressing mutant ataxin-7.
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PMID:Similarities between spinocerebellar ataxia type 7 (SCA7) cell models and human brain: proteins recruited in inclusions and activation of caspase-3. 1170 44

To understand the function of the individual oncogenes of HPV16 in modulating the cellular response to apoptogenic signals, we used human keratinocytes immortalized with either E6, E7 or E6/E7 oncoproteins as model system. Applying CD95 antibodies or recombinant CD95 ligand, only the E7-immortalized cells underwent extensive apoptosis. In contrast, E6- and E6/E7-expressing keratinocytes were resistant. Dominance of E6 correlated with significant down-regulation of p53, c-Myc, p21 and Bcl-2. CD95 was found to be reduced in resistant HPV-positive cells, while there were no quantitative differences in expression levels of FADD, FLICE/caspase-8 or caspase-3. Notably, in contrast to primary human keratinocytes, all immortalized cells showed a general reduction of c-FLIP, an inhibitory protein which normally prevents unscheduled CD95-induced apoptosis. E6- and E6/E7-positive keratinocytes, however, can be sensitized to CD95 apoptosis by blocking proteasome-mediated proteolysis. CD95-resistant HPV-positive cells underwent apoptosis within 3-5 h upon co-incubation with MG132 and agonistic antibodies or CD95 ligand, which was preceded by a strong re-expression of p53 and c-Myc, but not of other half-life controlled proteins such as Bax or IkappaBalpha. Blockage of proteasomal activity alone did not result in apoptosis, although the same set of pro-apoptotic proteins was up-regulated. Performing similar experiments with cervical carcinoma cells expressing mutated p53 (C33a) or with p53-'null' lung carcinoma cells (H1299), no CD95 cell killing occurred even though c-Myc was strongly induced. These data indicate that the reduced bioavailability of p53 is a key-regulatory event in perturbation of CD95 signaling in HPV16 immortalized keratinocytes.
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PMID:Restoration of p53 expression sensitizes human papillomavirus type 16 immortalized human keratinocytes to CD95-mediated apoptosis. 1180 60


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