Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P10415 (Bcl-2)
 33,771 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The human epithermoid carcinoma-derived cell line MA1, established by introduction of the adenovirus E1A 12 S cDNA linked to the mouse mammary tumor virus long terminal repeat, elicits apoptosis after induction of E1A12S in response to dexamethasone. The level of topoisomerase IIalpha begins to decrease steeply within 36 h preceding the onset of DNA fragmentation, whereas its mRNA level is unchanged (Nakajima, T., Ohi, N., Arai, T., Nozaki, N., Kikuchi, A., and Oda, K. (1995) Oncogene 10, 651-662). Topoisomerase IIalpha prepared by immunoprecipitation or extraction of the nuclear matrix was degraded much more efficiently in the S10 extract prepared from MA1 cells treated with dexamethasone for 42 h (the 42-h extract) than in the extract from untreated MA1 cells (the 0-h extract) in an ATP- and ubiquitin-dependent manner. The proteolytic activity for degradation of topoisomerase IIalpha was suppressed specifically by inhibitors for the proteasome and was much reduced in the 42-h extract prepared from MA1-derivative cell lines expressing E1B19k or Bcl-2. The proteolytic activity was lost after fractionation of the 42-h S10 extract into the S70 and P70 fractions by centrifugation at 70,000 x g for 6 h but partially recovered when these fractions were combined. Polyubiquitinated forms of topoisomerase IIalpha could be detected by incubating it in the S70 or S100 extract, which lacks most of the proteasome activity. The ubiquitination activity in S70 prepared from the 42-h extract was 4- to 5-fold higher than that prepared from the 0-h extract. These results suggest that a component(s) in the ubiquitin proteolysis pathway, responsible for ubiquitination and degradation of topoisomerase IIalpha, is activated or induced during the latent phase of E1A-induced apoptosis.
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PMID:Degradation of topoisomerase IIalpha during adenovirus E1A-induced apoptosis is mediated by the activation of the ubiquitin proteolysis system. 879 59

Induction of apoptosis in Ewing's sarcoma cells by ionizing radiation is accompanied by accumulation of ubiquitinated proteins preferentially in the form of conjugates with M(r) greater than 75,000. Furthermore, enhanced antiubiquitin immunofluorescence was detected only in cells that underwent radiation-induced apoptosis, suggesting that the observed alterations in protein ubiquitination are specific to the apoptotic process. To determine the role of the proteasome in apoptosis-associated accumulation of ubiquitin-protein conjugates, we used lactacystin, a highly selective inhibitor of proteasome proteolytic activity. Exposure of Ewing's sarcoma cells to lactacystin resulted in accumulation of ubiquitinated proteins and activation of a Bcl-2-sensitive apoptotic pathways. The latter led to proteolytic cleavage of poly(ADP-ribose) polymerase and fragmentation of nuclear DNA. These findings suggest that proteasome function is required for apoptosis-specific accumulation of ubiquitinated proteins and indicate that functional disorder of the ubiquitin-proteasome system may play an important role in the apoptotic cell death pathway.
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PMID:Apoptosis of Ewing's sarcoma cells is accompanied by accumulation of ubiquitinated proteins. 930 64

Nuclear factor kappaB (NFkappaB) is a ubiquitously expressed transcription factor that is regulated by the cytoplasmic inhibitor protein IkappaBalpha. Biological agents such as tumor necrosis factor alpha (TNFalpha), which activate NFkappaB, result in the rapid degradation of IkappaBalpha. Adenoviral-mediated gene transfer of Bcl-2 prevents apoptosis of neonatal ventricular myocytes induced by TNFalpha. In view of the growing evidence that NFkappaB may play an important role in regulating apoptosis, we determined whether TNFalpha and Bcl-2 could modulate the activity of NFkappaB in ventricular myocytes. Stimulation of myocytes with TNFalpha resulted in a 2.1-fold increase (p < 0.001) in NFkappaB-dependent gene transcription and nuclear DNA binding. Similarly, a 1.9-fold increase (p < 0.0002) in NFkappaB-dependent gene transcription was observed in myocytes expressing Bcl-2. Nuclear DNA binding activity of NFkappaB was significantly increased in myocytes expressing Bcl-2, with a concomitant reduction in IkappaBalpha protein level. The Bcl-2-mediated loss of IkappaBalpha could be prevented by the proteasome inhibitor lactacystin, consistent with the notion that the targeted degradation of IkappaBalpha consequent to overexpression of Bcl-2 utilizes the ubiquitin-proteasome pathway. This was further tested in human 293 cells in which the N-terminal region of IkappaBalpha was identified to be an important regulatory site for Bcl-2. Deletion of this region or a serine to alanine substitution mutant at amino acids 32 and 36, which are defective for both phosphorylation and degradation, were more resistant than wild type IkappaBalpha to the inhibitory effects of Bcl-2. To our knowledge, this provides the first evidence for the regulation of IkappaBalpha by Bcl-2 and suggests a link between Bcl-2 and the NFkappaB signaling pathway in the suppression of apoptosis.
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PMID:Bcl-2 activates the transcription factor NFkappaB through the degradation of the cytoplasmic inhibitor IkappaBalpha. 972 9

c-Fos is a transcription factor that promotes cell growth, differentiation, and transformation. We found that c-Fos was degraded when WEHI7.2 mouse lymphoma cells were induced to undergo apoptosis with the calcium ATPase inhibitor, thapsigargin, or the glucocorticoid hormone, dexamethasone. The degradation of c-Fos preceded caspase-3 activation and apoptotic nuclear chromatin condensation and was inhibited by the proteasome inhibitors MG132, N-acetyl-leucyl-leucyl-norleucinal, and lactacystin. Stable transfection of WEHI7.2 cells with a mutant form of c-Fos that was not degraded by the proteasome inhibited apoptosis. Also, overexpression of Bcl-2 in WEHI7.2 cells blocked c-Fos degradation and inhibited apoptosis. The results indicate that proteasome-mediated degradation of c-Fos is an early, Bcl-2-regulated step in apoptosis induction by thapsigargin and dexamethasone. These findings suggest that c-Fos may have a protective action that is eliminated by proteasome-mediated degradation and preserved by Bcl-2.
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PMID:c-Fos degradation by the proteasome. An early, Bcl-2-regulated step in apoptosis. 973 57

We characterized kinetic and biochemical changes during glucocorticoid (GC)-induced apoptosis of immature CD8+CD4+ double-positive (DP) thymocytes. A GC analog dexamethasone (Dex) induced rapid apoptotic commitment and a transient up-regulation of the NF-kappaB/RelA-p50-binding activity in DP cells. This required an early activation of proteasome, as judged by the ability of a specific proteasomal inhibitor, lactacystine, to delay apoptosis and to suppress Dex-dependent NF-kappaB activation. Dex-induced apoptotic commitment was preceded by the rapid (3 h) cleavage of both a typical caspase substrate, poly(ADP-ribose) polymerase (PARP), and of nuclear transcription factors AP-1, NF-kappaB p50-p50 and NUR-77. By contrast, phorbol myristate acetate (PMA) and/or ionomycin-induced apoptosis had much slower kinetics, were preceded by an early increase of NF-kappaB/RelA-p50, AP-1 and NUR-77 activities, and were insensitive to proteasome inhibition. Both the transgenic Bcl-2 and zVAD-fmk, an inhibitor of caspases, affected all features of Dex-induced apoptosis in a similar fashion, by inhibiting cell death and PARP cleavage, and by stabilizing AP-1, NF-kappaB p50-p50 and NUR-77 levels. Furthermore, Bcl-2 prevented Dex-induced RelA-p50 activation. However, a higher gene dosage of the transgenic Bcl-2 was required for protection against Dex, compared to the PMA and/or ionomycin-induced apoptosis. These findings highlight the unique mechanistic features of GC-induced apoptosis.
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PMID:Biochemical and kinetic characterization of the glucocorticoid-induced apoptosis of immature CD4+CD8+ thymocytes. 988 1

It has been suggested that overexpression of the Bcl-2 oncoprotein in human cancer cells contributes to their resistance to apoptosis induced by chemotherapy. We report here that a novel dipeptidyl proteasome inhibitor, CEP1612, at low concentrations rapidly induces apoptosis in human Jurkat T cells overexpressing Bcl-2 and also in all human prostate, breast, tongue and brain tumor cell lines we have tested to date, without exception. In contrast, etoposide, a standard anticancer drug, fails to kill these cells when employed under the same conditions. The apoptosis-inducing abilities of CEP1612 and its analogous compounds match precisely their order for inhibition of the proteasome chymotrypsin-like activity. CEP1612-induced apoptosis is p53-independent, inhibitable by a tetrapeptide caspase inhibitor, and associated with accumulation of the cyclin-dependent kinase inhibitors p21 and p27. Furthermore, CEP1612 selectively accumulates p27 and induces apoptosis in simian virus 40-transformed, but not the parental normal, human fibroblasts. Proteasome inhibitors such as those investigated herein might therefore have potential use as novel anticancer drugs.
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PMID:Novel dipeptidyl proteasome inhibitors overcome Bcl-2 protective function and selectively accumulate the cyclin-dependent kinase inhibitor p27 and induce apoptosis in transformed, but not normal, human fibroblasts. 989 13

The proteasome inhibitors lactacystin and AcLLNal induced p53-independent apoptosis in two human glioma cell lines, and the apoptosis was accompanied by up-regulation of immunoreactive wild-type p53, p21Waf1, Mdm2, and p27Kip1. Pretreatment with cycloheximide decreased the induction of cell death independently of p53 protein status, suggesting that the up-regulation of short-lived proteins is associated with proteasome inhibitor-induced apoptosis. Caspase-3-like proteases were activated in the proteasome inhibitor-mediated apoptosis, and the induction of cell death was inhibited more effectively in the presence of z-VAD.fmk than in the presence of Ac-DEVD.fmk, suggesting that caspases other than caspase-3 are involved. Nonetheless, there were no significant alterations in levels of immunoreactive Bcl-2, Bcl-X(L), Bax, Bad, and Bak, nor any evidence of cytochrome c release into cytosol and dissipation of delta(psi)m. Thus, the proteasome inhibitor-induced apoptosis is mediated by a mitochondria-independent mechanism, and the once activated caspase-3 does not cause the cytochrome c release and the delta(psi)m disruption.
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PMID:Proteasome inhibitors induce mitochondria-independent apoptosis in human glioma cells. 998 1

Endothelial cell death may contribute to tissue injury from ischemia. Little is known, however, about the characteristics of endothelial cell death in response to hypoxia. Using an in vitro model, we found that human umbilical vein endothelial cells were resistant to hypoxia-induced cell death with only a 2% reduction in viability at 24 h and 45% reduction in viability at 48 h. Overexpression of a mutant, IkappaBalpha, via adenoviral vector did not potentiate cell death in hypoxia, indicating that nuclear factor-kappaB activation was not involved in cytoprotection. Cell death in hypoxia was determined to be apoptotic by 3' labeling of DNA using terminal deoxynucleotidyl transferase staining and reversibility of cell death with a caspase inhibitor. Exposure of endothelial cells to hypoxia did not alter levels of proapoptotic and antiapoptotic Bcl-2 family members Bax and Bcl-XL by immunoblot analysis. In contrast, changes in p53 protein levels correlated with the induction of apoptosis in hypoxic endothelial cells. Inhibition of the proteasome increased p53 protein levels and accelerated cell death in hypoxia. Overexpression of p53 by adenoviral transduction was sufficient to initiate apoptosis of normoxic endothelial cells. These data provide a framework for the study of factors regulating endothelial cell survival and death in hypoxia.
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PMID:Mechanisms of hypoxia-induced endothelial cell death. Role of p53 in apoptosis. 1007 3

Here we examine a cell death process induced by reactive oxygen species (ROS) in the haemoflagellate Trypanosoma brucei brucei. Ca2+ distribution in cellular compartments was measured with stable transformants expressing aequorin targeted to the cytosol, nucleus or mitochondrion. Within 1.5 h of ROS production, mitochondrial Ca2+ transport was impaired and the Ca2+ barrier between the nuclear envelope and cytosol was disrupted. Consequently the mitochondrion did not accumulate Ca2+ efficiently in response to an extracellular stimulus, and excess Ca2+ accumulated in the nucleus. The terminal transferase deoxytidyl uridine end labelling assay revealed that, 5 h after treatment with ROS, extensive fragmentation of nuclear DNA occurred in over 90% of the cells. Permeability changes in the plasma membrane did not occur until an additional 2 h had elapsed. The intracellular Ca2+ buffer, EGTA acetoxymethyl ester, prevented DNA fragmentation and prolonged the onset of changes in cell permeability. Despite some similarities to apoptosis, nuclease activation was not a consequence of caspase 3, caspase 1, calpain, serine protease, cysteine protease or proteasome activity. Moreover, trypanosomes expressing mouse Bcl-2 were not protected from ROS even though protection from mitochondrial dysfunction and ROS have been reported for mammalian cells. Overall, these results demonstrate that Ca2+ pathways can induce pathology in trypanosomes, although the specific proteins involved might be distinct from those in metazoans.
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PMID:Reactive oxygen species activate a Ca2+-dependent cell death pathway in the unicellular organism Trypanosoma brucei brucei. 1022 56

The ubiquitin-proteasome pathway is the principal mechanism for the degradation of short-lived proteins in eukaryotic cells. Here we examine the possibility that ubiquitin-proteasome is involved in regulating the levels of Bcl-2, which is abundantly expressed in M-07e cells, a granulocyte/macrophage colony-stimulating factor (GM-CSF)-dependent human leukaemic cell line. Apoptosis in M-07e cells, induced by GM-CSF withdrawal, was associated with a gradual cleavage of Bcl-2 into a 22 kDa fragment. Treatment of M-07e cells with benzyloxycarbonyl-Leu-Leu-l-leucinal (Z-LLL-CHO; MG-132), a reversible ubiquitin-proteasome inhibitor, markedly accelerated the cleavage of Bcl-2 and promoted cell death through the apoptotic pathway. The cleavage of Bcl-2 was inhibited by a caspase-3 (CPP32)-specific inhibitor [acetyl-Asp-Glu-Val-Asp-CHO (DEVD-CHO)] but not caspase 1 inhibitor (acetyl-Tyr-Val-Ala-Asp-CHO), suggesting that Bcl-2 is a proteolytic substrate of a caspase-3-like protease activated during apoptosis. The simultaneous addition of recombinant human GM-CSF (rhGM-CSF) to M-07e cultures delayed the activation of caspase 3 and Bcl-2 cleavage triggered by Z-LLL-CHO, suggesting that the activation of the GM-CSF signalling pathway can partly overcome the apoptotic effect induced by Z-LLL-CHO. Apoptosis induced by inhibition of the proteasome pathway was verified in studies with lactacystin, a highly specific and irreversible proteasome inhibitor. Lactacystin-induced apoptosis in M-07e cells was remarkably similar to that induced by Z-LLL-CHO, which included caspase 3 activation, cleavage of Bcl-2 into a 22 kDa fragment and, ultimately, cell death. These results showed that inhibition of the ubiquitin-proteasome pathways can lead to the activation of a DEVD-CHO-sensitive caspase and induces Bcl-2 cleavage, which might have a role in mediating apoptosis in M-07e cells.
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PMID:Inhibition of ubiquitin-proteasome pathway activates a caspase-3-like protease and induces Bcl-2 cleavage in human M-07e leukaemic cells. 1022 67


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