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Query: UNIPROT:P10415 (Bcl-2)
 33,771 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The regulatory Tat protein of human immunodeficiency virus type-1 (HIV-1) exerts a pleyotropic activity on the survival and proliferation of different cell types in culture. In this report, we investigated the effect of either endogenous or exogenous Tat on Bcl-2 proto-oncogene expression and cell survival in Jurkat T-cell lines and primary peripheral blood mononuclear cells. Stable and transient transfections of Jurkat cells with the cDNA of tat and a plasmid containing Bcl-2 promoter in front of CAT (Bcl-2 Pr/CAT) stimulated CAT activity and showed an increase of Bcl-2 mRNA and protein expression. This effect was specifically related to tat, because Jurkat cells transfected with the cDNA of tat in antisense orientation, tat carrying a mutation in the amino acid cys22-gly22, or the control vector alone (pRPneo-SL3) did not show any significant difference in Bcl-2 promoter activity with respect to parental Jurkat cells. We also observed a specific correlation between tat-induced Bcl-2 gene expression and inhibition of apoptosis induced by serum withdrawal. Our results suggest that the structural integrity of the activation domain of Tat was required for the promotion of the Bcl-2 promoter and Jurkat cell survival, because a single mutation in the aminoacid cys22 was sufficient to completely block the upregulation of Bcl-2 and inhibition of apoptosis. Moreover, picomolar concentrations of native or recombinant Tat were able to upregulate Bcl-2 expression both in Jurkat and primary peripheral blood mononuclear cells, suggesting that extracellular Tat, actively released by infected cells, may also play a significant role in suppressing apoptosis. An aberrant cell survival of lymphoid cells consequent to the upregulation of Bcl-2 may represent an additional pathogenetic mechanism that could help explain both the dysregulated immune response and the frequent occurrence of hyperplastic/neoplastic disorders in HIV-1-seropositive individuals.
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PMID:The human immunodeficiency virus type-1 Tat protein upregulates Bcl-2 gene expression in Jurkat T-cell lines and primary peripheral blood mononuclear cells. 757 50

The endogenous expression of p53 and p53-regulated genes has been examined in a thymidylate synthase-deficient colon carcinoma cell line (TS-) and a derived mutant clone (Thy4) that exhibit acute or delayed apoptotic responses, respectively, when released from G0 synchrony under conditions of dThd starvation. These cell clones demonstrate heterozygosity in p53, thereby expressing one wt allele and one with an A-->C point mutation at codon 240. Following release from G0, upregulated expression of both alleles occurred. During apoptosis in TS-, a wtp53 phenotype was expressed and in Thy4 during cytostasis, a mp53 phenotype was manifested, as determined from the ratios of wtp53/mp53 proteins, transactivation of p50-2 (a wtp53-responsive CAT reporter construct) and the endogenous expression of MDM2. Neither cytotoxicity nor cytostasis correlated with expression of p21Waf1/Cip1 Thy4 cells sustained accumulation of high levels of Bax in a wtp53-independent and dThd-independent manner and survival was associated with upregulated expression of Bcl-2. In contrast, Bax expression decreased in TS- during apoptosis, except in a highly resistant subpopulation that retained high levels of Bax. Data suggest that resistant cells (Thy4) can sustain high Bax expression and that Bcl-2 is upregulated in response to an apoptotic stimulus due to the absence of negative regulation by wtp53.
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PMID:Acute and delayed apoptosis induced by thymidine deprivation correlates with expression of p53 and p53-regulated genes in colon carcinoma cells. 866 31

Programmed cell death (PCD) characteristically involves chromatin condensation, membrane blebbing, and DNA oligonucleosomal fragmentation. These events, collectively referred to as apoptosis, represent an active cell suicide mechanism that eliminates cellular threats including potentially cancerous or virus-infected cells. Various types of programmed cell death can be blocked by the proto-oncogene Bcl-2. Levels of this protein are consistently low or undetectable in human endothelial cells (EC), which are important for immunoregulation through their interactions with circulating lymphocytes and are potential targets for infection by virus-bearing T-cells. Accumulating evidence suggests that EC may be infected in vivo to play an important role in HTLV-I-associated neuromyelopathy. In the present study, we report the establishment and characterization of human endothelial cell lines stably transfected with an HTLV-I-derived molecular clone. We observed constitutive expression of HTLV-I genes coinciding with activated Bcl-2 expression. Transient transfection of EC with the viral transactivator Tax and a reporter construct Bcl-2 promoter-CAT did not result in a significant increase in CAT activity and suggests that, in EC, expression of a second viral protein might be required for Bcl-2 activation. Further, Tax-induced apoptosis in rat fibroblasts has been shown to be blocked by Bcl-2 expression. Thus, HTLV-I-mediated induction of Bcl-2 expression in EC may provide protection against viral-induced apoptosis or extend cellular survival and create a reservoir for viral gene expression.
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PMID:Activation of Bcl-2 expression in human endothelial cells chronically expressing the human T-cell lymphotropic virus type I. 929 16

Previously, we showed that the transcription factor Egr-1 suppressed the proliferation of v-sis transformed NIH3T3 cells and also a number of human tumor cells. Here, we investigate the possible mechanisms responsible for this function. We show that transfected Egr-1 in human fibrosarcoma cells HT1080 leads to down-regulation of Bcl-2. Transient CAT transfection assays reveal that expression of Egr-1 suppresses Bcl-2 promoter activity in a dose-dependent manner. Furthermore, overexpression of Bcl-2 in Egr-1-expressing HT1080 cells enhanced cell proliferation in monolayer culture and increased anchorage-independent growth. Our results suggest that suppression of tumor cell proliferation by Egr-1 may be at least partially mediated through the down-regulation of Bcl-2.
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PMID:Suppression of human fibrosarcoma cell growth by transcription factor, Egr-1, involves down-regulation of Bcl-2. 971 58

cAMP response element-binding protein (CREB) and activating transcription factor 1 (ATF-1), members of the CREB/ATF family, have been implicated in cAMP- and calcium-induced transcriptional activation. We have previously demonstrated that quenching of CREB-associated proteins in metastatic melanoma cells by a dominant-negative CREB (KCREB) that is mutated within its DNA-binding domain decreased their radiation resistance, and their tumorigenic and metastatic potential in nude mice. As the induction of apoptosis by diverse exogenous signals is dependent on the elevation of intracellular Ca2+, the purpose of this study was to determine the role of CREB and its associated proteins in apoptosis using KCREB. We used thapsigargin (Tg), which inhibits endoplasmic reticulum-dependent Ca2+-ATPase and thereby increases cytosolic Ca2+, to induce apoptosis. MeWo human melanoma cells were transfected with the KCREB expression vector and subsequently analyzed for their susceptibility to Tg-induced apoptosis. Here we demonstrate that expression of KCREB in MeWo cells rendered them susceptible to Tg-induced apoptosis. Tg treatment induced phosphorylation of CREB and possibly ATF-1 transcription factors. Treatment with Tg induced CRE-dependent transcription in parental cells, whereas this activation was reduced in the KCREB-transfected cells. In addition, CAT activity driven by the CRE-dependent promoter was inhibited in parental MeWo cells cotransfected with increasing concentrations of KCREB in a dose-dependent manner. We did not observe any changes in Bcl-2 or Bcl-2-related proteins (Bcl-x, Bax, and Bad) in control or KCREB-transfected cells before or after treatment with Tg. Collectively, these data indicate that CREB and its associated proteins act as survival factors for human melanoma cells, and hence contribute to the acquisition of the malignant phenotype.
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PMID:CREB and its associated proteins act as survival factors for human melanoma cells. 973 94

In the cellular response to genotoxic stress, cell cycle checkpoint and apoptosis are considered to be two of the major biological events in maintaining genomic stability. The tumor suppressor p53 has been shown to play critical roles in these stress-induced cellular responses at least in part through the activation of its down-stream genes, such as p21CIP1/WAF1, GADD45 and BAX. In addition, p53 has been found to down-regulate the expression of BCL-2, which is able to block apoptosis induced by both p53-dependent and independent signaling events. In this report, we have found that increased expression of Bcl-2 protein in the human Burkitt's lymphoma WMN cell line suppressed apoptosis induced by different DNA-damaging agents. The induction of p53-regulated genes including GADD45, p21CIP1/WAF1 and BAX by genotoxic stress was substantially reduced in cells expressing high levels of Bcl-2 protein. Furthermore, Bcl-2 protein was shown to specifically suppress the p53-mediated transactivation of p21CIP1/WAF1 and PG13-CAT, which is a typical p53-binding-site reporter construct. Similarly, the inhibitory effect of Bcl-2 protein was seen in a GADD45 promoter reporter construct after treatment with methylmethane sulfonate or UV-radiation. These results indicate that in addition to its apoptosis-suppressing activity, Bcl-2 protein is able to inhibit transactivation of p53-regulated genes, which function in multiple important cellular responses to genotoxic stress, including the control of cell cycle checkpoints, cell growth suppression and DNA repair.
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PMID:Inhibitory effect of Bcl-2 on p53-mediated transactivation following genotoxic stress. 992 86

Viral expression systems offer the ability to generate high levels of a particular protein within a relatively short period of time. In particular, alphavirus constructs based on Sindbis virus (SV) and Semliki Forest virus (SFV) are promising vehicles as they are cytoplasmic vectors with the potential for high expression levels. Two such alphavirus vectors were utilized during the current study to infect two commercially relevant cell lines, baby hamster kidney (BHK) and Chinese hamster ovary (CHO); the first was a fully competent SV derivative carrying the gene for chloramphenicol acetyltransferase (dsSV-CAT), while the second was a replication deficient SFV construct containing the human interleukin-12 (IL-12) p35 and p40 genes (SFV-IL-12). Since infection with these vectors induced apoptosis in both cell lines, the present effort was dedicated to determining the ability of anti-apoptosis genes to limit the cell death associated with these virus constructs. Infection with the dsSV-CAT vector resulted in the rapid death of BHK and CHO cells within 4 days, a phenomenon which was considerably delayed by stably overexpressing bcl-2 or bcl-x(L). In fact, cellular lifespans were doubled in both BHK-bcl2 and CHO-bclx(L) cells relative to the parental cell lines. Furthermore, the presence of these gene products provided increases of up to 2-fold in recombinant CAT production. Overexpression of bcl-2 and bcl-x(L) also altered the response of these cells upon infection with SFV-IL-12. While the parental cell lines were completely nonviable within 1 week, the BHK-bcl2, BHK-bclx(L), and CHO-bclx(L) cells each recovered from the infection, resuming exponential growth and regaining viabilities of over 90% by 9 days post-infection. Total IL-12 productivities were nearly doubled by Bcl-2 and Bcl-x(L) in the CHO cells, although this effect was apparently cell-line specific, as the native BHK cells were able to secrete more IL-12 than either of its transfected derivatives. Regardless, the presence of the anti-apoptosis genes allowed the production of IL-12 to be maintained, albeit at low levels, from each of the cell lines for the duration of the culture process. Therefore, overexpression of bcl-2 family members can have a significant impact on culture viabilities and recombinant protein production during alphavirus infections of mammalian cells.
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PMID:Part I. Bcl-2 and Bcl-x(L) limit apoptosis upon infection with alphavirus vectors. 1064 29

Emodin (1,3,8-trihydroxy-6-methylanthraquinone) is an active constituent of Rheum palmatum, and showed inhibitory activity on lipopolysaccharide-induced NO production in our previous study. However, the apoptosis-inducing activity of emodin has remained undefined. Among three structurally related anthraquinones, including emodin, physcion, and chrysophanol, emodin showed the most potent cytotoxic effects on HL-60 cells, accompanied by the dose- and time-dependent appearance of characteristics of apoptosis including an increase in DNA ladder intensity, morphological changes, appearance of apoptotic bodies, and an increase in hypodiploid cells. Emodin at apoptosis-inducing concentrations causes rapid and transient induction of caspase 3/CPP32 activity, but not caspase 1 activity, according to cleavage of caspase 3 substrates poly(ADP-ribose) polymerase and D4-GDI proteins, the appearance of cleaved caspase 3 fragments being detected in emodin- but not physcion- or chrysophanol-treated HL-60 cells. A decrease in the anti-apoptotic protein, Mcl-1, was detected in emodin-treated HL-60 cells, whereas other Bcl-2 family proteins including Bax, Bcl-2, Bcl-XL, and Bad remained unchanged. The caspase 3 inhibitor, Ac-DEVD-CHO, but not the caspase 1 inhibitor, Ac-YVAD-CHO, attenuated emodin-induced DNA ladders, associated with the blockage of PARP and D4-GDI cleavage. Free radical scavenging agents including NAC, catalase, SOD, ALL, DPI, L-NAME and PDTC showed no preventive effect on emodin-induced apoptotic responses, whereas NAC, CAT and PDTC prevented HL-60 cells from ROS (H(2)O(2))-induced apoptosis through inhibition of caspase 3 cascades. Induction of catalase, but not SOD, activity was detected in emodin-treated HL-60 cells by in gel activity assays, and H(2)O(2)-induced intracellular peroxide level was significantly reduced by prior treatment of emodin in HL-60 cells. Our experiments provide evidence that emodin is an effective apoptosis inducer in HL-60 cells through activation of the caspase 3 cascade, but that it is independent of ROS production.
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PMID:Emodin induces apoptosis in human promyeloleukemic HL-60 cells accompanied by activation of caspase 3 cascade but independent of reactive oxygen species production. 1244 60

Inherited defects of copper metabolism resulting in hepatic copper accumulation and oxidative-stress might cause breed-associated forms of hepatitis. Biliary excretion is the major elimination route of copper, therefore increased hepatic copper concentrations could also be caused by cholestasis. The aim of this study was to find criteria to determine whether copper-accumulation is primary or occurs secondary to hepatitis. Liver samples of Bedlington Terriers with copper toxicosis (CT), breeds with non-copper-associated chronic extrahepatic cholestasis (EC) or chronic hepatitis (CH), and healthy dogs were used. Copper metabolism was analyzed by means of histochemical staining (copper concentration) and quantitative reverse transcriptase polymerase chain reaction (Q-PCR) on copper excretion/storage (ATOX1, COX17, ATP7A, ATP7B, CP, MT1A, MURR1, XIAP). Oxidative stress was measured by determining GSH/GSSG ratios and gene-expression (SOD1, CAT, GSHS, GPX1, CCS, p27KIP, Bcl-2). Results revealed 5+ copper in CT, but no or 1-2+ copper in EC and CH. Most gene products for copper metabolism remained at concentrations similar to healthy dogs. Three clear exceptions were observed in CT: 3-fold mRNA increase of ATP7A and XIAP and complete absence of MURRI. The only quantitative differences between the diseased and the control groups were in oxidative stress, evidenced by reductions in all GSH/GSSG ratios. We conclude that 3+ or higher histochemical detection of copper indicates a primary copper storage disease. The expression profile of copper-associated genes can be used as a reference for future studies on copper-associated diseases. All 3 diseases have reduced protection against oxidative stress, opening a rationale to use antioxidants as possible therapy.
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PMID:Copper metabolism and oxidative stress in chronic inflammatory and cholestatic liver diseases in dogs. 1706

Acute exercise in mice induces intestinal lymphocyte (IL) apoptosis. Freewheel running reduces apoptosis and forced exercise training increases splenocyte antioxidant levels. The purpose of this study was to examine the effect of freewheel running and acute exercise on mouse IL numbers and concentrations of apoptosis and antioxidant proteins and pro-inflammatory cytokines in IL. Female C57BL/6 mice had access to in-cage running wheels (RW) or cages without wheels (NRW) for 16 weeks and were randomized at the end of training to no exercise control (TC) or to treadmill exercise with sacrifice after 90 min of running (TREAD; 30 min, 22 m min(-1); 30 min, 25 m min(-1); 30 min, 28 m min(-1); 2 degrees slope). IL were analyzed for pro-(caspase 3 and 7) and anti-(Bcl-2) apoptotic proteins, endogenous antioxidants (glutathione peroxidase: GPx; catalase: CAT) and the pro-inflammatory cytokine, TNF-alpha. RW mice had higher cytochrome oxidase (p<0.001) and citrate synthase (p<0.01) activities in plantaris and soleus muscles and higher GPx and CAT expression in IL (p<0.05) (indicative of training) compared with NRW mice. TNF-alpha expression was lower (p<0.05) and IL numbers higher (p<0.05) in RW vs. NRW mice. No training effect was observed for apoptotic protein expression, although TREAD resulted in higher caspase and lower Bcl-2. These results suggest that freewheel running in mice for 16 weeks enhances antioxidant and reduces TNF-alpha expression in IL but does not reduce pro-apoptotic protein expression after acute exercise. Results are discussed in terms of implications for inflammatory bowel diseases where apoptotic proteins and TNF-alpha levels are elevated.
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PMID:Voluntary exercise training in mice increases the expression of antioxidant enzymes and decreases the expression of TNF-alpha in intestinal lymphocytes. 1948 47


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