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

The bcl-2 gene encodes a 26 kDa protein, overexpression of which blocks cell apoptosis. Since conflicting data have been reported concerning the localization of the Bcl-2 protein with mitochondrial inner and outer membranes, we analyzed in vitro import of the human Bcl-2 protein into isolated rat liver mitochondria. The Bcl-2 protein translated in rabbit reticulocyte lysate was efficiently inserted into the mitochondrial outer rather than the inner membrane in a membrane potential-independent manner. The carboxyl-terminal hydrophobic stretch is essential for the Bcl-2 protein to integrate into the outer membrane. Binding of the Bcl-2 protein to the mitochondria was not affected by pretreatment of the mitochondria with trypsin, indicating that the Bcl-2 protein does not require protease-sensitive mitochondrial surface components for its membrane insertion.
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PMID:The bcl-2 protein is inserted into the outer membrane but not into the inner membrane of rat liver mitochondria in vitro. 821 96

Stimulation of the Fas (APO-1, CD95) receptor, which is present on a variety of cells, usually triggers a process of programmed cell death. Systemic injection of anti-Fas antibody into mice leads to fulminant liver destruction resulting from massive hepatocyte apoptosis, and to rapid death. Hepatocytes bear Fas but do not express Bcl-2, a protein that plays, in a number of conditions, a protective role against apoptosis. We have generated mice whose liver expresses Bcl-2 as the result of bcl-2 transgene placed under the control of the hepatocyte-specific alpha1-anti-trypsin gene promoter, but is otherwise not distinguishable from that of normal mice. These mice display a marked to almost total resistance to liver damage induced by anti-Fas antibody injection. This protective effect of Bcl-2 occurs in the absence of significant variations, in the stimulated livers, in the level of expression of other proteins also involved in resistance or sensitivity to apoptosis, namely Bcl-x, Bax, Bad, Bak, and p53. Mice with protected livers, however, die almost as rapidly as normal mice, which indicates that acute lethality results from stimulation of Fas receptors present on other target organs or cells.
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PMID:A bcl-2 transgene expressed in hepatocytes protects mice from fulminant liver destruction but not from rapid death induced by anti-Fas antibody injection. 864 44

During embryological development and throughout life, regulation of the thickness of skin is likely to involve modulation of keratinocyte proliferation, differentiation, and cell death. One major mechanism of cell death is apoptosis; but the precise relationship between apoptosis and differentiation has not been well-defined. In this report, we demonstrate that when cultured undifferentiated keratinocytes have their adhesive interactions interrupted by either enzymatic treatment (ie, trypsin) and suspension in a semi-solid methyl cellulose medium, or exposure to antibodies against beta 1 integrins and E-cadherin, induction of differentiation occurs (expression of involucrin), as well as apoptosis (positive terminal deoxynucleotidyl transferase (Tdt)-mediated dUTP-biotin nick end labeling (TUNEL) assay and DNA fragmentation). However, these events are not directly interdependent processes, as determined by two-color immunofluorescence staining. Thus, apoptosis can occur without evidence of differentiation and vice versa. The process o apoptosis in keratinocytes was dissected at the molecular level and found to be correlated with increased expression of Bax and decreased levels of Bcl-XL, with no role for either Bcl-2 or Bcl-XS. We conclude that keratinocytes do not need to undergo differentiation before undergoing apoptosis.
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PMID:Apoptosis in keratinocytes is not dependent on induction of differentiation. 901 Apr 53

Subcellular localization of proteins with carboxyl-terminal insertion sequences requires the molecule be both targeted to and integrated into the correct membrane. The mechanism of membrane integration of cytochrome b5 has been shown to be promiscuous, spontaneous, nonsaturable, and independent of membrane proteins. Thus endoplasmic reticulum localization for cytochrome b5 depends primarily on accurate targeting to the appropriate membrane. Here direct comparison of this mechanism with that of three other proteins integrated into membranes via carboxyl-terminal insertion sequences [vesicle-associated membrane protein 1(Vamp1), polyomavirus middle-T antigen, and Bcl-2] revealed that, unlike cytochrome b5, membrane selectivity for these molecules is conferred at least in part by the mechanisms of membrane integration. Bcl-2 membrane integration was similar to that of cytochrome b5 except that insertion into lipid vesicles was inefficient. Unlike cytochrome b5 and Bcl-2, Vamp1 binding to canine pancreatic microsomes was saturable, ATP-dependent, and abolished by mild trypsin treatment of microsomes. Surprisingly, although the insertion sequence of polyomavirus middle-T antigen was sufficient to mediate electrostatic binding to membranes, binding did not lead to integration into the bilayer. Together these results demonstrate that there are at least two different mechanisms for correct membrane integration of proteins with insertion sequences, one mediated primarily by targeting and one relying on factors in the target membrane to mediate selective integration. Our results also demonstrate that, contrary to expectation, hydrophobicity is not sufficient for insertion sequence-mediated membrane integration. We suggest that the structure of the insertion sequence determines whether or not specific membrane-bound receptor proteins are required for membrane integration.
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PMID:Evidence for multiple mechanisms for membrane binding and integration via carboxyl-terminal insertion sequences. 922 Sep 74

We report a novel mode of apoptosis induction observed in human leukemic HL-60 cells. These cells spontaneously underwent apoptosis in the course of proliferation when the cell density became higher than 1 x 10(6)/ml. This occurred under ordinary in vitro culture conditions, with or without fetal calf serum. Even the low density cells were committed to undergo apoptosis if they were cultured under artificially concentrated conditions. Replacement of the culture supernatant of the low density cells by that of the high density ones resulted in apoptosis induction in the former cells. This apoptosis-inducing activity of the high density cell culture supernatant was completely eliminated by the action of trypsin but was fully restored following ultrafiltration by 3-kDa pore-sized membrane. A strong apoptosis-inducing activity was recovered from the culture supernatant of the high density HL-60 cells at a specific fraction in reverse-phase column chromatography. Neither an interleukin-beta converting enzyme inhibitor nor CPP-32 inhibitor blocked the induction of cell density-dependent apoptosis in HL-60 cells, although overexpression of Bcl-2 protein markedly attenuated the induction of this mode. Surprisingly, transforming growth factor-beta1 and activin A did not induce but, rather, inhibited the induction of cell density-dependent apoptosis. These data suggest that HL-60 cells release an unknown low molecular weight peptide-containing factor in response to an increase in cell density to induce apoptosis in an autocrine manner and that the interleukin-beta converting enzyme-independent intracellular machinery for this mode of apoptosis is strongly affected by signaling events through the transforming growth factor-beta1 receptor and by the action of Bcl-2 oncoprotein.
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PMID:Cell density-dependent apoptosis in HL-60 cells, which is mediated by an unknown soluble factor, is inhibited by transforming growth factor beta1 and overexpression of Bcl-2. 924 70

Previous results showed that the synthetic compound amidinopiperidine-4-carboxylic acid 4-tert-butylphenyl ester (APCA-OPhBut), a trypsin inhibitor, could specifically inhibit the activity of proteinase In and lead to growth arrest of Hela cells in early S phase. In this study, APCA-OPhBut exhibited inhibitory effects on the growth of HL-60 cells. Apoptotic cells were observed when the cells were cultured with APCA-OPhBut above 50 microM. Time course studies demonstrated that apoptotic cells were increased in a dose- and time-dependent manner. Flowcytometric assays demonstrated that HL-60 cells underwent slight G1 growth arrest after treatment with APCA-OPhBut. No change of Bcl-2 protein level was detected. The findings suggest that the intracellular trypsin-like protease inhibited by APCA-OPhBut not only plays a key role in DNA synthesis initiation but is also necessary for survival of certain cell lines.
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PMID:Effects of amidinopiperidine-4-carboxylic acid 4-tert-butylphenyl ester, a specific trypsin inhibitor, on the growth of HL-60 cells. 967 58

Bcl-2, an anti-apoptotic protein, is believed to be localized in the outer mitochondrial membrane, endoplasmic reticulum, and nuclear envelope. However, Bcl-2 has also been suggested as playing a role in the maintenance of mitochondrial membrane potential, indicating its possible association with the inner mitochondrial membrane. We therefore further examined the exact localization of Bcl-2 in mitochondria purified from wild-type and bcl-2-transfected PC12 cells and pre- and postnatal rat brains. Double immunostaining demonstrated that Bcl-2 was co-localized with subunit beta of F1F0ATPase in the inner mitochondrial membrane. Biochemical analysis of isolated mitochondria using digitonin and trypsin suggests an association of Bcl-2 with the inner mitochondrial membrane. More interestingly, the majority of Bcl-2 disappeared from the inner membrane of mitochondria when cultured under serum deprivation. These results suggest that Bcl-2 acts as an anti-apoptotic regulator by localizing mainly to the inner mitochondrial and smooth ER membranes.
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PMID:Selective localization of Bcl-2 to the inner mitochondrial and smooth endoplasmic reticulum membranes in mammalian cells. 1088 11

Microwave heating of histologic sections in citrate buffer (MAR) is a widely used method of antigen recovery but often results in loss of tissue sections. Low-temperature antigen retrieval (LTAR), incubation at 80 degrees C in citrate buffer for 2 hours with trypsin pretreatment is an alternative method reported to result in better antigen recovery for specific antigens as well as decreased loss of tissue sections. To optimize our immunohistochemical evaluation of breast carcinomas, we compared the efficacy of these methods of antigen recovery for several important antigens. Ten breast carcinomas were immunostained for estrogen and progesterone receptors (ER and PR), Ki-67/ MIB 1, p27/Kip-1, and Bcl-2 after MAR, LTAR with enzymatic pretreatment, or no antigen recovery. The immunohistochemical staining was scored and compared for each antibody and antigen recovery combination. The proportion of tissue lost from each slide after staining also was assessed. More and stronger positive staining was achieved with antibodies to Ki67/MIB 1 and ER when LTAR was used compared with the other two methods; in contrast, optimal staining with antibodies to Bcl-2 was achieved when MAR was used. Staining with anti-p27/Kip- was nearly equal with either LTAR or MAR. Staining with anti-PR was slightly better with MAR than with LTAR. Tissue loss was greatest for MAR compared with LTAR or with no antigen recovery. For selected cases, LTAR caused focal tissue damage, and either the immunostaining with LTAR had to be repeated or only a portion of some tissue sections would be used for examination. LTAR was the most effective for ER and Ki-67/MIB 1. MAR provided the most intense staining for Bcl-2 and PR, but this enhanced staining must be weighed against the greater tissue section loss from MAR. This study demonstrated that AR methods are not equally applicable to all antibodies.
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PMID:Methods of antigen recovery vary in their usefulness in unmasking specific antigens in immunohistochemistry. 1098 77

We asked whether the antiangiogenic action of 16K human PRL (hPRL), in addition to blocking mitogen-induced vascular endothelial cell proliferation, involved activation of programmed cell death. Treatment with recombinant 16K hPRL increased DNA fragmentation in cultured bovine brain capillary endothelial (BBE) and human umbilical vein endothelial (HUVE) cells in a time- and dose-dependent fashion, independent of the serum concentration. The activation of apoptosis by 16K hPRL was specific for endothelial cells, and the activity of the peptide could be inhibited by heat denaturation, trypsin digestion, and immunoneutralization, but not by treatment with the endotoxin blocker, polymyxin-B. 16K hPRL-induced apoptosis was correlated with the rapid activation of caspases 1 and 3 and was blocked by pharmacological inhibition of caspase activity. Caspase activation was followed by inactivation of two caspase substrates, poly(ADP-ribose) polymerase (PARP) and the inhibitor of caspase-activated deoxyribonuclease (DNase) (ICAD). Furthermore, 16K hPRL increased the conversion of Bcl-X to its proapoptotic form, suggesting that the Bcl-2 protein family may also be involved in 16K hPRL-induced apoptosis. These findings support the hypothesis that the antiangiogenic action of 16K hPRL includes the activation of programmed cell death of vascular endothelial cells.
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PMID:The antiangiogenic factor 16K PRL induces programmed cell death in endothelial cells by caspase activation. 1104 70

BID is a BH3 domain-only member of the Bcl-2 family that acts as an apoptotic agonist in programmed cell death. After cleavage by caspase-8, the N-terminal of BID (N-BID) stays in the cytosol while the C-terminal of BID (C-BID) translocates to mitochondria, leading to cytochrome c release in vivo and in vitro. We have previously reported that BID or truncated BID (tBID) can induce the release of entrapped trypsin and cytochrome c from large unilamellar vesicles (LUVs). Further studies have been performed and are presented here; the results demonstrate that C-BID, like BID and tBID, induces vesicle leakage, whereas N-BID or the BID mutants BID (D59A) and BID (G94E) fail to have any significant effects. The affinity of the above-mentioned proteins for soybean phospholipid LUVs (SLUVs) decreased in an order similar to their leakage-inducing capability: tBID > BID > BID (D59A), while N-BID and BID (G94E) were unable to bind to the vesicles at all. BID-induced leakage was dependent on the lipid composition of vesicles. Acidic phospholipid (e.g. phosphatidic acid or phosphatidylglycerol) was necessary for BID-induced leakage while the presence of phosphatidylethanolamine or cholesterol reduced the leakage. It was also found C-BID is better able to penetrate the soybean phospholipid monolayer than BID or tBID. A further finding was that tBID, but not full-length BID, could stimulate the aggregation of SLUVs. Finally, Bcl-x(L), an apoptotic antagonist in programmed cell death, can prevent the aggregation of LUVs induced by tBID, but not the release of entrapped trypsin. It is postulated that two separate domains of tBID are responsible for inducing leakage and aggregation of phospholipid vesicles.
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PMID:Leakage and aggregation of phospholipid vesicles induced by the BH3-only Bcl-2 family member, BID. 1112 Nov 1


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