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)

Activated microglia have been implicated in the regulation of neuronal cell death. However, the biochemical mechanism for neuronal death triggered by activated microglia is still unclear. When treated with activated microglia, neuronal PC12 cells undergo apoptosis accompanied by caspase-3-like protease activation and DNA fragmentation. Apoptotic bodies formed were subsequently phagocytosed by neighboring activated microglia. Pretreatment of the cells with the caspase-3-like protease inhibitor N-acetyl-Asp-Glu-Val-Asp-aldehyde did not reverse this cell death. Although Bcl-2 overexpression in the cells caused the inhibition of caspase-3-like protease activity and DNA fragmentation and the effective interference of apoptosis induced by deprivation of trophic factors, it could not suppress the activated microglia-induced neuronal death. At the electron microscopic level, degenerating cells with high levels of Bcl-2 were characterized by slightly condensed chromatins forming irregular-shaped masses, severely disintegrated perikarya, and marked vacuolation. Various protease inhibitors tested did not inhibit this cell death, whereas the radical oxygen species scavenger N-acetyl-L-cysteine significantly suppressed this death. Altogether, our study provides an alternative death pathway for the activated microglia-induced neuronal death by blockage of the caspase-3 protease cascade.
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PMID:A predominant apoptotic death pathway of neuronal PC12 cells induced by activated microglia is displaced by a non-apoptotic death pathway following blockage of caspase-3-dependent cascade. 1033 72

Tumor necrosis factor-alpha (TNFalpha) may play a role in at least some of the neuronal death that occurs following brain insults or in neurodegenerative diseases. It is therefore important to characterize the mechanism underlying apoptosis induced by TNFalpha in neuronal cells and to identify factors capable of protecting neurons from this death. In the present study, we characterized the apoptotic effect of TNFalpha in PC12 cells, a model system commonly used for studying neuronal apoptosis, and examined the role of Bcl-2 and caspases in this process. We show that TNFalpha induces apoptosis in both naive and primed PC12 cells. The TNFalpha-induced apoptosis was inhibited by nerve growth factor (NGF) but not by insulin. These findings suggest that the apoptotic effect of TNFalpha can be inhibited by trophic factors and that the survival-promoting effect of NGF is mediated by a specific pathway not shared by all tyrosine kinase receptors. The effect of Bcl-2 on TNFalpha-induced apoptosis was examined in PC12 cells overexpressing Bcl-2. These cells were resistant to TNFalpha-induced apoptosis, suggesting that the apoptotic effect of TNFalpha in PC12 cells is mediated via a pathway controlled by Bcl-2. Examination of the role of caspase-3 like activity in TNFalpha-induced apoptosis showed that caspase-3-like proteases are activated, and their substrate, poly (ADP-ribose) polymerase, is cleaved following TNFalpha treatment. In addition, the broad-spectrum inhibitor of caspases, benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (Z-VAD-FMK), was found to inhibit the TNFalpha-induced apoptosis of PC12 cells. These results suggest that caspases are activated following TNFalpha treatment and are needed for TNFalpha-induced apoptosis in PC12 cells.
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PMID:Nerve growth factor inhibits apoptosis induced by tumor necrosis factor in PC12 cells. 1034 57

We investigated the ability of caspases (cysteine proteases with aspartic acid specificity) to induce cytochrome c release from mitochondria. When Jurkat cells were induced to undergo apoptosis by Fas receptor ligation, cytochrome c was released from mitochondria, an event that was prevented by the caspase inhibitor, zVAD-fmk (zVal-Ala-Asp-CH2F). Purified caspase-8 triggered rapid cytochrome c release from isolated mitochondria in vitro. The effect was indirect, as the presence of cytosol was required, suggesting that caspase-8 cleaves and activates a cytosolic substrate, which in turn is able to induce cytochrome c release from mitochondria. The cytochrome c releasing activity was not blocked by caspase inhibition, but was antagonized by Bcl-2 or Bcl-xL. Caspase-8 and caspase-3 cleaved Bid, a proapoptotic Bcl-2 family member, which gains cytochrome c releasing activity in response to caspase cleavage. However, caspase-6 and caspase-7 did not cleave Bid, although they initiated cytochrome c release from mitochondria in the presence of cytosol. Thus, effector caspases may cleave and activate another cytosolic substrate (other than Bid), which then promotes cytochrome c release from mitochondria. Mitochondria significantly amplified the caspase-8 initiated DEVD-specific cleavage activity. Our data suggest that cytochrome c release, initiated by the action of caspases on a cytosolic substrates, may act to amplify a caspase cascade during apoptosis.
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PMID:Caspases induce cytochrome c release from mitochondria by activating cytosolic factors. 1036 79

The ability of proteins of the Bcl-2 family to either induce or inhibit apoptosis is dependent on both cell type and the apoptotic stimulus. We have shown in the murine pro-B cell line FL5.12 that Bcl-2 is incapable of inhibiting tumor necrosis factor alpha (TNFalpha)-induced cell death and is cleaved during this process. One potential explanation for this observation is that caspase activation directly or indirectly inhibits Bcl-2 function. It has been suggested that caspase cleavage of Bcl-2 is responsible for its inability to block certain cell deaths. Consistent with Bcl-2 cleavage being a caspase-mediated event, this cleavage is inhibitable by 50 microM CBZ-Val-Ala-Asp-fluoromethylketone (zVAD-fmk). Furthermore, Bcl-2 can cooperate with the caspase inhibitor zVAD-fmk in a dose-dependent manner to block TNFalpha-induced cell death. Overexpression of Bcl-2 results in a 10-fold decrease in the amount of zVAD-fmk required to inhibit TNFalpha-induced apoptosis. However, cleavage-defective mutants (D31A and D34A) show no enhanced viability relative to wild-type Bcl-2 in response to TNFalpha-induced cell death and also show the same cooperativity with zVAD-fmk. These results suggest that Bcl-2 cleavage is not important for the inhibition of TNFalpha-induced cell death but do not preclude an involvement in a post-commitment phase of apoptosis.
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PMID:Bcl-2 and caspase inhibition cooperate to inhibit tumor necrosis factor-alpha-induced cell death in a Bcl-2 cleavage-independent fashion. 1037 64

We have assessed in detail the effect of cisplatin-activated programmed cell death in the cisplatin-sensitive human ovarian cancer cell line A2780 and two drug-resistant subclones, CP70 and C30. To determine whether the differential extent of apoptosis observed between the sensitive and resistant ovarian cancer cell lines was the result of dissimilar upstream signaling events, we assessed the execution of apoptotic events that precede target protein proteolysis and subsequent chromosomal DNA degradation. Proteolytic degradation of procaspase-3 was observed in both the CP70 and C30 cells following IC50 cisplatin treatment, whereas no proteolyzed caspase-3 subunits were detected in the A2780 cells. However, using a direct enzymatic assay measuring cleavage of the synthetic peptide substrate (N-acetyl-Asp-Glu-Val-Asp-p-nitroanilide), activity was detected in extracts prepared from A2780 cells treated at the IC90 level of cisplatin and was 2-3-fold less than that of extracts prepared from CP70 and C30 cells. Because the activation of procaspase-3 by caspase-9 requires the release of cytochrome c into the cytoplasm, we determined the level of cytoplasmic cytochrome c in each cell line in response to cisplatin treatment. Consistent with the caspase-3 activation data, a very small increase in cytoplasmic cytochrome c was observed in A2780 cells following cisplatin treatment, whereas dramatic increases were evident in both the CP70 and C30 cell lines. The expression of the mitochondrial factors Bcl-2, Bcl-x, and Bax was determined because each has been implicated in the regulation or release of cytochrome c at the level of the mitochondria. Bcl-2 and Bcl-xL proteins remained relatively unchanged in expression for over 48 h after exposure to cisplatin in the A2780 cell lines. However, within the same time period, expression of Bcl-2 decreased in the CP70- and C30-resistant cell lines, whereas an increase in Bcl-xL expression was observed. Expression of the proapoptotic Bcl-xS protein was observed in only the resistant CP70 and C30 cell lines independent of cisplatin treatment. A change in the expression of Mr 24,000 Bax to a Mr 21,000 isoform was evidenced in the A2780 cells within 48 h of cisplatin treatment and, to a greater extent, in the CP70 and C30 cells, which also expressed a Mr 16,000 Bax variant. Evidence for an alternative apoptotic pathway in A2780 cells was obtained by demonstrating increased FADD expression in response to cisplatin treatment. These results support a model in which cisplatin-induced programmed cell death in the cisplatin-sensitive A2780 and -resistant CP70 and C30 cells proceeds via caspase-3-independent and -dependent pathways, respectively.
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PMID:Cisplatin-induced apoptosis proceeds by caspase-3-dependent and -independent pathways in cisplatin-resistant and -sensitive human ovarian cancer cell lines. 1039 48

Cell-matrix adhesion is recognized as a physiologic determinant of cell growth and survival. Integrin occupancy seems to be a primary role. We sought to investigate the signal transduction pathways for integrin effects on cell survival in hepatic stellate cells. Integrin function was antagonized by the soluble integrin recognition sequence pentapeptide Gly-Arg-Gly-Asp-Ser (GRGDS) in primary cultures of rat hepatic stellate cells. Integrin antagonism with GRGDS peptide induced apoptosis. To investigate signal transduction mechanisms for the effect of integrins on cell survival in hepatic stellate cells, the expression of p53, Bcl-2, and Bax was analyzed. Incubation with soluble GRGDS peptide resulted in increased expression of p53 and decreased the Bcl-2/Bax ratio. In conclusion, these findings indicate that the abrogation of cell adhesion with soluble GRGDS peptide plays a critical role in the induction of apoptosis of rat hepatic stellate cells.
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PMID:Induction of apoptosis in rat hepatic stellate cells by disruption of integrin-mediated cell adhesion. 1040 63

Caspases are cysteine proteases that mediate apoptosis by proteolysis of specific substrates. Although many caspase substrates have been identified, for most substrates the physiologic caspase(s) required for cleavage is unknown. The Bcl-2 protein, which inhibits apoptosis, is cleaved at Asp-34 by caspases during apoptosis and by recombinant caspase-3 in vitro. In the present study, we show that endogenous caspase-3 is a physiologic caspase for Bcl-2. Apoptotic extracts from 293 cells cleave Bcl-2 but not Bax, even though Bax is cleaved to an 18-kDa fragment in SK-NSH cells treated with ionizing radiation. In contrast to Bcl-2, cleavage of Bax was only partially blocked by caspase inhibitors. Inhibitor profiles indicate that Bax may be cleaved by more than one type of noncaspase protease. Immunodepletion of caspase-3 from 293 extracts abolished cleavage of Bcl-2 and caspase-7, whereas immunodepletion of caspase-7 had no effect on Bcl-2 cleavage. Furthermore, MCF-7 cells, which lack caspase-3 expression, do not cleave Bcl-2 following staurosporine-induced cell death. However, transient transfection of caspase-3 into MCF-7 cells restores Bcl-2 cleavage after staurosporine treatment. These results demonstrate that in these models of apoptosis, specific cleavage of Bcl-2 requires activation of caspase-3. When the pro-apoptotic caspase cleavage fragment of Bcl-2 is transfected into baby hamster kidney cells, it localizes to mitochondria and causes the release of cytochrome c into the cytosol. Therefore, caspase-3-dependent cleavage of Bcl-2 appears to promote further caspase activation as part of a positive feedback loop for executing the cell.
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PMID:Caspase-3-dependent cleavage of Bcl-2 promotes release of cytochrome c. 1040 69

Bcl-2 family proteins and interleukin-1-beta converting enzyme/Caenorhabditis elegans cell death gene-3 (ICE/CED-3) family proteases (caspases) represent the basic regulators of apoptosis. However, the precise mechanism by which they interact is unclear. In this study, we found that gamma-radiation-induced apoptosis of leukemia cells was associated with activation of multiple caspases and bax up-regulation. Membrane changes and caspase activities were suppressed by specific caspase inhibitors. Similarly, the serine protease inhibitors z-Ala-Ala-Asp-cmk (AAD) and tosyl-lysine chloromethyl ketone (TLCK) also prevented caspase activation and poly(ADP-ribose) polymerase cleavage in vivo but had no effect on caspase activity in vitro. TLCK also prevented bax up-regulation as a result of its inhibitory effect on p53 function. Inhibitors of caspases and serine proteases partially prevented cell death, suggesting a caspase involvement in Bax-mediated cell death. We propose an ordering of signaling events in Bax-mediated cell death, including steps upstream and downstream of p53 and bax up-regulation.
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PMID:Ionizing radiation-induced, Bax-mediated cell death is dependent on activation of cysteine and serine proteases. 1043 17

We used the rat C6 gliomal cell line to investigate the potential role of ginsenoside Rh2 (G-Rh2) in brain tumor. G-Rh2 induced many apoptotic manifestations in C6 gliomal cells as evidenced by changes in cell morphology, generation of DNA fragmentation, activation of caspase and production of reactive oxygen species (ROS). As a result, cotreatment with antioxidants or a broad-spectrum caspase inhibitor, N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone effectively attenuated G-Rh2-induced cell death. However, specific cleavage of poly(ADP-ribose)polymerase into 85 kDa protein was not detected as demonstrated in many other apoptotic paradigms. Expression levels of Bcl-2 and Bax remained unchanged following G-Rh2 treatment. Furthermore, G-Rh2-induced cell death in C6 gliomal cells overexpressing antiapoptotic protein, Bcl-X(L), was comparable to that in parental cells. Taken together, our data indicate that G-Rh2-induced cell death is mediated by the generated ROS and the activation of caspase pathway in a Bcl-X(L)-independent manner.
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PMID:Ginsenoside RH-2 induces apoptotic cell death in rat C6 glioma via a reactive oxygen- and caspase-dependent but Bcl-X(L)-independent pathway. 1044 19

Certain nonmetallic porphyrins have potent antitumor activity upon visible light irradiation. Treatment of HeLa cells with nanomolar amounts of the photochemo therapeutic agent verteporfin and red light mobilized caspases 2, 3, 6, 7, 8, and 9, caused degradation of specific caspase substrates, and resulted in morphologic changes consistent with apoptosis. Caspase processing was detectable by 1 hour after light irradiation. The mitochondrial 7A6 epitope, recognized by monoclonal antibody APO2.7, became accessible, and cytochrome c was detectable within the cytosolic fraction of cells treated with verteporfin immediately after light irradiation. The general caspase inhibitor benzyloxycarboyl-Val-Ala-Asp-fluoromethylketone did not prevent 7A6 expression produced by photosensitization at peptide concentrations which completely prevented caspase activation and cleavage of caspase-specific substrates. Enforced overexpression of Bcl-2 or Bcl-xL prevented cytochrome c release and 7A6 expression produced by ultraviolet B light treatment, but did not prevent cytochrome c release or 7A6 expression elicited by verteporfin photosensitization. Bcl-2 or Bcl-xL overexpression delayed morphologic changes, depressed caspase activation, and limited substrate degradation, but did not protect against loss of viability after verteporfin photosensitization. This observation indicates that cells overexpressing Bcl-2 or Bcl-xL exhibit resistance to caspase activation even after the appearance of cytochrome c in the cytosol. Porphyrin photosensitizers are effective chemotherapeutic agents that elicit primary proapoptotic mitochondrial events even in the setting of heightened Bcl-2 or Bcl-xL expression.
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PMID:Early release of mitochondrial cytochrome c and expression of mitochondrial epitope 7A6 with a porphyrin-derived photosensitizer: Bcl-2 and Bcl-xL overexpression do not prevent early mitochondrial events but still depress caspase activity. 1046 33


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