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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 family of proteins regulates apoptosis, the cell death program triggered by activation of certain proteases (caspases). An attractive model for how Bcl-2 and its closest relatives prevent caspase activation is that they bind to and inactivate an adaptor protein required for procaspase processing. That model has been supported by reports that mammalian prosurvival Bcl-2 relatives bind the adaptor Apaf-1, which activates procaspase-9. However, the in vivo association studies reported here with both overexpressed and endogenous Apaf-1 challenge this notion. Apaf-1 could be immunoprecipitated together with procaspase-9, and the Apaf-1 caspase-recruitment domain was necessary and sufficient for their interaction. Apaf-1 did not bind, however, to any of the six known mammalian prosurvival family members (Bcl-2, Bcl-x(L), Bcl-w, A1, Mcl-1, or Boo), or their viral homologs adenovirus E1B 19K and Epstein-Barr virus BHRF-1. Endogenous Apaf-1 also failed to coimmunoprecipitate with endogenous Bcl-2 or Bcl-x(L), or with two proapoptotic relatives (Bax and Bim). Moreover, apoptotic stimuli did not induce Apaf-1 to bind to these family members. Thus, the prosurvival Bcl-2 homologs do not appear to act by sequestering Apaf-1 and probably instead constrain its activity indirectly.
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PMID:Bcl-2 family members do not inhibit apoptosis by binding the caspase activator Apaf-1. 1044 54

Although the study of germ cell death is arguably still in its infancy as a field, several recent breakthroughs have provided the fodder for a story, replete with episodes of apparent mass cellular suicide if not murder, that will undoubtedly serve as a research base for many laboratories over the next several years. Death is known to strike the male and female germlines with roughly equal intensity, but the innate feature of male germ cells being self-renewing while those of the female are not places the death of oocytes in a completely different light. Indeed, the functional life span of the female gonads is defined in most species, including humans, by the size and rate of depletion of the precious endowment of oocytes enclosed within follicles in the ovaries at birth. This continuous loss of oocytes throughout life, referred to by many as the female biological clock, appears to be driven by a genetic program of cell death that is composed of players and pathways conserved from worms to humans. It is on this genetic pathway, and the role of its constituent molecules in regulating female germ cell fate, that this review will focus. Emphasis will be placed on those studies using genetic-null or transgenic models to explore the functional requirement of proteins, such as Bcl-2 family members, Apaf-1, and caspases in vertebrates to CED-9, CED-4, and CED-3 in Caenorhabditis elegans, in oocyte survival and death. Furthermore, hypotheses regarding the potential impact of translating what is now known of the oocyte death pathway into new approaches for the clinical diagnosis and management of female infertility and the menopause will be offered as a means to stimulate further research in this new and exciting field.
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PMID:Oocyte apoptosis: like sand through an hourglass. 1045 43

Apoptosis, an evolutionarily conserved form of cell death, requires a regulated program. Central to the apoptotic program is a family of cysteine proteases, known as caspases, that cleave a subset of cellular proteins, resulting in the stereotypic morphological changes of apoptotic cell death. In living cells caspases are present as inactive zymogens and become activated in response to pro-apoptotic stimuli. Mitochondria participate in the activation of caspases by releasing cytochrome c into the cytosol where it binds to the adaptor molecule Apaf-1 (apoptotic protease activating factor 1) and causes its oligomerization. This renders Apaf-1 competent to recruit and activate the cell death initiator caspase, pro-caspase-9. Once caspase-9 is activated, it cleaves and activates downstream cell death effector caspases. Bcl-2, an apoptosis inhibitor localized to mitochondrial outer membranes, prevents cytochrome c release, caspase activation and cell death. This review discusses recent advances on the role of mitochondria and cytochrome c in the central pathway leading to apoptotic cell death.
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PMID:Apoptosis: checkpoint at the mitochondrial frontier. 1048 95

Programmed cell death is a common feature during animal development. In the nematode C. elegans, more than 12 genes have been identified that function in the apoptotic killing and elimination of 131 of the 1090 cells that are generated during hermaphrodite development. These genes divide the process of programmed cell death into three distinct steps: execution of the death sentence; engulfment of dying cells; and degradation of dead, engulfed cells. Biochemical characterization of the genes in this pathway has led to the identification of an apoptotic machinery that mediates apoptotic death in this species. The proximal cause of apoptosis in C. elegans is the activation of the caspase homolog CED-3 from the inactive zymogen (proCED-3) into the mature protease. This activation is mediated by the Apaf-1 homolog CED-4. In cells that should survive, CED-3 and CED-4 pro-apoptotic activity is antagonized by the Bcl-2 family member CED-9. CED-9 has been proposed to prevent death by sequestering CED-4 and proCED-3 in an inactive ternary complex, the apoptosome. In cells fated to die, CED-9 is, in turn, inactivated by the pro-apoptotic BH3 domain-containing protein EGL-1, likely through a direct protein-protein interaction. The structural and functional conservation of cell death genes between nematodes and mammals strongly suggests that the apoptotic program is ancient in origin and that all metazoans share a common mechanism of apoptotic cell killing.
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PMID:Programmed cell death in the nematode C. elegans. 1054 77

We investigated the in vitro growth inhibitory and apoptotic effects of clinically achievable concentrations of As(2)O(3) (0.5 to 2.0 micromol/L) against human myeloid leukemia cells known to be resistant to a number of apoptotic stimuli. These included chronic myelocytic leukemia (CML) blast crisis K562 and HL-60/Bcr-Abl cells, which contain p210 and p185 Bcr-Abl, respectively, and HL-60 cell types that overexpress Bcl-2 (HL-60/Bcl-2), Bcl-x(L) (HL-60/Bcl-x(L)), MDR (HL-60/VCR), or MRP (HL-60/AR) protein. The growth-inhibitory IC(50) values for As(2)O(3) treatment for 7 days against all these cell types ranged from 0.8 to 1.5 micromol/L. Exposure to 2 micromol/L As(2)O(3) for 7 days induced apoptosis of all cell types, including HL-60/Bcr-Abl and K562 cells. This was associated with the cytosolic accumulation of cyt c and preapoptotic mitochondrial events, such as the loss of inner membrane potential (DeltaPsim) and the increase in reactive oxygen species (ROS). Treatment with As(2)O(3) (2 micromol/L) generated the activities of caspases, which produced the cleavage of the BH3 domain containing proapoptotic Bid protein and poly (ADP-ribose) polymerase. Significantly, As(2)O(3)-induced apoptosis of HL-60/Bcr-Abl and K562 cells was associated with a decline in Bcr-Abl protein levels, without any significant alterations in the levels of Bcl-x(L), Bax, Apaf-1, Fas, and FasL. Although As(2)O(3 )treatment caused a marked increase in the expression of the myeloid differentiation marker CD11b, it did not affect Hb levels in HL-60/Bcr-Abl, K562, or HL-60/neo cells. However, in these cells, As(2)O(3 )potently induced hyper-acetylation of the histones H3 and H4. These findings characterize As(2)O(3) as a growth inhibiting and apoptosis-inducing agent against a variety of myeloid leukemia cells resistant to multiple apoptotic stimuli.
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PMID:Arsenic induces apoptosis of multidrug-resistant human myeloid leukemia cells that express Bcr-Abl or overexpress MDR, MRP, Bcl-2, or Bcl-x(L). 1064 17

Bcl-2 and its relative, Bcl-xL, inhibit apoptotic cell death primarily by controlling the activation of caspase proteases. Previous reports have suggested at least two distinct mechanisms: Bcl-2 and Bcl-xL may inhibit either the formation of the cytochrome c/Apaf-1/caspase-9 apoptosome complex (by preventing cytochrome c release from mitochondria) or the function of this apoptosome (through a direct interaction of Bcl-2 or Bcl-xL with Apaf-1). To evaluate this latter possibility, we added recombinant Bcl-xL protein to cell-free apoptotic systems derived from Jurkat cells and Xenopus eggs. At low concentrations (50 nM), Bcl-xL was able to block the release of cytochrome c from mitochondria. However, although Bcl-xL did associate with Apaf-1, it was unable to inhibit caspase activation induced by the addition of cytochrome c, even at much higher concentrations (1-5 microM). These observations, together with previous results obtained with Bcl-2, argue that Bcl-xL and Bcl-2 cannot block the apoptosome-mediated activation of caspase-9.
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PMID:Bcl-xL does not inhibit the function of Apaf-1. 1077 25

As with all metazoans, the fly makes extensive use of selective programmed cell death (PCD) to remove excess cells and properly sculpt developing tissues. Several core components of the cell death machinery have been identified in flies, including caspases and an Apaf-1 ortholog [1] [2] [3] [4]. One missing component has been a member of the Bcl-2 family of proteins, which act either pro- or anti-apoptotically as upstream regulatory proteins. Here, we report the identification of Bcl-2 family members in Drosophila - dBorg-1 (Drosophila Bcl-2 ortholog), also identified by Igaki et al. [5], and dBorg-2. Removal of dBorg-1 function during Drosophila embryonic development resulted in excess glial cells, demonstrating its pro-apoptotic function. In cell culture assays, dBorg-1 efficiently induced apoptosis but, remarkably, also demonstrated protective activity when death stimuli were introduced. Finally, ectopic expression of dBorg-1 in the eye led to subtle defects that were strongly potentiated by ultra violet (UV) irradiation, resulting in a dramatic loss of retinal cells.
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PMID:The Drosophila bcl-2 family member dBorg-1 functions in the apoptotic response to UV-irradiation. 1080 47

Reportedly, antiapoptotic Bcl-2 family proteins suppress apoptosis by binding to and inhibiting members of the CED-4 family of caspase activators. To explore this question, we used embryonic stem (ES) cells in which one (-/+) or both (-/-) copies of the gene encoding apoptotic protease activating factor 1 (Apaf-1), a CED-4 homologue, were disrupted by homologous recombination. Stable clones of heterozygous (-/+) and homozygous (-/-) Apaf-1 knockout ES cells that overexpressed Bcl-2 were generated. Withdrawal of serum growth factors or stimulation of heterozygous ES cells with staurosporine (STS), ultraviolet (UV)B irradiation, etoposide (VP16), or cisplatin induced apoptosis followed by cell death (determined by failure to exclude propidium iodide dye). These cell death stimuli also induced activation of several types of caspases and loss of mitochondrial membrane potential (DeltaPsi) in heterozygous (+/-) Apaf-1 knockout ES cells. In addition, overexpression of Bcl-2 protected against these events in Apaf-1-expressing ES cells. In contrast, STS, UVB, and VP16 induced little or no caspase activation and apoptosis in homozygous (-/-) Apaf-1 knockout ES cells. Nevertheless, Apaf-1-deficient ES cells subjected to these cell death stimuli or deprived of growth factors did eventually die through a nonapoptotic mechanism associated with loss of DeltaPsi. Moreover, Bcl-2 overprotection preserved DeltaPsi, reduced the percentage of Apaf-1(-/)- ES cells undergoing cell death, and increased clonigenic survival. The extent of Bcl-2-mediated cytoprotection was not significantly different for heterozygous (-/+) versus homozygous (-/-) Apaf-1 knockout cells. Furthermore, although Bcl-2 could be readily coimmunoprecipitated with Bax, associations with Apaf-1 were undetectable under conditions where Apaf-1 interactions with procaspase-9 were observed. We conclude that Bcl-2 has cytoprotective functions independent of Apaf-1, preserving mitochondrial function through a caspase-independent mechanism.
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PMID:Apoptotic protease activating factor 1 (Apaf-1)-independent cell death suppression by Bcl-2. 1081 64

In the nematode Caenorhabditis elegans, the apoptotic machinery is composed of four basic elements: the caspase CED-3, the Apaf-1 homologue CED-4, and the Bcl-2 family members CED-9 and EGL-1. The ced-9(n1950) gain-of-function mutation prevents most, if not all, somatic cell deaths in C. elegans. It encodes a CED-9 protein with a glycine-to-glutamate substitution at position 169, which is located within the highly conserved Bcl-2 homology 1 domain. We performed biochemical analyses with the CED-9G169E protein to gain insight into the mechanism of programmed cell death. We find that CED-9G169E retains the ability to bind both EGL-1 and CED-4, although its affinity for EGL-1 is reduced. In contrast to the behavior of wild-type CED-9, the interaction between CED-9G169E and CED-4 is not disrupted by expression of EGL-1. Furthermore, CED-4 and CED-9G169E co-localizes with EGL-1 to the mitochondria in mammalian cells, and expression of EGL-1 does not induce translocation of CED-4 to the cytosol. Finally, the ability of EGL-1 to promote apoptosis is impaired by the replacement of wild-type CED-9 with CED-9G169E, and this effect is correlated with the inability of EGL-1 to induce the displacement of CED-4 from the CED-9.CED-4 complex. These studies suggest that the release of CED-4 from the CED-9.CED-4 complex is a necessary step for induction of programmed cell death in C. elegans.
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PMID:Disruption of the CED-9.CED-4 complex by EGL-1 is a critical step for programmed cell death in Caenorhabditis elegans. 1084 74

Bcl-2 and related proteins are key regulators of apoptosis or programmed cell death implicated in human disease including cancer. We recently showed that cell-permeable Bcl-2 binding peptides could induce apoptosis of human myeloid leukemia in vitro and suppress its growth in severe combined immunodeficient mice. Here we report the discovery of HA14-1, a small molecule (molecular weight = 409) and nonpeptidic ligand of a Bcl-2 surface pocket, by using a computer screening strategy based on the predicted structure of Bcl-2 protein. In vitro binding studies demonstrated the interaction of HA14-1 with this Bcl-2 surface pocket that is essential for Bcl-2 biological function. HA14-1 effectively induced apoptosis of human acute myeloid leukemia (HL-60) cells overexpressing Bcl-2 protein that was associated with the decrease in mitochondrial membrane potential and activation of caspase-9 followed by caspase-3. Cytokine response modifier A, a potent inhibitor of Fas-mediated apoptosis, did not block apoptosis induced by HA14-1. Whereas HA14-1 strongly induced the death of NIH 3T3 (Apaf-1(+/+)) cells, it had little apoptotic effect on Apaf-1-deficient (Apaf-1(-/-)) mouse embryonic fibroblast cells. These data are consistent with a mechanism by which HA14-1 induces the activation of Apaf-1 and caspases, possibly by binding to Bcl-2 protein and inhibiting its function. The discovery of this cell-permeable molecule provides a chemical probe to study Bcl-2-regulated apoptotic pathways in vivo and could lead to the development of new therapeutic agents.
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PMID:Structure-based discovery of an organic compound that binds Bcl-2 protein and induces apoptosis of tumor cells. 1086 Sep 79


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