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

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

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

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

Demonstrating in vivo interaction of two important biomolecules and the relevance of the interaction to a biological process have been difficult issues in biomedical research. Here, we report the use of a homology modeling approach to establish the significance of protein interactions in governing the activation of programmed cell death in Caenorhabditis elegans. A protein interaction cascade has been postulated to mediate activation of cell death in nematodes, in which the BH3-domain-containing (Bcl-2 homology region 3) protein EGL-1 binds the cell-death inhibitor CED-9 and induces release of the death-activating protein CED-4 from inhibitory CED-4/CED-9 complexes. We show here that an unusual gain-of-function mutation in ced-9 (substitution of glycine 169 to glutamate) that results in potent inhibition of most nematode cell deaths impairs the binding of EGL-1 to CED-9 and EGL-1-induced release of CED-4 from CED-4/CED-9 complexes. Based on a modeled EGL-1/CED-9 complex structure, we generated second-site compensatory mutations in EGL-1 that partially restore the binding of EGL-1 to CED-9(G169E) and EGL-1-induced release of CED-4 from CED-4/CED-9(G169E) complexes. Importantly, these mutations also significantly suppress the death-protective activity of CED-9(G169E) in vivo. These results establish that direct physical interaction between EGL-1 and CED-9 is essential for the release of CED-4 and the activation of cell death. The structure-based design of second-site suppressors via homology modeling should be widely applicable for probing important molecular interactions that are implicated in fundamental biological processes.
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PMID:Demonstration of the in vivo interaction of key cell death regulators by structure-based design of second-site suppressors. 1102 3

CED-9 blocks programmed cell death (apoptosis) in the nematode C. elegans by binding to and neutralizing CED-4, an essential activator of the aspartate-directed cysteine protease (caspase) CED-3. In mammals, the CED-9 homologs Bcl-2 and Bcl-xL also block apoptosis by interfering with the activation of CED-3-like caspases. However, it is unknown whether this occurs by binding to the CED-4 homolog Apaf-1. Whilst two groups previously detected an interaction between Bcl-xL and Apaf-1 in immunoprecipitates,1,2 another group found no interaction between Apaf-1 and any of ten individual members of the Bcl-2 family using the same experimental approach.3 In this study, we aimed to resolve this discrepancy by monitoring the binding of Apaf-1 to three Bcl-2 family members within cells. Using immunofluorescence and Western blot analysis, we show that whilst Apaf-1 is a predominantly cytoplasmic protein, Bcl-2, Bcl-xL and Bax mostly reside on nuclear/ER and mitochondrial membranes. This pattern of localization is maintained when the proteins are co-expressed in both normal and apoptotic cells, suggesting that Bcl-2, Bcl-xL or Bax do not significantly sequester cytoplasmic Apaf-1 to intracellular membranes. In addition, we confirm that Apaf-1 does not interact with Bcl-2 and Bcl-xL in immunoprecipitates. Based on these data, we propose that Apaf-1 is not a direct, physiological target of Bcl-2, Bcl-xL or Bax.
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PMID:Failure of Bcl-2 family members to interact with Apaf-1 in normal and apoptotic cells. 1127 41

Activation of the caspases that initiate apoptosis typically requires cognate scaffold proteins, including CED-4 in Caenorhabditis elegans, Apaf-1 in mammals and Dark in Drosophila. Each scaffold protein oligomerizes procaspases into a complex called the apoptosome, but the regulation and biological roles of the scaffolds differ. Whereas CED-4 is restrained by the Bcl-2 homologue CED-9, Apaf-1 is inhibited by its WD40 repeat region, until it is activated by cytochrome c, derived from damaged mitochondria. Although Dark also has a WD40 region, its activation does not seem to involve cytochrome c. CED-4 is essential for apoptosis in the worm and Dark for many apoptotic responses in the fly, but the Apaf-1/caspase-9 system probably amplifies rather than initiates the mammalian caspase cascade.
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PMID:Apoptosomes: engines for caspase activation. 1247 44

CED-4, a pro-apoptotic factor in Caenorhabditis elegans, activates the cell death protease CED-3. CED-9 directly binds to CED-4 and represses this. However, it has remained unclear whether a mammalian CED-9 homologue, Bcl-XL, inhibits the function of the mammalian CED-4 homologue, Apaf-1, by direct binding. To analyze the interaction, we adopted a yeast two-hybrid system. Since Bcl-XL and the CED-4-like portion of Apaf-1 failed to exhibit a positive result in the assay, we prepared "fragment libraries" of bcl-XL or apaf-1 cDNA. By screening of the apaf-1 "fragment library," we obtained nine clones interacting with Bcl-XL, all containing the same region within the ATPase domain, designated BBR: the Bcl-XL binding region. Binding of BBR to Bcl-XL was also confirmed by immunoprecipitation assays. Bcl-2, Bcl-w, A1/Bfl-1, and Boo/Diva failed to show the same capacity for binding to BBR as Bcl-XL. These results indicate that Bcl-XL directly binds to a specific region in Apaf-1.
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PMID:Identification of a Bcl-XL binding region within the ATPase domain of Apaf-1. 1296 20

The genes ced-3, ced-4 and ced-9 are central components in the cell death pathway of the nematode C. elegans. Ced-9, which functions to inhibit cell death, is homologous to the Bcl-2 family of mammalian anti-apoptotic genes. The ced-3 gene encodes a protein homologous to the caspases, a family of cysteine proteases involved in the execution of programmed cell death. It has recently been demonstrated that CED-4, an inducer of apoptosis for which no mammalian equivalent has been reported, can interact with CED-9 and Bcl-x(L). Here we confirm that CED-9 and CED-4 interact and using a series of deletion mutants, demonstrate that only short N-terminal deletions are tolerated in each molecule without loss-of-interaction. Two loss-of-function point mutations in different regions of CED-4 also lead to a significant loss of interaction suggesting further that the relevant interaction domains are not short linear sequences, but rather, are formed by more complex structural determinants in each molecule. Furthermore, we demonstrate that CED-4 not only interacts with Bcl-x(L) but also with its homologue, Bcl-2, and that the unstructured loop region present in Bcl-x(L) and Bcl-2 can regulate the CED-4 interaction. Lastly, we show that a BH3 peptide that can inhibit Bcl-2 family interactions also inhibits the interaction between Bcl-x(L) and CED-4.
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PMID:Mutational analysis of the interacting cell death regulators CED-9 and CED-4. 1455 65

Genetic analyses in Caenorhabditis elegans have been instrumental in the elucidation of the central cell-death machinery, which is conserved from C. elegans to mammals. One possible difference that has emerged is the role of mitochondria. By releasing cytochrome c, mitochondria are involved in the activation of caspases in mammals. However, there has previously been no evidence that mitochondria are involved in caspase activation in C. elegans. Here we show that mitochondria fragment in cells that normally undergo programmed cell death during C. elegans development. Mitochondrial fragmentation is induced by the BH3-only protein EGL-1 and can be blocked by mutations in the bcl-2-like gene ced-9, indicating that members of the Bcl-2 family might function in the regulation of mitochondrial fragmentation in apoptotic cells. Mitochondrial fragmentation is independent of CED-4/Apaf-1 and CED-3/caspase, indicating that it occurs before or simultaneously with their activation. Furthermore, DRP-1/dynamin-related protein, a key component of the mitochondrial fission machinery, is required and sufficient to induce mitochondrial fragmentation and programmed cell death during C. elegans development. These results assign an important role to mitochondria in the cell-death pathway in C. elegans.
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PMID:DRP-1-mediated mitochondrial fragmentation during EGL-1-induced cell death in C. elegans. 1571 32


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