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)

Gain-of-function mutations in the Caenorhabditis elegans gene egl-1 cause the HSN neurons to undergo programmed cell death. By contrast, a loss-of-function egl-1 mutation prevents most if not all somatic programmed cell deaths. The egl-1 gene negatively regulates the ced-9 gene, which protects against cell death and is a member of the bcl-2 family. The EGL-1 protein contains a nine amino acid region similar to the Bcl-2 homology region 3 (BH3) domain but does not contain a BH1, BH2, or BH4 domain, suggesting that EGL-1 may be a member of a family of cell death activators that includes the mammalian proteins Bik, Bid, Harakiri, and Bad. The EGL-1 and CED-9 proteins interact physically. We propose that EGL-1 activates programmed cell death by binding to and directly inhibiting the activity of CED-9, perhaps by releasing the cell death activator CED-4 from a CED-9/CED-4-containing protein complex.
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PMID:The C. elegans protein EGL-1 is required for programmed cell death and interacts with the Bcl-2-like protein CED-9. 960 28

Bcr-Abl kinase is known to reverse apoptosis of cytokine-dependent cells due to cytokine deprivation, although it has been controversial whether chronic myeloid leukemia (CML) progenitors have the potential to survive under conditions in which there are limited amounts of cytokines. Here we demonstrate that early hematopoietic progenitors (Sca-1(+) c-Kit(+) Lin(-)) isolated from normal mice rapidly undergo apoptosis in the absence of cytokines. In these cells, the expression of Bim, a proapoptotic relative of Bcl-2 which plays a key role in the cytokine-mediated survival system, is induced. In contrast, those cells isolated from our previously established CML model mice resist apoptosis in cytokine-free medium without the induction of Bim expression, and these effects are reversed by the Abl-specific kinase inhibitor imatinib mesylate. In addition, the expression levels of Bim are uniformly low in cell lines established from patients in the blast crisis phase of CML, and imatinib induced Bim in these cells. Moreover, small interfering RNA that reduces the expression level of Bim effectively rescues CML cells from apoptosis caused by imatinib. These findings suggest that Bim plays an important role in the apoptosis of early hematopoietic progenitors and that Bcr-Abl supports cell survival in part through downregulation of this cell death activator.
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PMID:Roles of Bim in apoptosis of normal and Bcr-Abl-expressing hematopoietic progenitors. 1522 21

Pathways through which signals emanating from cytokine receptors support cell survival have long been a focus of intensive research. For Baf-3, a murine interleukin 3-dependent cell line, the 2 distinct pathways involved are JAK/STATs/Bcl-xL and Ras/PI3-K. The latter is indispensable for long-term cell survival through down-regulation of Bim, a BH3-only cell death activator of the Bcl-2 superfamily. Thus, Bim is likely to be a key factor for cytokine-initiated regulation of cell survival in both hematopoietic cells and neuronal cells. Cytokines (like neurotrophic factors) regulate Bim expression at at least 3 levels: (1) at the messenger RNA (mRNA) level through transcriptional regulation and possibly through mRNA stability, (2) at the protein level through proteasome-dependent regulation of protein degradation, and (3) by affecting subcellular localization through regulation of the potential to bind to the dynein motor complex. Bim function may be regulated in different ways in certain situations such that the relative importance of these 3 mechanisms may differ among cell types. For hematopoiesis, mRNA regulation seems to be the most important. Bim is also implicated in leukemogenesis caused by the Bcr-Abl chimeric tyrosine kinase and constitutively active mutants of receptor tyrosine kinases.
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PMID:Cytokine-mediated cell survival. 1554 Aug 94

Deprivation of cytokines induces cell cycle arrest and apoptosis in cytokine-dependent hematopoietic progenitors. Previous studies have indicated that in Baf-3, interleukin (IL)-3-dependent cells, apoptosis is caused predominantly by Bim, a BH3-only cell death activator that belongs to the Bcl-2 superfamily. Because Bim mRNA is induced by IL-3 starvation, we hypothesized that signals originating from the IL-3 receptor might regulate the expression of Bim at the level of its transcription. Here, we identified the transcriptional initiation site and three candidate remote enhancer/silencer regions of the Bim gene. We show that the region of the gene upstream of the initiation site exhibits strong promoter activity and that there are negative regulatory regions within the first intron. However, none of these transcriptional regulatory elements was IL-3-dependent. In addition, a nuclear run-off assay revealed a similar rate of transcription initiation in the absence or presence of IL-3. Although others have demonstrated the transcriptional regulation of Bim by nerve growth factor (NGF) in neuronally differentiated PC12 pheochromocytoma cells, this is unlikely to be the mechanism through which IL-3 downregulates the expression of Bim in Baf-3 cells.
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PMID:Structure of the human Bim gene and its transcriptional regulation in Baf-3, interleukin-3-dependent hematopoietic cells. 1602 80

Chronic myeloid leukemia (CML) is a myeloproliferative disease in which BCR/ABL enhances survival of leukemic cells through modulation of proapoptotic and antiapoptotic molecules. Recent data suggest that proapoptotic Bcl-2-interacting mediator (Bim) plays a role as a tumor suppressor in myeloid cells, and that leukemic cells express only low amounts of this cell death activator. We here show that primary CML cells express significantly lower amounts of bim mRNA and Bim protein compared with normal cells. The BCR/ABL inhibitors imatinib and AMN107 were found to promote expression of Bim in CML cells. To provide direct evidence for the role of BCR/ABL in Bim modulation, we employed Ba/F3 cells with doxycycline-inducible expression of BCR/ABL and found that BCR/ABL decreases expression of bim mRNA and Bim protein in these cells. The BCR/ABL-induced decrease in expression of Bim was found to be a posttranscriptional event that depended on signaling through the mitogen-activated protein kinase pathway and was abrogated by the proteasome inhibitor MG132. Interestingly, MG132 up-regulated the expression of bim mRNA and Bim protein and suppressed the growth of Ba/F3 cells containing wild-type BCR/ABL or imatinib-resistant mutants of BCR/ABL. To show functional significance of "Bim reexpression," a Bim-specific small interfering RNA was applied and found to rescue BCR/ABL-transformed leukemic cells from imatinib-induced cell death. In summary, our data identify BCR/ABL as a Bim suppressor in CML cells and suggest that reexpression of Bim by novel tyrosine kinase inhibitors, proteasome inhibition, or by targeting signaling pathways downstream of BCR/ABL may be an attractive therapeutic approach in imatinib-resistant CML.
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PMID:Low-level expression of proapoptotic Bcl-2-interacting mediator in leukemic cells in patients with chronic myeloid leukemia: role of BCR/ABL, characterization of underlying signaling pathways, and reexpression by novel pharmacologic compounds. 1623 Apr 7

Proteins belonging to Bcl-2 family regulate intrinsic cell death pathway. Although mammalian antiapoptotic Bcl-2 members interact with multiple proapoptotic proteins, the Caenorhabditis elegans Bcl-2 homolog CED-9 is known to have only two proapoptotic partners. The BH3-motif of proapoptotic proteins bind to the hydrophobic groove of prosurvival proteins formed by the Bcl-2 helical fold. CED-9 is also known to interact with CED-4, a homolog of the human cell death activator Apaf1. We have performed molecular dynamics simulations of CED-9 in two forms and compared the results with those of mammalian counterparts Bcl-XL, Bcl-w, and Bcl-2. Our studies demonstrate that the region forming the hydrophobic cleft is more flexible compared with the CED-4-binding region, and this is generally true for all antiapoptotic Bcl-2 proteins studied. CED-9 is the most stable protein during simulations and its hydrophobic pocket is relatively rigid explaining the absence of functional redundancy in CED-9. The BH3-binding region of Bcl-2 is less flexible among the mammalian proteins and this lends support to the studies that Bcl-2 binds to less number of BH3 peptides with high affinity. The C-terminal helix of CED-9 lost its helical character because of a large number of charged residues. We speculate that this region probably plays a role in intracellular localization of CED-9. The BH4-motif accessibility in CED-9 and Bcl-w is controlled by the loop connecting the first two helices. Although CED-9 adopts the same Bcl-2 fold, our studies highlight important differences in the dynamic behavior of CED-9 and mammalian antiapoptotic homologs.
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PMID:Antiapoptotic Bcl-2 homolog CED-9 in Caenorhabditis elegans: dynamics of BH3 and CED-4 binding regions and comparison with mammalian antiapoptotic Bcl-2 proteins. 2421 65