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)

The Bcl-2 oncogenic protein was synthesized in vitro and shown to post-translationally integrate asymmetrically into microsomal membranes with no requirement for an amino-terminal signal sequence. Instead, a carboxyl-terminal hydrophobic domain of Bcl-2 served as an insertion sequence essential for membrane assembly since a Bcl-2 mutant lacking this domain completely lost its ability to associate with microsomal membranes. The data demonstrate that Bcl-2 is tightly associated with the lipid bilayer with the nature of an integral membrane protein. The membrane orientation of Bcl-2 was determined using a protease protection assay, which showed that it is predominantly localized to the cytoplasmic face of membranes. A similar type of membrane processing has been shown for cytochrome b5 and also suggested for the viral oncogenic protein polyoma middle-T antigen.
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PMID:Membrane topology of the Bcl-2 proto-oncogenic protein demonstrated in vitro. 218 Sep 52

Bcl-2 is thought to associate spontaneously with membranes via a carboxyl-terminal hydrophobic domain by a mechanism analogous to that of cytochrome b5. We have examined the association of Bcl-2 with a variety of highly purified intracellular membranes in vitro. Fusion proteins were used to assess directly the role of the carboxyl-terminal hydrophobic domain of Bcl-2 in membrane association. Although this domain of Bcl-2 was sufficient to promote the association of a normally cytosolic polypeptide with either microsomal or mitochondrial membranes additional nonhydrophobic amino-terminal residues were required for membrane integration. Furthermore, direct comparison of membrane binding of Bcl-2 and cytochrome b5 revealed that similar to cytochrome b5, membrane targeting of Bcl-2 was not dependent on protease-sensitive components of the recipient membranes. In competition experiments, cytochrome b5 demonstrated the expected preference for integration into endoplasmic reticulum membranes. In contrast, the data presented here suggest that Bcl-2 is targeted to the cytoplasmic surface of multiple intracellular membranes, both in vitro and in human leukemic cells.
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PMID:Assembly of Bcl-2 into microsomal and outer mitochondrial membranes. 814 76

The survival motor neuron (SMN) gene is deleted or mutated in over 98% of spinal muscular atrophy patients who show specific motoneuron loss. By performing transfection experiments with rat smn cDNA, we show that two isoforms of SMN with Mr of 32 kDa and 35 kDa are produced by the same cDNA. In cultured motoneurons, both forms colocalize in coiled bodies and not in GEMS bodies as shown for HeLa cells. Subcellular fractionation of cells acutely dissociated from rat embryonic ventral spinal cord shows that the two SMN isoforms have a different subcellular localization, namely, that the 32 kDa isoform is enriched in the cytosol, whereas the 35 kDa isoform is segregating in the microsomal fraction. We show that the 35 kDa isoform of SMN is part of an insoluble complex but is absent from the cytoplasmic membranes and from the mitochondria. Immunostaining studies show that neither SMN isoform colocalizes with Bcl-2, the mitochondrial antiapoptotic protein suggested to bind to SMN in HeLa cells. Our results show that the isoforms of SMN protein have different subcellular localization and may therefore play independent biological roles. Moreover, the absence of colocalization of SMN with Bcl-2 in motoneurons suggests that some of the interactors of SMN may vary depending on the cell type, and this underscores the importance of identifying motoneuron-specific SMN interactors.
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PMID:Expression and subcellular localization of two isoforms of the survival motor neuron protein in different cell types. 1105 3

Thapsigargin (Tg), a selective inhibitor of sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase (SERCA), causes depletion of intracellular Ca(2+) stores, hence activation of capacitative Ca(2+) entry (CCE). Incubation of Xenopus laevis oocytes with Tg resulted in an increased rate of progesterone-induced meiotic maturation. Non-mitochondrial (45)Ca(2+) uptake by SERCA-containing microsomes prepared from control wild-type oocytes microinjected with sterile water was inhibited essentially 100% by Tg. However, overexpression of Bcl-2, an oncogene known to protect against Tg-induced apoptosis in certain cell types, resulted in only 40% inhibition of microsomal (45)Ca(2+) uptake by Tg while non-inhibited (45)Ca(2+) uptake remained unchanged. Moreover Bcl-2 overexpression also protected against inhibition of CCE. I(Cl(Ca)) was similar in Bcl-2-overexpressing and control oocytes when intracellular Ca(2+) store depletion was induced by microinjection of inositol 1,4,5-trisphosphate (InsP(3)) and other means and when CCE was induced by means independent of SERCA inhibition. Our data indicate that Bcl-2 affects neither the InsP(3) receptor nor Ca(2+) entry itself. At the end of a 24-h period after progesterone addition to the medium, only 25% of Bcl-2-overexpressing oocytes had matured compared to 85% of control oocytes. Our data suggest that SERCA participates in Xenopus oocyte maturation by controlling cytosolic Ca(2+) and/or intracellular Ca(2+) stores, hence CCE. An observed progesterone-dependent protein kinase-catalysed phosphorylation of SERCA is further indication of its role in oocyte maturation.
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PMID:Evidence for a role of the sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase in thapsigargin and Bcl-2 induced changes in Xenopus laevis oocyte maturation. 1131 28

An oligonucleotide-based microarray analysis of 9,500 genes and expressed sequence tags (ESTs) demonstrated that the type 1 inositol 1,4,5-trisphosphate receptor (IP(3)R) was significantly down-regulated in Bcl-X(L)-expressing as compared with control cells. This result was confirmed at the mRNA and protein levels by Northern and Western blot analyses of two independent hematopoietic cell lines and murine primary T cells. Bcl-X(L) expression resulted in a dose-dependent decrease in IP(3)R protein. IP(3)R expression is regulated as part of a mitochondrion-to-nucleus stress-responsive pathway. The uncoupling of mitochondrial oxidative phosphorylation resulted in induction of binding of the transcription factor NFATc2 to the IP(3)R promoter and transcriptional activation of IP(3)R. Expression of Bcl-X(L) led to a decreased induction of both NFATc2 DNA binding to the IP(3)R promoter and IP(3)R expression in response to the inhibition of mitochondrial oxidative phosphorylation. The Bcl-X(L)-dependent decrease in IP(3)R expression also correlated with a reduced T cell antigen receptor ligation-induced Ca(2+) flux in Bcl-X(L) transgenic murine T cells, and microsomal vesicles prepared from Bcl-X(L)-overexpressing cells exhibited lower IP(3)-mediated Ca(2+) release capacity. Furthermore, reintroducing IP(3)R into Bcl-X(L)-transfected cells partially reversed Bcl-X(L)-dependent anti-apoptotic activity. These results suggest that even under non-apoptotic conditions, expression of Bcl-2-family proteins influences a signaling network that links changes in mitochondrial metabolism to alterations in nuclear gene expression.
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PMID:Bcl-X(L) affects Ca(2+) homeostasis by altering expression of inositol 1,4,5-trisphosphate receptors. 1211 21

Calcineurin, a calmodulin-dependent protein phosphatase, regulates transcription and possibly apoptosis. Previous studies demonstrated that in baby hamster kidney-21 cells after co-transfection calcineurin interacts with Bcl-2, thereby altering transcription and apoptosis. Using co-immunoprecipitation and subcellular fractionation techniques, we observed that calcineurin occurred as a complex with Bcl-2 in various regions of rat and mouse brain. The calcineurin-Bcl-2 complex was identified in mitochondrial, nuclear, microsomal and cytosol fractions. In vitro induction of hypoxia and aglycia or N-methyl-D-aspartate treatment markedly altered both extent of complex formation and its subcellular localization. These observations suggest that Bcl-2 either sequesters calcineurin, that calcineurin dephosphorylates Bcl-2, or that Bcl-2 shuttles calcineurin to specific substrates. Calcineurin also co-immunoprecipitated with the inositol-tris-phosphate receptor. This interaction increased after in vitro hypoxia/aglycia. In Bcl-2 (-/-) mice, interactions between calcineurin- and inositol-tris-phosphate receptor occurred less frequently than in wild-type mice under both control and hypoxic conditions. Experiments involving cell-free systems, as well as brain slices treated with thapsigargin or with N-methyl-D-aspartate suggested that calcium and calmodulin activation of calcineurin leads to interactions between calcineurin and Bcl-2. These data indicate that during times of cellular stress and damage, Bcl-2 targets activated calcineurin to specific compartments and substrates.
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PMID:Calcium-dependent interaction of calcineurin with Bcl-2 in neuronal tissue. 1261 61

A variety of toxic insults can result in endoplasmic reticulum (ER)-stress that ultimately leads to apoptosis. beta-cells have a highly developed ER due to a great commitment to insulin production. The present study was carried out to determine the role of ER-stress in isolated human pancreatic islet apoptosis, and the potential protective effects of Bcl-2. Isolated human islets were infected with an adenoviral vector encoding Bcl-2 and then exposed to brefeldin-A, tunicamycin, A23187 and pro-inflammatory cytokines. Activation of caspase-12 was analyzed by means of Western blots. Apoptosis was evaluated using a commercial quantitative assay. ER-stress-inducers promoted caspase-12 activation and apoptosis, effect reversed by overexpression of Bcl-2. Co-localization of caspase-12 and Bcl-2 in the microsomal islet fractions were demonstrated by means of Western blots. We can conclude that the current studies highlight the importance of Bcl-2 as an anti-apoptotic protein, and shed new light on the mechanisms underlying its cytoprotective effects on pancreatic islets.
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PMID:Coupling endoplasmic reticulum stress to cell death program in isolated human pancreatic islets: effects of gene transfer of Bcl-2. 1281 63

The molecular regulation of seizure-induced neuronal death may involve interactions between proteins of the Bcl-2 and 14-3-3 families. To further examine these pathways we performed subcellular fractionation on hippocampi obtained following a brief period of status epilepticus in the rat. Western blotting determined seizures induced caspase-8 cleavage and increased Bcl-w levels within the cytoplasm. Bax, Bad and Bid were largely present within the cytoplasm before and after seizures, although some Bax and, following seizures, truncated Bid was detected in mitochondria. Levels of 14-3-3 were significantly reduced in the cytoplasm and microsomal fractions. These data establish the expression and distribution profile of key Bcl-2 family proteins and the signaling chaperone 14-3-3 in the rat and provide additional evidence for the activation of programmed cell death pathways by seizures.
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PMID:Subcellular distribution of Bcl-2 family proteins and 14-3-3 within the hippocampus during seizure-induced neuronal death in the rat. 1503 20

It has been reported that two inducible prostaglandin synthetic enzymes, cylooxygenase-2 (COX-2) and microsomal PGE synthase, are over-expressed in non-small cell lung cancer (NSCLC). Using quantitative reverse transcription-polymerase chain reaction, we analyzed RNA levels of the key prostaglandin catabolic enzyme, NAD+-linked 15-hydroxyprostaglandin dehydrogenase (15-PGDH), in 19 pairs of NSCLC tumors and adjacent non-malignant tissue from the same patient. We found that 100% of tumor-tissue pairs showed at least a 2-fold decrease and 61% showed a 10-fold decrease. This suggests that the increased expression of COX-2 and PGE synthase in tumors may work in concert with the decreased expression of 15-PGDH to amplify an increase in tissue levels of proliferative PGE2. To further explore if 15-PGDH is related to tumorigenesis, athymic nude mice were injected with control A549 cells or cells transiently over-expressing wild-type or mutant 15-PGDH (Y151F). It was found that mice injected with control A549 cells or with cells expressing mutant enzyme produced tumors normally. However, mice injected with A549 cells expressing wild-type 15-PGDH had a significant decrease in tumor growth. Examining the effects of 15-PGDH expression on cellular changes in A549 cells, we found that over-expression of 15-PGDH induced apoptosis of A549 cells as evidenced by fragmentation of DNA, activation of pro-caspase 3, cleavage of poly(ADP-ribose) polymerase and decreased expression of Bcl-2. We also found that the expression of 15-PGDH was negatively related to that of pro-adhesive and invasive CD44. Furthermore, the expression of 15-PGDH was found to be stimulated by hyaluronidase. These results suggest that 15-PGDH may decrease the level of proliferative PGE2, induce apoptosis and function like a tumor suppressor.
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PMID:NAD+-linked 15-hydroxyprostaglandin dehydrogenase (15-PGDH) behaves as a tumor suppressor in lung cancer. 1535 36

Apoptosis signaling pathways are implicated in the pathogenesis of temporal lobe epilepsy (TLE), but the role of endoplasmic reticulum (ER) stress and ER-localized apoptosis signaling components remains largely unexplored. Presently, we investigated ER stress and ER localization of proapoptotic Bcl-2 family members and initiator and effector caspases in resected hippocampus from patients with intractable TLE and compared findings with autopsy controls. Hippocampal immunoreactivity for KDEL (Lys-Asp-Glu-Leu), a motif in ER stress chaperones glucose-regulated proteins 78 and 94, and calnexin, was significantly higher in TLE hippocampus compared with controls. The ER-containing microsomal fraction in control brain contained Bid, Bim, and caspase 3, whereas Bad and caspases 6, 7, and 9 were very low or absent. In contrast, caspases 6, 7, and 9 were present within the microsomal fraction of TLE brain. Furthermore, cleaved caspases 7 and 9 were detected in TLE samples but not controls, and KDEL-expressing neurons coexpressed cleaved caspase 9. Potentially adaptive changes were also detected, including lowered Bim levels in this fraction, and binding of caspase 7 to the X-linked inhibitor of apoptosis protein. These data suggest seizures may induce ER stress and trigger proapoptotic signaling pathways in the ER that are counteracted by antiapoptotic signals in chronic human TLE.
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PMID:Endoplasmic reticulum stress and apoptosis signaling in human temporal lobe epilepsy. 1665 83


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