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

Bcl-2-related anti- and proapoptotic proteins are important in the decision step of the intracellular death program upstream from the caspase proteases. Targeted overexpression of Bcl-2 in ovarian somatic cells of transgenic mice leads to decreased apoptosis of granulosa cells and is associated with higher ovulation rate, increased litter size, and ovarian teratoma formation. The ability of exogenous Bcl-2 proteins to promote follicle cell survival suggests that the transgene can bind to endogenous ovarian Bcl-2 family members and modulate the intracellular apoptosis process in favor of cell survival. We used the yeast two-hybrid system to search for ovarian Bcl-2 interacting proteins. The screening of an ovarian fusion complementary DNA library yielded several clones encoding for the death agonist Bcl-XL/Bcl-2-associated death promoter (BAD). Dimerization of Bcl-2-related proteins mediated by the consensus Bcl-2 homology (BH) domains is essential for their apoptosis-regulating function. Consistent with these observations, yeast two-hybrid assays indicated that the interaction of Bcl-2 with BAD is dependent on both BH4 and BH2 domains of Bcl-2. Northern blot analysis showed a wide distribution of BAD messenger RNA (mRNA) in diverse tissues with highest levels in the lung, ovary, uterus, and brain. In situ hybridization analysis indicated BAD mRNA expression in granulosa cells of different sizes of follicles and also in the theca and interstitial cells. BAD mRNA was expressed in the ovaries between postnatal 15-27 days and did not alter during the developmentally occurring apoptosis found about postnatal day 18 when the first group of early antral follicles were formed. Similarly, BAD mRNA levels did not change during follicle atresia induced by estrogen withdrawal in immature rats. To study the role of BAD in the ovary, BAD complementary DNA was transfected into primary cultures of granulosa cells and in a gonadal tumor cell line. Overexpression of BAD induced apoptosis in both cell types, and the effect of BAD was reversed by a membrane-permeable caspase inhibitor, indicating that BAD induces apoptosis via the activation of caspase cysteine proteases. In summary, the death agonist BAD was identified as a Bcl-2-interacting protein in the ovary, and BAD mRNA is constitutively expressed in granulosa cells, suggesting that BAD is an essential part of the ovarian cell death process. Because BAD overexpression in granulosa cells leads to apoptosis, future studies on ovarian BAD binding proteins and hormonal regulation of the interactions among different Bcl-2 family members could provide a better understanding of the cellular mechanism of ovarian follicle atresia.
Endocrinology 1997 Dec
PMID:Expression and function of a proapoptotic Bcl-2 family member Bcl-XL/Bcl-2-associated death promoter (BAD) in rat ovary. 938 36

Galectin-3, a beta-galactoside-binding protein, has been shown to be involved in tumor progression and metastasis. Here, we demonstrate that expression of galectin-3 in human breast carcinoma BT549 cells inhibits cis-diamminedichloroplatinum (cisplatin)-induced poly(ADP-ribose) polymerase degradation and apoptosis, without altering Bcl-2, Bcl-X(L), or Bax expressions. Galectin-3 contains the NWGR amino acid sequence highly conserved in the BH1 domain of the bcl-2 gene family, and a substitution of glycine to alanine in this motif abrogated its antiapoptotic activity. Our findings demonstrate that galectin-3 inhibits apoptosis through a cysteine protease pathway and highlight the functional significance of the NWGR motif in apoptosis resistance of a non-Bcl-2 protein.
Cancer Res 1997 Dec 01
PMID:Galectin-3: a novel antiapoptotic molecule with a functional BH1 (NWGR) domain of Bcl-2 family. 939 48

Since apoptosis is observed in tuberculous granulomata, we investigated the molecular mechanisms underlying the apoptotic pathway in an in vitro model of mycobacterial infection of mononuclear phagocytes. We postulated that Mycobacterium tuberculosis could trigger the apoptotic pathway in macrophages, resulting in death of the microorganism by modulating the expression of bcl-2, bax, bcl-xL, and bcl-xS. We found that the mRNA of bcl-2, an inhibitor of apoptosis, was downregulated in peripheral blood monocytes (PBM) between 2 and 6 h following infection with M. bovis BCG or induction with heat-killed M. tuberculosis H37Ra. Western analysis showed a downregulation of the Bcl-2 protein, with a half-life of 24 h. At the same time points, there was no change in the expression of Bax or Bcl-xS, inducers of apoptosis, but Bcl-xL, another inhibitor of apoptosis, was minimally upregulated by BCG. To determine if apoptosis could be a mechanism for growth inhibition in vivo, we obtained alveolar macrophages by bronchoalveolar lavage from involved sites in patients with active pulmonary tuberculosis. Using the TUNEL (terminal deoxynucleotidyltransferase mediated nick end labeling) technique, we observed significantly more apoptosis in involved segments of five tuberculosis patients (14.8 +/- 1.9%) than in those of normal controls (<1%, P = 0.02) or in uninvolved segments (4.3 +/- 0.9%, P < 0.05). We conclude that apoptosis of mononuclear phagocytes induced by M. tuberculosis occurs in vivo and that in an in vitro model of mycobacterial infection, apoptosis may be mediated by downregulation of Bcl-2.
Infect Immun 1997 Dec
PMID:Effects of mycobacteria on regulation of apoptosis in mononuclear phagocytes. 939 26

Caspases are a family of cysteine proteases implicated in the biochemical and morphological changes that occur during apoptosis (programmed cell death). The loop domain of Bcl-2 is cleaved at Asp34 by caspase-3 (CPP32) in vitro, in cells overexpressing caspase-3, and after induction of apoptosis by Fas ligation and interleukin-3 withdrawal. The carboxyl-terminal Bcl-2 cleavage product triggered cell death and accelerated Sindbis virus-induced apoptosis, which was dependent on the BH3 homology and transmembrane domains of Bcl-2. Inhibitor studies indicated that cleavage of Bcl-2 may further activate downstream caspases and contribute to amplification of the caspase cascade. Cleavage-resistant mutants of Bcl-2 had increased protection from interleukin-3 withdrawal and Sindbis virus-induced apoptosis. Thus, cleavage of Bcl-2 by caspases may ensure the inevitability of cell death.
Science 1997 Dec 12
PMID:Conversion of Bcl-2 to a Bax-like death effector by caspases. 939 3

The pro-apoptotic protein Bax can homodimerize with itself and heterodimerize with the anti-apoptotic protein Bcl-2, but the significance of these protein-protein interactions remains unclear. Alanine substitution mutations were created in a well conserved IGDE motif found within the BH3 domain of Bax (residues 66-69) and the resulting mutant Bax proteins were tested for ability to homodimerize with themselves and to heterodimerize with Bcl-2. Correlations were made with cell death induction by these mutants of Bax both in mammalian cells where Bax may function through several mechanisms, and in yeast where Bax may exert its lethal actions through a more limited repertoire of mechanisms perhaps related to its ability to form ion channels in intracellular membranes. Two of the mutants, Bax(D68A) and Bax(E69A), retained the ability to homodimerize but failed to interact with Bcl-2 as determined by yeast two-hybrid assays and co-immunoprecipitation analysis using transfected mammalian cells. The Bax(E69A) protein exhibited a lethal phenotype in yeast, which could be specifically suppressed by co-expression of Bcl-2, despite its failure to dimerize with Bcl-2. Both the Bax(D68A) and Bax(E69A) proteins induced apoptosis when overexpressed in human 293 cells, despite an inability to bind to Bcl-2. Moreover, co-expression of Bcl-2 with Bax(D68A) and Bax(E69A) rescued mammalian cells from apoptosis. In contrast, a mutant of Bax lacking the IGDE motif, Bax(DeltaIGDE), was incapable of either homodimerizing with itself or heterodimerizing with Bcl-2 and was inactive at promoting cell death in either yeast or mammalian cells. Although failing to interact with Bcl-2, the Bax(D68A) and Bax(E69A) mutants retained the ability to bind to Bid, a putative Bax-activating member of the Bcl-2 family, and collaborated with Bid in inducing apoptosis. When taken together with previous observations, these findings indicate that (i) Bax can induce apoptosis in mammalian cells irrespective of heterodimerization with Bcl-2 and (ii) Bcl-2 can rescue both mammalian cells and yeast from the lethal effects of Bax without heterodimerizing with it. However, these results do not exclude the possibility that BH3-dependent homodimerization of Bax or interactions with Bax activators such as Bid may either assist or be required for the cell death-inducing mechanism of this protein.
J Biol Chem 1997 Dec 12
PMID:Heterodimerization-independent functions of cell death regulatory proteins Bax and Bcl-2 in yeast and mammalian cells. 939 83

The Bcl-2 oncoprotein is a key regulator of apoptosis and the Bag-1 protein interacts with Bcl-2 and cooperates with Bcl-2 to suppress apoptosis. The human Bag-1 cDNA is essentially identical with a previously described cDNA encoding RAP46, which interacts with activated steroid hormone receptors. However, there is considerable confusion over the structure of Bag-1/RAP46 proteins and their relationship to endogenous Bag-1 proteins. Here we have characterized Bag-1 expression in mammalian cells. We demonstrate that, in addition to the previously identified 32 kDa murine and 36 kDa human Bag-1 proteins, cells express a second 50 kDa Bag-1 isoform. In some murine cell lines p50 is expressed at the same level as p32 Bag-1, and p50 and p32 Bag-1 proteins have distinct subcellular localizations, suggesting that they are functionally distinct. The published mouse Bag-1 cDNA is partial, and sequencing of additional murine Bag-1 RNA 5' sequences demonstrated that human and murine Bag-1 cDNAs contain longer open reading frames than originally suspected. We determined which open reading frames gave rise to the Bag-1 isoforms in human cells. Surprisingly, translation of neither protein initiated at the first in-frame methionine, and cells do not express Bag-1/RAP46 proteins with the previously proposed structures; p50 Bag-1 initiates at an upstream CUG codon, whereas p36 Bag-1 initiates at a downstream AUG codon. Therefore, cells express two differently localized Bag-1 isoforms generated by alternative translation initiation, and Bag-1 proteins may play a dual role in regulating apoptosis and steroid hormone-dependent transcription.
Biochem J 1997 Dec 15
PMID:Mammalian cells express two differently localized Bag-1 isoforms generated by alternative translation initiation. 939 24

Nip3 (nineteen kD interacting protein-3) is an E1B 19K and Bcl-2 binding protein of unknown function. Nip3 is detected as both a 60- and 30-kD protein in vivo and in vitro and exhibits strong homologous interaction in a yeast two-hybrid system indicating that it can homodimerize. Nip3 is expressed in mitochondria and a mutant (Nip3(163)) lacking the putative transmembrane domain and COOH terminus does not dimerize or localize to mitochondria. Transient transfection of epitope-tagged Nip3 in Rat-1 fibroblasts and MCF-7 breast carcinoma induces apoptosis within 12 h while cells transfected with the Nip3(163) mutant have a normal phenotype, suggesting that mitochondrial localization is necessary for induction of cell death. Nip3 overexpression increases the sensitivity to apoptosis induced by granzyme B and topoisomerase I and II inhibitors. After transfection, both Nip3 and Nip3(163) protein levels decrease steadily over 48 h indicating that the protein is rapidly degraded and this occurs in the absence of cell death. Bcl-2 overexpression initially delays the onset of apoptosis induced by Nip3 but the resistance is completely overcome in longer periods of incubation. Nip3 protein levels are much higher and persist longer in Bcl-2 expressing cells. In conclusion, Nip3 is an apoptosis-inducing dimeric mitochondrial protein that can overcome Bcl-2 suppression.
J Exp Med 1997 Dec 15
PMID:The E1B 19K/Bcl-2-binding protein Nip3 is a dimeric mitochondrial protein that activates apoptosis. 939 66

The tyrosine kinase Syk has been implicated as a key signal transducer from the B cell antigen receptor (BCR). We show here that mutation of the Syk gene completely blocks the maturation of immature B cells into recirculating cells and stops their entry into B cell follicles. Furthermore, using radiation chimeras we demonstrate that this developmental block is due to the absence of Syk in the B cells themselves. Syk-deficient B cells are shown to have the life span of normal immature B cells. If this is extended by over-expression of Bcl-2, they accumulate in the T zone and red pulp of the spleen in increased numbers, but still fail to mature to become recirculating follicular B cells. Despite this defect in maturation, Syk-deficient B cells were seen to give rise to switched as well as nonswitched splenic plasma cells. Normally only a proportion of immature B cells is recruited into the recirculating pool. Our results suggest that Syk transduces a BCR signal that is absolutely required for the positive selection of immature B cells into the recirculating B cell pool.
J Exp Med 1997 Dec 15
PMID:Syk tyrosine kinase is required for the positive selection of immature B cells into the recirculating B cell pool. 939 70

The effects of the non-tumor-promoting protein kinase C (PKC) activator bryostatin 1 and the PKC inhibitors staurosporine and UCN-01 were examined with respect to modulation of 1-[beta-D-arabinofuranosyl]cytosine (ara-C)-induced apoptosis in human myeloid leukemia cells (HL-60) overexpressing the antiapoptotic protein Bcl-2. HL-60/Bcl-2 cells displayed a 5-fold increase in Bcl-2 protein compared with empty-vector counter-parts (HL-60/pCEP4) but comparable levels of Bax, Mcl-1, and Bcl-xL. After exposure to an equimolar concentration of ara-C (10 microM for 6 hr), HL-60/Bcl-2 cells were significantly less susceptible to apoptosis, DNA fragmentation, and loss of clonogenicity than HL-60/pCEP4 cells. The protective effect of increased Bcl-2 expression was manifested by a failure of ara-C to induce activation/cleavage of the Yama protease (CPP32; caspase-3) and degradation of one of its substrates, poly(ADP-ribose)polymerase to an 85-kDa cleavage product. When HL-60/Bcl-2 cells were preincubated with bryostatin 1 (10 nM; 24 hr) or coincubated with either staurosporine (50 nM; 6 hr) or UCN-01 (300 nM; 6 hr) after a 1-hr preincubation, exposures that exerted minimal effects alone, ara-C-induced apoptosis and DNA fragmentation were restored to levels equivalent to, or greater than, those observed in empty-vector controls. These events were accompanied by restoration of the ability of ara-C to induce CPP32 cleavage and activation, poly(ADP-ribose) polymerase degradation, and inhibition of colony formation. Western analysis of Bcl-2 protein obtained from overexpressing cells treated with bryostatin 1, staurosporine, or UCN-01 revealed the appearance of a slowly migrating species and a general broadening of the protein band, effects that were insensitive to the protein synthesis inhibitor cycloheximide. Alterations in Bcl-2 protein mobility on sodium dodecyl sulfate-polyacrylamide gel electrophoresis were reversed by treatment of lysates with alkaline phosphatase or protein phosphatase 2A; actions of the latter were blocked by the specific phosphatase inhibitor okadaic acid. In vivo labeling studies of Bcl-2 protein demonstrated increased incorporation of [32PO4]orthophosphate in drug-treated cells. Last, phosphorylated Bcl-2 failed to display decreased binding to the proapoptotic protein Bax. Collectively, these findings indicate that bryostatin 1, which down-regulates PKC, and staurosporine and UCN-01, which directly inhibit the enzyme, circumvent resistance of Bcl-2-overexpressing leukemic cells to ara-C-induced apoptosis and activation of the protease cascade. They also raise the possibility that modulation of Bcl-2 phosphorylation status contributes to this effect.
Mol Pharmacol 1997 Dec
PMID:Agents that down-regulate or inhibit protein kinase C circumvent resistance to 1-beta-D-arabinofuranosylcytosine-induced apoptosis in human leukemia cells that overexpress Bcl-2. 939 80

Keratinocyte apoptosis is a central element in the regulation of hair follicle regression (catagen), yet the exact location and the control of follicular keratinocyte apoptosis remain obscure. To generate an "apoptomap" of the hair follicle, we have studied selected apoptosis-associated parameters in the C57BL/6 mouse model for hair research during normal and pharmacologically manipulated, pathological catagen development. As assessed by terminal deoxynucleotide transferase dUTP fluorescein nick end-labeling (TUNEL) stain, apoptotic cells not only appeared in the regressing proximal follicle epithelium but, surprisingly, were also seen in the central inner root sheath, in the bulge/isthmus region, and in the secondary germ, but never in the dermal papilla. These apoptosis hot spots during catagen development correlated largely with a down-regulation of the Bcl-2/Bax ratio but only poorly with the expression patterns of interleukin-1beta converting enzyme, p55TNFR, and Fas/Apo-1 immunoreactivity. Instead, a higher correlation was found with p75NTR expression. During cyclophosphamide-induced follicle dystrophy and alopecia, massive keratinocyte apoptosis occurred in the entire proximal hair bulb, except in the dermal papilla, despite a strong up-regulation of Bax and p75NTR immunoreactivity. Selected receptors of the tumor necrosis factor/nerve growth factor family and members of the Bcl-2 family may also play a key role in the control of follicular keratinocyte apoptosis in situ.
Am J Pathol 1997 Dec
PMID:Analysis of apoptosis during hair follicle regression (catagen) 940 99


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