Biomedical subjects

J C Reed

Publications and source records attributed to J C Reed.

At least 19 recordsLinked to original sources

PubMed1995

Activin A-induced apoptosis is suppressed by BCL-2.

Activin A, a member of TGF beta superfamily has various activities including induction of apoptosis in mammalian cells. However, it remains unknown how activin A induces cell death. To clarify this, we investigated the expression of BCL-2 and BAX, and the effect of BCL-2 overexpression on activin A-induced apoptosis in B cell hybridoma cell lines. The activin A-sensitive cell lines expressed BAX but not BCL-2 and that activin A did not increase BAX levels. Overexpression of human BCL-2 suppressed activin A-induced apoptosis in these cells. Thus, activin A has been shown to induce apoptosis by a BCL-2-inhibitable mechanism without activating BAX.

Activins↗

PubMed1995

Overexpression of the Bcl-2 protein increases the half-life of p21Bax.

Bcl-2 and Bax are homologous proteins which can heterodimerize with each other. These proteins have opposing effects on cell survival when overexpressed in cells, with Bcl-2 blocking and Bax promoting apoptosis. Here we demonstrate that gene transfer-mediated elevations in Bcl-2 protein levels result in a marked increase in the steady-state levels of endogenous p21Bax protein as determined by immunoblotting in the Jurkat T-cell and 697 pre-B-cell leukemia cell lines, but not in several other cell lines including CEM T-cell leukemia, 32D.3 myeloid progenitor, PC12 pheochromocytoma, and NIH-3T3 fibroblasts. Steady-state levels of p21Bax protein were also elevated in the lymph nodes of Bcl-2 transgenic mice in which a BCL-2 transgene is expressed at high levels in B-cells. Northern blot analysis of BCL-2-transfected and control-transfected Jurkat and 697 leukemia cells revealed no Bcl-2-induced alterations in the steady-state levels of BAX mRNAs. In contrast, L-[35S]methionine pulse-chase analysis indicated a marked increase in the half-life (t1/2) of the p21Bax protein in BCL-2-transfected 697 cells compared to control-transfected cells (t1/2 > 24 h versus approximately 4 h), whereas the rate of Bax degradation was unaltered in Bcl-2-transfected CEM cells. The results demonstrate that levels of the proapoptotic p21Bax protein can be post-translationally regulated by Bcl-2, probably in a tissue-specific fashion, and suggest the existence of a feedback mechanism that may help to maintain the ratio of Bcl-2 to Bax protein in physiologically appropriate ranges.

3T3 Cells↗

PubMed1995

Cell-free reconstitution of Fas-, UV radiation- and ceramide-induced apoptosis.

Cell-free systems are valuable tools for the dissection of complex cellular processes. Here we show that cytoplasmic extracts from cells exposed to anti-Fas antibody or UV radiation contain an activity capable of reproducing morphological changes typical of apoptosis in nuclei added to these extracts, as well as internucleosomal cleavage of DNA and proteolysis of a protein known to be cleaved during the apoptosis of intact cells. Extracts from control cell populations were inactive in this respect. These effects were partly blocked by the addition of purified Bcl-2 protein or a competitive inhibitor peptide of interleukin-1 beta-converting enzyme to the extracts. Furthermore, apoptotic activity was induced in cytoplasmic extracts from untreated cells by the addition of ceramide, a lipid second messenger implicated recently in apoptosis signaling. These extracts should prove highly useful in the dissection of molecular events that occur during apoptosis.

Animals↗

PubMed1995

The control of apoptosis and drug resistance in ovarian cancer: influence of p53 and Bcl-2.

Modulation of apoptosis may influence resistance to chemotherapy and therefore affect the outcome of cancer treatment. Ovarian cancer, one of the most fatal malignancies in women, is often associated with drug resistance but the cellular pathways contributing to this effect remain obscure. We have found that Bcl-2 and p53, two proteins implicated in the control of apoptosis, are frequently expressed in fresh biopsies of primary ovarian carcinoma. Examination of Bcl-2 and p53 protein levels in pairs of cis-platin sensitive and resistant ovarian cell lines demonstrated that the resistant variants over-express Bcl-2 and/or p53, apparently due to progressive expansion of Bcl-2 and/or p53 positive subpopulations during the in vitro development of resistance. Exogenous expression of Bcl-2 or a temperature sensitive mutant p53 (ts p53) in the ovarian cell line A2780 resulted in protection from drug-induced apoptosis and a delay in drug-mediated S-phase arrest. Interestingly, p53 accumulation in response to DNA damage induced by different agents was significantly delayed and reduced in the Bcl-2 transfectants compared to the control A2780 line, suggesting that Bcl-2 may act upstream of the p53 pathway. Similarly, the induction of Bax mRNA and protein was also found to be delayed in the presence of Bcl-2. Overall, our data provide further evidence for cross-talk between Bcl-2, p53 and Bax and suggest that these genes are important determinants of drug-induced apoptosis thereby modulating resistance to chemotherapy.

Apoptosis↗

PubMed1995

Reduced expression of proapoptotic gene BAX is associated with poor response rates to combination chemotherapy and shorter survival in women with metastatic breast adenocarcinoma.

Bax is a homologue of Bcl-2 that promotes apoptosis. Bax protein levels were assessed by immunohistochemical methods in primary tumors derived from 119 women with metastatic breast cancer. These patients had received combination chemotherapy either with a once a month dosage schedule or in 4 weekly divided doses. The BAX immunostaining results were retrospectively compared with overall survival, time to tumor progression (TTP), and response, as well as several laboratory markers. Normal breast epithelium and in situ carcinomas immunostained positively for Bax. Marked reductions in Bax immunostaining were observed in 40 (34%) of 119 evaluable tumors. Reduced Bax correlated with shorter overall survival (median, 8.1 versus 15.7 months; P = 0.04), faster TTP (median, 2.0 versus 6.3 months; P = 0.009), and failure to respond (complete response, partial responses; 6% versus 42%, P = 0.01) in the subgroup of patients who received divided dose therapy. Reduced Bax immunostaining was not significant in the monthly dose group. When the two groups were combined, however, reduced Bax was significantly correlated in univariate analysis with failure to respond (21 versus 43% achieving complete response or partial response; P = 0.02), faster TTP (median, 3.7 versus 9.0 months; P = 0.02), and shorter survival (median, 10.7 versus 17.1 months; P = 0.04). Bax immunostaining was not significantly correlated with tumor histology, S-phase fraction, aneuploidy, p53 HER2, or cathepsin D, but was positively associated with Bcl-2 (P = 0.005). In multivariate analysis (Bax, tumor grade, and treatment group), reduced Bax was strongly associated with faster TTP (P approximately equal to 0.009) and shorter survival (P approximately equal to 0.001). Although highly preliminary, the finding suggest that loss of Bax immunostaining represents a novel prognostic indicator of poor response to chemotherapy and shorter survival in women with metastatic breast cancer, and raise the possibility that the subgroup of women with Bax-negative tumors may benefit from more aggressive therapy.

Adenocarcinoma↗

PubMed1995

IL-2-induced gene expression of protein-tyrosine phosphatase LC-PTP requires acidic and serine-rich regions within IL-2 receptor beta chain.

A protein-tyrosine phosphatase LC-PTP is preferentially expressed in hematopoietic cells and is an early response gene in lymphokine stimulated cells. Here, we found the LC-PTP mRNA induction by IL-2 was markedly inhibited by several tyrosine kinase inhibitors. The induction required both the acidic and serine-rich regions of the IL-2 receptor beta chain (IL-2R beta) in mouse IL-3-dependent pro-B BAF-B03 transfectants. This is strikingly different from the induction of c-myc gene expression, which requires the serine-rich region alone. In addition, overexpression of activated-Lck or -Raf kinases resulted in augmented LC-PTP mRNA expression in myeloid cell line 32D transfectants. Considering the previous findings that the acidic region of the IL-2R beta is responsible for association with Lck and activation of Raf kinase, IL-2-induced expression of LC-PTP mRNA may be primarily transduced through a Lck-Raf mediated signaling pathway.

Animals↗

PubMed1995

Estrogen promotes chemotherapeutic drug resistance by a mechanism involving Bcl-2 proto-oncogene expression in human breast cancer cells.

Recent studies have shown that the Bcl-2 protein suppresses programmed cell death or apoptosis induced by a variety of stimuli including chemotherapeutic drugs. Because estrogen promotes the survival of estrogen-dependent breast cancer cells in vivo, we investigated whether estrogen might regulate levels of Bcl-2 gene expression in an estrogen-responsive human breast cancer cell line. Estrogen receptor-positive MCF-7 human breast cancer cells cultured in the presence of estrogen express the 8.5-kb Bcl-2 mRNA transcript. Depletion of estrogen from the medium results in loss of expression of the mRNA, whereas reexposure to estrogen markedly induces the Bcl-2 transcript. The changes in Bcl-2 mRNA are paralleled by changes in Bcl-2 protein levels. Estrogen-induced increases in Bcl-2 are significantly inhibited by inclusion of the pure antiestrogen ICI 164,384 in the medium. The Bax protein that heterodimerizes with Bcl-2 and promotes cell death is expressed in MCF-7 cells grown in the presence of estrogen and is unaffected by culture in estrogen-free medium. Estrogen depletion doubles the sensitivity of MCF-7 cells to the cytotoxic effects of Adriamycin compared with cells cultured in medium supplemented with estrogen, consistent with a decrease in the Bcl-2 levels. MCF-7 cells treated simultaneously with estrogen and ICI 164,384 exhibit markedly lower resistance to Adriamycin compared with cells treated with estrogen alone. In the absence of estrogen, MCF-7 cells transfected with Bcl-2 expression plasmids display a marked increase in resistance to Adriamycin. In the presence of estrogen, MCF-7 cells expressing Bcl-2 antisense transcripts are rendered twice as sensitive to acute Adriamycin cytotoxicity as a control clone. We conclude that estrogen can promote resistance of estrogen receptor bearing human breast cancer cells to chemotherapeutic drugs through a mechanism that involves regulation of the Bcl-2 proto-oncogene.

Apoptosis↗

PubMed1995

Expression of Bcl-2, Bcl-x, and Bax after T cell activation and IL-2 withdrawal.

Bcl-2, bcl-x, and bax genes code for proteins that affect the susceptibility of cells to apoptosis. In general, the expression of bcl-2 or bcl-x inhibits apoptosis while bax promotes apoptosis. We examined the levels of these proteins by immunoblotting in resting and activated T cells and in thymocytes. Bcl-2 and Bax proteins vary coordinately, but Bcl-x varies independently: Bcl-2 and Bax are higher in splenic T cells than in thymocytes, and their levels increase even more after T cell activation. In contrast, Bcl-x is almost undetectable in splenic T cells but is manyfold greater in thymocytes and in activated splenic T cells. When CTLL-2 cells or activated T cells are starved of IL (IL-2), the level of Bcl-x but not Bcl-2 protein drops before the onset of apoptosis. Stable transfection of either bcl-2 or bcl-x expression plasmids promotes the survival of CTLL-2 cells in the setting of IL-2 withdrawal. Over 70 to 90% of the transfected cells remain viable at 48 h after IL-2 withdrawal when all of the control transfected cells are apoptotic. These findings suggest that a decrease in Bcl-x protein levels precedes apoptosis after IL-2 withdrawal in T cells and that transfected bcl-2 promotes survival after IL-2 withdrawal by functionally masking this drop in Bcl-x.

Animals↗

PubMed1995

The alpha 5 beta 1 integrin supports survival of cells on fibronectin and up-regulates Bcl-2 expression.

Anchorage-dependent cells that are prevented from attaching to an extracellular matrix substrate stop proliferating and may undergo apoptosis. Cell adhesion to a substrate is mediated by the integrin family of cell surface receptors, which are known to elicit intracellular signals upon cell adhesion. We show here that Chinese hamster ovary cells expressing the alpha 5 beta 1 integrin, which is a fibronectin receptor, do not undergo apoptosis upon serum withdrawal when the cells are plated on fibronectin. However, the alpha v beta 1 integrin, which is also a fibronectin receptor and binds fibronectin on the same RGD motif as alpha 5 beta 1, did not prevent apoptosis on fibronectin of the same cells. The cytoplasmic domain of the integrin alpha 5 subunit was required for the alpha 5 beta 1-mediated cell survival on fibronectin. The fibronectin-mediated survival effect appeared to be independent of the level of tyrosine phosphorylation of the focal adhesion kinase, which is induced by integrin-mediated cell attachment. The expression of the Bcl-2 protein, which counteracts apoptosis, was elevated in cells attaching to fibronectin through alpha 5 beta 1; cells attaching through alpha v beta 1 survived only if exogenous Bcl-2 was provided. Thus, alpha 5 beta 1, but not the closely related alpha v beta 1 integrin, appears to suppress apoptotic cell death through the Bcl-2 pathway.

Animals↗

PubMed1995

Structure-function analysis of Bcl-2 protein. Identification of conserved domains important for homodimerization with Bcl-2 and heterodimerization with Bax.

The Bcl-2 protein is a suppressor of programmed cell death that homodimerizes with itself and forms heterodimers with a homologous protein Bax, a promoter of cell death. Expression of Bax in Saccharomyces cerevisiae as a membrane-bound fusion protein results in a lethal phenotype that is suppressible by co-expression of Bcl-2. Functional analysis of deletion mutants of human Bcl-2 in yeast demonstrated the presence of at least three conserved domains that are required to suppress Bax-mediated cytotoxicity, termed domains A (amino acids 11-33), B (amino acids 138-154), and C (amino acids 188-196). In vitro binding experiments using GST-Bcl-2 fusion proteins demonstrated that Bcl-2(delta B) and Bcl-2(delta C) deletion mutants had a markedly impaired ability to heterodimerize with Bax but retained the ability to homodimerize with wild-type Bcl-2. In contrast, Bcl-2(delta A) and an NH2-terminal deletion mutant Bcl-2(delta 1-82) retained Bax binding activity in vitro but failed to suppress Bax-mediated cytotoxicity in yeast. Sequences downstream of domain C in the region 197-218 also were shown to be required for Bax-binding in vitro and anti-death function in yeast. Analysis of Bcl-2/Bcl-2 homodimerization using both in vitro binding assays as well as a yeast two-hybrid method provided evidence in support of a head-to-tail model for Bcl-2/Bcl-2 homodimerization and revealed that sequences within the NH2-terminal A domain interact with a structure that requires the presence of both the carboxyl B and C domains in combination. In addition to further delineating structural features within Bcl-2 that are required for homo-dimerization, the findings reported here support the hypothesis that Bcl-2 promotes cell survival by binding directly to Bax but suggest that ability to bind Bax can be insufficient for anti-cell death function.

Amino Acid Sequence↗

PubMed1995

High expression of the bcl-x gene in Reed-Sternberg cells of Hodgkin's disease.

The expression of bcl-x protein, a bcl-2-related protein present in cortical thymocytes, activated lymphocytes, and plasma cells of reactive lymph nodes, was investigated in 44 cases of Hodgkin's disease (HD) in parallel with bcl-2 and Epstein-Barr virus (EBV) status. Eighty-six percent of the cases were positive for bcl-x, among them 27% with a strong signal in more than 75% of the Reed-Sternberg cells. Positivity for bcl-x was found in, respectively, 100% and 92% of the nodular sclerosis and mixed cellularity subtypes, although 4 cases of lymphocyte predominance subtype were negative. This finding was in contrast with the weaker positivity for bcl-2 staining in 44% of the cases. EBV small RNAs were detected in 43% of the cases by using in situ hybridization. Of interest, 100% of the EBV-positive samples were positive for bcl-x, whereas only 38% of these cases were bcl-2 positive. Our findings show that the bcl-x gene expression is high in HD, suggesting that bcl-x may have a role in the pathogenesis of at least some cases of HD via apoptosis regulation.

DNA, Viral↗

PubMed1995

Cloning and disruption of CKB1, the gene encoding the 38-kDa beta subunit of Saccharomyces cerevisiae casein kinase II (CKII). Deletion of CKII regulatory subunits elicits a salt-sensitive phenotype.

Saccharomyces cerevisiae casein kinase II (CKII) contains two distinct catalytic (alpha and alpha') and regulatory (beta and beta') subunits. We report here the isolation and disruption of the gene, CKB1, encoding the 38-kDa beta subunit. The predicted Ckb1 sequence includes the N-terminal autophosphorylation site, internal acidic domain, and potential metal binding motif (CPX3C-X22-CPXC) present in other beta subunits but is unique in that it contains two additional autophosphorylation sites as well as a 30-amino-acid acidic insert. CKB1 is located on the left arm of chromosome VII, approximately 33 kilobases from the centromere and does not correspond to any previously characterized genetic locus. Haploid and diploid strains lacking either or both beta subunit genes are viable, demonstrating that the regulatory subunit of CKII is dispensable in S. cerevisiae. Such strains exhibit wild type behavior with regard to growth on both fermentable and nonfermentable carbon sources, mating, sporulation, spore germination, and resistance to heatshock and nitrogen starvation, but are salt-sensitive. Salt sensitivity is specific for NaCl and LiCl and is not observed with KCl or agents which increase osmotic pressure alone. These data suggest a role for CKII in ion homeostasis in S. cerevisiae.

Amino Acid Sequence↗

PubMed1995

FAP-1: a protein tyrosine phosphatase that associates with Fas.

Fas is a cell surface receptor that controls a poorly understood signal transduction pathway that leads to cell death by means of apoptosis. A protein tyrosine phosphatase, FAP-1, capable of interacting with the cytosolic domain of Fas, was identified. The carboxyl terminal 15 amino acids of Fas are necessary and sufficient for interaction with FAP-1. FAP-1 expression is highest in tissues and cell lines that are relatively resistant to Fas-mediated cytotoxicity. Gene transfer-mediated elevations in FAP-1 partially abolished Fas-induced apoptosis in a T cell line. These findings are consistent with an inhibitory effect of FAP-1 on Fas signal transduction.

Amino Acid Sequence↗

PubMed1995

Cytokine-mediated survival from lethal herpes simplex virus infection: role of programmed neuronal death.

The mechanisms responsible for cytokine-mediated antiviral effects are not fully understood. We approached this problem by studying the outcome of intraocular herpes simplex (HSV) infection in transgenic mice that express interferon gamma in the photoreceptor cells of the retina. These transgenic mice showed selective survival from lethal HSV-2 infection manifested in both eyes, the optic nerve, and the brain. Although transgenic mice developed greater inflammatory responses to the virus in the eyes, inflammation and viral titers in their brains were equivalent to nontransgenic mice. However, survival of transgenic mice correlated with markedly lower numbers of central neurons undergoing apoptosis. The protooncogene Bcl2 was found to be induced in the HSV-2-infected brains of transgenic mice, allowing us to speculate on its role in fostering neuronal survival in this model. These observations imply a complex interaction between cytokine, virus, and host cellular factors. Our results suggest a cytokine-regulated salvage pathway that allows for survival of infected neurons.

Animals↗

PubMed1995

Bcl-2 blocks degranulation but not fas-based cell-mediated cytotoxicity.

The ability of bcl-2 in target cells to block cell-mediated cytotoxicity by allospecific CTL was tested. The blocking effect was variable. Because killing by CTL involves two different pathways, degranulation (perforin plus granzymes) and fas, we examined the effect of bcl-2 on these pathways independently. Bcl-2 in target cells blocked apoptotic cell death induced either by cytotoxic granule extracts or by CTL killing under conditions in which the fas pathway is blocked. On the other hand, bcl-2 had no effect on target cell-killing either by Fas-specific mAb or by CTL capable of killing only via the fas pathway. These data suggest bcl-2 may block apoptotic lysis induced by perforin plus granzymes, but not apoptotic lysis induced via the fas pathway. Thus, any analysis of the effect of bcl-2 on apoptotic cell death in target cells killed by CTL must take into account the relative contributions of the degranulation vs fas pathways.

Animals↗

PubMed1995

Cloning and functional analysis of BAG-1: a novel Bcl-2-binding protein with anti-cell death activity.

Using a protein interaction cloning technique, we identified cDNAs that encode a novel Bcl-2-binding protein, termed BAG-1. The BAG-1 protein shares no significant homology with Bcl-2 or other Bcl-2 family proteins, which can form homo- and heterodimers. In gene transfer experiments using a human lymphoid cell line, Jurkat, coexpression of BAG-1 and Bcl-2 provided markedly increased protection from cell death induced by several stimuli, including staurosporine, anti-Fas antibody, and cytolytic T cells, relative to cells that contained gene transfer-mediated elevations in either BAG-1 or Bcl-2 protein alone. BAG-transfected 3T3 fibroblasts also exhibited prolonged cell survival in response to an apoptotic stimulus. The findings indicate that bag-1 represents a new type of anti-cell death gene and suggest that some routes of apoptosis induction previously ascribed to Bcl-2-independent pathways may instead reflect a need for the combination of Bcl-2 and BAG-1.

3T3 Cells↗

PubMed1995

Tumor suppressor p53 is a direct transcriptional activator of the human bax gene.

The bax gene promoter region contains four motifs with homology to consensus p53-binding sites. In cotransfection assays using p53-deficient tumor cell lines, wild-type but not mutant p53 expression plasmids transactivated a reporter gene plasmid that utilized the bax gene promoter to drive transcription of chloramphenicol acetyltransferase. In addition, wild-type p53 transactivated reporter gene constructs containing a heterologous minimal promoter and a 39-bp region from the bax gene promoter in which the p53-binding site consensus sequences reside. Introduction of mutations into the consensus p53-binding site sequences abolished p53 responsiveness of reporter gene plasmids. Wild-type but not mutant p53 protein bound to oligonucleotides corresponding to this region of the bax promoter, based on gel retardation assays. Taken together, the results suggest that bax is a p53 primary-response gene, presumably involved in a p53-regulated pathway for induction of apoptosis.

Base Sequence↗

PubMed1995

A novel member of the TRAF family of putative signal transducing proteins binds to the cytosolic domain of CD40.

CD40 is a member of the tumor necrosis factor receptor (TNF-R) family that regulates B-lymphocyte proliferation, immunoglobulin class-switching, and apoptosis through poorly defined signal transduction mechanisms. Using a yeast two-hybrid method, cDNAs were obtained that encode a novel protein, CD40-associated protein-1 (CAP-1), which binds specifically to the cytosolic domain of CD40 but not TNF-R1, TNF-R2, or Fas. The CAP-1 protein contains a C-terminal domain that shares strong amino acid sequence homology with a unique domain found recently in two putative signal transducing proteins that bind to the TNF-R2 cytosolic tail, TRAF1 and TRAF2. This C-terminal region of CAP-1 was sufficient to mediate binding to CD40 and homodimerization of CAP-1 proteins. The N-terminal portion of CAP-1 contains a RING finger motif and three zinc finger-like domains similar to those found in several regulatory proteins that interact with DNA or RNA. CAP-1 thus represents a new member of a family of potential signal transducing proteins that contain a conserved domain (the TRAF domain), bind to the cytosolic regions of particular members of TNF-R family proteins, and that can form homo- and heterotypic dimers.

Amino Acid Sequence↗