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

Heat shock enhances troponin expression and decreases differentiation-associated caspase-3 dependence in myoblasts under hypoxia

BACKGROUND

Myoblast transplantation can functionally restore muscle tissues damaged by ischemic or other insults. Despite promising results in clinical trials, however, myoblast transplantation still presents several challenges, with effective differentiation under harsh conditions of the host tissue being one of the most demanding. In keeping with a straightforward clinical application, heat shock (HS) pretreatment as a nonviral method can be utilized with promising results in cell therapy. The aim of this study was to demonstrate whether HS-pretreated cells would receive a differentiation benefit under hypoxic conditions.

MATERIALS AND METHODS

We studied HS preconditioning of C2C12 myoblasts in relation to their differentiation- and apoptosis-associated responses under normoxia or 1% hypoxia.

RESULTS

HS induced long-lasting expression of Hsp70/72 and Hsp90. Although myoblast differentiation proceeded in HS-pretreated and control cells under both normoxia and hypoxia, expression of differentiation-associated troponin was enhanced in HS-preconditioned cells under hypoxia. This effect persisted when differentiation was inhibited by Z-DEVD-FMK, a caspase-3 inhibitor.

CONCLUSIONS

HS preconditioning enhances expression of myoblast differentiation-associated troponin and may reduce dependence of differentiation on caspase-3.

"Rainbow" western blotting

The ''Rainbow western'' method permits detection of multiple antigens on a single protein blot. The procedure utilizes horseradish peroxidase (HRPase)-based detection with both a chemiluminescent and colorimetric substrate. In the ''Rainbow western'' procedure four different HRPase-colorimetric substrates that produce black, brown, red, and green colors are employed sequentially for detection and simultaneous display of four different antigens on the same blot. The Rainbow western methods have the potential to consolidate the work to analyze the expression levels of several proteins in studies of signaling pathways within biological samples. This technique could be particularly valuable for analysis of comigrating proteins, isoforms, and/or facilitating studies on phosphorylation, acetylation, and oligomerization of proteins tagged by the same epitope.

BAG-1 predicts patient outcome and tamoxifen responsiveness in ER-positive invasive ductal carcinoma of the breast

BAG-1 (bcl-2-associated athanogene) enhances oestrogen receptor (ER) function and may influence outcome and response to endocrine therapy in breast cancer. We determined relationships between BAG-1 expression, molecular phenotype, response to tamoxifen therapy and outcome in a cohort of breast cancer patients and its influence on tamoxifen sensitivity in MCF-7 breast cancer cells in vitro. Publically available gene expression data sets were analysed to identify relationships between BAG-1 mRNA expression and patient outcome. BAG-1 protein expression was assessed using immunohistochemistry in 292 patients with invasive ductal carcinoma and correlated with clinicopathological variables, therapeutic response and disease outcome. BAG-1-overexpressing MCF-7 cells were treated with antioestrogens to assess its effects on cell proliferation. Gene expression data demonstrated a consistent association between high BAG-1 mRNA and improved survival. In ER+ cancer (n=189), a high nuclear BAG-1 expression independently predicted improved outcome for local recurrence (P=0.0464), distant metastases (P=0.0435), death from breast cancer (P=0.009, hazards ratio 0.29, 95% CI: 0.114-0.735) and improved outcome in tamoxifen-treated patients (n=107; P=0.0191). BAG-1 overexpression in MCF-7 cells augmented antioestrogen-induced growth arrest. A high BAG-1 expression predicts improved patient outcome in ER+ breast carcinoma. This may reflect both a better definition of the hormone-responsive phenotype and a concurrent increased sensitivity to tamoxifen.

Bag-1 proteins in oral squamous cell carcinoma

Bag-1 is an anti-apoptotic protein that exhibits altered expression in many malignancies, including oral squamous cell carcinoma. The bag-1 gene gives rise to different protein products with different subcellular localisations through alternative translational initiation sites. In oral squamous cell carcinoma, cytoplasmic expression has been associated with metastasis to regional lymph nodes and poor prognosis. In contrast, the longest Bag-1 isoform is nuclear and may regulate differentiation in oral epithelium. In this review, the functions of the three isoforms of Bag-1 expressed in oral epithelial cells are discussed in relation to their contribution to oral carcinogenesis.

BAG1 promotes axonal outgrowth and regeneration in vivo via Raf-1 and reduction of ROCK activity

Improved survival of injured neurons and the inhibition of repulsive environmental signalling are prerequisites for functional regeneration. BAG1 (Bcl-2-associated athanogene-1) is an Hsp70/Hsc70-binding protein, which has been shown to suppress apoptosis and enhance neuronal differentiation. We investigated BAG1 as a therapeutic molecule in the lesioned visual system in vivo. Using an adeno-associated viral vector, BAG1 (AAV.BAG1) was expressed in retinal ganglion cells (RGC) and then tested in models of optic nerve axotomy and optic nerve crush. BAG1 significantly increased RGC survival as compared to adeno-associated viral vector enhanced green fluorescent protein (AAV.EGFP) treated controls and this was independently confirmed in transgenic mice over-expressing BAG1 in neurons. The numbers and lengths of regenerating axons after optic nerve crush were also significantly increased in the AAV.BAG1 group. In pRGC cultures, BAG1-over-expression resulted in a approximately 3-fold increase in neurite length and growth cone surface. Interestingly, BAG1 induced an intracellular translocation of Raf-1 and ROCK2 and ROCK activity was decreased in a Raf-1-dependent manner by BAG1-over-expression. In summary, we show that BAG1 acts in a dual role by inhibition of lesion-induced apoptosis and interaction with the inhibitory ROCK signalling cascade. BAG1 is therefore a promising molecule to be further examined as a putative therapeutic tool in neurorestorative strategies.

Endothelial cells expressing Bcl-2 promotes tumor metastasis by enhancing tumor angiogenesis, blood vessel leakiness and tumor invasion

Metastatic spread of tumor cells to vital organs is the major cause of mortality in cancer patients. Bcl-2, a key antiapoptotic protein, is expressed at high levels in a number of human tumors. We have recently shown that Bcl-2 is also overexpressed in tumor-associated blood vessels in head-and-neck cancer patients. Interestingly, enhanced Bcl-2 expression in tumor blood vessels is directly correlated with metastatic status of these cancer patients. In addition, endothelial cells (ECs) expressing Bcl-2 showed increased production of interleukin-8 (IL-8) resulting in significantly enhanced tumor cell proliferation and tumor cell invasion. Therefore, we hypothesized that Bcl-2 expression in tumor-associated ECs may promote tumor metastasis by enhancing tumor cell invasiveness and release in the circulation. To test our hypothesis, we coimplanted tumor cells along with ECs expressing Bcl-2 (EC-Bcl-2) in the flanks of SCID mice. Our results demonstrate that incorporation of EC-Bcl-2 in primary tumors significantly enhanced tumor cell metastasis to lungs and this EC-Bcl-2-mediated tumor metastasis was independent of primary tumor size. In addition, Bcl-2-mediated tumor metastasis directly correlated with increased tumor angiogenesis. Bcl-2 expression in ECs also promoted transendothelial cell permeability, blood vessel leakiness and tumor cell invasion. EC-Bcl-2-mediated tumor cell proliferation and tumor cell invasion were significantly mediated by IL-8. These results suggest that Bcl-2, when expressed at higher levels in tumor-associated ECs, may promote tumor metastasis by enhancing tumor angiogenesis, blood vessel leakiness and tumor cell invasiveness.

Plant programmed cell death: can't live with it; can't live without it

The decision of whether a cell should live or die is fundamental for the wellbeing of all organisms. Despite intense investigation into cell growth and proliferation, only recently has the essential and equally important idea that cells control/programme their own demise for proper maintenance of cellular homeostasis gained recognition. Furthermore, even though research into programmed cell death (PCD) has been an extremely active area of research there are significant gaps in our understanding of the process in plants. In this review, we discuss PCD during plant development and pathogenesis, and compare/contrast this with mammalian apoptosis.

Epstein-Barr virus nuclear antigen (EBNA) 3A induces the expression of and interacts with a subset of chaperones and co-chaperones

Viral nuclear oncoproteins EBNA3A and EBNA3C are essential for the efficient immortalization of B cells by Epstein–Barr virus (EBV) in vitro and it is assumed that they play an essential role in viral persistence in the human host. In order to identify cellular genes regulated by EBNA3A expression, cDNA encoding EBNA3A was incorporated into a recombinant adenoviral vector. Microarray analysis of human diploid fibroblasts infected with either adenovirus EBNA3A or an empty control adenovirus consistently showed an EBNA3A-specific induction of mRNA corresponding to the chaperones Hsp70 and Hsp70B/B′ and co-chaperones Bag3 and DNAJA1/Hsp40. Analysis of infected fibroblasts by real-time quantitative RT-PCR and Western blotting confirmed that EBNA3A, but not EBNA3C, induced expression of Hsp70, Hsp70B/B′, Bag3 and DNAJA1/Hsp40. This was also confirmed in a stable, inducible expression system. EBNA3A activated transcription from the Hsp70B promoter, but not multimerized heat-shock elements in transient transfection assays, consistent with specific chaperone and co-chaperone upregulation. Co-immunoprecipitation experiments suggest that EBNA3A can form a complex with the chaperone/co-chaperone proteins in both adenovirus-infected cells and EBV-immortalized lymphoblastoid cell lines. Consistent with this, induction of EBNA3A resulted in redistribution of Hsp70 from the cytoplasm to the nucleus. EBNA3A therefore specifically induces (and then interacts with) all of the factors necessary for an active Hsp70 chaperone complex.

BAG1 plays a critical role in regulating recovery from both manic-like and depression-like behavioral impairments

Recent microarray studies with stringent validating criteria identified Bcl-2-associated athanogene (BAG1) as a target for the actions of medications that are mainstays in the treatment of bipolar disorder (BPD). BAG1 is a Hsp70/Hsc70-regulating cochaperone that also interacts with glucocorticoid receptors (GRs) and attenuates their nuclear trafficking and function. Notably, glucocorticoids are one of the few agents capable of triggering both depressive and manic episodes in patients with BPD. As a nexus for the actions of glucocorticoids and bipolar medications, we hypothesized that the level of BAG1 expression would play a pivotal role in regulating affective-like behaviors. This hypothesis was investigated in neuron-selective BAG1 transgenic (TG) mice and BAG1 heterozygous knockout (+/-) mice. On mania-related tests, BAG1 TG mice recovered much faster than wild-type (WT) mice in the amphetamine-induced hyperlocomotion test and displayed a clear resistance to cocaine-induced behavioral sensitization. In contrast, BAG1+/- mice displayed an enhanced response to cocaine-induced behavioral sensitization. The BAG1 TG mice showed less anxious-like behavior on the elevated plus maze test and had higher spontaneous recovery rates from helplessness behavior compared with WT mice. In contrast, fewer BAG1+/- mice recovered from helplessness behavior compared with their WT controls. BAG1 TG mice also exhibited specific alterations of hippocampal proteins known to regulate GR function, including Hsp70 and FKBP51. These data suggest that BAG1 plays a key role in affective resilience and in regulating recovery from both manic-like and depression-like behavioral impairments.

Growth-compromised HSV-2 vector Delta RR protects from N-methyl-D-aspartate-induced neuronal degeneration through redundant activation of the MEK/ERK and PI3-K/Akt survival pathways, either one of which overrides apoptotic cascades

We have previously shown that intrastriatal injection of Delta RR, the growth-compromised herpes simplex virus type 2 (HSV-2) vector for the antiapoptotic protein ICP10PK, prevents apoptosis caused by the excitotoxin N-methyl-D-aspartate (NMDA) in a mouse model of glutamatergic neuronal cell death (Golembewski et al. [2007] Exp. Neurol. 203:381-393). Because apoptosis regulation is stimulus and cell type specific, our studies were designed to examine the mechanism of Delta RR-mediated neuroprotection in striatal neurons. Organotypic striatal cultures (OSC) that retain much of the synaptic circuitry of the intact striatum were infected with Delta RR or a growth-compromised HSV-2 vector that lacks ICP10PK (Delta PK) and examined for neuroprotection-associated signaling. The mutated ICP10 proteins (p175 and p95) were expressed in 70-80% of neurons from Delta RR- and Delta PK-infected cultures, respectively, as determined by double-immunofluorescent staining with antibodies to ICP10 and NeuN or GAD65. Delta RR- but not Delta PK-treated OSC were protected from NMDA-induced apoptosis, as verified by ethidium homodimer staining, TUNEL, caspase-3 activation, and poly(AD-ribose) polymerase (PARP) cleavage. Neuroprotection was through ICP10PK-mediated activation of the survival pathways MEK/ERK and PI3-K/Akt, up-regulation of the antiapoptotic proteins Bag-1 and Bcl-2, and phosphorylation (inactivation) of the proapoptotic protein Bad. It was blocked by the MEK inhibitor U0126 or the PI3-K inhibitor LY294002, suggesting that either pathway can prevent NMDA-induced apoptosis. The data indicate that Delta RR-delivered ICP10PK stimulates redundant survival pathways that override proapoptotic cascades. Delta RR is a promising gene therapy platform against glutamatergic cell death.

Expression patterns and prognostic value of Bag-1 and Bcl-2 in breast cancer

Introduction

Bcl-2 antanogene-1 (Bag-1) binds the anti-apoptotic mediator Bcl-2, and enhances its activity. Bcl-2 and Bag-1 are associated with chemotherapy resistance in cancer cells. Drugs that target Bcl-2 are currently in clinical development. The purpose of the present study was to examine expression patterns of Bag-1 in a large cohort of breast tumors and to assess the association with Bcl-2, estrogen receptor, progesterone receptor and Her2/neu, and other clinical/pathological variables.

Methods

Tissue microarrays containing primary specimens from 638 patients with 10-year follow-up were employed, and the expression of Bag-1, Bcl-2, estrogen receptor, progesterone receptor and Her2/neu was assessed using our automated quantitative analysis method. We used cytokeratin to define pixels as breast cancer (tumor mask) within the array spot, and we measured biomarker expression within the mask using Cy5 conjugated antibodies.

Results

High Bcl-2 expression was associated with improved survival in the entire cohort and in the node-positive subset (P = 0.008 and P = 0.002, respectively). High Bag-1 expression was associated with improved survival in the node-positive subset (P = 0.006). On multivariable analysis, neither Bcl-2 nor Bag-1 retained their independence as prognostic markers. Strong associations were found between Bag-1, Bcl-2, estrogen receptor and progesterone receptor.

Conclusion

Bag-1 and Bcl-2 expression in breast tumors is associated with improved outcome and steroid receptor positivity. Evaluation of Bcl-2 and Bag-1 expression in breast cancer may identify a subset of patients with a favorable prognosis, who might not benefit from chemotherapy or who might benefit from Bcl-2 targeting agents in addition to antihormonal therapy.

Hyperthermia induces differentiation without apoptosis in permissive temperatures in human erythroleukaemia cells

PURPOSE

The aim of the present study was to investigate whether induction of differentiation by hyperthermia is accompanied by apoptosis and necrosis to further evaluate the benefits of using hyperthermia as a differentiation inducing physical modality.

MATERIALS AND METHOD

Differentiation was evaluated in K562 erythroleukaemia cells by measuring haemoglobin synthesis and flow cytometric measurement of glycophorin A expression. Apoptosis was measured by Annexin-V-FITC and Propidium Iodide (PI) double staining assay. Apoptosis and necrosis was also evaluated morphologically using staining with acridine orange/ethidium bromide (AO/EtBr) by fluorescence microscopy. Heat shock protein 70 (HSP70) level was measured by ELISA kit.

RESULTS

Hyperthermia (43 degrees C) induced differentiation as judged by increased haemoglobin synthesis and glycophorin A expression. No sign of apoptosis or necrosis could be detected at this temperature. Cell viability did not change due to heat treatment, and cellular proliferation was reduced in a dose (heating time) dependent manner. At 45 degrees C, hyperthermia induced apoptosis and necrosis with minimal or no sign of differentiation. HSP70 level was significantly increased at 43 degrees C along with differentiation of leukaemic cells, while at 45 degrees C no significant effect on HSP70 production could be observed.

CONCLUSIONS

The encouraging results obtained here indicate that by heat treatment at 43 degrees C, hyperthermia can be used alone or in combination with other modalities as a differentiation inducing agent without any detectable apoptotic activity. Positive correlation between HSP70 production and induction of differentiation and lack of apoptosis by hyperthermia confirm the possible role of HSP70 in the heat-induced differentiation and apoptosis in leukaemic cells.

Heat shock proteins and Bcl-2 expression and function in relation to the differential hyperthermic sensitivity between leukemic and normal hematopoietic cells

A major problem in autologous stem cell transplantation is the occurrence of relapse by residual neoplastic cells from the graft. The selective toxicity of hyperthermia toward malignant hematopoietic progenitors compared with normal bone marrow cells has been utilized in purging protocols. The underlying mechanism for this selective toxicity has remained unclear. By using normal and leukemic cell line models, we searched for molecular mechanisms underlying this selective toxicity. We found that the differential heat sensitivity could not be explained by differences in the expression or inducibility of Hsp and also not by the overall chaperone capacity of the cells. Despite an apparent similarity in initial heat-induced damage, the leukemic cells underwent heat-induced apoptosis more readily than normal hematopoietic cells. The differences in apoptosis initiation were found at or upstream of cytochrome c release from the mitochondria. Sensitivity to staurosporine-induced apoptosis was similar in all cell lines tested, indicating that the apoptotic pathways were equally functional. The higher sensitivity to heat-induced apoptosis correlated with the level of Bcl-2 protein expression. Moreover, stable overexpression of Bcl-2 protected the most heat sensitive leukemic cells against heat-induced apoptosis. Our data indicate that leukemic cells have a specifically lower threshold for heat damage to initiate and execute apoptosis, which is due to an imbalance in the expression of the Bcl-2 family proteins in favor of the proapoptotic family members.

Differentially expressed pro- and anti-apoptogenic genes in response to benzene exposure: Immunohistochemical localization of p53, Bag, Bad, Bax, Bcl-2, and Bcl-w in lung epithelia

Benzene, a well-known human carcinogen, is a commonly used industrial chemical that evokes further toxicological concern because of its potential genotoxic risks as a constituent of petrol and the byproduct of combustion and cigarette smoke. The present study investigated the effects of benzene inhalation on the expression of pro- and antiapoptogenic genes in lung epithelia. Immunohistochemical expression was assessed for antiapoptotic Bcl-2 family proteins, including Bcl-2, Bcl-w, and Bag-1 as well as proapoptotic subfamily members with Bcl-2 homology (BH)1 1-3, namely Bax, those that consist of only the BH3 region, represented by Bad, and proapoptotic gene expression for p53. Rats exposed to benzene via inhalation (300 ppm) for 7 days showed a significant upregulation of proapoptotic gene expression for p53, Bax, and Bad as assessed by a semiquantitative segmental analysis of the lung epithelia, including bronchioles, terminal bronchioles, respiratory bronchioles, and alveoli. Bag-1, an antiapoptogenic gene, was also found to have significant upregulated expression in lung epithelia. Since the underlying mechanisms by which Bag-1 exerts its antiapoptogenic effects are not known, benzene may target the protein chaperones hsc70/hsp70, or RING finger protein associated with Bag-1 activity. Alternatively, the significant downregulation of Bcl-2 may have diminished the antiapoptotic synergism necessary for the effectiveness of Bag-1. Both Bcl-2 and Bcl-w were found to be significantly downregulated compared to the proapoptotic counterparts. These data support the role of benzene in activating proapoptogenic events that lead to the upregulation of gene expression that may provide a crucial defense mechanism within lung parenchyma to reduce mutation hazard and potential carcinogenic effects of benzene-initiated pathogenesis.

A novel role for Bcl-2 associated-athanogene-1 (Bag-1) in regulation of the endoplasmic reticulum stress response in mammalian chondrocytes

BAG-1 (Bcl-2 associated athanogene-1) is a multifunctional protein, linking cell proliferation, cell death, protein folding, and cell stress. In vivo, BAG-1 is expressed in growth plate and articular cartilage, and the expression of BAG-1 is decreased with aging. Chondrocytes respond to endoplasmic reticulum (ER) stress with decreased expression of extracellular matrix proteins, and prolonged ER stress leads to chondrocyte apoptosis. Here we demonstrate for the first time that BAG-1 is involved in ER stress-induced apoptosis in chondrocytes. Induction of ER stress through multiple mechanisms all resulted in downregulation of BAG-1 expression. In addition, direct suppression of BAG-1 expression resulted in chondrocyte growth arrest and apoptosis, while stable overexpression of BAG-1 delayed the onset of ER stress-mediated apoptosis. In addition to regulating apoptosis, we also observed decreased expression of collagen type II in BAG-1 deficient chondrocytes. In contrast, overexpression of BAG-1 resulted in increased expression of collagen type II. Moreover, under ER stress conditions, the reduced expression of collagen type II was delayed in chondrocytes overexpressing BAG-1. These results suggest a novel role for BAG-1 in supporting viability and matrix expression of chondrocytes.

Bcl-2-associated athanogene-1 (BAG-1): a transcriptional regulator mediating chondrocyte survival and differentiation during endochondral ossification

BAG-1, an anti-apoptotic protein, was identified by its ability to bind to BCL-2, HSP70-family molecular chaperones and nuclear hormone receptor family members. Two BAG-1 isoforms, BAG-1L (50 kDa) and BAG-1S (32 kDa) were identified in mouse cells and BAG-1 expression was reported in murine growth plate and articular chondrocytes. The present study aimed to elucidate the role of BAG-1 in the regulation of molecular mechanisms governing chondrocyte differentiation and turnover during endochondral ossification. In long bones of skeletally immature mice, we observed expression of BAG-1 in the perichondrium, osteoblasts, osteocytes in the bone shaft, bone marrow, growth plate and articular chondrocytes. Monolayer cultures of murine chondrocytic ATDC5 cells, which exhibited robust expression of both BAG-1 isoforms and the Bag-1 transcript, were utilized as an in vitro model to delineate the roles of BAG-1. Overexpression of BAG-1L in ATDC5 cells resulted in downregulation of Col2a1 expression, a gene characteristically downregulated at the onset of hypertrophy, and an increase in transcription of Runx-2 and Alkaline phosphatase, genes normally expressed at the onset of chondrocyte hypertrophy and cartilage mineralization in the process of endochondral ossification. We also demonstrated the anti-apoptotic role of BAG-1 in chondrocytes as overexpression of BAG-1 protected ATDC5 cells, which were subjected to heat-shock at 48 degrees C for 30 min, against heat-shock-induced apoptosis. Overexpression of the SOX-9 protein in ATDC5 cells resulted in increased Bag-1 gene expression. To further investigate the regulation of Bag-1 gene expression by SOX-9, CHO cells were co-transfected with the human Bag-1 gene promoter-Luciferase reporter construct and the human pSox-9 expression vector. Activity of the Bag-1 promoter was significantly enhanced by the SOX-9 protein. In conclusion, a novel finding of this study is the role of BAG-1 as a transcriptional regulator of genes involved in chondrocyte hypertrophy and cartilage mineralization during the process of endochondral ossification. Additionally, we have demonstrated for the first time the regulation of Bag-1 gene expression by SOX-9 and the anti-apoptotic role of BAG-1 in chondrocytic cells. Modulation of Bag-1 expression can therefore mediate chondrocyte differentiation and turnover, and offer further insight into the molecular regulation of endochondral ossification.

BAG3 regulates motility and adhesion of epithelial cancer cells

BAG3 protein binds to and regulates Hsp70 chaperone activity. The BAG3 protein contains a WW domain and a proline-rich region with SH3-binding motifs, suggesting that it may interact with proteins relevant to signal transduction, recruiting Hsp70 to signaling complexes and altering cell responses. BAG3 overexpression has been observed in human cancers. We show here that homozygous BAG3-deficient mouse embryonic fibroblasts (MEF) exhibit delayed formation of filopodia and focal adhesion complexes when freshly plated. BAG3-deficient MEFs show reduced cell motility in culture. We observed that endogenous BAG3 protein is highly expressed in many human epithelial cancer cell lines, especially adenocarcinomas. Gene transfer-mediated overexpression of BAG3 increased motility of Cos7 cell and several human cancer cell lines, including breast cancer MCF7 and prostate cancer DU145 and ALVA31 cell lines. Conversely, reduction of BAG3 protein by RNA interference (RNAi) decreased cell motility in four of four epithelial tumor lines tested. We observed an influence of BAG3 on cell adhesion in culture. In Cos7 kidney epithelial cells, BAG3 protein partially colocalizes with actin at the leading edge of migrating cells, wherein active actin polymerization and nucleation occur. RNAi-mediated reductions in BAG3 expression were associated with decreased Rac1 activity, suggesting a role for BAG3 in regulating this small GTPase involved in actin-cytoskeleton dynamics. In mice, RNAi-mediated reductions in BAG3 in a human tumor xenograft suppressed invasion and metastasis in vivo. Thus, the high levels of BAG3 protein seen in some epithelial cancer cell lines may be relevant to mechanisms of tumor invasion and metastasis.

Overexpression and gene amplification of BAG-1L in hormone-refractory prostate cancer

BAG-1L (Bcl-2-associated anthanogene 1) has been found to interact with androgen receptor (AR), and has been suggested to be involved in the development of prostate cancer. In order to determine the presence of genetic and/or expression alterations of BAG-1L in prostate cancer, we analysed human prostate cancer cell lines and xenografts as well as patient samples of untreated, hormone-naïve, and hormone-refractory prostate carcinomas for sequence variations using denaturing high-performance liquid chromatography (DHPLC), for gene copy number using fluorescence in situ hybridization (FISH), and for expression using both quantitative RT-PCR and immunostaining. Only one sequence variation was found in all 37 cell lines and xenografts analysed. BAG-1 gene amplification was detected in two xenografts. In addition, gene amplification was found in 6 of 81 (7.4%) hormone-refractory clinical tumours, whereas no amplification was found in any of the 130 untreated tumours analysed. Additionally, gain of the BAG-1 gene was observed in 27.2% of the hormone-refractory tumours and in 18.5% of the untreated carcinomas. In a set of 263 patient samples, BAG-1L protein expression was significantly higher in hormone-refractory tumours than in primary tumours (p = 0.002). Altogether, these data suggest that amplification and overexpression of BAG-1L may be involved in the progression of prostate cancer.

Concentration-dependent effects of genistein on global gene expression in MCF-7 breast cancer cells: an oligo microarray study

Breast cancer is the most commonly diagnosed cancer among US women; there is therefore great interest in developing preventive and treatment strategies for this disease. Because breast cancer incidence is much lower in countries where women consume high levels of soy, bioactive compounds in this food source have been studied for their effects on breast cancer. Genistein, found at high levels in soybeans and soy foods, is a controversial candidate breast cancer preventive phytochemical whose effects on breast cells are complex. To understand more clearly the molecular mechanisms underlying the effects of genistein on breast cancer cells, we used a DNA oligo microarray approach to examine the global gene expression patterns in MCF-7 breast cancer cells at both physiologic (1 or 5 microM) and pharmacologic (25 microM) genistein concentrations. Microarray analyses were performed on MCF-7 cells after 48 h of either vehicle or 1, 5, or 25 microM genistein treatment. We found that genistein altered the expression of genes belonging to a wide range of pathways, including estrogen- and p53-mediated pathways. At 1 and 5 microM, genistein elicited an expression pattern suggestive of increased mitogenic activity, confirming the proliferative response to genistein observed in cultured MCF-7 cells, while at 25 microM genistein effected a pattern that likely contributes to increased apoptosis, decreased proliferation and decreased total cell number, also consistent with cell culture results. These findings provide evidence for a molecular signature of genistein's effects in MCF-7 cells and lay the foundation for elucidating the mechanisms of genistein's biological impact in breast cancer cells.

Lithium toxicity and expression of stress-related genes or proteins in A549 cells

To unveil some molecular mechanisms underlying lithium toxicity, expression changes of stress-related genes or proteins were analysed in A549 cells, cultured for 3 days in presence of lithium. A dose-dependent cell-growth inhibition was found for concentrations ranging from 2 (toxicity threshold) to 12 mM (lethality threshold). cDNA arrays technology was used to analyse effects of 5 and 10 mM lithium. Among genes involved in cell cycle regulation, proliferating cell nuclear antigen (PCNA) was down-regulated and cyclin kinase inhibitor p21 (CDKN1A), up-regulated. Genes of paraoxonase 2, known to prevent LDL lipid peroxidation, and of catalase and SOD were found to be down-regulated whereas genes of cytochrome P450 (CYP2F1, CYP2E1) were up-regulated. This probably results in higher intracellular levels of reactive oxygen species and account for increased levels of lipid peroxidation commonly associated with lithium exposure. Moreover, lithium was found to down-regulate genes coding for anti-apoptotic gene BAG-1 and for most of the molecular chaperones (HSP, GRP). This might account for lithium toxicity since these proteins are critical for cell survival. At translational level, a 105 kDa protein was found to be over-expressed. This protein was recognized by the anti-GRP94, anti-KDEL and anti-phosphoserine monoclonal antibodies suggesting that, lithium could induce post-translational modifications of GRP94 phosphorylation. Using tunicamycin and thapsigargin, it was concluded that lithium effects are not related to defect in N-linked glycosylation and/or to changes in calcium homeostasis.

Subcellular localisation of BAG-1 and its regulation of vitamin D receptor-mediated transactivation and involucrin expression in oral keratinocytes: implications for oral carcinogenesis

In oral cancers, cytoplasmic BAG-1 overexpression is a marker of poor prognosis. BAG-1 regulates cellular growth, differentiation and survival through interactions with diverse proteins, including the vitamin D receptor (VDR), a key regulator of keratinocyte growth and differentiation. BAG-1 is expressed ubiquitously in human cells as three major isoforms of 50 kDa (BAG-1L), 46 kDa (BAG-1M) and 36 kDa (BAG-1S) from a single mRNA. In oral keratinocytes BAG-1L, but not BAG-1M and BAG-1S, enhanced VDR transactivation in response to 1alpha,25-dihydroxyvitamin D3. BAG-1L was nucleoplasmic and nucleolar, whereas BAG-1S and BAG-1M were cytoplasmic and nucleoplasmic in localisation. Having identified the nucleolar localisation sequence in BAG-1L, we showed that mutation of this sequence did not prevent BAG-1L from potentiating VDR activity. BAG-1L also potentiated transactivation of known vitamin-D-responsive gene promoters, osteocalcin and 24-hydroxylase, and enhanced VDR-dependent transcription and protein expression of the keratinocyte differentiation marker, involucrin. These results demonstrate endogenous gene regulation by BAG-1L by potentiating nuclear hormone receptor function and suggest a role for BAG-1L in 24-hydroxylase regulation of vitamin D metabolism and the cellular response of oral keratinocytes to 1alpha,25-dihydroxyvitamin D3. By contrast to the cytoplasmic BAG-1 isoforms, BAG-1L may act to suppress tumorigenesis.

Gene transfer of cyto-protective molecules in corneal endothelial cells and cultured corneas: analysis of protective effects in vitro and in vivo

The loss of corneal endothelial cells plays a critical role in many corneal diseases and is a common phenomenon following cornea transplantation. In addition, the non-regenerative capacity of human corneal endothelial cells (HCEC) ultimately requires appropriate protection of corneal tissues during ex vivo storage to ensure vitality of the cells. However, only 70% of donor corneas can be used for grafting because of endothelial deficiencies. Corneal endothelial cell loss during storage is mainly induced by apoptotic cell death. This study was undertaken, for proof of principle, to investigate whether over-expression of cyto-protective molecules Bcl-x(L), Bag-1, and HO-1 prevents the loss of corneal endothelial cells both in vitro and in vivo. We demonstrate that gene transfer of both Bcl-x(L) and HO-1 has cyto-protective effects on HCEC in vitro. However, gene transfer of a single cyto-protective molecule does not prevent its rejection upon transplantation in a MHC class I/II disparate rat model.

The human corneal endothelium: new insights into electrophysiology and ion channels

The corneal endothelium is a monolayer that mediates the flux of solutes and water across the posterior corneal surface. Thereby, it plays an essential role to maintain the transparency of the cornea. Unlike the epithelium, the human endothelium is an amitotic cell layer with a critical cell density and the risk of corneal decompensation. The number of endothelial cells subsequently decreases with age. Moreover, the endothelial cell loss is accelerated after various impairments such as surgical trauma (e.g. cataract extraction) and following corneal transplantation. This cell loss is associated with programmed cell death (apoptosis) and changed ion channel activity. However, little is known about the electrophysiology and ion channel expression (in particular Ca2+ channels) in corneal endothelial cells. This article reviews our current knowledge about the electrophysiology of the corneal endothelium. It highlights ion channel expression, which may have a major role in corneal cell physiology and pathological events. A better understanding of the (electro)physiological function of the cornea may lead to the development of clinical relevant new therapeutic and preventive measures.

Bcl-2 Protects Endothelial Cells against γ-Radiation via a Raf-MEK-ERK-Survivin Signaling Pathway That Is Independent of CytochromecRelease

The Bcl-2 oncoprotein is a potent inhibitor of apoptosis and is overexpressed in a wide variety of malignancies. Until recently, it was generally accepted that Bcl-2 primarily mediates its antiapoptotic function by regulating cytochrome c release from mitochondria. However, more recent studies have shown that Bcl-2 is present on several intracellular membranes and mitochondria may not be the only site where Bcl-2 exercises its survival function. In this study, we investigated if Bcl-2 can protect endothelial cells against gamma-radiation by a cytochrome c-independent signaling pathway. Human dermal microvascular endothelial cells (HDMEC), when exposed to gamma-radiation, exhibited a time-dependent activation of caspase-3 that was associated with increased cytochrome c release from mitochondria. Bcl-2 expression in endothelial cells (HDMEC-Bcl-2) significantly inhibited irradiation-induced caspase-3 activation. However, Bcl-2-mediated inhibition of caspase-3 was significantly reversed by inhibition of the Raf-mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) kinase (MEK)-ERK pathway. Interestingly, caspase-3 activation in HDMEC-Bcl-2 cells was not associated with cytochrome c release. We also observed that endothelial cell Bcl-2 expression significantly increased the expression of survivin and murine double minute-2 (Mdm2) via the Raf-MEK-ERK pathway. Endothelial cells expressing Bcl-2 also inhibited gamma-radiation-induced activation of p38 MAPK and p53 accumulation. Inhibition of p53 accumulation in HDMEC-Bcl-2 could be due to the enhanced expression of Mdm2 in these cells. Taken together, these results show three mechanisms by which Bcl-2 may mediate endothelial cell cytoprotection independently of cytochrome c release: (a) increased survivin expression, (b) inhibition of p53 accumulation, and (c) inhibition of p38 MAPK.

Downregulation of PAR-4, a pro-apoptotic gene, in pancreatic tumors harboring K-ras mutation

Oncogenic ras is known to inhibit cell death and growth inhibitory genes and activate prosurvival genes. Proapoptotic gene PAR-4, has been found to be downregulated by oncogenic ras. Since pancreatic tumors harbor a high incidence of K-ras point mutations, we hypothesized that oncogenic K-ras might influence the function and expression of PAR-4. PAR-4 expression levels were analyzed in 4 established pancreatic tumor cell lines, 10 normal pancreatic tissues, 44 frozen tumor tissues and 25 paraffin-embedded pancreatic adenocarcinoma samples by Real Time RT-PCR, Western blot analysis and immunohistochemistry. K-ras mutational status was analyzed by allele-specific oligonucleotide-hybridization. Expression levels of PAR-4 were correlated with the K-ras mutational status and clinical characteristics. Further, modulation of endogenous PAR-4 was tested by transiently expressing oncogenic ras in a wild-type K-ras pancreatic cancer cell line, BxPC-3. Three cell lines with K-ras mutations showed low levels of PAR-4 when compared to a normal pancreatic tissue. Of 44 frozen tumors, 16 showed appreciable upregulation of Par mRNA and 27 showed significant downregulation of PAR-4 mRNA when compared to normal pancreatic tissue and 1 had levels equivalent to normal pancreatic tissue. Of 25 paraffin-embedded tumors, 9 showed downregulation of PAR-4 protein and this downregulation of PAR-4 correlated significantly with K-ras mutational status (p < 0.00002). In addition, the presence of PAR-4 mRNA or protein expression in pancreatic tumors correlated with prolonged survival. Transient overexpression of oncogenic ras in wild-type K-ras BxPC-3 cells significantly downregulated the endogenous PAR-4 protein levels and conferred accelerated growth. Thus, downregulation or loss of PAR-4 expression by oncogenic ras may provide a selective survival advantage for pancreatic tumors, through inhibition of proapoptotic pathway mediated by PAR-4.

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The growth compromised HSV-2 mutant DeltaRR prevents kainic acid-induced apoptosis and loss of function in organotypic hippocampal cultures

We have previously shown that the HSV-2 anti-apoptotic protein ICP10PK is delivered by the replication incompetent virus mutant DeltaRR and prevents kainic acid (KA)-induced epileptiform seizures and neuronal cell loss in the mouse and rat models of temporal lobe epilepsy. The present studies used DeltaRR and the ICP10PK deleted virus mutant DeltaPK to examine the mechanism of neuroprotection. DeltaRR-infected neuronal cells expressed a chimeric protein in which ICP10PK is fused in frame to LacZ (p175) while retaining ICP10PK kinase activity. DeltaPK-infected neuronal cells expressed a mutant ICP10 protein that is deleted in the PK domain and is kinase negative (p95). p175 and p95 were expressed in CA3 (86+/-3%) and CA1 (69+/-7%) cells from DeltaRR or DeltaPK-infected organotypic hippocampal cultures (OHC) and 80-85% of the ICP10 positive cells co-stained with antibody to beta(III) Tubulin (neuronal marker). DeltaRR, but not DeltaPK, inhibited KA-induced cell death and caspase-3 activation in CA3 neurons, an inhibition seen whether DeltaRR was delivered 2 days before or 2 days after KA administration (95% neuroprotection). Neuroprotection was associated with ERK and Akt activation and was abrogated by simultaneous treatment with the MEK (U0126) and PI3-K (LY294002) inhibitors. DeltaRR-mediated neuroprotection was associated with increased expression of the anti-apoptotic protein Bag-1 and decreased expression of the pro-apoptotic protein Bad. The surviving neurons retained normal synaptic function potentially related to increased expression of the transcription factor CREB. The data indicate that DeltaRR is a promising platform for neuroprotection from excitotoxic injury.

Characterization of a novel cell penetrating peptide derived from Bag-1 protein

A highly cationic peptide (BagP), located within the normally expressed human protein Bag-1, was tested for its capacity to act as a cell penetrating peptide. BagP was found to translocate and transport high molecular weight cargos in several cell types, in varying degrees with a preference for adherent cells. The penetration phenomenon was not found to be subject to saturation for the highest amount of peptide tested (100 microM), whereas the time needed for maximum translocation to be achieved, was cell type-dependent. Finally, BagP internalization depends on its charge, cellular metabolism and cell-surface heparan sulfate proteoglycans.

Selective amino acid restriction targets mitochondria to induce apoptosis of androgen-independent prostate cancer cells

Relative specific amino acid dependency is one of the metabolic abnormalities of cancer cells, and restriction of specific amino acids induces apoptosis of prostate cancer cells. This study shows that restriction of tyrosine and phenylalanine (Tyr/Phe), glutamine (Gln), or methionine (Met), modulates Raf and Akt survival pathways and affects the function of mitochondria in DU145 and PC3, in vitro. These three restrictions inhibit energy production (ATP synthesis) and induce generation of reactive oxygen species (ROS). Restriction of Tyr/Phe or Met in DU145 and Met in PC3 reduces mitochondrial membrane potential (DeltaPsim) and induces caspase-dependent and -independent apoptosis. In DU145, Tyr/Phe or Met restriction reduces activity of Akt, mitochondrial distribution of phosphorylated Raf and apoptosis inducing factor (AIF), and increases mitochondrial distribution of Bak. Mitochondrial Bcl-XL is increased in Tyr/Phe-restricted but decreased in Met-restricted cells. Under Tyr/Phe or Met restriction, reduced mitochondrial Raf does not inactivate the pro-apoptotic function of Bak. Tyr/Phe restriction also inhibits Bcl-2 and Met restriction inhibits Bcl-XL in mitochondria. These comprehensive actions damage the integrity of the mitochondria and induce apoptosis of DU145. In PC3, apoptosis induced by Met restriction was not associated with alterations in intracellular distribution of Raf, Bcl-2 family proteins, or AIF. All of the amino acid restrictions inhibited Akt activity in this cell line. We conclude that specific amino acid restriction differentially interferes with homeostasis/balance between the Raf and Akt survival pathways and with the interaction of Raf and Bcl-2 family proteins in mitochondria to induce apoptosis of DU145 and PC3 cells.

BAG3 deficiency results in fulminant myopathy and early lethality

Bcl-2-associated athanogene 3 (BAG3) is a member of a conserved family of cyto-protective proteins that bind to and regulate Hsp70 family molecular chaperones. Here, we show that BAG3 is prominently expressed in striated muscle and colocalizes with Z-disks. Mice with homozygous disruption of the bag3 gene developed normally but deteriorated postnatally with stunted growth evident by 1 to 2 weeks of age and death by 4 weeks. BAG3-deficient animals developed a fulminant myopathy characterized by noninflammatory myofibrillar degeneration with apoptotic features. Knockdown of bag3 expression in cultured C2C12 myoblasts increased apoptosis on induction of differentiation, suggesting a need for bag3 for maintenance of myotube survival and confirming a cell autonomous role for bag3 in muscle. We conclude that although BAG3 is not required for muscle development, this co-chaperone appears to be critically important for maintenance of mature skeletal muscle.

Expression profile of Bag 1 in the postmortem brain

Bag 1 is a protein intimately involved in signaling pathways that regulate cell survival. Here we examined the expression profile of Bag 1 in the brain to consider issues associated with the sampling of anti-apoptotic proteins in a rat model of the human postmortem process. Following a 4h postmortem interval, we analyzed the hippocampus of rats maintained at 24 or 4 degrees C storage temperatures using immunocytochemical and Western blotting techniques. Remarkably, postmortem tissue (up to 4h) showed a significant and prominent up-regulation of Bag 1 in CA1 and CA3 subfields of the hippocampal formation. Over-expression of Bag 1, however, could only be traced down to a storage temperature of 24 degrees C. These data suggest that storage temperatures, but not postmortem intervals, significantly affect the expression profile and cellular stability of Bag 1 proteins.

Proteolysis of HIP during apoptosis occurs within a region similar to the BID loop

BID is an essential component of many apoptotic pathways. Cytosolic proteases cleave BID within an extended loop region, generating an active truncated fragment which synergizes with BAX and BAK to induce release of apoptogenic factors from mitochondria. To determine whether other proteins are cleaved in a similar manner as BID, we performed a database search for proteins which possess sequence similarity with the BID loop region. One of the proteins identified was the Hsc70-interacting protein (HIP). We analyzed the cleavage pattern of HIP using two known activators of BID: granzyme B and caspase-8. In in vitro cleavage assays using recombinant proteins, human and rat HIP were cleaved by granzyme B. Furthermore, the granzyme B-mediated cleavage site was mapped to the BID loop-like region of HIP by site-directed mutagenesis. This region was also the target for caspase-8-mediated cleavage in rat HIP. However, human HIP was not proteolyzed by caspase-8, which probably reflects sequence differences between human and rat HIP proteins at the P(1)' position of the caspase-8 recognition sequence. To determine whether HIP is cleaved during apoptosis, human Jurkat T cells were exposed to granzyme B and perforin. The results of these studies suggest that granzyme B-mediated loss of HIP expression occurs in vivo, and in a coordinate fashion with loss of BID, pro-caspase-8 and pro-caspase-3. These data implicate the Hsp70 co-chaperone HIP in the proteolytic cascade of some apoptotic pathways.

FAT10/diubiquitin-like protein-deficient mice exhibit minimal phenotypic differences

The FAT10 gene encodes a diubiquitin-like protein containing two tandem head-to-tail ubiquitin-like domains. There is a high degree of similarity between murine and human FAT10 sequences at both the mRNA and protein levels. In various cell lines, FAT10 expression was shown to be induced by gamma interferon or by tumor necrosis factor alpha. In addition, FAT10 expression was found to be up-regulated in some Epstein-Barr virus-infected B-cell lines, in activated dendritic cells, and in several epithelial tumors. However, forced expression of FAT10 in cultured cells was also found to produce apoptotic cell death. Overall, these findings suggest that FAT10 may modulate cellular growth or cellular viability. Here we describe the steps to generate, by genetic targeting, a FAT10 gene knockout mouse model. The FAT10 knockout homozygous mice are viable and fertile. No gross lesions or obvious histological differences were found in these mutated mice. Examination of lymphocyte populations from spleen, thymus, and bone marrow did not reveal any abnormalities. However, flow cytometry analysis demonstrated that the lymphocytes of FAT10 knockout mice were, on average, more prone to spontaneous apoptotic death. Physiologically, these mice demonstrated a high level of sensitivity toward endotoxin challenge. These findings indicate that FAT10 may function as a survival factor.

Hsp70 functions as a negative regulator of West Nile virus capsid protein through direct interaction

West Nile virus (WNV) is a member of the Flavivirus family and induces febrile illness, sporadic encephalitis, and paralysis. The capsid (Cp) of WNV is thought to play a role in inducing these symptoms through caspase-3- and caspase-9-dependent apoptosis. Using WNVCp as bait for a yeast two-hybrid assay, we identified that Hsp70 interacted with WNVCp. The interaction between Hsp70 and WNVCp was further substantiated using purified proteins. Deletion analysis of Hsp70 indicated that WNVCp could bind to the substrate binding domain of Hsp70. The presence of WNVCp in the Hsp70-dependent folding system inhibited the refolding of β-galactosidase (β-gal), which showed that WNVCp might function as a negative regulator of Hsp70. Finally, the cytotoxic effect of WNVCp in 293T cells was prevented by ectopic Hsp70, suggesting a negative regulatory role of Hsp70 on WNVCp. Our findings suggest a possible negative regulatory role of Hps70 in the pathway of WNV infection.

Identification and Functional Characterization of the BAG Protein Family in Arabidopsis thaliana

The genes that control mammalian programmed cell death are conserved across wide evolutionary distances. Although plant cells can undergo apoptosis-like cell death, plant homologs of mammalian regulators of apoptosis have, in general, not been found. This is in part due to the lack of primary sequence conservation between animal and putative plant regulators of apoptosis. Thus, alternative approaches beyond sequence similarities are required to find functional plant homologs of apoptosis regulators. Here, we present the results of using advanced bioinformatic tools to uncover the Arabidopsis family of BAG proteins. The mammalian BAG (Bcl-2-associated athanogene) proteins are a family of chaperone regulators that modulate a number of diverse processes ranging from proliferation to growth arrest and cell death. Such proteins are distinguished by a conserved BAG domain that directly interacts with Hsp70 and Hsc70 proteins to regulate their activity. Our searches of the Arabidopsis thaliana genome sequence revealed seven homologs of the BAG protein family. We further show that plant BAG family members are also multifunctional and remarkably similar to their animal counterparts, as they regulate apoptosis-like processes ranging from pathogen attack to abiotic stress and development.

Cellular plasticity cascades: genes-to-behavior pathways in animal models of bipolar disorder

BACKGROUND

Despite extensive research, the molecular/cellular underpinnings of bipolar disorder (BD) remain to be fully elucidated. Recent data has demonstrated that mood stabilizers exert major effects on signaling that regulate cellular plasticity; however, a direct extrapolation to mechanisms of disease demands proof that manipulation of candidate genes, proteins, or pathways result in relevant behavioral changes.

METHODS

We critique and evaluate the behavioral changes induced by manipulation of cellular plasticity cascades implicated in BD.

RESULTS

Not surprisingly, the behavioral data suggest that several important signaling molecules might play important roles in mediating facets of the complex symptomatology of BD. Notably, the protein kinase C and extracellular signal-regulated kinase cascades might play important roles in the antimanic effects of mood stabilizers, whereas glycogen synthase kinase (GSK)-3 might mediate facets of lithium's antimanic/antidepressant actions. Glucocorticoid receptor (GR) modulation also seems to be capable to inducing affective-like changes observed in mood disorders. And Bcl-2, amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptors, and inositol homeostasis represent important pharmacological targets for mood stabilizers, but additional behavioral research is needed to more fully delineate their behavioral effects.

CONCLUSIONS

Behavioral data support the notion that regulation of cellular plasticity is involved in affective-like behavioral changes observed in BD. These findings are leading to the development of novel therapeutics for this devastating illness.

Expression of BAG-1 protein correlates with aggressive behavior of prostate cancers

BACKGROUND

Differences in tumor behavior, ranging from indolent to aggressive, create a need for novel prognostic biomarkers. BAG-1 is a co-chaperone that regulates the activity of Hsp70, Bcl-2, Raf-1, growth factor, and steroid receptors (e.g., the Androgen Receptor).

METHODS

Using immunohistochemical method, we explored BAG-1 expression in prostate cancers and its association with clinicopathological parameters.

RESULTS

BAG-1 immunostaining was elevated in prostate cancer compared to normal prostatic epithelium. Higher nuclear BAG-1 in hormone-refractory (n = 34) compared to localized untreated tumors (n = 58) (P < 0.0001) suggested that upregulation of the nuclear isoform may contribute to disease progression. In 64 early-stage patients (T2N0M0) treated with external-beam irradiation, cytosolic BAG-1 correlated with higher pretreatment levels of serum Prostate specific antigen (P = 0.04) and shorter time to disease progression (P = 0.00004).

CONCLUSIONS

Increased cytosolic and nuclear BAG-1 expression may denote more aggressive variants of prostate cancer.

The zinc containing pro-apoptotic protein siva interacts with the peroxisomal membrane protein pmp22

Host answers to pathogen attacks define the course of pathogenic events and decide about the fate of the host organism. Infection with coxsackievirus B3 (CVB3) can induce severe myocarditis and pancreatitis. The interplay between host factors and virus components is crucial for the fate of the infected host. As we have shown before, expression of the pro-apoptotic host protein Siva is significantly increased after CVB3 infection, and infected cells are removed by programmed cell death. Analysis of Siva expressed in Escherichia coli revealed that this protein binds three zinc ions, suggesting a rather complex three-dimensional structure. By screening a human heart cDNA library we found a new interaction partner of Siva. The peroxisomal membrane protein PMP22 may be involved in the host response against CVB3. Previous investigations showed that Siva interacts with the cytoplasmic C-terminus of CD27, a member of the tumor necrosis factor receptor group, and transmits an apoptotic signal. With the help of directed two-hybrid assays we determined the N-terminal part of Siva as the binding region for CD27.

Developmental expression of Bis protein in the cerebral cortex and hippocampus of rats

Bis (Bcl-2 interacting death suppressor), identified as a Bcl-2-binding protein, has been suggested to have diverse functions in addition to binding to Bcl-2, thereby regulating cell death. To investigate the potential role of Bis in the developing brain, the spatiotemporal expression of Bis protein was studied in the rat forebrain during prenatal and early postnatal development using immunohistochemistry. Initial expression of Bis was detected in the medial telencephalic wall of the lateral ventricle, the area most likely corresponded to the cortical hem from the earliest age examined (E13). There was an abrupt increase of immunoreactive neurons in the cortex and hippocampus during the first postnatal week, which declined thereafter. Two populations of Bis-immunoreactive neurons can be clearly distinguished in the developing forebrain: a population of differentiating and postmitotic neurons coexpressing Bis and microtubule-associated protein-2 (MAP-2), and a population of neurons with the characteristic morphology of Cajal-Retzius cells located exclusively in the marginal zone/layer I of the cortex and in the hippocampal equivalents of the marginal zone. The latter neurons were colabeled with reelin, a marker for Cajal-Retzius cells. While Bis expression in the cerebral cortex and hippocampus exists only transiently by P14, considerable expression was found to be maintained in the rostral migratory stream and the subventricular zone of the lateral ventricle, where Bis-immunoreactive cells were glutamine synthetase-positive glial cells. Our results suggest that Bis may contribute to the developmental processes, including the differentiation and maturation of specific neuronal populations in relation to Bcl-2 in the developing rat forebrain.

Plant calmodulins and calmodulin-related proteins: multifaceted relays to decode calcium signals

The calmodulin (CaM) family is a major class of calcium sensor proteins which collectively play a crucial role in cellular signaling cascades through the regulation of numerous target proteins. Although CaM is one of the most conserved proteins in all eukaryotes, several features of CaM and its downstream effector proteins are unique to plants. The continuously growing repertoire of CaM-binding proteins includes several plant-specific proteins. Plants also possess a particular set of CaM isoforms and CaM-like proteins (CMLs) whose functions have just begun to be elucidated. This review summarizes recent insights that help to understand the role of this multigene family in plant development and adaptation to environmental stimuli.

Molecular chaperones in signal transduction

Many cellular signaling molecules exist in different conformations corresponding to active and inactive states. Transition between these states is regulated by reversible modifications, such as phosphorylation, or by binding of nucleotide triphosphates, their regulated hydrolysis to diphosphates, and their exchange against fresh triphosphates. Specificity and efficiency of cellular signaling is further maintained by regulated subcellular localization of signaling molecules as well as regulated protein-protein interaction. Hence, it is not surprising that molecular chaperones--proteins that are able to specifically interact with distinct conformations of other proteins--could per se interfere with cellular signaling. Hence, it is not surprising that chaperones have co-evolved as integral components of signaling networks where they can function in the maturation as well as in regulating the transition between active and inactive state of signaling molecules, such as receptors, transcriptional regulators and protein kinases. Furthermore, new classes of specific chaperones are emerging and their role in histone-mediated chromatin remodeling and RNA folding are under investigation.

The ubiquitin-like protein MNSFbeta regulates ERK-MAPK cascade

MNSFbeta is a ubiquitously expressed member of the ubiquitin-like family that has been implicated in various biological functions. Previous studies have demonstrated that MNSFbeta covalently binds to intracellular proapoptotic protein Bcl-G in mitogen-activated murine T cells. In this study, we further investigated the intracellular mechanism of action of MNSFbeta in macrophage cell line, Raw 264.7 cells. We present evidence that MNSFbeta.Bcl-G complex associates with ERKs in non-stimulated Raw 264.7. We found that MNSFbeta.Bcl-G directly bound to ERKs and inhibited ERK activation by MEK1. In Raw 264.7 cells treated with MNSFbeta small interfering RNA (siRNA) lipopolysaccharide (LPS)-induced ERK1/2 activation was enhanced and LPS-induced JNK and p38 activation was unaffected. SiRNA-mediated knockdown of MNSFbeta increased tumor necrosis factor alpha (TNFalpha) expression at mRNA and protein levels in LPS-stimulated Raw 264.7 cells. Finally, we found that transfection with MNSFbeta expression construct resulted in a significant inhibition of LPS-induced ERK activation and TNFalpha production. Co-transfection experiments with MNSFbeta and Bcl-G greatly enhanced this inhibition. Collectively, these findings indicate that MNSFbeta might be implicated in the macrophage response to LPS.

Bag-1 and Bcl-2 gene transfer in malignant glioma: modulation of cell cycle regulation and apoptosis

Bag-1 is a heat shock 70 kDa (Hsp70)-binding protein that can collaborate with Bcl-2 in suppressing apoptosis under some conditions. Here, we report that 11 of 12 human glioma cell lines express Bag-1 protein in vitro. Moreover, 15 of 19 human glioblastomas expressed Bag-1 as assessed by immunohistochemistry in primary tumor specimens. To examine the biological effects of Bag-1 in glioma cells, we expressed Bag-1 or Bcl-2 transgenes in 2 human malignant glioma cell lines, LN-18 and LN-229. Bag-1 significantly slowed glioma cell growth and reduced clonogenicity of both cell lines in vitro. Coexpressed Bcl-2 abrogated these effects of Bag-1. Intracranial LN-229 glioma xenografts implanted into nude mice revealed a substantial growth advantage afforded by Bcl-2. Bag-1 had no such effect, either in the absence or presence of Bcl-2. Upon serum starvation in vitro, Bcl-2 prevented cell death whereas Bag-1 did not. Both Bcl-2 and Bag-1 slowed proliferation of serum-starved cells when expressed alone. Importantly, coexpression of Bcl-2 and Bag-1 provided a distinct growth advantage under conditions of serum starvation that is probably the result of (i) the death-preventing activity of Bcl-2 and (ii) the property of Bag-1 to overcome a Bcl-2-mediated enhancement of exit from the cell cycle. In contrast to these Bcl-2/Bag-1 interactions observed under serum starvation conditions, Bag-1 did not further enhance the strong protection from staurosporine-, CD95 (Fas/Apo1) ligand-, Apo2 ligand (TRAIL)- or chemotherapeutic drug-induced apoptosis afforded by Bcl-2. Taken together, these results indicate a role for Bag-1/Bcl-2 interactions in providing a survival advantage to cancer cells in a deprived microenvironment that may be characteristic of ischemic/hypoxic tumors such as human glioblastoma multiforme, and suggest that Bcl-2/Bag-1 interactions also modulate cell proliferation.