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

Combined analysis of mRNA expression of ERCC1, BAG-1, BRCA1, RRM1 and TUBB3 to predict prognosis in patients with non-small cell lung cancer who received adjuvant chemotherapy

BACKGROUND

The aim of this study was to investigate prognostic value of excision repair cross-complementing 1 (ERCC1), BCL2-associated athanogene (BAG-1), the breast and ovarian cancer susceptibility gene 1 (BRCA1), ribonucleotide reductase subunit M1 (RRM1) and class III β-tubulin (TUBB3) in patients with non-small cell lung cancer (NSCLC) who received platinum- based adjuvant chemotherapy.

METHODS

Messenger RNA expressions of these genes were examined in 85 tumor tissues and 34 adjacent tissue samples using semi-quantitative RT-PCR. The expressions of these five genes were analyzed in relation to chemotherapy and progression-free survival (PFS) and overall survival (OS). Seventy-four patients were enrolled into chemotherapy.

RESULTS

Patients with ERCC1 or BAG-1 negative expression had a significantly longer PFS (P = 0.001 and P = 0.001) and OS (P = 0.001 and P = 0.001) than those with positive expression. Patients with negative ERCC1 and BAG-1 expression benefited more from platinum regimen (P = 0.001 and P = 0.002). Patients with BRCA1 negative expression might have a longer OS (P = 0.052), but not PFS (P = 0.088) than those with BRCA1 positive expression. A significant relationship was observed between the mRNA expression of ERCC1 and BAG-1 (P = 0.042). In multivariate analysis, ERCC1 and BAG-1 were significantly favorable factors for PFS (P = 0.018 and P = 0.017) and OS (P = 0.027 and P = 0.022).

CONCLUSIONS

ERCC1 and BAG-1 are determinants of survival after surgical treatment of NSCLC, and its mRNA expression in tumor tissues could be used to predict the prognosis of NSCLC treated by platinum.

BAG-1 diversely affects steroid receptor activity

Part of the cellular and physiological functions of BAG-1 (Bcl-2-associated athanogene 1) has been ascribed to the ability of this hsp70 (heat-shock protein 70) co-chaperone to regulate steroid receptor activity. BAG-1 has been reported to inhibit the GR (glucocorticoid receptor) and stimulate the androgen receptor, but to leave the activity of the MR (mineralocorticoid receptor) unchanged. Given the high homology between the MR and GR, this disparity in the actions of BAG-1 is surprising. In the present study, we analysed the effect of BAG-1 on the activity of the closely related PR (progesterone receptor). Similarly to the GR, the transcriptional activity of the PR is inhibited by the long and middle isoforms of BAG-1, BAG-1L and BAG-1M, but not by the short isoform, BAG-1S. We found this inhibition to require the hsp70-binding domain of BAG-1. To shed light on the mechanisms that could explain BAG-1's differential actions on steroid receptors, we tested the binding of BAG-1M to the PR. Mutational analyses of the PR and BAG-1M revealed that the mode of interaction and BAG-1M-mediated inhibition of the PR differs from the reported scenario for the GR. Surprisingly, we also found binding of BAG-1M to the MR. In addition, BAG-1M was able to inhibit the transcriptional activity of the MR. These data entail a reappraisal of the physiological actions of BAG-1M on steroid receptor activity.

Overexpression of cGMP-dependent protein kinase I (PKG-I) attenuates ischemia-reperfusion-induced kidney injury

cGMP-dependent protein kinase (PKG) is a multifunctional protein. Whether PKG plays a role in ischemia-reperfusion-induced kidney injury (IRI) is unknown. In this study, using an in vivo mouse model of renal IRI, we determined the effect of renal IRI on kidney PKG-I levels and also evaluated whether overexpression of PKG-I attenuates renal IRI. Our studies demonstrated that PKG-I levels (mRNA and protein) were significantly decreased in the kidney from mice undergoing renal IRI. Moreover, PKG-I transgenic mice had less renal IRI, showing improved renal function and less tubular damage compared with their wild-type littermates. Transgenic mice in the renal IRI group had decreased tubular cell apoptosis accompanied by decreased caspase 3 levels/activity and increased Bcl-2 and Bag-1 levels. In addition, transgenic mice undergoing renal IRI demonstrated reduced macrophage infiltration into the kidney and reduced production of inflammatory cytokines. In vitro studies showed that peritoneal macrophages isolated from transgenic mice had decreased migration compared with control macrophages. Taken together, these results suggest that PKG-I protects against renal IRI, at least in part through inhibiting inflammatory cell infiltration into the kidney, reducing kidney inflammation, and inhibiting tubular cell apoptosis.

BAG2 is a target of the c-Myc gene and is involved in cellular senescence via the p21(CIP1) pathway

Suppression of c-Myc is likely to induce cellular senescence in many tumors with unclear mechanisms. A proteomics survey indicated that high levels of BCL2-associated athanogene 2 (BAG2) were found in response to c-Myc repression in TRE293 cells. This observation led to the investigation into the role of BAG2 in c-Myc-induced senescence. The association of the c-Myc/SP1 complex with the BAG2 promoter verified the role of c-Myc/SP1 in regulating BAG2 transcription. Furthermore, high levels of BAG2 were found to induce p21(CIP1)-dependent senescence and subsequent carcinogenetic arrest, suggesting its possible role as an indirect activator of the p21(CIP1) pathway.

Effects of SMYD3 over-expression on cell cycle acceleration and cell proliferation in MDA-MB-231 human breast cancer cells

SET and MYND domain-containing protein 3 (SMYD3) is a histone methyltransferase that plays an important role in transcriptional regulation in human carcinogenesis. It can specifically methylate histone H3 at lysine 4 and activate the transcription of a set of downstream genes, including several oncogenes (e.g., N-myc, CrkL, Wnt10b, RIZ and hTERT) and genes involved in the control of cell cycle (e.g., CyclinG1 and CDK2) and signal transduction (e.g., STAT1, MAP3K11 and PIK3CB). To determine the effects of SMYD3 over-expression on cell proliferation, we transfected SMYD3 into MDA-MB-231 cells and found that these cells showed several transformed phenotypes as demonstrated by colony growth in soft agar. Besides, we show here that down-regulation of SMYD3 could induce G1-phase cell cycle arrest, indicating the potent induction of apoptosis by SMYD3 knockdown. These results suggest the regulatory mechanisms of SMYD3 on the acceleration of cell cycle and facilitate the development of strategies that may inhibit the progression of cell cycle in breast cancer cells.

BAG1: the guardian of anti-apoptotic proteins in acute myeloid leukemia

BCL2 associated Athano-Gene 1 (BAG1) is a multifunctional protein that has been described to be involved in different cell processes linked to cell survival. It has been reported as deregulated in diverse cancer types. Here, BAG1 protein was found highly expressed in children with acute myeloid leukemia at diagnosis, and in a cohort of leukemic cell lines. A silencing approach was used for determining BAG1's role in AML, finding that its down-regulation decreased expression of BCL2, BCL-XL, MCL1, and phospho-ERK1/2, all proteins able to sustain leukemia, without affecting the pro-apoptotic protein BAX. BAG1 down-regulation was also found to increase expression of BAG3, whose similar activity was able to compensate the loss of function of BAG1. BAG1/BAG3 co-silencing caused an enhanced cell predisposition to death in cell lines and also in primary AML cultures, affecting the same proteins. Cell death was CASPASE-3 dependent, was accompanied by PARP cleavage and documented by an increased release of pro-apoptotic molecules Smac/DIABLO and Cytochrome c. BAG1 was found to directly maintain BCL2 and to protect MCL1 from proteasomal degradation by controlling USP9X expression, which appeared to be its novel target. Finally, BAG1 was found able to affect leukemia cell fate by influencing the expression of anti-apoptotic proteins crucial for AML maintenance.

BAG-1L promotes keratinocyte differentiation in organotypic culture models and changes in relative BAG-1 isoform abundance may lead to defective stratification

In keratinocytes the human Bag-1 gene produces three different protein isoforms from a single messenger RNA, BAG-1L, BAG-1M and BAG-1S. In this study we questioned whether BAG-1L or the shorter isoforms would promote keratinocyte differentiation in organotypic cultures of HaCaT. HaCaT parental and vector cells showed stratification, but terminal differentiation was not complete. Cultures overexpressing BAG-1L isoform-specifically were of increased thickness, demonstrated pronounced expression of basal cytokeratin 5 and β1-integrin, suprabasal involucrin, cytokeratin 1 and plasma membrane-localised filaggrin, and a marked keratinized layer of cells at the surface. We were unable to overexpress BAG-1S and BAG-1M isoform-specifically. Overexpression of BAG-1M gave rise to organotypic cultures intermediate in differentiation to controls and those overexpressing BAG-1L. Cells overexpressing BAG-1S also exhibited elevated endogenous BAG-1. These produced slow growing cultures with high levels of basal cytokeratin 5, but little involucrin or cytokeratin 1. Suprabasal β1-integrin and Ki67 positive cells indicated defective stratification. The results suggest that BAG-1L potentiates epidermal differentiation, but disruption in the relative balance of isoforms towards overexpression of BAG-1S can lead to defective tissue patterning. Hence, a delicate balance of BAG-1 isoforms may be required to regulate normal epidermal stratification and differentiation, with important implications for aberrant differentiation in cancer.

HSG1, a grape Bcl-2-associated athanogene, promotes floral transition by activating CONSTANS expression in transgenic Arabidopsis plant

HSG1 (Heat shock-induced gene 1) is one of the high-temperature-induced proteins in grapevine. Sequence analysis has demonstrated that HSG1 is a grape Bcl-2-associated athanogene (BAG) that contains IQ and BAG domains in its sequence. HSG1 expression was not detected in leaves without heat treatment, while tendrils, stems, flowers, and berries expressed HSG1 even without heat treatment. By heat treatment at 45°C for 60 min, HSG1 expression was upregulated in both leaves and berries. HSG1-overexpressing Arabidopsis plant remained viable even after exposure to extremely high temperatures. Although no morphological changes were observed, the HSG1-overexpressing Arabidopsis plant exhibited faster floral transition than the control plant. Analysis of the transcription profile of HSG1-overexpressing seedling by cDNA microarray and quantitative RT-PCR demonstrated that the gene expression of the flowering promoter, CONSTANS (CO), in the photoperiod pathway was up-regulated in the seedling. Importantly, the overexpression of HSG1 increased CO expression by ~400% compared with the control seedling. Meanwhile, heat treatment upregulated grape CO expression in grape leaves. Our study provides the possibility that plant BAG protein may be related to the regulation of floral transition by activating CO expression in the photoperiod pathway.

The apoptotic regulator Nrz controls cytoskeletal dynamics via the regulation of Ca2+ trafficking in the zebrafish blastula

Bcl-2 family members are key regulators of apoptosis. Their involvement in other cellular processes has been so far overlooked. We have studied the role of the Bcl-2 homolog Nrz in the developing zebrafish. Nrz was found to be localized to the yolk syncytial layer, a region containing numerous mitochondria and ER membranes. Nrz knockdown resulted in developmental arrest before gastrulation, due to free Ca(2+) increase in the yolk cell, activating myosin light chain kinase, which led to premature contraction of actin-myosin cables in the margin and separation of the blastomeres from the yolk cell. In the yolk syncytial layer, Nrz appears to prevent the release of Ca(2+) from the endoplasmic reticulum by directly interacting with the IP3R1 Ca(2+) channel. Thus, the Bcl-2 family may participate in early development, not only by controlling apoptosis but also by acting on cytoskeletal dynamics and cell movements via Ca(2+) fluxes inside the embryo.

Two different docetaxel resistant MCF-7 sublines exhibited different gene expression pattern

The objective of the present study was to investigate gene expression pattern of two docetaxel resistant MCF-7 breast carcinoma sublines step wisely selected in 30 and 120 nM docetaxel. Cell proliferation assay was performed in order to demonstrate development of docetaxel resistance. cDNA microarray analysis was performed using Affymetrix(®) Human Genome U133 Plus 2.0 Arrays in duplicate experiments. Quantitative and semi-quantitative gene expression analysis was also performed to confirm gene expression analysis for selected genes. XTT results demonstrated that 30 (MCF-7/30nM DOC) and 120 nM (MCF-7/120nM DOC) docetaxel selected cells were 13- and 47-fold resistant, respectively. cDNA microarray analysis demonstrated that expression profiles of MCF-7 and MCF-7/30nM DOC were more similar to each other where expression profile of MCF-7/120nM DOC was different as examined by line graphs and scatter plots. 2,837 and 4,036 genes were significantly altered in 30 and 120 nM docetaxel resistant sublines, respectively. Among these, 849 genes were altered in common in two docetaxel resistant sublines. Antiapoptotic gene expression (e.g., Bcl-2 and APRIL) were noticeably altered in MCF-7/30nM DOC. However, docetaxel resistance in MCF-7/120nM DOC were more complicated with the involvement of ECM related gene expression, cytokine and growth factor signaling, ROS metabolism and EMT related gene expression together with higher level of MDR1 expression. Expression profiles in 30 and 120 nM docetaxel resistant sublines changed gradually with increasing resistance index. Drug resistance development seems to be step wise event in MCF-7 cells.

A β-glucuronidase (GUS) based cell death assay

We have developed a novel transient plant expression system that simultaneously expresses the reporter gene, β-glucuronidase (GUS), with putative positive or negative regulators of cell death. In this system, N. benthamiana leaves are co-infiltrated with a 35S driven expression cassette containing the gene to be analyzed, and the GUS vector pCAMBIA 2301 using Agrobacterium strain LBA4404 as a vehicle. Because live cells are required for GUS expression to occur, loss of GUS activity is expected when this marker gene is co-expressed with positive regulators of cell death. Equally, increased GUS activity is observed when anti-apoptotic genes are used compared to the vector control. As shown below, we have successfully used this system in our lab to analyze both pro- and anti-death players. These include the plant anti-apoptotic Bcl-2 Associated athanoGene (BAG) family, as well as, known mammalian inducers of cell death, such as BAX. Additionally, we have used this system to analyze the death function of specific truncations within proteins, which could provide clues on the possible post-translational modification/activation of these proteins. Here, we present a rapid and sensitive plant based method, as an initial step in investigating the death function of specific genes.

In animal models, psychosocial stress-induced (neuro)inflammation, apoptosis and reduced neurogenesis are associated to the onset of depression

Recently, the inflammatory and neurodegenerative (I&ND) hypothesis of depression was formulated (Maes et al., 2009), i.e. the neurodegeneration and reduced neurogenesis that characterize depression are caused by inflammation, cell-mediated immune activation and their long-term sequels. The aim of this paper is to review the body of evidence that external stressors may induce (neuro)inflammation, neurodegeneration and reduced neurogenesis; and that antidepressive treatments may impact on these pathways. The chronic mild stress (CMS) and learned helplessness (LH) models show that depression-like behaviors are accompanied by peripheral and central inflammation, neuronal cell damage, decreased neurogenesis and apoptosis in the hippocampus. External stress-induced depression-like behaviors are associated with a) increased interleukin-(IL)1β, tumor necrosis factor-α, IL-6, nuclear factor κB, cyclooxygenase-2, expression of Toll-like receptors and lipid peroxidation; b) antineurogenic effects and reduced brain-derived neurotrophic factor (BDNF) levels; and c) apoptosis with reduced levels of Bcl-2 and BAG1 (Bcl-2 associated athanogene 1), and increased levels of caspase-3. Stress-induced inflammation, e.g. increased IL-1β, but not reduced neurogenesis, is sufficient to cause depression. Antidepressants a) reduce peripheral and central inflammatory pathways by decreasing IL-1β, TNFα and IL-6 levels; b) stimulate neuronal differentiation, synaptic plasticity, axonal growth and regeneration through stimulatory effects on the expression of different neurotrophic factors, e.g. trkB, the receptor for brain-derived neurotrophic factor; and c) attenuate apoptotic pathways by activating Bcl-2 and Bcl-xl proteins, and suppressing caspase-3. It is concluded that external stressors may provoke depression-like behaviors through activation of inflammatory, oxidative, apoptotic and antineurogenic mechanisms. The clinical efficacity of antidepressants may be ascribed to their ability to reverse these different pathways.

Co-overexpression of Bag-1 and heat shock protein 70 in human epidermal squamous cell carcinoma: Bag-1-mediated resistance to 5-fluorouracil-induced apoptosis

BACKGROUND

The aim was to determine whether Bcl-2-associated athanogene-1 (Bag-1) and/or its binding protein heat shock protein-70 (Hsp70) exhibit deregulated expression in epidermal squamous cell carcinoma (SCC) and whether Bag-1 confers apoptosis resistance.

METHOD

Immunohistochemistry for Bag-1 and Hsp70 was performed on 60 epidermal SCC and 10 normal skin samples. The epidermal SCC cell line SCC-13 was treated with 5-fluorouracil (5-FU) after Bag-1 knockdown to determine whether high Bag-1 levels contribute to growth and/or apoptosis resistance.

RESULTS

Normal epithelium expressed primarily nuclear Bag-1. Most tumours showed reduced nuclear Bag-1 staining, but a subset exhibited strong Bag-1 staining, with cytoplasmic Bag-1 staining intensity correlating with cytoplasmic Hsp70 staining intensity (r(s)=0.462; P<0.001) and less differentiation (P<0.001). Bag-1 knockdown resulted in markedly reduced SCC-13 cell yield, increased spontaneous apoptosis and enhanced sensitivity to 5-FU-induced apoptosis. Apoptosis induced by 5-FU in the Bag-1-knockdown cells was significantly greater than the additive apoptotic effect of 5-FU or Bag-1 knockdown alone.

CONCLUSIONS

Overexpression of Bag-1 and Hsp70 in poorly differentiated SCC may confer both enhanced tumour cell growth and apoptosis resistance. Bag-1 may contribute to the resistance of more advanced epidermal SCC to chemotherapy.

Overexpression of peroxisomal testis-specific 1 protein induces germ cell apoptosis and leads to infertility in male mice

Peroxisomal testis-specific 1 gene (Pxt1) is the only male germ cell-specific gene that encodes a peroxisomal protein known to date. To elucidate the role of Pxt1 in spermatogenesis, we generated transgenic mice expressing a c-MYC-PXT1 fusion protein under the control of the PGK2 promoter. Overexpression of Pxt1 resulted in induction of male germ cells' apoptosis mainly in primary spermatocytes, finally leading to male infertility. This prompted us to analyze the proapoptotic character of mouse PXT1, which harbors a BH3-like domain in the N-terminal part. In different cell lines, the overexpression of PXT1 also resulted in a dramatic increase of apoptosis, whereas the deletion of the BH3-like domain significantly reduced cell death events, thereby confirming that the domain is functional and essential for the proapoptotic activity of PXT1. Moreover, we demonstrated that PXT1 interacts with apoptosis regulator BAT3, which, if overexpressed, can protect cells from the PXT1-induced apoptosis. The PXT1-BAT3 association leads to PXT1 relocation from the cytoplasm to the nucleus. In summary, we demonstrated that PXT1 induces apoptosis via the BH3-like domain and that this process is inhibited by BAT3.

BAG3 directly interacts with mutated alphaB-crystallin to suppress its aggregation and toxicity

A homozygous disruption or genetic mutation of the bag3 gene causes progressive myofibrillar myopathy in mouse and human skeletal and cardiac muscle disorder while mutations in the small heat shock protein αB-crystallin gene (CRYAB) are reported to be responsible for myofibrillar myopathy. Here, we demonstrate that BAG3 directly binds to wild-type αB-crystallin and the αB-crystallin mutant R120G, via the intermediate domain of BAG3. Peptides that inhibit this interaction in an in vitro binding assay indicate that two conserved Ile-Pro-Val regions of BAG3 are involved in the interaction with αB-crystallin, which is similar to results showing BAG3 binding to HspB8 and HspB6. BAG3 overexpression increased αB-crystallin R120G solubility and inhibited its intracellular aggregation in HEK293 cells. BAG3 suppressed cell death induced by αB-crystallin R120G overexpression in differentiating C2C12 mouse myoblast cells. Our findings indicate a novel function for BAG3 in inhibiting protein aggregation caused by the genetic mutation of CRYAB responsible for human myofibrillar myopathy.

Molecular chaperones as rational drug targets for Parkinson's disease therapeutics

Parkinson's disease is a neurodegenerative movement disorder that is caused, in part, by the loss of dopaminergic neurons within the substantia nigra pars compacta of the basal ganglia. The presence of intracellular protein aggregates, known as Lewy bodies and Lewy neurites, within the surviving nigral neurons is the defining neuropathological feature of the disease. Accordingly, the identification of specific genes mutated in families with Parkinson's disease and of genetic susceptibility variants for idiopathic Parkinson's disease has implicated abnormalities in proteostasis, or the handling and elimination of misfolded proteins, in the pathogenesis of this neurodegenerative disorder. Protein folding and the refolding of misfolded proteins are regulated by a network of interactive molecules, known as the chaperone system, which is composed of molecular chaperones and co-chaperones. The chaperone system is intimately associated with the ubiquitin-proteasome system and the autophagy-lysosomal pathway which are responsible for elimination of misfolded proteins and protein quality control. In addition to their role in proteostasis, some chaperone molecules are involved in the regulation of cell death pathways. Here we review the role of the molecular chaperones Hsp70 and Hsp90, and the cochaperones Hsp40, BAG family members such as BAG5, CHIP and Hip in modulating neuronal death with a focus on dopaminergic neurodegeneration in Parkinson's disease. We also review current progress in preclinical studies aimed at targetting the chaperone system to prevent neurodegeneration. Finally, we discuss potential future chaperone-based therapeutics for the symptomatic treatment and possible disease modification of Parkinson's disease.

Recent advances in psychoneuroimmunology: Inflammation in psychiatric disorders

Psychiatric disorders are common and complex and their precise biological underpinnings remain elusive. Multiple epidemiological, molecular, genetic and gene expression studies suggest that immune system dysfunction may contribute to the risk for developing psychiatric disorders including schizophrenia, bipolar disorder, and major depressive disorder. However, the precise mechanisms by which inflammation-related events confer such risk are unclear. In this review, we examine the peripheral and central evidence for inflammation in psychiatric disorders and the potential molecular mechanisms implicated including inhibition of neurogenesis, apoptosis, the HPA-axis, the role of brain-derived neurotrophic factor and the interplay between the glutamatergic, dopaminergic and serotonergic neurotransmitter systems.

IGFBP3 and BAG1 enhance radiation-induced apoptosis in squamous esophageal cancer cells

Identification of reliable markers of radiosensitivity and the key molecules that enhance the susceptibility of esophageal cancer cells to anticancer treatments would be highly desirable. To identify molecules that confer radiosensitivity to esophageal squamous carcinoma cells, we assessed the radiosensitivities of the TE-5, TE-9 and TE-12 cloneA1 cell lines. TE-12 cloneA1 cells showed significantly greater susceptibility to radiotherapy at 5 and 10Gy than either TE-5 or TE-9 cells. Consistent with that finding, 24h after irradiation (5Gy), TE-12 cloneA1 cells showed higher levels of caspase 3/7 activity than TE-5 or TE-9 cells. When we used DNA microarrays to compare the gene expression profiles of TE-5 and TE-12 cloneA1 cells, we found that the mRNA and protein expression of insulin-like growth factor binding protein 3 (IGFBP3) and Bcl-2-associated athanogene 1 (BAG1) was five or more times higher in TE-12 cloneA1 cells than TE-5 cells. Conversely, knocking down expression of IGFBP3 and BAG1 mRNA in TE-12 cloneA1 cells using small interfering RNA (siRNA) significantly reduced radiosensitivity. These data suggest that IGFBP3 and BAG1 may be key markers of radiosensitivity that enhance the susceptibility of squamous cell esophageal cancer to radiotherapy. IGFBP3 and BAG1 may thus be useful targets for improved and more individualized treatments for patients with esophageal squamous cell carcinoma.

Anti-apoptosis and cell survival: a review

Type I programmed cell death (PCD) or apoptosis is critical for cellular self-destruction for a variety of processes such as development or the prevention of oncogenic transformation. Alternative forms, including type II (autophagy) and type III (necrotic) represent the other major types of PCD that also serve to trigger cell death. PCD must be tightly controlled since disregulated cell death is involved in the development of a large number of different pathologies. To counter the multitude of processes that are capable of triggering death, cells have devised a large number of cellular processes that serve to prevent inappropriate or premature PCD. These cell survival strategies involve a myriad of coordinated and systematic physiological and genetic changes that serve to ward off death. Here we will discuss the different strategies that are used to prevent cell death and focus on illustrating that although anti-apoptosis and cellular survival serve to counteract PCD, they are nevertheless mechanistically distinct from the processes that regulate cell death.

Autoregulation of co-chaperone BAG3 gene transcription

The Bcl-2-associated athanogene, BAG, protein family through their BAG domain associates with the heat shock protein 70 (HSP-70) and modulates its chaperone activity. One member of this family, BAG3, appears to play an important role in protein homeostasis, as its expression promotes cell survival. Expression of BAG3 is enhanced by a variety of stress-inducing agents. Here we describe a role for BAG3 to modulate transcription of its own promoter through a positive feedback loop involving its 5'-UTR sequence. Activation of the BAG3 promoter is mediated by the BAG domain and is independent of BAG3 association with the UTR sequence. Autoactivation of the BAG3 gene is observed in several cultures of human glial cells including gliomas, but not in several other non-glial cell lines such as He La and others. Results from cell fractionation and immunocytochemistry showed BAG3 in the cytoplasm as well as the nuclei of glial cells. These observations suggest that BAG3 gene expression is controlled by its own product and that this may be critical for the biological activity of BAG3 in some cell types.

The C-terminal BAG domain of BAG5 induces conformational changes of the Hsp70 nucleotide-binding domain for ADP-ATP exchange

ADP-ATP exchange by the molecular chaperone Hsp70 is enhanced by several cochaperones. BAG5 consists of five BAG domains and associates with the nucleotide-binding domain (NBD) of Hsp70. The overexpression of BAG5 in the cytosol reportedly disturbs Hsp70-mediated protein refolding and induces Parkinson's disease. In the present study, we found that the fifth BAG domain (BD5) of BAG5 is responsible for the interaction between Hsp70 and BAG5. We also determined the crystal structures of the BD5*NBD complex. BD5 binding caused two different types of NBD conformational changes, which both disrupted the nucleotide-binding groove. In fact, BD5 reduced the affinity of the NBD for ADP. Moreover, BD5, as well as the full-length BAG5, accelerated Hsp70-mediated refolding in an in vitro assay. Therefore, BAG5 can function as the nucleotide exchange factor of Hsp70 for the enhancement of protein refolding.

Effect of chronic lead exposure on pro-apoptotic Bax and anti-apoptotic Bcl-2 protein expression in rat hippocampus in vivo

Despite reduction in environmental lead, chronic lead exposure still possess a public health hazard, particularly in children, with devastating effects on developing CNS. To investigate the mechanism of this neurotoxicity, young and adult rats were used to study whether exposure to 500 ppm concentrations of lead could induce apoptosis in hippocampus. 2-4 and 12-14-week-old rats received lead acetate in concentration of 500 ppm for 40 days. Control animals received deionized distilled water. In lead-treated groups, the blood lead levels were increased by 3-4 folds. Light and electron microscopical study of hippocampus revealed increased apoptotic cells. Western blot analysis of Bax and Bcl-2 (pro- and anti-apoptotic gene products, respectively) indicated higher expression of Bax protein and no significant change in bcl-2 expression and accordingly increased the Bax/Bcl-2 ratio compared to control group, confirming the histological study. In conclusion, these data suggest that neurotoxicity of chronic lead exposure in hippocampus in vivo may partly be due to facilitation of apoptosis.

Characterization of thermotolerance-related genes in grapevine (Vitis vinifera)

We report the cloning and characterization of heat shock-induced genes in grapevine (Vitis vinifera L.). Using the cDNA subtraction method, four heat shock-induced genes were identified in heat shock-treated Pinot noir grapevine. The four genes were immediately induced and upregulated in leaves and berry skins by heat treatment at 45 degrees C. The recovery treatment at 26 degrees C reduced the upregulated transcription of the heat shock-induced genes to near basal levels. The predicted amino acid sequences of three genes, HSG4, HSG14, and HSG19, showed high homologies to those of known small heat shock proteins of other plants. The predicted amino acid sequence of the fourth gene, HSG1, has two conserved motifs, the IQ motif and the Bcl-2-associated athanogene (BAG) domain, suggesting that HSG1 may be a member of the BAG family in grapevine. Although no morphological changes were observed, the overexpression Arabidopsis lines of HSG1, HSG4, HSG14, or HSG19 exhibited faster growth including floral transition than the control line, suggesting that the constitutive expression of HSG1, HSG4, HSG14, or HSG19 protein resulted in increased growth rates without any detectable harm. The thermotolerance test demonstrated that all of the overexpression lines remained viable and noticeably healthy compared with the control line even after exposure to severe heat shock, suggesting that HSG1, HSG4, HSG14, or HSG19 protein might be related to the acquisition of thermotolerance in grapevine.

Expressions of the anti-apoptotic genes Bag-1 and Bcl-2 in colon cancer and their relationship

BACKGROUND

The aims of this study were to investigate the expressions and significance of the antiapoptotic genes Bag-1 and Bcl-2 in colon cancer and to evaluate their relationship.

METHODS

The expressions of Bag-1 and Bcl-2 were examined in 128 colon cancer and 20 normal colon tissue samples by reverse-transcription polymerase chain reaction and immunohistochemical technique (streptavidin-biotin-peroxidase complex method).

RESULTS

Bag-1 and Bcl-2 were expressed in colorectal cancer tissues but not in normal colorectal tissues by reverse-transcription polymerase chain reaction. The expression of Bag-1 in colon cancer was closely correlated with pathologic grade, distance metastasis, Duke stage, and prognosis, but it had no effect on the pathologic type, tumor diameter, depth of invasion, and lymphoid node metastasis of the cancer. By contrast, Bcl-2 had no significant correlation with all the clinical and pathologic factors. There was a positive correlation between Bag-1 and Bcl-2 in the development of colon cancer.

CONCLUSIONS

High expressions of Bag-1 and Bcl-2 proteins in colon cancer were found. They might be regarded as biomarkers for the diagnosis of the early stage of colon cancer. In addition, they have significant relevance for the prognosis of colon cancer.

AtBAG7, an Arabidopsis Bcl-2-associated athanogene, resides in the endoplasmic reticulum and is involved in the unfolded protein response

The Bcl-2-associated athanogene (BAG) family is an evolutionarily conserved, multifunctional group of cochaperones that perform diverse cellular functions ranging from proliferation to growth arrest and cell death in yeast, in mammals, and, as recently observed, in plants. The Arabidopsis genome contains seven homologs of the BAG family, including four with domain organization similar to animal BAGs. In the present study we show that an Arabidopsis BAG, AtBAG7, is a uniquely localized endoplasmic reticulum (ER) BAG that is necessary for the proper maintenance of the unfolded protein response (UPR). AtBAG7 was shown to interact directly in vivo with the molecular chaperone, AtBiP2, by bimolecular fluorescence complementation assays, and the interaction was confirmed by yeast two-hybrid assay. Treatment with an inducer of UPR, tunicamycin, resulted in accelerated cell death of AtBAG7-null mutants. Furthermore, AtBAG7 knockouts were sensitive to known ER stress stimuli, heat and cold. In these knockouts heat sensitivity was reverted successfully to the wild-type phenotype with the addition of the chemical chaperone, tauroursodexycholic acid (TUDCA). Real-time PCR of ER stress proteins indicated that the expression of the heat-shock protein, AtBiP3, is selectively up-regulated in AtBAG7-null mutants upon heat and cold stress. Our results reveal an unexpected diversity of the plant's BAG gene family and suggest that AtBAG7 is an essential component of the UPR during heat and cold tolerance, thus confirming the cytoprotective role of plant BAGs.

BAG1 restores formation of functional DJ-1 L166P dimers and DJ-1 chaperone activity

The L166P mutation in DJ-1 is associated with Parkinson’s disease. DJ-1–interacting protein BAG1 chaperones mutant DJ-1 and reverses its mutant phenotype.

Mutations in the gene coding for DJ-1 protein lead to early-onset recessive forms of Parkinson’s disease. It is believed that loss of DJ-1 function is causative for disease, although the function of DJ-1 still remains a matter of controversy. We show that DJ-1 is localized in the cytosol and is associated with membranes and organelles in the form of homodimers. The disease-related mutation L166P shifts its subcellular distribution to the nucleus and decreases its ability to dimerize, impairing cell survival. Using an intracellular foldase biosensor, we found that wild-type DJ-1 possesses chaperone activity, which is abolished by the L166P mutation. We observed that this aberrant phenotype can be reversed by the expression of the cochaperone BAG1 (Bcl-2–associated athanogene 1), restoring DJ-1 subcellular distribution, dimer formation, and chaperone activity and ameliorating cell survival.

Cellular mechanisms underlying affective resiliency: the role of glucocorticoid receptor- and mitochondrially-mediated plasticity

Bipolar disorder (BPD) is a devastating psychiatric illness marked by recurrent episodes of mania and depression. While the underlying pathophysiology of BPD remains elusive, an abnormal hypothalamic-pituitary-adrenal (HPA) axis and dysfunctional glucocorticoid receptor (GR) signaling are considered hallmarks. This review will examine how targeting resiliency signaling cascades at the cellular level may serve as a mechanism to treat BPD. Here, cellular resiliency is defined as the ability of a cell to adapt to an insult or stressor. Such resiliency at the cellular level could confer resiliency at the systems level and, ultimately, help individuals to cope with stressors or recover from depressive or manic states. This review will focus on four molecular targets of mood stabilizers that are known to play integral roles in these cellular resiliency signaling pathways: (1) B-cell CLL/lymphoma 2 (Bcl-2), (2) Bcl-2-associated athanogene (BAG-1), (3) glucocorticoid receptors (GRs), and (4) 51 kDa FK506-binding protein (FKBP5). These targets have emerged from neurobiological and human genetic studies and employ mechanisms that modulate GR function or promote anti-apoptotic processes critical to affective resilience. Future research should focus on elucidating sustainable treatments that target resiliency factors-such as BAG-1 or FKBP5-which could ultimately be used to treat individuals suffering from BPD and prevent relapses in afflicted individuals. Further identification of resiliency and susceptibility factors will also be vital. Ultimately, these developments would allow for the treatment of susceptible individuals prior to the development of BPD.

Cytotoxicity of half sandwich ruthenium(II) complexes with strong hydrogen bond acceptor ligands and their mechanism of action

Neutral and cationic organometallic ruthenium(II) piano stool complexes of the type [(eta(6)-cymene)RuCl(X)(Y)] (complexes R1-R8) has been synthesized and characterized. In cationic complexes, X, Y is either a eta(2) phosphorus ligand such as 1,1-bis(diphenylphosphino)methane (DPPM) and 1,2-bis(diphenylphosphino)ethane (DPPE) or partially oxidized ligands such as 1,2-bis(diphenylphosphino)methane monooxide (DPPMO) and 1,2-bis(diphenylphosphino)ethane monooxide (DPPEO) which are strong hydrogen bond acceptors. In neutral complexes, X is chloride and Y is a monodentate phosphorous donor. Complexes with DPPM and DPPMO ligands ([(eta(6)-cymene)Ru(eta(2)-DPPM)Cl]PF(6) (R2), [(eta(6)-cymene)Ru(eta(2)-DPPMO)Cl]PF(6) (R3), [(eta(6)-cymene)Ru(eta(1)-DPPM)Cl(2)] (R5) and [(eta(6)-cymene)Ru(eta(1)-DPPMO)Cl(2)] (R6) show good cytotoxicity. Growth inhibition study of several human cancer cell lines by these complexes has been carried out. Mechanistic studies for R5 and R6 show that inhibition of cancer cell growth involves both cell cycle arrest and apoptosis induction. Using an apoptosis PCR array, we identified the sets of anti-apoptotic genes that were down regulated and pro-apoptotic genes that were up regulated. These complexes were also found to be potent metastasis inhibitors as they prevented cell invasion through matrigel. The complexes were shown to bind DNA in a non intercalative fashion and cause unwinding of plasmid DNA in cell-free medium by competitive ethidium bromide binding, viscosity measurements, thermal denaturation and gel mobility shift assays.

ATP hydrolysis is essential for Bag-1M-mediated inhibition of the DNA binding by the glucocorticoid receptor

The 70-kDa heat shock protein (Hsp70) is involved in providing the appropriate conformation of various nuclear hormone receptors, including the glucocorticoid receptor (GR). The Bcl-2 associated athanogene 1M (Bag-1M) is known to downregulate the DNA binding by the GR. Also, Bag-1M interacts with the ATPase domain of Hsp70 to modulate the release of the substrate from Hsp70. In this study, we demonstrate that ATP hydrolysis enhances Bag-1M-mediated inhibition of the DNA binding by the GR. However, the inhibitory effect of Bag-1M was abolished when the intracellular ATP was depleted. In addition, a Bag-1M mutant lacking the interaction with Hsp70 did not influence the GR to bind DNA, suggesting the interaction of Bag-1M with Hsp70 in needed for its negative effect. These results indicate that ATP hydrolysis is essential for Bag-1M-mediated inhibition of the DNA binding by the GR and Hsp70 is a mediator for this process.

Evidence for modulation of BAG3 by polyomavirus JC early protein

Polyomavirus JC (JCV) infects oligodendrocytes and astrocytes in the brain and is the cause of the demyelinating disease progressive multifocal leukoencephalopathy (PML). In cell culture, JCV infection is characterized by severe damage to cellular DNA, which begins early in infection, and a viral cytopathic effect, which is observed late in infection. Nevertheless, these JCV-infected cells show a low level of apoptosis, at both the early and late stages of infection. This suggests that there is conflicting interplay between viral anti-apoptotic pathways that seek to optimize virus production, e.g. through T antigen (T-Ag)-p53 interaction, and cellular pro-apoptotic pathways that seek to eliminate virally infected cells. The apoptosis regulatory protein BAG3 is a member of the human Bcl-2-associated athanogene (BAG) family of proteins, which function as molecular co-chaperones through their interaction with Hsc70/Hsp70 and function in the regulation of the cellular stress response, proliferation and apoptosis. This study showed that BAG3 protein is downregulated upon JCV infection and that this effect is mediated by JCV T-Ag via repression of the BAG3 promoter. The site of action of T-Ag was mapped to an AP2 site in the BAG3 promoter, and gel shift and chromatin immunoprecipitation assays showed that T-Ag inhibited AP2 binding to this site, resulting in downregulation of BAG3 promoter expression. Using BAG3 and T-Ag expression and BAG3 siRNA, it was found that BAG3 and T-Ag had antagonistic effects on the induction of apoptosis, being anti-apoptotic and pro-apoptotic, respectively. The significance of these interactions to the JCV life cycle is discussed.

Advanced osteoarthritis in humans is associated with altered collagen VI expression and upregulation of ER-stress markers Grp78 and bag-1

To test the hypothesis that a perturbation of endoplasmic reticulum (ER) function is involved in the pathogenesis of osteoarthritis (OA), articular cartilage was isolated from non-OA patients secondary to resection of osteo- or chondrosarcomas. Intra-joint samples of minimal and advanced osteoarthritic cartilage were isolated from patients undergoing total knee arthroplasty and scored for disease severity. Glucose-regulated protein-78 (grp78) and bcl-2-associated athanogene-1 (bag-1) were detected via immunofluorescence as markers of non-homeostatic ER function. Additionally, the expression of type VI collagen and its integrin receptor, NG2, was determined to examine cartilage matrix health and turnover. There was an upregulation of grp78 in advanced OA, and variable expression in minimal OA. Non-OA cartilage was consistently grp78 negative. The downstream regulator bag-1 was also upregulated in OA compared with normal cartilage. Collagen VI was mainly cell-associated in non-OA cartilage, with a more widespread distribution observed in OA cartilage along with increased intracellular staining intensity. The collagen VI integral membrane proteoglycan receptor NG2 was downregulated in advanced OA compared with its patient-matched minimally involved cartilage sample. These results suggest that chondrocytes exhibit ER stress during OA, in association with upregulation of a large secreted molecule, type VI collagen.

Chromosomal imbalances and partial uniparental disomies in primary central nervous system lymphoma

To determine the pattern of genetic alterations in primary central nervous system lymphomas (PCNSL), 19 PCNSL were studied by high-density single-nucleotide polymorphism arrays. Recurrent losses involved 6p21.32, 6q21, 8q12-12.2, 9p21.3, 3p14.2, 4q35.2, 10q23.21 and 12p13.2, whereas gains involved 18q21-23, 19q13.31, 19q13.43 and the entire chromosomes X and 12. Partial uniparental disomies (pUPDs) were identified in 6p and 9p21.3. These genomic alterations affected the HLA locus, the CDKN2A/p16, CDKN2B/p15 and MTAP, as well as the PRDM1, FAS, MALT1, and BCL2 genes. Increased methylation values of the CDKN2A/p16 promoter region were detected in 75% (6/8) PCNSL. Gene expression profiling showed 4/21 (20%) minimal common regions of imbalances to be associated with a differential mRNA expression affecting the FAS, STAT6, CD27, ARHGEF6 and SEPT6 genes. Collectively, this study unraveled novel genomic imbalances and pUPD with a high resolution in PCNSL and identified target genes of potential relevance in the pathogenesis of this lymphoma entity.

Apoptosis in human reproductive tissues: emerging concepts

In summary, apoptosis is an important concept in understanding many facets of human reproduction. Recent advances in the understanding of molecular mechanisms of apoptosis will allow us to understand this physiologically important process. How can the modulation of this process be applied to human reproduction? Studies to further understand the abnormalities of apoptosis, either too much or too little, may lead to a better understanding of the clinical problems in human reproduction.

We summarize future directions towards further understanding the roles of apoptotic processes in human reproduction in Table 3. The diseases listed in Table 3 are problems which could be approached from the apoptosis point of view. With further study using this concept as the lens, new diagnostic tools or therapies may be developed for these problems.

The anti-apoptotic activity of BAG3 is restricted by caspases and the proteasome

Background

Caspase-mediated cleavage and proteasomal degradation of ubiquitinated proteins are two independent mechanisms for the regulation of protein stability and cellular function. We previously reported BAG3 overexpression protected ubiquitinated clients, such as AKT, from proteasomal degradation and conferred cytoprotection against heat shock. We hypothesized that the BAG3 protein is regulated by proteolysis.

Methodology/Principal Findings

Staurosporine (STS) was used as a tool to test for caspase involvement in BAG3 degradation. MDA435 and HeLa human cancer cell lines exposed to STS underwent apoptosis with a concomitant time and dose-dependent loss of BAG3, suggesting the survival role of BAG3 was subject to STS regulation. zVAD-fmk or caspase 3 and 9 inhibitors provided a strong but incomplete protection of both cells and BAG3 protein. Two putative caspase cleavage sites were tested: KEVD (BAG3^E345A/D347A) within the proline-rich center of BAG3 (PXXP) and the C-terminal LEAD site (BAG3^E516A/D518A). PXXP deletion mutant and BAG3^E345A/D347A, or BAG3^E516A/D518A respectively slowed or stalled STS-mediated BAG3 loss. BAG3, ubiquitinated under basal growth conditions, underwent augmented ubiquitination upon STS treatment, while there was no increase in ubiquitination of the BAG3^E516A/D518A caspase-resistant mutant. Caspase and proteasome inhibition resulted in partial and independent protection of BAG3 whereas inhibitors of both blocked BAG3 degradation. STS-induced apoptosis was increased when BAG3 was silenced, and retention of BAG3 was associated with cytoprotection.

Conclusions/Significance

BAG3 is tightly controlled by selective degradation during STS exposure. Loss of BAG3 under STS injury required sequential caspase cleavage followed by polyubiquitination and proteasomal degradation. The need for dual regulation of BAG3 in apoptosis suggests a key role for BAG3 in cancer cell resistance to apoptosis.

The BAG-1 cochaperone is a negative regulator of p73-dependent transcription

High-level expression of Bcl-2 associated athanogene (BAG-1) protects cancer cells from stress-induced cell death and growth inhibition. These protective effects of BAG-1 are dependent on interactions with the HSC70 and HSP70 chaperones. However, the key stress-response molecules that are regulated by a BAG-1/chaperone mechanism have not been identified. In this study, we investigated the effects of BAG-1 overexpression on the function of p53 family proteins, p53, p63 and p73. Overexpression of BAG-1 isoforms interfered with the transactivating activity of p73 and p63, but had modest and variable effects on p53-dependent transcription. p73 and BAG-1 interacted in intact cells and overexpression of BAG-1 decreased the expression of p73. siRNA-mediated ablation of endogenous BAG-1 increased the activity of a p73-responsive promoter and this was reversed by knock-down of p73. The ability of BAG-1 to modulate p73 activity and expression, and to interact with p73 were dependent on amino acid residues required for the interaction of BAG-1 with HSC70 and HSP70. These results show that BAG-1 inhibits the transactivating functions of p73 and provide new insight into the mechanisms that control the expression of p73. Inhibition of p73 function may be one mechanism that contributes to the pro-survival activity of BAG-1.

A novel role for DYX1C1, a chaperone protein for both Hsp70 and Hsp90, in breast cancer

AIMS

With three consecutive tetratricopeptide repeat (TPR) motifs at its C-terminus essential for neuronal migration, and a p23 domain at its N-terminus, DYX1C1 was the first gene proposed to have a role in developmental dyslexia. In this study, we attempted to identify the potential interaction of DYX1C1 and heat shock protein, and the role of DYX1C1 in breast cancer.

MAIN METHODS

GST pull-down, a yeast two-hybrid system, RT-PCR, site-directed mutagenesis approach.

KEY FINDINGS

Our study initially confirmed DYX1C1, a dyslexia related protein, could interact with Hsp70 and Hsp90 via GST pull-down and a yeast two-hybrid system. And we verified that EEVD, the C-terminal residues of DYX1C1, is responsible for the identified association. Further, DYX1C1 mRNA was significantly overexpressed in malignant breast tumor, linking with the up-regulated expression of Hsp70 and Hsp90.

SIGNIFICANCE

These results suggest that DYX1C1 is a novel Hsp70 and Hsp90-interacting co-chaperone protein and its expression is associated with malignancy.

Multiple, but concerted cellular activities of the human protein Hap46/BAG-1M and isoforms

The closely related human and murine proteins Hap46/BAG-1M and BAG-1, respectively, were discovered more than a decade ago by molecular cloning techniques. These and the larger isoform Hap50/BAG-1L, as well as shorter isoforms, have the ability to interact with a seemingly unlimited array of proteins of completely unrelated structures. This problem was partially resolved when it was realized that molecular chaperones of the hsp70 heat shock protein family are major primary association partners, binding being mediated by the carboxy terminal BAG-domain and the ATP-binding domain of hsp70 chaperones. The latter, in turn, can associate with an almost unlimited variety of proteins through their substrate-binding domains, so that ternary complexes may result. The protein folding activity of hsp70 chaperones is affected by interactions with Hap46/BAG-1M or isoforms. However, there also exist several proteins which bind to Hap46/BAG-1M and isoforms independent of hsp70 mediation. Moreover, Hap46/BAG-1M and Hap50/BAG-1L, but not the shorter isoforms, can bind to DNA in a sequence-independent manner by making use of positively charged regions close to their amino terminal ends. This is the molecular basis for their effects on transcription which are of major physiological relevance, as discussed here in terms of a model. The related proteins Hap50/BAG-1L and Hap46/BAG-1M may thus serve as molecular links between such diverse bioactivities as regulation of gene expression and protein quality control. These activities are coordinated and synergize in helping cells to cope with conditions of external stress. Moreover, they recently became markers for the aggressiveness of several cancer types.

CD24 expression has a prognostic impact in breast carcinoma

We investigated the prognostic significance of BAG-1 and CD24 in invasive breast carcinomas. Seventy cases of invasive breast carcinoma were studied immunocytochemically for the expression of BAG-1 and CD24. The results were correlated with several prognostic parameters, including 5-year survival. Univariate analysis showed a significant correlation of BAG-1 and CD24 overall positive staining with several adverse prognostic parameters, such as increased stage (p<0.0001), tumor grade 3 (p=0.016 and p=0.02, respectively), positive lymph nodes (p<0.0001), and increased tumor size (p<0.0001). Similar results were found for BAG-1 nuclear staining, as well as for positive cytoplasmic CD24 expression. Both of our markers studied had a significant, negative effect on survival. Multivariate analysis further revealed an independent prognostic impact for CD24 overall staining. The results of our study showed that overall cytoplasmic and especially nuclear BAG-1 expression, as well as overall and cytoplasmic CD24 expression, correlates with adverse prognostic parameters. An independent prognostic value for overall CD24 staining was also demonstrated.

Insufficiency of pro-heparin-binding epidermal growth factor-like growth factor shedding enhances hypoxic cell death in H9c2 cardiomyoblasts via the activation of caspase-3 and c-Jun N-terminal kinase

Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a cardiogenic and cardiohypertrophic growth factor. ProHB-EGF, a product of the Hb-egf gene and the precursor of HB-EGF, is anchored to the plasma membrane. Its ectodomain region is shed by a disintegrin and metalloproteases (ADAMs) when activated by various stimulations. It has been reported that an uncleavable mutant of Hb-egf, uc-Hb-egf, produces uc-proHB-EGF, which is not cleaved by ADAMs and causes dilation of the heart in knock-in mice. This suggests that the shedding of proHB-EGF is essential for the development and survival of cardiomyocytes: however, the molecular mechanism involved has remained unclear. In this study, we investigated the relationship between uc-proHB-EGF expression and cardiomyocyte survival. Human uc-proHB-EGF was adenovirally introduced into the rat cardiomyoblast cell line H9c2, and the cells were cultured under normoxic and hypoxic conditions. Uc-proHB-EGF-expressing H9c2 cells underwent apoptosis under normoxic conditions, which distinctly increased under hypoxic conditions. Furthermore, we observed an increased Caspase-3 activity, reactive oxygen species accumulation, and an increased c-Jun N-terminal kinase (JNK) activity in the uc-proHB-EGF-expressing H9c2 cells. Treatment of the uc-proHB-EGF transfectants with inhibitors of Caspase-3, reactive oxygen species, and JNK, namely, Z-VAD-fmk, N-acetylcysteine, and SP600125, respectively, significantly reduced hypoxic cell death. These data indicate that insufficiency of proHB-EGF shedding under hypoxic stress leads to cardiomyocyte apoptosis via Caspase-3- and JNK-dependent pathways.

Different BAG-1 isoforms have distinct functions in modulating chemotherapeutic-induced apoptosis in breast cancer cells

AIM

BAG-1 is a multifunctional anti-apoptotic gene with four isoforms, and different BAG-1 isoforms have different anti-apoptotic functions. In this study, we transfected BAG-1 isoforms into the human breast cancer cell lines Hs578T (ER negative) and MCF-7 (ER positive) to study their effect on apoptosis with or without estrogens.

METHODS

The constructed recombinant expression vectors carrying individual BAG-1 isoforms was used to transfect human breast cancer cell lines Hs578T (ER negative) and MCF-7 (ER positive). After stable cell lines were made, a variety of apoptosis-inducing agents, including doxorubicin, docetaxel, and 5-FU, was used to treat these cell lines with or without estrogen to test the role of BAG-1. The mechanism by which BAG-1 affected the function of Bcl-2 was exploredby using the cycloheximide chase assay.

RESULTS

The BAG-1 p50 and p46 isoforms significantly enhanced the resistance to apoptosis in both cell lines according to flow cytometry analysis. BAG-1 p33 and p29 failed to protect the transfected cells from apoptosis. The cell viability assay showed that only BAG-1 p50, but not p46, p33, or p29, increased estrogen-dependent function in ER-positive cell line MCF-7. Only BAG-1 p50 dramatically increased its anti-apoptotic ability in the presence of estrogen, while estrogen has very little effect on the anti-apoptotic ability of other BAG-1 isoforms. In the detection of the expression of K-ras, Hsp70, cytochrome c, Raf-1, ER-alpha, and Bcl-2 in MCF-7 cells by Western blot, only Bcl-2 protein expression was significantly increased in MCF-7 cells transfected with BAG-1 p50 and p46, respectively. Furthermore, the cycloheximide chase assay indicated that the degradation of Bcl-2 protein was extended in the BAG-1 p50 and p46 transfected MCF-7 cells.

CONCLUSION

Distinct isoforms of BAG-1 have different anti-apoptotic functions in breast cancer cells, and that the BAG-1 p50 isoform can potentiate the role of estrogen in ER-positive breast cancer.

Statistical interpretation of CA125 and Bcl-2 in serum of patients with late stage ovarian cancer

OBJECTIVES

The present study was conducted to investigate the sensitivity, specificity, predictive values and accuracy of serum CA125 and Bcl-2 levels and their combination in advanced epithelial ovarian cancer patients.

METHODS

Healthy controls (n = 117) with no gynecologic problems and patients with ovarian carcinoma (n = 117), pathologically verified, consecutively admitted to the Istanbul University, Oncology Institute during a one-year period were investigated. Serum Bcl-2 and CA125 were determined by using enzyme linked immunosorbent assay method.

RESULTS

The serum bcl-2 and CA125 levels were significantly higher in patients with ovarian cancer than in the control group (P < 0.001). The diagnostic sensitivity and specificity, predictive values and accuracies were calculated for each marker and their combination.

CONCLUSION

The best result was achieved with the combination of CA125-bcl-2. This combination fulfills the need of diagnosis of ovarian carcinoma for the best sensitivity and specificity.