BAX inhibitor-1 is a Ca(2+) channel critically important for immune cell function and survival

The endoplasmic reticulum (ER) serves as the major intracellular Ca(2+) store and has a role in the synthesis and folding of proteins. BAX (BCL2-associated X protein) inhibitor-1 (BI-1) is a Ca(2+) leak channel also implicated in the response against protein misfolding, thereby connecting the Ca(2+) store and protein-folding functions of the ER. We found that BI-1-deficient mice suffer from leukopenia and erythrocytosis, have an increased number of splenic marginal zone B cells and higher abundance and nuclear translocation of NF-κB (nuclear factor-κ light-chain enhancer of activated B cells) proteins, correlating with increased cytosolic and ER Ca(2+) levels. When put into culture, purified knockout T cells and even more so B cells die spontaneously. This is preceded by increased activity of the mitochondrial initiator caspase-9 and correlated with a significant surge in mitochondrial Ca(2+) levels, suggesting an exhausted mitochondrial Ca(2+) buffer capacity as the underlying cause for cell death in vitro. In vivo, T-cell-dependent experimental autoimmune encephalomyelitis and B-cell-dependent antibody production are attenuated, corroborating the ex vivo results. These results suggest that BI-1 has a major role in the functioning of the adaptive immune system by regulating intracellular Ca(2+) homeostasis in lymphocytes.

Three-dimensional structure of Bax-mediated pores in membrane bilayers

B-cell lymphoma 2 (Bcl-2)-associated X protein (Bax) is a member of the Bcl-2 protein family having a pivotal role in triggering cell commitment to apoptosis. Bax is latent and monomeric in the cytosol but transforms into its lethal, mitochondria-embedded oligomeric form in response to cell stress, leading to the release of apoptogenic factors such as cytochrome C. Here, we dissected the structural correlates of Bax membrane insertion while oligomerization is halted. This strategy was enabled through the use of nanometer-scale phospholipid bilayer islands (nanodiscs) the size of which restricts the reconstituted system to single Bax-molecule activity. Using this minimal reconstituted system, we captured structural correlates that precede Bax homo-oligomerization elucidating previously inaccessible steps of the core molecular mechanism by which Bcl-2 family proteins regulate membrane permeabilization. We observe that, in the presence of BH3 interacting domain death agonist (Bid) BH3 peptide, Bax monomers induce the formation of ~3.5-nm diameter pores and significantly distort the phospholipid bilayer. These pores are compatible with promoting release of ions as well as proteinaceous components, suggesting that membrane-integrated Bax monomers in the presence of Bid BH3 peptides are key functional units for the activation of the cell demolition machinery.

Establishing apoptosis resistant cell lines for improving protein productivity of cell culture

The authors established apoptosis resistant COS-1, myeloma, hybridoma, and Friend leukemia cell lines by genetically engineering cells, aiming at more efficient protein production by cell culture. COS-1 cells, which are most widely used for eukariotic gene expression, were transfected with human bcl-2 gene. Both bcl-2 and mock transfected COS-1 cells were cultured at low (0.2%) serum concentration for 9 days. The final viable cell number of the bcl-2 transfected cells was ninefold of that of the mock transfectants. Both bcl-2 and mock transfectants were further transfected with the vector pcDNA-λ containing SV40 ori and immunoglobulin λ gene for transiently expressing λ protein. The bcl-2 expressing COS-1 cells produced more λ protein than the mock transfected COS-1 cells after 4 days posttransfection.Mouse myeloma p3-X63-Ag.8.653 cells, which are widely used as the partner for preparing hybridoma, and hybridoma 2E3 cells were transfected with human bcl-2 gene. Both bcl-2 transfected myeloma and hybridoma survived longer than the corresponding original cells in batch culture. The bcl-2 transfected 2E3 cells survived 2 to 4 four days longer in culture, producing 1.5- to 4-fold amount of antibody in comparison with the mock transfectants.Coexpression of bag-1 with bcl-2 improved survival of hybridoma 2E3 cells more than bcl-2 expression alone. The bag-1 and bcl-2 coexpressing cells produced more IgG than the the cells expressing bcl-2 alone.Apoptosis of Friend murine erythroleukemia(F-MEL) cells was suppressed with antisense c-jun expression. The antisense c-jun expressing cells survived 16 days at non-growth state.

Co-expression of bcl-2 and bag-1, apoptosis suppressing genes, prolonged viable culture period of hybridoma and enhanced antibody production

Human bcl-2 and bag-1 DNA were introduced into mouse hybridoma 2E3- O cells and expressed. The expression of bcl-2 in BCMGneo-bcl2 transfectants was confirmed by ELISA and that of bag-1 in pZeo-bag1 was confirmed by western blotting. In batch cultures, the over-expression of bcl-2 prolonged the culture period by 2 days and co-expression of bcl-2 and bag-1 prolonged the culture period by 3 days. The delayed increase in the dead cell number in culture of the bcl-2 and bag-1 cotransfectant indicated the additional antiapoptosis effect of bcl-2 and bag-1 cotransfection in comparison with the bcl-2 only transfection. The bcl-2 transfectants (2E3O-Bcl2) produced antibody twofold per batch culture in comparison with 2E3-O cells transfected with BCMGSneo (2E3O-Mock). Enhancement of this MoAb production was due to the improved survival of the cells and was not due to stimulation of antibody production rate per cell by Bcl-2 expression. And the bcl-2 and bag-1 co-transfectant (2E3O-Bcl2-BAG1) produced antibody approximately fourfold of 2E3O-Mock per batch culture. Enhancement of this MoAb production was due to the improved survival of the cells and was partly due to stimulation of MoAb production rate per cell in the non-growing phase by the cotransfection. The method to engineer hybridoma cells genetically with bcl-2 and bag-1 for increasing viability and productivity would be widely applied for improving antibody productivity of hybridoma cultures.

Targeting the BH3-interacting domain death agonist to develop mechanistically unique antidepressants

The BH3-interacting domain death agonist (Bid) is a pro-apoptotic member of the B-cell lymphoma-2 (Bcl-2) protein family. Previous studies have shown that stress reduces levels of Bcl-2 in brain regions implicated in the pathophysiology of mood disorders, whereas antidepressants and mood stabilizers increase Bcl-2 levels. The Bcl-2 protein family has an essential role in cellular resilience as well as synaptic and neuronal plasticity and may influence mood and affective behaviors. This study inhibited Bid in mice using two pharmacological antagonists (BI-11A7 and BI-2A7); the selective serotonin reuptake inhibitor citalopram was used as a positive control. These agents were studied in several well-known rodent models of depression-the forced swim test (FST), the tail suspension test (TST), and the learned helplessness (LH) paradigm-as well as in the female urine sniffing test (FUST), a measure of sex-related reward-seeking behavior. Citalopram and BI-11A7 both significantly reduced immobility time in the FST and TST and attenuated escape latencies in mice that underwent the LH paradigm. In the FUST, both agents significantly improved duration of female urine sniffing in mice that had developed helplessness. LH induction increased the activation of apoptosis-inducing factor (AIF), a caspase-independent cell death constituent activated by Bid, and mitochondrial AIF expression was attenuated by chronic BI-11A7 infusion. Taken together, the results suggest that functional perturbation of apoptotic proteins such as Bid and, alternatively, enhancement of Bcl-2 function, is a putative strategy for developing novel therapeutics for mood disorders.

CLIPR-59 regulates TNF-α-induced apoptosis by controlling ubiquitination of RIP1

Tumor necrosis factor-α (TNF-α) has important roles in several immunological events by regulating apoptosis and transcriptional activation of cytokine genes. Intracellular signaling mediated by TNF-receptor-type 1 (TNFR1) is constituted by two sequential protein complexes: Complex-I containing the receptor and Complex-II-containing Caspase-8. Protein modifications, particularly ubiquitination, are associated with the regulation of the formation of these complexes. However, the underlying mechanisms remain poorly defined. Here, we identified CLIP-170-related 59 kDa protein (CLIPR-59) as a novel adaptor protein for TNFR1. Experimental reduction of CLIPR-59 levels prevented induction of apoptosis and activation of caspases in the context of TNF-α signaling. CLIPR-59 binds TNFR1 but dissociates in response to TNF-α stimulation. However, CLIPR-59 is also involved in and needed for the formation of Complex-II. Moreover, CLIPR-59 regulates TNF-α-induced ubiquitination of receptor-interacting protein 1 (RIP1) by its association with CYLD, a de-ubiquitinating enzyme. These findings suggest that CLIPR-59 modulates ubiquitination of RIP1, resulting in the formation of Complex-II and thus promoting Caspase-8 activation to induce apoptosis by TNF-α.

Co-chaperone BAG3 and adenovirus penton base protein partnership

The BAG family of Hsp70/Hsc70 co‐chaperones is characterised by the presence of a conserved BAG domain at the carboxyl‐terminus. BAG3 protein is the only member of this family containing also the N‐terminally located WW domain. We describe here the identification of adenovirus (Ad) penton base protein as the first BAG3 partner recognising BAG3 WW domain. Ad penton base is the viral capsid constituent responsible for virus internalisation. It contains in the N‐terminal part two conserved PPxY motifs, known ligands of WW domains. In cells producing Ad penton base protein, cytoplasmic endogenous BAG3 interacts with it and co‐migrates to the nucleus. Preincubation of BAG3 with Ad base protein results in only slight modulation of BAG3 co‐chaperone activity, suggesting that this interaction is not related to the classical BAG3 co‐chaperone function. However, depletion of BAG3 impairs the cell entry of the virus and viral progeny production in Ad‐infected cells, suggesting that the interaction between virus penton base protein and cellular co‐chaperone BAG3 positively influences virus life cycle. These results thus demonstrate a novel host–pathogen interaction, which contributes to the successful infectious life cycle of adenoviruses. In addition, these data enrich our knowledge about the multifunctionality of the BAG3 co‐chaperone. J. Cell. Biochem. 111: 699–708, 2010. © 2010 Wiley‐Liss, Inc.

Zircon ages of felsic volcanic rocks in the upper precambrian of the blue ridge, appalachian mountains

Five Zirconi samples from Pennsylvania, Virginia, and North Carolina yield discordant uranium-lead ages which suggest an original age of 820 million years and an episodic lead loss at 240 million years. The indicated age of lead loss is interpreted as the age of movement of the Blue Ridge thrust sheet.

A survey of the anti-apoptotic Bcl-2 subfamily expression in cancer types provides a platform to predict the efficacy of Bcl-2 antagonists in cancer therapy

We investigated the mRNA expression levels of all six antiapoptotic Bcl-2 subfamily members in 68 human cancer cell lines using qPCR techniques and measured the ability of known Bcl-2 inhibitors to induce cell death in 36 of the studied tumor cell lines. Our study reveals that Mcl-1 represents the anti-apoptotic Bcl-2 subfamily member with the highest mRNA levels in the lung, prostate, breast, ovarian, renal, and glioma cancer cell lines. In leukemia/lymphoma and melanoma cancer cell lines, Bcl-2 and Bfl-1 had the highest levels of mRNA, respectively. The observed correlation between the cell killing properties of known Bcl-2 inhibitors and the relative mRNA expression levels of anti-apoptotic Bcl-2 proteins provide critical insights into apoptosis-based anticancer strategies that target Bcl-2 proteins. Our data may explain current challenges of selective Bcl-2 inhibitors in the clinic, given that severe expression of Bcl-2 seems to be limited to leukemia cell lines. Furthermore, our data suggest that in most cancer types a strategy targeted to Mcl-1 inhibition, or combination of Bfl-1 and Mcl-1 inhibition for melanoma, may prove to be more successful than therapies targeting only Bcl-2.

Neuron-specific overexpression of the co-chaperone Bcl-2-associated athanogene-1 in superoxide dismutase 1(G93A)-transgenic mice

Bcl-2-associated athanogene-1 (BAG1) binds heat-shock protein 70 (Hsp70)/Hsc70, increases intracellular chaperone activity in neurons and proved to be protective in several models for neurodegeneration. Mutations in the superoxide dismutase 1 (SOD1) gene account for approximately 20% of familial amyotrophic lateral sclerosis (ALS) cases. A common property shared by all mutant SOD1 (mtSOD1) species is abnormal protein folding and the propensity to form aggregates. Toxicity and aggregate formation of mutant SOD1 can be overcome by enhanced chaperone function in vitro. Moreover, expression of mtSOD1 decreases BAG1 levels in a motoneuronal cell line. Thus, several lines of evidence suggested a protective role of BAG1 in mtSOD1-mediated motoneuron degeneration. To explore the therapeutic potential of BAG1 in a model for ALS, we generated SOD1G93A/BAG1 double transgenic mice expressing BAG1 in a neuron-specific pattern. Surprisingly, substantially increased BAG1 protein levels in spinal cord neurons did not significantly alter the phenotype of SOD1G93A-transgenic mice. Hence, expression of BAG1 is not sufficient to protect against mtSOD1-induced motor dysfunction in vivo. Our work shows that, in contrast to the in vitro situation, modulation of multiple cellular functions in addition to enhanced expression of a single chaperone is required to protect against SOD1 toxicity, highlighting the necessity of combined treatment strategies for ALS.

BCIRG 001 molecular analysis: Identification of prognostic factors in patients (pts) receiving adjuvant therapy for node- positive (N+) breast cancer (BC)

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Background: BCIRG 001 (1,491 pts) demonstrated significant superiority of docetaxel/doxorubicin/cyclophosphamide (TAC) over fluorouracil/doxorubicin/cyclophosphamide (FAC) given as adjuvant therapy for N+ operable BC in terms of disease-free survival (DFS) and overall survival (OS) (Martin et al, N Eng J Med, 2005). This ancillary study was aimed to identify tumor-associated factors related to DFS and OS. Methods: Formalin-fixed primary tumors from pts in BCIRG 001 were analysed by immunohistochemistry. Protocol- specified assessment of histological grade (GR), tumor size (TS), estrogen (ER) and progesterone receptors (PR), lymph node status (LN), HER2, MUC1, Mib, p53, Bcl-2, Bax, Bcl-X, Bag-1, tubulin β isotypes II, III and IV, tau protein and detyrosinated a tubulin was performed. Parameters were scored as the percentage of positive cells and analysed as lower or greater than median values. The samples were randomly split into training (2/3) and validation (1/3) sets. Associations between selected parameters and DFS or OS were tested through univariate analyses using the Kaplan Meier method (log-rank test) on the training set. A backward stepwise Cox regression analysis was performed to identify the final model of prognostic factors on the training set. Multivariate analyses were applied to the validation set. Results: 1,350 samples were split into a training (n=906) and a validation (n=444) set. In univariate GR, TS, LN, ER and PR, Mib, tau protein and HER2 were correlated with DFS in both sets. In multivariate ER, PR, TS, LN, Mib (all p<0.01) and tau (p=0.043) were significantly associated with DFS in the training set. In univariate GR, TS, LN, ER and PR, Mib, MUC1, Bcl-2, tubulin III and IV and tau were correlated with OS in both sets, with a trend for p53. In multivariate ER, TS, LN, Mib, p53 (all p<0.01) and PR (p=0.028) were independently correlated with OS in the training set. Conclusions: These data suggest that tau and p53 are independent markers of DFS and OS, respectively, while Mib is correlated with both DFS and OS in pts receiving these forms of adjuvant chemotherapy for N+ BC. Complementary analyses will be presented.

No significant financial relationships to disclose.

Thymidine-phosphorothioate oligonucleotides induce activation and apoptosis of CLL cells independently of CpG motifs or BCL-2 gene interference

We compared antisense phosphorothioate oligonucleotides (PS-ODN) that target BCL-2 such as Genasense (G3139-PS), with other PS-ODN or phosphodiester-ODN (PO-ODN) in their relative capacity to induce apoptosis of chronic lymphocytic leukemia (CLL) B cells in vitro. Surprisingly, we found that thymidine-containing PS-ODN, but not PO-ODN, induced activation and apoptosis of CLL cells independent of BCL-2 antisense sequence or CpG motifs. All tested thimidine-containing PS-ODN, irrespective of their primary sequences, reduced the expression of Bcl-2 protein and increased the levels of the proapoptotic molecules p53, Bid, Bax in CLL cells. Apoptosis induced by thymidine-containing PS-ODN was preceded by cellular activation, could be blocked by the tyrosine-kinase inhibitor imatinib mesylate (Gleevec), and was dependent on ABL kinase. We conclude that thymidine-containing PS-ODN can activate CLL cells and induce apoptosis via a mechanism that is independent of BCL-2 gene interference or CpG motifs.

Targeting inhibition of K-ras enhances Ad.mda-7-induced growth suppression and apoptosis in mutant K-ras colorectal cancer cells

Melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24) is a cancer-specific, growth-suppressing and apoptosis-inducing gene with broad-spectrum antitumor activity. However, when administered by means of a replication-incompetent adenovirus, Ad.mda-7, several colorectal carcinoma cell lines are resistant to its antiproliferative and antisurvival effects. We have presently endeavored to determine if K-ras mutations, present in approximately 40-50% of colorectal cancers and which may mediate resistance to chemotherapy and radiotherapy, represent a predisposing genetic factor mitigating reduced sensitivity to Ad.mda-7. To suppress ras expression, three structurally different replication-incompetent adenoviral vectors were engineered that express (1) an intracellular, neutralizing single-chain antibody (scAb) to p21 ras (Ad.K-ras scAb), (2) an antisense (AS) K-ras gene (Ad.K-ras AS) or (3) both mda-7/IL-24 and a K-ras AS gene in a single bipartite virus (Ad.m7.KAS). Simultaneous inhibition of K-ras and expression of mda-7/IL-24 enhanced killing of colorectal carcinoma cells with mutated K-ras, but not with wild-type K-ras. The extent of killing depended on the degree of K-ras downregulation, with Ad.K-ras AS being generally more efficient than Ad.K-ras scAb in combination with Ad.mda-7. These findings support an effective dual-combinatorial approach for the therapy of colorectal cancers that employs a unique cancer-specific suppressor gene (mda-7/IL-24) with targeted inhibition of oncogene (ras) expression.

Quantitative determination of apogossypol, a pro-apoptotic analog of gossypol, in mouse plasma using LC/MS/MS

A simple and selective liquid chromatography/tandem mass spectrometry (LC/MS/MS) method based on internal standard quantitation using apigenin as the internal standard has been developed and validated for the analysis of the gossypol analog apogossypol, a pro-apoptotic compound, in mouse plasma. The methodology involves protein precipitation of plasma samples followed by LC/MS/MS analysis. Ascorbic acid was added to the spiking solutions and plasma samples to stabilize the easily oxidized compound. Separation of apogossypol and the internal standard from the plasma matrix was achieved using a C18 column with a gradient elution profile consisting of 5mM ammonium acetate and methanol. The validated range of the method extended from 10 to 2000 ng/mL with accuracies of 85-115% and precision of <15%. The average recovery of apogossypol at three concentrations (50, 200 and 1000 ng/mL) assayed in triplicate using this methodology was determined to be 90.8+/-12.9%. Recovery for the internal standard (apigenin) at a concentration of 500 ng/mL was found to be 99.9+/-6.41%. Apogossypol concentrations of 50 ng/mL and above were found to be stable in extracted plasma for 24h when stored at 25 degrees C. This method has been applied to the determination of apogossypol concentrations in plasma collected from mice given an IV dose of apogossypol.

Regulation of Nur77 nuclear export by c-Jun N-terminal kinase and Akt

Proapoptotic nuclear receptor family member Nur77 translocates from the nucleus to the mitochondria, where it interacts with Bcl-2 to trigger apoptosis. Nur77 translocation is induced by certain apoptotic stimuli, including the synthetic retinoid-related 6-[3-(1-adamantyl)-4-hydroxyphenyl]-2-naphthalenecarboxylic acid (AHPN)/CD437 class. In this study, we investigated the molecular mechanism by which AHPN/CD437 analog (E)-4-[3-(1-adamantyl)-4-hydroxyphenyl]-3-chlorocinnamic acid (3-Cl-AHPC) induces Nur77 nuclear export. Our results demonstrate that 3-Cl-AHPC effectively activated Jun N-terminal kinase (JNK), which phosphorylates Nur77. Inhibition of JNK activation by a JNK inhibitor suppressed 3-Cl-AHPC-induced Nur77 nuclear export and apoptosis. In addition, several JNK upstream activators, including the phorbol ester TPA, anisomycin and MAPK kinase kinase-1 (MEKK1), phosphorylated Nur77 and induced its nuclear export. However, Nur77 phosphorylation by JNK, although essential, was not sufficient for inducing Nur77 nuclear export. Induction of Nur77 nuclear export by MEKK1 required a prolonged MEKK1 activation and was attenuated by Akt activation. Expression of constitutively active Akt prevented MEKK1-induced Nur77 nuclear export. Conversely, transfection of dominant-negative Akt or treatment with a phosphatidylinositol 3-kinase (PI3-K) inhibitor accelerated MEKK1-induced Nur77 nuclear export. Furthermore, mutation of an Akt phosphorylation residue Ser351 in Nur77 abolished the effect of Akt or the PI3-K inhibitor. Together, our results demonstrate that both activation of JNK and inhibition of Akt play a role in translocation of Nur77 from the nucleus to the cytoplasm.

Select high risk genetic features predict earlier progression following chemotherapy in chronic lymphocytic leukemia: Prospective randomized trial (Intergroup E2997) to evaluate justification for risk-adapted therapy

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Background: Genomic features including lack of IgVH mutations, del(11q), del(17p), and p53 mutations have been reported to predict clinical course and overall survival in CLL patients (pts). Bcl-2 family proteins and ZAP-70 have also been explored as predictors in CLL. Methods: We prospectively evaluated the prognostic significance of clinical features and laboratory variables on response and progression-free survival (PFS) following treatment with fludarabine (F, n=132) or fludarabine plus cyclophosphamide (FC, n=137) as part of the US Intergroup Trial E2997 for previously untreated CLL. Results: FC therapy had higher complete response (CR) (23.4% versus 4.6%), overall response (OR) (74.3% versus 59%), and median PFS (31.6 mos versus 19.2 mos) compared to F. CR and OR were not significantly different based on interphase cytogenetics, IgVH status, or p53 mutation. IgVH status or levels of ZAP-70, Bcl-2, Bax, Mcl-1, XIAP, Caspase-3, and Traf-1 proteins were not associated with clinical response or PFS. IgVH status and ZAP-70 levels were associated with time from diagnosis to treatment. Using a model including treatment arm, pts with del(17p) or (11q) had significantly shorter PFS (hazard ratios 3.54 and 2.05 respectively). In pts with a p53 mutation without del(17p) there was no enhancement of the model predicting poorer outcome, nor did IgVH status enter the model for predicting PFS. Conclusions: Combination chemotherapy is associated with a higher CR, OR, and PFS. Also, initiation of therapy for pts with Rai stages 0/1 resulted in a higher response rate. Del(17p) and del(11q) are highly predictive of shortened PFS with fludarabine-based chemotherapy. IgVH and p53 mutational status, as well as expression of ZAP-70, Bcl-2 family proteins, and CD38, did not predict response or PFS. ZAP-70 expression is associated with cytogenetic subsets predicted to have a worse overall prognosis, but did not identify pts who will do poorly with therapy. A combination of clinical staging and cytogenetics provide support for future risk-stratified treatment of CLL. Pts with a projected short response duration can be identified for future investigational strategies.

No significant financial relationships to disclose.

Proapoptotic multidomain Bcl-2/Bax-family proteins: mechanisms, physiological roles, and therapeutic opportunities

Bcl-2-family proteins are central regulators of cell life and death. At least three major classes of Bcl-2-family proteins have been delineated, including proapoptotic proteins that contain several conserved regions of sequence similarity (termed 'multidomain'). In mammals, the multidomain proteins (MDPs) of the Bcl-2 family include Bax, Bak, and Bok. The founding member of the MDP group of Bcl-2-family proteins was discovered by Stanley Korsmeyer and co-workers, initiating an exciting area of cell death research. The status of current knowledge about the mechanisms and functions of MDPs is reviewed here, and some areas for future research are outlined. Therapeutic opportunities emerging from a growing understanding of MDPs with respect to their three-dimensional structures, biochemical actions, and roles in disease raise hopes that the foundation of basic research laid by Korsmeyer and others will eventually be translated into clinical benefits, leaving a legacy that benefits the world for many decades.

Ionizing radiation enhances therapeutic activity of mda-7/IL-24: overcoming radiation- and mda-7/IL-24-resistance in prostate cancer cells overexpressing the antiapoptotic proteins bcl-xL or bcl-2

Subtraction hybridization applied to terminally differentiating human melanoma cells identified mda-7/IL-24, a cytokine belonging to the IL-10 gene superfamily. Adenoviral-mediated delivery of mda-7/IL-24 (Ad.mda-7) provokes apoptosis selectively in a wide spectrum of cancers in vitro in cell culture, in vivo in human tumor xenograft animal models and in patients with advanced carcinomas and melanomas. In human prostate cancer cells, a role for mitochondrial dysfunction and induction of reactive oxygen species in the apoptotic process has been established. Ectopic overexpression of bcl-xL and bcl-2 prevents these changes including apoptosis induction in prostate tumor cells by Ad.mda-7. We now document that this resistance to apoptosis can be reversed by treating bcl-2 family overexpressing prostate tumor cells with ionizing radiation in combination with Ad.mda-7 or purified GST-MDA-7 protein. Additionally, radiation augments apoptosis induction by mda-7/IL-24 in parental and neomycin-resistant prostate tumor cells. Radiosensitization to mda-7/IL-24 is dependent on JNK signaling, as treatment with the JNK 1/2/3 inhibitor SP600125 abolishes this effect. Considering that elevated expression of bcl-xL and bcl-2 are frequent events in prostate cancer development and progression, the present studies support the use of ionizing radiation in combination with mda-7/IL-24 as a means of augmenting the therapeutic benefit of this gene in prostate cancer, particularly in the context of tumors displaying resistance to radiation therapy owing to bcl-2 family member overexpression.

Differential regulation of Bax, Bcl-2, and Bcl-X proteins in focal cortical ischemia in the rat

Focal ischemia in the parietal cortex of the rat results in massive neuronal death in the infarct zone and penumbra between 12 hours and 6 days after photothrombosis. To examine a possible role of Bcl-2 family proteins in this process of cell death, we investigated their expression by immunoblot assays and immunocytochemistry, and correlated expression patterns with TUNEL as well as morphological signs indicative of apoptosis. In the center of the lesion Bax immunostaining was increased in many degenerating neurons between 4 hours and 3 days after the induction of photothrombosis. At all time points examined, Bcl-2 and Bcl-X protein levels were markedly reduced in injured neurons as compared to the unlesioned side. At the border of the ischemic lesion, two areas were distinguished: 1 - 2 days after induction of photothrombosis, pyknotic cells located immediately adjacent to the lesion core displayed nuclear Bcl-X and Bax immunoreactivity. In contrast, large, morphologically intact neurons located more towards the healthy brain parenchyma displayed an increase in cytoplasmic Bcl-2 and Bcl-X proteins. Double staining for each of the Bcl-2 family proteins and TUNEL revealed that DNA strand breaks and nuclear fragmentation seen in cells located in the lesion core were often associated with increased levels of Bax, but not with elevated Bcl-2 or Bcl-X protein levels, suggesting a role for Bax in the induction of apoptotic death in these cells. The upregulation of Bcl-2 and Bcl-X expression in surviving neurons close to the penumbra might reflect an active survival mechanism that protects these neurons from cell death following a sublethal insult.

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.

Bcl-2 acts upstream of the PARP protease and prevents its activation

Apoptosis has recently been extensively studied and multiple factors have been implicated in its regulation. It remains unclear how these factors are ordered in the cell death pathway. Here we investigate the relationship between the inhibitor of apoptosis, bcl-2, and the PARP protease, prlCE/CPP32, recently implicated in apoptosis. Using PARP proteolysis as an indicator of the activation of the PARP protease, we find that the chemotherapeutic agent, etoposide, induces apoptosis and PARP proteolysis in Molt4 cells as early as 4 h with cell death lagging behind this event. In contrast, Molt4 cells that over-express bcl-2 show no PARP proteolysis or cell death. In order to determine if bcl-2 inhibits the PARP protease or its activation, we developed a cell-free system. Using this system with extracts from etoposide-treated cells and purified bovine PARP, we demonstrate that extracts from bcl-2 over-expressing cells cause little or no PARP proteolysis. Whereas, extracts from control vector cells contain an active PARP protease. This protease is inhibited by the tetrapeptide ICE-like protease inhibitor, YVAD-chloromethylketone. Interestingly, this protease is not inhibited by the addition of purified bcl-2 protein. These results rule out that bcl-2 directly inhibits the active protease or that it has an effect downstream of prlCE/CPP32 such as preventing access to the PARP substrate. These results also demonstrate a role of bcl-2 in interfering with an upstream signal required to activate the PARP protease and allow us to begin to order the components in the apoptotic pathway.

Bifunctional apoptosis inhibitor (BAR) protects neurons from diverse cell death pathways

The bifunctional apoptosis regulator (BAR) is a multidomain protein that was originally identified as an inhibitor of Bax-induced apoptosis. Immunoblot analysis of normal human tissues demonstrated high BAR expression in the brain, compared to low or absent expression in other organs. Immunohistochemical staining of human adult tissues revealed that the BAR protein is predominantly expressed by neurons in the central nervous system. Immunofluorescence microscopy indicated that BAR localizes mainly to the endoplasmic reticulum (ER) of cells. Overexpression of BAR in CSM 14.1 neuronal cells resulted in significant protection from a broad range of cell death stimuli, including agents that activate apoptotic pathways involving mitochondria, TNF-family death receptors, and ER stress. Downregulation of BAR by antisense oligonucleotides sensitized neuronal cells to induction of apoptosis. Moreover, the search for novel interaction partners of BAR identified several candidate proteins that might contribute to the regulation of neuronal apoptosis (HIP1, Hippi, and Bap31). Taken together, the expression pattern and functional data suggest that the BAR protein is involved in the regulation of neuronal survival.

The histone deacetylase inhibitor MS-275 induces caspase-dependent apoptosis in B-cell chronic lymphocytic leukemia cells

MS-275 is a histone deacetylase (HDAC) inhibitor that has been reported to mediate its cytotoxic effect through generation of reactive oxygen species (ROS) in proliferating hematopoietic cell lines. We examined efficacy of MS-275 in nonproliferating chronic lymphocytic leukemia (CLL) cells from patients. In these cells, MS-275 demonstrated an in vitro LC(50) that was one log lower than for normal mononuclear cells. Following MS-275 treatment, histones H3 and H4 showed increased acetylation and HDAC enzymatic activity was reduced. Caspase-8, -9, and -3 were activated, and caspase substrates PARP and BID were cleaved. Additionally, FLICE-inhibitory protein (FLIP) was downmodulated following MS-275 incubation. MS-275 treatment caused detectable ROS generation after 15 h of incubation, which was blocked by the caspase inhibitor Z-VAD-fmk. Overexpression of Bcl-2 protein protected against MS-275-induced apoptosis. These data demonstrate that MS-275 is a promising therapy for the treatment of CLL, but that in contrast to previous reports, ROS generation does not precede commitment to apoptosis. Similar to many other therapeutic targets, MS-275-mediated apoptosis is reduced by overexpression of Bcl-2, justifying strategies to combine HDAC inhibitors with Bcl-2 antagonists.

Role of apoptosis and apoptosis-related proteins in the cisplatin-resistant phenotype of human tumor cell lines

Since apoptosis is the primary mode of cell death induced by cisplatin, the role of apoptosis and apoptosis-related gene products in cisplatin resistance was investigated in four human cisplatin-resistant cell lines of different tumour type. A common feature of the resistant sublines was a reduced susceptibility to drug-induced apoptosis compared to parental sensitive lines. Loss of wild-type p53 function was not a general event associated with the development of drug resistance. An increased bcl-2 expression was found in resistant cells characterized by mutant p53 (A431/Pt and IGROV-1/Pt), whereas in osteosarcoma (U2-OS/Pt) and in ovarian carcinoma (A2780/CP) cells with wild-type p53, bcl-2 levels were markedly reduced. U2-OS/Pt cells had a 16-fold increase in the level of Bcl-xL protein. Stable transfection of U2-OS cells with bcl-xL cDNA conferred a low level of drug resistance to cisplatin, suggesting that overexpression of this gene contributes to the cisplatin-resistant phenotype of this osteosarcoma cell system. In conclusion, these observations suggest a variable contribution of apoptosis-related genes to cisplatin resistance depending on the biological background of the cell system and presumably reflecting different pathways of apoptosis.

Synthetic triterpenoids activate a pathway for apoptosis in AML cells involving downregulation of FLIP and sensitization to TRAIL

Acute myelogenous leukemia (AML) remains a deadly disease for most adult patients, due primarily to the emergence of chemoresistant cells. Defects in apoptosis pathways make important contributions to chemoresistance, suggesting a need to restore apoptosis sensitivity or to identify alternative pathways for apoptosis induction. Triterpenoids represent a class of naturally occurring and synthetic compounds with demonstrated antitumor activity, including 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid (CDDO) and its methyl ester (CDDO-m). We explored the effects of CDDO and CDDO-m in vitro on established AML cell lines (HL-60, U937, AML-2) and on freshly isolated AML blasts. CDDO and CDDO-m reduced the viability of all AML cell lines tested in a dose-dependent manner, with effective doses for killing 50% of cells (ED(50)) within 48 h of approximately 1 and 0.5 muM, respectively. CDDO or CDDO-m also induced substantial increases in cell death in five out of 10 samples of primary AML blasts. Cell death induced by CDDO and CDDO-m was attributed to apoptosis, based on characteristic cell morphology and evidence of caspase activation. Immunoblot analysis demonstrated proteolytic processing of caspase-3, -7, and -8, but not caspase-9, suggesting the involvement of the 'extrinsic' pathway, linked to apoptosis induction by TNF-family death receptors. Accordingly, CDDO and CDDO-m induced concentration-dependent reductions in the levels of FLIP protein, an endogenous antagonist of caspase-8, without altering the levels of several other apoptosis-relevant proteins. Reductions in FLIP were rapid, detectable within 3 h after exposure of AML cell lines to CDDO or CDDO-m. CDDO and CDDO-m also sensitized two of four leukemia lines to TRAIL, a TNF-family death ligand. The findings suggest that synthetic triterpenoids warrant further investigation in the treatment of AML, alone or in combination with TRAIL or other immune-based therapies.

Contribution of caspase-8 to apoptosis of axotomized rat retinal ganglion cells in vivo

We have investigated the role of caspase-8 and its mode of activation during apoptosis of adult rat retinal ganglion cells (RGCs) in vivo. Retinal pro-caspase-8 expression was almost completely restricted to RGCs. Although caspase-8 is known to be involved in death-receptor-dependent apoptosis, measurable caspase-8 activity or even RGC death could be induced by neither tumor necrosis factor-alpha nor Fas ligand injections into unlesioned eyes. However, substantial caspase-8 activation could be detected after optic nerve transection as shown by a fluorogenic activity assay and Western blot analysis. Intravitreal injection of caspase-8 inhibitors significantly attenuated degeneration of RGCs and reduced the number of RGCs showing caspase-3 activation. A late peak of caspase-8 activity and additive protective effects of caspase-8 and -9 inhibition on axotomized RGCs place caspase-8 in our model rather late in the apoptosis cascade, possibly after the onset of mitochondrial dysfunction.

The apoptosis database

The apoptosis database is a public resource for researchers and students interested in the molecular biology of apoptosis. The resource provides functional annotation, literature references, diagrams/images, and alternative nomenclatures on a set of proteins having 'apoptotic domains'. These are the distinctive domains that are often, if not exclusively, found in proteins involved in apoptosis. The initial choice of proteins to be included is defined by apoptosis experts and bioinformatics tools. Users can browse through the web accessible lists of domains, proteins containing these domains and their associated homologs. The database can also be searched by sequence homology using basic local alignment search tool, text word matches of the annotation, and identifiers for specific records. The resource is available at http://www.apoptosis-db.org and is updated on a regular basis.

Analysis of the mouse transcriptome based on functional annotation of 60,770 full-length cDNAs

Only a small proportion of the mouse genome is transcribed into mature messenger RNA transcripts. There is an international collaborative effort to identify all full-length mRNA transcripts from the mouse, and to ensure that each is represented in a physical collection of clones. Here we report the manual annotation of 60,770 full-length mouse complementary DNA sequences. These are clustered into 33,409 'transcriptional units', contributing 90.1% of a newly established mouse transcriptome database. Of these transcriptional units, 4,258 are new protein-coding and 11,665 are new non-coding messages, indicating that non-coding RNA is a major component of the transcriptome. 41% of all transcriptional units showed evidence of alternative splicing. In protein-coding transcripts, 79% of splice variations altered the protein product. Whole-transcriptome analyses resulted in the identification of 2,431 sense-antisense pairs. The present work, completely supported by physical clones, provides the most comprehensive survey of a mammalian transcriptome so far, and is a valuable resource for functional genomics.

Mild traumatic brain injury induces apoptotic cell death in the cortex that is preceded by decreases in cellular Bcl-2 immunoreactivity

Although mild traumatic brain injury is associated with behavioral dysfunction and histopathological alterations, few studies have assessed the temporal pattern of regional apoptosis following mild brain injury. Anesthetized rats were subjected to mild lateral fluid-percussion brain injury (1.1-1.3 atm), and brains were evaluated for the presence of in situ DNA fragmentation (terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling, TUNEL) and morphologic characteristics of apoptotic cell death (nuclear and cytoplasmic condensation, presence of apoptotic bodies). Significant numbers of apoptotic TUNEL(+) cells were observed in the injured parietal cortex and underlying white matter up to 72 h post-injury (P<0.05 compared to sham-injured-injured), with maximal numbers present at 24 h. Apoptosis was confirmed by the presence of 180-200 bp nuclear DNA fragments in tissue homogenates. The appearance of apoptotic TUNEL(+) cells in the injured cortex was preceded by a marked decrease in immunoreactivity for the anti-cell death protein, Bcl-2, as early as 2 h post-injury. This decrease in cellular Bcl-2 staining was not accompanied by a concomitant loss of staining for the pro-cell death Bax protein, suggesting that post-traumatic neuronal death in the cortex may be dependent on altered cellular ratios of Bcl-2:Bax. In the hippocampus, no significant increase in apoptotic TUNEL(+) cells was observed compared to sham-injured-injured animals. However, selective neuronal loss was evident in the CA3 region at 24 h post-injury, that was preceded by an overt loss of neuronal Bcl-2 immunoreactivity at 6 h. No changes in either cellular Bcl-2 or Bax expression were observed in the thalamus or white matter at any time post-injury. Taken together from these data, we suggest that apoptosis contributes to cell death in both gray and white matter, and that decreases in cellular Bcl-2 may, in part, be associated with both apoptotic and non-apoptotic cell death following mild brain trauma.

Expression of apoptotic regulators and their significance in cervical cancer

Insufficient apoptosis is implicated in many human cancers, including cervical carcinoma. The objectives of this study were to explore changes of apoptosis-regulating gene expression and their clinical significance in cervical cancer. The expression of apoptosis-regulating genes, including five Bcl-2 family and two caspase family members, was evaluated in 43 cervical invasive squamous cell carcinomas, using immunohistochemistry. Specimens in which >or=10% of the neoplastic cells showed cytosolic immunoreactivity were considered to be immunopositive. Results were correlated with clinico-pathologic characteristics of the subjects. All seven apoptotic regulators examined were positive in a proportion of the tumors. The percentage of cases expressing Bax was higher in the patients without evidence of disease after treatment than in the patients alive with disease or who died of disease (P<0.05). A significant difference in disease-free survival was detected between Bax-positive and -negative groups (P<0.05), and in overall survival between Mcl-1-positive and -negative groups (P<0.05). Significant association between the seven markers tested was only found for caspase 3 and Bak immunoreactivity in cervical carcinoma (P<0.05). The results demonstrate expression of multiple apoptosis-modulating proteins in cervical cancer. There appears to be complex regulation of apoptosis protein levels in association with clinical behavior of cervical squamous cell carcinoma.

Bag1 is a regulator and marker of neuronal differentiation

Bag 1 acts as a co-chaperone for Hsp70/Hsc70. We report here that stable over-expression of Bag1 in immortalized neuronal CSM14.1 cells prevents death following serum deprivation. Bag1 over-expression slowed the proliferative rate of CSM14.1 cells, resulted in increased levels of phospo-MAP kinases and accelerated neuronal differentiation. Immunocytochemistry revealed mostly nuclear localization of Bag1 protein in these cells. However, during differentiation in vitro, Bag1 protein shifted from predominantly nuclear to mostly cytosolic in CSM14.1 cells. To explore in vivo parallels of these findings, we investigated Bag1 expression in the developing mouse nervous system using immunohistochemical methods. Early in brain development, Bag1 was found in nuclei of neuronal precursor cells, whereas cytosolic Bag1 staining was observed mainly after completion of neuronal precursor migration and differentiation. Taken together, these findings raise the possibility that the Bag1 protein is expressed early in neurogenesis in vivo and is capable of modulating neuronal cell survival and differentiation at least in part from a nuclear location.

Differential sensitivity to apoptosis between the human small and large intestinal mucosae: linkage with segment-specific regulation of BCL-2 homologs and involvement of signaling pathways

The small and large intestines differ in their expression profiles of Bcl-2 homologs. Intestinal segment-specific Bcl-2 homolog expression profiles are acquired as early as by mid-gestation (18-20 weeks) in man. In the present study, we examined the question whether such distinctions underlie segment-specific control mechanisms of intestinal cell survival. Using mid-gestation human jejunum and colon organotypic cultures, we analyzed the impact of growth factors (namely insulin; 10 microg/ml) and pharmacological compounds that inhibit signal transduction molecules/pathways (namely tyrosine kinases, Fak, P13-K/Akt, and MEK/Erk) on cell survival and Bcl-2 homolog expression (anti-apoptotic: Bcl-2, Bcl-X(L), Mcl-1; pro-apoptotic: Bax, Bak, Bad). The relative activation levels of p125Fak, p42Erk-2, and p57Akt were analyzed as well. Herein, we report that (1) the inhibition of signal transduction molecules/pathways revealed striking differences in their impact on cell survival in the jejunum and colon (e.g., the inhibition of p125Fak induced apoptosis with a significantly greater extent in the jejunum [approximately 43%] than in the colon [approximately 24%]); (2) sharp distinctions between the two segments were noted in the modulatory effects of the various treatments on Bcl-2 homolog steady-state levels (e.g., inhibition of tyrosine kinase activities in the jejunum down-regulated all anti-apoptotics analyzed while increasing Bax, whereas the same treatment in the colon down-regulated Bcl-X(L) only and increased all pro-apoptotics); and (3) in addition to their differential impact on cell survival and Bcl-2 homolog expression, the MEK/Erk and P13-K/Akt pathways were found to be distinctively regulated in the jejunum and colon mucosae (e.g., insulin in the jejunum increased p42Erk-2 activation without affecting that of p57Akt, whereas the same treatment in the colon decreased p42Erk-2 activation while increasing that of p57Akt). Altogether, these data show that intestinal cell survival is characterized by segment-specific susceptibilities to apoptosis, which are in turn linked with segmental distinctions in the involvement of signaling pathways and the regulation of Bcl-2 homolog steady-state levels. Therefore, these indicate that cell survival is subject to segment-specific control mechanisms along the proximal-distal axis of the intestine.

Dynamics of expression of apoptosis-regulatory proteins Bid, Bcl-2, Bcl-X, Bax and Bak during development of murine nervous system

We have used immunohistochemistry and immunoblotting to examine the expression of Bid and four other Bcl-2 family proteins (Bcl-2, Bcl-X, Bax and Bak) in the developing and adult murine central nervous system (CNS). Bid protein is widespread in embryonic and postnatal brain, and its expression is maintained at a high level late into the adulthood. Bid is expressed both in the germ disc, early neural tube, proliferating stem cells of ventricular zones, and in postmitotic, differentiated neurons of the developing central and peripheral nervous system. As the differentiation proceeds, the neurons express higher levels of Bid than the stem cells of the paraventricular zone. Both in embryonic and postnatal life, Bid protein is present in the most vital regions of brain, such as the limbic system, basal ganglia, mesencephalic tectum, Purkinje cells in cerebellum, and the ventral columns of spinal cord. The p15 cleaved form of Bid was detectable in the brain specimens at fetal stages of development, consistent with caspase-mediated activation of this pro-apoptotic Bcl-2 family protein. Among the Bcl-2 family proteins only Bid and Bcl-XL continue to be expressed at high levels in the adult brain.

The carboxyl-terminal lobe of Hsc70 ATPase domain is sufficient for binding to BAG1

The molecular co-chaperone BAG1 and other members of the BAG family bind to Hsp70/Hsc70 heat shock proteins through a conserved BAG domain that interacts with the ATPase domain of the chaperone. BAG1 and other accessory proteins stimulate ATP hydrolysis and regulate the ATP-driven activity of the chaperone complexes. Contacts are made through residues in helices alpha2 and alpha3 of the BAG domain and predominantly residues in the C-terminal lobe of the bi-lobed Hsc70 ATPase domain. Within the C-terminal lobe, a subdomain exists that contains all the contacts shown by mutagenesis to be required for BAG1 recognition. In this study, the subdomain, representing Hsc70 residues 229-309, was cloned and expressed as a separately folded unit. The results of in vitro binding assays demonstrate that this subdomain is sufficient for binding to BAG1. Binding analyses with surface plasmon resonance indicated that the subdomain binds to BAG1 with a 10-fold decrease in equilibrium dissociation constant (K(D) = 22 nM) relative to the intact ATPase domain. This result suggests that the stabilizing contacts for docking of BAG1 to Hsc70 are located in the C-terminal lobe of the ATPase domain. These findings provide new insights into the role of co-chaperones as nucleotide exchange factors.

Microtubule-targeting drugs induce bcl-2 phosphorylation and association with Pin1

Bcl-2 is a critical suppressor of apoptosis that is overproduced in many types of cancer. Phosphorylation of the Bcl-2 protein is induced on serine residues in tumor cells arrested by microtubule-targeting drugs (paclitaxel, vincristine, nocodazole) and has been associated with inactivation of antiapoptotic function through an unknown mechanism. Comparison of a variety of pharmacological inhibitors of serine/threonine-specific protein kinases demonstrated that the cyclin-dependent kinase inhibitor, flavopiridol, selectively blocks Bcl-2 phosphorylation induced by antimicrotubule drugs. Bcl-2 could also be coimmunoprecipitated with the kinase Cdc2 in M-phase-arrested cells, suggesting that Cdc2 may be responsible for phosphorylation of Bcl-2 in cells treated with microtubule-targeting drugs. Examination of several serine-->alanine substitution mutants of Bcl-2 suggested that serine 70 and serine 87 represent major sites of Bcl-2 phosphorylation induced in response to microtubule-targeting drugs. Both these serines are within sequence contexts suitable for proline-directed kinases such as Cdc2. Phosphorylated Bcl-2 protein was discovered to associate in M-phase-arrested cells with Pin1, a mitotic peptidyl prolyl isomerase (PPIase) known to interact with substrates of Cdc2 during mitosis. In contrast, phosphorylation of Bcl-2 induced by microtubule-targeting drugs did not alter its ability to associate with Bcl-2 (homodimerization), Bax, BAG1, or other Bcl-2-binding proteins. Since the region in Bcl-2 containing serine 70 and serine 87 represents a proline-rich loop that has been associated with autorepression of its antiapoptotic activity, the discovery of Pin1 interactions with phosphorylated Bcl-2 raises the possibility that Pin1 alters the conformation of Bcl-2 and thereby modulates its function in cells arrested with antimicrotubule drugs.

The AKT kinase is activated in multiple myeloma tumor cells

Immunohistochemistry (IHC) was performed on archived bone marrow (BM) with a phosphospecific anti-AKT antibody. IHC on 26 BM biopsies from patients with multiple myeloma (MM) demonstrated phospho-AKT staining of malignant plasma cells in a cell membrane-specific pattern, whereas nonmalignant hematopoietic cells did not stain. Preabsorption of the antibody with phosphorylated AKT peptide, but not nonphosphorylated peptide, abrogated staining. Frequency of plasma cell staining in BMs of patients with stage I or smoldering MM was significantly less than that of stage III MM marrows. Plasma cells in 10 patients with monoclonal gammopathy of undetermined significance were not stained by the antibody. To investigate the significance of AKT activation, 2 cell lines initiated from cultures of primary MM cells were also studied. Both demonstrated constitutive AKT activation. Interruption of AKT activation and activity, achieved by either exposure to wortmannin or by ectopic expression of a dominant negative AKT mutant, resulted in inhibition of MM cell growth in vitro. These results indicate that activation of the AKT kinase is a characteristic of MM cells and suggest that AKT activity is important for MM cell expansion.

Molecular chaperone targeting and regulation by BAG family proteins

Regulated changes in protein conformation can have profound effects on protein function, although routine laboratory methods often fail to detect them. The recently discovered BAG-family proteins may operate as bridging molecules that recruit molecular chaperones to target proteins, presumably modulating protein functions through alterations in their conformations, and ultimately affecting diverse cellular behaviours including cell division, migration, differentiation and death. Emerging knowledge about BAG-family proteins indicates that there may be a mechanism for influencing signal transduction through non-covalent post-translational modifications.

Characterization of the 13q14 tumor suppressor locus in CLL: identification of ALT1, an alternative splice variant of the LEU2 gene

Chromosome 13q14 deletions constitute the most common genetic abnormality in chronic lymphocytic leukemia (CLL). To identify the putative tumor suppressor gene targeted by 13q14 genomic loss, we completely sequenced and characterized a segment of 790 kb at 13q14 spanning the minimal region of loss in CLL. Transcribed sequences in the region were identified through database homology searches and exon-prediction analysis. Two-hundred kb at the centromeric end of the sequence contain five CpG islands, three previously identified genes LEU5/RFP2, LEU2, and LEU1, seven of seven EST clusters composed of >10 ESTs, and a large number of predicted exons. Homology searches against the mouse EST database have allowed us to identify a highly conserved alternative first exon of the LEU2 gene, giving rise to a novel transcript, ALT1 (GenBank accession no. AF380424), which originates within a G+C region in the vicinity of the D13S272 marker. Two novel 3' exons of LEU2 were also identified and are present in both LEU2 and ALT1 transcripts. However, we have not identified any mutations in leukemia cases, or alterations in expression of mRNAs in the region, that might directly implicate these mRNAs in the pathology of CLL. The centromeric end of the sequence, where all reported genes are located, contains twice the expected amount of ALU repeats, whereas the telomeric end is LINE1 rich and contains four LINE1 elements longer than 4 kb, including two full-length LINE1 sequences. This feature of the sequence may favor the occurrence of chromosomal rearrangements and may confer instability to the region, resulting in deletions that may inactivate an as yet unidentified tumor suppressor.

Caspases 3 and 9 send a pro-apoptotic signal from synapse to cell body in olfactory receptor neurons

Caspase-9, an initiator caspase, and caspase-3, an effector caspase, have been suggested to mediate the terminal stages of neuronal apoptosis, but little is known about their activation in vivo. We examined temporal and spatial aspects of caspase-9 and -3 activation in olfactory receptor neurons (ORNs) undergoing apoptosis after target removal in vivo. After removal of the olfactory bulb, enhanced expression of procaspase-9 and -3 is observed in ORNs, followed by activation initially at the level of the lesion, then in axons, and only later in the ORN soma. We established the amyloid precursor-like protein-2 (APLP2) as a caspase substrate that is cleaved in an identical spatiotemporal pattern, suggesting its cleavage is the result of retrograde propagation of a pro-apoptotic signal in a caudorostral wave from the synapse through the axon to the ORN cell body. A null mutation in caspase-3 causes a change in axonal patterning indicative of an overall developmental expansion of the ORN population, and mature ORNs of caspase-3 knock-outs do not undergo caspase-dependent terminal dUTP nick end labeling-positive apoptosis after olfactory bulb removal. These results demonstrate that ORNs require caspase-3 activation to undergo normal developmental and mature target-deprived apoptosis. In addition, we demonstrate an axonal site of action for caspase-3 and -9 and show that regulation and activation of caspase-3 and -9 leading to apoptosis is a highly ordered process that occurs initially at the presynaptic level and only later at the cell body after deafferentation.

Cop, a caspase recruitment domain-containing protein and inhibitor of caspase-1 activation processing

The production of bio-active interleukin-1beta (IL-1beta), a pro-inflammatory cytokine, is mediated by activated caspase-1. One of the known molecular mechanisms underlying pro-caspase-1 processing and activation involves binding of the caspase-1 prodomain to a caspase recruitment domain (CARD)-containing serine/threonine kinase known as RIP2/CARDIAK/RICK. We have identified a novel protein, COP (CARD only protein), which has a high degree of sequence identity to the caspase-1 prodomain. COP binds to both RIP2 and the caspase-1 prodomain and inhibits RIP2-induced caspase-1 oligomerization. COP inhibits caspase- 1-induced IL-1beta secretion as well as lipopolysaccharide-induced IL-1beta secretion in transfected cells. Our data indicate that COP can regulate IL-1beta secretion, implying that COP may play a role in down-regulating inflammatory responses analogous to the CARD protein ICEBERG.

Intracellular delivery of proteins with a new lipid-mediated delivery system

There are many very effective methods to introduce transcriptionally active DNA into viable cells but approaches to deliver functional proteins are limited. We have developed a lipid-mediated delivery system that can deliver functional proteins or other bioactive molecules into living cells. This delivery system is composed of a new trifluoroacetylated lipopolyamine (TFA-DODAPL) and dioleoyl phosphatidylethanolamine (DOPE). This cationic formulation successfully delivered antibodies, dextran sulfates, phycobiliproteins, albumin, and enzymes (beta-galactosidase and proteases) into the cytoplasm of numerous adherent and suspension cells. Two systems were used to demonstrate that the proteins were delivered in a functionally active form. First, intracellular beta-galactosidase activity was clearly demonstrated within X-gal-stained cells after TFA-DODAPL:DOPE-mediated delivery of the enzyme. Second, the delivery system mediated delivery of several caspases (caspase 3, caspase 8, and granzyme B) into cultured cell lines and primary cells triggering apoptosis. Mechanistic studies showed that up to 100% of the protein mixed with the lipid formulation was captured into a lipid-protein complex, and up to 50% of the input protein associated with cells. This lipid-mediated transport system makes protein delivery into cultured cells as convenient, effective, and reliable as DNA transfection.

BAG-1M, an isoform of Bcl-2-interacting protein BAG-1, enhances gene expression driven by CMV promoter

BAG-1M, one of the isoforms of BAG-1, was reported to bind to DNA and stimulate general transcription when cells were stressed by heat shock (Zeiner, M., et al., Proc. Natl. Acad. Sci. USA 96, 10194-10199, 1999). Here we show that BAG-1M binds and enhances transcriptional activity of Cytomegalovirus (CMV) early gene promoter under unstressed conditions. This activity is unique to BAG-1M in that other isoforms, BAG-1S and BAG-1L, are much weaker in this activity, although all of the isoforms share common ubiquitin-like domain and BAG domain interacting with Hsp70/Hsc70. Deletion analysis of BAG-1M showed that C-terminal BAG domain is necessary to enhance the CMV promoter activity, suggesting that interaction with Hsp70/Hsc70 proteins may mediate this function. Another mutation in N-terminus, BAG-1M K(2-4)A, lost DNA binding capacity and majority of the promoter-enhancing activity. Our study demonstrates that both N-terminal DNA binding site and C-terminal Hsp70/Hsc70 binding site of BAG-1M play an important role in enhancing the CMV promoter activity.

A combinatorial approach for selectively inducing programmed cell death in human pancreatic cancer cells

Pancreatic cancer is an extremely aggressive neoplasm whose incidence equals its death rate. Despite intensive analysis, the genetic changes that mediate pancreatic cancer development and effective therapies for diminishing the morbidity associated with this disease remain unresolved. Through subtraction hybridization, we have identified a gene associated with induction of irreversible growth arrest, cancer reversion, and terminal differentiation in human melanoma cells, melanoma differentiation associated gene-7 (mda-7). Ectopic expression of mda-7 when using a recombinant adenovirus, Ad.mda-7, results in growth suppression and apoptosis in a broad spectrum of human cancers with diverse genetic defects, without exerting deleterious effects in normal human epithelial or fibroblast cells. Despite the apparently ubiquitous antitumor effects of mda-7, pancreatic carcinoma cells are remarkably refractory to Ad.mda-7 induced growth suppression and apoptosis. In contrast, the combination of Ad.mda-7 with antisense phosphorothioate oligonucleotides, which target the K-ras oncogene (a gene that is mutated in 85 to 95% of pancreatic carcinomas), induces a dramatic suppression in growth and a decrease in cell viability by induction of apoptosis. In mutant K-ras pancreatic carcinoma cells, programmed cell death correlates with expression and an increase, respectively, in MDA-7 and BAX proteins and increases in the ratio of BAX to BCL-2 proteins. Moreover, transfection of mutant K-ras pancreatic carcinoma cells with an antisense K-ras expression vector and infection with Ad.mda-7 inhibits colony formation in vitro and tumorigenesis in vivo in nude mice. These intriguing observations demonstrate that a combinatorial approach, consisting of a cancer-specific apoptosis-inducing gene and an oncogene inactivation strategy, may provide the foundation for developing an effective therapy for pancreatic cancer.

TUCAN, an antiapoptotic caspase-associated recruitment domain family protein overexpressed in cancer

Caspase-associated recruitment domains (CARDs) are protein interaction domains that participate in activation or suppression of CARD-carrying members of the caspase family of apoptosis-inducing proteases. A novel CARD-containing protein was identified that is overexpressed in some types of cancer and that binds and suppresses activation of procaspase-9, which we term TUCAN (tumor-up-regulated CARD-containing antagonist of caspase nine). The CARD domain of TUCAN selectively binds itself and procaspase-9. TUCAN interferes with binding of Apaf1 to procaspase-9 and suppresses caspase activation induced by the Apaf1 activator, cytochrome c. Overexpression of TUCAN in cells by stable or transient transfection inhibits apoptosis and caspase activation induced by Apaf1/caspase-9-dependent stimuli, including Bax, VP16, and staurosporine, but not by Apaf1/caspase-9-independent stimuli, Fas and granzyme B. High levels of endogenous TUCAN protein were detected in several tumor cell lines and in colon cancer specimens, correlating with shorter patient survival. Thus, TUCAN represents a new member of the CARD family that selectively suppresses apoptosis induced via the mitochondrial pathway for caspase activation.