Anti-apoptotic protein BRE/BRCC45 attenuates apoptosis through maintaining the expression of caspase inhibitor XIAP in mouse Lewis lung carcinoma D122 cells.

Brain and Reproductive Organ Expressed (BRE), or BRCC45, is a death receptor-associated antiapoptotic protein, which is also involved in DNA-damage repair, and K63-specific deubiquitination. BRE overexpression attenuates both death receptor- and stress-induced apoptosis, promotes experimental tumor growth, and is associated with human hepatocellular and esophageal carcinoma. How BRE mediates its antiapoptotic function is unknown. Here we report based on the use of a mouse Lewis lung carcinoma cell line D122 that BRE has an essential role in maintaining the cellular protein level of XIAP, which is the most potent endogenous inhibitor of the caspases functioning in both extrinsic and intrinsic apoptosis. shRNA-mediated exhaustive depletion of BRE sensitized D122 cells to apoptosis induced not only by etopoxide, but also by TNF-α even in the absence of cycloheximide, which blocks the synthesis of antiapoptotic proteins by TNF-α-activated NF-κB pathway. In BRE-depleted cells, protein level of XIAP was downregulated, but not the levels of other antiapoptotic proteins, cIAP-1, 2, and cFLIP, regulated by the same NF-κB pathway. Reconstitution of BRE restored XIAP levels and increased resistance to apoptosis. XIAP mRNA level was also reduced in the BRE-depleted cells, but the level of reduction was less profound than that of the protein level. However, BRE could not delay protein turnover of XIAP. Depletion of BRE also increased tumor cell apoptosis, and decreased both local and metastatic tumor growth. Taken together, these findings indicate that BRE and its XIAP-sustaining mechanism could represent novel targets for anti-cancer therapy.

Promyelocytic leukemia (PML) protein plays important roles in regulating cell adhesion, morphology, proliferation and migration.

PML protein plays important roles in regulating cellular homeostasis. It forms PML nuclear bodies (PML-NBs) that act like nuclear relay stations and participate in many cellular functions. In this study, we have examined the proteome of mouse embryonic fibroblasts (MEFs) derived from normal (PML(+/+)) and PML knockout (PML(-/-)) mice. The aim was to identify proteins that were differentially expressed when MEFs were incapable of producing PML. Using comparative proteomics, total protein were extracted from PML(-/-) and PML(+/+) MEFs, resolved by two dimensional electrophoresis (2-DE) gels and the differentially expressed proteins identified by LC-ESI-MS/MS. Nine proteins (PML, NDRG1, CACYBP, CFL1, RSU1, TRIO, CTRO, ANXA4 and UBE2M) were determined to be down-regulated in PML(-/-) MEFs. In contrast, ten proteins (CIAPIN1, FAM50A, SUMO2 HSPB1 NSFL1C, PCBP2, YWHAG, STMN1, TPD52L2 and PDAP1) were found up-regulated. Many of these differentially expressed proteins play crucial roles in cell adhesion, migration, morphology and cytokinesis. The protein profiles explain why PML(-/-) and PML(+/+) MEFs were morphologically different. In addition, we demonstrated PML(-/-) MEFs were less adhesive, proliferated more extensively and migrated significantly slower than PML(+/+) MEFs. NDRG1, a protein that was down-regulated in PML(-/-) MEFs, was selected for further investigation. We determined that silencing NDRG1expression in PML(+/+) MEFs increased cell proliferation and inhibited PML expression. Since NDRG expression was suppressed in PML(-/-) MEFs, this may explain why these cells proliferate more extensively than PML(+/+) MEFs. Furthermore, silencing NDRG1expression also impaired TGF-ß1 signaling by inhibiting SMAD3 phosphorylation.

Cardiac telocytes were decreased during myocardial infarction and their therapeutic effects for ischaemic heart in rat.

Recently, cardiac telocytes were found in the myocardium. However, the functional role of cardiac telocytes and possible changes in the cardiac telocyte population during myocardial infarction in the myocardium are not known. In this study, the role of the recently identified cardiac telocytes in myocardial infarction (MI) was investigated. Cardiac telocytes were distributed longitudinally and within the cross network of the myocardium, which was impaired during MI. Cardiac telocytes in the infarction zone were undetectable from approximately 4 days to 4 weeks after an experimental coronary occlusion was used to induce MI. Although cardiac telocytes in the non-ischaemic area of the ischaemic heart experienced cell death, the cell density increased approximately 2 weeks after experimental coronary occlusion. The cell density was then maintained at a level similar to that observed 1-4 days after left anterior descending coronary artery (LAD)-ligation, but was still lower than normal after 2 weeks. We also found that simultaneous transplantation of cardiac telocytes in the infarcted and border zones of the heart decreased the infarction size and improved myocardial function. These data indicate that cardiac telocytes, their secreted factors and microvesicles, and the microenvironment may be structurally and functionally important for maintenance of the physiological integrity of the myocardium. Rebuilding the cardiac telocyte network in the infarcted zone following MI may be beneficial for functional regeneration of the infarcted myocardium.

BDNF-mediated migration of cardiac microvascular endothelial cells is impaired during ageing.

This study indicates that brain-derived neurotrophic factor (BDNF) can promote young cardiac microvascular endothelial cells (CMECs) to migrate via the activation of the BDNF-TrkB-FL-PI3K/Akt pathway, which may benefit angiogenesis after myocardial infarction (MI). However, the ageing of CMECs led to changes in the expression of receptor Trk isoforms in that among the three isoforms (TrkB-FL, TrkB-T1 and TrkB-T2), only one of its truncated isoforms, TrkB-T1, continued to be expressed, which leads to the dysfunction of its ligand, a decrease in the migration of CMECs and increased injury in ageing hearts. This shift in receptor isoforms in aged CMECs, together with changes in the ageing microenvironment, might predispose ageing hearts to decreased angiogenic potential and increased cardiac pathology.

Gene expression profiling of CD3gamma, delta, epsilon, and zeta chains in CD4(+) and CD8(+) T cells from human umbilical cord blood.

In order to elucidate the feature of T-cell immune status in umbilical cord blood (CB) from humans, the expression levels of CD3gamma, delta, epsilon, and zeta chain genes in CD4(+) and CD8(+) T cells of CB were analysed by real-time PCR. CD4(+) and CD8(+) T cells sorted from 12 cases of CB and 10 peripheral blood (PB) samples from healthy adults were used in the study. The beta2-microglobulin gene was used as an endogenous reference, and the evaluations of mRNA expression level of each CD3 gene were used by the 2(-DeltaC(t)) x 100% method. In CD4(+) T cells, the expression levels of CD3gamma, delta, and zeta genes (16.54+/-6.49, 3.53+/-1.15, and 5.48+/-1.10%) from CB were significantly higher than those from PB (P=0.001, P=0.017, and P=0.000, respectively). Higher expression levels of CD3delta and zeta genes (3.43+/-1.19 and 5.24+/-1.42%) in CD8(+) T cells from CB were found than those from PB (P=0.000 and P=0.004). Moreover, the expression level of CD3epsilon gene in CD4(+) T cells from CB (13.29+/-5.72%) was significantly different from that in CD8(+) T cells (7.81+/-4.72%, P=0.018). Thus, the expression pattern of four CD3 genes were gamma>epsilon>zeta>delta in both CD4(+) and CD8(+) T cells from CB, while similar expression pattern was found in CD8(+) T cells from PB samples. In contrast, the expression pattern was presented as epsilon>gamma>zeta>delta in CD4(+) T cells from PB. In conclusion, the present study characterized the expression pattern of CD3gamma, delta, epsilon, and zeta chain genes in CD4(+) and CD8(+) T cells from CB, which might be very useful for further understanding the feature of T-cell immune status in umbilical cord blood. Higher expression of CD3 genes in CD4(+) T cells might relate to the strong ability of activation of TCR-mediated signals, and suggests that this is one of the features responsible for the low allo-reactivity of CB T cells.

Differential expression of a novel gene BRE (TNFRSF1A modulator/BRCC45) in response to stress and biological signals.

Stress-responsive genes play critical roles in many biological functions that includes apoptosis, survival, differentiation and regeneration. We have identified a novel stress-responsive gene called BRE which interacts with TNF-receptor-1 and blocks the apoptotic effect of TNF-alpha. BRE enhances tumor growth in vivo and is up-regulated in hepatocellular and esophageal carcinomas. BRE also regulates the ubiquitination of the DNA repair complex BRCC, and the synthesis of steroid hormones. Here, we examined BRE-mRNA in cells after treatments with UV and ionizing radiation (IR). UV and IR treatment alone suppressed BRE-mRNA levels by more than 90% at 24 h, while hydroxyurea, fluorodeoxyuridine, aphidicolin, known inhibitors of S-phase DNA synthesis, had no significant effect. BRE protein expression was unaltered in cells treated with TNF-alpha, Interleukin-1 and Dexamethasone, while a threefold increase was observed following chorionic gonadotropin exposure. Although BRE plays a regulatory role in many different pathways, yet its expression is apparently under very stringent control.

TRGV and TRDV repertoire distribution and clonality of T cells from umbilical cord blood.

Umbilical cord blood (CB) has been used as a valuable source of hematopoietic stem cells for allogeneic transplantation, specific CTL response and immunotherapy for decades. We previously analyzed the distribution and clonality of T-cell receptor alpha and beta variable region (TRAV) and (TRBV) of the subfamily T cell receptors in T cells from umbilical cord blood. Recent data indicated that gammadelta(+) T cells may play an important role in mediating the graft versus leukemia effect after stem cells transplantation and in anti-cancer response. In order to further characterize the repertoire of CB T-cells, the frequency of alphabeta(+) and gammadelta(+) T cells were examined in CB by FACS. The CDR3 size of 4 TRGV and 8 TRDV subfamily genes were analyzed in mononuclear cells (MCs) from 16 CB samples, using RT-PCR and genescan technique. To determine the expression level of TRGV subfamily genes, we performed quantitative analysis of TRGVI-III subfamilies by real-time PCR. Low percentage of CD3(+)TCRgammadelta(+) cells was observed in CB. The frequency of expression in TRGVI, TRGVII and TRGVIII in CBMCs was 93.75%, 81.25% and 56.25%, respectively. The mean value of the number of expressed TRDV subfamilies in CBMCs is higher than that from adult peripheral blood (PB) group. The frequently expressed members in CB were TRDV1 (100%), TRDV2 (93.75%), TRDV8 (93.75%) and TRDV3 (81.25%), respectively. The frequencies of TRDV5 and TRDV8 in CBMCs were significantly higher than those from PBMCs. Most of the PCR products of TRGV and TRDV subfamilies from 10 CB samples displayed polyclonal rearrangement pattern, whereas one or two PCR products from 6 CB samples showed oligoclonality or biclonality. In contrast, PCR products from 9 of 10 adult healthy controls contained at least an oligoclonal peak in different TRGV or TRDV subfamilies respectively. The pattern of TRGV subfamily expression level in CBMCs was TRGVI>TRGVIII>TRGVII, and in contrast, TRGVII>TRGVI>TRGVIII was found in PBMCs. In conclusion, our results indicate polyclonal and more diverse TRDV segment usage in CB gammadelta(+) T-cells. The pattern of TRGV expression levels in CB T cells was found to be quite different from the one in PB T cells. These findings are apparently the first report regarding the repression pattern of TRGV repertoire in CB. It also provides a detailed profile of the global TRGV and TRDV repertoire and TRGVI-III expression levels in cord blood T cells in Chinese subjects. The biological significance of the differences observed between CB and PB is at present obscure. However, this study will definitively contribute to understand the cellular immune features better and to exploit more efficiently the therapeutic potentials of CB.

Comparative proteomic analysis reveals a function of the novel death receptor-associated protein BRE in the regulation of prohibitin and p53 expression and proliferation.

The brain and reproductive organ expressed (BRE) gene encodes a highly conserved stress-modulating protein. To gain further insight into the function of this gene, we used comparative proteomics to investigate the protein profiles of C2C12 and D122 cells resulting from small interfering RNA (siRNA)-mediated silencing as well as overexpression of BRE. Silencing of BRE in C2C12 cells, using siRNA, resulted in up-regulated Akt-3 and carbonic anhydrase III expression, while the 26S proteasome regulatory subunit S14 and prohibitin were down-regulated. Prohibitin is a potential tumour suppressor gene, which can directly interact with p53. We found that cell proliferation was significantly increased after knockdown of BRE, concomitant with reduced p53 and prohibitin expression. In contrast, we observed decreased proliferation and up-regulation of p53 and prohibitin when BRE was overexpressed in the D122 cell line. In total, five proteins were found to be up-regulated after BRE over-expression. The majority of these proteins can target or crosstalk with NF-kappaB, which plays a central role in regulating cell proliferation, differentiation and survival. Our results establish a crucial role for BRE in the regulation of key proteins of the cellular stress-response machinery and provide an explanation for the multifunctional nature of BRE.

BRE enhances in vivo growth of tumor cells.

Human BRE, a death receptor-associating intracellular protein, attenuates apoptotic response of human and mouse tumor cell lines to death receptor stimuli in vitro. In this report, we addressed whether the in vitro antiapoptotic effect of BRE could impact on tumor growth in vivo. We have shown that the mouse Lewis lung carcinoma D122 stable transfectants of human BRE expression vector developed into local tumor significantly faster than the stable transfectants of empty vector and parental D122, in both the syngeneic C57BL/6 host and nude mice. In vitro growth of the BRE stable transfectants was, however, not accelerated. No significant difference in metastasis between the transfectants and the parental D122 was detected. Thus, overexpression of BRE promotes local tumor growth but not metastasis. We conclude that the enhanced tumor growth is more likely due to the antiapoptotic activity of BRE than any direct effect of the protein on cell proliferation.

A death receptor-associated anti-apoptotic protein, BRE, inhibits mitochondrial apoptotic pathway.

BRE, brain and reproductive organ-expressed protein, was found previously to bind the intracellular juxtamembrane domain of a ubiquitous death receptor, tumor necrosis factor receptor 1 (TNF-R1), and to down-regulate TNF-alpha-induced activation of NF-kappaB. Here we show that BRE also binds to another death receptor, Fas, and upon overexpression conferred resistance to apoptosis induced by TNF-alpha, anti-Fas agonist antibody, cycloheximide, and a variety of stress-related stimuli. However, down-regulation of the endogenous BRE by small interfering RNA increased apoptosis to TNF-alpha, but nottoetoposide, indicating that the physiological antiapoptotic role of this protein is specific to death receptor-mediated apoptosis. We further demonstrate that BRE mediates antiapoptosis by inhibiting the mitochondrial apoptotic machinery but without translocation to the mitochondria or nucleus or down-regulation of the cellular level of truncated Bid. Dissociation of BRE rapidly from TNF-R1, but not from Fas, upon receptor ligation suggests that this protein interacts with the death inducing signaling complex during apoptotic induction. Increased association of BREwith phosphorylated, sumoylated, and ubiquitinated proteins after death receptor stimulation was also detected. We conclude that in contrast to the truncated Bid that integrates mitochondrial apoptosis to death receptor-triggered apoptotic cascade, BRE inhibits the integration. We propose that BRE inhibits, by ubiquitination-like activity, components in or proximal to the death-inducing signaling complexes that are necessary for activation of the mitochondria.

Expression of a conserved mouse stress-modulating gene, Bre: comparison with the human ortholog.

Mouse Bre, an evolutionarily conserved stress-modulating gene, like its human counterpart, is expressed in multiple alternative transcripts. The main transcript, which is ubiquitously expressed, encodes a protein that binds tumor necrosis factor receptor 1 (TNF-R1) and downregulates TNF-induced activation of NF-kappaB. Alternative splicing of mouse Bre occurs only at the 5' region of the gene, generating either nonfunctional transcripts or transcripts that can encode putative protein isoforms differ at the N-terminal sequence. In contrast, alternative splicing of human BRE occurs at either or both ends of the gene; only the 3' alternative splicing can generate functional transcripts that encode putative protein isoforms differ at the C-terminus, occurrence of the 5' alternative splicing only results in forming nonfunctional transcripts. Unlike the human BRE alternative transcripts which are coexpressed at considerable levels with the main transcript, the mouse counterparts are expressed in a restricted pattern and generally in low abundance except in the heart. Both species, however, share a type of Bre alternative transcripts generated by cryptic splicing at a nonstandard, noncanonical acceptor site. Thus, a highly conserved gene in two species can generate alternative transcripts different in both of the sequence structure and expression pattern, as well as a similar class of transcripts resulting from unconventional transcript processing.