NRAGE induces ß-catenin/Arm O-GlcNAcylation and negatively regulates Wnt signaling.

The Wnt pathway is crucial for animal development, as well as tumor formation. Understanding the regulation of Wnt signaling will help to elucidate the mechanism of the cell cycle, cell differentiation and tumorigenesis. It is generally accepted that in response to Wnt signals, ß-catenin accumulates in the cytoplasm and is imported into the nucleus where it recruits LEF/TCF transcription factors to activate the expression of target genes. In this study, we report that human NRAGE, a neurotrophin receptor p75 (p75NTR) binding protein, markedly suppresses the expression of genes activated by the Wnt pathway. Consistent with this finding, loss of function of NRAGE by RNA interference (RNAi) activates the Wnt pathway. Moreover, NRAGE suppresses the induction of axis duplication by microinjected ß-catenin in Xenopus embryos. To our surprise, NRAGE induces nuclear localization of ß-catenin and increases its DNA binding ability. Further studies reveal that NRAGE leads to the modification of ß-catenin/Arm with O-linked beta-N-acetylglucosamine (O-GlcNAc), and failure of the association between ß-catenin/Arm and pygopus(pygo) protein, which is required for transcriptional activation of Wnt target genes. Therefore, our findings suggest a novel mechanism for regulating Wnt signaling.

MAGED1 is a negative regulator of bone remodeling in mice.

Melanoma antigen family D1 (MAGED1), an important adaptor protein, has been shown to ubiquitously express and play critical roles in many aspects of cellular events and physiological functions. However, its role in bone remodeling remains unknown. We, therefore, analyzed the bone phenotype of Maged1-deficient mice. Maged1-deficient mice displayed a significant osteoporotic phenotype with a marked decrease in bone density and deterioration of trabecular architecture. Histomorphometric analysis demonstrated an increased mineral apposition rate as well as increased osteoclast number and surface in Maged1 knockout mice. At the cellular level, Maged1-deficient osteoblasts exhibited an increased proliferation rate and accelerated differentiation. MAGED1 deficiency also caused a promotion in osteoclastogenesis, and that was attributed to the cell autonomous acceleration of differentiation in osteoclasts and an increased receptor activator of NF-κB ligand/osteoprotegerin ratio, a major index of osteoclastogenesis, in osteoblasts. Thus, we identified MAGED1 as a novel regulator of osteoblastogenesis, osteoclastogenesis, and bone remodeling in a mouse model.

NRAGE promotes cell proliferation by stabilizing PCNA in a ubiquitin-proteasome pathway in esophageal carcinomas.

Neurotrophin receptor-interacting melanoma antigen-encoding gene homolog (NRAGE) is generally recognized as a tumor suppressor as it induces cell apoptosis and suppresses cell metastasis. However, it has recently been reported that NRAGE is overexpressed in lung cancer, melanoma and colon cancer, implicating a complicated role of NRAGE as we have expected. In the study, we aim to elucidate the functional roles and molecular mechanisms of NRAGE in esophageal carcinoma. We found that both NRAGE mRNA and protein were significantly overexpressed in esophageal tumor tissues. Consistently, both in vivo and in vitro analyses demonstrated that knockdown of NRAGE apparently inhibited cell growth, and cell cycle analysis further demonstrated that NRAGE knockdown cells were mainly arrested in G2M cell phase, accompanied with an apparent reduction of S phase. In the process of exploring molecular mechanisms, we found that either knockdown in vitro or knockout in vivo of NRAGE reduced proliferating cell nuclear antigen (PCNA) protein, expression of which could completely rescue the inhibited proliferation in NRAGE defective cells. Furthermore, NRAGE physically interacted with PCNA in esophageal cancer cells through DNA polymerase III subunit, and knockdown of NRAGE facilitated PCNA K48-linked polyubiquitination, leading PCNA to the proteasome-dependent degradation and a ubiquitin-specific protease USP10 was identified to be a key regulator in the process of K48 polyubiquitination in NRAGE-deleted cells. In conclusion, our study highlights a unique role of NRAGE and implies that NRAGE is likely to be an attractive oncotarget in developing novel genetic anticancer therapeutic strategies for esophageal squamous cell carcinomas.

Tomatidine Suppresses the Destructive Behaviors of Fibroblast-Like Synoviocytes and Ameliorates Type II Collagen-Induced Arthritis in Rats.

Fibroblast-like synoviocytes (FLSs) are the prominent non-immune cells in synovium and play a pivotal role in rheumatoid arthritis (RA) pathogenesis. Searching for natural compounds that may suppress the pathological phenotypes of FLSs is important for the development of RA treatment. Tomatidine (Td), a steroidal alkaloid derived from the solanaceae family, has been reported to have anti-inflammatory, anti-tumor and immunomodulatory effects. However, its effect on RA remains unknown. Here, we examined the inhibitory effect of Td on TNFα-induced arthritic FLSs, and subsequently investigated its therapeutic effect on collagen-induced arthritis (CIA) rats. Our results revealed that Td significantly inhibited TNFα-induced proliferation and migration of arthritic FLSs. In addition, we found that Td treatment could efficaciously ameliorate synovial inflammation and joint destruction of rats with CIA. Both in vitro and in vivo studies showed that Td significantly suppressed the production of pro-inflammatory cytokines including IL-1ß, IL-6 and TNFα, and downregulated the expression of MMP-9 and RANKL. Further molecular mechanism studies revealed that the inhibitory effect of Td on RA might attribute to the decreased activations of MAPKs (ERK and JNK) and NF-κB. These findings provide evidence that Td has the potential to be developed into a complementary or alternative agent for RA therapy.

NRAGE is a negative regulator of nerve growth factor-stimulated neurite outgrowth in PC12 cells mediated through TrkA-ERK signaling.

NRAGE, also denominated as MAGE-D1 or Dlxin-1, is firstly identified as a molecule interacting with NGF low affinity receptor p75NTR. It facilitates cell cycle arrest and NGF-dependent neuronal apoptosis. Here we report that NRAGE is downregulated while p75NTR is upregulated during the process of NGF-induced neuronal differentiation of PC12 cells. Knockdown of NRAGE by RNA interference accelerates NGF-mediated neurite outgrowth. In addition, in the NRAGE-suppressed cells, NGF-induced ERK activation is increased and this activation is MEK-dependent. Conversely, NRAGE overexpression significantly represses NGF-induced ERK activation. Further studies revealed that NRAGE downregulates TrkA expression through a post-transcriptional manner and thereby blocks NGF-induced TrkA phosphrylation at tyrosine-490. Altogether, these data indicate for the first time that NRAGE is an endogenous inhibitor for NGF-induced neuronal differentiation of PC12 cells by regulating TrkA-ERK signaling.

NRAGE suppresses metastasis of melanoma and pancreatic cancer in vitro and in vivo.

We previously reported that human NRAGE could significantly alter the cellular skeleton and inhibit cell-cell adhesion, suggesting that human NRGAE play a potential role in cellular motility. Here, we report overexpression of human NRAGE in PANC-1 and B16-Bl6 cells could significantly suppress the metastasis of these cells in vitro and in vivo. Consistently, PANC-1 with stable silencing of NRAGE by RNA interference, exhibits a more metastatic phenotype than the native cell. Expression of epithelial proteins, including E-cadherin and beta-catenin is down regulated in siRNA-NRAGE PANC-1 cells. Further studies find that overexpression of human NRAGE suppresses the mRNA expression and activity of MMP2 significantly. Summary, our studies indicate for the first time that NRAGE could suppress metastasis of melanoma and pancreatic cancer probably through downregulation of MMP-2.

Knockdown of c-Met by adenovirus-delivered small interfering RNA inhibits hepatocellular carcinoma growth in vitro and in vivo.

c-Met is highly expressed and constitutively activated in various human tumors. We employed adenovirus-mediated RNA interference technique to knock down c-Met expression in hepatocellular carcinoma cells and observed its effects on hepatocellular carcinoma cell growth in vitro and in vivo. Among the five hepatocellular carcinoma and one normal human liver cell lines we analyzed, c-Met was highly expressed and constitutively tyrosine phosphorylated in only MHCC97-L and HCCLM3 hepatocellular carcinoma cells. Knockdown of c-Met could inhibit MHCC97-L cells proliferation by arresting cells at G0-G1 phase. Soft agar colony formation assay indicated that the colony forming ability of MHCC97-L cells decreased by approximately 70% after adenovirus AdH1-small interfering RNA (siRNA)/met infection. In vivo experiments showed that adenovirus AdH1-siRNA/met inhibited the tumorigenicity of MHCC97-L cells and significantly suppressed tumor growth when injected directly into tumors. These results suggest that knockdown of c-Met by adenovirus-delivered siRNA may be a potential therapeutic strategy for treatment of hepatocellular carcinoma in which c-Met is overexpressed.

Protective effect of pyrroloquinoline quinine on ultraviolet A irradiation-induced human dermal fibroblast senescence in vitro proceeds via the anti-apoptotic sirtuin 1/nuclear factor-derived erythroid 2-related factor 2/heme oxygenase 1 pathway.

The aim of the present study was to determine whether pyrroloquinoline quinine (PQQ) exerts a protective effect on ultraviolet A (UVA) irradiation­induced senescence in human dermal fibroblasts (HDFs) and to elucidate its mechanism of action in vitro. A senescence model was constructed as follows: HDFs (1x10(4)­1x10(6)) were cultured in a six­well plate in vitro and then exposed to UVA irradiation at a dosage of 9 J/cm2. Various concentrations of PQQ (50, 100 and 200 ng/ml) were added to the culture medium 24 h prior to UVA exposure. Following 72 h of irradiation, senescence­associated ß­galactosidase staining was performed in order to evaluate the senescence state. Furthermore, mRNA expression of the senescence marker genes matrix­metalloprotease (MMP)1 and MMP3 was determined using reverse transcription quantitative polymerase chain reaction. Protein expression of sirtuin (SIRT)1, SIRT6, nuclear factor erythroid 2­related factor 2 (Nrf2) and heme oxygenase 1 (HO­1) were detected using western blot analysis. The results showed that the percentage of cells stained by X­gal following 9 J/cm2 UVA irradiation was markedly increased compared with that of the control group (53 and 8%, respectively), while 50 ng/ml PQQ attenuated the ratio of positive staining compared with that of the UVA­only cells (29 vs. 53%, respectively). Expression of fibroblast senescence marker genes MMP1 and MMP3 was decreased in cells treated with UVA and 50 ng/ml PQQ compared with that of cells in the UVA­only group. Western blot analysis revealed significant effects of PQQ on SIRT1 and SIRT6. Nrf2 and HO­1 exbibited mild changes with the same trend when treated with or without UVA and PQQ. In conclusion, the results of the present study showed that pyrroloquinoline quinine may have a protective effect on UVA irradiation­induced HDF aging, which may be associated with the anti­apoptotic SIRT1/Nrf2/HO­1 pathway as well as SIRT6 signaling.

The association of calmodulin with central spindle regulates the initiation of cytokinesis in HeLa cells.

Calmodulin is a major cytoplasmic calcium receptor that performs multiple functions in the cell including cytokinesis. Central spindle appears between separating chromatin masses after metaphase-anaphase transition. The interaction of microtubules from central spindle with cell cortex regulates the cleavage furrow formation. In this paper, we use green fluorescence protein (GFP)-tagged calmodulin as a living cell probe to examine the detailed dynamic redistribution and co-localization of calmodulin with central spindle during cytokinesis and the function of this distribution pattern in a tripolar HeLa cell model. We found that calmodulin is associated with spindle microtubules during mitosis and begins to aggregate with central spindle after anaphase initiation. The absence of either central spindle or central spindle-distributed calmodulin is correlated with the defect in the formation of cleavage furrow, where contractile ring-distributed CaM is also extinct. Further analysis found that both the assembly of central spindle and the formation of cleavage furrow are affected by the W7 treatment. The microtubule density of central spindle was decreased after the treatment. Only less than 10% of the synchronized cells enter cytokinesis when treated with 25 microM W7, and the completion time of furrow regression is also delayed from 10 min to at least 40 min. It is suggested that calmodulin plays a significant role in cytokinesis including furrow formation and regression, The understanding of the interaction between calmodulin and microtubules may give us insight into the mechanism through which calmodulin regulates cytokinesis.

hNRAGE, a human neurotrophin receptor interacting MAGE homologue, regulates p53 transcriptional activity and inhibits cell proliferation.

hNRAGE, a neurotrophin receptor p75 interacting MAGE homologue, is cloned from a human placenta cDNA library. hNRAGE can inhibit the colony formation of and arrest cell proliferation at the G1/S and G2/M stages in hNRAGE overexpressing cells. Interestingly, hNRAGE also increases the p53 protein level as well as its phosphorylation (Ser392). Further studies demonstrated that hNRAGE does not affect the proliferation of mouse p53-/- embryonic fibroblasts, suggesting that p53 function is required for hNRAGE induced cell cycle arrest. Moreover, the cell cycle inhibiting protein p21(WAF) is induced by hNRAGE in a p53 dependent manner. The data provide original evidence that hNRAGE arrests cell growth through a p53 dependent pathway.

[A DNA vector-based RNAi technology to inhibit the activity of the telomerase of cell line HCCLM3].

OBJECTIVE: To develop a DNA vector-based RNA interference (RNAi) technology that inhibits the activity of the telomerase of the hepatocellular carcinoma cell line HCCLM3 in order to suppress the proliferation of the cells. METHODS: Hepatocellular carcinoma cells of the line HCCLM3 were cultured. mRNA interfering double-stranded DNA vector PSG-AS targeting the mRNA of human telomerase reverse transcriptase (hTERT) and the control vector PSG-CTR were constructed respectively, and then were transfected into the HCCLM3 cells. The expression of hTERT of the transfected cells was determined by Western blotting and the activity of telomerase was determined by telomeric repeat amplification-ELISA (TRAP-ELISA). Flow cytometry was used to detect the apoptosis of transfected cells and MTS method was used to measure the growth curve of the cells so as to observe the effect of the PSG-AS on the proliferation of HCCLM3 cell. RESULTS: TRAP-ELISA showed that the inhibition rate of PSG-AS on the telomerase activity was 76%. The apoptotic rate of the PSG-AS group was significantly higher than that of the PSG-CTR group (t = 11.48, P < 0.001). Western blotting showed a remarkable inhibition of hTERT protein in the PSG-AS group. CONCLUSION: Capable of suppressing the hTERT expression and the activity of telomerase, RNA interfering technology can be applied to treatment of tumors.

Ror2-Src signaling in metastasis of mouse melanoma cells is inhibited by NRAGE.

The receptor tyrosine kinase (RTK) Ror2 plays important roles in developmental morphogenesis and mediates the filopodia formation in Wnt5a-induced cell migration. However, the function of Ror2 in noncanonical Wnt signaling resulting in cancer metastasis is largely unknown. Here, we show that Ror2 expression is higher in the highly metastatic murine B16-BL6 melanoma cells than in the low metastatic variant B16 cells. Overexpression of Ror2 increases the metastasis ability of B16 cells, and knockdown of Ror2 reduces the migration ability of B16-BL6 cells. Furthermore, the inhibition of Src kinase activity is critical for the Ror2-mediated cell migration upon Wnt5a treatment. The C-terminus of Ror2, which is deleted in brachydactyly type B (BDB), is essential for the mutual interaction with the SH1 domain of Src. Intriguingly, the Neurotrophin receptor-interacting MAGE homologue (NRAGE), which, as we previously reported, can remodel the cellular skeleton and inhibit cell-cell adhesion and metastasis of melanoma and pancreatic cancer, sharply blocks the interaction between Src and Ror2 and inhibits Ror2-mediated B16 cell migration by decreasing the activity of Src and focal adhesion kinase (FAK). Our data show that Ror2 is a potential factor in the tumorigenesis and metastasis in a Src-dependent manner that is negatively regulated by NRAGE.

beta-Arrestins facilitate ubiquitin-dependent degradation of apoptosis signal-regulating kinase 1 (ASK1) and attenuate H2O2-induced apoptosis.

beta-Arrestins are ubiquitously expressed proteins that play important roles in receptor desensitization, endocytosis, proteosomal degradation, apoptosis and signaling. It has been reported that beta-Arrestin2 acts as a scaffold by directly interacting with the JNK3 isoform and recruiting MKK4 and the apoptosis-signaling kinase-1 (ASK1). Here, we report a novel function of beta-Arrestins in regulating H(2)O(2)-induced apoptosis. Our study demonstrates that beta-Arrestins physically associate with C-terminal domain of ASK1, and moreover, both over-expression and RNA interference (RNAi) experiments indicate that beta-Arrestins down-regulate ASK1 protein. In detail, beta-Arrestin-induced reduction of ASK1 protein is due to ubiquitination and proteasome-dependent degradation of ASK1 in response to association of beta-Arrestins and ASK1. Upon H(2)O(2) stimulation, the protein binding between beta-Arrestins and ASK1 increases and ASK1 degradation is expedited. In consequence, beta-Arrestins prevent ASK1-JNK signaling and as a result attenuate H(2)O(2)-induced apoptosis. Structurally, C-terminal domain of ASK1 is essential for beta-Arrestins and ASK1 association. We also found that CHIP is required for beta-Arrestins-induced ASK1 degradation, which suggested that beta-Arrestins function as a scaffold of ASK1 and CHIP, leading to CHIP-mediated ASK1 degradation. All these findings indicate that beta-Arrestins play a negative regulatory role in H(2)O(2)-induced apoptosis signaling through associating with ASK1 and CHIP and facilitating ASK1 degradation, which provides a new insight for analyzing the effects of beta-Arrestins on protecting cells from oxidative stress-induced apoptosis.

[Construction of recombinant adenovirus vector of hNRAGE gene and its effect on cell cycle of 293 cells].

AIM: To construct the recombinant adenovirus vector of hNRAGE gene and study its effect on the cell cycle of 293 cells. METHODS: hNRAGE gene was amplified by PCR and subcloned into the shuttle vector pAdTrack-CMV to construct a shuttle plasmid pAdTrack-CMV/hNRAGE. After sequencing, it was linearized with Pme I and cotransformed into E.coli BJ5183 cells with adenovirus genomic plasmid pAdEasy-1 by electroporation to achieve homologous recombination. After being digested with Pac I, the DNA of identified recombinant plasmid was transfected into QBI-293A cells by calcium phosphate transfection to package adenovirus. With the use of GFP gene expression in pAdTrack-CMV, the appearance of Ad-hNRAGE was observed and its concentration was measured. The expression of the target gene was detected by Western blot and its effect on cell cycle of 293 cells was examined by MTT colorimetry and FCM. RESULTS: The Ad-hNRAGE was successfully constructed and the expression of hNRAGE gene in 293 cells was proved by Western blot. After harvesting the virus particles, the concentration of Ad-hNRAGE was about 6.5x10(9) Ad/microL. The transfection of Ad-hNRAGE resulted in significantly lower proliferative rate of 293 cells compared with untransfected ones, with cell number of G0-G1 and G2-M phase increasing and that of S phase decreasing. CONCLUSION: hNRAGE gene can inhibit the growth of 293 cells.

Human NRAGE disrupts E-cadherin/beta-catenin regulated homotypic cell-cell adhesion.

Human NRAGE, a neurotrophin receptor p75 interaction MAGE homologue, confers NGF-dependent apoptosis of neuronal cells by inducing caspase activation through the JNK-c-jun-dependent pathway and arrests cell growth through the p53-dependent pathway. Our findings showed that human NRAGE could significantly alter the cell skeleton and inhibit homotypic cell-cell adhesion in U2OS cells. With further experiments, we revealed that human NRAGE disrupts colocalization of the E-cadherin/beta-catenin complex and translocates beta-catenin from the cell membrane into the cytoplasm and nucleus. Synchronously, NRAGE also decreases the total protein level of beta-catenin, especially when NRAGE expresses for a long time. More importantly, knock down of NRAGE by RNA interference in PANC-1 cell significantly reinforces E-cadherin/beta-catenin homotypic cell adhesion. The data demonstrate the importance of human NRAGE in homotypic cell-to-cell adhesion and illuminate the mechanism of human NRAGE in the process of inhibition of cell adhesion, which suggests that human NRGAE plays a potential negative role in cancer metastasis.