Tyrosine-phosphorylated DNER sensitizes insulin signaling in hepatic gluconeogenesis by inducing proteasomal degradation of TRB3

OBJECTIVE

Hepatic insulin resistance, which leads to increased hepatic gluconeogenesis, is a major contributor to fasting hyperglycemia in type 2 diabetes mellitus (T2DM). However, the mechanism of impaired insulin-dependent suppression of hepatic gluconeogenesis remains elusive. Delta/Notch-like epidermal growth factor (EGF)-related receptor (DNER), firstly described as a neuron-specific Notch ligand, has been recently identified as a susceptibility gene for T2DM through genome-wide association studies. We herein investigated whether DNER regulates hepatic gluconeogenesis and whether this is mediated by enhanced insulin signaling.

METHODS

The association between DNER, tribbles homolog 3 (TRB3) and Akt signaling was evaluated in C57BL/6J, ob/ob and db/db mice by western blot analysis. DNER loss-of-function and gain-of-function in hepatic gluconeogenesis were analyzed by western blot analysis, quantitative real-time PCR, glucose uptake and output assay in AML-12 cells and partially validated in primary mouse hepatocytes. Hepatic DNER knockdown mice were generated by tail vein injection of adenovirus to confirm the effects of DNER in vivo. The interaction between DNER and TRB3 was investigated by rescue experiments, cycloheximide chase analysis, co-immunoprecipitation and immunofluorescence. The potential insulin-stimulated phosphorylation sites of DNER were determined by co-immunoprecipitation, LC-MS/MS analysis and site-specific mutagenesis.

RESULTS

Here we show that DNER enhanced hepatic insulin signaling in gluconeogenesis by inhibiting TRB3, an endogenous Akt inhibitor, through the ubiquitin-proteasome degradation pathway. In AML-12 hepatocytes, insulin-stimulated activation of Akt and suppression of gluconeogenesis are attenuated by DNER knockdown, but potentiated by DNER over-expression. In C57BL/6J mice, hepatic DNER knockdown is accompanied by impaired glucose and pyruvate tolerance. Furthermore, the in vitro effects of DNER knockdown or over-expression on both Akt activity and hepatic gluconeogenesis can be rescued by TRB3 knockdown or over-expression, respectively. In response to insulin stimulation, DNER interacted directly with insulin receptor and was phosphorylated at Tyr677. This site-specific phosphorylation is essential for DNER to upregulate Akt activity and then downregulate G6Pase and PEPCK expression, by interacting with TRB3 directly and inducing TRB3 proteasome-dependent degradation.

CONCLUSIONS

Taken together, the crosstalk between insulin-Akt and DNER-TRB3 pathways represents a previously unrecognized mechanism by which insulin regulates hepatic gluconeogenesis.

Favorable Outcomes in a Case of Non-paraneoplastic DNER Ataxia Treated with Immunotherapy

Anti-DNER antibody is associated with paraneoplastic cerebellar degeneration (PCD) and Hodgkin's disease (HD). However, recent studies reported cases absence of HD and that non-tumor anti-DNER antibody-associated ataxia was not well characterized. We present a case of acute cerebellar ataxia and nystagmus with detected anti-DNER antibody. Brain magnetic resonance imaging (MRI) showed cerebellar atrophy. High titer of anti-DNER antibody was detected in CSF and serum. Positron emission tomography (PET) scanning was unremarkable at a 10-month follow up. The patient improved significantly after immunosuppressive therapy with intravenous steroids, immunoglobulin followed by rituximab. Our study suggest that the presence of such anti-neuronal antibodies might not come along with malignancy and that early onset non-tumor patients are more likely to have a better outcome after immunotherapy. Early diagnosis and timely immunosuppressive therapy may prove beneficial for these patients.

Delta/Notch-like Epidermal Growth Factor-Related Receptor (DNER), a Potential Prognostic Marker of Gastric Cancer Regulates Cell Survival and Cell Cycle Progression

Upregulation of the expression of Delta/notch-like epidermal growth factor-related receptor (DNER) and its oncogenic role have been reported in several cancers, including gastric, breast, and prostate cancers. This study aimed to investigate the oncogenic role of DNER and the mechanisms behind its oncogenic role in gastric cancer. Analysis of the RNASeq data of gastric cancer tissues obtained from the TCGA database revealed that the expression of DNER was associated with the pathology of advanced gastric cancer and the prognosis of patients. DNER expression was increased upon stem cell-enriching cancer spheroid culture. Knockdown of DNER expression inhibited cell proliferation and invasion, induced apoptosis, enhanced chemosensitivity, and decreased spheroid formation of SNU-638 gastric cancer cells. DNER silencing elevated the expression of p53, p21^cip/waf, and p27, and increased G₁ phase cells at the expense of S phase cells. Knockdown of p21^cip/waf expression in the DNER-silenced cells partially restored cell viability and S phase progression. DNER silencing also induced the apoptosis of SNU-638 cells. While both cleaved caspases-8 and 9 were detected in adherent cells, only cleaved caspase-8 was found to have increased in spheroid-cultured cells, suggesting a distinct activation pattern of caspase activation depending on the growth condition. Knockdown of p53 expression rescued the DNER-silenced cells from apoptosis and partially restored cell viability. In contrast, overexpression of the Notch intracellular domain (NICD) decreased the expression of p53, p21^cip/waf, and cleaved caspase-3 in DNER-silenced cells. Moreover, NICD expression fully reverted the cell viability reduction, arrest in the G₁ phase, and elevated apoptosis caused by DNER silencing, thereby suggesting activation of Notch signaling by DNER. Expression of a membrane-unbound mutant of mDNER also decreased cell viability and induced apoptosis. On the other hand, TGF-β signals were found to be involved in DNER expression in both adherent and spheroid-cultured cells. DNER could therefore be a link connecting TGF-β signaling to Notch signaling. Taken together, DNER regulates cell proliferation, survival, and invasive capacity of the gastric cancer cells through the activation of Notch signaling, which may facilitate tumor progression into an advanced stage. This study provides evidences suggesting that DNER could be a potential prognostic marker, a therapeutic target, and a drug candidate in the form of a cell-free mutant.

Role of Delta/Notch-like EGF-related receptor in blood glucose homeostasis

Cell-cell interactions are necessary for optimal endocrine functions in the pancreas. β-cells, characterized by the expression and secretion of the hormone insulin, are a major constituent of functional micro-organs in the pancreas known as islets of Langerhans. Cell-cell contacts between β-cells are required to regulate insulin production and glucose-stimulated insulin secretion, which are key determinants of blood glucose homeostasis. Contact-dependent interactions between β-cells are mediated by gap junctions and cell adhesion molecules such as E-cadherin and N-CAM. Recent genome-wide studies have implicated Delta/Notch-like EGF-related receptor (Dner) as a potential susceptibility locus for Type 2 Diabetes in humans. DNER is a transmembrane protein and a proposed Notch ligand. DNER has been implicated in neuron-glia development and cell-cell interactions. Studies herein demonstrate that DNER is expressed in β-cells with an onset during early postnatal life and sustained throughout adulthood in mice. DNER loss in adult β-cells in mice (β-Dner cKO mice) disrupted islet architecture and decreased the expression of N-CAM and E-cadherin. β-Dner cKO mice also exhibited impaired glucose tolerance, defects in glucose- and KCl-induced insulin secretion, and decreased insulin sensitivity. Together, these studies suggest that DNER plays a crucial role in mediating islet cell-cell interactions and glucose homeostasis.

Anti-Tr/DNER antibody-associated cerebellar ataxia: three rare cases report and literature review

BACKGROUND

To report three cases of autoimmune cerebellar ataxia related to anti-delta/notch-like epidermal growth factor-related receptor (Tr/DNER) antibodies.

CASE PRESENTATION

Patients with unknown cerebellar ataxia were screened with autoimmune cerebellar ataxia (ACA)-related antibody panel. The anti-Tr antibody was positive in three female patients in whom the onset ages were 43 years, 35 years and 43 years old. The antibody titres of serum and cerebrospinal fluid were all 1:32. Cerebral ataxia was the most prominent presentation. Mild cerebellar atrophy was found in one of the patients. Immunotherapy was effective in all three patients.

CONCLUSION

The Tr antibody is associated with autoimmune ataxia, and it has been suggested that the anti-Tr antibody should be tested in patients with cerebellar ataxia who are negative for routine ACA antibodies. Early immunotherapy may improve patient prognoses.

Combining Literature Mining and Machine Learning for Predicting Biomedical Discoveries

The major outcomes and insights of scientific research and clinical study end up in the form of publication or clinical record in an unstructured text format. Due to advancements in biomedical research, the growth of published literature is getting tremendous large in recent years. The scientists and clinical researchers are facing a big challenge to stay current with the knowledge and to extract hidden information from this sheer quantity of millions of published biomedical literature. The potential one-stop automated solution to this problem is biomedical literature mining. One of the long-standing goals in biology is to discover the disease-causing genes and their specific roles in personalized precision medicine and drug repurposing. However, the empirical approaches and clinical affirmation are expensive and time-consuming. In silico approach using text mining to identify the disease causing genes can contribute towards biomarker discovery. This chapter presents a protocol on combining literature mining and machine learning for predicting biomedical discoveries with a special emphasis on gene-disease relation based discovery. The protocol is presented as a literature based discovery (LBD) pipeline for gene-disease based discovery. The protocol includes our web based tools: (1) DNER (Disease Named Entity Recognizer) for disease entity recognition, (2) BCCNER (Bidirectional, Contextual clues Named Entity Tagger) for gene/protein entity recognition, (3) DisGeReExT (Disease-Gene Relation Extractor) for statistically validated results and visualization, and (4) a newly introduced deep learning based method for association discovery. Our proposed deep learning based method can be generalized and applied to other important biomedical discoveries focusing on entities such as drug/chemical, or miRNA.

Transcriptional Profiling Reveals the Regulatory Role of DNER in Promoting Pancreatic Neuroendocrine Neoplasms

Wnt/β-catenin and NOTCH signaling contribute to the pathogenesis and growth of (PanNENs). The wnt and Notch signaling pathways form an integrated signaling device termed "wntch" and regulate stochastic cell fate decisions, suggesting the essentiality of Wnt/Notch interactions in disease progression. However, the function of Wnt/Notch interactions in PanNENs is unclear. We analyzed RNA sequencing (RNA-seq) data to identify differentially expressed lncRNAs, mRNAs and pathways according to enriched Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways associated with PanNENs. RNA-seq analysis revealed that the levels of the lncRNA XLOC_221242 and the mRNA encoding Delta/Notch-like epidermal growth factor (EGF)-related receptor (DNER) were significantly increased in tumor tissues compared with normal tissues (n = 3). Protein-protein interaction (PPI) prediction combined with transcriptional profiling data analysis revealed that DNER expression levels were positively correlated with those of DNA-binding factor (RBPJ), S phase kinase-associated protein 1 (Skp1), CTNNB1 and Cadherin-2 (CDH2), which promote PanNEN tumorigenesis and progression. These results were consistent with those of immunohistochemical analysis of DNER, RBPJ, SKP1, CTNNB1, and CDH2 expression (n = 15). These findings provide compelling clinical and molecular evidence supporting the conclusion that DNER and the related RBPJ, SKP1, CTNNB1, and CDH2 signaling contribute to PanNEN tumorigenesis and progression by activating wnt/Notch interactions.

Delta/notch-like epidermal growth factor-related receptor promotes stemness to facilitate breast cancer progression

DNER, Delta/Notch-like epidermal growth factor (EGF)-related receptor, is a neuron-specific transmembrane protein carrying extracellular EGF-like repeats. The function of DNER in breast cancer has not been evaluated. The present study demonstrates that the expression of DNER in breast cancer tissue is significantly higher than its expression in breast benign disease and is associated with poor recurrence-free survival (RFS) of breast cancer patients. It demonstrated that DNER could enhance the proliferation and metastasis of breast cancer cells in vitro and significantly increases tumor growth in vivo. Our study uncovered that DNER can promote breast cancer cells proliferation and metastasis by activating Girdin/PI3K/AKT signaling and subsequently regulating several key genes involving the characters of cancer stem cells. Taken together, DNER promotes breast cancer growth and metastasis, which provided a theoretical basis for future applications of DNER inhibitors in the treatment of breast cancer.

The Notch ligand DNER regulates macrophage IFNγ release in chronic obstructive pulmonary disease

BACKGROUND

Chronic Obstructive Pulmonary Disease (COPD) is the third leading cause of death worldwide with no curative therapy. A non-canonical Notch ligand, DNER, has been recently identified in GWAS to associate with COPD severity, but its function and contribution to COPD is unknown.

METHODS

DNER localisation was assessed in lung tissue from healthy and COPD patients, and cigarette smoke (CS) exposed mice. Microarray analysis was performed on WT and DNER deficient M1 and M2 bone marrow-derived macrophages (BMDM), and gene set enrichment undertaken. WT and DNER deficient mice were exposed to CS or filtered air for 3 day and 2 months to assess IFNγ-expressing macrophages and emphysema development. Notch and NFKB active subunits were quantified in WT and DNER deficient LPS-treated and untreated BMDM.

FINDINGS

Immunofluorescence staining revealed DNER localised to macrophages in lung tissue from COPD patients and mice. Human and murine macrophages showed enhanced DNER expression in response to inflammation. Interestingly, pro-inflammatory DNER deficient BMDMs exhibited impaired NICD1/NFKB dependent IFNγ signalling and reduced nuclear NICD1/NFKB translocation. Furthermore, decreased IFNγ production and Notch1 activation in recruited macrophages from CS exposed DNER deficient mice were observed, protecting against emphysema and lung dysfunction.

INTERPRETATION

DNER is a novel protein induced in COPD patients and 6 months CS-exposed mice that regulates IFNγ secretion via non-canonical Notch in pro-inflammatory recruited macrophages. These results provide a new pathway involved in COPD immunity that could contribute to the discovery of innovative therapeutic targets.

FUNDING

This work was supported from the Helmholtz Alliance 'Aging and Metabolic Programming, AMPro'.

Oncogene Delta/Notch-Like EGF-Related Receptor Promotes Cell Proliferation, Invasion, and Migration in Hepatocellular Carcinoma and Predicts a Poor Prognosis

PURPOSE

To determine the expression and function of Delta/Notch-like EGF-related receptor (DNER) in hepatocellular carcinoma (HCC).

METHODS

The expression of DNER in 84 HCC tissue samples and matched adjacent noncancerous specimens, as well as HCC cells, were evaluated by quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting. Survival analysis was evaluated using Kaplan-Meier method. For experiments in vitro, cell viability was measured by Cell Counting Kit-8 Assay and Colony Formation Assay. Furthermore, cell invasion and migration assays were performed with Transwell Assay.

RESULTS

The results showed that DNER was overexpressed in the tissues and cell lines of HCC (all, p < 0.05), and the upregulated expression of DNER was significantly correlated with advanced pathologic stage (p = 0.013) and pathologic-M1 (p = 0.012) in HCC patients. Survival analysis revealed that patients with high DNER levels had worse overall survival (OS) than those with low DNER levels (p = 0.004). More importantly, DNER could be an independent predictor of prognosis for OS (HR = 2.582, 95% CI 1.239-5.380, p = 0.011). In vitro, knockdown of DNER significantly suppressed cell proliferation, colony formation, cell invasion, and cell migration in HepG2 cells. Moreover, inhibition of DNER inactivated PI3K/AKT signaling pathway by downregulating the expression of p-PI3K, p-AKT, and p-70s6k.

CONCLUSIONS

Taken together, DNER could promote proliferation, migration, and invasion of HCC cells by regulating the activation of PI3K/AKT pathway, and it might act as a potential prognostic biomarker for HCC.

Quantum dot-based immunofluorescent imaging and quantitative detection of DNER and prognostic value in prostate cancer

DNER, Delta/Notch-like epidermal growth factor (EGF)-related receptor, is a neuron-specific transmembrane protein carrying extracellular EGF-like repeats. The prognostic value of DNER in prostate cancer has not been evaluated. Here we showed that the up-regulation of DNER protein was observed in prostate cancer detected by immunohistochemistry (IHC) and quantum dot-based immunofluorescent imaging and quantitative analytical system (QD-IIQAS). However, a higher accuracy of measurements of DNER expression in prostate cancer was found by QD-IIQAS than by IHC (AUC = 0.817 and 0.617, respectively). DNER was significantly higher in patients undergoing bone metastasis (P = 0.045, RR = 3.624). In addition, DNER overexpression was associated with poor overall survival (OS) (P = 0.028, adjusted HR = 8.564) and recurrence-free survival (RFS) (P = 0.042, adjusted HR = 3.474) in patients suffering prostate cancer. Thus, QD-IIQAS is an easy and accurate method for assessing DNER and the DNER expression was an independent prognostic factor in prostate cancer.

Delta/notch-like epidermal growth factor-related receptor (DNER) orchestrates stemness and cancer progression in prostate cancer

DNER, Delta/Notch-like epidermal growth factor (EGF)-related receptor, is a neuron-specific transmembrane protein carrying extracellular EGF-like repeats. The function of DNER in prostate cancer has not been evaluated. Here, we showed that the upregulation of DNER is observed in various cancers, including prostate cancer. Knockdown of DNER in PC-3 cells inhibited cell proliferation, migration and invasion as well as tumorigenesis in PC-3 xenografts. DNER knockdown specifically inhibited cell growth in spheroids. RT-PCR and western blot analysis were performed, and CD44, HES1 and GLI1 expression was significantly decreased in DNER knockdown cells. Thus, DNER promotes prostate cancer progression and the growth of PC-3 cells by modulating the primary genes of cancer stem cells.