Identification of an Autoantibody Against ErbB-3-Binding Protein-1 in the Sera of Patients With Chronic Hepatitis B Virus Infection.

Background: Studies have shown that autoimmune response contributes to chronic hepatitis B (CHB) development. Aim: This study aimed to identify autoantibodies in the sera of patients with CHB and to investigate the association of autoimmune response with disease severity in CHB. Methods: Proteins from human liver carcinoma cell line HepG2 were separated by two-dimensional electrophoresis. The candidate autoantigens were recognized by serum autoantibodies from Chinese CHB patients. Immunohistochemical staining was performed to determine the hepatic expression of the autoantigen in CHB patients with different inflammatory grades. Enzyme-linked immunosorbent assay (ELISA) was conducted to measure the prevalence and the levels of serum autoantibody in CHB patients with different disease severity. Flow cytometry analysis was carried out to assess the autoreactive T cell response in the peripheral circulation of CHB patients. Results: ErbB-3-binding protein-1 (EBP-1) was identified as an autoantigen of serum autoantibodies in CBP patients. EBP-1 protein expression was upregulated in the liver of CHB patients with high-grade hepatic inflammation. The prevalence and levels of serum anti-EBP1 IgG were significantly increased in CHB patients with severe diseases compared with those with mild or moderate diseases, but none was detectable in the healthy controls. EBP-1 peptides induced proinflammatory cytokine expression in CD4+ T cells from CHB patients. Conclusion: Our results demonstrate the presence of an autoantibody against EBP-1 in the sera as well as EBP-1-reactive T cells in the peripheral blood of CHB patient. EBP-1-induced autoimmune response is positively associated with the disease severity, suggesting that EBP-1-induced autoimmune response possibly contributes to progressive liver failure.

A structural view of PA2G4 isoforms with opposing functions in cancer.

The role of proliferation-associated protein 2G4 (PA2G4), alternatively known as ErbB3-binding protein 1 (EBP1), in cancer has become apparent over the past 20 years. PA2G4 expression levels are correlated with prognosis in a range of human cancers, including neuroblastoma, cervical, brain, breast, prostate, pancreatic, hepatocellular, and other tumors. There are two PA2G4 isoforms, PA2G4-p42 and PA2G4-p48, and although both isoforms of PA2G4 regulate cellular growth and differentiation, these isoforms often have opposing roles depending on the context. Therefore, PA2G4 can function either as a contextual tumor suppressor or as an oncogene, depending on the tissue being studied. However, it is unclear how distinct structural features of the two PA2G4 isoforms translate into different functional outcomes. In this review, we examine published structures to identify important structural and functional components of PA2G4 and consider how they may explain its crucial role in the malignant phenotype. We will highlight the lysine-rich regions, protein-protein interaction sites, and post-translational modifications of the two PA2G4 isoforms and relate these to the functional cellular role of PA2G4. These data will enable a better understanding of the function and structure relationship of the two PA2G4 isoforms and highlight the care that will need to be undertaken for those who wish to conduct isoform-specific structure-based drug design campaigns.

The expression and prognostic role of EBP1 and relationship with AR in HER2+ breast cancer.

Human epidermal growth factor receptor (HER)-2 positive (HER2+) breast cancer (BC) has a poor survival rate and is more aggressive in nature. HER2-targeting agents could be beneficial for patients with HER2+ BC. In addition, targeted therapy and chemotherapy have been successfully used. However, a few patients are resistant to treatment. ErbB3 binding protein 1 (EBP1) binds to HER3 and inhibits the proliferation and invasive potential of tumor cells. However, its role in HER2+ BC has not been demonstrated. In this study, we aimed to analyze the relationship between androgen receptor (AR) and EBP1 expression in HER2+ BC. A total of 282 cases (140 cases of HER2+ invasive BC and 142 HER2-negative invasive BC) were included in this study. We performed immunohistochemistry (IHC) to analyze the expression of AR and EBP1; thereafter, we evaluated the relationship between these two biomarkers and estrogen receptor (ER), progesterone receptor (PR), HER2, p53, Ki67 expression, and other clinicopathological parameters. Of the HER2+ cases, 67 (47.9%) showed high expression of EBP1 (EBP1high) and 73 (52.1%) showed low/no expression of EBP1 (EBP1low/no). EBP1 expression was correlated with AR expression, histological grade, and lymphatic metastasis (p < 0.001, < 0.001, and 0.013, respectively). Kaplan-Meier analysis revealed that AR+ and EBP1low/no group had poorer overall survival (OS) and disease-free survival (DFS) compared with other groups (AR- and EBP1low/no, AR+ and EBP1high, and AR- and EBP1high). AR+ and EBP1low/no expression were independent prognostic factors for OS and DFS in HER2+ BC. This study showed the clinicopathological role of EBP1 and AR in HER2+ BC. Targeting EBP1 may be an effective treatment strategy for patients with AR+ HER2+ BC.

YC-1 Antagonizes Wnt/ß-Catenin Signaling Through the EBP1 p42 Isoform in Hepatocellular Carcinoma.

Novel drugs targeting Wnt signaling are gradually being developed for hepatocellular carcinoma (HCC) treatment. In this study, we used a Wnt-responsive Super-TOPflash (STF) luciferase reporter assay to screen a new compound targeting Wnt signaling. 3-(5'-Hydroxymethyl-2'-furyl)-1-benzylindazole (YC-1) was identified as a small molecule inhibitor of the Wnt/ß-catenin pathway. Our coimmunoprecipitation (co-IP) data showed that YC-1 did not affect the ß-catenin/TCF interaction. Then, by mass spectrometry, we identified the ErbB3 receptor-binding protein 1 (EBP1) interaction with the ß-catenin/TCF complex upon YC-1 treatment. EBP1 encodes two splice isoforms, p42 and p48. We further demonstrated that YC-1 enhances p42 isoform binding to the ß-catenin/TCF complex and reduces the transcriptional activity of the complex. The suppression of colony formation by YC-1 was significantly reversed after knockdown of both isoforms (p48 and p42); however, the inhibition of colony formation was maintained when only EBP1 p48 was silenced. Taken together, these results suggest that YC-1 treatment results in a reduction in Wnt-regulated transcription through EBP1 p42 and leads to the inhibition of tumor cell proliferation. These data imply that YC-1 is a drug that antagonizes Wnt/ß-catenin signaling in HCC.

Modulation of HCV replication and translation by ErbB3 binding protein1 isoforms.

We recently identified a cell-factor, ErbB3 binding protein 1 (Ebp-1), which specifically interacts with the viral RNA genome and modulates HCV replication and translation. Ebp1 has two isoforms, p48, and p42, that result from differential splicing. We found that both isoforms interact with HCV proteins NS5A and NS5B, as well as cell-factor PKR. The p48 isoform, which localizes in the cytoplasm and nuclei, promoted HCV replication, whereas the shorter p42 isoform, which resides exclusively in the cytoplasm, strongly inhibited HCV replication. Transient expression of individual isoforms in Ebp1-knockdown MH14 cells confirmed that the p48 isoform promotes HCV replication, while the p42 isoform inhibits it. We found that Ebp1-p42 significantly enhanced autophosphorylation of PKR, while Ebp1-p48 isoform strongly inhibited it. We propose that modulation of autophosphorylation of PKR by p48 isoform is an important mechanism whereby the HCV virus escapes innate antiviral immune responses by circumventing p42-mediated inhibition of its replication.

Overexpression of a Hevea brasiliensis ErbB-3 Binding protein 1 Gene Increases Drought Tolerance and Organ Size in Arabidopsis.

Rubber trees are economically important tropical tree species and the major source of natural rubber, which is an essential industrial material. This tropical perennial tree is susceptible to cold stress and other abiotic stresses, especially in the marginal northern tropics. Recent years, the genome sequencing and RNA-seq projects produced huge amount of sequence data, which greatly facilitated the functional genomics study. However, the characterization of individual functional gene is in urgent demands, especially for those involved in stress resistance. Here we identified and characterized the rubber tree gene ErbB-3 binding protein 1, which undergoes changes in expression in response to cold, drought stress and ABA treatment. HbEBP1 overexpression (OE) in Arabidopsis increased organ size, facilitated root growth and increased adult leaf number by delaying the vegetative-to-reproductive transition. In addition, HbEBP1 OE enhanced the resistance of the Arabidopsis plants to freezing and drought stress, demonstrating that this gene participates in the regulation of abiotic stress resistance. RD29a, RD22 and CYCD3;1 expression was also greatly enhanced by HbEBP1 OE, which explains its regulatory roles in organ size and stress resistance. The regulation of drought stress resistance is a novel function identified in plant EBP1 genes, which expands our understanding of the roles of EBP1 gene in response to the environment. Our results provide information that may lead to the use of HbEBP1 in genetically engineered crops to increase both biomass and abiotic stress resistance.

ErbB3 binding protein 1 (EBP1) participates in the regulation of intestinal inflammation via mediating Akt signaling pathway.

ErbB3 binding protein-1 (EBP1) belongs to a family of DNA/RNA binding proteins implicated in cell growth, differentiation and apoptosis. Previous data demonstrated that EBP1 regulates phosphorylation of Akt to drive tumor progress. However, the expression and biological functions of EBP1 in ulcerative colitis (UC) remain unclear. In this study, we reported for the first time that EBP1 was down-regulated in intestinal epithelial cell (IECs) of patients with UC. In DSS-induced colitis, we observed the down-regulation of EBP1 accompanied with the elevated levels of proinflammatory cytokines (IL-1ß, IL-6 and IL-8) and Akt activation indicators (phosphorylated Akt) in colitis IECs, indicating the possible involvement of EBP1 in regulation of intestinal inflammation via mediating Akt in UC. Employing the TNF-α-treated HT-29 cells as an IEC inflammatory model, we confirmed the negative correlation of EBP1 with Akt activation and Akt-dependent inflammation progress in vitro. EBP1 knocking down and over-expression significantly regulated TNF-α-induced Akt activation and proinflammatory cytokines expression in HT-29 cells. Taken together, our data suggested that EBP1 participates in the regulation of intestinal inflammation via mediating Akt signaling pathway.