CDB15:0000492 EFNA4 — EPHA2

ABSTRACT: In mammals, 14 members of the Eph receptor tyrosine kinase family have been described so far. Here we present a not yet described member of this family denoted EphA10. We report the identification of three putative EphA10 isoforms: one soluble and two transmembrane isoforms. One of the latter isoforms lacked the sterile alpha motif commonly found in Eph receptors. The gene encoding EphA10 is located on chromosome 1p34 and expression studies show that EphA10 mRNA is mainly expressed in testis. Binding studies to ephrin ligands suggests that this receptor belongs to the EphA subclass of Eph receptors binding mainly to ephrin-A ligands.

ABSTRACT: The Eph receptor tyrosine kinase family includes many members, which are often expressed together in various combinations and can promiscuously interact with multiple ephrin ligands, generating intricate networks of intracellular signals that control physiological and pathological processes. Knowing the entire repertoire of Eph receptors and ephrins expressed in a biological sample is important when studying their biological roles. Moreover, given the correlation between Eph receptor/ephrin expression and cancer pathogenesis, their expression patterns could serve important diagnostic and prognostic purposes. However, profiling Eph receptor and ephrin expression has been challenging. Here we describe a novel and straightforward approach to catalog the Eph receptors present in cultured cells and tissues. By measuring the binding of ephrin Fc fusion proteins to Eph receptors in ELISA and pull-down assays, we determined that a mixture of four ephrins is suitable for isolating both EphA and EphB receptors in a single pull-down. We then used mass spectrometry to identify the Eph receptors present in the pull-downs and estimate their relative levels. This approach was validated in cultured human cancer cell lines, human tumor xenograft tissue grown in mice, and mouse brain tissue. The new mass spectrometry approach we have developed represents a useful tool for the identification of the spectrum of Eph receptors present in a biological sample and could also be extended to profiling ephrin expression.

ABSTRACT: Rapid tumor progression, metastasis, and diagnosis in advanced stages of disease are the main reasons for the short survival time and high mortality rate of patients with hepatocellular carcinoma (HCC). Ephrin A4 (EFNA4), the ligand of the EPH family, participates in the development of blood vessels and epithelium by regulating cell migration and rejection. In our study, based on bioinformatics analyses, we found that EFNA4 was highly expressed and led to poor prognosis in patients with HCC. We demonstrated that overexpression of EFNA4 significantly promoted HCC cell proliferation and migration in vivo or in vitro. In addition, knockdown of EFNA4 inhibited the proliferation and migration of HCC cells. Furthermore, EFNA4 was found to directly interact with EPHA2 and promote its phosphorylation at Ser897, followed by recruitment of phosphoinositide-3-kinase regulatory subunit 2 (PIK3R2) and activation of the glycogen synthase kinase-3beta (GSK3β)/β-catenin signaling pathway. Moreover, overexpression of β-catenin further promoted the expression of PIK3R2, which formed a positive feedback loop. The results revealed that abnormal expression of EFNA4 is the main switch of the PIK3R2/GSK3β/β-catenin loop that influenced the proliferation and migration of HCC cells and suggest that EFNA4 is a potential prognostic marker and a prospective therapeutic target in patients with HCC.