β-Arrestin 1 as messenger of endothelin A receptor to mediate β-catenin signaling and epithelial to mesenchymal transition in human ovarian cancer cells Free

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The endothelin A receptor (ET_AR)/endothelin-1 (ET-1) axis is important in ovarian carcinoma growth and progression, with ET-1-induced epidermal growth factor receptor (EGFR) transactivation being a key downstream signaling event involved in these processes. It has become evident that β-arrestins can act as multifunctional adaptor proteins promoting G-protein-coupled receptor-signal transduction. The present study examines the role of β-arrestin-1 in the cross-communication between ET_AR and EGFR-regulated cell-cell adhesion and epithelial-mesenchymal transition (EMT) in HEY and OVCA 433 ovarian cancer cells. We report that ET-1 induces the translocation of β-arrestin-1, from the cytosol to the membrane, and dephosphorylation of serine-412 on β-arrestin-1. Together, these events regulate the association of β-arrestin-1 with Src, and the formation of a membrane-associated ET_AR/β-arrestin-1/Src signaling complex (‘signalplex’). By transfection with FLAG-tagged wild-type or mutant S412D-β-arrestin-1, we found the ‘signalplex’ to be crucial for transactivation of EGFR and downstream signaling. We also observed that it was critical for ET-1 to induce β-catenin tyrosine phosphorylation in a time-dependent manner to facilitate the loss of β-catenin/E-cadherin interactions. These effects were associated with reductions in β-catenin serine/threonine phosphorylation and parallel inhibition of glycogen synthase kinase (GSK)-3β, impairing β-catenin-complex degradation. ET-1-induced β-catenin nuclear translocation also enhanced transcriptional activity of β-catenin/TCF/LEF. The functional consequences of these events were upregulation of β-catenin target genes, and enhanced protease activation, cell migration and invasion, implying that the ET_AR/β-arrestin-1/Src complex and subsequent EGFR transactivation may account for the aggressive behavior of ovarian cancer cells. These effects were prevented by both ET_AR antagonists and ET_AR siRNA, validating ET_AR as the receptor involved. Moreover, in human ovarian carcinoma xenografts, ET_AR blockade by the selective ET_AR antagonist ZD4054 significantly inhibited tumor growth, peritoneal dissemination and expression of EMT effectors. In conclusion, our findings demonstrate a functional role for β-arrestin-1 as a mediator of ET_AR-induced ovarian cancer cell invasion and metastatic behavior, supporting the use of selective ET_AR antagonists in developing a new therapeutic approach to ovarian cancer. Supported by AIRC, AstraZeneca