β-Arrestin links endothelin A receptor to β-catenin signaling to induce ovarian cancer cell invasion and metastasis

Abstract

The activation of endothelin-A receptor (ET_AR) by endothelin-1 (ET-1) has a critical role in ovarian tumorigenesis and progression. To define the molecular mechanism in ET-1-induced tumor invasion and metastasis, we focused on β-arrestins as scaffold and signaling proteins of G protein-coupled receptors. Here, we demonstrate that, in ovarian cancer cells, β-arrestin is recruited to ET_AR to form two trimeric complexes: one through the interaction with Src leading to epithelial growth factor receptor (EGFR) transactivation and β-catenin Tyr phosphorylation, and the second through the physical association with axin, contributing to release and inactivation of glycogen synthase kinase (GSK)-3β and β-catenin stabilization. The engagement of β-arrestin in these two signaling complexes concurs to activate β-catenin signaling pathways. We then demonstrate that silencing of both β-arrestin-1 and β-arrestin-2 inhibits ET_AR-driven signaling, causing suppression of Src, mitogen-activated protein kinase (MAPK), AKT activation, as well as EGFR transactivation and a complete inhibition of ET-1-induced β-catenin/TCF transcriptional activity and cell invasion. ET_AR blockade with the specific ET_AR antagonist ZD4054 abrogates the engagement of β-arrestin in the interplay between ET_AR and the β-catenin pathway in the invasive program. Finally, ET_AR is expressed in 85% of human ovarian cancers and is preferentially co-expressed with β-arrestin-1 in the advanced tumors. In a xenograft model of ovarian metastasis, HEY cancer cells expressing β-arrestin-1 mutant metastasize at a reduced rate, highlighting the importance of this molecule in promoting metastases. ZD4054 treatment significantly inhibits metastases, suggesting that specific ET_AR antagonists, by disabling multiple signaling activated by ET_AR/β-arrestin, may represent new therapeutic opportunities for ovarian cancer.