Hyaluronan-CD44 Interaction with Neural Wiskott-Aldrich Syndrome Protein (N-WASP) Promotes Actin Polymerization and ErbB2 Activation Leading to β-Catenin Nuclear Translocation, Transcriptional Up-regulation, and Cell Migration in Ovarian Tumor Cells

Abstract

In this study we have investigated the interaction of hyaluronan (HA) and CD44 with the neuronal Wiskott-Aldrich syndrome protein (N-WASP) in regulating actin polymerization and ErbB2/beta-catenin signaling in human ovarian tumor cells (SK-OV-3.ipl cells). Biochemical and immunological analyses indicate that N-WASP is expressed in SK-OV-3.ipl cells and that the binding of HA stimulates N-WASP association with CD44 and Arp2/Arp3 leading to filamentous actin formation and ovarian tumor cell migration. In addition, HA binding promotes CD44-N-WASP association with ErbB2 and activates ErbB2 kinase activity that in turn increases phosphorylation of the cytoskeletal protein, beta-catenin. Subsequently, phosphorylated beta-catenin is transported into the nucleus leading to beta-catenin-mediated TCF/LEF-transcriptional co-activation. Because HA-induced beta-catenin phosphorylation, nuclear translocation, and TCF/LEF transcriptional activation is effectively blocked by the ErbB2 inhibitor, AG825, we conclude that HA/CD44-N-WASP-associated ErbB2 activation is required for beta-catenin-mediated signaling events. Transfection of SK-OV-3.ipl cells with N-WASP-VCA (verpolin homology, cofilin homology, and acidic domain) fragment cDNA not only blocks HA/CD44-induced N-WASP-Arp2/3 complex formation but also inhibits actin polymerization/F-actin assembly and tumor cell migration. Overexpression of the N-WASP-VCA domain also significantly reduces HA-induced ErbB2 recruitment to CD44, diminishes beta-catenin phosphorylation/nuclear translocation, and abrogates TCF/LEF-specific transcriptional co-activation by beta-catenin. Taken together, our findings strongly suggest that N-WASP plays a pivotal role in regulating HA-mediated CD44-ErbB2 interaction, beta-catenin signaling, and actin cytoskeleton functions that are required for tumor-specific behaviors and ovarian cancer progression.