Abstract:
Integrin-mediated adhesion regulates membrane trafficking to control anchorage-dependent signaling and growth that is deregulated in cancers. Downstream of integrins and oncogenic Ras, the small GTPase Ral, is a vital mediator of adhesion-dependent trafficking and signaling. While the role of RalA in these pathways is well established, what regulates the small GTPase downstream of integrin and oncogenic Ras is still elusive. In this study, we find a cell cycle protein Aurora Kinase A (AURKA) to be an important player that regulates RalA activity downstream of Integrin-mediated adhesion. We have developed and used a self-assembling dextran polymer nanovesicle (VMLN) to deliver the AURKA inhibitor Alisertib (MLN8237) and specifically target AURKA in cells in 2D as well as 3D microenvironments. Using this tool to specifically inhibit AURKA, we find it regulates integrin-dependent RalA activity and cell spreading in early adhesion, through the RalGEF, RGL1. This could be mediated by the effect AURKA has on RalA and RGL1 localization. In anchorage-independent cancers, the AURKA-RalA crosstalk is conserved in Ras-independent cancers and remains to be tested in Ras-dependent cancers. Using VMLN as a tool we have identified two Ras-independent cancer cell lines where targeting AURKA specifically inhibits RalA activity and RalA dependent anchorage-independent growth. Together these studies help identify AURKA as a key regulator of RalA, along with adhesion dependent pathways in normal and Ras-independent cancers.
