β-Spectrin regulates the Hippo signaling pathway and modulates the basal actin network

Abstract Emerging evidence suggests functional regulation of Hippo pathway by the actin cytoskeleton, although the detailed molecular mechanism remains incomplete. In a genetic screen we identified a requirement for β-Spectrin in the posterior follicle cells (PFCs) for the oocyte repolarization process during Drosophila mid-oogenesis. β-spectrin mutations lead to loss of Hippo signaling activity in the follicle cells. Similar reduction of Hippo signaling activity was observed after β-Spectrin knockdown in mammalian cells. We further demonstrated that β-spectrin mutations disrupt the basal actin network in the follicle cells. The abnormal stress-fiber-like actin structure on the basal side of the follicle cells provides a likely link between the β-spectrin mutations and the loss of Hippo signaling activity phenotype.