Nemo kinase phosphorylates β-catenin to promote ommatidial rotation and connects core PCP factors to E-cadherin–β-catenin

Abstract

Frizzled/planar cell polarity (PCP) signaling regulates cell motility in several tissues, including ommatidial rotation in Drosophila melanogaster. The Nemo kinase has also been linked to cell motility regulation and ommatidial rotation. The mechanistic role(s) of Nemo during rotation remain however obscure. We demonstrate that nemo functions throughout the entire rotation movement promoting rate of rotation. Genetic and molecular studies indicate that Nemo binds both the core PCP factor complex of Strabismus–Prickle, and the E-cadherin–β-catenin (Armadillo) complex, which colocalize and like Nemo also promote rotation. Strabismus/Vang binds and stabilizes Nemo asymmetrically within the ommatidial precluster. Nemo and β-catenin then act synergistically promoting rotation, which is mediated in vivo through Nemo phosphorylation of β-catenin. Our data suggest that Nemo serves as a conserved molecular link between core PCP factors and E-cad/β-catenin complexes, promoting ommatidial rotation and cell motility in general.