Unipolar membrane association of Dishevelled mediates Frizzled planar cell polarity signaling

TLDR

Drosophila epithelial cells establish planar cell polarity orthogonal to their apical‑basal axes, mediated by the Frizzled receptor and its downstream transducer Dishevelled. Unipolar relocalization of Dishevelled to the membrane is essential for planar cell polarity, reflecting a transition from symmetric to asymmetric signaling that amplifies a steep intracellular gradient, whereas this relocalization is not required for Wingless signaling.

Abstract

Drosophila epithelia acquire a planar cell polarity (PCP) orthogonal to their apical-basal axes. Frizzled (Fz) is the receptor for the PCP signal, and Dishevelled (Dsh) transduces the signal. Here, I demonstrate that unipolar relocalization of Dsh to the membrane is required to mediate PCP, but not Wingless (Wg) signaling. Dsh membrane localization reflects the activation of Fz/PCP signaling, revealing that the initially symmetric signal evolves to one that displays unipolar asymmetry, specifying the cells' ultimate polarity. This transition from symmetric to asymmetric Dsh localization requires Dsh function, and reflects an amplification process that generates a steep intracellular activity gradient necessary to determine PCP.