The polarity protein Yurt associates with the plasma membrane via basic and hydrophobic motifs embedded in its FERM domain

The subcellular distribution of the polarity protein Yrt is subjected to a spatio-temporal regulation in D. melanogaster embryonic epithelia. After cellularization, Yrt binds to the lateral membrane of ectodermal cells and maintains this localization throughout embryogenesis. During terminal differentiation of the epidermis, Yrt accumulates to septate junctions and is also recruited to the apical domain. While the mechanisms through which Yrt associates with septate junctions and the apical domain have been deciphered, how Yrt binds to the lateral membrane remains as an outstanding puzzle. Here, we show that the FERM domain of Yrt is necessary and sufficient for membrane localization. Our data also establish that the FERM domain of Yrt directly binds negatively charged phospholipids. Moreover, we demonstrate that positively charged amino acid motifs embedded within the FERM domain mediates Yrt membrane association. Finally, we provide evidence suggesting that Yrt membrane association is functionally important. Overall, our study highlights the molecular basis of how Yrt associates with the lateral membrane during the developmental time window where it is required for segregation of lateral and apical domains. Summarys: tatement This study reveals how Yurt associates with membrane lipids in epithelial cells, thereby further illuminating the mechanisms sustaining cell polarization and tissue morphogenesis.