Figure 1.

Left, schematic diagram of lipid-based direction sensing in migrating leukocytes. The accumulation of PIP3 (purple) at the leading edge is maintained by the coordinated activities of PI-3 kinases (red) and lipid phosphatases (e.g., PTEN, blue), which localize to the leading and lateral edges, respectively. Right, schematic diagram summarizing the interactions between polarity complexes in polarized epithelial cells. The Par complex (green) localizes to adherens junctions, and promotes the recruitment of the Crumbs/PATJ complex (yellow) to the apical membrane. The Scrib complex (purple) accumulates on basolateral membranes, and inhibits the spreading of the Par complex. The Crumbs/PATJ complex, in turn, inhibits the spreading of the Scrib complex.