FIGURE 1 Chemotaxis involves elevated levels of the signaling phospholipid PI(3,4,5)P₃, which signals to the actin cytoskeleton. (a) Summary of results of studies exploring the localization of components of signaling pathways (green) in Dictyostelium cells undergoing chemotaxis toward cAMP. Also shown are the localization of actin and myosin (red). (b) The enzyme PI-3 kinase, which generates PI(3,4,5)P₃, is enriched at the front of chemotaxing cells, whereas PTEN, the phosphatase that hydrolyzes PI(3,4,5)P₃, is enriched at the back. These distributions result in elevated PI(3,4,5)P₃ at the front of the cells, which signals the polarity for movement.

[Part (b) republished with permission of Elsevier, from Cell, Iijima et al., 3, 2002; permission conveyed through Copyright Clearance Center, Inc.]