Molecular basis of localized responses during chemotaxis in amoebae and leukocytes.

Free-living amoebae as well as mammalian leukocytes sense chemoattractants with seven helix receptors linked to G-proteins. The cells respond by extending pseudopods and moving in the direction of the highest concentration. Recent studies using GFP-tagged proteins in Dictyostelium have shown that the directional response becomes sharply localized downstream of the receptors and G-proteins but upstream of the actin cytoskeleton. These studies together with the isolation novel genes by insertional mutagenesis in Dictyostelium are leading to a new understanding of chemotaxis in eucaryotic cells.