Dynamics of the Dictyostelium cytoskeleton during chemotaxis.

Movement and chemotaxis are fundamental processes of cells and tissues and are based on the dynamics of the cytoskeleton. The cellular slime mold Dictyostelium discoideum is an excellent model system with which to study the molecular components and the key reactions that are required for a coordinated locomotion of single cells or a cell mass during development. The D. discoideum cytoskeleton relies mainly on the equilibrium between monomeric and filamentous actin and, like other nonmuscle cells, contains a large number of actin-binding proteins that either decrease or increase the rigidity of the microfilament system. The proteins themselves are regulated by phosphorylation, Ca2+, phospholipids, and/or pH and thus are targets for the intracellular changes that occur upon stimulation of a cell with chemoattractant. In a synopsis of the data published during the past years, the properties of numerous cytoskeletal components and the biochemical reactions of the signal transduction chain are combined here in a schematic model that attempts to explain how the directed movement of a cell could be coordinated at the molecular level.