CAPPING PROTEIN-LEVELS INFLUENCE ACTIN ASSEMBLY AND CELL MOTILITY IN DICTYOSTELIUM

Actin assembly is important for cell motility, but the mechanism of as sembly and how it relates to motility in vivo is largely unknown. In v itro, actin assembly can be controlled by proteins, such as capping pr otein, that bind filament ends. To investigate the function of actin a ssembly in vivo, we altered the levels of capping protein in Dictyoste lium cells and found changes in resting and chemoattractant-induced ac tin assembly that were consistent with the in vitro properties of capp ing protein in capping but not nucleation. Significantly, overexpresse rs moved faster and underexpressers moved slower than control cells. M utants also exhibited changes in cytoskeleton architecture. These resu lts provide insights into in vivo actin assembly and the role of the a ctin cytoskeleton in motility.