Final Report Summary - FORCEFULACTIN (Coordinated regulation of actin dynamics in cell motility and morphogenesis : from molecules to reconstituted biomimetic assays)
We have brought new insights into the molecular mechanisms that control actin filament assembly dynamics at the barbed ends, the major process by which force is produced for cell shape changes that lead to movements. We demonstrate that a small number of actin binding modules present in various regulators of actin assembly bind barbed ends in competitive and uncompetitive schemes. Kinetic analysis of their effects on actin filament dynamics in bulk solution and in single filament TIRF microscopy provide a comprehensive picture of the molecular mechanisms of barbed end reactivity at the origin of cell motility. We demonstrate how major players in actin regulation such as Capping Protein, profilin, formins, WH2 domain-containing proteins, the WASP-Arp2/3 complex filament branching machinery establish actin homeostasis in cells. We demonstrate that picoNewton forces affect elementary steps in the processive cycle of formin polymerases. The ensemble of our results has physiological relevance in cell motile processes.