"Matière et Systèmes Complexes"
11 janvier 2010 à 11h30
Bâtiment Condorcet, 4ème étage, salle 454 A.
Actin-based propulsion of vesicles: from mesoscopic observations to molecular mechanisms
Cell motility, in response to extracellular signals, allows directional movement, cell division or materials transport. The combined actions of molecular motors and remodeling of the cytoskeleton generate forces and movement. Biochemical studies of actin dynamics regulation shed light on several protein machineries that initiate actin filament assembly by different mechanisms, leading to varying ‘actin-based motile processes’ like cell protrusions, invaginations, organelles propulsion. In particular, the site-directed assembly of actin filaments in a branched network generates forces responsible for the formation of lamellipodial protrusion and for the propulsion of intracellular organelles and pathogens. To characterize the assembly of this branched actin array, we reconstituted the propulsion of Giant Unilamellar Vesicles (GUVs) functionalized with an activator of actin polymerization in a biochemically controlled medium. We showed that actin filaments bind transiently to membrane-bound activators via the Arp2/3 branching complex, and that the movement is driven by the balance between free diffusion and segregation of the activator at the membrane.