Séminaires
MSC
"Matière et Systèmes Complexes"
Lundi
11 janvier 2010 à 11h
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.