Giant vesicles compressed by actin polymerization

Abstract

Actin polymerization plays a critical role in generating propulsive force to drive many types of cell motility. The discovery of actin based motility of the bacterial pathogen Listeria monocytogenes has lead to clearer understandings of the essential ingredients required for cell motility. The biophysical mechanisms by which these proteins generate forces is the subject of intense investigation. A novel system to study force generation by this polymerization engine is introduced by combining the well characterized mechanical properties of synthetic Giant Vesicles with the well understood biochemistry of actin polymerization. Giant Vesicles mimic the structural features of eukaryotic cell membranes. We find that Giant Vesicles coated with a protein that catalyzes actin polymerization form thick actin shells which produce a compressive force. The polymerization force directed at the membrane interface causes the membrane to rupture. In the resulting collapse we find that the shell thickens inward with a constant radial velocity and is characterized by radial lines of lipid and actin. We show that actin polymerization is the primary force driving the collapse.