Actomyosin Dependent Clustering and Segregation of Cell Surface Molecules at Multiple Scales

Abstract

1-Subg Mechanical Action of BAR-Domain Proteins on Fluid Membranes Patricia Bassereau1, Coline Prevost1, Mijo Simunovic1,2, Andrew Callan-Jones3. PhysicoChimie Curie, Curie Institute, Paris, France, Department of Chemistry, The University of Chicago, Chicago, IL, USA, Laboratoire Matiere et Systemes Complexes, Universite Paris Diderot-Paris 7, Paris, France. Cell plasmamembranes are highly deformable and are strongly curved, even cut, upon membrane trafficking or during cell motility. BAR-domain proteins with their intrinsically curved shape and their interaction with the actin cytoskeleton are involved in many of these processes, including membrane scission in some cases. Inspired by in vivo experiments,we have used in vitro experiments to study the interaction of BAR-domain proteins with curved membranes for understanding the mechanical action of BAR-domain proteins on biological membranes. Our nanotube assay consists in pullingmembrane nanotubes of controlled curvature (diameter ranging between 15 to a few hundreds of nm) from Giant Unilamellar Vesicles (GUVs) using optical tweezers and micropipette aspiration. From force and quantitative fluorescence measurements, we analyze how proteins bound to these nanotubes affect their tube diameter and conditions required for their destabilization and scission. We compare our results to theoretical models based on membrane mechanics. Eventually, we propose new mechanisms: a) for the initiation of membrane deformations (protrusions or endocytic buds) by weakly bent BAR-domains b) for membrane scission when membrane tubules scaffolded by BAR-domains are extended by an external force.