Membrane elasticity and polymerization energy modulate the shape of clathrin coats

Abstract

Clathrin mediated endocytosis is the most widely used means of vesicular trafficking and membrane bending is the first step involved, believed to be facilitated by clathrin polymerization. The polymerization of clathrin is thought to force the membrane to adopt the shape of the clathrin coat by scaffolding mechanism. However the variety of clathrin lattice shapes found in vivo has challenged this model. The mechanism of membrane bending by clathrin is still highly debated1-3. Addressing this question, in this study, we have reconstituted clathrin budding in vitro with giant unilamellar vesicles (GUVs), purified adaptors and clathrin. By changing the osmotic conditions, we found that clathrin coats caused extensive budding of GUVs under low membrane tension, while polymerizing as a flat lattice under moderate tension. High tension and bending rigidity of the membrane fully inhibited polymerization. We hypothesize that membrane tension could oppose polymerization energy of clathrin. Us...