Vesicle protrusions shaped by actin-membrane interactions

When the surface to volume ratio of an actin filled vesicle is increased, f or instance by temperature elevation, small protrusions are found to emerge from the initially spherical vesicle. We suggest here that these structure s result from a balance between membrane-actin filaments interactions and t he membrane curvature elasticity, their diameter lambda (c) minimizing the sum of these two energies. When the actin-membrane interaction is the super position of the repulsive undulation force of the membrane, the attractive Van der Waals force between membrane and filaments, and the bending energy of filaments, the protrusion diameter is found to be between 0.1 mum and 1 mum, depending on parameters such as the vesicle radius, the monomeric acti n concentration, the membrane tension and the thickness of the actin sheet. (C) 2001 Academie des sciences/Editions scientifiques et medicales Elsevie r SAS.