Abstract
The plasma membrane is composed of several different lipids and can interact directly with the actin cytoskeleton via specific lipids and linker proteins. Among these is the ERM (Ezrin, Radixin, Moesin) family of proteins, which is involved in the direct linkage of the membrane to the actin cytoskeleton via a phosphatidylinositol (4,5) biphosphate (PIP2) lipid binding site. Our aim is to understand the interactions between these proteins and PIP2 using in vitro simplifed biomimetic systems like giant unilamellar vesicles (GUV) containing PIP2. We showed that a conformational change of ezrin occur when the protein binds to PIP2, this conformational change allowing ezrin to bind to actin filaments. We have characterized quantitatively the incorporation of PIP2 in the membrane of giant vesicles, and showed that the interaction of ezrin with GUV induce a partitioning of the lipid within the membrane as well as ezrin aggregates on the membrane. Likewise, ezrin oligomers were observed only in the presence of PIP2. A better understanding of the interplay between ezrin, PIP2-containing membranes and actin will help to get a better view of the role of ezrin in cellulo.