Phosphatidylinositol 4,5-Bisphosphate-Induced Conformational Change of Ezrin and Formation of Ezrin Oligomers

The plasma membrane-cytoskeleton interface is a dynamic structure involved in a variety of cellular events. Ezrin, a protein from the ERM family, provides a direct linkage between the cytoskeleton and the membrane via its interaction with phosphatidylinositol 4,5-bisphosphate (PIP2). In this paper, we investigate the interaction between PIP2 and ezrin in vitro using PIP2 dispersed in a unimolecular way in buffer. We compared the results obtained with full-length ezrin to those obtained with an ezrin mutant, which was previously found not to be localized at the cell membrane, and with the N-terminal membrane binding domain (FERM domain) of ezrin. We show that PIP2 induced a conformational change in full-length ezrin. PIP2 was also found to induce, in vitro, the formation of oligomers of wild-type ezrin, but not of mutant ezrin. These oligomers had previously been observed in vivo, but their role is yet to be clarified. Our finding hints at a possible role for PIP2 in the formation of ezrin oligomers.