Structural dynamics of wild type and mutant forms of CLIC4 and ezrin

Cell division is an extremely vital process in life that occurs continuously within all living beings to maintain genomic integrity, cell growth, reproduction and regeneration. It enables the cells to survive by replacing old, damaged, or dead ones with newly formed healthy daughter cells. Therefore, various types of cellular proteins have a role in this process to ensure to complete the division successfully. It has been demonstrated that during cytokinesis, the interaction of ezrin with Chloride Intracellular Channel 4 (CLIC4) protein at the plasma membrane is required for the completion of cytoplasmic division. Their co-localization anchors the plasma membrane and actin cytoskeleton at the cleavage furrow and the midbody providing cortical stability. The successful translocation of CLIC4 to the cleavage furrow and the midbody requires its conserved residues Cys35 and Phe37. When these two residues are mutated to C35A and F37D, respectively, the localization of CLIC4 to the mitotic cell surface and cleavage furrow is abolished. Moreover, ezrin needs to be activated to interact with CLIC4. First, it should bind to phosphatidylinositol-(4,5)-biphosphate (PIP2) and then be phosphorylated from its conserved residue threonine (Thr567) at the carboxyl terminus. However, the mutual interaction between ezrin and CLIC4 is still not well understood. Also, it is not clear how a mutation at the conserved residue Cys35 of CLIC4 or at the phosphorylation site of ezrin changes their structures. Since this interaction might have an important role in cancer therapy, this study aimed at unveiling the mystery behind structural information of these two proteins. Although the wild type structures of CLIC4 and ezrin proteins were previously determined, the structures of their mutant forms, CLIC4 C35A and ezrin T567D, are not available. Thus, this study has been motivated to analyze the structural dynamics of wild type and mutant forms of CLIC4 and ezrin with their mutual interaction.