Ezrin interacts with the scaffold protein IQGAP1 and affects its cortical localization.

The cortical cytoskeleton constitutes an important subcellular structure that determines cell shape and regulates cell migration as well as membrane traffic to and from the plasma membrane. Many components of the cortical cytoskeleton have been identified including structural and scaffolding proteins, membrane-cytoskeleton linker proteins and signaling intermediates. We describe here an association of the membrane-F-actin linker protein ezrin with the scaffolding protein IQGAP1 that serves as a hub for concentrating different signaling complexes. Both, ezrin and IQGAP1 bind in a Ca²⁺-dependent manner to the EF hand protein S100P and complexes consisting of Ca²⁺-bound S100P, IQGAP1 and ezrin can be isolated by immunoprecipitation. Ezrin and IQGAP1 also interact in the absence of Ca²⁺, thus independent of S100P. Direct ezrin-IQGAP1 interaction can be shown with the purified proteins. It is mediated via the N-terminal FERM domain of ezrin and the IQ domain of IQGAP1, respectively. Ezrin and IQGAP1 colocalize in the submembraneous cytoskeleton and in cellular protrusions of human epithelial cells and knockdown of ezrin reduces the cortical localization of IQGAP1. Thus, ezrin appears to participate in recruiting IQGAP1 to the cell cortex thereby establishing a close connection between membrane-F-actin contacts and actin regulators that can be assembled by IQGAP1. This article is part of a Special Issue entitled: 13th European Symposium on Calcium.