Properties of an ezrin mutant defective in F-actin binding

J Mol Biol. 2009 Jan 30;385(4):1015-31. doi: 10.1016/j.jmb.2008.11.051. Epub 2008 Dec 3.


Ezrin, radixin and moesin are a family of proteins that provide a link between the plasma membrane and the cortical actin cytoskeleton. The regulated targeting of ezrin to the plasma membrane and its association with cortical F-actin are more than likely functions necessary for a number of cellular processes, such as cell adhesion, motility, morphogenesis and cell signalling. The interaction with F-actin was originally mapped to the last 34 residues of ezrin, which correspond to the last three helices (alphaB, alphaC and alphaD) of the C-terminal tail. We set out to identify and mutate the ezrin/F-actin binding site in order to pinpoint the role of F-actin interaction in morphological processes as well as signal transduction. We report here the generation of an ezrin mutant defective in F-actin binding. We identified four actin-binding residues, T576, K577, R579 and I580, that form a contiguous patch on the surface of the last helix, alphaD. Interestingly, mutagenesis of R579 also eliminated the interaction of band four-point one, ezrin, radixin, moesin homology domains (FERM) and the C-terminal tail domain, identifying a hotspot of the FERM/tail interaction. In vivo expression of the ezrin mutant defective in F-actin binding and FERM/tail interaction (R579A) altered the normal cell surface structure dramatically and inhibited cell migration. Further, we showed that ezrin/F-actin binding is required for the receptor tyrosine kinase signal transfer to the Ras/MAP kinase signalling pathway. Taken together, these observations highlight the importance of ezrin/F-actin function in the development of dynamic membrane/actin structures critical for cell shape and motility, as well as signal transduction.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism*
  • Amino Acid Sequence
  • Amino Acid Substitution
  • Amino Acids / metabolism
  • Animals
  • Cell Membrane / metabolism
  • Cytoskeletal Proteins / chemistry
  • Cytoskeletal Proteins / metabolism*
  • Humans
  • Membrane Proteins / chemistry
  • Mice
  • Microfilament Proteins / chemistry
  • Models, Molecular
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Mutant Proteins / metabolism*
  • NIH 3T3 Cells
  • Phosphorylation
  • Phosphothreonine / metabolism
  • Point Mutation / genetics
  • Protein Binding
  • Protein Structure, Secondary
  • Protein Transport
  • Sus scrofa


  • Actins
  • Amino Acids
  • Cytoskeletal Proteins
  • Membrane Proteins
  • Microfilament Proteins
  • Mutant Proteins
  • ezrin
  • Phosphothreonine
  • moesin
  • radixin