→ ERM*|open@Cytosol References
PMID:9287351
ERM family (ezrin/radixin/moesin)
Direct interaction of the ARHGDI family with ERM family initiates the activation of the Rho small G protein.
PMID:10047517
Regulation of cortical structure by the ERM protein family.
PMID:12045227
Rho-dependent and -independent activation mechanisms of ERM proteins: an essential role for polyphosphoinositides in vivo.
ERM proteins crosslink actin filaments to plasma membranes and are involved in the organization of the cortical cytoskeleton, especially in the formation of microvilli.
ERM proteins are reported to be activated as crosslinkers in a Rho-dependent manner and are stabilized when phosphorylated at their C-terminal threonine residue to create C-terminal threonine- phosphorylated ERM proteins
However, ERM proteins appear to be activated in the absence of Rho activation and remain active without C-terminal phosphorylation.
Phosphatidylinositol (4,5)-bisphosphate (PtdIns(4,5)P2) affected the activation of ERM proteins regardless of cell type.
The Rho-independent activation mechanism of ERM proteins therefore exists.
Both Rho-dependent and -independent activation of ERM proteins require a local elevation of PtdIns(4,5)P2 concentration in vivo.
PMID:7579708
Cell extracts contain ezrin dimers and ezrin-moesin heterodimers in addition to monomers.
Dimerization in vivo requires an activation step that exposes this masked domain.
The conformationally inaccessible C-terminal region included the F-actin binding site, suggesting that this activity is likewise regulated by masking.
PMID:8527459
Ezrin, a membrane-microfilament linking protein, exists largely as a monomeric protein in solution.
Purified ezrin monomers normally have a masked C-terminal domain (termed a C-ERMAD) that, upon exposure, can associate with an N-terminal domain (termed N-ERMAD) of another ezrin molecule.
Purified ezrin dimers also have masked C-ERMADs.
Since radixin and moesin, the two other members of the closely related ERM protein family, both contain N- and C-ERMADs, the results we have documented and models proposed for ezrin are likely to apply to radixin and moesin as well
PMID:12802084
ERM proteins exist in the cytoplasm as dormant monomers in which the F-actin cytoskeleton and the plasma membrane binding sites are masked.
This closed conformation is due to an intramolecular N- to C-ERM association domain (ERMAD) interaction.
Abrogation of the N and C-ERMAD interaction is required to open up the molecules and to expose their cryptic binding sites
2 factors have been implicated in the activation of ERM proteins:
-The binding to phosphatidylinositol 4,5-biphosphate is required for their interaction with actin in vitro and with membrane proteins in vivo
-Phosphorylation of a conserved threonine residue in the C-ERMAD, T567, inhibits the N and C-ERMAD interaction in vitro and in vivo, converts inactive oligomers to active monomers
PMID:8522586
PMID:10970850
Phosphorylation of ezrin by the Rho kinase ROCK is required for Rho-induced focal adhesion assembly.