Ezrin and moesin co-localise with ICAM-1 in brain endothelial cells but are not directly associated

The precise mechanism by which ICAM-1 transduces signals from adherent lymphocytes remains elusive. The ERM proteins ezrin and moesin were found to strongly co-localise with both ICAM-1 and F-actin in brain microvascular endothelial cells suggesting a potential role in mediating ICAM-1 signalling. Such strong co-localisation was maintained following treatment of cells with cytochalasin D, which inhibits actin polymerization and which is capable of inhibiting ICAM-1-induced signalling. Cross-linking of ICAM-1 demonstrated ICAM-1 clustering which no longer associated with ezrin or moesin. In addition immunoprecipitation analysis revealed that ICAM-1 was incapable of precipitating ERM proteins under conditions where ezrin was efficiently precipitated with anti-ICAM-2 antibodies. Fractionation of cell lysates on sucrose density gradients shows ICAM-1 and ezrin to sediment at different densities, whereas ICAM-2 co-sediments with ezrin. Together these data suggest that ICAM-1 is not directly associated with ezrin and moesin in brain microvascular endothelial cells