Ezrin is a downstream effector of trafficking PKC-integrin complexes involved in the control of cell motility

Protein kinase C (PKC) a has been implicated in beta1 integrin-mediated cel l migration. Stable expression of PKC alpha is shown here to enhance wound closure. This PKC-driven migratory response directly correlates with increa sed C-terminal threonine phosphorylation of ezrin/moesin/radixin (ERM) at t he wound edge. Both the wound migratory response and ERM phosphorylation ar e dependent upon the catalytic function of PKC and are susceptible to inhib ition by phosphatidylinositol 3-kinase blockade. Upon phorbol 12,13-dibutyr ate stimulation, green fluorescent protein-PKC alpha and beta1 integrins co -sediment with ERM proteins in low-density sucrose gradient fractions that are enriched in transferrin receptors, Using fluorescence lifetime imaging microscopy, PKC alpha is shown to form a molecular complex with ezrin, and the PKC-co-precipitated endogenous ERR I is hyperphosphorylated at the C-te rminal threonine residue, i.e, activated. Electron microscopy showed an enr ichment of both proteins in plasma membrane protrusions. Finally, overexpre ssion of the C-terminal threonine phosphorylation site mutant of ezrin has a dominant inhibitory effect on PKC alpha -induced cell migration. We provi de the first evidence that PKC alpha or a PKC alpha -associated serine/thre onine kinase can phosphorylate the ERM C-terminal threonine residue within a kinase-ezrin molecular complex in vivo.