Abstract
PKCepsilon controls the transport of endocytosed beta1-integrins to the plasma membrane regulating directional cell motility. Vimentin, an intermediate filament protein upregulated upon epithelial cell transformation, is shown here to be a proximal PKCepsilon target within the recycling integrin compartment. On inhibition of PKC and vimentin phosphorylation, integrins become trapped in vesicles and directional cell motility towards matrix is severely attenuated. In vitro reconstitution assays showed that PKCepsilon dissociates from integrin containing endocytic vesicles in a selectively phosphorylated vimentin containing complex. Mutagenesis of PKC (controlled) sites on vimentin and ectopic expression of the variant leads to the accumulation of intracellular PKCepsilon/integrin positive vesicles. Finally, introduction of ectopic wild-type vimentin is shown to promote cell motility in a PKCepsilon-dependent manner; alanine substitutions in PKC (controlled) sites on vimentin abolishes the ability of vimentin to induce cell migration, whereas the substitution of these sites with acidic residues enables vimentin to rescue motility of PKCepsilon null cells. Our results indicate that PKC-mediated phosphorylation of vimentin is a key process in integrin traffic through the cell.