PKC epsilon controls the traffic of beta1 integrins in motile cells

Protein kinase C (PKC) has been implicated in beta 1 integrin-mediated cell migration. Expression of the novel PKC isoform, PKC epsilon, in PKC epsilon(-/-) cells is shown here to stimulate directional migration of cells towards beta 1 integrin substrates in a manner dependent on PKC catalytic activity. On PKC inhibition, integrin beta 1 and PKC epsilon become reversibly trapped in a tetraspanin (CD81)-positive intracellular compartment, correlating with reduced haptotaxis. Immunofluorescence and pulse labelling studies indicate that this is a previously uncharacterized recycling compartment trapped by inhibition of PKC. Electron microscopy demonstrated the co-localization of PKC epsilon and integrin beta 1 on the vesicular membranes. Finally, using a reconstituted in vitro system, the dissociation of PKC epsilon from these vesicles is shown to be dependent on both the presence of cytosolic components and energy, and on PKC catalytic activity. The evidence presented indicates that PKC epsilon controls an internal traffic step that under uninhibited conditions permits the recycling of beta 1 integrin, contributing to cell motility.