Phosphorylation of adducin by protein kinase Cdelta promotes cell motility

Protein kinase Cdelta (PKCdelta) has been implicated to play a crucial role in cell proliferation, differentiation and apoptosis. In this study, we have investigated the role of PKCdelta in cell motility using Madin-Darby canine kidney cells. Overexpression of PKCdelta promoted membrane protrusions, concomitant with increased cell motility. By contrast, suppression of PKCdelta expression by RNA interference inhibited cell motility. Moreover, a fraction of PKCdelta was detected at the edge of membrane protrusions in which it colocalized with adducin, a membrane skeletal protein whose phosphorylation state is important for remodeling of the cortical actin cytoskeleton. Elevated expression of PKCdelta correlated with increased phosphorylation of adducin at Ser726 in intact cells. In vitro, PKCdelta, but not PKCalpha, directly phosphorylated the Ser726 of adducin. Finally, we demonstrated that overexpression of both adducin and PKCdelta could generate a synergistic effect on promoting cell spreading and cell migration. Our results support a positive role for PKCdelta in cell motility and strongly suggest a link between PKCdelta activity, adducin phosphorylation and cell motility.