PKCα regulates β1 integrin-dependent cell motility through association and control of integrin traffic

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Abstract
Protein kinase C (PKC) has been implicated in integrin‐mediated spreading and migration. In mammary epithelial cells there is a partial co‐localization between β1 integrin and PKCα. This reflects complexes between these proteins as demonstrated by fluorescense resonance energy transfer (FRET) monitored by fluorescence lifetime imaging microscopy and also by coprecipitation. Constitutive complexes are observed for the intact PKCα and also form with the regulatory domain in an activation‐dependent manner. Expression of PKCα causes upregulation of β1 integrin on the cell surface, whereas stimulation of PKC induces internalization of β1 integrin. The integrin initially traffics to an endosomal compartment in a Ca2+/PI 3‐kinase/dynamin I‐dependent manner and subsequently enters an endocytic recycling pathway. This induction of endocytosis by PKCα is a function of activity and is not observed for the regulatory domain. PKCα, but not PKCα regulatory domain expression stimulates migration on β1 integrin substrates. This PKCα‐enhanced migratory response is inhibited by blockade of endocytosis.