Involvement of protein kinase Cα in invadopodia formation in Src‐3T3 cells

Abstract

Dynamic structures termed podosomes or invadopodia take the form of actin puncta or rings and are involved in extracellular matrix remodeling, adhesion, and invasion. Though various protein kinase C (PKC) isoforms are known to affect these structures, the precise role of PKCα in signaling upstream of invadopodia in transformed cells remains unclear. We have begun to analyze the role of PKCα in NIH 3T3 fibroblasts transformed with active Src (Src‐3T3 cells). PKCα colocalizes with actin and the invadopodia marker Tks5 at rosettes, and inhibition of conventional PKC isoforms interferes with PKCα localization and rosette formation. The target of PKC that is responsible for invadopodia formation is unknown; however, one possible candidate is Discs Large 1 (DLG1), which we show is a substrate of PKC. DLG1 is present at numerous actin‐based structures including invadopodia and is involved in motility and invasion. Strikingly, coexpression of DLG1 and PKCα in COS‐7 epithelial cells causes formation of actin‐based rosettes (in a cPKC‐dependent manner), suggesting that phosphorylated DLG is sufficient for establishment of these structures.This work was supported by NIH P01 DK54441 and NIH GM43154.