The class II phosphoinositide 3-kinase PI3K-C2β regulates cell migration by a PtdIns(3)P dependent mechanism

The biological and pathophysiological significance of class II phosphoinositide 3-kinase enzyme expression currently remains unclear. Using an in vitro scrape wound assay and time-lapse video microscopy, we demonstrate that cell motility is increased in cultures expressing recombinant PI3K-C2 beta enzyme. In addition, overexpression of PI3K-C2 beta transiently decreased cell adhesion, stimulated the formation of cytoplasmic processes, and decreased the rate of cell proliferation. Consistent with these observations, expression of PI3K-C2 beta also decreased expression of alpha4 betal integrin subunits. Using asynchronous cultures, we show that endogenous PI3K-C2 beta is present in lamellipoclia of motile cells. When cells expressing recombinant PI3K-C2 beta were plated onto fibronectin, cortical actin staining increased markedlyand actin rich lamellipodia and filopodia became evident. Overexpression of a 2xFYVE(Hrs) domain fusion protein abolished this response demonstrating that the effect of Pi3K-C2 beta on the reorganization of actin filaments is dependent upon PtdIns(3)P. Finally, overexpression of PI3K-C2 beta increased GTP loading of Cdc42. Our data demonstrates for the first time, that PI3K-C2 beta plays a regulatory role in cell motility and that the mechanism by which it reorganizes the actin cytoskeleton is dependent upon Ptdlns(3)P production.