Regulation of cell adhesion and anchorage-dependent growth by a new beta(1)-integrin-linked protein kinase

THE interaction of cells with the extracellular matrix regulates cell shape, motility, growth, survival, differentiation and gene expression, through integrin-mediated signal transduction(1-3). We used a two-hybrid screen to isolate genes encoding proteins that interact with the beta(1)-integrin cytoplasmic domain. The most frequently isolated complementary DNA encoded a new, 59K serine/threonine protein kinase, containing four ankyrin-like repeats. We report here that this integrin-linked kinase (ILK) phosphorylated a beta(1)-integrin cytoplasmic domain peptide in vitro and coimmunoprecipitated with beta(1) in lysates of mammalian cells. Endogenous ILK kinase activity was reduced in response to fibronectin. Overexpression of p59(ILK) disrupted epithelial cell architecture and inhibited adhesion to integrin substrates, while inducing anchorage-independent growth. We propose that ILK is a receptor-proximal protein kinase regulating integrin-mediated signal transduction.