Src-mediated activation of [alpha]-diacylglycerol kinase is required for hepatocyte growth factor-induced cell motility

Diacylglycerol kinases are involved in cell signaling, either as regulators of diacylglycerol levels or as intracellular signal-generating enzymes. However, neither their role in signal transduction nor their biochemical regulation has been elucidated. Hepatocyte growth factor (HGF), upon binding to its tyrosine kinase receptor, activates multiple signaling pathways stimulating cell motility, scattering, proliferation and branching morphogenesis. Herein we demonstrate that: (i) the enzymatic activity of [alpha]-diacylglycerol kinase ([alpha]Dgk) is stimulated by HGF in epithelial, endothelial and [alpha]Dgk-transfected COS cells; (ii) cellular expression of an [alpha]Dgk kinase-defective mutant inhibits activation of endogenous [alpha]Dgk acting as dominant negative; (iii) specific inhibition of [alpha]Dgk prevents HGF-induced cell movement of endothelial cells; (iv) HGF induces the association of [alpha]Dgk in a complex with Src, whose tyrosine kinase activity is required for [alpha]Dgk activation by HGF; (v) Src wild type stimulates [alpha]Dgk activity in vitro; and (vi) [alpha]Dgk can be tyrosine phosphorylated in intact cells.