Modulation of endothelial cell migration by extracellular nucleotides - Involvement of focal adhesion kinase and phosphatidylinositol 3-kinase-mediated pathways

Extracellular nucleoticles bind to type-2 purinergic/pyrimidinergic (P2) receptors that mediate various responses, such as cell activation, proliferation and apoptosis, implicated in inflammatory processes. The role of P2 receptors and their associated signal transduction pathways in endothelial cell responses has not been fully investigated. Here, it is shown that stimulation of human umbilical vein endothelial cells (HUVEC) with extracellular ATP or UTP increased intracellular free calcium ion concentrations ([Ca2+](i)), induced phosphorylation of focal adhesion kinase (FAK), p130(cas) and paxillin, and caused cytoskeletal rearrangements with consequent cell migration. Furthermore, UTP increased migration of HUVEC in a phosphaticlylinositol 3-kinase (P13-K)-dependent manner. BAPTA or thapsigargin in-hibited the extracellular nucleotide-incluced increase in [Ca2+](i), a response crucial for both FAK phosphorylation and cell migration. Furthermore, long-term exposure of HUVEC to ATP and UTR agonists of the G protein-coupled P2Y2 and P2Y4 receptor subtypes, caused upregulation of alpha(v) integrin expression, a cell adhesion molecule known to directly interact with P2Y2 receptors. Our results suggest that extracellular nucleotides modulate signaling pathways in HUVEC influencing cell functions, such as cytoskeletal changes, cellular adhesion and motility, typically associated with integrin-activation and the action of growth factors. We propose that P2Y2 and possibly P2Y4 receptors mediate those responses that are important in vascular inflammation, atherosclerosis and angiogenesis.