Posters

G protein-coupled receptors (GPCRs) belong to a large family of cell-surface receptors involved in many intracellular signaling pathways. Despite GPCRs lack intrinsic tyrosine kinase activity, tyrosine phosphorylation of a tyrosine kinase receptor (TKR) occurs in response to binding of specific agonists of several such receptors. Crosstalk between GPCRs and TKRs may occur by different molecular mechanism such as metalloproteases activation, non-receptor tyrosine kinases involvement, or reactive oxygen species (ROS) production, a process mediated by theNADPH oxidase enzymatic complex. Formyl-peptide receptors (FPRs) are seven transmembrane domain receptors, coupled to heterotrimeric Gi proteins and sensible to pertussis toxin (PTX). FPR1, FPR2 and FPR3 expression was observed in a wide variety of tissues and it has been implicated in tissue repair, angiogenesis and cancer. We investigated FPR1-mediated VEGFR2 transactivation and its involvement in angiogenesis processes in ECV304 endothelial cells. We demonstrated, by RT-PCR, that ECV304 cell line expresses p47phox, p67phox and p22phox subunits of NADPH oxidase, as well as FPR1, FPR3, VEGFR1 and VEGFR2 receptors. Stimulation of ECV304 with the FPR1 agonist N-fMLP induces p47phox phosphorylation, which is considered the key event of NADPH oxidase activation. Preincubation with PTX prevents p47phox phosphorylation. FPR1 stimulation by N-fMLP also triggers Y951, Y996 and Y1175 phosphorylation of cytosolic residues of VEGFR2, which elicits intracellular signaling cascades responsible of angiogenesis. Preincubation with PTX or FPR1 siRNA, or the inhibition of NADPH oxidase functions by apocynin or p22phox siRNA, prevents VEGFR2 tyrosine phosphorylation and, in turn, downstream signaling cascades.