Transformation by a nucleotide-activated P2Y receptor is mediated by activation of Gαi, Gαq and Rho-dependent signaling pathways

Here we demonstrate that an avian P2Y purinoceptor (tP2YR) with unique pharmacological and signal transduction properties induces morphologic and growth transformation of rodent fibroblasts. tP2YR induced a transformed phenotype similar to the mas oncogene, a G protein-coupled receptor which causes transformation by activation of Rac-dependent pathways. tP2YR-transformed cells exhibited increased steady-state activation of Rac1 and RhoA. Like activated Rho GTPases, tP2YR cooperated with activated Raf and caused synergistic transformation of NIH3T3 cells. Our data indicate that the ability of tP2YR to cause transformation is due to its unique ability among purinergic receptors to simultaneously activate Gαq and Gαi. Co-expression of constitutively activated mutants of these two Gα subunits caused the same transformed phenotype as tP2YR and Mas. Furthermore, transformation by both tP2YR and Mas was blocked by pharmacological inhibition of GαI by pertussis toxin (PTX) indicating an essential role for Gαi in transformation by these G-protein coupled receptors.Our data suggest that coordinated activation of Gαq and Gαi may link the tP2YR and possibility the Mas oncogene with signaling pathways resulting in activation of Rho family proteins to promote cellular transformation.Extracellular nucleotides such as adenosine 5'-triphosphate (ATP), adenosine 5'-diphosphate (ADP), uridine 5'-diphosphate (UDP) and uridine 5'-triphosphate (UTP) interact with purinergic receptors to modulate a broad spectrum of physiological responses [1]. Purinoceptors can be divided based on their pharmacological profiles into two major types: P1- and P2-purinoceptors [2]. Additionally, P2 receptors can be further subdivided into P2X-purinergic receptors which form ligand gated ion channels and P2Y-purinergic receptors which couple to heterotrimeric G-proteins. Most commonly, P2Y receptors activate phospholipase C (PLC) but some also inhibit or stimulate adenylyl cyclase or modulate ion channel act