title: A differential role of the platelet ADP receptors P2Y1 and P2Y12 in Rac activation.
abstract: The dynamics of the actin cytoskeleton, largely controlled by the Rho family of small GTPases (Rho, Rac and Cdc42), is critical for the regulation of platelet responses such as shape change, adhesion, spreading and aggregation. Here, we investigated the role of adenosine diphosphate (ADP), a major co-activator of platelets, on the activation of Rac. ADP rapidly activated Rac in a dose-dependent manner and independently of GPIIb/IIIa and phosphoinositide 3-kinase. ADP alone, used as a primary agonist, activated Rac and its effector PAK via its P2Y1 receptor, through a G(q)-dependent pathway and independently of P2Y12. The P2Y12 receptor appeared unable to activate the GTPase per se as also observed for the adenosine triphosphate receptor P2X1. Conversely, secreted ADP strongly potentiated Rac activation induced by FcgammaRIIa clustering or TRAP via its P2Y12 receptor, the target of antithrombotic thienopyridines. Stimulation of the alpha(2A)-adrenergic receptor/G(z) pathway by epinephrine was able to replace the P2Y12/G(i)-mediated pathway to amplify Rac activation by FcgammaRIIa or by the thrombin receptor PAR-1. This co-activation appeared necessary to reach a full stimulation of Rac as well as PAK activation and actin polymerization and was blocked by a G-protein betagamma subunits scavenger peptide.
authors.affiliation: Inserm U563, Département d'Oncogenèse et signalisation dans les cellules hématopoïétiques, Hôpital Purpan, Toulouse, France.
authors.forename: C
authors.initials: C
authors.lastname: Soulet
authors.forename: B
authors.initials: B
authors.lastname: Hechler
authors.forename: M-P
authors.initials: MP
authors.lastname: Gratacap
authors.forename: M
authors.initials: M
authors.lastname: Plantavid
authors.forename: S
authors.initials: S
authors.lastname: Offermanns
authors.forename: C
authors.initials: C
authors.lastname: Gachet
authors.forename: B
authors.initials: B
authors.lastname: Payrastre
mesh_terms: D000199:Actins / Q000378:metabolism; D000244:Adenosine Diphosphate / Q000494:pharmacology; D000818:Animals; D001792:Blood Platelets / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D020558:GTP Phosphohydrolases / Q000378:metabolism; D044385:GTP-Binding Protein alpha Subunits / Q000378:metabolism; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000378:metabolism; D008565:Membrane Proteins / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D018048:Receptors, Purinergic P2 / Q000502:physiology*; D058472:Receptors, Purinergic P2Y1; D058925:Receptors, Purinergic P2Y12; D054462:p21-Activated Kinases
chemical_list: D000199:Actins; D044385:GTP-Binding Protein alpha Subunits; C490964:Gnaz protein, mouse; D008565:Membrane Proteins; C546383:P2ry1 protein, mouse; C548577:P2ry12 protein, mouse; D018048:Receptors, Purinergic P2; D058472:Receptors, Purinergic P2Y1; D058925:Receptors, Purinergic P2Y12; D000244:Adenosine Diphosphate; C515909:Pak2 protein, mouse; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D054462:p21-Activated Kinases; D020558:GTP Phosphohydrolases; D043802:GTP-Binding Protein alpha Subunits, Gq-G11