title: Agonist concentration-dependent differential responsivity of a human platelet purinergic receptor: pharmacological and kinetic studies of aggregation, deaggregation and shape change responses mediated by the purinergic P2Y1 receptor in vitro.
abstract: Platelet shape change (SC), aggregation and deaggregation responses are integral components of hemostasis that are elicited and modulated in vivo by the simultaneous activation of several membrane receptors. Selective activation of the purinergic P2Y1 receptor in vivo elicits a sustained SC and a small, transient aggregation response that is reversed rapidly by a robust deaggregation response (Platelets 2003; 14: 89). Using a kinetics-based turbidimetric approach to study the modulation of these concurrent components of human platelet responses, we demonstrate that these P2Y1 receptor-related responses and a number of their kinetic and steady-state characteristics are differentially elicited and modulated. P2Y1 receptor agonist concentrations that elicited aggregation (pEC50 for ADP, 2-MeSADP; 5.88, 6.69) were 10-fold greater than those that elicited SC (7.33, 7.67). The magnitude of the aggregation response was agonist concentration-dependent, saturable and was associated with an agonist concentration-dependent deceleration of the deaggregation response. Gi-coupled receptor (alpha 2A-adrenoceptor, EP3 and P2Y12 receptors) agonists also enhanced aggregation through deceleration of the deaggregation response, and an inhibitor of PI3K activity (wortmannin) inhibited aggregation through acceleration of the deaggregation response. Neither treatment affected the extent or the kinetics of the SC response. The aggregation but not the SC response was rapidly desensitized by P2Y1 receptor activation by ADP. The affinity of the presence of a single P2Y1 receptor subtype. The differential characteristics and modulation of the SC and aggregation responses by a single receptor support the idea that different signaling pathways activated at different occupancy states of the same receptor underlie the two responses. P2Y1 receptor-mediated platelet aggregation and SC responses provide a convenient model for studying the phenomenon of agonist-directed signaling by differential occupancy of the same membrane receptor.
authors.affiliation: Department of Anesthesiology, Mount Sinai School of Medicine, New York, NY 10029, USA. saul.maayani@mssm.edu
authors.forename: Saul
authors.initials: S
authors.lastname: Maayani
authors.forename: Todd E
authors.initials: TE
authors.lastname: Schwarz
authors.forename: Nayana D
authors.initials: ND
authors.lastname: Patel
authors.forename: Barbara D
authors.initials: BD
authors.lastname: Craddock-Royal
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Tagliente
mesh_terms: D000244:Adenosine Diphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D000249:Adenosine Monophosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D000067956:Adenylyl Cyclase Inhibitors; D000465:Algorithms; D000730:Androstadienes / Q000494:pharmacology; D001792:Blood Platelets / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D048429:Cell Size / Q000187:drug effects / Q000502:physiology; D015232:Dinoprostone / Q000031:analogs & derivatives* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004837:Epinephrine / Q000494:pharmacology; D006801:Humans; D007650:Ketanserin / Q000494:pharmacology; D007700:Kinetics; D008565:Membrane Proteins / Q000819:agonists; D009391:Nephelometry and Turbidimetry / Q000379:methods; D010646:Phentolamine / Q000494:pharmacology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D015539:Platelet Activation / Q000187:drug effects / Q000502:physiology; D010974:Platelet Aggregation / Q000187:drug effects / Q000502:physiology*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D018078:Receptors, Prostaglandin E / Q000819:agonists; D058308:Receptors, Prostaglandin E, EP3 Subtype; D018048:Receptors, Purinergic P2 / Q000502:physiology*; D058472:Receptors, Purinergic P2Y1; D058925:Receptors, Purinergic P2Y12; D015398:Signal Transduction / Q000502:physiology; D013873:Thionucleotides / Q000494:pharmacology; D000077191:Wortmannin
chemical_list: D000067956:Adenylyl Cyclase Inhibitors; D000730:Androstadienes; D008565:Membrane Proteins; C546382:P2RY1 protein, human; C548576:P2RY12 protein, human; C545647:PTGER3 protein, human; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010975:Platelet Aggregation Inhibitors; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D018078:Receptors, Prostaglandin E; D058308:Receptors, Prostaglandin E, EP3 Subtype; D018048:Receptors, Purinergic P2; D058472:Receptors, Purinergic P2Y1; D058925:Receptors, Purinergic P2Y12; D013873:Thionucleotides; C002480:methylthio-ADP; D000249:Adenosine Monophosphate; C016767:sulprostone; D000244:Adenosine Diphosphate; C117446:cangrelor; D007650:Ketanserin; D011433:Propranolol; C010840:adenosine 3'-phosphate-5'-phosphate; D015232:Dinoprostone; D000077191:Wortmannin; D004837:Epinephrine; D010646:Phentolamine