title: P2Y1 and P2Y12 receptors for ADP desensitize by distinct kinase-dependent mechanisms.
abstract: Adenosine 5'-diphosphate (ADP) plays a central role in regulating platelet function by the activation of the G protein-coupled receptors P2Y(1) and P2Y(12). Although it is well established that aggregation responses of platelets to ADP desensitize, the underlying mechanisms involved remain unclear. In this study we demonstrate that P2Y(1)- and P2Y(12)-mediated platelet responses desensitize rapidly. Furthermore, we have established that these receptors desensitize by different kinase-dependent mechanisms. G protein-coupled receptor kinase (GRK) 2 and GRK6 are both endogenously expressed in platelets. Transient overexpression of dominant-negative mutants of these kinases or reductions in endogenous GRK expression by the use of specific siRNAs in 1321N1 cells showed that P2Y(12), but not P2Y(1), desensitization is mediated by GRKs. In contrast, desensitization of P2Y(1), but not P2Y(12), is largely dependent on protein kinase C activity. This study is the first to show that both P2Y(1) and P2Y(12) desensitize in human platelets, and it reveals ways in which their sensitivity to ADP may be differentially and independently altered.
authors.affiliation: Department of Pharmacology, School of Medical Sciences, University Walk, Bristol, BS8 1TD, United Kingdom.
authors.forename: Adam R
authors.initials: AR
authors.lastname: Hardy
authors.forename: Pamela B
authors.initials: PB
authors.lastname: Conley
authors.forename: Jiansong
authors.initials: J
authors.lastname: Luo
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Benovic
authors.forename: Alastair W
authors.initials: AW
authors.lastname: Poole
authors.forename: Stuart J
authors.initials: SJ
authors.lastname: Mundell
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology*; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism; D045744:Cell Line, Tumor; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D054768:G-Protein-Coupled Receptor Kinases; D006801:Humans; D008565:Membrane Proteins / Q000502:physiology*; D015539:Platelet Activation / Q000187:drug effects*; D011493:Protein Kinase C / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000502:physiology; D034741:RNA, Small Interfering / Q000494:pharmacology; D018048:Receptors, Purinergic P2 / Q000502:physiology*; D058472:Receptors, Purinergic P2Y1; D058925:Receptors, Purinergic P2Y12; D014162:Transfection; D051552:beta-Adrenergic Receptor Kinases
chemical_list: D008565:Membrane Proteins; C546382:P2RY1 protein, human; C548576:P2RY12 protein, human; D034741:RNA, Small Interfering; D018048:Receptors, Purinergic P2; D058472:Receptors, Purinergic P2Y1; D058925:Receptors, Purinergic P2Y12; D000244:Adenosine Diphosphate; D017346:Protein Serine-Threonine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D051552:beta-Adrenergic Receptor Kinases; D054768:G-Protein-Coupled Receptor Kinases; C089176:G-protein-coupled receptor kinase 6