title: Effects of ATP on ligand recognition of platelet fibrinogen receptor on GPIIb-IIIa.
abstract: The recent discovery of 8-azido-ATP binding sites on the platelet fibrinogen receptor glycoprotein complex GPIIb-IIIa suggests that extracellular ATP may directly modulate function of GPIIb-IIIa. In this study we investigated the effect of ATP on ligand binding to GPIIb-IIIa. Fibrinogen-mediated aggregation of washed platelets was inhibited by ATP and 8-azido-ATP in a dose-dependent manner, independent of the agonist (thrombin, collagen, epinephrine, phorbol 12-myristate 13-acetate) used to induce platelet activation. In addition, 8-azido-ATP and ATP inhibited binding of 125I-labeled fibrinogen to thrombin- and phorbol ester-activated platelets. Interaction of nonstimulated platelets with solid-phase fibrinogen was also reduced by 8-azido-ATP and ATP. Moreover, fibrinogen mimetic peptide-induced conformational change of GPIIb-IIIa on resting platelets was reduced in the presence of both nucleotides. Finally, photoincorporation of 8-azido-[gamma-32P]ATP into GPIIb-IIIa was suppressed by GRGDSP but not by the biologically inactive GRGESP peptide. Thus interaction of ATP with 8-azido-ATP binding sites present on GPIIb-IIIa modulate receptor function, which may play a role in regulation of in vivo platelet aggregation.
authors.affiliation: I Medical Department, Technical University Hospital, Rechts der Isar, Munich, Germany.
authors.forename: M P
authors.initials: MP
authors.lastname: Gawaz
authors.forename: P
authors.initials: P
authors.lastname: Mayinger
authors.forename: F J
authors.initials: FJ
authors.lastname: Neumann
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology*; D000345:Affinity Labels; D000595:Amino Acid Sequence; D001386:Azides / Q000378:metabolism / Q000494:pharmacology; D001792:Blood Platelets / Q000378:metabolism*; D002448:Cell Adhesion / Q000187:drug effects; D003435:Crotalid Venoms / Q000378:metabolism; D005340:Fibrinogen / Q000378:metabolism / Q000502:physiology; D006801:Humans; D008024:Ligands; D008027:Light; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D009711:Nucleotides / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology; D010974:Platelet Aggregation / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism*
chemical_list: D000345:Affinity Labels; D001386:Azides; D003435:Crotalid Venoms; D008024:Ligands; D009711:Nucleotides; D009842:Oligopeptides; D010455:Peptides; D010975:Platelet Aggregation Inhibitors; D010980:Platelet Membrane Glycoproteins; C017040:8-azidoadenosine 5'-triphosphate; D000255:Adenosine Triphosphate; D005340:Fibrinogen; C058161:glycyl-arginyl-glycyl-aspartyl-seryl-proline; C041603:Agkistrodon platelet aggregation inhibitor