title: ADP receptor-induced activation of guanine-nucleotide-binding proteins in human platelet membranes.
abstract: ADP receptor-regulated binding of the labeled GTP analog, guanosine 5'-O-(3-[35S]thiotriphosphate) ([35S]GTP[gamma S]), to guanine-nucleotide-binding proteins (G proteins) was studied in human platelet membranes. The potent ADP receptor agonist, 2-methyl-thio-adenosine 5'-diphosphate (2MeSADP), a non-hydrolyzable analog of ADP, increased the binding of [35S]GTP[gamma S] without apparent lag phase. Under optimal conditions, i.e. in the presence of GDP (1-10 microM), 2MeSADP increased the binding up to about threefold, with half-maximal and maximal increase observed at 10 nM and 1 microM 2MeSADP, respectively. ADP itself increased the binding of [35S]GTP[gamma S] by maximally about twofold, with half-maximal increase occurring at 0.1 microM ADP. The agonist-induced stimulation was competitively antagonized by the ADP receptor(s) antagonist, (1S)-adenosine 5'-O-(1-thiotriphosphate) [(Sp)-ATP[alpha S]]. Other platelet receptor agonists known to act through receptors coupled to G proteins also increased binding of [35S]GTP[gamma S] in human platelet membranes, but without being inhibited by (Sp)-ATP[alpha S]. The data presented indicate that the platelet ADP receptor(s) can interact with and efficiently activate G proteins, the nature of which remains to be identified.
authors.affiliation: INSERM U.311, Centre Régional de Transfusion Sanguine, Strasbourg, France.
authors.forename: C
authors.initials: C
authors.lastname: Gachet
authors.forename: J P
authors.initials: JP
authors.lastname: Cazenave
authors.forename: P
authors.initials: P
authors.lastname: Ohlmann
authors.forename: G
authors.initials: G
authors.lastname: Hilf
authors.forename: T
authors.initials: T
authors.lastname: Wieland
authors.forename: K H
authors.initials: KH
authors.lastname: Jakobs
mesh_terms: D010832:6-Phytase / Q000302:isolation & purification / Q000378:metabolism*; D000244:Adenosine Diphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000097:blood*; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D010974:Platelet Aggregation / Q000187:drug effects; D011983:Receptors, Purinergic / Q000187:drug effects / Q000502:physiology*; D013873:Thionucleotides / Q000494:pharmacology*
chemical_list: D011983:Receptors, Purinergic; D013873:Thionucleotides; C002480:methylthio-ADP; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D000244:Adenosine Diphosphate; D010832:6-Phytase; D019204:GTP-Binding Proteins