title: Inactivation of the human P2Y12 receptor by thiol reagents requires interaction with both extracellular cysteine residues, Cys17 and Cys270.
abstract: Human platelets express 2 G protein-coupled nucleotide receptors: the platelet adenosine diphosphate (ADP) receptor coupled to stimulation of phospholipase C (P2Y(1)) via heterotrimeric guanosine 5-triphosphate (GTP)-binding protein G(q), and the platelet ADP receptor coupled to inhibition of adenylyl cyclase (P2Y(12)) via heterotrimeric GTP-binding protein G(i). Although these 2 receptors are encoded on the same chromosome and have similar pharmacologic profiles, they have different reactivities toward thiol reagents. The thiol agent p-chloromercuribenzene sulfonic acid (pCMBS) and the active metabolites from antiplatelet drugs, clopidogrel and CS-747, inactivate the P2Y(12) receptor and are predicted to interact with the extracellular cysteine residues on the P2Y(12) receptor. In this study we identified the reactive cysteine residues on the human P2Y(12) receptor by site-directed mutagenesis using pCMBS as the thiol reagent. Cys97Ser and Cys175Ser mutants of the P2Y(12) receptor did not express when transfected into Chinese hamster ovary (CHO-K1) cells, indicating the essential nature of a disulfide bridge between these residues. The Cys17Ser, Cys270Ser, and Cys17Ser/Cys270Ser double mutants had similar median effective concentration (EC(50)) values for ADP and 2-methylthio-ADP (2-MeSADP) when compared with the wild-type P2Y(12). Similarly, the median inhibitory concentration (IC(50)) values for BzATP (2',3'-O-(4- benzoylbenzoyl) adenosine 5'-triphosphate), an antagonist of the P2Y(12) receptor, also did not differ dramatically among these mutants and the wild-type P2Y(12) receptor. pCMBS inactivated the wild-type P2Y(12) receptor in a concentration-dependent manner, whereas it had no effect on the P2Y(1) receptor. Finally, pCMBS partially affected the G(i) coupling of Cys17Ser or Cys270Ser receptor mutants, but had no effect on Cys17Ser/Cys270Ser P2Y(12) receptor-mediated inhibition of adenylyl cyclase. These results indicate that, unlike the P2Y(1) receptor, which has 2 essential disulfide bridges linking its extracellular domains, the P2Y(12) receptor has 2 free cysteines in its extracellular domains (Cys17 and Cys270), both of which are targets of thiol reagents. We speculate that the active metabolites of clopidogrel and CS-747 form disulfide bridges with both Cys17 and Cys270 in the P2Y(12) receptor, and thereby inactivate the receptor.
authors.affiliation: Department of Physiology, Temple University School of Medicine, Philadelphia, PA 19140, USA.
authors.forename: Zhongren
authors.initials: Z
authors.lastname: Ding
authors.forename: Soochong
authors.initials: S
authors.lastname: Kim
authors.forename: Robert T
authors.initials: RT
authors.lastname: Dorsam
authors.forename: Jianguo
authors.initials: J
authors.lastname: Jin
authors.forename: Satya P
authors.initials: SP
authors.lastname: Kunapuli
mesh_terms: D002731:4-Chloromercuribenzenesulfonate / Q000494:pharmacology; D000244:Adenosine Diphosphate / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D016466:CHO Cells; D006224:Cricetinae; D000242:Cyclic AMP / Q000378:metabolism; D003545:Cysteine; D017931:DNA Primers; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism; D007700:Kinetics; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2 / Q000737:chemistry* / Q000235:genetics; D058472:Receptors, Purinergic P2Y1; D058925:Receptors, Purinergic P2Y12; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000737:chemistry; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013438:Sulfhydryl Compounds / Q000494:pharmacology*; D014162:Transfection
chemical_list: D017931:DNA Primers; D007295:Inositol Phosphates; D008565:Membrane Proteins; C546382:P2RY1 protein, human; C548576:P2RY12 protein, human; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2; D058472:Receptors, Purinergic P2Y1; D058925:Receptors, Purinergic P2Y12; D011994:Recombinant Proteins; D013438:Sulfhydryl Compounds; D002731:4-Chloromercuribenzenesulfonate; D000244:Adenosine Diphosphate; D000242:Cyclic AMP; D003545:Cysteine