title: Role of G protein-gated inwardly rectifying potassium channels in P2Y12 receptor-mediated platelet functional responses.
abstract: The role of the G(i)-coupled platelet P2Y(12) receptor in platelet function has been well established. However, the functional effector or effectors contributing directly to alphaIIbbeta3 activation in human platelets has not been delineated. As the P2Y(12) receptor has been shown to activate G protein-gated, inwardly rectifying potassium (GIRK) channels, we investigated whether GIRK channels mediate any of the functional responses of the platelet P2Y(12) receptor. Western blot analysis revealed that platelets express GIRK1, GIRK2, and GIRK4. In aspirin-treated and washed human platelets, 2 structurally distinct GIRK inhibitors, SCH23390 (R(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrochloride) and U50488H (trans-(+/-)-3,4-dichloro-N-methyl-N-[2-(pyrrolidinyl)cyclohexyl] benzeneacetamide methanesulfonate), inhibited adenosine diphosphate (ADP)-, 2-methylthioADP (2-MeSADP)-, U46619-, and low-dose thrombin-mediated platelet aggregation. However, the GIRK channel inhibitors did not affect platelet aggregation induced by high concentrations of thrombin, AYPGKF, or convulxin. Furthermore, the GIRK channel inhibitors reversed SFLLRN-induced platelet aggregation, inhibited the P2Y(12)-mediated potentiation of dense granule secretion and Akt phosphorylation, and did not affect the agonist-induced G(q)-mediated platelet shape change and intracellular calcium mobilization. Unlike AR-C 69931MX, a P2Y(12) receptor-selective antagonist, the GIRK channel blockers did not affect the ADP-induced adenlylyl cyclase inhibition, indicating that they do not directly antagonize the P2Y(12) receptor. We conclude that GIRK channels are important functional effectors of the P2Y(12) receptor in human platelets.
authors.affiliation: Department of Physiology, Temple University, 3420 N Broad St, Philadelphia, PA 19140, USA. spk@temple.edu
authors.forename: Haripriya
authors.initials: H
authors.lastname: Shankar
authors.forename: Swaminathan
authors.initials: S
authors.lastname: Murugappan
authors.forename: Soochong
authors.initials: S
authors.lastname: Kim
authors.forename: Jianguo
authors.initials: J
authors.lastname: Jin
authors.forename: Zhongren
authors.initials: Z
authors.lastname: Ding
authors.forename: Kevin
authors.initials: K
authors.lastname: Wickman
authors.forename: Satya P
authors.initials: SP
authors.lastname: Kunapuli
mesh_terms: D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer / Q000494:pharmacology; D000244:Adenosine Diphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D001552:Benzazepines / Q000494:pharmacology; D001792:Blood Platelets / Q000378:metabolism*; D015153:Blotting, Western; D003594:Cytoplasmic Granules / Q000378:metabolism; D018492:Dopamine Antagonists / Q000494:pharmacology; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D010446:Peptide Fragments / Q000494:pharmacology; D010766:Phosphorylation; D010974:Platelet Aggregation / Q000187:drug effects; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism*; D024661:Potassium Channels, Inwardly Rectifying; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D058925:Receptors, Purinergic P2Y12; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013873:Thionucleotides / Q000494:pharmacology
chemical_list: D000959:Antihypertensive Agents; D001552:Benzazepines; D018492:Dopamine Antagonists; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D008565:Membrane Proteins; C548576:P2RY12 protein, human; C548577:P2ry12 protein, mouse; D010446:Peptide Fragments; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011518:Proto-Oncogene Proteins; D018048:Receptors, Purinergic P2; D058925:Receptors, Purinergic P2Y12; D013873:Thionucleotides; C082835:thrombin receptor peptide (42-47); C002480:methylthio-ADP; D000244:Adenosine Diphosphate; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D043802:GTP-Binding Protein alpha Subunits, Gq-G11