title: Succinate independently stimulates full platelet activation via cAMP and phosphoinositide 3-kinase-β signaling.
abstract: BACKGROUND
  The citric cycle intermediate succinate has recently been identified as a ligand for the G-protein-coupled receptor (GPCR) SUCNR1. We have previously found that this receptor is one of the most highly expressed GPCRs in human platelets.
  
  
  OBJECTIVE
  The aim of this study was to investigate the role of SUCNR1 in platelet aggregation and to explore the signaling pathways of this receptor in platelets.
  
  
  RESULTS
  Using real-time-PCR, we demonstrated that SUCNR1 is expressed in human platelets at a level corresponding to that of the P2Y(1) receptor. Light transmission aggregation experiments showed dose-dependent aggregation induced by succinate, reaching a maximum response at 0.5 mM. The effect of succinate on platelet aggregation was confirmed with flow cytometry, showing increased surface expression of activated glycoprotein IIb-IIIa and P-selectin. Intracellular SUCNR1 signaling was found to result in decreased cAMP levels, Akt phosphorylation mediated by phosphoinositide 3-kinase-β activation, and receptor desensitization. Furthermore, succinate-induced platelet aggregation was demonstrated to depend on Src, generation of thromboxane A(2), and ATP release. Platelet SUCNR1 is subject to desensitization through both homologous and heterologous mechanisms. In addition, the P2Y(12) receptor inhibitor ticagrelor completely prevented platelet aggregation induced by succinate.
  
  
  CONCLUSIONS
  Our experiments show that succinate induces full aggregation of human platelets via SUCNR1. Succinate-induced platelet aggregation depends on thromboxane A(2) generation, ATP release, and P2Y(12) activation.
authors.affiliation: Department of Cardiology, Lund University Hospital, Lund, Sweden.
authors.forename: C
authors.initials: C
authors.lastname: Högberg
authors.forename: O
authors.initials: O
authors.lastname: Gidlöf
authors.forename: C
authors.initials: C
authors.lastname: Tan
authors.forename: S
authors.initials: S
authors.lastname: Svensson
authors.forename: J
authors.initials: J
authors.lastname: Nilsson-Öhman
authors.forename: D
authors.initials: D
authors.lastname: Erlinge
authors.forename: B
authors.initials: B
authors.lastname: Olde
mesh_terms: D001792:Blood Platelets / Q000378:metabolism; D015153:Blotting, Western; D000242:Cyclic AMP / Q000378:metabolism*; D005434:Flow Cytometry; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006801:Humans; D008856:Microscopy, Fluorescence; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D015539:Platelet Activation / Q000187:drug effects*; D016133:Polymerase Chain Reaction; D015398:Signal Transduction; D019802:Succinic Acid / Q000494:pharmacology*
chemical_list: D016244:Guanosine 5'-O-(3-Thiotriphosphate); D019802:Succinic Acid; D000242:Cyclic AMP; D019869:Phosphatidylinositol 3-Kinases