PAR1, but not PAR4, activates human platelets through a G i/o/phosphoinositide-3 kinase signaling axis

Bryan Voss, Joseph N. McLaughlin, Michael Holinstat, Roy Zent, Heidi E. Hamm

Research output: Contribution to journalArticlepeer-review

66 Scopus citations


Thrombin-mediated activation of platelets is critical for hemostasis, but the signaling pathways responsible for this process are not completely understood. In addition, signaling within this cascade can also lead to thrombosis. In this study, we have defined a new signaling pathway for the thrombin receptor protease activated receptor-1 (PAR1) in human platelets. We show that PAR1 couples to Gi/o in human platelets and activates phosphoinositide-3 kinase (PI3K). PI3K activation regulates platelet integrin αIIbβ3 activation and platelet aggregation and potentiates the PAR1-mediated increase in intraplatelet calcium concentration. PI3K inhibitors eliminated these effects downstream of PAR1, but they had no effect on PAR4 signaling. This study has identified an important role for the direct activation of Gi/o by PAR1 in human platelets. Given the efficacy of clopidogrel, which blocks the Gi/o-coupled P2Y purinoceptor 12, as an antiplatelet/antithrombotic drug, our data suggest that specifically blocking only PAR1-mediated Gi/o signaling could also be an effective therapeutic approach with the possibility of less unwanted bleeding.

Original languageEnglish (US)
Pages (from-to)1399-1406
Number of pages8
JournalMolecular Pharmacology
Issue number5
StatePublished - May 2007
Externally publishedYes

ASJC Scopus subject areas

  • Molecular Medicine
  • Pharmacology


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