Thromb Haemost 2005; 93(05): 880-888
DOI: 10.1160/TH04-09-0612
Platelets and Blood Cells
Schattauer GmbH

P2Y12 ADP receptor-dependent tyrosine phosphorylation of proteins of 27 and 31 kDa in thrombin-stimulated human platelets

Knut Fälker*
1   Martin-Luther-University Halle-Wittenberg, Faculty of Medicine, Department of Pharmacology and Toxicology, Division of Clinical Pharmacology, Halle, Germany
,
Danica Lange*
1   Martin-Luther-University Halle-Wittenberg, Faculty of Medicine, Department of Pharmacology and Toxicology, Division of Clinical Pharmacology, Halle, Germany
,
Peter Presek
1   Martin-Luther-University Halle-Wittenberg, Faculty of Medicine, Department of Pharmacology and Toxicology, Division of Clinical Pharmacology, Halle, Germany
› Author Affiliations
Financial support: This work was supported by the NBL3 Wilhelm-Roux-Programm (FKZ 8/01) of the Faculty of Medicine, Martin-Luther-Universität Halle-Wittenberg, Germany
Further Information

Publication History

Received 20 September 2004

Accepted after resubmission 07 February 2005

Publication Date:
11 December 2017 (online)

Zoom Image

Summary

In thrombin-stimulated human platelets several proteins undergo rapid and transient changes in tyrosine phosphorylation. We demonstrate that a set of proteins of 27, 29, 31, 34, and 39 kDa is affected by released ADP and P2Y12 receptor signaling during platelet activation. AR-C69931MX, an antagonist of the Gi2-coupled P2Y12 ADP receptor, inhibits initial tyrosine phosphorylation of p27 and p31 and prevents subsequent dephosphorylation of p29, p34, and p39. Antagonists of the Gq-coupled P2Y1 ADP receptor have no effect. Precluding integrin αIIbβ3 outside-in signaling with RGDS or S1197 does not affect the increase in tyrosine phosphorylation of the set of proteins but inhibits their subsequent dephosphorylation. Besides the ADP analogue 2-MeS-ADP, other platelet agonists such as collagen and the TXA2-mimetic U46619 also induce p27 and p31 tyrosine phosphorylation in a P2Y12 receptor-dependent manner. Tyrosine phosphorylation of p27 and p31 in response to collagen, but not thrombin, is prevented by aspirin and the TXA2 receptor antagonist SQ29548, indicating that the effect of collagen strongly relies on TXA2 signaling. Furthermore, epinephrine, acting via inhibitory Gz-coupled α2A-adrenoceptors, bypasses the inhibitory effect of AR-C69931MX on thrombin-induced p27 and p31 tyrosine phosphorylation. Finally, we demonstrate that tyrosine phosphorylation of p27 and p31 downstream of P2Y12 receptors is due to the inhibition of adenylyl cyclase but not phosphoinositide 3-kinase (PI 3-K) activation. Elevating cAMP levels with PGI2 or forskolin precludes thrombin-induced p27 and p31 tyrosine phosphorylation. Moreover, direct inhibition of adenylyl cyclase by SQ22536 reverses the effect of AR-C69931MX. Our data indicate that the observed changes in tyrosine phosphorylation are the result of both primary Gq signaling, initiating the release of ADP, as well as subsequent P2Y12 receptor-mediated Gi coupling.

* KF and DL contributed equally