Departmental Papers (Dental)

Document Type

Technical Report

Date of this Version

2-15-2004

Publication Source

Blood

Volume

103

Issue

4

Start Page

1348

Last Page

1355

DOI

10.1182/blood-2003-06-1781

Abstract

We have previously shown that platelets express 2 receptor tyrosine kinases, EphA4 and EphB1, and the Eph kinase ligand, ephrinB1m and proposed that transcellular Eph/ephrin interactions made possible by the onset of platelet aggregation promote the further growth and stability of the hemostatic plug. The present study examines how this might occur. The results show that clustering of either ephrinB1 or EphA4 causes platelets to adhere to immobilized firinogen via αIIbβ3. Adhesion occurs more slowly than with adenosine diphosphate (ADP) abd requires phosphatidylinositol 3 (PI3)—kinase and protein kinase C activity but not ephrinB1 phosphorylation. By itself, Eph and ephrin signaling is insufficient to cause aggregation or the binding of soluble fibrinogen, but it can potentiate aggregation initiated by a Ca++ ionophore or by agonists for thrombin and thromboxane receptors. It also enhances Rap1 activation without requiring ADP secretion, ephrinB1 phosphorylation, or the activation of PI3-kinase and Src. From this we conclude that (1) Eph/ephrin signaling enhances the ability of platelet agonists to cause aggregation provided that those agonists can increase cytosolic Ca++; (2) this is accomplished in part by activating Rap1; and (3) these effects require not phosphotyrosine-based interactions with the ephrinB1 cytoplasmic domain.

Copyright/Permission Statement

Originally published in Blood © 2004 American Society of Hematology.

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Date Posted: 11 May 2018

This document has been peer reviewed.