What is vinculin needed for in platelets?

Abstract

Background: Vinculin links integrins to the cell cytoskeleton by virtue of its binding to proteins such as talin and F-actin. It has been implicated in the transmission of mechan-ical forces from the extracellular matrix to the cytoskeleton of migrating cells. Vinculin's function in platelets is unknown. Objective: To determine whether vinculin is required for the functions of platelets and their major integrin, αIIbβ3.Methods: The murine vinculin gene (Vcl) was deleted in the megakaryo-cyte/platelet lineage by breeding Vcl fl/fl mice with Pf4-Cre mice. Platelet and integrin functions were studied in vivo and ex vivo. Results: Vinculin was undetectable in platelets from Vcl fl/fl Cre+ mice, as determined by immunoblotting and uorescence microscopy. Vinculin-decient megakaryocytes exhibited increasedmembrane tethers in response tomechanical pulling on αIIbβ3 with laser tweezers, suggesting that vinculin helps to maintain membrane cytoskeleton integrity. Surpris-ingly, vinculin-decient platelets displayed normal agonist-induced brinogen binding to αIIbβ3, aggregation, spreading, actin polymerization/organization, clot retraction and the ability to form a procoagulant surface. Furthermore, vinculin-decient platelets adhered to immobilized brinogen or collagen normally, under both static and ow conditions. Tail bleeding times were prolonged in 59% of vinculin-decient mice. However, these mice exhibited no spontaneous bleeding and they formed occlusive platelet thrombi comparable to those in wild-type littermates in response to carotid artery injury with FeCl3. Conclusion: Despite promoting membrane cytoskeleton integrity when mechanical force is applied to αIIbβ3, vinculinis not required for the traditional functions of αIIbβ3 or the platelet actin cytoskeleton. © 2010 International Society on Thrombosis and Haemostasis.