Dok-2 regulates the shear-dependent adhesive function of platelet integrin {alpha}IIb{beta}3 in mice [Cell Biology]

January 2nd, 2014 by Hughan, S. C., Spring, C. M., Schoenwaelder, S. M., Sturgeon, S., Alwis, I., Yuan, Y., McFadyen, J. D., Westein, E., Goddard, D., Ono, A., Yamanashi, Y., Nesbitt, W. S., Jackson, S. P.

The Dok proteins are a family of adaptor molecules that have a well-defined role in regulating cellular migration, immune responses and tumor progression. Previous studies have demonstrated that Doks-1-3 are expressed in platelets, and that Dok-2 is tyrosine phosphorylated downstream of integrin αIIbβ3, raising the possibility that it participates in integrin αIIbβ3 outside-in signaling. We demonstrate that Dok-2 in platelets is primarily phosphorylated by Lyn kinase. Moreover, deficiency of Dok-2 leads to dysregulated integrin αIIbβ3-dependent cytosolic calcium flux and PtdIns(3,4)P2 accumulation. Whilst agonist-induced integrin αIIbβ3 affinity regulation was unaltered in Dok-2-/- platelets, Dok-2 deficiency was associated with a shear-dependent increase in integrin αIIbβ3 adhesive function, resulting in enhanced platelet-fibrinogen and platelet-platelet adhesive interactions under flow. This increase in adhesion was restricted to discoid platelets and involved the shear-dependent regulation of membrane tethers. Dok-2 deficiency was associated with an increased rate of platelet aggregate formation on thrombogenic surfaces, leading to accelerated thrombus growth in vivo. Overall, these studies define an important role for Dok-2 in regulating biomechanical adhesive function of discoid platelets. Moreover, they define a previously unrecognized prothrombotic mechanism that is not detected by conventional platelet function assays.