Dok-2 Adaptor Protein Regulates the Shear-dependent Adhesive Function of Platelet Integrin αIIbβ3 in Mice

• Published in: The Journal of biological chemistry 2014-02, Vol.289 (8), p.5051-5060
• Main Authors: Hughan, Sascha C., Spring, Christopher M., Schoenwaelder, Simone M., Sturgeon, Sharelle, Alwis, Imala, Yuan, Yuping, McFadyen, James D., Westein, Erik, Goddard, Duncan, Ono, Akiko, Yamanashi, Yuji, Nesbitt, Warwick S., Jackson, Shaun P.
• Format: Article
• Language: English
• Subjects: Adaptor Proteins; Adaptor Proteins, Signal Transducing - deficiency; Adaptor Proteins, Signal Transducing - metabolism; Animals; Blood Platelets - drug effects; Blood Platelets - metabolism; Blood Platelets - ultrastructure; Calcium - metabolism; Cell Membrane - drug effects; Cell Membrane - metabolism; Fibrinogen - pharmacology; Hemorheology - drug effects; Humans; Immobilized Proteins - pharmacology; Integrins; Mechanotransduction; Mice; Mice, Inbred C57BL; Phosphatidylinositol Phosphates - metabolism; Phosphoproteins - deficiency; Phosphoproteins - metabolism; Platelet Adhesiveness - drug effects; Platelet Adhesiveness - physiology; Platelet Glycoprotein GPIIb-IIIa Complex - metabolism; Platelets; Shear Strength - drug effects; Shear Stress; Signal Transduction; Thrombosis - metabolism; Thrombosis - pathology; Thrombosis - physiopathology; Time Factors
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M113.520148

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 to 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 phosphatidylinositol(3,4)P2 accumulation. Although 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, this study defines 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. Dok proteins are negative regulators of immunoreceptor signaling and, potentially, integrin adhesion receptors. Deficiency of Dok-2 results in enhanced shear-dependent integrin adhesion in platelets, leading to accelerated platelet thrombus growth. Dok-2 is a shear-specific negative regulator of blood clot formation. Dok-2 regulates biomechanical platelet adhesion, and targeting this molecule may provide new avenues to regulate thrombosis.