Platelets bind to exposed vascular matrix at a wound site through a highly specialized surface receptor, glycoprotein (GP) Ib-IX-V complex, which recognizes von Willebrand factor (VWF) in the matrix. GPIb-IX-V is a catch bond for it becomes more stable as force is applied to it. After attaching to the wound site, platelets generate cytoskeletal forces to compact and reinforce the hemostatic plu...

Platelet adhesion to an injured blood vessel wall is a critical initiating step in hemostasis mediated by a four member receptor complex (glycoprotein Ib/V/IX) interacting with plasma von Willebrand factor (vWF). The function of the GPV subunit within this complex is presently undefined. To study the role of glycoprotein (GP) V within the GPIb receptor complex, we transfected the GPV subunit ge...

We describe here the mechanism of platelet adhesion to immobilized von Willebrand factor (VWF) and subsequent formation of platelet-derived microparticles mediated by glycoprotein Ib (GPIb ) under high shear stress. As visualized in whole blood perfused in a flow chamber, platelet attachment to VWF involved one or few membrane areas of 0.05 to 0.1 m2 that formed discrete adhesion points (DAPs) ...

The conformation of the A1 domain of von Willebrand factor (vWF) is a critical determinant of its interaction with the glycoprotein (GP) Ib/V/IX complex. To better define the regulatory mechanisms of vWF A1 domain binding to the GPIb/V/IX complex, we studied vWF-dependent aggregation properties of a cell line overexpressing the GPIba, GPIbb, and GPIX subunits (CHO-GPIbab/IX cells). We found tha...

To clarify the mechanism of platelet activation by immune complexes and the possible involvement of surface glycoproteins (GPs), we studied platelet activation induced by heat-aggregated IgG (HAG). We examined the effects of monoclonal antibodies (MoAbs) against GPIb, GPIIb/IIIa, and the Fc receptor on resting platelets and on platelets stimulated by HAG. HAG increased the cytosolic ionized cal...

The glycoprotein profile of Bernard-Soulier platelets was examined by labeling washed platelets with periodate 3H-sodium borohydride, a procedure that labels greater than 30 glycoproteins on the membrane surface of normal platelets. Three Bernard-Soulier patients were studied; two were siblings and the third was unrelated. The platelet protein and glycoprotein profiles were evaluated under nonr...

Chronic immune thrombocytopenic purpura (ITP) is due to platelet destruction by circulating antiplatelet antibody. Although autoantibodies against the platelet glycoprotein IIb/IIIa (GPIIb/IIIa) complex and GPIb have been demonstrated using various methods, practical assays for detection of platelet-associated or plasma autoantibodies have not been available. We studied 59 patients with chronic...

In recent years, candidate genes and proteins implicated in platelet function have been identified by various genomic approaches. To elucidate their exact role, we aimed to develop a method to apply miRNA interference in platelet progenitor cells by using GPIbα as a proof-of-concept target protein. After in silico and in vitro screening of siRNAs targeting GPIbα (siGPIBAs), we developed artific...

Force-dependent binding of platelet glycoprotein Ib (GPIb) receptors to plasma von Willebrand factor (VWF) plays a key role in hemostasis and thrombosis. Previous studies have suggested that VWF activation requires force-induced exposure of the GPIb binding site in the A1 domain that is autoinhibited by the neighboring A2 domain. However, the biochemical basis of this "mechanopresentation" rema...

Platelet adhesion to fibrin at high shear rates depends on both the glycoprotein (GP) IIb:IIIa complex and a secondary interaction between GPIb and von Willebrand factor (vWF). This alternative link between platelets and vWF in promoting platelet adhesion to fibrin has been examined in flowing whole blood with a rectangular perfusion chamber. Optimal adhesion required both platelets and vWF, as...