Author:

Keywords:

Amino Acid Chloromethyl Ketones, Antithrombins, Blood Coagulation, Calcium Signaling, Collagen Type I, Humans, Integrin alpha2beta1, Platelet Adhesiveness, Platelet Glycoprotein GPIb-IX Complex, Platelet Membrane Glycoproteins, Pulsatile Flow, Receptors, Purinergic P2, Thrombosis, Science & Technology, Life Sciences & Biomedicine, Hematology, VON-WILLEBRAND-FACTOR, GLYCOPROTEIN IB-ALPHA, INTEGRIN ALPHA(2)BETA(1), PROCOAGULANT RESPONSE, ADHERENT PLATELETS, IMMUNOGLOBULIN SUPERFAMILY, CALCIUM SIGNALS, BINDING-SITES, III COLLAGEN, VI, Purinergic P2 Receptor Antagonists, 1102 Cardiorespiratory Medicine and Haematology, 1103 Clinical Sciences, 1114 Paediatrics and Reproductive Medicine, Immunology, 3101 Biochemistry and cell biology, 3201 Cardiovascular medicine and haematology, 3213 Paediatrics

Abstract:

The platelet glycoproteins (GPs) Ib, integrin alpha(2)beta(1), and GPVI are considered central to thrombus formation. Recently, their relative importance has been re-evaluated based on data from murine knockout models. To examine their relationship during human thrombus formation on collagen type I fibers at high shear (1000 s(-1)), we tested a novel antibody against GPVI, an immunoglobulin single-chain variable fragment, 10B12, together with specific antagonists for GPIb alpha (12G1 Fab(2)) and alpha(2)beta(1) (6F1 mAb or GFOGER-GPP peptide). GPVI was found to be crucial for aggregate formation, Ca(2+) signaling, and phosphatidylserine (PS) exposure, but not for primary adhesion, even with more than 97% receptor blockade. Inhibiting alpha(2)beta(1) revealed its involvement in regulating Ca(2+) signaling, PS exposure, and aggregate size. Both GPIb alpha and alpha(2)beta(1) contributed to primary adhesion, showing overlapping function. The coinhibition of receptors revealed synergism in thrombus formation: the coinhibition of adenosine diphosphate (ADP) receptors with collagen receptors further decreased adhesion and aggregation, and, crucially, the complete eradication of thrombus formation required the coinhibition of GPVI with either GPIb alpha or alpha(2)beta(1). In summary, human platelet deposition on collagen depends on the concerted interplay of several receptors: GPIb in synergy with alpha(2)beta(1) mediating primary adhesion, reinforced by activation through GPVI, which further regulates the thrombus formation.