title: Factor VIII coagulant moiety binds to platelets by binding to phospholipids of the platelet membrane.
abstract: Washed human platelets were incubated with commercial factor VIII concentrate, or with purified factor VIII coagulant moiety. Platelets were then washed again and lysed by sonication. VIII:Ag and vWf:Ag were measured in the platelet lysate prior to and after incubation of the lysate with phospholipase C (PL-C). Platelet bound VIII:Ag was significantly higher after incubation of washed platelets with factor VIII concentrate than after incubation with buffer. Platelet bound VIII:Ag was further increased when platelets had been incubated with concentrate in the presence of thrombin and collagen. In contrast, only a slight increase in platelet bound vWf:Ag was observed after incubation of platelets with concentrate. When washed platelets had been incubated with factor VIII coagulant moiety, also significantly more platelet bound VIII:Ag was observed than after incubation with buffer. Measurable VIII:Ag, but not vWf:Ag, increased significantly after incubation of the platelet lysate with PL-C. When intact washed platelets had been treated with PL-C prior to the incubation with concentrate, binding of VIII:Ag to platelets was nearly completely abolished. Our data suggest that the factor VIII coagulant moiety binds to phospholipids of the platelet membrane and thereby contributes to the assembly of the factor X activating complex on the platelet surface.
mesh_terms: D001792:Blood Platelets / Q000378:metabolism* / Q000648:ultrastructure; D002462:Cell Membrane / Q000378:metabolism; D005169:Factor VIII / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D008563:Membrane Lipids / Q000097:blood*; D010743:Phospholipids / Q000097:blood; D011485:Protein Binding; D010738:Type C Phospholipases / Q000494:pharmacology
chemical_list: D008563:Membrane Lipids; D010743:Phospholipids; D005169:Factor VIII; D010738:Type C Phospholipases