title: Role of glycoprotein Ibalpha mobility in platelet function.
abstract: Incubation at 0 degrees C is known to expose b- N -acetyl-D-glucosamine residues on glycoprotein (GP) Ibalpha inducing receptor clustering and alpha(M)beta(2)-mediated platelet destruction by macrophages. Here we show that incubation at 0/37 degrees C (4 hours at 0 degrees C, followed by 1 hour at 37 degrees C to mimic cold-storage and post-transfusion conditions) triggers a conformational change in the N -terminal flank (NTF, amino acids, aa 1-35) but not in aa 36-282 of GPIbalpha as detected by antibody binding. Addition of the sugar N -acetyl-D-glucosamine (GN) inhibits responses induced by 0/37 degrees C. Incubation at 0 degrees C shifts GPIbalpha from the membrane skeleton to the cytoskeleton. Different GPIbalpha conformations have little effect on VWF/ristocetin-induced aggregation, but arrest of NTF change by GN interferes with agglutination and spreading on a VWF-coated surface under flow. Strikingly, incubation at 0/37 degrees C initiates thromboxane A(2) formation through a von Willebrand factor (VWF)-independent and GPIbalpha-dependent mechanism, as confirmed in VWF- and GPIbalpha-deficient platelets. We conclude that the NTF change induced by 0/37 degrees C incubation reflects clustering of GPIbalpha supports VWF/ristocetin-induced agglutination and spreading and is sufficient to initiate platelet activation in the absence of VWF.
authors.affiliation: Department of Clinical Chemistry and Haematology, University Medical Centre Utrecht, Utrecht, The Netherlands.
authors.forename: Dianne E
authors.initials: DE
authors.lastname: van der Wal
authors.forename: Sandra
authors.initials: S
authors.lastname: Verhoef
authors.forename: Roger E G
authors.initials: RE
authors.lastname: Schutgens
authors.forename: Marjolein
authors.initials: M
authors.lastname: Peters
authors.forename: Yaping
authors.initials: Y
authors.lastname: Wu
authors.forename: Jan Willem N
authors.initials: JW
authors.lastname: Akkerman
mesh_terms: D000117:Acetylglucosamine / Q000737:chemistry / Q000378:metabolism*; D000911:Antibodies, Monoclonal; D001792:Blood Platelets / Q000378:metabolism* / Q000473:pathology; D001793:Blood Preservation; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000378:metabolism; D006801:Humans; D008262:Macrophage Activation; D016177:Macrophage-1 Antigen / Q000378:metabolism; D015539:Platelet Activation; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D017713:Platelet Transfusion; D011485:Protein Binding; D011487:Protein Conformation; D021381:Protein Transport; D011940:Receptor Aggregation / Q000502:physiology; D013696:Temperature; D013928:Thromboxane A2 / Q000096:biosynthesis / Q000235:genetics; D014842:von Willebrand Diseases / Q000097:blood / Q000378:metabolism* / Q000473:pathology / Q000628:therapy; D014841:von Willebrand Factor / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D016177:Macrophage-1 Antigen; D019038:Platelet Glycoprotein GPIb-IX Complex; D014841:von Willebrand Factor; D013928:Thromboxane A2; D000117:Acetylglucosamine