title: N1421K mutation in the glycoprotein Ib binding domain impairs ristocetin- and botrocetin-mediated binding of von Willebrand factor to platelets.
abstract: von Willebrand disease (VWD) is a common inheritable bleeding disorder caused by deficiency of von Willebrand Factor (VWF), which is involved in platelet adhesion and aggregation. We report a family consisting of three patients with VWD characterized by an apparently normal multimeric pattern, moderately decreased plasma factor VIII (FVIII) and VWF levels, and disproportionately low-plasma VWF:RCo levels. The patients were found to be heterozygous for the novel N1421K mutation, caused by a 4263C > G transversion in exon 28 of the VWF gene coding for the A1 domain. Botrocetin- and ristocetin-mediated binding of plasma VWF to GPIb were reduced in the patients. In vitro mutagenesis and expression in COS-7 cells confirmed the impairment of the mutant in botrocetin- and ristocetin-mediated VWF binding to GPIb. VWF collagen binding capacity was unaffected in plasma from the heterozygous individuals as well as in medium from transfected COS-7 cells. Our findings indicate that the N1421K substitution in the VWF affects the GPIb binding site or a recognition element by a conformational change of the A1 domain.
authors.affiliation: Department for Coagulation Disorders, University Hospital, Malmö, Sweden.
authors.forename: Elsa
authors.initials: E
authors.lastname: Lanke
authors.forename: Ann-Charlotte
authors.initials: AC
authors.lastname: Kristoffersson
authors.forename: Christina
authors.initials: C
authors.lastname: Isaksson
authors.forename: Lars
authors.initials: L
authors.lastname: Holmberg
authors.forename: Stefan
authors.initials: S
authors.lastname: Lethagen
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001665:Binding Sites / Q000235:genetics; D001792:Blood Platelets / Q000378:metabolism*; D019556:COS Cells; D002522:Chlorocebus aethiops; D003094:Collagen / Q000378:metabolism; D003435:Crotalid Venoms / Q000494:pharmacology; D005169:Factor VIII / Q000235:genetics / Q000378:metabolism; D005190:Family; D005260:Female; D006579:Heterozygote; D006801:Humans; D008297:Male; D020125:Mutation, Missense; D010375:Pedigree; D010973:Platelet Adhesiveness / Q000187:drug effects / Q000235:genetics; D010974:Platelet Aggregation / Q000187:drug effects / Q000235:genetics; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D012310:Ristocetin / Q000494:pharmacology; D014842:von Willebrand Diseases / Q000235:genetics* / Q000378:metabolism*; D014841:von Willebrand Factor / Q000235:genetics* / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D003435:Crotalid Venoms; D019038:Platelet Glycoprotein GPIb-IX Complex; D014841:von Willebrand Factor; D012310:Ristocetin; C078147:F8 protein, human; C030961:botrocetin; D005169:Factor VIII; D003094:Collagen