title: Deletion of alanine 2201 in the FVIII C2 domain results in mild hemophilia A by impairing FVIII binding to VWF and phospholipids and destroys a major FVIII antigenic determinant involved in inhibitor development.
abstract: The C2 domain of factor VIII (FVIII) mediates FVIII binding to von Willebrand factor (VWF) and phospholipids (PLs), thereby determining the stability and the activity of FVIII. A deletion of Ala2201 (Del2201) was identified in the FVIII C2 domain of 2 unrelated patients with mild hemophilia A (FVIII:C 11%-33%). This mutation prevents FVIII binding to a human monoclonal antibody recognizing the C2 domain and inhibiting FVIII binding to VWF and phospholipids. By comparison to healthy FVIII, Del2201 FVIII had a significantly reduced binding to VWF, which likely contributes to reduced FVIII levels in plasma. Del2201 FVIII interaction with phospholipids was evaluated in an FXa generation assay, using various concentrations of synthetic phospholipid vesicles mimicking an activated platelet surface. At the lowest phospholipid concentration allowing FXa generation, Del2201 FVIII activity was reduced 3-fold. This is the first report of a mutation altering FVIII binding to phospholipids and occurring in patients with hemophilia A.
authors.affiliation: Center for Molecular and Vascular Biology, University of Leuven, Leuven, Belgium.
authors.forename: Roseline
authors.initials: R
authors.lastname: d'Oiron
authors.forename: Jean-Maurice
authors.initials: JM
authors.lastname: Lavergne
authors.forename: Renaud
authors.initials: R
authors.lastname: Lavend'homme
authors.forename: Abdellah
authors.initials: A
authors.lastname: Benhida
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Bordet
authors.forename: Claude
authors.initials: C
authors.lastname: Negrier
authors.forename: Kathelijne
authors.initials: K
authors.lastname: Peerlinck
authors.forename: Jos
authors.initials: J
authors.lastname: Vermylen
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Saint-Remy
authors.forename: Marc
authors.initials: M
authors.lastname: Jacquemin
mesh_terms: D000409:Alanine / Q000737:chemistry; D000911:Antibodies, Monoclonal; D016022:Case-Control Studies; D000939:Epitopes / Q000737:chemistry / Q000235:genetics; D005169:Factor VIII / Q000737:chemistry* / Q000235:genetics* / Q000276:immunology / Q000502:physiology; D006467:Hemophilia A / Q000097:blood* / Q000235:genetics*; D006801:Humans; D066298:In Vitro Techniques; D008958:Models, Molecular; D010743:Phospholipids / Q000097:blood; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017384:Sequence Deletion; D014841:von Willebrand Factor / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D000939:Epitopes; D010743:Phospholipids; D014841:von Willebrand Factor; D005169:Factor VIII; D000409:Alanine