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.
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.
d'Oiron
Roseline
R
Center for Molecular and Vascular Biology, University of Leuven, Leuven, Belgium.
Lavergne
Jean-Maurice
JM
Lavend'homme
Renaud
R
Benhida
Abdellah
A
Bordet
Jean-Claude
JC
Negrier
Claude
C
Peerlinck
Kathelijne
K
Vermylen
Jos
J
Saint-Remy
Jean-Marie
JM
Jacquemin
Marc
M
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
D000911:Antibodies, Monoclonal; D000939:Epitopes; D010743:Phospholipids; D014841:von Willebrand Factor; D005169:Factor VIII; D000409:Alanine