title: Phospholipid-binding domain of factor VIII is involved in endothelial cell-mediated activation of factor X by factor IXa.
abstract: Apparently quiescent, nonapoptotic endothelial cells mediate the activation of factor X by activated factor IX in the presence of its cofactor, activated factor VIII. In a previous study, we reported that during the activation of factor X, the interaction of the cofactor with the endothelial cell membrane clearly differs from the interaction of the cofactor with artificial lipid membranes. In the present study, we identified the peptide domain of factor VIII involved in the assembly of the enzyme-cofactor complex on the endothelial cell surface. With the use of monoclonal antibodies against different peptide sequences on the factor VIII light chain, it was observed that the lipid-binding region of the C2 domain on the factor VIII light chain mediates the assembly of the factor X-activating complex on the endothelial cell surface. In addition, a synthetic peptide that constitutes region Ala2318-Tyr2332 of the C2 domain and that is known for its ability to inhibit the binding of factor VIII to artificial lipid membranes also showed inhibition of the cofactor activity of factor VIII on endothelial cells. Thus, the carboxy-terminal part of the factor VIII light chain not only contains sites involved in lipid binding but also contains sites involved in complex assembly on the endothelial cell membrane.
authors.affiliation: Department of Plasma Proteins and Blood Coagulation, CLB, Sanquin Blood Supply Foundation, Amsterdam, The Netherlands.
authors.forename: Herm-Jan M
authors.initials: HJ
authors.lastname: Brinkman
authors.forename: Koen
authors.initials: K
authors.lastname: Mertens
authors.forename: Jan A
authors.initials: JA
authors.lastname: van Mourik
mesh_terms: D017304:Annexin A5 / Q000378:metabolism; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D015949:Factor IXa / Q000502:physiology*; D005169:Factor VIII / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000276:immunology / Q000502:physiology*; D005170:Factor X / Q000378:metabolism*; D006801:Humans; D010455:Peptides / Q000494:pharmacology; D010718:Phosphatidylserines / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism; D017434:Protein Structure, Tertiary
chemical_list: D017304:Annexin A5; D000911:Antibodies, Monoclonal; D010455:Peptides; D010718:Phosphatidylserines; D010743:Phospholipids; D005169:Factor VIII; D005170:Factor X; D015949:Factor IXa