title: Polyphosphate binds to human von Willebrand factor in vivo and modulates its interaction with glycoprotein Ib.
abstract: BACKGROUND
  Polyphosphate, a phosphate polymer released by activated platelets, has recently been described as a potent modulator of blood coagulation and fibrinolysis. In blood plasma, polyphosphate binds to and alters the biological functions of factor XII, fibrin(ogen), thrombin and factor VII activating protease.
  
  
  OBJECTIVE
  The aim of the present study is to investigate whether polyphosphate also binds to von Willebrand factor (VWF) and alters some of its activities.
  
  
  RESULTS
  When studying patients with type 1 von Willebrand disease (VWD) and their healthy relatives, we discovered a significant correlation between von Willebrand factor (VWF) and platelet polyphosphate levels. We have also found polyphosphate in preparations of VWF isolated from normal platelets and plasma. Surface plasmon resonance and electrophoretic mobility assays indicated that polyphosphate interacts with VWF in a dose- and time-dependent manner. Treatment of normal plasma with active exopolyphosphatase decreased the VWF ristocetin cofactor (VWF:RCo) activity, a functional measure of VWF binding to platelet glycoprotein receptor Ib. VWF collagen binding and multimerization were unaltered after polyphosphate depletion. Moreover, addition of polyphosphate increased the deficient VWF:RCo activity presented by plasma from patients with type 1 VWD.
  
  
  CONCLUSIONS
  Our results reveal that a new role is played by polyphosphate in hemostasis by its interaction with VWF, and suggest that this polymer may be effective in the treatment of some types of VWD.
authors.affiliation: Unidad de Investigación, Hospital Universitario Puerta del Mar, Cádiz Facultad de Medicina, Universidad de Cádiz, Cádiz Servicio Hematología-Hemoterapia, Hospital U. Virgen del Rocio, Sevilla, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Montilla
authors.forename: L
authors.initials: L
authors.lastname: Hernández-Ruiz
authors.forename: F J
authors.initials: FJ
authors.lastname: García-Cozar
authors.forename: I
authors.initials: I
authors.lastname: Alvarez-Laderas
authors.forename: J
authors.initials: J
authors.lastname: Rodríguez-Martorell
authors.forename: F A
authors.initials: FA
authors.lastname: Ruiz
mesh_terms: D017766:Acid Anhydride Hydrolases / Q000737:chemistry; D001777:Blood Coagulation; D001792:Blood Platelets / Q000166:cytology; D003094:Collagen / Q000737:chemistry; D005174:Factor XII / Q000737:chemistry; D005340:Fibrinogen / Q000737:chemistry; D005342:Fibrinolysis; D006801:Humans; D018613:Microscopy, Confocal; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D011122:Polyphosphates / Q000737:chemistry*; D011485:Protein Binding; D012697:Serine Endopeptidases / Q000737:chemistry; D020349:Surface Plasmon Resonance; D013917:Thrombin / Q000737:chemistry; D014842:von Willebrand Diseases / Q000097:blood* / Q000276:immunology; D014841:von Willebrand Factor / Q000737:chemistry*
chemical_list: D019038:Platelet Glycoprotein GPIb-IX Complex; D011108:Polymers; D011122:Polyphosphates; D014841:von Willebrand Factor; D005174:Factor XII; D005340:Fibrinogen; D003094:Collagen; C433550:HABP2 protein, human; D012697:Serine Endopeptidases; D013917:Thrombin; D017766:Acid Anhydride Hydrolases; C020137:exopolyphosphatase