title: In vivo relevance for platelet glycoprotein Ibalpha residue Tyr276 in thrombus formation.
abstract: BACKGROUND
  Platelet glycoprotein (GP) Ib-IX-V supports platelet adhesion on damaged vascular walls by binding to von Willebrand factor (VWF). For several decades it has been recognized that the alpha-subunit of GP (GPIbalpha) also binds thrombin but the physiological relevance, if any, of this interaction was unknown. Previous studies have shown that a sulfated tyrosine 276 (Tyr276) is essential for thrombin binding to GPIbalpha.
  
  
  OBJECTIVE
  This study investigated the in vivo relevance of GPIbalpha residue Tyr276 in hemostasis and thrombosis.
  
  
  METHODS
  Transgenic mouse colonies expressing the normal human GPIbalpha subunit or a mutant human GPIbalpha containing a Phe substitution for Tyr276 (hTg(Y276F)) were generated. Both colonies were bred to mice devoid of murine GPIbalpha.
  
  
  RESULTS
  Surface-expressed GPIbalpha levels and platelet counts were similar in both colonies. hTg(Y276F) platelets were significantly impaired in binding alpha-thrombin but displayed normal binding to type I fibrillar collagen and human VWF in the presence of ristocetin. In vivo thrombus formation as a result of chemical damage (FeCl(3)) demonstrated that hTg(Y276F) mice have a delayed time to occlusion followed by unstable blood flow indicative of embolization. In models of laser-induced injury, thrombi developing in hTg(Y276F) animals were also less stable.
  
  
  CONCLUSIONS
  The results demonstrate that GPIbalpha residue Tyr276 is physiologically important, supporting stable thrombus formation in vivo.
authors.affiliation: Department of Physiology & Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Guerrero
authors.forename: G
authors.initials: G
authors.lastname: Shafirstein
authors.forename: S
authors.initials: S
authors.lastname: Russell
authors.forename: K I
authors.initials: KI
authors.lastname: Varughese
authors.forename: T
authors.initials: T
authors.lastname: Kanaji
authors.forename: J
authors.initials: J
authors.lastname: Liu
authors.forename: T K
authors.initials: TK
authors.lastname: Gartner
authors.forename: W
authors.initials: W
authors.lastname: Bäumler
authors.forename: G E
authors.initials: GE
authors.lastname: Jarvis
authors.forename: J
authors.initials: J
authors.lastname: Ware
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D001760:Bleeding Time; D001777:Blood Coagulation / Q000502:physiology*; D002341:Carotid Artery Thrombosis / Q000097:blood / Q000139:chemically induced / Q000209:etiology / Q000235:genetics; D002712:Chlorides; D024042:Collagen Type I / Q000378:metabolism; D005290:Ferric Compounds / Q000633:toxicity; D006801:Humans; D007834:Lasers / Q000009:adverse effects; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D020125:Mutation, Missense; D010974:Platelet Aggregation; D010976:Platelet Count; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D017354:Point Mutation; D012310:Ristocetin / Q000494:pharmacology; D013917:Thrombin / Q000378:metabolism; D014443:Tyrosine / Q000502:physiology*; D014841:von Willebrand Factor / Q000378:metabolism
chemical_list: D002712:Chlorides; D024042:Collagen Type I; D005290:Ferric Compounds; D019038:Platelet Glycoprotein GPIb-IX Complex; D014841:von Willebrand Factor; D012310:Ristocetin; D014443:Tyrosine; D013917:Thrombin; C024555:ferric chloride