title: Phosphotyrosine proteins in platelets from patients with storage pool disease: direct relation between granule defects and defective signal transduction.
abstract: OBJECTIVE
  Storage pool diseases (SPD) are heterogeneous disorders associated with an abnormal presence of intraplatelet granules, which cause mild to moderate bleeding diathesis. We investigated signaling through tyrosine phosphorylation of proteins occurring in platelets with total or partial absence of dense- and alpha-granules in response to activation.
  
  
  METHODS
  We included a patient with severe delta-SPD, a patient with severe alpha-SPD or gray platelet syndrome, and six patients with partial deficiency of dense or a-granules. SPD was confirmed by electron microscopy evaluation of platelet ultrastructure. Platelet function was evaluated by bleeding time determination and conventional aggregometry. Platelet suspensions were activated with collagen and thrombin to analyze changes in tyrosine phosphorylation of proteins by electrophoresis and Western-blotting.
  
  
  RESULTS
  Bleeding times were prolonged in all the patients included. Aggregation responses were slightly decreased in delta-SPD and normal in the rest of patients. Tyrosine phosphorylation in platelets from patients with partial forms of SPD was equivalent to that observed in control platelets, absent in response to collagen and thrombin activation in delta-SPD, and deficient only to thrombin activation in alpha-SPD.
  
  
  CONCLUSIONS
  Tyrosine phosphorylation of proteins in activated platelets is highly dependent on the substances contained in the dense-granules and moderately dependent on those contained in the alpha-granules. A minimum amount of intraplatelet granules ensures signaling through tyrosine phosphorylation of proteins.
authors.affiliation: Servei d'Hemoteràpia-Hemostàsia, Hospital Clinic, Universitat de Barcelona, Barcelona, Spain.
authors.forename: Gemma
authors.initials: G
authors.lastname: Arderiu
authors.forename: Maribel
authors.initials: M
authors.lastname: Díaz-Ricart
authors.forename: Pere
authors.initials: P
authors.lastname: Domenech
authors.forename: Ginés
authors.initials: G
authors.lastname: Escolar
authors.forename: Antonio
authors.initials: A
authors.lastname: Ordinas
authors.forename: Núria
authors.initials: N
authors.lastname: Pujol-Moix
mesh_terms: D000293:Adolescent; D000328:Adult; D001792:Blood Platelets / Q000378:metabolism* / Q000473:pathology / Q000648:ultrastructure; D016022:Case-Control Studies; D003594:Cytoplasmic Granules / Q000737:chemistry / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D010981:Platelet Storage Pool Deficiency / Q000378:metabolism / Q000473:pathology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014443:Tyrosine / Q000378:metabolism
chemical_list: D010750:Phosphoproteins; D014443:Tyrosine