Phosphotyrosine proteins in platelets from patients with storage pool disease: direct relation between granule defects and defective signal transduction.
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.
Arderiu
Gemma
G
Servei d'Hemoteràpia-Hemostàsia, Hospital Clinic, Universitat de Barcelona, Barcelona, Spain.
Díaz-Ricart
Maribel
M
Domenech
Pere
P
Escolar
Ginés
G
Ordinas
Antonio
A
Pujol-Moix
Núria
N
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
D010750:Phosphoproteins; D014443:Tyrosine