Involvement of GPIIb-IIIa on human platelets in phosphotyrosine-specific dephosphorylation.
Washed platelets from either normal donors or patients with thrombasthenia lacking in integrin GPIIb-IIIa were stimulated by thrombin or STA2 with stirring and their kinetics of protein-tyrosine phosphorylation were compared. The early increase in protein-tyrosine phosphorylation on 115 and 75 kDa protein bands was observed within 10 s after stimulation in both normal and thrombasthenic platelets. While both 115 and 75 kDa tyrosine-phosphorylated protein bands were quickly dephosphorylated in normal platelets, thrombin-induced 115 kDa or STA2-induced 115 and 75 kDa protein bands were not dephosphorylated in thrombasthenic platelets. The delay of phosphotyrosine-specific dephosphorylation on those protein bands was observed when thrombin- or STA2-induced aggregation of normal platelets was inhibited by RGDS, an inhibitor of fibrinogen binding to GPIIb-IIIa. These data indicate that fibrinogen binding to GPIIb-IIIa is involved in the regulation of phosphotyrosine-specific dephosphorylation on certain protein bands.
Takayama
H
H
Department of Internal Medicine, Faculty of Medicine, Kyoto University, Japan.
Ezumi
Y
Y
Ichinohe
T
T
Okuma
M
M
D000595:Amino Acid Sequence; D000906:Antibodies; D000911:Antibodies, Monoclonal; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D066298:In Vitro Techniques; D007700:Kinetics; D008970:Molecular Weight; D009842:Oligopeptides / Q000378:metabolism; D010750:Phosphoproteins / Q000097:blood* / Q000302:isolation & purification; D019000:Phosphotyrosine; D010980:Platelet Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D012016:Reference Values; D013915:Thrombasthenia / Q000097:blood*; D013917:Thrombin / Q000494:pharmacology; D013928:Thromboxane A2 / Q000031:analogs & derivatives / Q000494:pharmacology; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000097:blood
D000906:Antibodies; D000911:Antibodies, Monoclonal; D009842:Oligopeptides; D010750:Phosphoproteins; D010980:Platelet Membrane Glycoproteins; D019000:Phosphotyrosine; D014443:Tyrosine; D013928:Thromboxane A2; C037866:STA 2; C046617:arginyl-glycyl-aspartyl-serine; D013917:Thrombin