Characterization of Grb2-binding proteins in human platelets activated by Fc gamma RIIA cross-linking.
Glutathione-S-transferase (GST)-Grb2 fusion proteins have been used to identify the potential role of Grb2-binding proteins in platelet activation by the platelet low-affinity IgG receptor, Fc gamma RIIA. Two tyrosine phosphoproteins of 38 and 63 kD bind to the SH2 domain of Grb2 following Fc gamma RIIA stimulation of platelets. Both are located in the particulate fraction following platelet activation and are also able to bind to a GST-construct containing the SH2 and SH3 domains of phospholipase C gamma 1. p38 also forms a complex with the tyrosine kinase csk in stimulated cells and is a substrate for the kinase. The SH3 domains of Grb2 form a stable complex with SOS1 and two proteins of 75 kD and 120 kD, which undergo tyrosine phosphorylation in Fc gamma RIIA stimulated cells. The 75-kD protein is recognized by antibodies to SLP-76, which has recently been isolated from T cells and sequenced. Tyrosine phosphorylation of p38 and p63 is also observed in platelets stimulated by the tyrosine kinase-linked receptor agonist collagen and by the G protein-coupled receptor agonist thrombin, although phosphorylation of SLP-76 is only observed in collagen-stimulated platelets. p38 and p63 may provide a docking site for Grb2, thereby linking Grb2 SH3-binding proteins SOS1, SLP-76, and p120 to downstream signalling events.
Robinson
A
A
University Department of Pharmacology, Oxford, UK.
Gibbins
J
J
Rodríguez-Liñares
B
B
Finan
P M
PM
Wilson
L
L
Kellie
S
S
Findell
P
P
Watson
S P
SP
D048868:Adaptor Proteins, Signal Transducing; D015703:Antigens, CD / Q000502:physiology*; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D001798:Blood Proteins / Q000378:metabolism*; D000081247:CSK Tyrosine-Protein Kinase; D005656:Fungal Proteins / Q000378:metabolism; D051380:GRB2 Adaptor Protein; D005982:Glutathione Transferase / Q000235:genetics; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D008970:Molecular Weight; D051966:Phospholipase C gamma; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D015539:Platelet Activation; D011499:Protein Processing, Post-Translational; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D017452:Receptors, IgG / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D020837:SOS1 Protein; D010738:Type C Phospholipases / Q000378:metabolism; D018909:src Homology Domains; D019061:src-Family Kinases / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D015703:Antigens, CD; D001798:Blood Proteins; C080568:Fc gamma receptor IIA; D005656:Fungal Proteins; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; D007527:Isoenzymes; D010750:Phosphoproteins; D011506:Proteins; D017452:Receptors, IgG; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; C092947:SLP-76 signal Transducing adaptor proteins; D020837:SOS1 Protein; D005982:Glutathione Transferase; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; C000631346:CSK protein, human; D010738:Type C Phospholipases; D051966:Phospholipase C gamma