3900
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 .
 ( protein: collagen, None) , ( protein: p38, None) , ( protein: SLP-76, None) , ( protein: G protein, None) , ( protein: collagen, None) , ( protein: thrombin, None) , ( protein: tyrosine kinase, None) , ( cell type: platelets, None) , ( cell type: platelets, None) , ( protein: p63, None) 
Locate the role in the text that participated in the event based on the event type and return it in the event list. 
 Option: Event type: RNA,cell type,protein,cell line,DNA, Arguments type: . 
Text: {0} 
Answer:
 ( protein: collagen, None) , ( protein: p38, None) , ( protein: SLP-76, None) , ( protein: G protein, None) , ( protein: collagen, None) , ( protein: thrombin, None) , ( protein: tyrosine kinase, None) , ( cell type: platelets, None) , ( cell type: platelets, None) , ( protein: p63, None) 