13020
In this study, we present evidence indicating that signal transduction pathways induced by PGE2 necessitate the participation of cyclic AMP , protein kinase A , and Ca2+ .
 ( protein: protein kinase A, 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: protein kinase A, None) 