3321
Exchange protein directly activated by cAMP ( EPAC ) and cAMP - dependent protein kinase ( PKA ) are two intracellular receptors that mediate the effects of the prototypic second messenger cAMP .
 cAMP, cAMP, cAMP
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 cAMP, cAMP, cAMP