Activation Inhibition Indirectly activation Translocation Phosphorylation P Gene transcription Stimulatory ligand Inhibitory ligand Active Inactive Cell adhesion GPCR GPCR CNG channel cAMP cGMP cAMP AMP ATP RAP RAP PKAr PKAr PKAc PKAc PKAr PKAr PKAc PKAc AKAP AKAP CaM CAMKK CaMK CaMK EPAC EPAC CREB AC sAC PDE Gβ Gγ GαS Gβ Gγ Gαi GαS GDP GTP P Cytoplasm Nucleus Ca 2+ HCO 3 - Na + Na + Cl - Cl - Ca 2+ Ca 2+