Fig. 1

The cAMP signaling pathways. The extracellular cAMP can be converted into AMP by plasma membrane-anchored ecto-PDE, followed by the conversion of AMP into adenosine by CD73. Ligands-engaged Gs- or Gi-coupled receptors may stimulate or inhibit cAMP synthesis, respectively. The ABCC transporter family members ABCC4/5/11 mediate the export of cAMP to extracellular space. cAMP engages PKA, EPAC, POPDC, HCN and CNG channels to regulate diverse signaling pathways and the transcription activities