Figure 1.

Renin–angiotensin system. Renin cleaves angiotensinogen to form Ang I, which is then cleaved by angiotensin-converting enzyme (ACE) to generate Ang II. Ang II can bind to Ang II type 1 and 2 receptors (AT1/2R). ACE2 is a single transmembrane protein, which can recognize Ang I and cleave it into Ang 1-9, which is quickly converted to Ang 1-7 by ACE. Moreover, Ang-(1-7) has been identified as a ligand for Mas receptor, which is a seven-transmembrane G-protein coupled receptor. Mas receptor may induce intracellular signaling cascades such as protein kinase B and induction of nitric oxide (NO) production.