The Renin Receptor, also known as ATP6AP2 (ATPase H+-transporting lysosomal accessory protein 2), ATP6IP2 (ATPase H+-transporting lysosomal-interacting protein 2), CAPER or M8-9, is an ATPase-associated protein that functions as a Renin and prorenin cellular receptor. Expressed in the brain, heart, liver, kidney, placenta and pancreas, the Renin Receptor functions to activate ERK 1 and ERK 2, thereby mediating Renin-dependent cellular responses. The Renin Receptor has a subunit that associates with the transmembrane domain of V-type ATPases and interacts with Renin. These interactions increase the catalytic activity of Renin in the Renin-Angiotensin system (RAS), thus upregulating the conversion of angiotensinogen to Angiotensin.