(Pro)renin receptor, PRR or ATP6AP2, ATP6IP2, CAPER, ELDF10, of 350 aas and 2 TMSs at the N- and C-termini.  It plays a role in hypertensive disease (Danser 2015) and in planar cell polarity, including retinal laminar formation (Kanda 2015).  ATP6AP2 is necessary for cell division, cell cycle progression and mitosis, and it inhibits ciliogenesis, thus promoting proliferation and preventing differentiation (Wanka et al. 2017). It is an assembly factor in the endoplasmic reticulum for the V-type ATPase (Guida et al. 2018). It forms a complex with ATP6AP1 (Q15904; 470 aas, two TMSs, N- and C-terminal), also called ATP6S1 and VATPS1. It has roles in various physiological processes, such as the cell cycle, autophagy, acid-base balance, energy metabolism, embryonic development, T cell homeostasis, water balance, blood pressure regulation, cardiac remodelling and maintenance of podocyte structure. These roles of the (P)RR are mediated by its effects on important biological systems and pathways including the tissue RAS, vacuolar H⁺-ATPase.  It may contribute to the pathogenesis of diseases such as fibrosis, hypertension, pre-eclampsia, diabetic microangiopathy, acute kidney injury, cardiovascular disease, cancer and obesity (Ichihara and Yatabe 2019). PRR or ATP6AP2 is a type I transmembrane receptor that is capable of binding and activating prorenin and renin. Within the kidney, PRR is predominantly expressed in the distal nephron, particularly the intercalated cells, and activation of renal PRR contributes to renal injury in various rodent models of chronic kidney disease. Evidence has shwon that PRR is primarily cleaved by a site-1 protease to produce 28-kDa soluble PRR (sPRR) which seems to mediate most of the known pathophysiological functions of renal PRR through modulating the activity of the intrarenal renin-angiotensin system and provoking proinflammatory and profibrotic responses. Not only does sPRR activate renin, but it also directly binds and activates the angiotensin II type 1 receptor (Yang 2022). The protein binding site of the (pro)renin receptor using in silico 3D structural analysis has been mapped (Ebihara et al. 2023).  (Pro)renin receptor blockade prevents  increases in systolic blood pressure, sodium retention, and αENaC  protein expression in the kidney of 2K1C goldblatt mice (Cárdenas et al. 2025).  Downregulation of MPC1 promotes HCC cell proliferation and metastasis via the STAT3 pathway (Shan et al. 2025).