Title:Novel Insights into V-ATPase Functioning: Distinct Roles for its Accessory Subunits ATP6AP1/Ac45 and ATP6AP2/(pro) Renin Receptor
Volume: 13
Issue: 2
Author(s): Eric J.R. Jansen and Gerard J.M. Martens
Affiliation:
Keywords:
Acidification, secretory pathway, membrane fusion, neurodevelopment, osteoporosis, renin-angiotensin system, endocytosis, teoclasts, eurotransmitter transporters, F-ATPase complex
Abstract: The vacuolar (H+)-ATPase (V-ATPase) is a universal proton pump and its activity is required for a variety of
cell-biological processes such as membrane trafficking, receptor-mediated endocytosis, lysosomal protein degradation, osteoclastic
bone resorption and maintenance of acid-base homeostasis by renal intercalated cells. In neuronal and neuroendocrine
cells, the V-ATPase is the major regulator of intragranular acidification which is indispensable for correct prohormone
processing and neurotransmitter uptake. In these specialized cells, the V-ATPase is equipped with the accessory
subunits ATP6AP1/Ac45 and ATP6AP2/(pro) renin receptor. Recent studies have shown that Ac45 interacts with the V0-
sector of the V-ATPase complex, thereby regulating the intragranular pH and Ca2+-dependent exocytotic membrane fusion.
Thus, Ac45 can be considered as a V-ATPase regulator in the neuroendocrine secretory pathway. ATP6AP2 has recently
been found to be identical to the (pro) renin receptor and has a dual role: (i) in the renin-angiotensin system that
also regulates V-ATPase activity; (ii) acting as an adapter by binding to both the V-ATPase and the Wnt receptor complex,
thereby recruiting the receptor complex into an acidic microenvironment. We here provide an overview of the two
V-ATPase accessory subunits as novel key players in V-ATPase regulation. We argue that the accessory subunits are
candidate genes for V-ATPase-related human disorders and promising targets for manipulating V-ATPase functioning in
vivo.