Properties of Kidney Plasma Membrane Vacuolar H+-ATPases: Proton Pumps Responsible for Bicarbonate Transport, Urinary Acidification, and Acid-Base Homeostasis. Organellar Proton-ATPases. Berlin: Springer Berlin Heidelberg; 1995. pp. 163-221. [DOI: 10.1007/978-3-662-22265-2_6]

New insights into the regulation of V-ATPase-dependent proton secretion

The vacuolar H(+)-ATPase (V-ATPase) is a key player in several aspects of cellular function, including acidification of intracellular organelles and regulation of extracellular pH. In specialized cells of the kidney, male reproductive tract and osteoclasts, proton secretion via the V-ATPase represents a major process for the regulation of systemic acid/base status, sperm maturation and bone resorption, respectively. These processes are regulated via modulation of the plasma membrane expression and activity of the V-ATPase. The present review describes selected aspects of V-ATPase regulation, including recycling of V-ATPase-containing vesicles to and from the plasma membrane, assembly/disassembly of the two domains (V(0) and V(1)) of the holoenzyme, and the coupling ratio between ATP hydrolysis and proton pumping. Modulation of the V-ATPase-rich cell phenotype and the pathophysiology of the V-ATPase in humans and experimental animals are also discussed.

Selective assembly of V-ATPase subunit isoforms in mouse kidney

The kidney plays vital roles in acid-base homeostasis, and the reabsorption of water, ions, and proteins. These processes are achieved through acidification of urine and endosomes of proximal tubule epithelial cells. Multisubunit vacuolar-type proton ATPase (V-ATPase) is one of the major acidification-machinery proteins that localizes to the apical or basolateral plasma membranes of intercalated cells in collecting ducts and the endosomal region at the base of brush border microvilli in proximal tubules. Multiple subunit isoforms of V-ATPase, which are expressed in kidney, have been identified. One obvious question is whether the pumps at different locations in the kidney have their own unique subunit identities. We have used a combination of methods to study this enzyme in kidney including immunocytochemical staining and immunoprecipitation analyses. The subunit isoforms of V-ATPase exhibited selective association/assembly in kidney: kidney-specific isoforms predominantly formed the intercalated cell proton pump, whereas the pump located in the brush border comprised ubiquitously expressed counterparts.