ABSTRACT
The vacuolar (H+)-ATPases are multi-subunit enzymatic proton pump complex. It has two domains: cytoplasmic V1 domain and
transmembrane V0 [1]. The cytoplasmic V1 hydrolyzes ATP while
transmembrane V0 translocates protons. It is an ATP-dependent
proton pump that acidifies intracellular compartment or transport
protons (H+) across the plasmamembrane. It is found on the plasma membrane or in associationwith various intracellular organelles. V1
domain is composed of eight types of subunits (A-H), whereas V0
domain consist of six subunits (a, c, c′′, d, e, and Ac45) [1]. V-ATPase subunits gene have spatiotemporal gene expression pattern and is
tissue and cell type-specific [2]. V-ATPases have been identified in
the plasma membranes of various cells including renal intercalated
cells, osteoclasts, and macrophages [3]. The important subunits
reported to be involved in human diseases are A and B of the V0
and V1 domain, respectively [4]. Subunit A has four isoforms (a1-
a4) and subunit B has two isoforms (B1 and B2) [3]. Isoform that
are present in limited number of tissues such as the kidneys are B1
(ATP6V1B1), a4 (ATP6V0A4), G3, C2, and d2 [3]. Besides kidneys,
B1 subunits are also present in epididymis, ciliary body of the eye,
and in the inner ear. A4 subunits are present only in epididymis,
inner ear, and kidney. In the kidney, V-ATPases are localized in the
apical membrane of type A-intercalated cells, basolateral membrane
of type B-intercalated cells, and both apical and basolateral in non-A
and non-B type of cells [3].
