Functional roles of V-ATPase in the salivary gland

BackgroundResearch has clearly demonstrated that vacuolar H+-ATPase (V-ATPase) is involved in the acidification of intracellular organelles such as vacuoles, lysosomes, synaptic vesicles, endosomes, secretory granules, and the Golgi apparatus in all eukaryotic cells. V-ATPase is also involved in mediating proton transport across the plasma membrane of epithelial cells. Furthermore, V-ATPase senses and responds to acidic pH by mobilizing vesicle coat components that are critical for vesicle trafficking from the cytosol to the endosomal membrane. In the salivary gland, V-ATPase mRNA and protein were detected by RT-PCR, western blotting, and immunohistochemistry, although the function of V-ATPase remains unknown.HighlightThe present review aims to clarify our current understanding of the localization and functional roles of V-ATPase, and to discuss how this enzyme is regulated in the salivary glands.ConclusionAn increasing number of studies reveal that the immunoreactivity of V-ATPase is restricted to ductal cells with species- and gland-specific distribution, and that different subunit isoforms of V-ATPase could be involved in targeting it to various intracellular locations. Considering that the major function of salivary gland duct epithelial cells is the reabsorption of Na+ and Cl−, and secretion of K+ and HCO3−HCO3−, V-ATPase may primarily function in transporting protons out of cells across the plasma membrane, or acidifying compartments, resulting in modifying fluid and electrolyte transport.