Abstract
Gastric acid secretion in parietal cells is performed by proton pump, H+, K+- ATPase, in combination with several related ion transporters located on the apical and basolateral membranes. In this review I will introduce several recent topics about molecular basis of gastric acid secretion in parietal cells. First, I wish to introduce 3D structures of H+, K+-ATPase resolved recently. The structures demonstrated the interaction between the α- and β- subunits fixes and favors the E2P conformation (the “rachet effect”). The binding site of a K+-competitive inhibitor SCH 28080 on the α- subunit of H+, K+-ATPase was also identified in the 3D structure. Secondly, I wish to introduce ion transporters on the apical membrane necessary for gastric acid secretion. Among others KCNQ1/KCNE2 was identified as a K+ channel involved in K+ recycling and replenishment of K+ in the lumen. Thirdly, I wish to introduce actin-binding proteins, ezrin and Huntingtin interacting protein 1 related (Hip1r), which are necessary for gastric acid secretion. Ezrin is involved in membrane fusion between tubulovesicles and apical membrane whereas Hip1r is involved in endocytosis and regeneration of tubulovesicles from apical membrane. Finally, the roles of parietal cells in differentiation of gastric epithelial cells as well as gastric acid secretion will be introduced.
