The secretion of K + in the gastric lumen is essential to maintain the sustained activity of H + -K + -ATPase. H + -K + -ATPase activity could be inhibited in wild-type mice by exposure to a specific small molecule CFTR inhibitor.įurthermore, mice carrying the homozygous ΔF508 mutation (the most common CFTR mutation responsible for cystic fibrosis) have a significantly lower ability to secrete gastric acid.Ĭhloride channel type 2 (ClC-2) has been proposed as an alternative route for chloride secretion to CFTR and calcium-activated chloride channels in the intestine. The cystic fibrosis transmembrane regulator (CFTR) is a potential candidate for chloride secretion in the parietal cell.Īlthough its degree of expression is lower than in other tissues, such as intestinal or respiratory tract epithelia, it has been shown to play a fundamental role during acid secretion in the murine stomach. Pharmacological inhibition of chloride channels was shown to effectively inhibit gastric acid secretion, suggesting a close functional coupling between these channels and H + -K + -ATPase. Chloride secretionĬhloride is the second component, which must be secreted in the gastric lumen, to allow the formation of HCl. The importance of intact chloride secretion for successful proton extrusion was established very early. The α subunit of gastric H + -K + -ATPase consists of 1,035 amino acids that form 10 transmembrane segments and the β subunit of 291 amino acids with one transmembrane segment.īoth subunits are linked in the M7 / loop / M8 region (M7 describes the seventh transmembrane region) of the α subunit, with an additional binding present in the M5 / loop / M6 region of the α subunit when K + is present. This homology is also manifested in the functional characteristics of both proteins. The catalytic cycle of Na + -K + -ATPase, already established in the 1970s, shows significant similarity to that of H + -K + -ATPase. Although transport is specific for a particular cation, all ATPases share a significant degree of homology.Īpproximately 63% sequence homology is found between the α subunits of H + -K + -ATPase and Na + -K + -ATPase, while the β subunit genes share 35% of the nucleotides.
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