Stimulation of the gastric H,K-ATPase activity by CLC-5 Cl⁻ channel

Abstract

In the stomach, protons are actively secreted by the gastric H,K-ATPase, but it is unclear what molecule contributes to the secretion of Cl⁻. We have previously shown that CLC-2 may not be responsible for the Cl⁻ transport in the gastric acid secretion. However, we found that CLC-5 was expressed in the gastric parietal cells. Here, we examined the interaction between CLC-5 and the gastric H,K-ATPase. We constructed a tetracycline-regulated expression system of CLC-5 in the HEK293 cells stably expressing the gastric H,K-ATPase. The H,K-ATPase activity and the ⁸⁶Rb⁺ transporting activity were examined by using SCH 28080, a K⁺-competitive inhibitor of the H,K-ATPase. Expression of CLC-5 in the HEK293 cells significantly increased the H,K-ATPase activity by 24.1 ± 8.9% (n = 6) and ⁸⁶Rb⁺ transporting activity by 28.2 ± 5.9% (n = 5). The expression level of H,K-ATPase in the plasma membrane was not affected by CLC-5 in the HEK293 cells. Furthermore, we found that expression of CLC-5 significantly up-regulated the phosphorylation level of H,K-ATPase by 48 ± 18% (n = 4). These results suggest that CLC-5 may be a modulatory subunit of the gastric H,K-ATPase. [J Physiol Sci. 2006;56 Suppl:S66]