Novel physiological function of CLC-5 chloride channel associated with gastric proton pump

In the present study, we studied about the physiological function of CLC-5 in the parietal cells. We found that CLC-5 protein is co-localized with gastric H,K-ATPase in the tubulovesicles and the apical membrane of the parietal cells. Immunoprecipitation using the anti-H,K-ATPase antibody showed the association between CLC-5 and H,K-ATPase in isolated hog gastric vesicles. We succeeded to establish the tetracycline-regulated stable expression of CLC-5 in the HEK293 cells that stably express H,K-ATPase α- and β-subunits. When the cells were treated with tetracycline, CLC-5 was expressed in the plasma membrane and intracellular organelles, while no significant expression of CLC-5 was observed in the cells treated without tetracycline. CLC-5 was co-localized with gastric H,K-ATPase in the plasma membrane of the tetracycline-treated cells. In these cells, the expression of CLC-5 significantly increased the activity of H,K-ATPase, ^<86>Rb^+ transport and phosphorylation level (EP level) of the H,K-ATPase. In the cell surface biotinylation of H,K-ATPase α-subunit, we found that the expression of CLC-5 did not affect the expression level of H,K-ATPase in the plasma membrane. These results suggest that CLC-5 acts as a novel up-regulator of gastric H,K-ATPase.