title: Functional coupling of chloride-proton exchanger ClC-5 to gastric H+,K+-ATPase.
abstract: It has been reported that chloride-proton exchanger ClC-5 and vacuolar-type H(+)-ATPase are essential for endosomal acidification in the renal proximal cells. Here, we found that ClC-5 is expressed in the gastric parietal cells which secrete actively hydrochloric acid at the luminal region of the gland, and that it is partially localized in the intracellular tubulovesicles in which gastric H(+),K(+)-ATPase is abundantly expressed. ClC-5 was co-immunoprecipitated with H(+),K(+)-ATPase in the lysate of tubulovesicles. The ATP-dependent uptake of (36)Cl(-) into the vesicles was abolished by 2-methyl-8-(phenylmethoxy)imidazo[1,2-a]pyridine-3-acetonitrile (SCH28080), an inhibitor of H(+),K(+)-ATPase, suggesting functional expression of ClC-5. In the tetracycline-regulated expression system of ClC-5 in the HEK293 cells stably expressing gastric H(+),K(+)-ATPase, ClC-5 was co-immunoprecipitated with H(+),K(+)-ATPase, but not with endogenous Na(+),K(+)-ATPase. The SCH28080-sensitive (36)Cl(-) transporting activity was observed in the ClC-5-expressing cells, but not in the ClC-5-non-expressing cells. The mutant (E211A-ClC-5), which has no H(+) transport activity, did not show the SCH28080-sensitive (36)Cl(-) transport. On the other hand, both ClC-5 and its mutant (E211A) significantly increased the activity of H(+),K(+)-ATPase. Our results suggest that ClC-5 and H(+),K(+)-ATPase are functionally associated and that they may contribute to gastric acid secretion.
authors.affiliation: Department of Pharmaceutical Physiology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama 930-0194, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Takahashi
authors.forename: Takuto
authors.initials: T
authors.lastname: Fujii
authors.forename: Kyosuke
authors.initials: K
authors.lastname: Fujita
authors.forename: Takahiro
authors.initials: T
authors.lastname: Shimizu
authors.forename: Taiga
authors.initials: T
authors.lastname: Higuchi
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Tabuchi
authors.forename: Hisato
authors.initials: H
authors.lastname: Sakamoto
authors.forename: Ichiro
authors.initials: I
authors.lastname: Naito
authors.forename: Koji
authors.initials: K
authors.lastname: Manabe
authors.forename: Shinichi
authors.initials: S
authors.lastname: Uchida
authors.forename: Sei
authors.initials: S
authors.lastname: Sasaki
authors.forename: Akira
authors.initials: A
authors.lastname: Ikari
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Tsukada
authors.forename: Hideki
authors.initials: H
authors.lastname: Sakai
keywords: ClC-5; Gastric acid; H+,K+-ATPase; Parietal cell; Tubulovesicle