Tissue distribution and subcellular localization of the ClC-5 chloride channel in rat intestinal cells

ClC-5 is the Cl- channel that is mutated in Dent's disease, an X-chromosome -linked disease characterized by low molecular weight proteinuria, hypercal ciuria, and kidney stones. It is predominantly expressed in endocytically a ctive renal proximal cells. We investigated whether this Cl- channel could also be expressed in intestinal tissues that have endocytotic machinery. Cl C-5 mRNA was detected in the rat duodenum, jejunum, ileum, and colon. Weste rn blot analyses revealed the presence of the 83-kDa ClC-5 protein in these tissues. Indirect immunofluorescence studies showed that ClC-5 was mainly concentrated in the cytoplasm above the nuclei of enterocytes and colon cel ls. ClC-5 partially colocalized with the transcytosed polymeric immunoglobu lin receptor but was not detectable together with the brush-border-anchored sucrase isomaltase. A subfractionation of vesicles obtained by differentia l centrifugation showed that ClC-5 is associated with the vacuolar 70-kDa H +-ATPase and the small GTPases rab4 and rab5a, two markers of early endosom es. Thus these results indicate that ClC-5 is present in the small intestin e and colon of rats and suggest that it plays a role in the endocytotic pat hways of intestinal cells.