Expression and regulation of ClC-5 chloride channels: effects of antisenseand oxidants

Genetic mutations of the Cl- channel ClC-5 cause Dent's disease in humans. We recently cloned an amphibian ortholog of Xenopus ClC-5 (xClC-5) from the A6 cell line. We now compare the properties and regulation of ClC-5 curren ts expressed in mammalian (COS-7) cells and Xenopus oocytes. Whole cell cur rents in COS-7 cells transfected with xClC-5 cDNA had strong outward rectif ication, Cl- > I- anion sensitivity, and were inhibited at low pH, similar to previous results in oocytes. In oocytes, antisense xClC-5 cRNA injection had no effect on endogenous membrane currents or the heterologous expressi on of human ClC-5. Activators of cAMP and protein kinase C inhibitors had n o significant effects on ClC-5 currents expressed in either COS-7 cells or oocytes, whereas H-89, a cAMP-dependent protein kinase (PKA) inhibitor, and hydrogen peroxide decreased the currents. We conclude that the basic prope rties of ClC-5 currents were independent of the host cell type used for exp ression. In addition, ClC-5 channels may be modulated by PKA and reactive o xygen species.