Comparison of Amphibian and Human ClC-5: Similarity of Functional Properties and Inhibition by External pH

Comparison of Amphibian and Human ClC-5: Similarity of Functional Properties and Inhibition by... Loss of function mutations of the renal chloride channel, ClC-5, have been implicated in Dent's disease, a genetic disorder characterized by low weight proteinuria, hypercalciuria, nephrolithasis and, in some cases, eventual renal failure. Recently, our laboratory used an RT-PCR/RACE cloning strategy to isolate an amphibian cDNA from the renal epithelial cell line A6 that had high homology to human ClC-5. We now report a full-length native ClC-5 clone (xClC-5, containing 5′ and 3′ untranslated regions) isolated by screening a cDNA library from A6 cells that was successfully expressed in Xenopus oocytes. In addition, we compared the properties of xClC-5 and hClC-5 using isogenic constructs of xClC-5 and hClC-5 consisting of the open reading frame subcloned into an optimized Xenopus expression vector. Expression of the full-length ``native'' xClC-5 clone resulted in large, strongly rectifying, outward currents that were not significantly affected by the chloride channel blockers DIDS, DPC, and 9AC. The anion conductivity sequence was NO− 3 > Cl−= I− > HCO− 3 >> glutamate for xClC-5 and NO− 3 > Cl− > HCO− 3 > I− >> glutamate for hClC-5. Reduction of the extracellular pH (pH o ) from 7.5 to 5.7 inhibited outward ClC-5 currents by 27 ± 9% for xClC-5 and 39 ± 7% for hClC-5. The results indicate that amphibian and mammalian ClC-5 have highly similar functional properties. Unlike hClC-5 and most other ClC channels, expression of xClC-5 in oocytes does not require the removal of its untranslated 5′ and 3′ regions. Acidic solutions inhibited both amphibian and human ClC-5 currents, opposite to the stimulatory effects of low external pH on other ClC channels, suggesting a possibly distinct regulatory mechanism for ClC-5 channels. The Journal of Membrane Biology Springer Journals

Comparison of Amphibian and Human ClC-5: Similarity of Functional Properties and Inhibition by External pH

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Copyright © Inc. by 1999 Springer-Verlag New York
Life Sciences; Biochemistry, general; Human Physiology
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