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© The Rockefeller University Press, 0022-1295/1998//601/ $5.00
Journal of General Physiology, Volume 111, Number 4, 1998

Article

Adenosine Triphosphate–dependent Asymmetry of Anion Permeation in the Cystic Fibrosis Transmembrane Conductance Regulator Chloride Channel

Paul Linsdell and John W. Hanrahan

From the Department of Physiology, McGill University, Montréal, Québec, Canada H3G 1Y6

The cystic fibrosis transmembrane conductance regulator (CFTR) forms a tightly regulated channel that mediates the passive diffusion of Cl– ions. Here we show, using macroscopic current recording from excised membrane patches, that CFTR also shows significant, but highly asymmetrical, permeability to a broad range of large organic anions. Thus, all large organic anions tested were permeant when present in the intracellular solution under biionic conditions (PX/PCl = 0.048–0.25), whereas most were not measurably permeant when present in the extracellular solution. This asymmetry was not observed for smaller anions. ATPase inhibitors that "lock" CFTR channels in the open state (pyrophosphate, 5'-adenylylimidodiphosphate) disrupted the asymmetry of large anion permeation by allowing their influx from the extracellular solution, which suggests that ATP hydrolysis is required to maintain asymmetric permeability. The ability of CFTR to allow efflux of large organic anions represents a novel function of CFTR. Loss of this function may contribute to the pleiotropic symptoms seen in cystic fibrosis.

Key Words: anion permeation • anion selectivity • chloride channel • ATPase • cystic fibrosis

Address correspondence to Paul Linsdell, Department of Physiology, McGill University, 3655 Drummond Street, Montréal, Québec, H3G 1Y6, Canada. Fax: 514-398-7452; E-mail: linsdell{at}physio.mcgill.ca


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