The Molecular Biology of Chloride Secretion in Epithelia

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Abstract
The ion transport mechanisms involved in electrogenic Cl secretion include a Cl exit step through the Cl channel at the apical membrane. In cystic fibrosis (CF), Cl secretion is impaired due to a missing Cl permeability of the apical membrane. Patch-clamp experiments have demonstrated that Cl channels are present in CF cells; however, the regulation of channel activity via the cAMP-pathway is impaired. Recent studies have shown that the CF defect is very closely associated with the Cl channel itself or with an associated, membrane-bound regulatory subunit of the Cl channel complex. Because not much is known about the molecular details of the individual transport mechanisms and the signaling pathways involved in Cl secretion in epithelial cells, recent findings on the molecular biology of these mechanisms obtained in other cellular systems are discussed.