Molecular determinants of differential pore blocking of kidney CLC-K chloride channels.

TitleMolecular determinants of differential pore blocking of kidney CLC-K chloride channels.
Publication TypeJournal Article
Year of Publication2004
AuthorsPicollo A, Liantonio A, Didonna MPaola, Elia L, Camerino DConte, Pusch M
JournalEMBO Rep
Date Published2004 Jun
Keywords2-Methyl-4-chlorophenoxyacetic Acid, 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid, Amino Acid Motifs, Anion Transport Proteins, Binding Sites, Chloride Channels, Dose-Response Relationship, Drug, Humans, Membrane Proteins, Patch-Clamp Techniques, Point Mutation, Protein Structure, Tertiary

The highly homologous Cl(-) channels CLC-Ka and CLC-Kb are important for water and salt conservation in the kidney and for the production of endolymph in the inner ear. Mutations in CLC-Kb lead to Bartter's syndrome and mutations in the small CLC-K subunit barttin lead to Bartter's syndrome and deafness. Here we show that CLC-Ka is blocked by the recently identified blocker 2-(p-chlorophenoxy)-3-phenylpropionic acid of the rat channel CLC-K1 with an apparent K(D) approximately 80 microM. We also found that DIDS (4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid), a generic Cl(-) channel blocker, inhibits CLC-Ka (K(D) approximately 90 microM). Surprisingly, the highly homologous channel CLC-Kb is fivefold to sixfold less sensitive to both compounds. Guided by the crystal structure of bacterial CLC proteins, we identify two amino acids, N68/D68 and G72/E72, in CLC-Ka and CLC-Kb, respectively, that are responsible for the differential drug sensitivity. Both residues expose their side chains in the extracellular pore mouth, delineating the probable drug binding site. These novel CLC-K channel blockers are promising lead compounds for the development of new diuretic drugs.

Alternate JournalEMBO Rep.
PubMed ID15167890
PubMed Central IDPMC1299079