Abstract
Chloride absorption and bicarbonate secretion are vital functions of epithelia, as highlighted by cystic fibrosis and diseases associated with mutations in members of the SLC26 chloride-bicarbonate exchangers. Many SLC26 transporters (SLC26T) are expressed in the luminal membrane together with CFTR, which activates electrogenic chloride-bicarbonate exchange by SLC26T. However, the ability of SLC26T to regulate CFTR and the molecular mechanism of their interaction are not known. We report here a reciprocal regulatory interaction between the SLC26T DRA, SLC26A6 and CFTR. DRA markedly activates CFTR by increasing its overall open probablity (NP(o)) sixfold. Activation of CFTR by DRA was facilitated by their PDZ ligands and binding of the SLC26T STAS domain to the CFTR R domain. Binding of the STAS and R domains is regulated by PKA-mediated phosphorylation of the R domain. Notably, CFTR and SLC26T co-localize in the luminal membrane and recombinant STAS domain activates CFTR in native duct cells. These findings provide a new understanding of epithelial chloride and bicarbonate transport and may have important implications for both cystic fibrosis and diseases associated with SLC26T.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Antiporters*
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Bicarbonates / metabolism*
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Carrier Proteins / genetics
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Carrier Proteins / metabolism*
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Cell Line
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Cell Membrane / genetics
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Cell Membrane / metabolism
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Chloride-Bicarbonate Antiporters / metabolism*
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Chlorides / metabolism
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Cyclic AMP-Dependent Protein Kinases / metabolism
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Cystic Fibrosis / genetics
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Cystic Fibrosis / metabolism
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Cystic Fibrosis Transmembrane Conductance Regulator / genetics
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Cystic Fibrosis Transmembrane Conductance Regulator / metabolism*
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Epithelial Cells / metabolism*
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Humans
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Ion Channel Gating / genetics
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Ion Channel Gating / physiology*
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Ligands
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Membrane Proteins / genetics
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Membrane Proteins / metabolism*
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Membrane Transport Proteins*
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Phosphorylation
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Protein Binding / genetics
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Protein Structure, Tertiary / genetics
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Protein Structure, Tertiary / physiology
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Sulfate Transporters
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Water-Electrolyte Balance / genetics
Substances
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Antiporters
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Bicarbonates
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CFTR protein, human
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Carrier Proteins
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Chloride-Bicarbonate Antiporters
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Chlorides
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Ligands
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Membrane Proteins
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Membrane Transport Proteins
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SLC26A3 protein, human
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SLC26A6 protein, human
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Sulfate Transporters
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Cystic Fibrosis Transmembrane Conductance Regulator
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Cyclic AMP-Dependent Protein Kinases