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The Cytosolic Termini of the β- and γ-ENaC Subunits Are Involved in the Functional Interactions between Cystic Fibrosis Transmembrane Conductance Regulator and Epithelial Sodium Channel
- Source :
- Journal of Biological Chemistry. 275:27947-27956
- Publication Year :
- 2000
- Publisher :
- American Society for Biochemistry & Molecular Biology (ASBMB), 2000.
-
Abstract
- Epithelial sodium channel (ENaC) and cystic fibrosis transmembrane conductance regulator (CFTR) are co-localized in the apical membrane of many epithelia. These channels are essential for electrolyte and water secretion and/or reabsorption. In cystic fibrosis airway epithelia, a hyperactivated epithelial Na(+) conductance operates in parallel with defective Cl(-) secretion. Several groups have shown that CFTR down-regulates ENaC activity, but the mechanisms and the regulation of CFTR by ENaC are unknown. To test the hypothesis that ENaC and CFTR regulate each other, and to identify the region(s) of ENaC involved in the interaction between CFTR and ENaC, rENaC and its mutants were co-expressed with CFTR in Xenopus oocytes. Whole cell macroscopic sodium currents revealed that wild type (wt) alphabetagamma-rENaC-induced Na(+) current was inhibited by co-expression of CFTR, and further inhibited when CFTR was activated with a cAMP-raising mixture (CKT). Conversely, alphabetagamma-rENaC stimulated CFTR-mediated Cl(-) currents up to approximately 6-fold. Deletion mutations in the intracellular tails of the three rENaC subunits suggested that the carboxyl terminus of the beta subunit was required both for the down-regulation of ENaC by activated CFTR and the up-regulation of CFTR by ENaC. However, both the carboxyl terminus of the beta subunit and the amino terminus of the gamma subunit were essential for the down-regulation of rENaC by unstimulated CFTR. Interestingly, down-regulation of rENaC by activated CFTR was Cl(-)-dependent, while stimulation of CFTR by rENaC was not dependent on either cytoplasmic Na(+) or a depolarized membrane potential. In summary, there appear to be at least two different sites in ENaC involved in the intermolecular interaction between CFTR and ENaC.
- Subjects :
- Epithelial sodium channel
congenital, hereditary, and neonatal diseases and abnormalities
Macromolecular Substances
Recombinant Fusion Proteins
Green Fluorescent Proteins
Xenopus
Cystic Fibrosis Transmembrane Conductance Regulator
Biochemistry
Sodium Channels
Membrane Potentials
Amiloride
Xenopus laevis
Animals
Epithelial Sodium Channels
Molecular Biology
Sequence Deletion
Membrane potential
Binding Sites
biology
urogenital system
Chemistry
Reabsorption
Cell Membrane
Sodium
Wild type
Cell Biology
respiratory system
Apical membrane
biology.organism_classification
digestive system diseases
Cystic fibrosis transmembrane conductance regulator
Rats
respiratory tract diseases
Cell biology
Luminescent Proteins
Gene Expression Regulation
Protein Biosynthesis
Mutagenesis, Site-Directed
Oocytes
biology.protein
Intracellular
Subjects
Details
- ISSN :
- 00219258
- Volume :
- 275
- Database :
- OpenAIRE
- Journal :
- Journal of Biological Chemistry
- Accession number :
- edsair.doi.dedup.....118bb476944386c0c7f4f7d3033e84dd