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Conserved charged residues in the extracellular domain of epithelial sodium channel (ENaC) essential for cell‐surface expression
Author(s) -
Hanukoglu Israel,
Edelheit Oded,
Dascal Nathan,
Hanukoglu Aaron
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.lb126
Subject(s) - epithelial sodium channel , xenopus , chemistry , extracellular , sodium channel , microbiology and biotechnology , oocyte , mutant , alanine , amiloride , transmembrane domain , biophysics , sodium , biochemistry , biology , amino acid , gene , embryo , organic chemistry
Epithelial sodium channels (ENaC) are composed of three subunits whose extracellular domains (ECD) form a funnel that directs ions from the lumen into the pore of ENaC. To examine the roles of conserved charged residues on ECD, we mutated 16 residues in human α‐ENaC to alanine. The modified cRNAs were expressed in Xenopus oocytes together with wild type β‐ and γ‐ENaC. The effect of each mutation was examined on three parameters: amiloride‐sensitive Na + conductance, Na + ‐dependent self‐inhibition of ENaC and oocyte cell surface expression of ENaC (quantitated by confocal imaging of Yellow Fluorescent Protein linked to γ‐ENaC). All 16 mutants showed a strong correlation between ENaC activity and oocyte surface expression. Control mutations to a homologous charged residue (e.g. Asp to Glu) did not significantly affect ENaC activity. Changes in the two parameters, Na + self‐inhibition and oocyte surface expression level, accounted for the magnitude of reduction in ENaC activity as a result mutation to Ala. These results establish that while some conserved charged residues are part of the structure responsible for Na + self‐inhibition, most are essential for transport to the oocyte cell‐surface.