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Mapping an inhibitory domain in the alpha subunit of the epithelial sodium channel
Author(s) -
Carattino Marcelo Daniel,
Passero Christopher J.,
Maarouf Ahmad B.,
Bruns James B.,
Hughey Rebecca P.,
Kleyman Thomas R.
Publication year - 2007
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.21.5.a545-b
Subject(s) - furin , epithelial sodium channel , xenopus , protein subunit , cleavage (geology) , microbiology and biotechnology , biology , chemistry , sodium channel , inhibitory postsynaptic potential , transmembrane domain , apical membrane , extracellular , g alpha subunit , biochemistry , sodium , enzyme , endocrinology , amino acid , membrane , gene , organic chemistry , paleontology , fracture (geology)
Epithelial sodium channels (ENaCs) mediate Na + entry across the apical membrane of high‐resistance epithelia including the distal nephron, airway and alveoli, and distal colon. These channels are composed of three structurally related subunits, termed α, β, and γ. Maturation of ENaC requires furin‐dependent cleavage at two extracellular sites within the α subunit and at a single site within the γ subunit. Channels carrying mutations in the putative furin cleavage sites of the α subunit (αR205/A,R231/A) are uncleaved and have very low activity. We previously showed that the tract αAsp206–Arg231 functions as an inhibitor that stabilizes the channel in the closed conformation. To characterize the inhibitory domain within the αAsp206–Arg231 tract, we used the Xenopus laevis oocyte expression system. We generated serial deletions in the tract αAsp206–Arg231 in subunits also carrying mutations in the furin cleavage consensus sites. We found an eight‐residue tract that when deleted restored channel activity to the same level found in wild type ENaC expressing oocytes. A synthetic peptide representing this eight‐residue tract inhibited wild type ENaC with an IC 50 in the micromolar range. These findings suggest that the eight‐residue tract may account for the inhibitory effect of the tract αAsp206–Arg231.