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An extracellular subdomain of the epithelial Na+ channel gamma subunit confers Na+ self‐inhibition response
Author(s) -
Winarski Katie L.,
Sheng Nan,
Chen Jingxin,
Kleyman Thomas R.,
Sheng Shaohu
Publication year - 2010
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.24.1_supplement.611.25
Subject(s) - epithelial sodium channel , xenopus , extracellular , chemistry , protein subunit , biophysics , mutagenesis , residue (chemistry) , mutant , homeostasis , biochemistry , microbiology and biotechnology , sodium , biology , gene , organic chemistry
The epithelial Na + channel (ENaC) is a key component in regulation of body fluid volume homeostasis. Its activity is controlled in part by Na + self‐inhibition, a down regulation of channel activity by extracellular Na + . We previously showed that a His residue (γH239) within the extracellular domain (ECD) of γENaC subunit has a critical role in the Na + self‐inhibition response. We investigated the functional roles of residues in the vicinity of this γH239 by Cys scanning mutagenesis and analyses of Na + self‐inhibition responses in channel expressing Xenopus oocytes. Significant changes in the speed and magnitude of Na + self‐inhibition were observed with multiple mutants, which are distributed within a contiguous stretch of 22 residues within the scanned region of 47 residues. Cys substitution at three aromatic residues (γF225C, γW235C and γH239C) resulted in the greatest suppression on Na + self‐inhibition, suggesting a shared functional role. The distribution pattern of residues whose substitutions significantly altered Na + self‐inhibition is consistent with secondary structure predictions of one helix. We conclude that the critical γH239 residue functions within a subdomain of γECD that has a specific role in conferring the Na + self‐inhibition response of ENaC. (Supported by NIH ES014701, DK54354 and DK079307)