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XB-ART-41782
Am J Physiol Renal Physiol 2010 Oct 01;2994:F854-61. doi: 10.1152/ajprenal.00316.2010.
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Defining an inhibitory domain in the gamma subunit of the epithelial sodium channel.

Passero CJ, Carattino MD, Kashlan OB, Myerburg MM, Hughey RP, Kleyman TR.


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Proteases activate the epithelial sodium channel (ENaC) by cleaving the large extracellular domains of the α- and γ-subunits and releasing peptides with inhibitory properties. Furin and prostasin activate mouse ENaC by cleaving the γ-subunit at sites flanking a 43 residue inhibitory tract (γE144-K186). To determine whether there is a minimal inhibitory region within this 43 residue tract, we generated serial deletions in the inhibitory tract of the γ-subunit in channels resistant to cleavage by furin and prostasin. We found that partial or complete deletion of a short segment in the γ-subunit, R158-N171, enhanced channel activity. Synthetic peptides overlapping this segment in the γ-subunit further identified a key 11-mer tract, R158-F168 (RFLNLIPLLVF), which inhibited wild-type ENaC expressed in Xenopus laevis oocytes, and endogenous channels in mpkCCD cells and human airway epithelia. Further studies with amino acid-substituted peptides defined residues that are required for inhibition in this key 11-mer tract. The presence of the native γ inhibitory tract in ENaC weakened the intrinsic binding constant of the 11-mer peptide inhibitor, suggesting that the γ inhibitory tract and the 11-mer peptide interact at overlapping sites within the channel.

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Species referenced: Xenopus laevis
Genes referenced: furin prss8 prss8l

References [+] :
Adebamiro, A segment of gamma ENaC mediates elastase activation of Na+ transport. 2007, Pubmed