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XB-ART-41820
J Biol Chem 2010 Oct 01;28540:30453-62. doi: 10.1074/jbc.M110.151845.
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Cys palmitoylation of the beta subunit modulates gating of the epithelial sodium channel.

Mueller GM, Maarouf AB, Kinlough CL, Sheng N, Kashlan OB, Okumura S, Luthy S, Kleyman TR, Hughey RP.


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The epithelial Na(+) channel (ENaC) is comprised of three homologous subunits (α, β, and γ) that have a similar topology with two transmembrane domains, a large extracellular region, and cytoplasmic N and C termini. Although ENaC activity is regulated by a number of factors, palmitoylation of its cytoplasmic Cys residues has not been previously described. Fatty acid-exchange chemistry was used to determine whether channel subunits were Cys-palmitoylated. We observed that only the β and γ subunits were modified by Cys palmitoylation. Analyses of ENaCs with mutant β subunits revealed that Cys-43 and Cys-557 were palmitoylated. Xenopus oocytes expressing ENaC with a β C43A,C557A mutant had significantly reduced amiloride-sensitive whole cell currents, enhanced Na(+) self-inhibition, and reduced single channel P(o) when compared with wild-type ENaC, while membrane trafficking and levels of surface expression were unchanged. Computer modeling of cytoplasmic domains indicated that β Cys-43 is in proximity to the first transmembrane α helix, whereas β Cys-557 is within an amphipathic α-helix contiguous with the second transmembrane domain. We propose that β subunit palmitoylation modulates channel gating by facilitating interactions between cytoplasmic domains and the plasma membrane.

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References [+] :
Ahn, Cloning and functional expression of the mouse epithelial sodium channel. 1999, Pubmed, Xenbase