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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