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Lipid rafts mediate constitutive apical delivery of the epithelial sodium channel (ENaC)
Author(s) -
Hill Warren G.,
Butterworth Michael B.,
Wang Huamin,
Edinger Robert S.,
Frizzell Raymond A.,
Johnson John P.
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.21.6.a954-d
Subject(s) - epithelial sodium channel , forskolin , lipid raft , microbiology and biotechnology , apical membrane , endocytosis , chemistry , medicine , endocrinology , biology , stimulation , sodium , biochemistry , receptor , signal transduction , membrane , organic chemistry
ENaC was detected in lipid rafts in mouse cortical collecting duct (mCCD) cells by detergent insolubility, buoyancy on density gradients and colocalization with caveolin 1. Approximately 20% of cellular ENaC was present in raft fractions and this distribution was not altered by aldosterone or forskolin. ENaC in raft fractions colocalized with SNARE proteins, syntaxin 1A, Vamp 2 and SNAP23. Methyl‐β‐cyclodextrin (CD) added apically to mCCD cells resulted in slow decline in sodium transport over 60 min identical to the rate of decline in current seen with cycloheximide (CH). Neither CD nor CH blocked forskolin stimulation of ENaC or ENaC recycling. Disruption of lipid rafts by expression of dominant negative caveolin isoforms reduced basal ENaC currents by >70%. The increase in Na + current induced by forskolin in dominant negative caveolin cells was, however, similar to that seen in controls. This suggests that acute stimulation and membrane insertion of ENaC from recycling endosomes is unaffected by raft disruption. Collectively, the data point to a role for rafts in the constitutive apical delivery of ENaC and suggest that rafts are not involved in endocytosis or recycling of ENaC. Supported by NIH DK47874 and DK57718.