Inhibition of the epithelial Na+ channel by interaction of Nedd4 with a PY motif deleted in Liddle's syndrome.
The epithelial Na+ channel (ENaC) plays a critical role in Na+ absorption in the kidney and other epithelia. Mutations in the C terminus of the beta or gammaENaC subunits increase renal Na+ absorption, causing Liddle's syndrome, an inherited form of hypertension. These mutations delete or disrupt a PY motif that was recently shown to interact with Nedd4, a ubiquitin-protein ligase expressed in epithelia. We found that Nedd4 inhibited ENaC when they were coexpressed in Xenopus oocytes. Liddle's syndrome-associated mutations that prevent the interaction between Nedd4 and ENaC abolished inhibition, suggesting that a direct interaction is required for inhibition by Nedd4. Inhibition also required activity of a ubiquitin ligase domain within the C terminus of Nedd4. Nedd4 had no detectable effect on the single channel properties of ENaC. Rather, Nedd4 decreased cell surface expression of both ENaC and a chimeric protein containing the C terminus of the beta subunit. Decreased surface expression resulted from an increase in the rate of degradation of the channel complex. Thus, interaction of Nedd4 with the C terminus of ENaC inhibits Na+ absorption, and loss of this interaction may play a role in the pathogenesis of Liddle's syndrome and other forms of hypertension.
Goulet
C C
CC
Department of Internal Medicine, University of Iowa College of Medicine, Iowa City, Iowa 52242, USA.
Volk
K A
KA
Adams
C M
CM
Prince
L S
LS
Stokes
J B
JB
Snyder
P M
PM
D000818:Animals; D019556:COS Cells; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D056827:Endosomal Sorting Complexes Required for Transport; D004848:Epithelium / Q000378:metabolism; D006973:Hypertension / Q000235:genetics / Q000378:metabolism*; D008025:Ligases / Q000378:metabolism; D000075702:Nedd4 Ubiquitin Protein Ligases; D011485:Protein Binding; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D017384:Sequence Deletion; D026941:Sodium Channel Blockers; D013577:Syndrome; D044767:Ubiquitin-Protein Ligases; D014981:Xenopus; D029867:Xenopus Proteins
D002135:Calcium-Binding Proteins; D056827:Endosomal Sorting Complexes Required for Transport; D011993:Recombinant Fusion Proteins; D026941:Sodium Channel Blockers; D029867:Xenopus Proteins; C000618479:NEDD4L protein, rat; D000075702:Nedd4 Ubiquitin Protein Ligases; C000618482:Nedd4 protein, Xenopus; C000618484:Nedd4 protein, rat; C000618460:nedd4l protein, Xenopus; D044767:Ubiquitin-Protein Ligases; D008025:Ligases