Nedd4-2 modulates renal Na+-Cl- cotransporter via the aldosterone-SGK1-Nedd4-2 pathway

• Published in: Journal of the American Society of Nephrology 2011-09, Vol.22 (9), p.1707-1719
• Main Authors: Arroyo, Juan Pablo, Lagnaz, Dagmara, Ronzaud, Caroline, Vázquez, Norma, Ko, Benjamin S, Moddes, Lauren, Ruffieux-Daidié, Dorothée, Hausel, Pierrette, Koesters, Robert, Yang, Baoli, Stokes, John B, Hoover, Robert S, Gamba, Gerardo, Staub, Olivier
• Format: Article
• Language: English
• Subjects: 11-beta-Hydroxysteroid Dehydrogenase Type 2 - metabolism; Aldosterone - metabolism; Animals; Basic Research; Down-Regulation; Endosomal Sorting Complexes Required for Transport - metabolism; HEK293 Cells; Humans; Immediate-Early Proteins - metabolism; Kidney Tubules, Distal - enzymology; Mice; Mice, Knockout; Nedd4 Ubiquitin Protein Ligases; Phosphorylation; Protein-Serine-Threonine Kinases - metabolism; Signal Transduction; Sodium Chloride Symporters - metabolism; Ubiquitin-Protein Ligases - metabolism; Ubiquitination; Xenopus laevis; Xenopus Proteins
• ISSN: 1046-6673; 1533-3450
• DOI: 10.1681/ASN.2011020132

Regulation of renal Na(+) transport is essential for controlling blood pressure, as well as Na(+) and K(+) homeostasis. Aldosterone stimulates Na(+) reabsorption by the Na(+)-Cl(-) cotransporter (NCC) in the distal convoluted tubule (DCT) and by the epithelial Na(+) channel (ENaC) in the late DCT, connecting tubule, and collecting duct. Aldosterone increases ENaC expression by inhibiting the channel's ubiquitylation and degradation; aldosterone promotes serum-glucocorticoid-regulated kinase SGK1-mediated phosphorylation of the ubiquitin-protein ligase Nedd4-2 on serine 328, which prevents the Nedd4-2/ENaC interaction. It is important to note that aldosterone increases NCC protein expression by an unknown post-translational mechanism. Here, we present evidence that Nedd4-2 coimmunoprecipitated with NCC and stimulated NCC ubiquitylation at the surface of transfected HEK293 cells. In Xenopus laevis oocytes, coexpression of NCC with wild-type Nedd4-2, but not its catalytically inactive mutant, strongly decreased NCC activity and surface expression. SGK1 prevented this inhibition in a kinase-dependent manner. Furthermore, deficiency of Nedd4-2 in the renal tubules of mice and in cultured mDCT(15) cells upregulated NCC. In contrast to ENaC, Nedd4-2-mediated inhibition of NCC did not require the PY-like motif of NCC. Moreover, the mutation of Nedd4-2 at either serine 328 or 222 did not affect SGK1 action, and mutation at both sites enhanced Nedd4-2 activity and abolished SGK1-dependent inhibition. Taken together, these results suggest that aldosterone modulates NCC protein expression via a pathway involving SGK1 and Nedd4-2 and provides an explanation for the well-known aldosterone-induced increase in NCC protein expression.