Article: article from journal or magazin.
Renal tubular SGK1 deficiency causes impaired K+ excretion via loss of regulation of NEDD4-2/WNK1 and ENaC.
American journal of physiology. Renal physiology
Publication types: Journal Article
Publication Status: ppublish
Publication Status: ppublish
The stimulation of postprandial K(+) clearance involves aldosterone-independent and -dependent mechanisms. In this context, serum- and glucocorticoid-induced kinase (SGK)1, a ubiquitously expressed kinase, is one of the primary aldosterone-induced proteins in the aldosterone-sensitive distal nephron. Germline inactivation of SGK1 suggests that this kinase is fundamental for K(+) excretion under conditions of K(+) load, but the specific role of renal SGK1 remains elusive. To avoid compensatory mechanisms that may occur during nephrogenesis, we used inducible, nephron-specific Sgk1(Pax8/LC1) mice to assess the role of renal tubular SGK1 in K(+) regulation. Under a standard diet, these animals exhibited normal K(+) handling. When challenged by a high-K(+) diet, they developed severe hyperkalemia accompanied by a defect in K(+) excretion. Molecular analysis revealed reduced neural precursor cell expressed developmentally downregulated protein (NEDD)4-2 phosphorylation and total expression. γ-Epithelial Na(+) channel (ENaC) expression and α/γENaC proteolytic processing were also decreased in mutant mice. Moreover, with no lysine kinase (WNK)1, which displayed in control mice punctuate staining in the distal convoluted tubule and diffuse distribution in the connecting tubule/cortical colleting duct, was diffused in the distal convoluted tubule and less expressed in the connecting tubule/collecting duct of Sgk(Pax8/LC1) mice. Moreover, Ste20-related proline/alanine-rich kinase phosphorylation, and Na(+)-Cl(-) cotransporter phosphorylation/apical localization were reduced in mutant mice. Consistent with the altered WNK1 expression, increased renal outer medullary K(+) channel apical localization was observed. In conclusion, our data suggest that renal tubular SGK1 is important in the regulation of K(+) excretion via the control of NEDD4-2, WNK1, and ENaC.
Amino Acid Sequence, Animals, Antibodies, Blocking/pharmacology, Diet, Endosomal Sorting Complexes Required for Transport/metabolism, Epithelial Sodium Channels/metabolism, Gene Expression Regulation, Immediate-Early Proteins/deficiency, Immediate-Early Proteins/genetics, Kidney Tubules/metabolism, Male, Mice, Mice, Knockout, Minor Histocompatibility Antigens/metabolism, Potassium/urine, Potassium Channels, Inwardly Rectifying/antagonists & inhibitors, Potassium Channels, Inwardly Rectifying/immunology, Potassium, Dietary/pharmacology, Protein-Serine-Threonine Kinases/deficiency, Protein-Serine-Threonine Kinases/genetics, Protein-Serine-Threonine Kinases/metabolism, Ubiquitin-Protein Ligases/metabolism, aldosterone, epithelial Na+ channel, epithelial transport, neural precursor cell expressed developmentally downregulated protein 4-2, phosphorylation, potassium, serum- and glucocorticoid-induced kinase 1, ubiquitylation, with no lysine kinase 1
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