Regulation of epithelial Na+ channels by aldosterone: role of Sgk1.
1. The epithelial sodium channel (ENaC) is tightly regulated by hormonal and humoral factors, including cytosolic ion concentration and glucocorticoid and mineralocorticoid hormones. Many of these regulators of ENaC control its activity by regulating its surface expression via neural precursor cell-expressed developmentally downregulated (gene 4) protein (Nedd4-2). 2. During the early phase of aldosterone action, Nedd4-2-dependent downregulation of ENaC is inhibited by the serum- and glucocorticoid-induced kinase 1 (Sgk1). 3. Sgk1 phosphorylates Nedd4-2. Subsequently, phosphorylated Nedd4-2 binds to the 14-3-3 protein and, hence, reduces binding of Nedd4-2 to ENaC. 4. Nedd4-2 is also phosphorylated by protein kinase B (Akt1). Both Sgk1 and Akt1 are part of the insulin signalling pathway that increases transepithelial Na(+) absorption by inhibiting Nedd4-2 and activating ENaC.
Lee
Il-Ha
IH
School of Medical Science, Faculty of Medicine, University of Sydney, Sydney, New South Wales, Australia.
Campbell
Craig R
CR
Cook
David I
DI
Dinudom
Anuwat
A
D048948:14-3-3 Proteins / Q000378:metabolism; D000450:Aldosterone / Q000378:metabolism*; D056827:Endosomal Sorting Complexes Required for Transport; D053503:Epithelial Sodium Channels / Q000378:metabolism*; D006801:Humans; D017874:Immediate-Early Proteins / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism; D015640:Ion Channel Gating; D008297:Male; D000075702:Nedd4 Ubiquitin Protein Ligases; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction; D012964:Sodium / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D000099184:Serum-Glucocorticoid Regulated Kinases
D048948:14-3-3 Proteins; D000450:Aldosterone; D056827:Endosomal Sorting Complexes Required for Transport; D053503:Epithelial Sodium Channels; D017874:Immediate-Early Proteins; D007328:Insulin; D000075702:Nedd4 Ubiquitin Protein Ligases; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D012964:Sodium; D044767:Ubiquitin-Protein Ligases; D000099184:Serum-Glucocorticoid Regulated Kinases; C000618483:Nedd4 protein, human; C000618485:Nedd4L protein, human