Does the early aldosterone-induced SGK1 play a role in early Kaliuresis?

Autor: Al-Qusairi L; Division of Nephrology, Johns Hopkins University School of Medicine, Baltimore, USA.; Department of Biomedical Sciences, University of Lausanne, Lausanne, Switzerland., Basquin D; Department of Physiology, University of Maryland, Baltimore, USA.; Department of Biomedical Sciences, University of Lausanne, Lausanne, Switzerland., Stifanelli M; Department of Biomedical Sciences, University of Lausanne, Lausanne, Switzerland., Welling PA; Division of Nephrology, Johns Hopkins University School of Medicine, Baltimore, USA., Staub O; Department of Biomedical Sciences, University of Lausanne, Lausanne, Switzerland.
Jazyk: angličtina
Zdroj: Physiological reports [Physiol Rep] 2022 Feb; Vol. 10 (4), pp. e15188.
DOI: 10.14814/phy2.15188
Abstrakt: Urinary K + potassium excretion rapidly increases after a potassium-rich meal. The early aldosterone-induced sgk1 gene (encoding serum and glucocorticoid-induced kinase 1), activates potassium clearance, but the role of this kinase in the early activation of K + secretion has not been clearly defined. Here, we challenged inducible renal-tubule-specific Sgk1 Pax8 / LC1  knockout mice with an acute high-potassium load (HK:5%K + ) and compared the physiological and molecular responses to control mice. We observe that urinary excretion after a K + load over the first 3 h is not dependent on SGK1 but is coincident with the rapid dephosphorylation of the Na + ,Cl - -cotransporter (NCC) to increase distal salt delivery. Molecular analyses indicate that whereas SGK1-mediated phosphorylation of the ubiquitin-protein ligase NEDD4-2 begins to increase by 3h, SGK1-dependent proteolytic activation of ENaC only becomes detectable after 6 h of HK intake. Consistent with SGK1-dependent ENaC activation via inhibition of NEDD4-2-mediated ubiquitylation, Sgk1 Pax8 / LC1  mice are unable to efficiently inhibit NEDD4-2 or increase ENaC cleavage after 6 h of HK. Nevertheless, no defect in acute K + balance was detected in the mutant mice after 6 h of HK. Moreover, we found that Sgk1 Pax8 / LC1  mice reduce NCC phosphorylation and NCC-mediated salt absorption to a greater extent than control mice after a K + load, promoting increased amiloride-sensitive Na + -reabsorption via ENaC to maintain adequate kaliuresis. Together, these data indicate that: (a) during the early 3 h of HK intake, K + excretion is SGK1-independent even under an extreme K + challenge, (b) shortly after, SGK1 inhibits NEDD4-2 and activates ENaC to stimulate K + -secretion, (c) SGK1-dependent phosphorylation of NCC occurs, acting more likely as a brake pedal to prevent excessive K + loss.
(© 2022 The Authors. Physiological Reports published by Wiley Periodicals LLC on behalf of The Physiological Society and the American Physiological Society.)
Databáze: MEDLINE
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