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Regulation of ENaC by aldosterone and potassium
Author(s) -
Leite Dellova Deise C. A.,
Saha Bidisha,
Takagi Enzo,
Shabbir Waheed,
Pearce David
Publication year - 2020
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2020.34.s1.09387
Subject(s) - epithelial sodium channel , sgk1 , aldosterone , amiloride , medicine , endocrinology , chemistry , mineralocorticoid , phosphorylation , mineralocorticoid receptor , sodium , biology , biochemistry , organic chemistry
In the cortical collecting duct (CCD), aldosterone regulates the transcription of serum and glucocorticoid‐regulated kinase 1 (SGK1) and stimulates the activity of epithelial sodium channel (ENaC). In addition, an aldosterone‐independent mechanism contributes to regulation of ENaC. We have shown that K+ itself acts through the master kinase mTOR within its type 2 complex (mTORC2) to activate SGK1, which stimulates ENaC to enhance K+ excretion in principal cells. However, the potential interconnections of these mechanisms have not been determined. Here, we have explored the aldosterone effect in association with K+ effect on ENaC activity regulation in the distal nephron. mpkCCD cells were grown on type I collagen–coated filters and subjected to aldosterone treatment and changes in extracellular [K+]. Amiloride‐sensitive short‐circuit current (I SC ), which reflects ENaC activity, was measured by voltohmmeter (Millipore Millicell ERS). Following I SC measurements, cells were harvested and processed for immunoblot analysis. Exposure of mpkCCD cells to 1 μM aldosterone for 3 h increased I SC about 1.9‐fold compared to serum and hormone restricted cells. Elevation of basolateral [K+] to 3, 5 and 7 mM, after aldosterone treatment, promoted an additional increase in I SC of 1.5, 1.6 and 1.7‐fold, respectively. SGK1 HM phosphorylation increased proportionately to the increase in ENaC activity. The effect of K+ on ENaC activity and SGK1 HM phosphorylation is rapid and mediated by basolateral Kir 4.1 K+ channel activity. Overall, our data suggest that the effects of aldosterone and elevation of basolateral [K+] on ENaC activity and SGK1 phosphorylation were additive. Therefore, it is possible that basolateral [K+] acts in concert with aldosterone to regulate ENaC activity in CCD cells. However, in this cell culture model the effects are not synergistic suggesting that they do not proceed through convergent signaling pathways. Support or Funding Information This work was supported by NIH R01‐DK56695, Manning Foundation and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) – Finance Code 001.