Rapid Aldosterone-Mediated Signaling in the DCT Increases Activity of the Thiazide-Sensitive NaCl Cotransporter

Significance Statement The NaCl cotransporter NCC in the kidney distal convoluted tubule (DCT) regulates urinary NaCl excretion and BP. The long-term effects of the mineralocorticoid aldosterone on modulating NaCl reabsorption via NCC are well established, and their importance illustrated by the effects of NCC-targeting diuretics and the salt-wasting observed in Gitelman syndrome. In this study the authors demonstrate that aldosterone also has rapid effects on the DCT, partly via the membrane receptors EGFR and GPR30. Signaling from these receptors affect NCC activity so that when aldosterone is released in response to hypovolemia, aldosterone rapidly increases NaCl reabsorption to help restore blood volume. Background The NaCl cotransporter NCC in the kidney distal convoluted tubule (DCT) regulates urinary NaCl excretion and BP. Aldosterone increases NaCl reabsorption via NCC over the long-term by altering gene expression. But the acute effects of aldosterone in the DCT are less well understood. Methods Proteomics, bioinformatics, and cell biology approaches were combined with animal models and gene-targeted mice. Results Aldosterone significantly increases NCC activity within minutes in vivo or ex vivo . These effects were independent of transcription and translation, but were absent in the presence of high potassium. In vitro , aldosterone rapidly increased intracellular cAMP and inositol phosphate accumulation, and altered phosphorylation of various kinases/kinase substrates within the MAPK/ERK, PI3K/AKT, and cAMP/PKA pathways. Inhibiting GPR30, a membrane-associated receptor, limited aldosterone’s effects on NCC activity ex vivo , and NCC phosphorylation was reduced in GPR30 knockout mice. Phosphoproteomics, network analysis, and in vitro studies determined that aldosterone activates EGFR-dependent signaling. The EGFR immunolocalized to the DCT and EGFR tyrosine kinase inhibition decreased NCC activity ex vivo and in vivo . Conclusions Aldosterone acutely activates NCC to modulate renal NaCl excretion.