Dietary potassium stimulates Ppp1Ca-Ppp1r1a dephosphorylation of kidney NaCl cotransporter and reduces blood pressure
P. Richard Grimm, … , Robert A. Fenton, Paul A. Welling
P. Richard Grimm, … , Robert A. Fenton, Paul A. Welling
Published September 7, 2023
Citation Information: J Clin Invest. 2023;133(21):e158498. https://doi.org/10.1172/JCI158498.
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Research Article Nephrology

Dietary potassium stimulates Ppp1Ca-Ppp1r1a dephosphorylation of kidney NaCl cotransporter and reduces blood pressure

Abstract

Consumption of low dietary potassium, common with ultraprocessed foods, activates the thiazide-sensitive sodium chloride cotransporter (NCC) via the with no (K) lysine kinase/STE20/SPS1-related proline-alanine–rich protein kinase (WNK/SPAK) pathway to induce salt retention and elevate blood pressure (BP). However, it remains unclear how high-potassium “DASH-like” diets (dietary approaches to stop hypertension) inactivate the cotransporter and whether this decreases BP. A transcriptomics screen identified Ppp1Ca, encoding PP1A, as a potassium-upregulated gene, and its negative regulator Ppp1r1a, as a potassium-suppressed gene in the kidney. PP1A directly binds to and dephosphorylates NCC when extracellular potassium is elevated. Using mice genetically engineered to constitutively activate the NCC-regulatory kinase SPAK and thereby eliminate the effects of the WNK/SPAK kinase cascade, we confirmed that PP1A dephosphorylated NCC directly in a potassium-regulated manner. Prior adaptation to a high-potassium diet was required to maximally dephosphorylate NCC and lower BP in constitutively active SPAK mice, and this was associated with potassium-dependent suppression of Ppp1r1a and dephosphorylation of its cognate protein, inhibitory subunit 1 (I1). In conclusion, potassium-dependent activation of PP1A and inhibition of I1 drove NCC dephosphorylation, providing a mechanism to explain how high dietary K+ lowers BP. Shifting signaling of PP1A in favor of activation of WNK/SPAK may provide an improved therapeutic approach for treating salt-sensitive hypertension.

Authors

P. Richard Grimm, Anamaria Tatomir, Lena L. Rosenbaek, Bo Young Kim, Dimin Li, Eric J. Delpire, Robert A. Fenton, Paul A. Welling

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Figure 6

Potassium regulates PP1A interaction with and dephosphorylation of NCC.

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Potassium regulates PP1A interaction with and dephosphorylation of NCC. ...
(A) In vitro protein phosphatase (PP) assay. Representative immunoblots of p-NCC and t-NCC are shown for assays of NCC with PP1A (lanes 1 and 2), PP2A (lanes 5 and 6), and calcineurin A (CALNA) or vehicle (lanes 3, 7, and 11). For these studies, NCC was isolated by IP with an anti-NCC antibody (lanes 1, 2, 3, 5, 6, and 7) and compared with the negative control IgG (lanes 4, 8, and 12). (B) PP1A preferentially interacted with NCC in glutathione-agarose affinity chromatography assays with the GST fusion protein of the NCC terminus GST-NCC-(N), but not the negative control GST alone. Shown are representative immunoblot binding assays with recombinant PP1A, PP2A, and CALNA. Input protein phosphatase (lane 1) is shown relative to GST-bound (lane 2) or GST-NCC-(N) (lane 3). (C) A greater amount of PP1A co-immunoprecipitated with NCC when the extracellular K+ concentration was high. Representative immunoblots show NCC, PP1A, and p-NCC (T58) in anti-FLAG immunoprecipitated samples relative to input from FLAG-tagged NCC-expressing MDCKI cells incubated with 3.5 mM (control), 0.5 mM (low), or 8 mM (high) K+ buffers. Low-chloride buffer was used as a positive control to elevate p-NCC (T58) levels. Graphs show semiquantitative assessment of NCC, PP1, and p-NCC (T58) in NCC immunoprecipitated samples (bottom, right) relative to input. Data are from 3 individual experiments with 3 replicates for each condition (n = 9). *P < 0.05, relative to the low-K+ condition, by 1-way ANOVA followed by multiple-comparison test. Data are presented as the mean ± SEM. CALNA, calcineurin.