Dietary potassium stimulates Ppp1Ca-Ppp1r1a dephosphorylation of kidney NaCl cotransporter and reduces blood pressure
P. Richard Grimm, Anamaria Tatomir, Lena L. Rosenbaek, Bo Young Kim, Dimin Li, Eric J. Delpire, Robert A. Fenton, Paul A. Welling
P. Richard Grimm, Anamaria Tatomir, Lena L. Rosenbaek, Bo Young Kim, Dimin Li, Eric J. Delpire, Robert A. Fenton, Paul A. Welling
View: Text | PDF
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

×

Figure 6

Potassium regulates PP1A interaction with and dephosphorylation of NCC.

Options: View larger image (or click on image) Download as PowerPoint
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.