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
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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 2

Potassium-dependent NCC dephosphorylation in isolated DCT overrides constitutively active SPAK.

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Potassium-dependent NCC dephosphorylation in isolated DCT overrides cons...
(A) Typical confocal image of an isolated DCT labeled with p-NCC (T58) (red) and anti-parvalbumin antibodies (green). Scale bar: 20 μm. (B) Abundance of p-NCC (T58) in WT mice over a titration of extracellular potassium concentrations (K+o), 20 minutes after potassium was elevated from a preconditioning medium containing 2.0 mM K+o. Shown are p-NCC pixel intensities at each K+o relative to the maximum phosphorylation at 2.0 mM potassium. n >6 tubules per condition. (C) Acute NCC (T58) dephosphorylation, 20 minutes after K+o was increased from 2 mM to 6 mM in control mice (WT/WT SPAK), heterozygous CA-SPAK mice (CA/–), and homozygous CA-SPAK mice (CA/CA) fed a control potassium (1%) or high-potassium (5%) diet for 4 days. Each dot represents a separate mouse. *P < 0.05, by 1-way ANOVA with Tukey’s post hoc test. Data are the mean ± SEM. n > 4 per group.