Integrated compensatory network is activated in the absence of NCC phosphorylation
P. Richard Grimm, … , James B. Wade, Paul A. Welling
P. Richard Grimm, … , James B. Wade, Paul A. Welling
Published April 20, 2015
Citation Information: J Clin Invest. 2015;125(5):2136-2150. https://doi.org/10.1172/JCI78558.
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Research Article Nephrology

Integrated compensatory network is activated in the absence of NCC phosphorylation

Abstract

Thiazide diuretics are used to treat hypertension; however, compensatory processes in the kidney can limit antihypertensive responses to this class of drugs. Here, we evaluated compensatory pathways in SPAK kinase–deficient mice, which are unable to activate the thiazide-sensitive sodium chloride cotransporter NCC (encoded by Slc12a3). Global transcriptional profiling, combined with biochemical, cell biological, and physiological phenotyping, identified the gene expression signature of the response and revealed how it establishes an adaptive physiology. Salt reabsorption pathways were created by the coordinate induction of a multigene transport system, involving solute carriers (encoded by Slc26a4, Slc4a8, and Slc4a9), carbonic anhydrase isoforms, and V-type H+-ATPase subunits in pendrin-positive intercalated cells (PP-ICs) and ENaC subunits in principal cells (PCs). A distal nephron remodeling process and induction of jagged 1/NOTCH signaling, which expands the cortical connecting tubule with PCs and replaces acid-secreting α-ICs with PP-ICs, were partly responsible for the compensation. Salt reabsorption was also activated by induction of an α-ketoglutarate (α-KG) paracrine signaling system. Coordinate regulation of a multigene α-KG synthesis and transport pathway resulted in α-KG secretion into pro-urine, as the α-KG–activated GPCR (Oxgr1) increased on the PP-IC apical surface, allowing paracrine delivery of α-KG to stimulate salt transport. Identification of the integrated compensatory NaCl reabsorption mechanisms provides insight into thiazide diuretic efficacy.

Authors

P. Richard Grimm, Yoskaly Lazo-Fernandez, Eric Delpire, Susan M. Wall, Susan G. Dorsey, Edward J. Weinman, Richard Coleman, James B. Wade, Paul A. Welling

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Figure 6

NOTCH signaling is induced in SPAK KO mice.

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NOTCH signaling is induced in SPAK KO mice. (A) qPCR of NOTCH signaling ...
(A) qPCR of NOTCH signaling molecules identified in the SPAK KO profile as upregulated (Jag1, Hes1, Irx1, Irx2) or downregulated genes (Jag2). Data represent the mean ± SEM. n = 6 animals. *P < 0.05 by 2-tailed t test for WT versus KO. (B) Western blot analysis of the NOTCH effector molecule HES1 and the NOTCH ligand JAG1 and (C) quantitative summary of relative HES and JAG1 protein abundance. Data represent the mean ± SEM. n = 4 animals. *P < 0.05 by 2-tailed t test for WT versus KO. (D) Immunolocalization of HES1 in WT and SPAK KO CNT (HES1, red; AQP2-labeled PCs, green; CNTs identified as calbindin+ tubules, not shown. Scale bars: 10 μm. Note: HES1 was almost exclusively expressed in PC nuclei. (E) Quantitative summary of HES1+ PCs and PP-ICs in the CNT (percentage of total subtype). Data represent the mean ± SEM. n = 4 animals per genotype. *P < 0.05 by 2-tailed t test for WT versus KO.