A parathyroid hormone/salt-inducible kinase signaling axis controls renal vitamin D activation and organismal calcium homeostasis
Sung-Hee Yoon, … , Michael Mannstadt, Marc N. Wein
Sung-Hee Yoon, … , Michael Mannstadt, Marc N. Wein
Published March 2, 2023
Citation Information: J Clin Invest. 2023;133(9):e163627. https://doi.org/10.1172/JCI163627.
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Research Article Bone biology Nephrology

A parathyroid hormone/salt-inducible kinase signaling axis controls renal vitamin D activation and organismal calcium homeostasis

Abstract

The renal actions of parathyroid hormone (PTH) promote 1,25-vitamin D generation; however, the signaling mechanisms that control PTH-dependent vitamin D activation remain unknown. Here, we demonstrated that salt-inducible kinases (SIKs) orchestrated renal 1,25-vitamin D production downstream of PTH signaling. PTH inhibited SIK cellular activity by cAMP-dependent PKA phosphorylation. Whole-tissue and single-cell transcriptomics demonstrated that both PTH and pharmacologic SIK inhibitors regulated a vitamin D gene module in the proximal tubule. SIK inhibitors increased 1,25-vitamin D production and renal Cyp27b1 mRNA expression in mice and in human embryonic stem cell–derived kidney organoids. Global- and kidney-specific Sik2/Sik3 mutant mice showed Cyp27b1 upregulation, elevated serum 1,25-vitamin D, and PTH-independent hypercalcemia. The SIK substrate CRTC2 showed PTH and SIK inhibitor–inducible binding to key Cyp27b1 regulatory enhancers in the kidney, which were also required for SIK inhibitors to increase Cyp27b1 in vivo. Finally, in a podocyte injury model of chronic kidney disease–mineral bone disorder (CKD-MBD), SIK inhibitor treatment stimulated renal Cyp27b1 expression and 1,25-vitamin D production. Together, these results demonstrated a PTH/SIK/CRTC signaling axis in the kidney that controls Cyp27b1 expression and 1,25-vitamin D synthesis. These findings indicate that SIK inhibitors might be helpful for stimulation of 1,25-vitamin D production in CKD-MBD.

Authors

Sung-Hee Yoon, Mark B. Meyer, Carlos Arevalo, Murat Tekguc, Chengcheng Zhang, Jialiang S. Wang, Christian D. Castro Andrade, Katelyn Strauss, Tadatoshi Sato, Nancy A. Benkusky, Seong Min Lee, Rebecca Berdeaux, Marc Foretz, Thomas B. Sundberg, Ramnik J. Xavier, Charles H. Adelmann, Daniel J. Brooks, Anthony Anselmo, Ruslan I. Sadreyev, Ivy A. Rosales, David E. Fisher, Navin Gupta, Ryuji Morizane, Anna Greka, J. Wesley Pike, Michael Mannstadt, Marc N. Wein

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Figure 5

Renal pseudohyperparathyroidism upon kidney-specific SIK deletion.

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Renal pseudohyperparathyroidism upon kidney-specific SIK deletion. (A an...
(A and B) Six2-Cre and Six2-Cre;Sik1fl/+;Sik2fl/fl;Sik3fl/fl mice were crossed with Ai14 tdTomato reporter mice, and tdTomato-positive cells were sorted to assess gene deletion efficiency more accurately without other cell types, including blood and immune cells. Single-cell suspensions from kidneys were generated, and tdTomato-positive and -negative cells were sorted as shown. (C) tdTomato-positive cells showed approximately 98% Sik2 and Sik3 gene deletion efficiency in Six2-Cre;Sik1fl/+;Sik2fl/fl;Sik3fl/fl mice, and tdTomato-negative cells did not show any change in Sik mRNA expression levels. (D) Body weights and (E) serum blood urea nitrogen (BUN) are shown, (F) along with kidney histology (H&E stain) images from the indicated animals. No overt histologic differences were noted in mutants. Scale bars: 100 μm. (G) 1,25-vitamin D measurement in control and SIK mutant mice. (H) Renal Cyp27b1 expression by RT-qPCR. (I) Serum calcium, phosphorus, and PTH measurements are shown. (J and K) Renal RNA was isolated to measure 1,25-vitamin D–induced genes (Cyp24a1, TRPV5, and Calbindin D28k [Calb1]) by RT-qPCR. (L) Urine calcium and phosphorus are normalized to creatinine. (M) Bulk RNA-Seq from whole-kidney RNA from control and mutant mice showed increased Cyp27b1. (N) GO terms from dysregulated genes in SIK mutant mice. Data are shown as the mean ± SD, and each dot represents an individual mouse. Student’s t test was performed for statistical analysis, and P values are shown.