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 2

Single-cell RNA-Seq demonstrates cell type–specific renal PTH effects and proximal tubule segment 1–specific Cyp27b1 induction.

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Single-cell RNA-Seq demonstrates cell type–specific renal PTH effects an...
(A) 8-week-old male C57B6 mice were treated with a single dose of vehicle, PTH (300 μg/kg), or SK-124 (40 mg/kg) and sacrificed 90 minutes or 2.5–3 hours later for PTH or SK-124 treatment, respectively. Single-cell suspensions from kidneys were made for scRNA-Seq. UMAP projection demonstrating expected populations of kidney cells in aggregate data from all 12 samples. (B) Heatmap (each line is an individual gene) showing overall patterns of cluster-specific differential gene expression analysis. Distinct groups of genes are regulated by PTH and SIK inhibitors across different renal cell types. (C) Volcano plot showing differential gene expression analysis in PCT-S1 cells in response to PTH (versus vehicle). (D) Dot plot showing that segment 1 (S1) of proximal convoluted tubule (PCT) is where PTH-induced Cyp27b1 change is the most prominent. The color of the dots shows average gene expression level, while the size of the dots indicates the percentage of cells expressing the gene of interest in each cluster. (E) Cyp27b1 in situ hybridization (brown, RNAscope) in paraffin-embedded kidney sections. Periodic acid–Schiff stain was performed to mark tubular morphology. Scale bars: 250 μm.