Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI 53706, USA.
Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON K7L3N6, Canada.
Endocrinology. 2024 Sep 26;165(11). doi: 10.1210/endocr/bqae134.
CYP24A1 is a multifunctional, P450 mitochondrial enzyme that catabolizes the vitamin D hormone (calcitriol, 1,25(OH)2D3), its precursor (calcifediol, 25(OH)D3), and numerous vitamin D metabolites. In the kidney, Cyp24a1 is induced by 1,25(OH)2D3 and fibroblast growth factor 23 (FGF23) and potently suppressed by PTH to control the circulating levels of 1,25(OH)2D3. Cyp24a1 is controlled by a pair of promoter proximal (PRO) vitamin D response elements (VDREs) that are aided by distal, downstream (DS) enhancers. The downstream 1 region of Cyp24a1 (DS1) enhancer is kidney-specific and responsible for PTH and FGF23 actions, and the downstream 2 region of Cyp24a1 enhancer responds to 1,25(OH)2D3 in all tissues. Despite this knowledge, in vivo contributions of the PRO VDREs to basal expression, FGF23 activation, and PTH suppression of Cyp24a1 remain unknown. In this study, we selectively mutated the PRO VDREs in the mouse to address these questions. We found mutation of the VDREs leads to a dramatic loss of VDR occupancy, a reduction of 1,25(OH)D3-induced kidney Cyp24a1 expression, and near elimination of intestinal Cyp24a1 induction. FGF23 induction of Cyp24a1 was reduced but not eliminated and still showed a synergistic increase with 1,25(OH)2D3. PTH suppression of Cyp24a1 was unchanged, despite minor reductions in total for phosphorylated cAMP-response element binding protein occupancy. Finally, VDR recruitment was dramatically reduced across the DS enhancers in the Cyp24a1 locus. Taken together, our data suggest a cooperative relationship between the DS and PRO enhancers in the regulation of Cyp24a1 by 1,25(OH)2D3 and FGF23 and points to the DS1 region as a crucial basal switch for Cyp24a1 activity that further defines the interconnected genomic control in vitamin D catabolism.
CYP24A1 是一种多功能的 P450 线粒体酶，可代谢维生素 D 激素（骨化三醇，1,25(OH)2D3）、其前体（钙二醇，25(OH)D3）和许多维生素 D 代谢物。在肾脏中，Cyp24a1 由 1,25(OH)2D3 和成纤维细胞生长因子 23（FGF23）诱导，并被甲状旁腺素强烈抑制，以控制 1,25(OH)2D3 的循环水平。Cyp24a1 受一对位于启动子近端（PRO）的维生素 D 反应元件（VDREs）控制，这些元件由远端下游（DS）增强子辅助。Cyp24a1 的下游 1 区（DS1）增强子是肾脏特异性的，负责甲状旁腺素和 FGF23 的作用，而 Cyp24a1 增强子的下游 2 区则对所有组织中的 1,25(OH)2D3 作出反应。尽管有这些知识，但 PRO VDREs 在 Cyp24a1 的基础表达、FGF23 激活和甲状旁腺素抑制中的体内贡献仍然未知。在这项研究中，我们选择性地突变了小鼠中的 PRO VDREs 来解决这些问题。我们发现，VDRE 突变导致 VDR 占据的显著丧失，1,25(OH)D3 诱导的肾脏 Cyp24a1 表达减少，以及肠道 Cyp24a1 诱导的几乎消除。FGF23 诱导的 Cyp24a1 减少但未消除，并且仍然与 1,25(OH)2D3 表现出协同增加。尽管磷酸化 cAMP 反应元件结合蛋白占据略有减少，但 Cyp24a1 的甲状旁腺素抑制作用保持不变。最后，在 Cyp24a1 基因座中，DS 增强子上的 VDR 募集显著减少。总的来说，我们的数据表明，在 1,25(OH)2D3 和 FGF23 对 Cyp24a1 的调节中，DS 和 PRO 增强子之间存在合作关系，并指出 DS1 区域是 Cyp24a1 活性的关键基础开关，进一步定义了维生素 D 代谢中的相互关联的基因组控制。
