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Pflugers Arch ; 467(9): 1871-80, 2015 Sep.
Article in English | MEDLINE | ID: mdl-25319519

ABSTRACT

Checkpoint kinase 2 (Chk2) is the main effector kinase of ataxia telangiectasia mutated (ATM) and responsible for cell cycle regulation. ATM signaling has been shown to upregulate interferon-regulating factor-1 (IRF-1), a transcription factor also expressed in the kidney. Calcitriol (1,25 (OH)2D3), a major regulator of mineral metabolism, is generated by 25-hydroxyvitamin D 1α-hydroxylase in the kidney. Since 25-hydroxyvitamin D 1α-hydroxylase expression is enhanced by IRF-1, the present study explored the role of Chk2 for calcitriol formation and mineral metabolism. Chk2-deficient mice (chk2 (-/-)) were compared to wild-type mice (chk2 (+/+)). Transcript levels of renal 25-hydroxyvitamin D 1α-hydroxylase, Chk2, and IRF-1 were determined by RT-PCR; Klotho expression by Western blotting; bone density by µCT analysis; serum or plasma 1,25 (OH)2D3, PTH, and C-terminal FGF23 concentrations by immunoassays; and serum, fecal, and urinary calcium and phosphate concentrations by photometry. The renal expression of IRF-1 and 25-hydroxyvitamin D 1α-hydroxylase as well as serum 1,25 (OH)2D3 and FGF23 levels were significantly lower in chk2 (-/-) mice compared to chk2 (+/+) mice. Plasma PTH was not different between the genotypes. Renal calcium and phosphate excretion were significantly higher in chk2 (-/-) mice than in chk2 (+/+) mice despite hypophosphatemia and normocalcemia. Bone density was not different between the genotypes. We conclude that Chk2 regulates renal 25-hydroxyvitamin D 1α-hydroxylase expression thereby impacting on calcium and phosphate metabolism.


Subject(s)
25-Hydroxyvitamin D3 1-alpha-Hydroxylase/metabolism , Bone Density/physiology , Calcitriol/biosynthesis , Checkpoint Kinase 2/metabolism , Kidney/metabolism , Animals , Blotting, Western , Calcium/metabolism , Enzyme-Linked Immunosorbent Assay , Fibroblast Growth Factor-23 , Gene Expression Regulation/physiology , Glucuronidase/metabolism , HEK293 Cells , Humans , Klotho Proteins , Mice , Mice, Knockout , Phosphates/metabolism , Real-Time Polymerase Chain Reaction , X-Ray Microtomography
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