Impaired stimulation of 25-hydroxyvitamin D-24-hydroxylase in fibroblasts from a patient with vitamin D-dependent rickets, type II. A form of receptor-positive resistance to 1,25-dihydroxyvitamin D3.

Griffin, Jim E.; Zerwekh, Joseph E.

doi:10.1172/jci111074

Cited by 82 publications

(45 citation statements)

References 39 publications

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“…The individual described by Zerwekh et al (18) presented with a complex phenotype that was postulated to be due to mutations in both the vitamin D 25-hydroxylase and the VDR. We sequenced the exons of the CYP2R1 and CYP27A1 genes from this individual and found no mutations in either gene; however, biochemical and molecular analyses confirmed the presence of mutations in the VDR gene (41,42).…”

Section: -40)mentioning

confidence: 85%

Genetic evidence that the human CYP2R1 enzyme is a key vitamin D 25-hydroxylase

Cheng

Levine

Bell

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

654

399

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The synthesis of bioactive vitamin D requires hydroxylation at the 1␣ and 25 positions by cytochrome P450 enzymes in the kidney and liver, respectively. The mitochondrial enzyme CYP27B1 catalyzes 1␣-hydroxylation in the kidney but the identity of the hepatic 25-hydroxylase has remained unclear for >30 years. We previously identified the microsomal CYP2R1 protein as a potential candidate for the liver vitamin D 25-hydroxylase based on the enzyme's biochemical properties, conservation, and expression pattern. Here, we report a molecular analysis of a patient with low circulating levels of 25-hydroxyvitamin D and classic symptoms of vitamin D deficiency. This individual was found to be homozygous for a transition mutation in exon 2 of the CYP2R1 gene on chromosome 11p15.2. The inherited mutation caused the substitution of a proline for an evolutionarily conserved leucine at amino acid 99 in the CYP2R1 protein and eliminated vitamin D 25-hydroxylase enzyme activity. These data identify CYP2R1 as a biologically relevant vitamin D 25-hydroxylase and reveal the molecular basis of a human genetic disease, selective 25-hydroxyvitamin D deficiency.T he metabolic pathway leading to the synthesis of active vitamin D involves three reactions that occur in different tissues (1). The pathway is initiated in the skin with the UV light-mediated cleavage of 5,7,-cholestadien-3␤-ol to produce the secosteroid (3␤,5Z,7E)-9,10-secocholesta-5,7,10(19)-trien-3-ol (vitamin D 3 ). The second step occurs in the liver and is catalyzed by a cytochrome P450 (CYP) enzyme that hydroxylates carbon 25, producing the intermediate 25-hydroxyvitamin D 3 , which is the major circulatory form of the vitamin. The third and final step takes place in the kidney and involves 1␣-hydroxylation by another CYP, producing 1␣,25-dihydroxyvitamin D 3 . This product is a potent ligand of the vitamin D receptor (VDR) and mediates most of the physiological actions of the vitamin (1).Although the chemical and enzymatic steps in the vitamin D 3 biosynthetic pathway have been known for 30 years (1), the enzyme catalyzing the 25-hydroxylation step in the liver has never been identified. At least six CYPs can catalyze this reaction in vitro, including CYP2C11, CYP2D25, CYP3A4, CYP2J1, CYP27A1, and CYP2R1 (2-4). Of these CYPs, the two most viable candidates for the vitamin D 25-hydroxylase are CYP27A1 and CYP2R1 (2). Both enzymes are expressed in the liver and are conserved among species known to have an active vitamin D signaling pathway. However, mutations in the human and mouse genes encoding the mitochondrial CYP27A1 protein impair bile acid synthesis, but have no consequences for vitamin D metabolism (5-9). It is thus not clear whether the two vitamin D 3 25-hydroxylases represent an example of biological redundancy in an important biosynthetic pathway or whether CYP2R1 alone or some unidentified enzyme fulfills this essential role.In contrast to the uncertainty surrounding vitamin D 3 25-hydroxylase, the renal enzyme responsible for 1␣-hydroxylation of the vitamin...

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Section: -40)mentioning

confidence: 85%

Genetic evidence that the human CYP2R1 enzyme is a key vitamin D 25-hydroxylase

Cheng

Levine

Bell

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

654

399

View full text Add to dashboard Cite

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“…Hereditary 1,25-dihydroxyvitamin D resistant rickets (HVDRR), also known as vitamin D-dependent rickets, type II, is an autosomal recessive disorder that has been shown to be caused by mutations in the VDR (1,2). The disease is characterized by early onset rickets, hypocalcemia, secondary hyperparathyroidism, elevated 1,25(OH) 2 D 3 levels, and resistance to 1,25(OH) 2 (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18). In the receptor positive cases the VDR was shown to exhibit a decreased binding affinity for DNA.…”

Section: Introductionmentioning

confidence: 99%

Hereditary vitamin D resistant rickets caused by a novel mutation in the vitamin D receptor that results in decreased affinity for hormone and cellular hyporesponsiveness.

Malloy

Eccleshall²,

Gross³

et al. 1997

J. Clin. Invest.

126

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“…A frequently associated and unexplained finding in HVDRR is total scalp and body alopecia (3), a feature said to be present in the more severely affected patients (4). Studies from a number of laboratories have revealed that the cause of the target organ resistance in HVDRR is a defect in the intracellular vitamin D receptor (VDR) (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16).…”

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confidence: 99%

“…It was soon demonstrated that defects in the VDR were the likely cause of the HVDRR syndrome (5) and that different families exhibited different defects (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)). An additional useful finding was the demonstration that 1,25(OH)2D3 could induce the enzyme 25-hydroxyvitamin D-24-hydroxylase (24-hydroxylase) in multiple target tissues by a receptor-mediated process (27).…”

mentioning

confidence: 99%

“…It was subsequently found that 24-hydroxylase activity could be induced in cultured skin fibroblasts so that induction of 24-hydroxylase activity could be employed as a bioassay ofthe ability of cultured fibroblasts to respond to 1,25(OH)2D3 (5). Using this bioresponse marker, cells from a variety of patients with HVDRR were shown, in vitro, to be resistant to the action of 1,25(OH)2D3 (5,8,9,11,12,15).…”

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confidence: 99%

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The molecular basis of hereditary 1,25-dihydroxyvitamin D3 resistant rickets in seven related families.

Malloy¹,

Hochberg²,

Tiosano³

et al. 1990

J. Clin. Invest.

184

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Introduction Hereditary 1,25-dihydroxyvitamin D3 I1,25(OH)2D31 resistant rickets (HVDRR) is an autosomal recessive disease caused by target organ resistance to the action of 1,25(OH)1D3, the active form of the hormone. The defect in target cells is heterogenous and commonly appears to be a mutation in the gene encoding the vitamin D receptor (VDR). We have studied cultured skin fibroblasts and Epstein-Barr virus transformed lymphoblasts of seven family branches of an extended kindred having eight children affected with HVDRR. We have previously shown that cells from three affected children in this group contain an "ochre" nonsense mutation coding for a premature stop codon in exon 7 within the steroid-binding domain of the VDR gene.In The human VDR is a 50-kD protein and the cDNA has recently been cloned and sequenced (17) and found to belong to the steroid-thyroid-retinoic acid receptor superfamily of genes (18). Like the other members of this receptor family, VDR is comprised of at least two functional domains, a steroid hormone-binding domain and a DNA-binding domain (17-23). The steroid-binding domain stretches from amino acid 182 to the COOH-terminus at amino acid 427 and provides the molecule with high affinity, steroid-specific recognition of the 1,25(OH)2D3 metabolite. The DNA-binding domain, comprising amino acids 24-89, is a cysteine-rich region that contains two putative "zinc-fingers" (17). 1,25(OH)2D3 binding to the steroid-binding domain of the receptor "activates" the VDR to a form with high affinity for DNA. The DNA-binding domain of the VDR then binds to a vitamin D response element in the regulatory region of target genes to modulate transcription of responsive genes and thereby mediates hormone action (17)(18)(19)(20)(21)(22)(23).Progress to elucidate the molecular basis of HVDRR began with the demonstration that rodent skin possessed VDR (24, 25) and that cultured human dermal fibroblasts derived from skin biopsies could be used as a model system for the study of the VDR from patients (26). It was soon demonstrated that defects in the VDR were the likely cause of the HVDRR syndrome (5) and that different families exhibited different defects (5-16). An additional useful finding was the demonstration that 1,25(OH)2D3 could induce the enzyme 25-hydroxyvitamin D-24-hydroxylase (24-hydroxylase) in multiple target tissues by a receptor-mediated process (27). It was subsequently found that 24-hydroxylase activity could be induced in cultured skin fibroblasts so that induction of 24-hydroxylase activity could be employed as a bioassay ofthe ability of cultured fibroblasts to respond to 1,25(OH)2D3 (5). Using this bioresponse marker, cells from a variety of patients with HVDRR

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Impaired stimulation of 25-hydroxyvitamin D-24-hydroxylase in fibroblasts from a patient with vitamin D-dependent rickets, type II. A form of receptor-positive resistance to 1,25-dihydroxyvitamin D3.

Abstract: A B S T R A C T We describe studies of the molecular defect in 1,25-dihydroxyvitamin D3 [1,

Cited by 82 publications

References 39 publications

Genetic evidence that the human CYP2R1 enzyme is a key vitamin D 25-hydroxylase

Genetic evidence that the human CYP2R1 enzyme is a key vitamin D 25-hydroxylase

Hereditary vitamin D resistant rickets caused by a novel mutation in the vitamin D receptor that results in decreased affinity for hormone and cellular hyporesponsiveness.

The molecular basis of hereditary 1,25-dihydroxyvitamin D3 resistant rickets in seven related families.

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