Mouse vitamin D-24-hydroxylase: molecular cloning, tissue distribution, and transcriptional regulation by 1alpha,25-dihydroxyvitamin D3.
Vitamin D-24-hydroxylase (24-OHase) is a cytochrome P-450 enzyme that catalyzes the conversion of 25-hydroxyvitamin D3 (25OHD3) and 1alpha,25-dihydroxyvitamin D3 [1,25-(OH)2D3] to 24,25-dihydroxyvitamin D3 and 1,24,25-trihydroxyvitamin D3, respectively. A full-length complementary DNA for mouse 24-OHase has now been characterized. The complementary DNA consists of 3309 bp and encodes a protein of 514 amino acids that shows 82% and 95% sequence identity with the human and rat enzymes, respectively. Northern blot analysis of tissues from mice injected with 1,25-(OH)2D3 (24 pmol/g) revealed that the 3.4-kb 24-OHase messenger RNA (mRNA) is most abundant in kidney and intestine, with smaller amounts present in skin, thymus, and bone. RT-PCR and Southern blot analysis detected 24-OHase mRNA in several other tissues including lung, testis, spleen, pancreas, and heart. Intraperitoneal injection of 1,25-(OH)2D3 induced dose- and time-dependent increases in both 24-OHase mRNA abundance and enzyme activity in mouse kidney. Similarly, 1,25-(OH)2D3-induced increases in both 24-OHase mRNA and activity were apparent in the duodenum. Although 1,25-(OH)2D3 increased the amount of 24-OHase mRNA in skin, enzyme activity was not detected in this tissue. Pretreatment of mice with cycloheximide (400 microg/g), an inhibitor of protein synthesis, potentiated the increase in 24-OHase mRNA abundance, but blocked the increase in 24-OHase activity, induced by 1,25-(OH)2D3 in kidney and duodenum, suggesting that 24-OHase gene expression may be regulated not only by the vitamin D receptor but also by a short-lived repressor protein.
Akeno
N
N
Department of Biochemistry, Ohu University School of Dentistry, Koriyama, Japan.
Saikatsu
S
S
Kawane
T
T
Horiuchi
N
N
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002117:Calcitriol / Q000494:pharmacology*; D003001:Cloning, Molecular; D003513:Cycloheximide / Q000494:pharmacology; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D018076:DNA, Complementary; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D006801:Humans; D007668:Kidney / Q000201:enzymology; D007700:Kinetics; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D008969:Molecular Sequence Data; D009928:Organ Specificity; D016133:Polymerase Chain Reaction; D051381:Rats; D017386:Sequence Homology, Amino Acid; D013250:Steroid Hydroxylases / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects*; D065668:Vitamin D3 24-Hydroxylase
D018076:DNA, Complementary; D003577:Cytochrome P-450 Enzyme System; D003513:Cycloheximide; D013250:Steroid Hydroxylases; D065668:Vitamin D3 24-Hydroxylase; D002117:Calcitriol