Abstract
The presence of both 1alpha-hydroxylase activity and 25-hydroxylase activity is a biochemical prerequisite for the enzymatic generation of 1alpha,25(OH)2D3 from vitamin D3 in keratinocytes. In contrast to 1alpha-hydroxylase, however, activity of a 25-hydroxylase in keratinocytes has not previously been demonstrated. In this study, using RT-PCR we detected vitamin D3 25-hydroxylase mRNA in human keratinocytes. The expression of vitamin D3 25-hydroxylase mRNA in keratinocytes was identical to that of CYP27 expressed in mitochondria of human hepatoma HepG2 cells. CYP27 mRNA in keratinocytes is not constitutively expressed but is inducible both by vitamin D3 (780 nM) and by UVB radiation (300 nm, 30 mJ/cm2).
MeSH terms
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Carcinoma, Hepatocellular / metabolism
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Carcinoma, Hepatocellular / pathology
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Cholecalciferol / pharmacology*
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Cholestanetriol 26-Monooxygenase
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Cytochrome P-450 Enzyme System / metabolism
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Gene Expression Regulation / drug effects
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Gene Expression Regulation / radiation effects
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Humans
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Keratinocytes / drug effects*
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Keratinocytes / metabolism*
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Keratinocytes / radiation effects
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Mitochondria / metabolism
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RNA, Messenger / metabolism*
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Reverse Transcriptase Polymerase Chain Reaction
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Steroid Hydroxylases / genetics*
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Steroid Hydroxylases / metabolism
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Tumor Cells, Cultured
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Ultraviolet Rays*
Substances
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RNA, Messenger
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Cholecalciferol
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Cytochrome P-450 Enzyme System
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Steroid Hydroxylases
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CYP27A1 protein, human
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Cholestanetriol 26-Monooxygenase