title: A novel pathway for sequential transformation of 7-dehydrocholesterol and expression of the P450scc system in mammalian skin.
abstract: Following up on our previous findings that the skin possesses steroidogenic activity from progesterone, we now show widespread cutaneous expression of the full cytochrome P450 side-chain cleavage (P450scc) system required for the intracellular catalytic production of pregnenolone, i.e. the genes and proteins for P450scc enzyme, adrenodoxin, adrenodoxin reductase and MLN64. Functionality of the system was confirmed in mitochondria from skin cells. Moreover, purified mammalian P450scc enzyme and, most importantly, mitochondria isolated from placenta and adrenals produced robust transformation of 7-dehydrocholesterol (7-DHC; precursor to cholesterol and vitamin D3) to 7-dehydropregnenolone (7-DHP). Product identity was confirmed by comparison with the chemically synthesized standard and chromatographic, MS and NMR analyses. Reaction kinetics for the conversion of 7-DHC into 7-DHP were similar to those for cholesterol conversion into pregnenolone. Thus, 7-DHC can form 7-DHP through P450scc side-chain cleavage, which may serve as a substrate for further conversions into hydroxy derivatives through existing steroidogenic enzymes. In the skin, 5,7-steroidal dienes (7-DHP and its hydroxy derivatives), whether synthesized locally or delivered by the circulation, may undergo UVB-induced intramolecular rearrangements to vitamin D3-like derivatives. This novel pathway has the potential to generate a variety of molecules depending on local steroidogenic activity and access to UVB.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Tennessee, Health Science Center, Memphis, TN, USA. aslominski@utmem.edu <aslominski@utmem.edu>
authors.forename: Andrzej
authors.initials: A
authors.lastname: Slominski
authors.forename: Jordan
authors.initials: J
authors.lastname: Zjawiony
authors.forename: Jacobo
authors.initials: J
authors.lastname: Wortsman
authors.forename: Igor
authors.initials: I
authors.lastname: Semak
authors.forename: Jeremy
authors.initials: J
authors.lastname: Stewart
authors.forename: Alexander
authors.initials: A
authors.lastname: Pisarchik
authors.forename: Trevor
authors.initials: T
authors.lastname: Sweatman
authors.forename: Josep
authors.initials: J
authors.lastname: Marcos
authors.forename: Chuck
authors.initials: C
authors.lastname: Dunbar
authors.forename: Robert
authors.initials: R
authors.lastname: C Tuckey
mesh_terms: D000325:Adrenodoxin / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D002384:Catalysis; D002417:Cattle; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid; D002853:Chromatography, Liquid; D002855:Chromatography, Thin Layer; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry* / Q000378:metabolism; D017931:DNA Primers / Q000737:chemistry; D003684:Dehydrocholesterols / Q000737:chemistry*; D005287:Ferredoxin-NADP Reductase / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D013058:Mass Spectrometry; D051379:Mice; D008810:Mice, Inbred C57BL; D008928:Mitochondria / Q000378:metabolism; D008956:Models, Chemical; D010920:Placenta / Q000378:metabolism; D011284:Pregnenolone / Q000031:analogs & derivatives* / Q000737:chemistry*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012867:Skin / Q000378:metabolism*; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: C480635:7-dehydropregnenolone; D017931:DNA Primers; D003684:Dehydrocholesterols; D000325:Adrenodoxin; D011284:Pregnenolone; D003577:Cytochrome P-450 Enzyme System; C016705:7-dehydrocholesterol; D005287:Ferredoxin-NADP Reductase