Detection of P450c17-independent pathways for dehydroepiandrosterone (DHEA) biosynthesis in brain glial tumor cells.
Dehydroepiandrosterone (D) is biosynthesized in the brain by a pathway different from that existing in the adrenal cortex. C6 rat glioma tumor cells in culture biosynthesize both pregnenolone (P) and D. They possess the mRNA, protein, and side-chain cleavage activity of P450scc. On the other hand, P450c17 was not detected. Adding FeSO4 to C6 cells increased the synthesis of both P and D. Even in the presence of aminoglutethimide, an inhibitor of P450scc, FeSO4 increased the synthesis of both steroids, indicating that the Fe2+-sensitive process does not involve P450scc. Likewise, the FeSO4-induced formation of D was not blocked by the P450c17 inhibitor, SU-10603. These results suggest that the FeSO4-induced synthesis of D as well as of P in C6 cells may be due to the fragmentation of in situ-formed tertiary hydroperoxides. It is likely, however, that the effect of the Fe2+ is not limited to this one reaction. When exogenous P was added to C6 microsomes, along with FeSO4, the amount of D formed was greater than control values, indicating that Fe2+ facilitated the conversion of P to D. Unlike the constituents that are converted by Fe2+ to P, the precursor of D in C6 cells is not soluble in a 1:1 mixture of ether and ethylacetate. Treatment of C6 cells with KI, NaBH4, or HIO4 resulted in an increase in D synthesis. From this it seems clear that a precursor of the D produced in C6 cells is a steroid where both C-17 and C-20 are oxygenated.
Cascio
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Department of Cell Biology, Georgetown University Medical Center, Washington, DC 20007, USA.
Prasad
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VV
Lin
Y Y
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Lieberman
S
S
Papadopoulos
V
V
D000616:Aminoglutethimide / Q000494:pharmacology; D000818:Animals; D001932:Brain Neoplasms / Q000378:metabolism*; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000032:analysis / Q000037:antagonists & inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis*; D003687:Dehydroepiandrosterone / Q000096:biosynthesis*; D005296:Ferrous Compounds / Q000494:pharmacology; D005910:Glioma / Q000378:metabolism*; D007985:Leydig Cells / Q000378:metabolism; D008297:Male; D008861:Microsomes / Q000378:metabolism; D008956:Models, Chemical; D009457:Neuroglia / Q000378:metabolism*; D011284:Pregnenolone / Q000096:biosynthesis; D051381:Rats; D013254:Steroid 17-alpha-Hydroxylase / Q000032:analysis / Q000037:antagonists & inhibitors; D013764:Tetrahydronaphthalenes / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D005296:Ferrous Compounds; D013764:Tetrahydronaphthalenes; D000616:Aminoglutethimide; C020748:ferrous sulfate; D003687:Dehydroepiandrosterone; D011284:Pregnenolone; C001953:SU 10603; D003577:Cytochrome P-450 Enzyme System; D013254:Steroid 17-alpha-Hydroxylase; D002786:Cholesterol Side-Chain Cleavage Enzyme