Regulation of Cerebroside and Sulfatide Metabolism in Glia Cells

Abstract: Mouse oligodendroglioma cells, G‐26 clone 20 and 24, contain galactosylceramide (cerebroside) and sul‐fogalactosylceramide (sulfatide) as determined by an HPLC technique. The synthesis of both these lipids was stimulated by 10−‐6M hydrocortisone (cortisol) and also by the removal of serum from the culture medium. Forty‐eight hours after the addition of cortisol the incorporation of H235SO4 into sulfatide, the level of sulfatide and the specific activity of the enzyme 3′‐phosphoadenosine 5′‐phosphosulfate:galactosylceramide sulfotransferase in the cells increased three‐ to fourfold. The level of cerebroside and the specific activity of UDP‐galactose: hydroxyacyl sphingosine galactosyltransferase also increased threefold in the cells on treatment with cortisol. The effect of the hormone on the synthesis of cerebroside preceded the increase in sulfatide synthesis. Experiments with cycloheximide and actinomycin D showed that the effect of the hormone on glycolipid synthesis in these cells was mediated through de novo messenger RNA and protein synthesis. Removal of serum from the culture medium resulted in an approximately twofold enhancement of H235SO4 incorporation into sulfatide within 24 h. The levels of sulfatide and cerebroside and the specific activity of the galactosyltransferase and sulfotransferase also increased significantly after serum removal. However, in contrast to the effect of the steroid, the sulfotransferase activity and the level of sulfatide increased prior to elevations in galactosyltransferase and cerebroside. The effect of serum removal was also found to be mediated by de novo RNA and protein synthesis. The effects of cortisol and serum removal on the synthesis of cerebroside and sulfatide were strictly additive. This observation plus the different temporal patterns of induction suggest that two separate regulatory mechanisms at the nuclear level exist in oligodendroglioma cells for the biosynthesis of these glycolipids.