UDP-galactose-ceramide galactosyltransferase in rat brain myelin subfractions during development

Abstract

The localization and activity of the enzyme UDP-galactose-hydroxy fatty acid-containing ceramide galactosyltransferase is described in rat brain myelin subfractions during development. Other lipid-synthesizing enzymes, such as cerebroside sulphotransferase, UDP-glucose-ceramide glucosyltransferase and CDP-choline-1,2-diacylglycerol cholinephosphotransferase, were also studied for comparison in myelin subfractions and microsomal membranes. The purified myelin was subfractionated by isopycnic sucrose-density-gradient centrifugation. Four myelin subfractions, three floating respectively on 0.55 M- (light-myelin fraction), 0.75 M- (heavy-myelin fraction) and 0.85 M-sucrose (membrane fraction), and a pellet, were isolated and purified. At all ages, 70--75% of the total myelin proteins was found in the heavy-myelin fraction, whereas 2--5% of the protein was recovered in the light-myelin fraction, and about 7--12% in the membrane fraction. Most of the galactosyltransferase was associated with the heavy-myelin and membrane fractions. Other lipid-synthesizing enzymes studied appeared not to associate with purified myelin or myelin subfractions, but were enriched in the microsomal-membrane fraction. During development, the specific activity of the microsomal galactosyltransferase reached a maximum when the animals were about 20 days old and then declined. By contrast the specific activity of the galactosyltransferase in the heavy-myelin and membrane fractions was 3--4 times higher than that of the microsomal membranes in 16-day-old animals. The specific activity of the enzyme in the heavy-myelin fraction sharply declined with age. Chemical and enzymic analyses of the heavy-myelin and membrane myelin subfractions at various ages showed that the membrane fraction contained more proteins in relation to lipids than the heavy-myelin fraction. The membrane fraction was also enriched in phospholipids compared with cholesterol and contrined equivalent amounts of 2':3'-cyclic nucleotide 3'-phosphohydrolase compared with heavy- and light-myelin fractions. The membrane fraction was deficient in myelin basic protein and proteolipid protein and enriched in high-molecular-weight proteins. The specific localization of galactosyltransferase in heavy-myelin and membrane fractions at an early age when myelination is just beginning suggests that it may have some role in the myelination process.

t-SNARE Syntaxin2 (STX2) Is Implicated in Intracellular Transport of Sulfoglycolipids During Meiotic Prophase in Mouse Spermatogenesis

“…S7). Here we show that sulfoglycolipids are localized in ROLE OF STX2 IN SPERMATOGENESIS the plasma membrane of the wild-type spermatocytes, in agreement with previous reports [12,42,43], as wells as in the germ cell intercellular bridges. In mammals, two major sulfoglycolipids, sulfatide and galactosylsulfatide, are produced in the testis by interaction of alkylacylglycerol and ceramide with CST [14,44] and CGT [10].…”

Activation of the Mammalian Target of Rapamycin (mTOR) Is Essential for Oligodendrocyte Differentiation

“…Ugt-8 catalyzes the final step in the biosynthesis of cerebrosides (Koul et al, 1980), a major component of myelin membranes, and also is upregulated during oligodendrocyte differentiation (Dugas et al, 2006). Inhibiting mTOR decreased Ugt-8 mRNA by 58% following 3 days of differentiation (Fig.…”

Neonatal and adult O4+ oligodendrocyte lineage cells display different growth factor responses and different gene expression patterns

“…Enpp2 , which encodes ectonucleotide pyrophosphate/phosphodiesterase 2, is expressed by oligodendrocytes at the commencement of myelination, antagonizing adhesive interactions with extracellular matrix (Fox et al 2003). The enzyme encoded by Ugt8 is localized in myelin subfractions and is downregulated during demyelination in the twitcher mouse model for globoid cell leukodystrophy (Koul et al 1980; Taniike et al 1998). Zitter rats, which possess a mutation in the gene for attractin, exhibit hypomyelination (Kuramoto et al 2001).…”