PMID:12130651

Citation	Schwientek, T, Keck, B, Levery, SB, Jensen, MA, Pedersen, JW, Wandall, HH, Stroud, M, Cohen, SM, Amado, M and Clausen, H (2002) The Drosophila gene brainiac encodes a glycosyltransferase putatively involved in glycosphingolipid synthesis. J. Biol. Chem. 277:32421-9
Abstract	The Drosophila genes fringe and brainiac exhibit sequence similarities to glycosyltransferases. Drosophila and mammalian fringe homologs encode UDP-N-acetylglucosamine:fucose-O-Ser beta1,3-N-acetylglucosaminyltransferases that modulate the function of Notch family receptors. The biological function of brainiac is less well understood. brainiac is a member of a large homologous mammalian beta3-glycosyltransferase family with diverse functions. Eleven distinct mammalian homologs have been demonstrated to encode functional enzymes forming beta1-3 glycosidic linkages with different UDP donor sugars and acceptor sugars. The putative mammalian homologs with highest sequence similarity to brainiac encode UDP-N-acetylglucosamine:beta1,3-N-acetylglucosaminyltransferases (beta3GlcNAc-transferases), and in the present study we show that brainiac also encodes a beta3GlcNAc-transferase that uses beta-linked mannose as well as beta-linked galactose as acceptor sugars. The inner disaccharide core structures of glycosphingolipids in mammals (Galbeta1-4Glcbeta1-Cer) and insects (Manbeta1-4Glcbeta1-Cer) are different. Both disaccharide glycolipids served as substrates for brainiac, but glycolipids of insect cells have so far only been found to be based on the GlcNAcbeta1-3Manbeta1-4Glcbeta1-Cer core structure. Infection of High Five(TM) cells with baculovirus containing full coding brainiac cDNA markedly increased the ratio of GlcNAcbeta1-3Manbeta1-4Glcbeta1-Cer glycolipids compared with Galbeta1-4Manbeta1-4Glcbeta1-Cer found in wild type cells. We suggest that brainiac exerts its biological functions by regulating biosynthesis of glycosphingolipids.
Links	PubMed Online version:10.1074/jbc.M206213200
Keywords	Animals; Baculoviridae/metabolism; Cell Line; Chromatography, High Pressure Liquid; DNA, Complementary/metabolism; Databases as Topic; Disaccharides/metabolism; Dose-Response Relationship, Drug; Drosophila/enzymology; Drosophila Proteins; Genes, Insect; Glycoside Hydrolases/metabolism; Glycosphingolipids/biosynthesis; Glycosyltransferases/metabolism; Kinetics; Magnetic Resonance Spectroscopy; Membrane Proteins/metabolism; Membrane Proteins/physiology; Mutation; Phylogeny; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Substrate Specificity; Uridine Diphosphate/metabolism
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