title: Synthesis of a novel photoactivatable glucosylceramide cross-linker.
abstract: The biosynthesis of glucosylceramide (GlcCer) is a key rate-limiting step in complex glycosphingolipid (GSL) biosynthesis. To further define interacting partners of GlcCer, we have made a cleavable, biotinylated, photoreactive GlcCer analog in which the reactive nitrene is closely apposed to the GlcCer head group, by substituting the native fatty acid with d, l-2-aminohexadecanoic acid. Two amino-GlcCer diastereomer cross-linkers (XLA and XLB) were generated. XLB proved an effective lactosylceramide (LacCer) synthase substrate while XLA was inhibitory. Both probes specifically bound and cross-linked the GlcCer binding protein, glycolipid transfer protein (GLTP), but not other GSL binding proteins (Shiga toxin and cholera toxin). GlcCer inhibited GLTP cross-linking. Both GlcCer cross-linkers competed with microsomal nitrobenzoxadiazole (NBD)-GlcCer anabolism to NBD-LacCer. GLTP showed marked, ATP-dependent enhancement of cell-free intact microsomal LacCer synthesis from endogenous or exogenous liposomal GlcCer, supporting a role in the transport/membrane translocation of cytosolic and extra-Golgi GlcCer. GLTP was specifically labeled by either XLA or XLB GlcCer cross-linker during this process, together with a (the same) small subset of microsomal proteins. These cross-linkers will serve to probe physiologically relevant GlcCer-interacting cellular proteins.
authors.affiliation: Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada Division of Molecular Structure and Function, Peter Gilgan Centre for Research and Learning, Research Institute, Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada.
authors.forename: Monique
authors.initials: M
authors.lastname: Budani
authors.affiliation: Division of Molecular Structure and Function, Peter Gilgan Centre for Research and Learning, Research Institute, Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada.
authors.forename: Murugesapillai
authors.initials: M
authors.lastname: Mylvaganam
authors.affiliation: Division of Molecular Structure and Function, Peter Gilgan Centre for Research and Learning, Research Institute, Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada.
authors.forename: Beth
authors.initials: B
authors.lastname: Binnington
authors.affiliation: Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada Division of Molecular Structure and Function, Peter Gilgan Centre for Research and Learning, Research Institute, Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Clifford
authors.initials: C
authors.lastname: Lingwood
mesh_terms: D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D003432:Cross-Linking Reagents; D005227:Fatty Acids / Q000737:chemistry / Q000378:metabolism; D005732:Gangliosides / Q000235:genetics / Q000378:metabolism; D005963:Glucosylceramides / Q000096:biosynthesis* / Q000737:chemistry; D006017:Glycolipids / Q000737:chemistry / Q000378:metabolism; D006028:Glycosphingolipids / Q000096:biosynthesis* / Q000737:chemistry; D006056:Golgi Apparatus / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007097:Imines / Q000737:chemistry
chemical_list: D002352:Carrier Proteins; D003432:Cross-Linking Reagents; D005227:Fatty Acids; C511922:GLTP protein, human; D005732:Gangliosides; D005963:Glucosylceramides; D006017:Glycolipids; D006028:Glycosphingolipids; D007097:Imines; C030363:lipid transfer protein; C017621:phenylnitrene
keywords: Golgi apparatus; flippase; gangliosides; glycolipid transport; glycolipids; glycosphingolipid anabolism; lipid transfer proteins; lipids/chemistry