title: Developmental variation of glycosylphosphatidylinositol membrane anchors in Trypanosoma brucei. Identification of a candidate biosynthetic precursor of the glycosylphosphatidylinositol anchor of the major procyclic stage surface glycoprotein.
abstract: The major surface antigen of the mammalian bloodstream form of Trypanosoma brucei, the variant surface glycoprotein (VSG), is attached to the cell membrane by a glycosylphosphatidylinositol (GPI) anchor. The VSG anchor is susceptible to phosphatidylinositol-specific phospholipase C (PI-PLC). Candidate precursor glycolipids, P2 and P3, which are PI-PLC-sensitive and -resistant respectively, have been characterized in the bloodstream stage. In the insect midgut stage, the major surface glycoprotein, procyclic acidic repetitive glycoprotein, is also GPI-anchored but is resistant to PI-PLC. To determine how the structure of the GPI anchor is altered at different life stages, we characterized candidate GPI molecules in procyclic T. brucei. The structure of a major procyclic GPI, PP1, is ethanolamine-PO4-Man alpha 1-2Man alpha 1-6 Man alpha 1-GlcN-acylinositol, linked to lysophosphatidic acid. The inositol can be labeled with [3H]palmitic acid, and the glyceride with [3H]stearic acid. We have also found that all detectable ethanolamine-containing GPIs from procyclic cells contain acylinositol and are resistant to cleavage by PI-PLC. This suggests that the procyclic acidic repetitive glycoprotein GPI anchor structure differs from that of the VSG by virtue of the structures of the GPIs available for transfer.
authors.affiliation: Laboratory of Molecular Parasitology, Rockefeller University, New York, New York 10021.
authors.forename: M C
authors.initials: MC
authors.lastname: Field
authors.forename: A K
authors.initials: AK
authors.lastname: Menon
authors.forename: G A
authors.initials: GA
authors.lastname: Cross
mesh_terms: D000818:Animals; D002855:Chromatography, Thin Layer; D005227:Fatty Acids / Q000378:metabolism; D006017:Glycolipids / Q000378:metabolism*; D017261:Glycosylphosphatidylinositols; D008562:Membrane Glycoproteins / Q000378:metabolism; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D010716:Phosphatidylinositols / Q000378:metabolism*; D054801:Phosphoinositide Phospholipase C; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D011134:Polysaccharides / Q000378:metabolism; D015800:Protozoan Proteins; D014346:Trypanosoma brucei brucei / Q000254:growth & development / Q000378:metabolism*; D014415:Tunicamycin / Q000494:pharmacology; D014643:Variant Surface Glycoproteins, Trypanosoma / Q000378:metabolism*
chemical_list: D005227:Fatty Acids; D006017:Glycolipids; D017261:Glycosylphosphatidylinositols; D008562:Membrane Glycoproteins; D010716:Phosphatidylinositols; D011134:Polysaccharides; D015800:Protozoan Proteins; D014643:Variant Surface Glycoproteins, Trypanosoma; C053277:procyclic acidic repetitive protein, Trypanosoma; D014415:Tunicamycin; D010727:Phosphoric Diester Hydrolases; D054801:Phosphoinositide Phospholipase C; D043265:Phosphatidylinositol Diacylglycerol-Lyase