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.
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.
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Laboratory of Molecular Parasitology, Rockefeller University, New York, New York 10021.
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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*
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