THE GLYCOINOSITOLPHOSPHOLIPIDS FROM LEISHMANIA-PANAMENSIS CONTAIN UNUSUAL GLYCAN AND LIPID MOIETIES

The cell surface of Leishmania parasites is coated by glycosylphosphat idylinositol (GPI)-anchored macromolecules (glycoproteins and a lipoph osphoglycan) and a polymorphic family of free GPI glycolipids or glyco inositolphospholipids (GIPLs). Here we show that GIPLs with unusual gl ycan and lipid moieties are likely to be major cell surface components of L. panamensis (subgenus Viannia) promastigotes. These glycolipids were purified by high performance thin layer chromatography and their structures determined by gas-liquid chromatography-mass spectrometry, fast-atom bombardment mass spectrometry, methylation analysis and chem ical and enzymatic sequencing of the glycan headgroups. The major GIPL s contained two glycan core sequences, Man alpha 1-3Man alpha 1-4GlcN- phosphatidylinositol (type-2 series) or Man alpha 1-3 [Man alpha 1-2Ma n alpha 1-6]Man alpha 1-4GlcN-phosphatidylinositol (hybrid series), wh ich were elaborated with Gal alpha 1-2Gal beta 1- or Gal alpha 1-2/3Ga l alpha 1-2Gal beta 1-extensions that were attached to the 3-position of the alpha 1-3 Linked mannose. The phosphatidylinositol moiety conta ined exclusively diacylglycerol with palmitoyl, stearoyl and heptadeca noyl chains. Non-galactosylated GIPL species with the same core struct ures were also found. The galactose extensions and the presence of dia cylglycerol in the lipid moieties are novel features for the GIPLs of Leishmania spp. The implications of these structures for the biosynthe sis of leishmanial GIPLs and their putative function in the mammalian host are discussed. (C) 1998 Academic Press.