CHARACTERIZATION OF GLYCOINOSITOL PHOSPHOLIPIDS IN THE AMASTIGOTE STAGE OF THE PROTOZOAN PARASITE LEISHMANIA-MAJOR

The major macromolecules on the surface of the parasitic protozoan Lei shmania major appear to be down-regulated during transformation of the parasite from an insect-dwelling promastigote stage to an intracellul ar amastigote stage that invades mammalian macrophages. In contrast, t he major parasite glycolipids, the glycoinositol phospholipids (GIPLs) , are shown here to be expressed at near-constant levels in both devel opmental stages. The structures of the GIPLs from tissue-derived amast igotes have been determined by h.p.l.c. analysis of the deaminated and reduced glycan head groups, and by chemical and enzymic sequencing. T he deduced structures appear to form a complete biosynthetic series, r anging from Manalpha1-4GlcN-phosphatidyl-inositol (PI) to alalpha1-3Ga lfbeta1-3Manalpha1-3Manalpha1-4GlcN-PI (GIPL-2). A small proportion of GIPL-2 was further extended by addition of a Gal residue in either al pha1-6 or beta1-3 linkage. From g.c-m.s. analysis and mild base treatm ent, all the GIPLS were shown to contain either alkylacylglycerol or l yso-alkylglycerol lipid moieties, where the alkyl chains were predomin antly C18:0 with lower levels of C20:0, C22:0 and C24:0. L. major amas tigotes also contained at least two PI-specific phospholipase C-resist ant glycolipids which are absent from promastigotes. These neutral gly colipids were resistant to both mild acid and mild base hydrolysis. co ntained terminal beta-Gal residues and were not lost during extensive purification of amastigotes from host cell membranes. It is likely tha t these glycolipids are glycosphingolipids acquired from the mammalian host. The GIPL profile of L. major amastigotes is compared with the p rofiles found in L. major promastigotes and L. donovani amastigotes.