PLASMODIUM-FALCIPARUM - ASEXUAL ERYTHROCYTIC STAGES SYNTHESIZE 2 STRUCTURALLY DISTINCT FREE AND PROTEIN-BOUND GLYCOSYLPHOSPHATIDYLINOSITOLSIN A MATURATION-DEPENDENT MANNER

Glycosylphosphatidylinositols represent the predominant class of glyco lipids synthesized by the asexual, intraerythrocytic stages of Plasmod ium falciparum. These glycolipids have been implicated as malarial tox ins involved in parasite-induced release of cytokines, such as tumor n ecrosis factor-alpha and interleukin-l. Two potential glycosylphosphat idylinositol membrane-anchor precursors with the structures ethanolami ne phosphate (mannose-alpha 1,2)mannose-alpha 1,2-mannose-alpha 1,6-ma nnose-alpha 1,4-glucosamine-inositol(acyl)phosphate diacylglycerol (P. f.alpha) and ethanolamine-phosphate-mannose-alpha 1,2-mannose-alpha 1, 6-mannose-alpha 1,4-glucosamine-inositol(acyl)phosphate diacylglycerol (P.f.beta) have been described in P. falciparum. Only one (P.f.alpha) has been demonstrated to serve as an anchor for merozoite surface pro tein-1 and merozoite surface protein-2. In this report we present data showing that asexual, intraerythrocytic stages of P. falciparum use b oth glycosylphosphatidylinositols to anchor proteins. The synthesis of the two glycosylphosphatidylinositol membrane anchor precursors and t he protein-bound glycosylphosphatidylinositol anchors is tightly regul ated and varies throughout the intraerythrocytic development of the as exual stages of P. falciparum. The glycosylphosphatidylinositol membra ne-anchor precursor P.f.beta is synthesized and transferred to protein predominantly in trophozoite stages (about 30 h). (C) 1998 Academic P ress.