Formation and Remodeling of Inositolphosphoceramide during Differentiation of Trypanosoma cruzi from Trypomastigote to Amastigote

Abstract

Differentiation of Trypanosoma cruzi trypomastigotes to amastigotes inside myoblasts or in vitro, at low extracellular pH, in the presence of [3 H]palmitic acid or [ 3 H]inositol revealed differential labeling of inositolphosphoceramide and phosphatidylinositol, suggesting that a remodeling process takes place in both lipids. Using 3 H-labeled inositolphosphoceramide and phosphatidylinositol as substrates, we demonstrated the association of at least five enzymatic activities with the membranes of amastigotes and trypomastigotes. These included phospholipase A 1 , phospholipase A 2 , inositolphosphoceramide-fatty acid hydrolase, acyltransferase, and a phospholipase C releasing either ceramide or a glycerolipid from the inositolphospholipids. These enzymes may be acting in remodeling reactions leading to the anchor of mature glycoproteins or glycoinositolphospholipids and helping in the transformation of the plasma membrane, a necessary step in the differentiation of slender trypomastigotes to round amastigotes. Synthesis of inositolphosphoceramide and particularly of glycoinositolphospholipids was inhibited by aureobasidin A, a known inhibitor of fungal inositolphosphoceramide synthases. The antibiotic impaired the differentiation of trypomastigotes at acidic pH, as indicated by an increased appearance of intermediate forms and a decreased expression of the Ssp4 glycoprotein, a characteristic marker of amastigote forms. Aureobasidin A was also toxic to differentiating trypomastigotes at acidic pH but not to trypomastigotes maintained at neutral pH. Our data suggest that inositolphosphoceramide is implicated in T. cruzi differentiation and that its metabolism could provide important targets for the development of antiparasitic therapies.

In Vitro Activities of ER-119884 and E5700, Two Potent Squalene Synthase Inhibitors, against Leishmania amazonensis : Antiproliferative, Biochemical, and Ultrastructural Effects

“…Quinuclidine derivatives are also known to interfere with fatty acid and phospholipid biosynthesis in mammalian cells (22), and a similar phenomenon has been reported in Chritidia deanei cells after treatment with sterol 24-methenyltransferase inhibitors (35). Lipid inclu- sions were also observed in L. major null mutants for serine palmitoyltransferase, an enzyme involved in sphingolipid biosynthesis (54,55), and in T. cruzi epimastigotes after the perturbation of sphingolipid biosynthesis (40). However, large numbers of lipid inclusions have also been reported in taxoltreated T. cruzi (13), indicating that lipid body formation can occur as a consequence of many different perturbations to the parasite's cellular functions.…”

De Novo Sphingolipid Synthesis Is Essential for Viability, but Not for Transport of Glycosylphosphatidylinositol-Anchored Proteins, in African Trypanosomes

“…After the production of ceramide in the ER, eukaryotes go on to synthesize a diverse array of higher-order sphingolipids. Many of the lower eukaryotes, including fungi (38) and the kinetoplastids Leishmania (35) and Trypanosoma cruzi (54), synthesize IPC, and it has been generally assumed that African trypanosomes likewise synthesize IPC (18,19,32). In fact, earlier compositional analyses of African trypanosomes found no evidence for IPC; rather, sphingomyelin was detected at fairly high levels in bloodstream-stage parasites (49).…”

“…Among the lower eukaryotes Plasmodium spp. also make sphingomyelin (28), while many others, including fungi (38), Toxoplasma gondii (58), and the kinetoplastids Leishmania (35) and Trypanosoma cruzi (54), synthesize inositol phosphorylceramide (IPC). Surprisingly, in Leishmania major, synthesis of sphingolipids is not necessary for viability or virulence (17,68), provided the growth medium is supplemented with ethanolamine (67).…”

Phospholipid and glycolipid composition of acidocalcisomes of Trypanosoma cruzi

“…The plates were prepared by immersion in a solution containing 1.3% potassium oxalate and 2 mM EDTA in methanol/water (2/3, v/v) for 30 min at room temperature. Then plates were allowed to dry overnight and heated at 110°C for 30 min [26]. Radiolabeled lipids were detected by fluorography.…”