Toxoplasma gondii acyl-lipid metabolism: de novo synthesis from apicoplast-generated fatty acids versus scavenging of host cell precursors

Author:

Bisanz Cordelia1,Bastien Olivier23,Grando Delphine4,Jouhet Juliette2,Maréchal Eric2,Cesbron-Delauw Marie-France1

Affiliation:

1. Laboratoire Adaptation et Pathogénie des Micro-organismes, UMR 5163, CNRS-UJF, Grenoble, France

2. Département Réponse et Dynamique Cellulaire, UMR 5168, CNRS-CEA-UJF, Grenoble, France

3. Gene-IT, 147 avenue Paul Doumer, Rueil-Malmaison, France

4. Laboratoire Bioinformatique et RMN Structurale, Pole Bioinformatique Lyonnais, UMR 5086, CNRS-Université C. Bernard, Lyon, France

Abstract

Toxoplasma gondii is an obligate intracellular parasite that contains a relic plastid, called the apicoplast, deriving from a secondary endosymbiosis with an ancestral alga. Metabolic labelling experiments using [14C]acetate led to a substantial production of numerous glycero- and sphingo-lipid classes in extracellular tachyzoites. Syntheses of all these lipids were affected by the herbicide haloxyfop, demonstrating that their de novo syntheses necessarily required a functional apicoplast fatty acid synthase II. The complex metabolic profiles obtained and a census of glycerolipid metabolism gene candidates indicate that synthesis is probably scattered in the apicoplast membranes [possibly for PA (phosphatidic acid), DGDG (digalactosyldiacylglycerol) and PG (phosphatidylglycerol)], the endoplasmic reticulum (for major phospholipid classes and ceramides) and mitochondria (for PA, PG and cardiolipid). Based on a bioinformatic analysis, it is proposed that apicoplast produced acyl-ACP (where ACP is acyl-carrier protein) is transferred to glycerol-3-phosphate for apicoplast glycerolipid synthesis. Acyl-ACP is also probably transported outside the apicoplast stroma and irreversibly converted into acyl-CoA. In the endoplasmic reticulum, acyl-CoA may not be transferred to a three-carbon backbone by an enzyme similar to the cytosolic plant glycerol-3-phosphate acyltransferase, but rather by a dual glycerol-3-phosphate/dihydroxyacetone-3-phosphate acyltransferase like in animal and yeast cells. We further showed that intracellular parasites could also synthesize most of their lipids from scavenged host cell precursors. The observed appearance of glycerolipids specific to either the de novo pathway in extracellular parasites (unknown glycerolipid 1 and the plant like DGDG), or the intracellular stages (unknown glycerolipid 8), may explain the necessary coexistence of both de novo parasitic acyl-lipid synthesis and recycling of host cell compounds.

Publisher

Portland Press Ltd.

Subject

Cell Biology,Molecular Biology,Biochemistry

Reference54 articles.

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