J Biol Chem. 2017 Mar 17. pii: jbc.M116.765487. doi: 10.1074/jbc.M116.765487. [Epub ahead of print]
Toxoplasma gondii is among the most prevalent protozoan parasites, which infects a wide range of organisms including one-third of the human population. Its rapid intracellular replication within a vacuole requires efficient synthesis of glycerophospholipids. Cytidine diphosphate-diacylglycerol (CDP-DAG) serves as a major precursor for phospholipid synthesis. Given the peculiarities of lipid biogenesis, understanding the mechanism and physiological importance of CDP-DAG synthesis is particularly relevant in T. gondii Here, we report the occurrence of two phylogenetically divergent CDP-DAG synthase (CDS) enzymes in the parasite. The eukaryotic-type TgCDS1 and the prokaryotic-type TgCDS2 reside in the endoplasmic reticulum (ER) and apicoplast, respectively. Conditional knockdown of TgCDS1 severely attenuated the parasite growth and resulted in a nearly complete loss of virulence in a mouse model. Moreover, mice infected with the TgCDS1 mutant became fully resistant to challenge infection with a hyper-virulent strain of T. gondii The residual growth of the TgCDS1 mutant was abolished by consecutive deletion of TgCDS2. Lipidomic analyses of the mutants revealed significant and specific declines in phosphatidylinositol and phosphatidylglycerol levels upon repression of TgCDS1 and following deletion of TgCDS2, respectively. Our data suggest a division of labor model of lipid biogenesis in T. gondii, in which two discrete CDP-DAG pools produced in the ER and apicoplast are subsequently used for the synthesis of phosphatidylinositol in the Golgi bodies and phosphatidylglycerol in the mitochondrion. The essential and divergent nature of CDP-DAG synthesis in the parasite apicoplast offers a potential drug target to inhibit the asexual reproduction of T. gondii.
Copyright © 2017, The American Society for Biochemistry and Molecular Biology.
KEYWORDS:
Toxoplasma gondii; glycerophospholipid; parasite metabolism; phosphatidylglycerol; phosphatidylinositol
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