Neutral lipid synthesis and storage in the intraerythrocytic stages of Plasmodium falciparum

• Published in: Molecular and biochemical parasitology 2004-06, Vol.135 (2), p.197-209
• Main Authors: Vielemeyer, Ole, McIntosh, Michael T., Joiner, Keith A., Coppens, Isabelle
• Format: Article
• Language: English
• Subjects: ABO Blood-Group System; Acyl-CoA:diacylglycerol acyltransferase; Acyltransferases - blood; Acyltransferases - chemistry; Acyltransferases - genetics; Amino Acid Sequence; Animals; CHO Cells; Cricetinae; Diacylglycerol O-Acyltransferase; Erythrocyte Membrane - enzymology; Erythrocyte Membrane - parasitology; Erythrocytes - parasitology; Fatty acids; Humans; Kinetics; Lipid bodies; Lipid Metabolism; Lipids - biosynthesis; Malaria; Membrane Lipids - metabolism; Microscopy, Fluorescence; Molecular Sequence Data; Plasmodium falciparum; Plasmodium falciparum - growth & development; Plasmodium falciparum - pathogenicity; Sequence Alignment; Sequence Homology, Amino Acid; Triacylglycerides
• ISSN: 0166-6851; 1872-9428
• DOI: 10.1016/j.molbiopara.2003.08.017

In eukaryotic cells the neutral lipids, steryl esters and triacylglycerol, are synthesized by membrane-bound O-acyltransferases and stored in cytosolic lipid bodies. We show here that the intraerythrocytic stages of Plasmodium falciparum produce triacylglycerol using oleate and diacylglycerol as substrates. Parasite membrane preparations reveal a synthesis rate of 4.5±0.8 pmol min −1 mg −1 of protein with maximal production occurring in the mid- and late-trophozoite stages in both, membrane preparations and live parasites. In contrast to other eukaryotic cells, no discernable amounts of steryl esters are produced, and the parasite is insensitive to cholesterol esterification inhibitors. Synthesized neutral lipids are stored as lipid bodies in the parasite cytosol in a stage specific manner. Their biogenesis is not modified upon incubation with excess fatty acids or lipoproteins or after lipoprotein depletion of the culture medium. We investigated on the enzymes involved in neutral lipid synthesis and found that only one gene with significant homology to known members of the membrane-bound O-acyltransferase family is present in the P. falciparum genome. It encodes a microsomal transmembrane protein with a predicted size of 78.1 kDa, which we named PfDGAT because of its close identity with various known acyl-CoA:diacylglycerol acyltransferases. PfDGAT is expressed in a stage specific manner as documented by Western blotting and immunoprecipitation assays using antibodies against Toxoplasma DGAT, suggesting that PfDGAT is the most likely candidate for plasmodial triacylglycerol synthesis.