Subcellular localization and dynamics of a digalactolipid-like epitope in Toxoplasma gondii

Abstract

Toxoplasma gondii is a unicellular parasite characterized by unique extracellular and intracellular membrane compartments. The lipid composition of subcellular membranes has not been determined, limiting our understanding of lipid homeostasis, control, and trafficking, a series of processes involved in pathogenesis. In addition to a mitochondrion, Toxoplasma contains a plastid called the apicoplast. The occurrence of a plastid raised the question of the presence of chloroplast galactolipids. Using three independent rabbit and rat antibodies against digalactosyldiacylglycerol (DGDG) from plant chloroplasts, we detected a class of Toxoplasma lipids harboring a digalactolipid-like epitope (DGLE). Immunolabeling characterization supports the notion that the DGLE polar head is similar to that of DGDG. Mass spectrometry analyses indicated that dihexosyl lipids having various hydrophobic moieties (ceramide, diacylglycerol, and acylalkylglycerol) might react with anti-DGDG, but we cannot exclude the possibility that more complex dihexosyl-terminated lipids might also be immunolabeled. DGLE localization was analyzed by immunofluorescence and immunoelectron microscopy and confirmed by subcellular fractionation. No immunolabeling of the apicoplast could be observed. DGLE was scattered in pellicle membrane domains in extracellular tachyzoites and was relocalized to the anterior tip of the cell upon invasion in an actin-dependent manner, providing insights on a possible role in pathogenetic processes. DGLE was detected in other Apicomplexa (i.e

Lipidomic Analysis of Toxoplasma gondii Reveals Unusual Polar Lipids

“…Defining the composition and abundance of T. gondii lipids provides not only information about the nature of plasma and organelle membranes, but also insight into nutrient requirements for parasite metabolism and host parasite interactions (5,23). Collectively, this information might inform design of new antimicrobials.…”

Discovery of Compounds Blocking the Proliferation of Toxoplasma gondii and Plasmodium falciparum in a Chemical Space Based on Piperidinyl-Benzimidazolone Analogs

“…Considering MGDs, the incorporation of radiolabeled galactose from UDPgalactose into a lipid having chromatographic properties similar to those of MGDG has been reported in T. gondii-and P. falciparum-permeabilized cells (49) but was not detected in P. falciparum microsomes (50). The actual presence of MGDG in these parasites was not detected by sensitive mass spectrometry (15,51). In the absence of any clear homolog gene, it is thus likely that plastid MGDG synthases have been lost or have strongly diverged in the course of the Apicomplexa evolution.…”

“…In eukaryotes, two main subcellular compartments are responsible for the synthesis of complex glycerolipids: one is the ER, synthesizing phospholipids, and the other one is the plastid of photosynthetic organisms, synthesizing nonphosphated glycoglycerolipids, including monogalactosyldiacylglycerol (MGDG). Although the apicoplast derives from a photosynthetic plastid (14), no enzyme synthesizing glycoglycerolipids was identified in this organelle (15,16).…”

Role of phosphatidic acid in plant galactolipid synthesis

“…The apicoplast lipid composition remains unknown but synthesis of galactolipids could be detected by metabolic labelling in Apicomplexa lysates [44,45]. Immunodetection using a polyclonal antibody raised against plant DGDG allowed to detect a digalactolipid-like epitope in Toxoplasma gondii (the Apicomplexa responsible for toxoplasmosis) and P. falciparum membranes and total lipid extracts [45,46]. Furthermore LCeMS/ MS approach showed the presence of two hexosyllipids in the membranes of T. gondii: hexosylceramides and hexosylglycerolipids, hexosylceramides being the most predominant class [46].…”

“…Immunodetection using a polyclonal antibody raised against plant DGDG allowed to detect a digalactolipid-like epitope in Toxoplasma gondii (the Apicomplexa responsible for toxoplasmosis) and P. falciparum membranes and total lipid extracts [45,46]. Furthermore LCeMS/ MS approach showed the presence of two hexosyllipids in the membranes of T. gondii: hexosylceramides and hexosylglycerolipids, hexosylceramides being the most predominant class [46]. Together, these data are consistent with the potential synthesis of galactolipid classes in Apicomplexa by a pathway, which remains to be identified.…”