Mol Biochem Parasitol. 2012 Dec 13. pii: S0166-6851(12)00283-6. doi: 10.1016/j.molbiopara.2012.11.007. [Epub ahead of print]
Sphingolipid synthesis and scavenging in the intracellular apicomplexan parasite, Toxoplasma gondii
Pratt S, Wansadhipathi-Kannangara NK, Bruce CR, Mina JG, Shams-Eldin H, Casas J, Hanada K, Schwarz RT, Sonda S, Denny PW.
From the Biophysical Sciences Institute, Department of Chemistry and School of Biological Sciences, University Science Laboratories, South Road, Durham, DH1 3LE; School of Medicine and Health, Durham University, Queen's Campus, Stockton-on-Tees, TS17 6BH, UK.
Sphingolipids are essential components of eukaryotic cell membranes, particularly the plasma membrane, and are involved in a diverse array of signal transduction pathways. Mammals produce sphingomyelin (SM) as the primary complex sphingolipid via the well characterised SM synthase. In contrast yeast, plants and some protozoa utilise an evolutionarily related inositol phosphorylceramide (IPC) synthase to synthesize IPC. This activity has no mammalian equivalent and IPC synthase has been proposed as a target for anti-fungals and anti-protozoals. However, detailed knowledge of the sphingolipid biosynthetic pathway of the apicomplexan protozoan parasites was lacking. In this study bioinformatic analyses indicated a single copy orthologue of the putative SM synthase from the apicomplexan Plasmodium falciparum (the causative agent of malaria) was a bona fide sphingolipid synthase in the related model parasite, Toxoplasma gondii (TgSLS). Subsequently, TgSLS was indicated, by complementation of a mutant cell line, to be a functional orthologue of the yeast IPC synthase (AUR1p), demonstrating resistance to the well characterised AUR1p inhibitor aureobasidin A. In vitro, recombinant TgSLS exhibited IPC synthase activity and, for the first time, the presence of IPC was demonstrated in T. gondii lipid extracts by mass spectrometry. Furthermore, host sphingolipid biosynthesis was indicated to influence, but be non-essential for, T. gondii proliferation, suggesting that whilst scavenging does take place de novo sphingolipid synthesis may be important for parasitism.
PMID: 23246819 [PubMed - as supplied by publisher]