title: Phosphatidylethanolamine and phosphatidylcholine biosynthesis by the Kennedy pathway occurs at different sites in Trypanosoma brucei.
abstract: Phosphatidylethanolamine (PE) and phosphatidylcholine (PC) are among the most abundant phospholipids in biological membranes. In many eukaryotes, the CDP-ethanolamine and CDP-choline branches of the Kennedy pathway represent major and often essential routes for the production of PE and PC, with ethanolamine and choline/ethanolamine phosphotransferases (EPT and CEPT, respectively) catalysing the last reactions in the respective pathways. Although the site of PE and PC synthesis is commonly known to be the endoplasmic reticulum (ER), detailed information on the localization of the different phosphotransferases is lacking. In the unicellular parasite, Trypanosoma brucei, both branches of the Kennedy pathway are essential for cell growth in culture. We have previously reported that T. brucei EPT (TbEPT) catalyses the production of ether-type PE molecular species while T. brucei CEPT (TbCEPT) synthesizes diacyl-type PE and PC molecular species. We now show that the two enzymes localize to different sub-compartments of the ER. By expressing a series of tagged forms of the two enzymes in T. brucei parasites, in combination with sub-cellular fractionation and enzyme activity measurements, TbEPT was found exclusively in the perinuclear ER, a distinct area located close to but distinct from the nuclear membrane. In contrast, TbCEPT was detected in the bulk ER.
authors.affiliation: Institute of Biochemistry and Molecular Medicine, University of Bern, 3012 Bern, Switzerland.|Graduate School for Cellular and Biomedical Sciences, University of Bern, 3012 Bern, Switzerland.
authors.forename: Luce
authors.initials: L
authors.lastname: Farine
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, 3012 Bern, Switzerland.
authors.forename: Moritz
authors.initials: M
authors.lastname: Niemann
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, 3012 Bern, Switzerland.
authors.forename: André
authors.initials: A
authors.lastname: Schneider
authors.affiliation: Institute of Biochemistry and Molecular Medicine, University of Bern, 3012 Bern, Switzerland.
authors.forename: Peter
authors.initials: P
authors.lastname: Bütikofer
mesh_terms: D001692:Biological Transport; D053898:Biosynthetic Pathways; D042541:Intracellular Space; D010713:Phosphatidylcholines / Q000096:biosynthesis*; D010714:Phosphatidylethanolamines / Q000096:biosynthesis*; D015800:Protozoan Proteins / Q000378:metabolism; D014346:Trypanosoma brucei brucei / Q000378:metabolism*
chemical_list: D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D015800:Protozoan Proteins; C483858:phosphatidylethanolamine