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The Perinuclear Endoplasmic Reticulum as the Site of Phosphatidylethanolamine Synthesis in a Model Eukaryote
Author(s) -
Buetikofer Peter,
Farine Luce
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.568.32
Subject(s) - phosphatidylethanolamine , endoplasmic reticulum , biochemistry , eukaryote , trypanosoma brucei , phospholipid , phosphatidylcholine , biology , phosphotransferase , ethanolamine , enzyme , choline , microbiology and biotechnology , chemistry , membrane , gene , genome
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, respectively. While ethanolamine and choline phosphotransferases (EPT and CPT, respectively) catalyze the last reactions in the respective pathways, choline/ethanolamine phosphotransferase shows dual specificity for both CDP‐ethanolamine and CDP‐choline as substrates 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 model eukaryote, Trypanosoma brucei , both branches of the Kennedy pathway are essential for parasite growth in culture, making T. brucei an ideal organism to study eukaryotic phospholipid synthesis. We have previously reported that EPT catalyzes the production of alk‐1‐enyl‐acyl PE molecular species while CEPT 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 EPT and CEPT enzymes in T. brucei parasites, EPT was found exclusively in a distinct area located close to but different from the nuclear membrane, which we term perinuclear ER. In contrast, CEPT was detected in the bulk ER. The different localization pattern of EPT and CEPT was confirmed by subcellular fractionation experiments in combination with enzyme activity measurements and identification of the tagged proteins by immmunoblotting.