title: Two different pathways of phosphatidylcholine synthesis, the Kennedy Pathway and the Lands Cycle, differentially regulate cellular triacylglycerol storage.
abstract: BACKGROUND
  Lipids are stored within cells in lipid droplets (LDs). They consist of a core of neutral lipids surrounded by a monolayer of phospholipids, predominantly phosphatidylcholine (PC). LDs are very dynamic and can rapidly change in size upon lipid uptake or release. These dynamics require a fast adaptation of LD surface. We have recently shown that two Lands cycle PC synthesizing enyzmes, LPCAT1 and LPCAT2 can localize to the LD surface.
  
  
  RESULTS
  Here, we show that knock-down of both enzymes leads to an increase in LD size without changes in the total amount of neutral lipids, while interference with the de-novo Kennedy pathway PC biosynthesis is associated with changes in triacylglyceride synthesis. We show that function of LPCAT1 and 2 is conserved in Drosophila melanogaster by the ortholog CG32699. Furthermore we demonstrate that modulation of the LD pool by LPCAT1 influences the release of lipoprotein from liver cells.
  
  
  CONCLUSIONS
  Activity of the Kennedy pathway regulates the balance between phospholipids and neutral lipids, while the Lands cycle regulates lipid droplet size by regulating surface availability and influencing surface to volume ratio. Differences in lipid droplet size may account for differences in lipid dynamics and be relevant to understand lipid overload diseases.
authors.affiliation: Life and Medical Sciences Institute, University of Bonn, Carl-Troll-Str. 31, 53115, Bonn, Germany. christine.mossinger@ki.se.|Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, D-01307, Dresden, Germany. christine.mossinger@ki.se.
authors.forename: Christine
authors.initials: C
authors.lastname: Moessinger
authors.affiliation: Life and Medical Sciences Institute, University of Bonn, Carl-Troll-Str. 31, 53115, Bonn, Germany. s6krkliz@uni-bonn.de.
authors.forename: Kristina
authors.initials: K
authors.lastname: Klizaite
authors.affiliation: Life and Medical Sciences Institute, University of Bonn, Carl-Troll-Str. 31, 53115, Bonn, Germany. A.Steinhagen@uni-bonn.de.
authors.forename: Almut
authors.initials: A
authors.lastname: Steinhagen
authors.affiliation: Life and Medical Sciences Institute, University of Bonn, Carl-Troll-Str. 31, 53115, Bonn, Germany. massier@genzentrum.lmu.de.|Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, D-01307, Dresden, Germany. massier@genzentrum.lmu.de.
authors.forename: Julia
authors.initials: J
authors.lastname: Philippou-Massier
authors.affiliation: Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, D-01307, Dresden, Germany. shevchenko@mpi-cbg.de.
authors.forename: Andrej
authors.initials: A
authors.lastname: Shevchenko
authors.affiliation: Life and Medical Sciences Institute, University of Bonn, Carl-Troll-Str. 31, 53115, Bonn, Germany. m.hoch@uni-bonn.de.
authors.forename: Michael
authors.initials: M
authors.lastname: Hoch
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, 5230, Odense, Denmark. cse@bmb.sdu.dk.
authors.forename: Christer S
authors.initials: CS
authors.lastname: Ejsing
authors.affiliation: Life and Medical Sciences Institute, University of Bonn, Carl-Troll-Str. 31, 53115, Bonn, Germany. cthiele@uni-bonn.de.
authors.forename: Christoph
authors.initials: C
authors.lastname: Thiele
mesh_terms: D008243:1-Acylglycerophosphocholine O-Acyltransferase / Q000378:metabolism*; D000818:Animals; D045744:Cell Line, Tumor; D004331:Drosophila melanogaster; D022781:Hepatocytes / Q000378:metabolism; D006801:Humans; D050356:Lipid Metabolism; D008074:Lipoproteins / Q000378:metabolism; D010713:Phosphatidylcholines / Q000096:biosynthesis* / Q000378:metabolism; D014280:Triglycerides / Q000378:metabolism*
chemical_list: D008074:Lipoproteins; D010713:Phosphatidylcholines; D014280:Triglycerides; D008243:1-Acylglycerophosphocholine O-Acyltransferase