title: Control of membrane phosphatidylcholine biosynthesis by diacylglycerol levels in neuronal cells undergoing neurite outgrowth.
abstract: Phospholipids are the major components of cell membranes and are required for cellular growth. We studied membrane phosphatidylcholine (PtdCho) biosynthesis in neuronal cells undergoing neurite outgrowth, by using PC12 cells as a model system. When neurite outgrowth was induced by exposing PC12 cells to nerve growth factor for 2 and 4 days, the amounts of [14C]choline incorporated into [14C]phosphatidylcholine per cell (i.e., per DNA) increased approximately 5- and 10-fold, respectively, as compared with control cells, reflecting increases in the rate of PtdCho biosynthesis. [14C]choline uptake was not affected. Analysis of the three major PtdCho biosynthetic enzymes showed that the activity of CDPcholine:1,2-diacylglycerol cholinephosphotransferase was increased by approximately 50% after nerve growth factor treatment, but the activities of choline kinase or choline-phosphate cytidylyltransferase were unaltered; the cholinephosphotransferase displayed a high Km value ( approximately 1,200 microM) for diacylglycerol. Moreover, free cellular diacylglycerol levels increased by approximately 1.5- and 4-fold on the second and fourth days, respectively. These data indicate that PtdCho biosynthesis is enhanced when PC12 cells sprout neurites, and the enhancement is mediated primarily by changes in cholinephosphotransferase activity and its saturation with diacylglycerol. This suggests a novel regulatory role for diacylglycerol in membrane phospholipid biosynthesis.
authors.affiliation: Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: W
authors.initials: W
authors.lastname: Araki
authors.forename: R J
authors.initials: RJ
authors.lastname: Wurtman
mesh_terms: D000818:Animals; D004075:Diglycerides / Q000096:biosynthesis*; D004789:Enzyme Activation; D008563:Membrane Lipids / Q000096:biosynthesis*; D009414:Nerve Growth Factors / Q000494:pharmacology; D016501:Neurites / Q000187:drug effects / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D019884:Nitrogenous Group Transferases / Q000378:metabolism; D016716:PC12 Cells; D010713:Phosphatidylcholines / Q000096:biosynthesis*; D051381:Rats
chemical_list: D004075:Diglycerides; D008563:Membrane Lipids; D009414:Nerve Growth Factors; D010713:Phosphatidylcholines; D019884:Nitrogenous Group Transferases; C052328:glycerophosphorylcholine synthetase