Enhanced expression and activation of CTP:phosphocholine cytidylyltransferase beta2 during neurite outgrowth.
During differentiation neurons increase phospholipid biosynthesis to provide new membrane for neurite growth. We studied the regulation of phosphatidylcholine (PC) biosynthesis during differentiation of two neuronal cell lines: PC12 cells and Neuro2a cells. We hypothesized that in PC12 cells nerve growth factor (NGF) would up-regulate the activity and expression of the rate-limiting enzyme in PC biosynthesis, CTP:phosphocholine cytidylyltransferase (CT). During neurite outgrowth, NGF doubled the amount of cellular PC and CT activity. CTbeta2 mRNA increased within 1 day of NGF application, prior to the formation of visible neurites, and continued to increase during neurite growth. When neurites retracted in response to NGF withdrawal, CTbeta2 mRNA, protein, and CT activity decreased. NGF specifically activated CTbeta2 by promoting its translocation from cytosol to membranes. In contrast, NGF did not alter CTalpha expression or translocation. The increase in both CTbeta2 mRNA and CT activity was inhibited by U0126, an inhibitor of mitogen-activated kinase/extracellular signal-regulated kinase kinase 1/2 (MEK1/2). In Neuro2a cells, retinoic acid significantly increased CT activity (by 54%) and increased CTbeta2 protein, coincident with neurite outgrowth but did not change CTalpha expression. Together, these data suggest that the CTbeta2 isoform of CT is specifically up-regulated and activated during neuronal differentiation to increase PC biosynthesis for growing neurites.
Carter
Jodi M
JM
Canadian Institutes of Health Research Group on the Molecular and Cell Biology of Lipids, Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2S2, Canada.
Waite
Kristin A
KA
Campenot
Robert B
RB
Vance
Jean E
JE
Vance
Dennis E
DE
D000818:Animals; D002070:Butadienes / Q000494:pharmacology; D002454:Cell Differentiation; D002462:Cell Membrane / Q000201:enzymology; D019916:Choline-Phosphate Cytidylyltransferase / Q000235:genetics* / Q000378:metabolism*; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015870:Gene Expression; D007527:Isoenzymes / Q000235:genetics* / Q000378:metabolism*; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors; D020932:Nerve Growth Factor / Q000008:administration & dosage; D016501:Neurites / Q000502:physiology* / Q000648:ultrastructure; D009447:Neuroblastoma; D009474:Neurons / Q000648:ultrastructure*; D009570:Nitriles / Q000494:pharmacology; D016716:PC12 Cells; D010713:Phosphatidylcholines / Q000096:biosynthesis; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014212:Tretinoin / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D002070:Butadienes; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D009570:Nitriles; D010713:Phosphatidylcholines; D012333:RNA, Messenger; C113580:U 0126; D014212:Tretinoin; D020932:Nerve Growth Factor; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; C482127:Map2k1 protein, mouse; D020929:Mitogen-Activated Protein Kinase Kinases; D019916:Choline-Phosphate Cytidylyltransferase