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A more recent version of this article appeared on August 1, 2004

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J. Lipid Res., doi:10.1194/jlr.M400079-JLR200
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Submitted on February 25, 2004
Revised on May 21, 2004
Accepted on May 27, 2004

Phosphatidylcholine deficiency up-regulates enzymes of triacylglycerol metabolism in CHO cells

J. Matías Caviglia, I. Nelva T. de Gómez Dumm, Rosalind A. Coleman, and R. Ariel Igal

Instituto de Investigaciones Bioquímicas de La Plata, La Plata, Buenos Aires 1900

Corresponding Author: aigal{at}atlas.med.unlp.edu.ar

We studied the regulation of triacylglycerol metabolism by phosphatidylcholine in CHO MT58 cells, which are deficient in phosphatidylcholine synthesis because of a temperature-sensitive CTP:phosphocholine cytidylyltransferase. At the permissive growth temperature (34°C), these cells contained 49% less triacylglycerol and 30% less phosphatidylcholine than wild type CHO K1 cells. Treatment with dipalmitoylphosphatidylcholine normalized both the phosphatidylcholine and triacylglycerol levels. Despite low triacylglycerol levels, the incorporation of [14C]oleate into triacylglycerol was increased in CHO MT58 cells. The in vitro de novo synthesis of triacylglycerol and the activity of diacylglycerol acyltransferase were 90% and 34% higher, respectively. Two other key enzyme activities in triacylglycerol synthesis, acyl-CoA synthetase and mitochondrial glycerol-3-phosphate acyltransferase increased 48% and 2-fold, respectively, and mitochondrial glycerol-3-phosphate acyltransferase mRNA increased ~4-fold. Additionally, triacylglycerol hydrolysis was accelerated in CHO MT58 cells and in vitro lipolytic activity increased 68%. These studies suggest that a homeostatic mechanism increases triacylglycerol synthesis and recycling in response to phosphatidylcholine deficiency. Triacylglycerol recycling produces diacylglycerol and fatty acids that can be substrates for de novo phosphatidylcholine synthesis and for lysophosphatidylcholine acylation. In CHO MT58 cells, in which de novo phosphatidylcholine synthesis is blocked, lysophosphatidylcholine acylation with fatty acid originating from triacylglycerol may represent the main pathway for generating phosphatidylcholine.


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S. Jackowski and P. Fagone
CTP:Phosphocholine Cytidylyltransferase: Paving the Way from Gene to Membrane
J. Biol. Chem., January 14, 2005; 280(2): 853 - 856.
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