Abstract
Chinese hamster ovary cells were maintained in culture medium supplemented with delipidated serum to make them dependent on nonlipid components for lipid synthesis. Growth in lipid-free medium resulted in an increased flux through the CDP-choline pathway for phosphatidylcholine synthesis. The increased flux appeared to be mediated by the CTP:phosphocholine cytidylyltransferase because cellular phosphocholine levels decreased in cells grown in lipid-free medium, and both cell-free cytidylyltransferase activity and membrane-associated cytidylyltransferase activity increased in cells grown in lipid-free medium. Chinese hamster ovary cells maintained in culture medium supplemented with complete serum can grow at nearly normal rates in the presence of phospholipase C for many generations, even though the treatment enhances turnover of cellular phosphatidylcholine (R. Sleight and C. Kent (1983) J. Biol. Chem. 258, 824-830). The phospholipase C treatment, however, was toxic to cells maintained in medium supplemented with delipidated serum. Lysophosphatidylcholine protected cells from phospholipase toxicity, but did not support growth. The rate of utilization of lysophosphatidylcholine for phosphatidylcholine synthesis was about 8% of the turnover rate for phosphatidylcholine, and was not increased by phospholipase C treatment. Reconstitution of the medium with fractionated serum lipids showed that the cells required specific neutral lipids, namely, fatty acids plus cholesterol, in order to grow in the presence of phospholipase C. Either oleate or cholesterol (up to 80 microM) alone did not allow growth in phospholipase C, but a combination of these two lipids supported growth effectively.
Published Version
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