c-Ha-ras oncogene expression increases choline uptake,CTP:prosphocholine cytidylyltransferase activity and phosphatidylcholine biosynthesis in the immortalized human keratinocyte cell line HaCaT |
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Institution: | 1. Department of Internal Medicine IV, Heidelberg University Hospital, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany;2. Institute of Clinical Chemistry and Laboratory Medicine, University Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany;1. Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN 55905, United States of America;2. Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea |
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Abstract: | The effect of c-Ha-ras transfection on phosphatidylcholine biosynthesis of the keratinocyte cell line HaCaT was investigated. It was shown that ras-transfection caused a 3-fold increase of choline incorporation into phosphatidylcholine. By investigating the mechanisms underlying this phenomenon, two targets were obtained. First, the choline uptake was elevated by 2-fold in ras-transfected HaCaT cells as compared with untransfected HaCaT cells, and second, the activity of the rate-limiting enzyme of phosphatidylcholine biosynthesis, CTP:phosphocholine cytidylyltransferase, was increased by 43%. Stimulation of HaCaT cells and ras-transfected HaCaT cells with oleate revealed that the increased activity of cytidylyltransferase might be due to a higher level of enzyme. In these experiments, a 75% increase of the specific activity of fully stimulated, membrane-bound cytidylyltransferase was found in ras-transfected HaCaT cells. Choline kinase which has been previously descrived as a target of ras-transfection in fibroblasts was unaffected. |
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