c-Ha-ras oncogene expression increases choline uptake, CTP: phosphocholine cytidylyltransferase activity and phosphatidylcholine biosynthesis in the immortalized human keratinocyte cell line HaCaT.
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 described as a target of ras-transfection in fibroblasts was unaffected.
Geilen
C C
CC
Department of Dermatology, Univeristy Medical Center Benjamin Franklin, Free University of Berlin, Germany.
Wieder
T
T
Boremski
S
S
Wieprecht
M
M
Orfanos
C E
CE
D002455:Cell Division; D002460:Cell Line; D002794:Choline / Q000378:metabolism*; D019916:Choline-Phosphate Cytidylyltransferase; D004075:Diglycerides / Q000032:analysis; D015971:Gene Expression Regulation, Enzymologic; D011905:Genes, ras; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009713:Nucleotidyltransferases / Q000096:biosynthesis*; D019301:Oleic Acid; D009829:Oleic Acids / Q000494:pharmacology; D010713:Phosphatidylcholines / Q000096:biosynthesis*; D014162:Transfection
D004075:Diglycerides; D009829:Oleic Acids; D010713:Phosphatidylcholines; D019301:Oleic Acid; D009713:Nucleotidyltransferases; D019916:Choline-Phosphate Cytidylyltransferase; D002794:Choline