Expression of human choline kinase in NIH 3T3 fibroblasts increases the mitogenic potential of insulin and insulin-like growth factor I.
In mammalian cells, growth factors, oncogenes, and carcinogens stimulate phosphocholine (PCho) synthesis by choline kinase (CK), suggesting that PCho may regulate cell growth. To validate the role of PCho in mitogenesis, we determined the effects of insulin, insulin-like growth factor I (IGF-I), and other growth factors on DNA synthesis in NIH 3T3 fibroblast sublines highly expressing human choline kinase (CK) without increasing phosphatidylcholine synthesis. In serum-starved CK expressor cells, insulin and IGF-I stimulated DNA synthesis, p70 S6 kinase (p70 S6K) activity, phosphatidylinositol 3-kinase (PI3K) activity, and activating phosphorylation of p42/p44 mitogen-activated protein kinases (MAPK) to greater extents than in the corresponding vector control cells. Furthermore, the CK inhibitor hemicholinium-3 (HC-3) inhibited insulin- and IGF-I-induced DNA synthesis in the CK overexpressors, but not in the vector control cells. The results indicate that high cellular levels of PCho potentiate insulin- and IGF-I-induced DNA synthesis by MAPK- and p70 S6K-regulated mechanisms.
Chung
T
T
Department of Biochemistry, Yeungnam University, Keongsan, South Korea.
Huang
J S
JS
Mukherjee
J J
JJ
Crilly
K S
KS
Kiss
Z
Z
D016475:3T3 Cells; D000818:Animals; D002250:Carbon Radioisotopes; D002797:Choline Kinase / Q000235:genetics*; D018678:Cholinergic Agents / Q000494:pharmacology; D003001:Cloning, Molecular; D004247:DNA / Q000096:biosynthesis; D005346:Fibroblast Growth Factors / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D015971:Gene Expression Regulation, Enzymologic; D006426:Hemicholinium 3 / Q000494:pharmacology; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007328:Insulin / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D051379:Mice; D008934:Mitogens / Q000494:pharmacology*; D010713:Phosphatidylcholines / Q000096:biosynthesis; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology; D014316:Tritium
D002250:Carbon Radioisotopes; D018678:Cholinergic Agents; D007004:Hypoglycemic Agents; D007328:Insulin; D008934:Mitogens; D010713:Phosphatidylcholines; D010982:Platelet-Derived Growth Factor; D014316:Tritium; D006426:Hemicholinium 3; D005346:Fibroblast Growth Factors; D007334:Insulin-Like Growth Factor I; D004247:DNA; D019869:Phosphatidylinositol 3-Kinases; D002797:Choline Kinase; D019893:Ribosomal Protein S6 Kinases