ATP-dependent choline phosphate-induced mitogenesis in fibroblasts involves activation of pp70 S6 kinase and phosphatidylinositol 3'-kinase through an extracellular site. Synergistic mitogenic effects of choline phosphate and sphingosine 1-phosphate
| Autor: | T, Chung, K S, Crilly, W H, Anderson, J J, Mukherjee, Z, Kiss |
|---|---|
| Rok vydání: | 1997 |
| Předmět: |
Phosphorylcholine
Polyenes Protein Serine-Threonine Kinases Transfection Models Biological Phospholipases A Mice Phosphatidylinositol 3-Kinases Adenosine Triphosphate Sphingosine Animals Insulin Enzyme Inhibitors Sirolimus Ribosomal Protein S6 Kinases Drug Synergism 3T3 Cells DNA Recombinant Proteins Androstadienes Enzyme Activation Kinetics Phosphotransferases (Alcohol Group Acceptor) Calcium-Calmodulin-Dependent Protein Kinases Harvey murine sarcoma virus Lysophospholipids Wortmannin Cell Division Immunosuppressive Agents Thymidine |
| Zdroj: | The Journal of biological chemistry. 272(5) |
| ISSN: | 0021-9258 |
| Popis: | In serum-starved NIH 3T3 clone 7 fibroblasts, choline phosphate (ChoP) (0.5-1 mM) and insulin synergistically stimulate DNA synthesis. Here we report that ATP also greatly enhanced the mitogenic effects of ChoP (0.1-1 mM) both in the absence and presence of insulin; maximal potentiating effects required 50-100 microM ATP. The co-mitogenic effects of ATP were mimicked by adenosine 5'-O-(3-thiotriphosphate), adenosine 5'-O-(2-thiodiphosphate), ADP, and UTP, but not by AMP or adenosine, indicating the mediatory role of a purinergic P2 receptor. Externally added ChoP acted on DNA synthesis without its detectable uptake into fibroblasts, indicating that ChoP can be a mitogen only if it is released from cells. Extracellular ATP (10-100 microM) induced extensive release of ChoP from fibroblasts. ChoP had negligible effects, even in the presence of ATP or insulin, on the activity state of p42/p44 mitogen-activated protein kinases, while in combination these agents stimulated the activity of phosphatidylinositol 3'-kinase (PI 3'-kinase). Expression of a dominant negative mutant of the p85 subunit of PI 3'-kinase or treatments with the PI 3'-kinase inhibitor wortmannin only partially (approximately 40-50%) reduced the combined effects of ChoP, ATP, and insulin on DNA synthesis; in contrast, the pp70 S6 kinase inhibitor rapamycin almost completely inhibited these effects. ATP and insulin also potentiated, while rapamycin strongly inhibited, the mitogenic effects of sphingosine 1-phosphate (S1P). Furthermore, even maximally effective concentrations of ChoP and S1P synergistically stimulated DNA synthesis. The results indicate that in the presence of extracellular ATP and/or S1P, ChoP induces mitogenesis through an extracellular site by mechanisms involving the activation of pp70 S6 kinase and, to a lesser extent, PI 3'-kinase. |
| Databáze: | OpenAIRE |
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