Calcineurin is essential for DNA synthesis in Swiss 3T3 fibroblasts.
DNA synthesis was measured 16 h after stimulation of Swiss 3T3 fibroblasts in the resting phase with various growth factors (platelet-derived growth factor, fibroblast growth factor, lysophosphatidic acid and thrombin). When extracellular Ca2+ was chelated by EGTA, or when the influx of Ca2+ from outside to inside the cell was blocked by cobalt, DNA synthesis was completely inhibited. As there was no effect whatsoever on DNA synthesis when Ca2+ was chelated, or when the influx of Ca2+ was blocked up to the first 4 h after growth stimulation, it was concluded that, at an early stage, Ca2+ influx from outside to inside the cell is not related to the transition from the G1 to the S phase. A Ca2+/calmodulin-dependent protein kinase II inhibitor (KN-62) had no effect on DNA synthesis. However, cyclosporin A and FK-506, which are inhibitors of Ca2+/calmodulin-dependent protein phosphatase 2B (calcineurin), markedly inhibited DNA synthesis stimulated by all of the growth factors. These results indicate that calcineurin plays a role, not only in activation of T-cells of the immune system in the initial phase, but also in DNA synthesis in fibroblasts. It was concluded that Ca2+ influx from outside to inside the cell during the mid-to-late G1 phase, followed by calcineurin activation, is essential as a mechanism of growth signal transduction.
Tomono
M
M
Department of Biochemistry, Sakura Hospital, Toho University School of Medicine, Tokyo, Japan.
Toyoshima
K
K
Ito
M
M
Amano
H
H
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000031:analogs & derivatives*; D016475:3T3 Cells; D000818:Animals; D019703:Calcineurin; D002118:Calcium / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D002148:Calmodulin-Binding Proteins / Q000502:physiology*; D002470:Cell Survival / Q000187:drug effects; D016572:Cyclosporine / Q000494:pharmacology; D004261:DNA Replication / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism; D005346:Fibroblast Growth Factors / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D008246:Lysophospholipids / Q000494:pharmacology; D051379:Mice; D010749:Phosphoprotein Phosphatases / Q000502:physiology*; D010879:Piperazines / Q000494:pharmacology; D015398:Signal Transduction; D016559:Tacrolimus / Q000494:pharmacology
D002148:Calmodulin-Binding Proteins; D004791:Enzyme Inhibitors; D007546:Isoquinolines; D008246:Lysophospholipids; D010879:Piperazines; D005346:Fibroblast Growth Factors; C063302:KN 62; D016572:Cyclosporine; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019703:Calcineurin; D010749:Phosphoprotein Phosphatases; D002118:Calcium; D016559:Tacrolimus