Stimulation of quiescent cells by individual polypeptide growth factors is limited to one cell cycle.
Since little is known about the function of polypeptide growth factors as regulators of multiple cell cycles, we compared the ability of FGF1, PDGF-AB and serum to induce a second round of DNA synthesis in Swiss 3T3 cells previously exposed to either FGF1, PDGF-AB or serum during the first cell cycle using [14C]- and [3H]thymidine in a double labeling system to distinguish between the first and second cell cycles. Surprisingly, we observed that cells exposed to either FGF1 or PDGF-AB in the first cell cycle were unable to synthesize DNA in response to FGF1 or PDGF-AB in the second cell cycle; yet these cells responded well to serum as a second cycle mitogen. Interestingly, while cells exposed to either FGF1 or PDGF-AB in the second cycle displayed normal receptor-mediated signaling and expressed cyclin D and E, they, like senescent fibroblasts and endothelial cells, failed to express cyclin A, and the continuous exposure of cells to either FGF1 or PDGF-AB resulted in a decrease in the kinase activity of the cyclin E/cdk2 complex. In addition, an increased association of this complex was observed with p21 CIP in an FGF1-dependent manner as well as with p27 KIP in a PDGF-AB-dependent manner. Lastly, the downregulation of p21 expression using an antisense strategy was able to partially rescue the replicative response of Swiss 3T3 cells to FGF1 in the second cycle. These data suggest that (i) FGF1 and PDGF-AB may limit their mitogenic effect to a single cell cycle, (ii) entry into the second round of replication is serum dependent and (iii) the self-limiting nature of FGF1 and PDGF-AB correlates with the accumulation of the cdk inhibitors, p21 and p27, respectively.
Andreeva
Viktoria
V
Center for Molecular Medicine, Maine Medical Center Research Institute, 81 Research Drive, Scarborough, Maine 04074, USA.
Prudovsky
Igor
I
Thomas
Maciag
M
D000818:Animals; D042846:CDC2-CDC28 Kinases / Q000096:biosynthesis; D002417:Cattle; D002453:Cell Cycle / Q000187:drug effects*; D018797:Cell Cycle Proteins / Q000096:biosynthesis; D016895:Culture Media, Serum-Free; D056741:Cyclin D; D019927:Cyclin E / Q000096:biosynthesis*; D051357:Cyclin-Dependent Kinase 2; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D016213:Cyclins / Q000096:biosynthesis*; D004247:DNA / Q000096:biosynthesis*; D016220:Fibroblast Growth Factor 1 / Q000494:pharmacology*; D051379:Mice; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects; D041701:Swiss 3T3 Cells; D025521:Tumor Suppressor Proteins / Q000096:biosynthesis
C493957:Cdkn1a protein, mouse; C493961:Cdkn1b protein, mouse; D018797:Cell Cycle Proteins; D016895:Culture Media, Serum-Free; D056741:Cyclin D; D019927:Cyclin E; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D010982:Platelet-Derived Growth Factor; D025521:Tumor Suppressor Proteins; C095477:platelet-derived growth factor AB; D016220:Fibroblast Growth Factor 1; D050760:Cyclin-Dependent Kinase Inhibitor p27; D004247:DNA; D042846:CDC2-CDC28 Kinases; C495893:Cdk2 protein, mouse; D051357:Cyclin-Dependent Kinase 2