Buchou T, Charollais R H, Fagot D, Mester J
INSERM U55, Paris, France.
Exp Cell Res. 1989 May;182(1):129-43. doi: 10.1016/0014-4827(89)90285-1.
Mitogenic effects of agents activating either the protein kinase C (PDGF; phorbol esters) or the insulin-like growth factor 1 (IGF1)-receptor pathway were studied in quiescent chemically transformed mouse fibroblasts (BP-A31), by evaluating the rate of [3H]thymidine incorporation. Each of these pathways alone was found to be sufficient to sustain progression through the entire cell division cycle. The mitogenic activity of phorbol 12-myristate 13-acetate (PMA) but not that of insulin was blocked by staurosporine (an inhibitor of protein kinase C), in support of the notion that protein kinase C activation was required for the PMA-induced cell cycle progression. The mitogenic effects of PMA were potentiated by cycloheximide pretreatment, and they were abolished by 3-isobutyl-1-methyl xanthine (IBMX; a cyclic nucleotide phosphodiesterase inhibitor). PDGF (known to activate the phospholipase C-protein kinase C pathway) also displayed mitogenic activity in the cycloheximide-pretreated BP-A31 cells, and its effects were prevented by IBMX. In contrast, the mitogenic effects of insulin (at concentrations where it activates the IGF1 receptor) or of IGF1 neither were notably influenced by cycloheximide pretreatment nor were inhibited by IBMX (in the presence of IBMX, the onset of S-phase was delayed by several hours). The expression of the c-fos gene was absent at quiescence; its induction by growth factors was not proportional to their mitogenic potency. Thus, c-fos expression was strongly induced by PMA but only weakly by insulin. IBMX was a powerful inducer of c-fos gene expression but caused a decrease in the level of c-myc mRNA.
通过评估[3H]胸苷掺入率，研究了激活蛋白激酶C（血小板衍生生长因子；佛波酯）或胰岛素样生长因子1（IGF1）受体途径的试剂对静止的化学转化小鼠成纤维细胞（BP - A31）的促有丝分裂作用。发现单独的这些途径中的每一个都足以维持整个细胞分裂周期的进程。佛波醇12 - 肉豆蔻酸酯13 - 乙酸酯（PMA）的促有丝分裂活性而非胰岛素的促有丝分裂活性被星形孢菌素（蛋白激酶C的抑制剂）阻断，这支持了蛋白激酶C激活是PMA诱导的细胞周期进程所必需的这一观点。PMA的促有丝分裂作用通过环己酰亚胺预处理得到增强，并且被3 - 异丁基 - 1 - 甲基黄嘌呤（IBMX；一种环核苷酸磷酸二酯酶抑制剂）消除。血小板衍生生长因子（已知可激活磷脂酶C - 蛋白激酶C途径）在环己酰亚胺预处理的BP - A31细胞中也表现出促有丝分裂活性，并且其作用被IBMX阻止。相比之下，胰岛素（在其激活IGF1受体的浓度下）或IGF1的促有丝分裂作用既未受到环己酰亚胺预处理的显著影响，也未被IBMX抑制（在存在IBMX的情况下，S期的开始延迟了几个小时）。c - fos基因的表达在静止期不存在；其由生长因子诱导与它们的促有丝分裂效力不成比例。因此，c - fos表达被PMA强烈诱导，但仅被胰岛素微弱诱导。IBMX是c - fos基因表达的强力诱导剂，但导致c - myc mRNA水平下降。
