Uehara T, Chihara T, Tokumitsu Y, Nomura Y
Department of Pharmacology, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
Biochim Biophys Acta. 1991 Jan 17;1088(1):41-6. doi: 10.1016/0167-4781(91)90151-b.
Following the differentiation of 3T3-L1 fibroblasts by insulin/dexamethasone/methylisobutylxanthine, marked increases in cAMP levels by isoproterenol but not forskolin and in 2-deoxyglucose uptake by insulin occurred. Pertussis toxin-pretreatment prior to addition of insulin/dexamethasone/methylisobutylxanthine and exposure of cells to pertussis toxin during differentiation attenuated glycerophosphate dehydrogenase activity as a differentiation marker enzyme and the responses to isoproterenol and insulin by approximately 50% of those in pertussis toxin-untreated cells. On the other hand, insulin/dexamethasone/methylisobutylxanthine caused induction of c-fos proto-oncogene in confluent 3T3-L1 fibroblasts. This induction was also reduced in pertussis toxin-pretreated cells. These results suggested that pertussis toxin-sensitive GTP-binding protein(s) is involved in expression of c-fos mRNA accompanied by differentiation. In addition, accumulation of c-fos mRNA by insulin/dexamethasone/methylisobutylxanthine was enhanced in protein kinase C-depleted cells pretreated with phorbol 12-myristate 13-acetate, indicating that protein kinase C may negatively regulate c-fos expression induced by insulin/dexamethasone/methylisobutylxanthine.
在用胰岛素/地塞米松/甲基异丁基黄嘌呤诱导3T3-L1成纤维细胞分化后，异丙肾上腺素可使细胞内环磷酸腺苷（cAMP）水平显著升高，而福斯高林则无此作用；同时，胰岛素可使2-脱氧葡萄糖摄取量增加。在添加胰岛素/地塞米松/甲基异丁基黄嘌呤之前用百日咳毒素预处理细胞，以及在分化过程中使细胞暴露于百日咳毒素，可使作为分化标志物酶的甘油磷酸脱氢酶活性以及对异丙肾上腺素和胰岛素的反应减弱，约为未用百日咳毒素处理细胞的50%。另一方面，胰岛素/地塞米松/甲基异丁基黄嘌呤可诱导汇合的3T3-L1成纤维细胞中c-fos原癌基因的表达。在经百日咳毒素预处理的细胞中，这种诱导作用也减弱。这些结果表明，百日咳毒素敏感的GTP结合蛋白参与了伴随分化的c-fos mRNA的表达。此外，在用佛波酯12-肉豆蔻酸酯13-乙酸酯预处理的蛋白激酶C缺失的细胞中，胰岛素/地塞米松/甲基异丁基黄嘌呤诱导的c-fos mRNA积累增强，这表明蛋白激酶C可能对胰岛素/地塞米松/甲基异丁基黄嘌呤诱导的c-fos表达起负调节作用。
