Chang W C, Liu Y W, Ning C C, Suzuki H, Yoshimoto T, Yamamoto S
Department of Pharmacology, College of Medicine, National Cheng Kung University, Tainan, Taiwan, Republic of China.
J Biol Chem. 1993 Sep 5;268(25):18734-9.
12(S)-Hydroxyeicosatetraenoic acid is biosynthesized from arachidonic acid by the microsomal fraction of human epidermoid carcinoma A431 cells, and the microsomal 12-lipoxygenase activity is enhanced by about 2-fold by epidermal growth factor (EGF) with a 10-h lag period (Chang, W.C., Ning, C.C., Lin, M.T., and Huang, J.D. (1992) J. Biol. Chem. 267, 3657-3666). The microsomal 12-lipoxygenase in A431 cells was only 3% active with linoleic acid as compared with arachidonic acid. The enzyme was immunoprecipitated by a monoclonal antibody against human platelet 12-lipoxygenase but not by that against porcine leukocyte enzyme. A 3.1-kilobase mRNA was detected in A431 cells by Northern blot analyses using cDNA probe of human platelet 12-lipoxygenase. EGF could increase the 12-lipoxygenase mRNA level by about 2-fold with a lag period of 10 h, which was well parallel with the increase in the enzyme activity. The induction of the 12-lipoxygenase mRNA by EGF was completely blocked by 35 microM cycloheximide, if present in culture medium during EGF treatment, indicating that a de novo protein biosynthesis was essential for EGF-induced 12-lipoxygenase mRNA expression. Our data provide the first evidence for the inducibility of human 12-lipoxygenase gene expression by a growth factor.
12(S)-羟基二十碳四烯酸由人表皮样癌A431细胞的微粒体部分从花生四烯酸生物合成，表皮生长因子（EGF）可使微粒体12-脂氧合酶活性在10小时的延迟期后增强约2倍（Chang, W.C., Ning, C.C., Lin, M.T., and Huang, J.D. (1992) J. Biol. Chem. 267, 3657 - 3666）。与花生四烯酸相比，A431细胞中的微粒体12-脂氧合酶对亚油酸的活性仅为3%。该酶可被抗人血小板12-脂氧合酶的单克隆抗体免疫沉淀，但不能被抗猪白细胞酶的单克隆抗体免疫沉淀。使用人血小板12-脂氧合酶的cDNA探针通过Northern印迹分析在A431细胞中检测到一条3.1千碱基的mRNA。EGF可使12-脂氧合酶mRNA水平在10小时的延迟期后增加约2倍，这与酶活性的增加非常平行。如果在EGF处理期间培养基中存在35 microM放线菌酮，则EGF对12-脂氧合酶mRNA的诱导会被完全阻断，这表明从头进行蛋白质生物合成对于EGF诱导的12-脂氧合酶mRNA表达至关重要。我们的数据为生长因子可诱导人12-脂氧合酶基因表达提供了首个证据。
