Sheng H, Williams C S, Shao J, Liang P, DuBois R N, Beauchamp R D
Department of Surgery,the Vanderbilt Cancer Center, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA.
J Biol Chem. 1998 Aug 21;273(34):22120-7. doi: 10.1074/jbc.273.34.22120.
Elevated cyclooxygenase-2 (COX-2) expression and activity have been observed in several different transformed cell types that express mutated ras genes. To investigate the mechanism of increased COX-2 expression following Ras-mediated transformation, Rat-1:iRas cell line was transfected with an Ha-RasVal-12 cDNA expression vector that is under the transcriptional control of the lac operon and is inducible with isopropyl-1-thio-beta-D-galactopyranoside (IPTG). IPTG treatment caused parallel increases in the levels of Ha-Ras and COX-2 proteins in Rat-1:iRas cells. The increased expression of COX-2 was accompanied by increased prostaglandin E2 production. Selective inhibition of COX-2 activity suppressed the production of prostaglandin E2 by >90% but did not alter the progress of the morphological transformation. The level of COX-2 mRNA was up-regulated by activated Ha-Ras. Induction of Ras increased the transcription of COX-2 by 44.3 +/- 10.1% and increased the half-life of COX-2 mRNA by approximately 3.5-fold. A specific mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) inhibitor (PD 98059) caused a delay in both the activation of ERK1/2 and the induction of COX-2 in IPTG-induced Rat-1:iRas cells. Inhibition of ERK activity by PD 98059 also suppressed the induction of COX-2 by epidermal growth factor in intestinal epithelial cells and significantly reduced the expression of COX-2 in Ha-Ras-transformed rat intestinal epithelial cells. ERK activity appears to be required for induction of COX-2 by Ras.
在几种表达突变型ras基因的不同转化细胞类型中，已观察到环氧合酶-2（COX-2）的表达和活性升高。为了研究Ras介导的转化后COX-2表达增加的机制，将Rat-1:iRas细胞系用受乳糖操纵子转录控制且可被异丙基-1-硫代-β-D-吡喃半乳糖苷（IPTG）诱导的Ha-RasVal-12 cDNA表达载体进行转染。IPTG处理导致Rat-1:iRas细胞中Ha-Ras和COX-2蛋白水平平行增加。COX-2表达的增加伴随着前列腺素E2产生的增加。COX-2活性的选择性抑制使前列腺素E2的产生抑制>90%，但未改变形态转化的进程。活化的Ha-Ras上调了COX-2 mRNA的水平。Ras的诱导使COX-2的转录增加了44.3±10.1%，并使COX-2 mRNA的半衰期增加了约3.5倍。一种特异性丝裂原活化蛋白激酶/细胞外信号调节激酶（ERK）抑制剂（PD 98059）在IPTG诱导的Rat-1:iRas细胞中导致ERK1/2的活化和COX-2的诱导均延迟。PD 98059对ERK活性的抑制也抑制了表皮生长因子在肠上皮细胞中对COX-2的诱导，并显著降低了Ha-Ras转化的大鼠肠上皮细胞中COX-2的表达。ERK活性似乎是Ras诱导COX-2所必需的。
