Laboratory of Biochemistry, Faculty of Pharmacy, Osaka Ohtani University, Tondabayashi, Osaka 584-8540, Japan.
Laboratory of Biochemistry, Faculty of Pharmacy, Osaka Ohtani University, Tondabayashi, Osaka 584-8540, Japan.
Chem Biol Interact. 2019 Apr 1;302:36-45. doi: 10.1016/j.cbi.2019.01.024. Epub 2019 Jan 29.
Aldose reductase (AR), a member of aldo-keto reductase family, is the rate-limiting enzyme in the polyol pathway, and is known to play a key role in the pathogenesis of diabetic complications. AR also catalyzes the reduction of reactive aldehydes, thereby detoxifying endogenous as well as xenobiotic aldehydes in various tissues. The transcription of the AR gene was previously shown to be augmented by various stimuli including osmotic and oxidative stresses. A highly conserved region composed of an antioxidant response element (ARE), AP-1 site, and tonicity responsive enhancer (TonE) has been identified within the 5'-flanking region of the AR genes of humans, rats, and mice, which we designated as the multiple stress response region (MSRR). We previously showed that the transcription factor Nrf2 activated AR transcription via ARE within MSRR. In the present study, we examined the interactions among Nrf2, c-Jun, and the TonE-binding protein (TonEBP) in the regulation of AR gene transcription. In gene reporter assays using luciferase reporter constructs containing the MSRR of the mouse AR (AKR1B3) gene with HepG2 cells, the forced expression of Nrf2 or TonEBP significantly increased promoter activity. The synergistic augmentation of promoter activity was observed when Nrf2 and TonEBP were co-introduced. On the other hand, the co-expression of c-Jun repressed promoter activation by Nrf2 and TonEBP. The mutation of the AP-1 site within MSRR did not affect the repressive effects of c-Jun, while the introduction of truncated c-Jun proteins lacking the leucine zipper domain no longer suppressed Nrf2-or TonEBP-mediated transactivation, suggesting that c-Jun repressed promoter activity independently of the AP-1 site and that interactions with protein factors via the leucine zipper domain were necessary for its negative effects on Nrf2 and TonEBP. These results indicate that AR promoter activity is cooperatively regulated by multiple transcription factors via MSRR.
醛糖还原酶（AR）是醛酮还原酶家族的成员，是多元醇途径中的限速酶，已知在糖尿病并发症的发病机制中起关键作用。AR 还催化反应性醛的还原，从而解毒各种组织中的内源性和外源性醛。先前已经表明，AR 基因的转录可被各种刺激物增强，包括渗透和氧化应激。在人类、大鼠和小鼠的 AR 基因 5'侧翼区，已经鉴定出一个高度保守的区域，由抗氧化反应元件（ARE）、AP-1 位点和渗透压反应增强子（TonE）组成，我们将其命名为多应激反应区（MSRR）。我们之前表明，转录因子 Nrf2 通过 MSRR 中的 ARE 激活 AR 转录。在本研究中，我们研究了 Nrf2、c-Jun 和 TonE 结合蛋白（TonEBP）在调节 AR 基因转录中的相互作用。在使用包含小鼠 AR（AKR1B3）基因 MSRR 的荧光素酶报告基因构建体的基因报告测定中，Nrf2 或 TonEBP 的强制表达显著增加了启动子活性。当 Nrf2 和 TonEBP 共同引入时，观察到启动子活性的协同增强。另一方面，c-Jun 的共表达抑制了 Nrf2 和 TonEBP 对启动子激活的作用。MSRR 内的 AP-1 位点的突变不影响 c-Jun 的抑制作用，而缺乏亮氨酸拉链结构域的截断 c-Jun 蛋白的引入不再抑制 Nrf2 或 TonEBP 介导的转录激活，表明 c-Jun 独立于 AP-1 位点抑制启动子活性，并且通过亮氨酸拉链结构域与蛋白因子的相互作用是其对 Nrf2 和 TonEBP 产生负向作用所必需的。这些结果表明，AR 启动子活性通过 MSRR 被多个转录因子协同调节。
