Catalytic inactive heme oxygenase-1 protein regulates its own expression in oxidative stress
Catalytic inactive heme oxygenase-1 protein regulates its own expression in oxidative stress
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DOI：
10.1016/j.freeradbiomed.2007.11.012
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发表时间：
2008-03-01
影响因子：
7.4
通讯作者：
Dennery, Phyllis A.
中科院分区：
文献类型：
--
作者：
Lin, Qing S.;Weis, Sebastian;Dennery, Phyllis A.
血红素加氧酶-1（HO-1）催化血红素的降解并形成抗氧化剂胆色素以及信号分子一氧化碳。HO-1是可诱导的，响应于各种化学和物理应激条件，作为细胞保护分子发挥作用。因此，即使底物可用性有限，维持HO-1表达的基础水平也很重要。我们假设HO-1蛋白本身可以以正反馈的方式调节其自身的表达，并且这种正反馈在HO-1基因诱导响应氧化应激中是重要的。在培养的NIH 3 T3细胞中，HO-1 cDNA的转染或纯HO-1蛋白的细胞内递送导致荧光素酶上游15-kb HO-1启动子的激活，如通过生物发光技术观察到的，并增加HO-1 mRNA和蛋白水平。这些影响是独立的HO活性，因为HO-1的酶失活突变体形式类似地激活HO-1启动子，并且与HO抑制剂金属卟啉SnPP孵育不影响启动子激活。此外，HO-1特异性siRNA显着降低氯化血红素和氯化镉介导的HO-1诱导。此外，缺失分析表明，HO-1启动子的E1和E2远端增强子是HO-1自身调节所必需的。这些实验证明了HO-1在氧化应激中的前馈自动调节，并表明HO-1蛋白在诱导过程中起作用。我们推测，这种机制可能是有用的维持HO-1表达时，底物是有限的，也可能有助于上调其他基因，以促进细胞保护和调节细胞增殖。(c)2007年爱思唯尔公司All rights reserved.
Heme oxygenase-1 (HO-1) catalyzes the degradation of heme and forms antioxidant bile pigments as well as the signaling molecule carbon monoxide. HO-1 is inducible in response to a variety of chemical and physical stress conditions to function as a cytoprotective molecule. Therefore, it is important to maintain the basal level of HO-1 expression even when substrate availability is limited. We hypothesized that the HO-1 protein itself could regulate its own expression in a positive feedback manner, and that this positive feedback was important in the HO-1 gene induction in response to oxidative stress. In cultured NIH 3T3 cells, transfection of HO-1 cDNA or intracellular delivery of pure HO-1 protein resulted in activation of a 15-kb HO-1 promoter upstream of luciferase as visualized by bioluminescent technology and increased HO-I mRNA and protein levels. These effects were independent of HO activity because an enzymatically inactive mutant form of HO-1 similarly activated the HO-1 promoter and incubation with HO inhibitor metalloporphyrin SnPP did not affect the promoter activation. In addition, HO-1-specific siRNA significantly reduced hemin and cadmium chloride-mediated HO-1 induction. Furthermore, deletion analyses demonstrated that the E1 and E2 distal enhancers of the HO-1 promoter are required for this HO-1 autoregulation. These experiments document feed-forward autoregulation of HO-1 in oxidative stress and suggest that HO-1 protein has a role in the induction process. We speculate that this mechanism may be useful for maintaining HO-1 expression when substrate is limited and may also serve to up-regulate other genes to promote cytoprotection and to modulate cell proliferation. (c) 2007 Elsevier Inc. All rights reserved.