Lysophosphatidic acid induces early growth response gene 1 expression in vascular smooth muscle cells - CRE and SRE mediate the transcription
Lysophosphatidic acid induces early growth response gene 1 expression in vascular smooth muscle cells - CRE and SRE mediate the transcription
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DOI：
10.1161/01.atv.0000214980.90567.b5
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发表时间：
2006-05-01
影响因子：
8.7
通讯作者：
Xu, XM
中科院分区：
文献类型：
--
作者：
Cui, MZ;Laag, E;Xu, XM
目的：溶血磷脂酸（LPA）是一种有效的生物活性磷脂，是氧化低密度脂蛋白的一个组成部分。早期生长反应基因-1 （Egr-1）是一个重要的转录因子，调控一系列与血管疾病有关的基因的表达。LPA是否以及如何调节Egr-1基因的转录机制尚不清楚，本研究将对此进行研究。方法和结果-我们发现LPA显著诱导主动脉平滑肌细胞（SMCs）中Egr-1 mRNA和蛋白表达。RNA稳定性和核运行分析显示，lpa诱导的Egr-1基因表达在转录水平上受到控制。报告基因分析表明，Egr-1启动子的- 141至+ 20nt区域含有调控元件。电泳迁移位移分析显示，在LPA的作用下，CREB和SRF对Egr-1启动子的CRE和SRE基序的dna结合活性显著升高。结合活性的增加取决于CREB和SRF的磷酸化。对一系列缺失或突变的Egr-1启动子报告基因结构进行荧光素酶测定，以及显性阴性CREB转染分析显示，lpa诱导的Egr-1基因表达最大化需要Egr-1启动子中的2个CRE位点和2个近端SRE位点。结论-我们的数据显示LPA通过转录因子CREB和SRF调节Egr-1的表达。这些结果确立了CREB在介导lpa诱导的基因表达中的新作用。我们的研究结果表明，LPA水平升高可能通过激活调控一系列致动脉粥样硬化基因的Egr-1，从而加剧动脉粥样硬化病变。
Objective - Lysophosphatidic acid (LPA), one component of oxidized low-density lipoprotein, is a potent bioactive phospholipid. Early growth response gene-1 (Egr-1), an important transcription factor, regulates expression of an array of genes involved in vascular diseases. Whether and how LPA regulates the transcriptional machinery of Egr-1 gene is unknown and is addressed in this study.Method and Results - We found that LPA markedly induces Egr-1 mRNA and protein in aortic smooth muscle cells (SMCs). RNA stability and nuclear run-on assays reveal that LPA-induced Egr-1 gene expression is controlled at the transcriptional level. Reporter gene analyses have shown that the - 141 to + 20 nt region of the Egr-1 promoter contains regulatory elements. Electrophoretic mobility shift assays reveal that the DNA-binding activities of both CREB and SRF to the CRE and SRE motifs of the Egr-1 promoter are markedly elevated in response to LPA. The increased binding activity depends on the phosphorylation of CREB and SRF. Luciferase assays of a series of deleted or mutated Egr-1 promoter-reporter gene constructs, along with dominant negative CREB transfection analysis revealed that the 2 CRE sites and the 2 proximal SRE sites in the Egr-1 promoter are required for maximal LPA-induced Egr-1 gene expression.Conclusions - Our data reveal that LPA regulates Egr-1 expression via transcription factors CREB and SRF. These results establish a novel role for CREB in mediating LPA-induced gene expression. Our results imply that elevated LPA levels may, through activation of Egr-1, which regulates an array of atherogenic genes, exacerbate atheromatous lesions.