Fibulin-5 Is Up-regulated by Hypoxia in Endothelial Cells through a Hypoxia-inducible Factor-1 (HIF-1α)-dependent Mechanism
Fibulin-5 Is Up-regulated by Hypoxia in Endothelial Cells through a Hypoxia-inducible Factor-1 (HIF-1α)-dependent Mechanism
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DOI：
10.1074/jbc.m110.162917
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发表时间：
2011-03-04
影响因子：
4.8
通讯作者：
Rodriguez, Cristina
中科院分区：
文献类型：
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作者：
Guadall, Anna;Orriols, Mar;Rodriguez, Cristina
缺氧调节基因表达并影响内皮细胞生物学的多个方面。纤维蛋白-5（FBLN 5）是弹性纤维组装和血管发生所必需的细胞外基质蛋白，其参与血管重塑并控制内皮细胞粘附、运动和增殖。在这种情况下，我们的目的是分析FBLN 5调节缺氧内皮细胞。缺氧（1%O-2）以时间依赖的方式增加内皮细胞FBLN 5 mRNA的表达。在缺氧24小时后达到最大诱导（类似于2.5倍）。这种作用导致细胞内和细胞外FBLN 5蛋白水平的增加。在缺氧细胞中观察到的FBLN 5 mRNA水平的增加被PI 3 K/Akt/mTOR途径的抑制剂（LY 294002和雷帕霉素）阻断，并被二甲基草醛甘氨酸模拟，其防止脯氨酸羟化酶介导的HIF-1 α降解。HIF-1 α的沉默完全阻止了缺氧诱导的FBLN 5上调。因此，缺氧和HIF-1 α过表达都增加了FBLN 5的转录活性。系列启动子缺失和突变研究揭示了位于-78 bp处的推定缺氧反应元件（HRE）的参与。事实上，EMSA和ChIP检测表明，在缺氧细胞中，HIF-1与该位点的结合增加。有趣的是，在暴露于缺氧的培养物中经历细胞凋亡的内皮细胞的速率在FBLN 5敲除细胞中增加，表明缺氧诱导的FBLN 5表达有助于保持细胞存活。这些结果提供了证据表明，HIF-1信号转导的基础上的FBLN 5表达的增加引起的缺氧在内皮细胞中，并表明FBLN 5诱导可能参与适应性生存反应的内皮细胞缺氧。
Hypoxia modulates gene expression and affects multiple aspects of endothelial cell biology. Fibulin-5 (FBLN5) is an extracellular matrix protein essential for elastic fiber assembly and vasculogenesis that participates in vascular remodeling and controls endothelial cell adhesion, motility, and proliferation. In this context, we aimed to analyze FBLN5 regulation by hypoxia in endothelial cells. Hypoxia (1% O-2) increased FBLN5 mRNA levels in endothelial cells in a time-dependent manner. Maximal induction (similar to 2.5-fold) was achieved after 24 h of hypoxia. This effect paralleled an increase in both intracellular and extracellular FBLN5 protein levels. The increase in FBLN5 mRNA levels observed in hypoxic cells was blocked by inhibitors of the PI3K/Akt/mTOR pathway (LY294002 and rapamycin) and mimicked by dimethyl oxal glycine, which prevents proline hydroxylase-mediated degradation of HIF-1 alpha. Silencing of HIF-1 alpha completely prevented hypoxia-induced FBLN5 up-regulation. Accordingly, both hypoxia and HIF-1 alpha overexpression increased FBLN5 transcriptional activity. Serial promoter deletion and mutagenesis studies revealed the involvement of a putative hypoxia response element (HRE) located at -78 bp. In fact, EMSA and ChIP assays demonstrated increased HIF-1 binding to this site in hypoxic cells. Interestingly, the rate of endothelial cells undergoing apoptosis in cultures exposed to hypoxia increased in FBLN5 knockdown cells, suggesting that hypoxia-induced FBLN5 expression contributes to preserve cell survival. These results provide evidence that HIF-1 signaling underlies the increase of FBLN5 expression elicited by hypoxia in endothelial cells and suggest that FBLN5 induction could be involved in the adaptive survival response of endothelial cells to hypoxia.