Hypoxia-Suppressed Dicer and AGO1 Promote Angiogenesis

描述（由申请人提供）：项目摘要/摘要：缺氧抑制的Dicer和AGO 1促进血管生成缺氧诱导的血管生成是正常发育和疾病条件（如缺血）中的关键和复杂过程。为了应对缺氧，血管内皮细胞（EC）选择性上调一组血管生成分子通过一个复杂的协调网络组成的转录和转录后控制，以支持血管生成和新血管形成。microRNA（miRNAs或miRs）已经成为在转录后水平调节基因表达的重要调控因子。miRNAs的调控机制及其功能相关性在心血管生物学等领域得到了广泛的研究。迄今为止，大多数研究集中在miRNA的转录调控和单个miRNA-单个靶点通路的功能验证。我最近证明，缺氧诱导一组缺氧反应性miRNA（HRM），包括Let-7和miR-103/107，它们共同抑制Dicer和Argonaute 1（AGO 1），这是miRNA机制的两个关键组成部分。Dicer和AGO 1的显著降低表明缺氧可能导致miRNA生物合成和转录后水平靶向的全局重编程。功能获得和功能丧失实验提供了缺氧抑制的Dicer和AGO 1增强EC中血管生成因子（例如血管内皮生长因子（VEGF）、血小板衍生生长因子（PDGF）和胎盘生长因子（PlGF））的表达并因此促进血管生成的证据。在机制上，缺氧抑制的Dicer可以改变miRNA生物发生以促进HRM的选择性加工，其与缺氧抑制的AGO 1协同作用以减少血管生成分子的miRISC靶向。这些观察结果促使我假设缺氧抑制Dicer和AGO 1改变了miRNA的生物合成和miRNA靶向，从而增强了促进血管生成的基因的表达。为了验证这一假设，我提出了三个具体的目标：在目标1中，我将研究缺氧抑制Dicer重新编程内皮细胞中的miRNA生物合成以增强血管生成分子表达的分子基础。在目的2中，我将描述缺氧抑制AGO 1调节内皮细胞中miRNA靶组以促进血管生成的机制。在目标3中，我将研究缺氧抑制的Dicer和AGO 1在病理性血管生成中的功能相关性，即，在心肌缺血的情况下。总之，这些研究将揭示内皮细胞对缺氧和缺血应激反应中miRNA调控基因表达的新模式。此外，划定的途径可能会提供新的见解，未来的翻译研究涉及病理性血管生成。

DESCRIPTION (provided by applicant): Project Summary/Abstract: Hypoxia-suppressed Dicer and AGO1 promote angiogenesis Hypoxia-induced angiogenesis is a critical and complex process in normal development and disease conditions such as ischemia. In response to hypoxia, vascular endothelial cells (ECs) selectively upregulate a panel of angiogenic molecules through an intricately coordinated network consisting of transcriptional and post-transcriptional controls to support angiogenesis and new vessel formation. MicroRNAs (miRNAs or miRs) have emerged as essential regulators that modulate gene expression at post-transcriptional level. The regulatory mechanisms of miRNAs and their functional relevance have been intensively investigated in cardiovascular biology and other fields. Most studies to date have focused on transcriptional regulation of miRNAs and functional validation of single miRNA-single target pathways. I recently demonstrated that hypoxia induces a group of hypoxia-responsive miRNAs (HRMs) including Let-7 and miR-103/107, which jointly suppress Dicer and Argonaute 1 (AGO1), two key components of miRNA machinery. The marked decrease of Dicer and AGO1 indicate that hypoxia may cause a global reprogramming of miRNA biogenesis and targeting at post- transcriptional level. Gain- and loss-of-function experiments provide evidence that hypoxia- suppressed Dicer and AGO1 enhance expression of angiogenic factors in ECs, e.g. vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF), and placental growth factor (PlGF) and hence promote angiogenesis. Mechanistically, hypoxia-suppressed Dicer may alter miRNA biogenesis to promote selective processing of HRMs, which acts in concert with hypoxia- suppressed AGO1 to decrease the miRISC targeting of angiogenic molecules. These observations prompted me to hypothesize that hypoxia-suppressed Dicer and AGO1 alter miRNA biogenesis and miRNA targeting, which enhances the expression of genes promoting angiogenesis. To test this hypothesis, I proposed three specific aims: In Aim 1, I will investigate the molecular basis by which the hypoxia-suppressed Dicer reprograms miRNA biogenesis in ECs to enhance the expression of angiogenic molecules. In Aim 2, I will delineate the mechanism by which hypoxia- suppressed AGO1 regulates miRNA targetome in ECs to promote angiogenesis. In Aim 3, I will examine the functional relevance of hypoxia-suppressed Dicer and AGO1 in pathological angiogenesis, i.e., in the context of myocardial ischemia. Collectively, these studies will reveal a new paradigm of miRNA-regulated gene expression in ECs responding to hypoxic and ischemic stress. Furthermore, the delineated pathways may provide novel insights into future translational studies involving pathological angiogenesis.