Hypoxia-Suppressed Dicer and AGO1 Promote Angiogenesis

描述(申请人提供)：项目摘要/摘要：低氧抑制的Disher和Ago1促进血管生成在正常发育和疾病条件下，如缺血，低氧诱导的血管生成是一个关键而复杂的过程。作为对低氧的响应，血管内皮细胞(ECs)通过一个由转录和转录后调控组成的复杂协调网络选择性地上调一组血管生成分子，以支持血管生成和新血管的形成。MicroRNAs(miRNAs或miRs)已成为在转录后水平调节基因表达的重要调节因子。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。到目前为止，大多数研究都集中在miRNAs的转录调控和单个miRNA-单靶向通路的功能验证上。我最近证实，低氧诱导了一组低氧反应的miRNAs(HRMS)，包括let-7和miR-103/107，它们共同抑制了miRNA机制的两个关键组成部分Disher和ArgAerte 1(Ago1)。DICER和Ago1的显著下降表明低氧可能导致miRNA生物发生的全球重新编程，并在转录后水平进行靶向。功能获得和功能丧失实验证明，缺氧抑制的DICER和Ago1可促进内皮细胞血管生成因子的表达，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)，从而促进血管生成。从机制上讲，缺氧抑制的DICER可能会改变miRNA的生物合成，促进HRMS的选择性加工，这与缺氧抑制的Ago1协同作用，减少了miRISC对血管生成分子的靶向。这些观察结果促使我假设，低氧抑制的DICER和Ago1改变了miRNA的生物发生和miRNA靶向，从而增强了促进血管生成的基因的表达。为了验证这一假说，我提出了三个具体目标：在目标1中，我将研究缺氧抑制的Disher重新编程内皮细胞miRNA生物生成以增强血管生成分子表达的分子基础。在目标2中，我将描述缺氧抑制的Ago1调控内皮细胞miRNA靶组促进血管生成的机制。在目标3中，我将研究低氧抑制的DICER和Ago1在病理性血管生成中的功能相关性，即在心肌缺血的背景下。总之，这些研究将揭示一种由miRNA调控的内皮细胞对缺氧和缺血应激做出反应的基因表达的新范式。此外，所描绘的通路可能为未来涉及病理性血管生成的翻译研究提供新的见解。

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.