Hypoxia-Suppressed Dicer and AGO1 Promote Angiogenesis

项目摘要/摘要：缺氧抑制的Dicer和AGO1促进血管生成缺氧诱导的血管生成是正常发育和缺血等疾病条件下一个关键而复杂的过程。在缺氧的情况下，血管内皮细胞（ECs）通过转录和转录后调控组成的复杂协调网络选择性上调一系列血管生成分子，以支持血管生成和新血管形成。MicroRNAs （miRNAs或miRs）已成为在转录后水平调节基因表达的重要调控因子。mirna的调控机制及其功能相关性在心血管生物学和其他领域得到了广泛的研究。迄今为止，大多数研究都集中在mirna的转录调控和单个mirna -单个靶标通路的功能验证上。我最近证明，缺氧诱导了一组低氧响应miRNAs (HRMs)，包括Let-7和miR-103/107，它们共同抑制Dicer和Argonaute 1 (AGO1)，这是miRNA机制的两个关键组成部分。Dicer和AGO1的显著降低表明缺氧可能导致miRNA生物发生的全局重编程，并在转录后水平靶向。功能增益和功能丧失实验证明，缺氧抑制的Dicer和AGO1可增强内皮细胞血管生成因子（VEGF）、血小板源性生长因子（PDGF）和胎盘生长因子（PlGF）的表达，从而促进血管生成。在机制上，缺氧抑制的Dicer可能改变miRNA的生物发生，促进HRMs的选择性加工，这与缺氧抑制的AGO1协同作用，降低miRISC对血管生成分子的靶向性。这些观察结果促使我假设缺氧抑制的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。为了验证这一假设，我提出了三个具体目标：在Aim 1中，我将研究缺氧抑制的Dicer重编程ECs中miRNA生物发生以增强血管生成分子表达的分子基础。在Aim 2中，我将描述缺氧抑制的AGO1调节ECs中miRNA靶组促进血管生成的机制。在Aim 3中，我将研究缺氧抑制的Dicer和AGO1在病理性血管生成中的功能相关性，即在心肌缺血的情况下。总的来说，这些研究将揭示mirna调控的基因表达在ECs对缺氧和缺血应激反应中的新范式。此外，所描述的途径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.