Role of miRNAs in Vascular Physiology

描述（由申请人提供）：肺动脉高压（PAH）的特征是肺血管阻力增加，阻碍右心室射血，导致右心室衰竭。PAH是一种无法治愈的严重疾病。原发性PAH是一种罕见但进行性的疾病，4年内死亡率为30%。最近，在超过80%的家族性PAH患者和30%的散发性PAH病例中发现了骨形态发生蛋白受体II（BMPRII）（转化生长因子2（TGF 2）受体家族成员）的种系突变。本申请的长期目标是了解BMPRII突变导致PAH发病的分子机制。本申请的假设是BMPR 2及其下游信号对于维持正常肺血管结构和功能是必需的。我们以前已经表明，TGF-2家族的生长因子，TGF-2s和骨形成蛋白，通过诱导VSMC特异性基因的表达，促进肺动脉平滑肌细胞（PASMC）从“合成”表型到“收缩”表型的转变。我们最近证明，在PASMCs中用TGF 2或BMP处理后，microRNA-21（miR-21）的表达被迅速诱导。MiR-21属于称为microRNA（miRNAs）的短的非编码单链RNA（ssRNAs）家族，其通过以序列特异性方式靶向mRNA来调节基因表达，引起翻译抑制或mRNA降解。PASMC中miR-21的诱导导致程序性细胞死亡4（PDCD 4）的下调，这反过来又导致VSMC特异性基因表达的升高。有趣的是，我们的数据表明，TGF 2和BMP通过促进细胞核中Drosha微处理器复合物将miR-21的初级转录物（pri-miR-21）加工成前体miR- 21（pre-miR-21），在转录后介导miR-21诱导。本申请的主要目的是研究TGF 2和BMP调节miR-21生物合成的机制，这对于理解PAH发病机制中TGF 2/BMP介导的表型转换的分子机制至关重要。为此，SA 1将研究Smads与特定pri-miRNAs的关联机制。SA 2将阐明Smad蛋白在TGF 2/BMP调节的pri-miR-21加工中的作用。SA 3将探索miR-21靶点PDCD 4在调节血管平滑肌表型中的作用。本申请研究了以前未探索的TGF 2/BMP-Smad信号通路的基因调控机制，这是理解PAH发病机制和开发新疗法的基础。 公共卫生相关性：血管平滑肌细胞（VSMC）的特征部分在于其在静止的、分化的“收缩”状态和增殖的、分化较少的“合成”状态之间调节其表型的能力;此外，在血管损伤时，VSMC采用合成表型作为正常修复过程的一部分。这表明，VSMC的表型调节有助于肺动脉和体动脉中的各种疾病，包括血管成形术后再狭窄、移植血管病变、动脉粥样硬化、淋巴管平滑肌瘤病和肺动脉高压（PAH）。本申请将阐明一种新的机制，在正常生理，这是至关重要的了解心血管疾病的病因VSMC表型的调节。

DESCRIPTION (provided by applicant): Pulmonary arterial hypertension (PAH) is characterized by an increase in pulmonary vascular resistance that impedes ejection of blood by the right ventricle, leading to right ventricular failure. PAH is a serious condition for which there is no cure. Primary PAH is a rare but progressive disease with a mortality of 30 percent over 4 years. Recently germline mutations in bone morphogenetic protein receptor type II (BMPRII), a member of the transforming growth factor 2 (TGF2) receptor family, have been found in over 80 percent of familial PAH patients and in 30 percent of sporadic cases of PAH. The long-term objective of this application is to understand the molecular mechanism(s) by which BMPRII mutations contribute to the pathogenesis of PAH. The hypothesis of this application is that BMPR2 and its downstream signal are essential for maintenance of a normal pulmonary vascular structure and function. We have shown previously that the TGF2 family of growth factors, TGF2s and BMPs, promote a switch from a "synthetic" to "contractile" phenotype of pulmonary artery smooth muscle cells (PASMCs) by inducing the expression of VSMC-specific genes. We recently demonstrated that the expression of microRNA-21 (miR-21) is rapidly induced after a treatment with TGF2 or BMP in PASMCs. MiR-21 belongs to a family of short, noncoding, single-stranded RNAs (ssRNAs) called microRNAs (miRNAs) that regulate gene expression by targeting mRNAs in a sequence-specific manner, causing translational repression or mRNA degradation. Induction of miR-21 in PASMCs leads to downregulation of Programmed Cell Death 4 (PDCD4) which in turn leads to the elevation of VSMC-specific gene expression. Interestingly, our data indicate that TGF2 and BMP mediate miR-21 induction post- transcriptionally by promoting the processing of primary transcripts of miR-21 (pri-miR-21) into precursor miR- 21 (pre-miR-21) by the Drosha microprocessor complex in the nucleus. The main goal of this application is to investigate a mechanism of regulation of miR-21 biosynthesis by TGF2 and BMP, which is crucial for understanding a molecular mechanism of TGF2/BMP-mediated phenotype switch underlying the pathogenesis of PAH. To this end, SA1 will examine a mechanism of association of Smads with specific pri-miRNAs. SA2 will elucidate a role of Smad proteins in the TGF2/BMP-regulated pri-miR-21 processing. SA3 will explore a role of miR-21 target PDCD4 in the regulation of vascular smooth muscle phenotype. This application investigates the previously unexplored mechanism of gene regulation by the TGF2/BMP-Smad signaling pathway which is fundamental for understanding the pathogenesis and development of novel therapies for PAH. PUBLIC HEALTH RELEVANCE: Vascular smooth muscle cells (VSMC) are characterized in part by their ability to modulate their phenotype between a quiescent, differentiated "contractile" state and a proliferative, less differentiated, "synthetic" state; further, upon vascular damage, VSMCs adopt the synthetic phenotype as part of a normal repair process. It is suggested that the phenotypic modulation of VSMCs contributes to various disorders in the pulmonary and systemic arteries, including post-angioplasty re-stenosis, transplant vasculopathy, atherosclerosis, lymphangioleiomyomatosis, and pulmonary arterial hypertension (PAH). This application will elucidate a novel mechanism of regulation of VSMC phenotype in normal physiology, which is of fundamental importance in understanding the etiology of cardiovascular disorders.