The role of microRNA in cardiac cell death

microRNA在心肌细胞死亡中的作用

• 批准号: 8706601
• 负责人: Maha Abdellatif
• 金额: $ 36.76万
• 依托单位: RBHS-NEW JERSEY MEDICAL SCHOOL
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-15 至 2014-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8706601
• 关键词: 3' Untranslated Regions; AKT inhibition; Apoptosis; Apoptosis Inhibitor; Binding; Cancerous; Cardiac; Cardiac Myocytes; Cell Death; Cells; Chromosomes, Human, Pair 10; Chronic; Coronary artery; Dilatation - action; Down-Regulation; Feedback; Fibrosis; Gene Targeting; Genes; Heart; Homologous Gene; Hypoxia; Infarction; Injury; Ischemia; Knowledge; MicroRNAs; Mus; Muscle Cells; Myocardial Ischemia; Organogenesis; PTEN gene; Pathogenesis; Pathway interactions; Phenotype; Phosphoric Monoester Hydrolases; Process; Proteins; Proto-Oncogene Proteins c-akt; RNA-Binding Proteins; Regulation; Relative (related person); Role; Signal Pathway; Signal Transduction; Therapeutic; Transgenic Mice; Transgenic Organisms; Translations; Tumor Necrosis Factor Ligand Superfamily Member 6; Up-Regulation; Wild Type Mouse; artery occlusion; cell growth; in vivo; mouse model; preconditioning; tensin; therapeutic target

DESCRIPTION (provided by applicant): MicroRNA are major posttranscriptional regulatory molecules that mainly suppress protein translation through binding their 3'UTR. MicroRNA-21 (miR-21) is highly upregulated during hypertrophic or cancerous cell growth. In contrast, we found that it declines upon exposure of cardiac myocytes to prolonged hypoxia. Thus, our main objective is to investigate the signaling pathway that regulates miR-21, its targets, and their role in myocyte survival during hypoxia or ischemia. Our preliminary results show that miR-21 not only regulates phosphatase and tensin homologue deleted on chromosome 10 (PTEN), but also directly targets Fas Ligand (FasL). During hypoxia, downregulation of miR-21 is necessary and sufficient for enhancing the expression of both proteins. Consequently, supplementing the cells with exogenous miR-21 during hypoxia is an effective inhibitor of apoptosis. We also observed that activated AKT suppresses the expression of PTEN and FasL in myocytes and induces upregulation of miR-21. To explore the function of miR-21 in the heart in vivo, we generated a cardiac-specific miR-21 transgenic mouse model. These mice have no overt cardiac phenotype, however, following chronic coronary artery occlusion there was complete suppression of PTEN and FasL expression, smaller infarct size, and less fibrosis and chamber dilatation, in the miR-21 transgenic versus the wild type mice. Accordingly, cardiac functions were better preserved. Thus, our hypotheses are: 1) AKT is activated by brief hypoxic episodes [hypoxia preconditioning (HPC)] and induces upregulation of miR-21 in cardiac myocytes or the heart. Conversely, prolonged hypoxia is associated with inhibition of AKT, which results in downregulation of miR-21. 2) AKT phosphorylates the RNA-binding protein CUGBP1, which binds the loop region of primary miR-21 and enhances its processing, thus, increasing mature miR-21 levels. 3) MiR-21 directly targets and regulates translation of PTEN and FasL. Thus, downregulation of miR-21 during hypoxia is required and sufficient for enhancing their translation. 4) Modulation of PTEN levels by the AKT- miR-21 pathway inversely regulates AKT activity and, thus, creates a feedback loop that perpetuates signaling through this pathway. 5) FasL is strictly localized to the interface between myocytes and relays apoptosis signals between cells. Thus, suppression of FasL by miR-21 limits the spread of apoptosis. 6) Supplementing cells with exogenous miR-21 suppresses the expression of these targets and reduces myocyte apoptosis during hypoxia or ischemia. Thus, the aims are to: 1) Delineate the upstream pathways and mechanisms involved in the regulation of miR-21 and its functional signficance. 2) Examine the mechanisms of function of miR-21 and its target genes, FasL and PTEN, in cardiac myocytes. 3) Study the function of miR-21 and its regulation in vivo.

描述（申请人提供）：MicroRNA是主要的转录后调节分子，主要通过结合其3'UTR来抑制蛋白质翻译。 MicroRNA-21 (miR-21) 在肥大或癌细胞生长过程中高度上调。相反，我们发现当心肌细胞长期缺氧时，它会下降。因此，我们的主要目标是研究调节 miR-21 的信号通路、其靶标及其在缺氧或缺血期间心肌细胞存活中的作用。我们的初步结果表明，miR-21不仅调节10号染色体上删除的磷酸酶和张力蛋白同源物（PTEN），而且还直接靶向Fas配体（FasL）。缺氧期间，miR-21 的下调对于增强两种蛋白的表达是必要且充分的。因此，在缺氧期间向细胞补充外源miR-21是细胞凋亡的有效抑制剂。我们还观察到激活的 AKT 抑制肌细胞中 PTEN 和 FasL 的表达并诱导 miR-21 上调。为了探索 miR-21 在心脏中的体内功能，我们构建了心脏特异性 miR-21 转基因小鼠模型。这些小鼠没有明显的心脏表型，然而，与野生型小鼠相比，慢性冠状动脉闭塞后，miR-21转基因小鼠的PTEN和FasL表达完全受到抑制，梗塞面积更小，纤维化和心室扩张更少。因此，心脏功能得到了更好的保存。因此，我们的假设是：1) AKT 由短暂的缺氧事件 [缺氧预适应 (HPC)] 激活，并诱导心肌细胞或心脏中 miR-21 的上调。相反，长期缺氧与 AKT 抑制相关，从而导致 miR-21 下调。 2) AKT 磷酸化 RNA 结合蛋白 CUGBP1，该蛋白结合初级 miR-21 的环区域并增强其加工，从而提高成熟 miR-21 的水平。 3) MiR-21直接靶向并调节PTEN和FasL的翻译。因此，缺氧期间 miR-21 的下调是必要的，并且足以增强其翻译。 4) AKT-miR-21 途径对 PTEN 水平的调节反向调节 AKT 活性，从而创建一个反馈循环，通过该途径维持信号传导。 5) FasL严格定位于肌细胞之间的界面并在细胞之间传递凋亡信号。因此，miR-21 对 FasL 的抑制限制了细胞凋亡的扩散。 6) 给细胞补充外源性 miR-21 可抑制这些靶标的表达，并减少缺氧或缺血期间的心肌细胞凋亡。因此，我们的目标是：1）描绘miR-21调节涉及的上游途径和机制及其功能意义。 2) 检查心肌细胞中miR-21及其靶基因FasL和PTEN的功能机制。 3）研究miR-21的功能及其体内调控。