REGULATION OF MYOCARDIAL GROWTH AND DEATH BY THE HIPPO PATHWAY

描述(申请人提供)：哺乳动物不育20样激酶1(Mst1)是心肌细胞(CM)发生凋亡时最显著激活的丝氨酸/苏氨酸激酶之一。Mst1在介导心肌梗死后缺血再灌注损伤和心功能不全中起重要作用。MST1还抑制代偿性肥厚，从而启动由室壁变薄、室壁应力增加和房间扩张组成的恶性循环。尽管Mst1在调节CMS的生长和死亡中具有重要作用，但Mst1是如何被病理性损伤激活的，以及Mst1如何介导心肌细胞死亡，目前还知之甚少。在果蝇中的遗传学研究表明，河马是哺乳动物Mst1的同源物，属于被称为河马途径的信号级联，通过刺激细胞凋亡和抑制细胞增殖在调节器官大小方面发挥着重要作用。河马途径的细胞功能从果蝇到哺乳动物似乎都是保守的，这表明它的基本重要性。我们的长期假设是，哺乳动物河马途径调节CMS的生长和死亡。在本研究中，我们假设：1.K-RAS是由I/R通过氧化激活的，是线粒体Mst1的关键上游调节因子。K-RAS、Rassf1A和Mst1形成复合体，并磷酸化线粒体蛋白，包括Bclxl，从而刺激细胞凋亡。2.Rassf1A-Mst1通路在心肌I/R过程中的作用与细胞类型有关，通过抑制细胞因子激活心脏成纤维细胞中的Rassf1A-Mst1通路可能对心脏有益。3.慢性心肌梗死时，YAP核定位减少可促进心肌损伤，而YAP表达恢复可促进心肌存活和再生。我们将使用基因改变(功能的获得和丧失)小鼠模型以及蛋白质组学方法来解决这些问题。解决这些问题将使我们能够阐明Mst1上游和下游的信号机制在调节CMS对I/R反应的存活、死亡和生长中的作用。从这些实验中获得的知识将有助于开发特定的策略来限制缺血性心脏病患者的心肌损伤。 公共卫生相关性：尽管最近在医疗方面取得了进展，但缺血性心脏病造成的死亡率仍然很高，急性心脏病发作造成的心肌损伤是心力衰竭的一个重要原因。这项研究将研究哺乳动物河马通路在控制急性心脏病发作期间和之后心脏细胞死亡中的作用。我们的研究可能会导致开发一种新的治疗缺血性心脏病的方法。

DESCRIPTION (provided by applicant): Mammalian sterile 20 like kinase 1 (Mst1) is one of the most prominently activated serine/threonine kinases when cardiomyocytes (CMs) undergo apoptosis. Mst1 plays an important role in mediating ischemia/reperfusion (I/R) injury and cardiac dysfunction after myocardial infarction (MI). Mst1 also inhibits compensatory hypertrophy, thereby initiating a vicious cycle consisting of wall thinning, increases in wall stress, and chamber dilation. Despite the importance of Mst1 in regulating growth and death of CMs, how Mst1 is activated by pathological insults and how Mst1 mediates myocardial cell death are poorly understood. Genetic studies in Drosophila have suggested that hippo, a homolog of mammalian Mst1, belongs to a signaling cascade termed the hippo pathway, which plays an important role in regulating organ size through stimulation of apoptosis and suppression of cell proliferation. The cellular function of the hippo pathway appears to be conserved from Drosophila to mammals, indicating its fundamental importance. Our long-term hypothesis is that the mammalian hippo pathway regulates growth and death of CMs. In this study, we hypothesize: 1. K-Ras is activated by I/R through oxidation and serves as a critical upstream regulator of Mst1 at mitochondria. K-Ras, Rassf1A and Mst1 form a complex and phosphorylate mitochondrial proteins, including Bcl-xL, thereby stimulating apoptosis. 2. The function of the Rassf1A-Mst1 pathway during I/R is cell type- dependent, and activation of the Rassf1A-Mst1 pathway in cardiac fibroblasts could be salutary for the heart during I/R through suppression of cytokines. 3. Decreases in the nuclear localization of YAP promote myocardial injury, whereas restoration of YAP expression promotes myocardial survival and regeneration during chronic MI. We will address these issues using genetically altered (gain and loss of function) mouse models, as well as proteomic approaches. Addressing these issues will allow us to elucidate the role of signaling mechanisms both upstream and downstream of Mst1 in mediating survival, death and growth of CMs in response to I/R. The knowledge obtained from these experiments should be useful for developing specific strategies to limit myocardial injury in patients with ischemic heart disease. PUBLIC HEALTH RELEVANCE: Despite recent advancement in medical treatment, the mortality caused by ischemic heart disease remains high and myocardial injury caused by acute heart attack is a significant cause of heart failure. This study will investigate the role of the mammalian hippo pathway in controlling cell death in the heart during and after acute heart attack. Our study may lead to the development of a novel treatment for ischemic heart disease.