REGULATION OF MYOCARDIAL GROWTH AND DEATH BY THE HIPPO PATHWAY

描述（由申请人提供）：哺乳动物不育20样激酶1（Mst 1）是心肌细胞（CM）发生凋亡时最显著活化的丝氨酸/苏氨酸激酶之一。Mst 1在心肌梗死（MI）后缺血/再灌注（I/R）损伤和心功能不全中起重要作用。Mst 1还抑制代偿性肥大，从而启动由室壁变薄、室壁应力增加和室腔扩张组成的恶性循环。尽管Mst 1在调节CM的生长和死亡中的重要性，但对Mst 1如何被病理损伤激活以及Mst 1如何介导心肌细胞死亡知之甚少。果蝇的遗传学研究表明，hippo是哺乳动物Mst 1的同源物，属于称为hippo通路的信号级联，其通过刺激细胞凋亡和抑制细胞增殖在调节器官大小中起重要作用。从果蝇到哺乳动物，河马途径的细胞功能似乎是保守的，这表明了它的根本重要性。我们的长期假设是哺乳动物河马途径调节CM的生长和死亡。在这项研究中，我们假设：1。K-Ras通过氧化被I/R激活，并作为线粒体Mst 1的关键上游调节因子。K-Ras、Rassf 1A和Mst 1形成复合物并磷酸化线粒体蛋白，包括Bcl-xL，从而刺激细胞凋亡。2. Rassf 1A-Mst 1通路在I/R期间的功能是细胞类型依赖性的，并且在心脏成纤维细胞中Rassf 1A-Mst 1通路的激活可以通过抑制细胞因子在I/R期间对心脏有益。3.雅普核定位的减少促进心肌损伤，而雅普表达的恢复促进慢性MI期间的心肌存活和再生。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Mst 1的上游和下游信号机制在介导CM响应I/R的存活、死亡和生长中的作用。从这些实验中获得的知识应该是有用的，制定具体的战略，以限制缺血性心脏病患者的心肌损伤。

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.