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 （Mst1）是心肌细胞（CMs）凋亡时最显著激活的丝氨酸/苏氨酸激酶之一。Mst1在心肌梗死（MI）后缺血/再灌注（I/R）损伤和心功能障碍的介导中起重要作用。Mst1也抑制代偿性肥厚，从而启动由壁变薄、壁应力增加和室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如何被病理损伤激活以及Mst1如何介导心肌细胞死亡尚不清楚。果蝇的遗传学研究表明，hippo是哺乳动物Mst1的同系物，属于一个被称为hippo通路的信号级联，该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重要作用。从果蝇到哺乳动物，河马通路的细胞功能似乎是保守的，这表明它的基本重要性。我们的长期假设是哺乳动物河马通路调节CMs的生长和死亡。在本研究中，我们假设：1。K-Ras通过氧化被I/R激活，并作为线粒体Mst1的关键上游调节剂。K-Ras、Rassf1A和Mst1形成复合物，磷酸化线粒体蛋白，包括Bcl-xL，从而刺激细胞凋亡。2. Rassf1A-Mst1通路在I/R期间的功能是细胞类型依赖的，在心脏成纤维细胞中激活Rassf1A-Mst1通路可能通过抑制细胞因子对I/R期间的心脏有益。3. YAP核定位的减少促进心肌损伤，而YAP表达的恢复促进慢性心肌梗死期间心肌的存活和再生。我们将使用基因改变（功能获得和功能丧失）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I/R响应中介导CMs的生存、死亡和生长中的作用。从这些实验中获得的知识应该有助于制定限制缺血性心脏病患者心肌损伤的具体策略。

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.