Bmx Tyrosine Kinase Signaling in Cardiac Protection

描述（由申请人提供）：缺血预处理是预防心脏组织发生不可逆缺血性损伤的最有效且可持续重现的方法。这种现象的诱导可以通过一氧化氮（NO）供体等药物代替缺血来重现，这些药物可显著减少心肌梗死面积。已知缺血/再灌注损伤中的心脏细胞死亡主要涉及线粒体功能障碍（线粒体通透性转换[MPT]），因此保护需要预防MPT。虽然在心脏保护中防止线粒体功能障碍的信号传导机制是未知的，但基于酪氨酸激酶抑制剂阻断心脏保护的能力，酪氨酸激酶信号传导已被牵连。非受体酪氨酸激酶Bmx在非心脏细胞的细胞保护信号传导中具有确定的作用，最近在心脏组织中被鉴定。该蛋白已被证明在非心脏细胞中被PI 3-K和Src激活，尽管它在心肌细胞中如何被激活完全未知。我们的初步结果表明，Bmx基因敲除（KO）小鼠的心脏不能用NO供体保护，从而暗示Bmx是以前未被认识到的保护性信号传导的必要成分。由于这些观察结果，我们假设Bmx信号在心肌细胞中被激活以响应心脏保护，并至少部分地通过调节线粒体功能来促进细胞存活。我们提出了两个目标，结合联合收割机生物化学，蛋白质组学分析，共聚焦显微镜和细胞/细胞器生理学来验证这一假设：首先，我们将通过确定PI 3-K和Src的作用，识别Bmx的激活剂和映射心脏保护信号所需的磷酸化位点，来表征NO供体诱导的保护过程中小鼠心肌细胞中Bmx的激活。其次，我们将评估Bmx信号传导在NO供体诱导的心脏保护中的作用，通过测量Bmx KO小鼠中的线粒体功能，鉴定该细胞器中的Bmx相关蛋白，并确定线粒体蛋白表达中的Bmx依赖性变化。确定Bmx信号传导机制将建立对心脏中新发现的酪氨酸激酶家族的第一个见解，并允许更好地理解保护性表型，目标是开发治疗缺血性心脏病的分子方法。

DESCRIPTION (provided by applicant): Ischemic preconditioning is the most potent and consistently reproducible method of preventing heart tissue from undergoing irreversible ischemic damage. Induction of this phenomenon can be recapitulated in lieu of ischemia by drugs such as nitric oxide (NO) donors, which significantly reduce myocardial infarct size. Cardiac cell death in ischemia/reperfusion injury is known to centrally involve malfunction of the mitochondria (mitochondrial permeability transition [MPT]), and protection thus requires prevention of MPT. Although the signaling mechanisms which prevent mitochondrial dysfunction in cardiac protection are unknown, tyrosine kinase signaling has been implicated based on the ability of tyrosine kinase inhibitors to block cardiac protection. The non-receptor tyrosine kinase, Bmx, which has an established role in cytoprotective signaling in non-cardiac cells, was recently identified in cardiac tissue. This protein has been shown to be activated by PI3-K and Src in non-cardiac cells, although how it is activated in the cardiomyocyte is completely unknown. Our preliminary results have shown that the hearts of Bmx knockout (KO) mice cannot be protected with NO donors, thereby implicating Bmx as a previously unrecognized necessary component of protective signaling. Because of these observations, we hypothesize that Bmx signaling is activated in cardiomyocytes in response to cardiac protection and promotes cell survival, at least in part, by regulating mitochondrial function. We propose two Aims that combine biochemistry, proteomic analysis, confocal microscopy and cell/organelle physiology to test this hypothesis: First, we will characterize Bmx activation in mouse cardiomyocytes during NO donor induced protection by determining the role of PI3-K and Src, identifying activators of Bmx and mapping the phosphorylation sites necessary for cardiac protective signaling. Second, we will evaluate the role of Bmx signaling in NO donor induced cardiac protection by measuring mitochondrial function in Bmx KO mice, identifying Bmx associated proteins at this organelle, and determining Bmx-dependent changes in mitochondrial protein expression. Determining Bmx signaling mechanisms will establish the first insights into a newly discovered family of tyrosine kinases in the heart and allow a better understanding of the protective phenotype with the goal of developing molecular approaches to treat ischemic heart disease.