Bmx Tyrosine Kinase Signaling in Cardiac Protection

描述（由申请人提供）：缺血预处理是防止心脏组织遭受不可逆缺血损伤的最有效和持续可重复的方法。这种现象的诱导可以再现代替缺血的药物，如一氧化氮（NO）供体，其显著减少心肌梗死面积。缺血/再灌注损伤中的心肌细胞死亡主要涉及线粒体功能障碍（线粒体通透性过渡[MPT]），因此保护心肌细胞需要预防MPT。尽管在心脏保护中防止线粒体功能障碍的信号传导机制尚不清楚，但酪氨酸激酶信号传导已被认为是基于酪氨酸激酶抑制剂阻断心脏保护的能力。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起着既定的作用，最近在心脏组织中被发现。该蛋白在非心脏细胞中被PI3-K和Src激活，尽管其如何在心肌细胞中被激活尚不清楚。我们的初步结果表明，NO供体不能保护Bmx敲除（KO）小鼠的心脏，从而暗示Bmx是以前未被认识到的保护性信号的必要组成部分。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，并通过调节线粒体功能至少部分地促进细胞存活。我们提出了两个目标，结合生物化学，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PI3-K和Src的作用，鉴定Bmx的激活因子和绘制心脏保护信号所需的磷酸化位点来表征NO供体诱导保护期间小鼠心肌细胞的Bmx激活。其次，我们将通过测量Bmx KO小鼠的线粒体功能，鉴定该细胞器中的Bmx相关蛋白，并确定Bmx依赖性线粒体蛋白表达的变化，来评估Bmx信号在NO供体诱导的心脏保护中的作用。确定Bmx信号机制将建立对心脏中新发现的酪氨酸激酶家族的第一次见解，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.