Anchored Kinase Signaling Mechanisms in Cardiac Hypertrophy

描述(申请人提供)：心力衰竭是一种复杂的疾病，在西方世界是导致死亡的主要原因。在美国，大约有500万人(占人口的2%-3%)患有这种疾病。增加的危险因素，如动脉高血压和瓣膜心脏病，对心脏施加额外的生物力学压力，以诱导称为病理性心肌细胞肥大的细胞反应。这种情况的特点包括心肌细胞大小增加和肌节更有组织。在分子水平上，肥大信号，如儿茶酚胺的升高，引起心肌细胞增强因子(MEF2)途径的转录激活，从而改变蛋白质合成的模式。在过去的资助期间，我们已经开始破译一些蛋白质-蛋白质相互作用，这些相互作用有助于MEF2途径的空间和时间调节。我们已经确定了一种A-Kinase锚定蛋白，称为AKAP-LBC，它协调启动MEF2介导的转录重编程事件的信号蛋白的激活和移动。我们的工作假设是，AKAP-LBC同步蛋白激酶A(PKA)和蛋白激酶C(PKC)的磷酸化事件，以促进第三种酶的激活，称为蛋白激酶D(PKD)。反过来，PKD将组蛋白脱乙酰基酶HDAC5磷酸化，以促进其核出口。最后，伴随的核HDAC活性降低有利于MEF2转录和心肌肥厚的发生。为了检验这一假说，本文提出了两个具体目标。 具体目标1：AKAP-LBC是否组织转录重编程？我们的初步研究表明，AKAP-LBC支持PKD激活，并有利于HDAC5的核输出。实时荧光成像将用于确定锚定蛋白是否在大鼠新生脑室细胞(RNV)中组织这两个信号事件。相关研究将在AKAP/LBC-PKD/HDAC通路成员之间的蛋白质-蛋白质相互作用中断时测量MEF2的转录。 具体目标2：AKAP-LBC/PKD/HDAC5通路是否与心脏病有关？我们认为AKAP-LBC/PKD/HDAC5通路促进了心肌肥厚的发生。两种互补的方法将在体内测试这一理论。激活状态抗体将监测正常和疾病心脏组织中AKAP-LBC/PKD/HDAC通路的状态。对表达截短的AKAP-LBC形式的小鼠的敲门信号的分析将确定抑制这一信号通路是否保护心脏重构的某些方面。在美国，大约有500万人患有心力衰竭，这是一种复杂的疾病，是导致死亡的主要原因。心脏上生物力学压力的增加会引起一种称为病理性心肌细胞肥大的细胞反应。我们已经鉴定出一种A-Kinase锚定蛋白，称为AKAP-LBC，它在肥大的心肌细胞中上调表达，并协调MEF2介导的转录重编程事件上游信号蛋白的激活和移动。

DESCRIPTION (provided by applicant): Heart failure is a complex disorder that is a leading cause of death in the Western world. Approximately 5 million people (2-3 % of the population) are afflicted with this disease in the United States. Increased risk factors such as arterial hypertension and valvular heart diseases place additional biomechanical stress on the heart to induce a cellular response known as pathological cardiomyocyte hypertrophy. Hallmarks of this condition include increased cardiomyocyte size and a greater organization of the sarcomere. At the molecular level, hypertrophic signals such as elevated catecholamines evoke transcriptional activation of the Myocyte Enhancer Factor (MEF2) pathway to change the pattern of protein synthesis. During the past funding period we have begun to decipher some of the protein-protein interactions that contribute to the spatial and temporal modulation of the MEF2 pathway. We have identified an A-Kinase Anchoring protein, called AKAP-Lbc that coordinates the activation and movement of the signaling proteins that initiate MEF2 mediated transcriptional reprogramming events. Our working hypothesis is that AKAP-Lbc synchronizes protein kinase A (PKA) and protein kinase C (PKC) phosphorylation events to facilitate activation of a third enzyme, called protein kinase D (PKD). In turn, PKD phosphorylates the histone deacetylase HDAC5 to promote its nuclear export. Finally, the concomitant reduction in nuclear HDAC activity favors MEF2 transcription and the onset of cardiac hypertrophy. Two specific aims are proposed to test this hypothesis. Specific aim 1: Does AKAP-Lbc organize transcriptional reprogramming? Our preliminary studies show that AKAP-Lbc supports PKD activation and favors nuclear export of HDAC5. Real-time fluorescent imaging will be used to establish if the anchoring protein organizes both signaling events in rat neonatal ventriculocytes (RNV). Related studies will measure MEF2 transcription upon disruption of protein-protein interactions between members of the AKAP/Lbc-PKD/HDAC pathway. Specific aim 2: Does the AKAP-Lbc/PKD/HDAC5 pathway contribute to heart disease? We propose that the AKAP-Lbc/PKD/HDAC5 pathway facilitates the onset of cardiac hypertrophy. Two complementary approaches will test this theory in vivo. Activation state antibodies will monitor the status of the AKAP-Lbc/PKD/HDAC pathway in normal and diseased human heart tissue. Analysis of knock in mice expressing a truncated AKAP-Lbc form that blocks PKD activation will determine if suppression of this signaling pathway protects against certain aspects of cardiac remodeling. Within the United States approximately 5 million people are afflicted with heart failure, a complex disorder that is a leading cause of death. Increased biomechanical stress on the heart induces a cellular response known as pathological cardiomyocyte hypertrophy. We have identified an A-Kinase Anchoring protein, called AKAP-Lbc that is up regulated in hypertrophic cardiomyocytes and that coordinates the activation and movement of signaling proteins upstream of MEF2-mediated transcriptional reprogramming events.