Effect of protein kinase C on cardiac hypertrophy

肥大是终末分化心肌细胞对生长刺激的特征性反应。在新生儿心脏细胞中定义的细胞内信号传导过程级联已被提出介导这种反应的特征，其中一个核心组成部分是蛋白激酶c的激活。研究人员开发了一种新的转基因模型，该模型允许在小鼠心脏中有条件地表达蛋白激酶C异构体，并且他们已经确定该异构体的表达和激活足以影响不同发育阶段的特定适应。PKC β在新生儿中的表达可导致死亡，并与心肌细胞钙调节异常有关，而在成人中，转基因表达与调节有关，而在成人中，转基因表达与同心心肌肥厚、机械性能受损和缺血相对抵抗有关。在确认了这种方法的可行性之后，当前提案的重点将是确定蛋白激酶C （β和epsilon）的特定同工异构体的作用，并确定PKC的哪些特定靶标负责观察到的适应性。功能的获得和丧失将在转基因模型中重现，PKC表达的功能影响分析将在整个心脏水平和细胞水平上进行。评估影响钙通量和肌丝钙敏感性的因素。该项目的一个独特特点是使用条件转基因，可以评估基因激活在心脏不同发育阶段的生理和生化效应，同时它也改变了其表型。这为调查因果关系提供了一个独特而有力的工具。

(Adapted from the Applicant's Abstract) Hypertrophy is a characteristic response of the terminally differentiated cardiac myocyte to growth stimuli. A cascade of intracellular signaling processes, largely defined in neonatal cardiocytes, has been proposed to mediated features of this response, a central component of which is activation of protein kinase C. In previous work, the investigators have developed a novel transgenic model which allows conditional expression of a protein kinase C isoform in the murine heart and they have established that expression and activation of the isoform is sufficient to effect distinct developmental stage specific adaptations: PKC Beta expression in neonates causes death and is associated with abnormal myocardiocyte calcium regulation whereas in adults, expression of the transgene is associated with regulation whereas in adults, expression of the transgene is associated with concentric cardiac hypertrophy, impaired mechanical performance and relative resistance to ischemia. Having confirmed the feasibility of this approach, the focus of the current proposal, the focus of the current proposal will be to identify roles for specific isoforms of protein kinase C (beta and epsilon) and to define which specific targets of PKC are responsible for the observed adaptations. Both gain and loss of function will be recapitulated in transgenic models and analysis of the functional effects of PKC expression will be at the level of the whole heart and also at the cellular level. Factors which influence calcium flux and myofilament calcium sensitivity will be evaluated. A unique feature of the project is the use of conditional transgenesis which allows assessment of the physiologic and the biochemical effects of gene activation in the heart at different developmental stages and while it os on the process of altering its phenotypes. This provides a unique and powerful tool to investigate causality.