Inhibition of Cardiac Hypertrophy by Modulation Calcineurin-dependent Signal Transduction

心脏肥大代表心脏对增加的生物力学应力（如动脉高血压）的反应。虽然传统上被认为是一种代偿机制，但一些临床研究以及动物模型表明，持续的心脏肥大是相当不适应的，最终导致心力衰竭和猝死。磷酸酶钙调神经磷酸酶及其下游靶转录因子NFAT在心肌细胞肥大的发病机制中起着关键作用。钙调神经磷酸酶在小鼠心脏中的组成性激活导致心脏大面积扩大和心力衰竭。相反，心脏中钙调磷酸酶的消融使小鼠对肥大具有抵抗力。我们最近发现了一个新的家庭的肌肉特异性蛋白质，称为calsarcins，结合钙调神经磷酸酶。此外，我们产生了钙蛋白缺乏的小鼠，这揭示了一个显着夸张的肥大反应，压力超负荷和慢性钙调磷酸酶激活。为了研究钙调神经磷酸酶作为抗肥大策略的分子靶点，我们现在提出探索几种互补的实验方法：（1）利用腺病毒，我们首先旨在测试钙调神经磷酸酶-1或新型钙调神经磷酸酶/NFAT抑制激酶DYRK 1A的过表达是否足以抑制体外心肌细胞肥大。(2)我们已经产生了一种新的转基因小鼠模型与心脏过表达calsarcin-1，并计划检查calsarcin是否可以抑制肥大的几个实验模型，包括压力超负荷。(3)我们将分析编码钙肌蛋白-1的腺相关病毒是否能够在体内减弱肥大。(4)我们计划在稳定转染NFAT报告基因的肌肉细胞系中进行cDNA文库表达筛选，以确定钙调磷酸酶/NFAT途径的其他心脏特异性调节剂/抑制剂。总之，我们希望进一步阐明钙调神经磷酸酶依赖的信号转导在心脏以及确定新的分子靶点，用于预防和治疗心肌肥大和衰竭。

Cardiac hypertrophy represents the heart s response to increased biomechanical stress such as arterial hypertension. While traditionally viewed as a compensatory mechanism, several clinical studies as well as animal models have shown that sustained cardiac hypertrophy is rather maladaptive, ultimately leading to heart failure and sudden death. The phosphatase calcineurin and its downstream target, the transcription factor NFAT, have been shown to play a critical role in the pathogenesis of cardiomyocyte hypertrophy. Constitutive activation of calcineurin in mouse hearts leads to massive cardiac enlargement and heart failure. Conversely, ablation of calcineurin in the heart renders mice resistant to hypertrophy. We have recently identified a novel family of muscle-specific proteins, termed calsarcins, that bind to calcineurin. Moreover, we generated calsarcin-deficient mice, which reveal a markedly exaggerated hypertrophic response to both pressure overload and chronic calcineurin activation. To examine calcineurin as a molecular target for antihypertrophic strategies we now propose to explore several complimentary experimental approaches: (1) Utilizing adenoviruses, we first aim to test if overexpression of calsarcin-1 or the novel novel calcineurin-/NFAT-inhibiting kinase, DYRK1A, are sufficient to inhibit cardiomyocyte hypertrophy in vitro. (2) We have generated a novel transgenic mouse model with cardiac overexpression of calsarcin-1 and plan to examine if calsarcin can inhibit hypertrophy in several experimental models, including pressure overload. (3) We will analyze if adeno-associated viruses encoding for calsarcin-1 are able to attenuate hypertrophy in vivo. (4) We plan to perform a cDNA library expression screen in muscle cell lines stably transfected with a NFAT reporter gene in order to identify additional cardiacspecific modulators/inhibitors of the calcineurin/NFAT-pathway. In summary, we expect to further unravel calcineurin-dependent signal-transduction in the heart as well as to identify novel molecular targets for the prevention and treatment of myocardial hypertrophy and failure.