Inhibition of Cardiac Hypertrophy by Modulation Calcineurin-dependent Signal Transduction

心肌肥厚代表S心脏对动脉高血压等生物力学应力增加的反应。虽然传统上被认为是一种代偿机制，但一些临床研究和动物模型表明，持续性心肌肥厚是相当不适应的，最终会导致心力衰竭和猝死。磷酸酶钙调神经磷酸酶及其下游的转录因子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结构性激活会导致大量心脏增大和心力衰竭。相反，去除心脏中的钙调神经磷酸酶可使小鼠抵抗肥大。我们最近发现了一个新的肌肉特异性蛋白家族，称为calsarcins，它与钙调神经磷酸酶结合。此外，我们产生了钙调蛋白缺乏的小鼠，显示出对压力超负荷和慢性钙调神经磷酸酶激活的明显夸大的肥大反应。为了研究钙调神经磷酸酶作为抗肥厚策略的分子靶点，我们现在建议探索几种有益的实验方法：(1)使用腺病毒，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DYRK1A的过度表达是否足以在体外抑制心肌细胞肥大。(2)我们已经建立了一种新型的心脏过表达calsarcin-1的转基因小鼠模型，并计划在包括压力超负荷在内的几种实验模型上检测calsarcin是否能抑制肥厚。(3)我们将分析编码calsarcin-1的腺相关病毒是否能够在体内减轻肥大。(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，以确定钙调神经磷酸酶/NFAT途径的其他心脏特异性调节剂/抑制物。综上所述，我们期望进一步解开心脏中钙调神经磷酸酶依赖的信号转导途径，并为预防和治疗心肌肥厚和衰竭寻找新的分子靶点。

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.