FAK Signaling in cardiac growth and hypertrophy

描述（由申请人提供）：成年哺乳动物心肌细胞是终末分化的细胞，具有非常有限的分裂能力，因此，心脏损伤通常会导致肌肉质量的永久性损失，从而导致心室功能障碍和心力衰竭。因此，更好地了解如何控制心肌细胞的细胞周期应该提高我们的能力，提供有效的治疗，迄今为止，一些难治性心脏疾病。一些研究表明，在发育中的心脏的心肌细胞的生长状态与细胞外基质和整合素受体的表达和这些基质的能力，以支持心肌细胞在体外生长的调节转变。这些数据强调了整合素信号在调节心脏形态发生和心脏疾病进展中的重要性，但这些过程在心脏生长的不同阶段如何微调尚不清楚。从我们在过去的资助周期内完成的研究中可以清楚地看出，FAK在发育过程中介导心肌细胞增殖，在压力超负荷后介导心肌细胞肥大，以及在缺血损伤后介导心肌细胞存活。我们还发现FAK活性在出生后心脏中通过其内源性抑制剂FRNK的表达而动态调节。我们的研究结果表明，FRNK是瞬时表达在心脏中的峰值水平发生在出生后5-7天（细胞周期撤回之前），心脏选择性表达的FRNK开始于E10.5导致严重的心室非致密化缺陷和胚胎死亡与受损的心肌细胞增殖和受损的冠状神经丛形成。重要的是，心室心肌细胞特异性表达的超活化FAK变体（bMHC-SuperFAK）能够挽救这种表型，表明FAK在调节这些关键功能中的细胞自主作用。因此，我们的工作假设是，FAK信号的动态调节是重要的心肌细胞细胞周期的发育过程中退出的控制，并可能重新进入细胞周期，以响应心脏应激。我们已经产生了许多基因修饰的功能获得/功能丧失小鼠模型，这将使我们能够测试这一假设，并确定下游信号是重要的FAK/FRNK对心肌细胞增殖的影响。此外，由于FAK信号是由调节心脏发育和功能的许多环境因素调节的，或者是调节心脏发育和功能的许多环境因素的影响所必需的，我们强烈地认为，拟议研究的结果将对我们理解先天性心脏病和心力衰竭的进展产生广泛的影响。我们将利用转基因小鼠、已建立的心脏细胞培养模型和来自人类心脏库的样本来鉴定调节先天性和获得性心脏病发病机制的FAK依赖性机制。

DESCRIPTION (provided by applicant): Adult mammalian cardiomyocytes are terminally differentiated cells with very limited capabilities to divide, thus, injury to the heart typically causes permanent loss of muscle mass leading to ventricular dysfunction and heart failure. Therefore, a better understanding of how the myocyte cell cycle is controlled should enhance our ability to provide effective therapy for several heretofore-intractable cardiac diseases. Several studies indicate that the cardiomyocyte growth state in the developing heart correlates with regulated shifts in the expression of extracellular matrix and integrin receptors and the ability of these matrices to support myocyte growth in vitro. These data underscore the importance of integrin signaling in regulating both cardiac morphogenesis and the progression of cardiac disease, but how these processes are fine-tuned during the different phases of cardiac growth is unknown. It is clear from our studies completed within the past funding cycle that FAK functions to mediate cardiomyocyte proliferation during development, cardiomyocyte hypertrophy following pressure overload, and cardiomyocyte survival following an ischemic insult. We have also made the interesting discovery that FAK activity is dynamically regulated in the post-natal heart by expression of its endogenous inhibitor, FRNK. Our results demonstrate that FRNK is transiently expressed in the heart with peak levels occurring 5-7 days post-natal (just prior to cell cycle withdrawal) and that cardiac-selective expression of FRNK starting at E10.5 leads to a severe ventricular non-compaction defect and embryonic lethality associated with impaired cardiomyocyte proliferation and impaired coronary plexus formation. Importantly, ventricular cardiomyocyte-specific expression of a super-activatable FAK variant (bMHC-SuperFAK) was able to rescue this phenotype, indicating a cell autonomous role for FAK in regulating these critical functions. Thus, our working hypothesis is that dynamic regulation of FAK signaling is important for the control of cardiomyocyte cell cycle withdrawal during development and perhaps to cell-cycle re-entry in response to cardiac stress. We have generated many genetically modified gain-of-function/loss-of-function mouse models that will allow us to test this hypothesis and to identify the downstream signals that are important for the effects of FAK/FRNK on cardiomyocyte proliferation. In addition, since FAK signaling is regulated by, or required for, the effects of many of the environmental cues that regulate cardiac development and function, we strongly feel that the results from the proposed studies will have broad implications on our understanding of congenital cardiac disease and on the progression heart failure. We will utilize genetically modified mice, established cardiac cell culture models, and samples from a human heart repository to identify FAK-dependent mechanisms that regulate the pathogenesis of congenital and acquired heart disease.