FAK signaling in cardiac growth and hypertrophy

描述（由申请人提供）：最近的遗传证据表明，纤维连接蛋白结合粘附受体（5E1和其他）的整合素类可以调节心脏的形态和功能。整合素连接驱动许多结构和信号分子聚集到腹侧质膜，统称为“局灶黏附”，用于将细胞内产生力的肌动蛋白细胞骨架与细胞外基质（ECM）连接起来，并协调下游信号通路的激活。非受体酪氨酸激酶，Focal Adhesion kinase （FAK）被整合素和生长因子强烈激活，并且可能在生长和发育过程中整合来自这些不同途径的下游信号。事实上，FAK的种系缺失导致E7.5-10之间的中胚层缺陷和胚胎致死，这与在纤维连接蛋白缺失和d5缺失小鼠中观察到的表型相似。尽管FAK在心脏发育中的直接作用尚未被研究，但来自无FAK胚胎的心脏显示缺乏独立的心内膜和心内膜，这表明心肌细胞成熟存在缺陷。有趣的是，我们小组和其他人最近的工作清楚地表明，FAK在培养的心肌细胞中被各种肥厚性刺激激活，包括苯肾上腺素（PE）、内皮素I （ET-1）、血管紧张素II （AII）和低渗透应激，并且在肥厚性心脏中观察到心脏FAK活性的增加。FAK激活在心肌细胞肥大的发展中起直接作用的观点从我们的开创性发现中得到了证明，即FAK的激活是pe刺激的培养细胞肥大所必需的，以及其他人的类似发现，即FAK是体外最大ET-1和拉伸诱导的肥大所必需的。本研究的实验目的是验证FAK在体内调节心脏发育和病理性肥厚的假设，并确定参与这些过程的FAK依赖性信号通路。我们将使用Cre/LoxP技术产生转基因小鼠，其中FAK将以时间和心脏受限的方式被删除，以检查FAK在心脏生长中的功能作用。我们还将建立心脏细胞培养模型，以鉴定受肥厚刺激差异调节的fak依赖性信号和靶基因。

DESCRIPTION (provided by applicant): Recent genetic evidence indicates that the integrin class of fibronectin-binding adhesion receptors (5E1 and others) can regulate both the form and function of the heart. Integrin ligation drives recruitment of a number of structural and signaling molecules to the ventral plasma membrane collectively termed a "focal adhesion" which serves to link the force-generating actin cytoskeleton inside the cell to the extracellular matrix (ECM), and to coordinate activation of downstream signaling pathways. The non-receptor tyrosine kinase, Focal Adhesion Kinase (FAK) is strongly activated by both integrins and growth factors, and is a likely candidate to integrate downstream signals from these diverse pathways during growth and development. Indeed, germline deletion of FAK results in mesodermal defects and embryonic lethality between E7.5-10 similar to the phenotype observed in both fibronectin-, and D5-null mice. Although a direct role for FAK in cardiac development has yet to be examined, hearts from FAK-null embryos revealed a lack of separate mesocardial and endocardial layers, indicative of a defect in cardiomyocyte maturation. Interestingly, recent work by our group and others clearly indicate that FAK is activated in cultured cardiomyocytes by a variety of hypertrophic stimuli including, phenylephrine (PE), endothelin I (ET-1), angiotensin II (AII), and hypo-osmotic stress, and that increased cardiac FAK activity is observed in vivo in hypertrophic hearts. The idea that FAK activation plays a direct role in the development of cardiomyocyte hypertrophy is evident from our seminal findings that the activation of FAK is required for PE-stimulated hypertrophy of cultured cells and similar findings from others that FAK is required for maximal ET-1 and stretch-induced hypertrophy in vitro. The experimental goals of this proposal are to test the hypothesis that FAK regulates cardiac development and pathological hypertrophy in vivo and to identify the FAK-dependent signaling pathways involved in these processes. We will generate genetically modified mice in which FAK will be deleted in a temporal and cardiac-restricted fashion using Cre/LoxP technology to examine a functional role for FAK in cardiac growth. We will also establish a cardiac cell culture model to identify FAK-dependent signals and target genes that are differentially regulated by hypertrophic stimuli.