Function and Mechanism of the Intercalated Disc Protein XinB in Cardiomyocyte Proliferation and Cardiac Regeneration

摘要 心血管疾病仍然是人类死亡的主要原因， 这些毁灭性的病症的根本原因还没有完全阐明。心脏病尤其常见 在老年人中，随着全球人口老龄化，其发病率升高将构成严重的医疗保健挑战。 心肌细胞中的一个重要结构是闰盘（ICD），其介导心肌细胞之间的协调。 心脏合胞体它通过连接相邻的心肌细胞来发挥作用，从而维持功能性心肌细胞。 合胞体的完整性;这对心脏的正常收缩至关重要。虽然许多报道 尽管证明了ICD在心肌组织中的重要性，但对如何组织的了解相对较少 这些细胞-细胞连接在心肌细胞之间传递信息以调节基因表达， 心脏功能 含有Xin重复序列的接头蛋白Xinα和Xinβ，也分别称为XIRP 1和XIRP 2， 是私家侦探发现的这两种蛋白质位于成年心肌细胞的ICD中，并与 各种粘附连接蛋白，包括N-钙粘蛋白和β-连环蛋白，支持它们在 这种结构的形成/维持。它们在早期心脏发育过程中也起着重要作用 以及心脏病的发病机制。然而，Xin蛋白的作用仍然研究得很少， 具体的细胞和分子功能在很大程度上是未知的。我们最近的研究心脏的心敲除 (KO)小鼠已经鉴定出与受损的心肌细胞增殖相关的发育缺陷。我们 研究进一步证明了XinXin和NF 2之间的物理和遗传相互作用，NF 2是XinXin的一个组成部分。 重要的Hippo/雅普通路。Hippo-YAP通路是高度保守的细胞调节网络， 先前已涉及多种发育系统和疾病，包括心脏;然而， 其作用机制仍不清楚，与ICD的联系是一个新颖而令人兴奋的新发现。 因此，我们设计了两个综合性的特异性目标来测试ICD的机制， 蛋白质Xin β介导心肌细胞增殖、成熟和再生。第一个目标，我们 将研究Xinjiang与Hippo/雅普通路之间的相互作用。我们将研究心血管系统如何调节雅普 活动以及Xin β和Hippo-YAP信号传导之间的相互作用如何调节心脏功能， 再生第二个目的是研究雅普/Tead 1如何调控Xin β转录，并验证我们的实验结果。 假设Xin β-雅普交叉调节对心脏基因表达和心脏再生至关重要。 这里提出的研究将揭示新的分子机制， 病理生理学Hippo/雅普信号由心脏中的ICD蛋白Xin β调节。分子定义 在这项研究中，将成为治疗心脏疾病的治疗干预的目标。

ABSTRACT Cardiovascular diseases remain the leading cause of death in humans, yet the molecular mechanisms underlying these devastating conditions have not been fully elucidated. Cardiac disease is especially common in the elderly, and as the global population ages their elevated incidence will pose a serious healthcare challenge. An important structure in heart muscle cells is the intercalated disc (ICD), which mediates the coordination of the cardiac syncytium. It functions by connecting neighboring cardiomyocytes, thereby maintaining the functional integrity of this syncytium; this is crucial to the proper contraction of the heart. Although many reports demonstrate the importance of ICDs in the organization of the myocardium, relatively little is known about how these cell-to-cell junctions transmit information between cardiac muscle cells to modulate gene expression and cardiac function. The Xin-repeat containing adaptor proteins Xinα and Xinβ, also called XIRP1 and XIRP2 respectively, were first discovered by the PI. These two proteins are located in the ICD of adult cardiomyocytes and interact with various adherens junction proteins including N-cadherin and β-catenin, supporting an essential role for them in the formation/maintenance of this structure. They also play important roles during early cardiac development and in the pathogenesis of heart disease. However, the role of the Xin proteins remains poorly studied and their specific cellular and molecular functions are largely unknown. Our recent studies of the hearts of Xin knock-out (KO) mice have identified defects in development associated with impaired cardiomyocyte proliferation. Our studies further demonstrated a physical and genetic interaction between Xin and NF2, a component of the important Hippo/YAP pathway. The Hippo-YAP pathway is a highly conserved cellular regulatory network that has been previously implicated in multiple developmental systems and disease, including the heart; however, the mechanisms of its action remain unclear and a link to the ICD is a novel and exciting new discovery. Therefore, we have designed two integrative Specific Aims to test the mechanism by which the ICD protein Xin mediates cardiomyocyte proliferation, maturation, and regeneration. For the first Aim, we will investigate the interaction between Xin and the Hippo/YAP pathway. We will study how Xin regulates YAP activity and how the interaction between Xin and Hippo-YAP signaling regulates cardiac function and regeneration. For the second Aim, we will study how YAP/Tead1 regulates Xin transcription and test our hypothesis that Xin-YAP cross-regulation is crucial to cardiac gene expression and heart regeneration. The studies proposed here will reveal novel molecular mechanisms by which the important pathophysiological Hippo/YAP signal is modulated by the ICD protein Xin in the heart. The molecules defined in this study will become targets for therapeutic intervention in the treatment of cardiac diseases.