Role of PKP2 in epicardial structure and function

项目摘要 Plakophilin-2（PKP 2）是桥粒的一种组分。最近的研究表明，PKP 2也 作为细胞内信号复合物的支架，并作为微管锚定平台的一部分， 细胞接触的部位。PKP 2突变与约50%的致瘤性右室肥厚病例相关。 已知遗传起源的心室性心肌病（ARVC）。ARVC是一种遗传性疾病，其特征在于 纤维和脂肪组织替代心室质量，增加心室肌纤维化的易感性。 年轻人的心律失常和猝死。我们的长期目标是：1）建立细胞起源的 成纤维细胞和脂肪细胞，它们在受ARVC影响的心脏中占据心室壁，和2）定义了 作用于祖细胞群体以引起疾病表型的分子机制。我们 专注于心外膜细胞，一种心脏驻留的多能干细胞群，可产生各种非 心肌细胞，包括成纤维细胞。我们的中心假设是，在原位心外膜细胞中，PKP 2 缺乏破坏细胞间连接及其相关的细胞内信号节点的结构;这 破坏改变了细胞功能并导致促纤维化、促肿瘤发生表型。我们的具体目标 主要有：1）明确细胞间连接的分子解剖学，以及细胞间连接的结构/功能。 在心外膜细胞中相应的细胞内信号平台。假设：我们假设， PKP 2是以下功能性组分：a）细胞间连接，B）用于 微管正末端，和c）包括β-连环蛋白的细胞内信号传导枢纽的支架， PKCα和RhoA。我们进一步提出，在心外膜细胞中，PKP 2表达的缺失导致分离， 细胞间连接和信号传导节点的成分损失，因此在其他事件中， Rho依赖性MRTF活性，随之激活了运动基因程序，促进了细胞的增殖。 纤维化表型2)为了表征PKP 2缺陷对心外膜细胞功能的后果， 以及它们对心脏解剖和电生理的影响。假设：我们认为PKP 2缺失 在体内心外膜细胞中， 随后在发育过程中和对心脏损伤的反应中分化成纤维脂肪组织。我们 进一步提出在损伤时心外膜来源的成纤维细胞群的扩增产生 不均匀分布的解剖障碍的电脉冲的传播，这些 障碍的大小取决于PKP 2的表达。

PROJECT SUMMARY Plakophilin-2 (PKP2) is a component of the desmosome. Recent studies have demonstrated that PKP2 also acts as a scaffold for an intracellular signaling complex, and as part of the microtubule anchoring platform at the site of cell contact. Mutations in PKP2 associate with about 50% of cases of arrhythmogenic right ventricular cardiomyopathy (ARVC) of known genetic origin. ARVC is an inherited disease characterized by replacement of ventricular mass with fibrous and fatty tissue, and an increased susceptibility to ventricular arrhythmias and sudden death in the young. Our long-term goals are to: 1) establish the cellular origin of the fibroblasts and adipocytes that populate the ventricular wall in an ARVC-affected heart, and 2) define the molecular mechanisms that act on the progenitor cell population to bring about the disease phenotype. We focus on epicardial cells, a cardiac-resident pluripotent stem cell population that gives rise to various non- myocyte cardiac cells, including fibroblasts. Our central hypothesis is that, in epicardial cells in situ, PKP2 deficiency disrupts the structure of intercellular junctions and their associated intracellular signaling nodes; this disruption alters cellular function and leads to a pro-fibrotic, pro-arrhythmogenic phenotype. Our Specific Aims are: 1) To define the molecular anatomy of intercellular junctions, and the structure/function of the corresponding intracellular signaling platforms in epicardial cells. Hypothesis: We postulate that in epicardial cells, PKP2 is a functional component of: a) the intercellular junctions, b) the anchoring platform for the microtubule plus-end, and c) the scaffolding of an intracellular signaling hub that includes beta-catenin, PKCα, and RhoA. We further propose that in epicardial cells, loss of PKP2 expression leads to separation and loss of components of both the intercellular junction and the signaling node, thus driving –among other events- Rho-dependent MRTF activity, with the consequent activation of the motile gene program that facilitates the fibrotic phenotype. 2) To characterize the consequences of PKP2 deficiency on epicardial cell function, and their impact on cardiac anatomy and electrophysiology. Hypothesis: We propose that PKP2 deletion in epicardial cells in vivo drives excessive mobilization of epicardium-derived progenitor cells and their subsequent differentiation into fibro-fatty tissue both during development and in response to cardiac injury. We further propose that expansion of the epicardium-derived fibroblast population upon injury creates heterogeneously-distributed anatomic obstacles for propagation of the electrical impulse, and that these obstacles differ in dimensions depending on PKP2 expression.