Role of PKP2 in epicardial structure and function

项目总结 血小板亲和素-2(PKP2)是桥粒的组成部分。最近的研究表明，PKP2还 作为细胞内信号复合体的支架，并作为微管锚定平台的一部分 细胞接触的地点。约50%的致心律失常者与PKP2基因突变相关 已知遗传来源的室性心肌病(ARVC)。ARVC是一种遗传性疾病，其特征是 用纤维和脂肪组织替代脑室包块，增加了脑室的易感性 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 成纤维细胞和脂肪细胞填充在ARVC影响的心脏的室壁，以及2)定义 作用于祖细胞群体从而导致疾病表型的分子机制。我们 关注心外膜细胞，一种驻留在心脏的多能干细胞群体，它能产生各种非 心肌细胞，包括成纤维细胞。我们的中心假设是，在原位的心外膜细胞中，PKP2 缺乏会破坏细胞间连接及其相关的细胞内信号节点的结构；这 干扰会改变细胞功能，并导致促纤维化、促心律失常的表型。我们的具体目标 1)定义细胞间连接的分子解剖学，以及细胞间连接的结构/功能 心外膜细胞中相应的细胞内信号平台。假设：我们假设在 心外膜细胞，PKP2是一个功能成分：a)细胞间连接，b)锚定平台 微管加端，以及c)包括β-连环蛋白的细胞内信号枢纽的支架， PKcα和RhoA.我们进一步认为，在心外膜细胞中，PKP2表达的缺失导致分离和 细胞间连接和信令节点的组件丢失，从而导致-除其他事件外- 依赖于Rho的MRTF活性，从而激活运动基因程序，从而促进 纤维化表型。2)研究PKP2缺乏对心外膜细胞功能的影响。 以及它们对心脏解剖和电生理学的影响。假设：我们认为PKP2缺失 在体内的心外膜细胞驱动心外膜来源的祖细胞及其 在发育过程中和对心脏损伤的反应中，随后分化为纤维脂肪组织。我们 进一步提出，损伤时心外膜来源的成纤维细胞数量的扩大会产生 电脉冲传播的非均匀分布的解剖障碍，以及这些 根据PKP2表达的不同，障碍的大小也不同。

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.