Defining the role of Hippo signaling in airway injury repair and remodeling

描述（由申请人提供）：我们假设气道疾病和气道化生中的病理性上皮重塑是由通常控制损伤后气道上皮再生的信号级联失调引起的。这些失调的级联反应可以靶向逆转气道疾病中的病理性气道上皮变化。此外，适当调节这些级联反应可以用于再生医学方法，以促进正常的上皮修复。Hippo通路对于多器官系统中的上皮修复是必不可少的，并且已知其异常激活会导致化生和癌症。然而，在肺中的信号传导仍然在很大程度上未被探索。由于Yap1是Hippo信号转导的重要下游效应子，因此我们建议研究Yap1转录共激活因子在肺中的作用。值得注意的是，Yap1和Notch基因改变已在鳞状细胞肺癌中被鉴定。这是令人感兴趣的，因为Notch信号传导已显示出调节负责上皮再生的气道干细胞，并且Notch信号传导也已显示出与其他器官系统中的Hippo信号传导相互作用。总之，这些观察结果表明，Hippo和Notch途径将在气道再生过程中相互作用，并导致气道上皮化生。我们的初步数据显示，气道上皮中Yap1的基因激活导致上皮增生，类似于鳞状上皮化生相关的早期变化序列。我们还表明，Yap1表达诱导气道损伤后，然后消退气道上皮再生的进行。因此，我们假设Hippo通路是气道上皮再生所必需的，并且气道基底干细胞中这种信号级联的失调将导致鳞状上皮化生。该提案旨在通过（1）调节小鼠和人类模型系统中气道基底干细胞中的Yap1表达和（2）检查其与Notch通路的关系来确定Hippo信号传导在气道上皮修复和重塑中的机制作用。具体而言，在目标1中，我们将使用多西环素诱导的Yap1活化形式在气道基底干细胞中遗传地和可逆地活化Yap1，并且还测试了Yap1活化在小鼠和人气道上皮细胞中的离体作用。在目标2中，我们将从气道基底干细胞中基因删除Yap1，然后用二氧化硫激发小鼠以引起再生反应，以确定Yap1是否是气道上皮损伤修复所必需的。我们还将确定小鼠和人气道上皮离体Yap1损失的后果。在目标3中，我们将调节小鼠和人类气道祖细胞中的Notch和Yap 1，以确定一种信号通路如何影响另一种信号通路。然后，通过确定是否存在Hippo和Notch通路的下游靶点，在人鳞状化生和异型增生样本中检查这些信号级联的状态。

DESCRIPTION (provided by applicant): We hypothesize that pathologic epithelial remodeling in airways disease and airway metaplasia is caused by a deregulation of the signaling cascades that normally govern airway epithelial regeneration after injury. These deregulated cascades can then be targeted to reverse the pathologic airway epithelial changes in airway diseases. In addition, appropriately modulating these cascades could be used in a regenerative medicine approach in order to promote normal epithelial repair. The Hippo pathway is essential for epithelial repair in multiple organ systems and its aberrant activation is known to result in metaplasia and cancer. However, the signaling remains largely unexplored in the lung. We propose to study the role of the Yap1 transcriptional co-activator in the lung since Yap1 is a vita and easy to manipulate downstream effector of Hippo signaling. Of note, Yap1 and Notch genetic alterations have been identified in squamous cell lung cancer. This is of interest because Notch signaling has been shown to regulate the airway stem cells that are responsible for epithelial regeneration and Notch signaling has also been shown to interact with Hippo signaling in other organ systems. In aggregate, these observations suggest that the Hippo and Notch pathways will interact during airway regeneration and in causing airway epithelial metaplasia. Our preliminary data show that genetic activation of Yap1 in airway epithelium causes an epithelial hyperplasia resembling the early sequence of changes associated with squamous metaplasia. We also show that Yap1 expression is induced upon airway injury and then subsides as airway epithelial regeneration proceeds. We therefore hypothesize that the Hippo pathway is required for airway epithelial regeneration and that a deregulation of this signaling cascade in airway basal stem cells will cause squamous metaplasia. This proposal aims to define the mechanistic role of Hippo signaling in airway epithelial repair and remodeling by (1) modulating Yap1 expression in airway basal stem cells in both murine and human model systems and (2) by examining its relationship to the Notch pathway. Specifically, in Aim 1 we will genetically and reversibly activate Yap1 in airway basal stem cells using a doxycycline-inducible activated form of Yap1 and also test the role of Yap1 activation in both mouse and human airway epithelium ex vivo. In Aim 2, we will genetically delete Yap1 from airway basal stem cells and then challenge mice with sulfur dioxide to elicit a regenerative response to determine whether Yap1 is necessary for airway epithelial injury repair. We will also determine the consequences of Yap1 loss in mouse and human airway epithelium ex vivo. In Aim 3, we will modulate Notch and Yap1 in mouse and human airway progenitor cells to determine how one signaling pathway affects the other. The state of these signaling cascades will then be examined in samples of human squamous metaplasia and dysplasia by defining the presence or absence of downstream targets of the Hippo and Notch pathways.