Defining epithelial cell polarity cues that direct cell fate

描述（由申请人提供）：上皮细胞的极化对于大多数组织和器官的完整性和功能至关重要，并且上皮极性缺陷与广泛的疾病相关，包括90%以上的癌症。上皮极性的成熟与发育过程中的细胞分化有关。然而，极性是否控制细胞命运信号以及不受调节的极性如何与疾病进展相关联仍然知之甚少。我们工作的长期目标是获得迫切需要的机制洞察连接上皮细胞极性和细胞命运的线索，并了解这些信号的解除管制如何驱动发育和成人呼吸系统的缺陷。有三种进化上保守的蛋白质复合物控制着顶基上皮的极性：crumb、Par和Scribble复合物。我们的假设是，这些极性复合物的顶-底动力学指导了指定呼吸上皮细胞脂肪所需的细胞内信号。我们之前和初步的研究表明，crumb家族成员Crb3和极性调节的Par1b激酶介导转录调节因子YAP的定位和活性。YAP是Hippo信号通路的关键效应因子，在控制细胞增殖、存活和细胞命运方面发挥着重要作用。我们的初步工作表明，YAP定位的核质动力学指导了小鼠发育和成年呼吸道上皮细胞命运的规范，并且YAP定位受Crb3和Par1b的顶基动力学调节。我们发现了一种新的par1b诱导的翻译后修饰，可以指导YAP活性，为极性蛋白如何控制YAP定位以及极性如何最终控制细胞命运提供了直接机制。我们的目标是：1)分析Par1b和YAP之间的关系，并确定这如何影响呼吸上皮祖细胞的命运；2)确定顶尖决定因子Crb3如何控制YAP定位，并评估Crb3的缺失如何影响呼吸上皮的发育和稳态。综上所述，我们的研究将为指导上皮组织的机制提供见解，并定义与疾病（如癌症）发病相关的关键信号。因此，我们预计我们的工作将为上皮相关疾病提供有希望的线索，并将为理解基本的发育事件提供一个框架。

DESCRIPTION (provided by applicant): The polarization of epithelial cells is essential for the integrity and function of most tissues and organs, and defective epithelial polarity is associated with a broad range of diseases, including more than 90% of cancers. Maturation of epithelial polarity correlates with cell differentiation during development. However, whether polarity controls cell fate signals and how deregulated polarity is linked to disease progression is still poorly understood. The long term OBJECTIVE of our work is to gain much needed mechanistic insight into the cues bridging epithelial cell polarity and cell fate, and to understand how deregulation of these signals drives defects in the developing and adult respiratory system. There are three evolutionarily conserved protein complexes that govern apical-basal epithelial polarity: the Crumbs, Par and Scribble complexes. Our HYPOTHESIS is that the apical-basal dynamics of these polarity complexes directs intracellular signals required for specifying cell fat in the respiratory epithelium. Our prior and preliminary studies demonstrate that the Crumbs family member, Crb3, and the polarity-regulated Par1b kinase mediate the localization and activity of the transcriptional regulator YAP. YAP is a key effector of the Hippo signaling pathway that has vital roles controlling cell proliferation, survival and cell fate. Our preliminar work indicates that the nuclear-cytoplasmic dynamics of YAP localization directs cell fate specification in the developing and adult respiratory epithelium of the mouse, and that YAP localization is regulated by the apical-basal dynamics of Crb3 and Par1b. We have uncovered a novel Par1b-induced posttranslational modification that directs YAP activity, providing a direct mechanism for how polarity proteins control YAP localization, and ultimately how polarity may govern cell fate. Our AIMS are to: 1) dissect the relationship between Par1b and YAP, and define how this affects respiratory epithelial progenitor cell fate; and 2) determine how the apica determinant Crb3 controls YAP localization and assess how the loss of Crb3 affects respiratory epithelial development and homeostasis. Taken together, our studies will provide insight in the mechanisms directing epithelial organization and define crucial signals linked to the onset of diseases, such as cancer. As such, we anticipate our work will generate promising leads for epithelial-related diseases, and will provide a framework for understanding fundamental developmental events.