Defining epithelial cell polarity cues that direct cell fate

描述(申请人提供)：上皮细胞的极化对大多数组织和器官的完整性和功能是必不可少的，而上皮细胞极化缺陷与多种疾病有关，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，以及去调控的极性如何与疾病进展联系在一起，仍然知之甚少。我们工作的长期目标是获得亟需的机械性洞察，了解连接上皮细胞极性和细胞命运的线索，并了解这些信号的放松如何导致发育中和成人呼吸系统的缺陷。有三个进化保守的蛋白质复合体控制着顶端-基底上皮极性：Crumbs，PAR和Scribble复合体。我们的假设是，这些极性复合体的尖端-基础动力学引导细胞内信号，以指定呼吸道上皮中的细胞脂肪。我们前期和初步的研究表明，Crumbs家族成员Crb3和极性调节的Par1b激酶介导了转录调节因子Yap的定位和活性。YAP是河马信号通路的关键效应者，在控制细胞增殖、存活和细胞命运方面起着至关重要的作用。我们的初步工作表明，YAP定位的核质动力学决定了小鼠发育和成体呼吸道上皮细胞的命运，而YAP定位受Crb3和Par1b的顶底动力学调控。我们已经发现了一种由Par1b诱导的新型翻译后修饰，它可以指导YAP的活性，为极性蛋白如何控制YAP的定位提供了直接的机制，并最终决定了极性如何控制细胞的命运。我们的目标是：1)剖析Par1b和YAP之间的关系，并确定这如何影响呼吸道上皮祖细胞的命运；2)确定Apica决定簇Crb3如何控制YAP的定位，并评估Crb3的缺失如何影响呼吸道上皮细胞的发育和稳态。综上所述，我们的研究将为指导上皮组织的机制提供洞察力，并确定与癌症等疾病的发生有关的关键信号。因此，我们预计我们的工作将为上皮相关疾病带来有希望的线索，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.