Role of Membrane Trafficking in Epithelial Homeostasis

上皮细胞在许多器官中起着关键作用，并负责基本过程，如营养 吸收和废物分泌。为了实现这些功能，它们将质膜包裹在顶端， 和基底外侧区。为了维持组织的稳态，上皮细胞必须不断地进行新的分类， 合成并内化表面受体至正确的靶域。在组织损伤后，上皮细胞 细胞必须正确地迁移到伤口中并重新定殖于伤口区域。极性丧失与 许多疾病，包括转移性癌症、多囊肾病和克罗恩病。怎么上皮化 因此，细胞极性的调节是一个重要的细胞生物学问题，对人类健康具有深远的影响。 我们的工作确定了上皮细胞特异性网格蛋白接头复合物AP-1B对极化再循环至关重要 转移到基底外侧区依赖AP-1B进行基底外侧定位的货物包括重要的 信号受体，如表皮生长激素受体，其错配到顶端结构域已经被 与癌症和多囊肾疾病有关，Toll样受体3的错误分类导致慢性肾病。 炎症该领域一个主要的未解决的问题是AP-1B如何在上皮细胞中独特地发挥作用， 为什么它的近亲AP-1A大多无法替代。我们以前的工作表明，AP-1B改变了 再循环内体（RE）的组织以适应AP-1B在基底外侧分选中的功能。只有AP- AP-1B而非AP-1A定位于RE中，在RE中其触发富含PI（3，4，5）P3的脂质结构域的形成，并且 促进辅助因子的募集，包括囊泡束缚复合物（外囊）和脂质 激酶（PIPKIg-90）。我们最近发现AP-1B表达降低了细胞集体迁移的速度， 单层创伤后，一种新的功能独立于基底外侧分选。我们将检验中心假设 AP-1B在上皮细胞单层的建立和维持中起着双重作用：1）引导货物， 通过在稳态下在RE中产生分选平台和2）在细胞迁移期间 通过调节质膜上粘着斑分子的可用性。我们将检验这一假设 在我们提出的实验中，通过使用最先进的成像技术，包括实时TIRF显微镜， 结合光活化和无偏筛选，包括BioID和质谱，以补充 创新的细胞生物学和生物化学方法：1。确定AP-1B如何产生基底外侧 分拣平台，以及2. AP-1B如何控制细胞迁移我们的研究将定义新的机制 在稳态和细胞迁移期间控制极化上皮细胞的组织。

Epithelial cells play critical roles in many organs and are responsible for elemental processes such as nutrient uptake and waste product secretion. To fulfill these functions, they polarize their plasma membrane into apical and basolateral domains. To maintain tissue homeostasis, epithelial cells must continuously sort newly synthesized and internalized surface receptors to the correct target domain. And after tissue damage, epithelial cells must correctly migrate into the wound and re-colonize the wound area. Loss of polarity is associated with numerous diseases including metastatic cancer, polycystic kidney disease, and Crohn’s disease. How epithelial cell polarity is regulated is thus an important cell biological question with profound implications for human health. Our work identified the epithelial cell-specific clathrin adaptor complex AP-1B as crucial for polarized recycling of cargos to the basolateral domain. Cargos that depend on AP-1B for basolateral localization include important signaling receptors such as epidermal growth hormone receptor whose missorting to the apical domain has been implicated in cancer and polycystic kidney disease, and toll-like receptor 3 whose missorting results in chronic inflammation. A major unresolved question in the field is how AP-1B uniquely functions in epithelial cells, and why its close cousin AP-1A mostly fails to substitute. Our previous work suggested that AP-1B changes the organization of recycling endosomes (REs) to accommodate AP-1B’s function in basolateral sorting. Only AP- 1B but not AP-1A localizes in REs where it triggers the formation of a lipid domain enriched in PI(3,4,5)P3, and facilitates the recruitment of accessory factors including a vesicle-tethering complex (the exocyst) and a lipid kinase (PIPKIg-90). We recently showed that AP-1B expression reduced the speed of collective cell migration after monolayer wounding, a novel function independent of basolateral sorting. We will test the central hypothesis that AP-1B plays dual roles in establishment and maintenance of epithelial monolayers by 1) directing cargos to the basolateral membrane by generating a sorting platform in REs at steady-state and 2) during cell migration by modulating the availability of focal adhesion molecules at the plasma membrane. We will test this hypothesis in our proposed experiments by using state-of-the-art imaging techniques including live TIRF microscopy in combination with photoactivation and unbiased screens including BioID and mass spectrometry to complement innovative cell biological and biochemistry approaches to: 1. Determine how AP-1B generates a basolateral sorting platform, and 2. Determine how AP-1B controls cell migration. Our studies will define new mechanisms governing the organization of polarized epithelial cells at steady-state and during cell migration.