How do cell contacts regulate the expression of their components?

上皮细胞是排列在肾脏、肠道、肺和其他内脏器官体腔内的特殊细胞。它们阻止有机体与其环境之间分子的自由交换。它们的功能要求其顶部和底部不同（极化结构）。这种差异是通过在细胞间连接处将两个上皮细胞连接在一起的特殊蛋白质（连接蛋白）来维持的。连接本身受到细胞内部框架（细胞骨架）的调节。连接处蛋白质组成的改变可以由不同的化学和物理信号引起，但我们不明白这些信号如何调节连接处每种蛋白质的含量。连接蛋白水平的变化会影响多种功能，包括屏障形成和细胞运动。我们发现，随着连接在不断生长的上皮层中组装，一种重要蛋白质 Claudin-2 的存在量也会增加。这表明存在一种反馈机制，该机制向细胞核报告新形成的连接的存在，并导致启动claudin-2的产生。 Claudin-2 是上皮层对水和钠的渗透性的重要决定因素，并且还调节细胞运动。使用培养的肾细胞，我们将探索连接如何调节细胞中 Claduin-2 的含量。我们的方法将包括生化测定、最先进的显微方法和测量细胞生长和连接形成方式的电学方法 (ECIS)。我们将专门干扰那些被怀疑参与介导 Claudin-2 产生的蛋白质的功能。最后，我们将通过探索对照细胞和 Cld-2 产生受到抑制的细胞中的关键信号通路来了解 Cld-2 的存在如何影响细胞迁移。我们期望这些实验能够更好地理解连接的调节和重要的上皮功能。

Epithelial cells are specialized cells that line body cavities in the kidney, gut, lung and other internal organs. They prevent free exchange of molecules between the organism and its environment. Their functions require that their top and bottom differs (polarized structure). This difference is maintained by specialized proteins connecting two epithelial cells together at the intercellular junctions (junction proteins). The junctions themselves are regulated by the cell's internal frame, the cytoskeleton. Alteration in the protein composition of junctions can be brought about by different chemical and physical signals, but we do not understand how these regulate how much of each protein is present in the junctions. Changes in the levels of give junction proteins affect various functions, including barrier formation and movement of cells. We found that as junctions are assembled in a growing epithelial layer, the presence of one important protein, claudin-2 increases. This suggests the existence of a feed-back mechanism that reports the presence of newly formed junctions to the cell nucleus and causes the turning on of claudin-2 production. Claudin-2 is an important determinant of permeability of the epithelial layers for water and sodium, and it also regulates cell movement. Using cultured kidney cells, we will explore how the junctions regulate how much Claduin-2 is present in the cells. Our methods will include biochemical assays, state-of-the-art microscopic methods and an electrical method to measure how cells grow and junctions form (ECIS). We will specifically interfere with functions of proteins that are suspected to be involved in mediating effects on Claudin-2 production. Finally, we will ask how the presence of Cld-2 affects cell migration by exploring key signaling pathways in control cells and in cells where Cld-2 production is inhibited. We expect that these experiments will provide a better understanding of regulation of junctions and vital epithelial functions.