How do cell contacts regulate the expression of their components?

上皮细胞是一种特殊的细胞，排列在肾脏、肠道、肺和其他内部器官的体腔内。它们阻止了有机体与其环境之间的分子自由交换。它们的功能要求它们的顶部和底部不同(极化结构)。这种差异是由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)维持的。连接本身受细胞内部框架--细胞骨架--的调节。不同的化学和物理信号可以改变连接的蛋白质组成，但我们不知道这些信号是如何调节连接中每种蛋白质的含量的。给予连接蛋白水平的变化会影响多种功能，包括屏障的形成和细胞的运动。我们发现，随着连接在不断增长的上皮层中组装，一种重要的蛋白质Claudin-2的存在会增加。这表明存在一种反馈机制，该机制报告存在新形成的连接到细胞核，并导致Claudin-2产生的启动。Claudin-2是决定上皮层对水和钠的通透性的重要决定因素，它还调节细胞的运动。利用培养的肾脏细胞，我们将探索连接如何调节细胞中存在多少Claduin-2。我们的方法将包括生化分析、最先进的显微镜方法和测量细胞生长和连接形成的电学方法(ECIS)。我们将特别干扰被怀疑参与调节Claudin-2产生的影响的蛋白质的功能。最后，我们将通过探索控制细胞中的关键信号通路和抑制Cld-2产生的细胞中的关键信号通路，来探讨Cld-2的存在如何影响细胞迁移。我们希望这些实验将提供更好的了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.