Regulation of Intestinal Tight Junction Structure by Membrane Traffic

描述(申请人提供)：建立和维持上皮紧密连接的完整性对于上皮器官的正常功能是必不可少的；最重要的是，肠道上皮在吸收营养的同时作为对抗原和病原体的选择性屏障的能力是肠道功能的基础。此外，紧密连接和相关的极性复合体对于维持上皮极性也是至关重要的。我们对上皮发育和极性的研究主要集中在内体蛋白--内皮管素上。Endotubin是一种完整的膜蛋白，存在于极化上皮细胞的顶端内吞体内。它在发育中的肠道中高水平表达，特别是当肠细胞正在建立极性时。此外，内皮管素可能通过与aPKC和Rab14相互作用来调节连接的完整性和上皮的极性。在这项提案中，我们将阐明内皮管素和Rab14在建立和维持上皮紧密连接和极性方面的作用机制。本提案中概述的实验将确定内皮管素和Rab14在靶向连接蛋白和顶端蛋白中的作用，并阐明对建立和维持上皮连接至关重要的内管素模体。我们的假设是，内管素作为一种支架蛋白，组织和靶向顶端内体中的连接蛋白和极性蛋白。内皮功能的丧失可能导致屏障功能和/或心尖-基底外侧极性的丧失，导致新生儿免疫功能受损，增加炎症性肠病和/或癌症的易感性。

DESCRIPTION (provided by applicant): The establishment and maintenance of epithelial tight junction integrity is essential to the normal function of epithelial organs; above all, the ability of the intestinal epithelium to serve as a selective barrier to antigens and pathogens while absorbing nutrients is fundamental to intestinal function. Also, tight junctions together with associated polarity complexes are critical for the maintenance of epithelial polarity. Our investigations of epithelial development and polarity have focused on the endosomal protein, endotubin. Endotubin is an integral membrane protein that is resident in apical endosomes of polarized epithelial cells. It is expressed at high levels in developing intestine, particularly when the enterocytes are establishing polarity. Moreover, endotubin regulates junctional integrity and epithelial polarity, possibly through interaction with aPKC and Rab14. In this proposal, we will elucidate the mechanism of action of endotubin and Rab14 in the establishment and maintenance of epithelial tight junctions and polarity. Experiments outlined in this proposal will define the role of endotubin and Rab14 in targeting of junctional and apical proteins and elucidate the motifs of endotubin critical for the establishment and maintenance of epithelial junctions. Our hypothesis is that endotubin serves as a scaffolding protein to organize and target junctional and polarity proteins from the apical endosomes. Loss of endotubin function could result in loss of barrier function and/or apical-basolateral polarity, leading to compromised immunity in the newborn, increased susceptibility to inflammatory bowel disease, and/or cancer.