Regulation of Intestinal Tight Junction Structure by Membrane Traffic

描述（由申请人提供）：上皮紧密连接完整性的建立和维持对上皮器官的正常功能至关重要；综上所述，肠上皮作为抗原和病原体的选择性屏障，同时吸收营养物质的能力是肠道功能的基础。此外，紧密连接和相关极性复合物对于维持上皮极性至关重要。我们对上皮发育和极性的研究主要集中在内体蛋白，内管素上。内管蛋白是一种完整的膜蛋白，存在于极化上皮细胞的顶端内体中。它在发育中的肠中高水平表达，特别是在肠细胞形成极性时。此外，内皮素可能通过与aPKC和Rab14的相互作用调节连接完整性和上皮极性。在本课题中，我们将阐明内皮素和Rab14在上皮紧密连接和极性的建立和维持中的作用机制。本提案中概述的实验将定义内管素和Rab14在连接蛋白和根尖蛋白靶向中的作用，并阐明内管素对上皮连接的建立和维持至关重要的基序。我们的假设是，内管蛋白作为一种支架蛋白来组织和靶向来自顶端内体的连接蛋白和极性蛋白。内皮素功能的丧失可能导致屏障功能和/或根尖-基底侧极性的丧失，导致新生儿免疫力低下，增加对炎症性肠病和/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.