THE ROLE OF INTESTINAL EPITHELIAL BARRIER FUNCTION AND HOST DEFENSE

肠上皮与肠道微生物群的动态相互作用需要屏障功能与宿主防御反应的协调，以维持肠道内稳态。然而，这种真核生物和原核生物之间的相互作用的机制只被部分理解。为了克服肠道屏障，几种肠道病原体已经进化出不同的策略来干扰紧密连接的功能，紧密连接是一种专门的功能。 肠上皮细胞最顶端区域的膜结构域，其维持细胞极性并为离子和大分子创造选择性和调节性屏障。概述的实验将继续我们的目标，即解开促进宿主防御反应期间肠道屏障功能维持的机制。在上一个资助期间，我们已经确定了一个鸟嘌呤核苷酸交换因子RhoA，GEF-H1，在紧密连接的肠上皮细胞。GEF-H1通过控制紧密连接的形成、病原体对细胞的侵袭和炎症宿主反应的激活，可能是上皮细胞防御病原体的中心。GEF-H1在紧密连接中的定位机制以及负责其释放和启动肠上皮细胞中信号事件的机制尚不清楚。我们假设GEF-H1是Rho的关键调节因子， 紧密连接中的GTP酶依赖性机制;它们共同决定肠道屏障功能对肠道和病原菌挑战的适应性。该提案的总体目标是表征GEF-H1在调节肠上皮屏障功能中的生物学功能，并定义负责GEF-H1介导的保护免受病原体细胞侵袭的分子机制。

The dynamic interactions of the intestinal epithelium with the intestinal microbiota require the co-ordination of the barrier function with host defense responses to maintain intestinal homeostasis. However, the mechanisms involved in this eukaryotic and prokaryotic cross-talk are only partially understood. To overcome the intestinal barrier, several enteric pathogens have evolved distinct strategies to interfere with the function of tight junctions, a specialized membrane domain at the most apical region of intestinal epithelial cells that maintains the cellular polarity and creates a selective and regulated barrier for ions and macromolecules. The outlined experiments will continue our goal to unravel the mechanisms, which facilitate the maintenance of the intestinal barrier function during host defense responses. During the previous funding period, we have identified a guanine nucleotide exchange factor for RhoA, GEF-H1, in tight junctions of intestinal epithelial cells. GEF-H1 may be central to epithelial cell defenses to pathogens by controlling the formation of tight junctions, cell invasion by pathogens, and activation of inflammatory host responses. The mechanisms, which localize GEF-H1 in tight junctions, and those responsible for its release and initiation of signaling events in intestinal epithelial cells are unknown. We hypothesize that GEF-H1 is a key regulator of Rho GTPase dependent mechanisms in tight junctions; which together, determine the adaptation of the intestinal barrier function to challenges by commensal and pathogenic bacteria. The overall goals of this proposal are to characterize the biological functions of GEF-H1 in the regulation of the intestinal epithelial barrier function and to define the molecular mechanisms, which are responsible for GEF-H1 mediated protection from pathogen cell invasion.