Calcium Dependent Signaling in Airway Epithelial Cells

描述（由申请人提供）：气道上皮通过向感染部位招募吞噬细胞的信号启动对吸入肺部病原体的防御。这种信号是通过toll样受体完成的，toll样受体被保守的细菌成分激活，刺激mapk和NF-？B信号级联引发IL-8等趋化因子的表达，将pmn招募到气道中。为了使pmn在上皮屏障的紧密连接上迁移，必须修饰紧密连接和粘附连接的几种膜跨越蛋白。我们提出由TLR2和可能的TLR5启动的TLR信号激活Ca2+依赖性蛋白酶calpain，其靶向上皮连接蛋白occludin和E-cadherin，以促进PMNs通过细胞旁通道进入气道。同样，LPS激活TLR4诱导Ca2+非依赖性蛋白酶（如TACE）裂解连接蛋白，促进PMN转运。这些相同的连接成分也是细菌毒力因子（P. aeruginosa的III型分泌毒素）的目标，这些毒力因子进一步修饰上皮屏障以促进细菌入侵。GTPase抑制和ADP核糖基化的联合作用以及P. aeruginosa毒素的活性改变了连接蛋白的定位和功能，这些连接蛋白对维持上皮细胞骨架及其屏障功能至关重要。在提出的实验中，我们将描述促进PMN通过上皮屏障迁移的信号过程，以及细菌病原体如何利用相同的靶标。肺炎是肺部炎症细胞的积聚，是发病率和死亡率的主要原因。该项目旨在了解通过多形核白细胞被招募到呼吸道以应对细菌感染的基本过程。

DESCRIPTION (provided by applicant): The airway epithelium initiates defenses against inhaled pulmonary pathogens by signaling to recruit phagocytic cells to the site of infection. This signaling is accomplished by toll-like receptors that are activated by conserved bacterial components, stimulate MAPKs and NF-?B signaling cascades to elicit expression of chemokines such as IL-8 that recruit PMNs into the airway. For PMNs to transmigrate across the tight junctions of the epithelial barrier, several membrane spanning proteins of the tight and adherens junctions must be modified. We propose that TLR signaling initiated by TLR2 and possibly TLR5 activates the Ca2+ dependent protease calpain, which targets the epithelial junctional proteins occludin and E-cadherin to facilitate paracellular passage of PMNs into the airway. Similarly, LPS activation of TLR4 induces cleavage of junctional proteins by Ca2+-independent proteases, such as TACE to facilitate PMN transmigration. These same junctional components are also the targets of bacterial virulence factors, the type III secreted toxins of P. aeruginosa, which further modify the epithelial barrier to facilitate bacterial invasion. The combined effects of GTPase inhibition and ADP ribosylation, the activities of P. aeruginosa toxins, alters the localization and functions of junctional proteins critical for the maintenance of the epithelial cytoskeleton and its barrier function. In the experiments proposed we will characterize the signaling process that facilitates PMN migration through the epithelial barrier and how the same targets can be exploited by bacterial pathogens. PUBLIC HEALTH RELEVANCE: Calcium dependent signaling in airway epithelial cells Pneumonia, the accumulation of inflammatory cells in the lung, is a major cause of morbidity and mortality. This project seeks to understand the fundamental process through which polymorphonuclear leukocytes are recruited into the airway in response to bacterial infection.