GC Tfp Retraction and Stress-Responsive Host Signaling

淋病奈瑟氏菌(GC)IV型菌毛(TFP)是一种伸缩结构，具有运动、黏附宿主细胞和遗传能力等功能。回缩、伸展和底物拴系的循环使GC爬行(抽动运动)并影响上皮细胞信号。回收需要PILT，假设PILT起TFP拆卸马达的作用。回缩经常发生，而且有很大的力量。CG在上皮细胞表面爬行，并聚集成微集落，在感染期间这些微集落本身可以长时间移动。微菌落的TFP回缩力被计算为落在已知触发细胞反应的生理范围内。因此，我们使用感染的组织培养模型和基因定义的 一对表达TFP但不表达OpA的wt和PILT菌株。感染激活了应激反应的PI-3K/Akt通路，而不依赖于OpA。功能性PILT可显著增强活性。感染后0.5-2小时可检测到PI-3K/Akt的激活。PIP3是PI-3K的产物，转运到上皮膜的外叶，并聚集在微集落下。PIP3刺激微集落形成，增加p/VTm RNA水平。因此，TFP回缩触发宿主产生效应器，进而影响GC的运动行为。感染也会影响上皮细胞基因的表达。超过300个上皮基因在感染3小时后受到差异调控，此时GC已在细胞表面形成微克隆，但 尚未进入细胞的PILT在涉及MAPK通路的过程中增强了这些基因的子集的表达。PILT基因表达增强的一个结果是创造了一个允许细胞经受住凋亡的环境。这些与PILT相关的反应可以通过磁铁拉动种植在细胞上的GC膜涂层磁珠来复制。这些结果表明，TFP回缩的力量在上皮细胞中触发了保护性的应激反应通路。基于这些发现，我们提出了TFP回缩在上皮细胞信号转导中的作用模型。我们建议测试该模型，以更好地了解TFP回缩在细菌发病中的作用。

The N. gonorrhoeas (GC) type IV pilus (Tfp) is a retractile structure that functions in motility, adherence to host cells, and genetic competence. Cycles of retraction, extension, and substrate tethering enable GC to crawl (twitching motility) and influence epithelial cell signaling. Retraction requires PilT, which is hypothesized to function as a Tfp disassembly motor. Retraction occurs often and with substantial force. CG crawl on the epithelial cell surface and aggregate into microcolonies that are themselves motile for long periods during infection. Tfp retraction forces from a microcolony is calculated to fall within the physiologic range known to trigger cellular responses. We therefore tested the hypothesis that epithelial cells sense and respond to Tfp retraction during infection, using a tissue culture model of infection and a genetically-defined pair of wt and pilT strain expressing Tfp but not Opa. Infection activates the stress-responsive PI-3K/Akt pathway, independent of Opa. A functional pilT strongly enhances activation. PI-3K/Akt activation is detected 0.5-2 hours after infection. PIP3, the product of PI-3K, translocates to the outer leaflet of the epithelial membrane and accumulates beneath microcolonies. PIP3 stimulates microcolony formation and increased p/VTmRNA levels. Thus, Tfp retraction triggers the host to produce an effector that, in turn, influences GC motility behavior. Infection also influences epithelial cell gene expression. Over 300 epithelial genes are differentially regulated after 3 hours of infection, a time when GC have formed microcolonies on the cell surface but have not yet entered the cell pilT enhances the expression of a subset of these genes, in a process that involves the MAPK pathway. One consequence of pilT-ehnancement of gene expression is the creation of an environment that allows the cell to withstand apoptosis. These pilT-related responses can be replicated by a magnet pulling on GC membrane-coated magnetic beads seeded on cells. These results suggest that the force of Tfp retraction triggers protective stress-response pathways in the epithelial cell. Based on these findings, we propose a model for the role of Tfp retraction in epithelial cell signaling. We propose to test the model to better understand the role of Tfp retraction in bacterial pathogenesis.