&ITShigella&IT depends on SepA to destabilize the intestinal epithelial integrity via cofilin activation
&ITShigella&IT depends on SepA to destabilize the intestinal epithelial integrity via cofilin activation
复制标题
DOI：
10.1080/19490976.2017.1339006
复制
发表时间：
2017-01-01
期刊：
影响因子：
12.2
通讯作者：
McCormick, Beth A.
中科院分区：
文献类型：
--
作者：
Maldonado-Contreras, Ana;Birtley, James R.;McCormick, Beth A.
志贺氏菌在肠道病原体中是独特的，因为它通过基底外侧极侵入结肠上皮。因此，它进化出了突破肠上皮屏障以部署效应蛋白库的能力，这允许细菌入侵并导致严重的炎症反应。然而，志贺氏菌调节上皮屏障通透性的机制仍然未知。为了解决这个问题，我们使用肠道极化模型和人类离体模型来进一步表征宿主-细菌相互作用的早期事件。我们的研究结果表明，分泌型丝氨酸蛋白酶 A (SepA) 属于肠杆菌科丝氨酸蛋白酶自转运蛋白，负责严重破坏肠上皮屏障。这种破坏促进细菌转移到上皮的基底外侧极，最终形成疾病病理学的特征。 SepA 被发现会导致活性 LIM 激酶 1 (LIMK1) 水平降低，LIMK1 是肌动蛋白重塑蛋白（即 cofilin）的负抑制剂。相应地，我们观察到肌丝蛋白丝切蛋白（cofilin）的激活增加，丝丝蛋白丝切蛋白是一种主要的肌动蛋白聚合因子，已知可控制上皮屏障处紧密连接的打开。此外，我们解析了 SepA 的晶体结构，以阐明其在肌动蛋白动力学和屏障破坏中的作用。研究发现 SepA 的丝氨酸蛋白酶活性是对 LIMK1 和丝切蛋白的调节作用所必需的，从而导致感染期间上皮屏障的破坏。总而言之，我们证明 SepA 对于屏障破坏是不可或缺的，最终促进志贺氏菌转运到基底外侧极，在那里它有效地侵入上皮。
Shigella is unique among enteric pathogens, as it invades colonic epithelia through the basolateral pole. Therefore, it has evolved the ability to breach the intestinal epithelial barrier to deploy an arsenal of effector proteins, which permits bacterial invasion and leads to a severe inflammatory response. However, the mechanisms used by Shigella to regulate epithelial barrier permeability remain unknown. To address this question, we used both an intestinal polarized model and a human ex-vivo model to further characterize the early events of host-bacteria interactions. Our results showed that secreted Serine Protease A (SepA), which belongs to the serine protease autotransporter of Enterobacteriaceae family, is responsible for critically disrupting the intestinal epithelial barrier. Such disruption facilitates bacterial transit to the basolateral pole of the epithelium, ultimately fostering the hallmarks of the disease pathology. SepA was found to cause a decrease in active LIM Kinase 1 (LIMK1) levels, a negative inhibitor of actin-remodeling proteins, namely cofilin. Correspondingly, we observed increased activation of cofilin, a major actin-polymerization factor known to control opening of tight junctions at the epithelial barrier. Furthermore, we resolved the crystal structure of SepA to elucidate its role on actin-dynamics and barrier disruption. The serine protease activity of SepA was found to be required for the regulatory effects on LIMK1 and cofilin, resulting in the disruption of the epithelial barrier during infection. Altogether, we demonstrate that SepA is indispensable for barrier disruption, ultimately facilitating Shigella transit to the basolateral pole where it effectively invades the epithelium.