Listeria monocytogenes invades the epithelial junctions at sites of cell extrusion.
Listeria monocytogenes invades the epithelial junctions at sites of cell extrusion.
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DOI：
10.1371/journal.ppat.0020003
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发表时间：
2006-01
期刊：
影响因子：
6.7
通讯作者：
Amieva, Manuel R
中科院分区：
文献类型：
--
作者：
Pentecost, Mickey;Otto, Glen;Theriot, Julie A;Amieva, Manuel R
单核细胞增生李斯特菌通过穿过肠上皮屏障引起侵袭性疾病。这个过程取决于细菌表面蛋白Internalin A和宿主蛋白E-钙粘蛋白之间的相互作用，位于上皮细胞间横向接触的紧密连接下方。我们使用极化的MDCK细胞作为上皮细胞模型来确定L。单核细胞增多症破坏紧密连接以接近该基底外侧受体蛋白。我们确定L.单核细胞增生并不主动破坏紧密连接，但发现E-钙粘蛋白在形态学上不同的细胞间连接的子集。我们将这些部位确定为自然发生的区域，其中单个衰老细胞通过挤出从上皮中排出并分离。周围的细胞重组形成多细胞连接，维持上皮的连续性。我们发现，E-钙粘蛋白在细胞挤压过程中和挤压后瞬时暴露于多细胞连接处的管腔表面，L。单核细胞增多症利用连接重塑粘附于上皮并随后侵入上皮。在完整的上皮细胞单层中，抗E-钙粘蛋白抗体特异性修饰多细胞连接并阻断L。单核细胞增生粘附此外，L.内化素A基因中的单核细胞增多症突变体完全缺乏对上皮顶端表面的附着并且不能侵入。我们假设L.单核细胞增多症在体内利用类似的挤出位点进行上皮侵入。通过感染家兔回肠袢，发现肠绒毛末端细胞挤出区的连接处是L.单核细胞增生粘附和侵袭。因此，L.单核细胞增多症利用上皮更新和连接重塑的动态性质来破坏肠屏障。微生物致病机理的研究刚刚开始解决上皮细胞极性和宿主组织结构如何影响宿主-病原体相互作用。长期以来，人们已经知道单核细胞增生李斯特菌侵入上皮细胞需要宿主细胞E-钙粘蛋白（一种细胞与细胞连接蛋白）的结合。然而，一个持续的问题是L。单核细胞增多症到达该受体，因为E-钙粘蛋白位于肠细胞的基底外侧膜中，并且肠腔中的细菌无法接近。通过观察组织培养和活体兔小肠中极化上皮细胞单层，作者研究了L。单核细胞增生破坏紧密连接，与E-钙粘蛋白相互作用并侵入。它们表明L.单核细胞增多症利用连接重组的时间窗，其在衰老细胞被挤出并从上皮移除的位点暴露E-钙粘蛋白。在小肠中，细胞挤出仅限于肠绒毛的尖端，作者表明，在绒毛尖端的连接处是L。单核细胞增多症体内侵袭。如果基底外侧蛋白质暴露在细胞挤出位点，那么利用基底外侧细胞受体的其他微生物也会发现它们吗？
Listeria monocytogenes causes invasive disease by crossing the intestinal epithelial barrier. This process depends on the interaction between the bacterial surface protein Internalin A and the host protein E-cadherin, located below the epithelial tight junctions at the lateral cell-to-cell contacts. We used polarized MDCK cells as a model epithelium to determine how L. monocytogenes breaches the tight junctions to gain access to this basolateral receptor protein. We determined that L. monocytogenes does not actively disrupt the tight junctions, but finds E-cadherin at a morphologically distinct subset of intercellular junctions. We identified these sites as naturally occurring regions where single senescent cells are expelled and detached from the epithelium by extrusion. The surrounding cells reorganize to form a multicellular junction that maintains epithelial continuity. We found that E-cadherin is transiently exposed to the lumenal surface at multicellular junctions during and after cell extrusion, and that L. monocytogenes takes advantage of junctional remodeling to adhere to and subsequently invade the epithelium. In intact epithelial monolayers, an anti-E-cadherin antibody specifically decorates multicellular junctions and blocks L. monocytogenes adhesion. Furthermore, an L. monocytogenes mutant in the Internalin A gene is completely deficient in attachment to the epithelial apical surface and is unable to invade. We hypothesized that L. monocytogenes utilizes analogous extrusion sites for epithelial invasion in vivo. By infecting rabbit ileal loops, we found that the junctions at the cell extrusion zone of villus tips are the specific target for L. monocytogenes adhesion and invasion. Thus, L. monocytogenes exploits the dynamic nature of epithelial renewal and junctional remodeling to breach the intestinal barrier. Studies in microbial pathogenesis are just beginning to address how epithelial cell polarity and host tissue architecture influence host-pathogen interactions. It has long been known that Listeria monocytogenes invasion of epithelial cells requires binding of host cell E-cadherin, a cell-to-cell junction protein. However, an ongoing question has been how L. monocytogenes reaches this receptor, since E-cadherin is located in the basolateral membrane of enterocytes and is inaccessible to bacteria in the intestinal lumen. By examining polarized epithelial monolayers in tissue culture and rabbit intestine in vivo, the authors investigate how and where L. monocytogenes breaches the tight junctions to interact with E-cadherin and invade. They show that L. monocytogenes takes advantage of a temporal window of junctional reorganization that exposes E-cadherin at sites where senescent cells are extruded and removed from the epithelium. In the small intestine, cell extrusion is confined to the tips of the intestinal villi, and the authors show that junctions at the villus tips are the sites of L. monocytogenes invasion in vivo. If basolateral proteins are exposed at cell extrusion sites, do other microbes that utilize basolateral cellular receptors also find them?