Chlamydia trachomatis type III secretion:: evidence for a functional apparatus during early-cycle development
Chlamydia trachomatis type III secretion:: evidence for a functional apparatus during early-cycle development
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DOI：
10.1046/j.1365-2958.2003.03462.x
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发表时间：
2003-05-01
影响因子：
3.6
通讯作者：
Hackstadt, T
中科院分区：
文献类型：
--
作者：
Fields, KA;Mead, DJ;Hackstadt, T
专性细胞内细菌沙眼衣原体占据一个称为包涵体的寄生液泡。在其细胞内发育周期中，沙眼衣原体可能通过表达 III 型分泌系统来维持这种细胞内生态位，该系统部署了一组宿主细胞相互作用蛋白，包括称为 Incs 的包涵膜定位蛋白。一些 Incs 在感染后 2 小时（周期早期）表达和分泌，而 III 型特异性基因的表达直到 6-12 小时（周期中期）才可检测到。为了解决这个悖论，我们研究了可能在感染早期发挥作用的基本体（EB）上是否存在 III 型装置。我们通过基质辅助激光解吸电离飞行时间 (MALDI-TOF) 和纯化 EB 提取物的免疫印迹分析证明了 III 型分泌装置的存在。使用对核心装置成分 CdsJ 具有特异性的多克隆抗体进行免疫印迹，在 EB 和网状体 (RB) 提取物中鉴定出该蛋白质。此外，在检测cdsJ特异性信息之前，有时通过整个感染培养物提取物的免疫印迹和感染单层的间接免疫荧光来检测CdsJ特异性信号。最后，在沙眼衣原体感染期间感染后2小时表达的IncC在假结核耶尔森氏菌中的表达导致其通过耶尔森氏菌III型装置分泌。基于这些数据，我们提出了一个模型，其中 EB 上存在 III 型分泌孔，并介导早期 Incs 和可能的其他效应器的分泌。 III型基因的中期表达将补充营养RB上的分泌装置，并作为随后形成的EB的分泌孔的来源。
The obligate intracellular bacterium Chlamydia trachomatis occupies a parasitophorous vacuole termed an inclusion. During its intracellular developmental cycle, C. trachomatis maintains this intracellular niche, presumably by expressing a type III secretion system, which deploys a set of host cell-interactive proteins including inclusion membrane-localized proteins termed Incs. Some Incs are expressed and secreted by 2 h (early cycle) after infection, whereas the expression of type III-specific genes is not detectable until 6-12 h (mid-cycle). To resolve this paradox, we investigated the presence of a type III apparatus on elementary bodies (EBs) that might function early in infection. We demonstrate the existence of the type III secretory apparatus by matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) and immunoblot analyses of purified EB extracts. Immunoblots using polyclonal antibodies specific for the core apparatus component CdsJ identified this protein in both EB and reticulate body (RB) extracts. Furthermore, CdsJ-specific signals were detected by immunoblot of whole infected-culture extracts and by indirect immunofluorescence of infected monolayers at times before the detection of cdsJ -specific message. Finally, expression of IncC, expressed by 2 h after infection during C. trachomatis infections, in Yersinia pseudotuberculosis resulted in its secretion via the Yersinia type III apparatus. Based on these data, we propose a model in which type III secretion pores are present on EBs and mediate secretion of early Incs and possible additional effectors. Mid-cycle expression of type III genes would then replenish secretion apparatus on vegetative RBs and serve as a source of secretion pores for subsequently formed EBs.