Subtil Agathe, Delevoye Cédric, Balañá María-Eugenia, Tastevin Laurence, Perrinet Stéphanie, Dautry-Varsat Alice
Unité de Biologie des Interactions Cellulaires, Institut Pasteur, CNRS URA 2582, 25 rue du Docteur Roux, 75015 Paris, France.
Mol Microbiol. 2005 Jun;56(6):1636-47. doi: 10.1111/j.1365-2958.2005.04647.x.
Chlamydiae are strict intracellular parasites that induce their internalization upon contact with the host cell and grow inside an intracellular compartment called an inclusion. They possess a type III secretion (TTS) apparatus, which allows for the translocation of specific proteins in the host cell cytosol. In particular, chlamydial proteins of the Inc family are secreted to the inclusion membrane by a TTS mechanism; other TTS substrates are mostly unknown. Using a secretion assay based on the recognition of TTS signals in Shigella flexneri, we searched for TTS signals in the proteins of unknown function, conserved between three different chlamydial species, Chlamydia pneumoniae, C. trachomatis and C. caviae. We identified 24 new candidate proteins which did not belong to the Inc family. Four of these proteins were also secreted as full-length proteins by a TTS mechanism in S. flexneri, indicating that their translocation does not require other chlamydial proteins. One of these proteins was detected in the cytosol of infected cells using specific antibodies, directly demonstrating that it is translocated in the host cell during bacterial proliferation. More generally, this work represents the first directed search for TTS effectors not based on genetic information or sequence similarity. It reveals the abundance of proteins secreted in the host cell by chlamydiae.
衣原体是严格的细胞内寄生虫，与宿主细胞接触时会诱导自身内化，并在称为包涵体的细胞内区室中生长。它们拥有一种III型分泌（TTS）装置，可使特定蛋白质转运至宿主细胞胞质溶胶中。特别是，Inc家族的衣原体蛋白通过TTS机制分泌到包涵体膜上；其他TTS底物大多未知。我们利用基于对福氏志贺氏菌中TTS信号识别的分泌分析方法，在肺炎衣原体、沙眼衣原体和豚鼠衣原体这三种不同衣原体物种间保守的未知功能蛋白质中寻找TTS信号。我们鉴定出24种不属于Inc家族的新候选蛋白质。其中四种蛋白质也通过TTS机制在福氏志贺氏菌中作为全长蛋白质分泌，这表明它们的转运不需要其他衣原体蛋白。利用特异性抗体在感染细胞的胞质溶胶中检测到了其中一种蛋白质，直接证明它在细菌增殖过程中转运至宿主细胞内。更普遍地说，这项工作代表了首次不基于遗传信息或序列相似性对TTS效应蛋白进行的定向搜索。它揭示了衣原体在宿主细胞中分泌的蛋白质数量之多。
