The Legionella IcmSW complex directly interacts with DotL to mediate translocation of adaptor-dependent substrates.
The Legionella IcmSW complex directly interacts with DotL to mediate translocation of adaptor-dependent substrates.
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DOI：
10.1371/journal.ppat.1002910
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发表时间：
2012-09
期刊：
影响因子：
6.7
通讯作者：
Vogel JP
中科院分区：
文献类型：
--
作者：
Sutherland MC;Nguyen TL;Tseng V;Vogel JP
嗜肺军团菌是一种革兰氏阴性细菌，通过形成复制液泡逃避宿主内吞途径，在人肺泡巨噬细胞内进行复制。该液泡的产生取决于超过 275 种效应蛋白通过 Dot/Icm 型 IVB 分泌系统 (T4SS) 分泌到宿主细胞中。最近定义了 IV 型偶联蛋白 (T4CP) 亚复合体，由 DotL、DotM、DotN、IcmS 和 IcmW 组成。基于 DotL 与已知 T4CP 的同源性，DotL 被认为是嗜肺军团菌 T4SS 的 T4CP，已知 T4CP 充当底物的内膜受体。因此，推测 DotL 在嗜肺军团菌 T4SS 的底物接合和易位方面发挥着不可或缺的作用。为了阐明这一作用，采用遗传方法筛选无法在宿主细胞内存活的 dotL 突变体。一种突变体 dotLY725Stop 不与 IV 型接头蛋白 IcmS/IcmW (IcmSW) 相互作用，从而在 DotL 上鉴定出 IcmSW 结合域。有趣的是，dotLY725Stop 突变体能够输出一类分泌效应子，即 IcmSW 独立的底物，但在 IcmSW 依赖性底物的分泌方面表现出特定的缺陷。这种差异性分泌说明 DotL 需要与 IV 型接头蛋白直接相互作用才能分泌主要一类底物。因此，通过确定 IcmSW 的新靶标，我们发现 IV 型适配器在嗜肺军团菌 Dot/Icm T4SS 输出底物中发挥着额外的作用。许多病原体能够在真核宿主细胞内生存和生长。其中一种病原体，嗜肺军团菌，能够在巨噬细胞内复制，导致一种称为军团病的肺炎。嗜肺军团菌引起疾病的关键之一是它能够将数百种蛋白质转移到宿主细胞中。这些蛋白质通常被称为“效应子”，其功能是改变宿主细胞，为细菌创造一个适宜的环境。嗜肺军团菌效应子由专门的输出装置输出，该装置由 dot/icm 基因编码。然而，人们对这些底物的分泌机制知之甚少。众所周知，这些效应子的一部分需要 IV 型接头蛋白 IcmS 和 IcmW 的帮助才能转运出细菌。研究表明，IcmSW 在细菌细胞质中的接头依赖性分泌蛋白输出之前与它们结合。在这里，我们报告 DotL（Dot/Icm 分泌系统的内膜成分）也结合 IcmSW，并且这种相互作用对于适配器依赖性底物的输出是必需的。这定义了 IV 型适配器 IcmSW 的新角色，并进一步加深了我们对军团菌如何将底物输出到宿主细胞中的理解。
Legionella pneumophila is a Gram-negative bacterium that replicates within human alveolar macrophages by evasion of the host endocytic pathway through the formation of a replicative vacuole. Generation of this vacuole is dependent upon the secretion of over 275 effector proteins into the host cell via the Dot/Icm type IVB secretion system (T4SS). The type IV coupling protein (T4CP) subcomplex, consisting of DotL, DotM, DotN, IcmS and IcmW, was recently defined. DotL is proposed to be the T4CP of the L. pneumophila T4SS based on its homology to known T4CPs, which function as inner-membrane receptors for substrates. As a result, DotL is hypothesized to play an integral role(s) in the L. pneumophila T4SS for the engagement and translocation of substrates. To elucidate this role, a genetic approach was taken to screen for dotL mutants that were unable to survive inside host cells. One mutant, dotLY725Stop, did not interact with the type IV adaptor proteins IcmS/IcmW (IcmSW) leading to the identification of an IcmSW-binding domain on DotL. Interestingly, the dotLY725Stop mutant was competent for export of one class of secreted effectors, the IcmSW-independent substrates, but exhibited a specific defect in secretion of IcmSW-dependent substrates. This differential secretion illustrates that DotL requires a direct interaction with the type IV adaptor proteins for the secretion of a major class of substrates. Thus, by identifying a new target for IcmSW, we have discovered that the type IV adaptors perform an additional role in the export of substrates by the L. pneumophila Dot/Icm T4SS. Many pathogens are able to survive and grow within eukaryotic host cells. One such pathogen, Legionella pneumophila, is able to replicate within macrophages, resulting in a form of pneumonia called Legionnaires' Disease. One key to L. pneumophila's capacity to cause disease is its ability to translocate several hundred proteins into the host cell. These proteins, typically referred to as “effectors”, function to alter the host cell to create a hospitable environment for the bacteria. L. pneumophila effectors are exported by a specialized export apparatus, which is encoded by the dot/icm genes. However, the mechanism of secretion for these substrates is poorly understood. It is known that a subset of these effectors requires assistance from the type IV adaptor proteins IcmS and IcmW for transport out of the bacterium. It has been shown that IcmSW binds adaptor-dependent secreted proteins in the bacterial cytoplasm prior to their export. Here we report that DotL, an inner membrane component of the Dot/Icm secretion system, also binds IcmSW and this interaction is required for the export of adaptor-dependent substrates. This defines a new role for the type IV adaptors IcmSW and furthers our understanding of how Legionella exports substrates into its host cell.
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影响因子：
3.4
作者：
Heidtman M;Chen EJ;Moy MY;Isberg RR
通讯作者：
Isberg RR
影响因子：
3.6
作者：
Bardill, JP;Miller, JL;Vogel, JP
通讯作者：
Vogel, JP
DOI：
10.1038/nrmicro2218
发表时间：
2009-10
期刊：
Nature reviews. Microbiology
影响因子：
--
作者：
通讯作者：
--
影响因子：
3.6
作者：
Ninio, S;Zuckman-Cholon, DM;Roy, CR
通讯作者：
Roy, CR
影响因子：
158.5
作者：
MCDADE, JE;SHEPARD, CC;DOWDLE, WR
通讯作者：
DOWDLE, WR