Spatiotemporal regulation of a Legionella pneumophila T4SS substrate by the metaeffector SidJ.
Spatiotemporal regulation of a Legionella pneumophila T4SS substrate by the metaeffector SidJ.
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DOI：
10.1371/journal.ppat.1004695
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发表时间：
2015-03
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：
Jeong KC;Sexton JA;Vogel JP
宿主细胞功能的调节对于胞内病原体在宿主细胞内存活和复制至关重要。最常见的是，这些病原体利用专门的分泌系统来注射在宿主细胞内起毒素作用的底物（也称为效应蛋白）。由于细胞内病原体立即杀死其宿主细胞是有害的，因此分泌的毒素在达到其目的后被灭活或降解是至关重要的。病原体嗜肺军团菌代表了研究毒素之间相互作用的理想系统，因为它在宿主细胞内存活约一天，并且其Dot/Icm型IVB分泌系统（T4 SS）注入大量毒素。以前，我们报道了Dot/Icm底物SidE，SdeA，SdeB和SdeC（称为SidE效应子家族）分泌到宿主细胞中，在感染的早期阶段，它们定位于军团菌空泡（LCV）的细胞质表面。SidJ是另一种与SidE家族无关的效应子，也在sdeC-sdeA基因座中编码。有趣的是，虽然SidE家族蛋白在野生型军团菌菌株中的过表达没有影响，但我们发现它们在军团菌J突变体中的过表达完全抑制了菌株的细胞内生长。此外，我们发现SidE蛋白在酵母和哺乳动物HEK 293细胞中的表达都是有毒性的，但这种毒性可以通过SidJ的共表达来抑制，这表明SidJ可以调节SidE家族蛋白的功能。最后，我们能够在体内和体外证明SidJ作用于SidE蛋白以介导它们从LCV中消失，从而防止宿主细胞的致命中毒。基于这些发现，我们提出SidJ作为一种元效应子来控制其他军团菌效应子的活性。许多病原体的关键属性是它们在真核宿主细胞内存活和复制的能力。其中一种病原体，嗜肺军团菌，能够在肺部的巨噬细胞内生长，从而引起一种称为军团菌病的肺炎。L.嗜肺菌通过将数百种蛋白质转移到宿主细胞中而引起疾病。这些蛋白质通常被称为“效应物”，因为它们作为毒素来改变正常的宿主细胞功能。然而，自从L.当嗜肺菌在宿主细胞内停留约一天时，细菌效应物对真核细胞的持续中毒将导致宿主细胞的过早死亡，从而限制病原体的生长。此前，L。嗜肺菌分泌的蛋白LubX被描述为“元效应子”，其被定义为直接作用于另一个效应子以调节其在宿主细胞内的功能的效应子。LubX通过指导另一个效应器SidH的降解来完成这项任务。在这里，我们报告了第二个L。嗜肺菌超效应子SidJ以类似的方式起作用，通过将SidE家族效应子从含有细菌的细胞内区室中除去来中和SidE家族效应子。这进一步确立了元效应子的概念，这可能对军团菌和许多其他病原体如何引起疾病至关重要。
Modulation of host cell function is vital for intracellular pathogens to survive and replicate within host cells. Most commonly, these pathogens utilize specialized secretion systems to inject substrates (also called effector proteins) that function as toxins within host cells. Since it would be detrimental for an intracellular pathogen to immediately kill its host cell, it is essential that secreted toxins be inactivated or degraded after they have served their purpose. The pathogen Legionella pneumophila represents an ideal system to study interactions between toxins as it survives within host cells for approximately a day and its Dot/Icm type IVB secretion system (T4SS) injects a vast number of toxins. Previously we reported that the Dot/Icm substrates SidE, SdeA, SdeB, and SdeC (known as the SidE family of effectors) are secreted into host cells, where they localize to the cytoplasmic face of the Legionella containing vacuole (LCV) in the early stages of infection. SidJ, another effector that is unrelated to the SidE family, is also encoded in the sdeC-sdeA locus. Interestingly, while over-expression of SidE family proteins in a wild type Legionella strain has no effect, we found that their over-expression in a ∆sidJ mutant completely inhibits intracellular growth of the strain. In addition, we found expression of SidE proteins is toxic in both yeast and mammalian HEK293 cells, but this toxicity can be suppressed by co-expression of SidJ, suggesting that SidJ may modulate the function of SidE family proteins. Finally, we were able to demonstrate both in vivo and in vitro that SidJ acts on SidE proteins to mediate their disappearance from the LCV, thereby preventing lethal intoxication of host cells. Based on these findings, we propose that SidJ acts as a metaeffector to control the activity of other Legionella effectors. A key attribute of many pathogens is their ability to survive and replicate within eukaryotic host cells. One such pathogen, Legionella pneumophila, is able to grow within macrophages in the lungs, thereby causing a form of pneumonia called Legionnaires’ Disease. L. pneumophila causes disease by translocating several hundred proteins into the host cell. These proteins are typically referred to as ‘‘effectors’’, as they function as toxins to alter normal host cell function. However, since L. pneumophila remains within the host cells for approximately one day, continual poisoning of the eukaryotic cells by the bacterial effectors will result in the premature death of the host cell, thus restricting the growth of the pathogen. Previously the L. pneumophila secreted protein LubX was described as a “metaeffector”, which has been defined as an effector that acts directly on another effector to modulate its function inside the host cell. LubX accomplishes this task by directing the degradation of another effector, SidH. Here we report a second L. pneumophila metaeffector, SidJ, acts in a similar manner to neutralize SidE family effectors by removing them from the intracellular compartment that contains the bacterium. This further establishes the concept of metaeffectors, which are likely to be critical to how Legionella and many other pathogens cause disease.
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影响因子：
3.1
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通讯作者：
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