A mutagenesis-based approach identifies amino acids in the N-terminal part of Francisella tularensis IglE that critically control Type VI system-mediated secretion.
A mutagenesis-based approach identifies amino acids in the N-terminal part of Francisella tularensis IglE that critically control Type VI system-mediated secretion.
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DOI：
10.1080/21505594.2016.1258507
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发表时间：
2017-08-18
期刊：
影响因子：
5.2
通讯作者：
Sjöstedt A
中科院分区：
文献类型：
--
作者：
Bröms JE;Meyer L;Sjöstedt A
革兰氏阴性杆菌是人畜共患病图拉热症的病原菌。其生命周期的特征是通过吞噬小体逃逸和胞浆中的复制在吞噬细胞内生存，最终导致炎性小体激活和宿主细胞死亡。这些过程所需的是方济各氏菌致病岛(FPI)，它编码一种在细胞内感染时活跃的VI型分泌系统(T6SS)。在这项研究中，我们分析了FPI组分IglE的作用，这是一种我们之前已经证明以T6SS依赖的方式分泌的脂蛋白。我们证明，在图拉尔华山菌的LVS中，IglE是一种外膜蛋白。在感染J774细胞后，ΔiglE突变体不能逃脱吞噬小体，继而增殖并引起细胞致病。此外，ΔiglE不能激活炎症小体，抑制内毒素刺激的肿瘤坏死因子-α的分泌，并在小鼠模型上表现出明显的减弱。在新月形藻中，IglE是体外分泌IglC和VgrG所必需的。一种基于突变的方法涉及IglE的第一个∼38残基内的移码突变和丙氨酸替代突变，揭示了极端N末端(残基2-6)序列的剧烈变化很好地被耐受，有趣的是，在细胞内感染期间导致IglE的高分泌，而即使是进一步下游的微小突变也会导致蛋白质功能受损。综上所述，这项研究强调了IglE在图拉氏肺吸虫致病中的重要性，以及N末端在上述所有过程中的作用。
The Gram-negative bacterium Francisella tularensis is the etiological agent of the zoonotic disease tularemia. Its life cycle is characterized by an ability to survive within phagocytic cells through phagosomal escape and replication in the cytosol, ultimately causing inflammasome activation and host cell death. Required for these processes is the Francisella Pathogenicity Island (FPI), which encodes a Type VI secretion system (T6SS) that is active during intracellular infection. In this study, we analyzed the role of the FPI-component IglE, a lipoprotein which we previously have shown to be secreted in a T6SS-dependent manner. We demonstrate that in F. tularensis LVS, IglE is an outer membrane protein. Upon infection of J774 cells, an ΔiglE mutant failed to escape from phagosomes, and subsequently, to multiply and cause cytopathogenicity. Moreover, ΔiglE was unable to activate the inflammasome, to inhibit LPS-stimulated secretion of TNF-α, and showed marked attenuation in the mouse model. In F. novicida, IglE was required for in vitro secretion of IglC and VgrG. A mutagenesis-based approach involving frameshift mutations and alanine substitution mutations within the first ∼ 38 residues of IglE revealed that drastic changes in the sequence of the extreme N-terminus (residues 2–6) were well tolerated and, intriguingly, caused hyper-secretion of IglE during intracellular infection, while even subtle mutations further downstream lead to impaired protein function. Taken together, this study highlights the importance of IglE in F. tularensis pathogenicity, and the contribution of the N-terminus for all of the above mentioned processes.
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影响因子：
64.5
作者：
Clemens DL;Ge P;Lee BY;Horwitz MA;Zhou ZH
通讯作者：
Zhou ZH
DOI：
10.1073/pnas.0504271103
发表时间：
2006-01-03
影响因子：
11.1
作者：
Gavrilin, MA;Bouakl, IJ;Wewers, MD
通讯作者：
Wewers, MD
影响因子：
3.1
作者：
Golovliov, I;Baranov, V;Sjöstedt, A
通讯作者：
Sjöstedt, A
影响因子：
3.7
作者：
Abplanalp, Allison L.;Morris, Ian R.;Berton, Michael T.
通讯作者：
Berton, Michael T.
影响因子：
3.1
作者：
Broms, Jeanette E.;Lavander, Moa;Sjostedt, Anders
通讯作者：
Sjostedt, Anders