An intra-bacterial activity for a T3SS effector
An intra-bacterial activity for a T3SS effector
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DOI：
10.1038/s41598-020-58062-y
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发表时间：
2020-01-23
影响因子：
4.6
通讯作者：
Hardwidge, Philip R.
中科院分区：
文献类型：
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作者：
El Qaidi, Samir;Scott, Nichollas E.;Hardwidge, Philip R.
许多革兰氏阴性细菌病原体通过使用III型分泌系统（T3 SS）将毒力蛋白注入宿主细胞而与哺乳动物细胞相互作用。这些注射的蛋白质“效应物”的一个子集是通过催化添加不寻常的翻译后修饰来抑制宿主蛋白质功能的酶。急诊大肠杆菌和啮齿类柠檬酸杆菌NleB效应子以及肠道沙门氏菌SseK效应子是用精氨酸残基上的N-乙酰葡糖胺（GlcNAc）修饰宿主蛋白质底物的糖基转移酶。这种翻译后修饰破坏了宿主免疫应答蛋白的正常功能。T3 SS效应子被认为在细菌内是无活性的，并且在它们被注射后折叠成它们的活性构象，这是由于分子伴侣的活性，其使效应子保持在允许分泌的结构状态。在进行质谱实验以鉴定NleB直系同源物的糖基化底物时，我们意外地观察到细菌谷胱甘肽合成酶（GshB）在精氨酸残基R256上被NleB糖基化。NleB介导的GshB糖基化导致GshB活性增强，导致谷胱甘肽产量增加，并促进C.啮齿动物在氧化应激条件下的生存。据我们所知，这些数据代表了T3 SS效应子的第一个细菌内活性，并表明曾经被认为限于宿主细胞区室的精氨酸-GlcNAc酰化在调节细菌生理学中也起重要作用。
Many Gram-negative bacterial pathogens interact with mammalian cells by using type III secretion systems (T3SS) to inject virulence proteins into host cells. A subset of these injected protein 'effectors' are enzymes that inhibit the function of host proteins by catalyzing the addition of unusual post-translational modifications. The E. coli and Citrobacter rodentium NleB effectors, as well as the Salmonella enterica SseK effectors are glycosyltransferases that modify host protein substrates with N-acetyl glucosamine (GlcNAc) on arginine residues. This post-translational modification disrupts the normal functioning of host immune response proteins. T3SS effectors are thought to be inactive within the bacterium and fold into their active conformations after they are injected, due to the activity of chaperones that keep the effectors in a structural state permissive for secretion. While performing mass spectrometry experiments to identify glycosylation substrates of NleB orthologs, we unexpectedly observed that the bacterial glutathione synthetase (GshB) is glycosylated by NleB on arginine residue R256. NleB-mediated glycosylation of GshB resulted in enhanced GshB activity, leading to an increase in glutathione production, and promoted C. rodentium survival in oxidative stress conditions. These data represent, to our knowledge, the first intra-bacterial activity for a T3SS effector and show that arginine-GlcNAcylation, once thought to be restricted to host cell compartments, also plays an important role in regulating bacterial physiology.