Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, ON M5S 3E5, Canada.
Department of Biochemistry and Biomedical Sciences, Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON L8S 4K1, Canada.
Proc Natl Acad Sci U S A. 2018 Oct 2;115(40):10004-10009. doi: 10.1073/pnas.1718350115. Epub 2018 Sep 14.
The pathogenic strategy of and many other gram-negative pathogens relies on the translocation of a specific set of proteins, called effectors, into the eukaryotic host cell during infection. These effectors act in concert to modulate host cell processes in favor of the invading pathogen. Injected by the type III secretion system (T3SS), the effector arsenal of enterohemorrhagic (EHEC) O157:H7 features at least eight individual NleG effectors, which are also found across diverse attaching and effacing pathogens. NleG effectors share a conserved C-terminal U-box E3 ubiquitin ligase domain that engages with host ubiquitination machinery. However, their specific functions and ubiquitination targets have remained uncharacterized. Here, we identify host proteins targeted for ubiquitination-mediated degradation by two EHEC NleG family members, NleG5-1 and NleG2-3. NleG5-1 localizes to the host cell nucleus and targets the MED15 subunit of the Mediator complex, while NleG2-3 resides in the host cytosol and triggers degradation of Hexokinase-2 and SNAP29. Our structural studies of NleG5-1 reveal a distinct N-terminal α/β domain that is responsible for interacting with host protein targets. The core of this domain is conserved across the NleG family, suggesting this domain is present in functionally distinct NleG effectors, which evolved diversified surface residues to interact with specific host proteins. This is a demonstration of the functional diversification and the range of host proteins targeted by the most expanded effector family in the pathogenic arsenal of .
和许多其他革兰氏阴性病原体的致病策略依赖于在感染过程中将一组特定的蛋白质（称为效应子）易位到真核宿主细胞中。这些效应子协同作用，调节宿主细胞过程，有利于入侵的病原体。产志贺样毒素大肠杆菌（EHEC）O157：H7 的 III 型分泌系统（T3SS）注射的效应子武器库至少包含 8 种个体 NleG 效应子，这些效应子也存在于各种附着和破坏病原体中。NleG 效应子共享保守的 C 末端 U 盒 E3 泛素连接酶结构域，该结构域与宿主泛素化机制结合。然而，它们的具体功能和泛素化靶标仍未被描述。在这里，我们确定了两种 EHEC NleG 家族成员 NleG5-1 和 NleG2-3 靶向的宿主蛋白进行泛素化介导降解。NleG5-1 定位于宿主细胞核，并靶向 Mediator 复合物的 MED15 亚基，而 NleG2-3 位于宿主细胞质中，并触发己糖激酶-2 和 SNAP29 的降解。我们对 NleG5-1 的结构研究揭示了一个独特的 N 端 α/β 结构域，该结构域负责与宿主蛋白靶标相互作用。该结构域的核心在 NleG 家族中是保守的，这表明该结构域存在于功能不同的 NleG 效应子中，这些效应子进化出了多样化的表面残基，以与特定的宿主蛋白相互作用。这证明了功能多样化和最广泛的效应子家族在病原体武器库中靶向的宿主蛋白的范围。
