Hou Mingyu, Chen Ran, Yang Dahai, Núñez Gabriel, Wang Zhuang, Wang Qiyao, Zhang Yuanxing, Liu Qin
State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, 200237, China.
Shanghai Engineering Research Center of Marine Cultured Animal Vaccines, Shanghai, 200237, China.
Cell Microbiol. 2017 Jan;19(1). doi: 10.1111/cmi.12638. Epub 2016 Jul 26.
Edwardsiella piscicida, a bacterial pathogen in fish and humans, expresses a type III secretion system (T3SS) that is critical for pathogen virulence and disease development. However, little is known about the associated effectors and their functional importance. In this study, we identified the ETAE_1757 encoded protein, termed here E. piscicida secretion effector H (EseH) as a novel T3SS effector. We found that upon infection with E. piscicida, EseH is translocated into nucleus of host cells which required the T3SS. Homology modelling analysis suggests that EseH is an enzyme that belongs to the family of phosphothreothine lyases. Consistently, EseH inhibited phosphorylation of ERK1/2, p38α and JNK MAPK pathways in host cells, but had no effect on the NF-kB pathway. Furthermore, mutation of the critical amino acid residues predicted to confer phosphothreonine lyase activity abolished the ability of EseH to inhibit phosphorylation of ERK1/2, p38α and JNK MAPK pathways in host cells. In addition, we found an increase in transcript levels of TNF-α, IL-12, IL-10 and IFN-γ in zebrafish infected with the eseH mutant when compared with the wild type bacterium. Importantly, the virulence of E. piscicida deficient in EseH was highly attenuated in the zebrafish infection model which correlated with decreased loads of the mutant bacterium in both liver and kidney. Complementation of the E. piscicida mutant strain with EseH restored virulence in zebrafish. These results identified EseH as a critical T3SS effector that contributes to virulence by targeting MAPK signalling during E. piscicida infection.
杀鱼爱德华氏菌是一种感染鱼类和人类的细菌病原体，它表达一种III型分泌系统（T3SS），该系统对病原体的毒力和疾病发展至关重要。然而，关于相关效应蛋白及其功能重要性却知之甚少。在本研究中，我们鉴定出由ETAE_1757编码的蛋白，在此称为杀鱼爱德华氏菌分泌效应蛋白H（EseH），它是一种新型的T3SS效应蛋白。我们发现，在感染杀鱼爱德华氏菌后，EseH被转运到宿主细胞的细胞核中，这一过程需要T3SS。同源建模分析表明，EseH是一种属于磷酸苏氨酸裂解酶家族的酶。一致的是，EseH抑制宿主细胞中ERK1/2、p38α和JNK MAPK信号通路的磷酸化，但对NF-κB信号通路没有影响。此外，预测赋予磷酸苏氨酸裂解酶活性的关键氨基酸残基发生突变后，EseH在宿主细胞中抑制ERK1/2、p38α和JNK MAPK信号通路磷酸化的能力丧失。此外，我们发现与野生型细菌相比，感染eseH突变体的斑马鱼中TNF-α、IL-12、IL-10和IFN-γ的转录水平有所增加。重要的是，在斑马鱼感染模型中，缺乏EseH的杀鱼爱德华氏菌的毒力大大减弱，这与突变菌在肝脏和肾脏中的载量减少有关。用EseH对杀鱼爱德华氏菌突变株进行互补可恢复其在斑马鱼中的毒力。这些结果表明，EseH是一种关键的T3SS效应蛋白，它在杀鱼爱德华氏菌感染过程中通过靶向MAPK信号通路来促进毒力。
