Excellence in Research: Role of the T3SS effector EseN of E. ictaluri in virulence and host immune response.

鲶鱼是世界各地的食物来源。减少鱼类损失是鲶鱼产业保障粮食安全的一项重要任务。爱德华氏杆菌是一种细菌，它是导致鲶鱼患病和死亡的主要原因。这个项目的目标是确定这种细菌是如何导致鲶鱼生病和死亡的。我们证明了EseN细菌产物是一个毒力因子。这里的实验将确定这种EseN蛋白是如何参与疾病发展的。这些发现将增加对宿主-病原体相互作用的基本认识。EseN在真核生物中没有等价物，因此可以成为间接窄谱抗生素的有吸引力的靶标。该项目的研究成果可应用于疾病预防、疾病控制和减毒活疫苗的开发。最近，在其他鱼类中也报道了爱德华氏菌病，这增加了这项工作的重要性。拟议的工作也将对南方大学的研究和研究生产力产生广泛的影响。它包括一个针对本科生和服务不足的高中生的指导计划，向他们介绍研究，并为他们在生物科学领域的职业生涯做好准备。本研究的目的是确定拟南芥T3SS效应物EseN作为毒力因子对宿主生理产生影响的分子机制。这将通过研究EseN对宿主细胞基因表达的调节，确定EseN与宿主蛋白的相互作用，建立与特定基因突变相关的表型变化，以及确定参与宿主先天免疫反应的基因表达来实现。ictaluri T3SS效应物EseN与志氏菌OspF和沙门氏菌SpvC相似，在感染过程中选择性地使细胞外信号调节激酶1/2 （ERK1/2）、p38和c- jun - n末端/应激激活蛋白激酶（JNK）去磷酸化，导致丝裂原激活蛋白激酶（MAPK）信号通路失活。然而，即使同源蛋白的生化活性相同，EseN氨基酸与这些其他效应物的相似性也不能保证具有相似的活性。事实上，我们发现除了ERK1/2外，EseN还靶向主要的拱顶蛋白和潜在的磷脂酰肌苷3-激酶（PI3）。这证明了EseN的独特功能，而这些功能在其同系物中没有描述。当这些数据与EseN敲除突变体的高水平衰减相结合时，我们假设EseN是一个主要的毒力因子，在操纵宿主细胞因子的产生和限制宿主先天和适应性免疫反应的诱导方面起着重要作用。该项目由卓越研究（EiR）和促进竞争研究的既定计划（EPSCoR）共同资助。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Catfish are a food source around the world. Reducing fish loss is an essential task in the catfish industry for food security. Edwardsiella ictaluri is a bacterium, and it is a leading cause of catfish disease and loss. The goal of this project is to identify how this bacterium causes disease and death in catfish. We show that the EseN bacterial product is a virulence factor. Experiments here will identify how this EseN protein is involved in the disease development. These findings will increase basic knowledge about host-pathogen interactions. EseN has no equivalents in eukaryotes, and can therefore be an attractive target for indirect narrow-spectrum antibiotics. Findings from this project could be applied for disease prevention, disease control, and the development of a live-attenuated vaccine. Recently, Edwardsiellosis was also reported in other fish species that increases the importance of this work. The proposed work will also have a broad impact on research and research productivity at Southern University. It includes a mentoring program for undergraduate students and under-served high school students introduce them to research and to prepare them for careers in the Biological Sciences. The goal of this work is to determine the molecular mechanism(s) that the E. ictaluri T3SS effector EseN employs to accomplish its impact as a virulence factor on host physiology. This will be accomplished by investigating EseN modulation of host cell gene expression, determining EseN-host protein interactions, establishing phenotypic changes associated with specific gene mutations, and determining expression of genes involved in the host innate immune response. The E. ictaluri T3SS effector EseN is similar to Shigella OspF and Salmonella SpvC, which selectively dephosphorylate extracellular signal regulated kinase 1/2 (ERK1/2), p38, and c-Jun-N-terminal/stress-activated protein kinase (JNK) during infections, resulting in inactivation of mitogen-activated protein kinase (MAPK) signaling pathways. The EseN amino acid similarity to these other effectors, however, does not ensure similar activity, even if the biochemical activity of the homologous proteins is the same. Indeed, we find that EseN also targets the major vault protein and potentially phosphatidylinositide 3-kinase (PI3), in addition to ERK1/2. This demonstrates unique functions of EseN that are not described in its homologs. When these data are combined with the demonstrated high level of attenuation of an EseN knock-out mutant, we hypothesize that EseN is a major virulence factor that plays an essential role in manipulating host cytokine production and limiting induction of the host innate and adaptive immune responses. This project is jointly funded by Excellence in Research (EiR), and the Established Program to Stimulate Competitive Research (EPSCoR).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.